content: /*
   ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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   ~ The MIT License (MIT)                                                         ~
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   ~ Copyright (c) 2015-2025 miaixz.org and other contributors.                    ~
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   ~ Permission is hereby granted, free of charge, to any person obtaining a copy  ~
   ~ of this software and associated documentation files (the "Software"), to deal ~
   ~ in the Software without restriction, including without limitation the rights  ~
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   ~ copies of the Software, and to permit persons to whom the Software is         ~
   ~ furnished to do so, subject to the following conditions:                      ~
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   ~ all copies or substantial portions of the Software.                           ~
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   ~ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,      ~
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  */
  package org.miaixz.bus.crypto.center;
  
  import org.miaixz.bus.core.codec.binary.Base32;
  import org.miaixz.bus.core.lang.Algorithm;
  import org.miaixz.bus.core.xyz.RandomKit;
  
  /**
   * HMAC-based one-time passwords (HOTP) 基于HMAC算法一次性密码生成器， 规范见：<a href="https://tools.ietf.org/html/rfc4226">RFC 4226</a>
   *
   * <p>
   * 基于事件同步，通过某一特定的事件次序及相同的种子值作为输入，通过HASH算法运算出一致的密码。
   * </p>
   *
   * <p>
   * 参考：https://github.com/jchambers/java-otp
   * </p>
   *
   * @author Kimi Liu
   * @since Java 17+
   */
  public class HOTP {
  
      /**
       * 默认密码长度.
       */
      public static final int DEFAULT_PASSWORD_LENGTH = 6;
  
      /**
       * 数子量级
       */
      private static final int[] MOD_DIVISORS = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 };
      private final HMac mac;
      private final int passwordLength;
      private final int modDivisor;
  
      private final byte[] buffer;
  
      /**
       * 构造，使用默认密码长度和默认HMAC算法(HmacSHA1)
       *
       * @param key 共享密码，RFC 4226要求最少128位
       */
      public HOTP(final byte[] key) {
          this(DEFAULT_PASSWORD_LENGTH, key);
      }
  
      /**
       * 构造，使用默认HMAC算法(HmacSHA1)
       *
       * @param passwordLength 密码长度，可以是6,7,8
       * @param key            共享密码，RFC 4226要求最少128位
       */
      public HOTP(final int passwordLength, final byte[] key) {
          this(passwordLength, Algorithm.HMACSHA1, key);
      }
  
      /**
       * 构造
       *
       * @param passwordLength 密码长度，可以是6,7,8
       * @param algorithm      HMAC算法枚举
       * @param key            共享密码，RFC 4226要求最少128位
       */
      public HOTP(final int passwordLength, final Algorithm algorithm, final byte[] key) {
          if (passwordLength >= MOD_DIVISORS.length) {
              throw new IllegalArgumentException("Password length must be < " + MOD_DIVISORS.length);
          }
          this.mac = new HMac(algorithm, key);
          this.modDivisor = MOD_DIVISORS[passwordLength];
          this.passwordLength = passwordLength;
          this.buffer = new byte[8];
      }
  
      /**
       * 生成共享密钥的Base32表示形式
       *
       * @param numBytes 将生成的种子字节数量。
       * @return 共享密钥
       */
      public static String generateSecretKey(final int numBytes) {
          return Base32.encode(RandomKit.getSHA1PRNGRandom(RandomKit.randomBytes(256)).generateSeed(numBytes));
      }
  
      /**
       * 生成一次性密码
       *
       * @param counter 事件计数的值，8 字节的整数，称为移动因子（moving factor）， 可以是基于计次的动移动因子，也可以是计时移动因子
       * @return 一次性密码的int值
       */
      public synchronized int generate(final long counter) {
          // C 的整数值需要用二进制的字符串表达，比如某个事件计数为 3，
          // 则C是 "11"（此处省略了前面的二进制的数字0）
          this.buffer[0] = (byte) ((counter & 0xff00000000000000L) >>> 56);
          this.buffer[1] = (byte) ((counter & 0x00ff000000000000L) >>> 48);
          this.buffer[2] = (byte) ((counter & 0x0000ff0000000000L) >>> 40);
          this.buffer[3] = (byte) ((counter & 0x000000ff00000000L) >>> 32);
          this.buffer[4] = (byte) ((counter & 0x00000000ff000000L) >>> 24);
          this.buffer[5] = (byte) ((counter & 0x0000000000ff0000L) >>> 16);
          this.buffer[6] = (byte) ((counter & 0x000000000000ff00L) >>> 8);
          this.buffer[7] = (byte) (counter & 0x00000000000000ffL);
  
          final byte[] digest = this.mac.digest(this.buffer);
  
          return truncate(digest);
      }
  
      /**
       * 获取密码长度，可以是6,7,8
       *
       * @return 密码长度，可以是6,7,8
       */
      public int getPasswordLength() {
          return this.passwordLength;
      }
  
      /**
       * 获取HMAC算法
       *
       * @return HMAC算法
       */
      public String getAlgorithm() {
          return this.mac.getAlgorithm();
      }
  
      /**
       * 截断
       *
       * @param digest HMAC的hash值
       * @return 截断值
       */
      private int truncate(final byte[] digest) {
          final int offset = digest[digest.length - 1] & 0x0f;
          return ((digest[offset] & 0x7f) << 24 | (digest[offset + 1] & 0xff) << 16 | (digest[offset + 2] & 0xff) << 8
                  | (digest[offset + 3] & 0xff)) % this.modDivisor;
      }
  
  }
  