Add GATEWAY_SECRET support for MCP server to API gateway auth (#721)

Pass bearer token from GATEWAY_SECRET environment variable as a
URL query parameter on websocket connections to the API gateway.
When unset or empty, no auth is applied (backwards compatible).

trustgraph-mcp/trustgraph/mcp_server/mcp.py

@@ -24,9 +24,10 @@ from . tg_socket import WebSocketManager
 class AppContext:
     sockets: dict[str, WebSocketManager]
     websocket_url: str
+    gateway_token: str
 
 @asynccontextmanager
-async def app_lifespan(server: FastMCP, websocket_url: str = "ws://api-gateway:8088/api/v1/socket") -> AsyncIterator[AppContext]:
+async def app_lifespan(server: FastMCP, websocket_url: str = "ws://api-gateway:8088/api/v1/socket", gateway_token: str = "") -> AsyncIterator[AppContext]:
 
     """
     Manage application lifecycle with type-safe context
@@ -36,7 +37,7 @@ async def app_lifespan(server: FastMCP, websocket_url: str = "ws://api-gateway:8
     sockets = {}
 
     try:
-        yield AppContext(sockets=sockets, websocket_url=websocket_url)
+        yield AppContext(sockets=sockets, websocket_url=websocket_url, gateway_token=gateway_token)
     finally:
 
         # Cleanup on shutdown
@@ -53,15 +54,16 @@ async def get_socket_manager(ctx, user):
     lifespan_context = ctx.request_context.lifespan_context
     sockets = lifespan_context.sockets
     websocket_url = lifespan_context.websocket_url
+    gateway_token = lifespan_context.gateway_token
 
     if user in sockets:
         logging.info("Return existing socket manager")
         return sockets[user]
 
     logging.info(f"Opening socket to {websocket_url}...")
-    
+
     # Create manager with empty pending requests
-    manager = WebSocketManager(websocket_url)
+    manager = WebSocketManager(websocket_url, token=gateway_token)
     
     # Start reader task with the proper manager
     await manager.start()
@@ -193,13 +195,14 @@ class GetSystemPromptResponse:
     prompt: str
 
 class McpServer:
-    def __init__(self, host: str = "0.0.0.0", port: int = 8000, websocket_url: str = "ws://api-gateway:8088/api/v1/socket"):
+    def __init__(self, host: str = "0.0.0.0", port: int = 8000, websocket_url: str = "ws://api-gateway:8088/api/v1/socket", gateway_token: str = ""):
         self.host = host
         self.port = port
         self.websocket_url = websocket_url
-        
+        self.gateway_token = gateway_token
+
         # Create a partial function to pass websocket_url to app_lifespan
-        lifespan_with_url = partial(app_lifespan, websocket_url=websocket_url)
+        lifespan_with_url = partial(app_lifespan, websocket_url=websocket_url, gateway_token=gateway_token)
         
         self.mcp = FastMCP(
             "TrustGraph", dependencies=["trustgraph-base"],
@@ -2060,8 +2063,11 @@ def main():
     # Setup logging before creating server
     setup_logging(vars(args))
 
+    # Read gateway auth token from environment
+    gateway_token = os.environ.get("GATEWAY_SECRET", "")
+
     # Create and run the MCP server
-    server = McpServer(host=args.host, port=args.port, websocket_url=args.websocket_url)
+    server = McpServer(host=args.host, port=args.port, websocket_url=args.websocket_url, gateway_token=gateway_token)
     server.run()
 
 def run():

trustgraph-mcp/trustgraph/mcp_server/tg_socket.py

@@ -1,6 +1,7 @@
 
 from dataclasses import dataclass
 from websockets.asyncio.client import connect
+from urllib.parse import urlencode, urlparse, urlunparse, parse_qs
 import asyncio
 import logging
 import json
@@ -9,12 +10,22 @@ import time
 
 class WebSocketManager:
 
-    def __init__(self, url):
+    def __init__(self, url, token=None):
         self.url = url
+        self.token = token
         self.socket = None
 
+    def _build_url(self):
+        if not self.token:
+            return self.url
+        parsed = urlparse(self.url)
+        params = parse_qs(parsed.query)
+        params["token"] = [self.token]
+        new_query = urlencode(params, doseq=True)
+        return urlunparse(parsed._replace(query=new_query))
+
     async def start(self):
-        self.socket = await connect(self.url)
+        self.socket = await connect(self._build_url())
         self.pending_requests = {}
         self.running = True
         self.reader_task = asyncio.create_task(self.reader())