> 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.
If any permission check fails an `exceptions.PermissionDenied` exception will be raised, and the main body of the view will not run.
## 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.
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.
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.
This permission is suitable is 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.
This permission class ties into Django's standard `django.contrib.auth` [model permissions][contribauth]. When applied to a view that has a `.model` property, 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.
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].
When applied to a view that has a `.model` property, 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 `DjangoModelPermissions` and setting the `.perms_map` property. Refer to the source code for details. Note that if you add a custom `view` permission for `GET`, `HEAD` and `OPTIONS` requests, you'll probably also want to consider adding the `DjangoObjectPermissionsFilter` class to ensure that list endpoints only return results including objects for which the user has appropriate view permissions.
This permission class is intended for use with either of the `OAuthAuthentication` and `OAuth2Authentication` classes, and ties into the scoping that their backends provide.
Requests with a safe methods of `GET`, `OPTIONS` or `HEAD` will be allowed if the authenticated token has read permission.
Requests for `POST`, `PUT`, `PATCH` and `DELETE` will be allowed if the authenticated token has write permission.
This permission class relies on the implementations of the [django-oauth-plus][django-oauth-plus] and [django-oauth2-provider][django-oauth2-provider] libraries, which both provide limited support for controlling the scope of access tokens:
*`django-oauth-plus`: Tokens are associated with a `Resource` class which has a `name`, `url` and `is_readonly` properties.
*`django-oauth2-provider`: Tokens are associated with a bitwise `scope` attribute, that defaults to providing bitwise values for `read` and/or `write`.
If you require more advanced scoping for your API, such as restricting tokens to accessing a subset of functionality of your API then you will need to provide a custom permission class. See the source of the `django-oauth-plus` or `django-oauth2-provider` package for more details on scoping token access.
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**: In versions 2.0 and 2.1, the signature for the permission checks always included an optional `obj` parameter, like so: `.has_permission(self, request, view, obj=None)`. The method would be called twice, first for the global permission checks, with no object supplied, and second for the object-level check when required.
As of version 2.2 this signature has now been replaced with two separate method calls, which is more explicit and obvious. The old style signature continues to work, but its use will result in a `PendingDeprecationWarning`, which is silent by default. In 2.3 this will be escalated to a `DeprecationWarning`, and in 2.4 the old-style signature will be removed.
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 [DRF Any Permissions][drf-any-permissions] packages provides a different permission behavior in contrast to REST framework. Instead of all specified permissions being required, only one of the given permissions has to be true in order to get access to the view.
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] yet another but simple and convenient extension for complex permissions tree. The extension allows to combine permissions with logical operators rules. Logical expressions can be used along with the usual permissions classes in api views.
