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SEBWIN-220: Added functionality to suspend / resume the explorer shell process for kiosk mode Create New Desktop, since setting of the working area does not succeed as long as the shell is running.

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This commit is contained in:
dbuechel 2018-09-21 11:33:32 +02:00
parent d4295b3753
commit bedfc5eac0
11 changed files with 205 additions and 13 deletions
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2
SafeExamBrowser.Configuration/ConfigurationRepository.cs
View file

@ -88,7 +88,7 @@ namespace SafeExamBrowser.Configuration
CurrentSettings = new Settings();
CurrentSettings.KioskMode = KioskMode.None;
CurrentSettings.KioskMode = KioskMode.CreateNewDesktop;
CurrentSettings.ServicePolicy = ServicePolicy.Optional;
CurrentSettings.Browser.StartUrl = "https://www.safeexambrowser.org/testing";

10
SafeExamBrowser.Contracts/WindowsApi/IExplorerShell.cs
View file

@ -13,11 +13,21 @@ namespace SafeExamBrowser.Contracts.WindowsApi
/// </summary>
public interface IExplorerShell
{
/// <summary>
/// Resumes the explorer shell process, if it was previously suspended.
/// </summary>
void Resume();
/// <summary>
/// Starts the Windows explorer shell, if it isn't already running.
/// </summary>
void Start();
/// <summary>
/// Suspends the explorer shell process, if it is running.
/// </summary>
void Suspend();
/// <summary>
/// Gracefully terminates the Windows explorer shell, if it is running.
/// </summary>

12
SafeExamBrowser.Contracts/WindowsApi/INativeMethods.cs
View file

@ -153,6 +153,12 @@ namespace SafeExamBrowser.Contracts.WindowsApi
/// </summary>
void RestoreWindow(IntPtr window);
/// <summary>
/// Attempts to resume the thread referenced by the given thread ID. Returns <c>true</c> if the thread was successfully resumed,
/// otherwise <c>false</c>.
/// </summary>
bool ResumeThread(int threadId);
/// <summary>
/// Sends a close message to the given window.
/// </summary>
@ -173,5 +179,11 @@ namespace SafeExamBrowser.Contracts.WindowsApi
/// If the working area could not be set.
/// </exception>
void SetWorkingArea(IBounds bounds);
/// <summary>
/// Attempts to suspend the thread referenced by the given thread ID. Returns <c>true</c> if the thread was successfully suspended,
/// otherwise <c>false</c>.
/// </summary>
bool SuspendThread(int threadId);
}
}

21
SafeExamBrowser.Runtime.UnitTests/Operations/KioskModeOperationTests.cs
View file

@ -52,6 +52,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
var createNew = 0;
var activate = 0;
var setStartup = 0;
var suspend = 0;
settings.KioskMode = KioskMode.CreateNewDesktop;
@ -59,6 +60,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
desktopFactory.Setup(f => f.CreateNew(It.IsAny<string>())).Callback(() => createNew = ++order).Returns(newDesktop.Object);
newDesktop.Setup(d => d.Activate()).Callback(() => activate = ++order);
processFactory.SetupSet(f => f.StartupDesktop = It.IsAny<IDesktop>()).Callback(() => setStartup = ++order);
explorerShell.Setup(s => s.Suspend()).Callback(() => suspend = ++order);
sut.Perform();
@ -66,11 +68,13 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
desktopFactory.Verify(f => f.CreateNew(It.IsAny<string>()), Times.Once);
newDesktop.Verify(d => d.Activate(), Times.Once);
processFactory.VerifySet(f => f.StartupDesktop = newDesktop.Object, Times.Once);
explorerShell.Verify(s => s.Suspend(), Times.Once);
Assert.AreEqual(1, getCurrrent);
Assert.AreEqual(2, createNew);
Assert.AreEqual(3, activate);
Assert.AreEqual(4, setStartup);
Assert.AreEqual(5, suspend);
}
[TestMethod]
@ -92,6 +96,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
var activate = 0;
var setStartup = 0;
var close = 0;
var resume = 0;
settings.KioskMode = KioskMode.CreateNewDesktop;
@ -100,6 +105,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
originalDesktop.Setup(d => d.Activate()).Callback(() => activate = ++order);
processFactory.SetupSet(f => f.StartupDesktop = It.Is<IDesktop>(d => d == originalDesktop.Object)).Callback(() => setStartup = ++order);
newDesktop.Setup(d => d.Close()).Callback(() => close = ++order);
explorerShell.Setup(s => s.Resume()).Callback(() => resume = ++order);
sut.Perform();
sut.Revert();
@ -107,10 +113,12 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
originalDesktop.Verify(d => d.Activate(), Times.Once);
processFactory.VerifySet(f => f.StartupDesktop = originalDesktop.Object, Times.Once);
newDesktop.Verify(d => d.Close(), Times.Once);
explorerShell.Verify(s => s.Resume(), Times.Once);
Assert.AreEqual(1, activate);
Assert.AreEqual(2, setStartup);
Assert.AreEqual(3, close);
Assert.AreEqual(4, resume);
}
[TestMethod]
@ -138,6 +146,8 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
explorerShell.Verify(s => s.Terminate(), Times.Never);
explorerShell.Verify(s => s.Start(), Times.Never);
explorerShell.Verify(s => s.Resume(), Times.Never);
explorerShell.Verify(s => s.Suspend(), Times.Once);
newDesktop.Verify(d => d.Activate(), Times.Once);
newDesktop.Verify(d => d.Close(), Times.Never);
originalDesktop.Verify(d => d.Activate(), Times.Never);
@ -145,7 +155,9 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
settings.KioskMode = KioskMode.DisableExplorerShell;
sut.Repeat();
explorerShell.Verify(s => s.Resume(), Times.Once);
explorerShell.Verify(s => s.Terminate(), Times.Once);
explorerShell.Verify(s => s.Suspend(), Times.Once);
explorerShell.Verify(s => s.Start(), Times.Never);
newDesktop.Verify(d => d.Activate(), Times.Once);
newDesktop.Verify(d => d.Close(), Times.Once);
@ -154,7 +166,9 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
settings.KioskMode = KioskMode.CreateNewDesktop;
sut.Repeat();
explorerShell.Verify(s => s.Resume(), Times.Once);
explorerShell.Verify(s => s.Terminate(), Times.Once);
explorerShell.Verify(s => s.Suspend(), Times.Once);
explorerShell.Verify(s => s.Start(), Times.Once);
newDesktop.Verify(d => d.Activate(), Times.Exactly(2));
newDesktop.Verify(d => d.Close(), Times.Once);
@ -197,6 +211,7 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
desktopFactory.Verify(f => f.CreateNew(It.IsAny<string>()), Times.Once);
newDesktop.Verify(d => d.Activate(), Times.Once);
processFactory.VerifySet(f => f.StartupDesktop = newDesktop.Object, Times.Once);
explorerShell.Verify(s => s.Suspend(), Times.Once);
}
[TestMethod]
@ -213,11 +228,5 @@ namespace SafeExamBrowser.Runtime.UnitTests.Operations
explorerShell.Verify(s => s.Terminate(), Times.Once);
}
[TestMethod]
public void MustRestoreOriginalDesktopInCaseOfFailure()
{
}
}
}

6
SafeExamBrowser.Runtime/CompositionRoot.cs
View file

@ -41,7 +41,7 @@ namespace SafeExamBrowser.Runtime
internal void BuildObjectGraph(Action shutdown)
{
const int TEN_SECONDS = 10000;
const int STARTUP_TIMEOUT_MS = 30000;
var args = Environment.GetCommandLineArgs();
var configuration = BuildConfigurationRepository();
@ -73,9 +73,9 @@ namespace SafeExamBrowser.Runtime
sessionOperations.Enqueue(new ConfigurationOperation(appConfig, configuration, logger, messageBox, resourceLoader, runtimeHost, text, uiFactory, args));
sessionOperations.Enqueue(new SessionInitializationOperation(configuration, logger, runtimeHost));
sessionOperations.Enqueue(new ServiceOperation(configuration, logger, serviceProxy, text));
sessionOperations.Enqueue(new ClientTerminationOperation(configuration, logger, processFactory, proxyFactory, runtimeHost, TEN_SECONDS));
sessionOperations.Enqueue(new ClientTerminationOperation(configuration, logger, processFactory, proxyFactory, runtimeHost, STARTUP_TIMEOUT_MS));
sessionOperations.Enqueue(new KioskModeOperation(configuration, desktopFactory, explorerShell, logger, processFactory));
sessionOperations.Enqueue(new ClientOperation(configuration, logger, processFactory, proxyFactory, runtimeHost, TEN_SECONDS));
sessionOperations.Enqueue(new ClientOperation(configuration, logger, processFactory, proxyFactory, runtimeHost, STARTUP_TIMEOUT_MS));
var bootstrapSequence = new OperationSequence(logger, bootstrapOperations);
var sessionSequence = new OperationSequence(logger, sessionOperations);

6
SafeExamBrowser.Runtime/Operations/KioskModeOperation.cs
View file

@ -6,9 +6,9 @@
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
using SafeExamBrowser.Contracts.Core.OperationModel;
using SafeExamBrowser.Contracts.Configuration;
using SafeExamBrowser.Contracts.Configuration.Settings;
using SafeExamBrowser.Contracts.Core.OperationModel;
using SafeExamBrowser.Contracts.I18n;
using SafeExamBrowser.Contracts.Logging;
using SafeExamBrowser.Contracts.UserInterface;
@ -110,6 +110,8 @@ namespace SafeExamBrowser.Runtime.Operations
newDesktop.Activate();
processFactory.StartupDesktop = newDesktop;
logger.Info("Successfully activated new desktop.");
explorerShell.Suspend();
}
private void CloseNewDesktop()
@ -134,6 +136,8 @@ namespace SafeExamBrowser.Runtime.Operations
{
logger.Warn($"No new desktop found when attempting to close new desktop!");
}
explorerShell.Resume();
}
private void TerminateExplorerShell()

29
SafeExamBrowser.WindowsApi/Constants/ThreadAccess.cs Normal file
View file

@ -0,0 +1,29 @@
/*
* 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;
namespace SafeExamBrowser.WindowsApi.Constants
{
/// <remarks>
/// See https://docs.microsoft.com/en-us/windows/desktop/ProcThread/thread-security-and-access-rights.
/// </remarks>
[Flags]
internal enum ThreadAccess : int
{
TERMINATE = 0x1,
SUSPEND_RESUME = 0x2,
GET_CONTEXT = 0x8,
SET_CONTEXT = 0x10,
SET_INFORMATION = 0x20,
QUERY_INFORMATION = 0x40,
SET_THREAD_TOKEN = 0x80,
IMPERSONATE = 0x100,
DIRECT_IMPERSONATION = 0x200
}
}

69
SafeExamBrowser.WindowsApi/ExplorerShell.cs
View file

@ -7,6 +7,8 @@
*/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Threading;
@ -19,11 +21,43 @@ namespace SafeExamBrowser.WindowsApi
{
private ILogger logger;
private INativeMethods nativeMethods;
private IList<ProcessThread> suspendedThreads;
public ExplorerShell(ILogger logger, INativeMethods nativeMethods)
{
this.logger = logger;
this.nativeMethods = nativeMethods;
this.suspendedThreads = new List<ProcessThread>();
}
public void Resume()
{
const int MAX_ATTEMPTS = 3;
logger.Debug($"Attempting to resume all {suspendedThreads.Count} previously suspended explorer shell threads...");
for (var attempts = 0; suspendedThreads.Any(); attempts++)
{
var thread = suspendedThreads.First();
var success = nativeMethods.ResumeThread(thread.Id);
if (success || attempts == MAX_ATTEMPTS)
{
attempts = 0;
suspendedThreads.Remove(thread);
if (success)
{
logger.Debug($"Successfully resumed thread #{thread.Id} of explorer shell process.");
}
else
{
logger.Warn($"Failed to resume thread #{thread.Id} of explorer shell process within {MAX_ATTEMPTS} attempts!");
}
}
}
logger.Info($"Successfully resumed explorer shell process.");
}
public void Start()
@ -47,6 +81,39 @@ namespace SafeExamBrowser.WindowsApi
process.Close();
}
public void Suspend()
{
var processId = nativeMethods.GetShellProcessId();
var explorerProcesses = System.Diagnostics.Process.GetProcessesByName("explorer");
var shellProcess = explorerProcesses.FirstOrDefault(p => p.Id == processId);
if (shellProcess != null)
{
logger.Debug($"Found explorer shell processes with PID = {processId}.");
foreach (ProcessThread thread in shellProcess.Threads)
{
var success = nativeMethods.SuspendThread(thread.Id);
if (success)
{
suspendedThreads.Add(thread);
logger.Debug($"Successfully suspended thread #{thread.Id} of explorer shell process.");
}
else
{
logger.Warn($"Failed to suspend thread #{thread.Id} of explorer shell process!");
}
}
logger.Info($"Successfully suspended explorer shell process with PID = {processId}.");
}
else
{
logger.Info("The explorer shell can't be suspended, as it seems to not be running.");
}
}
public void Terminate()
{
var processId = nativeMethods.GetShellProcessId();
@ -69,7 +136,7 @@ namespace SafeExamBrowser.WindowsApi
}
else
{
logger.Info("The explorer shell seems to already be terminated. Skipping this step...");
logger.Info("The explorer shell seems to already be terminated.");
}
}
}

14
SafeExamBrowser.WindowsApi/Kernel32.cs
View file

@ -8,6 +8,7 @@
using System;
using System.Runtime.InteropServices;
using SafeExamBrowser.WindowsApi.Constants;
using SafeExamBrowser.WindowsApi.Types;
namespace SafeExamBrowser.WindowsApi
@ -17,6 +18,10 @@ namespace SafeExamBrowser.WindowsApi
/// </summary>
internal class Kernel32
{
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
internal static extern bool CloseHandle(IntPtr hObject);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool CreateProcess(
string lpApplicationName,
@ -36,7 +41,16 @@ namespace SafeExamBrowser.WindowsApi
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern IntPtr GetModuleHandle(string lpModuleName);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern int ResumeThread(IntPtr hThread);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern int SuspendThread(IntPtr hThread);
}
}

48
SafeExamBrowser.WindowsApi/NativeMethods.cs
View file

@ -291,6 +291,29 @@ namespace SafeExamBrowser.WindowsApi
User32.ShowWindow(window, (int)ShowWindowCommand.Restore);
}
public bool ResumeThread(int threadId)
{
const int FAILURE = -1;
var handle = Kernel32.OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint) threadId);
if (handle == IntPtr.Zero)
{
return false;
}
try
{
var result = Kernel32.ResumeThread(handle);
var success = result != FAILURE;
return success;
}
finally
{
Kernel32.CloseHandle(handle);
}
}
public void SendCloseMessageTo(IntPtr window)
{
User32.SendMessage(window, Constant.WM_SYSCOMMAND, (IntPtr) SystemCommand.CLOSE, IntPtr.Zero);
@ -309,12 +332,35 @@ namespace SafeExamBrowser.WindowsApi
public void SetWorkingArea(IBounds bounds)
{
var workingArea = new RECT { Left = bounds.Left, Top = bounds.Top, Right = bounds.Right, Bottom = bounds.Bottom };
var success = User32.SystemParametersInfo(SPI.SETWORKAREA, 0, ref workingArea, SPIF.UPDATEANDCHANGE);
var success = User32.SystemParametersInfo(SPI.SETWORKAREA, 0, ref workingArea, SPIF.NONE);
if (!success)
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
public bool SuspendThread(int threadId)
{
const int FAILURE = -1;
var handle = Kernel32.OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint) threadId);
if (handle == IntPtr.Zero)
{
return false;
}
try
{
var result = Kernel32.SuspendThread(handle);
var success = result != FAILURE;
return success;
}
finally
{
Kernel32.CloseHandle(handle);
}
}
}
}

1
SafeExamBrowser.WindowsApi/SafeExamBrowser.WindowsApi.csproj
View file

@ -53,6 +53,7 @@
<ItemGroup>
<Compile Include="Constants\Constant.cs" />
<Compile Include="Constants\HookType.cs" />
<Compile Include="Constants\ThreadAccess.cs" />
<Compile Include="Delegates\EnumDesktopDelegate.cs" />
<Compile Include="Delegates\EnumWindowsDelegate.cs" />
<Compile Include="Delegates\EventDelegate.cs" />