Pimcore\Update::isWriteable PHP Method

    public static function isWriteable()
    {
        if (self::$dryRun) {
            return true;
        }
        // check permissions
        $files = rscandir(PIMCORE_PATH . "/");
        foreach ($files as $file) {
            if (!is_writable($file)) {
                return false;
            }
        }
        return true;
    }

 public function checkFilePermissionsAction()
 {
     $success = false;
     if (Update::isWriteable()) {
         $success = true;
     }
     $this->_helper->json(array("success" => $success));
 }