====================================
Authentication using ``REMOTE_USER``
====================================

This document describes how to make use of external authentication sources
(where the Web server sets the ``REMOTE_USER`` environment variable) in your
Django applications.  This type of authentication solution is typically seen on
intranet sites, with single sign-on solutions such as IIS and Integrated
Windows Authentication or Apache and `mod_authnz_ldap`_, `CAS`_, `Cosign`_,
`WebAuth`_, `mod_auth_sspi`_, etc.

.. _mod_authnz_ldap: http://httpd.apache.org/docs/2.2/mod/mod_authnz_ldap.html
.. _CAS: http://www.jasig.org/cas
.. _Cosign: http://weblogin.org
.. _WebAuth: http://www.stanford.edu/services/webauth/
.. _mod_auth_sspi: http://sourceforge.net/projects/mod-auth-sspi

When the Web server takes care of authentication it typically sets the
``REMOTE_USER`` environment variable for use in the underlying application.  In
Django, ``REMOTE_USER`` is made available in the :attr:`request.META
<django.http.HttpRequest.META>` attribute.  Django can be configured to make
use of the ``REMOTE_USER`` value using the ``RemoteUserMiddleware`` and
:class:`~django.contrib.auth.backends.RemoteUserBackend` classes found in
:mod:`django.contrib.auth`.

Configuration
=============

First, you must add the
:class:`django.contrib.auth.middleware.RemoteUserMiddleware` to the
:setting:`MIDDLEWARE_CLASSES` setting **after** the
:class:`django.contrib.auth.middleware.AuthenticationMiddleware`::

    MIDDLEWARE_CLASSES = (
        '...',
        'django.contrib.auth.middleware.AuthenticationMiddleware',
        'django.contrib.auth.middleware.RemoteUserMiddleware',
        '...',
    )

Next, you must replace the :class:`~django.contrib.auth.backends.ModelBackend`
with :class:`~django.contrib.auth.backends.RemoteUserBackend` in the
:setting:`AUTHENTICATION_BACKENDS` setting::

    AUTHENTICATION_BACKENDS = (
        'django.contrib.auth.backends.RemoteUserBackend',
    )

With this setup, ``RemoteUserMiddleware`` will detect the username in
``request.META['REMOTE_USER']`` and will authenticate and auto-login that user
using the :class:`~django.contrib.auth.backends.RemoteUserBackend`.

.. note::
   Since the ``RemoteUserBackend`` inherits from ``ModelBackend``, you will
   still have all of the same permissions checking that is implemented in
   ``ModelBackend``.

If your authentication mechanism uses a custom HTTP header and not
``REMOTE_USER``, you can subclass ``RemoteUserMiddleware`` and set the
``header`` attribute to the desired ``request.META`` key.  For example::

    from django.contrib.auth.middleware import RemoteUserMiddleware

    class CustomHeaderMiddleware(RemoteUserMiddleware):
        header = 'HTTP_AUTHUSER'

If you need more control, you can create your own authentication backend
that inherits from :class:`~django.contrib.auth.backends.RemoteUserBackend` and
override one or more of its attributes and methods.