// Copyright (c) 2004, 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;
using Sog.Properties;

namespace MySql.Data.MySqlClient
{
    /// <summary>
    /// Summary description for Crypt.
    /// </summary>
    internal class Crypt
    {
        /// <summary>
        /// Simple XOR scramble
        /// </summary>
        /// <param name="from">Source array</param>
        /// <param name="fromIndex">Index inside source array</param>
        /// <param name="to">Destination array</param>
        /// <param name="toIndex">Index inside destination array</param>
        /// <param name="password">Password used to xor the bits</param>
        /// <param name="length">Number of bytes to scramble</param>
        private static void XorScramble(byte[] from, int fromIndex, byte[] to, int toIndex,
                        byte[] password, int length)
        {
            // make sure we were called properly
            if (fromIndex < 0 || fromIndex >= from.Length)
            {
                throw new ArgumentException(Resources.IndexMustBeValid, nameof(fromIndex));
            }

            if ((fromIndex + length) > from.Length)
            {
                throw new ArgumentException(Resources.FromAndLengthTooBig, nameof(fromIndex));
            }

            if (from == null)
            {
                throw new ArgumentException(Resources.BufferCannotBeNull, nameof(@from));
            }

            if (to == null)
            {
                throw new ArgumentException(Resources.BufferCannotBeNull, nameof(to));
            }

            if (toIndex < 0 || toIndex >= to.Length)
            {
                throw new ArgumentException(Resources.IndexMustBeValid, nameof(toIndex));
            }

            if ((toIndex + length) > to.Length)
            {
                throw new ArgumentException(Resources.IndexAndLengthTooBig, nameof(toIndex));
            }

            if (password == null || password.Length < length)
            {
                throw new ArgumentException(Resources.PasswordMustHaveLegalChars, nameof(password));
            }

            if (length < 0)
            {
                throw new ArgumentException(Resources.ParameterCannotBeNegative, nameof(length));
            }

            // now perform the work
            for (int i = 0; i < length; i++)
            {
                to[toIndex++] = (byte)(from[fromIndex++] ^ password[i]);
            }
        }

        /// <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="seed"></param>
        /// <returns></returns>
        public static byte[] Get411Password(string password, string seed)
        {
            // if we have no password, then we just return 2 zero bytes
            if (password.Length == 0)
            {
                return new byte[1];
            }

            SHA1 sha = SHA1.Create();

            byte[] firstHash = sha.ComputeHash(Encoding.Default.GetBytes(password));
            byte[] secondHash = sha.ComputeHash(firstHash);
            byte[] seedBytes = Encoding.Default.GetBytes(seed);

            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;

            // byte[] buffer = new byte[finalHash.Length - 1];
            // Array.Copy(finalHash, 1, buffer, 0, finalHash.Length - 1);
            // return buffer;
        }

        private static double rand(ref long seed1, ref long seed2, long max)
        {
            seed1 = (seed1 * 3) + seed2;
            seed1 %= max;
            seed2 = (seed1 + seed2 + 33) % max;
            return (seed1 / (double)max);
        }

        /// <summary>
        /// Encrypts a password using the MySql encryption scheme
        /// </summary>
        /// <param name="password">The password to encrypt</param>
        /// <param name="seed">The encryption seed the server gave us</param>
        /// <param name="new_ver">Indicates if we should use the old or new encryption scheme</param>
        /// <returns></returns>
        public static String EncryptPassword(String password, String seed, bool new_ver)
        {
            long max = 0x3fffffff;
            if (!new_ver)
            {
                max = 0x01FFFFFF;
            }

            if (string.IsNullOrEmpty(password))
            {
                return password;
            }

            long[] hash_seed = Hash(seed);
            long[] hash_pass = Hash(password);

            long seed1 = (hash_seed[0] ^ hash_pass[0]) % max;
            long seed2 = (hash_seed[1] ^ hash_pass[1]) % max;
            if (!new_ver)
            {
                seed2 = seed1 / 2;
            }

            char[] scrambled = new char[seed.Length];
            for (int x = 0; x < seed.Length; x++)
            {
                double r = rand(ref seed1, ref seed2, max);
                scrambled[x] = (char)(Math.Floor(r * 31) + 64);
            }

            if (new_ver)
            {
                /* Make it harder to break */
                char extra = (char)Math.Floor(rand(ref seed1, ref seed2, max) * 31);
                for (int x = 0; x < scrambled.Length; x++)
                {
                    scrambled[x] ^= extra;
                }
            }

            return new string(scrambled);
        }

        /// <summary>
        /// Hashes a password using the algorithm from Monty's code.
        /// The first element in the return is the result of the "old" hash.
        /// The second element is the rest of the "new" hash.
        /// </summary>
        /// <param name="P">Password to be hashed</param>
        /// <returns>Two element array containing the hashed values</returns>
        private static long[] Hash(String P)
        {
            long val1 = 1345345333;
            long val2 = 0x12345671;
            long inc = 7;

            for (int i = 0; i < P.Length; i++)
            {
                if (P[i] == ' ' || P[i] == '\t')
                {
                    continue;
                }

                long temp = (0xff & P[i]);
                val1 ^= (((val1 & 63) + inc) * temp) + (val1 << 8);
                val2 += (val2 << 8) ^ val1;
                inc += temp;
            }

            long[] hash = new long[2];
            hash[0] = val1 & 0x7fffffff;
            hash[1] = val2 & 0x7fffffff;
            return hash;
        }
    }
}