fix(proxy): apply full key/team/user filter on by-id /v1/model/info

Addresses veria-ai Finding 2 on #29748. The 5638d58e bypass keyed
off `user_api_key_dict.user_id is None` to short-circuit by-id
authorization, but service-account virtual keys can carry
`user_id=None` AND still have `models` / `team_models` restrictions
— so a restricted service account could pull metadata for any
deployment via `/v1/model/info?litellm_model_id=<disallowed-id>`.

Drop the explicit master-key short-circuit and call
`get_available_models_for_user` unconditionally — same call the
listing path uses. `_apply_user_models_filter` already bypasses
the user.models step when `user_id is None` (master key / service
account), but `get_key_models` + `get_team_models` still narrow
to the key/team allowlist for service accounts. By-id authorization
now tracks the listing path exactly.

Test fixes:
- `test_model_info_endpoint_returns_defaults_for_specific_model_id`:
  add the missing patches for `get_key_models` / `get_team_models` /
  `get_complete_model_list` + stub `mock_router.get_model_names` /
  `.get_model_access_groups` so by-id authorization sees a valid
  allowlist. 18/18 pass locally.

403 message broadened to "not authorized for this key/user" since
the rejection can fire on key/team restrictions, not just user.models.

litellm/proxy/proxy_server.py

@@ -13445,33 +13445,37 @@ async def model_info_v1(
                     "error": f"Model id = {litellm_model_id} not found on litellm proxy"
                 },
             )
-        # Authorize against user.models — by-id was previously
-        # short-circuiting before the listing-path filter. Master
-        # key / service accounts (no user_id) bypass, matching
-        # `_apply_user_models_filter` semantics.
-        if user_api_key_dict.user_id is not None:
-            from litellm.proxy.utils import get_available_models_for_user
+        # Authorize against key/team/user models — by-id was previously
+        # short-circuiting before the listing-path filter, letting a
+        # restricted virtual key (including service accounts with no
+        # user_id but with key.models or team_models constraints) pull
+        # metadata for any deployment via /v1/model/info?litellm_model_id=.
+        # Reuse `get_available_models_for_user` so by-id authorization
+        # tracks the listing-path filter exactly: key.models, team_models,
+        # and user.models all narrow the allowlist; `_apply_user_models_filter`
+        # bypasses the user.models step when user_id is absent.
+        from litellm.proxy.utils import get_available_models_for_user
 
-            authorized_models = await get_available_models_for_user(
-                user_api_key_dict=user_api_key_dict,
-                llm_router=llm_router,
-                general_settings=general_settings,
-                user_model=user_model,
-                prisma_client=prisma_client,
-                proxy_logging_obj=proxy_logging_obj,
-                team_id=None,
-                include_model_access_groups=False,
-                only_model_access_groups=False,
-                return_wildcard_routes=False,
-                user_api_key_cache=user_api_key_cache,
+        authorized_models = await get_available_models_for_user(
+            user_api_key_dict=user_api_key_dict,
+            llm_router=llm_router,
+            general_settings=general_settings,
+            user_model=user_model,
+            prisma_client=prisma_client,
+            proxy_logging_obj=proxy_logging_obj,
+            team_id=None,
+            include_model_access_groups=False,
+            only_model_access_groups=False,
+            return_wildcard_routes=False,
+            user_api_key_cache=user_api_key_cache,
+        )
+        if deployment_info.model_name not in authorized_models:
+            raise HTTPException(
+                status_code=403,
+                detail={
+                    "error": f"Model id = {litellm_model_id} not authorized for this key/user"
+                },
             )
-            if deployment_info.model_name not in authorized_models:
-                raise HTTPException(
-                    status_code=403,
-                    detail={
-                        "error": f"Model id = {litellm_model_id} not authorized for this user"
-                    },
-                )
         _deployment_info_dict = _get_proxy_model_info(
             model=deployment_info.model_dump(exclude_none=True)
         )

tests/test_litellm/proxy/test_model_info_default_limits.py

@@ -115,6 +115,11 @@ class TestModelInfoEndpointWithRouter:
 
         mock_router = MagicMock()
         mock_router.get_deployment.return_value = deployment
+        # By-id now authorizes against the listing-path filter; stub
+        # what `get_available_models_for_user` reads from the router so
+        # "model1" is in the allowlist.
+        mock_router.get_model_names.return_value = ["model1"]
+        mock_router.get_model_access_groups.return_value = {}
 
         user_api_key_dict = UserAPIKeyAuth(api_key="sk-test")
 
@@ -122,6 +127,14 @@ class TestModelInfoEndpointWithRouter:
             patch("litellm.proxy.proxy_server.llm_router", mock_router),
             patch("litellm.proxy.proxy_server.llm_model_list", []),
             patch("litellm.proxy.proxy_server.user_model", None),
+            patch("litellm.proxy.proxy_server.get_key_models", return_value=["model1"]),
+            patch(
+                "litellm.proxy.proxy_server.get_team_models", return_value=["model1"]
+            ),
+            patch(
+                "litellm.proxy.proxy_server.get_complete_model_list",
+                return_value=["model1"],
+            ),
         ):
             response = await model_info_v1(
                 user_api_key_dict=user_api_key_dict,