============================= 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 user can log into the Django admin. Set this 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.objects.groups = [group_list] myuser.objects.groups.add(group, group,...) myuser.objects.groups.remove(group, group,...) myuser.objects.groups.clear() myuser.objects.permissions = [permission_list] myuser.objects.permissions.add(permission, permission, ...) myuser.objects.permissions.remove(permission, permission, ...] myuser.objects.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 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 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"``. * ``has_perms(perm_list)`` -- Returns ``True`` if the user has each of the specified permissions, where each perm is in the format ``"package.codename"``. * ``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.contrib.auth.models.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 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``. * ``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_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 .. _session documentation: http://www.djangoproject.com/documentation/sessions/ How to log a user in -------------------- To log a user in, do the following within a view:: from django.contrib.auth.models import SESSION_KEY request.session[SESSION_KEY] = some_user.id Because this uses sessions, you'll need to make sure you have ``SessionMiddleware`` enabled. See the `session documentation`_ for more information. This assumes ``some_user`` is your ``User`` instance. Depending on your task, you'll probably want to make sure to validate the user's username and password. 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.http import HttpResponseRedirect def my_view(request): if request.user.is_anonymous(): return HttpResponseRedirect('/login/?next=%s' % request.path) # ... ...or display an error message:: def my_view(request): if request.user.is_anonymous(): 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``. 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`_. 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 %}

Your username and password didn't match. Please try again.

{% endif %}
{{ form.username }}
{{ form.password }}
{% endblock %} .. _forms documentation: http://www.djangoproject.com/documentation/forms/ .. _site framework docs: http://www.djangoproject.com/documentation/sites/ 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 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.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) 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): # ... 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: http://www.djangoproject.com/documentation/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: http://www.djangoproject.com/documentation/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: http://www.djangoproject.com/documentation/templates_python/#subclassing-context-djangocontext Users ----- The currently logged-in user, either a ``User`` instance or an``AnonymousUser`` instance, is stored in the template variable ``{{ user }}``:: {% if user.is_anonymous %}

Welcome, new user. Please log in.

{% else %}

Welcome, {{ user.username }}. Thanks for logging in.

{% 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 %}

You have permission to do something in the foo app.

{% if perms.foo.can_vote %}

You can vote!

{% endif %} {% if perms.foo.can_drive %}

You can drive!

{% endif %} {% else %}

You don't have permission to do anything in the foo app.

{% endif %} .. _template context: http://www.djangoproject.com/documentation/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 %} {% 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: http://www.djangoproject.com/documentation/sessions/