Отключение dll от стороннего процесса

library Drawer;
 
uses
  Windows, Messages;
 
var
  hWindow: HWND;
  processId: DWORD;
  hWndDc, hBitmapDc: HDC;
  hBitmap: HGDIOBJ;
  hPen, hBrush1, hBrush2: HGDIOBJ;
  wndRect: TRect;
  wndWidth, wndHeight, wndCX, wndCY, size: LongInt;
  prevWindowProc: Pointer;
 
function WindowProc(hWnd: HWND; Msg: UINT; wParam: WPARAM;
  lParam: LPARAM): LRESULT; stdcall;
begin
  Result := 0;
  case Msg of
    WM_ERASEBKGND:
    begin
      CallWindowProc(prevWindowProc, hWnd, Msg, wParam, lParam);
      BitBlt(wParam, 0, 0, wndWidth - 1, wndHeight - 1, hBitmapDc, 0, 0, SRCAND);
      Result := 1;
    end;
    else
      Result := CallWindowProc(prevWindowProc, hWnd, Msg, wParam, lParam);
  end;
end;
 
procedure DllEntryPoint(Reason: Integer);
var
  ProcessId: Cardinal;
begin
  GetWindowThreadProcessID(hWindow, ProcessId);
  if ProcessID <> GetCurrentProcessID() then
    exit;
  if Reason = DLL_PROCESS_DETACH then
  begin
    SetWindowLong(hWindow, GWL_WNDPROC, Integer(prevWindowProc));
 
    DeleteDc(hBitmapDc);
    DeleteObject(hBitmap);
    DeleteObject(hPen);
    DeleteObject(hBrush1);
    DeleteObject(hBrush2);
  end;
end;
 
begin
  DisableThreadLibraryCalls(hInstance);
 
  hWindow := FindWindow('Progman', nil);
  hWindow := GetWindow(hWindow, GW_CHILD);
 
  GetWindowThreadProcessID(hWindow, ProcessId);
  if ProcessID <> GetCurrentProcessID() then
    exit;
 
  GetWindowRect(hWindow, wndRect);
  wndWidth := wndRect.Right - wndRect.Left + 1;
  wndHeight := wndRect.Bottom - wndRect.Top + 1;
  wndCX := wndWidth div 2;
  wndCY := wndHeight div 2;
  if wndWidth > wndHeight then
    size := wndHeight div 4
  else
    size := wndWidth div 4;
 
  hWndDc := GetDC(hWindow);
  hBitmap := CreateCompatibleBitmap(hWndDc, wndWidth, wndHeight);
  hBitmapDc := CreateCompatibleDC(hWndDc);
  ReleaseDc(hWindow, hWndDc);
  hPen := GetStockObject(BLACK_PEN);
  hBrush1 := CreateHatchBrush(HS_CROSS, RGB(0, 0, 0));
  hBrush2 := GetStockObject(WHITE_BRUSH);
 
  SelectObject(hBitmapDc, hBitmap);
  SelectObject(hBitmapDc, hPen);
  SelectObject(hBitmapDc, hBrush1);
  PatBlt(hBitmapDc, 0, 0, wndWidth - 1, wndHeight - 1, PATCOPY);
  SelectObject(hBitmapDc, hBrush2);
  Ellipse(hBitmapDc, wndCX - size, wndCY - size, wndCX + size, wndCY + size);
 
  prevWindowProc := Pointer(
    SetWindowLong(hWindow, GWL_WNDPROC, Integer(@WindowProc))
    );
 
  DllProc := DllEntryPoint;
end.

uses
  Windows;
 
var
  hWindow: HWND;
  hProcess, hThread: THandle;
  processId, threadId: Cardinal;
  pFileName: PChar;
  n: Cardinal;
  pLoadLibrary, pFreeLibrary: Pointer;
  hKernel32, hDrawerDll: HMODULE;
  fileName: array [0..MAX_PATH] of Char;
 
begin
  SearchPath(nil, 'drawer.dll', nil, sizeof(fileName), @fileName, PPChar(nil)^);
  hWindow := FindWindow('ProgMan', nil);
  GetWindowThreadProcessId(hWindow, processId);
  hProcess := OpenProcess(PROCESS_ALL_ACCESS, false, processId);
  pFileName := VirtualAllocEx(hProcess, nil, sizeof(fileName),
    MEM_RESERVE or MEM_COMMIT, PAGE_READWRITE);
  WriteProcessMemory(hProcess, pFileName, @fileName, sizeof(fileName), n);
  hKernel32 := GetModuleHandle('kernel32.dll');
  pLoadLibrary := GetProcAddress(hKernel32, 'LoadLibraryA');
  pFreeLibrary := GetProcAddress(hKernel32, 'FreeLibrary');
  hThread := CreateRemoteThread(hProcess, nil, 0, pLoadLibrary,
    pFileName, 0, threadId);
  WaitForSingleObject(hThread, INFINITE);
  GetExitCodeThread(hThread, hDrawerDll);
  CloseHandle(hThread);
  VirtualFreeEx(hProcess, pFileName, 0, MEM_RELEASE);
  MessageBox(0, 'Press OK to unload', '...', 0);
  hThread := CreateRemoteThread(hProcess, nil, 0, pFreeLibrary,
    Pointer(hDrawerDll), 0, threadId);
 
  WaitForSingleObject(hThread, INFINITE);
  GetExitCodeThread(hThread, hDrawerDll);
 
  CloseHandle(hThread);
  CloseHandle(hProcess);
end.