Django_rest_permissions

Together with authentication and throttling, permissions determine whether a request should be granted or denied access.

Permission checks are always run at the very start of the view, before any other code is allowed to proceed. Permission checks will typically use the authentication information in the request.user and request.auth properties to determine if the incoming request should be permitted.

Permissions are used to grant or deny access for different classes of users to different parts of the API.

The simplest style of permission would be to allow access to any authenticated user, and deny access to any unauthenticated user. This corresponds to the IsAuthenticated class in REST framework.

A slightly less strict style of permission would be to allow full access to authenticated users, but allow read-only access to unauthenticated users. This corresponds to the IsAuthenticatedOrReadOnly class in REST framework.

How permissions are determined

Permissions in REST framework are always defined as a list of permission classes.
Before running the main body of the view each permission in the list is checked. If any permission check fails an exceptions.PermissionDenied or exceptions.NotAuthenticated exception will be raised, and the main body of the view will not run.
When the permissions checks fail either a “403 Forbidden” or a “401 Unauthorized” response will be returned, according to the following rules:

The request was successfully authenticated, but permission was denied. — An HTTP 403 Forbidden response will be returned.

The request was not successfully authenticated, and the highest priority authentication class does not use WWW-Authenticate headers. — An HTTP 403 Forbidden response will be returned.

The request was not successfully authenticated, and the highest priority authentication class does use WWW-Authenticate headers. — An HTTP 401 Unauthorized response, with an appropriate WWW-Authenticate header will be returned.

Object level permissions

REST framework permissions also support object-level permissioning. Object level permissions are used to determine if a user should be allowed to act on a particular object, which will typically be a model instance.

Object level permissions are run by REST framework’s generic views when .get_object() is called. As with view level permissions, an exceptions.PermissionDenied exception will be raised if the user is not allowed to act on the given object.

If you’re writing your own views and want to enforce object level permissions, or if you override the get_object method on a generic view, then you’ll need to explicitly call the .check_object_permissions(request, obj) method on the view at the point at which you’ve retrieved the object.

This will either raise a PermissionDenied or NotAuthenticated exception, or simply return if the view has the appropriate permissions.

For example:

def get_object(self):
    obj = get_object_or_404(self.get_queryset(), pk=self.kwargs["pk"])
    self.check_object_permissions(self.request, obj)
    return obj

Note: With the exception of DjangoObjectPermissions, the provided permission classes in rest_framework.permissions do not implement the methods necessary to check object permissions.

If you wish to use the provided permission classes in order to check object permissions, you must subclass them and implement the has_object_permission() method described in the Custom permissions section (below).

Limitations of object level permissions

For performance reasons the generic views will not automatically apply object level permissions to each instance in a queryset when returning a list of objects.

Often when you’re using object level permissions you’ll also want to filter the queryset appropriately, to ensure that users only have visibility onto instances that they are permitted to view.

Because the get_object() method is not called, object level permissions from the has_object_permission() method are not applied when creating objects. In order to restrict object creation you need to implement the permission check either in your Serializer class or override the perform_create() method of your ViewSet class.

Setting the permission policy

The default permission policy may be set globally, using the DEFAULT_PERMISSION_CLASSES setting. For example.

REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': [
        'rest_framework.permissions.IsAuthenticated',
    ]
}

If not specified, this setting defaults to allowing unrestricted access:

'DEFAULT_PERMISSION_CLASSES': [
   'rest_framework.permissions.AllowAny',
]

You can also set the authentication policy on a per-view, or per-viewset basis, using the APIView class-based views.

from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

class ExampleView(APIView):
    permission_classes = [IsAuthenticated]

    def get(self, request, format=None):
        content = {
            'status': 'request was permitted'
        }
        return Response(content)

Or, if you’re using the @api_view decorator with function based views.

from rest_framework.decorators import api_view, permission_classes
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response

@api_view(['GET'])
@permission_classes([IsAuthenticated])
def example_view(request, format=None):
    content = {
        'status': 'request was permitted'
    }
    return Response(content)

Note: when you set new permission classes via the class attribute or decorators you’re telling the view to ignore the default list set in the settings.py file.

Provided they inherit from rest_framework.permissions.BasePermission, permissions can be composed using standard Python bitwise operators. For example, IsAuthenticatedOrReadOnly could be written:

from rest_framework.permissions import BasePermission, IsAuthenticated, SAFE_METHODS
from rest_framework.response import Response
from rest_framework.views import APIView

class ReadOnly(BasePermission):
    def has_permission(self, request, view):
        return request.method in SAFE_METHODS

class ExampleView(APIView):
    permission_classes = [IsAuthenticated|ReadOnly]

    def get(self, request, format=None):
        content = {
            'status': 'request was permitted'
        }
        return Response(content)

_Note: it supports & (and),

(or) and ~ (not)._

AllowAny

The AllowAny permission class will allow unrestricted access, regardless of if the request was authenticated or unauthenticated.

This permission is not strictly required, since you can achieve the same result by using an empty list or tuple for the permissions setting, but you may find it useful to specify this class because it makes the intention explicit.

IsAuthenticated

The IsAuthenticated permission class will deny permission to any unauthenticated user, and allow permission otherwise.

This permission is suitable if you want your API to only be accessible to registered users.

IsAdminUser

The IsAdminUser permission class will deny permission to any user, unless user.is_staff is True in which case permission will be allowed.

This permission is suitable if you want your API to only be accessible to a subset of trusted administrators.

IsAuthenticatedOrReadOnly

The IsAuthenticatedOrReadOnly will allow authenticated users to perform any request. Requests for unauthorised users will only be permitted if the request method is one of the “safe” methods; GET, HEAD or OPTIONS.

This permission is suitable if you want to your API to allow read permissions to anonymous users, and only allow write permissions to authenticated users.

DjangoModelPermissions

This permission class ties into Django’s standard django.contrib.auth model permissions. This permission must only be applied to views that have a .queryset property or get_queryset() method. Authorization will only be granted if the user is authenticated and has the relevant model permissions assigned.

POST requests require the user to have the add permission on the model.

PUT and PATCH requests require the user to have the change permission on the model.

DELETE requests require the user to have the delete permission on the model.

The default behaviour can also be overridden to support custom model permissions. For example, you might want to include a view model permission for GET requests.

To use custom model permissions, override DjangoModelPermissions and set the .perms_map property. Refer to the source code for details.

DjangoModelPermissionsOrAnonReadOnly

Similar to DjangoModelPermissions, but also allows unauthenticated users to have read-only access to the API.

DjangoObjectPermissions

This permission class ties into Django’s standard object permissions framework that allows per-object permissions on models. In order to use this permission class, you’ll also need to add a permission backend that supports object-level permissions, such as django-guardian.

As with DjangoModelPermissions, this permission must only be applied to views that have a .queryset property or .get_queryset() method. Authorization will only be granted if the user is authenticated and has the relevant per-object permissions and relevant model permissions assigned.

POST requests require the user to have the add permission on the model instance.

PUT and PATCH requests require the user to have the change permission on the model instance.

DELETE requests require the user to have the delete permission on the model instance.

Note that DjangoObjectPermissions does not require the django-guardian package, and should support other object-level backends equally well.

As with DjangoModelPermissions you can use custom model permissions by overriding DjangoObjectPermissions and setting the .perms_map property. Refer to the source code for details.

Note: If you need object level view permissions for GET, HEAD and OPTIONS requests and are using django-guardian for your object-level permissions backend, you’ll want to consider using the DjangoObjectPermissionsFilter class provided by the djangorestframework-guardian package. It ensures that list endpoints only return results including objects for which the user has appropriate view permissions.

Custom permissions

To implement a custom permission, override BasePermission and implement either, or both, of the following methods:

.has_permission(self, request, view)

.has_object_permission(self, request, view, obj)

The methods should return True if the request should be granted access, and False otherwise.

If you need to test if a request is a read operation or a write operation, you should check the request method against the constant SAFE_METHODS, which is a tuple containing ‘GET’, ‘OPTIONS’ and ‘HEAD’.