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125 lines
5.7 KiB
Text
125 lines
5.7 KiB
Text
====================================
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Authentication using ``REMOTE_USER``
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====================================
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This document describes how to make use of external authentication sources
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(where the Web server sets the ``REMOTE_USER`` environment variable) in your
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Django applications. This type of authentication solution is typically seen on
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intranet sites, with single sign-on solutions such as IIS and Integrated
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Windows Authentication or Apache and `mod_authnz_ldap`_, `CAS`_, `Cosign`_,
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`WebAuth`_, `mod_auth_sspi`_, etc.
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.. _mod_authnz_ldap: https://httpd.apache.org/docs/2.2/mod/mod_authnz_ldap.html
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.. _CAS: https://www.apereo.org/projects/cas
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.. _Cosign: http://weblogin.org
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.. _WebAuth: https://www.stanford.edu/services/webauth/
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.. _mod_auth_sspi: http://sourceforge.net/projects/mod-auth-sspi
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When the Web server takes care of authentication it typically sets the
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``REMOTE_USER`` environment variable for use in the underlying application. In
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Django, ``REMOTE_USER`` is made available in the :attr:`request.META
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<django.http.HttpRequest.META>` attribute. Django can be configured to make
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use of the ``REMOTE_USER`` value using the ``RemoteUserMiddleware``
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or ``PersistentRemoteUserMiddleware``, and
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:class:`~django.contrib.auth.backends.RemoteUserBackend` classes found in
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:mod:`django.contrib.auth`.
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Configuration
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=============
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First, you must add the
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:class:`django.contrib.auth.middleware.RemoteUserMiddleware` to the
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:setting:`MIDDLEWARE` setting **after** the
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:class:`django.contrib.auth.middleware.AuthenticationMiddleware`::
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MIDDLEWARE = [
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'...',
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'django.contrib.auth.middleware.AuthenticationMiddleware',
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'django.contrib.auth.middleware.RemoteUserMiddleware',
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'...',
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]
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Next, you must replace the :class:`~django.contrib.auth.backends.ModelBackend`
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with :class:`~django.contrib.auth.backends.RemoteUserBackend` in the
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:setting:`AUTHENTICATION_BACKENDS` setting::
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AUTHENTICATION_BACKENDS = [
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'django.contrib.auth.backends.RemoteUserBackend',
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]
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With this setup, ``RemoteUserMiddleware`` will detect the username in
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``request.META['REMOTE_USER']`` and will authenticate and auto-login that user
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using the :class:`~django.contrib.auth.backends.RemoteUserBackend`.
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Be aware that this particular setup disables authentication with the default
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``ModelBackend``. This means that if the ``REMOTE_USER`` value is not set
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then the user is unable to log in, even using Django's admin interface.
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Adding ``'django.contrib.auth.backends.ModelBackend'`` to the
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``AUTHENTICATION_BACKENDS`` list will use ``ModelBackend`` as a fallback
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if ``REMOTE_USER`` is absent, which will solve these issues.
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Django's user management, such as the views in ``contrib.admin`` and
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the :djadmin:`createsuperuser` management command, doesn't integrate with
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remote users. These interfaces work with users stored in the database
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regardless of ``AUTHENTICATION_BACKENDS``.
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.. note::
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Since the ``RemoteUserBackend`` inherits from ``ModelBackend``, you will
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still have all of the same permissions checking that is implemented in
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``ModelBackend``.
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Users with :attr:`is_active=False
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<django.contrib.auth.models.User.is_active>` won't be allowed to
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authenticate. Use
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:class:`~django.contrib.auth.backends.AllowAllUsersRemoteUserBackend` if
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you want to allow them to.
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If your authentication mechanism uses a custom HTTP header and not
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``REMOTE_USER``, you can subclass ``RemoteUserMiddleware`` and set the
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``header`` attribute to the desired ``request.META`` key. For example::
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from django.contrib.auth.middleware import RemoteUserMiddleware
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class CustomHeaderMiddleware(RemoteUserMiddleware):
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header = 'HTTP_AUTHUSER'
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.. warning::
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Be very careful if using a ``RemoteUserMiddleware`` subclass with a custom
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HTTP header. You must be sure that your front-end web server always sets or
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strips that header based on the appropriate authentication checks, never
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permitting an end-user to submit a fake (or "spoofed") header value. Since
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the HTTP headers ``X-Auth-User`` and ``X-Auth_User`` (for example) both
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normalize to the ``HTTP_X_AUTH_USER`` key in ``request.META``, you must
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also check that your web server doesn't allow a spoofed header using
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underscores in place of dashes.
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This warning doesn't apply to ``RemoteUserMiddleware`` in its default
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configuration with ``header = 'REMOTE_USER'``, since a key that doesn't
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start with ``HTTP_`` in ``request.META`` can only be set by your WSGI
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server, not directly from an HTTP request header.
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If you need more control, you can create your own authentication backend
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that inherits from :class:`~django.contrib.auth.backends.RemoteUserBackend` and
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override one or more of its attributes and methods.
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.. _persistent-remote-user-middleware-howto:
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Using ``REMOTE_USER`` on login pages only
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=========================================
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The ``RemoteUserMiddleware`` authentication middleware assumes that the HTTP
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request header ``REMOTE_USER`` is present with all authenticated requests. That
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might be expected and practical when Basic HTTP Auth with ``htpasswd`` or other
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simple mechanisms are used, but with Negotiate (GSSAPI/Kerberos) or other
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resource intensive authentication methods, the authentication in the front-end
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HTTP server is usually only set up for one or a few login URLs, and after
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successful authentication, the application is supposed to maintain the
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authenticated session itself.
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:class:`~django.contrib.auth.middleware.PersistentRemoteUserMiddleware`
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provides support for this use case. It will maintain the authenticated session
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until explicit logout by the user. The class can be used as a drop-in
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replacement of :class:`~django.contrib.auth.middleware.RemoteUserMiddleware`
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in the documentation above.
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