[grade=B] fix(auth): reuse valid session for cross-host SSO

status/js/auth-gate.js

@@ -267,6 +267,42 @@
     }
   }
 
+  function buildSsoHandoffTarget(returnUrl, token) {
+    const parsed = new URL(returnUrl, window.location.origin);
+    if (parsed.origin === window.location.origin) return parsed.toString();
+
+    const suffix = SITE.tld.startsWith('.') ? SITE.tld : `.${SITE.tld}`;
+    const isPrivateHost = parsed.hostname === suffix.slice(1) || parsed.hostname.endsWith(suffix);
+    if (parsed.protocol !== 'https:' || !isPrivateHost || !token) return null;
+
+    const returnPath = `${parsed.pathname}${parsed.search}${parsed.hash}`;
+    parsed.pathname = '/dashcaddy-sso';
+    parsed.search = '';
+    parsed.hash = '';
+    parsed.searchParams.set('token', token);
+    parsed.searchParams.set('return', returnPath);
+    return parsed.toString();
+  }
+
+  async function resumeExistingSession(returnUrl) {
+    if (!returnUrl || !isAllowedReturnUrl(returnUrl)) return false;
+    try {
+      const res = await fetch('/api/v1/auth/sso-handoff', {
+        credentials: 'include',
+        cache: 'no-store',
+      });
+      if (!res.ok) return false;
+      const data = await res.json();
+      const target = data.success && buildSsoHandoffTarget(returnUrl, data.ssoToken);
+      if (!target) return false;
+      try { sessionStorage.removeItem('totp_redirect'); } catch (_) {}
+      window.location.replace(target);
+      return true;
+    } catch (_) {
+      return false;
+    }
+  }
+
   const urlParams = new URLSearchParams(window.location.search);
   if (urlParams.get('auth') === 'required') {
     // Preserve the gated service destination so submitTotpCode() can append
@@ -277,8 +313,12 @@
     }
     // Clean URL — happens after we've captured the redirect
     window.history.replaceState({}, '', window.location.pathname);
-    // Show on next tick so the DOM (the .totp-card) is ready
-    setTimeout(show, 0);
+    // Reuse the valid status.sami session first. Only show the TOTP/provider
+    // challenge when that session is genuinely absent or expired.
+    setTimeout(async () => {
+      if (await resumeExistingSession(returnUrl)) return;
+      await show();
+    }, 0);
   }
 
   // Expose for hot-trigger from other modules (e.g. logout)