SEBWIN-221: Implemented scaffolding for loading and parsing of configuration resources.

SafeExamBrowser.Browser/BrowserApplicationInstance.cs

@@ -103,9 +103,17 @@ namespace SafeExamBrowser.Browser
 
 		private void DownloadHandler_ConfigurationDownloadRequested(string fileName, DownloadEventArgs args)
 		{
-			args.BrowserWindow = window;
+			if (settings.AllowConfigurationDownloads)
+			{
+				args.BrowserWindow = window;
+				logger.Debug($"Forwarding download request for configuration file '{fileName}'.");
 
-			ConfigurationDownloadRequested?.Invoke(fileName, args);
+				ConfigurationDownloadRequested?.Invoke(fileName, args);
+			}
+			else
+			{
+				logger.Debug($"Discarded download request for configuration file '{fileName}'.");
+			}
 		}
 
 		private void Window_AddressChanged(string address)

SafeExamBrowser.Browser/Handlers/RequestHandler.cs

@@ -31,11 +31,11 @@ namespace SafeExamBrowser.Browser.Handlers
 
 			if (uri.Scheme == appConfig.SebUriScheme)
 			{
-				request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttp }.ToString();
+				request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttp }.Uri.AbsoluteUri;
 			}
 			else if (uri.Scheme == appConfig.SebUriSchemeSecure)
 			{
-				request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttps }.ToString();
+				request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttps }.Uri.AbsoluteUri;
 			}
 
 			return base.OnBeforeResourceLoad(browserControl, browser, frame, request, callback);

SafeExamBrowser.Client/ClientController.cs

@@ -206,7 +206,7 @@ namespace SafeExamBrowser.Client
 		{
 			if (Settings.ConfigurationMode == ConfigurationMode.ConfigureClient)
 			{
-				logger.Debug($"Received download request for configuration file '{fileName}'. Asking user to confirm the reconfiguration...");
+				logger.Info($"Received download request for configuration file '{fileName}'. Asking user to confirm the reconfiguration...");
 
 				var message = TextKey.MessageBox_ReconfigurationQuestion;
 				var title = TextKey.MessageBox_ReconfigurationQuestionTitle;

SafeExamBrowser.Configuration.UnitTests/ConfigurationRepositoryTests.cs

@@ -9,7 +9,9 @@
 using System;
 using System.Reflection;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
 using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Logging;
 
 namespace SafeExamBrowser.Configuration.UnitTests
 {
@@ -22,8 +24,9 @@ namespace SafeExamBrowser.Configuration.UnitTests
 		public void Initialize()
 		{
 			var executablePath = Assembly.GetExecutingAssembly().Location;
+			var logger = new Mock<ILogger>();
 
-			sut = new ConfigurationRepository(executablePath, string.Empty, string.Empty, string.Empty);
+			sut = new ConfigurationRepository(logger.Object, executablePath, string.Empty, string.Empty, string.Empty);
 		}
 
 		[TestMethod]

SafeExamBrowser.Configuration/ConfigurationRepository.cs

@@ -7,7 +7,11 @@
  */
 
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.IO.Compression;
+using System.Linq;
+using SafeExamBrowser.Configuration.DataFormats;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Configuration.Settings;
 using SafeExamBrowser.Contracts.Logging;
@@ -24,9 +28,16 @@ namespace SafeExamBrowser.Configuration
 		private readonly string programVersion;
 
 		private AppConfig appConfig;
+		private IList<IDataFormat> dataFormats;
+		private ILogger logger;
+		private IList<IResourceLoader> resourceLoaders;
 
-		public ConfigurationRepository(string executablePath, string programCopyright, string programTitle, string programVersion)
+		public ConfigurationRepository(ILogger logger, string executablePath, string programCopyright, string programTitle, string programVersion)
 		{
+			dataFormats = new List<IDataFormat>();
+			resourceLoaders = new List<IResourceLoader>();
+
+			this.logger = logger;
 			this.executablePath = executablePath ?? string.Empty;
 			this.programCopyright = programCopyright ?? string.Empty;
 			this.programTitle = programTitle ?? string.Empty;
@@ -73,38 +84,28 @@ namespace SafeExamBrowser.Configuration
 
 			UpdateAppConfig();
 
-			configuration.AppConfig = CloneAppConfig();
+			configuration.AppConfig = appConfig.Clone();
 			configuration.Id = Guid.NewGuid();
 			configuration.StartupToken = Guid.NewGuid();
 
 			return configuration;
 		}
 
-		public LoadStatus TryLoadSettings(Uri resource, out Settings settings, string adminPassword = null, string settingsPassword = null)
-		{
-			// TODO: Implement loading mechanism
-
-			settings = LoadDefaultSettings();
-
-			return LoadStatus.Success;
-		}
-
 		public Settings LoadDefaultSettings()
 		{
-			// TODO: Implement default settings
-
 			var settings = new Settings();
 
-			settings.KioskMode = new Random().Next(10) < 5 ? KioskMode.CreateNewDesktop : KioskMode.DisableExplorerShell;
+			settings.KioskMode = KioskMode.None;
 			settings.ServicePolicy = ServicePolicy.Optional;
 
 			settings.Browser.StartUrl = "https://www.safeexambrowser.org/testing";
 			settings.Browser.AllowAddressBar = true;
 			settings.Browser.AllowBackwardNavigation = true;
+			settings.Browser.AllowConfigurationDownloads = true;
 			settings.Browser.AllowDeveloperConsole = true;
+			settings.Browser.AllowDownloads = true;
 			settings.Browser.AllowForwardNavigation = true;
 			settings.Browser.AllowReloading = true;
-			settings.Browser.AllowDownloads = true;
 
 			settings.Taskbar.AllowApplicationLog = true;
 			settings.Taskbar.AllowKeyboardLayout = true;
@@ -113,33 +114,90 @@ namespace SafeExamBrowser.Configuration
 			return settings;
 		}
 
-		private AppConfig CloneAppConfig()
+		public void Register(IDataFormat dataFormat)
 		{
-			return new AppConfig
+			dataFormats.Add(dataFormat);
+		}
+
+		public void Register(IResourceLoader resourceLoader)
+		{
+			resourceLoaders.Add(resourceLoader);
+		}
+
+		public LoadStatus TryLoadSettings(Uri resource, out Settings settings, string adminPassword = null, string settingsPassword = null)
+		{
+			settings = default(Settings);
+
+			logger.Info($"Attempting to load '{resource}'...");
+
+			try
 			{
-				AppDataFolder = appConfig.AppDataFolder,
+				var resourceLoader = resourceLoaders.FirstOrDefault(l => l.CanLoad(resource));
-				ApplicationStartTime = appConfig.ApplicationStartTime,
+
-				BrowserCachePath = appConfig.BrowserCachePath,
+				if (resourceLoader != null)
-				BrowserLogFile = appConfig.BrowserLogFile,
+				{
-				ClientAddress = appConfig.ClientAddress,
+					var data = resourceLoader.Load(resource);
-				ClientExecutablePath = appConfig.ClientExecutablePath,
+					var dataFormat = dataFormats.FirstOrDefault(f => f.CanParse(data));
-				ClientId = appConfig.ClientId,
+
-				ClientLogFile = appConfig.ClientLogFile,
+					logger.Info($"Successfully loaded {data.Length / 1000.0} KB data from '{resource}' using {resourceLoader.GetType().Name}.");
-				ConfigurationFileExtension = appConfig.ConfigurationFileExtension,
+
-				DefaultSettingsFileName = appConfig.DefaultSettingsFileName,
+					if (dataFormat is HtmlFormat)
-				DownloadDirectory = appConfig.DownloadDirectory,
+					{
-				LogLevel = appConfig.LogLevel,
+						return HandleHtml(resource, out settings);
-				ProgramCopyright = appConfig.ProgramCopyright,
+					}
-				ProgramDataFolder = appConfig.ProgramDataFolder,
+
-				ProgramTitle = appConfig.ProgramTitle,
+					if (dataFormat != null)
-				ProgramVersion = appConfig.ProgramVersion,
+					{
-				RuntimeAddress = appConfig.RuntimeAddress,
+						return dataFormat.TryParse(data, out settings, adminPassword, settingsPassword);
-				RuntimeId = appConfig.RuntimeId,
+					}
-				RuntimeLogFile = appConfig.RuntimeLogFile,
+				}
-				SebUriScheme = appConfig.SebUriScheme,
+
-				SebUriSchemeSecure = appConfig.SebUriSchemeSecure,
+				logger.Warn($"No {(resourceLoader == null ? "resource loader" : "data format")} found for '{resource}'!");
-				ServiceAddress = appConfig.ServiceAddress
+
-			};
+				return LoadStatus.NotSupported;
+			}
+			catch (Exception e)
+			{
+				logger.Error($"Unexpected error while trying to load '{resource}'!", e);
+
+				return LoadStatus.UnexpectedError;
+			}
+		}
+
+		private LoadStatus HandleHtml(Uri resource, out Settings settings)
+		{
+			logger.Info($"Loaded data appears to be HTML, loading default settings and using '{resource}' as startup URL.");
+
+			settings = LoadDefaultSettings();
+			settings.Browser.StartUrl = resource.AbsoluteUri;
+
+			return LoadStatus.Success;
+		}
+
+		private byte[] Decompress(byte[] bytes)
+		{
+			try
+			{
+				var buffer = new byte[4096];
+
+				using (var stream = new GZipStream(new MemoryStream(bytes), CompressionMode.Decompress))
+				using (var decompressed = new MemoryStream())
+				{
+					var bytesRead = 0;
+
+					do
+					{
+						bytesRead = stream.Read(buffer, 0, buffer.Length);
+						decompressed.Write(buffer, 0, bytesRead);
+					} while (bytesRead > 0);
+
+					return decompressed.ToArray();
+				}
+			}
+			catch (InvalidDataException)
+			{
+				return bytes;
+			}
 		}
 
 		private void UpdateAppConfig()

SafeExamBrowser.Configuration/DataFormats/DefaultFormat.cs

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Configuration.Settings;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Configuration.DataFormats
+{
+	public class DefaultFormat : IDataFormat
+	{
+		private ILogger logger;
+
+		public DefaultFormat(ILogger logger)
+		{
+			this.logger = logger;
+		}
+
+		public bool CanParse(byte[] data)
+		{
+			return true;
+		}
+
+		public LoadStatus TryParse(byte[] data, out Settings settings, string adminPassword = null, string settingsPassword = null)
+		{
+			settings = new Settings();
+			settings.ServicePolicy = ServicePolicy.Optional;
+
+			return LoadStatus.Success;
+		}
+	}
+}

SafeExamBrowser.Configuration/DataFormats/HtmlFormat.cs

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Configuration.Settings;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Configuration.DataFormats
+{
+	public class HtmlFormat : IDataFormat
+	{
+		private ILogger logger;
+
+		public HtmlFormat(ILogger logger)
+		{
+			this.logger = logger;
+		}
+
+		public bool CanParse(byte[] data)
+		{
+			return false;
+		}
+
+		public LoadStatus TryParse(byte[] data, out Settings settings, string adminPassword = null, string settingsPassword = null)
+		{
+			throw new System.NotImplementedException();
+		}
+	}
+}

SafeExamBrowser.Configuration/DataFormats/XmlFormat.cs

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Configuration.Settings;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Configuration.DataFormats
+{
+	public class XmlFormat : IDataFormat
+	{
+		private ILogger logger;
+
+		public XmlFormat(ILogger logger)
+		{
+			this.logger = logger;
+		}
+
+		public bool CanParse(byte[] data)
+		{
+			return false;
+		}
+
+		public LoadStatus TryParse(byte[] data, out Settings settings, string adminPassword = null, string settingsPassword = null)
+		{
+			throw new System.NotImplementedException();
+		}
+	}
+}

SafeExamBrowser.Configuration/ResourceLoader.cs

@@ -1,22 +0,0 @@
-/*
- * Copyright (c) 2018 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;
-using SafeExamBrowser.Contracts.Configuration;
-
-namespace SafeExamBrowser.Configuration
-{
-	public class ResourceLoader : IResourceLoader
-	{
-		public bool IsHtmlResource(Uri resource)
-		{
-			// TODO: Implement resource loader
-			return false;
-		}
-	}
-}

SafeExamBrowser.Configuration/ResourceLoaders/FileResourceLoader.cs

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2018 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;
+using System.IO;
+using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Configuration.ResourceLoaders
+{
+	public class FileResourceLoader : IResourceLoader
+	{
+		private ILogger logger;
+
+		public FileResourceLoader(ILogger logger)
+		{
+			this.logger = logger;
+		}
+
+		public bool CanLoad(Uri resource)
+		{
+			if (resource.IsFile && File.Exists(resource.AbsolutePath))
+			{
+				logger.Debug($"Can load '{resource}' as it references an existing file.");
+
+				return true;
+			}
+
+			logger.Debug($"Can't load '{resource}' since it isn't a file URI or no file exists at the specified path.");
+
+			return false;
+		}
+
+		public byte[] Load(Uri resource)
+		{
+			logger.Debug($"Loading data from '{resource}'...");
+
+			return File.ReadAllBytes(resource.AbsolutePath);
+		}
+	}
+}

SafeExamBrowser.Configuration/ResourceLoaders/NetworkResourceLoader.cs

@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2018 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;
+using System.Linq;
+using System.Net.Http;
+using System.Threading.Tasks;
+using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Configuration.ResourceLoaders
+{
+	public class NetworkResourceLoader : IResourceLoader
+	{
+		private AppConfig appConfig;
+		private ILogger logger;
+
+		private string[] SupportedSchemes => new[]
+		{
+			appConfig.SebUriScheme,
+			appConfig.SebUriSchemeSecure,
+			Uri.UriSchemeHttp,
+			Uri.UriSchemeHttps
+		};
+
+		public NetworkResourceLoader(AppConfig appConfig, ILogger logger)
+		{
+			this.appConfig = appConfig;
+			this.logger = logger;
+		}
+
+		public bool CanLoad(Uri resource)
+		{
+			if (SupportedSchemes.Contains(resource.Scheme) && IsAvailable(resource))
+			{
+				logger.Debug($"Can load '{resource}' as it references an existing network resource.");
+
+				return true;
+			}
+
+			logger.Debug($"Can't load '{resource}' since its URI scheme is not supported or the resource is unavailable.");
+
+			return false;
+		}
+
+		public byte[] Load(Uri resource)
+		{
+			var uri = BuildUriFor(resource);
+
+			logger.Debug($"Downloading data from '{uri}'...");
+
+			var request = new HttpRequestMessage(HttpMethod.Get, uri);
+			var response = Execute(request);
+
+			logger.Debug($"Sent GET request for '{uri}', received response '{(int) response.StatusCode} - {response.ReasonPhrase}'.");
+
+			var data = Extract(response.Content);
+
+			logger.Debug($"Extracted {data.Length / 1000.0} KB data from response.");
+
+			return data;
+		}
+
+		private bool IsAvailable(Uri resource)
+		{
+			try
+			{
+				var uri = BuildUriFor(resource);
+				var request = new HttpRequestMessage(HttpMethod.Head, uri);
+				var response = Execute(request);
+
+				logger.Debug($"Sent HEAD request for '{uri}', received response '{(int) response.StatusCode} - {response.ReasonPhrase}'.");
+
+				return response.IsSuccessStatusCode;
+			}
+			catch (Exception e)
+			{
+				logger.Error($"Failed to check availability of '{resource}'!", e);
+
+				return false;
+			}
+		}
+
+		private Uri BuildUriFor(Uri resource)
+		{
+			var scheme = GetSchemeFor(resource);
+			var builder = new UriBuilder(resource) { Scheme = scheme };
+
+			return builder.Uri;
+		}
+
+		private string GetSchemeFor(Uri resource)
+		{
+			if (resource.Scheme == appConfig.SebUriScheme)
+			{
+				return Uri.UriSchemeHttp;
+			}
+
+			if (resource.Scheme == appConfig.SebUriSchemeSecure)
+			{
+				return Uri.UriSchemeHttps;
+			}
+
+			return resource.Scheme;
+		}
+
+		private HttpResponseMessage Execute(HttpRequestMessage request)
+		{
+			var task = Task.Run(async () =>
+			{
+				using (var client = new HttpClient())
+				{
+					return await client.SendAsync(request);
+				}
+			});
+
+			return task.GetAwaiter().GetResult();
+		}
+
+		private byte[] Extract(HttpContent content)
+		{
+			var task = Task.Run(async () =>
+			{
+				return await content.ReadAsByteArrayAsync();
+			});
+
+			return task.GetAwaiter().GetResult();
+		}
+	}
+}

SafeExamBrowser.Configuration/SafeExamBrowser.Configuration.csproj

@@ -48,13 +48,18 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
+    <Reference Include="System.Net.Http" />
     <Reference Include="System.Windows.Forms" />
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="ResourceLoader.cs" />
+    <Compile Include="DataFormats\DefaultFormat.cs" />
+    <Compile Include="DataFormats\HtmlFormat.cs" />
+    <Compile Include="DataFormats\XmlFormat.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="ConfigurationRepository.cs" />
+    <Compile Include="ResourceLoaders\FileResourceLoader.cs" />
+    <Compile Include="ResourceLoaders\NetworkResourceLoader.cs" />
     <Compile Include="SessionConfiguration.cs" />
     <Compile Include="SystemInfo.cs" />
   </ItemGroup>

SafeExamBrowser.Contracts/Configuration/AppConfig.cs

@@ -126,5 +126,13 @@ namespace SafeExamBrowser.Contracts.Configuration
 		/// The communication address of the service component.
 		/// </summary>
 		public string ServiceAddress { get; set; }
+
+		/// <summary>
+		/// Creates a shallow clone.
+		/// </summary>
+		public AppConfig Clone()
+		{
+			return MemberwiseClone() as AppConfig;
+		}
 	}
 }

SafeExamBrowser.Contracts/Configuration/IConfigurationRepository.cs

@@ -25,16 +25,25 @@ namespace SafeExamBrowser.Contracts.Configuration
 		/// </summary>
 		ISessionConfiguration InitializeSessionConfiguration();
 
-		/// <summary>
-		/// Attempts to load settings from the specified resource, using the optional passwords. Returns a <see cref="LoadStatus"/>
-		/// indicating the result of the operation. As long as the result is not <see cref="LoadStatus.Success"/>, the declared
-		/// <paramref name="settings"/> will be <c>null</c>!
-		/// </summary>
-		LoadStatus TryLoadSettings(Uri resource, out Settings.Settings settings, string adminPassword = null, string settingsPassword = null);
-
 		/// <summary>
 		/// Loads the default settings.
 		/// </summary>
 		Settings.Settings LoadDefaultSettings();
+
+		/// <summary>
+		/// Registers the specified <see cref="IDataFormat"/> as option to parse configuration data.
+		/// </summary>
+		void Register(IDataFormat dataFormat);
+
+		/// <summary>
+		/// Registers the specified <see cref="IResourceLoader"/> as option to load configuration data.
+		/// </summary>
+		void Register(IResourceLoader resourceLoader);
+
+		/// <summary>
+		/// Attempts to load settings from the specified resource, using the optional passwords. As long as the result is not
+		/// <see cref="LoadStatus.Success"/>, the referenced settings may be <c>null</c> or in an undefinable state!
+		/// </summary>
+		LoadStatus TryLoadSettings(Uri resource, out Settings.Settings settings, string adminPassword = null, string settingsPassword = null);
 	}
 }

SafeExamBrowser.Contracts/Configuration/IDataFormat.cs

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2018 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/.
+ */
+
+namespace SafeExamBrowser.Contracts.Configuration
+{
+	/// <summary>
+	/// Defines the data format for a configuration file.
+	/// </summary>
+	public interface IDataFormat
+	{
+		/// <summary>
+		/// Indicates whether the given data complies with the required format.
+		/// </summary>
+		bool CanParse(byte[] data);
+
+		/// <summary>
+		/// Attempts to parse the given binary data.
+		/// </summary>
+		LoadStatus TryParse(byte[] data, out Settings.Settings settings, string adminPassword = null, string settingsPassword = null);
+	}
+}

SafeExamBrowser.Contracts/Configuration/IResourceLoader.cs

@@ -11,13 +11,18 @@ using System;
 namespace SafeExamBrowser.Contracts.Configuration
 {
 	/// <summary>
-	/// Loads configuration data from various sources (e.g. the internet) and provides related resource handling functionality.
+	/// Loads binary data from a particular resource.
 	/// </summary>
 	public interface IResourceLoader
 	{
 		/// <summary>
-		/// Indicates whether the given <see cref="Uri"/> identifies a HTML resource.
+		/// Indicates whether the resource loader is able to load data from the specified resource.
 		/// </summary>
-		bool IsHtmlResource(Uri resource);
+		bool CanLoad(Uri resource);
+
+		/// <summary>
+		/// Loads the binary data from the specified resource.
+		/// </summary>
+		byte[] Load(Uri resource);
 	}
 }

SafeExamBrowser.Contracts/Configuration/LoadStatus.cs

@@ -9,7 +9,7 @@
 namespace SafeExamBrowser.Contracts.Configuration
 {
 	/// <summary>
-	/// Defines all possible results of <see cref="IConfigurationRepository.LoadSettings(System.Uri)"/>.
+	/// Defines all possible results of an attempt to load a configuration file.
 	/// </summary>
 	public enum LoadStatus
 	{
@@ -23,14 +23,24 @@ namespace SafeExamBrowser.Contracts.Configuration
 		/// </summary>
 		InvalidData,
 
+		/// <summary>
+		/// Indicates that a resource is not supported.
+		/// </summary>
+		NotSupported,
+
 		/// <summary>
 		/// Indicates that a settings password is needed in order to load the settings.
 		/// </summary>
 		SettingsPasswordNeeded,
 
 		/// <summary>
-		/// The <see cref="Settings.Settings"/> were loaded successfully.
+		/// The settings were loaded successfully.
 		/// </summary>
-		Success
+		Success,
+
+		/// <summary>
+		/// An unexpected error occurred while trying to load the settings.
+		/// </summary>
+		UnexpectedError
 	}
 }

SafeExamBrowser.Contracts/Configuration/Settings/BrowserSettings.cs

@@ -26,13 +26,18 @@ namespace SafeExamBrowser.Contracts.Configuration.Settings
 		/// </summary>
 		public bool AllowBackwardNavigation { get; set; }
 
+		/// <summary>
+		/// Determines whether the user should be allowed to download configuration files.
+		/// </summary>
+		public bool AllowConfigurationDownloads { get; set; }
+
 		/// <summary>
 		/// Determines whether the user should be allowed to open the developer console of a browser window.
 		/// </summary>
 		public bool AllowDeveloperConsole { get; set; }
 
 		/// <summary>
-		/// Determines whether the user should be allowed to download files.
+		/// Determines whether the user should be allowed to download files (excluding configuration files).
 		/// </summary>
 		public bool AllowDownloads { get; set; }
 

SafeExamBrowser.Contracts/I18n/TextKey.cs

@@ -22,6 +22,10 @@ namespace SafeExamBrowser.Contracts.I18n
 		MessageBox_ClientConfigurationQuestionTitle,
 		MessageBox_ConfigurationDownloadError,
 		MessageBox_ConfigurationDownloadErrorTitle,
+		MessageBox_InvalidConfigurationData,
+		MessageBox_InvalidConfigurationDataTitle,
+		MessageBox_NotSupportedConfigurationResource,
+		MessageBox_NotSupportedConfigurationResourceTitle,
 		MessageBox_Quit,
 		MessageBox_QuitTitle,
 		MessageBox_QuitError,
@@ -42,6 +46,8 @@ namespace SafeExamBrowser.Contracts.I18n
 		MessageBox_SingleInstanceTitle,
 		MessageBox_StartupError,
 		MessageBox_StartupErrorTitle,
+		MessageBox_UnexpectedConfigurationError,
+		MessageBox_UnexpectedConfigurationErrorTitle,
 		Notification_AboutTooltip,
 		Notification_LogTooltip,
 		OperationStatus_CloseRuntimeConnection,

SafeExamBrowser.Contracts/SafeExamBrowser.Contracts.csproj

@@ -53,6 +53,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Communication\Events\ClientConfigurationEventArgs.cs" />
+    <Compile Include="Configuration\IDataFormat.cs" />
     <Compile Include="Core\Events\InstanceTerminatedEventHandler.cs" />
     <Compile Include="Core\Events\NameChangedEventHandler.cs" />
     <Compile Include="Core\IApplicationController.cs" />

SafeExamBrowser.I18n/Text.xml

@@ -24,6 +24,18 @@
   <Entry key="MessageBox_ConfigurationDownloadErrorTitle">
     Download Error
   </Entry>
+  <Entry key="MessageBox_InvalidConfigurationData">
+    The configuration resource '%%URI%%' contains invalid data!
+  </Entry>
+  <Entry key="MessageBox_InvalidConfigurationDataTitle">
+    Configuration Error
+  </Entry>
+  <Entry key="MessageBox_NotSupportedConfigurationResource">
+    The configuration resource '%%URI%%' is not supported!
+  </Entry>
+  <Entry key="MessageBox_NotSupportedConfigurationResourceTitle">
+    Configuration Error
+  </Entry>
   <Entry key="MessageBox_Quit">
     Would you really like to quit the application?
   </Entry>
@@ -78,6 +90,12 @@
   <Entry key="MessageBox_StartupErrorTitle">
     Startup Error
   </Entry>
+  <Entry key="MessageBox_UnexpectedConfigurationError">
+    An unexpected error occurred while trying to load configuration resource '%%URI%%'! Please consult the application log for more information...
+  </Entry>
+  <Entry key="MessageBox_UnexpectedConfigurationErrorTitle">
+    Configuration Error
+  </Entry>
   <Entry key="Notification_AboutTooltip">
     About Safe Exam Browser
   </Entry>

SafeExamBrowser.Runtime.UnitTests/Operations/ConfigurationOperationTests.cs

@@ -26,7 +26,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		private AppConfig appConfig;
 		private Mock<ILogger> logger;
 		private Mock<IConfigurationRepository> repository;
-		private Mock<IResourceLoader> resourceLoader;
 		private Mock<ISessionConfiguration> session;
 		private SessionContext sessionContext;
 		private Settings settings;
@@ -39,7 +38,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			appConfig = new AppConfig();
 			logger = new Mock<ILogger>();
 			repository = new Mock<IConfigurationRepository>();
-			resourceLoader = new Mock<IResourceLoader>();
 			session = new Mock<ISessionConfiguration>();
 			sessionContext = new SessionContext();
 			settings = new Settings();
@@ -64,7 +62,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
 			var resource = new Uri(url);
@@ -82,7 +80,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
 			var resource = new Uri(Path.Combine(location, "SettingsDummy.txt"));
@@ -99,7 +97,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
 			var resource = new Uri(Path.Combine(location, "SettingsDummy.txt"));
@@ -110,10 +108,19 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		[TestMethod]
 		public void MustFallbackToDefaultsAsLastPrio()
 		{
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			var actualSettings = default(Settings);
+			var defaultSettings = new Settings();
+
+			repository.Setup(r => r.LoadDefaultSettings()).Returns(defaultSettings);
+			session.SetupSet<Settings>(s => s.Settings = It.IsAny<Settings>()).Callback(s => actualSettings = s);
+
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
 			repository.Verify(r => r.LoadDefaultSettings(), Times.Once);
+			session.VerifySet(s => s.Settings = defaultSettings);
+
+			Assert.AreSame(defaultSettings, actualSettings);
 		}
 
 		[TestMethod]
@@ -122,7 +129,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			appConfig.ProgramDataFolder = Path.Combine(Path.GetDirectoryName(GetType().Assembly.Location), nameof(Operations));
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is ConfigurationCompletedEventArgs c)
@@ -141,7 +148,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		{
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is ConfigurationCompletedEventArgs c)
@@ -161,7 +168,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			settings.ConfigurationMode = ConfigurationMode.Exam;
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is ConfigurationCompletedEventArgs c)
@@ -176,15 +183,25 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		[TestMethod]
 		public void MustNotFailWithoutCommandLineArgs()
 		{
-			repository.Setup(r => r.LoadDefaultSettings());
+			var actualSettings = default(Settings);
+			var defaultSettings = new Settings();
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			repository.Setup(r => r.LoadDefaultSettings()).Returns(defaultSettings);
+			session.SetupSet<Settings>(s => s.Settings = It.IsAny<Settings>()).Callback(s => actualSettings = s);
+
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
-			sut = new ConfigurationOperation(new string[] { }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			repository.Verify(r => r.LoadDefaultSettings(), Times.Once);
+
+			Assert.AreSame(defaultSettings, actualSettings);
+
+			sut = new ConfigurationOperation(new string[] { }, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 
 			repository.Verify(r => r.LoadDefaultSettings(), Times.Exactly(2));
+
+			Assert.AreSame(defaultSettings, actualSettings);
 		}
 
 		[TestMethod]
@@ -192,7 +209,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 		{
 			var uri = @"an/invalid\uri.'*%yolo/()你好";
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", uri }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", uri }, repository.Object, logger.Object, sessionContext);
 			sut.Perform();
 		}
 
@@ -203,7 +220,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.AdminPasswordNeeded);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -224,7 +241,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.SettingsPasswordNeeded);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -247,7 +264,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.AdminPasswordNeeded);
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, password, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -272,7 +289,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.SettingsPasswordNeeded);
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, password)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -295,7 +312,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.AdminPasswordNeeded);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -316,7 +333,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.SettingsPasswordNeeded);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -341,7 +358,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, settingsPassword)).Returns(LoadStatus.AdminPasswordNeeded);
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, adminPassword, settingsPassword)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, sessionContext);
 			sut.ActionRequired += args =>
 			{
 				if (args is PasswordRequiredEventArgs p)
@@ -358,37 +375,6 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			repository.Verify(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, adminPassword, settingsPassword), Times.Once);
 		}
 
-		[TestMethod]
-		public void MustHandleInvalidData()
-		{
-			var url = @"http://www.safeexambrowser.org/whatever.seb";
-
-			resourceLoader.Setup(r => r.IsHtmlResource(It.IsAny<Uri>())).Returns(false);
-			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.InvalidData);
-
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
-
-			var result = sut.Perform();
-
-			Assert.AreEqual(OperationResult.Failed, result);
-		}
-
-		[TestMethod]
-		public void MustHandleHtmlAsInvalidData()
-		{
-			var url = "http://www.blubb.org/some/resource.html";
-
-			resourceLoader.Setup(r => r.IsHtmlResource(It.IsAny<Uri>())).Returns(true);
-			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.InvalidData);
-
-			sut = new ConfigurationOperation(new[] { "blubb.exe", url }, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
-
-			var result = sut.Perform();
-
-			Assert.AreEqual(OperationResult.Success, result);
-			Assert.AreEqual(url, settings.Browser.StartUrl);
-		}
-
 		[TestMethod]
 		public void MustReconfigureSuccessfullyWithCorrectUri()
 		{
@@ -398,7 +384,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			sessionContext.ReconfigurationFilePath = resource.AbsolutePath;
 			repository.Setup(r => r.TryLoadSettings(It.Is<Uri>(u => u.Equals(resource)), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 
 			var result = sut.Repeat();
 
@@ -415,7 +401,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
 			sessionContext.ReconfigurationFilePath = null;
 			repository.Setup(r => r.TryLoadSettings(It.IsAny<Uri>(), out settings, null, null)).Returns(LoadStatus.Success);
 
-			sut = new ConfigurationOperation(null, repository.Object, logger.Object, resourceLoader.Object, sessionContext);
+			sut = new ConfigurationOperation(null, repository.Object, logger.Object, sessionContext);
 
 			var result = sut.Repeat();
 

SafeExamBrowser.Runtime.UnitTests/app.config

@@ -6,6 +6,10 @@
         <assemblyIdentity name="System.Threading.Tasks.Extensions" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
         <bindingRedirect oldVersion="0.0.0.0-4.1.1.0" newVersion="4.1.1.0" />
       </dependentAssembly>
+      <dependentAssembly>
+        <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
+        <bindingRedirect oldVersion="0.0.0.0-4.0.2.0" newVersion="4.0.2.0" />
+      </dependentAssembly>
     </assemblyBinding>
   </runtime>
 </configuration>

SafeExamBrowser.Runtime/CompositionRoot.cs

@@ -13,6 +13,8 @@ using System.Reflection;
 using SafeExamBrowser.Communication.Hosts;
 using SafeExamBrowser.Communication.Proxies;
 using SafeExamBrowser.Configuration;
+using SafeExamBrowser.Configuration.DataFormats;
+using SafeExamBrowser.Configuration.ResourceLoaders;
 using SafeExamBrowser.Contracts.Configuration;
 using SafeExamBrowser.Contracts.Core;
 using SafeExamBrowser.Contracts.Core.OperationModel;
@@ -32,6 +34,7 @@ namespace SafeExamBrowser.Runtime
 	internal class CompositionRoot
 	{
 		private AppConfig appConfig;
+		private IConfigurationRepository configuration;
 		private ILogger logger;
 		private ISystemInfo systemInfo;
 		private IText text;
@@ -45,13 +48,12 @@ namespace SafeExamBrowser.Runtime
 			const int FIFTEEN_SECONDS = 15000;
 
 			var args = Environment.GetCommandLineArgs();
-			var configuration = BuildConfigurationRepository();
 			var nativeMethods = new NativeMethods();
 
 			logger = new Logger();
-			appConfig = configuration.InitializeAppConfig();
 			systemInfo = new SystemInfo();
 
+			InitializeConfiguration();
 			InitializeLogging();
 			InitializeText();
 
@@ -60,7 +62,6 @@ namespace SafeExamBrowser.Runtime
 			var explorerShell = new ExplorerShell(new ModuleLogger(logger, nameof(ExplorerShell)), nativeMethods);
 			var processFactory = new ProcessFactory(new ModuleLogger(logger, nameof(ProcessFactory)));
 			var proxyFactory = new ProxyFactory(new ProxyObjectFactory(), logger);
-			var resourceLoader = new ResourceLoader();
 			var runtimeHost = new RuntimeHost(appConfig.RuntimeAddress, new HostObjectFactory(), new ModuleLogger(logger, nameof(RuntimeHost)), FIVE_SECONDS);
 			var serviceProxy = new ServiceProxy(appConfig.ServiceAddress, new ProxyObjectFactory(), new ModuleLogger(logger, nameof(ServiceProxy)));
 			var sessionContext = new SessionContext();
@@ -73,7 +74,7 @@ namespace SafeExamBrowser.Runtime
 			bootstrapOperations.Enqueue(new CommunicationHostOperation(runtimeHost, logger));
 
 			sessionOperations.Enqueue(new SessionInitializationOperation(configuration, logger, runtimeHost, sessionContext));
-			sessionOperations.Enqueue(new ConfigurationOperation(args, configuration, logger, resourceLoader, sessionContext));
+			sessionOperations.Enqueue(new ConfigurationOperation(args, configuration, logger, sessionContext));
 			sessionOperations.Enqueue(new ClientTerminationOperation(logger, processFactory, proxyFactory, runtimeHost, sessionContext, FIFTEEN_SECONDS));
 			sessionOperations.Enqueue(new KioskModeTerminationOperation(desktopFactory, explorerShell, logger, processFactory, sessionContext));
 			sessionOperations.Enqueue(new ServiceOperation(logger, serviceProxy, sessionContext));
@@ -105,15 +106,22 @@ namespace SafeExamBrowser.Runtime
 			logger?.Log($"# Application terminated at {DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")}");
 		}
 
-		private IConfigurationRepository BuildConfigurationRepository()
+		private void InitializeConfiguration()
 		{
 			var executable = Assembly.GetExecutingAssembly();
 			var programCopyright = executable.GetCustomAttribute<AssemblyCopyrightAttribute>().Copyright;
 			var programTitle = executable.GetCustomAttribute<AssemblyTitleAttribute>().Title;
 			var programVersion = executable.GetCustomAttribute<AssemblyInformationalVersionAttribute>().InformationalVersion;
-			var repository = new ConfigurationRepository(executable.Location, programCopyright, programTitle, programVersion);
+			var moduleLogger = new ModuleLogger(logger, nameof(ConfigurationRepository));
 
-			return repository;
+			configuration = new ConfigurationRepository(moduleLogger, executable.Location, programCopyright, programTitle, programVersion);
+			appConfig = configuration.InitializeAppConfig();
+
+			configuration.Register(new DefaultFormat(new ModuleLogger(logger, nameof(DefaultFormat))));
+			configuration.Register(new HtmlFormat(new ModuleLogger(logger, nameof(HtmlFormat))));
+			configuration.Register(new XmlFormat(new ModuleLogger(logger, nameof(XmlFormat))));
+			configuration.Register(new FileResourceLoader(new ModuleLogger(logger, nameof(FileResourceLoader))));
+			configuration.Register(new NetworkResourceLoader(appConfig, new ModuleLogger(logger, nameof(NetworkResourceLoader))));
 		}
 
 		private void InitializeLogging()

SafeExamBrowser.Runtime/Operations/ConfigurationOperation.cs

@@ -24,7 +24,6 @@ namespace SafeExamBrowser.Runtime.Operations
 		private string[] commandLineArgs;
 		private IConfigurationRepository configuration;
 		private ILogger logger;
-		private IResourceLoader resourceLoader;
 
 		public override event ActionRequiredEventHandler ActionRequired;
 		public override event StatusChangedEventHandler StatusChanged;
@@ -33,13 +32,11 @@ namespace SafeExamBrowser.Runtime.Operations
 			string[] commandLineArgs,
 			IConfigurationRepository configuration,
 			ILogger logger,
-			IResourceLoader resourceLoader,
 			SessionContext sessionContext) : base(sessionContext)
 		{
 			this.commandLineArgs = commandLineArgs;
 			this.logger = logger;
 			this.configuration = configuration;
-			this.resourceLoader = resourceLoader;
 		}
 
 		public override OperationResult Perform()
@@ -51,7 +48,7 @@ namespace SafeExamBrowser.Runtime.Operations
 
 			if (isValidUri)
 			{
-				logger.Info($"Attempting to load settings from '{uri.AbsolutePath}'...");
+				logger.Info($"Attempting to load settings from '{uri}'...");
 
 				var result = LoadSettings(uri);
 
@@ -62,7 +59,7 @@ namespace SafeExamBrowser.Runtime.Operations
 			}
 
 			logger.Info("No valid settings resource specified nor found in PROGRAMDATA or APPDATA - loading default settings...");
-			configuration.LoadDefaultSettings();
+			Context.Next.Settings = configuration.LoadDefaultSettings();
 
 			return OperationResult.Success;
 		}
@@ -76,7 +73,7 @@ namespace SafeExamBrowser.Runtime.Operations
 
 			if (isValidUri)
 			{
-				logger.Info($"Attempting to load settings from '{uri.AbsolutePath}'...");
+				logger.Info($"Attempting to load settings from '{uri}'...");
 
 				var result = LoadSettings(uri);
 
@@ -126,11 +123,6 @@ namespace SafeExamBrowser.Runtime.Operations
 				}
 			}
 
-			if (status == LoadStatus.InvalidData)
-			{
-				HandleInvalidData(ref status, uri);
-			}
-
 			if (status == LoadStatus.Success)
 			{
 				Context.Next.Settings = settings;
@@ -138,6 +130,18 @@ namespace SafeExamBrowser.Runtime.Operations
 				return OperationResult.Success;
 			}
 
+			switch (status)
+			{
+				case LoadStatus.InvalidData:
+					ActionRequired?.Invoke(new InvalidDataMessageArgs(uri.ToString()));
+					break;
+				case LoadStatus.NotSupported:
+					ActionRequired?.Invoke(new NotSupportedMessageArgs(uri.ToString()));
+					break;
+				case LoadStatus.UnexpectedError:
+					ActionRequired?.Invoke(new UnexpectedErrorMessageArgs(uri.ToString()));
+					break;
+			}
 
 			return OperationResult.Failed;
 		}
@@ -152,22 +156,6 @@ namespace SafeExamBrowser.Runtime.Operations
 			return args;
 		}
 
-		private void HandleInvalidData(ref LoadStatus status, Uri uri)
-		{
-			if (resourceLoader.IsHtmlResource(uri))
-			{
-				configuration.LoadDefaultSettings();
-				Context.Next.Settings.Browser.StartUrl = uri.AbsoluteUri;
-				logger.Info($"The specified URI '{uri.AbsoluteUri}' appears to point to a HTML resource, setting it as startup URL.");
-
-				status = LoadStatus.Success;
-			}
-			else
-			{
-				logger.Error($"The specified settings resource '{uri.AbsoluteUri}' is invalid!");
-			}
-		}
-
 		private bool TryInitializeSettingsUri(out Uri uri)
 		{
 			var path = string.Empty;

SafeExamBrowser.Runtime/Operations/Events/InvalidDataMessageArgs.cs

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.I18n;
+using SafeExamBrowser.Contracts.UserInterface.MessageBox;
+
+namespace SafeExamBrowser.Runtime.Operations.Events
+{
+	internal class InvalidDataMessageArgs : MessageEventArgs
+	{
+		internal InvalidDataMessageArgs(string uri)
+		{
+			Icon = MessageBoxIcon.Error;
+			Message = TextKey.MessageBox_InvalidConfigurationData;
+			MessagePlaceholders["%%URI%%"] = uri;
+			Title = TextKey.MessageBox_InvalidConfigurationDataTitle;
+		}
+	}
+}

SafeExamBrowser.Runtime/Operations/Events/MessageEventArgs.cs

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2018 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.Collections.Generic;
+using SafeExamBrowser.Contracts.Core.OperationModel.Events;
+using SafeExamBrowser.Contracts.I18n;
+using SafeExamBrowser.Contracts.UserInterface.MessageBox;
+
+namespace SafeExamBrowser.Runtime.Operations.Events
+{
+	internal class MessageEventArgs : ActionRequiredEventArgs
+	{
+		internal MessageBoxIcon Icon { get; set; }
+		internal TextKey Message { get; set; }
+		internal TextKey Title { get; set; }
+		internal Dictionary<string, string> MessagePlaceholders { get; private set; }
+		internal Dictionary<string, string> TitlePlaceholders { get; private set; }
+
+		public MessageEventArgs()
+		{
+			MessagePlaceholders = new Dictionary<string, string>();
+			TitlePlaceholders = new Dictionary<string, string>();
+		}
+	}
+}

SafeExamBrowser.Runtime/Operations/Events/NotSupportedMessageArgs.cs

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.I18n;
+using SafeExamBrowser.Contracts.UserInterface.MessageBox;
+
+namespace SafeExamBrowser.Runtime.Operations.Events
+{
+	internal class NotSupportedMessageArgs : MessageEventArgs
+	{
+		internal NotSupportedMessageArgs(string uri)
+		{
+			Icon = MessageBoxIcon.Error;
+			Message = TextKey.MessageBox_NotSupportedConfigurationResource;
+			MessagePlaceholders["%%URI%%"] = uri;
+			Title = TextKey.MessageBox_NotSupportedConfigurationResourceTitle;
+		}
+	}
+}

SafeExamBrowser.Runtime/Operations/Events/UnexpectedErrorMessageArgs.cs

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2018 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 SafeExamBrowser.Contracts.I18n;
+using SafeExamBrowser.Contracts.UserInterface.MessageBox;
+
+namespace SafeExamBrowser.Runtime.Operations.Events
+{
+	internal class UnexpectedErrorMessageArgs : MessageEventArgs
+	{
+		internal UnexpectedErrorMessageArgs(string uri)
+		{
+			Icon = MessageBoxIcon.Error;
+			Message = TextKey.MessageBox_UnexpectedConfigurationError;
+			MessagePlaceholders["%%URI%%"] = uri;
+			Title = TextKey.MessageBox_UnexpectedConfigurationErrorTitle;
+		}
+	}
+}

SafeExamBrowser.Runtime/Operations/KioskModeOperation.cs

@@ -35,10 +35,6 @@ namespace SafeExamBrowser.Runtime.Operations
 			set { Context.OriginalDesktop = value; }
 		}
 
-		/// <summary>
-		/// TODO: This mechanism exposes the internal state of the operation! Find better solution which will keep the
-		/// state internal but still allow unit testing of both kiosk mode operations independently!
-		/// </summary>
 		protected KioskMode? ActiveMode
 		{
 			get { return Context.ActiveMode; }

SafeExamBrowser.Runtime/RuntimeController.cs

@@ -363,6 +363,9 @@ namespace SafeExamBrowser.Runtime
 				case ConfigurationCompletedEventArgs a:
 					AskIfConfigurationSufficient(a);
 					break;
+				case MessageEventArgs m:
+					ShowMessageBox(m);
+					break;
 				case PasswordRequiredEventArgs p:
 					AskForPassword(p);
 					break;
@@ -393,6 +396,24 @@ namespace SafeExamBrowser.Runtime
 			}
 		}
 
+		private void ShowMessageBox(MessageEventArgs args)
+		{
+			var message = text.Get(args.Message);
+			var title = text.Get(args.Title);
+
+			foreach (var placeholder in args.MessagePlaceholders)
+			{
+				message = message.Replace(placeholder.Key, placeholder.Value);
+			}
+
+			foreach (var placeholder in args.TitlePlaceholders)
+			{
+				title = title.Replace(placeholder.Key, placeholder.Value);
+			}
+
+			messageBox.Show(message, title, MessageBoxAction.Confirm, args.Icon, runtimeWindow);
+		}
+
 		private void TryGetPasswordViaDialog(PasswordRequiredEventArgs args)
 		{
 			var isAdmin = args.Purpose == PasswordRequestPurpose.Administrator;

SafeExamBrowser.Runtime/SafeExamBrowser.Runtime.csproj

@@ -90,7 +90,11 @@
     <Compile Include="Operations\ClientTerminationOperation.cs" />
     <Compile Include="Operations\ConfigurationOperation.cs" />
     <Compile Include="Operations\Events\ConfigurationCompletedEventArgs.cs" />
+    <Compile Include="Operations\Events\InvalidDataMessageArgs.cs" />
+    <Compile Include="Operations\Events\MessageEventArgs.cs" />
+    <Compile Include="Operations\Events\NotSupportedMessageArgs.cs" />
     <Compile Include="Operations\Events\PasswordRequiredEventArgs.cs" />
+    <Compile Include="Operations\Events\UnexpectedErrorMessageArgs.cs" />
     <Compile Include="Operations\KioskModeOperation.cs" />
     <Compile Include="Operations\KioskModeTerminationOperation.cs" />
     <Compile Include="Operations\ServiceOperation.cs" />

SafeExamBrowser.WindowsApi/ExplorerShell.cs

@@ -64,6 +64,7 @@ namespace SafeExamBrowser.WindowsApi
 				logger.Info($"Restored window '{window.Title}' with handle = {window.Handle}.");
 			}
 
+			minimizedWindows.Clear();
 			logger.Info("Minimized windows successfully restored.");
 		}