/// <summary>
        /// Ensure that federated authentication option is valid
        /// </summary>
        protected virtual TDSMessageCollection CheckFederatedAuthenticationOption(ITDSServerSession session, TDSLogin7FedAuthOptionToken federatedAuthenticationOption)
        {
            // Check if server's prelogin response for FedAuthRequired prelogin option is echoed back correctly in FedAuth Feature Extenion Echo
            if (federatedAuthenticationOption.Echo != (session as GenericTDSServerSession).FedAuthRequiredPreLoginServerResponse)
            {
                // Create Error message
                string message =
                    string.Format("FEDAUTHREQUIRED option in the prelogin response is not echoed back correctly: in prelogin response, it is {0} and in login, it is {1}: ",
                                  (session as GenericTDSServerSession).FedAuthRequiredPreLoginServerResponse,
                                  federatedAuthenticationOption.Echo);

                // Create errorToken token
                TDSErrorToken errorToken = new TDSErrorToken(3456, 34, 23, message);

                // Log response
                TDSUtilities.Log(Arguments.Log, "Response", errorToken);

                // Create DONE token
                TDSDoneToken doneToken = new TDSDoneToken(TDSDoneTokenStatusType.Final | TDSDoneTokenStatusType.Error);

                // Log response
                TDSUtilities.Log(Arguments.Log, "Response", doneToken);

                // Build a collection with a single message of two tokens
                return(new TDSMessageCollection(new TDSMessage(TDSMessageType.Response, errorToken, doneToken)));
            }

            // Check if the nonce exists
            if ((federatedAuthenticationOption.Nonce == null && federatedAuthenticationOption.Library == TDSFedAuthLibraryType.IDCRL) ||
                !AreEqual((session as GenericTDSServerSession).ServerNonce, federatedAuthenticationOption.Nonce))
            {
                // Error message
                string message = string.Format("Unexpected NONCEOPT specified in the Federated authentication feature extension");

                // Create errorToken token
                TDSErrorToken errorToken = new TDSErrorToken(5672, 32, 87, message);

                // Log response
                TDSUtilities.Log(Arguments.Log, "Response", errorToken);

                // Create DONE token
                TDSDoneToken doneToken = new TDSDoneToken(TDSDoneTokenStatusType.Final | TDSDoneTokenStatusType.Error);

                // Log response
                TDSUtilities.Log(Arguments.Log, "Response", doneToken);

                // Build a collection with a single message of two tokens
                return(new TDSMessageCollection(new TDSMessage(TDSMessageType.Response, errorToken, doneToken)));
            }

            // We're good
            return(null);
        }
        /// <summary>
        /// Handler for login request
        /// </summary>
        public virtual TDSMessageCollection OnLogin7Request(ITDSServerSession session, TDSMessage request)
        {
            // Inflate login7 request from the message
            TDSLogin7Token loginRequest = request[0] as TDSLogin7Token;

            // Log request
            TDSUtilities.Log(Arguments.Log, "Request", loginRequest);

            // Update server context
            session.Database = string.IsNullOrEmpty(loginRequest.Database) ? "master" : loginRequest.Database;

            // Resolve TDS version
            session.TDSVersion = TDSVersion.Resolve(TDSVersion.GetTDSVersion(Arguments.ServerVersion), loginRequest.TDSVersion);

            // Check for the TDS version
            TDSMessageCollection collection = CheckTDSVersion(session);

            // Check if any errors are posted
            if (collection != null)
            {
                // Version check needs to send own message hence we can't proceed
                return(collection);
            }

            // Indicates federated authentication
            bool bIsFedAuthConnection = false;

            // Federated authentication option to be used later
            TDSLogin7FedAuthOptionToken federatedAuthenticationOption = null;

            // Check if feature extension block is available
            if (loginRequest.FeatureExt != null)
            {
                // Go over the feature extension data
                foreach (TDSLogin7FeatureOptionToken option in loginRequest.FeatureExt)
                {
                    // Check option type
                    switch (option.FeatureID)
                    {
                    case TDSFeatureID.SessionRecovery:
                    {
                        // Enable session recovery
                        session.IsSessionRecoveryEnabled = true;

                        // Cast to session state options
                        TDSLogin7SessionRecoveryOptionToken sessionStateOption = option as TDSLogin7SessionRecoveryOptionToken;

                        // Inflate session state
                        (session as GenericTDSServerSession).Inflate(sessionStateOption.Initial, sessionStateOption.Current);

                        break;
                    }

                    case TDSFeatureID.FederatedAuthentication:
                    {
                        // Cast to federated authentication option
                        federatedAuthenticationOption = option as TDSLogin7FedAuthOptionToken;

                        // Mark authentication as federated
                        bIsFedAuthConnection = true;

                        // Validate federated authentication option
                        collection = CheckFederatedAuthenticationOption(session, option as TDSLogin7FedAuthOptionToken);

                        if (collection != null)
                        {
                            // Version error happened.
                            return(collection);
                        }

                        // Save the fed auth library to be used
                        (session as GenericTDSServerSession).FederatedAuthenticationLibrary = federatedAuthenticationOption.Library;

                        break;
                    }

                    default:
                    {
                        // Do nothing
                        break;
                    }
                    }
                }
            }

            // Check if SSPI authentication is requested
            if (loginRequest.OptionalFlags2.IntegratedSecurity == TDSLogin7OptionalFlags2IntSecurity.On)
            {
                // Delegate to SSPI authentication
                return(ContinueSSPIAuthentication(session, loginRequest.SSPI));
            }

            // If it is not a FedAuth connection or the server has been started up as not supporting FedAuth, just ignore the FeatureExtension
            // Yes unfortunately for the fake server, supporting FedAuth = Requiring FedAuth
            if (!bIsFedAuthConnection ||
                Arguments.FedAuthRequiredPreLoginOption == TdsPreLoginFedAuthRequiredOption.FedAuthNotRequired)
            {
                // We use SQL authentication
                session.SQLUserID = loginRequest.UserID;

                // Process with the SQL login.
                return(OnSqlAuthenticationCompleted(session));
            }
            else
            {
                // Fedauth feature extension is present and server has been started up as Requiring (or Supporting) FedAuth
                if (federatedAuthenticationOption.IsRequestingAuthenticationInfo)
                {
                    // Must provide client with more info before completing authentication
                    return(OnFederatedAuthenticationInfoRequest(session));
                }
                else
                {
                    return(OnFederatedAuthenticationCompleted(session, federatedAuthenticationOption.Token));
                }
            }
        }