content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.aliyun.oss.crypto;
  
  import javax.crypto.Cipher;
  import javax.crypto.SecretKey;
  import com.aliyun.oss.ClientException;
  
  /**
   * The crypto module specified to AES_CTR crypto shecme.
   * that it will encrypt content with AES_CTR algothrim.
   */
  class CryptoModuleAesCtr extends CryptoModuleBase {    
      CryptoModuleAesCtr(OSSDirect OSS,
                       EncryptionMaterials encryptionMaterials,
                       CryptoConfiguration cryptoConfig) {
          super(OSS, encryptionMaterials, cryptoConfig);
      }
  
      /**
       * @return an array of bytes representing the content crypto cipher start counter.
       */
      @Override
      final byte[] generateIV() {
          final byte[] iv = new byte[contentCryptoScheme.getContentChiperIVLength()];
          cryptoConfig.getSecureRandom().nextBytes(iv);
          if (cryptoConfig.getContentCryptoMode().equals(ContentCryptoMode.AES_CTR_MODE)) {
              for (int i = 8; i < 12; i++) {
                  iv[i] = 0;
              }
          }
          return iv;
      }
  
      /**
       *Creates a cipher from a {@link ContentCryptoMaterial} instance, it used to encrypt/decrypt data.
       *
       * @param cekMaterial
       *             It provides the cek iv and crypto algorithm to build an crypto cipher.
       * @param cipherMode
       *             Cipher.ENCRYPT_MODE or Cipher.DECRYPT_MODE
       * @param cryptoRange
       *             The first element of the crypto range is the offset of the acquired object,
       *             and it should be allgned with cipher block if it was not null.
       * @param skipBlock
       *              the number of blocks should be skiped when the cipher created.
       * @return a {@link CryptoCipher} instance for encrypt/decrypt data.         
       */
      final CryptoCipher createCryptoCipherFromContentMaterial(ContentCryptoMaterial cekMaterial, int cipherMode,
              long[] cryptoRange, long skipBlock) {
          if (cipherMode != Cipher.ENCRYPT_MODE && cipherMode != Cipher.DECRYPT_MODE) {
              throw new ClientException("Invalid cipher mode.");
          }
          byte[] iv = cekMaterial.getIV();
          SecretKey cek = cekMaterial.getCEK();
          String cekAlgo = cekMaterial.getContentCryptoAlgorithm();
          CryptoScheme tmpContentCryptoScheme = CryptoScheme.fromCEKAlgo(cekAlgo);
          // Adjust the IV if needed
          boolean isRangeGet = (cryptoRange != null);
          if (isRangeGet) {
              iv = tmpContentCryptoScheme.adjustIV(iv, cryptoRange[0]);
          } else if (skipBlock > 0) {
              iv = CryptoScheme.incrementBlocks(iv, skipBlock);
          }
          return tmpContentCryptoScheme.createCryptoCipher(cek, iv, cipherMode, cryptoConfig.getContentCryptoProvider());
      }
  }
  