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Diffstat (limited to 'docs/api-guide/permissions.md')
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1 files changed, 86 insertions, 25 deletions
diff --git a/docs/api-guide/permissions.md b/docs/api-guide/permissions.md index 2c0a055c..8731cab0 100644 --- a/docs/api-guide/permissions.md +++ b/docs/api-guide/permissions.md @@ -1,4 +1,4 @@ -<a class="github" href="permissions.py"></a> +source: permissions.py # Permissions @@ -10,12 +10,24 @@ Together with [authentication] and [throttling], permissions determine whether a 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. + ## How permissions are determined -Permissions in REST framework are always defined as a list of permission classes. +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` exception will be raised, and the main body of the view will not run. +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 @@ -25,9 +37,23 @@ Object level permissions are run by REST framework's generic views when `.get_ob 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, -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. +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()) + self.check_object_permissions(self.request, obj) + return obj + +#### 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][filtering] appropriately, to ensure that users only have visibility onto instances that they are permitted to view. + ## Setting the permission policy The default permission policy may be set globally, using the `DEFAULT_PERMISSION_CLASSES` setting. For example. @@ -47,6 +73,10 @@ If not specified, this setting defaults to allowing unrestricted access: 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,) @@ -86,7 +116,7 @@ This permission is suitable if you want your API to only be accessible to regist 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 is you want your API to only be accessible to a subset of trusted administrators. +This permission is suitable if you want your API to only be accessible to a subset of trusted administrators. ## IsAuthenticatedOrReadOnly @@ -96,7 +126,7 @@ This permission is suitable if you want to your API to allow read permissions to ## DjangoModelPermissions -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. +This permission class ties into Django's standard `django.contrib.auth` [model permissions][contribauth]. This permission must only be applied to views that has a `.queryset` property set. 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. @@ -106,24 +136,35 @@ The default behaviour can also be overridden to support custom model permissions To use custom model permissions, override `DjangoModelPermissions` and set the `.perms_map` property. Refer to the source code for details. +#### Using with views that do not include a `queryset` attribute. + +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 sential queryset, so that this class can determine the required permissions. For example: + + queryset = User.objects.none() # Required for DjangoModelPermissions + ## DjangoModelPermissionsOrAnonReadOnly -Similar to `DjangoModelPermissions`, but also allows unauthenticated users to have read-only access to the API. +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]. -## TokenHasReadWriteScope +As with `DjangoModelPermissions`, this permission must only be applied to views that have a `.queryset` property. Authorization will only be granted if the user *is authenticated* and has the *relevant per-object permissions* and *relevant model permissions* assigned. -This permission class is intended for use with either of the `OAuthAuthentication` and `OAuth2Authentication` classes, and ties into the scoping that their backends provide. +* `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. -Requests with a safe methods of `GET`, `OPTIONS` or `HEAD` will be allowed if the authenticated token has read permission. +Note that `DjangoObjectPermissions` **does not** require the `django-guardian` package, and should support other object-level backends equally well. -Requests for `POST`, `PUT`, `PATCH` and `DELETE` will be allowed if the authenticated token has write permission. +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. -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`. +**Note**: If you need object level `view` permissions for `GET`, `HEAD` and `OPTIONS` requests, you'll want to consider also adding the `DjangoObjectPermissionsFilter` class to ensure that list endpoints only return results including objects for which the user has appropriate view permissions. -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. +--- --- @@ -145,11 +186,7 @@ If you need to test if a request is a read operation or a write operation, you s --- -**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 explict and obvious. The old style signature continues to work, but it's 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. - -For more details see the [2.2 release announcement][2.2-announcement]. +**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. --- @@ -157,6 +194,8 @@ For more details see the [2.2 release announcement][2.2-announcement]. 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. + from rest_framework import permissions + class BlacklistPermission(permissions.BasePermission): """ Global permission check for blacklisted IPs. @@ -178,9 +217,9 @@ As well as global permissions, that are run against all incoming requests, you c def has_object_permission(self, request, view, obj): # Read permissions are allowed to any request, # so we'll always allow GET, HEAD or OPTIONS requests. - if request.method in permissions.SAFE_METHODS: + if request.method in permissions.SAFE_METHODS: return True - + # Instance must have an attribute named `owner`. return obj.owner == request.user @@ -188,12 +227,34 @@ Note that the generic views will check the appropriate object level permissions, 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. +--- + +# Third party packages + +The following third party packages are also available. + +## DRF Any Permissions + +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. + +## Composed Permissions + +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. + +## REST Condition + +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. + [cite]: https://developer.apple.com/library/mac/#documentation/security/Conceptual/AuthenticationAndAuthorizationGuide/Authorization/Authorization.html [authentication]: authentication.md [throttling]: throttling.md -[contribauth]: https://docs.djangoproject.com/en/1.0/topics/auth/#permissions +[filtering]: filtering.md +[contribauth]: https://docs.djangoproject.com/en/dev/topics/auth/customizing/#custom-permissions +[objectpermissions]: https://docs.djangoproject.com/en/dev/topics/auth/customizing/#handling-object-permissions [guardian]: https://github.com/lukaszb/django-guardian -[django-oauth-plus]: http://code.larlet.fr/django-oauth-plus -[django-oauth2-provider]: https://github.com/caffeinehit/django-oauth2-provider +[get_objects_for_user]: http://pythonhosted.org/django-guardian/api/guardian.shortcuts.html#get-objects-for-user [2.2-announcement]: ../topics/2.2-announcement.md [filtering]: filtering.md +[drf-any-permissions]: https://github.com/kevin-brown/drf-any-permissions +[composed-permissions]: https://github.com/niwibe/djangorestframework-composed-permissions +[rest-condition]: https://github.com/caxap/rest_condition |