> Authentication or identification by itself is not usually sufficient to gain access to information or code. For that, the entity requesting access must have authorization.
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 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 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.
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.*
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.
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.
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][filtering] appropriately, to ensure that users only have visibility onto instances that they are permitted to view.
__Note:__ when you set new permission classes through class attribute or decorators you're telling the view to ignore the default list set over 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
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.
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.
This permission class ties into Django's standard `django.contrib.auth` [model permissions][contribauth]. This permission must only be applied to views that have a `.queryset` property set. Authorization will only be granted if the user *is authenticated* and has the *relevant model permissions* assigned.
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.
If you're using this permission with a view that uses an overridden `get_queryset()` method there may not be a `queryset` attribute on the view. In this case we suggest also marking the view with a sentinel queryset, so that this class can determine the required permissions. For example:
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][objectpermissions] 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][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.
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][django-rest-framework-guardian]. It ensures that list endpoints only return results including objects for which the user has appropriate view permissions.
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'`. For example:
**Note**: The instance-level `has_object_permission` method will only be called if the view-level `has_permission` checks have already passed. Also note that in order for the instance-level checks to run, the view code should explicitly call `.check_object_permissions(request, obj)`. If you are using the generic views then this will be handled for you by default. (Function-based views will need to check object permissions explicitly, raising `PermissionDenied` on failure.)
Custom permissions will raise a `PermissionDenied` exception if the test fails. To change the error message associated with the exception, implement a `message` attribute directly on your custom permission. Otherwise the `default_detail` attribute from `PermissionDenied` will be used.
The following is an example of a permission class that checks the incoming request's IP address against a blacklist, and denies the request if the IP has been blacklisted.
As well as global permissions, that are run against all incoming requests, you can also create object-level permissions, that are only run against operations that affect a particular object instance. For example:
class IsOwnerOrReadOnly(permissions.BasePermission):
"""
Object-level permission to only allow owners of an object to edit it.
Note that the generic views will check the appropriate object level permissions, but if you're writing your own custom views, you'll need to make sure you check the object level permission checks yourself. You can do so by calling `self.check_object_permissions(request, obj)` from the view once you have the object instance. This call will raise an appropriate `APIException` if any object-level permission checks fail, and will otherwise simply return.
Also note that the generic views will only check the object-level permissions for views that retrieve a single model instance. If you require object-level filtering of list views, you'll need to filter the queryset separately. See the [filtering documentation][filtering] for more details.
The [Composed Permissions][composed-permissions] package provides a simple way to define complex and multi-depth (with logic operators) permission objects, using small and reusable components.
The [REST Condition][rest-condition] package is another extension for building complex permissions in a simple and convenient way. The extension allows you to combine permissions with logical operators.
The [DRY Rest Permissions][dry-rest-permissions] package provides the ability to define different permissions for individual default and custom actions. This package is made for apps with permissions that are derived from relationships defined in the app's data model. It also supports permission checks being returned to a client app through the API's serializer. Additionally it supports adding permissions to the default and custom list actions to restrict the data they retrieve per user.
The [Django Rest Framework API Key][django-rest-framework-api-key] package allows you to ensure that every request made to the server requires an API key header. You can generate one from the django admin interface.
