EasyHook中英文教程
从网上找到一篇easyhook的中英文教程，因为GOOGLE随时会被封赶紧记下来，以后慢慢翻译补全
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1 Continuing Detours: the reinvention of Windows API Hooking
1继续截获:重新改造Windows API 挂钩
Microsoft® Detours latest release was in December 2006. Now times have changed and the NET Framework has become more and more popular. Besides the well known unmanaged code hooking, EasyHook provides a way to hook unmanaged code from a managed environment. This implies several advantages:
微软的Detours最新的版本是在2006年12月发布。而现在.Net框架越来越流行，除了大家知道的非托管理代码挂接，EasyHook提供一个从托管环境挂接非托管代码的方法。这意味着几个优点：
No resource or memory leaks are left in the target
在目标中不会有资源和内存泄漏。
You can write pure managed hook handlers for unmanaged APIs
你能够针对非托管API写纯粹的托管钩子句柄
All hooks are installed and automatically removed in a stable manner
所有挂构的安装和自动移除通过稳定的方式。
You can use all the convenience managed code provides, like NET Remoting, WCF and WPF
你可以使用所有托管代码的便利,像Net Rmoting, WCF 和 WPF。
You will be able to write injection libraries and host processes compiled for AnyCPU, which will allow you to inject your code into 32- and 64-Bit processes from 64- and 32-Bit processes by using the very same assembly in all cases.
你可以为各种CPU写注入库和托管进程，你可以用相同的汇编将你的代码注入32和64位进程。
This way hooking has become a simple task and you can now write hooking applications like FileMon or RegMon with a few lines of code.
这使得使用钩子变为一个简单的工作，你只需要少许代码就能够马上写像FileMon 或者 RegMon这样的程序。
Further EasyHook 2.5 provides additional features like:
此外EasyHook2.5提供其它的功能如下：
Experimental stealth injection for unmanaged code not raising attention of any current AV
未被重视的，对目前任何反病毒软件，尝试秘密注入非托管代码
32- and 64-Bit Kernel mode hooking support, since Windows XP.
从Windows XP以后，32位和64位核心模式钩子的支持。
A pure unmanaged hooking core which will improve performance, stability and compatibility.
一个纯非托管钩子核心，将提升性能，稳定性和兼容性。
A solid unmanaged API for writing hooking apps and libraries without the NET Framework
一个稳定的非托管API用于在没有.NET环境下使用钩子应用和库。
The unmanaged core does not require CRT bindings and thus will reduce deployment size about some megabytes. Also Windows 2000 SP4 and Windows Server 2008 SP1 can now be targeted with the same EasyHook binary.
非托管核心不需要CRT绑定，因此将减少部署大小。并且现在有针对Windows 2000 SP4和Windows Server 2008 SP1的EasyHook二进制版本。
Minimal software requirements for end-users to execute applications using EasyHook:
Windows 2000 SP4 or later
Microsoft NET Framework 2.0 Redistributable
最终用户使用EasyHook最小软件需求：
Windows 2000 SP4 或者 更高版本
Microsoft NET Framework 2.0 Redistributable
Table of Content
1 Continuing Detours: the reinvention of Windows API Hooking
1.1 Security Advisor
1.2 A simple FileMon derivate
2 A deep look under the hook
2.1 Global Assembly Cache
2.2 Windows Defender
2.3 Injection – A burden made easy
2.3.1 Creating an already hooked process
2.4 The injected library entry point
2.4.1 The library constructor
2.4.2 The library Run-Method
2.5 Injection helper routines
2.6 How to install a hook
2.7 How to write a hook handler
2.8 Using Thread ACLs
2.9 Using handler utilities
2.10 The IPC helper API
2.11 Guidelines for stable hooking
2.12 A look into the future
ATTENTION
This Guide will cover the managed part of EasyHook only. Most things also apply to the unmanaged API. Refer to the “Unmanaged API Reference” for more information. The “Managed API Reference” also contains much additional information to the stuff covered here.
LICENSE CHANGE
EasyHook is now released under the Lesser GPL instead of the MIT License.
ProcessMonitor Screenshot
The following is a screenshot of my ProcessMonitor demo, shipping with the source code and the binary package:
It allows you to intercept CreateFile calls of any process currently running in your system.
1.1 Security Advisor
Unlike what some (commercial) hooking libraries out there are advertising to boost sales, user-mode hooking can NEVER be an option to apply additional security checks in any safe manner. If you only want to “sandbox” a dedicated process, you know well about, and the process in fact doesn’t know about EasyHook, this might succeed! But don’t ever attempt to write any security software based on user mode hooking. It won’t work, I promise you… This is also why EasyHook does not support a so called “System wide” injection, which in fact is just an illusion, because as I said, with user-mode hooks this will always be impossible. But if you want to keep this illusion you may stick with other (commercial) libraries attempting to do so…
Since EasyHook 2.5, you are able to easily hook 32-Bit kernels. Even if EasyHook would allow hooking 64-Bit kernels, I don’t recommend this because then you would get trouble with PatchGuard. Bypassing PatchGuard is possible, at least these days, but the chance of BSODing your customer’s PCs is too big. You should consider purchasing the PatchGuard API which will allow you to write security apps based on kernel mode interceptions. Kernel mode hooking (or the PatchGuard API) is the only option to apply additional security checks. Since Windows Vista, also the Windows Filtering Platform and other Vista specific APIs will be helpful to write security software!
So what is user-mode hooking for? In general, user-mode hooking is intended for API monitoring, like Mark Russinovich’s ProcessMonitor (alias FileMon/RegMon), resource leak detection, various malware which doesn’t need to care about security issues, extending applications and libraries you don’t have the source code for (also cracks may fall in this category), adding a compatibility layer for existing applications to run on newer OSes, etc.
If anyone uses security in context of user-mode hooks, your alarm bells should ring!
1.2 A simple FileMon derivate
1.2一个简单的文件监视程序
To prove that EasyHook really makes hooking simple, look at the following demo application, which will log all file accesses from a given process. We need a host process which injects the library and displays file accesses. It is possible to combine injection library and host process in one file as both are just threaded as valid NET assemblies, but I think to separate them is a more consistent approach. This demo will be used throughout the whole guide:
为了证明EasyHook的确让挂接变得简单,看看下面的常规应用,它会将所有给定进程的文件获取全部记录下来.我们需要一个托管进程将库注入并显示文件访问信息.我们可能通过注入库和托管进程在一个文件中结合并作为有效的NET程序集,但我想还是把它们分开更协调一点，该演示会在整个指南中使用。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | using System; using System.Collections.Generic; using System.Runtime.Remoting; using System.Text; using System.Runtime.InteropServices; using EasyHook; namespace FileMon { public class FileMonInterface : MarshalByRefObject { public void IsInstalled(Int32 InClientPID) { Console.WriteLine("文件访问监视器将被安装到目标 {0} 中.\r\n", InClientPID); } public void OnCreateFile(Int32 InClientPID, String[] InFileNames) { for(int i = 0; i < InFileNames.Length; i++) { Console.WriteLine(InFileNames[i]); } } public void ReportException(Exception InInfo) { Console.WriteLine("目标进程报告错误：\r\n" + InInfo.ToString()); } public void Ping() { } } class Program { static String ChannelName = null; static void Main(string[] args) { try { Config.Register("文件访问监视类演示程序", "FileMon.exe", "FileMonInject.dll"); RemoteHooking.IpcCreateServer(ref ChannelName, WellKnownObjectMode.SingleCall); RemoteHooking.Inject(Int32.Parse(args[0]), "FileMonInject.dll", "FileMonInject.dll", ChannelName); Console.ReadLine(); } catch(Exception ExtInfo) { Console.WriteLine("当连接到目标时出现错误:\r\n{0}", ExtInfo.ToString()); } } } } |
The most complex part is the injected library which has to fulfill various requirements. We are hooking the CreateFile-API and redirecting all requests to our host process. The library will be unloaded if the host process is terminated:
最复杂的部分是应用于各种需求的注入库。我们现在挂在CreateFile-API并重定向所有的请求到我们的托管进程。如果托管进程结束，库将卸载。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | using System; using System.Collections.Generic; using System.Text; using System.Threading; using System.Runtime.InteropServices; using EasyHook; namespace FileMonInject { public class Main : EasyHook.IEntryPoint { FileMon.FileMonInterface Interface; LocalHook CreateFileHook; Stack Queue = new Stack(); public Main(RemoteHooking.IContext InContext, String InChannelName) { // 连接到托管… Interface = RemoteHooking.IpcConnectClient(InChannelName); } public void Run(RemoteHooking.IContext InContext, String InChannelName) { // 按装挂钩… try { CreateFileHook = LocalHook.Create(LocalHook.GetProcAddress("kernel32.dll", "CreateFileW"), new DCreateFile(CreateFile_Hooked), this); CreateFileHook.ThreadACL.SetExclusiveACL(new Int32[] { 0 }); } catch (Exception ExtInfo) { Interface.ReportException(ExtInfo); return; } Interface.IsInstalled(RemoteHooking.GetCurrentProcessId()); // 等待托管进程结束… try { while (true) { Thread.Sleep(500); // 传送最新监视到的文件访问… if (Queue.Count > 0) { String[] Package = null; lock (Queue) { Package = Queue.ToArray(); Queue.Clear(); } Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package); } else { Interface.Ping(); } } } catch { // NET Remoting在托管不可达时会触发异常 } } [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode, SetLastError = true)] delegate IntPtr DCreateFile(String InFileName, UInt32 InDesiredAccess, UInt32 InShareMode, IntPtr InSecurityAttributes, UInt32 InCreationDisposition, UInt32 InFlagsAndAttributes, IntPtr InTemplateFile); // 就使用P-Invoke执行获得从C#访问原始APIC# (这一步对 C++.NET来说没必要) [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true, CallingConvention = CallingConvention.StdCall)] static extern IntPtr CreateFile(String InFileName, UInt32 InDesiredAccess, UInt32 InShareMode, IntPtr InSecurityAttributes, UInt32 InCreationDisposition, UInt32 InFlagsAndAttributes, IntPtr InTemplateFile); // 这里就是所有文件访问截取的地方! static IntPtr CreateFile_Hooked(String InFileName, UInt32 InDesiredAccess, UInt32 InShareMode, IntPtr InSecurityAttributes, UInt32 InCreationDisposition, UInt32 InFlagsAndAttributes, IntPtr InTemplateFile) { try { Main This = (Main)HookRuntimeInfo.Callback; lock (This.Queue) { This.Queue.Push(InFileName); } } catch { } // 调用原始的API… return CreateFile(InFileName, InDesiredAccess, InShareMode, InSecurityAttributes, InCreationDisposition, InFlagsAndAttributes, InTemplateFile); } } } |
Even if this might look strange, the next chapters will explain what is done there and why. You may start this application with a user defined target process ID as one and only parameter from command line. I recommend using the PID of “explorer.exe” because this will immediately produce output! Just browse your file system while running the FileMon utility:
即使看上去挺奇怪，下一章将解释来龙去脉。你可以使用一自定义的进程ID启动该程序，只需要一个参数。我建议使用”exploerer.exe”进程，因为他很快就会有输出。只要在命令行上这样运行程序即可：
Command line utility-> FileMon.exe %PID%
It is also possible to output the whole thing into a file what might provide more convenience:
也可以这样输出放到一个文件中：
Command line utility-> FileMon.exe %PID% > “C:\MyLog.txt”
2 A deep look under the hook
深入查看挂钩
Now that you have seen the basic ideas of EasyHook and some sample code, we should start to discover what is really going on under the hood. In this chapter you will learn how to utilize most parts of the EasyHook API, injecting libraries into any process and hooking any API you want.
现在你已经看到EasyHook的一些基本思想和一些示例代码,我们开始看看到底是怎么回事.这一章你会学到怎样用EasyHook API的主要部分，把库注入到任何进程和挂接任何你想要的API。
2.1 Global Assembly Cache
全局程序集缓存
Currently EasyHook is expecting every injected assembly including all of its dependencies in the Global Assembly Cache (GAC). This is because the CLR will only search for assemblies in directories relative to the current application base directory and the GAC and therefore a target process normally has no access to EasyHook or your injected library. EasyHook is using a reference counter to make sure that multiple installations of the same assemblies from different applications can be managed. The following will register all EasyHook components and the two user assemblies required for injection in the GAC. The first parameter is just an uninterpreted string which should describe what your service is doing. All further parameters are expected to be relative/absolute file paths referring to all assemblies that should be temporarily registered in GAC. Please note that only strongly named assemblies are accepted.
当前 EasyHook是怀着每个注入程序集包括所有的组件都在全局程序集缓存中(GAC).这是因为CLR将只在与当前应用主目录相关的当前目录程序集和GAC中搜索程序集,而GAC因此一个目标进程通常不能在你注入库中访问EasyHook.EasyHook正使用引用计数确定同一程序集不同的应用能被管理和安装。以下将注册所有的EasyHook组件和两个所需注入的用户程序集到GAC中。首先暂时在GAC中注册。请注意，只有强命名应用才可以。
1 2 3 4 | Config.Register( “文件访问监视类演示程序.”, “FileMon.exe”, “FileMonInject.dll”); |
It is guaranteed that your libraries will be removed from GAC if the injecting process is being terminated in all common cases. Of course there are some rare exceptions, for example if you shutdown your PC by disconnecting the power cable. In such a case the assemblies will remain in the GAC, forever, which is no bad thing in end-user scenarios but truly during development. You may use the Gacutil.exe that ships with Visual Studio to remove all temporary GAC assemblies.
当注入进程在所有普通情况下终止时保证你的库会从GAC中移除。当然会有很少的异常情况，例如，直接停电导致你的电脑关闭。这时程序集还会在GAC中，这在最终用户的情况下也不怎么糟，但在开发时不大好。你可以使用Visual Stuido的Gacutil.exe工具卸除所有临时的GAC程序集。
Open the “Visual Studio Command Promt” as administrator.
以管理员身份打开“Visual Studio 命令行工具”
Run the command: gacutil /uf EasyHook
运行命令:gacutil /uf EasyHook
Run additional commands for each of your assemblies that should be removed from the GAC…
运行其它需要移徐出GAC程序集的命令。
2.2 Windows Defender
Windows防火墙
Injection will sometimes make the Windows Defender complain. This does not only apply to EasyHook, but to every library using remote thread creation for injection:
注入有时会导至Windows防火墙的警告。这不仅仅是对EasyHook，几乎使用远程线程注入的所有库都会这样：
Windows Defender Real-Time Protection agent has detected changes.
Microsoft recommends you analyze the software that made these changes
for potential risks. You can use information about how these programs
operate to choose whether to allow them to run or remove them from your
computer. Allow changes only if you trust the program or the software
publisher. Windows Defender can’t undo changes that you allow.
For more information please see the following:
Not Applicable
Scan ID: {44726E79-4262-454E-AFED-51A30D34BF67}
User: Lynn-PC\Lynn
Name: Unknown
ID:
Severity ID:
Category ID:
Path Found: process:pid:864;service:EasyHook64Svc;file:D:\Projects\EasyHook 2.0.0.0\Debug\x64\EasyHook64Svc.exe
Alert Type: Unclassified software
Detection Type:
Such warnings are immediately followed by information pointing out that Windows Defender has prevented a malicious attempt. I think this will vanish if you sign all executable binaries of EasyHook with AuthentiCode. Such blocking only occurs when injecting into essential system services.
2.3 Injection – A burden made easy
2.3注入-负担变得简单了
In general, library injection is one of the most complicated parts of any hooking library. But EasyHook goes further. It provides three layers of injection abstraction and your library is the fourth one. The first layer is pure, relocatable assembler code. It launches the second layer, an unmanaged C++ method. The assembler code itself is really stable. It provides extensive error information and is able to unload itself without leaving any resource leaks in the target. The C++ layer starts the managed injection loader and adjusts the target’s
PATH variable by adding the injecting process’ application base directory as first entry. This way you will have access to any file you would also have access to from your injecting process. The managed injection loader uses NET Reflection and NET Remoting to provide extensive error reports in case of failure and to find a proper entry point in your injection library. It also cares about graceful hook removal and resource cleanup. It is supported to load the same library multiple times into the same target!
一般来说，库注入时所有挂接库中最复杂的部分。但是EasyHook让他不一样了。它提供了注入抽像的三个层而你的库在第四个。第一层是纯的汇编代码。它运行第二层，非托管的C++方法。汇编代码本身相当稳定。它提供很多的错误信息并能够将自己在目标中卸除不会留下资源泄露。C++层开始管理注入装载器并调整目标路径变量，通过添加进程应用主目录作为第一个入口。这样你可能访问任何你被注入进程能够访问的任何文件。托管的注入装载器使用NET反射和Net Remoting进供很多的在出错时的错误报告并发现在你注入库中的正确的入口点。它还关注挂钩的移除和资源的清除。它支持将同一个库多次的装入到同一目标中！
Another complex part is run on host side. It is supported to inject libraries into other terminal sessions, system services and even through WOW64 boundaries. To you, all cases seem the same. EasyHook will automatically select the right injection procedure. If EasyHook has succeeded injection, you can be 99% sure that your library has been successfully loaded and executed. If it fails you can be 99% sure that no resource leaks are left in the target and it remains in a stable, hookable state! Nearly all possible failures are being caught and it would be like a lottery win to see a target getting crashed by library injection!
另一个复杂的疗分时在托管这边运行。它支持将库注入到其它终端会话，系统服务甚至WOW64边界。对你来说，所以有情况都是一样。EasyHook可以自动的选择正确的注入进程。如果EasyHook成功 注入，你可99%确定你的库成功装载并运行。如果失败，则99%确保隐定和不泄露。几乎所有可能的错误都能被捕捉到，如果注入失败那时您摸彩中奖了。
Please note that Windows Vista has advanced security for its subsystem services. They are running in a protected environment like the “Protected Media Path”. It is not possible to hook such services with EasyHook or any other user-mode library.
The following shows the API method that we are talking about:
1 2 3 4 5 | RemoteHooking.Inject( Int32.Parse(args[0]), “FileMonInject.dll”, // 32-Bit version “FileMonInject.dll”, // 64-Bit version ChannelName); |
The first four parameters are required. If you only want to hook either 32- or 64-Bit targets, you can set the unused path to null. You may either specify a file path that EasyHook will automatically translate to a full qualified assembly name or a partial assembly name like “FileMonInject, PublicKeyToken = 3287453648abcdef”. Currently there is only one injection option preventing EasyHook from attaching a debugger to the target but you should only set this option if the target does not like an attached debugger. EasyHook will detach it before injection is completed so in general there is nothing to worry about and it increases injection stability about magnitudes by using the target symbol addresses instead of assuming that the local ones remain valid in the target!
You can pass as many additional parameters as you like but be aware of that you shall only pass types that are accessible through GAC, otherwise the injected library is not able to deserialize the parameter list. In such a case the exception will be redirected to the host process and you may catch it with a try-catch statement around RemoteHooking.Inject. That’s one of the great advantages!
The injected library will automatically get access to all additional parameters you specify after the fourth one. This way you can easily pass channel names to the target so that your injected library is able to connect to your host.
Attention
Keep in mind that the CLR will unload your library only if the target is being terminated. Even if EasyHook releases all associated resources much earlier, you won’t be able to change the injected DLL which implies that the corresponding GAC library is not updateable until the target is terminated. So if you need to change your injected library very frequently (during development) you should always terminate the target after each debugging session. This will ensure that no application depends on the library and it can be removed from the GAC.
2.3.1 Creating an already hooked process
2.3.1创建一个已经存在的挂钩进程
Sometimes it is necessary to hook a process from the beginning. This is no big deal, just call
RemoteHooking.CreateAndInject instead of Inject. This will execute your library main method before any other instruction. You can resume the newly created process by calling RemoteHooking.WakeUpProcess from your injected library Run method. This only makes sense in conjunction with CreateAndInject, otherwise it will do nothing.
有时需要在进程开始时挂接。这没有什和大不了。不用注入调用RemoteHooking.CreateAndInject 即可。这会在其它指令前执行你的库主方法。你可继续通过调用 RemoteHooking.WakeUpProcess 最新创建的进程从你注入库运行方法中。这只在CreatAndJnject 连接时有意义，不然没什么用。
2.4 The injected library entry point
注入库入口点
All injected libraries have to export at least one public class implementing the
EasyHook.IEntryPoint interface. The interface itself is empty but identifies your class as entry point. A class marked as entry point this way, is expected to export an instance constructor and a Run instance method having the signature “void Run(IContext, %ArgumentList%)” and “.ctor(IContext, %ArgumentList%)”. Please note that “%ArgumentList%” is a placeholder for additional parameters passed to RemoteHooking.Inject. The list is starting with the fifth parameter you passed to Inject and will be passed to both, the constructor and Run. The list is not passed as array but as expanded parameter list. For example if you called Inject(Target, Options, Path32, Path64, String, Int32, MemoryStream), then %ArgumentList% would be “String, Int32, MemoryStream” and your expected Run signature “void Run(IContext, String, Int32, MemoryStream)”. EasyHook enforces strict binding which means that the parameter list is not casted in any way. The types passed to Inject shall be exactly the same as in the Run signature. I hope this explains it.
The next thing to mention is that you should avoid using static fields or properties. Only if you know for sure that it is not possible having two instances of your library in the same target simultaneously, you can safely use static variables!
所有注入库都必须导出至少一个公共类执行 EasyHook.IEntryPoint 接口。该接口本身是空的但将把你的类确定为入口。 一个类通过这种方法标记为入口点，认为导出实例构造并有一个RUN实例方法有着签我 “void Run(IContext, %ArgumentList%)” 和 “.ctor(IContext, %ArgumentList%)”. 请注意 “%ArgumentList%” 是传入 RemoteHooking.Inject附加参数的占位符。列表开始于第五个参数传入到Inject 并传入到两者，构造函数和Run. 列表不是以数组而是以扩展参数列表传入。例如，你已调用 Inject(Target, Options, Path32, Path64, String, Int32, MemoryStream), 则 %ArgumentList% 将是 “String, Int32, MemoryStream” 并且你期待 Run 签名为 “void Run(IContext, String, Int32, MemoryStream)”. EasyHook 执行研究的绑定意味着参数列表没有在任何情况下封装。这个类型传到Inject将一模一样的传入Run签名。我希望这能解释。另一个需要提的事是你应该避免使用静态的字段和属性。只在你确保在你的库上不可能有两个相同目标同时存在实例，才可以安全使用静态变量。
2.4.1 The library constructor
2.4.1 库构造器
The constructor is called immediately after EasyHook has gained control in the target process. You should only connect to your host and validate the parameters. At this point EasyHook already has a working connection to the host so all exceptions you are leaving unhandled, will automatically be redirected to the host process. A common constructor may look like this:
构造器在EasyHook获得目标进程控制权时调用。你只能连接到你的托管并检验参数。这一点上EasyHook已经工作连接到托管，所以所有的异常都没有处理，并自动重定向到托管进程。一个普通的构造象这样：
1 2 3 4 5 6 7 8 9 10 11 12 13 | public class Main : EasyHook.IEntryPoint { FileMon.FileMonInterface Interface; LocalHook CreateFileHook; Stack Queue = new Stack(); public Main(RemoteHooking.IContext InContext, String InChannelName) { // 连接到托管… Interface = RemoteHooking.IpcConnectClient(InChannelName); // 检查连接… Interface.Ping... } } |
2.4.2 The library Run-Method
2.4.2 库的Run方法
The Run method can be threaded as application entry point. If you return from it, your library will be unloaded. But this is not really true . In fact your library stays alive until the CLR decides to unload it. This
behavior might change in future EasyHook versions by utilizing the CLR Hosting API, but currently we simply don’t know about!
Run方法能作为应用入口点线程。如果从它近回，库将卸除。但这不是这样。实际上，你的库会直到CLR决定卸除时才终止。这会在以后的版本中通过使用CLR托管API改烃，现在不要关心它就行了。
In contrast to the constructor, your Run method has no exception redirection. If you leave any exception unhandled, it will just initiate the usual unload procedure. In debug versions of EasyHook, you will find such unhandled exceptions in event logs. You should install all hooks and notify your host about success, what might look like this:
同构造器相比，你的RUN方法没有格外的重定向。如果你有没处理的异常，则会初始化通常的卸除进程。在EasyHook的调试版本，你会发现未处理的异常在事件日志中。你可以安装所有的挂钩并通知你的托管是否成功，看起来就象这样：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | public void Run(RemoteHooking.IContext InContext, String InChannelName) { // 按装挂钩… try { CreateFileHook = LocalHook.Create(LocalHook.GetProcAddress("kernel32.dll", "CreateFileW"), new DCreateFile(CreateFile_Hooked), this); CreateFileHook.ThreadACL.SetExclusiveACL(new Int32[] { 0 }); } catch(Exception ExtInfo) { Interface.ReportException(ExtInfo); return; } Interface.IsInstalled(RemoteHooking.GetCurrentProcessId()); // 等待托管进程结束… try { while(true) { Thread.Sleep(500); // 传送最新监视到的文件访问… if(Queue.Count > 0) { String[] Package = null; lock(Queue) { Package = Queue.ToArray(); Queue.Clear(); } Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package); } else { Interface.Ping(); } } } catch { // NET Remoting在托管不可达时会触发异常 } } |
The loop simply sends the currently queued files accesses to the host process. If the host process is being terminated, such attempts throw an exception which causes the CLR to return from the Run method and automatically unload your library!
循环部分简单的发送当前排对文件访问到托管进程。如果托管进程结束，这个偿试会抛出异常将导至CLR从RUN方法返回并自动卸除你的库。
2.5 Injection helper routines
There are several methods that you will find useful when dealing with injection.
在处理注入时有几个比较有用的方法。
To query if the current user is administrator, you can use
RemoteHooking.IsAdministrator. Please note that injection will fail in most cases if you don’t have admin privileges! Vista is using the UAC for evaluating to admin privileges and so you should read some MSDN articles about how to utilize it.
查看肖前用户是不是系统管理员，可以使用
RemoteHooking.IsAdministrator. 注意如果你没有管理权限，注入常常会失入。Vista使用UAC确定管理权限，所以你可以阅读MSDN看看怎么用。
If you already are admin, you may use the
RemoteHooking.ExecuteAsService method to execute a given static method under system privileges without the need to start a service. This is potentially useful when enumerating running processes of all sessions or for any other information querying task, which might require highest privileges. Keep in mind that the static method will be executed within a system service. So any handle or other process related information will be invalid when transmitted back into your process. You should design such a method so that you retrieve all information and store it in a serializable, process independent form. This form shall be an object that is returned and this way sent back to your application by NET Remoting.
如果你已经是管理员，可可以使用 RemoteHooking.ExecuteAsService 方法在系统权限下执行静态方法而不需要启动服务。这在其它信息查询任务中列举所有会活的运行进程会有用，这会需要较高的权限。记住静态方法可以作为系统服务执行。所以任何其它相关进程信息当传回你的进程时都有效。你可以设计这样的方法来获得所有的信息并存在序列化的进程独立的表单中。该表单会是一个对象返回，并通过Net Remoting发到您的应用中。
If you want to determine whether a target process is 64-Bit or not, you may use
RemoteHooking.IsX64Process. But be aware of that you need PROCESS_QUERY_INFORMATION access to complete the call. It will also work on 32-Bit only Windows versions like Windows 2000, of course, by returning false in any case.
Further there are
RemoteHooking.GetCurrentProcessId and GetCurrentThreadId which might help to query the real native values in a pure managed environment! Managed thread IDs don’t necessarily map to native ones, when thinking about the coming NET 4.0.
2.6 How to install a hook
2.6如何安装挂钩
To install a hook you are required to pass at least two parameters. The first one is the entry point address you want to hook and the second one is the delegate where calls should be redirected to. The delegate shall have the
UnmanagedFunctionPointerAttribute and also the exact call signature as the corresponding P-Invoke implementation. The best way is to look for a well tested P-Invoke implementation already out in the net and just make a delegate out of it. The managed hook handler also has to match this signature what is automatically enforced by the compiler… A P-Invoke implementation with the DllImportAttribute may be used to call the original API within the handler which will be necessary in most cases. Don’t forget that most APIs are expected to SetLastError in case of failure. So you should set it to ERROR_ACCESS_DENIED or ERROR_INTERNAL_ERROR for example if your code does not want to execute the call. Otherwise external code might behave unexpected!
A third parameter provides a way to associate an uninterpreted callback object with the hook. This is exactly the object accessible through
HookRuntimeInfo.Callback later in the handler.
要安装挂钩你需要传送至少两个参数。第一个你想挂接的入口地址而第二个是你想调用重定向的代理。代理需要有UnmanagedFunctionPointerAttribute 并要有正确的与相应P-Invode执行相对应的调用签名。最好的方法是找一个测试好的P-Invoke执行，而只是代理一下。托管的挂钩处理还有相应的自动的编译指定的签名…一个用 DllImportAttribute 执行可以在大多情况行用句柄调用原命名API。不要忘了很多API都在错误时需要SetLastError 。所你你应将它设为第三个参数提供一个解释回调挂钩的方法。这就是对象通过HookRuntimeInfo.Callback 在句柄中访问的地方。
To uninstall a hook just remove all references to the object obtained during creation. To prevent it from being uninstalled you have to keep the reference of course… This is always a delayed removal because you won’t know when a hook is finally removed and your handler is never called again. If you want to remove it immediately you have to call
LocalHook.Dispose like known from dealing with unmanaged resources as file streams are.
要卸载挂钩只要将所有创建对象的引用删除即可。当然，要不被卸除，只要保存这些引用即可…
The following code snipped is an example of how to install a hook that is excluding the current thread from being intercepted:
1 2 3 4 5 | CreateFileHook = LocalHook.Create( LocalHook.GetProcAddress("kernel32.dll", "CreateFileW"), new DCreateFile(CreateFile_Hooked), this); CreateFileHook.ThreadACL.SetExclusiveACL(new Int32[] {0}); |
EasyHook also does provide a way to install pure unmanaged hooks using
LocalHook.CreateUnmanaged. You may write them using C++.NET that allows you to combine managed and unmanaged code. But keep in mind that you won’t have access to the HookRuntimeInformation class. You would need to directly call the unmanaged API available since EasyHook 2.5, to access runtime information from unmanaged code.
But, all protection mechanisms (see next paragraph) will still wrap around your unmanaged code. An empty unmanaged hook is about magnitudes faster than an empty managed one. If your handler once has gained execution, both are running with the same speed. The costly operation is the switch from unmanaged to managed environment and vice versa, which is not required when using pure unmanaged hooks! So your handler will be invoked in approx. 70 nanoseconds whereas a managed handler requires up to some microseconds… In some scenarios you will need this speed gain and this is why EasyHook offers it.
2.7 How to write a hook handler
2.7怎样写一个挂钩处理
Until now there was nothing complicated and I hope you agree. But writing a hook handler is something very strange. EasyHook already does provide several mechanisms to make writing hook handlers much easier or let’s say possible at all:
A Thread Deadlock Barrier (TDB) which will allow you and any subcalls to invoke the hooked API from within its handler again. Normally this would lead into a deadlock because the handler would invoke itself again and again. EasyHook will prevent such loops! This also provides the advantage that you don’t need to keep track of a clean entry point.
An OS loader lock protection which will prevent your handler from being executed in an OS loader lock and in case of managed handler code attempting so would crash the process!
A Thread ACL model allowing you to exclude well known dedicated threads, used to manage your hooking library (for example threads that are communicating with your host), from being intercepted. Refer to the chapter “Guidelines for stable hooking”, to learn about the differences and why the TDB is not enough!
A mechanism to provide hook specific callbacks through a static class named HookRuntimeInfo. This way you are able to access the library instance without using a static variable for example.
Additionally since EasyHook 2.5, you may generate call stack traces; determine the calling module, the handler return address, the address of this return address, etc.
Without some of the above mechanisms it would be simply impossible to use managed code as hook handler and this is what is unique to EasyHook. All of those mechanisms are very stable and heavily tested with hundred simultaneous threads executing hundred thousands of hooks (on a quad-core CPU). And the best thing is that all of them are also available in kernel-mode.
Using a hook handler you can simply provide your own implementation for the hooked API. But you should read and understand the related API documentation in detail, to provide the correct behavior for external code. If it is possible you should handle an interception as fast as possible and negotiate access or whatever within the injected library. Only in rare cases you should redirect calls to the host application in a synchronous manner as this will heavily slow down the hooked application; for example if an access negotiation can’t be completed with the knowledge of the library. In a real world application you should queue all requests and transmit them periodically as an array and not every single call. This can be done like it is shown in the FileMon demo.
使用挂够处理你可以简单的为你挂接的API添加你自己的处理，但是你要详细理解和阅读相应的API文档。以提供外部代码正确的行为。
Keep in mind that if you are compiling for 64-Bit or AnyCPU, you have to use the right type replacements. For example
HANDLE does NOT map to Int32, but to IntPtr. In case of 32-Bit this is not important but when switching to 64-Bit a handle is 64-Bit wide, like IntPtr. A DWORD in contrast will always be 32-Bit as its name implies.
The following is an example hook handler as used in the FileMon demo:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | // 这里就是所有文件访问截取的地方! static IntPtr CreateFile_Hooked(String InFileName, UInt32 InDesiredAccess, UInt32 InShareMode, IntPtr InSecurityAttributes, UInt32 InCreationDisposition, UInt32 InFlagsAndAttributes, IntPtr InTemplateFile) { try { Main This = (Main)HookRuntimeInfo.Callback; lock(This.Queue) { This.Queue.Push(InFileName); } } catch { } // 调用原始的API… return CreateFile(InFileName, InDesiredAccess, InShareMode, InSecurityAttributes, InCreationDisposition, InFlagsAndAttributes, InTemplateFile); } |
You may wonder about the queue limitation of 1000. The problem is that both demo applications were not designed to handle huge amounts of interceptions. I had Tortiose SVN installed and this caused my explorer to raise hundred thousands of pipe accesses. For my surprise, IPC and the injected library have no problems in dealing with that much data, but the ProcessMonitor blocked with 100% CPU usage while trying to add about 300.000 entries to the data grid. I suppose FileMon would react equally, because it will take a while to write 300.000 console lines. As the overall remote hooking mechanism seems to be stable even in such high performance scenarios, it just depends on your host application whether you can handle it or not. To keep things simple, both demos are NOT able to handle high-performance scenarios!
Thus, if your host application is fast enough, you can safely remove the queue limitation.
何能能奇怪对列限制为1000。这是因为演示不想处理大量的交互。
2.8 Using Thread ACLs
EasyHook manages a global
ThreadACL and also an ACL for every hook. Further each ACL can either be inclusive or exclusive. This allows you to compose nearly any kind of access negotiation based on thread IDs without much effort. By default EasyHook sets an empty global exclusive ACL, which will grant access for all threads, and an empty inclusive local ACL for every hook, which will finally deny access for all threads. All hooks are installed virtually suspended meaning no threads will pass access negotiation. This is to prevent hook handler invocation before you are able to initialize possible structures, like ACLs for example. To enable a hook for all threads just set its local ACL to an empty exclusive one. To enable it for the current thread only, just set a local inclusive ACL with zero as one and only entry. A thread ID of zero will automatically be replaced by the current thread ID BEFORE the ACL is set (this is negotiation will later use your thread ID and doesn’t know anything about zero). The following is a pseudo-code of IsThreadIntercepted:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | if(ACLContains(&Unit.GlobalACL, CheckID)) { if(ACLContains(LocalACL, CheckID)) { if(LocalACL->IsExclusive) return FALSE; } else { if(!LocalACL->IsExclusive) return FALSE; } return !Unit.GlobalACL.IsExclusive; } else { if(ACLContains(LocalACL, CheckID)) { if(LocalACL->IsExclusive) return FALSE; } else { if(!LocalACL->IsExclusive) return FALSE; } return Unit.GlobalACL.IsExclusive; } |
The code does nothing more than computing an intersection of the thread ID sets represented by the global and local ACL. An ACL always describes a set of threads that will be intercepted. The fact that an ACL may be inclusive or exclusive has no impact on this computation. It is just a way for you to make it easier to define a set of threads. An exclusive ACL start with ALL threads and you can specify threads that should be removed from the set. An inclusive ACL start with an empty thread set and you may specify this set manually.
The method returns
TRUE, if the intersection of the global and local set of intercepted threads contains the given thread ID, FALSE otherwise.
Just play around with them and use
LocalHook.IsThreadIntercepted to check whether your ACLs will provide expected access negotiation.
2.9 Using handler utilities
EasyHook exposes some debugging routines which may be extended in future versions. They are statically available through the
EasyHook.LocalHook class. Currently they solve the following issues which are common when writing hook handlers:
Translate a thread handle back to its thread ID (requires the handle to have THREAD_QUERY_INFORMATION access).
Translate a process handle back to its process ID (requires the handle to have PROCESS_QUERY_INFORMATION access).
Query kernel object name for any given handle. This way you are able to convert a file handle obtained by CreateFile back to its file name. This will even work if the handle has no access to anything!
In contrast to EasyHook 2.0, the latest version does not require a debugger for any of the handler utilities. The only thing is that a debugger is still required to relocate RIP-relative addresses. By default a debugger is disabled. To get support for RIP relocation (which is in general not necessary for the Windows API), just call LocalHook.EnableRIPRelocation before hook installation.
Additionally EasyHook 2.5 exposes the
HookRuntimeInformation class, which provides handler-specific support routines:
Query ReturnAddress, query AddressOfReturnAddress, generate managed/unmanaged module stack backtrace, query calling managed/unmanaged module and the callback specified during hook creation.
Setup a proper stack frame to allow exception throwing and custom stack traces. EasyHook technically would make such a stack trace impossible, but since version 2.5 the stack image can be restored for a defined code section to get rid of this issue.
2.10 The IPC helper API
The core part of any target-host scenario is IPC. With NET remoting this has become really amazing. As you can see in the FileMon demo it is a thing of two lines to setup a stable, fast and secure IPC channel between the injected library and host. Of course this is only possible with the IPC helper routines exposed by EasyHook. Using the native
IpcChannels the code blows up to three A4 pages which is still quiet small. The helper routines will take care of serialization setup and channel privileges so that you can even connect a system service with a normal user application running without admin privileges. It also offers to generate a random port name. This service should always be used because it is the only way to get a connection secure! If you want to provide your own name, you also have to specify proper well known SIDs, which are allowed to access the channel. You should always specify the built in admin group in this case, because all admin users could crash the whole system so you don’t have to worry about being exploited by an admin!
To create a server with a random port name, just call:
1 2 | String ChannelName = null; RemoteHooking.IpcCreateServer(ref ChannelName, WellKnownObjectMode.SingleCall); |
Pass the generated port name to the client and call:
1 | FileMon.FileMonInterface Interface = RemoteHooking.IpcConnectClient(InChannelName); |
From now on you are able to call the server by using the client instance of the returned underlying
MarshalByRefObject and those calls will be automatically redirected to the server. Isn’t that great?! But be aware of that this will only apply to instance members! Static members and fields will always be processed locally…
2.11 Guidelines for stable hooking
Even if EasyHook provides a new dimension of API hooking, there are still several things that you should know about, before starting to write your own handlers. The TDB will protect you from per thread deadlocks but during hooking you will often run into multi-thread deadlocks which are covered here.
Scenario 1
Imagine you would rewrite the FileMon demo sending the intercepted call directly to the target, without going through any asynchronous queue. Even if this might look correct, because the TDB should take care of it, there is indeed a big bug in it. The issue is not within your code itself but within the code your code is calling. And that is nearly always the source of bugs in hook handlers.
The problem is within NET Remoting. You already established a connection before hook installation and this is why the above approach, directly sending the interceptions back to the host, might initially work. But from time to time the CLR will reconnect to the host using
CreateFile. This wouldn’t be messy because the TDB would take care of it, but obviously NET Remoting does it in a queued worker item. This will call CreateFile in another thread while the intercepted one is waiting for it to complete. But because it is executed in another thread, it is also intercepted again. The CLR is still not connected and will start the whole procedure again and again until the worker item queue is full and no further threads are available. This is the time where the target will hang.
Of course I am only speculating because I don’t know about the internals of NET Remoting, but this deadlock will occur! Someone might say that a solution would be to call the original API before sending the interception back to the host and maybe it would be, but keep in mind how easy our hook handler was and this simple deadlock scenario can easily apply to any complex one which you can’t solve this way. It was just to show you the basic idea…
Scenario 2
We now have learned and would never make the above mistake again, would we? Let’s say we are using a dedicated thread to send our queued interceptions to our host. The Stack class will usually be a good choice and to make our code thread safe, we are using a lock, which we are entering once to transmit the stack content and once to add a new interception from within our hook handler.
Now the following happens. To send the result back to our host, the dedicated thread might call CreateFile again while holding the lock. If NET Remoting would use the same thread to call this API, the recursive lock capabilities of Monitor::Enter and the TDB would do their part and prevent any deadlock. But sometimes NET Remoting will use another thread and as we are already holding the lock it could never enter it. Of course you can again solve this by just filling a temporary buffer in the lock and send the result back outside, like done in the FileMon demo.
A universal solution
What we have learned? Writing stable hook handlers is not only a matter of a good hooking library like EasyHook, but also a matter of experiences with windows API programming and issues that will show up in your own applications. Be careful when dealing with multi-thread code because the TDB won’t fully protect you in this case. Don’t call APIs or NET members which internally are using or waiting for other threads to complete. If you need to do this, use dedicated threads and exclude them from being intercepted. By the time you will write more and more stable hook handlers and don’t worry about the very beginnings where things will cause the targets to crash or hang. With EasyHook you got a great utility in your hands, the rest depends on you!
Another side-effect that you should know about occurs when dealing with NET Remoting, again, is that you are usually implementing the shared class in the host application. This will cause the CLR to load your host assembly and initialize all associated static variables in related classes. This is why you shouldn’t initialize any static variables in classes that are associated with ones used as remote interface.
2.12 A look into the future
With the latest version “EasyHook 2.5 Beta”, all desired features are currently implemented. If you miss anything, don’t hesitate to request a new feature. I plan a first release candidate during the next two months. Please report any bug you find, otherwise a stable release candidate is not possible!
Currently I am working on an OpenSource clone for the mentioned ProcessMonitor available at www.microsoft.com. Mine will only use user-mode hooks to accomplish its task and should be a good example of how to write hooking applications. I plan to publish it in late August 2008.
I don’t have the time to test EasyHook all day long. I will always make sure that all shipped demos and test suites are working on all supported OS versions, but that is all I can do so far. Not only in case of OpenSource, is the customer the tester. But any bug you report will be fixed soon!
还不如直接看英文。
人有的时候很无聊，力所能及做点善事