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The receiver limiter keyed buckets on (client IP, request path). The
route pattern /webhook/{uuid} matches any single segment, so a client
that invented a fresh path per request minted a fresh bucket per
request and never refilled one: its aggregate rate against the only
unauthenticated, internet-exposed endpoint was unbounded, and every
one of those requests reached an entrypoint lookup before it 404ed.
Put a second limiter in front of it, keyed on the client IP alone and
covering the whole route at ten times the configured per-entrypoint
limit (1200/min by default). The per-entrypoint limit is unchanged and
still wanted; it just bounds nothing in aggregate on its own. Ten
entrypoints' worth of headroom lets one sender address drive several
entrypoints at full rate while still capping what one address costs
the receiver. The multiplication saturates rather than wrapping, since
nothing bounds RECEIVER_RATE_LIMIT from above and a negative limit
would reject every request.
Move the handler's INFO line for an incoming webhook below the
entrypoint lookup. The UUID is attacker-controlled path text, so
logging it first let a client write an INFO line per invented path; a
miss is already logged at DEBUG and the request is already in the
access log.
1.4 KiB
1.4 KiB