CryptoHack Requester Package

This is a simple python package to ease interaction with CryptoHack's challenges over Netcat and Web API.

Installing / Getting started

The project has been tested with python >= 3.6.9. It may works with previous version, but nothing sure.

To install the package simply use pip:

python3 -m pip install CHRequester

Features

CryptoHack has some challenges working with a Web API (Block Cipher Mode challenges), and some through server comunication. They generaly need automation so it is recommanded in the FAQ to use the Requets package for web challenges and Pwntools to communicate to a challenge on a server. This package offer a more user-firendly and less time-consuming way to communicate with these challenges.

Example of usage with the Web API:

from ch_requester import URLRequester

if __name__ == "__main__":
    BASE_URL = "http://aes.cryptohack.org/oh_snap/"

    R = URLRequester(BASE_URL)
    # adding actions to the requester
    # first give the name of the action
    # then specify a tuple of inputs that are needed for this action
    # then specify a tuple of outputs that can given in return

    # 'error' can be specified as an output if the challenge returns
    # useful information through an error message
    # else, an Exception will be raised if an error is returned
    # and the user does not specify it as a desired output.
    # inputs must be in the order of the url, e.g.
    # http://aes.cryptohack.org/oh_snap/ciphertext/nonce/
    R.add_action('send_cmd', ('ciphertext', 'nonce'), ('msg', 'error'))

    # we can then execute an action, by giving its name as first parameters.
    # The following ordered arguments are the wanted outputs from this action.
    # Even if we specified multiple possible outputs for this actions ('error')
    # and 'msg', it is possible to retrieve a subset. If only one output is 
    # asked, then its value is returned by the function. Else a dictionnary
    # is returned.
    # Then inputs are specified through unordered arguments. There must always
    # be given as bytes, the requester is in charge to send it as hex to the web 
    # server. If some day the Web API changes, and some arguments are not expected
    # to be in hexadecimal, changes will be needed.
    error_message = R.do_action('send_cmd', 'error', ciphertext=b'\xff', nonce=b'\xff')

    # do awesome things to find the flag

Example of usage with server communication using 'option' parameters:

from ch_requester import NCRequester

if __name__ == "__main__":

    R = NCRequester(13397)
    # adding actions to the requester
    # first give the name of the action, and must match the option
    # paramete of the server-side.
    # then specify a tuple of inputs that are needed for this action
    # then specify a tuple of outputs that can given in return.
    # No particular ordering is needed here.
    R.add_action("insert_key", ("key",), ("msg"))
    R.add_action("unlock", (), ("msg",))

    # we then open the connection (using pwntools)
    R.open()
    # some challenges print a line to welcome the challenger
    # we can skip it
    R.flush_line()

    # As for the Web API, we can execute action, except this time
    # the user is responsible to put input data into the correct
    # format used by the server-side.
    msg = R.do_action("insert_key", "msg", key=(b"\x00" * 16).hex())

    print(msg)

    flag = R.do_action("unlock", "msg")

    # do awesome things to find the flag

    R.close()

Example of usage with server communication without 'option' parameters:

from ch_requester import NCRequester
from base64 import b64decode

if __name__ == "__main__":

    R = NCRequester(13370)
    # some challenges don't use the 'option' parameters
    # so you can send your own dictionnary payload to the server

    # we then open the connection (using pwntools)
    R.open()
    # some challenges print a line to welcome the challenger
    # we can skip it
    R.flush_line()

    PAYLOAD = {'msg': 'request'}
    ciphertext = b64decode(R.send_recv_raw_payload(PAYLOAD, 'ciphertext'))

    # do awesome things to find the flag

    R.close()

Contributing

If you'd like to contribute, please fork the repository and use a feature branch. Pull requests are warmly welcome.

Licensing

The code in this project is licensed under MIT license.