SEBWIN-732: Implemented random desktop functionality.

SafeExamBrowser.Client/CompositionRoot.cs

@@ -54,6 +54,7 @@ using SafeExamBrowser.UserInterface.Contracts.Shell;
 using SafeExamBrowser.UserInterface.Shared.Activators;
 using SafeExamBrowser.WindowsApi;
 using SafeExamBrowser.WindowsApi.Contracts;
+using SafeExamBrowser.WindowsApi.Processes;
 using Desktop = SafeExamBrowser.UserInterface.Desktop;
 using Mobile = SafeExamBrowser.UserInterface.Mobile;
 

SafeExamBrowser.Runtime/CompositionRoot.cs

@@ -35,6 +35,8 @@ using SafeExamBrowser.SystemComponents.Contracts;
 using SafeExamBrowser.SystemComponents.Registry;
 using SafeExamBrowser.UserInterface.Desktop;
 using SafeExamBrowser.WindowsApi;
+using SafeExamBrowser.WindowsApi.Desktops;
+using SafeExamBrowser.WindowsApi.Processes;
 
 namespace SafeExamBrowser.Runtime
 {

SafeExamBrowser.Runtime/Operations/KioskModeOperation.cs

@@ -17,14 +17,15 @@ namespace SafeExamBrowser.Runtime.Operations
 {
 	internal class KioskModeOperation : SessionOperation
 	{
-		private IDesktop newDesktop;
+		private readonly IDesktopFactory desktopFactory;
-		private IDesktop originalDesktop;
+		private readonly IDesktopMonitor desktopMonitor;
-		private IDesktopFactory desktopFactory;
+		private readonly IExplorerShell explorerShell;
-		private IDesktopMonitor desktopMonitor;
+		private readonly ILogger logger;
-		private IExplorerShell explorerShell;
+		private readonly IProcessFactory processFactory;
+
 		private KioskMode? activeMode;
-		private ILogger logger;
+		private IDesktop customDesktop;
-		private IProcessFactory processFactory;
+		private IDesktop originalDesktop;
 
 		public override event ActionRequiredEventHandler ActionRequired { add { } remove { } }
 		public override event StatusChangedEventHandler StatusChanged;
@@ -54,7 +55,7 @@ namespace SafeExamBrowser.Runtime.Operations
 			switch (Context.Next.Settings.Security.KioskMode)
 			{
 				case KioskMode.CreateNewDesktop:
-					CreateNewDesktop();
+					CreateCustomDesktop();
 					break;
 				case KioskMode.DisableExplorerShell:
 					TerminateExplorerShell();
@@ -80,7 +81,7 @@ namespace SafeExamBrowser.Runtime.Operations
 				switch (activeMode)
 				{
 					case KioskMode.CreateNewDesktop:
-						CloseNewDesktop();
+						CloseCustomDesktop();
 						break;
 					case KioskMode.DisableExplorerShell:
 						RestartExplorerShell();
@@ -92,7 +93,7 @@ namespace SafeExamBrowser.Runtime.Operations
 				switch (newMode)
 				{
 					case KioskMode.CreateNewDesktop:
-						CreateNewDesktop();
+						CreateCustomDesktop();
 						break;
 					case KioskMode.DisableExplorerShell:
 						TerminateExplorerShell();
@@ -111,7 +112,7 @@ namespace SafeExamBrowser.Runtime.Operations
 			switch (activeMode)
 			{
 				case KioskMode.CreateNewDesktop:
-					CloseNewDesktop();
+					CloseCustomDesktop();
 					break;
 				case KioskMode.DisableExplorerShell:
 					RestartExplorerShell();
@@ -121,26 +122,26 @@ namespace SafeExamBrowser.Runtime.Operations
 			return OperationResult.Success;
 		}
 
-		private void CreateNewDesktop()
+		private void CreateCustomDesktop()
 		{
 			originalDesktop = desktopFactory.GetCurrent();
 			logger.Info($"Current desktop is {originalDesktop}.");
 
-			newDesktop = desktopFactory.CreateNew(nameof(SafeExamBrowser));
+			customDesktop = desktopFactory.CreateRandom();
-			logger.Info($"Created new desktop {newDesktop}.");
+			logger.Info($"Created custom desktop {customDesktop}.");
 
-			newDesktop.Activate();
+			customDesktop.Activate();
-			processFactory.StartupDesktop = newDesktop;
+			processFactory.StartupDesktop = customDesktop;
-			logger.Info("Successfully activated new desktop.");
+			logger.Info("Successfully activated custom desktop.");
 
-			desktopMonitor.Start(newDesktop);
+			desktopMonitor.Start(customDesktop);
 		}
 
-		private void CloseNewDesktop()
+		private void CloseCustomDesktop()
 		{
 			desktopMonitor.Stop();
 
-			if (originalDesktop != null)
+			if (originalDesktop != default)
 			{
 				originalDesktop.Activate();
 				processFactory.StartupDesktop = originalDesktop;
@@ -151,14 +152,14 @@ namespace SafeExamBrowser.Runtime.Operations
 				logger.Warn($"No original desktop found to activate!");
 			}
 
-			if (newDesktop != null)
+			if (customDesktop != default)
 			{
-				newDesktop.Close();
+				customDesktop.Close();
-				logger.Info($"Closed new desktop {newDesktop}.");
+				logger.Info($"Closed custom desktop {customDesktop}.");
 			}
 			else
 			{
-				logger.Warn($"No new desktop found to close!");
+				logger.Warn($"No custom desktop found to close!");
 			}
 		}
 

SafeExamBrowser.WindowsApi.Contracts/IDesktopFactory.cs

@@ -19,6 +19,12 @@ namespace SafeExamBrowser.WindowsApi.Contracts
 		/// <exception cref="System.ComponentModel.Win32Exception">If the desktop could not be created.</exception>
 		IDesktop CreateNew(string name);
 
+		/// <summary>
+		/// Creates a new desktop with a random name.
+		/// </summary>
+		/// <exception cref="System.ComponentModel.Win32Exception">If the desktop could not be created.</exception>
+		IDesktop CreateRandom();
+
 		/// <summary>
 		/// Retrieves the currently active desktop.
 		/// </summary>

SafeExamBrowser.WindowsApi/Desktops/Desktop.cs

@@ -11,9 +11,9 @@ using System.ComponentModel;
 using System.Runtime.InteropServices;
 using SafeExamBrowser.WindowsApi.Contracts;
 
-namespace SafeExamBrowser.WindowsApi
+namespace SafeExamBrowser.WindowsApi.Desktops
 {
-	public class Desktop : IDesktop
+	internal class Desktop : IDesktop
 	{
 		public IntPtr Handle { get; private set; }
 		public string Name { get; private set; }

SafeExamBrowser.WindowsApi/Desktops/DesktopFactory.cs

@@ -10,18 +10,20 @@ using System;
 using System.ComponentModel;
 using System.Runtime.InteropServices;
 using SafeExamBrowser.Logging.Contracts;
-using SafeExamBrowser.WindowsApi.Contracts;
 using SafeExamBrowser.WindowsApi.Constants;
+using SafeExamBrowser.WindowsApi.Contracts;
 
-namespace SafeExamBrowser.WindowsApi
+namespace SafeExamBrowser.WindowsApi.Desktops
 {
 	public class DesktopFactory : IDesktopFactory
 	{
-		private ILogger logger;
+		private readonly ILogger logger;
+		private readonly Random random;
 
 		public DesktopFactory(ILogger logger)
 		{
 			this.logger = logger;
+			this.random = new Random();
 		}
 
 		public IDesktop CreateNew(string name)
@@ -44,11 +46,34 @@ namespace SafeExamBrowser.WindowsApi
 			return desktop;
 		}
 
+		public IDesktop CreateRandom()
+		{
+			logger.Debug($"Attempting to create random desktop...");
+
+			var name = GenerateRandomDesktopName();
+			var handle = User32.CreateDesktop(name, IntPtr.Zero, IntPtr.Zero, 0, (uint) AccessMask.GENERIC_ALL, IntPtr.Zero);
+
+			if (handle == IntPtr.Zero)
+			{
+				logger.Error($"Failed to create random desktop '{name}'!");
+
+				throw new Win32Exception(Marshal.GetLastWin32Error());
+			}
+
+			var obfuscatedHandle = new IntPtr(random.Next(100, 10000));
+			var obfuscatedName = GenerateRandomDesktopName();
+			var desktop = new ObfuscatedDesktop(handle, name, obfuscatedHandle, obfuscatedName);
+
+			logger.Debug($"Successfully created random desktop {desktop}.");
+
+			return desktop;
+		}
+
 		public IDesktop GetCurrent()
 		{
 			var threadId = Kernel32.GetCurrentThreadId();
 			var handle = User32.GetThreadDesktop(threadId);
-			var name = String.Empty;
+			var name = string.Empty;
 			var nameLength = 0;
 
 			if (handle == IntPtr.Zero)
@@ -81,5 +106,18 @@ namespace SafeExamBrowser.WindowsApi
 
 			return desktop;
 		}
+
+		private string GenerateRandomDesktopName()
+		{
+			var length = random.Next(5, 20);
+			var name = new char[length];
+
+			for (var letter = 0; letter < length; letter++)
+			{
+				name[letter] = (char) (random.Next(2) == 0 && letter != 0 ? random.Next('a', 'z' + 1) : random.Next('A', 'Z' + 1));
+			}
+
+			return new string(name);
+		}
 	}
 }

SafeExamBrowser.WindowsApi/Desktops/DesktopMonitor.cs

@@ -13,7 +13,7 @@ using SafeExamBrowser.Logging.Contracts;
 using SafeExamBrowser.WindowsApi.Constants;
 using SafeExamBrowser.WindowsApi.Contracts;
 
-namespace SafeExamBrowser.WindowsApi
+namespace SafeExamBrowser.WindowsApi.Desktops
 {
 	public class DesktopMonitor : IDesktopMonitor
 	{

SafeExamBrowser.WindowsApi/Desktops/ObfuscatedDesktop.cs

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2023 ETH Zürich, Educational Development and Technology (LET)
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+
+namespace SafeExamBrowser.WindowsApi.Desktops
+{
+	internal class ObfuscatedDesktop : Desktop
+	{
+		private readonly IntPtr? obfuscatedHandle;
+		private readonly string obfuscatedName;
+
+		public ObfuscatedDesktop(IntPtr handle, string name, IntPtr? obfuscatedHandle, string obfuscatedName) : base(handle, name)
+		{
+			this.obfuscatedHandle = obfuscatedHandle;
+			this.obfuscatedName = obfuscatedName;
+		}
+
+		public override string ToString()
+		{
+			return $"'{obfuscatedName}' [{obfuscatedHandle}]";
+		}
+	}
+}

SafeExamBrowser.WindowsApi/Processes/Process.cs

@@ -12,7 +12,7 @@ using SafeExamBrowser.Logging.Contracts;
 using SafeExamBrowser.WindowsApi.Contracts;
 using SafeExamBrowser.WindowsApi.Contracts.Events;
 
-namespace SafeExamBrowser.WindowsApi
+namespace SafeExamBrowser.WindowsApi.Processes
 {
 	internal class Process : IProcess
 	{

SafeExamBrowser.WindowsApi/Processes/ProcessFactory.cs

@@ -20,7 +20,7 @@ using SafeExamBrowser.WindowsApi.Constants;
 using SafeExamBrowser.WindowsApi.Contracts;
 using SafeExamBrowser.WindowsApi.Types;
 
-namespace SafeExamBrowser.WindowsApi
+namespace SafeExamBrowser.WindowsApi.Processes
 {
 	public class ProcessFactory : IProcessFactory
 	{

SafeExamBrowser.WindowsApi/SafeExamBrowser.WindowsApi.csproj

@@ -63,14 +63,15 @@
     <Compile Include="Delegates\EnumWindowsDelegate.cs" />
     <Compile Include="Delegates\EventDelegate.cs" />
     <Compile Include="Delegates\HookDelegate.cs" />
-    <Compile Include="Desktop.cs" />
+    <Compile Include="Desktops\Desktop.cs" />
-    <Compile Include="DesktopFactory.cs" />
+    <Compile Include="Desktops\DesktopFactory.cs" />
-    <Compile Include="DesktopMonitor.cs" />
+    <Compile Include="Desktops\DesktopMonitor.cs" />
+    <Compile Include="Desktops\ObfuscatedDesktop.cs" />
     <Compile Include="ExplorerShell.cs" />
     <Compile Include="Hooks\MouseHook.cs" />
     <Compile Include="Hooks\SystemHook.cs" />
-    <Compile Include="Process.cs" />
+    <Compile Include="Processes\Process.cs" />
-    <Compile Include="ProcessFactory.cs" />
+    <Compile Include="Processes\ProcessFactory.cs" />
     <Compile Include="Constants\AccessMask.cs" />
     <Compile Include="Types\Bounds.cs" />
     <Compile Include="Types\EXECUTION_STATE.cs" />