sessionFromDecoded validated sessions with a blocklist — it rejected a
token only when `decoded.stage` was present (the TOTP challenge). Because
every JWT is signed with the same JWT_SECRET and distinguished only by
claims, the SSO transaction cookie (sso_tx, which carries kind:'sso_tx'
and id:'sso' but no stage) passed validation and was accepted as a bogus
{ userId:'sso' } session.
requireAuth's DB re-load blocked protected admin routes, but non-DB
identity checks were fooled — notably siteMode's maintenance-preview
bypass, which trusts any truthy getUserFromRequest. An attacker could
start an SSO flow to obtain an sso_tx cookie and replay it as the auth
cookie / Bearer token to bypass the maintenance gate. The broader risk
was latent: any future code path trusting attachSession/getUserFromRequest
without a DB round-trip inherited an auth bypass.
Make session validation positively typed: real sessions are now stamped
with typ:'session' (createSession + mintMobileTokens), and
sessionFromDecoded accepts a token only when that marker is present. As
belt-and-suspenders it also rejects any token carrying a non-session
marker (stage || kind). Flow/challenge tokens are never stamped, so they
can no longer be mistaken for sessions.
Note: existing web cookie sessions predating this change lack the typ
claim and will be rejected once — users re-login. Mobile clients recover
automatically on next refresh.
Adds regression tests: the sso_tx flow token and a bare identity token
are both rejected by validateSession / decodeIdentity / getUserFromRequest.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
