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| 1 | +/* | |
| 2 | + * Copyright (c) 1998, 2003, 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 sun.security.provider; | |
| 27 | + | |
| 28 | +import java.io.IOException; | |
| 29 | +import java.security.MessageDigest; | |
| 30 | +import java.security.SecureRandomSpi; | |
| 31 | +import java.security.NoSuchAlgorithmException; | |
| 32 | + | |
| 33 | +/** | |
| 34 | + * <p>This class provides a crytpographically strong pseudo-random number | |
| 35 | + * generator based on the SHA-1 hash algorithm. | |
| 36 | + * | |
| 37 | + * <p>Note that if a seed is not provided, we attempt to provide sufficient | |
| 38 | + * seed bytes to completely randomize the internal state of the generator | |
| 39 | + * (20 bytes). However, our seed generation algorithm has not been thoroughly | |
| 40 | + * studied or widely deployed. | |
| 41 | + * | |
| 42 | + * <p>Also note that when a random object is deserialized, | |
| 43 | + * <a href="#engineNextBytes(byte[])">engineNextBytes</a> invoked on the | |
| 44 | + * restored random object will yield the exact same (random) bytes as the | |
| 45 | + * original object. If this behaviour is not desired, the restored random | |
| 46 | + * object should be seeded, using | |
| 47 | + * <a href="#engineSetSeed(byte[])">engineSetSeed</a>. | |
| 48 | + * | |
| 49 | + * @author Benjamin Renaud | |
| 50 | + * @author Josh Bloch | |
| 51 | + * @author Gadi Guy | |
| 52 | + */ | |
| 53 | + | |
| 54 | +public final class SecureRandom extends SecureRandomSpi | |
| 55 | +implements java.io.Serializable { | |
| 56 | + | |
| 57 | + private static final long serialVersionUID = 3581829991155417889L; | |
| 58 | + | |
| 59 | + /** | |
| 60 | + * This static object will be seeded by SeedGenerator, and used | |
| 61 | + * to seed future instances of SecureRandom | |
| 62 | + */ | |
| 63 | + private static SecureRandom seeder; | |
| 64 | + | |
| 65 | + private static final int DIGEST_SIZE = 20; | |
| 66 | + private transient MessageDigest digest; | |
| 67 | + private byte[] state; | |
| 68 | + private byte[] remainder; | |
| 69 | + private int remCount; | |
| 70 | + | |
| 71 | + /** | |
| 72 | + * This empty constructor automatically seeds the generator. We attempt | |
| 73 | + * to provide sufficient seed bytes to completely randomize the internal | |
| 74 | + * state of the generator (20 bytes). Note, however, that our seed | |
| 75 | + * generation algorithm has not been thoroughly studied or widely deployed. | |
| 76 | + * | |
| 77 | + * <p>The first time this constructor is called in a given Virtual Machine, | |
| 78 | + * it may take several seconds of CPU time to seed the generator, depending | |
| 79 | + * on the underlying hardware. Successive calls run quickly because they | |
| 80 | + * rely on the same (internal) pseudo-random number generator for their | |
| 81 | + * seed bits. | |
| 82 | + */ | |
| 83 | + public SecureRandom() { | |
| 84 | + init(null); | |
| 85 | + } | |
| 86 | + | |
| 87 | + /** | |
| 88 | + * This constructor is used to instatiate the private seeder object | |
| 89 | + * with a given seed from the SeedGenerator. | |
| 90 | + * | |
| 91 | + * @param seed the seed. | |
| 92 | + */ | |
| 93 | + private SecureRandom(byte seed[]) { | |
| 94 | + init(seed); | |
| 95 | + } | |
| 96 | + | |
| 97 | + /** | |
| 98 | + * This call, used by the constructors, instantiates the SHA digest | |
| 99 | + * and sets the seed, if given. | |
| 100 | + */ | |
| 101 | + private void init(byte[] seed) { | |
| 102 | + try { | |
| 103 | + digest = MessageDigest.getInstance ("SHA"); | |
| 104 | + } catch (NoSuchAlgorithmException e) { | |
| 105 | + throw new InternalError("internal error: SHA-1 not available."); | |
| 106 | + } | |
| 107 | + | |
| 108 | + if (seed != null) { | |
| 109 | + engineSetSeed(seed); | |
| 110 | + } | |
| 111 | + } | |
| 112 | + | |
| 113 | + /** | |
| 114 | + * Returns the given number of seed bytes, computed using the seed | |
| 115 | + * generation algorithm that this class uses to seed itself. This | |
| 116 | + * call may be used to seed other random number generators. While | |
| 117 | + * we attempt to return a "truly random" sequence of bytes, we do not | |
| 118 | + * know exactly how random the bytes returned by this call are. (See | |
| 119 | + * the empty constructor <a href = "#SecureRandom">SecureRandom</a> | |
| 120 | + * for a brief description of the underlying algorithm.) | |
| 121 | + * The prudent user will err on the side of caution and get extra | |
| 122 | + * seed bytes, although it should be noted that seed generation is | |
| 123 | + * somewhat costly. | |
| 124 | + * | |
| 125 | + * @param numBytes the number of seed bytes to generate. | |
| 126 | + * | |
| 127 | + * @return the seed bytes. | |
| 128 | + */ | |
| 129 | + public byte[] engineGenerateSeed(int numBytes) { | |
| 130 | + byte[] b = new byte[numBytes]; | |
| 131 | + SeedGenerator.generateSeed(b); | |
| 132 | + return b; | |
| 133 | + } | |
| 134 | + | |
| 135 | + /** | |
| 136 | + * Reseeds this random object. The given seed supplements, rather than | |
| 137 | + * replaces, the existing seed. Thus, repeated calls are guaranteed | |
| 138 | + * never to reduce randomness. | |
| 139 | + * | |
| 140 | + * @param seed the seed. | |
| 141 | + */ | |
| 142 | + synchronized public void engineSetSeed(byte[] seed) { | |
| 143 | + if (state != null) { | |
| 144 | + digest.update(state); | |
| 145 | + for (int i = 0; i < state.length; i++) | |
| 146 | + state[i] = 0; | |
| 147 | + } | |
| 148 | + state = digest.digest(seed); | |
| 149 | + } | |
| 150 | + | |
| 151 | + private static void updateState(byte[] state, byte[] output) { | |
| 152 | + int last = 1; | |
| 153 | + int v = 0; | |
| 154 | + byte t = 0; | |
| 155 | + boolean zf = false; | |
| 156 | + | |
| 157 | + // state(n + 1) = (state(n) + output(n) + 1) % 2^160; | |
| 158 | + for (int i = 0; i < state.length; i++) { | |
| 159 | + // Add two bytes | |
| 160 | + v = (int)state[i] + (int)output[i] + last; | |
| 161 | + // Result is lower 8 bits | |
| 162 | + t = (byte)v; | |
| 163 | + // Store result. Check for state collision. | |
| 164 | + zf = zf | (state[i] != t); | |
| 165 | + state[i] = t; | |
| 166 | + // High 8 bits are carry. Store for next iteration. | |
| 167 | + last = v >> 8; | |
| 168 | + } | |
| 169 | + | |
| 170 | + // Make sure at least one bit changes! | |
| 171 | + if (!zf) | |
| 172 | + state[0]++; | |
| 173 | + } | |
| 174 | + | |
| 175 | + /** | |
| 176 | + * Generates a user-specified number of random bytes. | |
| 177 | + * | |
| 178 | + * @param bytes the array to be filled in with random bytes. | |
| 179 | + */ | |
| 180 | + public synchronized void engineNextBytes(byte[] result) { | |
| 181 | + int index = 0; | |
| 182 | + int todo; | |
| 183 | + byte[] output = remainder; | |
| 184 | + | |
| 185 | + if (state == null) { | |
| 186 | + if (seeder == null) { | |
| 187 | + seeder = new SecureRandom(SeedGenerator.getSystemEntropy()); | |
| 188 | + seeder.engineSetSeed(engineGenerateSeed(DIGEST_SIZE)); | |
| 189 | + } | |
| 190 | + | |
| 191 | + byte[] seed = new byte[DIGEST_SIZE]; | |
| 192 | + seeder.engineNextBytes(seed); | |
| 193 | + state = digest.digest(seed); | |
| 194 | + } | |
| 195 | + | |
| 196 | + // Use remainder from last time | |
| 197 | + int r = remCount; | |
| 198 | + if (r > 0) { | |
| 199 | + // How many bytes? | |
| 200 | + todo = (result.length - index) < (DIGEST_SIZE - r) ? | |
| 201 | + (result.length - index) : (DIGEST_SIZE - r); | |
| 202 | + // Copy the bytes, zero the buffer | |
| 203 | + for (int i = 0; i < todo; i++) { | |
| 204 | + result[i] = output[r]; | |
| 205 | + output[r++] = 0; | |
| 206 | + } | |
| 207 | + remCount += todo; | |
| 208 | + index += todo; | |
| 209 | + } | |
| 210 | + | |
| 211 | + // If we need more bytes, make them. | |
| 212 | + while (index < result.length) { | |
| 213 | + // Step the state | |
| 214 | + digest.update(state); | |
| 215 | + output = digest.digest(); | |
| 216 | + updateState(state, output); | |
| 217 | + | |
| 218 | + // How many bytes? | |
| 219 | + todo = (result.length - index) > DIGEST_SIZE ? | |
| 220 | + DIGEST_SIZE : result.length - index; | |
| 221 | + // Copy the bytes, zero the buffer | |
| 222 | + for (int i = 0; i < todo; i++) { | |
| 223 | + result[index++] = output[i]; | |
| 224 | + output[i] = 0; | |
| 225 | + } | |
| 226 | + remCount += todo; | |
| 227 | + } | |
| 228 | + | |
| 229 | + // Store remainder for next time | |
| 230 | + remainder = output; | |
| 231 | + remCount %= DIGEST_SIZE; | |
| 232 | + } | |
| 233 | + | |
| 234 | + /* | |
| 235 | + * readObject is called to restore the state of the random object from | |
| 236 | + * a stream. We have to create a new instance of MessageDigest, because | |
| 237 | + * it is not included in the stream (it is marked "transient"). | |
| 238 | + * | |
| 239 | + * Note that the engineNextBytes() method invoked on the restored random | |
| 240 | + * object will yield the exact same (random) bytes as the original. | |
| 241 | + * If you do not want this behaviour, you should re-seed the restored | |
| 242 | + * random object, using engineSetSeed(). | |
| 243 | + */ | |
| 244 | + private void readObject(java.io.ObjectInputStream s) | |
| 245 | + throws IOException, ClassNotFoundException { | |
| 246 | + | |
| 247 | + s.defaultReadObject (); | |
| 248 | + | |
| 249 | + try { | |
| 250 | + digest = MessageDigest.getInstance ("SHA"); | |
| 251 | + } catch (NoSuchAlgorithmException e) { | |
| 252 | + throw new InternalError("internal error: SHA-1 not available."); | |
| 253 | + } | |
| 254 | + } | |
| 255 | +} | |