fix(proxy): only re-authorize when the URL model overrides the body model

Gate the allowlist re-check so it runs only when the endpoint model from the URL
is present and differs from the body model auth already validated. A request
whose model comes from the body, or whose endpoint model equals it, was already
checked, so pass-through and search routes that resolve the body model are left
alone and only a real URL override is re-authorized.

Tracking issue: https://github.com/BerriAI/litellm/issues/48760

Signed-off-by: Atharva-Kanherkar <atharvakanherkar25@gmail.com>

litellm/proxy/common_request_processing.py

@@ -2373,9 +2373,11 @@ class ProxyBaseLLMRequestProcessing:
             kind="image_edit" if route_type == "aimage_edit" else "completion",
         )
         self.data["model"] = resolved_model
-        # Auth checked the body model; the endpoint model from the URL wins here, so
-        # authorize the resolved name before any alias rewrite.
-        if llm_router is not None:
+        # Auth read the body model (requested_model above). When the endpoint model from
+        # the URL overrides it, the served model was never checked, so authorize the
+        # resolved name here, before any alias rewrite. A request whose model came from
+        # the body was already checked by auth, so it is left alone.
+        if llm_router is not None and isinstance(model, str) and model and model != requested_model:
             await can_key_call_requested_models(
                 model=resolved_model, valid_token=user_api_key_dict, llm_router=llm_router
             )

litellm/proxy/image_endpoints/endpoints.py

@@ -123,13 +123,15 @@ async def image_generation(
         if isinstance(model, str):
             reject_url_valued_destination("model", model)
 
+        body_model: Final = data.get("model")  # pyright: ignore[reportUnknownMemberType, reportUnknownVariableType]  # data is an untyped dict body
         resolved_model: Final = resolve_inference_model(
-            data.get("model"), general_settings, user_model, model, kind="image_generation"
+            body_model, general_settings, user_model, model, kind="image_generation"
         )
         data["model"] = resolved_model
-        # Auth checked the body model; the deployment path model wins here, so
-        # authorize the resolved name before any alias rewrite.
-        if llm_router is not None:
+        # Auth read the body model. When the deployment or query model from the URL
+        # overrides it, the served model was never checked, so authorize the resolved
+        # name here, before any alias rewrite. A body model was already checked by auth.
+        if llm_router is not None and isinstance(model, str) and model and model != body_model:
             await can_key_call_requested_models(
                 model=resolved_model, valid_token=user_api_key_dict, llm_router=llm_router
             )