providers/oidc: fix error when using with app_gw

passbook/lib/views.py

@@ -20,6 +20,5 @@ class CreateAssignPermView(CreateView):
                 self.object._meta.app_label,
                 self.object._meta.model_name,
             )
-            print(full_permission)
             assign_perm(full_permission, self.request.user, self.object)
         return response

passbook/providers/oidc/lib.py

@@ -1,21 +1,38 @@
 """OIDC Permission checking"""
+from typing import Optional
+
 from django.contrib import messages
+from django.http import HttpRequest, HttpResponse
 from django.shortcuts import redirect
+from oidc_provider.models import Client
 from structlog import get_logger
+from django.db.models.deletion import Collector
 
 from passbook.audit.models import Event, EventAction
-from passbook.core.models import Application
+from passbook.core.models import Application, User, Provider
 from passbook.policies.engine import PolicyEngine
 
 LOGGER = get_logger()
 
 
-def check_permissions(request, user, client):
+def check_permissions(
+    request: HttpRequest, user: User, client: Client
+) -> Optional[HttpResponse]:
     """Check permissions, used for
     https://django-oidc-provider.readthedocs.io/en/latest/
     sections/settings.html#oidc-after-userlogin-hook"""
     try:
-        application = client.openidprovider.application
+        # because oidc_provider is also used by app_gw, we can't be
+        # sure an OpenIDPRovider instance exists. hence we look through all related models
+        # and choose the one that inherits from Provider, which is guaranteed to
+        # have the application property
+        collector = Collector(using="default")
+        collector.collect([client])
+        for _, related in collector.data.items():
+            related_object = next(iter(related))
+            if isinstance(related_object, Provider):
+                application = related.application
+                break
     except Application.DoesNotExist:
         return redirect("passbook_providers_oauth:oauth2-permission-denied")
     LOGGER.debug(