createSignature method

String createSignature(String authId, String helloNonce, Extra extra, HashMap<String, Object?> authExtra,)

Calculates the client proof according to the WAMP-SCRAM specs where authId is the username that has already been saslpreped with Saslprep.saslprep(input) and helloNonce is a randomly generated nonce according to the WAMP-SCRAM specs. The keylength is 32 according to the WAMP-SCRAM specs

Implementation

String createSignature(String authId, String helloNonce, Extra extra,
    HashMap<String, Object?> authExtra) {
  if (!_reuseClientKey || _clientKey == null) {
    late Uint8List saltedPassword;
    if (extra.kdf == kdfPbkdf2) {
      saltedPassword = CraAuthentication.deriveKey(
          _secret!,
          extra.salt == null
              ? CraAuthentication.defaultKeySalt
              : base64.decode(extra.salt!),
          iterations: extra.iterations!,
          keylen: defaultKeyLength);
    } else if (extra.kdf == kdfArgon) {
      saltedPassword = Uint8List(32);
      Argon2BytesGenerator()
        ..init(Argon2Parameters(Argon2Parameters.ARGON2_id,
            Uint8List.fromList(base64.decode(extra.salt!)),
            desiredKeyLength: defaultKeyLength,
            iterations: extra.iterations ?? 1000,
            memory: extra.memory ?? 100,
            version: Argon2Parameters.ARGON2_VERSION_13))
        ..deriveKey(
            Uint8List.fromList(_secret!.codeUnits), 0, saltedPassword, 0);
    }
    _clientKey = CraAuthentication.encodeByteHmac(
        saltedPassword, defaultKeyLength, 'Client Key'.codeUnits);
    if (!_firstClientKeyCompleter.isCompleted) {
      _firstClientKeyCompleter.complete(_clientKey);
    }
  }

  var storedKey = SHA256Digest().process(Uint8List.fromList(_clientKey!));
  var clientSignature = CraAuthentication.encodeByteHmac(
      storedKey,
      defaultKeyLength,
      createAuthMessage(authId, helloNonce, authExtra, extra).codeUnits);
  var signature = [
    for (int i = 0; i < _clientKey!.length; i++)
      _clientKey![i] ^ clientSignature[i]
  ];
  return base64.encode(signature);
}