======================================
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 :djadminopt:`--username` or the
:djadminopt:`--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:: python

    >>> 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.

.. versionadded:: 1.7

Changing a user's password will log out all their sessions if the
:class:`~django.contrib.auth.middleware.SessionAuthenticationMiddleware` is
enabled. See :ref:`session-invalidation-on-password-change` for details.

Authenticating Users
--------------------

.. function:: authenticate(\**credentials)

    To authenticate a given username and password, use
    :func:`~django.contrib.auth.authenticate()`. It takes credentials in the
    form of keyword arguments, for the default configuration this is
    ``username`` and ``password``, and it returns
    a :class:`~django.contrib.auth.models.User` object if the password is valid
    for the given username. If the password is invalid,
    :func:`~django.contrib.auth.authenticate()` returns ``None``. Example::

        from django.contrib.auth import authenticate
        user = authenticate(username='john', password='secret')
        if user is not None:
            # the password verified for the user
            if user.is_active:
                print("User is valid, active and authenticated")
            else:
                print("The password is valid, but the account has been disabled!")
        else:
            # the authentication system was unable to verify the username and password
            print("The username and password were incorrect.")

    .. 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 are looking for a way to limit access to logged in
        users, see the :func:`~django.contrib.auth.decorators.login_required`
        decorator.

.. _topic-authorization:

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

Django comes with a simple 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 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_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>`:

.. code-block:: python

    myuser.groups = [group_list]
    myuser.groups.add(group, group, ...)
    myuser.groups.remove(group, group, ...)
    myuser.groups.clear()
    myuser.user_permissions = [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 three default permissions -- add, change and
delete -- 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>`.

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')``

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 Group, 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.

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 are not 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.shortcuts import get_object_or_404

    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_bar')

        permission = Permission.objects.get(codename='change_bar')
        user.user_permissions.add(permission)

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

        # Request new instance of User
        user = get_object_or_404(User, pk=user_id)

        # Permission cache is repopulated from the database
        user.has_perm('myapp.change_bar')  # 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
:meth:`~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()

    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(username=username, password=password)
            if user is not None:
                if user.is_active:
                    login(request, user)
                    # Redirect to a success page.
                else:
                    # Return a 'disabled account' error message
                    ...
            else:
                # Return an 'invalid login' error message.
                ...

.. admonition:: Calling ``authenticate()`` first

    When you're manually logging a user in, you *must* successfully authenticate
    the user with :func:`~django.contrib.auth.authenticate()` before you call
    :func:`~django.contrib.auth.login()`.
    :func:`~django.contrib.auth.authenticate()`
    sets an attribute on the :class:`~django.contrib.auth.models.User` noting
    which authentication backend successfully authenticated that user (see the
    :ref:`backends documentation <authentication-backends>` for details), and
    this information is needed later during the login process. An error will be
    raised if you try to login a user object retrieved from the database
    directly.

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

.. function:: logout()

    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 simple, raw way to limit access to pages is to check
:meth:`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=REDIRECT_FIELD_NAME, 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 line to your URLconf::

        (r'^accounts/login/$', 'django.contrib.auth.views.login'),

    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.

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.

The simple way is to 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(func, [login_url=None])

    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 an
    optional ``login_url`` argument, which lets you specify the URL for your
    login page (:setting:`settings.LOGIN_URL <LOGIN_URL>` by default).

    For example::

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

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.can_vote')
        def my_view(request):
            ...

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

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

        from django.contrib.auth.decorators import permission_required

        @permission_required('polls.can_vote', 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.

    .. versionchanged:: 1.7

        The :func:`~django.contrib.auth.decorators.permission_required`
        decorator can take a list of permissions as well as a single permission.

.. _applying-permissions-to-generic-views:

Applying permissions to generic views
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To apply a permission to a :doc:`class-based generic view
</ref/class-based-views/index>`, decorate the :meth:`View.dispatch
<django.views.generic.base.View.dispatch>` method on the class. See
:ref:`decorating-class-based-views` for details. Another approach is to
:ref:`write a mixin that wraps as_view() <mixins_that_wrap_as_view>`.

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

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

.. versionadded:: 1.7

.. warning::

    This protection only applies if
    :class:`~django.contrib.auth.middleware.SessionAuthenticationMiddleware`
    is enabled in :setting:`MIDDLEWARE_CLASSES`. It's included if
    ``settings.py`` was generated by :djadmin:`startproject` on Django ≥ 1.7.

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. If the
:class:`~django.contrib.auth.middleware.SessionAuthenticationMiddleware` is
enabled, Django verifies that the hash sent along with each request matches
the one that's computed server-side. This allows a user to log out all of their
sessions by changing their password.

The default password change views included with Django,
:func:`django.contrib.auth.views.password_change` 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 this 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. 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:
                ...

If you are upgrading an existing site and wish to enable this middleware without
requiring all your users to re-login afterward, you should first upgrade to
Django 1.7 and run it for a while so that as sessions are naturally recreated
as users login, they include the session hash as described above. Once you
start running your site with
:class:`~django.contrib.auth.middleware.SessionAuthenticationMiddleware`, any
users who have not logged in and had their session updated with the verification
hash will have their existing session invalidated and be required to login.

.. 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 = [
        url('^', include('django.contrib.auth.urls'))
    ]

This will include the following URL patterns::

    ^login/$ [name='login']
    ^logout/$ [name='logout']
    ^password_change/$ [name='password_change']
    ^password_change/done/$ [name='password_change_done']
    ^password_reset/$ [name='password_reset']
    ^password_reset/done/$ [name='password_reset_done']
    ^reset/(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})/$ [name='password_reset_confirm']
    ^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::

    urlpatterns = [
        url('^change-password/', 'django.contrib.auth.views.password_change')
    ]

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 = [
        url(
            '^change-password/',
            'django.contrib.auth.views.password_change',
            {'template_name': 'change-password.html'}
        )
    ]

All views return a :class:`~django.template.response.TemplateResponse`
instance, which allows you to easily customize the response data before
rendering. A way to do this is to wrap a view in your own view::

    from django.contrib.auth import views

    def change_password(request):
        template_response = views.password_change(request)
        # Do something with `template_response`
        return template_response

For more details, see the :doc:`TemplateResponse documentation
</ref/template-response>`.

.. _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`.

.. function:: login(request, [template_name, redirect_field_name, authentication_form, current_app, extra_context])

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

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

    **Optional arguments:**

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

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

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

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

    Here's what ``django.contrib.auth.views.login`` 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 view in your URLconf. For example, this URLconf line would use
    :file:`myapp/login.html` instead::

        (r'^accounts/login/$', 'django.contrib.auth.views.login', {'template_name': 'myapp/login.html'}),

    You can also specify the name of the ``GET`` field which contains the URL
    to redirect to after login by passing ``redirect_field_name`` to the view.
    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 %}

        <form method="post" action="{% url 'django.contrib.auth.views.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>

        {% endblock %}

    If you have customized authentication (see
    :doc:`Customizing Authentication </topics/auth/customizing>`) you can pass a custom authentication form
    to the login view via the ``authentication_form`` parameter. 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).

    .. _forms documentation: ../forms/
    .. _site framework docs: ../sites/


.. function:: logout(request, [next_page, template_name, redirect_field_name, current_app, extra_context])

    Logs a user out.

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

    **Optional arguments:**

    * ``next_page``: The URL to redirect to after logout.

    * ``template_name``: The full name of a template to display after
      logging the user out. Defaults to
      :file:`registration/logged_out.html` if no argument is supplied.

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

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

    **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`.

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

.. function:: logout_then_login(request[, login_url, current_app, extra_context])

    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.

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

.. function:: password_change(request[, template_name, post_change_redirect, password_change_form, current_app, extra_context])

    Allows a user to change their password.

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

    **Optional arguments:**

    * ``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.

    * ``post_change_redirect``: The URL to redirect to after a successful
      password change.

    * ``password_change_form``: 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`.

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``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 ``password_change_form`` above).

.. function:: password_change_done(request[, template_name, current_app, extra_context])

    The page shown after a user has changed their password.

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

    **Optional arguments:**

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

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

.. function:: password_reset(request[, is_admin_site, template_name, email_template_name, password_reset_form, token_generator, post_reset_redirect, from_email, current_app, extra_context, html_email_template_name])

    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
    ``password_reset_form`` argument.


    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.

    .. versionchanged:: 1.6

        Previously, error messages indicated whether a given email was
        registered.

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

    **Optional arguments:**

    * ``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.

    * ``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.

    * ``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.

    * ``password_reset_form``: 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`.

    * ``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``.

    * ``post_reset_redirect``: The URL to redirect to after a successful
      password reset request.

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

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

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

    .. versionadded:: 1.7

        ``html_email_template_name`` was added.

    **Template context:**

    * ``form``: The form (see ``password_reset_form`` 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 %}

    .. versionchanged:: 1.6

      Reversing ``password_reset_confirm`` takes a ``uidb64`` argument instead
      of ``uidb36``.

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


.. function:: password_reset_done(request[, template_name, current_app, extra_context])

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

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

    .. 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.

    **Optional arguments:**

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

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

.. function:: password_reset_confirm(request[, uidb64, token, template_name, token_generator, set_password_form, post_reset_redirect, current_app, extra_context])

    Presents a form for entering a new password.

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

    **Optional arguments:**

    * ``uidb64``: The user's id encoded in base 64. Defaults to ``None``.

      .. versionchanged:: 1.6

          The ``uidb64`` parameter was previously base 36 encoded and named
          ``uidb36``.

    * ``token``: Token to check that the password is valid. Defaults to
      ``None``.

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

    * ``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``.

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

    * ``post_reset_redirect``: URL to redirect after the password reset
      done. Defaults to ``None``.

    * ``current_app``: A hint indicating which application contains the current
      view. See the :ref:`namespaced URL resolution strategy
      <topics-http-reversing-url-namespaces>` for more information.

    * ``extra_context``: A dictionary of context data that will be added to the
      default context data passed to the template.

    **Template context:**

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

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

.. function:: password_reset_complete(request[,template_name, current_app, extra_context])

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

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

   **Optional arguments:**

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

   * ``current_app``: A hint indicating which application contains the current
     view. See the :ref:`namespaced URL resolution strategy
     <topics-http-reversing-url-namespaces>` for more information.

   * ``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, redirect_field_name])

    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)

        .. versionadded:: 1.7

        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

        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 forms.ValidationError(
                            _("This account is inactive."),
                            code='inactive',
                        )
                    if user.username.startswith('b'):
                        raise forms.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.

.. 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 form for creating a new user.

.. 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* your
   :setting:`TEMPLATE_CONTEXT_PROCESSORS` setting contains
   ``"django.contrib.auth.context_processors.auth"``, which is default. 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.

In the ``{{ perms }}`` object, single-attribute lookup is a proxy to
:meth:`User.has_module_perms <django.contrib.auth.models.User.has_module_perms>`.
This example would display ``True`` if the logged-in user had any permissions
in the ``foo`` app::

    {{ perms.foo }}

Two-level-attribute lookup is a proxy to
:meth:`User.has_perm <django.contrib.auth.models.User.has_perm>`. This example
would display ``True`` if the logged-in user had the permission
``foo.can_vote``::

    {{ perms.foo.can_vote }}

Thus, you can check permissions in template ``{% if %}`` statements:

.. code-block:: html+django

    {% if perms.foo %}
        <p>You have permission to do something in the foo app.</p>
        {% if perms.foo.can_vote %}
            <p>You can vote!</p>
        {% endif %}
        {% if perms.foo.can_drive %}
            <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.can_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.
