Doc side of website + Android-app feat/sso-trusted-device.
TRUSTED_DEVICES_MFA.md §6 gains an "SSO login paths" subsection: SSO is not
exempt from the second factor, and a trusted device skips it exactly as on the
password path (previously SSO consulted trust nowhere, so an external-identity
user was asked for a code on every sign-in). Documents the callback-side skip,
the new trustDevice/deviceName on POST /auth/sso/totp, and why recovery codes
stay password-login only.
Also writes down how this reaches the Android app, since it is not obvious: the
app's SSO runs in a Custom Tab that shares the system browser's cookie jar, so
the rg_trust cookie covers native SSO with no app change and no trust token in a
start URL (which would leak a secret into query strings and logs). The app's own
token is minted at /auth/mobile/sso/exchange instead — an authenticated
app→server call — so it never travels in the deep link, and the bridge row holds
only a boolean. Notes that one tick yields two independently-revocable rows.
§4 documents the new mobile_auth_sessions.trust_device column; BACKEND_DESIGN.md
gets the same column in its bridge table, the trust note on the /exchange row,
and a pointer from the bridge intro to the Custom Tab cookie model.
Co-Authored-By: Claude <noreply@anthropic.com>
Add TRUSTED_DEVICES_MFA.md (the approved design/implementation plan) and fold
the feature into BACKEND_DESIGN §3 (trusted_devices + recovery_codes schema),
§4 (login/totp trust+recovery, /auth/me/trusted-devices*, recovery-codes*,
admin trusted-device + /mfa/reset routes), and §6 (trusted-device security
model + audit actions). Note the app-side trust/recovery flow in android PLAN §4.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
