django-cedar 0.1.0

Cedar policy-based authorization for Django

django-cedar

Cedar policy-based authorization for Django.

Cedar is an open-source policy language for expressive, analyzable permissions. django-cedar lets you express who can do what in Cedar policy files instead of scattering permission logic through your views, and enforces those policies with class-based-view mixins.

Requirements

• Python 3.12+
• Django 5.2+

Your user model must subclass django.contrib.auth.models.AbstractUser. The Cedar principal type is always User, regardless of the model's class name.

Installation

pip install django-cedar

Add the app (optional, but recommended — it enables startup-time configuration checks via Django's system check framework):

INSTALLED_APPS = [
    # ...
    "django_cedar",
]

Quickstart

1. Write a policy file (policies.cedar next to manage.py):

// Staff can do anything
permit(principal, action, resource)
when { principal.is_staff };

// Anyone signed in can view widgets
permit(principal is User, action == Action::"ViewWidget", resource);

2. Point Django at it:

CEDAR_POLICY_PATH = "policies.cedar"  # relative paths resolve against BASE_DIR

3. Enforce it in your views:

from django_cedar.views import AuthorizedDetailView

from .models import Widget


class WidgetDetailView(AuthorizedDetailView):
    model = Widget
    action_names = {"GET": "ViewWidget"}

Every request is authorized in dispatch(). The Cedar request is built as:

• principal — User::"<pk>" for authenticated users, Anonymous::"guest" otherwise. User entities carry id, is_staff and is_superuser attributes, and the user's Django groups become parent entities (Group::"<name>"), so principal in Group::"editors" works out of the box.
• action — Action::"<name>" from the view's action_names mapping (HTTP method → action name). HEAD requests are authorized using the view's "GET" action mapping; a "HEAD" key in action_names is not consulted.
• resource — the object returned by the view's get_resource() hook, as <ModelClass>::"<pk>"; System::"global" when there is no resource.

Denied requests raise django.core.exceptions.PermissionDenied (HTTP 403).

Views and mixins

Class	Resource used for the check
AuthorizedDetailView / AuthorizedUpdateView / AuthorizedDeleteView	self.get_object()
AuthorizedListView / AuthorizedCreateView / AuthorizedTemplateView / AuthorizedFormView	System::"global" (override get_resource())

Compose the behavior yourself with CedarAuthorizationMixin plus:

• ResourceIsCurrentObjectMixin — authorize against self.get_object().
• CurrentUserScopedMixin — authorize against the current user and filter the queryset to user=<request.user>.
• AsyncLoginRequiredMixin — a LoginRequiredMixin that works on async views. CedarAuthorizationMixin itself supports async views too.

Custom scoping is one method:

class ProjectScopedView(CedarAuthorizationMixin, ListView):
    action_names = {"GET": "ListTasks"}

    def get_resource(self, request):
        return Project.objects.get(pk=self.kwargs["project_pk"])

Exposing model attributes to policies

Models opt in to exposing attributes with authz_fields(), and pull related entities into the request with authz_related_entities():

class Task(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    status = models.CharField(max_length=20)

    def authz_fields(self):
        return {"status": self.status, "project": str(self.project_id)}

    def authz_related_entities(self):
        return [self.project]

permit(principal, action == Action::"CloseTask", resource is Task)
when { resource.status == "open" };

Settings

Setting	Required	Description
CEDAR_POLICY_PATH	yes	Path to the Cedar policy file. Relative paths resolve against BASE_DIR.
CEDAR_PRINCIPAL_ATTRIBUTE_PROVIDERS	no	List of dotted paths to classes with get_attributes(user) -> dict (extra principal attributes) and optionally get_entities(user) -> iterable[Entity] (extra entities).
CEDAR_CONTEXT_PROVIDERS	no	List of dotted paths to classes with get_context(user, action, resource) -> dict. Results are deep-merged into the Cedar request context in list order; a per-call context= argument merges last and wins.

Example context provider:

class FeatureFlagContext:
    def get_context(self, user, action, resource):
        return {"allow": {"self_signup": settings.ALLOW_SELF_SIGNUP}}

Using the engine directly

from django_cedar import create_authz

authz = create_authz()  # loads policies + providers from settings (cached)
authz.authorize(request.user, "ExportReport", report)  # raises PermissionDenied on deny

System checks

With django_cedar in INSTALLED_APPS, manage.py check (and every server start) verifies that CEDAR_POLICY_PATH is set and the file exists (django_cedar.E001/E002), that it parses as Cedar (E003), that the provider settings are lists or tuples (E006), and that all configured providers import and have the right methods (E004/E005).

License

Apache-2.0