using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace MySQLPassword
{
    public partial class Form1 : Form
    {
        private static string MemoryMasterKey = "!ZEqy2Zsb#VK6<8`H6;W~VxJ$r:w.{ffzwDt=<yKC6m6N3;T<9nyeF&+.4&D@rhK";

        public Form1()
        {
            InitializeComponent();
        }

        private void btnEncrypt_Click(object sender, EventArgs e)
        {
            try
            {
                if (string.IsNullOrEmpty(txtHost.Text))
                {
                    MessageBox.Show("Bitte geben Sie einen Hostnamen oder eine IP des Servers ein");
                }
                else if (txtPort.Value <= 0)
                {
                    MessageBox.Show("Bitte geben Sie eine gültige Port des MySQL Servers ein");
                }
                else if (string.IsNullOrEmpty(txtDatabase.Text))
                {
                    MessageBox.Show("Bitte geben Sie den Datenbanknamen ein");
                }
                else if (string.IsNullOrEmpty(txtUser.Text))
                {
                    MessageBox.Show("Bitte geben Sie den Benutzernamen der Datenbank ein");
                }
                else if (string.IsNullOrEmpty(txtPassword.Text))
                {
                    MessageBox.Show("Bitte geben Sie das Passwort des Datenbankbenutzers ein");
                }
                else
                {
                    string cs = "Server=" + txtHost.Text + ";Port=" + txtPort.Value.ToString() + ";Database=" + txtDatabase.Text + ";Uid=" + txtUser.Text + ";Pwd=" + txtPassword + ";";

                    txtOutput.Text = Encrypt(cs);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        public static string Encrypt(string value, byte[] deriveKey = null)
        {
            string result = null;

            try
            {
                if (deriveKey == null)
                {
                    deriveKey = GetKey(MemoryMasterKey);
                }

                using (AesGcm aes = new AesGcm(deriveKey))
                {
                    byte[] nonce = new byte[AesGcm.NonceByteSizes.MaxSize];
                    RandomNumberGenerator.Fill(nonce);
                    byte[] plainText = Encoding.UTF8.GetBytes(value);
                    byte[] chiperBuffer = new byte[plainText.Length];
                    byte[] tag = new byte[AesGcm.TagByteSizes.MaxSize];
                    aes.Encrypt(nonce, plainText, chiperBuffer, tag);
                    byte[] resultBuffer = nonce.Concat(chiperBuffer).Concat(tag).ToArray();
                    result = Convert.ToBase64String(resultBuffer);
                }
            }
            catch
            {
                result = null;
            }

            return result;
        }

        public static byte[] GetKey(string password)
        {
            byte[] result = null;

            try
            {
                if (!string.IsNullOrEmpty(password))
                {
                    if (password.Length < 32)
                    {
                        password = password.PadRight(32, '@');
                    }
                    else if (password.Length > 32)
                    {
                        password = MD5Encrypt(password);
                    }

                    result = Encoding.ASCII.GetBytes(password);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

            return result;
        }

        public static string MD5Encrypt(string value)
        {
            string result = null;

            try
            {
                byte[] bytes = Encoding.UTF8.GetBytes(value);

                using (System.Security.Cryptography.MD5 hash = System.Security.Cryptography.MD5.Create())
                {
                    byte[] hashedInputBytes = hash.ComputeHash(bytes);

                    StringBuilder hashedInputStringBuilder = new StringBuilder(128);

                    foreach (var b in hashedInputBytes)
                    {
                        hashedInputStringBuilder.Append(b.ToString("X2"));
                    }

                    result = hashedInputStringBuilder.ToString().ToLower();
                }
            }
            catch
            {
                result = null;
            }

            return result;
        }
    }
}