program NitradoDec;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Classes,
  zlib,
  Math,
  AnsiStrings;

var
  ms1, ms2: TMemoryStream;
  z: TZDecompressionStream;
  i, j: Integer;
  b, count: Byte;
  size: Integer;
  temp: Cardinal;

const
  Vigenère: AnsiString = '2lly4t4SI8cHoU4h.rk90bk/CvYUq8c4Ols1STx';
  Base64: AnsiString = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

begin
  try
    writeln('Nitrado-Snapshot-Dekoder // yat.qa // 10. Dezember 2016');
    ms1 := TMemoryStream.Create;
    ms2 := TMemoryStream.Create;
    ms1.LoadFromFile(paramstr(1));
    z := TZDecompressionStream.Create(ms1);
    ms2.CopyFrom(z, z.Size);
    // Nicht-Base64-Zeichen löschen
    ms2.Position := 0;
    ms1.Clear;
    for i := 0 to ms2.Size - 1 do
    begin
      ms2.ReadBuffer(b, 1);
      case b of
        $2b, $2f, $30..$39, $41..$5a, $61..$7a: ms1.WriteBuffer(b, 1);
      end;
    end;
    // Base64-Decoder (binary-safe)
    ms1.Position := 0;
    ms2.Clear;
    size := ms1.Size;
    for i := 0 to (size + 3) div 4 - 1 do
    begin
      count := Min(size - i * 4, 4); // Größe des Base64-Blocks (max. 24 Bits, also 4 Zeichen)
      temp := 0;
      for j := 1 to count do
      begin
        ms1.ReadBuffer(b, 1);
        temp := temp shl 6 + Byte(AnsiStrings.PosEx(AnsiChar(b), Base64)) - 1;
      end;
      temp := temp shl (24 - count * 6);
      temp := temp and $ff00 + temp shl 16 + temp shr 16; // Endianness drehen (vereinfacht weil nur 3 Byte verwendet)
      ms2.WriteBuffer(temp, count - 1);
    end;
    // Entschlüsseln
    ms2.Position := 0;
    ms1.Clear;
    for i := 0 to ms2.Size - 1 do
    begin
      ms2.ReadBuffer(b, 1);
      b := b - Byte(Vigenère[i mod 39 + 1]);
      ms1.WriteBuffer(b, 1);
    end;
    ms1.SaveToFile(paramstr(1) + '.decoded');
    writeln('Erfolgreich dekodiert!');
  except
    on E:Exception do
      Writeln(E.Classname, ': ', E.Message);
  end;
  readln;
end.