/**
  * 验证子系统请求头,确保是子系统的请求
  */
 public function authenticate($user, $request, $response)
 {
     $headers = $request->headers;
     $ticket = $request->get('ticket');
     if (isset($headers['app-id']) && isset($headers['signkey']) && isset($headers['once'])) {
         if (!$this->checkHeader($headers)) {
             return null;
         }
         $user = User::findIdentityByTicket($ticket);
         if ($user != null) {
             \Yii::$app->user->login($user);
             return $user;
         }
     }
     if ($ticket !== null) {
         $this->handleFailure($response);
     }
     return null;
 }