1 import datetime

     2 from django.core.exceptions import ImproperlyConfigured

     3 from django.utils.importlib import import_module

     4 

     5 SESSION_KEY = '_auth_user_id'

     6 BACKEND_SESSION_KEY = '_auth_user_backend'

     7 REDIRECT_FIELD_NAME = 'next'

     8 

     9 def load_backend(path):

    10     i = path.rfind('.')

    11     module, attr = path[:i], path[i+1:]

    12     try:

    13         mod = import_module(module)

    14     except ImportError, e:

    15         raise ImproperlyConfigured, 'Error importing authentication backend %s: "%s"' % (module, e)

    16     except ValueError, e:

    17         raise ImproperlyConfigured, 'Error importing authentication backends. Is AUTHENTICATION_BACKENDS a correctly defined list or tuple?'

    18     try:

    19         cls = getattr(mod, attr)

    20     except AttributeError:

    21         raise ImproperlyConfigured, 'Module "%s" does not define a "%s" authentication backend' % (module, attr)

    22     return cls()

    23 

    24 def get_backends():

    25     from django.conf import settings

    26     backends = []

    27     for backend_path in settings.AUTHENTICATION_BACKENDS:

    28         backends.append(load_backend(backend_path))

    29     return backends

    30 

    31 def authenticate(**credentials):

    32     """

    33     If the given credentials are valid, return a User object.

    34     """

    35     for backend in get_backends():

    36         try:

    37             user = backend.authenticate(**credentials)

    38         except TypeError:

    39             # This backend doesn't accept these credentials as arguments. Try the next one.

    40             continue

    41         if user is None:

    42             continue

    43         # Annotate the user object with the path of the backend.

    44         user.backend = "%s.%s" % (backend.__module__, backend.__class__.__name__)

    45         return user

    46 

    47 def login(request, user):

    48     """

    49     Persist a user id and a backend in the request. This way a user doesn't

    50     have to reauthenticate on every request.

    51     """

    52     if user is None:

    53         user = request.user

    54     # TODO: It would be nice to support different login methods, like signed cookies.

    55     user.last_login = datetime.datetime.now()

    56     user.save()

    57 

    58     if SESSION_KEY in request.session:

    59         if request.session[SESSION_KEY] != user.id:

    60             # To avoid reusing another user's session, create a new, empty

    61             # session if the existing session corresponds to a different

    62             # authenticated user.

    63             request.session.flush()

    64     else:

    65         request.session.cycle_key()

    66     request.session[SESSION_KEY] = user.id

    67     request.session[BACKEND_SESSION_KEY] = user.backend

    68     if hasattr(request, 'user'):

    69         request.user = user

    70 

    71 def logout(request):

    72     """

    73     Removes the authenticated user's ID from the request and flushes their

    74     session data.

    75     """

    76     request.session.flush()

    77     if hasattr(request, 'user'):

    78         from django.contrib.auth.models import AnonymousUser

    79         request.user = AnonymousUser()

    80 

    81 def get_user(request):

    82     from django.contrib.auth.models import AnonymousUser

    83     try:

    84         user_id = request.session[SESSION_KEY]

    85         backend_path = request.session[BACKEND_SESSION_KEY]

    86         backend = load_backend(backend_path)

    87         user = backend.get_user(user_id) or AnonymousUser()

    88     except KeyError:

    89         user = AnonymousUser()

    90     return user