wtf.py

import re
import sys
import os.path

def xor(data, key):
    l = len(key)

    decoded = "U"
    for i in range(1, len(data)):
        decoded += chr(data[i] ^ key[(i-1) % l])
    return decoded

def mkKey(length):
    return ([0xFF] * length) + ([0x00] * (length + 2))

pattern = re.compile("CAB-" + "\w" * 32)

assert len(sys.argv) == 2, ("Usage: python " + sys.argv[0] + " <input file>")
assert os.path.isfile(sys.argv[1]), "File doesn't exist"

data = bytearray(open(sys.argv[1], "rb").read())

for i in range(0, 10):
    key = mkKey(i)
    decoded = xor(data, key)
    if pattern.search(decoded) != None:
        handle = open("out.unity3d", "w")
        handle.write(decoded)
        handle.close()
        print("Managed to extract with key " + str(i) + " into out.unity3d")