1 /*
2 * Copyright (c) 1996, 2014, 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 import java.util.*;
29 import java.util.regex.*;
30
31 import java.security.Provider.Service;
32
33 import sun.security.jca.*;
34 import sun.security.jca.GetInstance.Instance;
35 import sun.security.util.Debug;
36
37 /**
38 * This class provides a cryptographically strong random number
39 * generator (RNG).
40 *
41 * <p>A cryptographically strong random number
42 * minimally complies with the statistical random number generator tests
43 * specified in
44 * <a href="http://csrc.nist.gov/publications/fips/fips140-2/fips1402.pdf">
45 * <i>FIPS 140-2, Security Requirements for Cryptographic Modules</i></a>,
46 * section 4.9.1.
47 * Additionally, SecureRandom must produce non-deterministic output.
48 * Therefore any seed material passed to a SecureRandom object must be
49 * unpredictable, and all SecureRandom output sequences must be
50 * cryptographically strong, as described in
51 * <a href="http://tools.ietf.org/html/rfc4086">
52 * <i>RFC 4086: Randomness Requirements for Security</i></a>.
53 *
54 * <p>A caller obtains a SecureRandom instance via the
55 * no-argument constructor or one of the {@code getInstance} methods:
56 *
57 * <pre>
58 * SecureRandom random = new SecureRandom();
59 * </pre>
60 *
61 * <p> Many SecureRandom implementations are in the form of a pseudo-random
62 * number generator (PRNG), which means they use a deterministic algorithm
63 * to produce a pseudo-random sequence from a true random seed.
64 * Other implementations may produce true random numbers,
65 * and yet others may use a combination of both techniques.
66 *
67 * <p> Typical callers of SecureRandom invoke the following methods
68 * to retrieve random bytes:
69 *
70 * <pre>
71 * SecureRandom random = new SecureRandom();
72 * byte bytes[] = new byte[20];
73 * random.nextBytes(bytes);
74 * </pre>
75 *
76 * <p> Callers may also invoke the {@code generateSeed} method
77 * to generate a given number of seed bytes (to seed other random number
78 * generators, for example):
79 * <pre>
80 * byte seed[] = random.generateSeed(20);
81 * </pre>
82 *
83 * Note: Depending on the implementation, the {@code generateSeed} and
84 * {@code nextBytes} methods may block as entropy is being gathered,
85 * for example, if they need to read from /dev/random on various Unix-like
86 * operating systems.
87 *
88 * @see java.security.SecureRandomSpi
89 * @see java.util.Random
90 *
91 * @author Benjamin Renaud
92 * @author Josh Bloch
93 */
94
95 public class SecureRandom extends java.util.Random {
96
97 private static final Debug pdebug =
98 Debug.getInstance("provider", "Provider");
99 private static final boolean skipDebug =
100 Debug.isOn("engine=") && !Debug.isOn("securerandom");
101
102 /**
103 * The provider.
104 *
105 * @serial
106 * @since 1.2
107 */
108 private Provider provider = null;
109
110 /**
111 * The provider implementation.
112 *
113 * @serial
114 * @since 1.2
115 */
116 private SecureRandomSpi secureRandomSpi = null;
117
118 /*
119 * The algorithm name of null if unknown.
120 *
121 * @serial
122 * @since 1.5
123 */
124 private String algorithm;
125
126 // Seed Generator
127 private static volatile SecureRandom seedGenerator = null;
128
129 /**
130 * Constructs a secure random number generator (RNG) implementing the
131 * default random number algorithm.
132 *
133 * <p> This constructor traverses the list of registered security Providers,
134 * starting with the most preferred Provider.
135 * A new SecureRandom object encapsulating the
136 * SecureRandomSpi implementation from the first
137 * Provider that supports a SecureRandom (RNG) algorithm is returned.
138 * If none of the Providers support a RNG algorithm,
139 * then an implementation-specific default is returned.
140 *
141 * <p> Note that the list of registered providers may be retrieved via
142 * the {@link Security#getProviders() Security.getProviders()} method.
143 *
144 * <p> See the SecureRandom section in the <a href=
145 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
146 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
147 * for information about standard RNG algorithm names.
148 *
149 * <p> The returned SecureRandom object has not been seeded. To seed the
150 * returned object, call the {@code setSeed} method.
151 * If {@code setSeed} is not called, the first call to
152 * {@code nextBytes} will force the SecureRandom object to seed itself.
153 * This self-seeding will not occur if {@code setSeed} was
154 * previously called.
155 */
156 public SecureRandom() {
157 /*
158 * This call to our superclass constructor will result in a call
159 * to our own {@code setSeed} method, which will return
160 * immediately when it is passed zero.
161 */
162 super(0);
163 getDefaultPRNG(false, null);
164 }
165
166 /**
167 * Constructs a secure random number generator (RNG) implementing the
168 * default random number algorithm.
169 * The SecureRandom instance is seeded with the specified seed bytes.
170 *
171 * <p> This constructor traverses the list of registered security Providers,
172 * starting with the most preferred Provider.
173 * A new SecureRandom object encapsulating the
174 * SecureRandomSpi implementation from the first
175 * Provider that supports a SecureRandom (RNG) algorithm is returned.
176 * If none of the Providers support a RNG algorithm,
177 * then an implementation-specific default is returned.
178 *
179 * <p> Note that the list of registered providers may be retrieved via
180 * the {@link Security#getProviders() Security.getProviders()} method.
181 *
182 * <p> See the SecureRandom section in the <a href=
183 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
184 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
185 * for information about standard RNG algorithm names.
186 *
187 * @param seed the seed.
188 */
189 public SecureRandom(byte seed[]) {
190 super(0);
191 getDefaultPRNG(true, seed);
192 }
193
194 private void getDefaultPRNG(boolean setSeed, byte[] seed) {
195 String prng = getPrngAlgorithm();
196 if (prng == null) {
197 // bummer, get the SUN implementation
198 prng = "SHA1PRNG";
199 this.secureRandomSpi = new sun.security.provider.SecureRandom();
200 this.provider = Providers.getSunProvider();
201 if (setSeed) {
202 this.secureRandomSpi.engineSetSeed(seed);
203 }
204 } else {
205 try {
206 SecureRandom random = SecureRandom.getInstance(prng);
207 this.secureRandomSpi = random.getSecureRandomSpi();
208 this.provider = random.getProvider();
209 if (setSeed) {
210 this.secureRandomSpi.engineSetSeed(seed);
211 }
212 } catch (NoSuchAlgorithmException nsae) {
213 // never happens, because we made sure the algorithm exists
214 throw new RuntimeException(nsae);
215 }
216 }
217 // JDK 1.1 based implementations subclass SecureRandom instead of
218 // SecureRandomSpi. They will also go through this code path because
219 // they must call a SecureRandom constructor as it is their superclass.
220 // If we are dealing with such an implementation, do not set the
221 // algorithm value as it would be inaccurate.
222 if (getClass() == SecureRandom.class) {
223 this.algorithm = prng;
224 }
225 }
226
227 /**
228 * Creates a SecureRandom object.
229 *
230 * @param secureRandomSpi the SecureRandom implementation.
231 * @param provider the provider.
232 */
233 protected SecureRandom(SecureRandomSpi secureRandomSpi,
234 Provider provider) {
235 this(secureRandomSpi, provider, null);
236 }
237
238 private SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider,
239 String algorithm) {
240 super(0);
241 this.secureRandomSpi = secureRandomSpi;
242 this.provider = provider;
243 this.algorithm = algorithm;
244
245 if (!skipDebug && pdebug != null) {
246 pdebug.println("SecureRandom." + algorithm +
247 " algorithm from: " + this.provider.getName());
248 }
249 }
250
251 /**
252 * Returns a SecureRandom object that implements the specified
253 * Random Number Generator (RNG) algorithm.
254 *
255 * <p> This method traverses the list of registered security Providers,
256 * starting with the most preferred Provider.
257 * A new SecureRandom object encapsulating the
258 * SecureRandomSpi implementation from the first
259 * Provider that supports the specified algorithm is returned.
260 *
261 * <p> Note that the list of registered providers may be retrieved via
262 * the {@link Security#getProviders() Security.getProviders()} method.
263 *
264 * <p> The returned SecureRandom object has not been seeded. To seed the
265 * returned object, call the {@code setSeed} method.
266 * If {@code setSeed} is not called, the first call to
267 * {@code nextBytes} will force the SecureRandom object to seed itself.
268 * This self-seeding will not occur if {@code setSeed} was
269 * previously called.
270 *
271 * @param algorithm the name of the RNG algorithm.
272 * See the SecureRandom section in the <a href=
273 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
274 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
275 * for information about standard RNG algorithm names.
276 *
277 * @return the new SecureRandom object.
278 *
279 * @exception NoSuchAlgorithmException if no Provider supports a
280 * SecureRandomSpi implementation for the
281 * specified algorithm.
282 *
283 * @see Provider
284 *
285 * @since 1.2
286 */
287 public static SecureRandom getInstance(String algorithm)
288 throws NoSuchAlgorithmException {
289 Instance instance = GetInstance.getInstance("SecureRandom",
290 SecureRandomSpi.class, algorithm);
291 return new SecureRandom((SecureRandomSpi)instance.impl,
292 instance.provider, algorithm);
293 }
294
295 /**
296 * Returns a SecureRandom object that implements the specified
297 * Random Number Generator (RNG) algorithm.
298 *
299 * <p> A new SecureRandom object encapsulating the
300 * SecureRandomSpi implementation from the specified provider
301 * is returned. The specified provider must be registered
302 * in the security provider list.
303 *
304 * <p> Note that the list of registered providers may be retrieved via
305 * the {@link Security#getProviders() Security.getProviders()} method.
306 *
307 * <p> The returned SecureRandom object has not been seeded. To seed the
308 * returned object, call the {@code setSeed} method.
309 * If {@code setSeed} is not called, the first call to
310 * {@code nextBytes} will force the SecureRandom object to seed itself.
311 * This self-seeding will not occur if {@code setSeed} was
312 * previously called.
313 *
314 * @param algorithm the name of the RNG algorithm.
315 * See the SecureRandom section in the <a href=
316 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
317 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
318 * for information about standard RNG algorithm names.
319 *
320 * @param provider the name of the provider.
321 *
322 * @return the new SecureRandom object.
323 *
324 * @exception NoSuchAlgorithmException if a SecureRandomSpi
325 * implementation for the specified algorithm is not
326 * available from the specified provider.
327 *
328 * @exception NoSuchProviderException if the specified provider is not
329 * registered in the security provider list.
330 *
331 * @exception IllegalArgumentException if the provider name is null
332 * or empty.
333 *
334 * @see Provider
335 *
336 * @since 1.2
337 */
338 public static SecureRandom getInstance(String algorithm, String provider)
339 throws NoSuchAlgorithmException, NoSuchProviderException {
340 Instance instance = GetInstance.getInstance("SecureRandom",
341 SecureRandomSpi.class, algorithm, provider);
342 return new SecureRandom((SecureRandomSpi)instance.impl,
343 instance.provider, algorithm);
344 }
345
346 /**
347 * Returns a SecureRandom object that implements the specified
348 * Random Number Generator (RNG) algorithm.
349 *
350 * <p> A new SecureRandom object encapsulating the
351 * SecureRandomSpi implementation from the specified Provider
352 * object is returned. Note that the specified Provider object
353 * does not have to be registered in the provider list.
354 *
355 * <p> The returned SecureRandom object has not been seeded. To seed the
356 * returned object, call the {@code setSeed} method.
357 * If {@code setSeed} is not called, the first call to
358 * {@code nextBytes} will force the SecureRandom object to seed itself.
359 * This self-seeding will not occur if {@code setSeed} was
360 * previously called.
361 *
362 * @param algorithm the name of the RNG algorithm.
363 * See the SecureRandom section in the <a href=
364 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
365 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
366 * for information about standard RNG algorithm names.
367 *
368 * @param provider the provider.
369 *
370 * @return the new SecureRandom object.
371 *
372 * @exception NoSuchAlgorithmException if a SecureRandomSpi
373 * implementation for the specified algorithm is not available
374 * from the specified Provider object.
375 *
376 * @exception IllegalArgumentException if the specified provider is null.
377 *
378 * @see Provider
379 *
380 * @since 1.4
381 */
382 public static SecureRandom getInstance(String algorithm,
383 Provider provider) throws NoSuchAlgorithmException {
384 Instance instance = GetInstance.getInstance("SecureRandom",
385 SecureRandomSpi.class, algorithm, provider);
386 return new SecureRandom((SecureRandomSpi)instance.impl,
387 instance.provider, algorithm);
388 }
389
390 /**
391 * Returns the SecureRandomSpi of this SecureRandom object.
392 */
393 SecureRandomSpi getSecureRandomSpi() {
394 return secureRandomSpi;
395 }
396
397 /**
398 * Returns the provider of this SecureRandom object.
399 *
400 * @return the provider of this SecureRandom object.
401 */
402 public final Provider getProvider() {
403 return provider;
404 }
405
406 /**
407 * Returns the name of the algorithm implemented by this SecureRandom
408 * object.
409 *
410 * @return the name of the algorithm or {@code unknown}
411 * if the algorithm name cannot be determined.
412 * @since 1.5
413 */
414 public String getAlgorithm() {
415 return (algorithm != null) ? algorithm : "unknown";
416 }
417
418 /**
419 * Reseeds this random object. The given seed supplements, rather than
420 * replaces, the existing seed. Thus, repeated calls are guaranteed
421 * never to reduce randomness.
422 *
423 * @param seed the seed.
424 *
425 * @see #getSeed
426 */
427 synchronized public void setSeed(byte[] seed) {
428 secureRandomSpi.engineSetSeed(seed);
429 }
430
431 /**
432 * Reseeds this random object, using the eight bytes contained
433 * in the given {@code long seed}. The given seed supplements,
434 * rather than replaces, the existing seed. Thus, repeated calls
435 * are guaranteed never to reduce randomness.
436 *
437 * <p>This method is defined for compatibility with
438 * {@code java.util.Random}.
439 *
440 * @param seed the seed.
441 *
442 * @see #getSeed
443 */
444 @Override
445 public void setSeed(long seed) {
446 /*
447 * Ignore call from super constructor (as well as any other calls
448 * unfortunate enough to be passing 0). It's critical that we
449 * ignore call from superclass constructor, as digest has not
450 * yet been initialized at that point.
451 */
452 if (seed != 0) {
453 secureRandomSpi.engineSetSeed(longToByteArray(seed));
454 }
455 }
456
457 /**
458 * Generates a user-specified number of random bytes.
459 *
460 * <p> If a call to {@code setSeed} had not occurred previously,
461 * the first call to this method forces this SecureRandom object
462 * to seed itself. This self-seeding will not occur if
463 * {@code setSeed} was previously called.
464 *
465 * @param bytes the array to be filled in with random bytes.
466 */
467 @Override
468 synchronized public void nextBytes(byte[] bytes) {
469 secureRandomSpi.engineNextBytes(bytes);
470 }
471
472 /**
473 * Generates an integer containing the user-specified number of
474 * pseudo-random bits (right justified, with leading zeros). This
475 * method overrides a {@code java.util.Random} method, and serves
476 * to provide a source of random bits to all of the methods inherited
477 * from that class (for example, {@code nextInt},
478 * {@code nextLong}, and {@code nextFloat}).
479 *
480 * @param numBits number of pseudo-random bits to be generated, where
481 * {@code 0 <= numBits <= 32}.
482 *
483 * @return an {@code int} containing the user-specified number
484 * of pseudo-random bits (right justified, with leading zeros).
485 */
486 @Override
487 final protected int next(int numBits) {
488 int numBytes = (numBits+7)/8;
489 byte b[] = new byte[numBytes];
490 int next = 0;
491
492 nextBytes(b);
493 for (int i = 0; i < numBytes; i++) {
494 next = (next << 8) + (b[i] & 0xFF);
495 }
496
497 return next >>> (numBytes*8 - numBits);
498 }
499
500 /**
501 * Returns the given number of seed bytes, computed using the seed
502 * generation algorithm that this class uses to seed itself. This
503 * call may be used to seed other random number generators.
504 *
505 * <p>This method is only included for backwards compatibility.
506 * The caller is encouraged to use one of the alternative
507 * {@code getInstance} methods to obtain a SecureRandom object, and
508 * then call the {@code generateSeed} method to obtain seed bytes
509 * from that object.
510 *
511 * @param numBytes the number of seed bytes to generate.
512 *
513 * @return the seed bytes.
514 *
515 * @see #setSeed
516 */
517 public static byte[] getSeed(int numBytes) {
518 if (seedGenerator == null) {
519 seedGenerator = new SecureRandom();
520 }
521 return seedGenerator.generateSeed(numBytes);
522 }
523
524 /**
525 * Returns the given number of seed bytes, computed using the seed
526 * generation algorithm that this class uses to seed itself. This
527 * call may be used to seed other random number generators.
528 *
529 * @param numBytes the number of seed bytes to generate.
530 *
531 * @return the seed bytes.
532 */
533 public byte[] generateSeed(int numBytes) {
534 return secureRandomSpi.engineGenerateSeed(numBytes);
535 }
536
537 /**
538 * Helper function to convert a long into a byte array (least significant
539 * byte first).
540 */
541 private static byte[] longToByteArray(long l) {
542 byte[] retVal = new byte[8];
543
544 for (int i = 0; i < 8; i++) {
545 retVal[i] = (byte) l;
546 l >>= 8;
547 }
548
549 return retVal;
550 }
551
552 /**
553 * Gets a default PRNG algorithm by looking through all registered
554 * providers. Returns the first PRNG algorithm of the first provider that
555 * has registered a SecureRandom implementation, or null if none of the
556 * registered providers supplies a SecureRandom implementation.
557 */
558 private static String getPrngAlgorithm() {
559 for (Provider p : Providers.getProviderList().providers()) {
560 for (Service s : p.getServices()) {
561 if (s.getType().equals("SecureRandom")) {
562 return s.getAlgorithm();
563 }
564 }
565 }
566 return null;
567 }
568
569 /*
570 * Lazily initialize since Pattern.compile() is heavy.
571 * Effective Java (2nd Edition), Item 71.
572 */
573 private static final class StrongPatternHolder {
574 /*
575 * Entries are alg:prov separated by ,
576 * Allow for prepended/appended whitespace between entries.
577 *
578 * Capture groups:
579 * 1 - alg
580 * 2 - :prov (optional)
581 * 3 - prov (optional)
582 * 4 - ,nextEntry (optional)
583 * 5 - nextEntry (optional)
584 */
585 private static Pattern pattern =
586 Pattern.compile(
587 "\\s*([\\S&&[^:,]]*)(\\:([\\S&&[^,]]*))?\\s*(\\,(.*))?");
588 }
589
590 /**
591 * Returns a {@code SecureRandom} object that was selected by using
592 * the algorithms/providers specified in the {@code
593 * securerandom.strongAlgorithms} {@link Security} property.
594 * <p>
595 * Some situations require strong random values, such as when
596 * creating high-value/long-lived secrets like RSA public/private
597 * keys. To help guide applications in selecting a suitable strong
598 * {@code SecureRandom} implementation, Java distributions
599 * include a list of known strong {@code SecureRandom}
600 * implementations in the {@code securerandom.strongAlgorithms}
601 * Security property.
602 * <p>
603 * Every implementation of the Java platform is required to
604 * support at least one strong {@code SecureRandom} implementation.
605 *
606 * @return a strong {@code SecureRandom} implementation as indicated
607 * by the {@code securerandom.strongAlgorithms} Security property
608 *
609 * @throws NoSuchAlgorithmException if no algorithm is available
610 *
611 * @see Security#getProperty(String)
612 *
613 * @since 1.8
614 */
615 public static SecureRandom getInstanceStrong()
616 throws NoSuchAlgorithmException {
617
618 String property = AccessController.doPrivileged(
619 new PrivilegedAction<String>() {
620 @Override
621 public String run() {
622 return Security.getProperty(
623 "securerandom.strongAlgorithms");
624 }
625 });
626
627 if ((property == null) || (property.length() == 0)) {
628 throw new NoSuchAlgorithmException(
629 "Null/empty securerandom.strongAlgorithms Security Property");
630 }
631
632 String remainder = property;
633 while (remainder != null) {
634 Matcher m;
635 if ((m = StrongPatternHolder.pattern.matcher(
636 remainder)).matches()) {
637
638 String alg = m.group(1);
639 String prov = m.group(3);
640
641 try {
642 if (prov == null) {
643 return SecureRandom.getInstance(alg);
644 } else {
645 return SecureRandom.getInstance(alg, prov);
646 }
647 } catch (NoSuchAlgorithmException |
648 NoSuchProviderException e) {
649 }
650 remainder = m.group(5);
651 } else {
652 remainder = null;
653 }
654 }
655
656 throw new NoSuchAlgorithmException(
657 "No strong SecureRandom impls available: " + property);
658 }
659
660 // Declare serialVersionUID to be compatible with JDK1.1
661 static final long serialVersionUID = 4940670005562187L;
662
663 // Retain unused values serialized from JDK1.1
664 /**
665 * @serial
666 */
667 private byte[] state;
668 /**
669 * @serial
670 */
671 private MessageDigest digest = null;
672 /**
673 * @serial
674 *
675 * We know that the MessageDigest class does not implement
676 * java.io.Serializable. However, since this field is no longer
677 * used, it will always be NULL and won't affect the serialization
678 * of the SecureRandom class itself.
679 */
680 private byte[] randomBytes;
681 /**
682 * @serial
683 */
684 private int randomBytesUsed;
685 /**
686 * @serial
687 */
688 private long counter;
689 }