6920e5bf7a
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>
Migrations
SQLx-managed Postgres migrations. Each NNN_topic.up.sql has a matching
NNN_topic.down.sql. Run by sqlx::migrate!() at app start.
Rules
- Never edit a shipped migration. If a column needs to change or a fix needs to land, write a new migration. Production has already applied the old one and SQLx tracks each by checksum — editing in place will fail to apply on existing databases.
- Always pair
.up.sqlwith a.down.sql. Reverts may not be perfect (data loss is sometimes unavoidable) but the file must exist and do the best it can. - Prefer additive changes. New columns, new tables, new keys in
config. Drop / rename only when there is no alternative. - No business logic in migrations. Schema + seeds only. Anything that needs Rust code goes in a one-off binary, not a migration file.
- One concern per migration. Easier to revert. Easier to read in
git log.
Numbering
Zero-padded three digits, monotonically increasing. The next free number lives at the bottom of the directory listing — pick that.
Seed-only migrations
When you only need to add config keys (feature flags, defaults), use
INSERT … ON CONFLICT DO NOTHING so existing operator overrides survive. See
009_feature_toggles.up.sql for the canonical shape.