EPFL's CTF team

TU CTF 2018 - Danger Zone


Difficulty: easy Legend says, this program was written by Kenny Loggins himself.

Given files


The .pyc extension indicates python compiled code. So let’s decompile it using uncompyle6.

import base64

def reverse(s):
    return s[::-1]

def b32decode(s):
    return base64.b32decode(s)

def reversePigLatin(s):
    return s[-1] + s[:-1]

def rot13(s):
    return s.decode('rot13')

def main():
    print 'Something Something Danger Zone'

if __name__ == '__main__':
    s = main()
    print s

The string returned by the main function seems to be a reversed base64 string.

Looking at the decompiled code, the first function in the file is reverse, the second one b32decode. First we conclude that it’s actually base32 and not base64. But, more importantly, it seems that applying the functions in the same order as they appear on the file will decode the string.

Let’s give it a try and run: rot13(reversePigLatin(b32decode(reverse('=YR2XYRGQJ6KWZENQZXGTQFGZ3XCXZUM33UOEIBJ'))))

This holds the flag!