The app refuses a JMAP server over plain http (loopback aside), yet the
desktop issued a code, reported "Signed in on your phone" once it was
redeemed, and the phone failed. Linking now stops before the step-up
with an explanation.
The token proxy trusted the endpoint sealed into a phone's refresh token
for good: after a server was removed or its provider moved, it kept
posting there with the plain fetch and whichever secret the server id
now maps to. Trust is now re-derived on every renewal; an endpoint the
webmail is no longer configured for gets neither the secret nor the
unguarded fetch.
The step-up's failure count was keyed on the cookie slot, which the
client chooses, so a session could spread guesses over 50 slots; and
even one key allowed 480 failures a day, well above Stalwart's ban of
100 a day per address, which would ban the webmail's own IP for every
user. Failures now count per server and login name, 5 per 15 minutes
and 20 a day.
"Link Mobile App" only appeared for OAuth sessions, its step-up could
only go through the identity provider (which failed without an OAuth
client and bounced password+TOTP users to the provider's login page),
and it handed the phone the desktop's own refresh token. Revoking that
token on sign-out, or a rotating provider, signed the phone out too; a
confidential client stopped the phone at its first token expiry; and an
identity provider on another host was refused by the app.
The step-up now mints the phone's own grant:
- Password and password+TOTP accounts confirm the current password (and
code) in the dialog. The server uses it once to get an OAuth grant
from Stalwart's structured login for the app's own client, retries
with the webmail's client when the server insists on a registered one,
and falls back to an app password ("Bulwark mobile (paired <date>)")
or, on servers that offer neither, the verified password. Failed
attempts are limited per account so the webmail's address cannot be
banned by guessing through it.
- SSO accounts keep the provider round trip, now with `offline_access`
where offered; its fresh tokens become the phone's grant instead of
being thrown away, and must belong to the account being paired.
- The account and server always come from the slot's verified session
context, never from the request.
Grants live 5 minutes server-side, codes 2 minutes, both single use; the
store is pinned on `globalThis`. Redeem answers `invalid_code`,
`expired_code` or `used_code`, and the desktop polls a separate status
id to replace the QR with "Signed in on your phone". A phone whose
client is confidential, or whose provider is on another host, renews
through `/api/auth/pair/token` with a sealed refresh token, so current
app builds work unchanged. Signing out discards a pending grant but no
longer affects a paired phone.
The dialog shows for every account (not in Lite), with a copyable
sign-in link, a TOTP field when needed, and the app's own "Scan a
sign-in code" wording.
Linus Rath