XFF[0] is attacker-controllable; a crafted X-Forwarded-For header could
attribute login failures to a victim IP, triggering their lockout while
the attacker accumulates none. ingress-nginx sets X-Real-IP via its
realip module using an authoritative CIDR allowlist and overwrites any
client-supplied value, making it spoof-resistant. Fallback to XFF[0]
is retained for defence in depth but now emits a warning if reached.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
After LOGIN_MAX_FAILURES consecutive failed attempts from the same source
IP within LOGIN_WINDOW_SECONDS, POST /api/v1/auth/token returns HTTP 429
with a Retry-After header for LOGIN_COOLDOWN_SECONDS. A successful login
resets the counter. Trusted upstream proxy IPs/CIDRs can be declared via
LOGIN_TRUSTED_PROXY_IPS so X-Forwarded-For is honoured correctly behind
nginx ingress or similar reverse proxies.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
