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

dashcaddy-api/__tests__/sso-handoff-exchange.test.js

@@ -2,14 +2,15 @@ const express = require('express');
 const request = require('supertest');
 const createSsoRouter = require('../routes/auth/sso-gate');
 
-function createApp({ redeem = true } = {}) {
+function createApp({ redeem = true, valid = true } = {}) {
   const app = express();
   const session = {
-    redeemHandoffToken: jest.fn().mockReturnValue(redeem),
+    redeemHandoffToken: jest.fn((token) => (typeof redeem === 'function' ? redeem(token) : redeem)),
     setCookieHostOnly: jest.fn((res) => {
       res.setHeader('Set-Cookie', 'dashcaddy_session=test; Path=/; HttpOnly; Secure; SameSite=Lax');
     }),
-    isValid: jest.fn().mockReturnValue(true),
+    isValid: jest.fn().mockReturnValue(valid),
+    createHandoffToken: jest.fn().mockReturnValue('fresh-sso-handoff-token'),
   };
   const asyncHandler = (fn) => (req, res, next) => Promise.resolve(fn(req, res, next)).catch(next);
   const errorResponse = (res, status, message, extra = {}) => res.status(status).json({ success: false, error: message, ...extra });
@@ -82,3 +83,47 @@ describe('cross-host SSO exchange redirect', () => {
     expect(session.setCookieHostOnly).not.toHaveBeenCalled();
   });
 });
+
+describe('existing-session SSO handoff', () => {
+  test('mints a handoff token without asking for TOTP again', async () => {
+    const { app, session } = createApp();
+    const res = await request(app)
+      .get('/api/v1/auth/sso-handoff')
+      .set('Cookie', 'dashcaddy_session=valid-session');
+
+    expect(res.status).toBe(200);
+    expect(res.body).toMatchObject({ success: true, ssoToken: 'fresh-sso-handoff-token' });
+    expect(session.createHandoffToken).toHaveBeenCalledTimes(1);
+  });
+
+  test('refuses to mint a handoff token without a valid session', async () => {
+    const { app, session } = createApp({ valid: false });
+    const res = await request(app).get('/api/v1/auth/sso-handoff');
+
+    expect(res.status).toBe(401);
+    expect(session.createHandoffToken).not.toHaveBeenCalled();
+  });
+
+  test('completes the full mint, exchange, cookie, redirect lifecycle', async () => {
+    const issued = new Set(['fresh-sso-handoff-token']);
+    const redeemOnce = (token) => issued.delete(token);
+    const { app } = createApp({ redeem: redeemOnce });
+
+    const mint = await request(app)
+      .get('/api/v1/auth/sso-handoff')
+      .set('Cookie', 'dashcaddy_session=valid-session');
+    const exchange = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: mint.body.ssoToken, return: '/web/' });
+
+    expect(exchange.status).toBe(303);
+    expect(exchange.headers.location).toBe('/web/');
+    expect(exchange.headers['set-cookie'][0]).toContain('dashcaddy_session=');
+    expect(exchange.headers['set-cookie'][0]).not.toMatch(/Domain=/i);
+
+    const replay = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: mint.body.ssoToken, return: '/web/' });
+    expect(replay.status).toBe(401);
+  });
+});

dashcaddy-api/routes/auth/sso-gate.js

@@ -203,8 +203,22 @@ module.exports = function(deps) {
     }
   }, 'auth-app-token'));
 
+  // A browser that already has a valid status.sami session must not be asked
+  // for TOTP again just because it opened another private-TLD service host.
+  // Mint a fresh one-time token that the target host can exchange for its own
+  // host-only cookie. This route is intentionally session-protected both by
+  // the global middleware and here (defence in depth).
+  router.get('/auth/sso-handoff', (req, res) => {
+    res.setHeader('Cache-Control', 'no-store');
+    if (!session.isValid(req)) {
+      return errorResponse(res, 401, 'Session expired or invalid');
+    }
+    ok(res, { ssoToken: session.createHandoffToken() });
+  });
+
   // Cross-subdomain SSO handoff: exchanges a short-lived single-use token
-  // (minted by /totp/verify) for a HOST-ONLY session cookie on whichever
+  // (minted by /totp/verify or /auth/sso-handoff) for a HOST-ONLY session
+  // cookie on whichever
   // *.sami origin calls this. Needed because Domain=.sami cookies are
   // silently rejected by real browsers (.sami is an unregistered TLD, so
   // browsers treat "sami" as the effective public suffix and refuse to set