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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.
+Overview
+========
+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.
+Installation
+============
+Authentication support is bundled as a Django application in
+``django.contrib.auth``. To install it, do the following:
+1. Put ``'django.contrib.auth'`` in your ``INSTALLED_APPS`` setting.
+2. Run the command ``manage.py syncdb``.
+Note that the default ``settings.py`` file created by
+``django-admin.py startproject`` includes ``'django.contrib.auth'`` in
+``INSTALLED_APPS`` for convenience. If your ``INSTALLED_APPS`` already contains
+``'django.contrib.auth'``, feel free to run ``manage.py syncdb`` again; you
+can run that command as many times as you'd like, and each time it'll only
+install what's needed.
+The ``syncdb`` command creates the necessary database tables, creates
+permission objects for all installed apps that need 'em, and prompts you to
+create a superuser account the first time you run it.
+Once you've taken those steps, that's it.
+Users
+=====
+Users are represented by a standard Django model, which lives in
+`django/contrib/auth/models.py`_.
+.. _django/contrib/auth/models.py: http://code.djangoproject.com/browser/django/trunk/django/contrib/auth/models.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`` -- 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 "Passwords" section below.
+* ``is_staff`` -- Boolean. Designates whether this user can access the
+admin site.
+* ``is_active`` -- Boolean. Designates whether this account can be used
+to log in. Set this flag to ``False`` instead of deleting accounts.
+* ``is_superuser`` -- Boolean. Designates that this user has all permissions
+without explicitly assigning them.
+* ``last_login`` -- A datetime of the user's last login. Is set to the
+current date/time by default.
+* ``date_joined`` -- A datetime designating when the account was created.
+Is set to the current date/time by default when the account is created.
+Methods
+~~~~~~~
+``User`` objects have two many-to-many fields: ``groups`` and
+``user_permissions``. ``User`` objects can access their related
+objects in the same way as any other `Django model`_::
+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()
+In addition to those automatic API methods, ``User`` objects have the following
+custom methods:
+* ``is_anonymous()`` -- Always returns ``False``. This is a way of
+differentiating ``User`` and ``AnonymousUser`` objects. Generally, you
+should prefer using ``is_authenticated()`` to this method.
+* ``is_authenticated()`` -- Always returns ``True``. 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 - it only indicates
+that the user has provided a valid username and password.
+* ``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 password 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. (This takes care of the
+password hashing in making the comparison.)
+* ``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, where perm is in the format ``"package.codename"``.
+If the user is inactive, this method will always return ``False``.
+* ``has_perms(perm_list)`` -- Returns ``True`` if the user has each of the
+specified permissions, where each perm is in the format
+``"package.codename"``. If the user is inactive, this method will
+always return ``False``.
+* ``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``.
+* ``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.contrib.auth.models.SiteProfileNotAvailable`` if the current site
+doesn't allow profiles.
+.. _Django model: ../model_api/
+.. _DEFAULT_FROM_EMAIL: ../settings/#default-from-email
+Manager functions
+~~~~~~~~~~~~~~~~~
+The ``User`` model has a custom manager that 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``.
+See _`Creating users` for example usage.
+* ``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 ``create_user`` helper
+function that comes with Django::
+>>> 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 ready to be saved
+# to the database. You can continue to change its attributes
+# if you want to change other fields.
+>>> user.is_staff = True
+>>> user.save()
+Changing passwords
+~~~~~~~~~~~~~~~~~~
+Change a password with ``set_password()``::
+>>> from django.contrib.auth.models import User
+>>> u = User.objects.get(username__exact='john')
+>>> u.set_password('new password')
+>>> u.save()
+Don't set the ``password`` attribute directly unless you know what you're
+doing. This is explained in the next section.
+Passwords
+---------
+The ``password`` attribute of a ``User`` object is a string in this format::
+hashtype$salt$hash
+That's hashtype, salt and hash, separated by the dollar-sign character.
+Hashtype is either ``sha1`` (default) or ``md5`` -- the algorithm used to
+perform a one-way hash of the password. Salt is a random string used to salt
+the raw password to create the hash.
+For example::
+sha1$a1976$a36cc8cbf81742a8fb52e221aaeab48ed7f58ab4
+The ``User.set_password()`` and ``User.check_password()`` functions handle
+the setting and checking of these values behind the scenes.
+Previous Django versions, such as 0.90, used simple MD5 hashes without password
+salts. For backwards compatibility, those are still supported; they'll be
+converted automatically to the new style the first time ``check_password()``
+works correctly for a given user.
+Anonymous users
+---------------
+``django.contrib.auth.models.AnonymousUser`` is a class that implements
+the ``django.contrib.auth.models.User`` interface, with these differences:
+* ``id`` is always ``None``.
+* ``is_anonymous()`` returns ``True`` instead of ``False``.
+* ``is_authenticated()`` returns ``False`` instead of ``True``.
+* ``has_perm()`` always returns ``False``.
+* ``set_password()``, ``check_password()``, ``save()``, ``delete()``,
+``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.
+Creating superusers
+-------------------
+``manage.py syncdb`` prompts you to create a superuser the first time you run
+it after adding ``'django.contrib.auth'`` to your ``INSTALLED_APPS``. But if
+you need to create a superuser after that via the command line, you can use the
+``create_superuser.py`` utility. Just run this command::
+python /path/to/django/contrib/auth/create_superuser.py
+Make sure to substitute ``/path/to/`` with the path to the Django codebase on
+your filesystem.
+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 can hook this
+authentication framework into its system of `request objects`_.
+First, install the ``SessionMiddleware`` and ``AuthenticationMiddleware``
+middlewares by adding them to your ``MIDDLEWARE_CLASSES`` setting. See the
+`session documentation`_ for more information.
+Once you have those middlewares installed, you'll be able to access
+``request.user`` in views. ``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_authenticated()``, like so::
+if request.user.is_authenticated():
+# Do something for authenticated users.
+else:
+# Do something for anonymous users.
+.. _request objects: ../request_response/#httprequest-objects
+.. _session documentation: ../sessions/
+How to log a user in
+--------------------
+Django provides two functions in ``django.contrib.auth``: ``authenticate()``
+and ``login()``.
+To authenticate a given username and password, use ``authenticate()``. It
+takes two keyword arguments, ``username`` and ``password``, and it returns
+a ``User`` object if the password is valid for the given username. If the
+password is invalid, ``authenticate()`` returns ``None``. Example::
+from django.contrib.auth import authenticate
+user = authenticate(username='john', password='secret')
+if user is not None:
+if user.is_active:
+print "You provided a correct username and password!"
+else:
+print "Your account has been disabled!"
+else:
+print "Your username and password were incorrect."
+To log a user in, in a view, use ``login()``. It takes an ``HttpRequest``
+object and a ``User`` object. ``login()`` saves the user's ID in the session,
+using Django's session framework, so, as mentioned above, you'll need to make
+sure to have the session middleware installed.
+This example shows how you might use both ``authenticate()`` and ``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.
+Manually checking a user's password
+-----------------------------------
+If you'd like to manually authenticate a user by comparing a
+plain-text password to the hashed password in the database, use the
+convenience function `django.contrib.auth.models.check_password`. It
+takes two arguments: the plain-text password to check, and the full
+value of a user's ``password`` field in the database to check against,
+and returns ``True`` if they match, ``False`` otherwise.
+How to log a user out
+---------------------
+To log out a user who has been logged in via ``django.contrib.auth.login()``,
+use ``django.contrib.auth.logout()`` within your view. It takes an
+``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 ``logout()`` doesn't throw any errors if the user wasn't logged in.
+Limiting access to logged-in users
+----------------------------------
+The raw way
+~~~~~~~~~~~
+The simple, raw way to limit access to pages is to check
+``request.user.is_authenticated()`` and either redirect to a login page::
+from django.http import HttpResponseRedirect
+def my_view(request):
+if not request.user.is_authenticated():
+return HttpResponseRedirect('/login/?next=%s' % request.path)
+# ...
+...or display an error message::
+def my_view(request):
+if not request.user.is_authenticated():
+return render_to_response('myapp/login_error.html')
+# ...
+The login_required decorator
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+As a shortcut, you can use the convenient ``login_required`` decorator::
+from django.contrib.auth.decorators import login_required
+def my_view(request):
+# ...
+my_view = login_required(my_view)
+Here's an equivalent example, using the more compact decorator syntax
+introduced in Python 2.4::
+from django.contrib.auth.decorators 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.
+Note that you'll need to map the appropriate Django view to ``/accounts/login/``.
+To do this, add the following line to your URLconf::
+(r'^accounts/login/$', 'django.contrib.auth.views.login'),
+Here's what ``django.contrib.auth.views.login`` does:
+* If called via ``GET``, it displays a login form that POSTs to the same
+URL. More on this in a bit.
+* If called via ``POST``, it tries to log the user in. If login is
+successful, the view redirects to the URL specified in ``next``. If
+``next`` isn't provided, it redirects to ``/accounts/profile/`` (which is
+currently hard-coded). If login isn't successful, it redisplays the login
+form.
+It's your responsibility to provide the login form in a template called
+``registration/login.html`` by default. This template gets passed three
+template context variables:
+* ``form``: A ``FormWrapper`` object representing the login form. See the
+`forms documentation`_ for more on ``FormWrapper`` objects.
+* ``next``: The URL to redirect to after successful login. This may contain
+a query string, too.
+* ``site_name``: The name of the current ``Site``, according to the
+``SITE_ID`` setting. See the `site framework docs`_.
+If you'd prefer not to call the template ``registration/login.html``, you can
+pass the ``template_name`` parameter via the extra arguments to the view in
+your URLconf. For example, this URLconf line would use ``myapp/login.html``
+instead::
+(r'^accounts/login/$', 'django.contrib.auth.views.login', {'template_name': 'myapp/login.html'}),
+Here's a sample ``registration/login.html`` template you can use as a starting
+point. It assumes you have a ``base.html`` template that defines a ``content``
+block::
+{% extends "base.html" %}
+{% block content %}
+{% if form.has_errors %}
+<p>Your username and password didn't match. Please try again.</p>
+{% endif %}
+<form method="post" action=".">
+<table>
+<tr><td><label for="id_username">Username:</label></td><td>{{ form.username }}</td></tr>
+<tr><td><label for="id_password">Password:</label></td><td>{{ form.password }}</td></tr>
+</table>
+<input type="submit" value="login" />
+<input type="hidden" name="next" value="{{ next }}" />
+</form>
+{% endblock %}
+.. _forms documentation: ../forms/
+.. _site framework docs: ../sites/
+Other built-in views
+--------------------
+In addition to the `login` view, the authentication system includes a
+few other useful built-in views:
+``django.contrib.auth.views.logout``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+Logs a user out.
+**Optional arguments:**
+* ``template_name``: The full name of a template to display after
+logging the user out. This will default to
+``registration/logged_out.html`` if no argument is supplied.
+**Template context:**
+* ``title``: The string "Logged out", localized.
+``django.contrib.auth.views.logout_then_login``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+Logs a user out, then redirects to the login page.
+**Optional arguments:**
+* ``login_url``: The URL of the login page to redirect to. This
+will default to ``/accounts/login/`` if not supplied.
+``django.contrib.auth.views.password_change``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+Allows a user to change their password.
+**Optional arguments:**
+* ``template_name``: The full name of a template to use for
+displaying the password change form. This will default to
+``registration/password_change_form.html`` if not supplied.
+**Template context:**
+* ``form``: The password change form.
+``django.contrib.auth.views.password_change_done``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+The page shown after a user has changed their password.
+**Optional arguments:**
+* ``template_name``: The full name of a template to use. This will
+default to ``registration/password_change_done.html`` if not
+supplied.
+``django.contrib.auth.views.password_reset``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+Allows a user to reset their password, and sends them the new password
+in an email.
+**Optional arguments:**
+* ``template_name``: The full name of a template to use for
+displaying the password reset form. This will default to
+``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 new password. This will default to
+``registration/password_reset_email.html`` if not supplied.
+**Template context:**
+* ``form``: The form for resetting the user's password.
+``django.contrib.auth.views.password_reset_done``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+The page shown after a user has reset their password.
+**Optional arguments:**
+* ``template_name``: The full name of a template to use. This will
+default to ``registration/password_reset_done.html`` if not
+supplied.
+``django.contrib.auth.views.redirect_to_login``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**Description:**
+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. This
+will default to ``/accounts/login/`` if not supplied.
+Built-in manipulators
+---------------------
+If you don't want to use the built-in views, but want the convenience
+of not having to write manipulators for this functionality, the
+authentication system provides several built-in manipulators:
+* ``django.contrib.auth.forms.AdminPasswordChangeForm``: A
+manipulator used in the admin interface to change a user's
+password.
+* ``django.contrib.auth.forms.AuthenticationForm``: A manipulator
+for logging a user in.
+* ``django.contrib.auth.forms.PasswordChangeForm``: A manipulator
+for allowing a user to change their password.
+* ``django.contrib.auth.forms.PasswordResetForm``: A manipulator
+for resetting a user's password and emailing the new password to
+them.
+* ``django.contrib.auth.forms.UserCreationForm``: A manipulator
+for creating a new 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 ``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 not (request.user.is_authenticated() and 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.contrib.auth.decorators import user_passes_test
+def my_view(request):
+# ...
+my_view = user_passes_test(lambda u: u.has_perm('polls.can_vote'))(my_view)
+We're using this particular test as a relatively simple example. However, if
+you just want to test whether a permission is available to a user, you can use
+the ``permission_required()`` decorator, described later in this document.
+Here's the same thing, using Python 2.4's decorator syntax::
+from django.contrib.auth.decorators 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.
+Note that ``user_passes_test`` does not automatically check that the ``User``
+is not anonymous.
+``user_passes_test()`` takes an optional ``login_url`` argument, which lets you
+specify the URL for your login page (``/accounts/login/`` by default).
+Example in Python 2.3 syntax::
+from django.contrib.auth.decorators import user_passes_test
+def my_view(request):
+# ...
+my_view = user_passes_test(lambda u: u.has_perm('polls.can_vote'), login_url='/login/')(my_view)
+Example in Python 2.4 syntax::
+from django.contrib.auth.decorators import user_passes_test
+@user_passes_test(lambda u: u.has_perm('polls.can_vote'), login_url='/login/')
+def my_view(request):
+# ...
+The permission_required decorator
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**New in Django development version**
+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
+``permission_required()`` decorator. Using this decorator, the earlier example
+can be written as::
+from django.contrib.auth.decorators import permission_required
+def my_view(request):
+# ...
+my_view = permission_required('polls.can_vote')(my_view)
+Note that ``permission_required()`` also takes an optional ``login_url``
+parameter. Example::
+from django.contrib.auth.decorators import permission_required
+def my_view(request):
+# ...
+my_view = permission_required('polls.can_vote', login_url='/loginpage/')(my_view)
+As in the ``login_required`` decorator, ``login_url`` defaults to
+``'/accounts/login/'``.
+Limiting access to generic views
+--------------------------------
+To limit access to a `generic view`_, write a thin wrapper around the view,
+and point your URLconf to your wrapper instead of the generic view itself.
+For example::
+from django.views.generic.date_based import object_detail
+@login_required
+def limited_object_detail(*args, **kwargs):
+return object_detail(*args, **kwargs)
+.. _generic view: ../generic_views/
+Permissions
+===========
+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 are set globally per type of object, not per specific object
+instance. For example, it's possible to say "Mary may change news stories," but
+it's not currently possible to say "Mary may change news stories, but only the
+ones she created herself" or "Mary may only change news stories that have a
+certain status, publication date or ID." The latter functionality is something
+Django developers are currently discussing.
+Default permissions
+-------------------
+Three basic permissions -- add, create and delete -- are automatically created
+for each Django model that has a ``class Admin`` set. Behind the scenes, these
+permissions are added to the ``auth_permission`` database table when you run
+``manage.py syncdb``.
+Note that if your model doesn't have ``class Admin`` set when you run
+``syncdb``, the permissions won't be created. If you initialize your database
+and add ``class Admin`` to models after the fact, you'll need to run
+``manage.py syncdb`` again. It will create any missing permissions for
+all of your installed apps.
+Custom permissions
+------------------
+To create custom permissions for a given model object, use the ``permissions``
+`model Meta attribute`_.
+This example model creates three custom permissions::
+class USCitizen(models.Model):
+# ...
+class Meta:
+permissions = (
+("can_drive", "Can drive"),
+("can_vote", "Can vote in elections"),
+("can_drink", "Can drink alcohol"),
+)
+The only thing this does is create those extra permissions when you run
+``syncdb``.
+.. _model Meta attribute: ../model_api/#meta-options
+API reference
+-------------
+Just like users, permissions are implemented in a Django model that lives in
+`django/contrib/auth/models.py`_.
+.. _django/contrib/auth/models.py: http://code.djangoproject.com/browser/django/trunk/django/contrib/auth/models.py
+Fields
+~~~~~~
+``Permission`` objects have the following fields:
+* ``name`` -- Required. 50 characters or fewer. Example: ``'Can vote'``.
+* ``content_type`` -- Required. A reference to the ``django_content_type``
+database table, which contains a record for each installed Django model.
+* ``codename`` -- Required. 100 characters or fewer. Example: ``'can_vote'``.
+Methods
+~~~~~~~
+``Permission`` objects have the standard data-access methods like any other
+`Django model`_.
+Authentication data in templates
+================================
+The currently logged-in user and his/her permissions are made available in the
+`template context`_ when you use ``RequestContext``.
+.. admonition:: Technicality
+Technically, these variables are only made available in the template context
+if you use ``RequestContext`` *and* your ``TEMPLATE_CONTEXT_PROCESSORS``
+setting contains ``"django.core.context_processors.auth"``, which is default.
+For more, see the `RequestContext docs`_.
+.. _RequestContext docs: ../templates_python/#subclassing-context-requestcontext
+Users
+-----
+The currently logged-in user, either a ``User`` instance or an``AnonymousUser``
+instance, is stored in the template variable ``{{ user }}``::
+{% if user.is_authenticated %}
+<p>Welcome, {{ user.username }}. Thanks for logging in.</p>
+{% else %}
+<p>Welcome, new user. Please log in.</p>
+{% endif %}
+Permissions
+-----------
+The currently logged-in user's permissions are stored in the template variable
+``{{ perms }}``. This is an instance of ``django.core.context_processors.PermWrapper``,
+which is a template-friendly proxy of permissions.
+In the ``{{ perms }}`` object, single-attribute lookup is a proxy to
+``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 ``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::
+{% 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 %}
+.. _template context: ../templates_python/
+Groups
+======
+Groups 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 e-mail
+messages.
+Messages
+========
+The message system is a lightweight way to queue messages for given users.
+A message is associated with a ``User``. There's no concept of expiration or
+timestamps.
+Messages are used by the Django admin after successful actions. For example,
+``"The poll Foo was created successfully."`` is a message.
+The API is simple:
+* To create a new message, use
+``user_obj.message_set.create(message='message_text')``.
+* To retrieve/delete messages, use ``user_obj.get_and_delete_messages()``,
+which returns a list of ``Message`` objects in the user's queue (if any)
+and deletes the messages from the queue.
+In this example view, the system saves a message for the user after creating
+a playlist::
+def create_playlist(request, songs):
+# Create the playlist with the given songs.
+# ...
+request.user.message_set.create(message="Your playlist was added successfully.")
+return render_to_response("playlists/create.html",
+context_instance=RequestContext(request))
+When you use ``RequestContext``, the currently logged-in user and his/her
+messages are made available in the `template context`_ as the template variable
+``{{ messages }}``. Here's an example of template code that displays messages::
+{% if messages %}
+<ul>
+{% for message in messages %}
+<li>{{ message }}</li>
+{% endfor %}
+</ul>
+{% endif %}
+Note that ``RequestContext`` calls ``get_and_delete_messages`` behind the
+scenes, so any messages will be deleted even if you don't display them.
+Finally, note that this messages framework only works with users in the user
+database. To send messages to anonymous users, use the `session framework`_.
+.. _session framework: ../sessions/
+Other authentication sources
+============================
+The authentication that comes with Django is good enough for most common cases,
+but you may have the need to hook into another authentication source -- that
+is, another source of usernames and passwords or authentication methods.
+For example, your company may already have an LDAP setup that stores a username
+and password for every employee. It'd be a hassle for both the network
+administrator and the users themselves if users had separate accounts in LDAP
+and the Django-based applications.
+So, to handle situations like this, the Django authentication system lets you
+plug in another authentication sources. You can override Django's default
+database-based scheme, or you can use the default system in tandem with other
+systems.
+Specifying authentication backends
+----------------------------------
+Behind the scenes, Django maintains a list of "authentication backends" that it
+checks for authentication. When somebody calls
+``django.contrib.auth.authenticate()`` -- as described in "How to log a user in"
+above -- Django tries authenticating across all of its authentication backends.
+If the first authentication method fails, Django tries the second one, and so
+on, until all backends have been attempted.
+The list of authentication backends to use is specified in the
+``AUTHENTICATION_BACKENDS`` setting. This should be a tuple of Python path
+names that point to Python classes that know how to authenticate. These classes
+can be anywhere on your Python path.
+By default, ``AUTHENTICATION_BACKENDS`` is set to::
+('django.contrib.auth.backends.ModelBackend',)
+That's the basic authentication scheme that checks the Django users database.
+The order of ``AUTHENTICATION_BACKENDS`` matters, so if the same username and
+password is valid in multiple backends, Django will stop processing at the
+first positive match.
+Writing an authentication backend
+---------------------------------
+An authentication backend is a class that implements two methods:
+``get_user(id)`` and ``authenticate(**credentials)``.
+The ``get_user`` method takes an ``id`` -- which could be a username, database
+ID or whatever -- and returns a ``User`` object.
+The  ``authenticate`` method takes credentials as keyword arguments. Most of
+the time, it'll just look like this::
+class MyBackend:
+def authenticate(self, username=None, password=None):
+# Check the username/password and return a User.
+But it could also authenticate a token, like so::
+class MyBackend:
+def authenticate(self, token=None):
+# Check the token and return a User.
+Either way, ``authenticate`` should check the credentials it gets, and it
+should return a ``User`` object that matches those credentials, if the
+credentials are valid. If they're not valid, it should return ``None``.
+The Django admin system is tightly coupled to the Django ``User`` object
+described at the beginning of this document. For now, the best way to deal with
+this is to create a Django ``User`` object for each user that exists for your
+backend (e.g., in your LDAP directory, your external SQL database, etc.) You
+can either write a script to do this in advance, or your ``authenticate``
+method can do it the first time a user logs in.
+Here's an example backend that authenticates against a username and password
+variable defined in your ``settings.py`` file and creates a Django ``User``
+object the first time a user authenticates::
+from django.conf import settings
+from django.contrib.auth.models import User, check_password
+class SettingsBackend:
+"""
+Authenticate against the settings ADMIN_LOGIN and ADMIN_PASSWORD.
+Use the login name, and a hash of the password. For example:
+ADMIN_LOGIN = 'admin'
+ADMIN_PASSWORD = 'sha1$4e987$afbcf42e21bd417fb71db8c66b321e9fc33051de'
+"""
+def authenticate(self, username=None, password=None):
+login_valid = (settings.ADMIN_LOGIN == username)
+pwd_valid = check_password(password, settings.ADMIN_PASSWORD)
+if login_valid and pwd_valid:
+try:
+user = User.objects.get(username=username)
+except User.DoesNotExist:
+# Create a new user. Note that we can set password
+# to anything, because it won't be checked; the password
+# from settings.py will.
+user = User(username=username, password='get from settings.py')
+user.is_staff = True
+user.is_superuser = True
+user.save()
+return user
+return None
+def get_user(self, user_id):
+try:
+return User.objects.get(pk=user_id)
+except User.DoesNotExist:
+return None