反远程进程注入DLL

******参考GitHub上的AntiInject******

1，远程进程注入DLL调用CreateRemoteThread这个API进行注入，而这个API会在目标进程中创建一个进程来调用LoadLibrary来加载自己想注入的DLL从而达到注入效果。

2，在一个进程已经加载的DLL中，每当一个Thread创建的时候就会给每一个加载的DLL发送一个消息DLL_THREAD_ATTACH，我们可以在自己的DLL中来截获每一个线程创建时候的消息，然后判断这个线程起始地址是否是LoadLibraryA/W来判断这个线程是否是通过远程线程注入进来的。

实现代码：

void CheckInject(DWORD dwProcessId);

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
					 )
{
	switch (ul_reason_for_call)
	{
	case DLL_THREAD_ATTACH:
		CheckInject(GetCurrentProcessId());    //每次新的线程创建时候检测
		break;
	}
	return TRUE;
}

DWORD GetThreadStartAddr(DWORD dwThreadId)
{
	HANDLE hThread = OpenThread(THREAD_QUERY_INFORMATION,FALSE,dwThreadId);
	DWORD dwStartAddr,dwReturnLen;
	if (hThread == NULL)
		return 0;
	NtQueryInformationThread(hThread,            //查询线程起始地址
		ThreadQuerySetWin32StartAddress,
		&dwStartAddr,
		4,
		&dwReturnLen);
	return dwStartAddr;
}

void Check_StartAddr(DWORD dwStartAddr,DWORD dwThreadId)
{
	DWORD dwAddr_LoadLibraryA = (DWORD)GetProcAddress(GetModuleHandleA("Kernel32.dll"), "LoadLibraryA");
	DWORD dwAddr_LoadLibraryW = (DWORD)GetProcAddress(GetModuleHandleA("Kernel32.dll"), "LoadLibraryW");

	if (dwStartAddr == dwAddr_LoadLibraryA || dwStartAddr == dwAddr_LoadLibraryW)
	{
		if (MessageBoxA(0, "发现注入的DLL线程，是否杀掉？", "提示", MB_OKCANCEL) == IDOK)
		{
			TerminateThread(OpenThread(THREAD_ALL_ACCESS,FALSE,dwThreadId),0);
		}
	}
}

void CheckInject(DWORD dwProcessId)
{
	HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, dwProcessId);

	THREADENTRY32 te32 = { sizeof(te32) };
	Thread32First(hSnapshot, &te32);
	do
	{
		if (te32.th32OwnerProcessID == dwProcessId)
		{
			Check_StartAddr(GetThreadStartAddr(te32.th32ThreadID),te32.th32ThreadID);    //遍历当前进程所有线程的起始地址
		}
	} while (Thread32Next(hSnapshot, &te32));
}