Round 1 gave /join a per-IP ceiling and left /recover with only its
`recover:{ip}:{name}` bucket. That key is right for the job it was written for —
stopping someone who knows a display name (they're listed on the feed) from
burning the victim's 3-strike PIN counter and locking them out on repeat. But the
name is ATTACKER-CHOSEN, so cycling names mints a fresh 5-attempt bucket every
time and the per-IP cost is unbounded.
What sits behind that limiter makes it worse than a normal flood: every call runs
a cost-12 bcrypt verify, including an UNCONDITIONAL throwaway verify for names
that don't exist — added deliberately to close a timing oracle. So an unknown name
is the single cheapest way to make the server do ~200ms of hashing.
Adds `recover_ip_rate_per_min` (default 30, migration 019), checked BEFORE the
per-name bucket so a name generator can't walk past it. 30/min is far above any
real recovery attempt while capping a flood. The per-name bucket is untouched and
remains the anti-guessing control.
The second half matters as much as the first: bcrypt was running inline on the
async runtime everywhere. At cost 12 that pins a tokio worker thread for ~200ms,
and there is only one per core — so a login flood stalled every other request on
the box, including the feed. There was no spawn_blocking anywhere in the auth
module, despite SECURITY-BACKLOG claiming bcrypt had been offloaded.
Route all of it through `verify_password` / `hash_password` on the blocking pool.
That covers /recover, /admin/login, the host PIN reset, and — the one most likely
to bite at a real event — the PIN hash minted on every single /join. Saturating
the blocking pool degrades logins; saturating the worker threads degrades
everything.
Tests: cycling distinct names from one IP now hits the ceiling with a Retry-After,
and — the assertion that keeps the fix honest — repeated wrong PINs against ONE
name are still throttled with the ceiling set generously high, so the ceiling
added protection rather than replacing it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
At a venue every guest is behind one NAT, so an IP-keyed limiter hands the
whole party a single bucket. On a fresh deploy 12 guests arriving together
meant 5 joined and 7 were turned away, with no Retry-After telling them when
to retry. `/feed` (60/min) and `/export` (3 per DAY — the fourth guest to
fetch their keepsake locked out until tomorrow) had the same defect.
`feed_delta` was already keyed per-user and its comment states the exact
rationale ("so one client can't starve others behind a shared NAT"); this
makes its siblings match.
- feed:{ip} -> feed:{user_id} (auth was already in scope)
- export:{ip} -> export:{user_id} (resolved from the download ticket's
session, which was previously looked up and discarded)
- join:{ip}: pre-auth, so there is no user to key on. Split in two — a loose
per-IP ceiling that only bounds raw volume (new `join_ip_rate_per_min`,
default 60, migration 017), plus the real 5/60s anti-spam bucket keyed
per (ip, name), mirroring the existing `recover:{ip}:{name}`.
admin_login / recover / pin_reset_req stay IP-keyed on purpose and are now
commented as such: they guard credential guessing, where a per-user or
per-name key would just hand an attacker a fresh bucket per guess.
Retry-After: the machinery existed but 7 of 8 sites called `check()` and
hard-coded `None`, so a throttled client was told to back off but never for
how long. Delete the bool `check()` wrapper entirely so `check_with_retry`
is the only entry point and the delay cannot be discarded by accident. Also
surface it for the PIN lockout, where the deadline was already known.
Fix the "unknown" fallback while here: every client_ip() caller passed that
literal, so any request without X-Forwarded-For — anything reaching the app
directly rather than through Caddy — shared ONE global bucket. Serve with
connect-info and use the peer address.
Tests: the reseed forces every limiter toggle off before each test, which is
why this whole class was invisible. Add 01-auth/rate-limit-shared-nat, which
enables them and asserts 12 guests share an IP without collision, that one
guest hammering their own name IS still throttled (so the fix re-keys rather
than removes the limit), and that feed/export buckets are per-user. Retarget
the ddos join test at the new per-IP ceiling — it asserted the defect.
Also seed `admin_login_rate_enabled` (read by the handler, seeded by no
migration and no reseed) and register `join_ip_rate_per_min` in the admin
config allowlist. Unrelated pre-existing red test fixed: 01-auth/join
asserted a "Willkommen!" heading the wedding redesign removed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
