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 auth system consists of:
Authentication support is bundled as a Django application in django.contrib.auth. To install it, do the following:
Note that the default settings.py file created by django-admin.py startproject includes 'django.contrib.auth' and 'django.contrib.contenttypes' in INSTALLED_APPS for convenience. If your INSTALLED_APPS already contains these apps, 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.
User objects have the following fields:
Required. 30 characters or fewer. Usernames may contain alphanumeric, _, @, +, . and - characters.
Optional. 30 characters or fewer.
Optional. 30 characters or fewer.
Optional. Email address.
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.
Boolean. Designates whether this user can access the admin site.
Boolean. Designates whether this user account should be considered active. We recommend that you set this flag to False instead of deleting accounts; that way, if your applications have any foreign keys to users, the foreign keys won’t break.
This doesn’t necessarily control whether or not the user can log in. Authentication backends aren’t required to check for the is_active flag, and the default backends do not. If you want to reject a login based on is_active being False, it’s up to you to check that in your own login view or a custom authentication backend. However, the AuthenticationForm used by the login() view (which is the default) does perform this check, as do the permission-checking methods such as has_perm() and the authentication in the Django admin. All of those functions/methods will return False for inactive users.
Boolean. Designates that this user has all permissions without explicitly assigning them.
A datetime of the user’s last login. Is set to the current date/time by default.
A datetime designating when the account was created. Is set to the current date/time by default when the account is created.
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:
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.
Always returns False. This is a way of differentiating User and AnonymousUser objects. Generally, you should prefer using is_authenticated() to this method.
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.
Returns the first_name plus the last_name, with a space in between.
Sets the user’s password to the given raw string, taking care of the password hashing. Doesn’t save the User object.
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.)
Marks the user as having no password set. This isn’t the same as having a blank string for a password. check_password() for this user will never return True. Doesn’t save the User object.
You may need this if authentication for your application takes place against an existing external source such as an LDAP directory.
Returns False if set_unusable_password() has been called for this user.
Returns a set of permission strings that the user has, through his/her groups.
If obj is passed in, only returns the group permissions for this specific object.
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.
Returns True if the user has the specified permission, where perm is in the format "<app label>.<permission codename>". (see permissions section below). If the user is inactive, this method will always return False.
If obj is passed in, this method won’t check for a permission for the model, but for this specific object.
Returns True if the user has each of the specified permissions, where each perm is in the format "<app label>.<permission codename>". If the user is inactive, this method will always return False.
If obj is passed in, this method won’t check for permissions for the model, but for the specific object.
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.
Sends an email to the user. If from_email is None, Django uses the DEFAULT_FROM_EMAIL.
Returns a site-specific profile for this user. Raises django.contrib.auth.models.SiteProfileNotAvailable if the current site doesn’t allow profiles, or django.core.exceptions.ObjectDoesNotExist if the user does not have a profile. For information on how to define a site-specific user profile, see the section on storing additional user information below.
The User model has a custom manager that has the following helper functions:
Creates, saves and returns a User.
The username and password are set as given. The domain portion of email is automatically converted to lowercase, and the returned User object will have is_active set to True.
If no password is provided, set_unusable_password() will be called.
See Creating users for example usage.
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 letters that can cause user confusion, including:
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 that has already been saved
# to the database. You can continue to change its attributes
# if you want to change other fields.
>>> user.is_staff = True
>>> user.save()
You can also create users using the Django admin site. Assuming you’ve enabled the admin site and hooked it to the URL /admin/, the “Add user” page is at /admin/auth/user/add/. You should also see a link to “Users” in the “Auth” section of the main admin index page. The “Add user” admin page is different than standard admin pages in that it requires you to choose a username and password before allowing you to edit the rest of the user’s fields.
Also note: if you want your own user account to be able to create users using the Django admin site, you’ll need to give yourself permission to add users and change users (i.e., the “Add user” and “Change user” permissions). If your account has permission to add users but not to change them, you won’t be able to add users. Why? Because if you have permission to add users, you have the power to create superusers, which can then, in turn, change other users. So Django requires add and change permissions as a slight security measure.
manage.py changepassword *username* offers a method of changing a User’s password from the command line. It prompts you to change the password of a given user which you must enter twice. If they both match, the new password will be changed immediately. If you do not supply a user, the command will attempt to change the password whose username matches the current user.
You can also change a password programmatically, using 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.
The password attribute of a User object is a string in this format:
algorithm$hash
That’s a storage algorithm, and hash, separated by the dollar-sign character. The algorithm is one of a number of one way hashing or password storage algorithms Django can use; see below. The hash is the result of the one- way function.
By default, Django uses the PBKDF2 algorithm with a SHA256 hash, a password stretching mechanism recommended by NIST. This should be sufficient for most users: it’s quite secure, requiring massive amounts of computing time to break.
However, depending on your requirements, you may choose a different algorithm, or even use a custom algorithm to match your specific security situation. Again, most users shouldn’t need to do this – if you’re not sure, you probably don’t. If you do, please read on:
Django chooses the an algorithm by consulting the PASSWORD_HASHERS setting. This is a list of hashing algorithm classes that this Django installation supports. The first entry in this list (that is, settings.PASSWORD_HASHERS[0]) will be used to store passwords, and all the other entries are valid hashers that can be used to check existing passwords. This means that if you want to use a different algorithm, you’ll need to modify PASSWORD_HASHERS to list your preferred algorithm first in the list.
The default for PASSWORD_HASHERS is:
PASSWORD_HASHERS = (
'django.contrib.auth.hashers.PBKDF2PasswordHasher',
'django.contrib.auth.hashers.PBKDF2SHA1PasswordHasher',
'django.contrib.auth.hashers.BCryptPasswordHasher',
'django.contrib.auth.hashers.SHA1PasswordHasher',
'django.contrib.auth.hashers.MD5PasswordHasher',
'django.contrib.auth.hashers.CryptPasswordHasher',
)
This means that Django will use PBKDF2 to store all passwords, but will support checking passwords stored with PBKDF2SHA1, bcrypt, SHA1, etc. The next few sections describe a couple of common ways advanced users may want to modify this setting.
Bcrypt is a popular password storage algorithm that’s specifically designed for long-term password storage. It’s not the default used by Django since it requires the use of third-party libraries, but since many people may want to use it Django supports bcrypt with minimal effort.
To use Bcrypt as your default storage algorithm, do the following:
Install the py-bcrypt library (probably by running sudo pip install py-bcrypt, or downloading the library and installing it with python setup.py install).
Modify PASSWORD_HASHERS to list BCryptPasswordHasher first. That is, in your settings file, you’d put:
PASSWORD_HASHERS = (
'django.contrib.auth.hashers.BCryptPasswordHasher',
'django.contrib.auth.hashers.PBKDF2PasswordHasher',
'django.contrib.auth.hashers.PBKDF2SHA1PasswordHasher',
'django.contrib.auth.hashers.SHA1PasswordHasher',
'django.contrib.auth.hashers.MD5PasswordHasher',
'django.contrib.auth.hashers.CryptPasswordHasher',
)
(You need to keep the other entries in this list, or else Django won’t be able to upgrade passwords; see below).
That’s it – now your Django install will use Bcrypt as the default storage algorithm.
Other bcrypt implementations
There are several other implementations that allow bcrypt to be used with Django. Django’s bcrypt support is NOT directly compatible with these. To upgrade, you will need to modify the hashes in your database to be in the form bcrypt$(raw bcrypt output). For example: bcrypt$$2a$12$NT0I31Sa7ihGEWpka9ASYrEFkhuTNeBQ2xfZskIiiJeyFXhRgS.Sy.
The PBKDF2 and bcrypt algorithms use a number of iterations or rounds of hashing. This deliberately slows down attackers, making attacks against hashed passwords harder. However, as computing power increases, the number of iterations needs to be increased. We’ve chosen a reasonable default (and will increase it with each release of Django), but you may wish to tune it up or down, depending on your security needs and available processing power. To do so, you’ll subclass the appropriate algorithm and override the iterations parameters. For example, to increase the number of iterations used by the default PBKDF2 algorithm:
Create a subclass of django.contrib.auth.hashers.PBKDF2PasswordHasher:
from django.contrib.auth.hashers import PBKDF2PasswordHasher
class MyPBKDF2PasswordHasher(PBKDF2PasswordHasher):
"""
A subclass of PBKDF2PasswordHasher that uses 100 times more iterations.
"""
iterations = PBKDF2PasswordHasher.iterations * 100
Save this somewhere in your project. For example, you might put this in a file like myproject/hashers.py.
Add your new hasher as the first entry in PASSWORD_HASHERS:
PASSWORD_HASHERS = (
'myproject.hashers.MyPBKDF2PasswordHasher',
'django.contrib.auth.hashers.PBKDF2PasswordHasher',
'django.contrib.auth.hashers.PBKDF2SHA1PasswordHasher',
'django.contrib.auth.hashers.BCryptPasswordHasher',
'django.contrib.auth.hashers.SHA1PasswordHasher',
'django.contrib.auth.hashers.MD5PasswordHasher',
'django.contrib.auth.hashers.CryptPasswordHasher',
)
That’s it – now your Django install will use more iterations when it stores passwords using PBKDF2.
When users log in, if their passwords are stored with anything other than the preferred algorithm, Django will automatically upgrade the algorithm to the preferred one. This means that old installs of Django will get automatically more secure as users log in, and it also means that you can switch to new (and better) storage algorithms as they get invented.
However, Django can only upgrade passwords that use algorithms mentioned in PASSWORD_HASHERS, so as you upgrade to new systems you should make sure never to remove entries from this list. If you do, users using un- mentioned algorithms won’t be able to upgrade.
django.contrib.auth.models.AnonymousUser is a class that implements the django.contrib.auth.models.User interface, with these differences:
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.
manage.py syncdb prompts you to create a superuser the first time you run it after adding 'django.contrib.auth' to your INSTALLED_APPS. If you need to create a superuser at a later date, you can use a command line utility:
manage.py createsuperuser --username=joe --email=joe@example.com
You will be prompted for a password. After you enter one, the user will be created immediately. If you leave off the --username or the --email options, it will prompt you for those values.
If you’re using an older release of Django, the old way of creating a superuser on the command line still works:
python /path/to/django/contrib/auth/create_superuser.py
...where /path/to is the path to the Django codebase on your filesystem. The manage.py command is preferred because it figures out the correct path and environment for you.
If you’d like to store additional information related to your users, Django provides a method to specify a site-specific related model – termed a “user profile” – for this purpose.
To make use of this feature, define a model with fields for the additional information you’d like to store, or additional methods you’d like to have available, and also add a OneToOneField named user from your model to the User model. This will ensure only one instance of your model can be created for each User. For example:
from django.contrib.auth.models import User
class UserProfile(models.Model):
# This field is required.
user = models.OneToOneField(User)
# Other fields here
accepted_eula = models.BooleanField()
favorite_animal = models.CharField(max_length=20, default="Dragons.")
To indicate that this model is the user profile model for a given site, fill in the setting AUTH_PROFILE_MODULE with a string consisting of the following items, separated by a dot:
For example, if the profile model was a class named UserProfile and was defined inside an application named accounts, the appropriate setting would be:
AUTH_PROFILE_MODULE = 'accounts.UserProfile'
When a user profile model has been defined and specified in this manner, each User object will have a method – get_profile() – which returns the instance of the user profile model associated with that User.
The method get_profile() does not create a profile if one does not exist. You need to register a handler for the User model’s django.db.models.signals.post_save signal and, in the handler, if created is True, create the associated user profile:
# in models.py
from django.contrib.auth.models import User
from django.db.models.signals import post_save
# definition of UserProfile from above
# ...
def create_user_profile(sender, instance, created, **kwargs):
if created:
UserProfile.objects.create(user=instance)
post_save.connect(create_user_profile, sender=User)
See also
Signals for more information on Django’s signal dispatcher.
To add the UserProfile fields to the user page in the admin, define an InlineModelAdmin (for this example, we’ll use a StackedInline) in your app’s admin.py and add it to a UserAdmin class which is registered with the User class:
from django.contrib import admin
from django.contrib.auth.admin import UserAdmin
from django.contrib.auth.models import User
from my_user_profile_app.models import UserProfile
# Define an inline admin descriptor for UserProfile model
# which acts a bit like a singleton
class UserProfileInline(admin.StackedInline):
model = UserProfile
can_delete = False
verbose_name_plural = 'profile'
# Define a new User admin
class UserAdmin(UserAdmin):
inlines = (UserProfileInline, )
# Re-register UserAdmin
admin.site.unregister(User)
admin.site.register(User, UserAdmin)
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.
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.
Note that data set during the anonymous session is retained when the user logs in.
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.
Calling authenticate() first
When you’re manually logging a user in, you must call authenticate() before you call login(). authenticate() sets an attribute on the User noting which authentication backend successfully authenticated that user (see the backends documentation for details), and this information is needed later during the login process.
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.hashers.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.
Creates a hashed password in the format used by this application. It takes one mandatory argument: the password in plain-text. Optionally, you can provide a salt and a hashing algorithm to use, if you don’t want to use the defaults (first entry of PASSWORD_HASHERS setting). Currently supported algorithms are: 'pbkdf2_sha256', 'pbkdf2_sha1', 'bcrypt' (see Using bcrypt with Django), 'sha1', 'md5', 'unsalted_md5' (only for backward compatibility) and 'crypt' if you have the crypt library installed. If the password argument is None, an unusable password is returned (a one that will be never accepted by django.contrib.auth.hashers.check_password()).
Checks if the given string is a hashed password that has a chance of being verified against django.contrib.auth.hashers.check_password().
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.
When you call logout(), the session data for the current request is completely cleaned out. All existing data is removed. This is to prevent another person from using the same Web browser to log in and have access to the previous user’s session data. If you want to put anything into the session that will be available to the user immediately after logging out, do that after calling django.contrib.auth.logout().
The auth framework uses two signals that can be used for notification when a user logs in or out.
Sent when a user logs in successfully.
Arguments sent with this signal:
Sent when the logout method is called.
Sent when the user failed to login successfully
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')
# ...
As a shortcut, you can use the convenient login_required() decorator:
from django.contrib.auth.decorators import login_required
@login_required
def my_view(request):
...
login_required() does the following:
By default, the path that the user should be redirected to upon successful authentication is stored in a query string parameter called "next". If you would prefer to use a different name for this parameter, login_required() takes an optional redirect_field_name parameter:
from django.contrib.auth.decorators import login_required
@login_required(redirect_field_name='my_redirect_field')
def my_view(request):
...
Note that if you provide a value to redirect_field_name, you will most likely need to customize your login template as well, since the template context variable which stores the redirect path will use the value of redirect_field_name as its key rather than "next" (the default).
login_required() also takes an optional login_url parameter. Example:
from django.contrib.auth.decorators import login_required
@login_required(login_url='/accounts/login/')
def my_view(request):
...
Note that if you don’t specify the login_url parameter, you’ll need to map the appropriate Django view to settings.LOGIN_URL. For example, using the defaults, add the following line to your URLconf:
(r'^accounts/login/$', 'django.contrib.auth.views.login'),
As of version 1.5 settings.LOGIN_URL now also accepts view function names and named URL patterns. This allows you to freely remap your login view within your URLconf without having to update the setting.
URL name: login
See the URL documentation for details on using named URL patterns.
Here’s what django.contrib.auth.views.login does:
It’s your responsibility to provide the login form in a template called registration/login.html by default. This template gets passed four template context variables:
If you’d prefer not to call the template registration/login.html, you can pass the template_name parameter via the extra arguments to the view in your URLconf. For example, this URLconf line would use myapp/login.html instead:
(r'^accounts/login/$', 'django.contrib.auth.views.login', {'template_name': 'myapp/login.html'}),
You can also specify the name of the GET field which contains the URL to redirect to after login by passing redirect_field_name to the view. By default, the field is called next.
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.errors %}
<p>Your username and password didn't match. Please try again.</p>
{% endif %}
<form method="post" action="{% url 'django.contrib.auth.views.login' %}">
{% csrf_token %}
<table>
<tr>
<td>{{ form.username.label_tag }}</td>
<td>{{ form.username }}</td>
</tr>
<tr>
<td>{{ form.password.label_tag }}</td>
<td>{{ form.password }}</td>
</tr>
</table>
<input type="submit" value="login" />
<input type="hidden" name="next" value="{{ next }}" />
</form>
{% endblock %}
If you are using alternate authentication (see Other authentication sources) you can pass a custom authentication form to the login view via the authentication_form parameter. This form must accept a request keyword argument in its __init__ method, and provide a get_user method which returns the authenticated user object (this method is only ever called after successful form validation).
The login() view and the Other built-in views now all return a TemplateResponse instance, which allows you to easily customize the response data before rendering. For more details, see the TemplateResponse documentation.
In addition to the login() view, the authentication system includes a few other useful built-in views located in django.contrib.auth.views:
Logs a user out.
URL name: logout
See the URL documentation for details on using named URL patterns.
Optional arguments:
Template context:
Logs a user out, then redirects to the login page.
URL name: No default URL provided
Optional arguments:
Allows a user to change their password.
URL name: password_change
Optional arguments:
Template context:
The page shown after a user has changed their password.
URL name: password_change_done
Optional arguments:
Allows a user to reset their password by generating a one-time use link that can be used to reset the password, and sending that link to the user’s registered email address.
URL name: password_reset
Optional arguments:
template_name: The full name of a template to use for displaying the password reset form. Defaults 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 reset password link. Defaults to registration/password_reset_email.html if not supplied.
subject_template_name: The full name of a template to use for the subject of the email with the reset password link. Defaults to registration/password_reset_subject.txt if not supplied.
password_reset_form: Form that will be used to get the email of the user to reset the password for. Defaults to PasswordResetForm.
token_generator: Instance of the class to check the one time link. This will default to default_token_generator, it’s an instance of django.contrib.auth.tokens.PasswordResetTokenGenerator.
post_reset_redirect: The URL to redirect to after a successful password reset request.
from_email: A valid email address. By default Django uses the DEFAULT_FROM_EMAIL.
Template context:
Email template context:
Sample registration/password_reset_email.html (email body template):
Someone asked for password reset for email {{ email }}. Follow the link below:
{{ protocol}}://{{ domain }}{% url 'password_reset_confirm' uidb36=uid token=token %}
The same template context is used for subject template. Subject must be single line plain text string.
The page shown after a user has been emailed a link to reset their password. This view is called by default if the password_reset() view doesn’t have an explicit post_reset_redirect URL set.
URL name: password_reset_done
Optional arguments:
Presents a form for entering a new password.
URL name: password_reset_confirm
Optional arguments:
Template context:
Presents a view which informs the user that the password has been successfully changed.
URL name: password_reset_complete
Optional arguments:
Redirects to the login page, and then back to another URL after a successful login.
Required arguments:
Optional arguments:
If you don’t want to use the built-in views, but want the convenience of not having to write forms for this functionality, the authentication system provides several built-in forms located in django.contrib.auth.forms:
A form used in the admin interface to change a user’s password.
A form for logging a user in.
A form for allowing a user to change their password.
A form for generating and emailing a one-time use link to reset a user’s password.
A form that lets a user change his/her password without entering the old password.
A form used in the admin interface to change a user’s information and permissions.
A form for creating a new user.
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.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
@user_passes_test(lambda u: u.has_perm('polls.can_vote'))
def my_view(request):
...
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.
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 (settings.LOGIN_URL by default).
For example:
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):
...
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
@permission_required('polls.can_vote')
def my_view(request):
...
As for the User.has_perm() method, permission names take the form "<app label>.<permission codename>" (i.e. polls.can_vote for a permission on a model in the polls application).
Note that permission_required() also takes an optional login_url parameter. Example:
from django.contrib.auth.decorators import permission_required
@permission_required('polls.can_vote', login_url='/loginpage/')
def my_view(request):
...
As in the login_required() decorator, login_url defaults to settings.LOGIN_URL.
Added raise_exception parameter. If given, the decorator will raise PermissionDenied, prompting the 403 (HTTP Forbidden) view instead of redirecting to the login page.
To apply a permission to a class-based generic view, decorate the View.dispatch method on the class. See Decorating the class for details.
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:
Permissions can be set not only per type of object, but also per specific object instance. By using the has_add_permission(), has_change_permission() and has_delete_permission() methods provided by the ModelAdmin class, it is possible to customize permissions for different object instances of the same type.
When django.contrib.auth is listed in your INSTALLED_APPS setting, it will ensure that three default permissions – add, change and delete – are created for each Django model defined in one of your installed applications.
These permissions will be created when you run manage.py syncdb; the first time you run syncdb after adding django.contrib.auth to INSTALLED_APPS, the default permissions will be created for all previously-installed models, as well as for any new models being installed at that time. Afterward, it will create default permissions for new models each time you run manage.py syncdb.
Assuming you have an application with an app_label foo and a model named Bar, to test for basic permissions you should use:
To create custom permissions for a given model object, use the permissions model Meta attribute.
This example Task model creates three custom permissions, i.e., actions users can or cannot do with Task instances, specific to your application:
class Task(models.Model):
...
class Meta:
permissions = (
("view_task", "Can see available tasks"),
("change_task_status", "Can change the status of tasks"),
("close_task", "Can remove a task by setting its status as closed"),
)
The only thing this does is create those extra permissions when you run manage.py syncdb. Your code is in charge of checking the value of these permissions when an user is trying to access the functionality provided by the application (viewing tasks, changing the status of tasks, closing tasks.) Continuing the above example, the following checks if a user may view tasks:
user.has_perm('app.view_task')
Permission objects have the following fields:
Required. 50 characters or fewer. Example: 'Can vote'.
Required. A reference to the django_content_type database table, which contains a record for each installed Django model.
Required. 100 characters or fewer. Example: 'can_vote'.
Permission objects have the standard data-access methods like any other Django model.
While custom permissions can be defined within a model’s Meta class, you can also create permissions directly. For example, you can create the can_publish permission for a BlogPost model in myapp:
from django.contrib.auth.models import Group, Permission
from django.contrib.contenttypes.models import ContentType
content_type = ContentType.objects.get(app_label='myapp', model='BlogPost')
permission = Permission.objects.create(codename='can_publish',
name='Can Publish Posts',
content_type=content_type)
The permission can then be assigned to a User via its user_permissions attribute or to a Group via its permissions attribute.
The currently logged-in user and his/her permissions are made available in the template context when you use RequestContext.
Technicality
Technically, these variables are only made available in the template context if you use RequestContext and your TEMPLATE_CONTEXT_PROCESSORS setting contains "django.contrib.auth.context_processors.auth", which is default. For more, see the RequestContext docs.
When rendering a template RequestContext, 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 %}
This template context variable is not available if a RequestContext is not being used.
The currently logged-in user’s permissions are stored in the template variable {{ perms }}. This is an instance of django.contrib.auth.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 %}
It is possible to also look permissions up by {% if in %} statements. For example:
{% if 'foo' in perms %}
{% if 'foo.can_vote' in perms %}
<p>In lookup works, too.</p>
{% endif %}
{% endif %}
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 email messages.
Group objects have the following fields:
Required. 80 characters or fewer. Any characters are permitted. Example: 'Awesome Users'.
Many-to-many field to Permissions:
group.permissions = [permission_list]
group.permissions.add(permission, permission, ...)
group.permissions.remove(permission, permission, ...)
group.permissions.clear()
Some kinds of projects may have authentication requirements for which Django’s built-in User model is not always appropriate. For instance, on some sites it makes more sense to use an email address as your identification token instead of a username.
Django allows you to override the default User model by providing a value for the AUTH_USER_MODEL setting that references a custom model:
AUTH_USER_MODEL = 'myapp.MyUser'
This dotted pair describes the name of the Django app, and the name of the Django model that you wish to use as your User model.
Warning
Changing AUTH_USER_MODEL has a big effect on your database structure. It changes the tables that are available, and it will affect the construction of foreign keys and many-to-many relationships. If you intend to set AUTH_USER_MODEL, you should set it before running manage.py syncdb for the first time.
If you have an existing project and you want to migrate to using a custom User model, you may need to look into using a migration tool like South to ease the transition.
If you reference User directly (for example, by referring to it in a foreign key), your code will not work in projects where the AUTH_USER_MODEL setting has been changed to a different User model.
Instead of referring to User directly, you should reference the user model using django.contrib.auth.get_user_model(). This method will return the currently active User model – the custom User model if one is specified, or User otherwise.
When you define a foreign key or many-to-many relations to the User model, you should specify the custom model using the AUTH_USER_MODEL setting. For example:
from django.conf import settings
from django.db import models
class Article(models.Model)
author = models.ForeignKey(settings.AUTH_USER_MODEL)
Model design considerations
Think carefully before handling information not directly related to authentication in your custom User Model.
It may be better to store app-specific user information in a model that has a relation with the User model. That allows each app to specify its own user data requirements without risking conflicts with other apps. On the other hand, queries to retrieve this related information will involve a database join, which may have an effect on performance.
Django expects your custom User model to meet some minimum requirements.
The easiest way to construct a compliant custom User model is to inherit from AbstractBaseUser. AbstractBaseUser provides the core implementation of a User model, including hashed passwords and tokenized password resets. You must then provide some key implementation details:
A string describing the name of the field on the User model that is used as the unique identifier. This will usually be a username of some kind, but it can also be an email address, or any other unique identifier. In the following example, the field identifier is used as the identifying field:
class MyUser(AbstractBaseUser):
identifier = models.CharField(max_length=40, unique=True, db_index=True)
...
USERNAME_FIELD = 'identifier'
A list of the field names that must be provided when creating a user. For example, here is the partial definition for a User model that defines two required fields - a date of birth and height:
class MyUser(AbstractBaseUser):
...
date_of_birth = models.DateField()
height = models.FloatField()
...
REQUIRED_FIELDS = ['date_of_birth', 'height']
Note
REQUIRED_FIELDS must contain all required fields on your User model, but should not contain the USERNAME_FIELD.
A boolean attribute that indicates whether the user is considered “active”. This attribute is provided as an attribute on AbstractBaseUser defaulting to True. How you choose to implement it will depend on the details of your chosen auth backends. See the documentation of the attribute on the builtin user model for details.
A longer formal identifier for the user. A common interpretation would be the full name name of the user, but it can be any string that identifies the user.
A short, informal identifier for the user. A common interpretation would be the first name of the user, but it can be any string that identifies the user in an informal way. It may also return the same value as django.contrib.auth.User.get_full_name().
The following methods are available on any subclass of AbstractBaseUser:
Returns the value of the field nominated by USERNAME_FIELD.
Always returns False. This is a way of differentiating from AnonymousUser objects. Generally, you should prefer using is_authenticated() to this method.
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.
Sets the user’s password to the given raw string, taking care of the password hashing. Doesn’t save the AbstractBaseUser object.
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.)
Marks the user as having no password set. This isn’t the same as having a blank string for a password. check_password() for this user will never return True. Doesn’t save the AbstractBaseUser object.
You may need this if authentication for your application takes place against an existing external source such as an LDAP directory.
Returns False if set_unusable_password() has been called for this user.
You should also define a custom manager for your User model. If your User model defines username and email fields the same as Django’s default User, you can just install Django’s UserManager; however, if your User model defines different fields, you will need to define a custom manager that extends BaseUserManager providing two additional methods:
The prototype of create_user() should accept the username field, plus all required fields as arguments. For example, if your user model uses email as the username field, and has date_of_birth as a required fields, then create_user should be defined as:
def create_user(self, email, date_of_birth, password=None):
# create user here
The prototype of create_superuser() should accept the username field, plus all required fields as arguments. For example, if your user model uses email as the username field, and has date_of_birth as a required fields, then create_superuser should be defined as:
def create_superuser(self, email, date_of_birth, password):
# create superuser here
Unlike create_user(), create_superuser() must require the caller to provider a password.
BaseUserManager provides the following utility methods:
A classmethod that normalizes email addresses by lowercasing the domain portion of the email address.
Retrieves a user instance using the contents of the field nominated by USERNAME_FIELD.
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 letters that can cause user confusion, including:
If you’re entirely happy with Django’s User model and you just want to add some additional profile information, you can simply subclass AbstractUser and add your custom profile fields.
As you may expect, built-in Django’s forms and views make certain assumptions about the user model that they are working with.
If your user model doesn’t follow the same assumptions, it may be necessary to define a replacement form, and pass that form in as part of the configuration of the auth views.
Depends on the User model. Must be re-written for any custom user model.
Depends on the User model. Must be re-written for any custom user model.
Works with any subclass of AbstractBaseUser, and will adapt to use the field defined in USERNAME_FIELD.
Assumes that the user model has an integer primary key, has a field named email that can be used to identify the user, and a boolean field named is_active to prevent password resets for inactive users.
Works with any subclass of AbstractBaseUser
Works with any subclass of AbstractBaseUser
Works with any subclass of AbstractBaseUser
If you want your custom User model to also work with Admin, your User model must define some additional attributes and methods. These methods allow the admin to control access of the User to admin content:
Returns True if the user is allowed to have access to the admin site.
Returns True if the user account is currently active.
Returns True if the user has the named permission. If obj is provided, the permission needs to be checked against a specific object instance.
Returns True if the user has permission to access models in the given app.
You will also need to register your custom User model with the admin. If your custom User model extends AbstractUser, you can use Django’s existing UserAdmin class. However, if your User model extends AbstractBaseUser, you’ll need to define a custom ModelAdmin class. It may be possible to subclass the default UserAdmin; however, you’ll need to override any of the definitions that refer to fields on AbstractUser that aren’t on your custom User class.
To make it easy to include Django’s permission framework into your own User class, Django provides PermissionsMixin. This is an abstract model you can include in the class heirarchy for your User model, giving you all the methods and database fields necessary to support Django’s permission model.
PermissionsMixin provides the following methods and attributes:
Boolean. Designates that this user has all permissions without explicitly assigning them.
Returns a set of permission strings that the user has, through his/her groups.
If obj is passed in, only returns the group permissions for this specific object.
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.
Returns True if the user has the specified permission, where perm is in the format "<app label>.<permission codename>" (see permissions). If the user is inactive, this method will always return False.
If obj is passed in, this method won’t check for a permission for the model, but for this specific object.
Returns True if the user has each of the specified permissions, where each perm is in the format "<app label>.<permission codename>". If the user is inactive, this method will always return False.
If obj is passed in, this method won’t check for permissions for the model, but for the specific object.
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.
ModelBackend
If you don’t include the PermissionsMixin, you must ensure you don’t invoke the permissions methods on ModelBackend. ModelBackend assumes that certain fields are available on your user model. If your User model doesn’t provide those fields, you will receive database errors when you check permissions.
One limitation of custom User models is that installing a custom User model will break any proxy model extending User. Proxy models must be based on a concrete base class; by defining a custom User model, you remove the ability of Django to reliably identify the base class.
If your project uses proxy models, you must either modify the proxy to extend the User model that is currently in use in your project, or merge your proxy’s behavior into your User subclass.
Another limitation of custom User models is that you can’t use django.contrib.auth.get_user_model() as the sender or target of a signal handler. Instead, you must register the handler with the actual User model.
If you are writing an application that interacts with the User model, you must take some precautions to ensure that your test suite will run regardless of the User model that is being used by a project. Any test that instantiates an instance of User will fail if the User model has been swapped out. This includes any attempt to create an instance of User with a fixture.
To ensure that your test suite will pass in any project configuration, django.contrib.auth.tests.utils defines a @skipIfCustomUser decorator. This decorator will cause a test case to be skipped if any User model other than the default Django user is in use. This decorator can be applied to a single test, or to an entire test class.
Depending on your application, tests may also be needed to be added to ensure that the application works with any user model, not just the default User model. To assist with this, Django provides two substitute user models that can be used in test suites:
You can then use the @override_settings decorator to make that test run with the custom User model. For example, here is a skeleton for a test that would test three possible User models – the default, plus the two User models provided by auth app:
from django.contrib.auth.tests.utils import skipIfCustomUser
from django.test import TestCase
from django.test.utils import override_settings
class ApplicationTestCase(TestCase):
@skipIfCustomUser
def test_normal_user(self):
"Run tests for the normal user model"
self.assertSomething()
@override_settings(AUTH_USER_MODEL='auth.CustomUser')
def test_custom_user(self):
"Run tests for a custom user model with email-based authentication"
self.assertSomething()
@override_settings(AUTH_USER_MODEL='auth.ExtensionUser')
def test_extension_user(self):
"Run tests for a simple extension of the built-in User."
self.assertSomething()
Here is an example of an admin-compliant custom user app. This user model uses an email address as the username, and has a required date of birth; it provides no permission checking, beyond a simple admin flag on the user account. This model would be compatible with all the built-in auth forms and views, except for the User creation forms.
This code would all live in a models.py file for a custom authentication app:
from django.db import models
from django.contrib.auth.models import (
BaseUserManager, AbstractBaseUser
)
class MyUserManager(BaseUserManager):
def create_user(self, email, date_of_birth, password=None):
"""
Creates and saves a User with the given email, date of
birth and password.
"""
if not email:
raise ValueError('Users must have an email address')
user = self.model(
email=MyUserManager.normalize_email(email),
date_of_birth=date_of_birth,
)
user.set_password(password)
user.save(using=self._db)
return user
def create_superuser(self, email, date_of_birth, password):
"""
Creates and saves a superuser with the given email, date of
birth and password.
"""
user = self.create_user(email,
password=password,
date_of_birth=date_of_birth
)
user.is_admin = True
user.save(using=self._db)
return user
class MyUser(AbstractBaseUser):
email = models.EmailField(
verbose_name='email address',
max_length=255,
unique=True,
db_index=True,
)
date_of_birth = models.DateField()
is_active = models.BooleanField(default=True)
is_admin = models.BooleanField(default=False)
objects = MyUserManager()
USERNAME_FIELD = 'email'
REQUIRED_FIELDS = ['date_of_birth']
def get_full_name(self):
# The user is identified by their email address
return self.email
def get_short_name(self):
# The user is identified by their email address
return self.email
def __unicode__(self):
return self.email
def has_perm(self, perm, obj=None):
"Does the user have a specific permission?"
# Simplest possible answer: Yes, always
return True
def has_module_perms(self, app_label):
"Does the user have permissions to view the app `app_label`?"
# Simplest possible answer: Yes, always
return True
@property
def is_staff(self):
"Is the user a member of staff?"
# Simplest possible answer: All admins are staff
return self.is_admin
Then, to register this custom User model with Django’s admin, the following code would be required in the app’s admin.py file:
from django import forms
from django.contrib import admin
from django.contrib.auth.models import Group
from django.contrib.auth.admin import UserAdmin
from django.contrib.auth.forms import ReadOnlyPasswordHashField
from customauth.models import MyUser
class UserCreationForm(forms.ModelForm):
"""A form for creating new users. Includes all the required
fields, plus a repeated password."""
password1 = forms.CharField(label='Password', widget=forms.PasswordInput)
password2 = forms.CharField(label='Password confirmation', widget=forms.PasswordInput)
class Meta:
model = MyUser
fields = ('email', 'date_of_birth')
def clean_password2(self):
# Check that the two password entries match
password1 = self.cleaned_data.get("password1")
password2 = self.cleaned_data.get("password2")
if password1 and password2 and password1 != password2:
raise forms.ValidationError("Passwords don't match")
return password2
def save(self, commit=True):
# Save the provided password in hashed format
user = super(UserCreationForm, self).save(commit=False)
user.set_password(self.cleaned_data["password1"])
if commit:
user.save()
return user
class UserChangeForm(forms.ModelForm):
"""A form for updating users. Includes all the fields on
the user, but replaces the password field with admin's
password hash display field.
"""
password = ReadOnlyPasswordHashField()
class Meta:
model = MyUser
def clean_password(self):
# Regardless of what the user provides, return the initial value.
# This is done here, rather than on the field, because the
# field does not have access to the initial value
return self.initial["password"]
class MyUserAdmin(UserAdmin):
# The forms to add and change user instances
form = UserChangeForm
add_form = UserCreationForm
# The fields to be used in displaying the User model.
# These override the definitions on the base UserAdmin
# that reference specific fields on auth.User.
list_display = ('email', 'date_of_birth', 'is_admin')
list_filter = ('is_admin',)
fieldsets = (
(None, {'fields': ('email', 'password')}),
('Personal info', {'fields': ('date_of_birth',)}),
('Permissions', {'fields': ('is_admin',)}),
('Important dates', {'fields': ('last_login',)}),
)
add_fieldsets = (
(None, {
'classes': ('wide',),
'fields': ('email', 'date_of_birth', 'password1', 'password2')}
),
)
search_fields = ('email',)
ordering = ('email',)
filter_horizontal = ()
# Now register the new UserAdmin...
admin.site.register(MyUser, MyUserAdmin)
# ... and, since we're not using Django's builtin permissions,
# unregister the Group model from admin.
admin.site.unregister(Group)
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 other authentication sources. You can override Django’s default database-based scheme, or you can use the default system in tandem with other systems.
See the authentication backend reference for information on the authentication backends included with Django.
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 backend that checks the Django users database and queries the builtin permissions. It does not provide protection against brute force attacks via any rate limiting mechanism. You may either implement your own rate limiting mechanism in a custom auth backend, or use the mechanisms provided by most Web servers.
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.
Note
Once a user has authenticated, Django stores which backend was used to authenticate the user in the user’s session, and re-uses the same backend for the duration of that session whenever access to the currently authenticated user is needed. This effectively means that authentication sources are cached on a per-session basis, so if you change AUTHENTICATION_BACKENDS, you’ll need to clear out session data if you need to force users to re-authenticate using different methods. A simple way to do that is simply to execute Session.objects.all().delete().
If a backend raises a PermissionDenied exception, authentication will immediately fail. Django won’t check the backends that follow.
An authentication backend is a class that implements two required methods: get_user(user_id) and authenticate(**credentials), as well as a set of optional permission related authorization methods.
The get_user method takes a user_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(object):
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(object):
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(object):
"""
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
Custom auth backends can provide their own permissions.
The user model will delegate permission lookup functions (get_group_permissions(), get_all_permissions(), has_perm(), and has_module_perms()) to any authentication backend that implements these functions.
The permissions given to the user will be the superset of all permissions returned by all backends. That is, Django grants a permission to a user that any one backend grants.
The simple backend above could implement permissions for the magic admin fairly simply:
class SettingsBackend(object):
# ...
def has_perm(self, user_obj, perm, obj=None):
if user_obj.username == settings.ADMIN_LOGIN:
return True
else:
return False
This gives full permissions to the user granted access in the above example. Notice that in addition to the same arguments given to the associated django.contrib.auth.models.User functions, the backend auth functions all take the user object, which may be an anonymous user, as an argument.
A full authorization implementation can be found in the ModelBackend class in django/contrib/auth/backends.py, which is the default backend and queries the auth_permission table most of the time. If you wish to provide custom behavior for only part of the backend API, you can take advantage of Python inheritence and subclass ModelBackend instead of implementing the complete API in a custom backend.
An anonymous user is one that is not authenticated i.e. they have provided no valid authentication details. However, that does not necessarily mean they are not authorized to do anything. At the most basic level, most Web sites authorize anonymous users to browse most of the site, and many allow anonymous posting of comments etc.
Django’s permission framework does not have a place to store permissions for anonymous users. However, the user object passed to an authentication backend may be an django.contrib.auth.models.AnonymousUser object, allowing the backend to specify custom authorization behavior for anonymous users. This is especially useful for the authors of re-usable apps, who can delegate all questions of authorization to the auth backend, rather than needing settings, for example, to control anonymous access.
An inactive user is a one that is authenticated but has its attribute is_active set to False. However this does not mean they are not authorized to do anything. For example they are allowed to activate their account.
The support for anonymous users in the permission system allows for a scenario where anonymous users have permissions to do something while inactive authenticated users do not.
Do not forget to test for the is_active attribute of the user in your own backend permission methods.
Django’s permission framework has a foundation for object permissions, though there is no implementation for it in the core. That means that checking for object permissions will always return False or an empty list (depending on the check performed). An authentication backend will receive the keyword parameters obj and user_obj for each object related authorization method and can return the object level permission as appropriate.
Dec 23, 2012