Optional "Sign in with Google" with auto-provisioning, fully config-gated:
without GOOGLE_CLIENT_ID/SECRET and OAUTH_REDIRECT_URL the routes 404 and the
button is hidden, so deployments without SSO are unaffected.
- migration 028: users.google_sub (unique) + email; password_hash nullable
for OAuth-only accounts
- src/auth/google-oauth.js: lazy google-auth-library, ID-token verify,
GOOGLE_ALLOWED_DOMAIN enforcement, requires email_verified === true
- auth routes: /auth/google (state-CSRF redirect), /auth/google/callback,
/auth/google/enabled; reuses establishSession
- web-ui: "Sign in with Google" on the login screen (shown only when enabled),
friendly callback error handling
- .env.example documents all new vars
Security hardening (from review of this + the TOTP work):
- resolveGoogleUser links ONLY by google_sub, never by email — a Google login
can never seize a pre-existing local account (account-takeover fix)
- a Google-linked account with TOTP still requires the second factor (ticket
in session, /?mfa=1 step) instead of bypassing it
- /login/totp now applies the per-IP login backoff
- recovery-code consumption is atomic (WHERE used_at IS NULL + rowCount)
- concurrent first-login race on google_sub is caught and re-resolved
- tests: google-oauth config helpers + google-link takeover/dedup regression
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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