HTTPX <https://github.com/encode/httpx>_ is a full featured Python HTTP library with both sync and async APIs
designed to be a next generation HTTP client for Python. This library is a port
of Requests GSSAPI <https://github.com/pythongssapi/requests-gssapi>_ to HTTPX which adds optional GSSAPI authentication support and
supports mutual authentication.
Basic GET usage:
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth
>>> r = httpx.get("http://example.org", auth=HTTPSPNEGOAuth())
Both the sync and async HTTPX APIs should be fully supported.
In order to use this library, there must already be a Kerberos Ticket-Granting
Ticket (TGT) in a credential cache (ccache). 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 (for instance, 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 a credentials are available and valid is the responsibility of the user.
Client authentication failures will be communicated to the caller by returning a 401 response. A 401 response may also be the result of expired credentials (including the TGT).
Mutual authentication is a poorly-named feature of the GSSAPI which doesn't provide any additional security benefit to most possible uses of httpx_gssapi. Practically speaking, in most mechanism implementations (including krb5), it requires another round-trip between the client and server during the authentication handshake. Many clients and servers do not properly handle the authentication handshake taking more than one round-trip. If you encounter a MutualAuthenticationError, this is probably why.
So long as you're running over a TLS link whose security guarantees you trust, there's no benefit to mutual authentication. If you don't trust the link at all, mutual authentication won't help (since it's not tamper-proof, and GSSAPI isn't being used post-authentication. There's some middle ground between the two where it helps a small amount (e.g., passive adversary over encrypted-but-unverified channel), but for Negotiate (what we're doing here), it's not generally helpful.
For a more technical explanation of what mutual authentication actually guarantees, I refer you to rfc2743 (GSSAPIv2), rfc4120 (krb5 in GSSAPI), rfc4178 (SPNEGO), and rfc4559 (HTTP Negotiate).
DISABLED ^^^^^^^^
By default, there's no need to explicitly disable mutual authentication. However, for compatability with older versions of requests_gssapi or requests_kerberos, you can explicitly request it not be attempted:
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, DISABLED
>>> gssapi_auth = HTTPSPNEGOAuth(mutual_authentication=DISABLED)
>>> r = httpx.get("https://example.org", auth=gssapi_auth)
...
REQUIRED ^^^^^^^^
This was historically the default, but no longer is. If requested,
HTTPSPNEGOAuth will require mutual authentication from the server, and if
a server emits a non-error response which cannot be authenticated, a
httpx_gssapi.errors.MutualAuthenticationError will be raised. (See
above for what this means.) 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 httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, REQUIRED
>>> gssapi_auth = HTTPSPNEGOAuth(mutual_authentication=REQUIRED, sanitize_mutual_error_response=False)
>>> r = httpx.get("https://windows.example.org/wsman", auth=gssapi_auth)
...
OPTIONAL ^^^^^^^^
This will cause httpx_gssapi 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. This is probably not
what you want: link tampering will either cause hard failures, or silently
cause it to not happen at all. It is retained for compatability.
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, OPTIONAL
>>> gssapi_auth = HTTPSPNEGOAuth(mutual_authentication=OPTIONAL)
>>> r = httpx.get("https://example.org", auth=gssapi_auth)
...
HTTPSPNEGOAuth can be forced to preemptively initiate the GSSAPI
exchange and present a token on the initial request (and all
subsequent). By default, authentication only occurs after a
401 Unauthorized response containing a 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 GSSAPI challenges are sent after the initial auth handshake. This
behavior can be altered by setting opportunistic_auth=True:
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, REQUIRED
>>> gssapi_auth = HTTPSPNEGOAuth(mutual_authentication=REQUIRED, opportunistic_auth=True)
>>> r = httpx.get("https://windows.example.org/wsman", auth=gssapi_auth)
...
If communicating with a host whose DNS name doesn't match its
hostname (eg, behind a content switch or load balancer),
the hostname used for the GSSAPI exchange can be overridden by
passing in a custom name (string or gssapi.Name):
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, REQUIRED
>>> gssapi_auth = HTTPSPNEGOAuth(target_name="internalhost.local")
>>> r = httpx.get("https://externalhost.example.org/", auth=gssapi_auth)
...
HTTPSPNEGOAuth 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 credential can be in instead, if desired.
.. code-block:: python
>>> import gssapi
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth, REQUIRED
>>> name = gssapi.Name("user@REALM", gssapi.NameType.hostbased_service)
>>> creds = gssapi.Credentials(name=name, usage="initiate")
>>> gssapi_auth = HTTPSPNEGOAuth(creds=creds)
>>> r = httpx.get("http://example.org", auth=gssapi_auth)
...
HTTPSPNEGOAuth normally lets the underlying gssapi library decide which
negotiation mechanism to use. However, an explicit mechanism can be used instead
if desired. The mech parameter will be passed straight through to gssapi
without interference. It is expected to be an instance of gssapi.mechs.Mechanism.
.. code-block:: python
>>> import gssapi
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth
>>> try:
... spnego = gssapi,mechs.Mechanism.from_sasl_name("SPNEGO")
... except AttributeError:
... spnego = gssapi.OID.from_int_seq("1.3.6.1.5.5.2")
>>> gssapi_auth = HTTPSPNEGOAuth(mech=spnego)
>>> r = httpx.get("http://example.org", auth=gssapi_auth)
...
httpx_gssapi supports credential delegation (GSS_C_DELEG_FLAG).
To enable delegation of credentials to a server that requests delegation, pass
delegate=True to HTTPSPNEGOAuth:
.. code-block:: python
>>> import httpx
>>> from httpx_gssapi import HTTPSPNEGOAuth
>>> r = httpx.get("http://example.org", auth=HTTPSPNEGOAuth(delegate=True))
...
Be careful to only allow delegation to servers you trust as they will be able to impersonate you using the delegated credentials.
This library makes extensive use of Python's logging facilities.
Log messages are logged to the httpx_gssapi and
httpx_gssapi.gssapi named loggers.
If you are having difficulty we suggest you configure logging. Issues with the underlying GSSAPI 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.
principal keyword argument to
kerberos-sspi on Windows.Support for principal, hostname, and realm override.
Added support for mutual auth.
Support for Kerberos delegation.
Fixed problems declaring kerberos-sspi on Windows installs.
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.
Fix HTTPKerberosAuth not to treat non-file as a file
Prevent infinite recursion when GSSErrors occurs
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/
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.
FAQs
A Python GSSAPI authentication handler for HTTPX
We found that httpx-gssapi demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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