[loop-cycle-2] fix: resolve endpoint before execution in CSRF middleware (#626) (#656)

src/dashboard/middleware/csrf.py

@@ -175,15 +175,10 @@ class CSRFMiddleware(BaseHTTPMiddleware):
             return await call_next(request)
 
         # Token validation failed and path is not exempt
-        # We still need to call the app to check if the endpoint is decorated
-        # with @csrf_exempt, so we'll let it through and check after routing
-        response = await call_next(request)
-
-        # After routing, check if the endpoint is marked as exempt
-        endpoint = request.scope.get("endpoint")
+        # Resolve the endpoint WITHOUT executing it to check @csrf_exempt
+        endpoint = self._resolve_endpoint(request)
         if endpoint and is_csrf_exempt(endpoint):
-            # Endpoint is marked as exempt, allow the response
-            return response
+            return await call_next(request)
 
         # Endpoint is not exempt and token validation failed
         # Return 403 error
@@ -196,6 +191,41 @@ class CSRFMiddleware(BaseHTTPMiddleware):
             },
         )
 
+    def _resolve_endpoint(self, request: Request) -> Callable | None:
+        """Resolve the route endpoint without executing it.
+
+        Walks the Starlette/FastAPI router to find which endpoint function
+        handles this request, so we can check @csrf_exempt before any
+        side effects occur.
+
+        Returns:
+            The endpoint callable, or None if no route matched.
+        """
+        # If routing already happened (endpoint in scope), use it
+        endpoint = request.scope.get("endpoint")
+        if endpoint:
+            return endpoint
+
+        # Walk the middleware/app chain to find something with routes
+        from starlette.routing import Match
+
+        app = self.app
+        while app is not None:
+            if hasattr(app, "routes"):
+                for route in app.routes:
+                    match, _ = route.matches(request.scope)
+                    if match == Match.FULL:
+                        return getattr(route, "endpoint", None)
+            # Try .router (FastAPI stores routes on app.router)
+            if hasattr(app, "router") and hasattr(app.router, "routes"):
+                for route in app.router.routes:
+                    match, _ = route.matches(request.scope)
+                    if match == Match.FULL:
+                        return getattr(route, "endpoint", None)
+            app = getattr(app, "app", None)
+
+        return None
+
     def _is_likely_exempt(self, path: str) -> bool:
         """Check if a path is likely to be CSRF exempt.