REST Framework Roles

A security-centric DRF plugin aimed at decoupling permissions from your models and views in an easy intuitive manner. We believe views should hold business logic, not accessibility logic.

Features:

• Least privilege by default.
• Guard your application before a request reaches a view.
• Secure chained views (redirections), removing potential vulnerabilities.
• Backwards compatibility with DRF's permission_classes.
• Enforce decoupled and abstracted permission logic, away from models and views.

We provide view_permissions as an alternative to permission_classes, which in our opinion makes things more intuitive and with greater security. The combination of least-privilege by default and the decision of guarding directly views, covers edge cases that are not addressed in vanilla DRF (e.g. security holes via view redirections).

Note that DEFAULT_PERMISSIONS_CLASSES is patched so by default all endpoints will be denied access by simply installing this.

Installation

Install

pip install rest-framework-roles

Edit your settings.py file

INSTALLED_APPS = {
    ..
    'rest_framework',
    'rest_framework_roles',  # Must be after rest_framework
}

REST_FRAMEWORK_ROLES = {
  'ROLES': 'myproject.roles.ROLES',
}

Now all your endpoints default to 403 Forbidden unless you specifically use view_permissions or DRF's permission_classes in view classes.

By default endpoints from django.contrib won't be patched. If you wish to explicitly set what modules are skipped you can edit the SKIP_MODULES setting like below.

REST_FRAMEWORK_ROLES = {
  'ROLES': 'myproject.roles.ROLES',
  'SKIP_MODULES': [
    'django.*',
    'myproject.myapp55.*',
  ],
}

Setting permissions

First you need to define some roles like below

roles.py

from rest_framework_roles.roles import is_user, is_anon, is_admin


def is_buyer(request, view):
    return is_user(request, view) and request.user.usertype == 'buyer'

def is_seller(request, view):
    return is_user(request, view) and request.user.usertype == 'seller'


ROLES = {
    # Django out-of-the-box
    'admin': is_admin,
    'user': is_user,
    'anon': is_anon,

    # Some custom role examples
    'buyer': is_buyer,
    'seller': is_seller,
}

is_admin, is_user, etc. are simple functions that take request and view as parameters, similar to DRF's behaviour.

Next we need to define permissions for the views with view_permissions.

views.py

from rest_framework.viewsets import ModelViewSet
from rest_framework.decorators import action
from rest_framework_roles.granting import is_self


class UserViewSet(ModelViewSet):
    serializer_class = UserSerializer
    queryset = User.objects.all()
    view_permissions = {
        'create': {'anon': True},  # only anonymous visitors allowed
        'list': {'admin': True}, 
        'retrieve,me': {'user': is_self},
        'update,partial_update': {'user': is_self, 'admin': True},
    }

    @action(detail=False, methods=['get'])
    def me(self, request):
        self.kwargs['pk'] = request.user.pk
        return self.retrieve(request)

By default everyone is denied access to everything. So we need to 'whitelist' any views we want to give permission explicitly.

For redirections like me (which redirects to retrieve), we need to whitelist both or else we'll get 403 Forbidden.

In a view you can always check _view_permissions to see what permissions are in effect.

A request keeps track of all permissions checked so far. So redirections don't affect performance since the same permissions are never checked twice.

Advanced setup

Bypassing the framework

To fallback to the default DRF behaviour simply add permission_classes to a class like below.

class MyViewSet():
    permission_classes = [AllowAny]  # Default DRF (dangerous) behaviour

Granting permission

You can use the helper functions allof or anyof when deciding if a matched role should be granted access

from rest_framework_roles.granting import allof

def not_updating_email(request, view):
    return 'email' not in request.data

class UserViewSet(ModelViewSet):
    view_permissions = {
        'update,partial_update': {
            'user': allof(is_self, not_updating_email),
            'admin': True,
        },
    }

In the above example the user can only update their information only while not trying to update their email.

You can put all these functions inside a new file granting.py or just keep them close to the views, depending on what makes sense for your case. It's important to not mix them with the roles though to keeps things clean; (1) a role identifies someone making the request while (2) granting determines if the person fitting tha role should be granted permission for their request.

Keep in mind that someone can fit multiple roles. E.g. admin is also a user (unless you change the implementation of is_user and is_admin).

Optimizing role checking

You can change the order of how roles are checked. This makes sense if you want less frequent or expensive checks to happen prior to infrequent and slower ones.

from rest_framework_roles.decorators import role_checker


@role_checker(cost=0)
def is_freebie_user(request, view):
    return request.user.is_authenticated and request.user.plan == 'freebie'


@role_checker(cost=0)
def is_payed_user(request, view):
    return request.user.is_authenticated and not request.user.plan


@role_checker(cost=50)
def is_creator(request, view):
    obj = view.get_object()
    if hasattr(obj, 'creator'):
        return request.user == obj.creator
    return False

In this example, roles with cost 0 would be checked first, and lastly the creator role would be checked since it has the highest cost.

Note this is similar to Django REST's check_permissions and check_object_permissions but more generic & adjustable since you can have arbitrary number of costs (instead of 2).