About

A native Kerberos client implementation for Python on Windows. This module mimics the API of pykerberos to implement Kerberos authentication with Microsoft’s Security Support Provider Interface (SSPI). It supports Python 3.8+.

Installation

WinKerberos is in the Python Package Index (pypi). Use pip to install it:

python -m pip install winkerberos

WinKerberos requires Windows 7 / Windows Server 2008 R2 or newer.

Building and installing from source

You must have the correct version of VC++ installed for your version of Python:

• Python 3.8+ - Visual Studio 2015+ (Any version)

Once you have the required compiler installed, run the following command from the root directory of the WinKerberos source:

pip install .

Building HTML documentation

First install Sphinx:

python -m pip install Sphinx

Then run the following command from the root directory of the WinKerberos source:

pip install -e .
python -m sphinx -b html doc doc/_build

Examples

This is a simplified example of a complete authentication session following RFC-4752, section 3.1:

import winkerberos as kerberos


def send_response_and_receive_challenge(response):
    # Your server communication code here...
    pass


def authenticate_kerberos(service, user, channel_bindings=None):
    # Initialize the context object with a service principal.
    status, ctx = kerberos.authGSSClientInit(service)

    # GSSAPI is a "client goes first" SASL mechanism. Send the
    # first "response" to the server and receive its first
    # challenge.
    if channel_bindings is not None:
        status = kerberos.authGSSClientStep(ctx, "", channel_bindings=channel_bindings)
    else:
        status = kerberos.authGSSClientStep(ctx, "")
    response = kerberos.authGSSClientResponse(ctx)
    challenge = send_response_and_receive_challenge(response)

    # Keep processing challenges and sending responses until
    # authGSSClientStep reports AUTH_GSS_COMPLETE.
    while status == kerberos.AUTH_GSS_CONTINUE:
        if channel_bindings is not None:
            status = kerberos.authGSSClientStep(
                ctx, challenge, channel_bindings=channel_bindings
            )
        else:
            status = kerberos.authGSSClientStep(ctx, challenge)

        response = kerberos.authGSSClientResponse(ctx) or ""
        challenge = send_response_and_receive_challenge(response)

    # Decrypt the server's last challenge
    kerberos.authGSSClientUnwrap(ctx, challenge)
    data = kerberos.authGSSClientResponse(ctx)
    # Encrypt a response including the user principal to authorize.
    kerberos.authGSSClientWrap(ctx, data, user)
    response = kerberos.authGSSClientResponse(ctx)

    # Complete authentication.
    send_response_and_receive_challenge(response)

Channel bindings can be generated with help from the cryptography module. See https://tools.ietf.org/html/rfc5929#section-4.1 for the rules regarding hash algorithm choice:

from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes


def channel_bindings(ssl_socket):
    server_certificate = ssl_socket.getpeercert(True)
    cert = x509.load_der_x509_certificate(server_certificate, default_backend())
    hash_algorithm = cert.signature_hash_algorithm
    if hash_algorithm.name in ("md5", "sha1"):
        digest = hashes.Hash(hashes.SHA256(), default_backend())
    else:
        digest = hashes.Hash(hash_algorithm, default_backend())
    digest.update(server_certificate)
    application_data = b"tls-server-end-point:" + digest.finalize()
    return kerberos.channelBindings(application_data=application_data)

Viewing API Documentation without Sphinx

Use the help function in the python interactive shell:

>>> import winkerberos
>>> help(winkerberos)