= Django CAS =
`django_cas` is a [http://www.ja-sig.org/products/cas/ CAS] 1.0 and CAS 2.0
authentication backend for [http://www.djangoproject.com/ Django]. It allows
you to use Django's built-in authentication mechanisms and `User` model while
adding support for CAS.
It also includes a middleware that intercepts calls to the original login
and logout pages and forwards them to the CASified versions, and adds
CAS support to the admin interface.
== Installation ==
Run `python setup.py install`, or place the `django_cas` directory in your
`PYTHONPATH` directly. (Note: If you're using Python 2.4 or older, you'll need
to install [http://pypi.python.org/pypi/elementtree/ ElementTree] to use
CAS 2.0 functionality.)
Now add it to the middleware and authentication backends in your settings.
Make sure you also have the authentication middleware installed. Here's what
mine looks like:
MIDDLEWARE_CLASSES = (
AUTHENTICATION_BACKENDS = (
Set the following required setting in `settings.py`:
* `CAS_SERVER_URL`: This is the only setting you must explicitly define.
Set it to the base URL of your CAS source (e.g.
Optional settings include:
* `CAS_ADMIN_PREFIX`: The URL prefix of the Django administration site.
If undefined, the CAS middleware will check the view being rendered to
see if it lives in `django.contrib.admin.views`.
* `CAS_IGNORE_REFERER`: If `True`, logging out of the application will
always send the user to the URL specified by `CAS_REDIRECT_URL`.
* `CAS_LOGOUT_COMPLETELY`: If `False`, logging out of the application
won't log the user out of CAS as well.
* `CAS_REDIRECT_URL`: Where to send a user after logging in or out if
there is no referrer and no next page set. Default is `/`.
* `CAS_VERSION`: The CAS protocol version to use. `'1'` and `'2'` are
supported, with `'2'` being the default.
Make sure your project knows how to log users in and out by adding these to
your URL mappings:
Users should now be able to log into your site (and staff into the
administration interface) using CAS.
== Populating User Data ==
To add user data, subclass `CASBackend` and specify that as your
from django_cas.backend import CASBackend
"""CAS authentication backend with user data populated from AD"""
def authenticate(self, ticket, service):
"""Authenticates CAS ticket and retrieves user data"""
user = super(PopulatedCASBackend, self).authenticate(
# Connect to AD, modify user object, etc.
== Preventing Infinite Redirects ==
Django's current implementation of its `permission_required` and
`user_passes_test` decorators (in `django.contrib.auth.decorators`) has a
known issue that can cause users to experience infinite redirects. The
decorators return the user to the login page, even if they're already logged
in, which causes a loop with SSO services like CAS.
`django_cas` provides fixed versions of these decorators in
`django_cas.decorators`. Usage is unchanged, and in the event that this issue
is fixed, the decorators should still work without issue.
For more information see http://code.djangoproject.com/ticket/4617.
== Customizing the 403 Error Page ==
Django doesn't provide a simple way to customize 403 error pages, so you'll
have to make a response middleware that handles `HttpResponseForbidden`.
For example, in `views.py`:
from django.http import HttpResponseForbidden
from django.template import RequestContext, loader
def forbidden(request, template_name='403.html'):
"""Default 403 handler"""
t = loader.get_template(template_name)
And in `middleware.py`:
from django.http import HttpResponseForbidden
from yourapp.views import forbidden
"""Catches 403 responses and renders 403.html"""
def process_response(self, request, response):
if isinstance(response, HttpResponseForbidden):
Now add `yourapp.middleware.Custom403Middleware` to your `MIDDLEWARE_CLASSES`
setting and create a template named `403.html`.
== CAS 2.0 support ==
The CAS 2.0 protocol is supported in the same way that 1.0 is; no extensions
or new features from the CAS 2.0 specification are implemented. `elementtree`
is required to use this functionality. (`elementtree` is also included in
Python 2.5's standard library.)
Note: The CAS 3.x server uses the CAS 2.0 protocol. There is no CAS 3.0
protocol, though the CAS 3.x server does allow extensions to the protocol.
== Differences Between Django CAS 1.0 and 2.0 ==
Version 2.0 of `django_cas` breaks compatibility in some small ways, in order
simplify the library. The following settings have been removed:
* `CAS_LOGIN_URL` and `CAS_LOGOUT_URL`: Version 2.0 is capable of
determining these automatically.
* `CAS_POPULATE_USER`: Subclass `CASBackend` instead (see above).
* `CAS_REDIRECT_FIELD_NAME`: Django's own `REDIRECT_FIELD_NAME` is now