delphi xe3 dll injection for 64bit dll to 64bit process doesn't work

Question

I'm using this code to inject my 64bit dll into a 64bit process on windows 7 64 bit,CreateRemoteThread return 200 but still the dll does not injected, I tested my dll with another source and it works fine, Process Explorer shows that my code does not work,What can be wrong with this code, I'm using delphi XE3 and i have compile the code on 64bit target platform.

function InjectDLL(dwPID: DWORD; DLLPath: pwidechar): integer;
var
dwThreadID: Cardinal;
hProc, hThread, hKernel: NativeUInt;
BytesWritten: NativeUInt;
pRemoteBuffer, pLoadLibrary: Pointer;
begin
try
hProc := OpenProcess(PROCESS_ALL_ACCESS, False, dwPID);
if hProc = 0 then
begin
  Result := 0;
  Exit;
end;
pRemoteBuffer := VirtualAllocEx(hProc, nil, Length(DLLPath) + 1, MEM_COMMIT,
  PAGE_READWRITE);
if pRemoteBuffer = nil then
begin
  Result := 0;
  Exit;
end;
if WriteProcessMemory(hProc, Pointer(pRemoteBuffer), lpvoid(DLLPath),
  Length(DLLPath) + 1, BytesWritten) = False then
begin
  Result := 0;
  Exit;
end;
hKernel := GetModuleHandle(pwidechar('kernel32.dll'));
pLoadLibrary := (GetProcAddress(hKernel, pansichar('LoadLibraryA')));
hThread := CreateRemoteThread(hProc, Pointer(nil), 0, Pointer(pLoadLibrary),
  Pointer(pRemoteBuffer), 0, dwThreadID);

WaitForSingleObject(hThread, INFINITE);
VirtualFreeEx(hProc, Pointer(pRemoteBuffer), Length(DLLPath) + 1,
  MEM_RELEASE);
CloseHandle(hThread);
CloseHandle(hProc);
// ShowMessage(IntToStr(hThread)+' '+ inttostr(dwThreadID));
Result := 1;
except
on d: exception do
begin
end;
end;
end;

Answer 1

You are calling LoadLibraryA, but passing it UTF-16 encoded data. Either switch to LoadLibraryW or convert the module name to ANSI.

I would do the former. As well as switching to LoadLibraryW, you need to copy the entire buffer. Achieve that by replacing the two instances of Length(DLLPath) + 1 with SizeOf(Char)*(Length(DLLPath) + 1).

Some more comments:

• Using PROCESS_ALL_ACCESS is excessive. You only need PROCESS_CREATE_THREAD or PROCESS_QUERY_INFORMATION or PROCESS_VM_OPERATION or PROCESS_VM_WRITE or PROCESS_VM_READ.
• The PAnsiChar cast in GetProcAddress(hKernel, pansichar('LoadLibraryA')) looks wrong. Because 'LoadLibraryA' is UTF-16 encoded. Just use GetProcAddress(hKernel, 'LoadLibraryA'). Or 'LoadLibraryW' if you go down that route.
• Using NativeUInt for handles is wrong. It doesn't actually matter, but you should use THandle.
• When using MEM_RELEASE you must pass 0 for the size parameter.

Put that all together and the code should look like this:

function InjectDLL(dwPID: DWORD; DLLPath: PWideChar): integer;
var
  dwThreadID: Cardinal;
  hProc, hThread, hKernel: THandle;
  BytesToWrite, BytesWritten: SIZE_T;
  pRemoteBuffer, pLoadLibrary: Pointer;
begin
  hProc := OpenProcess(PROCESS_CREATE_THREAD or PROCESS_QUERY_INFORMATION or PROCESS_VM_OPERATION or PROCESS_VM_WRITE or PROCESS_VM_READ, False, dwPID);
  if hProc = 0 then
    exit(0);
  try
    BytesToWrite := SizeOf(WideChar)*(Length(DLLPath) + 1);
    pRemoteBuffer := VirtualAllocEx(hProc, nil, BytesToWrite, MEM_COMMIT, PAGE_READWRITE);
    if pRemoteBuffer = nil then
      exit(0);
    try
      if not WriteProcessMemory(hProc, pRemoteBuffer, DLLPath, BytesToWrite, BytesWritten) then
        exit(0);
      hKernel := GetModuleHandle('kernel32.dll');
      pLoadLibrary := GetProcAddress(hKernel, 'LoadLibraryW');
      hThread := CreateRemoteThread(hProc, nil, 0, pLoadLibrary, pRemoteBuffer, 0, dwThreadID);
      try
        WaitForSingleObject(hThread, INFINITE);
      finally
        CloseHandle(hThread);
      end;
    finally
      VirtualFreeEx(hProc, pRemoteBuffer, 0, MEM_RELEASE);
    end;
  finally
    CloseHandle(hProc);
  end;
  exit(1);
end;

Personally, I'd probably pass in a string rather than a PWideChar, but perhaps you have some other motivation for doing that.