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Python Kerberos library used by CalendarServer
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Integrate fix from behackett, and additional tests
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PyKerberos Package

This Python package is a high-level wrapper for Kerberos (GSSAPI) operations. The goal is to avoid having to build a module that wraps the entire Kerberos.framework, and instead offer a limited set of functions that do what is needed for client/server Kerberos authentication based on <>.

Much of the C-code here is adapted from Apache's mod_auth_kerb-5.0rc7.


In this directory, run:

python build


To run the tests in the tests folder, you must have a valid Kerberos setup on the test machine. You can use the script as quick and easy way to setup a Kerberos KDC and Apache web endpoint that can be used for the tests. Otherwise you can also run the following to run a self contained Docker container

The docker command needs to be run in the same directory as this library and you can test it with different Python versions by changing the value of the PYENV environment value set in the command.

Please have a look at for more information.


The checkPassword method provided by this library is meant only for testing purposes as it does not offer any protection against possible KDC spoofing. That method should not be used in any production code.

Channel Bindings

You can use this library to authenticate with Channel Binding support. Channel Bindings are tags that identify the particular data channel being used with the authentication. You can use Channel bindings to offer more proof of a valid identity. Some services like Microsoft's Extended Protection can enforce Channel Binding support on authorisation and you can use this library to meet those requirements.

More details on Channel Bindings as set through the GSSAPI can be found here <>. Using TLS as a example this is how you would add Channel Binding support to your authentication mechanism. The following code snippet is based on RFC5929 <> using the 'tls-server-endpoint-point' type.

import hashlib

 def get_channel_bindings_application_data(socket):
     # This is a highly simplified example, there are other use cases
     # where you might need to use different hash types or get a socket
     # object somehow.
     server_certificate = socket.getpeercert(True)
     certificate_hash = hashlib.sha256(server_certificate).hexdigest().upper()
     certificate_digest = base64.b16decode(certificate_hash)
     application_data = b'tls-server-end-point:%s' % certificate_digest

     return application_data

 def main():
     # Code to setup a socket with the server
     # A lot of code to setup the handshake and start the auth process
     socket = getsocketsomehow()

     # Connect to the host and start the auth process

     # Build the channel bindings object
     application_data = get_channel_bindings_application_data(socket)
     channel_bindings = kerberos.channelBindings(application_data=application_data)

     # More work to get responses from the server

     result, context = kerberos.authGSSClientInit(kerb_spn, gssflags=gssflags, principal=principal)

     # Pass through the channel_bindings object as created in the kerberos.channelBindings method
     result = kerberos.authGSSClientStep(context, neg_resp_value, channel_bindings=channel_bindings)

     # Repeat as necessary

Python APIs


Copyright and License

Copyright (c) 2006-2018 Apple Inc. All rights reserved.

This software is licensed under the Apache License, Version 2.0. The Apache License is a well-established open source license, enabling collaborative open source software development.

See the "LICENSE" file for the full text of the license terms.

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