/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package com.github.netty.protocol.mysql;

import com.github.netty.protocol.mysql.client.ClientHandshakePacket;
import io.netty.buffer.ByteBuf;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Calculates a password hash for {@code mysql_native_password} authentication.
 */
public class MysqlNativePasswordUtil {

	public static byte[] hashPassword(String password, ByteBuf saltBuf) {
		byte[] salt = new byte[saltBuf.readableBytes()];
		saltBuf.readBytes(salt);
		return hashPassword(password, salt);
	}

	/**
	 * Calculates a hash of the user's password.
	 *
	 * @param password the user's password
	 * @param salt     the salt send from the server in the {@link ClientHandshakePacket} packet.
	 * @return the hashed password
	 */
	public static byte[] hashPassword(String password, byte[] salt) {
		try {
			MessageDigest md = MessageDigest.getInstance("SHA-1");

			byte[] hashedPassword = md.digest(password.getBytes());

			md.reset();
			byte[] doubleHashedPassword = md.digest(hashedPassword);

			md.reset();
			md.update(salt, 0, 20);
			md.update(doubleHashedPassword);

			byte[] hash = md.digest();
			for (int i = 0; i < hash.length; i++) {
				hash[i] = (byte) (hash[i] ^ hashedPassword[i]);
			}
			return hash;
		} catch (NoSuchAlgorithmException e) {
			throw new RuntimeException(e);
		}
	}

}