#23925: django.contrib.auth.authenticate sets the wrong backend path
------------------------------+--------------------
     Reporter:  sdeprez       |      Owner:  nobody
         Type:  Bug           |     Status:  new
    Component:  contrib.auth  |    Version:  1.7
     Severity:  Normal        |   Keywords:
 Triage Stage:  Unreviewed    |  Has patch:  1
Easy pickings:  0             |      UI/UX:  0
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 The `django.contrib.auth.authenticate` function currently tries to
 authenticate a user by checking each backend in
 `settings.AUTHENTICATION_BACKENDS`, and when it has found one that works,
 it annotates the user by adding a `path` attribute that is the path of the
 backend (as a Python object). However the path is computed based on the
 `__class__` attribute of the backend object, which give the "real" path of
 the object, and NOT based on the path given by
 `settings.AUTHENTICATION_BACKENDS`.

 This is problematic beacause they may differ, and thus the later check `if
 backend_path in settings.AUTHENTICATION_BACKENDS` in
 `django.contrib.auth.get_user` can fail whereas it should not.

 Steps to reproduce the bug :
 - create a custom backend in some module :
 `my_app.my_module_backend.CustomBackend`

 - create another module that imports this module. For instance, it's
 common practice to import it in the `__init__.py` file of the package. So,
 in `my_app/__init__.py` put `from my_app import CustomBackend`.

 - Set `AUTHENTICATION_BACKENDS = my_app.CustomBackend`

 - Run django, create an user and try to login. Everything will go fine (no
 errors), except that you WON'T be logged, because of
 `django.contrib.auth.get_user` that will return an AnonymousUser. This can
 be very painful to track and this can even lead to infinite loops if your
 `LOGIN_REDIRECT_URL` is an url that requires login, because the session
 key will be set but an `AnonymousUser` is returned.

 I attached a patch that fixes that, by setting the actual path used in
 `AUTHENTICATION_BACKENDS` in the user, without any changes to the working
 public API.

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Ticket URL: <https://code.djangoproject.com/ticket/23925>
Django <https://code.djangoproject.com/>
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