from struct import unpack as up, pack as pk
from binascii import unhexlify as uhx, hexlify as hx
from Crypto.Cipher import AES
from Crypto.Util import Counter
import sys

pk11key = uhx('') # Insert key here.

def string_to_ctr(ctr):
    return Counter.new(128, initial_value=int(hx(ctr), 16))

def main(argc, argv):
    if argc == 2:
        out_fn = '%s.dec' % argv[1]
    elif argc == 3:
        out_fn = argv[2]
    else:
        print 'Usage: %s package1 out_fn' % argv[0]
        sys.exit(1)
    try:
        with open(argv[1], 'rb') as f:
            pk11 = f.read()
    except IOError:
        print 'Failed to read %s!' % argv[1]
        sys.exit(1)
    sz, padding, ctr = up('<I12s16s', pk11[0x3FE0:0x4000])
    aes = AES.new(pk11key, AES.MODE_CTR, counter=string_to_ctr(ctr))
    dec = aes.decrypt(pk11[0x4000:])
    if not dec.startswith('PK11'):
        print '%s is not a decryptable package1!' % argv[1]
        sys.exit(1)
    try:
        with open(out_fn, 'wb') as f:
            f.write(dec)
    except IOError:
        print 'Failed to write to %s' % out_fn
    return 0
    

if __name__ == '__main__':
    sys.exit(main(len(sys.argv), sys.argv))