flows: fix invalid background URL when using manually set static or http

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

authentik/flows/api/flows.py

@@ -1,6 +1,5 @@
 """Flow API Views"""
 from dataclasses import dataclass
-from typing import Optional
 
 from django.core.cache import cache
 from django.db.models import Model
@@ -11,7 +10,7 @@ from drf_spectacular.types import OpenApiTypes
 from drf_spectacular.utils import OpenApiResponse, extend_schema, inline_serializer
 from guardian.shortcuts import get_objects_for_user
 from rest_framework.decorators import action
-from rest_framework.fields import FileField
+from rest_framework.fields import FileField, ReadOnlyField
 from rest_framework.parsers import MultiPartParser
 from rest_framework.request import Request
 from rest_framework.response import Response
@@ -43,15 +42,7 @@ class FlowSerializer(ModelSerializer):
 
     cache_count = SerializerMethodField()
 
-    background = SerializerMethodField()
-
-    def get_background(self, instance: Flow) -> Optional[str]:
-        """When background was set to a URL, return the name as-is"""
-        if not instance.background:
-            return None
-        if instance.background.name.startswith("http"):
-            return instance.background.name
-        return instance.background.url
+    background = ReadOnlyField(source="background_url")
 
     def get_cache_count(self, flow: Flow) -> int:
         """Get count of cached flows"""
@@ -324,7 +315,7 @@ class FlowViewSet(ModelViewSet):
         url = request.data.get("url", None)
         if not url:
             return HttpResponseBadRequest()
-        flow.background = url
+        flow.background.name = url
         flow.save()
         return Response({})
 

authentik/flows/models.py

@@ -115,6 +115,18 @@ class Flow(SerializerModel, PolicyBindingModel):
         help_text=_("Background shown during execution"),
     )
 
+    @property
+    def background_url(self) -> Optional[str]:
+        """Get the URL to the background image. If the name is /static or starts with http
+        it is returned as-is"""
+        if not self.background:
+            return None
+        if self.background.name.startswith("http") or self.background.name.startswith(
+            "/static"
+        ):
+            return self.background.name
+        return self.background.url
+
     stages = models.ManyToManyField(Stage, through="FlowStageBinding", blank=True)
 
     @property

authentik/flows/stage.py

@@ -96,7 +96,7 @@ class ChallengeStageView(StageView):
         if "title" not in challenge.initial_data:
             challenge.initial_data["title"] = self.executor.flow.title
         if "background" not in challenge.initial_data:
-            challenge.initial_data["background"] = self.executor.flow.background.url
+            challenge.initial_data["background"] = self.executor.flow.background_url
         if isinstance(challenge, WithUserInfoChallenge):
             # If there's a pending user, update the `username` field
             # this field is only used by password managers.