Locust spawns N virtual users (default 1000), all from 127.0.0.1 as
admin. /auth/login is rate-limited 10/5min per-IP AND per-username, so
the 11th on_start() got 429 and a RuntimeError. A @task(2) login in
the task weights turned the whole run into a 429 factory even after
ramp-up. And _login_with_retry treated 429 as non-retryable, so there
was no graceful degradation path.
Three changes, one root cause:
- decnet/web/limiter.py: read DECNET_LIMITER_ENABLED (default true).
When false, slowapi's Limiter(enabled=False) makes @limiter.limit a
no-op. Default ships unchanged; nobody should ever release with this
off.
- tests/stress/conftest.py: set DECNET_LIMITER_ENABLED=false in the
uvicorn subprocess env. Stress tests measure throughput, not rate
limiting.
- tests/stress/locustfile.py: drop the @task(2) login — it added zero
coverage (every user already logs in at on_start) and only generated
contention. Teach _login_with_retry to honour 429 + Retry-After so a
Locust pointed at a limiter-enabled server degrades gracefully
instead of crashing on_start.
Adds slowapi two-bucket rate limit on /auth/login — 10 attempts per
5 minutes per-IP AND per-username, tripping either → 429. Per-IP
catches botnets hitting one account; per-username catches distributed
credential stuffing against one account. In-memory storage: dashboard
API is single-process, Redis is disproportionate for v1.
X-Forwarded-For is deliberately NOT trusted (spoofable); reverse-proxy
deployments get one shared bucket per proxy IP. Logged in the threat
model as accepted risk DA-08, to be revisited when a verified-proxy
config lands.
Also scaffolds development/THREAT_MODEL.md with STRIDE-per-element
methodology, system-context DFD, and Dashboard↔API as the first fully
worked component (7 sub-flows, ~50 threat entries). F1 Authn ships
with 3 threats mitigated: rate limit (new), uniform 401 (verified
already in place), bcrypt length clamp (verified already in place via
Pydantic max_length=72).
