feat(host-agent): add BearerAuthMiddleware for MCP server

apps/device-host-agent/host_agent/web/mcp_auth.py

@@ -0,0 +1,36 @@
+"""Bearer-token auth middleware for the MCP sub-app.
+
+Mounted on the FastMCP ``streamable_http_app()`` (NOT the console FastAPI),
+so cookie-session auth on console routes is unaffected.
+"""
+
+from __future__ import annotations
+
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.requests import Request
+from starlette.responses import JSONResponse, Response
+
+from host_agent.mcp_token import McpTokenStore
+
+
+class BearerAuthMiddleware(BaseHTTPMiddleware):
+    def __init__(self, app, token_store: McpTokenStore) -> None:
+        super().__init__(app)
+        self._store = token_store
+
+    async def dispatch(self, request: Request, call_next) -> Response:  # type: ignore[no-untyped-def]
+        header = request.headers.get("Authorization")
+        if not header or not header.lower().startswith("bearer "):
+            return _unauthorized()
+        presented = header.split(" ", 1)[1].strip()
+        if not self._store.verify(presented):
+            return _unauthorized()
+        return await call_next(request)
+
+
+def _unauthorized() -> JSONResponse:
+    return JSONResponse(
+        status_code=401,
+        content={"error": "invalid token"},
+        headers={"WWW-Authenticate": "Bearer"},
+    )

apps/device-host-agent/tests/test_mcp_auth.py

@@ -0,0 +1,58 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from starlette.applications import Starlette
+from starlette.responses import JSONResponse
+from starlette.testclient import TestClient
+
+from host_agent.mcp_token import McpTokenStore
+from host_agent.web.mcp_auth import BearerAuthMiddleware
+
+
+def _make_client(tmp_path: Path) -> tuple[TestClient, str]:
+    store = McpTokenStore(tmp_path / "host_mcp_token.json")
+    token = store.load_or_create().token
+
+    async def hello(request):  # type: ignore[no-untyped-def]
+        return JSONResponse({"ok": True})
+
+    inner = Starlette(routes=[])
+    inner.router.add_route("/", hello, methods=["GET"])
+    wrapped = Starlette()
+    wrapped.add_middleware(BearerAuthMiddleware, token_store=store)
+    wrapped.mount("/", inner)
+    return TestClient(wrapped), token
+
+
+def test_no_header_returns_401(tmp_path: Path) -> None:
+    client, _ = _make_client(tmp_path)
+    resp = client.get("/")
+    assert resp.status_code == 401
+    assert resp.headers["WWW-Authenticate"] == "Bearer"
+    assert resp.json() == {"error": "invalid token"}
+
+
+def test_wrong_token_returns_401(tmp_path: Path) -> None:
+    client, _ = _make_client(tmp_path)
+    resp = client.get("/", headers={"Authorization": "Bearer wrong"})
+    assert resp.status_code == 401
+
+
+def test_correct_token_passes_through(tmp_path: Path) -> None:
+    client, token = _make_client(tmp_path)
+    resp = client.get("/", headers={"Authorization": f"Bearer {token}"})
+    assert resp.status_code == 200
+    assert resp.json() == {"ok": True}
+
+
+def test_non_bearer_scheme_returns_401(tmp_path: Path) -> None:
+    client, token = _make_client(tmp_path)
+    resp = client.get("/", headers={"Authorization": f"Basic {token}"})
+    assert resp.status_code == 401
+
+
+def test_header_case_insensitive(tmp_path: Path) -> None:
+    client, token = _make_client(tmp_path)
+    resp = client.get("/", headers={"authorization": f"Bearer {token}"})
+    assert resp.status_code == 200