fix: harden MCP endpoint after code review

Critical: the MCP SDK auto-enables DNS-rebinding protection when its host
parameter is left at the 127.0.0.1 default, hard-coding a loopback-only Host
allow-list. Every remote client (the only deployment this feature targets) was
refused with HTTP 421 before auth or the tool ran. Now driven by a new
MCP_ALLOWED_HOSTS setting, with '*' as an explicit, logged opt-out.

Also bounds query/top_k to match AskRequest (top_k is amplified 4x downstream,
so an unbounded value was a resource-exhaustion vector), decodes the
Authorization header as latin-1 per the ASGI spec instead of raising a 500 on
malformed bytes, and returns WWW-Authenticate on 401 per RFC 7235.

Moves the psycopg2 import guard into backend/tests/conftest.py: duplicated
across four test modules, it only worked because of alphabetical collection
order, and any earlier-sorting package would have reintroduced a live
connection attempt against the production database.

Registers the mcp module in the authoritative backend architecture doc.

84 backend tests pass. Verified against a live server: allowed remote Host
returns a valid initialize result, unknown Host returns 421, missing token
returns 401 with WWW-Authenticate.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
wangwei
2026-07-29 17:11:54 +08:00
co-authored by Copilot
parent bd3dc38d1d
commit 49ee50c104
13 changed files with 330 additions and 51 deletions
@@ -12,17 +12,10 @@ is needed anywhere in this file — asyncio.create_task itself is also mocked.
from __future__ import annotations
import sys
from unittest.mock import MagicMock, patch
# Patch psycopg2 before importing anything that transitively imports it, in
# case this file is collected before test_model_usage_persistence.py.
mock_psycopg2 = MagicMock()
mock_psycopg2.extras = MagicMock()
sys.modules.setdefault("psycopg2", mock_psycopg2)
sys.modules.setdefault("psycopg2.extras", mock_psycopg2.extras)
sys.modules.setdefault("psycopg2.pool", MagicMock())
# psycopg2 is mocked centrally in backend/tests/conftest.py, which pytest
# imports before any test module regardless of collection order.
from app.shared import bootstrap
from app.shared.model_usage_tracker import ModelUsageEntry, ModelUsageTracker
@@ -6,17 +6,11 @@ Mirrors the mocking pattern in backend/tests/perception/test_postgres_event_stor
from __future__ import annotations
import sys
from datetime import datetime, timezone
from unittest.mock import MagicMock, patch
# Patch psycopg2 before importing the module under test.
mock_psycopg2 = MagicMock()
mock_psycopg2.extras = MagicMock()
sys.modules.setdefault("psycopg2", mock_psycopg2)
sys.modules.setdefault("psycopg2.extras", mock_psycopg2.extras)
sys.modules.setdefault("psycopg2.pool", MagicMock())
# psycopg2 is mocked centrally in backend/tests/conftest.py, so importing the
# module under test here never binds the real driver.
from app.shared.model_usage_tracker import ModelUsageEntry