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

In order to use this library, there must already be a Kerberos Ticket-Granting Ticket(TGT) cached in a Kerberos credential cache. Whether a TGT is available can be easily determined by running the klist command. If no TGT is available, then it first must be obtained by running the kinit command, or pointing the $KRB5CCNAME to a credential cache with a valid TGT.

In short, the library will handle the "negotiations" of Kerberos authentication, but ensuring that an initial TGT is available and valid is the responsibility of the user.

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, as well as working principal support in PyKerberos (it is broken in many builds). 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)
...

On Windows, WinKerberos is used instead of PyKerberos. WinKerberos allows the use of arbitrary principals instead of a credential cache. Passwords can be specified by following the form user@realm:password for principal.

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.

History

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)
• 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