requests-kerberos 0.15.0

A Kerberos authentication handler for python-requests

requests Kerberos/GSSAPI authentication library

Requests is an HTTP library, written in Python, for human beings. This library adds optional Kerberos/GSSAPI authentication support and supports mutual authentication. Basic GET usage:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth
>>> r = requests.get("http://example.org", auth=HTTPKerberosAuth())
...

The entire requests.api should be supported.

Setup

Before installing this module, the underlying Kerberos C libraries and Python development headers need to be installed. An example of how to do this for some Linux distributions is shown below:

# For Debian based distros
apt-get install gcc python3-dev libkrb5-dev

# For EL based distros
dnf install gcc python3-devel krb5-devel

The names of the packages may vary across the distribution so use this as a general guide. MacOS and Windows users should not need these development libraries as the underlying Kerberos Python module for those platforms are provided as a wheel and the C library is already preinstalled.

While it is possible to use Kerberos authentication with an explicit principal and password as an arg to HTTPKerberosAuth, it is recommended to use an existing credential cache to store the credentials instead. The credential cache can store a Kerberos Ticket-Granting Ticket (TGT) which is then used for authentication when no password is given to HTTPKerberosAuth. The credential cache can store a TGT by using the kinit command and klist can be used to view the contents of the cache. The environment variable KRB5CCNAME can be used to specify the location of a custom credential cache.

Authentication Failures

Client authentication failures will be communicated to the caller by returning the 401 response. A 401 response may also come from an expired Ticket-Granting Ticket.

Mutual Authentication

REQUIRED

By default, HTTPKerberosAuth will require mutual authentication from the server, and if a server emits a non-error response which cannot be authenticated, a requests_kerberos.errors.MutualAuthenticationError will be raised. If a server emits an error which cannot be authenticated, it will be returned to the user but with its contents and headers stripped. If the response content is more important than the need for mutual auth on errors, (eg, for certain WinRM calls) the stripping behavior can be suppressed by setting sanitize_mutual_error_response=False:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, REQUIRED
>>> kerberos_auth = HTTPKerberosAuth(mutual_authentication=REQUIRED, sanitize_mutual_error_response=False)
>>> r = requests.get("https://windows.example.org/wsman", auth=kerberos_auth)
...

OPTIONAL

If you’d prefer to not require mutual authentication, you can set your preference when constructing your HTTPKerberosAuth object:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, OPTIONAL
>>> kerberos_auth = HTTPKerberosAuth(mutual_authentication=OPTIONAL)
>>> r = requests.get("http://example.org", auth=kerberos_auth)
...

This will cause requests_kerberos to attempt mutual authentication if the server advertises that it supports it, and cause a failure if authentication fails, but not if the server does not support it at all.

DISABLED

While we don’t recommend it, if you’d prefer to never attempt mutual authentication, you can do that as well:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, DISABLED
>>> kerberos_auth = HTTPKerberosAuth(mutual_authentication=DISABLED)
>>> r = requests.get("http://example.org", auth=kerberos_auth)
...

Preemptive Authentication

HTTPKerberosAuth can be forced to preemptively initiate the Kerberos GSS exchange and present a Kerberos ticket on the initial request (and all subsequent). By default, authentication only occurs after a 401 Unauthorized response containing a Kerberos or Negotiate challenge is received from the origin server. This can cause mutual authentication failures for hosts that use a persistent connection (eg, Windows/WinRM), as no Kerberos challenges are sent after the initial auth handshake. This behavior can be altered by setting force_preemptive=True:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, REQUIRED
>>> kerberos_auth = HTTPKerberosAuth(mutual_authentication=REQUIRED, force_preemptive=True)
>>> r = requests.get("https://windows.example.org/wsman", auth=kerberos_auth)
...

Hostname Override

If communicating with a host whose DNS name doesn’t match its kerberos hostname (eg, behind a content switch or load balancer), the hostname used for the Kerberos GSS exchange can be overridden by setting the hostname_override arg:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, REQUIRED
>>> kerberos_auth = HTTPKerberosAuth(hostname_override="internalhost.local")
>>> r = requests.get("https://externalhost.example.org/", auth=kerberos_auth)
...

Explicit Principal

HTTPKerberosAuth normally uses the default principal (ie, the user for whom you last ran kinit or kswitch, or an SSO credential if applicable). However, an explicit principal can be specified, which will cause Kerberos to look for a matching credential cache for the named user. This feature depends on OS support for collection-type credential caches. An explicit principal can be specified with the principal arg:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, REQUIRED
>>> kerberos_auth = HTTPKerberosAuth(principal="user@REALM")
>>> r = requests.get("http://example.org", auth=kerberos_auth)
...

Password Authentication

HTTPKerberosAuth can be used with an explicit principal and password instead of using a credential stored in the credential cache. An explicit username and password can be specified with the principal and password arg respectively:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth, REQUIRED
>>> kerberos_auth = HTTPKerberosAuth(
...     principal="user@REALM",
...     password="SecretPassword",
...)
>>> r = requests.get("http://example.org", auth=kerberos_auth)

When specifing a custom principal and password, the underlying Kerberos library will request a TGT from the KDC before using that TGT to retrieve the service ticket for authentication.

Delegation

requests_kerberos supports credential delegation (GSS_C_DELEG_FLAG). To enable delegation of credentials to a server that requests delegation, pass delegate=True to HTTPKerberosAuth:

>>> import requests
>>> from requests_kerberos import HTTPKerberosAuth
>>> r = requests.get("http://example.org", auth=HTTPKerberosAuth(delegate=True))
...

Be careful to only allow delegation to servers you trust as they will be able to impersonate you using the delegated credentials.

Logging

This library makes extensive use of Python’s logging facilities.

Log messages are logged to the requests_kerberos and requests_kerberos.kerberos_ named loggers.

If you are having difficulty we suggest you configure logging. Issues with the underlying kerberos libraries will be made apparent. Additionally, copious debug information is made available which may assist in troubleshooting if you increase your log level all the way up to debug.

Channel Binding

Since v0.12.0 this library automatically attempts to bind the authentication token with the channel binding data when connecting over a TLS connection. Channel Binding is also known as Extended Protection for Authentication (EPA) from Microsoft. This should be ignored by servers which do not implement support for CB but in the rare case this still fails it can be disabled by setting send_cbt=False.

History

0.15.0: 2024-06-04

• Make Channel Binding data per-host

• Added support for explicit passwords using the password kwarg

0.14.0: 2021-12-05

• Added support for proxy authentication with HTTP endpoints.

• Support for proxying HTTPS endpoints is not available due to limitations of the underlying requests/urllib3 library.

• Fixed up stray bytes to str conversion.

0.13.0: 2021-11-03

• Change Kerberos dependencies to pyspnego to modernise the underlying Kerberos library that is used.

• Removed the wrap_winrm and unwrap_winrm functions

• Dropped support for Python 2 and raised minimum Python version to 3.6.

• Renamed the context attribute to _context to indicate it’s meant for internal use only.

• Fix Negotiate header regex pattern to avoid DoS affected patterns

0.12.0: 2017-12-20

• Add support for channel binding tokens (assumes pykerberos support >= 1.2.1)

• CBT is enabled by default but for older servers which might have compatibility issues this can be disabled with send_cbt=False.

• Add support for kerberos message encryption (assumes pykerberos support >= 1.2.1)

• Misc CI/test fixes

0.11.0: 2016-11-02

• Switch dependency on Windows from kerberos-sspi/pywin32 to WinKerberos. This brings Custom Principal support to Windows users.

0.10.0: 2016-05-18

• Make it possible to receive errors without having their contents and headers stripped.

• Resolve a bug caused by passing the principal keyword argument to kerberos-sspi on Windows.

0.9.0: 2016-05-06

• Support for principal, hostname, and realm override.

• Added support for mutual auth.

0.8.0: 2016-01-07

• Support for Kerberos delegation.

• Fixed problems declaring kerberos-sspi on Windows installs.

0.7.0: 2015-05-04

• Added Windows native authentication support by adding kerberos-sspi as an alternative backend.

• Prevent infinite recursion when a server returns 401 to an authorization attempt.

• Reduce the logging during successful responses.

0.6.1: 2014-11-14

• Fix HTTPKerberosAuth not to treat non-file as a file

• Prevent infinite recursion when GSSErrors occurs

0.6: 2014-11-04

• Handle mutual authentication (see pull request 36)

  All users should upgrade immediately. This has been reported to oss-security and we are awaiting a proper CVE identifier.

  Update: We were issued CVE-2014-8650

• Distribute as a wheel.

0.5: 2014-05-14

• Allow non-HTTP service principals with HTTPKerberosAuth using a new optional argument service.

• Fix bug in setup.py on distributions where the compiler module is not available.

• Add test dependencies to setup.py so python setup.py test will work.

0.4: 2013-10-26

• Minor updates in the README

• Change requirements to depend on requests above 1.1.0

0.3: 2013-06-02

• Work with servers operating on non-standard ports

0.2: 2013-03-26

• Not documented

0.1: Never released

• Initial Release