From 0da587e521c479aae08be98836d47d87b12a81b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Damian=20B=C3=BCchel?= <damian.buechel@let.ethz.ch>
Date: Mon, 18 Oct 2021 12:06:10 +0200
Subject: [PATCH] SEBWIN-508: Implemented basic JavaScript API.

---
 .../Handlers/RequestHandlerTests.cs           |  5 +-
 .../Handlers/ResourceHandlerTests.cs          | 14 +++-
 SafeExamBrowser.Browser/BrowserApplication.cs | 39 +++++++---
 .../BrowserApplicationInstance.cs             | 25 ++++---
 SafeExamBrowser.Browser/BrowserControl.cs     | 18 +++--
 SafeExamBrowser.Browser/Content/Api.js        |  8 ++
 .../{Pages => Content}/BlockedContent.html    |  0
 .../{Pages => Content}/BlockedPage.html       |  0
 .../ContentLoader.cs}                         | 38 ++++++++--
 .../Handlers/RenderProcessMessageHandler.cs   | 54 +++++++++++++
 .../Handlers/ResourceHandler.cs               | 66 +++++-----------
 .../SafeExamBrowser.Browser.csproj            | 10 ++-
 SafeExamBrowser.Client/CompositionRoot.cs     | 13 +++-
 .../Cryptography/IKeyGenerator.cs             | 26 +++++++
 ...ExamBrowser.Configuration.Contracts.csproj |  1 +
 .../DataMapping/BrowserDataMapper.cs          |  4 +-
 .../Cryptography/KeyGenerator.cs              | 75 +++++++++++++++++++
 .../SafeExamBrowser.Configuration.csproj      |  1 +
 .../Browser/BrowserSettings.cs                | 14 ++--
 19 files changed, 311 insertions(+), 100 deletions(-)
 create mode 100644 SafeExamBrowser.Browser/Content/Api.js
 rename SafeExamBrowser.Browser/{Pages => Content}/BlockedContent.html (100%)
 rename SafeExamBrowser.Browser/{Pages => Content}/BlockedPage.html (100%)
 rename SafeExamBrowser.Browser/{Pages/HtmlLoader.cs => Content/ContentLoader.cs} (55%)
 create mode 100644 SafeExamBrowser.Browser/Handlers/RenderProcessMessageHandler.cs
 create mode 100644 SafeExamBrowser.Configuration.Contracts/Cryptography/IKeyGenerator.cs
 create mode 100644 SafeExamBrowser.Configuration/Cryptography/KeyGenerator.cs

diff --git a/SafeExamBrowser.Browser.UnitTests/Handlers/RequestHandlerTests.cs b/SafeExamBrowser.Browser.UnitTests/Handlers/RequestHandlerTests.cs
index 1b528c93..903d3d86 100644
--- a/SafeExamBrowser.Browser.UnitTests/Handlers/RequestHandlerTests.cs
+++ b/SafeExamBrowser.Browser.UnitTests/Handlers/RequestHandlerTests.cs
@@ -13,6 +13,7 @@ using Moq;
 using SafeExamBrowser.Browser.Contracts.Filters;
 using SafeExamBrowser.Browser.Handlers;
 using SafeExamBrowser.Configuration.Contracts;
+using SafeExamBrowser.Configuration.Contracts.Cryptography;
 using SafeExamBrowser.I18n.Contracts;
 using SafeExamBrowser.Logging.Contracts;
 using SafeExamBrowser.Settings.Browser;
@@ -29,6 +30,7 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 	{
 		private AppConfig appConfig;
 		private Mock<IRequestFilter> filter;
+		private Mock<IKeyGenerator> keyGenerator;
 		private Mock<ILogger> logger;
 		private BrowserSettings settings;
 		private WindowSettings windowSettings;
@@ -41,11 +43,12 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 		{
 			appConfig = new AppConfig();
 			filter = new Mock<IRequestFilter>();
+			keyGenerator = new Mock<IKeyGenerator>();
 			logger = new Mock<ILogger>();
 			settings = new BrowserSettings();
 			windowSettings = new WindowSettings();
 			text = new Mock<IText>();
-			resourceHandler = new ResourceHandler(appConfig, filter.Object, logger.Object, settings, windowSettings, text.Object);
+			resourceHandler = new ResourceHandler(appConfig, filter.Object, keyGenerator.Object, logger.Object, settings, windowSettings, text.Object);
 
 			sut = new TestableRequestHandler(appConfig, filter.Object, logger.Object, resourceHandler, settings, windowSettings, text.Object);
 		}
diff --git a/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs b/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
index 45cf3a33..b848f5de 100644
--- a/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
+++ b/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
@@ -15,6 +15,7 @@ using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using SafeExamBrowser.Browser.Contracts.Filters;
 using SafeExamBrowser.Configuration.Contracts;
+using SafeExamBrowser.Configuration.Contracts.Cryptography;
 using SafeExamBrowser.I18n.Contracts;
 using SafeExamBrowser.Logging.Contracts;
 using SafeExamBrowser.Settings.Browser;
@@ -30,6 +31,7 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 	{
 		private AppConfig appConfig;
 		private Mock<IRequestFilter> filter;
+		private Mock<IKeyGenerator> keyGenerator;
 		private Mock<ILogger> logger;
 		private BrowserSettings settings;
 		private WindowSettings windowSettings;
@@ -41,12 +43,13 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 		{
 			appConfig = new AppConfig();
 			filter = new Mock<IRequestFilter>();
+			keyGenerator = new Mock<IKeyGenerator>();
 			logger = new Mock<ILogger>();
 			settings = new BrowserSettings();
 			windowSettings = new WindowSettings();
 			text = new Mock<IText>();
 
-			sut = new TestableResourceHandler(appConfig, filter.Object, logger.Object, settings, windowSettings, text.Object);
+			sut = new TestableResourceHandler(appConfig, filter.Object, keyGenerator.Object, logger.Object, settings, windowSettings, text.Object);
 		}
 
 		[TestMethod]
@@ -57,11 +60,13 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 			var request = new Mock<IRequest>();
 
 			browser.SetupGet(b => b.Address).Returns("http://www.host.org");
+			keyGenerator.Setup(g => g.CalculateBrowserExamKeyHash(It.IsAny<string>())).Returns(new Random().Next().ToString());
+			keyGenerator.Setup(g => g.CalculateConfigurationKeyHash(It.IsAny<string>())).Returns(new Random().Next().ToString());
 			request.SetupGet(r => r.Headers).Returns(new NameValueCollection());
 			request.SetupGet(r => r.Url).Returns("http://www.host.org");
 			request.SetupSet(r => r.Headers = It.IsAny<NameValueCollection>()).Callback<NameValueCollection>((h) => headers = h);
 			settings.SendConfigurationKey = true;
-			settings.SendExamKey = true;
+			settings.SendBrowserExamKey = true;
 
 			var result = sut.OnBeforeResourceLoad(browser.Object, Mock.Of<IBrowser>(), Mock.Of<IFrame>(), request.Object, Mock.Of<IRequestCallback>());
 
@@ -85,7 +90,7 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 			request.SetupGet(r => r.Url).Returns("http://www.host.org");
 			request.SetupSet(r => r.Headers = It.IsAny<NameValueCollection>()).Callback<NameValueCollection>((h) => headers = h);
 			settings.SendConfigurationKey = true;
-			settings.SendExamKey = true;
+			settings.SendBrowserExamKey = true;
 
 			var result = sut.OnBeforeResourceLoad(browser.Object, Mock.Of<IBrowser>(), Mock.Of<IFrame>(), request.Object, Mock.Of<IRequestCallback>());
 
@@ -291,10 +296,11 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 			internal TestableResourceHandler(
 				AppConfig appConfig,
 				IRequestFilter filter,
+				IKeyGenerator keyGenerator,
 				ILogger logger,
 				BrowserSettings settings,
 				WindowSettings windowSettings,
-				IText text) : base(appConfig, filter, logger, settings, windowSettings, text)
+				IText text) : base(appConfig, filter, keyGenerator, logger, settings, windowSettings, text)
 			{
 			}
 
diff --git a/SafeExamBrowser.Browser/BrowserApplication.cs b/SafeExamBrowser.Browser/BrowserApplication.cs
index dae25635..b9e8e5b9 100644
--- a/SafeExamBrowser.Browser/BrowserApplication.cs
+++ b/SafeExamBrowser.Browser/BrowserApplication.cs
@@ -38,16 +38,17 @@ namespace SafeExamBrowser.Browser
 	{
 		private int instanceIdCounter = default(int);
 
-		private AppConfig appConfig;
-		private List<BrowserApplicationInstance> instances;
-		private IFileSystemDialog fileSystemDialog;
-		private IHashAlgorithm hashAlgorithm;
-		private INativeMethods nativeMethods;
-		private IMessageBox messageBox;
-		private IModuleLogger logger;
-		private BrowserSettings settings;
-		private IText text;
-		private IUserInterfaceFactory uiFactory;
+		private readonly AppConfig appConfig;
+		private readonly IFileSystemDialog fileSystemDialog;
+		private readonly IHashAlgorithm hashAlgorithm;
+		private readonly List<BrowserApplicationInstance> instances;
+		private readonly IKeyGenerator keyGenerator;
+		private readonly IModuleLogger logger;
+		private readonly IMessageBox messageBox;
+		private readonly INativeMethods nativeMethods;
+		private readonly BrowserSettings settings;
+		private readonly IText text;
+		private readonly IUserInterfaceFactory uiFactory;
 
 		public bool AutoStart { get; private set; }
 		public IconResource Icon { get; private set; }
@@ -65,6 +66,7 @@ namespace SafeExamBrowser.Browser
 			BrowserSettings settings,
 			IFileSystemDialog fileSystemDialog,
 			IHashAlgorithm hashAlgorithm,
+			IKeyGenerator keyGenerator,
 			INativeMethods nativeMethods,
 			IMessageBox messageBox,
 			IModuleLogger logger,
@@ -74,10 +76,11 @@ namespace SafeExamBrowser.Browser
 			this.appConfig = appConfig;
 			this.fileSystemDialog = fileSystemDialog;
 			this.hashAlgorithm = hashAlgorithm;
-			this.nativeMethods = nativeMethods;
 			this.instances = new List<BrowserApplicationInstance>();
+			this.keyGenerator = keyGenerator;
 			this.logger = logger;
 			this.messageBox = messageBox;
+			this.nativeMethods = nativeMethods;
 			this.settings = settings;
 			this.text = text;
 			this.uiFactory = uiFactory;
@@ -172,7 +175,19 @@ namespace SafeExamBrowser.Browser
 			var isMainInstance = instances.Count == 0;
 			var instanceLogger = logger.CloneFor($"Browser Instance #{id}");
 			var startUrl = url ?? GenerateStartUrl();
-			var instance = new BrowserApplicationInstance(appConfig, settings, id, isMainInstance, fileSystemDialog, hashAlgorithm, messageBox, instanceLogger, text, uiFactory, startUrl);
+			var instance = new BrowserApplicationInstance(
+				appConfig,
+				settings,
+				id,
+				isMainInstance,
+				fileSystemDialog,
+				hashAlgorithm,
+				keyGenerator,
+				messageBox,
+				instanceLogger,
+				text,
+				uiFactory,
+				startUrl);
 
 			instance.ConfigurationDownloadRequested += (fileName, args) => ConfigurationDownloadRequested?.Invoke(fileName, args);
 			instance.PopupRequested += Instance_PopupRequested;
diff --git a/SafeExamBrowser.Browser/BrowserApplicationInstance.cs b/SafeExamBrowser.Browser/BrowserApplicationInstance.cs
index a945bab5..a8c14895 100644
--- a/SafeExamBrowser.Browser/BrowserApplicationInstance.cs
+++ b/SafeExamBrowser.Browser/BrowserApplicationInstance.cs
@@ -41,19 +41,21 @@ namespace SafeExamBrowser.Browser
 	{
 		private const double ZOOM_FACTOR = 0.2;
 
-		private AppConfig appConfig;
+		private readonly AppConfig appConfig;
+		private readonly IFileSystemDialog fileSystemDialog;
+		private readonly IHashAlgorithm hashAlgorithm;
+		private readonly HttpClient httpClient;
+		private readonly IKeyGenerator keyGenerator;
+		private readonly IModuleLogger logger;
+		private readonly IMessageBox messageBox;
+		private readonly IText text;
+		private readonly IUserInterfaceFactory uiFactory;
+
 		private IBrowserControl control;
 		private IBrowserWindow window;
-		private HttpClient httpClient;
 		private bool isMainInstance;
-		private IFileSystemDialog fileSystemDialog;
-		private IHashAlgorithm hashAlgorithm;
-		private IMessageBox messageBox;
-		private IModuleLogger logger;
 		private BrowserSettings settings;
 		private string startUrl;
-		private IText text;
-		private IUserInterfaceFactory uiFactory;
 		private double zoomLevel;
 
 		private WindowSettings WindowSettings
@@ -84,6 +86,7 @@ namespace SafeExamBrowser.Browser
 			bool isMainInstance,
 			IFileSystemDialog fileSystemDialog,
 			IHashAlgorithm hashAlgorithm,
+			IKeyGenerator keyGenerator,
 			IMessageBox messageBox,
 			IModuleLogger logger,
 			IText text,
@@ -96,6 +99,7 @@ namespace SafeExamBrowser.Browser
 			this.isMainInstance = isMainInstance;
 			this.fileSystemDialog = fileSystemDialog;
 			this.hashAlgorithm = hashAlgorithm;
+			this.keyGenerator = keyGenerator;
 			this.messageBox = messageBox;
 			this.logger = logger;
 			this.settings = settings;
@@ -130,9 +134,11 @@ namespace SafeExamBrowser.Browser
 			var downloadHandler = new DownloadHandler(appConfig, downloadLogger, settings, WindowSettings);
 			var keyboardHandler = new KeyboardHandler();
 			var lifeSpanHandler = new LifeSpanHandler();
+			var renderProcessMessageLogger = logger.CloneFor($"{nameof(RenderProcessMessageHandler)} #{Id}");
+			var renderProcessMessageHandler = new RenderProcessMessageHandler(appConfig, renderProcessMessageLogger, keyGenerator, text);
 			var requestFilter = new RequestFilter();
 			var requestLogger = logger.CloneFor($"{nameof(RequestHandler)} #{Id}");
-			var resourceHandler = new ResourceHandler(appConfig, requestFilter, logger, settings, WindowSettings, text);
+			var resourceHandler = new ResourceHandler(appConfig, requestFilter, keyGenerator, logger, settings, WindowSettings, text);
 			var requestHandler = new RequestHandler(appConfig, requestFilter, requestLogger, resourceHandler, settings, WindowSettings, text);
 
 			Icon = new BrowserIconResource();
@@ -162,6 +168,7 @@ namespace SafeExamBrowser.Browser
 				downloadHandler,
 				keyboardHandler,
 				lifeSpanHandler,
+				renderProcessMessageHandler,
 				requestHandler,
 				startUrl);
 			control.AddressChanged += Control_AddressChanged;
diff --git a/SafeExamBrowser.Browser/BrowserControl.cs b/SafeExamBrowser.Browser/BrowserControl.cs
index e9c539f3..cb14d3cf 100644
--- a/SafeExamBrowser.Browser/BrowserControl.cs
+++ b/SafeExamBrowser.Browser/BrowserControl.cs
@@ -16,13 +16,14 @@ namespace SafeExamBrowser.Browser
 {
 	internal class BrowserControl : ChromiumWebBrowser, IBrowserControl
 	{
-		private IContextMenuHandler contextMenuHandler;
-		private IDialogHandler dialogHandler;
-		private IDisplayHandler displayHandler;
-		private IDownloadHandler downloadHandler;
-		private IKeyboardHandler keyboardHandler;
-		private ILifeSpanHandler lifeSpanHandler;
-		private IRequestHandler requestHandler;
+		private readonly IContextMenuHandler contextMenuHandler;
+		private readonly IDialogHandler dialogHandler;
+		private readonly IDisplayHandler displayHandler;
+		private readonly IDownloadHandler downloadHandler;
+		private readonly IKeyboardHandler keyboardHandler;
+		private readonly ILifeSpanHandler lifeSpanHandler;
+		private readonly IRenderProcessMessageHandler renderProcessMessageHandler;
+		private readonly IRequestHandler requestHandler;
 
 		private AddressChangedEventHandler addressChanged;
 		private LoadFailedEventHandler loadFailed;
@@ -63,6 +64,7 @@ namespace SafeExamBrowser.Browser
 			IDownloadHandler downloadHandler,
 			IKeyboardHandler keyboardHandler,
 			ILifeSpanHandler lifeSpanHandler,
+			IRenderProcessMessageHandler renderProcessMessageHandler,
 			IRequestHandler requestHandler,
 			string url) : base(url)
 		{
@@ -72,6 +74,7 @@ namespace SafeExamBrowser.Browser
 			this.downloadHandler = downloadHandler;
 			this.keyboardHandler = keyboardHandler;
 			this.lifeSpanHandler = lifeSpanHandler;
+			this.renderProcessMessageHandler = renderProcessMessageHandler;
 			this.requestHandler = requestHandler;
 		}
 
@@ -97,6 +100,7 @@ namespace SafeExamBrowser.Browser
 			KeyboardHandler = keyboardHandler;
 			LifeSpanHandler = lifeSpanHandler;
 			MenuHandler = contextMenuHandler;
+			RenderProcessMessageHandler = renderProcessMessageHandler;
 			RequestHandler = requestHandler;
 		}
 
diff --git a/SafeExamBrowser.Browser/Content/Api.js b/SafeExamBrowser.Browser/Content/Api.js
new file mode 100644
index 00000000..ea2daacb
--- /dev/null
+++ b/SafeExamBrowser.Browser/Content/Api.js
@@ -0,0 +1,8 @@
+SafeExamBrowser = {
+    version: 'SEB_Windows_%%_VERSION_%%',
+    security: {
+        browserExamKey: '%%_BEK_%%',
+        configKey: '%%_CK_%%',
+        updateKeys: (callback) => callback()
+    }
+}
\ No newline at end of file
diff --git a/SafeExamBrowser.Browser/Pages/BlockedContent.html b/SafeExamBrowser.Browser/Content/BlockedContent.html
similarity index 100%
rename from SafeExamBrowser.Browser/Pages/BlockedContent.html
rename to SafeExamBrowser.Browser/Content/BlockedContent.html
diff --git a/SafeExamBrowser.Browser/Pages/BlockedPage.html b/SafeExamBrowser.Browser/Content/BlockedPage.html
similarity index 100%
rename from SafeExamBrowser.Browser/Pages/BlockedPage.html
rename to SafeExamBrowser.Browser/Content/BlockedPage.html
diff --git a/SafeExamBrowser.Browser/Pages/HtmlLoader.cs b/SafeExamBrowser.Browser/Content/ContentLoader.cs
similarity index 55%
rename from SafeExamBrowser.Browser/Pages/HtmlLoader.cs
rename to SafeExamBrowser.Browser/Content/ContentLoader.cs
index 42c45cd6..c5551da7 100644
--- a/SafeExamBrowser.Browser/Pages/HtmlLoader.cs
+++ b/SafeExamBrowser.Browser/Content/ContentLoader.cs
@@ -10,21 +10,45 @@ using System.IO;
 using System.Reflection;
 using SafeExamBrowser.I18n.Contracts;
 
-namespace SafeExamBrowser.Browser.Pages
+namespace SafeExamBrowser.Browser.Content
 {
-	internal class HtmlLoader
+	internal class ContentLoader
 	{
+		private string api;
 		private IText text;
 
-		internal HtmlLoader(IText text)
+		internal ContentLoader(IText text)
 		{
 			this.text = text;
 		}
 
+		internal string LoadApi(string browserExamKey, string configurationKey, string version)
+		{
+			if (api == default(string))
+			{
+				var assembly = Assembly.GetAssembly(typeof(ContentLoader));
+				var path = $"{typeof(ContentLoader).Namespace}.Api.js";
+
+				using (var stream = assembly.GetManifestResourceStream(path))
+				using (var reader = new StreamReader(stream))
+				{
+					api = reader.ReadToEnd();
+				}
+			}
+
+			var js = api;
+
+			js = js.Replace("%%_BEK_%%", browserExamKey);
+			js = js.Replace("%%_CK_%%", configurationKey);
+			js = js.Replace("%%_VERSION_%%", version);
+
+			return js;
+		}
+
 		internal string LoadBlockedContent()
 		{
-			var assembly = Assembly.GetAssembly(typeof(HtmlLoader));
-			var path = $"{typeof(HtmlLoader).Namespace}.BlockedContent.html";
+			var assembly = Assembly.GetAssembly(typeof(ContentLoader));
+			var path = $"{typeof(ContentLoader).Namespace}.BlockedContent.html";
 
 			using (var stream = assembly.GetManifestResourceStream(path))
 			using (var reader = new StreamReader(stream))
@@ -39,8 +63,8 @@ namespace SafeExamBrowser.Browser.Pages
 
 		internal string LoadBlockedPage()
 		{
-			var assembly = Assembly.GetAssembly(typeof(HtmlLoader));
-			var path = $"{typeof(HtmlLoader).Namespace}.BlockedPage.html";
+			var assembly = Assembly.GetAssembly(typeof(ContentLoader));
+			var path = $"{typeof(ContentLoader).Namespace}.BlockedPage.html";
 
 			using (var stream = assembly.GetManifestResourceStream(path))
 			using (var reader = new StreamReader(stream))
diff --git a/SafeExamBrowser.Browser/Handlers/RenderProcessMessageHandler.cs b/SafeExamBrowser.Browser/Handlers/RenderProcessMessageHandler.cs
new file mode 100644
index 00000000..583c01e4
--- /dev/null
+++ b/SafeExamBrowser.Browser/Handlers/RenderProcessMessageHandler.cs
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2021 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 CefSharp;
+using SafeExamBrowser.Browser.Content;
+using SafeExamBrowser.Configuration.Contracts;
+using SafeExamBrowser.Configuration.Contracts.Cryptography;
+using SafeExamBrowser.I18n.Contracts;
+using SafeExamBrowser.Logging.Contracts;
+
+namespace SafeExamBrowser.Browser.Handlers
+{
+	internal class RenderProcessMessageHandler : IRenderProcessMessageHandler
+	{
+		private readonly AppConfig appConfig;
+		private readonly ContentLoader contentLoader;
+		private readonly ILogger logger;
+		private readonly IKeyGenerator generator;
+
+		internal RenderProcessMessageHandler(AppConfig appConfig, ILogger logger, IKeyGenerator generator, IText text)
+		{
+			this.appConfig = appConfig;
+			this.contentLoader = new ContentLoader(text);
+			this.logger = logger;
+			this.generator = generator;
+		}
+
+		public void OnContextCreated(IWebBrowser webBrowser, IBrowser browser, IFrame frame)
+		{
+			var browserExamKey = generator.CalculateBrowserExamKeyHash(webBrowser.Address);
+			var configurationKey = generator.CalculateConfigurationKeyHash(webBrowser.Address);
+			var api = contentLoader.LoadApi(browserExamKey, configurationKey, appConfig.ProgramBuildVersion);
+
+			frame.ExecuteJavaScriptAsync(api);
+		}
+
+		public void OnContextReleased(IWebBrowser webBrowser, IBrowser browser, IFrame frame)
+		{
+		}
+
+		public void OnFocusedNodeChanged(IWebBrowser webBrowser, IBrowser browser, IFrame frame, IDomNode node)
+		{
+		}
+
+		public void OnUncaughtException(IWebBrowser webBrowser, IBrowser browser, IFrame frame, JavascriptException exception)
+		{
+		}
+	}
+}
diff --git a/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs b/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
index 0ef0e69a..6eeeb9a6 100644
--- a/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
+++ b/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
@@ -12,16 +12,15 @@ using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Net.Mime;
-using System.Security.Cryptography;
-using System.Text;
 using System.Threading.Tasks;
 using CefSharp;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using SafeExamBrowser.Browser.Content;
 using SafeExamBrowser.Browser.Contracts.Events;
 using SafeExamBrowser.Browser.Contracts.Filters;
-using SafeExamBrowser.Browser.Pages;
 using SafeExamBrowser.Configuration.Contracts;
+using SafeExamBrowser.Configuration.Contracts.Cryptography;
 using SafeExamBrowser.I18n.Contracts;
 using SafeExamBrowser.Logging.Contracts;
 using SafeExamBrowser.Settings.Browser;
@@ -33,33 +32,34 @@ namespace SafeExamBrowser.Browser.Handlers
 {
 	internal class ResourceHandler : CefSharp.Handler.ResourceRequestHandler
 	{
-		private SHA256Managed algorithm;
-		private AppConfig appConfig;
-		private string browserExamKey;
+		private readonly AppConfig appConfig;
+		private readonly ContentLoader contentLoader;
+		private readonly IRequestFilter filter;
+		private readonly IKeyGenerator keyGenerator;
+		private readonly ILogger logger;
+		private readonly BrowserSettings settings;
+		private readonly IText text;
+		private readonly WindowSettings windowSettings;
+
 		private IResourceHandler contentHandler;
-		private IRequestFilter filter;
-		private HtmlLoader htmlLoader;
-		private ILogger logger;
 		private IResourceHandler pageHandler;
 		private string sessionIdentifier;
-		private BrowserSettings settings;
-		private WindowSettings windowSettings;
-		private IText text;
 
 		internal event SessionIdentifierDetectedEventHandler SessionIdentifierDetected;
 
 		internal ResourceHandler(
 			AppConfig appConfig,
 			IRequestFilter filter,
+			IKeyGenerator keyGenerator,
 			ILogger logger,
 			BrowserSettings settings,
 			WindowSettings windowSettings,
 			IText text)
 		{
 			this.appConfig = appConfig;
-			this.algorithm = new SHA256Managed();
 			this.filter = filter;
-			this.htmlLoader = new HtmlLoader(text);
+			this.contentLoader = new ContentLoader(text);
+			this.keyGenerator = keyGenerator;
 			this.logger = logger;
 			this.settings = settings;
 			this.windowSettings = windowSettings;
@@ -123,22 +123,15 @@ namespace SafeExamBrowser.Browser.Handlers
 			if (pageUrl?.Host?.Equals(requestUrl?.Host) == true)
 			{
 				var headers = new NameValueCollection(request.Headers);
-				var urlWithoutFragment = request.Url.Split('#')[0];
 
 				if (settings.SendConfigurationKey)
 				{
-					var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + settings.ConfigurationKey));
-					var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
-
-					headers["X-SafeExamBrowser-ConfigKeyHash"] = key;
+					headers["X-SafeExamBrowser-ConfigKeyHash"] = keyGenerator.CalculateConfigurationKeyHash(request.Url);
 				}
 
-				if (settings.SendExamKey)
+				if (settings.SendBrowserExamKey)
 				{
-					var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + (browserExamKey ?? ComputeBrowserExamKey())));
-					var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
-
-					headers["X-SafeExamBrowser-RequestHash"] = key;
+					headers["X-SafeExamBrowser-RequestHash"] = keyGenerator.CalculateBrowserExamKeyHash(request.Url);
 				}
 
 				request.Headers = headers;
@@ -169,27 +162,6 @@ namespace SafeExamBrowser.Browser.Handlers
 			return block;
 		}
 
-		private string ComputeBrowserExamKey()
-		{
-			var salt = settings.ExamKeySalt;
-
-			if (salt == default(byte[]))
-			{
-				salt = new byte[0];
-				logger.Warn("The current configuration does not contain a salt value for the browser exam key!");
-			}
-
-			using (var algorithm = new HMACSHA256(salt))
-			{
-				var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(appConfig.CodeSignatureHash + appConfig.ProgramBuildVersion + settings.ConfigurationKey));
-				var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
-
-				browserExamKey = key;
-
-				return browserExamKey;
-			}
-		}
-
 		private bool IsMailtoUrl(string url)
 		{
 			return url.StartsWith(Uri.UriSchemeMailto);
@@ -234,12 +206,12 @@ namespace SafeExamBrowser.Browser.Handlers
 		{
 			if (contentHandler == default(IResourceHandler))
 			{
-				contentHandler = CefSharp.ResourceHandler.FromString(htmlLoader.LoadBlockedContent());
+				contentHandler = CefSharp.ResourceHandler.FromString(contentLoader.LoadBlockedContent());
 			}
 
 			if (pageHandler == default(IResourceHandler))
 			{
-				pageHandler = CefSharp.ResourceHandler.FromString(htmlLoader.LoadBlockedPage());
+				pageHandler = CefSharp.ResourceHandler.FromString(contentLoader.LoadBlockedPage());
 			}
 
 			switch (resourceType)
diff --git a/SafeExamBrowser.Browser/SafeExamBrowser.Browser.csproj b/SafeExamBrowser.Browser/SafeExamBrowser.Browser.csproj
index c1950ca4..1c48536d 100644
--- a/SafeExamBrowser.Browser/SafeExamBrowser.Browser.csproj
+++ b/SafeExamBrowser.Browser/SafeExamBrowser.Browser.csproj
@@ -104,9 +104,10 @@
     <Compile Include="Handlers\DownloadHandler.cs" />
     <Compile Include="Handlers\KeyboardHandler.cs" />
     <Compile Include="Handlers\LifeSpanHandler.cs" />
+    <Compile Include="Handlers\RenderProcessMessageHandler.cs" />
     <Compile Include="Handlers\RequestHandler.cs" />
     <Compile Include="Handlers\ResourceHandler.cs" />
-    <Compile Include="Pages\HtmlLoader.cs" />
+    <Compile Include="Content\ContentLoader.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>
@@ -148,8 +149,8 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="Pages\BlockedContent.html" />
-    <EmbeddedResource Include="Pages\BlockedPage.html" />
+    <EmbeddedResource Include="Content\BlockedContent.html" />
+    <EmbeddedResource Include="Content\BlockedPage.html" />
   </ItemGroup>
   <ItemGroup>
     <None Include="app.config" />
@@ -157,6 +158,9 @@
       <SubType>Designer</SubType>
     </None>
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Content\Api.js" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
     <PostBuildEvent>
diff --git a/SafeExamBrowser.Client/CompositionRoot.cs b/SafeExamBrowser.Client/CompositionRoot.cs
index 415131c7..5d17da06 100644
--- a/SafeExamBrowser.Client/CompositionRoot.cs
+++ b/SafeExamBrowser.Client/CompositionRoot.cs
@@ -209,8 +209,19 @@ namespace SafeExamBrowser.Client
 		private IOperation BuildBrowserOperation()
 		{
 			var fileSystemDialog = BuildFileSystemDialog();
+			var keyGenerator = new KeyGenerator(context.AppConfig, ModuleLogger(nameof(KeyGenerator)), context.Settings);
 			var moduleLogger = ModuleLogger(nameof(BrowserApplication));
-			var browser = new BrowserApplication(context.AppConfig, context.Settings.Browser, fileSystemDialog, new HashAlgorithm(), nativeMethods, messageBox, moduleLogger, text, uiFactory);
+			var browser = new BrowserApplication(
+				context.AppConfig,
+				context.Settings.Browser,
+				fileSystemDialog,
+				new HashAlgorithm(),
+				keyGenerator,
+				nativeMethods,
+				messageBox,
+				moduleLogger,
+				text,
+				uiFactory);
 			var operation = new BrowserOperation(actionCenter, context, logger, taskbar, taskview, uiFactory);
 
 			context.Browser = browser;
diff --git a/SafeExamBrowser.Configuration.Contracts/Cryptography/IKeyGenerator.cs b/SafeExamBrowser.Configuration.Contracts/Cryptography/IKeyGenerator.cs
new file mode 100644
index 00000000..00f5267a
--- /dev/null
+++ b/SafeExamBrowser.Configuration.Contracts/Cryptography/IKeyGenerator.cs
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2021 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.Configuration.Contracts.Cryptography
+{
+	/// <summary>
+	/// Provides funcionality to calculate keys for integrity checks.
+	/// </summary>
+	public interface IKeyGenerator
+	{
+		/// <summary>
+		/// Calculates the hash value of the browser exam key (BEK) for the given URL.
+		/// </summary>
+		string CalculateBrowserExamKeyHash(string url);
+
+		/// <summary>
+		/// Calculates the hash value of the configuration key (CK) for the given URL.
+		/// </summary>
+		string CalculateConfigurationKeyHash(string url);
+	}
+}
diff --git a/SafeExamBrowser.Configuration.Contracts/SafeExamBrowser.Configuration.Contracts.csproj b/SafeExamBrowser.Configuration.Contracts/SafeExamBrowser.Configuration.Contracts.csproj
index a40f1ea6..4717e9bb 100644
--- a/SafeExamBrowser.Configuration.Contracts/SafeExamBrowser.Configuration.Contracts.csproj
+++ b/SafeExamBrowser.Configuration.Contracts/SafeExamBrowser.Configuration.Contracts.csproj
@@ -59,6 +59,7 @@
     <Compile Include="Cryptography\EncryptionParameters.cs" />
     <Compile Include="Cryptography\ICertificateStore.cs" />
     <Compile Include="Cryptography\IHashAlgorithm.cs" />
+    <Compile Include="Cryptography\IKeyGenerator.cs" />
     <Compile Include="Cryptography\IPasswordEncryption.cs" />
     <Compile Include="Cryptography\IPublicKeyEncryption.cs" />
     <Compile Include="Cryptography\PasswordParameters.cs" />
diff --git a/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/BrowserDataMapper.cs b/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/BrowserDataMapper.cs
index c0568c1d..b9932e44 100644
--- a/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/BrowserDataMapper.cs
+++ b/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/BrowserDataMapper.cs
@@ -346,7 +346,7 @@ namespace SafeExamBrowser.Configuration.ConfigurationData.DataMapping
 		{
 			if (value is byte[] salt)
 			{
-				settings.Browser.ExamKeySalt = salt;
+				settings.Browser.BrowserExamKeySalt = salt;
 			}
 		}
 
@@ -487,7 +487,7 @@ namespace SafeExamBrowser.Configuration.ConfigurationData.DataMapping
 			if (value is bool send)
 			{
 				settings.Browser.SendConfigurationKey = send;
-				settings.Browser.SendExamKey = send;
+				settings.Browser.SendBrowserExamKey = send;
 			}
 		}
 
diff --git a/SafeExamBrowser.Configuration/Cryptography/KeyGenerator.cs b/SafeExamBrowser.Configuration/Cryptography/KeyGenerator.cs
new file mode 100644
index 00000000..2aa9baa7
--- /dev/null
+++ b/SafeExamBrowser.Configuration/Cryptography/KeyGenerator.cs
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2021 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.Security.Cryptography;
+using System.Text;
+using SafeExamBrowser.Configuration.Contracts;
+using SafeExamBrowser.Configuration.Contracts.Cryptography;
+using SafeExamBrowser.Logging.Contracts;
+using SafeExamBrowser.Settings;
+
+namespace SafeExamBrowser.Configuration.Cryptography
+{
+	public class KeyGenerator : IKeyGenerator
+	{
+		private readonly SHA256Managed algorithm;
+		private readonly AppConfig appConfig;
+		private readonly ILogger logger;
+		private readonly AppSettings settings;
+
+		private string browserExamKey;
+
+		public KeyGenerator(AppConfig appConfig, ILogger logger, AppSettings settings)
+		{
+			this.algorithm = new SHA256Managed();
+			this.appConfig = appConfig;
+			this.logger = logger;
+			this.settings = settings;
+		}
+
+		public string CalculateBrowserExamKeyHash(string url)
+		{
+			var urlWithoutFragment = url.Split('#')[0];
+			var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + (browserExamKey ?? ComputeBrowserExamKey())));
+			var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
+
+			return key;
+		}
+
+		public string CalculateConfigurationKeyHash(string url)
+		{
+			var urlWithoutFragment = url.Split('#')[0];
+			var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + settings.Browser.ConfigurationKey));
+			var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
+
+			return key;
+		}
+
+		private string ComputeBrowserExamKey()
+		{
+			var salt = settings.Browser.BrowserExamKeySalt;
+
+			if (salt == default(byte[]))
+			{
+				salt = new byte[0];
+				logger.Warn("The current configuration does not contain a salt value for the browser exam key!");
+			}
+
+			using (var algorithm = new HMACSHA256(salt))
+			{
+				var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(appConfig.CodeSignatureHash + appConfig.ProgramBuildVersion + settings.Browser.ConfigurationKey));
+				var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
+
+				browserExamKey = key;
+
+				return browserExamKey;
+			}
+		}
+	}
+}
diff --git a/SafeExamBrowser.Configuration/SafeExamBrowser.Configuration.csproj b/SafeExamBrowser.Configuration/SafeExamBrowser.Configuration.csproj
index 6b609add..ce86a006 100644
--- a/SafeExamBrowser.Configuration/SafeExamBrowser.Configuration.csproj
+++ b/SafeExamBrowser.Configuration/SafeExamBrowser.Configuration.csproj
@@ -74,6 +74,7 @@
     <Compile Include="ConfigurationData\Keys.cs" />
     <Compile Include="ConfigurationData\DataValues.cs" />
     <Compile Include="Cryptography\CertificateStore.cs" />
+    <Compile Include="Cryptography\KeyGenerator.cs" />
     <Compile Include="DataCompression\GZipCompressor.cs" />
     <Compile Include="Cryptography\PasswordEncryption.cs" />
     <Compile Include="Cryptography\PublicKeyEncryption.cs" />
diff --git a/SafeExamBrowser.Settings/Browser/BrowserSettings.cs b/SafeExamBrowser.Settings/Browser/BrowserSettings.cs
index 5d120e23..5235dafc 100644
--- a/SafeExamBrowser.Settings/Browser/BrowserSettings.cs
+++ b/SafeExamBrowser.Settings/Browser/BrowserSettings.cs
@@ -66,6 +66,11 @@ namespace SafeExamBrowser.Settings.Browser
 		/// </summary>
 		public bool AllowUploads { get; set; }
 
+		/// <summary>
+		/// The salt value for the calculation of the browser exam key which is used for integrity checks with server applications (see also <see cref="SendBrowserExamKey"/>).
+		/// </summary>
+		public byte[] BrowserExamKeySalt { get; set; }
+
 		/// <summary>
 		/// The configuration key used for integrity checks with server applications (see also <see cref="SendConfigurationKey"/>).
 		/// </summary>
@@ -108,11 +113,6 @@ namespace SafeExamBrowser.Settings.Browser
 		/// </summary>
 		public bool EnableBrowser { get; set; }
 
-		/// <summary>
-		/// The salt value for the calculation of the exam key which is used for integrity checks with server applications (see also <see cref="SendExamKey"/>).
-		/// </summary>
-		public byte[] ExamKeySalt { get; set; }
-
 		/// <summary>
 		/// The settings to be used for the browser request filter.
 		/// </summary>
@@ -169,9 +169,9 @@ namespace SafeExamBrowser.Settings.Browser
 		public bool SendConfigurationKey { get; set; }
 
 		/// <summary>
-		/// Determines whether the exam key header is sent with every HTTP request (see also <see cref="ExamKeySalt"/>).
+		/// Determines whether the browser exam key header is sent with every HTTP request (see also <see cref="BrowserExamKeySalt"/>).
 		/// </summary>
-		public bool SendExamKey { get; set; }
+		public bool SendBrowserExamKey { get; set; }
 
 		/// <summary>
 		/// The URL with which the main browser window will be loaded.