Make sure we use a nonce when a nonce is required
[openssl.git] / crypto / rand / drbg_lib.c
1 /*
2  * Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
3  *
4  * Licensed under the OpenSSL license (the "License").  You may not use
5  * this file except in compliance with the License.  You can obtain a copy
6  * in the file LICENSE in the source distribution or at
7  * https://www.openssl.org/source/license.html
8  */
9
10 #include <string.h>
11 #include <openssl/crypto.h>
12 #include <openssl/err.h>
13 #include <openssl/rand.h>
14 #include "rand_lcl.h"
15 #include "internal/thread_once.h"
16 #include "internal/rand_int.h"
17 #include "internal/cryptlib_int.h"
18
19 /*
20  * Support framework for NIST SP 800-90A DRBG
21  *
22  * See manual page RAND_DRBG(7) for a general overview.
23  *
24  * The OpenSSL model is to have new and free functions, and that new
25  * does all initialization.  That is not the NIST model, which has
26  * instantiation and un-instantiate, and re-use within a new/free
27  * lifecycle.  (No doubt this comes from the desire to support hardware
28  * DRBG, where allocation of resources on something like an HSM is
29  * a much bigger deal than just re-setting an allocated resource.)
30  */
31
32 /*
33  * The three shared DRBG instances
34  *
35  * There are three shared DRBG instances: <master>, <public>, and <private>.
36  */
37
38 /*
39  * The <master> DRBG
40  *
41  * Not used directly by the application, only for reseeding the two other
42  * DRBGs. It reseeds itself by pulling either randomness from os entropy
43  * sources or by consuming randomness which was added by RAND_add().
44  *
45  * The <master> DRBG is a global instance which is accessed concurrently by
46  * all threads. The necessary locking is managed automatically by its child
47  * DRBG instances during reseeding.
48  */
49 static RAND_DRBG *master_drbg;
50 /*
51  * The <public> DRBG
52  *
53  * Used by default for generating random bytes using RAND_bytes().
54  *
55  * The <public> DRBG is thread-local, i.e., there is one instance per thread.
56  */
57 static CRYPTO_THREAD_LOCAL public_drbg;
58 /*
59  * The <private> DRBG
60  *
61  * Used by default for generating private keys using RAND_priv_bytes()
62  *
63  * The <private> DRBG is thread-local, i.e., there is one instance per thread.
64  */
65 static CRYPTO_THREAD_LOCAL private_drbg;
66
67
68
69 /* NIST SP 800-90A DRBG recommends the use of a personalization string. */
70 static const char ossl_pers_string[] = "OpenSSL NIST SP 800-90A DRBG";
71
72 static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;
73
74
75
76 static int rand_drbg_type = RAND_DRBG_TYPE;
77 static unsigned int rand_drbg_flags = RAND_DRBG_FLAGS;
78
79 static unsigned int master_reseed_interval = MASTER_RESEED_INTERVAL;
80 static unsigned int slave_reseed_interval  = SLAVE_RESEED_INTERVAL;
81
82 static time_t master_reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
83 static time_t slave_reseed_time_interval  = SLAVE_RESEED_TIME_INTERVAL;
84
85 static RAND_DRBG *drbg_setup(RAND_DRBG *parent);
86
87 static RAND_DRBG *rand_drbg_new(int secure,
88                                 int type,
89                                 unsigned int flags,
90                                 RAND_DRBG *parent);
91
92 /*
93  * Set/initialize |drbg| to be of type |type|, with optional |flags|.
94  *
95  * If |type| and |flags| are zero, use the defaults
96  *
97  * Returns 1 on success, 0 on failure.
98  */
99 int RAND_DRBG_set(RAND_DRBG *drbg, int type, unsigned int flags)
100 {
101     int ret = 1;
102
103     if (type == 0 && flags == 0) {
104         type = rand_drbg_type;
105         flags = rand_drbg_flags;
106     }
107
108     drbg->state = DRBG_UNINITIALISED;
109     drbg->flags = flags;
110     drbg->type = type;
111
112     switch (type) {
113     default:
114         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
115         return 0;
116     case 0:
117         /* Uninitialized; that's okay. */
118         return 1;
119     case NID_aes_128_ctr:
120     case NID_aes_192_ctr:
121     case NID_aes_256_ctr:
122         ret = drbg_ctr_init(drbg);
123         break;
124     }
125
126     if (ret == 0)
127         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
128     return ret;
129 }
130
131 /*
132  * Set/initialize default |type| and |flag| for new drbg instances.
133  *
134  * Returns 1 on success, 0 on failure.
135  */
136 int RAND_DRBG_set_defaults(int type, unsigned int flags)
137 {
138     int ret = 1;
139
140     switch (type) {
141     default:
142         RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_TYPE);
143         return 0;
144     case NID_aes_128_ctr:
145     case NID_aes_192_ctr:
146     case NID_aes_256_ctr:
147         break;
148     }
149
150     if ((flags & ~RAND_DRBG_USED_FLAGS) != 0) {
151         RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_FLAGS);
152         return 0;
153     }
154
155     rand_drbg_type  = type;
156     rand_drbg_flags = flags;
157
158     return ret;
159 }
160
161
162 /*
163  * Allocate memory and initialize a new DRBG. The DRBG is allocated on
164  * the secure heap if |secure| is nonzero and the secure heap is enabled.
165  * The |parent|, if not NULL, will be used as random source for reseeding.
166  *
167  * Returns a pointer to the new DRBG instance on success, NULL on failure.
168  */
169 static RAND_DRBG *rand_drbg_new(int secure,
170                                 int type,
171                                 unsigned int flags,
172                                 RAND_DRBG *parent)
173 {
174     RAND_DRBG *drbg = secure ?
175         OPENSSL_secure_zalloc(sizeof(*drbg)) : OPENSSL_zalloc(sizeof(*drbg));
176
177     if (drbg == NULL) {
178         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
179         return NULL;
180     }
181
182     drbg->secure = secure && CRYPTO_secure_allocated(drbg);
183     drbg->fork_count = rand_fork_count;
184     drbg->parent = parent;
185
186     if (parent == NULL) {
187         drbg->reseed_interval = master_reseed_interval;
188         drbg->reseed_time_interval = master_reseed_time_interval;
189     } else {
190         drbg->reseed_interval = slave_reseed_interval;
191         drbg->reseed_time_interval = slave_reseed_time_interval;
192     }
193
194     if (RAND_DRBG_set(drbg, type, flags) == 0)
195         goto err;
196
197     if (parent != NULL) {
198         rand_drbg_lock(parent);
199         if (drbg->strength > parent->strength) {
200             /*
201              * We currently don't support the algorithm from NIST SP 800-90C
202              * 10.1.2 to use a weaker DRBG as source
203              */
204             rand_drbg_unlock(parent);
205             RANDerr(RAND_F_RAND_DRBG_NEW, RAND_R_PARENT_STRENGTH_TOO_WEAK);
206             goto err;
207         }
208         rand_drbg_unlock(parent);
209     }
210
211     if (!RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
212                                  rand_drbg_cleanup_entropy,
213                                  NULL, NULL))
214         goto err;
215
216     return drbg;
217
218 err:
219     if (drbg->secure)
220         OPENSSL_secure_free(drbg);
221     else
222         OPENSSL_free(drbg);
223
224     return NULL;
225 }
226
227 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
228 {
229     return rand_drbg_new(0, type, flags, parent);
230 }
231
232 RAND_DRBG *RAND_DRBG_secure_new(int type, unsigned int flags, RAND_DRBG *parent)
233 {
234     return rand_drbg_new(1, type, flags, parent);
235 }
236
237 /*
238  * Uninstantiate |drbg| and free all memory.
239  */
240 void RAND_DRBG_free(RAND_DRBG *drbg)
241 {
242     if (drbg == NULL)
243         return;
244
245     if (drbg->meth != NULL)
246         drbg->meth->uninstantiate(drbg);
247     CRYPTO_THREAD_lock_free(drbg->lock);
248     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
249
250     if (drbg->secure)
251         OPENSSL_secure_clear_free(drbg, sizeof(*drbg));
252     else
253         OPENSSL_clear_free(drbg, sizeof(*drbg));
254 }
255
256 /*
257  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
258  * |perslen| as prediction-resistance input.
259  *
260  * Requires that drbg->lock is already locked for write, if non-null.
261  *
262  * Returns 1 on success, 0 on failure.
263  */
264 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
265                           const unsigned char *pers, size_t perslen)
266 {
267     unsigned char *nonce = NULL, *entropy = NULL;
268     size_t noncelen = 0, entropylen = 0;
269     size_t min_entropy = drbg->strength;
270     size_t min_entropylen = drbg->min_entropylen;
271     size_t max_entropylen = drbg->max_entropylen;
272
273     if (perslen > drbg->max_perslen) {
274         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
275                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
276         goto end;
277     }
278
279     if (drbg->meth == NULL)
280     {
281         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
282                 RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
283         goto end;
284     }
285
286     if (drbg->state != DRBG_UNINITIALISED) {
287         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
288                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
289                                           : RAND_R_ALREADY_INSTANTIATED);
290         goto end;
291     }
292
293     drbg->state = DRBG_ERROR;
294
295     /*
296      * NIST SP800-90Ar1 section 9.1 says you can combine getting the entropy
297      * and nonce in 1 call by increasing the entropy with 50% and increasing
298      * the minimum length to accomadate the length of the nonce.
299      * We do this in case a nonce is require and get_nonce is NULL.
300      */
301     if (drbg->min_noncelen > 0 && drbg->get_nonce == NULL) {
302         min_entropy += drbg->strength / 2;
303         min_entropylen += drbg->min_noncelen;
304         max_entropylen += drbg->max_noncelen;
305     }
306
307     if (drbg->get_entropy != NULL)
308         entropylen = drbg->get_entropy(drbg, &entropy, min_entropy,
309                                        min_entropylen, max_entropylen, 0);
310     if (entropylen < min_entropylen
311         || entropylen > max_entropylen) {
312         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
313         goto end;
314     }
315
316     if (drbg->min_noncelen > 0 && drbg->get_nonce != NULL) {
317         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
318                                    drbg->min_noncelen, drbg->max_noncelen);
319         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
320             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_NONCE);
321             goto end;
322         }
323     }
324
325     if (!drbg->meth->instantiate(drbg, entropy, entropylen,
326                          nonce, noncelen, pers, perslen)) {
327         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
328         goto end;
329     }
330
331     drbg->state = DRBG_READY;
332     drbg->generate_counter = 0;
333     drbg->reseed_time = time(NULL);
334     if (drbg->reseed_counter > 0) {
335         if (drbg->parent == NULL)
336             drbg->reseed_counter++;
337         else
338             drbg->reseed_counter = drbg->parent->reseed_counter;
339     }
340
341 end:
342     if (entropy != NULL && drbg->cleanup_entropy != NULL)
343         drbg->cleanup_entropy(drbg, entropy, entropylen);
344     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
345         drbg->cleanup_nonce(drbg, nonce, noncelen);
346     if (drbg->pool != NULL) {
347         if (drbg->state == DRBG_READY) {
348             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
349                     RAND_R_ERROR_ENTROPY_POOL_WAS_IGNORED);
350             drbg->state = DRBG_ERROR;
351         }
352         rand_pool_free(drbg->pool);
353         drbg->pool = NULL;
354     }
355     if (drbg->state == DRBG_READY)
356         return 1;
357     return 0;
358 }
359
360 /*
361  * Uninstantiate |drbg|. Must be instantiated before it can be used.
362  *
363  * Requires that drbg->lock is already locked for write, if non-null.
364  *
365  * Returns 1 on success, 0 on failure.
366  */
367 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
368 {
369     if (drbg->meth == NULL)
370     {
371         RANDerr(RAND_F_RAND_DRBG_UNINSTANTIATE,
372                 RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
373         return 0;
374     }
375
376     /* Clear the entire drbg->ctr struct, then reset some important
377      * members of the drbg->ctr struct (e.g. keysize, df_ks) to their
378      * initial values.
379      */
380     drbg->meth->uninstantiate(drbg);
381     return RAND_DRBG_set(drbg, drbg->type, drbg->flags);
382 }
383
384 /*
385  * Reseed |drbg|, mixing in the specified data
386  *
387  * Requires that drbg->lock is already locked for write, if non-null.
388  *
389  * Returns 1 on success, 0 on failure.
390  */
391 int RAND_DRBG_reseed(RAND_DRBG *drbg,
392                      const unsigned char *adin, size_t adinlen,
393                      int prediction_resistance)
394 {
395     unsigned char *entropy = NULL;
396     size_t entropylen = 0;
397
398     if (drbg->state == DRBG_ERROR) {
399         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
400         return 0;
401     }
402     if (drbg->state == DRBG_UNINITIALISED) {
403         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
404         return 0;
405     }
406
407     if (adin == NULL)
408         adinlen = 0;
409     else if (adinlen > drbg->max_adinlen) {
410         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
411         return 0;
412     }
413
414     drbg->state = DRBG_ERROR;
415     if (drbg->get_entropy != NULL)
416         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
417                                        drbg->min_entropylen,
418                                        drbg->max_entropylen,
419                                        prediction_resistance);
420     if (entropylen < drbg->min_entropylen
421         || entropylen > drbg->max_entropylen) {
422         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
423         goto end;
424     }
425
426     if (!drbg->meth->reseed(drbg, entropy, entropylen, adin, adinlen))
427         goto end;
428
429     drbg->state = DRBG_READY;
430     drbg->generate_counter = 0;
431     drbg->reseed_time = time(NULL);
432     if (drbg->reseed_counter > 0) {
433         if (drbg->parent == NULL)
434             drbg->reseed_counter++;
435         else
436             drbg->reseed_counter = drbg->parent->reseed_counter;
437     }
438
439 end:
440     if (entropy != NULL && drbg->cleanup_entropy != NULL)
441         drbg->cleanup_entropy(drbg, entropy, entropylen);
442     if (drbg->state == DRBG_READY)
443         return 1;
444     return 0;
445 }
446
447 /*
448  * Restart |drbg|, using the specified entropy or additional input
449  *
450  * Tries its best to get the drbg instantiated by all means,
451  * regardless of its current state.
452  *
453  * Optionally, a |buffer| of |len| random bytes can be passed,
454  * which is assumed to contain at least |entropy| bits of entropy.
455  *
456  * If |entropy| > 0, the buffer content is used as entropy input.
457  *
458  * If |entropy| == 0, the buffer content is used as additional input
459  *
460  * Returns 1 on success, 0 on failure.
461  *
462  * This function is used internally only.
463  */
464 int rand_drbg_restart(RAND_DRBG *drbg,
465                       const unsigned char *buffer, size_t len, size_t entropy)
466 {
467     int reseeded = 0;
468     const unsigned char *adin = NULL;
469     size_t adinlen = 0;
470
471     if (drbg->pool != NULL) {
472         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
473         rand_pool_free(drbg->pool);
474         drbg->pool = NULL;
475     }
476
477     if (buffer != NULL) {
478         if (entropy > 0) {
479             if (drbg->max_entropylen < len) {
480                 RANDerr(RAND_F_RAND_DRBG_RESTART,
481                     RAND_R_ENTROPY_INPUT_TOO_LONG);
482                 return 0;
483             }
484
485             if (entropy > 8 * len) {
486                 RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
487                 return 0;
488             }
489
490             /* will be picked up by the rand_drbg_get_entropy() callback */
491             drbg->pool = rand_pool_new(entropy, len, len);
492             if (drbg->pool == NULL)
493                 return 0;
494
495             rand_pool_add(drbg->pool, buffer, len, entropy);
496         } else {
497             if (drbg->max_adinlen < len) {
498                 RANDerr(RAND_F_RAND_DRBG_RESTART,
499                         RAND_R_ADDITIONAL_INPUT_TOO_LONG);
500                 return 0;
501             }
502             adin = buffer;
503             adinlen = len;
504         }
505     }
506
507     /* repair error state */
508     if (drbg->state == DRBG_ERROR)
509         RAND_DRBG_uninstantiate(drbg);
510
511     /* repair uninitialized state */
512     if (drbg->state == DRBG_UNINITIALISED) {
513         /* reinstantiate drbg */
514         RAND_DRBG_instantiate(drbg,
515                               (const unsigned char *) ossl_pers_string,
516                               sizeof(ossl_pers_string) - 1);
517         /* already reseeded. prevent second reseeding below */
518         reseeded = (drbg->state == DRBG_READY);
519     }
520
521     /* refresh current state if entropy or additional input has been provided */
522     if (drbg->state == DRBG_READY) {
523         if (adin != NULL) {
524             /*
525              * mix in additional input without reseeding
526              *
527              * Similar to RAND_DRBG_reseed(), but the provided additional
528              * data |adin| is mixed into the current state without pulling
529              * entropy from the trusted entropy source using get_entropy().
530              * This is not a reseeding in the strict sense of NIST SP 800-90A.
531              */
532             drbg->meth->reseed(drbg, adin, adinlen, NULL, 0);
533         } else if (reseeded == 0) {
534             /* do a full reseeding if it has not been done yet above */
535             RAND_DRBG_reseed(drbg, NULL, 0, 0);
536         }
537     }
538
539     /* check whether a given entropy pool was cleared properly during reseed */
540     if (drbg->pool != NULL) {
541         drbg->state = DRBG_ERROR;
542         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
543         rand_pool_free(drbg->pool);
544         drbg->pool = NULL;
545         return 0;
546     }
547
548     return drbg->state == DRBG_READY;
549 }
550
551 /*
552  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
553  * to or if |prediction_resistance| is set.  Additional input can be
554  * sent in |adin| and |adinlen|.
555  *
556  * Requires that drbg->lock is already locked for write, if non-null.
557  *
558  * Returns 1 on success, 0 on failure.
559  *
560  */
561 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
562                        int prediction_resistance,
563                        const unsigned char *adin, size_t adinlen)
564 {
565     int reseed_required = 0;
566
567     if (drbg->state != DRBG_READY) {
568         /* try to recover from previous errors */
569         rand_drbg_restart(drbg, NULL, 0, 0);
570
571         if (drbg->state == DRBG_ERROR) {
572             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
573             return 0;
574         }
575         if (drbg->state == DRBG_UNINITIALISED) {
576             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
577             return 0;
578         }
579     }
580
581     if (outlen > drbg->max_request) {
582         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
583         return 0;
584     }
585     if (adinlen > drbg->max_adinlen) {
586         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
587         return 0;
588     }
589
590     if (drbg->fork_count != rand_fork_count) {
591         drbg->fork_count = rand_fork_count;
592         reseed_required = 1;
593     }
594
595     if (drbg->reseed_interval > 0) {
596         if (drbg->generate_counter >= drbg->reseed_interval)
597             reseed_required = 1;
598     }
599     if (drbg->reseed_time_interval > 0) {
600         time_t now = time(NULL);
601         if (now < drbg->reseed_time
602             || now - drbg->reseed_time >= drbg->reseed_time_interval)
603             reseed_required = 1;
604     }
605     if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
606         if (drbg->reseed_counter != drbg->parent->reseed_counter)
607             reseed_required = 1;
608     }
609
610     if (reseed_required || prediction_resistance) {
611         if (!RAND_DRBG_reseed(drbg, adin, adinlen, prediction_resistance)) {
612             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
613             return 0;
614         }
615         adin = NULL;
616         adinlen = 0;
617     }
618
619     if (!drbg->meth->generate(drbg, out, outlen, adin, adinlen)) {
620         drbg->state = DRBG_ERROR;
621         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
622         return 0;
623     }
624
625     drbg->generate_counter++;
626
627     return 1;
628 }
629
630 /*
631  * Generates |outlen| random bytes and stores them in |out|. It will
632  * using the given |drbg| to generate the bytes.
633  *
634  * Requires that drbg->lock is already locked for write, if non-null.
635  *
636  * Returns 1 on success 0 on failure.
637  */
638 int RAND_DRBG_bytes(RAND_DRBG *drbg, unsigned char *out, size_t outlen)
639 {
640     unsigned char *additional = NULL;
641     size_t additional_len;
642     size_t chunk;
643     size_t ret;
644
645     additional_len = rand_drbg_get_additional_data(&additional, drbg->max_adinlen);
646
647     for ( ; outlen > 0; outlen -= chunk, out += chunk) {
648         chunk = outlen;
649         if (chunk > drbg->max_request)
650             chunk = drbg->max_request;
651         ret = RAND_DRBG_generate(drbg, out, chunk, 0, additional, additional_len);
652         if (!ret)
653             goto err;
654     }
655     ret = 1;
656
657 err:
658     if (additional_len != 0)
659         OPENSSL_secure_clear_free(additional, additional_len);
660
661     return ret;
662 }
663
664 /*
665  * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
666  *
667  * Setting the callbacks is allowed only if the drbg has not been
668  * initialized yet. Otherwise, the operation will fail.
669  *
670  * Returns 1 on success, 0 on failure.
671  */
672 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
673                             RAND_DRBG_get_entropy_fn get_entropy,
674                             RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
675                             RAND_DRBG_get_nonce_fn get_nonce,
676                             RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
677 {
678     if (drbg->state != DRBG_UNINITIALISED)
679         return 0;
680     drbg->get_entropy = get_entropy;
681     drbg->cleanup_entropy = cleanup_entropy;
682     drbg->get_nonce = get_nonce;
683     drbg->cleanup_nonce = cleanup_nonce;
684     return 1;
685 }
686
687 /*
688  * Set the reseed interval.
689  *
690  * The drbg will reseed automatically whenever the number of generate
691  * requests exceeds the given reseed interval. If the reseed interval
692  * is 0, then this feature is disabled.
693  *
694  * Returns 1 on success, 0 on failure.
695  */
696 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
697 {
698     if (interval > MAX_RESEED_INTERVAL)
699         return 0;
700     drbg->reseed_interval = interval;
701     return 1;
702 }
703
704 /*
705  * Set the reseed time interval.
706  *
707  * The drbg will reseed automatically whenever the time elapsed since
708  * the last reseeding exceeds the given reseed time interval. For safety,
709  * a reseeding will also occur if the clock has been reset to a smaller
710  * value.
711  *
712  * Returns 1 on success, 0 on failure.
713  */
714 int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
715 {
716     if (interval > MAX_RESEED_TIME_INTERVAL)
717         return 0;
718     drbg->reseed_time_interval = interval;
719     return 1;
720 }
721
722 /*
723  * Set the default values for reseed (time) intervals of new DRBG instances
724  *
725  * The default values can be set independently for master DRBG instances
726  * (without a parent) and slave DRBG instances (with parent).
727  *
728  * Returns 1 on success, 0 on failure.
729  */
730
731 int RAND_DRBG_set_reseed_defaults(
732                                   unsigned int _master_reseed_interval,
733                                   unsigned int _slave_reseed_interval,
734                                   time_t _master_reseed_time_interval,
735                                   time_t _slave_reseed_time_interval
736                                   )
737 {
738     if (_master_reseed_interval > MAX_RESEED_INTERVAL
739         || _slave_reseed_interval > MAX_RESEED_INTERVAL)
740         return 0;
741
742     if (_master_reseed_time_interval > MAX_RESEED_TIME_INTERVAL
743         || _slave_reseed_time_interval > MAX_RESEED_TIME_INTERVAL)
744         return 0;
745
746     master_reseed_interval = _master_reseed_interval;
747     slave_reseed_interval = _slave_reseed_interval;
748
749     master_reseed_time_interval = _master_reseed_time_interval;
750     slave_reseed_time_interval = _slave_reseed_time_interval;
751
752     return 1;
753 }
754
755 /*
756  * Locks the given drbg. Locking a drbg which does not have locking
757  * enabled is considered a successful no-op.
758  *
759  * Returns 1 on success, 0 on failure.
760  */
761 int rand_drbg_lock(RAND_DRBG *drbg)
762 {
763     if (drbg->lock != NULL)
764         return CRYPTO_THREAD_write_lock(drbg->lock);
765
766     return 1;
767 }
768
769 /*
770  * Unlocks the given drbg. Unlocking a drbg which does not have locking
771  * enabled is considered a successful no-op.
772  *
773  * Returns 1 on success, 0 on failure.
774  */
775 int rand_drbg_unlock(RAND_DRBG *drbg)
776 {
777     if (drbg->lock != NULL)
778         return CRYPTO_THREAD_unlock(drbg->lock);
779
780     return 1;
781 }
782
783 /*
784  * Enables locking for the given drbg
785  *
786  * Locking can only be enabled if the random generator
787  * is in the uninitialized state.
788  *
789  * Returns 1 on success, 0 on failure.
790  */
791 int rand_drbg_enable_locking(RAND_DRBG *drbg)
792 {
793     if (drbg->state != DRBG_UNINITIALISED) {
794         RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
795                 RAND_R_DRBG_ALREADY_INITIALIZED);
796         return 0;
797     }
798
799     if (drbg->lock == NULL) {
800         if (drbg->parent != NULL && drbg->parent->lock == NULL) {
801             RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
802                     RAND_R_PARENT_LOCKING_NOT_ENABLED);
803             return 0;
804         }
805
806         drbg->lock = CRYPTO_THREAD_lock_new();
807         if (drbg->lock == NULL) {
808             RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
809                     RAND_R_FAILED_TO_CREATE_LOCK);
810             return 0;
811         }
812     }
813
814     return 1;
815 }
816
817 /*
818  * Get and set the EXDATA
819  */
820 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
821 {
822     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
823 }
824
825 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
826 {
827     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
828 }
829
830
831 /*
832  * The following functions provide a RAND_METHOD that works on the
833  * global DRBG.  They lock.
834  */
835
836 /*
837  * Allocates a new global DRBG on the secure heap (if enabled) and
838  * initializes it with default settings.
839  *
840  * Returns a pointer to the new DRBG instance on success, NULL on failure.
841  */
842 static RAND_DRBG *drbg_setup(RAND_DRBG *parent)
843 {
844     RAND_DRBG *drbg;
845
846     drbg = RAND_DRBG_secure_new(rand_drbg_type, rand_drbg_flags, parent);
847     if (drbg == NULL)
848         return NULL;
849
850     /* Only the master DRBG needs to have a lock */
851     if (parent == NULL && rand_drbg_enable_locking(drbg) == 0)
852         goto err;
853
854     /* enable seed propagation */
855     drbg->reseed_counter = 1;
856
857     /*
858      * Ignore instantiation error so support just-in-time instantiation.
859      *
860      * The state of the drbg will be checked in RAND_DRBG_generate() and
861      * an automatic recovery is attempted.
862      */
863     RAND_DRBG_instantiate(drbg,
864                           (const unsigned char *) ossl_pers_string,
865                           sizeof(ossl_pers_string) - 1);
866     return drbg;
867
868 err:
869     RAND_DRBG_free(drbg);
870     return NULL;
871 }
872
873 /*
874  * Initialize the global DRBGs on first use.
875  * Returns 1 on success, 0 on failure.
876  */
877 DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
878 {
879     int ret = 1;
880
881     /*
882      * ensure that libcrypto is initialized, otherwise the
883      * DRBG locks are not cleaned up properly
884      */
885     if (!OPENSSL_init_crypto(0, NULL))
886         return 0;
887
888     ossl_init_thread_start(OPENSSL_INIT_THREAD_RAND);
889
890     master_drbg = drbg_setup(NULL);
891
892     ret &= CRYPTO_THREAD_init_local(&private_drbg, NULL);
893     ret &= CRYPTO_THREAD_init_local(&public_drbg, NULL);
894
895     if (master_drbg == NULL || ret == 0)
896         return 0;
897
898     return 1;
899 }
900
901 /* Clean up the global DRBGs before exit */
902 void rand_drbg_cleanup_int(void)
903 {
904     RAND_DRBG_free(master_drbg);
905     master_drbg = NULL;
906
907     CRYPTO_THREAD_cleanup_local(&private_drbg);
908     CRYPTO_THREAD_cleanup_local(&public_drbg);
909 }
910
911 void drbg_delete_thread_state()
912 {
913     RAND_DRBG *drbg;
914
915     drbg = CRYPTO_THREAD_get_local(&public_drbg);
916     RAND_DRBG_free(drbg);
917
918     drbg = CRYPTO_THREAD_get_local(&private_drbg);
919     RAND_DRBG_free(drbg);
920 }
921
922 /* Implements the default OpenSSL RAND_bytes() method */
923 static int drbg_bytes(unsigned char *out, int count)
924 {
925     int ret;
926     RAND_DRBG *drbg = RAND_DRBG_get0_public();
927
928     if (drbg == NULL)
929         return 0;
930
931     ret = RAND_DRBG_bytes(drbg, out, count);
932
933     return ret;
934 }
935
936 /* Implements the default OpenSSL RAND_add() method */
937 static int drbg_add(const void *buf, int num, double randomness)
938 {
939     int ret = 0;
940     RAND_DRBG *drbg = RAND_DRBG_get0_master();
941
942     if (drbg == NULL)
943         return 0;
944
945     if (num < 0 || randomness < 0.0)
946         return 0;
947
948     if (randomness > (double)drbg->max_entropylen) {
949         /*
950          * The purpose of this check is to bound |randomness| by a
951          * relatively small value in order to prevent an integer
952          * overflow when multiplying by 8 in the rand_drbg_restart()
953          * call below.
954          */
955         return 0;
956     }
957
958     rand_drbg_lock(drbg);
959     ret = rand_drbg_restart(drbg, buf,
960                             (size_t)(unsigned int)num,
961                             (size_t)(8*randomness));
962     rand_drbg_unlock(drbg);
963
964     return ret;
965 }
966
967 /* Implements the default OpenSSL RAND_seed() method */
968 static int drbg_seed(const void *buf, int num)
969 {
970     return drbg_add(buf, num, num);
971 }
972
973 /* Implements the default OpenSSL RAND_status() method */
974 static int drbg_status(void)
975 {
976     int ret;
977     RAND_DRBG *drbg = RAND_DRBG_get0_master();
978
979     if (drbg == NULL)
980         return 0;
981
982     rand_drbg_lock(drbg);
983     ret = drbg->state == DRBG_READY ? 1 : 0;
984     rand_drbg_unlock(drbg);
985     return ret;
986 }
987
988 /*
989  * Get the master DRBG.
990  * Returns pointer to the DRBG on success, NULL on failure.
991  *
992  */
993 RAND_DRBG *RAND_DRBG_get0_master(void)
994 {
995     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
996         return NULL;
997
998     return master_drbg;
999 }
1000
1001 /*
1002  * Get the public DRBG.
1003  * Returns pointer to the DRBG on success, NULL on failure.
1004  */
1005 RAND_DRBG *RAND_DRBG_get0_public(void)
1006 {
1007     RAND_DRBG *drbg;
1008
1009     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
1010         return NULL;
1011
1012     drbg = CRYPTO_THREAD_get_local(&public_drbg);
1013     if (drbg == NULL) {
1014         ossl_init_thread_start(OPENSSL_INIT_THREAD_RAND);
1015         drbg = drbg_setup(master_drbg);
1016         CRYPTO_THREAD_set_local(&public_drbg, drbg);
1017     }
1018     return drbg;
1019 }
1020
1021 /*
1022  * Get the private DRBG.
1023  * Returns pointer to the DRBG on success, NULL on failure.
1024  */
1025 RAND_DRBG *RAND_DRBG_get0_private(void)
1026 {
1027     RAND_DRBG *drbg;
1028
1029     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
1030         return NULL;
1031
1032     drbg = CRYPTO_THREAD_get_local(&private_drbg);
1033     if (drbg == NULL) {
1034         ossl_init_thread_start(OPENSSL_INIT_THREAD_RAND);
1035         drbg = drbg_setup(master_drbg);
1036         CRYPTO_THREAD_set_local(&private_drbg, drbg);
1037     }
1038     return drbg;
1039 }
1040
1041 RAND_METHOD rand_meth = {
1042     drbg_seed,
1043     drbg_bytes,
1044     NULL,
1045     drbg_add,
1046     drbg_bytes,
1047     drbg_status
1048 };
1049
1050 RAND_METHOD *RAND_OpenSSL(void)
1051 {
1052     return &rand_meth;
1053 }