using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.Contracts;
using System.IO;
using System.Runtime.InteropServices;

/// <summary>
/// Dll Injector
/// Made by BahNahNah
/// uid=2388291
/// </summary>
public class DllInjector
{
    /// <summary>
    /// Gets the last error
    /// </summary>
    /// <returns></returns>
    public static string GetLastError()
    {
        return new Win32Exception(Marshal.GetLastWin32Error()).Message;
    }

    /// <summary>
    /// Injects a dll into the target process
    /// </summary>
    /// <param name="TargetProcess">Process to inject into</param>
    /// <param name="dll">Path to dll</param>
    /// <returns>Success of injection</returns>
    public static bool Inject(Process TargetProcess, string dll)
    {
        if (TargetProcess == null) throw new ArgumentNullException("TargetProcess");
        if (TargetProcess.HasExited) throw new ArgumentException("Process must be running", "TargetProcess");
        return Inject(TargetProcess.Id, dll);
    }

    /// <summary>
    /// Injects a dll into the target process
    /// </summary>
    /// <param name="pID">Process ID of target process</param>
    /// <param name="DllPath">Path to dll</param>
    /// <returns>Success of injection</returns>
    public static bool Inject(int pID, string DllPath)
    {
        IntPtr Handle = OpenProcess( 0x8 | 0x2 | 0x400 | 0x10 | 0x20, false, pID);
        if (Handle == IntPtr.Zero) throw new ArgumentException("Invalid process id", "pID");
        return Inject(Handle, DllPath) != IntPtr.Zero;
    }


    /// <summary>
    /// Injects a dll into the target process
    /// </summary>
    /// <param name="Handle">Handle of target process</param>
    /// <param name="DllPath">Path to dll</param>
    /// <returns>Handle of DLL thread or IntPtr.Zero on fail</returns>
    public static IntPtr Inject(IntPtr Handle, string DllPath)
    {
        if (Handle == IntPtr.Zero) throw new ArgumentNullException("Handle");
        if (!File.Exists(DllPath)) throw new ArgumentException("Must point to a valid file", "DllPath");
        string FullDllPath = Path.GetFullPath(DllPath);

        IntPtr vAlloc = VirtualAllocEx(Handle, 0, FullDllPath.Length + 1, 0x1000, 0x40);
        if(vAlloc == IntPtr.Zero)
        {
            CloseHandle(Handle);
            return IntPtr.Zero;
        }

        if(WriteProcessMemory(Handle, vAlloc, FullDllPath, FullDllPath.Length, 0) == 0)
        {
            CloseHandle(Handle);
            return IntPtr.Zero;
        }

        IntPtr hKernel32 = GetModuleHandle("kernel32.dll");
        IntPtr hLoadLibrary = GetProcAddress(hKernel32, "LoadLibraryA");
        if(hLoadLibrary == IntPtr.Zero)
        {
            CloseHandle(Handle);
            return IntPtr.Zero;
        }

        IntPtr hThread = CreateRemoteThread(Handle, 0, 0, hLoadLibrary, vAlloc, 0, 0);

        CloseHandle(Handle);
        return hThread;
    }

    #region " WinApi "

    [DllImport("kernel32.dll", SetLastError=true)]
    private static extern IntPtr VirtualAllocEx(IntPtr hProcess, int lpAddress, int dwSize, uint flAllocationType, uint flProtect);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern uint WaitForSingleObject(IntPtr handle, int timeout);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr OpenProcess(uint dwDesiredAccess, bool bInheritHandle, int dwProcessId);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern bool CloseHandle(IntPtr handle);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern int WriteProcessMemory(IntPtr handle, IntPtr address, string buffer, int blength, int readwrite);

    [DllImport("kernel32.dll", SetLastError=true)]
    private static extern IntPtr GetModuleHandle(string name);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr GetProcAddress(IntPtr mHandle, string fname);

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern IntPtr CreateRemoteThread(IntPtr pHandle, int att_0, int stacksize_0, IntPtr callingFunction, IntPtr paramiters, uint createFlags_0, int tID);

    #endregion
}