1 /*
2 * Copyright (c) 1996, 2016, 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;
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 * @implNote
272 * The JDK Reference Implementation additionally uses the
273 * {@code jdk.security.provider.preferred} property to determine
274 * the preferred provider order for the specified algorithm. This
275 * may be different than the order of providers returned by
276 * {@link Security#getProviders() Security.getProviders()}.
277 *
278 * @param algorithm the name of the RNG algorithm.
279 * See the SecureRandom section in the <a href=
280 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
281 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
282 * for information about standard RNG algorithm names.
283 *
284 * @return the new SecureRandom object.
285 *
286 * @exception NoSuchAlgorithmException if no Provider supports a
287 * SecureRandomSpi implementation for the
288 * specified algorithm.
289 *
290 * @see Provider
291 *
292 * @since 1.2
293 */
294 public static SecureRandom getInstance(String algorithm)
295 throws NoSuchAlgorithmException {
296 Instance instance = GetInstance.getInstance("SecureRandom",
297 SecureRandomSpi.class, algorithm);
298 return new SecureRandom((SecureRandomSpi)instance.impl,
299 instance.provider, algorithm);
300 }
301
302 /**
303 * Returns a SecureRandom object that implements the specified
304 * Random Number Generator (RNG) algorithm.
305 *
306 * <p> A new SecureRandom object encapsulating the
307 * SecureRandomSpi implementation from the specified provider
308 * is returned. The specified provider must be registered
309 * in the security provider list.
310 *
311 * <p> Note that the list of registered providers may be retrieved via
312 * the {@link Security#getProviders() Security.getProviders()} method.
313 *
314 * <p> The returned SecureRandom object has not been seeded. To seed the
315 * returned object, call the {@code setSeed} method.
316 * If {@code setSeed} is not called, the first call to
317 * {@code nextBytes} will force the SecureRandom object to seed itself.
318 * This self-seeding will not occur if {@code setSeed} was
319 * previously called.
320 *
321 * @param algorithm the name of the RNG algorithm.
322 * See the SecureRandom section in the <a href=
323 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
324 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
325 * for information about standard RNG algorithm names.
326 *
327 * @param provider the name of the provider.
328 *
329 * @return the new SecureRandom object.
330 *
331 * @exception NoSuchAlgorithmException if a SecureRandomSpi
332 * implementation for the specified algorithm is not
333 * available from the specified provider.
334 *
335 * @exception NoSuchProviderException if the specified provider is not
336 * registered in the security provider list.
337 *
338 * @exception IllegalArgumentException if the provider name is null
339 * or empty.
340 *
341 * @see Provider
342 *
343 * @since 1.2
344 */
345 public static SecureRandom getInstance(String algorithm, String provider)
346 throws NoSuchAlgorithmException, NoSuchProviderException {
347 Instance instance = GetInstance.getInstance("SecureRandom",
348 SecureRandomSpi.class, algorithm, provider);
349 return new SecureRandom((SecureRandomSpi)instance.impl,
350 instance.provider, algorithm);
351 }
352
353 /**
354 * Returns a SecureRandom object that implements the specified
355 * Random Number Generator (RNG) algorithm.
356 *
357 * <p> A new SecureRandom object encapsulating the
358 * SecureRandomSpi implementation from the specified Provider
359 * object is returned. Note that the specified Provider object
360 * does not have to be registered in the provider list.
361 *
362 * <p> The returned SecureRandom object has not been seeded. To seed the
363 * returned object, call the {@code setSeed} method.
364 * If {@code setSeed} is not called, the first call to
365 * {@code nextBytes} will force the SecureRandom object to seed itself.
366 * This self-seeding will not occur if {@code setSeed} was
367 * previously called.
368 *
369 * @param algorithm the name of the RNG algorithm.
370 * See the SecureRandom section in the <a href=
371 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
372 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
373 * for information about standard RNG algorithm names.
374 *
375 * @param provider the provider.
376 *
377 * @return the new SecureRandom object.
378 *
379 * @exception NoSuchAlgorithmException if a SecureRandomSpi
380 * implementation for the specified algorithm is not available
381 * from the specified Provider object.
382 *
383 * @exception IllegalArgumentException if the specified provider is null.
384 *
385 * @see Provider
386 *
387 * @since 1.4
388 */
389 public static SecureRandom getInstance(String algorithm,
390 Provider provider) throws NoSuchAlgorithmException {
391 Instance instance = GetInstance.getInstance("SecureRandom",
392 SecureRandomSpi.class, algorithm, provider);
393 return new SecureRandom((SecureRandomSpi)instance.impl,
394 instance.provider, algorithm);
395 }
396
397 /**
398 * Returns the SecureRandomSpi of this SecureRandom object.
399 */
400 SecureRandomSpi getSecureRandomSpi() {
401 return secureRandomSpi;
402 }
403
404 /**
405 * Returns the provider of this SecureRandom object.
406 *
407 * @return the provider of this SecureRandom object.
408 */
409 public final Provider getProvider() {
410 return provider;
411 }
412
413 /**
414 * Returns the name of the algorithm implemented by this SecureRandom
415 * object.
416 *
417 * @return the name of the algorithm or {@code unknown}
418 * if the algorithm name cannot be determined.
419 * @since 1.5
420 */
421 public String getAlgorithm() {
422 return Objects.toString(algorithm, "unknown");
423 }
424
425 /**
426 * Reseeds this random object. The given seed supplements, rather than
427 * replaces, the existing seed. Thus, repeated calls are guaranteed
428 * never to reduce randomness.
429 *
430 * @param seed the seed.
431 *
432 * @see #getSeed
433 */
434 public synchronized void setSeed(byte[] seed) {
435 secureRandomSpi.engineSetSeed(seed);
436 }
437
438 /**
439 * Reseeds this random object, using the eight bytes contained
440 * in the given {@code long seed}. The given seed supplements,
441 * rather than replaces, the existing seed. Thus, repeated calls
442 * are guaranteed never to reduce randomness.
443 *
444 * <p>This method is defined for compatibility with
445 * {@code java.util.Random}.
446 *
447 * @param seed the seed.
448 *
449 * @see #getSeed
450 */
451 @Override
452 public void setSeed(long seed) {
453 /*
454 * Ignore call from super constructor (as well as any other calls
455 * unfortunate enough to be passing 0). It's critical that we
456 * ignore call from superclass constructor, as digest has not
457 * yet been initialized at that point.
458 */
459 if (seed != 0) {
460 secureRandomSpi.engineSetSeed(longToByteArray(seed));
461 }
462 }
463
464 /**
465 * Generates a user-specified number of random bytes.
466 *
467 * <p> If a call to {@code setSeed} had not occurred previously,
468 * the first call to this method forces this SecureRandom object
469 * to seed itself. This self-seeding will not occur if
470 * {@code setSeed} was previously called.
471 *
472 * @param bytes the array to be filled in with random bytes.
473 */
474 @Override
475 public void nextBytes(byte[] bytes) {
476 secureRandomSpi.engineNextBytes(bytes);
477 }
478
479 /**
480 * Generates an integer containing the user-specified number of
481 * pseudo-random bits (right justified, with leading zeros). This
482 * method overrides a {@code java.util.Random} method, and serves
483 * to provide a source of random bits to all of the methods inherited
484 * from that class (for example, {@code nextInt},
485 * {@code nextLong}, and {@code nextFloat}).
486 *
487 * @param numBits number of pseudo-random bits to be generated, where
488 * {@code 0 <= numBits <= 32}.
489 *
490 * @return an {@code int} containing the user-specified number
491 * of pseudo-random bits (right justified, with leading zeros).
492 */
493 @Override
494 protected final int next(int numBits) {
495 int numBytes = (numBits+7)/8;
496 byte[] b = new byte[numBytes];
497 int next = 0;
498
499 nextBytes(b);
500 for (int i = 0; i < numBytes; i++) {
501 next = (next << 8) + (b[i] & 0xFF);
502 }
503
504 return next >>> (numBytes*8 - numBits);
505 }
506
507 /**
508 * Returns the given number of seed bytes, computed using the seed
509 * generation algorithm that this class uses to seed itself. This
510 * call may be used to seed other random number generators.
511 *
512 * <p>This method is only included for backwards compatibility.
513 * The caller is encouraged to use one of the alternative
514 * {@code getInstance} methods to obtain a SecureRandom object, and
515 * then call the {@code generateSeed} method to obtain seed bytes
516 * from that object.
517 *
518 * @param numBytes the number of seed bytes to generate.
519 *
520 * @return the seed bytes.
521 *
522 * @see #setSeed
523 */
524 public static byte[] getSeed(int numBytes) {
525 SecureRandom seedGen = seedGenerator;
526 if (seedGen == null) {
527 seedGen = new SecureRandom();
528 seedGenerator = seedGen;
529 }
530 return seedGen.generateSeed(numBytes);
531 }
532
533 /**
534 * Returns the given number of seed bytes, computed using the seed
535 * generation algorithm that this class uses to seed itself. This
536 * call may be used to seed other random number generators.
537 *
538 * @param numBytes the number of seed bytes to generate.
539 *
540 * @return the seed bytes.
541 */
542 public byte[] generateSeed(int numBytes) {
543 return secureRandomSpi.engineGenerateSeed(numBytes);
544 }
545
546 /**
547 * Helper function to convert a long into a byte array (least significant
548 * byte first).
549 */
550 private static byte[] longToByteArray(long l) {
551 byte[] retVal = new byte[8];
552
553 for (int i = 0; i < 8; i++) {
554 retVal[i] = (byte) l;
555 l >>= 8;
556 }
557
558 return retVal;
559 }
560
561 /**
562 * Gets a default PRNG algorithm by looking through all registered
563 * providers. Returns the first PRNG algorithm of the first provider that
564 * has registered a SecureRandom implementation, or null if none of the
565 * registered providers supplies a SecureRandom implementation.
566 */
567 private static String getPrngAlgorithm() {
568 for (Provider p : Providers.getProviderList().providers()) {
569 for (Service s : p.getServices()) {
570 if (s.getType().equals("SecureRandom")) {
571 return s.getAlgorithm();
572 }
573 }
574 }
575 return null;
576 }
577
578 /*
579 * Lazily initialize since Pattern.compile() is heavy.
580 * Effective Java (2nd Edition), Item 71.
581 */
582 private static final class StrongPatternHolder {
583 /*
584 * Entries are alg:prov separated by ,
585 * Allow for prepended/appended whitespace between entries.
586 *
587 * Capture groups:
588 * 1 - alg
589 * 2 - :prov (optional)
590 * 3 - prov (optional)
591 * 4 - ,nextEntry (optional)
592 * 5 - nextEntry (optional)
593 */
594 private static Pattern pattern =
595 Pattern.compile(
596 "\\s*([\\S&&[^:,]]*)(\\:([\\S&&[^,]]*))?\\s*(\\,(.*))?");
597 }
598
599 /**
600 * Returns a {@code SecureRandom} object that was selected by using
601 * the algorithms/providers specified in the {@code
602 * securerandom.strongAlgorithms} {@link Security} property.
603 * <p>
604 * Some situations require strong random values, such as when
605 * creating high-value/long-lived secrets like RSA public/private
606 * keys. To help guide applications in selecting a suitable strong
607 * {@code SecureRandom} implementation, Java distributions
608 * include a list of known strong {@code SecureRandom}
609 * implementations in the {@code securerandom.strongAlgorithms}
610 * Security property.
611 * <p>
612 * Every implementation of the Java platform is required to
613 * support at least one strong {@code SecureRandom} implementation.
614 *
615 * @return a strong {@code SecureRandom} implementation as indicated
616 * by the {@code securerandom.strongAlgorithms} Security property
617 *
618 * @throws NoSuchAlgorithmException if no algorithm is available
619 *
620 * @see Security#getProperty(String)
621 *
622 * @since 1.8
623 */
624 public static SecureRandom getInstanceStrong()
625 throws NoSuchAlgorithmException {
626
627 String property = AccessController.doPrivileged(
628 new PrivilegedAction<>() {
629 @Override
630 public String run() {
631 return Security.getProperty(
632 "securerandom.strongAlgorithms");
633 }
634 });
635
636 if ((property == null) || (property.length() == 0)) {
637 throw new NoSuchAlgorithmException(
638 "Null/empty securerandom.strongAlgorithms Security Property");
639 }
640
641 String remainder = property;
642 while (remainder != null) {
643 Matcher m;
644 if ((m = StrongPatternHolder.pattern.matcher(
645 remainder)).matches()) {
646
647 String alg = m.group(1);
648 String prov = m.group(3);
649
650 try {
651 if (prov == null) {
652 return SecureRandom.getInstance(alg);
653 } else {
654 return SecureRandom.getInstance(alg, prov);
655 }
656 } catch (NoSuchAlgorithmException |
657 NoSuchProviderException e) {
658 }
659 remainder = m.group(5);
660 } else {
661 remainder = null;
662 }
663 }
664
665 throw new NoSuchAlgorithmException(
666 "No strong SecureRandom impls available: " + property);
667 }
668
669 // Declare serialVersionUID to be compatible with JDK1.1
670 static final long serialVersionUID = 4940670005562187L;
671
672 // Retain unused values serialized from JDK1.1
673 /**
674 * @serial
675 */
676 private byte[] state;
677 /**
678 * @serial
679 */
680 private MessageDigest digest = null;
681 /**
682 * @serial
683 *
684 * We know that the MessageDigest class does not implement
685 * java.io.Serializable. However, since this field is no longer
686 * used, it will always be NULL and won't affect the serialization
687 * of the SecureRandom class itself.
688 */
689 private byte[] randomBytes;
690 /**
691 * @serial
692 */
693 private int randomBytesUsed;
694 /**
695 * @serial
696 */
697 private long counter;
698 }