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With TRUSTED_PROXIES empty behind the reverse proxy production is required to run behind, every login POST keyed on the proxy's address and shared one 5/minute bucket. A stranger sending five POSTs a minute -- 0.08 requests per second, from anywhere -- kept that bucket permanently full, and the operator's own correct password was answered 429 indefinitely with no second administrative path. The login POST no longer has a pre-emptive limiter. The handler verifies credentials first and spends budget only on a FAILED attempt, so a correct password is never throttled whatever the counters hold. Three things follow, and are implemented together because the first is unsafe without the other two: - Failures are counted per (client bucket, submitted username), five per minute, after which further failures get 429 with a Retry-After. A successful login clears the counter, so mistyping and then succeeding does not leave the operator throttled. - Both key sets are capped at 1024 entries. The submitted username is attacker-controlled, so past the first cap failures fall back to a counter keyed on the client alone, and past both caps a failure is answered as throttled without being recorded. Tracked state stays under half a megabyte and does not grow with invented usernames. - Concurrent Argon2id verifications are capped at two, a 128 MB ceiling at 64 MB per hash. Every password-hashing endpoint takes a slot, including the password-change endpoint, which holds one across both its hashes. A request that waits five seconds without a slot is answered 503 and no hash runs for it. An unknown username is verified against a dummy hash instead of returning early, so a nonexistent account costs the same time as a real one and the response cannot be used to enumerate usernames. The password-change limiter is unchanged: RequireAuth runs ahead of it, so only a request already carrying a valid session reaches its bucket. Also adds the missing test for the third bucketKey call site, where the peer is a trusted proxy but the forwarded chain names no client. Every existing test of that fallback uses an IPv4 proxy, where bucketKey is the identity function, so dropping the /64 masking there left the suite green. README and the TRUSTED_PROXIES startup warning updated: a shared bucket now costs precision, not the availability of the admin path.
8.8 KiB
8.8 KiB