Simple prevention of multiple malicious machine submission attacks

Let’s talk about the background first: the machine’s continuous sending of requests or malicious submissions will put a lot of pressure on the server; the best strategy for this kind of attack is to determine the number of submissions and generate a dynamic verification code , that is, determine the IP within the specified time Send the pop-up verification code repeatedly for N times. The following is a simple process of identifying IP and using session recording and defense in practice.

The process of identifying and verifying ip

is as follows;

• Identify ip

• ip belongs to the whitelist directly through [whitelist policy: intranet ip + designated ip table]

• Use session to store ip Request timestamp

• Verify the number of IP requests within the specified time

• Take corresponding measures

<code>/**
 * 获取和校验ip；同时防止短时间内多次提交
 *
 * @notice        ：弹出验证码，需要替换掉echo $echo_str 即可。
 * @return string ：返回校验成功的ip
 */
protected function getAndCheckIP()
{

    // 获取环境ip
    if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))
        $ip = getenv("HTTP_CLIENT_IP");
    else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown"))
        $ip = getenv("HTTP_X_FORWARDED_FOR");
    else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown"))
        $ip = getenv("REMOTE_ADDR");
    else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown"))
        $ip = $_SERVER['REMOTE_ADDR'];
    else
        $ip = "unknown";

    // check 环境ip
    if (!$this->isWhiteList($ip)) {
        $echo_str = "提交过于频繁,请稍后再试！";
        // 构建ip的时间栈数据
        if (!is_array($_SESSION[$ip])) {
            $_SESSION[$ip] = array();
        }

        if (isset($_SESSION[$ip][0])) {
            $_SESSION[$ip][] = time();

            // session 保存时间为6小时。清理session
            $post_interval_first = time() - $_SESSION[$ip][0];
            if ($post_interval_first > 21600) {
                $_SESSION[$ip] = array();
            }

            // 两次提交小于1s，禁止提交
            $post_interval_pre = time() - $_SESSION[$ip][count($_SESSION[$ip]) - 3];
            if ($post_interval_pre < 1) {
                echo $echo_str;
                exit;
            };

            // 您在10s内已经提交了3请求，禁止提交
            $post_interval_third = time() - $_SESSION[$ip][count($_SESSION[$ip]) - 3];
            if (isset($_SESSION[$ip][3]) && ($post_interval_third < 10)) {
                echo $echo_str;
                exit;
            }

            // 您在1分钟期间已经提交了5请求，禁止提交
            $post_interval_fifth = time() - $_SESSION[$ip][count($_SESSION[$ip]) - 3];
            if (isset($_SESSION[$ip][5]) && ($post_interval_fifth < 60)) {
                echo $echo_str;
                exit;
            }

            // 6小时内提交10次，禁止提交
            if (isset($_SESSION[$ip][10])) {
                echo $echo_str;
                exit;
            }
        } else {
            $_SESSION[$ip][] = time();
        }
    }

    return ($ip);
}
</code>

Whitelist strategy

The whitelist strategy adopts: intranet IP release and specific IP release

<code>/**
 * 检验是否存在于白名单中
 *
 * @param $ip    ：校验的ip
 * @return bool  ：校验结果
 */
function isWhiteList($ip){
    /**
     * 内网ip默认全部存在于白名单中
     */
    if(!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE)){
        return true;
    }

    // 是否在写死的whitelist 里面
    return in_array($ip,$this->_WHTTE_LIST);
}
</code>

Anti-attack strategy

Xiaoya adopts a relatively simple strategy, such as the above code, which can be combined with business needs in the actual process.

• No repeated submissions within 1s

• Maximum submission 3 times within 5s

• Maximum submission 5 times within 60s

• Maximum submission 10 times within 6 hours

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The above introduces the simple prevention of multiple malicious submission attacks on the machine, including aspects of the attack. I hope it will be helpful to friends who are interested in PHP tutorials.