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 org.apache.shiro.crypto.CryptoException;
  import org.apache.shiro.lang.util.ByteSource;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  
  /**
   * A {@code CipherService} uses a cryptographic algorithm called a
   * <a href="http://en.wikipedia.org/wiki/Cipher">Cipher</a> to convert an original input source using a {@code key} to
   * an uninterpretable format.  The resulting encrypted output is only able to be converted back to original form with
   * a {@code key} as well.  {@code CipherService}s can perform both encryption and decryption.
   * <h2>Cipher Basics</h2>
   * For what is known as <em>Symmetric</em> {@code Cipher}s, the {@code Key} used to encrypt the source is the same
   * as (or trivially similar to) the {@code Key} used to decrypt it.
   * <p/>
   * For <em>Asymmetric</em> {@code Cipher}s, the encryption {@code Key} is not the same as the decryption {@code Key}.
   * The most common type of Asymmetric Ciphers are based on what is called public/private key pairs:
   * <p/>
   * A <em>private</em> key is known only to a single party, and as its name implies, is supposed be kept very private
   * and secure.  A <em>public</em> key that is associated with the private key can be disseminated freely to anyone.
   * Then data encrypted by the public key can only be decrypted by the private key and vice versa, but neither party
   * need share their private key with anyone else.  By not sharing a private key, you can guarantee no 3rd party can
   * intercept the key and therefore use it to decrypt a message.
   * <p/>
   * This asymmetric key technology was created as a
   * more secure alternative to symmetric ciphers that sometimes suffer from man-in-the-middle attacks since, for
   * data shared between two parties, the same Key must also be shared and may be compromised.
   * <p/>
   * Note that a symmetric cipher is perfectly fine to use if you just want to encode data in a format no one else
   * can understand and you never give away the key.  Shiro uses a symmetric cipher when creating certain
   * HTTP Cookies for example - because it is often undesirable to have user's identity stored in a plain-text cookie,
   * that identity can be converted via a symmetric cipher.  Since the the same exact Shiro application will receive
   * the cookie, it can decrypt it via the same {@code Key} and there is no potential for discovery since that Key
   * is never shared with anyone.
   * <h2>{@code CipherService}s vs JDK {@link javax.crypto.Cipher Cipher}s</h2>
   * Shiro {@code CipherService}s essentially do the same things as JDK {@link javax.crypto.Cipher Cipher}s, but in
   * simpler and easier-to-use ways for most application developers.  When thinking about encrypting and decrypting data
   * in an application, most app developers want what a {@code CipherService} provides, rather than having to manage the
   * lower-level intricacies of the JDK's {@code Cipher} API.  Here are a few reasons why most people prefer
   * {@code CipherService}s:
   * <ul>
   * <li><b>Stateless Methods</b> - {@code CipherService} method calls do not retain state between method invocations.
   * JDK {@code Cipher} instances do retain state across invocations, requiring its end-users to manage the instance
   * and its state themselves.</li>
   * <li><b>Thread Safety</b> - {@code CipherService} instances are thread-safe inherently because no state is
   * retained across method invocations.  JDK {@code Cipher} instances retain state and cannot be used by multiple
   * threads concurrently.</li>
   * <li><b>Single Operation</b> - {@code CipherService} method calls are single operation methods: encryption or
   * decryption in their entirety are done as a single method call.  This is ideal for the large majority of developer
   * needs where you have something unencrypted and just want it decrypted (or vice versa) in a single method call.  In
   * contrast, JDK {@code Cipher} instances can support encrypting/decrypting data in chunks over time (because it
   * retains state), but this often introduces API clutter and confusion for most application developers.</li>
   * <li><b>Type Safe</b> - There are {@code CipherService} implementations for different Cipher algorithms
   * ({@code AesCipherService}, {@code BlowfishCipherService}, etc.).  There is only one JDK {@code Cipher} class to
   * represent all cipher algorithms/instances.
   * <li><b>Simple Construction</b> - Because {@code CipherService} instances are type-safe, instantiating and using
   * one is often as simple as calling the default constructor, for example, <code>new AesCipherService();</code>.  The
   * JDK {@code Cipher} class however requires using a procedural factory method with String arguments to indicate how
   * the instance should be created.  The String arguments themselves are somewhat cryptic and hard to
   * understand unless you're a security expert.  Shiro hides these details from you, but allows you to configure them
   * if you want.</li>
   * </ul>
   *
   * @see BlowfishCipherService
   * @see AesCipherService
   * @since 1.0
   */
  public interface CipherService {
  
      /**
       * Decrypts encrypted data via the specified cipher key and returns the original (pre-encrypted) data.
       * Note that the key must be in a format understood by the CipherService implementation.
       *
       * @param encrypted     the previously encrypted data to decrypt
       * @param decryptionKey the cipher key used during decryption.
       * @return a byte source representing the original form of the specified encrypted data.
       * @throws CryptoException if there is an error during decryption
       */
      ByteSourceBroker decrypt(byte[] encrypted, byte[] decryptionKey) throws CryptoException;
  
      /**
       * Receives encrypted data from the given {@code InputStream}, decrypts it, and sends the resulting decrypted data
       * to the given {@code OutputStream}.
       * <p/>
       * <b>NOTE:</b> This method <em>does NOT</em> flush or close either stream prior to returning - the caller must
       * do so when they are finished with the streams.  For example:
       * <pre>
       * try {
       *     InputStream in = ...
       *     OutputStream out = ...
       *     cipherService.decrypt(in, out, decryptionKey);
       * } finally {
       *     if (in != null) {
       *         try {
       *             in.close();
       *         } catch (IOException ioe1) { ... log, trigger event, etc. }
       *     }
       *     if (out != null) {
       *         try {
       *             out.close();
       *         } catch (IOException ioe2) { ... log, trigger event, etc. }
       *     }
       * }
       * </pre>
       *
       * @param in            the stream supplying the data to decrypt
       * @param out           the stream to send the decrypted data
       * @param decryptionKey the cipher key to use for decryption
       * @throws CryptoException if there is any problem during decryption.
       */
      void decrypt(InputStream in, OutputStream out, byte[] decryptionKey) throws CryptoException;
  
      /**
       * Encrypts data via the specified cipher key.  Note that the key must be in a format understood by
       * the {@code CipherService} implementation.
       *
       * @param raw           the data to encrypt
       * @param encryptionKey the cipher key used during encryption.
       * @return a byte source with the encrypted representation of the specified raw data.
       * @throws CryptoException if there is an error during encryption
       */
      ByteSource encrypt(byte[] raw, byte[] encryptionKey) throws CryptoException;
  
      /**
       * Receives the data from the given {@code InputStream}, encrypts it, and sends the resulting encrypted data to the
       * given {@code OutputStream}.
       * <p/>
       * <b>NOTE:</b> This method <em>does NOT</em> flush or close either stream prior to returning - the caller must
       * do so when they are finished with the streams.  For example:
       * <pre>
       * try {
       *     InputStream in = ...
       *     OutputStream out = ...
       *     cipherService.encrypt(in, out, encryptionKey);
       * } finally {
       *     if (in != null) {
       *         try {
       *             in.close();
       *         } catch (IOException ioe1) { ... log, trigger event, etc. }
       *     }
       *     if (out != null) {
       *         try {
       *             out.close();
       *         } catch (IOException ioe2) { ... log, trigger event, etc. }
       *     }
       * }
       * </pre>
       *
       * @param in            the stream supplying the data to encrypt
       * @param out           the stream to send the encrypted data
       * @param encryptionKey the cipher key to use for encryption
       * @throws CryptoException if there is any problem during encryption.
       */
      void encrypt(InputStream in, OutputStream out, byte[] encryptionKey) throws CryptoException;
  
  }
  