1 /*
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  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 /**
 29  * This class generates seeds for the SHA1PRNG cryptographically strong
 30  * random number generator.
 31  * <p>
 32  * The seed is produced using one of two techniques, via a computation
 33  * of current system activity or from an entropy gathering device.
 34  * <p>
 35  * In the default technique the seed is produced by counting the
 36  * number of times the VM manages to loop in a given period. This number
 37  * roughly reflects the machine load at that point in time.
 38  * The samples are translated using a permutation (s-box)
 39  * and then XORed together. This process is non linear and
 40  * should prevent the samples from "averaging out". The s-box
 41  * was designed to have even statistical distribution; it's specific
 42  * values are not crucial for the security of the seed.
 43  * We also create a number of sleeper threads which add entropy
 44  * to the system by keeping the scheduler busy.
 45  * Twenty such samples should give us roughly 160 bits of randomness.
 46  * <p>
 47  * These values are gathered in the background by a daemon thread
 48  * thus allowing the system to continue performing it's different
 49  * activites, which in turn add entropy to the random seed.
 50  * <p>
 51  * The class also gathers miscellaneous system information, some
 52  * machine dependent, some not. This information is then hashed together
 53  * with the 20 seed bytes.
 54  * <p>
 55  * The alternative to the above approach is to acquire seed material
 56  * from an entropy gathering device, such as /dev/random. This can be
 57  * accomplished by setting the value of the {@code securerandom.source}
 58  * Security property to a URL specifying the location of the entropy
 59  * gathering device, or by setting the {@code java.security.egd} System
 60  * property.
 61  * <p>
 62  * In the event the specified URL cannot be accessed the default
 63  * threading mechanism is used.
 64  *
 65  * @author Joshua Bloch
 66  * @author Gadi Guy
 67  */
 68 
 69 import java.security.*;
 70 import java.io.*;
 71 import java.util.Properties;
 72 import java.util.Enumeration;
 73 import java.net.*;
 74 import java.nio.file.DirectoryStream;
 75 import java.nio.file.Files;
 76 import java.nio.file.Path;
 77 import java.util.Random;
 78 import sun.security.util.Debug;
 79 
 80 abstract class SeedGenerator {
 81 
 82     // Static instance is created at link time
 83     private static SeedGenerator instance;
 84 
 85     private static final Debug debug = Debug.getInstance("provider");
 86 
 87     // Static initializer to hook in selected or best performing generator
 88     static {
 89         String egdSource = SunEntries.getSeedSource();
 90 
 91         /*
 92          * Try the URL specifying the source (e.g. file:/dev/random)
 93          *
 94          * The URLs "file:/dev/random" or "file:/dev/urandom" are used to
 95          * indicate the SeedGenerator should use OS support, if available.
 96          *
 97          * On Windows, this causes the MS CryptoAPI seeder to be used.
 98          *
 99          * On Solaris/Linux/MacOS, this is identical to using
100          * URLSeedGenerator to read from /dev/[u]random
101          */
102         if (egdSource.equals(SunEntries.URL_DEV_RANDOM) ||
103                 egdSource.equals(SunEntries.URL_DEV_URANDOM)) {
104             try {
105                 instance = new NativeSeedGenerator(egdSource);
106                 if (debug != null) {
107                     debug.println(
108                         "Using operating system seed generator" + egdSource);
109                 }
110             } catch (IOException e) {
111                 if (debug != null) {
112                     debug.println("Failed to use operating system seed "
113                                   + "generator: " + e.toString());
114                 }
115             }
116         } else if (!egdSource.isEmpty()) {
117             try {
118                 instance = new URLSeedGenerator(egdSource);
119                 if (debug != null) {
120                     debug.println("Using URL seed generator reading from "
121                                   + egdSource);
122                 }
123             } catch (IOException e) {
124                 if (debug != null) {
125                     debug.println("Failed to create seed generator with "
126                                   + egdSource + ": " + e.toString());
127                 }
128             }
129         }
130 
131         // Fall back to ThreadedSeedGenerator
132         if (instance == null) {
133             if (debug != null) {
134                 debug.println("Using default threaded seed generator");
135             }
136             instance = new ThreadedSeedGenerator();
137         }
138     }
139 
140     /**
141      * Fill result with bytes from the queue. Wait for it if it isn't ready.
142      */
143     public static void generateSeed(byte[] result) {
144         instance.getSeedBytes(result);
145     }
146 
147     abstract void getSeedBytes(byte[] result);
148 
149     /**
150      * Retrieve some system information, hashed.
151      */
152     @SuppressWarnings("removal")
153     static byte[] getSystemEntropy() {
154         final MessageDigest md;
155 
156         try {
157             md = MessageDigest.getInstance("SHA");
158         } catch (NoSuchAlgorithmException nsae) {
159             throw new InternalError("internal error: SHA-1 not available.",
160                     nsae);
161         }
162 
163         // The current time in millis
164         byte b =(byte)System.currentTimeMillis();
165         md.update(b);
166 
167         java.security.AccessController.doPrivileged
168             (new java.security.PrivilegedAction<>() {
169                 @Override
170                 public Void run() {
171                     try {
172                         // System properties can change from machine to machine
173                         Properties p = System.getProperties();
174                         for (String s: p.stringPropertyNames()) {
175                             md.update(s.getBytes());
176                             md.update(p.getProperty(s).getBytes());
177                         }
178 
179                         // Include network adapter names (and a Mac address)
180                         addNetworkAdapterInfo(md);
181 
182                         // The temporary dir
183                         File f = new File(p.getProperty("java.io.tmpdir"));
184                         int count = 0;
185                         try (
186                             DirectoryStream<Path> stream =
187                                 Files.newDirectoryStream(f.toPath())) {
188                             // We use a Random object to choose what file names
189                             // should be used. Otherwise on a machine with too
190                             // many files, the same first 1024 files always get
191                             // used. Any, We make sure the first 512 files are
192                             // always used.
193                             Random r = new Random();
194                             for (Path entry: stream) {
195                                 if (count < 512 || r.nextBoolean()) {
196                                     md.update(entry.getFileName()
197                                         .toString().getBytes());
198                                 }
199                                 if (count++ > 1024) {
200                                     break;
201                                 }
202                             }
203                         }
204                     } catch (Exception ex) {
205                         md.update((byte)ex.hashCode());
206                     }
207 
208                     // get Runtime memory stats
209                     Runtime rt = Runtime.getRuntime();
210                     byte[] memBytes = longToByteArray(rt.totalMemory());
211                     md.update(memBytes, 0, memBytes.length);
212                     memBytes = longToByteArray(rt.freeMemory());
213                     md.update(memBytes, 0, memBytes.length);
214 
215                     return null;
216                 }
217             });
218         return md.digest();
219     }
220 
221     /*
222      * Include network adapter names and, if available, a Mac address
223      *
224      * See also java.util.concurrent.ThreadLocalRandom.initialSeed()
225      */
226     private static void addNetworkAdapterInfo(MessageDigest md) {
227 
228         try {
229             Enumeration<NetworkInterface> ifcs =
230                 NetworkInterface.getNetworkInterfaces();
231             while (ifcs.hasMoreElements()) {
232                 NetworkInterface ifc = ifcs.nextElement();
233                 md.update(ifc.toString().getBytes());
234                 if (!ifc.isVirtual()) { // skip fake addresses
235                     byte[] bs = ifc.getHardwareAddress();
236                     if (bs != null) {
237                         md.update(bs);
238                         break;
239                     }
240                 }
241             }
242         } catch (Exception ignore) {
243         }
244     }
245 
246     /**
247      * Helper function to convert a long into a byte array (least significant
248      * byte first).
249      */
250     private static byte[] longToByteArray(long l) {
251         byte[] retVal = new byte[8];
252 
253         for (int i=0; i<8; i++) {
254             retVal[i] = (byte) l;
255             l >>= 8;
256         }
257 
258         return retVal;
259     }
260 
261     /*
262     // This method helps the test utility receive unprocessed seed bytes.
263     public static int genTestSeed() {
264         return myself.getByte();
265     }
266     */
267 
268 
269     private static class ThreadedSeedGenerator extends SeedGenerator
270             implements Runnable {
271         // Queue is used to collect seed bytes
272         private byte[] pool;
273         private int start, end, count;
274 
275         // Thread group for our threads
276         ThreadGroup seedGroup;
277 
278         /**
279          * The constructor is only called once to construct the one
280          * instance we actually use. It instantiates the message digest
281          * and starts the thread going.
282          */
283         ThreadedSeedGenerator() {
284             pool = new byte[20];
285             start = end = 0;
286 
287             MessageDigest digest;
288 
289             try {
290                 digest = MessageDigest.getInstance("SHA");
291             } catch (NoSuchAlgorithmException e) {
292                 throw new InternalError("internal error: SHA-1 not available."
293                         , e);
294             }
295 
296             final ThreadGroup[] finalsg = new ThreadGroup[1];
297             @SuppressWarnings("removal")
298             Thread t = java.security.AccessController.doPrivileged
299                 (new java.security.PrivilegedAction<>() {
300                         @Override
301                         public Thread run() {
302                             ThreadGroup parent, group =
303                                 Thread.currentThread().getThreadGroup();
304                             while ((parent = group.getParent()) != null) {
305                                 group = parent;
306                             }
307                             finalsg[0] = new ThreadGroup
308                                 (group, "SeedGenerator ThreadGroup");
309                             Thread newT = new Thread(finalsg[0],
310                                 ThreadedSeedGenerator.this,
311                                 "SeedGenerator Thread",
312                                 0,
313                                 false);
314                             newT.setPriority(Thread.MIN_PRIORITY);
315                             newT.setDaemon(true);
316                             return newT;
317                         }
318                     });
319             seedGroup = finalsg[0];
320             t.start();
321         }
322 
323         /**
324          * This method does the actual work. It collects random bytes and
325          * pushes them into the queue.
326          */
327         @Override
328         public final void run() {
329             try {
330                 while (true) {
331                     // Queue full? Wait till there's room.
332                     synchronized(this) {
333                         while (count >= pool.length) {
334                             wait();
335                         }
336                     }
337 
338                     int counter, quanta;
339                     byte v = 0;
340 
341                     // Spin count must not be under 64000
342                     for (counter = quanta = 0;
343                             (counter < 64000) && (quanta < 6); quanta++) {
344 
345                         // Start some noisy threads
346                         try {
347                             BogusThread bt = new BogusThread();
348                             Thread t = new Thread
349                                 (seedGroup, bt, "SeedGenerator Thread", 0,
350                                         false);
351                             t.start();
352                         } catch (Exception e) {
353                             throw new InternalError("internal error: " +
354                                 "SeedGenerator thread creation error.", e);
355                         }
356 
357                         // We wait 250milli quanta, so the minimum wait time
358                         // cannot be under 250milli.
359                         int latch = 0;
360                         long startTime = System.nanoTime();
361                         while (System.nanoTime() - startTime < 250000000) {
362                             synchronized(this){};
363                             // Mask the sign bit and keep latch non-negative
364                             latch = (latch + 1) & 0x1FFFFFFF;
365                         }
366 
367                         // Translate the value using the permutation, and xor
368                         // it with previous values gathered.
369                         v ^= rndTab[latch % 255];
370                         counter += latch;
371                     }
372 
373                     // Push it into the queue and notify anybody who might
374                     // be waiting for it.
375                     synchronized(this) {
376                         pool[end] = v;
377                         end++;
378                         count++;
379                         if (end >= pool.length) {
380                             end = 0;
381                         }
382 
383                         notifyAll();
384                     }
385                 }
386             } catch (Exception e) {
387                 throw new InternalError("internal error: " +
388                     "SeedGenerator thread generated an exception.", e);
389             }
390         }
391 
392         @Override
393         void getSeedBytes(byte[] result) {
394             for (int i = 0; i < result.length; i++) {
395                 result[i] = getSeedByte();
396             }
397         }
398 
399         byte getSeedByte() {
400             byte b;
401 
402             try {
403                 // Wait for it...
404                 synchronized(this) {
405                     while (count <= 0) {
406                         wait();
407                     }
408                 }
409             } catch (Exception e) {
410                 if (count <= 0) {
411                     throw new InternalError("internal error: " +
412                         "SeedGenerator thread generated an exception.", e);
413                 }
414             }
415 
416             synchronized(this) {
417                 // Get it from the queue
418                 b = pool[start];
419                 pool[start] = 0;
420                 start++;
421                 count--;
422                 if (start == pool.length) {
423                     start = 0;
424                 }
425 
426                 // Notify the daemon thread, just in case it is
427                 // waiting for us to make room in the queue.
428                 notifyAll();
429             }
430 
431             return b;
432         }
433 
434         // The permutation was calculated by generating 64k of random
435         // data and using it to mix the trivial permutation.
436         // It should be evenly distributed. The specific values
437         // are not crucial to the security of this class.
438         private static final byte[] rndTab = {
439             56, 30, -107, -6, -86, 25, -83, 75, -12, -64,
440             5, -128, 78, 21, 16, 32, 70, -81, 37, -51,
441             -43, -46, -108, 87, 29, 17, -55, 22, -11, -111,
442             -115, 84, -100, 108, -45, -15, -98, 72, -33, -28,
443             31, -52, -37, -117, -97, -27, 93, -123, 47, 126,
444             -80, -62, -93, -79, 61, -96, -65, -5, -47, -119,
445             14, 89, 81, -118, -88, 20, 67, -126, -113, 60,
446             -102, 55, 110, 28, 85, 121, 122, -58, 2, 45,
447             43, 24, -9, 103, -13, 102, -68, -54, -101, -104,
448             19, 13, -39, -26, -103, 62, 77, 51, 44, 111,
449             73, 18, -127, -82, 4, -30, 11, -99, -74, 40,
450             -89, 42, -76, -77, -94, -35, -69, 35, 120, 76,
451             33, -73, -7, 82, -25, -10, 88, 125, -112, 58,
452             83, 95, 6, 10, 98, -34, 80, 15, -91, 86,
453             -19, 52, -17, 117, 49, -63, 118, -90, 36, -116,
454             -40, -71, 97, -53, -109, -85, 109, -16, -3, 104,
455             -95, 68, 54, 34, 26, 114, -1, 106, -121, 3,
456             66, 0, 100, -84, 57, 107, 119, -42, 112, -61,
457             1, 48, 38, 12, -56, -57, 39, -106, -72, 41,
458             7, 71, -29, -59, -8, -38, 79, -31, 124, -124,
459             8, 91, 116, 99, -4, 9, -36, -78, 63, -49,
460             -67, -87, 59, 101, -32, 92, 94, 53, -41, 115,
461             -66, -70, -122, 50, -50, -22, -20, -18, -21, 23,
462             -2, -48, 96, 65, -105, 123, -14, -110, 69, -24,
463             -120, -75, 74, 127, -60, 113, 90, -114, 105, 46,
464             27, -125, -23, -44, 64
465         };
466 
467         /**
468          * This inner thread causes the thread scheduler to become 'noisy',
469          * thus adding entropy to the system load.
470          * At least one instance of this class is generated for every seed byte.
471          */
472         private static class BogusThread implements Runnable {
473             @Override
474             public final void run() {
475                 try {
476                     for (int i = 0; i < 5; i++) {
477                         Thread.sleep(50);
478                     }
479                     // System.gc();
480                 } catch (Exception e) {
481                 }
482             }
483         }
484     }
485 
486     static class URLSeedGenerator extends SeedGenerator {
487 
488         private String deviceName;
489         private InputStream seedStream;
490 
491         /**
492          * The constructor is only called once to construct the one
493          * instance we actually use. It opens the entropy gathering device
494          * which will supply the randomness.
495          */
496 
497         URLSeedGenerator(String egdurl) throws IOException {
498         if (egdurl == null) {
499                 throw new IOException("No random source specified");
500             }
501             deviceName = egdurl;
502             init();
503         }
504 
505         @SuppressWarnings("removal")
506         private void init() throws IOException {
507             final URL device = new URL(deviceName);
508             try {
509                 seedStream = java.security.AccessController.doPrivileged
510                     (new java.security.PrivilegedExceptionAction<>() {
511                         @Override
512                         public InputStream run() throws IOException {
513                             /*
514                              * return a shared InputStream for file URLs and
515                              * avoid buffering.
516                              * The URL.openStream() call wraps InputStream in a
517                              * BufferedInputStream which
518                              * can buffer up to 8K bytes. This read is a
519                              * performance issue for entropy sources which
520                              * can be slow to replenish.
521                              */
522                             if (device.getProtocol().equalsIgnoreCase("file")) {
523                                 File deviceFile =
524                                     SunEntries.getDeviceFile(device);
525                                 return FileInputStreamPool
526                                     .getInputStream(deviceFile);
527                             } else {
528                                 return device.openStream();
529                             }
530                         }
531                     });
532             } catch (Exception e) {
533                 throw new IOException(
534                     "Failed to open " + deviceName, e.getCause());
535             }
536         }
537 
538         @Override
539         void getSeedBytes(byte[] result) {
540             int len = result.length;
541             int read = 0;
542             try {
543                 while (read < len) {
544                     int count = seedStream.read(result, read, len - read);
545                     // /dev/random blocks - should never have EOF
546                     if (count < 0) {
547                         throw new InternalError(
548                             "URLSeedGenerator " + deviceName +
549                             " reached end of file");
550                     }
551                     read += count;
552                 }
553             } catch (IOException ioe) {
554                 throw new InternalError("URLSeedGenerator " + deviceName +
555                     " generated exception: " + ioe.getMessage(), ioe);
556             }
557         }
558     }
559 }