001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.shiro.crypto.hash;
020
021/**
022 * A {@code HashService} hashes input sources utilizing a particular hashing strategy.
023 * <p/>
024 * A {@code HashService} sits at a higher architectural level than Shiro's simple {@link Hash} classes:  it allows
025 * for salting and iteration-related strategies to be configured and internalized in a
026 * single component that can be re-used in multiple places in the application.
027 * <p/>
028 * For example, for the most secure hashes, it is highly recommended to use a randomly generated salt, potentially
029 * paired with an configuration-specific private salt, in addition to using multiple hash iterations.
030 * <p/>
031 * While one can do this easily enough using Shiro's {@link Hash} implementations directly, this direct approach could
032 * quickly lead to copy-and-paste behavior.  For example, consider this logic which might need to repeated in an
033 * application:
034 * <pre>
035 * int numHashIterations = ...
036 * ByteSource privateSalt = ...
037 * ByteSource randomSalt = {@link org.apache.shiro.crypto.RandomNumberGenerator randomNumberGenerator}.nextBytes();
038 * ByteSource combined = combine(privateSalt, randomSalt);
039 * Hash hash = Sha512Hash(source, combined, numHashIterations);
040 * save(hash);
041 * </pre>
042 * In this example, often only the input source will change during runtime, while the hashing strategy (how salts
043 * are generated or acquired, how many hash iterations will be performed, etc.) usually remain consistent.  A HashService
044 * internalizes this logic so the above becomes simply this:
045 * <pre>
046 * HashRequest request = new HashRequest.Builder().source(source).build();
047 * Hash result = hashService.hash(request);
048 * save(result);
049 * </pre>
050 *
051 * @since 1.2
052 */
053public interface HashService {
054
055    /**
056     * Computes a hash based on the given request.
057     *
058     * <h3>Salt Notice</h3>
059     * <p>
060     * If a salt accompanies the return value
061     * (i.e. <code>returnedHash.{@link org.apache.shiro.crypto.hash.Hash#getSalt() getSalt()} != null</code>), this
062     * same exact salt <b><em>MUST</em></b> be presented back to the {@code HashService} if hash
063     * comparison/verification will be performed at a later time (for example, for password hash or file checksum
064     * comparison).
065     * <p/>
066     * For additional security, the {@code HashService}'s internal implementation may use more complex salting
067     * strategies than what would be achieved by computing a {@code Hash} manually.
068     * <p/>
069     * In summary, if a {@link HashService} returns a salt in a returned Hash, it is expected that the same salt
070     * will be provided to the same {@code HashService} instance.
071     *
072     * @param request the request to process
073     * @return the hashed data
074     * @see Hash#getSalt()
075     */
076    Hash computeHash(HashRequest request);
077
078    /**
079     * @return Default algorithm name for this hash service
080     * @since 2.0
081     */
082    String getDefaultAlgorithmName();
083}