decryptToBytes method

Implementation

Future<List<int>> decryptToBytes(String envelopeString, String passphrase) async {
  if (type == CryptoType.none) {
    // No encryption: interpret envelopeString as base64 of raw bytes
    try {
      final bytes = base64Decode(envelopeString);
      _log(LogLevel.debug, 'DecryptBytes none base64 -> len=${bytes.length}');
      return bytes;
    } catch (_) {
      // If not base64, maybe it was plaintext string -> return UTF-8 bytes
      final bytes = await JsonIsolates.utf8Encode(envelopeString);
      _log(LogLevel.debug, 'DecryptBytes none plaintext -> len=${bytes.length}');
      return bytes;
    }
  }
  try {
    // Parse envelope JSON in an isolate
    final j = await JsonIsolates.decodeMap(envelopeString);
    final s = base64Decode(j['salt']);
    final n = base64Decode(j['nonce']);
    final c = base64Decode(j['ciphertext']);
    final m = Mac(base64Decode(j['mac']));
    final ti = type.index - 1;
    final kb = const [128, 256, 256][ti];
    final k = await _deriveKey(passphrase, s, bits: kb);
    final sb = SecretBox(c, nonce: n, mac: m);
    final algos = [_aesGcm128, _aesGcm256, _chacha20];
    final algo = algos[ti];
    final x = await algo.decrypt(sb, secretKey: k);
    _log(LogLevel.debug, 'DecryptBytes ok len=${x.length}');
    return x;
  } catch (e) {
    throw GitStorageException('Erro ao descriptografar: $e');
  }
}