VolgaCTF Quals 2014 - Reverse 200

Reverse Code Engineering — 200

You just need to put 2 numbers in ascending order without spaces.
btsync: BNBPTYNHZR2FGRLULM5G3XHT4T6XDZK4E
direct link

 You can read my write-up at the Hardc0de team blog.

CSCAMP CTF Quals 2013 - Reverse 150 write-up

In this task we are given a x86-64 binary that prints a string.

CSCAMP CTF Quals 2013 - Reverse 100 write-up

Unfortunately tasks currently are unavailable, so I cannot copy task and its name.

We are given a .NET application (You can verify this using file utility.) which checks password. You can try to guess it, but this won't help you anyhow.

Crackmes [Reverse write-up] - Trojaner's Patch/InjectMe write-up (DLL injection)

Task from crackmes:

Patch or Inject it with a DLL, so that it will show the goodboy message :)
Happy Hacking!

Hacklu CTF 2013 - Reverse 150 - RoboAuth

Task:

Oh boy, those crazy robots can't catch a break! Now they're even stealing our liquid gold from one of our beer tents! And on top of that they lock it behind some authentication system. Quick! Access it before they consume all of our precious beverage!

Download: https://ctf.fluxfingers.net/static/downloads/roboauth/RoboAuth.exe

Flag: password1_password2

Sharif CTF Quals 2013 - Exploiting 200 - sweet

Task:

nc ctf.sharif.edu 15478

Download

This service accepts our input and echoes it using variant of printf function. As you might have already understood there will be a format string vulnerability.

Sharif CTF Quals 2013 - Reverse 300 - HelpMe

Task:

Download

We are provided with a Java archive (jar) that can be used to encrypt a file using an AES block cipher.

Sharif CTF Quals 2013 - Reverse 200 - Reverse200

Task:

Download

We are provided with an x86 ELF executable that crashes while trying to decrypt a key.

Sharif CTF Quals 2013 - Reverse 100 - Vault

Task:

Download

In this task we have to open a huge lock. We are provided with .NET binary and the task is the same as usual: get a flag!

Sharif CTF Quals 2013 - Steganography 200 - muse

Task:

Another hidden message!

Download

 We are provided with the mp3 "Knights of Cydonia" song by Muse. This container should have something hidden, therefore it is task on audio steganography topic, let's capture the flag.

Crackmes [Reverse] - TRVCrackme v1.0 (MIPS) [Very easy level]

In this task we are given a binary compiled for MIPS architecture. Therefore to execute it you have to find workstation that have MIPS architecture or emulate its behavior. Of course you can produce keygen without even executing it, because the logic is quite straighforward. By the time I managed to execute it I have already understood what it does.

CSAW CTF Quals 2013 - Reverse 500 - Impossible

Task:

Impossible - 500 Points

Solved by 82 teams.

WTF, his hp is over 9000! Beat the game to get your key.
impossible.nds

In this task we are provided with an image of the Nintendo DS cartridge with a game. The task clearly says we have to win probably cheating. Firstly I installed IDA loader for .nds files (You can find it in the net) but this haven't helped me a lot: there were a lot of ARM code and no clues how to get to the flag.

CSAW CTF Quals 2013 - Reverse 400 - keygenme

Task:

keygenme - 400 Points

Solved by 100 teams.

nc 128.238.66.219 14549
keygenme32.elf

We are given a x86 ELF executable. It takes 3 arguments(username, token1, token2) and prints whether they are good(*<:-)) or not. ( :-( ). In this task we need to write a keygen that will communicate with judges server, which sends username to keygen, and then send them valid token pair for each username.

Exploit exercises - Protostar - Net 3

Last network level is a bit more challenging. There are a couple of traps here. The idea of the program is like that: it reads length(16-bit) of the future input, then reads that amount of bytes. First byte of the input should have the value of 23 to proceed to login function. Buffer with input data is used as an argument to the login function.

Exploit exercises - Protostar - Net 2

Third network level requires to sum 4 integers and send result. They are provided by the server. Nothing special just use of pack and unpack methods.

Exploit exercises - Protostar - Net 1

Next level requires to convert binary integer to its string representation. All we have to do is read 4 bytes, convert bytes to int then convert it into string. Ruby have unpack method of String class to do required transformation.

Exploit exercises - Protostar - Net 0

In this task we have to work with byte ordering and ways to send/receive them. I wouldn't tell about endianness because there are a lot of good internet sources that cover it. (e.g. wiki ).

Task binary sends a number and waits when we will provide little endian version of it. Our task is to get number from incoming message, convert it into binary form and then send it backwards. To get numbet you will probably want to use regular expression which will cut out contiguous digit string between quotation marks. Then there is a fast solution in Ruby to use pack method of the Array class which allows to convert integer from string to binary. Then we will just send it and receive congratulation message.

Exploit exercises - Protostar - Heap 3

In the heap 3 task 3 portions of memory are allocated on the heap. Then 3 command-line arguments are copied without bounds checking and later the allocated memory is freed. We are supposed to exploit Doug Lea way of allocation and deallocation of memory. There is a nice online page with a description of the way how to exploit it.

Exploitation is based on the fact that while memory is being freed, if there is a free block next to the one that is being freed, free function merges two blocks and write some metadata at the calculated addresses. That means that we can make free function overwrite value at the user provided address after corrupting metadata of the allocated blocks. We should make free think that previous block is free and change metadata to influence address calculation. In the task blocks are allocated in a way that is pictured on the image:

ASIS CTF 2013 - Reverse 200 - Masterpiece

Task:

file

ASIS CTF 2013 - Forensics 100 - pcap

Task:

Find the flag. file

You can download the missing parts of pcap forensic challenge from here:
053dc897d3e154dd5ed27c46b738850d
21eae902cf5b82c7b207e963a130856d