library outputdebugstring;

Uses
  Windows;

function Enigma_Plugin_About : PWideChar;
begin
  Enigma_Plugin_About := 'Enigma anti-debugger plugin - OutputDebugString © Vladimir Sukhov 30 August 2008';
end;

function Enigma_Plugin_Description : PWideChar;
begin
  Enigma_Plugin_Description := 'This plugin uses OutputDebugString function to find a debugger.'#10#13 +
                               'If debugger is found, plugin shows a message and terminates application.';
end;

const
  MB_ICONERROR = $00000010;

  Title : pchar = 'Error';
  Text : pchar = 'Debugger is found on this machine!';

var
  TimerID : cardinal;

procedure ExitWithMessage; assembler;
asm
  // Clear some addresses in stack
  mov ecx, 5
  @clear_loop:
  dec ecx
  mov dword ptr [ecx * 4 + esp], 0
  cmp ecx, 0
  jnz @clear_loop
  // Parametr for ExitProcess
  push 0
  // Parameters for MessageBoxA
  push MB_ICONERROR
  push Title
  push Text
  push 0
  // Return address of MessageBox that points to ExitProcess
  lea eax, ExitProcess
  push eax
  jmp MessageBoxA
end;

procedure CheckDebugger;
begin
  // This plugin uses OutputDebugString function to find a debugger
  // This function is placed into timer loop with 2 seconds delay and works all the time when
  // main application is working
  OutputDebugStringA('Debug');
  if GetLastError = 0 then
  begin
    KillTimer(0, TimerID);
    ExitWithMessage;
  end;
end;

procedure CheckDebugger_Timer(hwnd : cardinal; uMsg, idEvent, dwTime : cardinal); stdcall;
begin
  if idEvent <> TimerID then Exit;
  CheckDebugger;
end;

procedure Enigma_Plugin_OnInit;
var
  lpVersionInfo : _OSVERSIONINFOA;
begin
  // it works only on XP! On other Os it always detects a debugger.
  lpVersionInfo.dwOSVersionInfoSize := sizeof(lpVersionInfo);
  if not GetVersionExA(lpVersionInfo) then Exit;
  if (lpVersionInfo.dwMajorVersion = 5) and (lpVersionInfo.dwMinorVersion = 2) then
  begin
    CheckDebugger;
    TimerID := SetTimer(0, 1, 2000, @CheckDebugger_Timer);
  end;
end;

exports
  Enigma_Plugin_About,
  Enigma_Plugin_Description,
  Enigma_Plugin_OnInit;

begin
end.

