ring3 hook ZwWriteVirtualMemory

typedef LONG NTSTATUS;
typedef NTSTATUS (NTAPI
*PNtZwWriteVirtualMemory) ( IN HANDLE hProcess, IN PVOID BaseAddress, IN
PVOID Buffer, IN ULONG BytesToWrite, OUT PULONG BytesWritten );
PNtZwWriteVirtualMemory ZwWriteVirtualMemory;

BYTE m_OldZwWVMBytes[5];
BYTE m_HookJmpByte[5];

NTSTATUS WINAPI Mine_ZwWriteVirtualMemory( IN HANDLE hProcess, IN
PVOID BaseAddress, IN PVOID Buffer, IN ULONG BytesToWrite, OUT PULONG
BytesWritten )
{
    memcpy(ZwWriteVirtualMemory,m_OldZwWVMBytes,sizeof(m_OldZwWVMBytes));
    BOOL ret=ZwWriteVirtualMemory(hProcess,BaseAddress,Buffer,BytesToWrite,BytesWritten);
   
char buf[1024];wsprintf(buf,"ZWWPM : %X  %X  %X  %d
%d",hProcess,BaseAddress,Buffer,BytesToWrite,ret);OutputDebugString(buf);
    memcpy(ZwWriteVirtualMemory,m_HookJmpByte,sizeof(m_HookJmpByte));
    return ret;
}

VOID _START()
{
    ZwWriteVirtualMemory = (PNtZwWriteVirtualMemory)GetProcAddress(::GetModuleHandle("ntdll.dll"),"ZwWriteVirtualMemory" );
    CString strMsg;
    strMsg.Format("ZwWriteVirtualMemory:  %X",ZwWriteVirtualMemory);OutputDebugString(strMsg);

ReadProcessMemory(GetCurrentProcess(),(LPVOID)ZwWriteVirtualMemory,m_OldZwWVMBytes,5,NULL);
   
strMsg.Format("m_OldRecvBytes: %x %x %x %x %x", m_OldZwWVMBytes[0],
m_OldZwWVMBytes[1], m_OldZwWVMBytes[2], m_OldZwWVMBytes[3],
m_OldZwWVMBytes[4]);OutputDebugString(strMsg);   
    
    m_HookJmpByte[0]=0xE9;
    DWORD data=(DWORD)Mine_ZwWriteVirtualMemory-(DWORD)ZwWriteVirtualMemory-5;
    memcpy(m_HookJmpByte+1,(VOID*)&data,4);
   
strMsg.Format("JmpByte: %x %x %x %x %x", m_HookJmpByte[0],
m_HookJmpByte[1], m_HookJmpByte[2], m_HookJmpByte[3],
m_HookJmpByte[4]);OutputDebugString(strMsg);
    DWORD dwScratch;
    VirtualProtectEx(GetCurrentProcess(),(LPVOID)ZwWriteVirtualMemory, 10, PAGE_EXECUTE_READWRITE, &dwScratch);
    memcpy(ZwWriteVirtualMemory,m_HookJmpByte,sizeof(m_HookJmpByte));
}

BOOL CInjectDllApp::InitInstance()
{
    OutputDebugString("InitInstance");
    ::CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)_START, NULL, 0, NULL);
    return CWinApp::InitInstance();
}