public function role($src, $value = '') {
        if (isset($this->_config->config['firewall']['' . $src . ''])) {
            if ($value == '') {
                $role = explode('.', $this->_config->config['firewall']['' . $src . '']['roles']['name']);

                return $this->_getSession($role);
            }
            else {
                $role = explode('.', $this->_config->config['firewall']['' . $src . '']['roles']['name']);
                $this->_setSession($role, $value);
            }
        }
        else {
            throw new MissingConfigException('the module ' . $src . ' doesn\'t exist');
        }

        return false;
    }