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====================================
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: https://httpd.apache.org/docs/2.2/mod/mod_authnz_ldap.html
.. _CAS: https://www.apereo.org/projects/cas
.. _Cosign: http://weblogin.org
.. _WebAuth: https://www.stanford.edu/services/webauth/
.. _mod_auth_sspi: https://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``
or ``PersistentRemoteUserMiddleware``, 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` setting **after** the
:class:`django.contrib.auth.middleware.AuthenticationMiddleware`::
MIDDLEWARE = [
'...',
'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`.
Be aware that this particular setup disables authentication with the default
``ModelBackend``. This means that if the ``REMOTE_USER`` value is not set
then the user is unable to log in, even using Django's admin interface.
Adding ``'django.contrib.auth.backends.ModelBackend'`` to the
``AUTHENTICATION_BACKENDS`` list will use ``ModelBackend`` as a fallback
if ``REMOTE_USER`` is absent, which will solve these issues.
Django's user management, such as the views in ``contrib.admin`` and
the :djadmin:`createsuperuser` management command, doesn't integrate with
remote users. These interfaces work with users stored in the database
regardless of ``AUTHENTICATION_BACKENDS``.
.. note::
Since the ``RemoteUserBackend`` inherits from ``ModelBackend``, you will
still have all of the same permissions checking that is implemented in
``ModelBackend``.
Users with :attr:`is_active=False
<django.contrib.auth.models.User.is_active>` won't be allowed to
authenticate. Use
:class:`~django.contrib.auth.backends.AllowAllUsersRemoteUserBackend` if
you want to allow them to.
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'
.. warning::
Be very careful if using a ``RemoteUserMiddleware`` subclass with a custom
HTTP header. You must be sure that your front-end web server always sets or
strips that header based on the appropriate authentication checks, never
permitting an end-user to submit a fake (or "spoofed") header value. Since
the HTTP headers ``X-Auth-User`` and ``X-Auth_User`` (for example) both
normalize to the ``HTTP_X_AUTH_USER`` key in ``request.META``, you must
also check that your web server doesn't allow a spoofed header using
underscores in place of dashes.
This warning doesn't apply to ``RemoteUserMiddleware`` in its default
configuration with ``header = 'REMOTE_USER'``, since a key that doesn't
start with ``HTTP_`` in ``request.META`` can only be set by your WSGI
server, not directly from an HTTP request header.
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.
.. _persistent-remote-user-middleware-howto:
Using ``REMOTE_USER`` on login pages only
=========================================
The ``RemoteUserMiddleware`` authentication middleware assumes that the HTTP
request header ``REMOTE_USER`` is present with all authenticated requests. That
might be expected and practical when Basic HTTP Auth with ``htpasswd`` or other
simple mechanisms are used, but with Negotiate (GSSAPI/Kerberos) or other
resource intensive authentication methods, the authentication in the front-end
HTTP server is usually only set up for one or a few login URLs, and after
successful authentication, the application is supposed to maintain the
authenticated session itself.
:class:`~django.contrib.auth.middleware.PersistentRemoteUserMiddleware`
provides support for this use case. It will maintain the authenticated session
until explicit logout by the user. The class can be used as a drop-in
replacement of :class:`~django.contrib.auth.middleware.RemoteUserMiddleware`
in the documentation above.
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