SEBWIN-301: Changed service procedure so that the service initiates a system configuration update on command from the runtime. Added functionality to terminate the application on service connection loss.

SafeExamBrowser.Client/Communication/ClientHost.cs

@@ -18,7 +18,7 @@ namespace SafeExamBrowser.Client.Communication
 {
 	internal class ClientHost : BaseHost, IClientHost
 	{
-		private bool allowConnection = true;
+		private bool allowConnection;
 		private int processId;
 
 		public Guid AuthenticationToken { private get; set; }
@@ -37,6 +37,7 @@ namespace SafeExamBrowser.Client.Communication
 			int processId,
 			int timeout_ms) : base(address, factory, logger, timeout_ms)
 		{
+			this.allowConnection = true;
 			this.processId = processId;
 		}
 

SafeExamBrowser.Communication.UnitTests/Proxies/ServiceProxyTests.cs

@@ -7,14 +7,14 @@
  */
 
 using System;
-using System.ServiceModel;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
-using SafeExamBrowser.Contracts.Communication.Data;
-using SafeExamBrowser.Contracts.Communication.Proxies;
-using SafeExamBrowser.Contracts.Logging;
 using SafeExamBrowser.Communication.Proxies;
 using SafeExamBrowser.Contracts.Communication;
+using SafeExamBrowser.Contracts.Communication.Data;
+using SafeExamBrowser.Contracts.Communication.Proxies;
+using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Logging;
 
 namespace SafeExamBrowser.Communication.UnitTests.Proxies
 {
@@ -39,18 +39,19 @@ namespace SafeExamBrowser.Communication.UnitTests.Proxies
 			proxyObjectFactory = new Mock<IProxyObjectFactory>();
 			proxy = new Mock<IProxyObject>();
 
-			proxy.Setup(p => p.Connect(It.IsAny<Guid>())).Returns(response);
+			proxy.Setup(p => p.Connect(null)).Returns(response);
-			proxy.Setup(o => o.State).Returns(CommunicationState.Opened);
+			proxy.Setup(o => o.State).Returns(System.ServiceModel.CommunicationState.Opened);
 			proxyObjectFactory.Setup(f => f.CreateObject(It.IsAny<string>())).Returns(proxy.Object);
 
 			sut = new ServiceProxy("net.pipe://random/address/here", proxyObjectFactory.Object, logger.Object, default(Interlocutor));
+			sut.Connect();
 		}
 
 		[TestMethod]
 		public void MustIgnoreConnectIfUnavailable()
 		{
 			sut.Ignore = true;
-			sut.Connect(Guid.NewGuid());
+			sut.Connect();
 
 			proxy.Verify(p => p.Connect(It.IsAny<Guid>()), Times.Never);
 		}
@@ -64,6 +65,61 @@ namespace SafeExamBrowser.Communication.UnitTests.Proxies
 			proxy.Verify(p => p.Disconnect(It.IsAny<DisconnectionMessage>()), Times.Never);
 		}
 
+		[TestMethod]
+		public void MustCorrectlySendSystemConfigurationUpdate()
+		{
+			proxy.Setup(p => p.Send(It.Is<SimpleMessage>(m => m.Purport == SimpleMessagePurport.UpdateSystemConfiguration))).Returns(new SimpleResponse(SimpleResponsePurport.Acknowledged));
+
+			var communication = sut.RunSystemConfigurationUpdate();
+
+			proxy.Verify(p => p.Send(It.Is<SimpleMessage>(m => m.Purport == SimpleMessagePurport.UpdateSystemConfiguration)), Times.Once);
+
+			Assert.IsTrue(communication.Success);
+		}
+
+		[TestMethod]
+		public void MustFailIfSystemConfigurationUpdateNotAcknowledged()
+		{
+			proxy.Setup(p => p.Send(It.Is<SimpleMessage>(m => m.Purport == SimpleMessagePurport.UpdateSystemConfiguration))).Returns<Response>(null);
+
+			var communication = sut.RunSystemConfigurationUpdate();
+
+			Assert.IsFalse(communication.Success);
+		}
+
+		[TestMethod]
+		public void MustIgnoreSystemConfigurationUpdateIfUnavailable()
+		{
+			sut.Ignore = true;
+			sut.RunSystemConfigurationUpdate();
+
+			proxy.Verify(p => p.Send(It.IsAny<Message>()), Times.Never);
+		}
+
+		[TestMethod]
+		public void MustCorrectlyStartSession()
+		{
+			var configuration = new ServiceConfiguration { SessionId = Guid.NewGuid() };
+
+			proxy.Setup(p => p.Send(It.IsAny<SessionStartMessage>())).Returns(new SimpleResponse(SimpleResponsePurport.Acknowledged));
+
+			var communication = sut.StartSession(configuration);
+
+			proxy.Verify(p => p.Send(It.Is<SessionStartMessage>(m => m.Configuration.SessionId == configuration.SessionId)), Times.Once);
+
+			Assert.IsTrue(communication.Success);
+		}
+
+		[TestMethod]
+		public void MustFailIfSessionStartNotAcknowledged()
+		{
+			proxy.Setup(p => p.Send(It.IsAny<SessionStartMessage>())).Returns<Response>(null);
+
+			var communication = sut.StartSession(new ServiceConfiguration());
+
+			Assert.IsFalse(communication.Success);
+		}
+
 		[TestMethod]
 		public void MustIgnoreStartSessionIfUnavaiable()
 		{
@@ -75,6 +131,30 @@ namespace SafeExamBrowser.Communication.UnitTests.Proxies
 			proxy.Verify(p => p.Send(It.IsAny<Message>()), Times.Never);
 		}
 
+		[TestMethod]
+		public void MustCorrectlyStopSession()
+		{
+			var sessionId = Guid.NewGuid();
+
+			proxy.Setup(p => p.Send(It.IsAny<SessionStopMessage>())).Returns(new SimpleResponse(SimpleResponsePurport.Acknowledged));
+
+			var communication = sut.StopSession(sessionId);
+
+			proxy.Verify(p => p.Send(It.Is<SessionStopMessage>(m => m.SessionId == sessionId)), Times.Once);
+
+			Assert.IsTrue(communication.Success);
+		}
+
+		[TestMethod]
+		public void MustFailIfSessionStopNotAcknowledged()
+		{
+			proxy.Setup(p => p.Send(It.IsAny<SessionStopMessage>())).Returns<Response>(null);
+
+			var communication = sut.StopSession(Guid.Empty);
+
+			Assert.IsFalse(communication.Success);
+		}
+
 		[TestMethod]
 		public void MustIgnoreStopSessionIfUnavaiable()
 		{

SafeExamBrowser.Communication/Proxies/ServiceProxy.cs

@@ -46,6 +46,37 @@ namespace SafeExamBrowser.Communication.Proxies
 			return base.Disconnect();
 		}
 
+		public CommunicationResult RunSystemConfigurationUpdate()
+		{
+			if (IgnoreOperation(nameof(RunSystemConfigurationUpdate)))
+			{
+				return new CommunicationResult(true);
+			}
+
+			try
+			{
+				var response = Send(SimpleMessagePurport.UpdateSystemConfiguration);
+				var success = IsAcknowledged(response);
+
+				if (success)
+				{
+					Logger.Debug("Service acknowledged system configuration update.");
+				}
+				else
+				{
+					Logger.Error($"Service did not acknowledge system configuration update! Received: {ToString(response)}.");
+				}
+
+				return new CommunicationResult(success);
+			}
+			catch (Exception e)
+			{
+				Logger.Error($"Failed to perform '{nameof(RunSystemConfigurationUpdate)}'", e);
+
+				return new CommunicationResult(false);
+			}
+		}
+
 		public CommunicationResult StartSession(ServiceConfiguration configuration)
 		{
 			if (IgnoreOperation(nameof(StartSession)))

SafeExamBrowser.Contracts/Communication/Data/SimpleMessagePurport.cs

@@ -44,6 +44,11 @@ namespace SafeExamBrowser.Contracts.Communication.Data
 		/// <summary>
 		/// Sent form the runtime to the client to command the latter to shut itself down.
 		/// </summary>
-		Shutdown
+		Shutdown,
+
+		/// <summary>
+		/// Sent from the runtime to the service to command the latter to update the system configuration.
+		/// </summary>
+		UpdateSystemConfiguration
 	}
 }

SafeExamBrowser.Contracts/Communication/Hosts/IServiceHost.cs

@@ -15,11 +15,6 @@ namespace SafeExamBrowser.Contracts.Communication.Hosts
 	/// </summary>
 	public interface IServiceHost : ICommunicationHost
 	{
-		/// <summary>
-		/// Determines whether another application component may establish a connection with the host.
-		/// </summary>
-		bool AllowConnection { get; set; }
-
 		/// <summary>
 		/// Event fired when the runtime requested to start a new session.
 		/// </summary>
@@ -29,5 +24,10 @@ namespace SafeExamBrowser.Contracts.Communication.Hosts
 		/// Event fired when the runtime requested to stop a running session.
 		/// </summary>
 		event CommunicationEventHandler<SessionStopEventArgs> SessionStopRequested;
+
+		/// <summary>
+		/// Event fired when the runtime requested to update the system configuration.
+		/// </summary>
+		event CommunicationEventHandler SystemConfigurationUpdateRequested;
 	}
 }

SafeExamBrowser.Contracts/Communication/Proxies/IServiceProxy.cs

@@ -22,6 +22,11 @@ namespace SafeExamBrowser.Contracts.Communication.Proxies
 		/// </summary>
 		bool Ignore { set; }
 
+		/// <summary>
+		/// Instructs the service to start a system configuration update.
+		/// </summary>
+		CommunicationResult RunSystemConfigurationUpdate();
+
 		/// <summary>
 		/// Instructs the service to start a new session according to the given configuration.
 		/// </summary>

SafeExamBrowser.Contracts/I18n/TextKey.cs

@@ -91,7 +91,6 @@ namespace SafeExamBrowser.Contracts.I18n
 		OperationStatus_StopWindowMonitoring,
 		OperationStatus_TerminateBrowser,
 		OperationStatus_TerminateShell,
-		OperationStatus_UpdateSystemConfiguration,
 		OperationStatus_WaitExplorerStartup,
 		OperationStatus_WaitExplorerTermination,
 		OperationStatus_WaitRuntimeDisconnection,

SafeExamBrowser.I18n/Text.xml

@@ -231,9 +231,6 @@
   <Entry key="OperationStatus_TerminateShell">
     Terminating user interface
   </Entry>
-  <Entry key="OperationStatus_UpdateSystemConfiguration">
-    Updating system configuration
-  </Entry>
   <Entry key="OperationStatus_WaitExplorerStartup">
     Waiting for Windows explorer to start up
   </Entry>

SafeExamBrowser.Runtime.UnitTests/Operations/ServiceOperationTests.cs

@@ -15,7 +15,6 @@ using SafeExamBrowser.Contracts.Communication.Proxies;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Configuration.Settings;
 using SafeExamBrowser.Contracts.Core.OperationModel;
-using SafeExamBrowser.Contracts.Lockdown;
 using SafeExamBrowser.Contracts.Logging;
 using SafeExamBrowser.Contracts.SystemComponents;
 using SafeExamBrowser.Contracts.UserInterface.MessageBox;
@@ -35,7 +34,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		private SessionConfiguration session;
 		private SessionContext sessionContext;
 		private Settings settings;
-		private Mock<ISystemConfigurationUpdate> systemConfigurationUpdate;
 		private Mock<IUserInfo> userInfo;
 		private ServiceOperation sut;
 
@@ -52,7 +50,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			session = new SessionConfiguration();
 			sessionContext = new SessionContext();
 			settings = new Settings();
-			systemConfigurationUpdate = new Mock<ISystemConfigurationUpdate>();
 			userInfo = new Mock<IUserInfo>();
 
 			appConfig.ServiceEventName = serviceEventName;
@@ -63,7 +60,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			session.Settings = settings;
 			settings.Service.Policy = ServicePolicy.Mandatory;
 
-			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, systemConfigurationUpdate.Object, 0, userInfo.Object);
+			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, 0, userInfo.Object);
 		}
 
 		[TestMethod]
@@ -92,7 +89,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			var result = sut.Perform();
 
 			service.Verify(s => s.StartSession(It.IsAny<ServiceConfiguration>()), Times.Once);
-			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Once);
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Never);
 			userInfo.Verify(u => u.GetUserName(), Times.Once);
 			userInfo.Verify(u => u.GetUserSid(), Times.Once);
 
@@ -125,7 +122,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			service.Setup(s => s.Connect(null, true)).Returns(true);
 			service.Setup(s => s.StartSession(It.IsAny<ServiceConfiguration>())).Returns(new CommunicationResult(true));
 
-			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, systemConfigurationUpdate.Object, TIMEOUT, userInfo.Object);
+			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, TIMEOUT, userInfo.Object);
 
 			before = DateTime.Now;
 			var result = sut.Perform();
@@ -158,7 +155,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			var result = sut.Perform();
 
 			service.Verify(s => s.StartSession(It.IsAny<ServiceConfiguration>()), Times.Once);
-			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Never);
 
 			Assert.AreEqual(OperationResult.Failed, result);
 		}
@@ -213,7 +209,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		{
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true)).Callback(() => serviceEvent.Set());
 			PerformNormally();
-			systemConfigurationUpdate.Reset();
 
 			var result = sut.Repeat();
 
@@ -221,7 +216,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			service.Verify(s => s.StopSession(It.IsAny<Guid>()), Times.Once);
 			service.Verify(s => s.StartSession(It.IsAny<ServiceConfiguration>()), Times.Exactly(2));
 			service.Verify(s => s.Disconnect(), Times.Never);
-			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Exactly(2));
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Never);
 
 			Assert.AreEqual(OperationResult.Success, result);
 		}
@@ -268,7 +263,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			var before = default(DateTime);
 
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true));
-			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, systemConfigurationUpdate.Object, TIMEOUT, userInfo.Object);
+			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, TIMEOUT, userInfo.Object);
 
 			PerformNormally();
 
@@ -288,6 +283,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		{
 			service.Setup(s => s.Disconnect()).Returns(true);
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true)).Callback(() => serviceEvent.Set());
+			service.Setup(s => s.RunSystemConfigurationUpdate()).Returns(new CommunicationResult(true));
 
 			PerformNormally();
 
@@ -303,14 +299,15 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		{
 			service.Setup(s => s.Disconnect()).Returns(true);
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true)).Callback(() => serviceEvent.Set());
+			service.Setup(s => s.RunSystemConfigurationUpdate()).Returns(new CommunicationResult(true));
+
 			PerformNormally();
-			systemConfigurationUpdate.Reset();
 
 			var result = sut.Revert();
 
 			service.Verify(s => s.StopSession(It.IsAny<Guid>()), Times.Once);
 			service.Verify(s => s.Disconnect(), Times.Once);
-			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Once);
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Once);
 
 			Assert.AreEqual(OperationResult.Success, result);
 		}
@@ -319,14 +316,31 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		public void Revert_MustHandleCommunicationFailureWhenStoppingSession()
 		{
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(false));
+
 			PerformNormally();
-			systemConfigurationUpdate.Reset();
 
 			var result = sut.Revert();
 
 			service.Verify(s => s.StopSession(It.IsAny<Guid>()), Times.Once);
 			service.Verify(s => s.Disconnect(), Times.Once);
-			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Never);
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Never);
+
+			Assert.AreEqual(OperationResult.Failed, result);
+		}
+
+		[TestMethod]
+		public void Revert_MustHandleCommunicationFailureWhenInitiatingSystemConfigurationUpdate()
+		{
+			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true)).Callback(() => serviceEvent.Set());
+			service.Setup(s => s.RunSystemConfigurationUpdate()).Returns(new CommunicationResult(false));
+
+			PerformNormally();
+
+			var result = sut.Revert();
+
+			service.Verify(s => s.StopSession(It.IsAny<Guid>()), Times.Once);
+			service.Verify(s => s.Disconnect(), Times.Once);
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Once);
 
 			Assert.AreEqual(OperationResult.Failed, result);
 		}
@@ -340,6 +354,8 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			var result = sut.Revert();
 
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Never);
+
 			Assert.AreEqual(OperationResult.Failed, result);
 		}
 
@@ -352,7 +368,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			var before = default(DateTime);
 
 			service.Setup(s => s.StopSession(It.IsAny<Guid>())).Returns(new CommunicationResult(true));
-			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, systemConfigurationUpdate.Object, TIMEOUT, userInfo.Object);
+			sut = new ServiceOperation(logger.Object, runtimeHost.Object, service.Object, sessionContext, TIMEOUT, userInfo.Object);
 
 			PerformNormally();
 
@@ -362,6 +378,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			service.Verify(s => s.StopSession(It.IsAny<Guid>()), Times.Once);
 			service.Verify(s => s.Disconnect(), Times.Once);
+			service.Verify(s => s.RunSystemConfigurationUpdate(), Times.Never);
 
 			Assert.AreEqual(OperationResult.Failed, result);
 			Assert.IsTrue(after - before >= new TimeSpan(0, 0, 0, 0, TIMEOUT));

SafeExamBrowser.Runtime.UnitTests/RuntimeControllerTests.cs

@@ -389,6 +389,42 @@ namespace SafeExamBrowser.Runtime.UnitTests
 			runtimeWindow.Verify(s => s.UpdateStatus(It.Is<TextKey>(k => k == key), It.IsAny<bool>()), Times.Once);
 		}
 
+		[TestMethod]
+		public void ServiceProxy_MustShutdownWhenConnectionLostAndMandatory()
+		{
+			currentSettings.Service.Policy = ServicePolicy.Mandatory;
+
+			StartSession();
+			service.Raise(c => c.ConnectionLost += null);
+
+			messageBox.Verify(m => m.Show(
+				It.IsAny<TextKey>(),
+				It.IsAny<TextKey>(),
+				It.IsAny<MessageBoxAction>(),
+				It.Is<MessageBoxIcon>(i => i == MessageBoxIcon.Error),
+				It.IsAny<IWindow>()), Times.Once);
+			sessionSequence.Verify(s => s.TryRevert(), Times.Once);
+			shutdown.Verify(s => s(), Times.Once);
+		}
+
+		[TestMethod]
+		public void ServiceProxy_MustNotShutdownWhenConnectionLostAndNotMandatory()
+		{
+			currentSettings.Service.Policy = ServicePolicy.Optional;
+
+			StartSession();
+			service.Raise(c => c.ConnectionLost += null);
+
+			messageBox.Verify(m => m.Show(
+				It.IsAny<TextKey>(),
+				It.IsAny<TextKey>(),
+				It.IsAny<MessageBoxAction>(),
+				It.Is<MessageBoxIcon>(i => i == MessageBoxIcon.Error),
+				It.IsAny<IWindow>()), Times.Never);
+			sessionSequence.Verify(s => s.TryRevert(), Times.Never);
+			shutdown.Verify(s => s(), Times.Never);
+		}
+
 		[TestMethod]
 		public void Shutdown_MustRevertSessionThenBootstrapSequence()
 		{

SafeExamBrowser.Runtime/CompositionRoot.cs

@@ -27,7 +27,6 @@ using SafeExamBrowser.Contracts.SystemComponents;
 using SafeExamBrowser.Core.OperationModel;
 using SafeExamBrowser.Core.Operations;
 using SafeExamBrowser.I18n;
-using SafeExamBrowser.Lockdown;
 using SafeExamBrowser.Logging;
 using SafeExamBrowser.Runtime.Communication;
 using SafeExamBrowser.Runtime.Operations;
@@ -71,7 +70,6 @@ namespace SafeExamBrowser.Runtime
 			var runtimeHost = new RuntimeHost(appConfig.RuntimeAddress, new HostObjectFactory(), ModuleLogger(nameof(RuntimeHost)), FIVE_SECONDS);
 			var serviceProxy = new ServiceProxy(appConfig.ServiceAddress, new ProxyObjectFactory(), ModuleLogger(nameof(ServiceProxy)), Interlocutor.Runtime);
 			var sessionContext = new SessionContext();
-			var systemConfigurationUpdate = new SystemConfigurationUpdate(ModuleLogger(nameof(SystemConfigurationUpdate)));
 			var uiFactory = new UserInterfaceFactory(text);
 			var userInfo = new UserInfo();
 
@@ -83,7 +81,7 @@ namespace SafeExamBrowser.Runtime
 
 			sessionOperations.Enqueue(new SessionInitializationOperation(configuration, logger, runtimeHost, sessionContext));
 			sessionOperations.Enqueue(new ConfigurationOperation(args, configuration, new HashAlgorithm(), logger, sessionContext));
-			sessionOperations.Enqueue(new ServiceOperation(logger, runtimeHost, serviceProxy, sessionContext, systemConfigurationUpdate, THIRTY_SECONDS, userInfo));
+			sessionOperations.Enqueue(new ServiceOperation(logger, runtimeHost, serviceProxy, sessionContext, THIRTY_SECONDS, userInfo));
 			sessionOperations.Enqueue(new ClientTerminationOperation(logger, processFactory, proxyFactory, runtimeHost, sessionContext, THIRTY_SECONDS));
 			sessionOperations.Enqueue(new KioskModeOperation(desktopFactory, explorerShell, logger, processFactory, sessionContext));
 			sessionOperations.Enqueue(new ClientOperation(logger, processFactory, proxyFactory, runtimeHost, sessionContext, THIRTY_SECONDS));

SafeExamBrowser.Runtime/Operations/ServiceOperation.cs

@@ -16,7 +16,6 @@ using SafeExamBrowser.Contracts.Configuration.Settings;
 using SafeExamBrowser.Contracts.Core.OperationModel;
 using SafeExamBrowser.Contracts.Core.OperationModel.Events;
 using SafeExamBrowser.Contracts.I18n;
-using SafeExamBrowser.Contracts.Lockdown;
 using SafeExamBrowser.Contracts.Logging;
 using SafeExamBrowser.Contracts.SystemComponents;
 using SafeExamBrowser.Contracts.UserInterface.MessageBox;
@@ -29,7 +28,6 @@ namespace SafeExamBrowser.Runtime.Operations
 		private ILogger logger;
 		private IRuntimeHost runtimeHost;
 		private IServiceProxy service;
-		private ISystemConfigurationUpdate systemConfigurationUpdate;
 		private int timeout_ms;
 		private IUserInfo userInfo;
 
@@ -41,14 +39,12 @@ namespace SafeExamBrowser.Runtime.Operations
 			IRuntimeHost runtimeHost,
 			IServiceProxy service,
 			SessionContext sessionContext,
-			ISystemConfigurationUpdate systemConfigurationUpdate,
 			int timeout_ms,
 			IUserInfo userInfo) : base(sessionContext)
 		{
 			this.logger = logger;
 			this.runtimeHost = runtimeHost;
 			this.service = service;
-			this.systemConfigurationUpdate = systemConfigurationUpdate;
 			this.timeout_ms = timeout_ms;
 			this.userInfo = userInfo;
 		}
@@ -103,7 +99,7 @@ namespace SafeExamBrowser.Runtime.Operations
 			{
 				if (Context.Current != null)
 				{
-					success &= TryStopSession();
+					success &= TryStopSession(true);
 				}
 
 				success &= TryTerminateConnection();
@@ -192,21 +188,18 @@ namespace SafeExamBrowser.Runtime.Operations
 				{
 					logger.Error($"Failed to start new service session within {timeout_ms / 1000} seconds!");
 				}
-
-				StatusChanged?.Invoke(TextKey.OperationStatus_UpdateSystemConfiguration);
-				systemConfigurationUpdate.Execute();
 			}
 			else
 			{
-				logger.Error("Failed to communicate session start to service!");
+				logger.Error("Failed to communicate session start command to service!");
 			}
 
 			return started;
 		}
 
-		private bool TryStopSession()
+		private bool TryStopSession(bool isFinalSession = false)
 		{
-			var stopped = false;
+			var success = false;
 
 			logger.Info("Stopping current service session...");
 
@@ -214,9 +207,9 @@ namespace SafeExamBrowser.Runtime.Operations
 
 			if (communication.Success)
 			{
-				stopped = TryWaitForServiceEvent(Context.Current.AppConfig.ServiceEventName);
+				success = TryWaitForServiceEvent(Context.Current.AppConfig.ServiceEventName);
 
-				if (stopped)
+				if (success)
 				{
 					logger.Info("Successfully stopped service session.");
 				}
@@ -224,16 +217,28 @@ namespace SafeExamBrowser.Runtime.Operations
 				{
 					logger.Error($"Failed to stop service session within {timeout_ms / 1000} seconds!");
 				}
-
-				StatusChanged?.Invoke(TextKey.OperationStatus_UpdateSystemConfiguration);
-				systemConfigurationUpdate.Execute();
 			}
 			else
 			{
-				logger.Error("Failed to communicate session stop to service!");
+				logger.Error("Failed to communicate session stop command to service!");
 			}
 
-			return stopped;
+			if (success && isFinalSession)
+			{
+				communication = service.RunSystemConfigurationUpdate();
+				success = communication.Success;
+
+				if (communication.Success)
+				{
+					logger.Info("Instructed service to perform system configuration update.");
+				}
+				else
+				{
+					logger.Error("Failed to communicate system configuration update command to service!");
+				}
+			}
+
+			return success;
 		}
 
 		private bool TryWaitForServiceEvent(string eventName)

SafeExamBrowser.Runtime/RuntimeController.cs

@@ -260,6 +260,7 @@ namespace SafeExamBrowser.Runtime
 			runtimeHost.ClientConfigurationNeeded += RuntimeHost_ClientConfigurationNeeded;
 			runtimeHost.ReconfigurationRequested += RuntimeHost_ReconfigurationRequested;
 			runtimeHost.ShutdownRequested += RuntimeHost_ShutdownRequested;
+			service.ConnectionLost += ServiceProxy_ConnectionLost;
 		}
 
 		private void DeregisterEvents()
@@ -267,6 +268,7 @@ namespace SafeExamBrowser.Runtime
 			runtimeHost.ClientConfigurationNeeded -= RuntimeHost_ClientConfigurationNeeded;
 			runtimeHost.ReconfigurationRequested -= RuntimeHost_ReconfigurationRequested;
 			runtimeHost.ShutdownRequested -= RuntimeHost_ShutdownRequested;
+			service.ConnectionLost -= ServiceProxy_ConnectionLost;
 		}
 
 		private void RegisterSessionEvents()
@@ -358,6 +360,21 @@ namespace SafeExamBrowser.Runtime
 			shutdown.Invoke();
 		}
 
+		private void ServiceProxy_ConnectionLost()
+		{
+			if (SessionIsRunning && Session.Settings.Service.Policy == ServicePolicy.Mandatory)
+			{
+				logger.Error("Lost connection to the service component!");
+				StopSession();
+				messageBox.Show(TextKey.MessageBox_ApplicationError, TextKey.MessageBox_ApplicationErrorTitle, icon: MessageBoxIcon.Error, parent: runtimeWindow);
+				shutdown.Invoke();
+			}
+			else
+			{
+				logger.Warn("Lost connection to the service component!");
+			}
+		}
+
 		private void SessionSequence_ActionRequired(ActionRequiredEventArgs args)
 		{
 			switch (args)

SafeExamBrowser.Runtime/SafeExamBrowser.Runtime.csproj

@@ -155,10 +155,6 @@
       <Project>{10c62628-8e6a-45aa-9d97-339b119ad21d}</Project>
       <Name>SafeExamBrowser.I18n</Name>
     </ProjectReference>
-    <ProjectReference Include="..\SafeExamBrowser.Lockdown\SafeExamBrowser.Lockdown.csproj">
-      <Project>{386b6042-3e12-4753-9fc6-c88ea4f97030}</Project>
-      <Name>SafeExamBrowser.Lockdown</Name>
-    </ProjectReference>
     <ProjectReference Include="..\SafeExamBrowser.Logging\SafeExamBrowser.Logging.csproj">
       <Project>{e107026c-2011-4552-a7d8-3a0d37881df6}</Project>
       <Name>SafeExamBrowser.Logging</Name>

SafeExamBrowser.Service.UnitTests/Communication/ServiceHostTests.cs

@@ -48,7 +48,6 @@ namespace SafeExamBrowser.Service.UnitTests.Communication
 			var response3 = sut.Connect();
 
 			Assert.IsTrue(response.ConnectionEstablished);
-			Assert.IsFalse(sut.AllowConnection);
 			Assert.IsFalse(response2.ConnectionEstablished);
 			Assert.IsFalse(response3.ConnectionEstablished);
 		}
@@ -59,15 +58,33 @@ namespace SafeExamBrowser.Service.UnitTests.Communication
 			var connect = sut.Connect();
 			var disconnect = sut.Disconnect(new DisconnectionMessage { CommunicationToken = connect.CommunicationToken.Value, Interlocutor = Interlocutor.Runtime });
 
-			Assert.IsTrue(sut.AllowConnection);
 			Assert.IsTrue(disconnect.ConnectionTerminated);
 
 			var connect2 = sut.Connect();
 
-			Assert.IsFalse(sut.AllowConnection);
 			Assert.IsTrue(connect2.ConnectionEstablished);
 		}
 
+		[TestMethod]
+		public void Send_MustHandleSystemConfigurationUpdate()
+		{
+			var sync = new AutoResetEvent(false);
+			var systemConfigurationUpdateRequested = false;
+
+			sut.SystemConfigurationUpdateRequested += () => { systemConfigurationUpdateRequested = true; sync.Set(); };
+
+			var token = sut.Connect().CommunicationToken.Value;
+			var message = new SimpleMessage(SimpleMessagePurport.UpdateSystemConfiguration) { CommunicationToken = token };
+			var response = sut.Send(message);
+
+			sync.WaitOne();
+
+			Assert.IsTrue(systemConfigurationUpdateRequested);
+			Assert.IsNotNull(response);
+			Assert.IsInstanceOfType(response, typeof(SimpleResponse));
+			Assert.AreEqual(SimpleResponsePurport.Acknowledged, (response as SimpleResponse)?.Purport);
+		}
+
 		[TestMethod]
 		public void Send_MustHandleSessionStartRequest()
 		{

SafeExamBrowser.Service.UnitTests/Operations/SessionInitializationOperationTests.cs

@@ -11,7 +11,6 @@ using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
-using SafeExamBrowser.Contracts.Communication.Hosts;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Configuration.Settings;
 using SafeExamBrowser.Contracts.Core.OperationModel;
@@ -26,7 +25,6 @@ namespace SafeExamBrowser.Service.UnitTests.Operations
 	{
 		private Mock<IAutoRestoreMechanism> autoRestoreMechanism;
 		private Mock<ILogger> logger;
-		private Mock<IServiceHost> serviceHost;
 		private Mock<Func<string, EventWaitHandle>> serviceEventFactory;
 		private SessionContext sessionContext;
 		private SessionInitializationOperation sut;
@@ -36,7 +34,6 @@ namespace SafeExamBrowser.Service.UnitTests.Operations
 		{
 			autoRestoreMechanism = new Mock<IAutoRestoreMechanism>();
 			logger = new Mock<ILogger>();
-			serviceHost = new Mock<IServiceHost>();
 			serviceEventFactory = new Mock<Func<string, EventWaitHandle>>();
 			sessionContext = new SessionContext();
 
@@ -48,17 +45,7 @@ namespace SafeExamBrowser.Service.UnitTests.Operations
 				Settings = new Settings()
 			};
 
-			sut = new SessionInitializationOperation(logger.Object, serviceEventFactory.Object, serviceHost.Object, sessionContext);
+			sut = new SessionInitializationOperation(logger.Object, serviceEventFactory.Object, sessionContext);
-		}
-
-		[TestMethod]
-		public void Perform_MustDisableNewConnections()
-		{
-			var result = sut.Perform();
-
-			serviceHost.VerifySet(h => h.AllowConnection = false, Times.Once);
-
-			Assert.AreEqual(OperationResult.Success, result);
 		}
 
 		[TestMethod]
@@ -97,17 +84,6 @@ namespace SafeExamBrowser.Service.UnitTests.Operations
 			Assert.IsNull(sessionContext.Configuration);
 		}
 
-		[TestMethod]
-		public void Revert_MustEnableNewConnections()
-		{
-			sessionContext.ServiceEvent = new EventStub();
-
-			var result = sut.Revert();
-
-			serviceHost.VerifySet(h => h.AllowConnection = true, Times.Once);
-			Assert.AreEqual(OperationResult.Success, result);
-		}
-
 		[TestMethod]
 		public void Revert_MustSetServiceEvent()
 		{

SafeExamBrowser.Service.UnitTests/ServiceControllerTests.cs

@@ -7,6 +7,7 @@
  */
 
 using System;
+using System.Threading;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using SafeExamBrowser.Contracts.Communication.Events;
@@ -14,6 +15,7 @@ using SafeExamBrowser.Contracts.Communication.Hosts;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Configuration.Settings;
 using SafeExamBrowser.Contracts.Core.OperationModel;
+using SafeExamBrowser.Contracts.Lockdown;
 using SafeExamBrowser.Contracts.Logging;
 
 namespace SafeExamBrowser.Service.UnitTests
@@ -27,6 +29,7 @@ namespace SafeExamBrowser.Service.UnitTests
 		private SessionContext sessionContext;
 		private Mock<IOperationSequence> sessionSequence;
 		private Mock<IServiceHost> serviceHost;
+		private Mock<ISystemConfigurationUpdate> systemConfigurationUpdate;
 		private ServiceController sut;
 
 		[TestInitialize]
@@ -38,10 +41,18 @@ namespace SafeExamBrowser.Service.UnitTests
 			sessionContext = new SessionContext();
 			sessionSequence = new Mock<IOperationSequence>();
 			serviceHost = new Mock<IServiceHost>();
+			systemConfigurationUpdate = new Mock<ISystemConfigurationUpdate>();
 
 			logWriterFactory.Setup(f => f.Invoke(It.IsAny<string>())).Returns(new Mock<ILogObserver>().Object);
 
-			sut = new ServiceController(logger.Object, logWriterFactory.Object, bootstrapSequence.Object, sessionSequence.Object, serviceHost.Object, sessionContext);
+			sut = new ServiceController(
+				logger.Object,
+				logWriterFactory.Object,
+				bootstrapSequence.Object,
+				sessionSequence.Object,
+				serviceHost.Object,
+				sessionContext,
+				systemConfigurationUpdate.Object);
 		}
 
 		[TestMethod]
@@ -160,6 +171,23 @@ namespace SafeExamBrowser.Service.UnitTests
 			sessionSequence.Verify(s => s.TryRevert(), Times.Never);
 		}
 
+		[TestMethod]
+		public void Communication_MustStartSystemConfigurationUpdate()
+		{
+			var sync = new AutoResetEvent(false);
+
+			bootstrapSequence.Setup(b => b.TryPerform()).Returns(OperationResult.Success);
+			systemConfigurationUpdate.Setup(u => u.ExecuteAsync()).Callback(() => sync.Set());
+
+			sut.TryStart();
+			serviceHost.Raise(h => h.SystemConfigurationUpdateRequested += null);
+
+			sync.WaitOne();
+
+			systemConfigurationUpdate.Verify(u => u.Execute(), Times.Never);
+			systemConfigurationUpdate.Verify(u => u.ExecuteAsync(), Times.Once);
+		}
+
 		[TestMethod]
 		public void Start_MustOnlyPerformBootstrapSequence()
 		{

SafeExamBrowser.Service/Communication/ServiceHost.cs

@@ -18,47 +18,34 @@ namespace SafeExamBrowser.Service.Communication
 {
 	internal class ServiceHost : BaseHost, IServiceHost
 	{
-		private readonly object @lock = new object();
-
 		private bool allowConnection;
 
-		public bool AllowConnection
-		{
-			get { lock (@lock) { return allowConnection; } }
-			set { lock (@lock) { allowConnection = value; } }
-		}
-
 		public event CommunicationEventHandler<SessionStartEventArgs> SessionStartRequested;
 		public event CommunicationEventHandler<SessionStopEventArgs> SessionStopRequested;
+		public event CommunicationEventHandler SystemConfigurationUpdateRequested;
 
 		internal ServiceHost(string address, IHostObjectFactory factory, ILogger logger, int timeout_ms) : base(address, factory, logger, timeout_ms)
 		{
-			AllowConnection = true;
+			allowConnection = true;
 		}
 
 		protected override bool OnConnect(Guid? token)
 		{
-			lock (@lock)
+			var allow = allowConnection;
+
+			if (allow)
 			{
-				var allow = AllowConnection;
+				allowConnection = false;
-
-				if (allow)
-				{
-					AllowConnection = false;
-				}
-
-				return allow;
 			}
+
+			return allow;
 		}
 
 		protected override void OnDisconnect(Interlocutor interlocutor)
 		{
 			if (interlocutor == Interlocutor.Runtime)
 			{
-				lock (@lock)
+				allowConnection = true;
-				{
-					AllowConnection = true;
-				}
 			}
 		}
 
@@ -79,6 +66,13 @@ namespace SafeExamBrowser.Service.Communication
 
 		protected override Response OnReceive(SimpleMessagePurport message)
 		{
+			switch (message)
+			{
+				case SimpleMessagePurport.UpdateSystemConfiguration:
+					SystemConfigurationUpdateRequested?.InvokeAsync();
+					return new SimpleResponse(SimpleResponsePurport.Acknowledged);
+			}
+
 			return new SimpleResponse(SimpleResponsePurport.UnknownMessage);
 		}
 	}

SafeExamBrowser.Service/CompositionRoot.cs

@@ -57,14 +57,14 @@ namespace SafeExamBrowser.Service
 			bootstrapOperations.Enqueue(new CommunicationHostOperation(serviceHost, logger));
 			bootstrapOperations.Enqueue(new ServiceEventCleanupOperation(logger, sessionContext));
 
-			sessionOperations.Enqueue(new SessionInitializationOperation(logger, ServiceEventFactory, serviceHost, sessionContext));
+			sessionOperations.Enqueue(new SessionInitializationOperation(logger, ServiceEventFactory, sessionContext));
 			sessionOperations.Enqueue(new LockdownOperation(featureBackup, featureFactory, logger, sessionContext));
 			sessionOperations.Enqueue(new SessionActivationOperation(logger, sessionContext));
 
 			var bootstrapSequence = new OperationSequence(logger, bootstrapOperations);
 			var sessionSequence = new OperationSequence(logger, sessionOperations);
 
-			ServiceController = new ServiceController(logger, LogWriterFactory, bootstrapSequence, sessionSequence, serviceHost, sessionContext);
+			ServiceController = new ServiceController(logger, LogWriterFactory, bootstrapSequence, sessionSequence, serviceHost, sessionContext, systemConfigurationUpdate);
 		}
 
 		private string BuildBackupFilePath()

SafeExamBrowser.Service/Operations/SessionInitializationOperation.cs

@@ -8,7 +8,6 @@
 
 using System;
 using System.Threading;
-using SafeExamBrowser.Contracts.Communication.Hosts;
 using SafeExamBrowser.Contracts.Core.OperationModel;
 using SafeExamBrowser.Contracts.Logging;
 
@@ -18,17 +17,11 @@ namespace SafeExamBrowser.Service.Operations
 	{
 		private ILogger logger;
 		private Func<string, EventWaitHandle> serviceEventFactory;
-		private IServiceHost serviceHost;
 
-		public SessionInitializationOperation(
+		public SessionInitializationOperation(ILogger logger, Func<string, EventWaitHandle> serviceEventFactory, SessionContext sessionContext) : base(sessionContext)
-			ILogger logger,
-			Func<string, EventWaitHandle> serviceEventFactory,
-			IServiceHost serviceHost,
-			SessionContext sessionContext) : base(sessionContext)
 		{
 			this.logger = logger;
 			this.serviceEventFactory = serviceEventFactory;
-			this.serviceHost = serviceHost;
 		}
 
 		public override OperationResult Perform()
@@ -41,9 +34,6 @@ namespace SafeExamBrowser.Service.Operations
 			logger.Info("Stopping auto-restore mechanism...");
 			Context.AutoRestoreMechanism.Stop();
 
-			logger.Info("Disabling service host...");
-			serviceHost.AllowConnection = false;
-
 			InitializeServiceEvent();
 
 			return OperationResult.Success;
@@ -72,9 +62,6 @@ namespace SafeExamBrowser.Service.Operations
 			logger.Info("Starting auto-restore mechanism...");
 			Context.AutoRestoreMechanism.Start();
 
-			logger.Info("Enabling service host...");
-			serviceHost.AllowConnection = true;
-
 			logger.Info("Clearing session data...");
 			Context.Configuration = null;
 			Context.IsRunning = false;

SafeExamBrowser.Service/ServiceController.cs

@@ -11,6 +11,7 @@ using SafeExamBrowser.Contracts.Communication.Events;
 using SafeExamBrowser.Contracts.Communication.Hosts;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Core.OperationModel;
+using SafeExamBrowser.Contracts.Lockdown;
 using SafeExamBrowser.Contracts.Logging;
 using SafeExamBrowser.Contracts.Service;
 
@@ -24,6 +25,7 @@ namespace SafeExamBrowser.Service
 		private IOperationSequence sessionSequence;
 		private IServiceHost serviceHost;
 		private SessionContext sessionContext;
+		private ISystemConfigurationUpdate systemConfigurationUpdate;
 		private ILogObserver sessionWriter;
 
 		private ServiceConfiguration Session
@@ -42,7 +44,8 @@ namespace SafeExamBrowser.Service
 			IOperationSequence bootstrapSequence,
 			IOperationSequence sessionSequence,
 			IServiceHost serviceHost,
-			SessionContext sessionContext)
+			SessionContext sessionContext,
+			ISystemConfigurationUpdate systemConfigurationUpdate)
 		{
 			this.logger = logger;
 			this.logWriterFactory = logWriterFactory;
@@ -50,6 +53,7 @@ namespace SafeExamBrowser.Service
 			this.sessionSequence = sessionSequence;
 			this.serviceHost = serviceHost;
 			this.sessionContext = sessionContext;
+			this.systemConfigurationUpdate = systemConfigurationUpdate;
 		}
 
 		public bool TryStart()
@@ -141,12 +145,14 @@ namespace SafeExamBrowser.Service
 		{
 			serviceHost.SessionStartRequested += ServiceHost_SessionStartRequested;
 			serviceHost.SessionStopRequested += ServiceHost_SessionStopRequested;
+			serviceHost.SystemConfigurationUpdateRequested += ServiceHost_SystemConfigurationUpdateRequested;
 		}
 
 		private void DeregisterEvents()
 		{
 			serviceHost.SessionStartRequested -= ServiceHost_SessionStartRequested;
 			serviceHost.SessionStopRequested -= ServiceHost_SessionStopRequested;
+			serviceHost.SystemConfigurationUpdateRequested -= ServiceHost_SystemConfigurationUpdateRequested;
 		}
 
 		private void ServiceHost_SessionStartRequested(SessionStartEventArgs args)
@@ -182,6 +188,12 @@ namespace SafeExamBrowser.Service
 			}
 		}
 
+		private void ServiceHost_SystemConfigurationUpdateRequested()
+		{
+			logger.Info("Received request to initiate system configuration update.");
+			systemConfigurationUpdate.ExecuteAsync();
+		}
+
 		private string AppendDivider(string message)
 		{
 			var dashesLeft = new String('-', 48 - message.Length / 2 - message.Length % 2);