SharpMonoInjector - a Mono/Unity injector written in C#

using System;
using System****;
using Process.NET;
using Process.NE*****mory;
using Process.NET.Assembly;
using Process.NET.Native.Types;
using Binarysharp.Assemblers.Fasm;
using Process.NET.Assembly.Assemblers;

namespace Injector
{
    class Assembler : IAssembler
    {
        public static bool Attach = false;
        public static IntPtr MonoThreadAttach;
        public static IntPtr MonoRootDomain;

        public byte[] Assemble(string asm)
        {
            return Assemble(asm, IntPtr.Zero);
        }

        public byte[] Assemble(string asm, IntPtr baseAddress)
        {
            if (!Attach)
                asm = $"use32\norg {baseAddress}\n" + asm;
            else
                // Ensure mono_thread_attach is called first
                asm = $"use32\norg {baseAddress}\npush {MonoRootDomain}\ncall {MonoThreadAttach}\nadd esp, 4\n" + asm;
            return FasmNet.Assemble(asm);
        }
    }

    class Program
    {
        static ProcessSharp target;
        static AssemblyFactory factory;

        static void Main(string[] args)
        {
            System.Diagnostics.Process p =
                System.Diagnostics.Process.GetProcessesByName("target")[0];

            target = new ProcessSharp(p, MemoryType.Remote);
            factory = new AssemblyFactory(target, new Assembler());

            byte[] data = File.ReadAllBytes("ExampleAssembly.dll");

            string nameSpace = "ExampleAssembly",
                   klass = "Loader",
                   method = "Load";

            IntPtr rawImage = OpenImageFromData(data);

            /* From this point on, the threads created by AssemblyFactory.Execute
               will have to be registered with the Mono runtime since we
               are accessing Mono objects. Otherwise the target process crashes. */

            Assembler.MonoThreadAttach = target.ModuleFactory["mono.dll"]["mono_thread_attach"].BaseAddress;
            Assembler.MonoRootDomain = GetRootDomain();

            Assembler.Attach = true;

            RuntimeInvoke(
                GetMethodFromName(
                    GetClassFromName(
                        GetImageFromAssembly(
                            OpenAssemblyFromImage(
                                rawImage)), 
                        nameSpace, klass), 
                    method));

            factory.Dispose();
            target.Dispose();
        }

        static IntPtr GetRootDomain()
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_get_root_domain"].BaseAddress;
            return factory.Execute<IntPtr>(addr, CallingConventions.Cdecl);
        }

        static IntPtr OpenImageFromData(byte[] assembly)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_image_open_from_data"].BaseAddress;
            IAllocatedMemory alloc = targe*****moryFactory.Allocate("assembly", assembly.Length);
            alloc.Write(0, assembly);
            IntPtr image = factory.Execute<IntPtr>(addr, CallingConventions.Cdecl, alloc.BaseAddress, assembly.Length, 1, IntPtr.Zero);
            targe*****moryFactory.Deallocate(alloc);
            return image;
        }

        static IntPtr OpenAssemblyFromImage(IntPtr image)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_assembly_load_from_full"].BaseAddress;
            return factory.Execute<IntPtr>(addr, CallingConventions.Cdecl, image, "UNUSED", IntPtr.Zero, 0);
        }

        static IntPtr GetImageFromAssembly(IntPtr assembly)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_assembly_get_image"].BaseAddress;
            return factory.Execute<IntPtr>(addr, CallingConventions.Cdecl, assembly);
        }

        static IntPtr GetClassFromName(IntPtr image, string name_space, string klass)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_class_from_name"].BaseAddress;
            return factory.Execute<IntPtr>(addr, CallingConventions.Cdecl, image, name_space, klass);
        }

        static IntPtr GetMethodFromName(IntPtr klass, string method)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_class_get_method_from_name"].BaseAddress;
            return factory.Execute<IntPtr>(addr, CallingConventions.Cdecl, klass, method, 0);
        }

        static int RuntimeInvoke(IntPtr method)
        {
            IntPtr addr = target.ModuleFactory["mono.dll"]["mono_runtime_invoke"].BaseAddress;
            return factory.Execute<int>(addr, CallingConventions.Cdecl, method, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero);
        }
    }
}