A simple utility to decrypt cisco Type 7 passwords

cisco7decrypt.py

#!/usr/bin/env python3

"""
Based on the documentation from:
- http://pen-testing.sans.org/resources/papers/gcih/cisco-ios-type-7-password-vulnerability-100566
- http://wiki.nil.com/Deobfuscating_Cisco_IOS_Passwords

translation = [
    0x64, 0x73, 0x66, 0x64, 0x3b, 0x6b, 0x66, 0x6f, 0x41, 0x2c, 0x2e,
    0x69, 0x79, 0x65, 0x77, 0x72, 0x6b, 0x6c, 0x64, 0x4a, 0x4b, 0x44,
    0x48, 0x53, 0x55, 0x42, 0x73, 0x67, 0x76, 0x63, 0x61, 0x36, 0x39,
    0x38, 0x33, 0x34, 0x6e, 0x63, 0x78, 0x76, 0x39, 0x38, 0x37, 0x33,
    0x32, 0x35, 0x34, 0x6b, 0x3b, 0x66, 0x67, 0x38, 0x37
]
"""

import argparse


translation = [
    hex(ord(char)) for char in 'dsfd;kfoA,.iyewrkldJKDHSUBsgvca69834ncxv9873254k;fg87'
]


def hexadecimal(text):
    return int(text, 16)


def decrypt(text):
    password = ''
    jump, text = int(text[:2]), text[2:]
    for i in range(0, len(text), 2):
        password += chr(hexadecimal(text[i:i+2]) ^ hexadecimal(translation[jump]))
        jump += 1 % len(translation)
    return password


def argument_parser():
    parser = argparse.ArgumentParser(description='A simple utility to decrypt cisco Type 7 passwords')
    parser.add_argument('text', nargs='+', help='the encrypted password that you want to decrypt')
    parser.add_argument('-l', '--long-output', action='store_true', help='show a message with the encrypted and decrypted password')
    return parser


def main():
    args = argument_parser().parse_args()
    for text in args.text:
        if args.long_output:
            print('{}::{}'.format(text, decrypt(text)))
        else:
            print(decrypt(text))


if __name__ == '__main__':
    main()