PicoCTF - fixme1.py

Download the fixme1.py file, open it in an editor and change it to the following.

import random

def str_xor(secret, key):
    #extend key to secret length
    new_key = key
    i = 0
    while len(new_key) < len(secret):
        new_key = new_key + key[i]
        i = (i + 1) % len(key)        
    return "".join([chr(ord(secret_c) ^ ord(new_key_c)) for (secret_c,new_key_c) in zip(secret,new_key)])

flag_enc = chr(0x15) + chr(0x07) + chr(0x08) + chr(0x06) + chr(0x27) + chr(0x21) + chr(0x23) + chr(0x15) + chr(0x5a) + chr(0x07) + chr(0x00) + chr(0x46) + chr(0x0b) + chr(0x1a) + chr(0x5a) + chr(0x1d) + chr(0x1d) + chr(0x2a) + chr(0x06) + chr(0x1c) + chr(0x5a) + chr(0x5c) + chr(0x55) + chr(0x40) + chr(0x3a) + chr(0x5f) + chr(0x53) + chr(0x5b) + chr(0x57) + chr(0x41) + chr(0x57) + chr(0x08) + chr(0x5c) + chr(0x14)
  
flag = str_xor(flag_enc, 'enkidu')
print('That is correct! Here\'s your flag: ' + flag)

The problem was to the last line. Python syntax is very strict with the indentation, which means the commands need to be indented properly in order for the program to run and be logically correct.

After you fix the program, open up a terminal and type the following.

python3 fixme1.py

Nice, you’ve got the flag!