<?php
session_start();

$ip = $_SERVER['REMOTE_ADDR'];
$user_agent = $_SERVER['HTTP_USER_AGENT'];

// 1. 从文件中读取黑名单IP地址
$blacklist_file = fopen("/blacklist.txt", "r");
$blacklist = array();
while (($line = fgets($blacklist_file)) !== false) {
    $blacklist[] = trim($line);
}
fclose($blacklist_file);

// 将攻击者IP地址添加到黑名单中
if (in_array($_SERVER['REMOTE_ADDR'], $blacklist)) {
    die("停下您的攻击,您已被禁止访问！");
}

// 2. 访问频率限制
$count = 0;
$time = time() - 180; // 限制3分钟内的访问频率
$req_count_diff = 0; // 记录请求次数的变量
// 检查来自同一IP地址的请求频率
$access_log = file("/log");
foreach ($access_log as $line) {
    $tokens = explode(" ", $line);
    $timestamp = strtotime($tokens[3]);
    if (($tokens[0] == $ip) && ($timestamp > $time)) {
        $count++;
        $req_count_diff++;
    }
}
// 如果访问频率超过限制，则延迟3秒
if ($count > 100) {
    sleep(3);
}

// 3. 用户行为分析
if ($_SESSION['last_request']) {
    $last_request = $_SESSION['last_request'];
    $req_count_diff = $req_count_diff - $last_request['req_count'];
    $ua_diff = strcmp($last_request['user_agent'], $user_agent);

    // 如果请求异常，则将IP地址添加到黑名单中
    if (($ua_diff !== 0) || ($req_count_diff >= 100)) {
        $blacklist_file = fopen("/blacklist.txt", "a");
        fwrite($blacklist_file, "$ip\n");
        fclose($blacklist_file);
        die("Your IP address has been banned from accessing this website.");
    }
}

// 记录最后一个请求
$_SESSION['last_request'] = array(
    "req_count" => $req_count_diff,
    "user_agent" => $user_agent
);

// 正常的页面渲染代码
echo "Hello, World!";
?>