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.

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 request.META attribute. Django can be configured to make use of the REMOTE_USER value using the RemoteUserMiddleware and RemoteUserBackend classes found in django.contrib.auth.

Configuration

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

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

Next, you must replace the ModelBackend with RemoteUserBackend in the 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 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'

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 RemoteUserBackend and override one or more of its attributes and methods.

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