wangweiandCopilot
49ee50c104
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>