django/docs/ref/contrib/auth.txt

=======================
``django.contrib.auth``
=======================

This document provides API reference material for the components of Django's
authentication system. For more details on the usage of these components or
how to customize authentication and authorization see the :doc:`authentication
topic guide </topics/auth/index>`.

.. currentmodule:: django.contrib.auth

``User`` model
==============

Fields
------

.. class:: models.User

    :class:`~django.contrib.auth.models.User` objects have the following
    fields:

    .. attribute:: username

        Required. 150 characters or fewer. Usernames may contain alphanumeric,
        ``_``, ``@``, ``+``, ``.`` and ``-`` characters.

        The ``max_length`` should be sufficient for many use cases. If you need
        a longer length, please use a :ref:`custom user model
        <specifying-custom-user-model>`. If you use MySQL with the ``utf8mb4``
        encoding (recommended for proper Unicode support), specify at most
        ``max_length=191`` because MySQL can only create unique indexes with
        191 characters in that case by default.

        .. admonition:: Usernames and Unicode

            Django originally accepted only ASCII letters and numbers in
            usernames. Although it wasn't a deliberate choice, Unicode
            characters have always been accepted when using Python 3. Django
            1.10 officially added Unicode support in usernames, keeping the
            ASCII-only behavior on Python 2, with the option to customize the
            behavior using :attr:`.User.username_validator`.

    .. attribute:: first_name

        Optional (:attr:`blank=True <django.db.models.Field.blank>`). 30
        characters or fewer.

    .. attribute:: last_name

        Optional (:attr:`blank=True <django.db.models.Field.blank>`). 150
        characters or fewer.

        .. versionchanged:: 2.0

            The ``max_length`` increased from 30 to 150 characters.

    .. attribute:: email

        Optional (:attr:`blank=True <django.db.models.Field.blank>`). Email
        address.

    .. attribute:: password

        Required. A hash of, and metadata about, the password. (Django doesn't
        store the raw password.) Raw passwords can be arbitrarily long and can
        contain any character. See the :doc:`password documentation
        </topics/auth/passwords>`.

    .. attribute:: groups

        Many-to-many relationship to :class:`~django.contrib.auth.models.Group`

    .. attribute:: user_permissions

         Many-to-many relationship to :class:`~django.contrib.auth.models.Permission`

    .. attribute:: is_staff

        Boolean. Designates whether this user can access the admin site.

    .. attribute:: is_active

        Boolean. Designates whether this user account should be considered
        active. We recommend that you set this flag to ``False`` instead of
        deleting accounts; that way, if your applications have any foreign keys
        to users, the foreign keys won't break.

        This doesn't necessarily control whether or not the user can log in.
        Authentication backends aren't required to check for the ``is_active``
        flag but the default backend
        (:class:`~django.contrib.auth.backends.ModelBackend`) and the
        :class:`~django.contrib.auth.backends.RemoteUserBackend` do. You can
        use :class:`~django.contrib.auth.backends.AllowAllUsersModelBackend`
        or :class:`~django.contrib.auth.backends.AllowAllUsersRemoteUserBackend`
        if you want to allow inactive users to login. In this case, you'll also
        want to customize the
        :class:`~django.contrib.auth.forms.AuthenticationForm` used by the
        :class:`~django.contrib.auth.views.LoginView` as it rejects inactive
        users. Be aware that the permission-checking methods such as
        :meth:`~django.contrib.auth.models.User.has_perm` and the
        authentication in the Django admin all return ``False`` for inactive
        users.

    .. attribute:: is_superuser

        Boolean. Designates that this user has all permissions without
        explicitly assigning them.

    .. attribute:: last_login

        A datetime of the user's last login.

    .. attribute:: date_joined

        A datetime designating when the account was created. Is set to the
        current date/time by default when the account is created.

Attributes
----------

.. class:: models.User

    .. attribute:: is_authenticated

        Read-only attribute which is always ``True`` (as opposed to
        ``AnonymousUser.is_authenticated`` which is always ``False``). This is
        a way to tell if the user has been authenticated. This does not imply
        any permissions and doesn't check if the user is active or has a valid
        session. Even though normally you will check this attribute on
        ``request.user`` to find out whether it has been populated by the
        :class:`~django.contrib.auth.middleware.AuthenticationMiddleware`
        (representing the currently logged-in user), you should know this
        attribute is ``True`` for any :class:`~models.User` instance.

    .. attribute:: is_anonymous

        Read-only attribute which is always ``False``. This is a way of
        differentiating :class:`~models.User` and :class:`~models.AnonymousUser`
        objects. Generally, you should prefer using
        :attr:`~django.contrib.auth.models.User.is_authenticated` to this
        attribute.

    .. attribute:: username_validator

        Points to a validator instance used to validate usernames. Defaults to
        :class:`validators.UnicodeUsernameValidator`.

        To change the default username validator, you can subclass the ``User``
        model and set this attribute to a different validator instance. For
        example, to use ASCII usernames::

            from django.contrib.auth.models import User
            from django.contrib.auth.validators import ASCIIUsernameValidator

            class CustomUser(User):
                username_validator = ASCIIUsernameValidator()

                class Meta:
                    proxy = True  # If no new field is added.

Methods
-------

.. class:: models.User

    .. method:: get_username()

        Returns the username for the user. Since the ``User`` model can be
        swapped out, you should use this method instead of referencing the
        username attribute directly.

    .. method:: get_full_name()

        Returns the :attr:`~django.contrib.auth.models.User.first_name` plus
        the :attr:`~django.contrib.auth.models.User.last_name`, with a space in
        between.

    .. method:: get_short_name()

        Returns the :attr:`~django.contrib.auth.models.User.first_name`.

    .. method:: set_password(raw_password)

        Sets the user's password to the given raw string, taking care of the
        password hashing. Doesn't save the
        :class:`~django.contrib.auth.models.User` object.

        When the ``raw_password`` is ``None``, the password will be set to an
        unusable password, as if
        :meth:`~django.contrib.auth.models.User.set_unusable_password()`
        were used.

    .. method:: check_password(raw_password)

        Returns ``True`` if the given raw string is the correct password for
        the user. (This takes care of the password hashing in making the
        comparison.)

    .. method:: set_unusable_password()

        Marks the user as having no password set.  This isn't the same as
        having a blank string for a password.
        :meth:`~django.contrib.auth.models.User.check_password()` for this user
        will never return ``True``. Doesn't save the
        :class:`~django.contrib.auth.models.User` object.

        You may need this if authentication for your application takes place
        against an existing external source such as an LDAP directory.

    .. method:: has_usable_password()

        Returns ``False`` if
        :meth:`~django.contrib.auth.models.User.set_unusable_password()` has
        been called for this user.

        .. versionchanged:: 2.1

            In older versions, this also returns ``False`` if the password is
            ``None`` or an empty string, or if the password uses a hasher
            that's not in the :setting:`PASSWORD_HASHERS` setting. That
            behavior is considered a bug as it prevents users with such
            passwords from requesting a password reset.

    .. method:: get_group_permissions(obj=None)

        Returns a set of permission strings that the user has, through their
        groups.

        If ``obj`` is passed in, only returns the group permissions for
        this specific object.

    .. method:: get_all_permissions(obj=None)

        Returns a set of permission strings that the user has, both through
        group and user permissions.

        If ``obj`` is passed in, only returns the permissions for this
        specific object.

    .. method:: has_perm(perm, obj=None)

        Returns ``True`` if the user has the specified permission, where perm
        is in the format ``"<app label>.<permission codename>"``. (see
        documentation on :ref:`permissions <topic-authorization>`). If the user is
        inactive, this method will always return ``False``.

        If ``obj`` is passed in, this method won't check for a permission for
        the model, but for this specific object.

    .. method:: has_perms(perm_list, obj=None)

        Returns ``True`` if the user has each of the specified permissions,
        where each perm is in the format
        ``"<app label>.<permission codename>"``. If the user is inactive,
        this method will always return ``False``.

        If ``obj`` is passed in, this method won't check for permissions for
        the model, but for the specific object.

    .. method:: has_module_perms(package_name)

        Returns ``True`` if the user has any permissions in the given package
        (the Django app label). If the user is inactive, this method will
        always return ``False``.

    .. method:: email_user(subject, message, from_email=None, **kwargs)

        Sends an email to the user. If ``from_email`` is ``None``, Django uses
        the :setting:`DEFAULT_FROM_EMAIL`. Any ``**kwargs`` are passed to the
        underlying :meth:`~django.core.mail.send_mail()` call.

Manager methods
---------------

.. class:: models.UserManager

    The :class:`~django.contrib.auth.models.User` model has a custom manager
    that has the following helper methods (in addition to the methods provided
    by :class:`~django.contrib.auth.models.BaseUserManager`):

    .. method:: create_user(username, email=None, password=None, **extra_fields)

        Creates, saves and returns a :class:`~django.contrib.auth.models.User`.

        The :attr:`~django.contrib.auth.models.User.username` and
        :attr:`~django.contrib.auth.models.User.password` are set as given. The
        domain portion of :attr:`~django.contrib.auth.models.User.email` is
        automatically converted to lowercase, and the returned
        :class:`~django.contrib.auth.models.User` object will have
        :attr:`~django.contrib.auth.models.User.is_active` set to ``True``.

        If no password is provided,
        :meth:`~django.contrib.auth.models.User.set_unusable_password()` will
        be called.

        The ``extra_fields`` keyword arguments are passed through to the
        :class:`~django.contrib.auth.models.User`’s ``__init__`` method to
        allow setting arbitrary fields on a :ref:`custom user model
        <auth-custom-user>`.

        See :ref:`Creating users <topics-auth-creating-users>` for example usage.

    .. method:: create_superuser(username, email, password, **extra_fields)

        Same as :meth:`create_user`, but sets :attr:`~models.User.is_staff` and
        :attr:`~models.User.is_superuser` to ``True``.

``AnonymousUser`` object
========================

.. class:: models.AnonymousUser

    :class:`django.contrib.auth.models.AnonymousUser` is a class that
    implements the :class:`django.contrib.auth.models.User` interface, with
    these differences:

    * :ref:`id <automatic-primary-key-fields>` is always ``None``.
    * :attr:`~django.contrib.auth.models.User.username` is always the empty
      string.
    * :meth:`~django.contrib.auth.models.User.get_username()` always returns
      the empty string.
    * :attr:`~django.contrib.auth.models.User.is_anonymous` is ``True``
      instead of ``False``.
    * :attr:`~django.contrib.auth.models.User.is_authenticated` is
      ``False`` instead of ``True``.
    * :attr:`~django.contrib.auth.models.User.is_staff` and
      :attr:`~django.contrib.auth.models.User.is_superuser` are always
      ``False``.
    * :attr:`~django.contrib.auth.models.User.is_active` is always ``False``.
    * :attr:`~django.contrib.auth.models.User.groups` and
      :attr:`~django.contrib.auth.models.User.user_permissions` are always
      empty.
    * :meth:`~django.contrib.auth.models.User.set_password()`,
      :meth:`~django.contrib.auth.models.User.check_password()`,
      :meth:`~django.db.models.Model.save` and
      :meth:`~django.db.models.Model.delete()` raise :exc:`NotImplementedError`.

In practice, you probably won't need to use
:class:`~django.contrib.auth.models.AnonymousUser` objects on your own, but
they're used by Web requests, as explained in the next section.

``Permission`` model
====================

.. class:: models.Permission

Fields
------

:class:`~django.contrib.auth.models.Permission` objects have the following
fields:

.. class:: models.Permission

    .. attribute:: name

        Required. 255 characters or fewer. Example: ``'Can vote'``.

    .. attribute:: content_type

        Required. A reference to the ``django_content_type`` database table,
        which contains a record for each installed model.

    .. attribute:: codename

        Required. 100 characters or fewer. Example: ``'can_vote'``.

Methods
-------

:class:`~django.contrib.auth.models.Permission` objects have the standard
data-access methods like any other :doc:`Django model </ref/models/instances>`.

``Group`` model
===============

.. class:: models.Group

Fields
------

:class:`~django.contrib.auth.models.Group` objects have the following fields:

.. class:: models.Group

    .. attribute:: name

        Required. 80 characters or fewer. Any characters are permitted. Example:
        ``'Awesome Users'``.

    .. attribute:: permissions

        Many-to-many field to :class:`~django.contrib.auth.models.Permission`::

            group.permissions.set([permission_list])
            group.permissions.add(permission, permission, ...)
            group.permissions.remove(permission, permission, ...)
            group.permissions.clear()

Validators
==========

.. class:: validators.ASCIIUsernameValidator

    A field validator allowing only ASCII letters and numbers, in addition to
    ``@``, ``.``, ``+``, ``-``, and ``_``.

.. class:: validators.UnicodeUsernameValidator

    A field validator allowing Unicode characters, in addition to ``@``, ``.``,
    ``+``, ``-``, and ``_``. The default validator for ``User.username``.

.. _topics-auth-signals:

Login and logout signals
========================

.. module:: django.contrib.auth.signals

The auth framework uses the following :doc:`signals </topics/signals>` that
can be used for notification when a user logs in or out.

.. function:: user_logged_in

    Sent when a user logs in successfully.

    Arguments sent with this signal:

    ``sender``
        The class of the user that just logged in.

    ``request``
        The current :class:`~django.http.HttpRequest` instance.

    ``user``
        The user instance that just logged in.

.. function:: user_logged_out

    Sent when the logout method is called.

    ``sender``
        As above: the class of the user that just logged out or ``None``
        if the user was not authenticated.

    ``request``
        The current :class:`~django.http.HttpRequest` instance.

    ``user``
        The user instance that just logged out or ``None`` if the
        user was not authenticated.

.. function:: user_login_failed

    Sent when the user failed to login successfully

    ``sender``
        The name of the module used for authentication.

    ``credentials``
        A dictionary of keyword arguments containing the user credentials that were
        passed to :func:`~django.contrib.auth.authenticate()` or your own custom
        authentication backend. Credentials matching a set of 'sensitive' patterns,
        (including password) will not be sent in the clear as part of the signal.

    ``request``
        The :class:`~django.http.HttpRequest` object, if one was provided to
        :func:`~django.contrib.auth.authenticate`.

.. _authentication-backends-reference:

Authentication backends
=======================

.. module:: django.contrib.auth.backends
   :synopsis: Django's built-in authentication backend classes.

This section details the authentication backends that come with Django. For
information on how to use them and how to write your own authentication
backends, see the :ref:`Other authentication sources section
<authentication-backends>` of the :doc:`User authentication guide
</topics/auth/index>`.


Available authentication backends
---------------------------------

The following backends are available in :mod:`django.contrib.auth.backends`:

.. class:: ModelBackend

    This is the default authentication backend used by Django.  It
    authenticates using credentials consisting of a user identifier and
    password.  For Django's default user model, the user identifier is the
    username, for custom user models it is the field specified by
    USERNAME_FIELD (see :doc:`Customizing Users and authentication
    </topics/auth/customizing>`).

    It also handles the default permissions model as defined for
    :class:`~django.contrib.auth.models.User` and
    :class:`~django.contrib.auth.models.PermissionsMixin`.

    :meth:`has_perm`, :meth:`get_all_permissions`, :meth:`get_user_permissions`,
    and :meth:`get_group_permissions` allow an object to be passed as a
    parameter for object-specific permissions, but this backend does not
    implement them other than returning an empty set of permissions if
    ``obj is not None``.

    .. method:: authenticate(request, username=None, password=None, **kwargs)

        Tries to authenticate ``username`` with ``password`` by calling
        :meth:`User.check_password
        <django.contrib.auth.models.User.check_password>`. If no ``username``
        is provided, it tries to fetch a username from ``kwargs`` using the
        key :attr:`CustomUser.USERNAME_FIELD
        <django.contrib.auth.models.CustomUser.USERNAME_FIELD>`. Returns an
        authenticated user or ``None``.

        ``request`` is an :class:`~django.http.HttpRequest` and may be ``None``
        if it wasn't provided to :func:`~django.contrib.auth.authenticate`
        (which passes it on to the backend).

    .. method:: get_user_permissions(user_obj, obj=None)

        Returns the set of permission strings the ``user_obj`` has from their
        own user permissions. Returns an empty set if
        :attr:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
        :attr:`~django.contrib.auth.models.CustomUser.is_active` is ``False``.

    .. method:: get_group_permissions(user_obj, obj=None)

        Returns the set of permission strings the ``user_obj`` has from the
        permissions of the groups they belong. Returns an empty set if
        :attr:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
        :attr:`~django.contrib.auth.models.CustomUser.is_active`  is ``False``.

    .. method:: get_all_permissions(user_obj, obj=None)

        Returns the set of permission strings the ``user_obj`` has, including both
        user permissions and group permissions. Returns an empty set if
        :attr:`~django.contrib.auth.models.AbstractBaseUser.is_anonymous` or
        :attr:`~django.contrib.auth.models.CustomUser.is_active` is ``False``.

    .. method:: has_perm(user_obj, perm, obj=None)

        Uses :meth:`get_all_permissions` to check if ``user_obj`` has the
        permission string ``perm``. Returns ``False`` if the user is not
        :attr:`~django.contrib.auth.models.CustomUser.is_active`.

    .. method:: has_module_perms(user_obj, app_label)

        Returns whether the ``user_obj`` has any permissions on the app
        ``app_label``.

    .. method:: ModelBackend.user_can_authenticate()

        Returns whether the user is allowed to authenticate. To match the
        behavior of :class:`~django.contrib.auth.forms.AuthenticationForm`
        which :meth:`prohibits inactive users from logging in
        <django.contrib.auth.forms.AuthenticationForm.confirm_login_allowed>`,
        this method returns ``False`` for users with :attr:`is_active=False
        <django.contrib.auth.models.User.is_active>`. Custom user models that
        don't have an :attr:`~django.contrib.auth.models.CustomUser.is_active`
        field are allowed.

.. class:: AllowAllUsersModelBackend

   Same as :class:`ModelBackend` except that it doesn't reject inactive users
   because :meth:`~ModelBackend.user_can_authenticate` always returns ``True``.

   When using this backend, you'll likely want to customize the
   :class:`~django.contrib.auth.forms.AuthenticationForm` used by the
   :class:`~django.contrib.auth.views.LoginView` by overriding the
   :meth:`~django.contrib.auth.forms.AuthenticationForm.confirm_login_allowed`
   method as it rejects inactive users.

.. class:: RemoteUserBackend

    Use this backend to take advantage of external-to-Django-handled
    authentication.  It authenticates using usernames passed in
    :attr:`request.META['REMOTE_USER'] <django.http.HttpRequest.META>`.  See
    the :doc:`Authenticating against REMOTE_USER </howto/auth-remote-user>`
    documentation.

    If you need more control, you can create your own authentication backend
    that inherits from this class and override these attributes or methods:

.. attribute:: RemoteUserBackend.create_unknown_user

    ``True`` or ``False``. Determines whether or not a user object is created
    if not already in the database  Defaults to ``True``.

.. method:: RemoteUserBackend.authenticate(request, remote_user)

    The username passed as ``remote_user`` is considered trusted. This method
    simply returns the user object with the given username, creating a new
    user object if :attr:`~RemoteUserBackend.create_unknown_user` is ``True``.

    Returns ``None`` if :attr:`~RemoteUserBackend.create_unknown_user` is
    ``False`` and a ``User`` object with the given username is not found in the
    database.

    ``request`` is an :class:`~django.http.HttpRequest` and may be ``None`` if
    it wasn't provided to :func:`~django.contrib.auth.authenticate` (which
    passes it on to the backend).

.. method:: RemoteUserBackend.clean_username(username)

   Performs any cleaning on the ``username`` (e.g. stripping LDAP DN
   information) prior to using it to get or create a user object. Returns the
   cleaned username.

.. method:: RemoteUserBackend.configure_user(user)

   Configures a newly created user.  This method is called immediately after a
   new user is created, and can be used to perform custom setup actions, such
   as setting the user's groups based on attributes in an LDAP directory.
   Returns the user object.

.. method:: RemoteUserBackend.user_can_authenticate()

    Returns whether the user is allowed to authenticate. This method returns
    ``False`` for users with :attr:`is_active=False
    <django.contrib.auth.models.User.is_active>`. Custom user models that don't
    have an :attr:`~django.contrib.auth.models.CustomUser.is_active` field are
    allowed.

.. class:: AllowAllUsersRemoteUserBackend

   Same as :class:`RemoteUserBackend` except that it doesn't reject inactive
   users because :attr:`~RemoteUserBackend.user_can_authenticate` always
   returns ``True``.

Utility functions
=================

.. currentmodule:: django.contrib.auth

.. function:: get_user(request)

    Returns the user model instance associated with the given ``request``’s
    session.

    It checks if the authentication backend stored in the session is present in
    :setting:`AUTHENTICATION_BACKENDS`. If so, it uses the backend's
    ``get_user()`` method to retrieve the user model instance and then verifies
    the session by calling the user model's
    :meth:`~django.contrib.auth.models.AbstractBaseUser.get_session_auth_hash`
    method.

    Returns an instance of :class:`~django.contrib.auth.models.AnonymousUser`
    if the authentication backend stored in the session is no longer in
    :setting:`AUTHENTICATION_BACKENDS`, if a user isn't returned by the
    backend's ``get_user()`` method, or if the session auth hash doesn't
    validate.