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=============================
User authentication in Django
=============================
Django comes with a user authentication system. It handles user accounts,
groups, permissions and cookie-based user sessions. This document explains how
things work.
The basics
==========
Django supports authentication out of the box. The ``django-admin.py init``
command, used to initialize a database with Django's core database tables,
creates the infrastructure for the auth system. You don't have to do anything
else to use authentication.
The auth system consists of:
* Users
* Permissions: Binary (yes/no) flags designating whether a user may perform
a certain task.
* Groups: A generic way of applying labels and permissions to more than one
user.
* Messages: A simple way to queue messages for given users.
Users
=====
Users are represented by a standard Django model, which lives in
`django/models/auth.py`_.
.. _django/models/auth.py: http://code.djangoproject.com/browser/django/trunk/django/models/auth.py
API reference
-------------
Fields
~~~~~~
``User`` objects have the following fields:
* ``username`` -- Required. 30 characters or fewer. Alphanumeric characters
only (letters, digits and underscores).
* ``first_name`` -- Optional. 30 characters or fewer.
* ``last_name`` -- Optional. 30 characters or fewer.
* ``email`` -- Optional. E-mail address.
* ``password_md5`` -- Required. An MD5 hash of the password. (Django
doesn't store the raw password.) Raw passwords can be arbitrarily long
and can contain any character.
* ``is_staff`` -- Boolean. Designates whether this user can access the
admin site.
* ``is_active`` -- Boolean. Designates whether this user account is valid.
Set this to ``False`` instead of deleting accounts.
* ``is_superuser`` -- Boolean. Designates whether this user has permission
to do anything (according to the permission system).
* ``last_login`` -- A datetime of the user's last login. Is set to "now" by
default.
* ``date_joined`` -- A datetime designating when the account was created.
Is set to "now" by default when the account is created.
Methods
~~~~~~~
``User`` objects have two many-to-many fields: ``groups`` and
``user_permissions``. Because of those relationships, ``User`` objects get
data-access methods like any other `Django model`_:
* ``get_group_list(**kwargs)``
* ``set_groups(id_list)``
* ``get_permission_list(**kwargs)``
* ``set_user_permissions(id_list)``
In addition to those automatic API methods, ``User`` objects have the following
methods:
* ``is_anonymous()`` -- Always returns ``False``. This is a way of
comparing ``User`` objects to anonymous users.
* ``get_full_name()`` -- Returns the ``first_name`` plus the ``last_name``,
with a space in between.
* ``set_password(raw_password)`` -- Sets the user's password to the given
raw string, taking care of the MD5 hashing. Doesn't save the ``User``
object.
* ``check_password(raw_password)`` -- Returns ``True`` if the given raw
string is the correct password for the user.
* ``get_group_permissions()`` -- Returns a list of permission strings that
the user has, through his/her groups.
* ``get_all_permissions()`` -- Returns a list of permission strings that
the user has, both through group and user permissions.
* ``has_perm(perm)`` -- Returns ``True`` if the user has the specified
permission.
* ``has_perms(perm_list)`` -- Returns ``True`` if the user has each of the
specified permissions.
* ``has_module_perms(package_name)`` -- Returns ``True`` if the user has
any permissions in the given package (the Django app label).
* ``get_and_delete_messages()`` -- Returns a list of ``Message`` objects in
the user's queue and deletes the messages from the queue.
* ``email_user(subject, message, from_email=None)`` -- Sends an e-mail to
the user. If ``from_email`` is ``None``, Django uses the
`DEFAULT_FROM_EMAIL`_ setting.
* ``get_profile()`` -- Returns a site-specific profile for this user.
Raises ``django.models.auth.SiteProfileNotAvailable`` if the current site
doesn't allow profiles.
.. _Django model: http://www.djangoproject.com/documentation/model_api/
.. _DEFAULT_FROM_EMAIL: http://www.djangoproject.com/documentation/settings/#default-from-email
Module functions
~~~~~~~~~~~~~~~~
The ``django.models.users`` module has the following helper functions:
* ``create_user(username, email, password)`` -- Creates, saves and returns
a ``User``. The ``username``, ``email`` and ``password`` are set as
given, and the ``User`` gets ``is_active=True``.
* ``make_random_password(length=10, allowed_chars='abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789')``
-- Returns a random password with the given length and given string of
allowed characters. (Note that the default value of ``allowed_chars``
doesn't contain ``"I"`` or letters that look like it, to avoid user
confusion.
Basic usage
-----------
Creating users
~~~~~~~~~~~~~~
The most basic way to create users is to use the standard Django
`database API`_. Just create and save a ``User`` object::
>>> from django.models.auth import users
>>> import md5
>>> p = md5.new('johnpassword').hexdigest()
>>> u = users.User(username='john', first_name='John', last_name='lennon',
... email='lennon@thebeatles.com', password_md5=p, is_staff=True,
... is_active=True, is_superuser=False)
>>> u.save()
Note that ``password_md5`` requires the raw MD5 hash. Because that's a pain,
there's a ``create_user`` helper function::
>>> from django.models.auth import users
>>> u = users.create_user('john', 'lennon@thebeatles.com', 'johnpassword')
.. _database API: http://www.djangoproject.com/documentation/db_api/
Changing passwords
~~~~~~~~~~~~~~~~~~
Change a password with ``set_password()``::
>>> from django.models.auth import users
>>> u = users.get_object(username__exact='john')
>>> u.set_password('new password')
>>> u.save()
Anonymous users
---------------
``django.parts.auth.anonymoususers.AnonymousUser`` is a class that implements
the ``django.models.auth.users.User`` interface, with these differences:
* ``is_anonymous()`` returns ``True`` instead of ``False``.
* ``has_perm()`` always returns ``False``.
* ``set_password()``, ``check_password()``, ``set_groups()`` and
``set_permissions()`` raise ``NotImplementedError``.
In practice, you probably won't need to use ``AnonymousUser`` objects on your
own, but they're used by Web requests, as explained in the next section.
Authentication in Web requests
==============================
Until now, this document has dealt with the low-level APIs for manipulating
authentication-related objects. On a higher level, Django hooks this
authentication framework into its system of `request objects`_.
In any Django view, ``request.user`` will give you a ``User`` object
representing the currently logged-in user. If a user isn't currently logged in,
``request.user`` will be set to an instance of ``AnonymousUser`` (see the
previous section). You can tell them apart with ``is_anonymous()``, like so::
if request.user.is_anonymous():
# Do something for anonymous users.
else:
# Do something for logged-in users.
.. _request objects: http://www.djangoproject.com/documentation/request_response/#httprequest-objects
Limiting access to logged-in users
----------------------------------
The raw way
~~~~~~~~~~~
The simple, raw way to limit access to pages is to check
``request.user.is_anonymous()`` and either redirect to a login page::
from django.utils.httpwrappers import HttpResponseRedirect
def my_view(request):
if request.user.is_anonymous():
return HttpResponseRedirect('/login/?next=%s' % request.path)
# ...
...or displaying an error message::
def my_view(request):
if request.user.is_anonymous():
return render_to_response('myapp/login_error')
# ...
The login_required decorator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As a shortcut, you can use the convenient ``login_required`` decorator::
from django.views.decorators.auth import login_required
def my_view(request):
# ...
my_view = login_required(my_view)
Here's the same, using Python 2.4's decorator syntax::
from django.views.decorators.auth import login_required
@login_required
def my_view(request):
# ...
``login_required`` does the following:
* If the user isn't logged in, redirect to ``/accounts/login/``, passing
the current absolute URL in the query string as ``next``. For 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.
Limiting access to logged-in users that pass a test
---------------------------------------------------
To limit access based on certain permissions or another test, you'd do the same
thing as described in the previous section.
The simple way is to run your test on ``request.user`` in the view directly.
For example, this view checks to make sure the user is logged in and has the
permission ``polls.can_vote``::
def my_view(request):
if request.user.is_anonymous() or not request.user.has_perm('polls.can_vote'):
return HttpResponse("You can't vote in this poll.")
# ...
As a shortcut, you can use the convenient ``user_passes_test`` decorator::
from django.views.decorators.auth import user_passes_test
@user_passes_test(lambda u: u.has_perm('polls.can_vote'))
def my_view(request):
# ...
``user_passes_test`` takes a required argument: a callable that takes a
``User`` object and returns ``True`` if the user is allowed to view the page.
Permissions
===========
Groups
======
Messages
========