No cON Name CTF Quals 2014

The task was to find vulnerability in binary service explicit (binary and exploit). Like other tasks at this CTF, this one was easy enouth.

After downloading file and opening it in IDA I'd found that it's x86 ELF which has no imported functions. Unfortunately Hex-Rays FLIRT didn't help me that time, but x86 decompiler works fine and few minutes was enouth to reconstruct main function and identify high level apis. Result I've got is the next:

We got an archive with directory "ctf" with only one file "flag.txt" which contains next text:

Nothing to see here, moving along... 

In this task we got a large text file where obviously was a substitution cipher.

In this task we have a gzip compressed python file which contained rot13-encoded source code. After decoding we got right source code that was simple to understand - there was creation of function with marshal python module and execution it.