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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 | } | ||