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 org.apache.shiro.crypto.cipher;
  
  import javax.crypto.spec.GCMParameterSpec;
  import java.security.spec.AlgorithmParameterSpec;
  
  /**
   * {@code CipherService} using the {@code AES} cipher algorithm for all encryption, decryption, and key operations.
   * <p/>
   * The AES algorithm can support key sizes of {@code 128}, {@code 192} and {@code 256} bits<b>*</b>.  This implementation
   * defaults to 128 bits.
   * <p/>
   * Note that this class retains changes the parent class's default {@link OperationMode#CBC CBC} mode to {@link OperationMode#GCM GCM} of operation
   * instead of the typical JDK default of {@link OperationMode#ECB ECB}.  {@code ECB} should not be used in
   * security-sensitive environments because {@code ECB} does not allow for initialization vectors, which are
   * considered necessary for strong encryption.  See the {@link DefaultBlockCipherService parent class}'s JavaDoc and the
   * {@link JcaCipherService JcaCipherService} JavaDoc for more on why the JDK default should not be used and is not
   * used in this implementation.
   * <p/>
   * <b>*</b> Generating and using AES key sizes greater than 128 require installation of the
   * <a href="http://java.sun.com/javase/downloads/index.jsp">Java Cryptography Extension (JCE) Unlimited Strength
   * Jurisdiction Policy files</a>.
   *
   * @since 1.0
   */
  public class AesCipherService extends DefaultBlockCipherService {
  
      private static final String ALGORITHM_NAME = "AES";
  
      /**
       * Creates a new {@link CipherService} instance using the {@code AES} cipher algorithm with the following
       * important cipher default attributes:
       * <table>
       * <tr>
       * <th>Attribute</th>
       * <th>Value</th>
       * </tr>
       * <tr>
       * <td>{@link #setKeySize keySize}</td>
       * <td>{@code 128} bits</td>
       * </tr>
       * <tr>
       * <td>{@link #setBlockSize blockSize}</td>
       * <td>{@code 128} bits (required for {@code AES}</td>
       * </tr>
       * <tr>
       * <td>{@link #setMode mode}</td>
       * <td>{@link OperationMode#GCM GCM}<b>*</b></td>
       * </tr>
       * <tr>
       * <td>{@link #setPaddingScheme paddingScheme}</td>
       * <td>{@link PaddingScheme#NONE NoPadding}***</td>
       * </tr>
       * <tr>
       * <td>{@link #setInitializationVectorSize(int) initializationVectorSize}</td>
       * <td>{@code 128} bits</td>
       * </tr>
       * <tr>
       * <td>{@link #setGenerateInitializationVectors(boolean) generateInitializationVectors}</td>
       * <td>{@code true}<b>**</b></td>
       * </tr>
       * </table>
       * <p/>
       * <b>*</b> The {@link OperationMode#GCM GCM} operation mode is used instead of the JDK default {@code ECB} to
       * ensure strong encryption.  {@code ECB} should not be used in security-sensitive environments - see the
       * {@link DefaultBlockCipherService DefaultBlockCipherService} class JavaDoc's &quot;Operation Mode&quot; section
       * for more.
       * <p/>
       * <b>**</b>In conjunction with the default {@code GCM} operation mode, initialization vectors are generated by
       * default to ensure strong encryption.  See the {@link JcaCipherService JcaCipherService} class JavaDoc for more.
       * <p/>
       * <b>**</b>Since {@code GCM} is a stream cipher, padding is implemented in the operation mode and an external padding scheme
       * cannot be used in conjunction with {@code GCM}. In fact, {@code AES/GCM/PKCS5Padding} is just an alias in most JVM for
       * {@code AES/GCM/NoPadding}.
       * <p/>
       * <b>NOTE:</b> As of Java 14, setting a streaming padding for the above example will throw a NoSuchAlgorithmException
       * @see <a href="https://www.oracle.com/java/technologies/javase/14-relnote-issues.html#JDK-8180392">JDK-8180392</a>
       */
      public AesCipherService() {
          super(ALGORITHM_NAME);
          setMode(OperationMode.GCM);
          setStreamingMode(OperationMode.GCM);
          setPaddingScheme(PaddingScheme.NONE);
          setStreamingPaddingScheme(PaddingScheme.NONE);
      }
  
      @Override
      protected AlgorithmParameterSpec createParameterSpec(byte[] iv, boolean streaming) {
  
          if ((streaming && OperationMode.GCM.name().equals(getStreamingModeName()))
          || (!streaming && OperationMode.GCM.name().equals(getModeName()))) {
              return new GCMParameterSpec(getKeySize(), iv);
          }
  
          return super.createParameterSpec(iv, streaming);
      }
  }
  