1 /*
2 * Copyright (c) 1996, 2017, 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 minimally complies with the
42 * statistical random number generator tests specified in
43 * <a href="http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.140-2.pdf">
44 * <i>FIPS 140-2, Security Requirements for Cryptographic Modules</i></a>,
45 * section 4.9.1.
46 * Additionally, {@code SecureRandom} must produce non-deterministic output.
47 * Therefore any seed material passed to a {@code SecureRandom} object must be
48 * unpredictable, and all {@code SecureRandom} output sequences must be
49 * cryptographically strong, as described in
50 * <a href="http://tools.ietf.org/html/rfc4086">
51 * <i>RFC 4086: Randomness Requirements for Security</i></a>.
52 *
53 * <p> Many {@code SecureRandom} implementations are in the form of a
54 * pseudo-random number generator (PRNG, also known as deterministic random
55 * bits generator or DRBG), which means they use a deterministic algorithm
56 * to produce a pseudo-random sequence from a random seed.
57 * Other implementations may produce true random numbers,
58 * and yet others may use a combination of both techniques.
59 *
60 * <p>A caller obtains a {@code SecureRandom} instance via the
61 * no-argument constructor or one of the {@code getInstance} methods.
62 * For example:
63 *
64 * <blockquote><pre>
65 * SecureRandom r1 = new SecureRandom();
66 * SecureRandom r2 = SecureRandom.getInstance("NativePRNG");
67 * SecureRandom r3 = SecureRandom.getInstance("DRBG",
68 * DrbgParameters.instantiation(128, RESEED_ONLY, null));</pre>
69 * </blockquote>
70 *
71 * <p> The third statement above returns a {@code SecureRandom} object of the
72 * specific algorithm supporting the specific instantiate parameters. The
73 * implementation's effective instantiated parameters must match this minimum
74 * request but is not necessarily the same. For example, even if the request
75 * does not require a certain feature, the actual instantiation can provide
76 * the feature. An implementation may lazily instantiate a {@code SecureRandom}
77 * until it's actually used, but the effective instantiate parameters must be
78 * determined right after it's created and {@link #getParameters()} should
79 * always return the same result unchanged.
80 *
81 * <p> Typical callers of {@code SecureRandom} invoke the following methods
82 * to retrieve random bytes:
83 *
84 * <blockquote><pre>
85 * SecureRandom random = new SecureRandom();
86 * byte[] bytes = new byte[20];
87 * random.nextBytes(bytes);</pre>
88 * </blockquote>
89 *
90 * <p> Callers may also invoke the {@link #generateSeed} method
91 * to generate a given number of seed bytes (to seed other random number
92 * generators, for example):
93 *
94 * <blockquote><pre>
95 * byte[] seed = random.generateSeed(20);</pre>
96 * </blockquote>
97 *
98 * <p> A newly created PRNG {@code SecureRandom} object is not seeded (except
99 * if it is created by {@link #SecureRandom(byte[])}). The first call to
100 * {@code nextBytes} will force it to seed itself from an implementation-
101 * specific entropy source. This self-seeding will not occur if {@code setSeed}
102 * was previously called.
103 *
104 * <p> A {@code SecureRandom} can be reseeded at any time by calling the
105 * {@code reseed} or {@code setSeed} method. The {@code reseed} method
106 * reads entropy input from its entropy source to reseed itself.
107 * The {@code setSeed} method requires the caller to provide the seed.
108 *
109 * <p> Please note that {@code reseed} may not be supported by all
110 * {@code SecureRandom} implementations.
111 *
112 * <p> Some {@code SecureRandom} implementations may accept a
113 * {@link SecureRandomParameters} parameter in its
114 * {@link #nextBytes(byte[], SecureRandomParameters)} and
115 * {@link #reseed(SecureRandomParameters)} methods to further
116 * control the behavior of the methods.
117 *
118 * <p> Note: Depending on the implementation, the {@code generateSeed},
119 * {@code reseed} and {@code nextBytes} methods may block as entropy is being
120 * gathered, for example, if the entropy source is /dev/random on various
121 * Unix-like operating systems.
122 *
123 * <h2> Thread safety </h2>
124 * {@code SecureRandom} objects are safe for use by multiple concurrent threads.
125 *
126 * @implSpec
127 * A {@code SecureRandom} service provider can advertise that it is thread-safe
128 * by setting the <a href=
129 * "{@docRoot}/../technotes/guides/security/StandardNames.html#Service">service
130 * provider attribute</a> "ThreadSafe" to "true" when registering the provider.
131 * Otherwise, this class will instead synchronize access to the following
132 * methods of the {@code SecureRandomSpi} implementation:
133 * <ul>
134 * <li>{@link SecureRandomSpi#engineSetSeed(byte[])}
135 * <li>{@link SecureRandomSpi#engineNextBytes(byte[])}
136 * <li>{@link SecureRandomSpi#engineNextBytes(byte[], SecureRandomParameters)}
137 * <li>{@link SecureRandomSpi#engineGenerateSeed(int)}
138 * <li>{@link SecureRandomSpi#engineReseed(SecureRandomParameters)}
139 * </ul>
140 *
141 * @see java.security.SecureRandomSpi
142 * @see java.util.Random
143 *
144 * @author Benjamin Renaud
145 * @author Josh Bloch
146 */
147
148 public class SecureRandom extends java.util.Random {
149
150 private static final Debug pdebug =
151 Debug.getInstance("provider", "Provider");
152 private static final boolean skipDebug =
153 Debug.isOn("engine=") && !Debug.isOn("securerandom");
154
155 /**
156 * The provider.
157 *
158 * @serial
159 * @since 1.2
160 */
161 private Provider provider = null;
162
163 /**
164 * The provider implementation.
165 *
166 * @serial
167 * @since 1.2
168 */
169 private SecureRandomSpi secureRandomSpi = null;
170
171 /**
172 * Thread safety.
173 *
174 * @serial
175 * @since 9
176 */
177 private final boolean threadSafe;
178
179 /*
180 * The algorithm name of null if unknown.
181 *
182 * @serial
183 * @since 1.5
184 */
185 private String algorithm;
186
187 // Seed Generator
188 private static volatile SecureRandom seedGenerator;
189
190 /**
191 * Constructs a secure random number generator (RNG) implementing the
192 * default random number algorithm.
193 *
194 * <p> This constructor traverses the list of registered security Providers,
195 * starting with the most preferred Provider.
196 * A new {@code SecureRandom} object encapsulating the
197 * {@code SecureRandomSpi} implementation from the first
198 * Provider that supports a {@code SecureRandom} (RNG) algorithm is returned.
199 * If none of the Providers support a RNG algorithm,
200 * then an implementation-specific default is returned.
201 *
202 * <p> Note that the list of registered providers may be retrieved via
203 * the {@link Security#getProviders() Security.getProviders()} method.
204 *
205 * <p> See the {@code SecureRandom} section in the <a href=
206 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
207 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
208 * for information about standard RNG algorithm names.
209 */
210 public SecureRandom() {
211 /*
212 * This call to our superclass constructor will result in a call
213 * to our own {@code setSeed} method, which will return
214 * immediately when it is passed zero.
215 */
216 super(0);
217 getDefaultPRNG(false, null);
218 this.threadSafe = getThreadSafe();
219 }
220
221 private boolean getThreadSafe() {
222 if (provider == null || algorithm == null) {
223 return false;
224 } else {
225 return Boolean.parseBoolean(provider.getProperty(
226 "SecureRandom." + algorithm + " ThreadSafe", "false"));
227 }
228 }
229
230 /**
231 * Constructs a secure random number generator (RNG) implementing the
232 * default random number algorithm.
233 * The {@code SecureRandom} instance is seeded with the specified seed bytes.
234 *
235 * <p> This constructor traverses the list of registered security Providers,
236 * starting with the most preferred Provider.
237 * A new {@code SecureRandom} object encapsulating the
238 * {@code SecureRandomSpi} implementation from the first
239 * Provider that supports a {@code SecureRandom} (RNG) algorithm is returned.
240 * If none of the Providers support a RNG algorithm,
241 * then an implementation-specific default is returned.
242 *
243 * <p> Note that the list of registered providers may be retrieved via
244 * the {@link Security#getProviders() Security.getProviders()} method.
245 *
246 * <p> See the {@code SecureRandom} section in the <a href=
247 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
248 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
249 * for information about standard RNG algorithm names.
250 *
251 * @param seed the seed.
252 */
253 public SecureRandom(byte[] seed) {
254 super(0);
255 getDefaultPRNG(true, seed);
256 this.threadSafe = getThreadSafe();
257 }
258
259 private void getDefaultPRNG(boolean setSeed, byte[] seed) {
260 String prng = getPrngAlgorithm();
261 if (prng == null) {
262 // bummer, get the SUN implementation
263 prng = "SHA1PRNG";
264 this.secureRandomSpi = new sun.security.provider.SecureRandom();
265 this.provider = Providers.getSunProvider();
266 if (setSeed) {
267 this.secureRandomSpi.engineSetSeed(seed);
268 }
269 } else {
270 try {
271 SecureRandom random = SecureRandom.getInstance(prng);
272 this.secureRandomSpi = random.getSecureRandomSpi();
273 this.provider = random.getProvider();
274 if (setSeed) {
275 this.secureRandomSpi.engineSetSeed(seed);
276 }
277 } catch (NoSuchAlgorithmException nsae) {
278 // never happens, because we made sure the algorithm exists
279 throw new RuntimeException(nsae);
280 }
281 }
282 // JDK 1.1 based implementations subclass SecureRandom instead of
283 // SecureRandomSpi. They will also go through this code path because
284 // they must call a SecureRandom constructor as it is their superclass.
285 // If we are dealing with such an implementation, do not set the
286 // algorithm value as it would be inaccurate.
287 if (getClass() == SecureRandom.class) {
288 this.algorithm = prng;
289 }
290 }
291
292 /**
293 * Creates a {@code SecureRandom} object.
294 *
295 * @param secureRandomSpi the {@code SecureRandom} implementation.
296 * @param provider the provider.
297 */
298 protected SecureRandom(SecureRandomSpi secureRandomSpi,
299 Provider provider) {
300 this(secureRandomSpi, provider, null);
301 }
302
303 private SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider,
304 String algorithm) {
305 super(0);
306 this.secureRandomSpi = secureRandomSpi;
307 this.provider = provider;
308 this.algorithm = algorithm;
309 this.threadSafe = getThreadSafe();
310
311 if (!skipDebug && pdebug != null) {
312 pdebug.println("SecureRandom." + algorithm +
313 " algorithm from: " + getProviderName());
314 }
315 }
316
317 private String getProviderName() {
318 return (provider == null) ? "(no provider)" : provider.getName();
319 }
320
321 /**
322 * Returns a {@code SecureRandom} object that implements the specified
323 * Random Number Generator (RNG) algorithm.
324 *
325 * <p> This method traverses the list of registered security Providers,
326 * starting with the most preferred Provider.
327 * A new {@code SecureRandom} object encapsulating the
328 * {@code SecureRandomSpi} implementation from the first
329 * Provider that supports the specified algorithm is returned.
330 *
331 * <p> Note that the list of registered providers may be retrieved via
332 * the {@link Security#getProviders() Security.getProviders()} method.
333 *
334 * @implNote
335 * The JDK Reference Implementation additionally uses the
336 * {@code jdk.security.provider.preferred}
337 * {@link Security#getProperty(String) Security} property to determine
338 * the preferred provider order for the specified algorithm. This
339 * may be different than the order of providers returned by
340 * {@link Security#getProviders() Security.getProviders()}.
341 *
342 * @param algorithm the name of the RNG algorithm.
343 * See the {@code SecureRandom} section in the <a href=
344 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
345 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
346 * for information about standard RNG algorithm names.
347 *
348 * @return the new {@code SecureRandom} object
349 *
350 * @throws NoSuchAlgorithmException if no {@code Provider} supports a
351 * {@code SecureRandomSpi} implementation for the
352 * specified algorithm
353 *
354 * @throws NullPointerException if {@code algorithm} is {@code null}
355 *
356 * @see Provider
357 *
358 * @since 1.2
359 */
360 public static SecureRandom getInstance(String algorithm)
361 throws NoSuchAlgorithmException {
362 Objects.requireNonNull(algorithm, "null algorithm name");
363 Instance instance = GetInstance.getInstance("SecureRandom",
364 SecureRandomSpi.class, algorithm);
365 return new SecureRandom((SecureRandomSpi)instance.impl,
366 instance.provider, algorithm);
367 }
368
369 /**
370 * Returns a {@code SecureRandom} object that implements the specified
371 * Random Number Generator (RNG) algorithm.
372 *
373 * <p> A new {@code SecureRandom} object encapsulating the
374 * {@code SecureRandomSpi} implementation from the specified provider
375 * is returned. The specified provider must be registered
376 * in the security provider list.
377 *
378 * <p> Note that the list of registered providers may be retrieved via
379 * the {@link Security#getProviders() Security.getProviders()} method.
380 *
381 * @param algorithm the name of the RNG algorithm.
382 * See the {@code SecureRandom} section in the <a href=
383 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
384 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
385 * for information about standard RNG algorithm names.
386 *
387 * @param provider the name of the provider.
388 *
389 * @return the new {@code SecureRandom} object
390 *
391 * @throws IllegalArgumentException if the provider name is {@code null}
392 * or empty
393 *
394 * @throws NoSuchAlgorithmException if a {@code SecureRandomSpi}
395 * implementation for the specified algorithm is not
396 * available from the specified provider
397 *
398 * @throws NoSuchProviderException if the specified provider is not
399 * registered in the security provider list
400 *
401 * @throws NullPointerException if {@code algorithm} is {@code null}
402 *
403 * @see Provider
404 *
405 * @since 1.2
406 */
407 public static SecureRandom getInstance(String algorithm, String provider)
408 throws NoSuchAlgorithmException, NoSuchProviderException {
409 Objects.requireNonNull(algorithm, "null algorithm name");
410 Instance instance = GetInstance.getInstance("SecureRandom",
411 SecureRandomSpi.class, algorithm, provider);
412 return new SecureRandom((SecureRandomSpi)instance.impl,
413 instance.provider, algorithm);
414 }
415
416 /**
417 * Returns a {@code SecureRandom} object that implements the specified
418 * Random Number Generator (RNG) algorithm.
419 *
420 * <p> A new {@code SecureRandom} object encapsulating the
421 * {@code SecureRandomSpi} implementation from the specified {@code Provider}
422 * object is returned. Note that the specified {@code Provider} object
423 * does not have to be registered in the provider list.
424 *
425 * @param algorithm the name of the RNG algorithm.
426 * See the {@code SecureRandom} section in the <a href=
427 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
428 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
429 * for information about standard RNG algorithm names.
430 *
431 * @param provider the provider.
432 *
433 * @return the new {@code SecureRandom} object
434 *
435 * @throws IllegalArgumentException if the specified provider is
436 * {@code null}
437 *
438 * @throws NoSuchAlgorithmException if a {@code SecureRandomSpi}
439 * implementation for the specified algorithm is not available
440 * from the specified {@code Provider} object
441 *
442 * @throws NullPointerException if {@code algorithm} is {@code null}
443 *
444 * @see Provider
445 *
446 * @since 1.4
447 */
448 public static SecureRandom getInstance(String algorithm,
449 Provider provider) throws NoSuchAlgorithmException {
450 Objects.requireNonNull(algorithm, "null algorithm name");
451 Instance instance = GetInstance.getInstance("SecureRandom",
452 SecureRandomSpi.class, algorithm, provider);
453 return new SecureRandom((SecureRandomSpi)instance.impl,
454 instance.provider, algorithm);
455 }
456
457 /**
458 * Returns a {@code SecureRandom} object that implements the specified
459 * Random Number Generator (RNG) algorithm and supports the specified
460 * {@code SecureRandomParameters} request.
461 *
462 * <p> This method traverses the list of registered security Providers,
463 * starting with the most preferred Provider.
464 * A new {@code SecureRandom} object encapsulating the
465 * {@code SecureRandomSpi} implementation from the first
466 * Provider that supports the specified algorithm and the specified
467 * {@code SecureRandomParameters} is returned.
468 *
469 * <p> Note that the list of registered providers may be retrieved via
470 * the {@link Security#getProviders() Security.getProviders()} method.
471 *
472 * @implNote
473 * The JDK Reference Implementation additionally uses the
474 * {@code jdk.security.provider.preferred} property to determine
475 * the preferred provider order for the specified algorithm. This
476 * may be different than the order of providers returned by
477 * {@link Security#getProviders() Security.getProviders()}.
478 *
479 * @param algorithm the name of the RNG algorithm.
480 * See the {@code SecureRandom} section in the <a href=
481 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
482 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
483 * for information about standard RNG algorithm names.
484 *
485 * @param params the {@code SecureRandomParameters}
486 * the newly created {@code SecureRandom} object must support.
487 *
488 * @return the new {@code SecureRandom} object
489 *
490 * @throws IllegalArgumentException if the specified params is
491 * {@code null}
492 *
493 * @throws NoSuchAlgorithmException if no Provider supports a
494 * {@code SecureRandomSpi} implementation for the specified
495 * algorithm and parameters
496 *
497 * @throws NullPointerException if {@code algorithm} is {@code null}
498 *
499 * @see Provider
500 *
501 * @since 9
502 */
503 public static SecureRandom getInstance(
504 String algorithm, SecureRandomParameters params)
505 throws NoSuchAlgorithmException {
506 Objects.requireNonNull(algorithm, "null algorithm name");
507 if (params == null) {
508 throw new IllegalArgumentException("params cannot be null");
509 }
510 Instance instance = GetInstance.getInstance("SecureRandom",
511 SecureRandomSpi.class, algorithm, params);
512 return new SecureRandom((SecureRandomSpi)instance.impl,
513 instance.provider, algorithm);
514 }
515
516 /**
517 * Returns a {@code SecureRandom} object that implements the specified
518 * Random Number Generator (RNG) algorithm and supports the specified
519 * {@code SecureRandomParameters} request.
520 *
521 * <p> A new {@code SecureRandom} object encapsulating the
522 * {@code SecureRandomSpi} implementation from the specified provider
523 * is returned. The specified provider must be registered
524 * in the security provider list.
525 *
526 * <p> Note that the list of registered providers may be retrieved via
527 * the {@link Security#getProviders() Security.getProviders()} method.
528 *
529 * @param algorithm the name of the RNG algorithm.
530 * See the {@code SecureRandom} section in the <a href=
531 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
532 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
533 * for information about standard RNG algorithm names.
534 *
535 * @param params the {@code SecureRandomParameters}
536 * the newly created {@code SecureRandom} object must support.
537 *
538 * @param provider the name of the provider.
539 *
540 * @return the new {@code SecureRandom} object
541 *
542 * @throws IllegalArgumentException if the provider name is {@code null}
543 * or empty, or params is {@code null}
544 *
545 * @throws NoSuchAlgorithmException if the specified provider does not
546 * support a {@code SecureRandomSpi} implementation for the
547 * specified algorithm and parameters
548 *
549 * @throws NoSuchProviderException if the specified provider is not
550 * registered in the security provider list
551 *
552 * @throws NullPointerException if {@code algorithm} is {@code null}
553 *
554 * @see Provider
555 *
556 * @since 9
557 */
558 public static SecureRandom getInstance(String algorithm,
559 SecureRandomParameters params, String provider)
560 throws NoSuchAlgorithmException, NoSuchProviderException {
561 Objects.requireNonNull(algorithm, "null algorithm name");
562 if (params == null) {
563 throw new IllegalArgumentException("params cannot be null");
564 }
565 Instance instance = GetInstance.getInstance("SecureRandom",
566 SecureRandomSpi.class, algorithm, params, provider);
567 return new SecureRandom((SecureRandomSpi)instance.impl,
568 instance.provider, algorithm);
569 }
570
571 /**
572 * Returns a {@code SecureRandom} object that implements the specified
573 * Random Number Generator (RNG) algorithm and supports the specified
574 * {@code SecureRandomParameters} request.
575 *
576 * <p> A new {@code SecureRandom} object encapsulating the
577 * {@code SecureRandomSpi} implementation from the specified
578 * {@code Provider} object is returned. Note that the specified
579 * {@code Provider} object does not have to be registered in the
580 * provider list.
581 *
582 * @param algorithm the name of the RNG algorithm.
583 * See the {@code SecureRandom} section in the <a href=
584 * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">
585 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
586 * for information about standard RNG algorithm names.
587 *
588 * @param params the {@code SecureRandomParameters}
589 * the newly created {@code SecureRandom} object must support.
590 *
591 * @param provider the provider.
592 *
593 * @return the new {@code SecureRandom} object
594 *
595 * @throws IllegalArgumentException if the specified provider or params
596 * is {@code null}
597 *
598 * @throws NoSuchAlgorithmException if the specified provider does not
599 * support a {@code SecureRandomSpi} implementation for the
600 * specified algorithm and parameters
601 *
602 * @throws NullPointerException if {@code algorithm} is {@code null}
603 *
604 * @see Provider
605 *
606 * @since 9
607 */
608 public static SecureRandom getInstance(String algorithm,
609 SecureRandomParameters params, Provider provider)
610 throws NoSuchAlgorithmException {
611 Objects.requireNonNull(algorithm, "null algorithm name");
612 if (params == null) {
613 throw new IllegalArgumentException("params cannot be null");
614 }
615 Instance instance = GetInstance.getInstance("SecureRandom",
616 SecureRandomSpi.class, algorithm, params, provider);
617 return new SecureRandom((SecureRandomSpi)instance.impl,
618 instance.provider, algorithm);
619 }
620
621 /**
622 * Returns the {@code SecureRandomSpi} of this {@code SecureRandom} object.
623 */
624 SecureRandomSpi getSecureRandomSpi() {
625 return secureRandomSpi;
626 }
627
628 /**
629 * Returns the provider of this {@code SecureRandom} object.
630 *
631 * @return the provider of this {@code SecureRandom} object.
632 */
633 public final Provider getProvider() {
634 return provider;
635 }
636
637 /**
638 * Returns the name of the algorithm implemented by this
639 * {@code SecureRandom} object.
640 *
641 * @return the name of the algorithm or {@code unknown}
642 * if the algorithm name cannot be determined.
643 * @since 1.5
644 */
645 public String getAlgorithm() {
646 return Objects.toString(algorithm, "unknown");
647 }
648
649 /**
650 * Returns a Human-readable string representation of this
651 * {@code SecureRandom}.
652 *
653 * @return the string representation
654 */
655 @Override
656 public String toString() {
657 return secureRandomSpi.toString();
658 }
659
660 /**
661 * Returns the effective {@link SecureRandomParameters} for this
662 * {@code SecureRandom} instance.
663 * <p>
664 * The returned value can be different from the
665 * {@code SecureRandomParameters} object passed into a {@code getInstance}
666 * method, but it cannot change during the lifetime of this
667 * {@code SecureRandom} object.
668 * <p>
669 * A caller can use the returned value to find out what features this
670 * {@code SecureRandom} supports.
671 *
672 * @return the effective {@link SecureRandomParameters} parameters,
673 * or {@code null} if no parameters were used.
674 *
675 * @since 9
676 * @see SecureRandomSpi
677 */
678 public SecureRandomParameters getParameters() {
679 return secureRandomSpi.engineGetParameters();
680 }
681
682 /**
683 * Reseeds this random object with the given seed. The seed supplements,
684 * rather than replaces, the existing seed. Thus, repeated calls are
685 * guaranteed never to reduce randomness.
686 * <p>
687 * A PRNG {@code SecureRandom} will not seed itself automatically if
688 * {@code setSeed} is called before any {@code nextBytes} or {@code reseed}
689 * calls. The caller should make sure that the {@code seed} argument
690 * contains enough entropy for the security of this {@code SecureRandom}.
691 *
692 * @param seed the seed.
693 *
694 * @see #getSeed
695 */
696 public void setSeed(byte[] seed) {
697 if (threadSafe) {
698 secureRandomSpi.engineSetSeed(seed);
699 } else {
700 synchronized (this) {
701 secureRandomSpi.engineSetSeed(seed);
702 }
703 }
704 }
705
706 /**
707 * Reseeds this random object, using the eight bytes contained
708 * in the given {@code long seed}. The given seed supplements,
709 * rather than replaces, the existing seed. Thus, repeated calls
710 * are guaranteed never to reduce randomness.
711 *
712 * <p>This method is defined for compatibility with
713 * {@code java.util.Random}.
714 *
715 * @param seed the seed.
716 *
717 * @see #getSeed
718 */
719 @Override
720 public void setSeed(long seed) {
721 /*
722 * Ignore call from super constructor (as well as any other calls
723 * unfortunate enough to be passing 0). It's critical that we
724 * ignore call from superclass constructor, as digest has not
725 * yet been initialized at that point.
726 */
727 if (seed != 0) {
728 setSeed(longToByteArray(seed));
729 }
730 }
731
732 /**
733 * Generates a user-specified number of random bytes.
734 *
735 * @param bytes the array to be filled in with random bytes.
736 */
737 @Override
738 public void nextBytes(byte[] bytes) {
739 if (threadSafe) {
740 secureRandomSpi.engineNextBytes(bytes);
741 } else {
742 synchronized (this) {
743 secureRandomSpi.engineNextBytes(bytes);
744 }
745 }
746 }
747
748 /**
749 * Generates a user-specified number of random bytes with
750 * additional parameters.
751 *
752 * @param bytes the array to be filled in with random bytes
753 * @param params additional parameters
754 * @throws NullPointerException if {@code bytes} is null
755 * @throws UnsupportedOperationException if the underlying provider
756 * implementation has not overridden this method
757 * @throws IllegalArgumentException if {@code params} is {@code null},
758 * illegal or unsupported by this {@code SecureRandom}
759 *
760 * @since 9
761 */
762 public void nextBytes(byte[] bytes, SecureRandomParameters params) {
763 if (params == null) {
764 throw new IllegalArgumentException("params cannot be null");
765 }
766 if (threadSafe) {
767 secureRandomSpi.engineNextBytes(
768 Objects.requireNonNull(bytes), params);
769 } else {
770 synchronized (this) {
771 secureRandomSpi.engineNextBytes(
772 Objects.requireNonNull(bytes), params);
773 }
774 }
775 }
776
777 /**
778 * Generates an integer containing the user-specified number of
779 * pseudo-random bits (right justified, with leading zeros). This
780 * method overrides a {@code java.util.Random} method, and serves
781 * to provide a source of random bits to all of the methods inherited
782 * from that class (for example, {@code nextInt},
783 * {@code nextLong}, and {@code nextFloat}).
784 *
785 * @param numBits number of pseudo-random bits to be generated, where
786 * {@code 0 <= numBits <= 32}.
787 *
788 * @return an {@code int} containing the user-specified number
789 * of pseudo-random bits (right justified, with leading zeros).
790 */
791 @Override
792 protected final int next(int numBits) {
793 int numBytes = (numBits+7)/8;
794 byte[] b = new byte[numBytes];
795 int next = 0;
796
797 nextBytes(b);
798 for (int i = 0; i < numBytes; i++) {
799 next = (next << 8) + (b[i] & 0xFF);
800 }
801
802 return next >>> (numBytes*8 - numBits);
803 }
804
805 /**
806 * Returns the given number of seed bytes, computed using the seed
807 * generation algorithm that this class uses to seed itself. This
808 * call may be used to seed other random number generators.
809 *
810 * <p>This method is only included for backwards compatibility.
811 * The caller is encouraged to use one of the alternative
812 * {@code getInstance} methods to obtain a {@code SecureRandom} object, and
813 * then call the {@code generateSeed} method to obtain seed bytes
814 * from that object.
815 *
816 * @param numBytes the number of seed bytes to generate.
817 *
818 * @throws IllegalArgumentException if {@code numBytes} is negative
819 * @return the seed bytes.
820 *
821 * @see #setSeed
822 */
823 public static byte[] getSeed(int numBytes) {
824 SecureRandom seedGen = seedGenerator;
825 if (seedGen == null) {
826 seedGen = new SecureRandom();
827 seedGenerator = seedGen;
828 }
829 return seedGen.generateSeed(numBytes);
830 }
831
832 /**
833 * Returns the given number of seed bytes, computed using the seed
834 * generation algorithm that this class uses to seed itself. This
835 * call may be used to seed other random number generators.
836 *
837 * @param numBytes the number of seed bytes to generate.
838 * @throws IllegalArgumentException if {@code numBytes} is negative
839 * @return the seed bytes.
840 */
841 public byte[] generateSeed(int numBytes) {
842 if (numBytes < 0) {
843 throw new IllegalArgumentException("numBytes cannot be negative");
844 }
845 if (threadSafe) {
846 return secureRandomSpi.engineGenerateSeed(numBytes);
847 } else {
848 synchronized (this) {
849 return secureRandomSpi.engineGenerateSeed(numBytes);
850 }
851 }
852 }
853
854 /**
855 * Helper function to convert a long into a byte array (least significant
856 * byte first).
857 */
858 private static byte[] longToByteArray(long l) {
859 byte[] retVal = new byte[8];
860
861 for (int i = 0; i < 8; i++) {
862 retVal[i] = (byte) l;
863 l >>= 8;
864 }
865
866 return retVal;
867 }
868
869 /**
870 * Gets a default PRNG algorithm by looking through all registered
871 * providers. Returns the first PRNG algorithm of the first provider that
872 * has registered a {@code SecureRandom} implementation, or null if none of
873 * the registered providers supplies a {@code SecureRandom} implementation.
874 */
875 private static String getPrngAlgorithm() {
876 for (Provider p : Providers.getProviderList().providers()) {
877 for (Service s : p.getServices()) {
878 if (s.getType().equals("SecureRandom")) {
879 return s.getAlgorithm();
880 }
881 }
882 }
883 return null;
884 }
885
886 /*
887 * Lazily initialize since Pattern.compile() is heavy.
888 * Effective Java (2nd Edition), Item 71.
889 */
890 private static final class StrongPatternHolder {
891 /*
892 * Entries are alg:prov separated by ,
893 * Allow for prepended/appended whitespace between entries.
894 *
895 * Capture groups:
896 * 1 - alg
897 * 2 - :prov (optional)
898 * 3 - prov (optional)
899 * 4 - ,nextEntry (optional)
900 * 5 - nextEntry (optional)
901 */
902 private static Pattern pattern =
903 Pattern.compile(
904 "\\s*([\\S&&[^:,]]*)(\\:([\\S&&[^,]]*))?\\s*(\\,(.*))?");
905 }
906
907 /**
908 * Returns a {@code SecureRandom} object that was selected by using
909 * the algorithms/providers specified in the {@code
910 * securerandom.strongAlgorithms} {@link Security} property.
911 * <p>
912 * Some situations require strong random values, such as when
913 * creating high-value/long-lived secrets like RSA public/private
914 * keys. To help guide applications in selecting a suitable strong
915 * {@code SecureRandom} implementation, Java distributions
916 * include a list of known strong {@code SecureRandom}
917 * implementations in the {@code securerandom.strongAlgorithms}
918 * Security property.
919 * <p>
920 * Every implementation of the Java platform is required to
921 * support at least one strong {@code SecureRandom} implementation.
922 *
923 * @return a strong {@code SecureRandom} implementation as indicated
924 * by the {@code securerandom.strongAlgorithms} Security property
925 *
926 * @throws NoSuchAlgorithmException if no algorithm is available
927 *
928 * @see Security#getProperty(String)
929 *
930 * @since 1.8
931 */
932 public static SecureRandom getInstanceStrong()
933 throws NoSuchAlgorithmException {
934
935 String property = AccessController.doPrivileged(
936 new PrivilegedAction<>() {
937 @Override
938 public String run() {
939 return Security.getProperty(
940 "securerandom.strongAlgorithms");
941 }
942 });
943
944 if ((property == null) || (property.length() == 0)) {
945 throw new NoSuchAlgorithmException(
946 "Null/empty securerandom.strongAlgorithms Security Property");
947 }
948
949 String remainder = property;
950 while (remainder != null) {
951 Matcher m;
952 if ((m = StrongPatternHolder.pattern.matcher(
953 remainder)).matches()) {
954
955 String alg = m.group(1);
956 String prov = m.group(3);
957
958 try {
959 if (prov == null) {
960 return SecureRandom.getInstance(alg);
961 } else {
962 return SecureRandom.getInstance(alg, prov);
963 }
964 } catch (NoSuchAlgorithmException |
965 NoSuchProviderException e) {
966 }
967 remainder = m.group(5);
968 } else {
969 remainder = null;
970 }
971 }
972
973 throw new NoSuchAlgorithmException(
974 "No strong SecureRandom impls available: " + property);
975 }
976
977 /**
978 * Reseeds this {@code SecureRandom} with entropy input read from its
979 * entropy source.
980 *
981 * @throws UnsupportedOperationException if the underlying provider
982 * implementation has not overridden this method.
983 *
984 * @since 9
985 */
986 public void reseed() {
987 if (threadSafe) {
988 secureRandomSpi.engineReseed(null);
989 } else {
990 synchronized (this) {
991 secureRandomSpi.engineReseed(null);
992 }
993 }
994 }
995
996 /**
997 * Reseeds this {@code SecureRandom} with entropy input read from its
998 * entropy source with additional parameters.
999 * <p>
1000 * Note that entropy is obtained from an entropy source. While
1001 * some data in {@code params} may contain entropy, its main usage is to
1002 * provide diversity.
1003 *
1004 * @param params extra parameters
1005 * @throws UnsupportedOperationException if the underlying provider
1006 * implementation has not overridden this method.
1007 * @throws IllegalArgumentException if {@code params} is {@code null},
1008 * illegal or unsupported by this {@code SecureRandom}
1009 *
1010 * @since 9
1011 */
1012 public void reseed(SecureRandomParameters params) {
1013 if (params == null) {
1014 throw new IllegalArgumentException("params cannot be null");
1015 }
1016 if (threadSafe) {
1017 secureRandomSpi.engineReseed(params);
1018 } else {
1019 synchronized (this) {
1020 secureRandomSpi.engineReseed(params);
1021 }
1022 }
1023 }
1024
1025 // Declare serialVersionUID to be compatible with JDK1.1
1026 static final long serialVersionUID = 4940670005562187L;
1027
1028 // Retain unused values serialized from JDK1.1
1029 /**
1030 * @serial
1031 */
1032 private byte[] state;
1033 /**
1034 * @serial
1035 */
1036 private MessageDigest digest = null;
1037 /**
1038 * @serial
1039 *
1040 * We know that the MessageDigest class does not implement
1041 * java.io.Serializable. However, since this field is no longer
1042 * used, it will always be NULL and won't affect the serialization
1043 * of the {@code SecureRandom} class itself.
1044 */
1045 private byte[] randomBytes;
1046 /**
1047 * @serial
1048 */
1049 private int randomBytesUsed;
1050 /**
1051 * @serial
1052 */
1053 private long counter;
1054 }