外部 Powershell / C# keyhook 脚本 NullReferenceException

Powershell / C# keyhook script NullReferenceException externally

我正在尝试使用 powershell 脚本(使用 C#)来监听击键。它在出错之前工作了很短的时间。有趣的是,在我添加了一些控制台写入之后,错误似乎发生在我的代码外部。

这是 powreshell 脚本:

Add-Type -TypeDefinition @"
    using System;
    using System.Diagnostics;
    using System.Runtime.InteropServices;
    using System.Windows.Forms;

    namespace KeyLogger {
        public static class Program {
            private const int WH_KEYBOARD_LL = 13;
            private static IntPtr hookId = IntPtr.Zero;

            public static void Begin() {
                hookId = SetHook();
                Application.Run();
                UnhookWindowsHookEx(hookId);
            }

            private static IntPtr SetHook() {
                IntPtr moduleHandle = GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName);
                return SetWindowsHookEx(WH_KEYBOARD_LL, HookCallback, moduleHandle, 0);
            }

            private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam) {
                Console.WriteLine('0');
                if (nCode == 0) {
                    Console.WriteLine('1');
                    Console.WriteLine(Marshal.ReadInt32(lParam) + " " + wParam + " ");
                }
                Console.WriteLine('2');
                IntPtr x = CallNextHookEx(hookId, nCode, wParam, lParam);
                Console.WriteLine('3');
                return x;
            }

            private delegate IntPtr HookProc(int nCode, IntPtr wParam, IntPtr lParam);

            [DllImport("user32.dll")]
            private static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hMod, uint dwThreadId);
            [DllImport("user32.dll")]
            private static extern bool UnhookWindowsHookEx(IntPtr hhk);
            [DllImport("user32.dll")]
            private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
            [DllImport("kernel32.dll")]
            private static extern IntPtr GetModuleHandle(string lpModuleName);
        }
    }
"@ -ReferencedAssemblies System.Windows.Forms

[KeyLogger.Program]::Begin();

错误是:

An error has occurred that was not properly handled. Additional information is shown below. The Windows PowerShell process will exit. Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.

注意 HookCallback 方法中的 Console.WriteLine 。但最后打印的调试行是 3,表明错误发生在 HookCallback 之外。更有趣的是,如果我有多个脚本实例 运行,它们不会同时出错;一个可能会崩溃,但其余的会继续多一点。

我不太熟悉 powershell 或 C#,所以想知道如何获取更多调试信息?我希望出现错误的行号或文件或库名称,但我不确定如何获取该信息。

免责声明,我从这里 https://blogs.msdn.microsoft.com/toub/2006/05/03/low-level-keyboard-hook-in-c/ 获取脚本(略有修改)。

编辑:我接受了 Stuartd 的回答,因为它非常有帮助,但正如我在评论中所说,它需要进行小的修改才能工作。 为了方便未来的读者,以下是有效的修改:

 private static HookProc callback;
 ...

 private static IntPtr SetHook() {
     callback = HookCallback;
     IntPtr moduleHandle = GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName);
     return SetWindowsHookEx(WH_KEYBOARD_LL, callback, moduleHandle, 0);
 }
 ...

我在 C# 上做了更多的搜索和阅读,似乎原因是 SetWindowsHookEx 没有管理/保持它的 hookProc 委托参数,传递静态方法直接创建一个本地 (本地方法)一旦 SetHook 方法 returns.

就可以删除的委托

可能会这样做:创建一个引用 HookProc 的字段,并告诉 GC 使其保持活动状态:

public static class Program
{
    private const int WH_KEYBOARD_LL = 13;
    private static IntPtr hookId = IntPtr.Zero;
    private static HookProc proc;

    public static void Begin()
    {
        proc = HookCallback;
        hookId = SetHook();
        GC.KeepAlive(proc);
        Application.Run();
        UnhookWindowsHookEx(hookId);
    }

     … etc