hasDerEs256Signature method

bool hasDerEs256Signature(Map<String, dynamic> credential)

Whether credential contains a structurally complete DER sequence.

Implementation

bool hasDerEs256Signature(Map<String, dynamic> credential) {
  final response = credential['response'];
  if (response is! Map || response['signature'] is! String) return false;
  try {
    final bytes = _decodeBase64Url(response['signature'] as String);
    if (bytes.length < 8 ||
        bytes.first != 0x30 ||
        bytes[1] != bytes.length - 2 ||
        bytes[2] != 0x02) {
      return false;
    }
    final rLength = bytes[3];
    final sTag = 4 + rLength;
    if (rLength < 1 ||
        rLength > 33 ||
        sTag + 2 > bytes.length ||
        bytes[sTag] != 0x02) {
      return false;
    }
    final sLength = bytes[sTag + 1];
    return sLength >= 1 &&
        sLength <= 33 &&
        sTag + 2 + sLength == bytes.length;
  } on FormatException {
    return false;
  }
}