Adds rate limiting to /api/auth/login and /api/auth/register and removes
their wide-open CORS allowlist.
Rate limiting (@upstash/ratelimit + @upstash/redis):
- 5 attempts per 15-minute sliding window per IP, prefix "tcgvault:auth"
- new lib/rate-limit.js, lazy singleton, single source of truth
- reads KV_REST_API_URL / KV_REST_API_TOKEN (Vercel Upstash Marketplace
convention — auto-provisioned, no manual env-var setup needed)
- fail-closed in production if env vars are missing (better to error
one login than silently disable brute-force protection on live)
- fail-open in dev/test if env vars are missing (single console.warn)
- fail-open on Upstash backend outage (defense-in-depth — don't lock
the entire userbase out if Upstash is down)
- IP extracted from x-forwarded-for first hop, with socket fallback;
NOT req.body.email (rotates) or Authorization header (absent on
unauthenticated login)
CORS:
- Removed Access-Control-Allow-Origin: * + companion headers + OPTIONS
preflight from login.js and register.js
- These are first-party endpoints called from the same-origin SPA; the
"*" allowlist was a development convenience that shipped to prod
- verify.js is OUT OF SCOPE per architect's "cors-tighten" deferral
(see convoy plan § Architect's calls)
Other handler ordering preserved verbatim per brief: method gate first,
then rate-limit check (returns 429 with Retry-After header), then the
existing try/catch + body parsing + DB work.
Pre-merge requirements: KV_REST_API_URL + KV_REST_API_TOKEN must be set
in Vercel Production (already done — Upstash marketplace integration
auto-provisioned both, confirmed by maintainer 2026-05-23).
Convoy: fix-auth-bypass / Brief 4
Co-authored-by: Cursor <cursoragent@cursor.com>
