J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2003-2004 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.security.provider; |
| 27 | |
| 28 | import java.io.*; |
| 29 | |
| 30 | import java.security.*; |
| 31 | import java.security.SecureRandom; |
| 32 | |
| 33 | /** |
| 34 | * Native PRNG implementation for Solaris/Linux. It interacts with |
| 35 | * /dev/random and /dev/urandom, so it is only available if those |
| 36 | * files are present. Otherwise, SHA1PRNG is used instead of this class. |
| 37 | * |
| 38 | * getSeed() and setSeed() directly read/write /dev/random. However, |
| 39 | * /dev/random is only writable by root in many configurations. Because |
| 40 | * we cannot just ignore bytes specified via setSeed(), we keep a |
| 41 | * SHA1PRNG around in parallel. |
| 42 | * |
| 43 | * nextBytes() reads the bytes directly from /dev/urandom (and then |
| 44 | * mixes them with bytes from the SHA1PRNG for the reasons explained |
| 45 | * above). Reading bytes from /dev/urandom means that constantly get |
| 46 | * new entropy the operating system has collected. This is a notable |
| 47 | * advantage over the SHA1PRNG model, which acquires entropy only |
| 48 | * initially during startup although the VM may be running for months. |
| 49 | * |
| 50 | * Also note that we do not need any initial pure random seed from |
| 51 | * /dev/random. This is an advantage because on some versions of Linux |
| 52 | * it can be exhausted very quickly and could thus impact startup time. |
| 53 | * |
| 54 | * Finally, note that we use a singleton for the actual work (RandomIO) |
| 55 | * to avoid having to open and close /dev/[u]random constantly. However, |
| 56 | * there may me many NativePRNG instances created by the JCA framework. |
| 57 | * |
| 58 | * @since 1.5 |
| 59 | * @author Andreas Sterbenz |
| 60 | */ |
| 61 | public final class NativePRNG extends SecureRandomSpi { |
| 62 | |
| 63 | private static final long serialVersionUID = -6599091113397072932L; |
| 64 | |
| 65 | // name of the pure random file (also used for setSeed()) |
| 66 | private static final String NAME_RANDOM = "/dev/random"; |
| 67 | // name of the pseudo random file |
| 68 | private static final String NAME_URANDOM = "/dev/urandom"; |
| 69 | |
| 70 | // singleton instance or null if not available |
| 71 | private static final RandomIO INSTANCE = initIO(); |
| 72 | |
| 73 | private static RandomIO initIO() { |
| 74 | Object o = AccessController.doPrivileged(new PrivilegedAction() { |
| 75 | public Object run() { |
| 76 | File randomFile = new File(NAME_RANDOM); |
| 77 | if (randomFile.exists() == false) { |
| 78 | return null; |
| 79 | } |
| 80 | File urandomFile = new File(NAME_URANDOM); |
| 81 | if (urandomFile.exists() == false) { |
| 82 | return null; |
| 83 | } |
| 84 | try { |
| 85 | return new RandomIO(randomFile, urandomFile); |
| 86 | } catch (Exception e) { |
| 87 | return null; |
| 88 | } |
| 89 | } |
| 90 | }); |
| 91 | return (RandomIO)o; |
| 92 | } |
| 93 | |
| 94 | // return whether the NativePRNG is available |
| 95 | static boolean isAvailable() { |
| 96 | return INSTANCE != null; |
| 97 | } |
| 98 | |
| 99 | // constructor, called by the JCA framework |
| 100 | public NativePRNG() { |
| 101 | super(); |
| 102 | if (INSTANCE == null) { |
| 103 | throw new AssertionError("NativePRNG not available"); |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | // set the seed |
| 108 | protected void engineSetSeed(byte[] seed) { |
| 109 | INSTANCE.implSetSeed(seed); |
| 110 | } |
| 111 | |
| 112 | // get pseudo random bytes |
| 113 | protected void engineNextBytes(byte[] bytes) { |
| 114 | INSTANCE.implNextBytes(bytes); |
| 115 | } |
| 116 | |
| 117 | // get true random bytes |
| 118 | protected byte[] engineGenerateSeed(int numBytes) { |
| 119 | return INSTANCE.implGenerateSeed(numBytes); |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * Nested class doing the actual work. Singleton, see INSTANCE above. |
| 124 | */ |
| 125 | private static class RandomIO { |
| 126 | |
| 127 | // we buffer data we read from /dev/urandom for efficiency, |
| 128 | // but we limit the lifetime to avoid using stale bits |
| 129 | // lifetime in ms, currently 100 ms (0.1 s) |
| 130 | private final static long MAX_BUFFER_TIME = 100; |
| 131 | |
| 132 | // size of the /dev/urandom buffer |
| 133 | private final static int BUFFER_SIZE = 32; |
| 134 | |
| 135 | // In/OutputStream for /dev/random and /dev/urandom |
| 136 | private final InputStream randomIn, urandomIn; |
| 137 | private OutputStream randomOut; |
| 138 | |
| 139 | // flag indicating if we have tried to open randomOut yet |
| 140 | private boolean randomOutInitialized; |
| 141 | |
| 142 | // SHA1PRNG instance for mixing |
| 143 | // initialized lazily on demand to avoid problems during startup |
| 144 | private volatile sun.security.provider.SecureRandom mixRandom; |
| 145 | |
| 146 | // buffer for /dev/urandom bits |
| 147 | private final byte[] urandomBuffer; |
| 148 | |
| 149 | // number of bytes left in urandomBuffer |
| 150 | private int buffered; |
| 151 | |
| 152 | // time we read the data into the urandomBuffer |
| 153 | private long lastRead; |
| 154 | |
| 155 | // mutex lock for nextBytes() |
| 156 | private final Object LOCK_GET_BYTES = new Object(); |
| 157 | |
| 158 | // mutex lock for getSeed() |
| 159 | private final Object LOCK_GET_SEED = new Object(); |
| 160 | |
| 161 | // mutex lock for setSeed() |
| 162 | private final Object LOCK_SET_SEED = new Object(); |
| 163 | |
| 164 | // constructor, called only once from initIO() |
| 165 | private RandomIO(File randomFile, File urandomFile) throws IOException { |
| 166 | randomIn = new FileInputStream(randomFile); |
| 167 | urandomIn = new FileInputStream(urandomFile); |
| 168 | urandomBuffer = new byte[BUFFER_SIZE]; |
| 169 | } |
| 170 | |
| 171 | // get the SHA1PRNG for mixing |
| 172 | // initialize if not yet created |
| 173 | private sun.security.provider.SecureRandom getMixRandom() { |
| 174 | sun.security.provider.SecureRandom r = mixRandom; |
| 175 | if (r == null) { |
| 176 | synchronized (LOCK_GET_BYTES) { |
| 177 | r = mixRandom; |
| 178 | if (r == null) { |
| 179 | r = new sun.security.provider.SecureRandom(); |
| 180 | try { |
| 181 | byte[] b = new byte[20]; |
| 182 | readFully(urandomIn, b); |
| 183 | r.engineSetSeed(b); |
| 184 | } catch (IOException e) { |
| 185 | throw new ProviderException("init failed", e); |
| 186 | } |
| 187 | mixRandom = r; |
| 188 | } |
| 189 | } |
| 190 | } |
| 191 | return r; |
| 192 | } |
| 193 | |
| 194 | // read data.length bytes from in |
| 195 | // /dev/[u]random are not normal files, so we need to loop the read. |
| 196 | // just keep trying as long as we are making progress |
| 197 | private static void readFully(InputStream in, byte[] data) |
| 198 | throws IOException { |
| 199 | int len = data.length; |
| 200 | int ofs = 0; |
| 201 | while (len > 0) { |
| 202 | int k = in.read(data, ofs, len); |
| 203 | if (k <= 0) { |
| 204 | throw new EOFException("/dev/[u]random closed?"); |
| 205 | } |
| 206 | ofs += k; |
| 207 | len -= k; |
| 208 | } |
| 209 | if (len > 0) { |
| 210 | throw new IOException("Could not read from /dev/[u]random"); |
| 211 | } |
| 212 | } |
| 213 | |
| 214 | // get true random bytes, just read from /dev/random |
| 215 | private byte[] implGenerateSeed(int numBytes) { |
| 216 | synchronized (LOCK_GET_SEED) { |
| 217 | try { |
| 218 | byte[] b = new byte[numBytes]; |
| 219 | readFully(randomIn, b); |
| 220 | return b; |
| 221 | } catch (IOException e) { |
| 222 | throw new ProviderException("generateSeed() failed", e); |
| 223 | } |
| 224 | } |
| 225 | } |
| 226 | |
| 227 | // supply random bytes to the OS |
| 228 | // write to /dev/random if possible |
| 229 | // always add the seed to our mixing random |
| 230 | private void implSetSeed(byte[] seed) { |
| 231 | synchronized (LOCK_SET_SEED) { |
| 232 | if (randomOutInitialized == false) { |
| 233 | randomOutInitialized = true; |
| 234 | randomOut = AccessController.doPrivileged( |
| 235 | new PrivilegedAction<OutputStream>() { |
| 236 | public OutputStream run() { |
| 237 | try { |
| 238 | return new FileOutputStream(NAME_RANDOM, true); |
| 239 | } catch (Exception e) { |
| 240 | return null; |
| 241 | } |
| 242 | } |
| 243 | }); |
| 244 | } |
| 245 | if (randomOut != null) { |
| 246 | try { |
| 247 | randomOut.write(seed); |
| 248 | } catch (IOException e) { |
| 249 | throw new ProviderException("setSeed() failed", e); |
| 250 | } |
| 251 | } |
| 252 | getMixRandom().engineSetSeed(seed); |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | // ensure that there is at least one valid byte in the buffer |
| 257 | // if not, read new bytes |
| 258 | private void ensureBufferValid() throws IOException { |
| 259 | long time = System.currentTimeMillis(); |
| 260 | if ((buffered > 0) && (time - lastRead < MAX_BUFFER_TIME)) { |
| 261 | return; |
| 262 | } |
| 263 | lastRead = time; |
| 264 | readFully(urandomIn, urandomBuffer); |
| 265 | buffered = urandomBuffer.length; |
| 266 | } |
| 267 | |
| 268 | // get pseudo random bytes |
| 269 | // read from /dev/urandom and XOR with bytes generated by the |
| 270 | // mixing SHA1PRNG |
| 271 | private void implNextBytes(byte[] data) { |
| 272 | synchronized (LOCK_GET_BYTES) { |
| 273 | try { |
| 274 | getMixRandom().engineNextBytes(data); |
| 275 | int len = data.length; |
| 276 | int ofs = 0; |
| 277 | while (len > 0) { |
| 278 | ensureBufferValid(); |
| 279 | int bufferOfs = urandomBuffer.length - buffered; |
| 280 | while ((len > 0) && (buffered > 0)) { |
| 281 | data[ofs++] ^= urandomBuffer[bufferOfs++]; |
| 282 | len--; |
| 283 | buffered--; |
| 284 | } |
| 285 | } |
| 286 | } catch (IOException e) { |
| 287 | throw new ProviderException("nextBytes() failed", e); |
| 288 | } |
| 289 | } |
| 290 | } |
| 291 | |
| 292 | } |
| 293 | |
| 294 | } |