428 lines
12 KiB
C#
428 lines
12 KiB
C#
/*
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* Copyright (c) 2021 ETH Zürich, Educational Development and Technology (LET)
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Threading.Tasks;
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using System.Timers;
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using SafeExamBrowser.Logging.Contracts;
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using SafeExamBrowser.Monitoring.Contracts.Applications;
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using SafeExamBrowser.Monitoring.Contracts.Applications.Events;
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using SafeExamBrowser.Settings.Applications;
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using SafeExamBrowser.WindowsApi.Contracts;
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namespace SafeExamBrowser.Monitoring.Applications
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{
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public class ApplicationMonitor : IApplicationMonitor
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{
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private IList<BlacklistApplication> blacklist;
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private Guid? captureHookId;
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private Guid? foregroundHookId;
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private ILogger logger;
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private INativeMethods nativeMethods;
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private IList<IProcess> processes;
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private IProcessFactory processFactory;
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private Timer timer;
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private IList<WhitelistApplication> whitelist;
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private Window activeWindow;
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public event ExplorerStartedEventHandler ExplorerStarted;
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public event InstanceStartedEventHandler InstanceStarted;
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public event TerminationFailedEventHandler TerminationFailed;
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public ApplicationMonitor(int interval_ms, ILogger logger, INativeMethods nativeMethods, IProcessFactory processFactory)
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{
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this.blacklist = new List<BlacklistApplication>();
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this.logger = logger;
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this.nativeMethods = nativeMethods;
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this.processes = new List<IProcess>();
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this.processFactory = processFactory;
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this.timer = new Timer(interval_ms);
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this.whitelist = new List<WhitelistApplication>();
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}
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public InitializationResult Initialize(ApplicationSettings settings)
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{
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var result = new InitializationResult();
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InitializeProcesses();
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InitializeBlacklist(settings, result);
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InitializeWhitelist(settings, result);
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return result;
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}
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public void Start()
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{
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timer.AutoReset = false;
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timer.Elapsed += Timer_Elapsed;
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timer.Start();
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logger.Info("Started monitoring applications.");
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captureHookId = nativeMethods.RegisterSystemCaptureStartEvent(SystemEvent_WindowChanged);
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logger.Info($"Registered system capture start event with ID = {captureHookId}.");
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foregroundHookId = nativeMethods.RegisterSystemForegroundEvent(SystemEvent_WindowChanged);
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logger.Info($"Registered system foreground event with ID = {foregroundHookId}.");
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}
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public void Stop()
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{
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timer.Stop();
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timer.Elapsed -= Timer_Elapsed;
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logger.Info("Stopped monitoring applications.");
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if (captureHookId.HasValue)
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{
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nativeMethods.DeregisterSystemEventHook(captureHookId.Value);
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logger.Info($"Unregistered system capture start event with ID = {captureHookId}.");
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}
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if (foregroundHookId.HasValue)
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{
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nativeMethods.DeregisterSystemEventHook(foregroundHookId.Value);
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logger.Info($"Unregistered system foreground event with ID = {foregroundHookId}.");
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}
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}
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public bool TryTerminate(RunningApplication application)
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{
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var success = true;
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foreach (var process in application.Processes)
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{
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success &= TryTerminate(process);
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}
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return success;
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}
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private void SystemEvent_WindowChanged(IntPtr handle)
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{
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if (handle != IntPtr.Zero && activeWindow?.Handle != handle)
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{
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var title = nativeMethods.GetWindowTitle(handle);
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var window = new Window { Handle = handle, Title = title };
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logger.Debug($"Window has changed from {activeWindow} to {window}.");
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activeWindow = window;
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Task.Run(() =>
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{
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if (!IsAllowed(window) && !TryHide(window))
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{
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Close(window);
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}
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});
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}
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}
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private void Timer_Elapsed(object sender, ElapsedEventArgs e)
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{
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var failed = new List<RunningApplication>();
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var running = processFactory.GetAllRunning();
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var started = running.Where(r => processes.All(p => p.Id != r.Id)).ToList();
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var terminated = processes.Where(p => running.All(r => r.Id != p.Id)).ToList();
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foreach (var process in started)
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{
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logger.Debug($"Process {process} has been started.");
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processes.Add(process);
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if (process.Name == "explorer.exe")
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{
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HandleExplorerStart(process);
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}
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else if (!IsAllowed(process) && !TryTerminate(process))
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{
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AddFailed(process, failed);
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}
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else if (IsWhitelisted(process, out var applicationId))
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{
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HandleInstanceStart(applicationId.Value, process);
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}
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}
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foreach (var process in terminated)
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{
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logger.Debug($"Process {process} has been terminated.");
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processes.Remove(process);
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}
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if (failed.Any())
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{
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logger.Warn($"Failed to terminate these blacklisted applications: {string.Join(", ", failed.Select(a => a.Name))}.");
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TerminationFailed?.Invoke(failed);
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}
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timer.Start();
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}
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private void AddFailed(IProcess process, List<RunningApplication> failed)
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{
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var name = blacklist.First(a => BelongsToApplication(process, a)).ExecutableName;
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var application = failed.FirstOrDefault(a => a.Name == name);
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if (application == default(RunningApplication))
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{
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application = new RunningApplication(name);
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failed.Add(application);
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}
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application.Processes.Add(process);
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}
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private void AddFailed(string name, IProcess process, InitializationResult result)
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{
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var application = result.FailedAutoTerminations.FirstOrDefault(a => a.Name == name);
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if (application == default(RunningApplication))
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{
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application = new RunningApplication(name);
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result.FailedAutoTerminations.Add(application);
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}
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application.Processes.Add(process);
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logger.Error($"Process {process} belongs to application '{application.Name}' and could not be terminated automatically!");
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}
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private void AddForTermination(string name, IProcess process, InitializationResult result)
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{
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var application = result.RunningApplications.FirstOrDefault(a => a.Name == name);
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if (application == default(RunningApplication))
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{
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application = new RunningApplication(name);
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result.RunningApplications.Add(application);
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}
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application.Processes.Add(process);
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logger.Debug($"Process {process} belongs to application '{application.Name}' and needs to be terminated.");
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}
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private bool BelongsToApplication(IProcess process, BlacklistApplication application)
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{
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var sameName = process.Name.Equals(application.ExecutableName, StringComparison.OrdinalIgnoreCase);
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var sameOriginalName = process.OriginalName?.Equals(application.OriginalName, StringComparison.OrdinalIgnoreCase) == true;
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return sameName || sameOriginalName;
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}
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private bool BelongsToApplication(IProcess process, WhitelistApplication application)
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{
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var ignoreOriginalName = string.IsNullOrWhiteSpace(application.OriginalName);
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var sameName = process.Name.Equals(application.ExecutableName, StringComparison.OrdinalIgnoreCase);
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var sameOriginalName = process.OriginalName?.Equals(application.OriginalName, StringComparison.OrdinalIgnoreCase) == true;
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return sameName && (ignoreOriginalName || sameOriginalName);
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}
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private bool BelongsToSafeExamBrowser(IProcess process)
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{
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var isRuntime = process.Name == "SafeExamBrowser.exe" && process.OriginalName == "SafeExamBrowser.exe";
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var isClient = process.Name == "SafeExamBrowser.Client.exe" && process.OriginalName == "SafeExamBrowser.Client.exe";
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var isWebView = process.Name == "msedgewebview2.exe" && process.OriginalName == "msedgewebview2.exe";
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return isRuntime || isClient || isWebView;
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}
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private void Close(Window window)
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{
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nativeMethods.SendCloseMessageTo(window.Handle);
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logger.Info($"Sent close message to window {window}.");
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}
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private void HandleExplorerStart(IProcess process)
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{
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logger.Warn($"A new instance of Windows Explorer {process} has been started!");
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Task.Run(() => ExplorerStarted?.Invoke());
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}
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private void HandleInstanceStart(Guid applicationId, IProcess process)
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{
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logger.Debug($"Detected start of whitelisted application instance {process}.");
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Task.Run(() => InstanceStarted?.Invoke(applicationId, process));
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}
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private void InitializeProcesses()
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{
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processes = processFactory.GetAllRunning();
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logger.Debug($"Initialized {processes.Count} currently running processes.");
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}
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private void InitializeBlacklist(ApplicationSettings settings, InitializationResult result)
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{
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foreach (var application in settings.Blacklist)
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{
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blacklist.Add(application);
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}
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logger.Debug($"Initialized blacklist with {blacklist.Count} applications{(blacklist.Any() ? $": {string.Join(", ", blacklist.Select(a => a.ExecutableName))}" : ".")}");
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foreach (var process in processes)
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{
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foreach (var application in blacklist)
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{
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var isBlacklisted = BelongsToApplication(process, application);
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if (isBlacklisted)
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{
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if (!application.AutoTerminate)
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{
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AddForTermination(application.ExecutableName, process, result);
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}
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else if (application.AutoTerminate && !TryTerminate(process))
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{
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AddFailed(application.ExecutableName, process, result);
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}
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break;
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}
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}
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}
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}
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private void InitializeWhitelist(ApplicationSettings settings, InitializationResult result)
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{
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foreach (var application in settings.Whitelist)
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{
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whitelist.Add(application);
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}
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logger.Debug($"Initialized whitelist with {whitelist.Count} applications{(whitelist.Any() ? $": {string.Join(", ", whitelist.Select(a => a.ExecutableName))}" : ".")}");
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foreach (var process in processes)
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{
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foreach (var application in whitelist)
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{
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var isWhitelisted = BelongsToApplication(process, application);
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if (isWhitelisted)
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{
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if (!application.AllowRunning && !application.AutoTerminate)
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{
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AddForTermination(application.ExecutableName, process, result);
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}
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else if (!application.AllowRunning && application.AutoTerminate && !TryTerminate(process))
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{
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AddFailed(application.ExecutableName, process, result);
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}
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break;
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}
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}
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}
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}
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private bool IsAllowed(IProcess process)
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{
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foreach (var application in blacklist)
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{
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if (BelongsToApplication(process, application))
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{
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logger.Warn($"Process {process} belongs to blacklisted application '{application.ExecutableName}'!");
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return false;
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}
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}
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return true;
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}
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private bool IsAllowed(Window window)
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{
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var processId = Convert.ToInt32(nativeMethods.GetProcessIdFor(window.Handle));
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if (processFactory.TryGetById(processId, out var process))
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{
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if (BelongsToSafeExamBrowser(process) || IsWhitelisted(process, out _))
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{
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return true;
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}
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logger.Warn($"Window {window} belongs to not whitelisted process '{process.Name}'!");
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}
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else
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{
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logger.Error($"Could not find process for window {window} and process ID = {processId}!");
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}
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return false;
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}
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private bool IsWhitelisted(IProcess process, out Guid? applicationId)
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{
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applicationId = default(Guid?);
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foreach (var application in whitelist)
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{
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if (BelongsToApplication(process, application))
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{
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applicationId = application.Id;
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return true;
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}
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}
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return false;
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}
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private bool TryHide(Window window)
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{
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var success = nativeMethods.HideWindow(window.Handle);
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if (success)
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{
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logger.Info($"Successfully hid window {window}.");
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}
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else
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{
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logger.Warn($"Failed to hide window {window}!");
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}
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return success;
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}
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private bool TryTerminate(IProcess process)
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{
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const int MAX_ATTEMPTS = 5;
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const int TIMEOUT = 500;
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for (var attempt = 0; attempt < MAX_ATTEMPTS; attempt++)
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{
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if (process.TryClose(TIMEOUT))
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{
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break;
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}
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}
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if (!process.HasTerminated)
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{
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for (var attempt = 0; attempt < MAX_ATTEMPTS; attempt++)
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{
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if (process.TryKill(TIMEOUT))
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{
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break;
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}
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}
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}
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if (process.HasTerminated)
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{
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logger.Info($"Successfully terminated process {process}.");
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}
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else
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{
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logger.Warn($"Failed to terminate process {process}!");
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}
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return process.HasTerminated;
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}
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}
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}
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