// Copyright (c) 2012, 2019, Oracle and/or its affiliates. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System;
using System.Security.Cryptography;
using System.Text;

namespace MySql.Data.MySqlClient.Authentication
{
    /// <summary>
    /// Allows connections to a user account set with the mysql_native_password authentication plugin.
    /// </summary>
    public class MySqlNativePasswordPlugin : MySqlAuthenticationPlugin
    {
        public override string PluginName => "mysql_native_password";

        protected override void SetAuthData(byte[] data)
        {
            // if the data given to us is a null terminated string, we need to trim off the trailing zero
            if (data[data.Length - 1] == 0)
            {
                byte[] b = new byte[data.Length - 1];
                Buffer.BlockCopy(data, 0, b, 0, data.Length - 1);
                base.SetAuthData(b);
            }
            else
            {
                base.SetAuthData(data);
            }
        }

        protected override byte[] MoreData(byte[] data)
        {
            byte[] passBytes = (this.GetPassword() ?? new byte[1]) as byte[];
            byte[] buffer = new byte[passBytes.Length - 1];
            Array.Copy(passBytes, 1, buffer, 0, passBytes.Length - 1);
            return buffer;
        }

        public override object GetPassword()
        {
            byte[] bytes = this.Get411Password(this.Settings.Password, this.AuthenticationData);
            if (bytes != null && bytes.Length == 1 && bytes[0] == 0)
            {
                return null;
            }

            return bytes;
        }

        /// <summary>
        /// Returns a byte array containing the proper encryption of the 
        /// given password/seed according to the new 4.1.1 authentication scheme.
        /// </summary>
        /// <param name="password"></param>
        /// <param name="seedBytes"></param>
        /// <returns></returns>
        protected byte[] Get411Password(string password, byte[] seedBytes)
        {
            // if we have no password, then we just return 1 zero byte
            if (password.Length == 0)
            {
                return new byte[1];
            }

            // SHA1 sha = new SHA1CryptoServiceProvider();
            SHA1 sha = SHA1.Create();
            byte[] firstHash = null;
            try
            {
                firstHash = sha.ComputeHash(this.Encoding.GetBytes(password));
            }
            catch (NullReferenceException)
            {
                firstHash = sha.ComputeHash(Encoding.Default.GetBytes(password));
            }

            byte[] secondHash = sha.ComputeHash(firstHash);

            byte[] input = new byte[seedBytes.Length + secondHash.Length];
            Array.Copy(seedBytes, 0, input, 0, seedBytes.Length);
            Array.Copy(secondHash, 0, input, seedBytes.Length, secondHash.Length);
            byte[] thirdHash = sha.ComputeHash(input);

            byte[] finalHash = new byte[thirdHash.Length + 1];
            finalHash[0] = 0x14;
            Array.Copy(thirdHash, 0, finalHash, 1, thirdHash.Length);

            for (int i = 1; i < finalHash.Length; i++)
            {
                finalHash[i] = (byte)(finalHash[i] ^ firstHash[i - 1]);
            }

            return finalHash;
        }
    }
}