/qr/{address} is reachable without auth (the dashboard renders it with a
plain <img> tag, which cannot carry a bearer token), and it did two things
it should not: it accepted any plm1-prefixed string matching a shape regex,
without checking the bech32 checksum, and it ran qrcode.make on the event
loop — a free CPU amplifier that also stalled the scheduler and the
listener for the duration of every request.
Validation now goes through is_valid_plm_address, the same check
withdrawals and the admin fee_address validator use, behind a length guard
so an oversized path never reaches embit. The render is memoized per
address in a bounded LRU (valid addresses are cheap to generate, so an
unbounded cache would just move the amplification to memory) and pushed
off the loop with run_in_threadpool, and the response carries a
Cache-Control so a browser stops re-asking for an image that never changes.
The rejection now uses the structured error contract (invalid_address),
which already has its i18n key.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
davideandClaude Opus 5
5f6abe5b32