decrypt_cpassword.py

import argparse
from base64 import b64decode
from binascii import unhexlify
from Crypto.Cipher import AES

########
# Author: David Cannings
#   Date: 7th November 2018
#
# Quick and dirty cpassword decryption tool, ported to Python from the
# Ruby version in this blogpost: https://pentestlab.blog/tag/cpassword/
#
# See also: https://blogs.technet.microsoft.com/ash/2014/11/10/dont-set-or-save-passwords-using-group-policy-preferences/
########

def main():
    parser = argparse.ArgumentParser(description='Decrypt Active Directory cpassword data')
    parser.add_argument('data', type=str, help='cpassword base64 data')
    args = parser.parse_args()

    key = "4e9906e8fcb66cc9faf49310620ffee8f496e806cc057990209b09a433b66c1b"
    key = unhexlify(key)

    cipher = AES.new(key, AES.MODE_CBC, "\x00" * 16)

    data = args.data
    data += '=' * (-len(data) % 4)
    data = b64decode(data)

    plaintext = cipher.decrypt(data)
    print("Password is: {}".format(plaintext))

if __name__ == "__main__":
    main()