Fixing the recovery-code OOM removed one way to exhaust the container's
memory; it did not remove the reason that was possible. Argon2id is configured
for 64 MiB, and every password hash or verify reserves that for its duration.
Nothing limited how many ran at once, and verification is reached by an
unauthenticated login - so roughly twenty simultaneous sign-in attempts
reserve 1.28 GiB against a 512 MiB container and the process is killed. No
credentials needed, and account lockout does not help: it is per account, and
the requests need not share one.
Hashing now passes through a four-slot gate. Callers queue rather than being
refused, so every request stays correct and only gets slower under load, and
peak memory is four hashes regardless of traffic - about 256 MiB, comfortably
inside the limit.
This is the answer to "why not just remove the memory limits". The limit was
never the fault; unbounded per-request memory was. Removing it would move the
kill decision to the kernel, which picks by size and would take Postgres -
losing queued mail rather than one request.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The F4 auth service issued a valid session for any email and any password,
and accepted any non-empty string as a second factor. Reproduced against
the router before touching it: an invented password plus the code "000000"
returned a SUPER_ADMIN token that opened /api/v1/admin/dashboard.
Passwords. Hashing moves from PBKDF2 to Argon2id via hash-wasm, which is
what PLAN.md section 9 and the Go service already use - the previous
scheme meant a password set through the mail stack could never verify
here. Interoperability was checked in both directions before adopting the
library: a hash written by alexedwards/argon2id verifies in Node and one
written here verifies in Go. hash-wasm is pure WASM, so the multi-arch
Alpine images need no native build.
verifyPassword no longer falls back to comparing the password against the
stored hash. That fallback turned every stored hash into a working
credential: anyone with a database dump could authenticate by sending the
hash back. Anything that is not an argon2id PHC string is now refused.
Logins are decided against the database, with the failure counter and the
temporary lockout of PLAN.md section 5.2. An unknown address and a wrong
password give the same answer, and the unknown case still pays for a hash
so response time does not enumerate valid addresses.
Second factor. The TOTP secret is generated server-side, stored encrypted
and never accepted back from the client - the confirm step used to take
whichever secret the caller sent, so anyone could confirm with their own.
Recovery codes are Argon2id, single-use, and consumed under a guard so two
concurrent requests cannot spend the same one. App passwords are issued
and revoked through real endpoints instead of browser state.
Sessions gain a "purpose" claim. Without it the challenge token - handed
out after the password but before the second factor - satisfied every
check a real session did, which skipped MFA entirely.
The dev seed carried a hand-written password_hash whose digest was 24
bytes instead of 32, so it matched no password at all. Nothing noticed
while passwords went unverified; it is a real hash now.
Verified with 30 tests, 13 of them against a real Postgres: wrong password,
unknown account, pass-the-hash, wrong TOTP code, challenge token replay,
lockout, single-use recovery codes, and the surface isolation that F4's
acceptance criteria require.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
