challenge method

@override Future<Authenticate> challenge(Extra extra)

Called when the router sends a challenge (CHALLENGE frame).

Implementation

@override
Future<Authenticate> challenge(Extra extra) async {
  _ensureUsable();
  final generation = ++_attemptGeneration;
  await _cancelTaskOnly();
  _clearExpectedVerifier();
  await AbstractAuthentication.streamAddAwaited<Extra>(
    _challengeStreamController,
    extra,
  );

  final helloNonce = _helloNonce;
  final authId = _authid;
  final serverNonce = extra.nonce;
  if (serverNonce == null ||
      helloNonce == null ||
      serverNonce.length < helloNonce.length ||
      !serverNonce.startsWith(helloNonce)) {
    throw Exception('Wrong nonce');
  }
  if (authId == null) throw StateError('SCRAM authid is required');
  _validateChallenge(extra);

  final authExtra = HashMap<String, Object?>()
    ..['nonce'] = serverNonce
    ..['channel_binding'] = null
    ..['cbind_data'] = null;
  final signature = await _createSignatureAsync(
    authId,
    helloNonce,
    extra,
    authExtra,
    generation,
  );
  if (_attemptGeneration != generation || _disposed) {
    throw const ScramKeyDerivationCancelledException();
  }
  return Authenticate()
    ..extra = authExtra
    ..signature = signature;
}