django/docs/topics/auth/default.txt

======================================
Using the Django authentication system
======================================

.. currentmodule:: django.contrib.auth

This document explains the usage of Django's authentication system in its
default configuration. This configuration has evolved to serve the most common
project needs, handling a reasonably wide range of tasks, and has a careful
implementation of passwords and permissions. For projects where authentication
needs differ from the default, Django supports extensive :doc:`extension and
customization </topics/auth/customizing>` of authentication.

Django authentication provides both authentication and authorization together
and is generally referred to as the authentication system, as these features
are somewhat coupled.

.. _user-objects:

``User`` objects
================

:class:`~django.contrib.auth.models.User` objects are the core of the
authentication system. They typically represent the people interacting with
your site and are used to enable things like restricting access, registering
user profiles, associating content with creators etc. Only one class of user
exists in Django's authentication framework, i.e., :attr:`'superusers'
<django.contrib.auth.models.User.is_superuser>` or admin :attr:`'staff'
<django.contrib.auth.models.User.is_staff>` users are just user objects with
special attributes set, not different classes of user objects.

The primary attributes of the default user are:

* :attr:`~django.contrib.auth.models.User.username`
* :attr:`~django.contrib.auth.models.User.password`
* :attr:`~django.contrib.auth.models.User.email`
* :attr:`~django.contrib.auth.models.User.first_name`
* :attr:`~django.contrib.auth.models.User.last_name`

See the :class:`full API documentation <django.contrib.auth.models.User>` for
full reference, the documentation that follows is more task oriented.

.. _topics-auth-creating-users:

Creating users
--------------

The most direct way to create users is to use the included
:meth:`~django.contrib.auth.models.UserManager.create_user` helper function::

    >>> from django.contrib.auth.models import User
    >>> user = User.objects.create_user('john', 'lennon@thebeatles.com', 'johnpassword')

    # At this point, user is a User object that has already been saved
    # to the database. You can continue to change its attributes
    # if you want to change other fields.
    >>> user.last_name = 'Lennon'
    >>> user.save()

If you have the Django admin installed, you can also :ref:`create users
interactively <auth-admin>`.

.. _topics-auth-creating-superusers:

Creating superusers
-------------------

Create superusers using the :djadmin:`createsuperuser` command::

    $ python manage.py createsuperuser --username=joe --email=joe@example.com

You will be prompted for a password. After you enter one, the user will be
created immediately. If you leave off the :option:`--username <createsuperuser
--username>` or :option:`--email <createsuperuser --email>` options, it will
prompt you for those values.

Changing passwords
------------------

Django does not store raw (clear text) passwords on the user model, but only
a hash (see :doc:`documentation of how passwords are managed
</topics/auth/passwords>` for full details). Because of this, do not attempt to
manipulate the password attribute of the user directly. This is why a helper
function is used when creating a user.

To change a user's password, you have several options:

:djadmin:`manage.py changepassword *username* <changepassword>` offers a method
of changing a user's password from the command line. It prompts you to
change the password of a given user which you must enter twice. If
they both match, the new password will be changed immediately. If you
do not supply a user, the command will attempt to change the password
whose username matches the current system user.

You can also change a password programmatically, using
:meth:`~django.contrib.auth.models.User.set_password()`:

.. code-block:: pycon

    >>> from django.contrib.auth.models import User
    >>> u = User.objects.get(username='john')
    >>> u.set_password('new password')
    >>> u.save()

If you have the Django admin installed, you can also change user's passwords
on the :ref:`authentication system's admin pages <auth-admin>`.

Django also provides :ref:`views <built-in-auth-views>` and :ref:`forms
<built-in-auth-forms>` that may be used to allow users to change their own
passwords.

Changing a user's password will log out all their sessions. See
:ref:`session-invalidation-on-password-change` for details.

Authenticating users
--------------------

.. function:: authenticate(request=None, **credentials)

    Use :func:`~django.contrib.auth.authenticate()` to verify a set of
    credentials. It takes credentials as keyword arguments, ``username`` and
    ``password`` for the default case, checks them against each
    :ref:`authentication backend <authentication-backends>`, and returns a
    :class:`~django.contrib.auth.models.User` object if the credentials are
    valid for a backend. If the credentials aren't valid for any backend or if
    a backend raises :class:`~django.core.exceptions.PermissionDenied`, it
    returns ``None``. For example::

        from django.contrib.auth import authenticate
        user = authenticate(username='john', password='secret')
        if user is not None:
            # A backend authenticated the credentials
        else:
            # No backend authenticated the credentials

    ``request`` is an optional :class:`~django.http.HttpRequest` which is
    passed on the ``authenticate()`` method of the authentication backends.

    .. note::

        This is a low level way to authenticate a set of credentials; for
        example, it's used by the
        :class:`~django.contrib.auth.middleware.RemoteUserMiddleware`. Unless
        you are writing your own authentication system, you probably won't use
        this. Rather if you're looking for a way to login a user, use the
        :class:`~django.contrib.auth.views.LoginView`.

.. _topic-authorization:

Permissions and Authorization
=============================

Django comes with a built-in permissions system. It provides a way to assign
permissions to specific users and groups of users.

It's used by the Django admin site, but you're welcome to use it in your own
code.

The Django admin site uses permissions as follows:

* Access to view objects is limited to users with the "view" or "change"
  permission for that type of object.
* Access to view the "add" form and add an object is limited to users with
  the "add" permission for that type of object.
* Access to view the change list, view the "change" form and change an
  object is limited to users with the "change" permission for that type of
  object.
* Access to delete an object is limited to users with the "delete"
  permission for that type of object.

Permissions can be set not only per type of object, but also per specific
object instance. By using the
:meth:`~django.contrib.admin.ModelAdmin.has_view_permission`,
:meth:`~django.contrib.admin.ModelAdmin.has_add_permission`,
:meth:`~django.contrib.admin.ModelAdmin.has_change_permission` and
:meth:`~django.contrib.admin.ModelAdmin.has_delete_permission` methods provided
by the :class:`~django.contrib.admin.ModelAdmin` class, it is possible to
customize permissions for different object instances of the same type.

:class:`~django.contrib.auth.models.User` objects have two many-to-many
fields: ``groups`` and ``user_permissions``.
:class:`~django.contrib.auth.models.User` objects can access their related
objects in the same way as any other :doc:`Django model
</topics/db/models>`::

    myuser.groups.set([group_list])
    myuser.groups.add(group, group, ...)
    myuser.groups.remove(group, group, ...)
    myuser.groups.clear()
    myuser.user_permissions.set([permission_list])
    myuser.user_permissions.add(permission, permission, ...)
    myuser.user_permissions.remove(permission, permission, ...)
    myuser.user_permissions.clear()

Default permissions
-------------------

When ``django.contrib.auth`` is listed in your :setting:`INSTALLED_APPS`
setting, it will ensure that four default permissions -- add, change, delete,
and view -- are created for each Django model defined in one of your installed
applications.

These permissions will be created when you run :djadmin:`manage.py migrate
<migrate>`; the first time you run ``migrate`` after adding
``django.contrib.auth`` to :setting:`INSTALLED_APPS`, the default permissions
will be created for all previously-installed models, as well as for any new
models being installed at that time. Afterward, it will create default
permissions for new models each time you run :djadmin:`manage.py migrate
<migrate>` (the function that creates permissions is connected to the
:data:`~django.db.models.signals.post_migrate` signal).

Assuming you have an application with an
:attr:`~django.db.models.Options.app_label` ``foo`` and a model named ``Bar``,
to test for basic permissions you should use:

* add: ``user.has_perm('foo.add_bar')``
* change: ``user.has_perm('foo.change_bar')``
* delete: ``user.has_perm('foo.delete_bar')``
* view: ``user.has_perm('foo.view_bar')``

The :class:`~django.contrib.auth.models.Permission` model is rarely accessed
directly.

Groups
------

:class:`django.contrib.auth.models.Group` models are a generic way of
categorizing users so you can apply permissions, or some other label, to those
users. A user can belong to any number of groups.

A user in a group automatically has the permissions granted to that group. For
example, if the group ``Site editors`` has the permission
``can_edit_home_page``, any user in that group will have that permission.

Beyond permissions, groups are a convenient way to categorize users to give
them some label, or extended functionality. For example, you could create a
group ``'Special users'``, and you could write code that could, say, give them
access to a members-only portion of your site, or send them members-only email
messages.

Programmatically creating permissions
-------------------------------------

While :ref:`custom permissions <custom-permissions>` can be defined within
a model's ``Meta`` class, you can also create permissions directly. For
example, you can create the ``can_publish`` permission for a ``BlogPost`` model
in ``myapp``::

    from myapp.models import BlogPost
    from django.contrib.auth.models import Permission
    from django.contrib.contenttypes.models import ContentType

    content_type = ContentType.objects.get_for_model(BlogPost)
    permission = Permission.objects.create(
        codename='can_publish',
        name='Can Publish Posts',
        content_type=content_type,
    )

The permission can then be assigned to a
:class:`~django.contrib.auth.models.User` via its ``user_permissions``
attribute or to a :class:`~django.contrib.auth.models.Group` via its
``permissions`` attribute.

.. admonition:: Proxy models need their own content type

    If you want to create :ref:`permissions for a proxy model
    <proxy-models-permissions-topic>`, pass ``for_concrete_model=False`` to
    :meth:`.ContentTypeManager.get_for_model` to get the appropriate
    ``ContentType``::

        content_type = ContentType.objects.get_for_model(BlogPostProxy, for_concrete_model=False)

Permission caching
------------------

The :class:`~django.contrib.auth.backends.ModelBackend` caches permissions on
the user object after the first time they need to be fetched for a permissions
check. This is typically fine for the request-response cycle since permissions
aren't typically checked immediately after they are added (in the admin, for
example). If you are adding permissions and checking them immediately
afterward, in a test or view for example, the easiest solution is to re-fetch
the user from the database. For example::

    from django.contrib.auth.models import Permission, User
    from django.contrib.contenttypes.models import ContentType
    from django.shortcuts import get_object_or_404

    from myapp.models import BlogPost

    def user_gains_perms(request, user_id):
        user = get_object_or_404(User, pk=user_id)
        # any permission check will cache the current set of permissions
        user.has_perm('myapp.change_blogpost')

        content_type = ContentType.objects.get_for_model(BlogPost)
        permission = Permission.objects.get(
            codename='change_blogpost',
            content_type=content_type,
        )
        user.user_permissions.add(permission)

        # Checking the cached permission set
        user.has_perm('myapp.change_blogpost')  # False

        # Request new instance of User
        # Be aware that user.refresh_from_db() won't clear the cache.
        user = get_object_or_404(User, pk=user_id)

        # Permission cache is repopulated from the database
        user.has_perm('myapp.change_blogpost')  # True

        ...

.. _proxy-models-permissions-topic:

Proxy models
------------

Proxy models work exactly the same way as concrete models. Permissions are
created using the own content type of the proxy model. Proxy models don't
inherit the permissions of the concrete model they subclass::

    class Person(models.Model):
        class Meta:
            permissions = [('can_eat_pizzas', 'Can eat pizzas')]

    class Student(Person):
        class Meta:
            proxy = True
            permissions = [('can_deliver_pizzas', 'Can deliver pizzas')]

    >>> # Fetch the content type for the proxy model.
    >>> content_type = ContentType.objects.get_for_model(Student, for_concrete_model=False)
    >>> student_permissions = Permission.objects.filter(content_type=content_type)
    >>> [p.codename for p in student_permissions]
    ['add_student', 'change_student', 'delete_student', 'view_student',
    'can_deliver_pizzas']
    >>> for permission in student_permissions:
    ...     user.user_permissions.add(permission)
    >>> user.has_perm('app.add_person')
    False
    >>> user.has_perm('app.can_eat_pizzas')
    False
    >>> user.has_perms(('app.add_student', 'app.can_deliver_pizzas'))
    True

.. _auth-web-requests:

Authentication in Web requests
==============================

Django uses :doc:`sessions </topics/http/sessions>` and middleware to hook the
authentication system into :class:`request objects <django.http.HttpRequest>`.

These provide a :attr:`request.user <django.http.HttpRequest.user>`  attribute
on every request which represents the current user. If the current user has not
logged in, this attribute will be set to an instance
of :class:`~django.contrib.auth.models.AnonymousUser`, otherwise it will be an
instance of :class:`~django.contrib.auth.models.User`.

You can tell them apart with
:attr:`~django.contrib.auth.models.User.is_authenticated`, like so::

    if request.user.is_authenticated:
        # Do something for authenticated users.
        ...
    else:
        # Do something for anonymous users.
        ...

.. _how-to-log-a-user-in:

How to log a user in
--------------------

If you have an authenticated user you want to attach to the current session
- this is done with a :func:`~django.contrib.auth.login` function.

.. function:: login(request, user, backend=None)

    To log a user in, from a view, use :func:`~django.contrib.auth.login()`. It
    takes an :class:`~django.http.HttpRequest` object and a
    :class:`~django.contrib.auth.models.User` object.
    :func:`~django.contrib.auth.login()` saves the user's ID in the session,
    using Django's session framework.

    Note that any data set during the anonymous session is retained in the
    session after a user logs in.

    This example shows how you might use both
    :func:`~django.contrib.auth.authenticate()` and
    :func:`~django.contrib.auth.login()`::

        from django.contrib.auth import authenticate, login

        def my_view(request):
            username = request.POST['username']
            password = request.POST['password']
            user = authenticate(request, username=username, password=password)
            if user is not None:
                login(request, user)
                # Redirect to a success page.
                ...
            else:
                # Return an 'invalid login' error message.
                ...

Selecting the authentication backend
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When a user logs in, the user's ID and the backend that was used for
authentication are saved in the user's session. This allows the same
:ref:`authentication backend <authentication-backends>` to fetch the user's
details on a future request. The authentication backend to save in the session
is selected as follows:

#. Use the value of the optional ``backend`` argument, if provided.
#. Use the value of the ``user.backend`` attribute, if present. This allows
   pairing :func:`~django.contrib.auth.authenticate()` and
   :func:`~django.contrib.auth.login()`:
   :func:`~django.contrib.auth.authenticate()`
   sets the ``user.backend`` attribute on the user object it returns.
#. Use the ``backend`` in :setting:`AUTHENTICATION_BACKENDS`, if there is only
   one.
#. Otherwise, raise an exception.

In cases 1 and 2, the value of the ``backend`` argument or the ``user.backend``
attribute should be a dotted import path string (like that found in
:setting:`AUTHENTICATION_BACKENDS`), not the actual backend class.

How to log a user out
---------------------

.. function:: logout(request)

    To log out a user who has been logged in via
    :func:`django.contrib.auth.login()`, use
    :func:`django.contrib.auth.logout()` within your view. It takes an
    :class:`~django.http.HttpRequest` object and has no return value.
    Example::

        from django.contrib.auth import logout

        def logout_view(request):
            logout(request)
            # Redirect to a success page.

    Note that :func:`~django.contrib.auth.logout()` doesn't throw any errors if
    the user wasn't logged in.

    When you call :func:`~django.contrib.auth.logout()`, the session data for
    the current request is completely cleaned out. All existing data is
    removed. This is to prevent another person from using the same Web browser
    to log in and have access to the previous user's session data. If you want
    to put anything into the session that will be available to the user
    immediately after logging out, do that *after* calling
    :func:`django.contrib.auth.logout()`.

Limiting access to logged-in users
----------------------------------

The raw way
~~~~~~~~~~~

The raw way to limit access to pages is to check
:attr:`request.user.is_authenticated
<django.contrib.auth.models.User.is_authenticated>` and either redirect to a
login page::

    from django.conf import settings
    from django.shortcuts import redirect

    def my_view(request):
        if not request.user.is_authenticated:
            return redirect('%s?next=%s' % (settings.LOGIN_URL, request.path))
        # ...

...or display an error message::

    from django.shortcuts import render

    def my_view(request):
        if not request.user.is_authenticated:
            return render(request, 'myapp/login_error.html')
        # ...

.. currentmodule:: django.contrib.auth.decorators

The ``login_required`` decorator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. function:: login_required(redirect_field_name='next', login_url=None)

    As a shortcut, you can use the convenient
    :func:`~django.contrib.auth.decorators.login_required` decorator::

        from django.contrib.auth.decorators import login_required

        @login_required
        def my_view(request):
            ...

    :func:`~django.contrib.auth.decorators.login_required` does the following:

    * If the user isn't logged in, redirect to
      :setting:`settings.LOGIN_URL <LOGIN_URL>`, passing the current absolute
      path in the query string. Example: ``/accounts/login/?next=/polls/3/``.

    * If the user is logged in, execute the view normally. The view code is
      free to assume the user is logged in.

    By default, the path that the user should be redirected to upon
    successful authentication is stored in a query string parameter called
    ``"next"``. If you would prefer to use a different name for this parameter,
    :func:`~django.contrib.auth.decorators.login_required` takes an
    optional ``redirect_field_name`` parameter::

        from django.contrib.auth.decorators import login_required

        @login_required(redirect_field_name='my_redirect_field')
        def my_view(request):
            ...

    Note that if you provide a value to ``redirect_field_name``, you will most
    likely need to customize your login template as well, since the template
    context variable which stores the redirect path will use the value of
    ``redirect_field_name`` as its key rather than ``"next"`` (the default).

    :func:`~django.contrib.auth.decorators.login_required` also takes an
    optional ``login_url`` parameter. Example::

        from django.contrib.auth.decorators import login_required

        @login_required(login_url='/accounts/login/')
        def my_view(request):
            ...

    Note that if you don't specify the ``login_url`` parameter, you'll need to
    ensure that the :setting:`settings.LOGIN_URL <LOGIN_URL>` and your login
    view are properly associated. For example, using the defaults, add the
    following lines to your URLconf::

        from django.contrib.auth import views as auth_views

        path('accounts/login/', auth_views.LoginView.as_view()),

    The :setting:`settings.LOGIN_URL <LOGIN_URL>` also accepts view function
    names and :ref:`named URL patterns <naming-url-patterns>`. This allows you
    to freely remap your login view within your URLconf without having to
    update the setting.

.. note::

    The ``login_required`` decorator does NOT check the ``is_active`` flag on a
    user, but the default :setting:`AUTHENTICATION_BACKENDS` reject inactive
    users.

.. seealso::

    If you are writing custom views for Django's admin (or need the same
    authorization check that the built-in views use), you may find the
    :func:`django.contrib.admin.views.decorators.staff_member_required`
    decorator a useful alternative to ``login_required()``.

.. currentmodule:: django.contrib.auth.mixins

The ``LoginRequired`` mixin
~~~~~~~~~~~~~~~~~~~~~~~~~~~

When using :doc:`class-based views </topics/class-based-views/index>`, you can
achieve the same behavior as with ``login_required`` by using the
``LoginRequiredMixin``. This mixin should be at the leftmost position in the
inheritance list.

.. class:: LoginRequiredMixin

    If a view is using this mixin, all requests by non-authenticated users will
    be redirected to the login page or shown an HTTP 403 Forbidden error,
    depending on the
    :attr:`~django.contrib.auth.mixins.AccessMixin.raise_exception` parameter.

    You can set any of the parameters of
    :class:`~django.contrib.auth.mixins.AccessMixin` to customize the handling
    of unauthorized users::


        from django.contrib.auth.mixins import LoginRequiredMixin

        class MyView(LoginRequiredMixin, View):
            login_url = '/login/'
            redirect_field_name = 'redirect_to'

.. note::

    Just as the ``login_required`` decorator, this mixin does NOT check the
    ``is_active`` flag on a user, but the default
    :setting:`AUTHENTICATION_BACKENDS` reject inactive users.

.. currentmodule:: django.contrib.auth.decorators

Limiting access to logged-in users that pass a test
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To limit access based on certain permissions or some other test, you'd do
essentially the same thing as described in the previous section.

You can run your test on :attr:`request.user <django.http.HttpRequest.user>` in
the view directly. For example, this view checks to make sure the user has an
email in the desired domain and if not, redirects to the login page::

    from django.shortcuts import redirect

    def my_view(request):
        if not request.user.email.endswith('@example.com'):
            return redirect('/login/?next=%s' % request.path)
        # ...

.. function:: user_passes_test(test_func, login_url=None, redirect_field_name='next')

    As a shortcut, you can use the convenient ``user_passes_test`` decorator
    which performs a redirect when the callable returns ``False``::

        from django.contrib.auth.decorators import user_passes_test

        def email_check(user):
            return user.email.endswith('@example.com')

        @user_passes_test(email_check)
        def my_view(request):
            ...

    :func:`~django.contrib.auth.decorators.user_passes_test` takes a required
    argument: a callable that takes a
    :class:`~django.contrib.auth.models.User` object and returns ``True`` if
    the user is allowed to view the page. Note that
    :func:`~django.contrib.auth.decorators.user_passes_test` does not
    automatically check that the :class:`~django.contrib.auth.models.User` is
    not anonymous.

    :func:`~django.contrib.auth.decorators.user_passes_test` takes two
    optional arguments:

    ``login_url``
       Lets you specify the URL that users who don't pass the test will be
       redirected to. It may be a login page and defaults to
       :setting:`settings.LOGIN_URL <LOGIN_URL>` if you don't specify one.

    ``redirect_field_name``
       Same as for :func:`~django.contrib.auth.decorators.login_required`.
       Setting it to ``None`` removes it from the URL, which you may want to do
       if you are redirecting users that don't pass the test to a non-login
       page where there's no "next page".

    For example::

        @user_passes_test(email_check, login_url='/login/')
        def my_view(request):
            ...

.. currentmodule:: django.contrib.auth.mixins

.. class:: UserPassesTestMixin

    When using :doc:`class-based views </topics/class-based-views/index>`, you
    can use the ``UserPassesTestMixin`` to do this.

    .. method:: test_func()

        You have to override the ``test_func()`` method of the class to
        provide the test that is performed. Furthermore, you can set any of the
        parameters of :class:`~django.contrib.auth.mixins.AccessMixin` to
        customize the handling of unauthorized users::

            from django.contrib.auth.mixins import UserPassesTestMixin

            class MyView(UserPassesTestMixin, View):

                def test_func(self):
                    return self.request.user.email.endswith('@example.com')

    .. method:: get_test_func()

        You can also override the ``get_test_func()`` method to have the mixin
        use a differently named function for its checks (instead of
        :meth:`test_func`).

    .. admonition:: Stacking ``UserPassesTestMixin``

        Due to the way ``UserPassesTestMixin`` is implemented, you cannot stack
        them in your inheritance list. The following does NOT work::

            class TestMixin1(UserPassesTestMixin):
                def test_func(self):
                    return self.request.user.email.endswith('@example.com')

            class TestMixin2(UserPassesTestMixin):
                def test_func(self):
                    return self.request.user.username.startswith('django')

            class MyView(TestMixin1, TestMixin2, View):
                ...

        If ``TestMixin1`` would call ``super()`` and take that result into
        account, ``TestMixin1`` wouldn't work standalone anymore.

.. currentmodule:: django.contrib.auth.decorators

The ``permission_required`` decorator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. function:: permission_required(perm, login_url=None, raise_exception=False)

    It's a relatively common task to check whether a user has a particular
    permission. For that reason, Django provides a shortcut for that case: the
    :func:`~django.contrib.auth.decorators.permission_required()` decorator.::

        from django.contrib.auth.decorators import permission_required

        @permission_required('polls.add_choice')
        def my_view(request):
            ...

    Just like the :meth:`~django.contrib.auth.models.User.has_perm` method,
    permission names take the form ``"<app label>.<permission codename>"``
    (i.e. ``polls.add_choice`` for a permission on a model in the ``polls``
    application).

    The decorator may also take an iterable of permissions, in which case the
    user must have all of the permissions in order to access the view.

    Note that :func:`~django.contrib.auth.decorators.permission_required()`
    also takes an optional ``login_url`` parameter::

        from django.contrib.auth.decorators import permission_required

        @permission_required('polls.add_choice', login_url='/loginpage/')
        def my_view(request):
            ...

    As in the :func:`~django.contrib.auth.decorators.login_required` decorator,
    ``login_url`` defaults to :setting:`settings.LOGIN_URL <LOGIN_URL>`.

    If the ``raise_exception`` parameter is given, the decorator will raise
    :exc:`~django.core.exceptions.PermissionDenied`, prompting :ref:`the 403
    (HTTP Forbidden) view<http_forbidden_view>` instead of redirecting to the
    login page.

    If you want to use ``raise_exception`` but also give your users a chance to
    login first, you can add the
    :func:`~django.contrib.auth.decorators.login_required` decorator::

        from django.contrib.auth.decorators import login_required, permission_required

        @login_required
        @permission_required('polls.add_choice', raise_exception=True)
        def my_view(request):
            ...

    This also avoids a redirect loop when :class:`.LoginView`'s
    ``redirect_authenticated_user=True`` and the logged-in user doesn't have
    all of the required permissions.

.. currentmodule:: django.contrib.auth.mixins

The ``PermissionRequiredMixin`` mixin
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To apply permission checks to :doc:`class-based views
</ref/class-based-views/index>`, you can use the ``PermissionRequiredMixin``:

.. class:: PermissionRequiredMixin

    This mixin, just like the ``permission_required``
    decorator, checks whether the user accessing a view has all given
    permissions. You should specify the permission (or an iterable of
    permissions) using the ``permission_required`` parameter::

        from django.contrib.auth.mixins import PermissionRequiredMixin

        class MyView(PermissionRequiredMixin, View):
            permission_required = 'polls.add_choice'
            # Or multiple of permissions:
            permission_required = ('polls.view_choice', 'polls.change_choice')

    You can set any of the parameters of
    :class:`~django.contrib.auth.mixins.AccessMixin` to customize the handling
    of unauthorized users.

    You may also override these methods:

    .. method:: get_permission_required()

        Returns an iterable of permission names used by the mixin. Defaults to
        the ``permission_required`` attribute, converted to a tuple if
        necessary.

    .. method:: has_permission()

        Returns a boolean denoting whether the current user has permission to
        execute the decorated view. By default, this returns the result of
        calling :meth:`~django.contrib.auth.models.User.has_perms()` with the
        list of permissions returned by :meth:`get_permission_required()`.

Redirecting unauthorized requests in class-based views
------------------------------------------------------

To ease the handling of access restrictions in :doc:`class-based views
</ref/class-based-views/index>`, the ``AccessMixin`` can be used to configure
the behavior of a view when access is denied. Authenticated users are denied
access with an HTTP 403 Forbidden response. Anonymous users are redirected to
the login page or shown an HTTP 403 Forbidden response, depending on the
:attr:`~django.contrib.auth.mixins.AccessMixin.raise_exception` attribute.

.. class:: AccessMixin

    .. attribute:: login_url

        Default return value for :meth:`get_login_url`.  Defaults to ``None``
        in which case :meth:`get_login_url` falls back to
        :setting:`settings.LOGIN_URL <LOGIN_URL>`.

    .. attribute:: permission_denied_message

        Default return value for :meth:`get_permission_denied_message`.
        Defaults to an empty string.

    .. attribute:: redirect_field_name

        Default return value for :meth:`get_redirect_field_name`. Defaults to
        ``"next"``.

    .. attribute:: raise_exception

        If this attribute is set to ``True``, a
        :class:`~django.core.exceptions.PermissionDenied` exception is raised
        when the conditions are not met.  When ``False`` (the default),
        anonymous users are redirected to the login page.

    .. method:: get_login_url()

         Returns the URL that users who don't pass the test will be redirected
         to. Returns :attr:`login_url` if set, or :setting:`settings.LOGIN_URL
         <LOGIN_URL>` otherwise.

    .. method:: get_permission_denied_message()

        When :attr:`raise_exception` is ``True``, this method can be used to
        control the error message passed to the error handler for display to
        the user. Returns the :attr:`permission_denied_message` attribute by
        default.

    .. method:: get_redirect_field_name()

        Returns the name of the query parameter that will contain the URL the
        user should be redirected to after a successful login. If you set this
        to ``None``, a query parameter won't be added. Returns the
        :attr:`redirect_field_name` attribute by default.

    .. method:: handle_no_permission()

        Depending on the value of ``raise_exception``, the method either raises
        a :exc:`~django.core.exceptions.PermissionDenied` exception or
        redirects the user to the ``login_url``, optionally including the
        ``redirect_field_name`` if it is set.

.. currentmodule:: django.contrib.auth

.. _session-invalidation-on-password-change:

Session invalidation on password change
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If your :setting:`AUTH_USER_MODEL` inherits from
:class:`~django.contrib.auth.models.AbstractBaseUser` or implements its own
:meth:`~django.contrib.auth.models.AbstractBaseUser.get_session_auth_hash()`
method, authenticated sessions will include the hash returned by this function.
In the :class:`~django.contrib.auth.models.AbstractBaseUser` case, this is an
HMAC of the password field. Django verifies that the hash in the session for
each request matches the one that's computed during the request. This allows a
user to log out all of their sessions by changing their password.

The default password change views included with Django,
:class:`~django.contrib.auth.views.PasswordChangeView` and the
``user_change_password`` view in the :mod:`django.contrib.auth` admin, update
the session with the new password hash so that a user changing their own
password won't log themselves out. If you have a custom password change view
and wish to have similar behavior, use the :func:`update_session_auth_hash`
function.

.. function:: update_session_auth_hash(request, user)

    This function takes the current request and the updated user object from
    which the new session hash will be derived and updates the session hash
    appropriately. It also rotates the session key so that a stolen session
    cookie will be invalidated.

    Example usage::

        from django.contrib.auth import update_session_auth_hash

        def password_change(request):
            if request.method == 'POST':
                form = PasswordChangeForm(user=request.user, data=request.POST)
                if form.is_valid():
                    form.save()
                    update_session_auth_hash(request, form.user)
            else:
                ...

.. note::

    Since
    :meth:`~django.contrib.auth.models.AbstractBaseUser.get_session_auth_hash()`
    is based on :setting:`SECRET_KEY`, updating your site to use a new secret
    will invalidate all existing sessions.

.. _built-in-auth-views:

Authentication Views
--------------------

.. module:: django.contrib.auth.views

Django provides several views that you can use for handling login, logout, and
password management. These make use of the :ref:`stock auth forms
<built-in-auth-forms>` but you can pass in your own forms as well.

Django provides no default template for the authentication views. You should
create your own templates for the views you want to use. The template context
is documented in each view, see :ref:`all-authentication-views`.

.. _using-the-views:

Using the views
~~~~~~~~~~~~~~~

There are different methods to implement these views in your project. The
easiest way is to include the provided URLconf in ``django.contrib.auth.urls``
in your own URLconf, for example::

    urlpatterns = [
        path('accounts/', include('django.contrib.auth.urls')),
    ]

This will include the following URL patterns::

    accounts/login/ [name='login']
    accounts/logout/ [name='logout']
    accounts/password_change/ [name='password_change']
    accounts/password_change/done/ [name='password_change_done']
    accounts/password_reset/ [name='password_reset']
    accounts/password_reset/done/ [name='password_reset_done']
    accounts/reset/<uidb64>/<token>/ [name='password_reset_confirm']
    accounts/reset/done/ [name='password_reset_complete']

The views provide a URL name for easier reference. See :doc:`the URL
documentation </topics/http/urls>` for details on using named URL patterns.

If you want more control over your URLs, you can reference a specific view in
your URLconf::

    from django.contrib.auth import views as auth_views

    urlpatterns = [
        path('change-password/', auth_views.PasswordChangeView.as_view()),
    ]

The views have optional arguments you can use to alter the behavior of the
view. For example, if you want to change the template name a view uses, you can
provide the ``template_name`` argument. A way to do this is to provide keyword
arguments in the URLconf, these will be passed on to the view. For example::

    urlpatterns = [
        path(
            'change-password/',
            auth_views.PasswordChangeView.as_view(template_name='change-password.html'),
        ),
    ]

All views are :doc:`class-based </topics/class-based-views/index>`, which allows
you to easily customize them by subclassing.

.. _all-authentication-views:

All authentication views
~~~~~~~~~~~~~~~~~~~~~~~~

This is a list with all the views ``django.contrib.auth`` provides. For
implementation details see :ref:`using-the-views`.

.. class:: LoginView

    **URL name:** ``login``

    See :doc:`the URL documentation </topics/http/urls>` for details on using
    named URL patterns.

    **Attributes:**

    .. attribute:: template_name

        The name of a template to display for the view used to log the user in.
        Defaults to :file:`registration/login.html`.

    .. attribute:: redirect_field_name

        The name of a ``GET`` field containing the URL to redirect to after
        login. Defaults to ``next``.

    .. attribute:: authentication_form

        A callable (typically a form class) to use for authentication. Defaults
        to :class:`~django.contrib.auth.forms.AuthenticationForm`.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

    .. attribute:: redirect_authenticated_user

        A boolean that controls whether or not authenticated users accessing
        the login page will be redirected as if they had just successfully
        logged in. Defaults to ``False``.

        .. warning::

            If you enable ``redirect_authenticated_user``, other websites will
            be able to determine if their visitors are authenticated on your
            site by requesting redirect URLs to image files on your website. To
            avoid this "`social media fingerprinting
            <https://robinlinus.github.io/socialmedia-leak/>`_" information
            leakage, host all images and your favicon on a separate domain.

            Enabling ``redirect_authenticated_user`` can also result in a
            redirect loop when using the :func:`.permission_required` decorator
            unless the ``raise_exception`` parameter is used.

    .. attribute:: success_url_allowed_hosts

        A :class:`set` of hosts, in addition to :meth:`request.get_host()
        <django.http.HttpRequest.get_host>`, that are safe for redirecting
        after login. Defaults to an empty :class:`set`.

    Here's what ``LoginView`` does:

    * If called via ``GET``, it displays a login form that POSTs to the
      same URL. More on this in a bit.

    * If called via ``POST`` with user submitted credentials, it tries to log
      the user in. If login is successful, the view redirects to the URL
      specified in ``next``. If ``next`` isn't provided, it redirects to
      :setting:`settings.LOGIN_REDIRECT_URL <LOGIN_REDIRECT_URL>` (which
      defaults to ``/accounts/profile/``). If login isn't successful, it
      redisplays the login form.

    It's your responsibility to provide the html for the login template
    , called ``registration/login.html`` by default. This template gets passed
    four template context variables:

    * ``form``: A :class:`~django.forms.Form` object representing the
      :class:`~django.contrib.auth.forms.AuthenticationForm`.

    * ``next``: The URL to redirect to after successful login. This may
      contain a query string, too.

    * ``site``: The current :class:`~django.contrib.sites.models.Site`,
      according to the :setting:`SITE_ID` setting. If you don't have the
      site framework installed, this will be set to an instance of
      :class:`~django.contrib.sites.requests.RequestSite`, which derives the
      site name and domain from the current
      :class:`~django.http.HttpRequest`.

    * ``site_name``: An alias for ``site.name``. If you don't have the site
      framework installed, this will be set to the value of
      :attr:`request.META['SERVER_NAME'] <django.http.HttpRequest.META>`.
      For more on sites, see :doc:`/ref/contrib/sites`.

    If you'd prefer not to call the template :file:`registration/login.html`,
    you can pass the ``template_name`` parameter via the extra arguments to
    the ``as_view`` method in your URLconf. For example, this URLconf line would
    use :file:`myapp/login.html` instead::

        path('accounts/login/', auth_views.LoginView.as_view(template_name='myapp/login.html')),

    You can also specify the name of the ``GET`` field which contains the URL
    to redirect to after login using ``redirect_field_name``. By default, the
    field is called ``next``.

    Here's a sample :file:`registration/login.html` template you can use as a
    starting point. It assumes you have a :file:`base.html` template that
    defines a ``content`` block:

    .. code-block:: html+django

        {% extends "base.html" %}

        {% block content %}

        {% if form.errors %}
        <p>Your username and password didn't match. Please try again.</p>
        {% endif %}

        {% if next %}
            {% if user.is_authenticated %}
            <p>Your account doesn't have access to this page. To proceed,
            please login with an account that has access.</p>
            {% else %}
            <p>Please login to see this page.</p>
            {% endif %}
        {% endif %}

        <form method="post" action="{% url 'login' %}">
        {% csrf_token %}
        <table>
        <tr>
            <td>{{ form.username.label_tag }}</td>
            <td>{{ form.username }}</td>
        </tr>
        <tr>
            <td>{{ form.password.label_tag }}</td>
            <td>{{ form.password }}</td>
        </tr>
        </table>

        <input type="submit" value="login">
        <input type="hidden" name="next" value="{{ next }}">
        </form>

        {# Assumes you setup the password_reset view in your URLconf #}
        <p><a href="{% url 'password_reset' %}">Lost password?</a></p>

        {% endblock %}

    If you have customized authentication (see :doc:`Customizing Authentication
    </topics/auth/customizing>`) you can use a custom authentication form by
    setting the ``authentication_form`` attribute. This form must accept a
    ``request`` keyword argument in its ``__init__()`` method and provide a
    ``get_user()`` method which returns the authenticated user object (this
    method is only ever called after successful form validation).

.. class:: LogoutView

    Logs a user out.

    **URL name:** ``logout``

    **Attributes:**

    .. attribute:: next_page

        The URL to redirect to after logout. Defaults to
        :setting:`LOGOUT_REDIRECT_URL`.

    .. attribute:: template_name

        The full name of a template to display after logging the user out.
        Defaults to :file:`registration/logged_out.html`.

    .. attribute:: redirect_field_name

        The name of a ``GET`` field containing the URL to redirect to after log
        out. Defaults to ``'next'``. Overrides the
        :attr:`next_page` URL if the given ``GET`` parameter is
        passed.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

    .. attribute:: success_url_allowed_hosts

        A :class:`set` of hosts, in addition to :meth:`request.get_host()
        <django.http.HttpRequest.get_host>`, that are safe for redirecting
        after logout. Defaults to an empty :class:`set`.

    **Template context:**

    * ``title``: The string "Logged out", localized.

    * ``site``: The current :class:`~django.contrib.sites.models.Site`,
      according to the :setting:`SITE_ID` setting. If you don't have the
      site framework installed, this will be set to an instance of
      :class:`~django.contrib.sites.requests.RequestSite`, which derives the
      site name and domain from the current
      :class:`~django.http.HttpRequest`.

    * ``site_name``: An alias for ``site.name``. If you don't have the site
      framework installed, this will be set to the value of
      :attr:`request.META['SERVER_NAME'] <django.http.HttpRequest.META>`.
      For more on sites, see :doc:`/ref/contrib/sites`.

.. function:: logout_then_login(request, login_url=None)

    Logs a user out, then redirects to the login page.

    **URL name:** No default URL provided

    **Optional arguments:**

    * ``login_url``: The URL of the login page to redirect to.
      Defaults to :setting:`settings.LOGIN_URL <LOGIN_URL>` if not supplied.

.. class:: PasswordChangeView

    **URL name:** ``password_change``

    Allows a user to change their password.

    **Attributes:**

    .. attribute: template_name

        The full name of a template to use for displaying the password change
        form. Defaults to :file:`registration/password_change_form.html` if not
        supplied.

    .. attribute:: success_url

        The URL to redirect to after a successful password change. Defaults to
        ``'password_change_done'``.

    .. attribute:: form_class

        A custom "change password" form which must accept a ``user`` keyword
        argument. The form is responsible for actually changing the user's
        password. Defaults to
        :class:`~django.contrib.auth.forms.PasswordChangeForm`.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

    **Template context:**

    * ``form``: The password change form (see ``form_class`` above).

.. class:: PasswordChangeDoneView

    **URL name:** ``password_change_done``

    The page shown after a user has changed their password.

    **Attributes:**

    .. attribute:: template_name

        The full name of a template to use. Defaults to
        :file:`registration/password_change_done.html` if not supplied.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

.. class:: PasswordResetView

    **URL name:** ``password_reset``

    Allows a user to reset their password by generating a one-time use link
    that can be used to reset the password, and sending that link to the
    user's registered email address.

    If the email address provided does not exist in the system, this view
    won't send an email, but the user won't receive any error message either.
    This prevents information leaking to potential attackers. If you want to
    provide an error message in this case, you can subclass
    :class:`~django.contrib.auth.forms.PasswordResetForm` and use the
    ``form_class`` attribute.

    .. note::

        Be aware that sending an email costs extra time, hence you may be
        vulnerable to an email address enumeration timing attack due to a
        difference between the duration of a reset request for an existing
        email address and the duration of a reset request for a nonexistent
        email address. To reduce the overhead, you can use a 3rd party package
        that allows to send emails asynchronously, e.g. `django-mailer
        <https://pypi.org/project/django-mailer/>`_.

    Users flagged with an unusable password (see
    :meth:`~django.contrib.auth.models.User.set_unusable_password()` aren't
    allowed to request a password reset to prevent misuse when using an
    external authentication source like LDAP. Note that they won't receive any
    error message since this would expose their account's existence but no
    mail will be sent either.

    **Attributes:**

    .. attribute:: template_name

        The full name of a template to use for displaying the password reset
        form. Defaults to :file:`registration/password_reset_form.html` if not
        supplied.

    .. attribute:: form_class

        Form that will be used to get the email of the user to reset the
        password for. Defaults to
        :class:`~django.contrib.auth.forms.PasswordResetForm`.

    .. attribute:: email_template_name

        The full name of a template to use for generating the email with the
        reset password link. Defaults to
        :file:`registration/password_reset_email.html` if not supplied.

    .. attribute:: subject_template_name

        The full name of a template to use for the subject of the email with
        the reset password link. Defaults to
        :file:`registration/password_reset_subject.txt` if not supplied.

    .. attribute:: token_generator

        Instance of the class to check the one time link. This will default to
        ``default_token_generator``, it's an instance of
        ``django.contrib.auth.tokens.PasswordResetTokenGenerator``.

    .. attribute:: success_url

        The URL to redirect to after a successful password reset request.
        Defaults to ``'password_reset_done'``.

    .. attribute:: from_email

        A valid email address. By default Django uses the
        :setting:`DEFAULT_FROM_EMAIL`.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

    .. attribute:: html_email_template_name

        The full name of a template to use for generating a
        :mimetype:`text/html` multipart email with the password reset link. By
        default, HTML email is not sent.

    .. attribute:: extra_email_context

        A dictionary of context data that will be available in the email
        template. It can be used to override default template context values
        listed below e.g. ``domain``.

    **Template context:**

    * ``form``: The form (see ``form_class`` above) for resetting the user's
      password.

    **Email template context:**

    * ``email``: An alias for ``user.email``

    * ``user``: The current :class:`~django.contrib.auth.models.User`,
      according to the ``email`` form field. Only active users are able to
      reset their passwords (``User.is_active is True``).

    * ``site_name``: An alias for ``site.name``. If you don't have the site
      framework installed, this will be set to the value of
      :attr:`request.META['SERVER_NAME'] <django.http.HttpRequest.META>`.
      For more on sites, see :doc:`/ref/contrib/sites`.

    * ``domain``: An alias for ``site.domain``. If you don't have the site
      framework installed, this will be set to the value of
      ``request.get_host()``.

    * ``protocol``: http or https

    * ``uid``: The user's primary key encoded in base 64.

    * ``token``: Token to check that the reset link is valid.

    Sample ``registration/password_reset_email.html`` (email body template):

    .. code-block:: html+django

        Someone asked for password reset for email {{ email }}. Follow the link below:
        {{ protocol}}://{{ domain }}{% url 'password_reset_confirm' uidb64=uid token=token %}

    The same template context is used for subject template. Subject must be
    single line plain text string.

.. class:: PasswordResetDoneView

    **URL name:** ``password_reset_done``

    The page shown after a user has been emailed a link to reset their
    password. This view is called by default if the :class:`PasswordResetView`
    doesn't have an explicit ``success_url`` URL set.

    .. note::

        If the email address provided does not exist in the system, the user is
        inactive, or has an unusable password, the user will still be
        redirected to this view but no email will be sent.

    **Attributes:**

    .. attribute:: template_name

        The full name of a template to use. Defaults to
        :file:`registration/password_reset_done.html` if not supplied.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

.. class:: PasswordResetConfirmView

    **URL name:** ``password_reset_confirm``

    Presents a form for entering a new password.

    **Keyword arguments from the URL:**

    * ``uidb64``: The user's id encoded in base 64.

    * ``token``: Token to check that the password is valid.

    **Attributes:**

    .. attribute:: template_name

        The full name of a template to display the confirm password view.
        Default value is :file:`registration/password_reset_confirm.html`.

    .. attribute:: token_generator

        Instance of the class to check the password. This will default to
        ``default_token_generator``, it's an instance of
        ``django.contrib.auth.tokens.PasswordResetTokenGenerator``.

    .. attribute:: post_reset_login

        A boolean indicating if the user should be automatically authenticated
        after a successful password reset. Defaults to ``False``.

    .. attribute:: post_reset_login_backend

        A dotted path to the authentication backend to use when authenticating
        a user if ``post_reset_login`` is ``True``. Required only if you have
        multiple :setting:`AUTHENTICATION_BACKENDS` configured. Defaults to
        ``None``.

    .. attribute:: form_class

        Form that will be used to set the password. Defaults to
        :class:`~django.contrib.auth.forms.SetPasswordForm`.

    .. attribute:: success_url

        URL to redirect after the password reset done. Defaults to
        ``'password_reset_complete'``.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

    .. attribute:: reset_url_token

        Token parameter displayed as a component of password reset URLs.
        Defaults to ``'set-password'``.

    **Template context:**

    * ``form``: The form (see ``form_class`` above) for setting the new user's
      password.

    * ``validlink``: Boolean, True if the link (combination of ``uidb64`` and
      ``token``) is valid or unused yet.

.. class:: PasswordResetCompleteView

    **URL name:** ``password_reset_complete``

    Presents a view which informs the user that the password has been
    successfully changed.

    **Attributes:**

    .. attribute:: template_name

        The full name of a template to display the view. Defaults to
        :file:`registration/password_reset_complete.html`.

    .. attribute:: extra_context

        A dictionary of context data that will be added to the default context
        data passed to the template.

Helper functions
----------------

.. currentmodule:: django.contrib.auth.views

.. function:: redirect_to_login(next, login_url=None, redirect_field_name='next')

    Redirects to the login page, and then back to another URL after a
    successful login.

    **Required arguments:**

    * ``next``: The URL to redirect to after a successful login.

    **Optional arguments:**

    * ``login_url``: The URL of the login page to redirect to.
      Defaults to :setting:`settings.LOGIN_URL <LOGIN_URL>` if not supplied.

    * ``redirect_field_name``: The name of a ``GET`` field containing the
      URL to redirect to after log out. Overrides ``next`` if the given
      ``GET`` parameter is passed.

.. _built-in-auth-forms:

Built-in forms
--------------

.. module:: django.contrib.auth.forms

If you don't want to use the built-in views, but want the convenience of not
having to write forms for this functionality, the authentication system
provides several built-in forms located in :mod:`django.contrib.auth.forms`:

.. note::
    The built-in authentication forms make certain assumptions about the user
    model that they are working with. If you're using a :ref:`custom user model
    <auth-custom-user>`, it may be necessary to define your own forms for the
    authentication system. For more information, refer to the documentation
    about :ref:`using the built-in authentication forms with custom user models
    <custom-users-and-the-built-in-auth-forms>`.

.. class:: AdminPasswordChangeForm

    A form used in the admin interface to change a user's password.

    Takes the ``user`` as the first positional argument.

.. class:: AuthenticationForm

    A form for logging a user in.

    Takes ``request`` as its first positional argument, which is stored on the
    form instance for use by sub-classes.

    .. method:: confirm_login_allowed(user)

        By default, ``AuthenticationForm`` rejects users whose ``is_active``
        flag is set to ``False``. You may override this behavior with a custom
        policy to determine which users can log in. Do this with a custom form
        that subclasses ``AuthenticationForm`` and overrides the
        ``confirm_login_allowed()`` method. This method should raise a
        :exc:`~django.core.exceptions.ValidationError` if the given user may
        not log in.

        For example, to allow all users to log in regardless of "active"
        status::

            from django.contrib.auth.forms import AuthenticationForm

            class AuthenticationFormWithInactiveUsersOkay(AuthenticationForm):
                def confirm_login_allowed(self, user):
                    pass

        (In this case, you'll also need to use an authentication backend that
        allows inactive users, such as
        :class:`~django.contrib.auth.backends.AllowAllUsersModelBackend`.)

        Or to allow only some active users to log in::

            class PickyAuthenticationForm(AuthenticationForm):
                def confirm_login_allowed(self, user):
                    if not user.is_active:
                        raise ValidationError(
                            _("This account is inactive."),
                            code='inactive',
                        )
                    if user.username.startswith('b'):
                        raise ValidationError(
                            _("Sorry, accounts starting with 'b' aren't welcome here."),
                            code='no_b_users',
                        )

.. class:: PasswordChangeForm

    A form for allowing a user to change their password.

.. class:: PasswordResetForm

    A form for generating and emailing a one-time use link to reset a
    user's password.

    .. method:: send_mail(subject_template_name, email_template_name, context, from_email, to_email, html_email_template_name=None)

        Uses the arguments to send an ``EmailMultiAlternatives``.
        Can be overridden to customize how the email is sent to the user.

        :param subject_template_name: the template for the subject.
        :param email_template_name: the template for the email body.
        :param context: context passed to the ``subject_template``,
            ``email_template``, and ``html_email_template`` (if it is not
            ``None``).
        :param from_email: the sender's email.
        :param to_email: the email of the requester.
        :param html_email_template_name: the template for the HTML body;
            defaults to ``None``, in which case a plain text email is sent.

        By default, ``save()`` populates the ``context`` with the
        same variables that
        :class:`~django.contrib.auth.views.PasswordResetView` passes to its
        email context.

.. class:: SetPasswordForm

    A form that lets a user change their password without entering the old
    password.

.. class:: UserChangeForm

    A form used in the admin interface to change a user's information and
    permissions.

.. class:: UserCreationForm

    A :class:`~django.forms.ModelForm` for creating a new user.

    It has three fields: ``username`` (from the user model), ``password1``,
    and ``password2``. It verifies that ``password1`` and ``password2`` match,
    validates the password using
    :func:`~django.contrib.auth.password_validation.validate_password`, and
    sets the user's password using
    :meth:`~django.contrib.auth.models.User.set_password()`.

.. currentmodule:: django.contrib.auth

Authentication data in templates
--------------------------------

The currently logged-in user and their permissions are made available in the
:doc:`template context </ref/templates/api>` when you use
:class:`~django.template.RequestContext`.

.. admonition:: Technicality

    Technically, these variables are only made available in the template
    context if you use :class:`~django.template.RequestContext` and the
    ``'django.contrib.auth.context_processors.auth'`` context processor is
    enabled. It is in the default generated settings file. For more, see the
    :ref:`RequestContext docs <subclassing-context-requestcontext>`.

Users
~~~~~

When rendering a template :class:`~django.template.RequestContext`, the
currently logged-in user, either a  :class:`~django.contrib.auth.models.User`
instance or an :class:`~django.contrib.auth.models.AnonymousUser` instance, is
stored in the template variable ``{{ user }}``:

.. code-block:: html+django

    {% if user.is_authenticated %}
        <p>Welcome, {{ user.username }}. Thanks for logging in.</p>
    {% else %}
        <p>Welcome, new user. Please log in.</p>
    {% endif %}

This template context variable is not available if a ``RequestContext`` is not
being used.

Permissions
~~~~~~~~~~~

The currently logged-in user's permissions are stored in the template variable
``{{ perms }}``. This is an instance of
``django.contrib.auth.context_processors.PermWrapper``, which is a
template-friendly proxy of permissions.

Evaluating a single-attribute lookup of ``{{ perms }}`` as a boolean is a proxy
to :meth:`User.has_module_perms()
<django.contrib.auth.models.User.has_module_perms>`. For example, to check if
the logged-in user has any permissions in the ``foo`` app::

    {% if perms.foo %}

Evaluating a two-level-attribute lookup as a boolean is a proxy to
:meth:`User.has_perm() <django.contrib.auth.models.User.has_perm>`. For example,
to check if the logged-in user has the permission ``foo.add_vote``::

    {% if perms.foo.add_vote %}

Here's a more complete example of checking permissions in a template:

.. code-block:: html+django

    {% if perms.foo %}
        <p>You have permission to do something in the foo app.</p>
        {% if perms.foo.add_vote %}
            <p>You can vote!</p>
        {% endif %}
        {% if perms.foo.add_driving %}
            <p>You can drive!</p>
        {% endif %}
    {% else %}
        <p>You don't have permission to do anything in the foo app.</p>
    {% endif %}

It is possible to also look permissions up by ``{% if in %}`` statements.
For example:

.. code-block:: html+django

    {% if 'foo' in perms %}
        {% if 'foo.add_vote' in perms %}
            <p>In lookup works, too.</p>
        {% endif %}
    {% endif %}

.. _auth-admin:

Managing users in the admin
===========================

When you have both ``django.contrib.admin`` and ``django.contrib.auth``
installed, the admin provides a convenient way to view and manage users,
groups, and permissions. Users can be created and deleted like any Django
model. Groups can be created, and permissions can be assigned to users or
groups. A log of user edits to models made within the admin is also stored and
displayed.

Creating users
--------------

You should see a link to "Users" in the "Auth"
section of the main admin index page. The "Add user" admin page is different
than standard admin pages in that it requires you to choose a username and
password before allowing you to edit the rest of the user's fields.

Also note: if you want a user account to be able to create users using the
Django admin site, you'll need to give them permission to add users *and*
change users (i.e., the "Add user" and "Change user" permissions). If an
account has permission to add users but not to change them, that account won't
be able to add users. Why? Because if you have permission to add users, you
have the power to create superusers, which can then, in turn, change other
users. So Django requires add *and* change permissions as a slight security
measure.

Be thoughtful about how you allow users to manage permissions. If you give a
non-superuser the ability to edit users, this is ultimately the same as giving
them superuser status because they will be able to elevate permissions of
users including themselves!

Changing passwords
------------------

User passwords are not displayed in the admin (nor stored in the database), but
the :doc:`password storage details </topics/auth/passwords>` are displayed.
Included in the display of this information is a link to
a password change form that allows admins to change user passwords.