multi-auth: Implemented new auth api.

git-svn-id: http://code.djangoproject.com/svn/django/branches/multi-auth@2884 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/auth/__init__.py

@@ -1,2 +1,71 @@
+from django.core.exceptions import ImproperlyConfigured
+
+SESSION_KEY = '_auth_user_id'
+BACKEND_SESSION_KEY = '_auth_user_backend'
 LOGIN_URL = '/accounts/login/'
 REDIRECT_FIELD_NAME = 'next'
+
+def load_backend(path):
+    i = path.rfind('.')
+    module, attr = path[:i], path[i+1:]
+    try:
+        mod = __import__(module, '', '', [attr])
+    except ImportError, e:
+        raise ImproperlyConfigured, 'Error importing authentication backend %s: "%s"' % (module, e)
+    try:
+        cls = getattr(mod, attr)
+    except AttributeError:
+        raise ImproperlyConfigured, 'Module "%s" does not define a "%s" authentication backend' % (module, attr)
+    return cls()
+
+def get_backends():
+    from django.conf import settings
+    backends = []
+    for backend_path in settings.AUTHENTICATION_BACKENDS:
+        backends.append(load_backend(backend_path))
+    return backends
+
+def authenticate(**credentials):
+    """
+    If the given credentials, return a user object.
+    """
+    for backend in get_backends():
+        try:
+            user = backend.authenticate(**credentials)
+        except TypeError:
+            # this backend doesn't accept these credentials as arguments, try the next one.
+            continue
+        if user is None:
+            continue
+        # annotate the user object with the path of the backend
+        user.backend = str(backend.__class__)
+        return user
+
+def login(request, user):
+    """
+    Persist a user id and a backend in the request. This way a user doesn't
+    have to reauthenticate on every request.
+    """
+    if user is None:
+        user = request.user
+    # TODO: It would be nice to support different login methods, like signed cookies.
+    request.session[SESSION_KEY] = user.id
+    request.session[BACKEND_SESSION_KEY] = user.backend
+
+def logout(request):
+    """
+    Remove the authenticated user's id from request.
+    """
+    del request.session[SESSION_KEY]
+    del request.session[BACKEND_SESSION_KEY]
+
+def get_user(request):
+    from django.contrib.auth.models import AnonymousUser
+    try:
+        user_id = request.session[SESSION_KEY]
+        backend_path = request.session[BACKEND_SESSION_KEY]
+        backend = load_backend(backend_path)
+        user = backend.get_user(user_id) or AnonymousUser()
+    except KeyError:
+        user = AnonymousUser()
+    return user