Hook managed function

DumbHook.cs

// MIT License
//
// Copyright (c) 2022 Michael Pekar
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// ------------------------------------------------------------------------
// Originally released on unknowncheats.me by me in 2017:
// https://www.unknowncheats.me/forum/c-/213492-hook-managed-function.html#post1700496

using System;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
 
class DumbHook
{
	private const uint HOOK_SIZE_X64 = 12;
	private const uint HOOK_SIZE_X86 = 7;
	private byte[] original;

	public MethodInfo OriginalMethod { get; private set; }
	public MethodInfo HookMethod { get; private set; }


	public DumbHook()
	{
		original = null;
		OriginalMethod = HookMethod = null;
	}

	public DumbHook(MethodInfo orig, MethodInfo hook)
	{
		original = null;
		Init(orig, hook);
	}

	public DumbHook(Type typeOrig, string nameOrig, Type typeHook, string nameHook)
	{
		original = null;
		Init(Util.GetMethodByName(typeOrig, nameOrig), Util.GetMethodByName(typeHook, nameHook));
	}

	public void Init(MethodInfo orig, MethodInfo hook)
	{
		if (Util.IsNull(orig) || Util.IsNull(hook))
			throw new ArgumentException("Both original and hook need to be valid methods");

		RuntimeHelpers.PrepareMethod(orig.MethodHandle);
		RuntimeHelpers.PrepareMethod(hook.MethodHandle);

		OriginalMethod = orig;
		HookMethod = hook;
	}

	public void Hook()
	{
		// Valid params?
		if (Util.IsNull(OriginalMethod) || Util.IsNull(HookMethod))
			throw new ArgumentException("Hook has to be properly Init'd before use");

		// Check if function is already hooked
		if (original != null)
			return;

		// Patch it
		IntPtr funcFrom = OriginalMethod.MethodHandle.GetFunctionPointer();
		IntPtr funcTo = HookMethod.MethodHandle.GetFunctionPointer();
		uint oldProt;
		if (IntPtr.Size == 8) //x86-64
		{
			original = new byte[HOOK_SIZE_X64];

			Import.VirtualProtect(funcFrom, HOOK_SIZE_X64, 0x40, out oldProt);
			unsafe
			{
				byte* ptr = (byte*)funcFrom;

				for (int i = 0; i < HOOK_SIZE_X64; ++i)
				{
					original[i] = ptr[i];
				}

				// movabs rax, addy
				// jmp rax
				*(ptr) = 0x48;
				*(ptr + 1) = 0xb8;
				*(IntPtr*)(ptr + 2) = funcTo;
				*(ptr + 10) = 0xff;
				*(ptr + 11) = 0xe0;
			}
			Import.VirtualProtect(funcFrom, HOOK_SIZE_X64, oldProt, out oldProt);
		}
		else //assume x86
		{
			original = new byte[HOOK_SIZE_X86];

			Import.VirtualProtect(funcFrom, HOOK_SIZE_X86, 0x40, out oldProt);
			unsafe
			{
				byte* ptr = (byte*)funcFrom;

				for (int i = 0; i < HOOK_SIZE_X86; ++i)
				{
					original[i] = ptr[i];
				}

				// mov eax, addy
				// jmp eax
				*(ptr) = 0xb8;
				*(IntPtr*)(ptr + 1) = funcTo;
				*(ptr + 5) = 0xff;
				*(ptr + 6) = 0xe0;
			}
			Import.VirtualProtect(funcFrom, HOOK_SIZE_X86, oldProt, out oldProt);

		}
	}

	public void Unhook()
	{
		// Check if function is hooked
		if (original == null)
			return;

		// Restore original code
		uint oldProt;
		uint codeSize = (uint)original.Length;
		IntPtr origAddr = OriginalMethod.MethodHandle.GetFunctionPointer();
		Import.VirtualProtect(origAddr, codeSize, 0x40, out oldProt);
		unsafe
		{
			byte* ptr = (byte*)origAddr;
			for (var i = 0; i < codeSize; ++i)
			{
				ptr[i] = original[i];
			}
		}
		Import.VirtualProtect(origAddr, codeSize, 0x40, out oldProt);

		// The original function has been restored.
		original = null;
	}

	internal class Import
	{
		[DllImport("kernel32.dll", SetLastError = true)]
		internal static extern bool VirtualProtect(IntPtr address, uint size, uint newProtect, out uint oldProtect);
	}
}

/* Usage pseudo:
   [MethodImpl(MethodImplOptions.NoInlining)]
   public void HelloWorldHook(string hi)
   {
        // call original
        hook.Unhook();
        hook.OriginalMethod.Invoke(this, null);
        hook.Hook();
    }
    public void GameAwake()
    {
        hook = new DumbHook(typeof(SomeClass), "HelloWorld", typeof(Program), "HelloWorldHook");
        hook.Hook();
    }
*/