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doc/development/api/auth.rst

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+.. highlight:: python
+   :linenothreshold: 5
+
+Pluggable authentication backends
+=================================
+
+Plugins can supply additional authentication backends. This is mainly useful in self-hosted installations
+and allows you to use company-wide login mechanisms such as LDAP or OAuth for accessing pretix' backend.
+
+Every authentication backend contains an implementation of the interface defined in ``pretix.base.auth.BaseAuthBackend``
+(see below). Note that pretix authentication backends work differently than plain Django authentication backends.
+Basically, three pre-defined flows are supported:
+
+* Authentication mechanisms that rely on a **set of input parameters**, e.g. a username and a password. These can be
+  implemented by supplying the ``login_form_fields`` property and a ``form_authenticate`` method.
+
+* Authentication mechanisms that rely on **external sessions**, e.g. a cookie or a proxy HTTP header. These can be
+  implemented by supplying a ``request_authenticate`` method.
+
+* Authentication mechanisms that rely on **redirection**, e.g. to an OAuth provider. These can be implemented by
+  supplying a ``authentication_url`` method and implementing a custom return view.
+
+Authentication backends are *not* collected through a signal. Instead, they must explicitly be set through the
+``auth_backends`` directive in the ``pretix.cfg`` :ref:`configuration file <config>`.
+
+In each of these methods (``form_authenticate``, ``request_authenticate`` or your custom view) you are supposed to
+either get an existing :py:class:`pretix.base.models.User` object from the database or create a new one. There are a
+few rules you need to follow:
+
+* You **MUST** only return users with the ``auth_backend`` attribute set to the ``identifier`` value of your backend.
+
+* You **MUST** create new users with the ``auth_backend`` attribute set to the ``identifier`` value of your backend.
+
+* Every user object **MUST** have an email address. Email addresses are globally unique. If the email address is
+  already registered to a user who signs in through a different backend, you **SHOULD** refuse the login.
+
+The backend interface
+---------------------
+
+.. class:: pretix.base.auth.BaseAuthBackend
+
+   The central object of each backend is the subclass of ``BaseAuthBackend``.
+
+   .. autoattribute:: identifier
+
+      This is an abstract attribute, you **must** override this!
+
+   .. autoattribute:: verbose_name
+
+      This is an abstract attribute, you **must** override this!
+
+   .. autoattribute:: login_form_fields
+
+   .. autoattribute:: visible
+
+   .. automethod:: form_authenticate
+
+   .. automethod:: request_authenticate
+
+   .. automethod:: authentication_url
+
+Logging users in
+----------------
+
+If you return a user from ``form_authenticate`` or ``request_authenticate``, the system will handle everything else
+for you correctly. However, if you use a redirection method and build a custom view to verify the login, we strongly
+recommend that you use the following utility method to correctly set session values and enforce two-factor
+authentication (if activated):
+
+.. autofunction:: pretix.control.views.auth.process_login