[grade=B] fix(auth): use host-only session cookies on custom TLDs

Codex: urn:ump:7c22nwh67kot23f6czg5ax7e47hu2r7vowjpz3q6z63o73ti67vq

dashcaddy-api/__tests__/session-cookie-scope.test.js

@@ -0,0 +1,64 @@
+'use strict';
+
+const configureMiddleware = require('../src/utilities/middleware');
+
+function buildSession() {
+  const app = {
+    param: jest.fn(),
+    set: jest.fn(),
+    use: jest.fn(),
+  };
+
+  return configureMiddleware(app, {
+    siteConfig: { dashboardHost: 'status.sami', tld: '.sami' },
+    totpConfig: { enabled: true, sessionDuration: '24h' },
+    tailscaleConfig: { enabled: false, requireAuth: false },
+    metrics: { recordRequest: jest.fn() },
+    auditLogger: { middleware: () => (_req, _res, next) => next() },
+    authManager: { verifyJWT: jest.fn(), verifyAPIKey: jest.fn() },
+    log: { debug: jest.fn(), info: jest.fn(), warn: jest.fn(), error: jest.fn() },
+    cryptoUtils: { loadOrCreateKey: () => Buffer.alloc(32, 7) },
+    isValidContainerId: () => true,
+    isTailscaleIP: () => false,
+    getTailscaleStatus: async () => null,
+  });
+}
+
+function captureCookie(setCookie) {
+  const headers = {};
+  setCookie({ setHeader: (name, value) => { headers[name.toLowerCase()] = value; } }, '24h');
+  return headers['set-cookie'];
+}
+
+describe('TOTP session cookie scope', () => {
+  test('primary login cookie is host-only for custom TLD deployments', () => {
+    const session = buildSession();
+    const cookie = captureCookie(session.setSessionCookie);
+
+    expect(cookie).toContain('dashcaddy_session=');
+    expect(cookie).toContain('HttpOnly');
+    expect(cookie).toContain('Secure');
+    expect(cookie).toContain('SameSite=Lax');
+    expect(cookie).not.toMatch(/(?:^|;)\s*Domain=/i);
+  });
+
+  test('SSO exchange uses the same host-only cookie contract', () => {
+    const session = buildSession();
+    const cookie = captureCookie(session.setHostOnlySessionCookie);
+
+    expect(cookie).toContain('dashcaddy_session=');
+    expect(cookie).not.toMatch(/(?:^|;)\s*Domain=/i);
+  });
+
+  test('logout clears the host-only secure cookie', () => {
+    const session = buildSession();
+    const headers = {};
+    session.clearSessionCookie({
+      setHeader: (name, value) => { headers[name.toLowerCase()] = value; },
+    });
+
+    expect(headers['set-cookie']).toContain('Max-Age=0');
+    expect(headers['set-cookie']).toContain('Secure');
+    expect(headers['set-cookie']).not.toMatch(/(?:^|;)\s*Domain=/i);
+  });
+});

dashcaddy-api/src/utilities/middleware.js

@@ -227,6 +227,10 @@ module.exports = function configureMiddleware(app, {
     ipSessions.delete(getClientIP(req));
   }
 
+  // Session cookies are intentionally host-only. Browsers reject Domain=.sami
+  // because .sami is an unregistered custom TLD and therefore treated as a
+  // public suffix. Cross-subdomain login is handled by the one-time SSO
+  // handoff below, which mints a separate host-only cookie on each service.
   function setSessionCookie(res, durationKey) {
     const durationMs = SESSION_DURATIONS[durationKey];
     if (!durationMs) return;
@@ -235,9 +239,8 @@ module.exports = function configureMiddleware(app, {
     const payloadB64 = Buffer.from(JSON.stringify(payload)).toString('base64url');
     const key = cryptoUtils.loadOrCreateKey();
     const sig = crypto.createHmac('sha256', key).update(payloadB64).digest('base64url');
-    const domainAttr = siteConfig.tld ? `; Domain=${siteConfig.tld}` : '';
     res.setHeader('Set-Cookie',
-      `${SESSION_COOKIE_NAME}=${payloadB64}.${sig}${domainAttr}; Max-Age=${maxAge}; Path=/; HttpOnly; Secure; SameSite=Lax`
+      `${SESSION_COOKIE_NAME}=${payloadB64}.${sig}; Max-Age=${maxAge}; Path=/; HttpOnly; Secure; SameSite=Lax`
     );
   }
 
@@ -268,9 +271,8 @@ module.exports = function configureMiddleware(app, {
   }
 
   function clearSessionCookie(res) {
-    const domainAttr = siteConfig.tld ? `; Domain=${siteConfig.tld}` : '';
     res.setHeader('Set-Cookie',
-      `${SESSION_COOKIE_NAME}=; Max-Age=0${domainAttr}; Path=/; HttpOnly; SameSite=Lax`
+      `${SESSION_COOKIE_NAME}=; Max-Age=0; Path=/; HttpOnly; Secure; SameSite=Lax`
     );
   }
 
@@ -278,11 +280,12 @@ module.exports = function configureMiddleware(app, {
   // + the write-back in this function) caused cross-subdomain SSO breakage when
   // Caddy on --network host forwards auth to the container: req.ip arrives as
   // 100.121.150.22 (DNS2's tailnet IP) instead of the user's real IP, so the
-  // IP cache misses even when the cookie is valid. The cookie is signed with a
-  // persisted HMAC key (loadOrCreateKey()), scoped to .sami via Domain attr,
-  // HttpOnly + Secure + SameSite=Lax — it's a stronger credential than the IP
-  // cache. Ref: skill auth-and-monitoring-pitfalls.md "TOTP session validation
-  // IP-key issue" (FIXED 2026-07-21).
+  // IP cache misses even when the cookie is valid. The host-only cookie is
+  // signed with a persisted HMAC key (loadOrCreateKey()). Cross-subdomain
+  // authentication uses the one-time SSO handoff because browsers reject
+  // Domain=.sami. HttpOnly + Secure + SameSite=Lax makes it a stronger
+  // credential than the IP cache. Ref: skill auth-and-monitoring-pitfalls.md
+  // "TOTP session validation IP-key issue" (FIXED 2026-07-21).
   function isSessionValid(req) {
     const cookies = parseCookies(req.headers.cookie);
     if (verifySessionCookie(cookies[SESSION_COOKIE_NAME])) {
@@ -333,18 +336,7 @@ module.exports = function configureMiddleware(app, {
   }
 
   function setHostOnlySessionCookie(res, durationKey) {
-    const durationMs = SESSION_DURATIONS[durationKey];
-    if (!durationMs) return;
-    const maxAge = Math.floor(durationMs / 1000);
-    const payload = { v: true, exp: Date.now() + durationMs };
-    const payloadB64 = Buffer.from(JSON.stringify(payload)).toString('base64url');
-    const key = cryptoUtils.loadOrCreateKey();
-    const sig = crypto.createHmac('sha256', key).update(payloadB64).digest('base64url');
-    // No Domain attribute — host-only, so it's always accepted regardless of
-    // the .sami public-suffix issue described above.
-    res.setHeader('Set-Cookie',
-      `${SESSION_COOKIE_NAME}=${payloadB64}.${sig}; Max-Age=${maxAge}; Path=/; HttpOnly; Secure; SameSite=Lax`
-    );
+    setSessionCookie(res, durationKey);
   }
 
   // ── Public routes (bypass TOTP and JWT auth) ──