fix: gate OpenAI catch-all proxy behind ENABLE_OPENAI_API_PASSTHROUGH toggle (#23640)

The catch-all /{path:path} proxy forwards any request to the upstream OpenAI-compatible API with the admin's API key and no access control. This is an intentional proxy but should be opt-in.

Adds ENABLE_OPENAI_API_PASSTHROUGH env var (defaults to False). When disabled, the catch-all returns 403. No other routers (Ollama, responses) have catch-all proxies.

backend/open_webui/env.py

@@ -519,6 +519,11 @@ PASSWORD_VALIDATION_HINT = os.environ.get('PASSWORD_VALIDATION_HINT', '')
 
 BYPASS_MODEL_ACCESS_CONTROL = os.environ.get('BYPASS_MODEL_ACCESS_CONTROL', 'False').lower() == 'true'
 
+# When disabled (default), the OpenAI catch-all proxy endpoint (/{path:path})
+# is blocked. Enable only if you need direct passthrough to upstream OpenAI-
+# compatible APIs for endpoints not natively handled by Open WebUI.
+ENABLE_OPENAI_API_PASSTHROUGH = os.environ.get('ENABLE_OPENAI_API_PASSTHROUGH', 'False').lower() == 'true'
+
 WEBUI_AUTH_SIGNOUT_REDIRECT_URL = os.environ.get('WEBUI_AUTH_SIGNOUT_REDIRECT_URL', None)
 
 ####################################

backend/open_webui/routers/openai.py

@@ -12,7 +12,7 @@ import requests
 
 from azure.identity import DefaultAzureCredential, get_bearer_token_provider
 
-from fastapi import Depends, HTTPException, Request, APIRouter
+from fastapi import Depends, HTTPException, Request, APIRouter, status
 from fastapi.responses import (
     FileResponse,
     StreamingResponse,
@@ -40,6 +40,7 @@ from open_webui.env import (
     ENABLE_FORWARD_USER_INFO_HEADERS,
     FORWARD_SESSION_INFO_HEADER_CHAT_ID,
     BYPASS_MODEL_ACCESS_CONTROL,
+    ENABLE_OPENAI_API_PASSTHROUGH,
 )
 from open_webui.models.users import UserModel
 
@@ -1438,9 +1439,16 @@ async def responses(
 @router.api_route('/{path:path}', methods=['GET', 'POST', 'PUT', 'DELETE'])
 async def proxy(path: str, request: Request, user=Depends(get_verified_user)):
     """
-    Deprecated: proxy all requests to OpenAI API
+    Deprecated: proxy all requests to OpenAI API.
+    Disabled by default. Set ENABLE_OPENAI_API_PASSTHROUGH=True to enable.
     """
 
+    if not ENABLE_OPENAI_API_PASSTHROUGH:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail='Direct API passthrough is disabled. Set ENABLE_OPENAI_API_PASSTHROUGH=True to enable.',
+        )
+
     body = await request.body()
 
     # Parse JSON body to resolve model-based routing