1 /* 2 * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.security; 27 28 /** 29 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>) 30 * for the {@link SecureRandom} class. 31 * <p> 32 * All the abstract methods in this class must be implemented by each 33 * service provider who wishes to supply the implementation 34 * of a cryptographically strong pseudo-random number generator. 35 * 36 * @implSpec 37 * If the {@link #SecureRandomSpi(SecureRandomParameters)} 38 * constructor is overridden in an implementation, it will always be called 39 * whenever a {@code SecureRandom} is instantiated. Precisely, if an object is 40 * instantiated with one of {@code SecureRandom}'s {@code getInstance} methods 41 * <em>without</em> a {@link SecureRandomParameters} parameter, 42 * the constructor will be called with a {@code null} argument and the 43 * implementation is responsible for creating its own 44 * {@code SecureRandomParameters} parameter for use when 45 * {@link #engineGetParameters()} is called. If an object 46 * is instantiated with one of {@code SecureRandom}'s {@code getInstance} 47 * methods <em>with</em> a {@code SecureRandomParameters} argument, 48 * the constructor will be called with that argument. The 49 * {@link #engineGetParameters()} method must not return {@code null}. 50 * <p> 51 * Otherwise, if the {@code SecureRandomSpi(SecureRandomParameters)} 52 * constructor is not overridden in an implementation, the 53 * {@link #SecureRandomSpi()} constructor must be overridden and it will be 54 * called if an object is instantiated with one of {@code SecureRandom}'s 55 * {@code getInstance} methods <em>without</em> a 56 * {@code SecureRandomParameters} argument. Calling one of 57 * {@code SecureRandom}'s {@code getInstance} methods <em>with</em> 58 * a {@code SecureRandomParameters} argument will never 59 * return an instance of this implementation. The 60 * {@link #engineGetParameters()} method must return {@code null}. 61 * <p> 62 * See {@link SecureRandom} for additional details on thread safety. By 63 * default, a {@code SecureRandomSpi} implementation is considered to be 64 * not safe for use by multiple concurrent threads and {@code SecureRandom} 65 * will synchronize access to each of the applicable engine methods 66 * (see {@link SecureRandom} for the list of methods). However, if a 67 * {@code SecureRandomSpi} implementation is thread-safe, the <a href= 68 * "{@docRoot}/../specs/security/standard-names.html#service-attributes"> 69 * service provider attribute</a> "ThreadSafe" should be set to "true" during 70 * its registration, as follows: 71 * <blockquote><pre> 72 * put("SecureRandom.AlgName ThreadSafe", "true");</pre> 73 * </blockquote> 74 * or 75 * <blockquote><pre> 76 * putService(new Service(this, "SecureRandom", "AlgName", className, 77 * null, Map.of("ThreadSafe", "true")));</pre> 78 * </blockquote> 79 * {@code SecureRandom} will call the applicable engine methods 80 * without any synchronization. 81 * 82 * @since 1.2 83 */ 84 85 public abstract class SecureRandomSpi implements java.io.Serializable { 86 87 private static final long serialVersionUID = -2991854161009191830L; 88 89 /** 90 * Constructor without a parameter. 91 */ SecureRandomSpi()92 public SecureRandomSpi() { 93 // ignored 94 } 95 96 /** 97 * Constructor with a parameter. 98 * 99 * @param params the {@link SecureRandomParameters} object. 100 * This argument can be {@code null}. 101 * @throws IllegalArgumentException if {@code params} is 102 * unrecognizable or unsupported by this {@code SecureRandom} 103 * 104 * @since 9 105 */ SecureRandomSpi(SecureRandomParameters params)106 protected SecureRandomSpi(SecureRandomParameters params) { 107 // ignored 108 } 109 110 /** 111 * Reseeds this random object with the given seed. The seed supplements, 112 * rather than replaces, the existing seed. Thus, repeated calls 113 * are guaranteed never to reduce randomness. 114 * 115 * @param seed the seed. 116 */ engineSetSeed(byte[] seed)117 protected abstract void engineSetSeed(byte[] seed); 118 119 /** 120 * Generates a user-specified number of random bytes. 121 * <p> 122 * Some random number generators can only generate a limited amount 123 * of random bytes per invocation. If the size of {@code bytes} 124 * is greater than this limit, the implementation should invoke 125 * its generation process multiple times to completely fill the 126 * buffer before returning from this method. 127 * 128 * @param bytes the array to be filled in with random bytes. 129 */ engineNextBytes(byte[] bytes)130 protected abstract void engineNextBytes(byte[] bytes); 131 132 /** 133 * Generates a user-specified number of random bytes with 134 * additional parameters. 135 * <p> 136 * Some random number generators can only generate a limited amount 137 * of random bytes per invocation. If the size of {@code bytes} 138 * is greater than this limit, the implementation should invoke 139 * its generation process multiple times to completely fill the 140 * buffer before returning from this method. 141 * 142 * @implSpec The default implementation throws 143 * an {@link UnsupportedOperationException}. 144 * 145 * @param bytes the array to be filled in with random bytes 146 * @param params additional parameters 147 * @throws UnsupportedOperationException if the implementation 148 * has not overridden this method 149 * @throws IllegalArgumentException if {@code params} is {@code null}, 150 * illegal or unsupported by this {@code SecureRandom} 151 * 152 * @since 9 153 */ engineNextBytes( byte[] bytes, SecureRandomParameters params)154 protected void engineNextBytes( 155 byte[] bytes, SecureRandomParameters params) { 156 throw new UnsupportedOperationException(); 157 } 158 159 /** 160 * Returns the given number of seed bytes. This call may be used to 161 * seed other random number generators. 162 * 163 * @param numBytes the number of seed bytes to generate. 164 * 165 * @return the seed bytes. 166 */ engineGenerateSeed(int numBytes)167 protected abstract byte[] engineGenerateSeed(int numBytes); 168 169 /** 170 * Reseeds this random object with entropy input read from its 171 * entropy source with additional parameters. 172 * <p> 173 * If this method is called by {@link SecureRandom#reseed()}, 174 * {@code params} will be {@code null}. 175 * <p> 176 * Do not override this method if the implementation does not 177 * support reseeding. 178 * 179 * @implSpec The default implementation throws 180 * an {@link UnsupportedOperationException}. 181 * 182 * @param params extra parameters, can be {@code null}. 183 * @throws UnsupportedOperationException if the implementation 184 * has not overridden this method 185 * @throws IllegalArgumentException if {@code params} is 186 * illegal or unsupported by this {@code SecureRandom} 187 * 188 * @since 9 189 */ engineReseed(SecureRandomParameters params)190 protected void engineReseed(SecureRandomParameters params) { 191 throw new UnsupportedOperationException(); 192 } 193 194 /** 195 * Returns the effective {@link SecureRandomParameters} for this 196 * {@code SecureRandom} instance. 197 * 198 * @implSpec The default implementation returns {@code null}. 199 * 200 * @return the effective {@link SecureRandomParameters} parameters, 201 * or {@code null} if no parameters were used. 202 * 203 * @since 9 204 */ engineGetParameters()205 protected SecureRandomParameters engineGetParameters() { 206 return null; 207 } 208 209 /** 210 * Returns a Human-readable string representation of this 211 * {@code SecureRandom}. 212 * 213 * @return the string representation 214 */ 215 @Override toString()216 public String toString() { 217 return getClass().getSimpleName(); 218 } 219 } 220