Fixes three issues in the authentication system:
C1: Add boot-time warning when AUTH_ENABLED=true but TRUST_PROXY!=true.
Without TRUST_PROXY=true behind nginx, req.ip becomes the proxy IP for all
clients, collapsing per-IP rate limiting into a shared pool. Operators must
explicitly set TRUST_PROXY=true to make per-IP rate limiting effective.
C2: Mount requireUiHeader middleware in test helpers (auth.test.js,
users.test.js, tokens.test.js). The CSRF header validation was not being
exercised in the test suite. Tests now send X-Requested-With: dragonflight-ui
headers that are actually validated by the middleware.
I1: Implement bounded rate-limit Map with MAX_ENTRIES=10000 and LRU eviction.
Unbounded Maps are vulnerable to spray attacks: attackers can force memory
exhaustion by requesting with distinct IPs. Now we evict the oldest entry
(by insertion order) when the map reaches capacity.
Code-review feedback:
- Dummy hash for user-enumeration-defense timing was 63 chars (bcrypt strings
are 60 chars). Worked by accident because bcrypt 5.x is lenient about
trailing chars; a future tightening would silently regress the timing
defense. Replaced with a real pre-computed bcrypt hash.
- last_login_at UPDATE now logs errors instead of silently swallowing them,
matching the pattern in requireAuth for api_tokens.last_used_at.
- Removed dead import of comparePassword from auth.test.js.
