[grade=B] fix(auth): generalize cross-host SSO handoff

Codex deployment review: urn:ump:sufisot7ewy33mhjude3ly6wxcjizagt42ywaicwve6qufqdtvbq

Caddy path-order correction: urn:ump:o6apvvpvhynkouii4cl5ghxpprrwtilrg2dejdy2lqsupoktc6tq

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

@@ -0,0 +1,84 @@
+const express = require('express');
+const request = require('supertest');
+const createSsoRouter = require('../routes/auth/sso-gate');
+
+function createApp({ redeem = true } = {}) {
+  const app = express();
+  const session = {
+    redeemHandoffToken: jest.fn().mockReturnValue(redeem),
+    setCookieHostOnly: jest.fn((res) => {
+      res.setHeader('Set-Cookie', 'dashcaddy_session=test; Path=/; HttpOnly; Secure; SameSite=Lax');
+    }),
+    isValid: jest.fn().mockReturnValue(true),
+  };
+  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 });
+  const router = createSsoRouter({
+    totpConfig: { enabled: true, sessionDuration: '24h' },
+    session,
+    asyncHandler,
+    errorResponse,
+    log: { warn: jest.fn(), info: jest.fn(), debug: jest.fn(), error: jest.fn() },
+    getAppSession: jest.fn(),
+    appSessionCache: new Map(),
+    credentialManager: { retrieve: jest.fn() },
+    fetchT: jest.fn(),
+    getServiceById: jest.fn(),
+    licenseManager: {
+      hasFeature: jest.fn().mockReturnValue(true),
+      requirePremium: jest.fn(() => (_req, _res, next) => next()),
+    },
+    servicesStateManager: { read: jest.fn().mockResolvedValue([]) },
+  });
+  app.use('/api/v1', router);
+  return { app, session };
+}
+
+describe('cross-host SSO exchange redirect', () => {
+  test('sets a host-only cookie and redirects to a relative service path', async () => {
+    const { app, session } = createApp();
+    const res = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: 'one-time', return: '/settings?tab=network#dns' });
+
+    expect(res.status).toBe(303);
+    expect(res.headers.location).toBe('/settings?tab=network#dns');
+    expect(res.headers['set-cookie'][0]).not.toMatch(/Domain=/i);
+    expect(session.redeemHandoffToken).toHaveBeenCalledWith('one-time');
+  });
+
+  test.each([
+    'https://evil.example/phish',
+    '//evil.example/phish',
+    '/\\evil.example/phish',
+  ])('rejects cross-origin return value %s', async (returnValue) => {
+    const { app } = createApp();
+    const res = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: 'one-time', return: returnValue });
+
+    expect(res.status).toBe(303);
+    expect(res.headers.location).toBe('/');
+  });
+
+  test('keeps the existing JSON exchange behavior when no return is supplied', async () => {
+    const { app } = createApp();
+    const res = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: 'one-time' });
+
+    expect(res.status).toBe(200);
+    expect(res.body).toMatchObject({ success: true, authenticated: true });
+  });
+
+  test('does not set a cookie or redirect for an invalid token', async () => {
+    const { app, session } = createApp({ redeem: false });
+    const res = await request(app)
+      .get('/api/v1/auth/sso-exchange')
+      .query({ token: 'bad', return: '/settings' });
+
+    expect(res.status).toBe(401);
+    expect(res.headers['set-cookie']).toBeUndefined();
+    expect(session.setCookieHostOnly).not.toHaveBeenCalled();
+  });
+});