From 15be4cbaf774456d1765217bb8d1dc8b25752c14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Damian=20B=C3=BCchel?= <damian.buechel@let.ethz.ch>
Date: Mon, 30 Nov 2020 18:30:29 +0100
Subject: [PATCH] SEBWIN-442: Implemented mechanism to automatically select
 server exam via configuration.

---
 .../Handlers/ResourceHandlerTests.cs          | 30 +++++++++++++++++--
 .../Handlers/ResourceHandler.cs               |  6 ++--
 .../DataMapping/ServerDataMapper.cs           |  5 ++++
 .../ConfigurationData/Keys.cs                 |  1 +
 .../Operations/ServerOperation.cs             | 15 ++++++++--
 .../IServerProxy.cs                           |  4 +--
 SafeExamBrowser.Server/ServerProxy.cs         |  4 +--
 .../Server/ServerSettings.cs                  |  5 ++++
 8 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs b/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
index cc921db6..cd27be64 100644
--- a/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
+++ b/SafeExamBrowser.Browser.UnitTests/Handlers/ResourceHandlerTests.cs
@@ -49,18 +49,20 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 		}
 
 		[TestMethod]
-		public void MustAppendCustomHeaders()
+		public void MustAppendCustomHeadersForSameDomain()
 		{
+			var browser = new Mock<IWebBrowser>();
 			var headers = default(NameValueCollection);
 			var request = new Mock<IRequest>();
 
+			browser.SetupGet(b => b.Address).Returns("http://www.host.org");
 			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;
 
-			var result = sut.OnBeforeResourceLoad(Mock.Of<IWebBrowser>(), Mock.Of<IBrowser>(), Mock.Of<IFrame>(), request.Object, Mock.Of<IRequestCallback>());
+			var result = sut.OnBeforeResourceLoad(browser.Object, Mock.Of<IBrowser>(), Mock.Of<IFrame>(), request.Object, Mock.Of<IRequestCallback>());
 
 			request.VerifyGet(r => r.Headers, Times.AtLeastOnce);
 			request.VerifySet(r => r.Headers = It.IsAny<NameValueCollection>(), Times.AtLeastOnce);
@@ -70,6 +72,30 @@ namespace SafeExamBrowser.Browser.UnitTests.Handlers
 			Assert.IsNotNull(headers["X-SafeExamBrowser-RequestHash"]);
 		}
 
+		[TestMethod]
+		public void MustNotAppendCustomHeadersForCrossDomain()
+		{
+			var browser = new Mock<IWebBrowser>();
+			var headers = new NameValueCollection();
+			var request = new Mock<IRequest>();
+
+			browser.SetupGet(b => b.Address).Returns("http://www.otherhost.org");
+			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;
+
+			var result = sut.OnBeforeResourceLoad(browser.Object, Mock.Of<IBrowser>(), Mock.Of<IFrame>(), request.Object, Mock.Of<IRequestCallback>());
+
+			request.VerifyGet(r => r.Headers, Times.Never);
+			request.VerifySet(r => r.Headers = It.IsAny<NameValueCollection>(), Times.Never);
+
+			Assert.AreEqual(CefReturnValue.Continue, result);
+			Assert.IsNull(headers["X-SafeExamBrowser-ConfigKeyHash"]);
+			Assert.IsNull(headers["X-SafeExamBrowser-RequestHash"]);
+		}
+
 		[TestMethod]
 		public void MustBlockMailToUrls()
 		{
diff --git a/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs b/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
index 829954a2..3d2c704d 100644
--- a/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
+++ b/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs
@@ -114,14 +114,14 @@ namespace SafeExamBrowser.Browser.Handlers
 
 		private void AppendCustomHeaders(IWebBrowser webBrowser, IRequest request)
 		{
-			var headers = new NameValueCollection(request.Headers);
-			var urlWithoutFragment = request.Url.Split('#')[0];
-
 			Uri.TryCreate(webBrowser.Address, UriKind.Absolute, out var pageUrl);
 			Uri.TryCreate(request.Url, UriKind.Absolute, out var requestUrl);
 
 			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));
diff --git a/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/ServerDataMapper.cs b/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/ServerDataMapper.cs
index 3c0523a2..278d1b42 100644
--- a/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/ServerDataMapper.cs
+++ b/SafeExamBrowser.Configuration/ConfigurationData/DataMapping/ServerDataMapper.cs
@@ -60,6 +60,11 @@ namespace SafeExamBrowser.Configuration.ConfigurationData.DataMapping
 					settings.Server.ClientSecret = secret;
 				}
 
+				if (configuration.TryGetValue(Keys.Server.ExamId, out v) && v is string examId)
+				{
+					settings.Server.ExamId = examId;
+				}
+
 				if (configuration.TryGetValue(Keys.Server.Institution, out v) && v is string institution)
 				{
 					settings.Server.Institution = institution;
diff --git a/SafeExamBrowser.Configuration/ConfigurationData/Keys.cs b/SafeExamBrowser.Configuration/ConfigurationData/Keys.cs
index e7c4e127..44e37051 100644
--- a/SafeExamBrowser.Configuration/ConfigurationData/Keys.cs
+++ b/SafeExamBrowser.Configuration/ConfigurationData/Keys.cs
@@ -233,6 +233,7 @@ namespace SafeExamBrowser.Configuration.ConfigurationData
 			internal const string ClientName = "clientName";
 			internal const string ClientSecret = "clientSecret";
 			internal const string Configuration = "sebServerConfiguration";
+			internal const string ExamId = "exam";
 			internal const string FallbackPasswordHash = "sebServerFallbackPasswordHash";
 			internal const string Institution = "institution";
 			internal const string PerformFallback = "sebServerFallback";
diff --git a/SafeExamBrowser.Runtime/Operations/ServerOperation.cs b/SafeExamBrowser.Runtime/Operations/ServerOperation.cs
index dcf56c69..3646c08e 100644
--- a/SafeExamBrowser.Runtime/Operations/ServerOperation.cs
+++ b/SafeExamBrowser.Runtime/Operations/ServerOperation.cs
@@ -8,6 +8,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using SafeExamBrowser.Configuration.Contracts;
 using SafeExamBrowser.Core.Contracts.OperationModel;
 using SafeExamBrowser.Core.Contracts.OperationModel.Events;
@@ -58,11 +59,21 @@ namespace SafeExamBrowser.Runtime.Operations
 
 				if (success)
 				{
-					(abort, fallback, success) = TryPerformWithFallback(() => server.GetAvailableExams(), out var exams);
+					(abort, fallback, success) = TryPerformWithFallback(() => server.GetAvailableExams(Context.Next.Settings.Server.ExamId), out var exams);
 
 					if (success)
 					{
-						success = TrySelectExam(exams, out var exam);
+						var exam = default(Exam);
+
+						if (!string.IsNullOrWhiteSpace(Context.Next.Settings.Server.ExamId))
+						{
+							exam = exams.First();
+							logger.Info("Automatically selected exam as defined in configuration.");
+						}
+						else
+						{
+							success = TrySelectExam(exams, out exam);
+						}
 
 						if (success)
 						{
diff --git a/SafeExamBrowser.Server.Contracts/IServerProxy.cs b/SafeExamBrowser.Server.Contracts/IServerProxy.cs
index 2bf43432..fab90235 100644
--- a/SafeExamBrowser.Server.Contracts/IServerProxy.cs
+++ b/SafeExamBrowser.Server.Contracts/IServerProxy.cs
@@ -35,9 +35,9 @@ namespace SafeExamBrowser.Server.Contracts
 		ServerResponse Disconnect();
 
 		/// <summary>
-		/// Retrieves a list of all currently available exams.
+		/// Retrieves a list of all currently available exams, or a list containing the specified exam.
 		/// </summary>
-		ServerResponse<IEnumerable<Exam>> GetAvailableExams();
+		ServerResponse<IEnumerable<Exam>> GetAvailableExams(string examId = default(string));
 
 		/// <summary>
 		/// Retrieves the URI of the configuration file for the given exam.
diff --git a/SafeExamBrowser.Server/ServerProxy.cs b/SafeExamBrowser.Server/ServerProxy.cs
index 57e87a6a..b6506fec 100644
--- a/SafeExamBrowser.Server/ServerProxy.cs
+++ b/SafeExamBrowser.Server/ServerProxy.cs
@@ -116,10 +116,10 @@ namespace SafeExamBrowser.Server
 			return new ServerResponse(success, message);
 		}
 
-		public ServerResponse<IEnumerable<Exam>> GetAvailableExams()
+		public ServerResponse<IEnumerable<Exam>> GetAvailableExams(string examId = default(string))
 		{
 			var authorization = ("Authorization", $"Bearer {oauth2Token}");
-			var content = $"institutionId={settings.Institution}";
+			var content = $"institutionId={settings.Institution}{(examId == default(string) ? "" : $"&examId={examId}")}";
 			var contentType = "application/x-www-form-urlencoded";
 			var exams = default(IList<Exam>);
 
diff --git a/SafeExamBrowser.Settings/Server/ServerSettings.cs b/SafeExamBrowser.Settings/Server/ServerSettings.cs
index 90212f72..323e7de0 100644
--- a/SafeExamBrowser.Settings/Server/ServerSettings.cs
+++ b/SafeExamBrowser.Settings/Server/ServerSettings.cs
@@ -31,6 +31,11 @@ namespace SafeExamBrowser.Settings.Server
 		/// </summary>
 		public string ClientSecret { get; set; }
 
+		/// <summary>
+		/// The identifier of the exam to be started. If present, the exam will be automatically started, i.e. the exam selection will be skipped.
+		/// </summary>
+		public string ExamId { get; set; }
+
 		/// <summary>
 		/// The hash code of the password required to perform a fallback.
 		/// </summary>