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django/docs/ref/contrib/auth.txt
Adrien b8a476b745 [5.0.x] Improved wording in auth.models.User field docs. 
Co-authored-by: Lily Foote <code@lilyf.org>

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=======================
``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
==============
.. class:: models.User
Fields
------
.. class:: models.User
:noindex:
: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.
.. attribute:: first_name
Optional (:attr:`blank=True <django.db.models.Field.blank>`). 150
characters or fewer.
.. attribute:: last_name
Optional (:attr:`blank=True <django.db.models.Field.blank>`). 150
characters or fewer.
.. 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. Allows this user to access the admin site.
.. attribute:: is_active
Boolean. Marks this user account as 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. Treats this user as having all permissions without assigning
any permission to it in particular.
.. attribute:: last_login
A datetime of the user's last login.
.. attribute:: date_joined
The date/time when the account was created.
Attributes
----------
.. class:: models.User
:noindex:
.. 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.
Methods
-------
.. class:: models.User
:noindex:
.. 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)
.. method:: acheck_password(raw_password)
*Asynchronous version*: ``acheck_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.)
.. versionchanged:: 5.0
``acheck_password()`` method was added.
.. 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.
.. method:: get_user_permissions(obj=None)
Returns a set of permission strings that the user has directly.
If ``obj`` is passed in, only returns the user permissions for this
specific object.
.. 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``. For an active
superuser, this method will always return ``True``.
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``. For an active superuser, this
method will always return ``True``.
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``. For an active superuser, this method will
always return ``True``.
.. 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=None, password=None, **extra_fields)
Same as :meth:`create_user`, but sets :attr:`~models.User.is_staff` and
:attr:`~models.User.is_superuser` to ``True``.
.. method:: with_perm(perm, is_active=True, include_superusers=True, backend=None, obj=None)
Returns users that have the given permission ``perm`` either in the
``"<app label>.<permission codename>"`` format or as a
:class:`~django.contrib.auth.models.Permission` instance. Returns an
empty queryset if no users who have the ``perm`` found.
If ``is_active`` is ``True`` (default), returns only active users, or
if ``False``, returns only inactive users. Use ``None`` to return all
users irrespective of active state.
If ``include_superusers`` is ``True`` (default), the result will
include superusers.
If ``backend`` is passed in and it's defined in
:setting:`AUTHENTICATION_BACKENDS`, then this method will use it.
Otherwise, it will use the ``backend`` in
:setting:`AUTHENTICATION_BACKENDS`, if there is only one, or raise an
exception.
``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
:noindex:
.. 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
:noindex:
.. attribute:: name
Required. 150 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.
.. data:: 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.
.. data:: 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.
.. data:: 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:: BaseBackend
A base class that provides default implementations for all required
methods. By default, it will reject any user and provide no permissions.
.. method:: get_user_permissions(user_obj, obj=None)
Returns an empty set.
.. method:: get_group_permissions(user_obj, obj=None)
Returns an empty set.
.. method:: get_all_permissions(user_obj, obj=None)
Uses :meth:`get_user_permissions` and :meth:`get_group_permissions` to
get the set of permission strings the ``user_obj`` has.
.. method:: has_perm(user_obj, perm, obj=None)
Uses :meth:`get_all_permissions` to check if ``user_obj`` has the
permission string ``perm``.
.. 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``.
:meth:`with_perm` also allows an object to be passed as a parameter, but
unlike others methods it returns an empty queryset 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:: 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.
.. method:: with_perm(perm, is_active=True, include_superusers=True, obj=None)
Returns all active users who have the permission ``perm`` either in
the form of ``"<app label>.<permission codename>"`` or a
:class:`~django.contrib.auth.models.Permission` instance. Returns an
empty queryset if no users who have the ``perm`` found.
If ``is_active`` is ``True`` (default), returns only active users, or
if ``False``, returns only inactive users. Use ``None`` to return all
users irrespective of active state.
If ``include_superusers`` is ``True`` (default), the result will
include superusers.
.. 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:: 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:: authenticate(request, remote_user)
The username passed as ``remote_user`` is considered trusted. This
method 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:: 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:: configure_user(request, user, created=True)
Configures the user on each authentication attempt. This method is
called immediately after fetching or creating the user being
authenticated, 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.
The setup can be performed either once when the user is created
(``created`` is ``True``) or on existing users (``created`` is
``False``) as a way of synchronizing attributes between the remote and
the local systems.
``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:: 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)
.. function:: aget_user(request)
*Asynchronous version*: ``aget_user()``
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. If the verification fails and :setting:`SECRET_KEY_FALLBACKS` are
provided, it verifies the session against each fallback key using
:meth:`~django.contrib.auth.models.AbstractBaseUser.\
get_session_auth_fallback_hash`.
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.
.. versionchanged:: 4.1.8
Fallback verification with :setting:`SECRET_KEY_FALLBACKS` was added.
.. versionchanged:: 5.0
``aget_user()`` function was added.
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