content: /*
   * Copyright 2022 paxos.cn.
   *
   * Licensed 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 cn.paxos.mysql.codec;
  
  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 Handshake} 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);
  		}
  	}
  
  }
  