API: add endpoint to show by what objects an object is used (#995)

* core: add used_by API to show what objects are affected before deletion

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* web/elements: add support for used_by API

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* core: add authentik_used_by_shadows to shadow other models

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* web: implement used_by API

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* *: fix duplicate imports

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* core: add action field to used_by api

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* web: add UI for used_by action

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* web: add notice to tenant form

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* core: fix naming in used_by

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* web: check length for used_by

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* core: fix used_by for non-pk models

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* *: improve __str__ on models

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* core: add support for many to many in used_by

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/core/api/applications.py

@@ -29,6 +29,7 @@ from structlog.stdlib import get_logger
 from authentik.admin.api.metrics import CoordinateSerializer, get_events_per_1h
 from authentik.api.decorators import permission_required
 from authentik.core.api.providers import ProviderSerializer
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.models import Application, User
 from authentik.events.models import EventAction
 from authentik.policies.api.exec import PolicyTestResultSerializer
@@ -73,7 +74,7 @@ class ApplicationSerializer(ModelSerializer):
         }
 
 
-class ApplicationViewSet(ModelViewSet):
+class ApplicationViewSet(UsedByMixin, ModelViewSet):
     """Application Viewset"""
 
     queryset = Application.objects.all()

authentik/core/api/authenticated_sessions.py

@@ -11,6 +11,7 @@ from rest_framework.serializers import ModelSerializer
 from rest_framework.viewsets import GenericViewSet
 from ua_parser import user_agent_parser
 
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.models import AuthenticatedSession
 from authentik.events.geo import GEOIP_READER, GeoIPDict
 
@@ -92,6 +93,7 @@ class AuthenticatedSessionSerializer(ModelSerializer):
 class AuthenticatedSessionViewSet(
     mixins.RetrieveModelMixin,
     mixins.DestroyModelMixin,
+    UsedByMixin,
     mixins.ListModelMixin,
     GenericViewSet,
 ):

authentik/core/api/groups.py

@@ -5,6 +5,7 @@ from rest_framework.serializers import ModelSerializer
 from rest_framework.viewsets import ModelViewSet
 from rest_framework_guardian.filters import ObjectPermissionsFilter
 
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import is_dict
 from authentik.core.models import Group
 
@@ -20,7 +21,7 @@ class GroupSerializer(ModelSerializer):
         fields = ["pk", "name", "is_superuser", "parent", "users", "attributes"]
 
 
-class GroupViewSet(ModelViewSet):
+class GroupViewSet(UsedByMixin, ModelViewSet):
     """Group Viewset"""
 
     queryset = Group.objects.all()

authentik/core/api/propertymappings.py

@@ -14,6 +14,7 @@ from rest_framework.serializers import ModelSerializer, SerializerMethodField
 from rest_framework.viewsets import GenericViewSet
 
 from authentik.api.decorators import permission_required
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import (
     MetaNameSerializer,
     PassiveSerializer,
@@ -65,6 +66,7 @@ class PropertyMappingSerializer(ManagedSerializer, ModelSerializer, MetaNameSeri
 class PropertyMappingViewSet(
     mixins.RetrieveModelMixin,
     mixins.DestroyModelMixin,
+    UsedByMixin,
     mixins.ListModelMixin,
     GenericViewSet,
 ):

authentik/core/api/providers.py

@@ -9,6 +9,7 @@ from rest_framework.response import Response
 from rest_framework.serializers import ModelSerializer, SerializerMethodField
 from rest_framework.viewsets import GenericViewSet
 
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import MetaNameSerializer, TypeCreateSerializer
 from authentik.core.models import Provider
 from authentik.lib.utils.reflection import all_subclasses
@@ -48,6 +49,7 @@ class ProviderSerializer(ModelSerializer, MetaNameSerializer):
 class ProviderViewSet(
     mixins.RetrieveModelMixin,
     mixins.DestroyModelMixin,
+    UsedByMixin,
     mixins.ListModelMixin,
     GenericViewSet,
 ):

authentik/core/api/sources.py

@@ -10,6 +10,7 @@ from rest_framework.serializers import ModelSerializer, SerializerMethodField
 from rest_framework.viewsets import GenericViewSet
 from structlog.stdlib import get_logger
 
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import MetaNameSerializer, TypeCreateSerializer
 from authentik.core.models import Source
 from authentik.core.types import UserSettingSerializer
@@ -52,6 +53,7 @@ class SourceSerializer(ModelSerializer, MetaNameSerializer):
 class SourceViewSet(
     mixins.RetrieveModelMixin,
     mixins.DestroyModelMixin,
+    UsedByMixin,
     mixins.ListModelMixin,
     GenericViewSet,
 ):

authentik/core/api/tokens.py

@@ -9,6 +9,7 @@ from rest_framework.serializers import ModelSerializer
 from rest_framework.viewsets import ModelViewSet
 
 from authentik.api.decorators import permission_required
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.users import UserSerializer
 from authentik.core.api.utils import PassiveSerializer
 from authentik.core.models import Token, TokenIntents
@@ -43,7 +44,7 @@ class TokenViewSerializer(PassiveSerializer):
     key = CharField(read_only=True)
 
 
-class TokenViewSet(ModelViewSet):
+class TokenViewSet(UsedByMixin, ModelViewSet):
     """Token Viewset"""
 
     lookup_field = "identifier"

authentik/core/api/used_by.py

@@ -0,0 +1,102 @@
+"""used_by mixin"""
+from enum import Enum
+from inspect import getmembers
+
+from django.db.models.base import Model
+from django.db.models.deletion import SET_DEFAULT, SET_NULL
+from django.db.models.manager import Manager
+from drf_spectacular.utils import extend_schema
+from guardian.shortcuts import get_objects_for_user
+from rest_framework.decorators import action
+from rest_framework.fields import CharField, ChoiceField
+from rest_framework.request import Request
+from rest_framework.response import Response
+
+from authentik.core.api.utils import PassiveSerializer
+
+
+class DeleteAction(Enum):
+    """Which action a delete will have on a used object"""
+
+    CASCADE = "cascade"
+    CASCADE_MANY = "cascade_many"
+    SET_NULL = "set_null"
+    SET_DEFAULT = "set_default"
+
+
+class UsedBySerializer(PassiveSerializer):
+    """A list of all objects referencing the queried object"""
+
+    app = CharField()
+    model_name = CharField()
+    pk = CharField()
+    name = CharField()
+    action = ChoiceField(choices=[(x.name, x.name) for x in DeleteAction])
+
+
+def get_delete_action(manager: Manager) -> str:
+    """Get the delete action from the Foreign key, falls back to cascade"""
+    if hasattr(manager, "field"):
+        if manager.field.remote_field.on_delete.__name__ == SET_NULL.__name__:
+            return DeleteAction.SET_NULL.name
+        if manager.field.remote_field.on_delete.__name__ == SET_DEFAULT.__name__:
+            return DeleteAction.SET_DEFAULT.name
+    if hasattr(manager, "source_field"):
+        return DeleteAction.CASCADE_MANY.name
+    return DeleteAction.CASCADE.name
+
+
+class UsedByMixin:
+    """Mixin to add a used_by endpoint to return a list of all objects using this object"""
+
+    @extend_schema(
+        responses={200: UsedBySerializer(many=True)},
+    )
+    @action(detail=True, pagination_class=None, filter_backends=[])
+    # pylint: disable=invalid-name, unused-argument, too-many-locals
+    def used_by(self, request: Request, *args, **kwargs) -> Response:
+        """Get a list of all objects that use this object"""
+        # pyright: reportGeneralTypeIssues=false
+        model: Model = self.get_object()
+        used_by = []
+        shadows = []
+        for attr_name, manager in getmembers(model, lambda x: isinstance(x, Manager)):
+            if attr_name == "objects":  # pragma: no cover
+                continue
+            manager: Manager
+            if manager.model._meta.abstract:
+                continue
+            app = manager.model._meta.app_label
+            model_name = manager.model._meta.model_name
+            delete_action = get_delete_action(manager)
+
+            # To make sure we only apply shadows when there are any objects,
+            # but so we only apply them once, have a simple flag for the first object
+            first_object = True
+
+            for obj in get_objects_for_user(
+                request.user, f"{app}.view_{model_name}", manager
+            ).all():
+                # Only merge shadows on first object
+                if first_object:
+                    shadows += getattr(
+                        manager.model._meta, "authentik_used_by_shadows", []
+                    )
+                first_object = False
+                serializer = UsedBySerializer(
+                    data={
+                        "app": app,
+                        "model_name": model_name,
+                        "pk": str(obj.pk),
+                        "name": str(obj),
+                        "action": delete_action,
+                    }
+                )
+                serializer.is_valid()
+                used_by.append(serializer.data)
+        # Check the shadows map and remove anything that should be shadowed
+        for idx, user in enumerate(used_by):
+            full_model_name = f"{user['app']}.{user['model_name']}"
+            if full_model_name in shadows:
+                del used_by[idx]
+        return Response(used_by)

authentik/core/api/users.py

@@ -25,6 +25,7 @@ from rest_framework_guardian.filters import ObjectPermissionsFilter
 from authentik.admin.api.metrics import CoordinateSerializer, get_events_per_1h
 from authentik.api.decorators import permission_required
 from authentik.core.api.groups import GroupSerializer
+from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import LinkSerializer, PassiveSerializer, is_dict
 from authentik.core.middleware import (
     SESSION_IMPERSONATE_ORIGINAL_USER,
@@ -131,7 +132,7 @@ class UsersFilter(FilterSet):
         fields = ["username", "name", "is_active", "is_superuser", "attributes"]
 
 
-class UserViewSet(ModelViewSet):
+class UserViewSet(UsedByMixin, ModelViewSet):
     """User Viewset"""
 
     queryset = User.objects.none()