a23_decpak.py

a23_decpak.py

from struct import unpack
from sys import argv, exit
import os
from itertools import cycle

def xor(a,b):
    return bytes([i ^ j for i,j in zip(a, cycle(b))])

f = open(argv[1], 'rb')

base_header_size = 4 * 4
file_entry_size = 184

magic, num_files, hunk1, hunk2 = unpack("<IIII", f.read(base_header_size))
offset_base = base_header_size + num_files * file_entry_size

if magic != 0x20000 or hunk1 != 0x10 or hunk2 != 0x0d:
    print('bad magic', hex(magic), hex(hunk1), hex(hunk2))
    exit(0)

    
file_entries = []
print("Number of files:", num_files)

for i in range(num_files):
    
    f.seek(base_header_size + i * file_entry_size, 0)
    s = f.read(file_entry_size)
    name, flen, file_key, offset, feunk1, feunk2, feunk3 = unpack("<128sI32sQIII", s)
    key = bytes([int(i, 16) for  i in "64 47 47 4B 58 4C 48 4C 75 43 4A 77 76 38 61 42 63 33 59 51 58 36 58 36 73 52 45 56 50 63 68 73".split(' ')])
    
    final_key = xor(key, file_key)

    xored = xor(name, final_key)
    name = xored.split(b'\x00')[0]
    
    file_entries.append({'name':name, 'len':flen, 'offset':offset, 'key':final_key})
    
for i, fe in enumerate(file_entries):
    name, flen, offset, key = fe['name'], fe['len'], fe['offset'], fe['key']
    
    base, fname = os.path.split(name)
    base = b"." + base
    print(name)
    if not os.path.exists(base):
        os.makedirs(base)
    with open(b'.'+ name, 'wb') as out:
        out.write(xor(f.read(flen), key))