Java tutorial
/* * 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; import org.apache.shiro.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 */ ByteSource 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; }