requests Kerberos/GSSAPI authentication library
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:target: https://github.com/requests/requests-kerberos/actions/workflows/ci.yml
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:
.. code-block:: python
>>> 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:
.. code-block:: bash
# 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
:
.. code-block:: python
>>> 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:
.. code-block:: python
>>> 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:
.. code-block:: python
>>> 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
:
.. code-block:: python
>>> 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:
.. code-block:: python
>>> 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:
.. code-block:: python
>>> 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:
.. code-block:: python
>>> 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
:
.. code-block:: python
>>> 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
.. _pyspnego: https://github.com/jborean93/pyspnego
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
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
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.
.. _36: https://github.com/requests/requests-kerberos/pull/36
.. _oss-security: http://www.openwall.com/lists/oss-security/
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
0.1: Never released