How to authenticate 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 or PersistentRemoteUserMiddleware, and RemoteUserBackend classes found in django.contrib.auth.

Configuration

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

MIDDLEWARE = [
    "...",
    "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.

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 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 is_active=False won’t be allowed to authenticate. Use 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 RemoteUserBackend and override one or more of its attributes and methods.

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 similar 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.

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 RemoteUserMiddleware in the documentation above.

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