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
  18 /*
  19  * Support framework for NIST SP 800-90A DRBG, AES-CTR mode.
  20  * The RAND_DRBG is OpenSSL's pointer to an instance of the DRBG.
  21  *
  22  * The OpenSSL model is to have new and free functions, and that new
  23  * does all initialization.  That is not the NIST model, which has
  24  * instantiation and un-instantiate, and re-use within a new/free
  25  * lifecycle.  (No doubt this comes from the desire to support hardware
  26  * DRBG, where allocation of resources on something like an HSM is
  27  * a much bigger deal than just re-setting an allocated resource.)
  28  */
  29
  30 /*
  31  * THE THREE SHARED DRBGs
  32  *
  33  * There are three shared DRBGs (master, public and private), which are
  34  * accessed concurrently by all threads.
  35  *
  36  * THE MASTER DRBG
  37  *
  38  * Not used directly by the application, only for reseeding the two other
  39  * DRBGs. It reseeds itself by pulling either randomness from os entropy
  40  * sources or by consuming randomnes which was added by RAND_add()
  41  */
  42 static RAND_DRBG *drbg_master;
  43 /*
  44  * THE PUBLIC DRBG
  45  *
  46  * Used by default for generating random bytes using RAND_bytes().
  47  */
  48 static RAND_DRBG *drbg_public;
  49 /*
  50  * THE PRIVATE DRBG
  51  *
  52  * Used by default for generating private keys using RAND_priv_bytes()
  53  */
  54 static RAND_DRBG *drbg_private;
  55 /*+
  56  * DRBG HIERARCHY
  57  *
  58  * In addition there are DRBGs, which are not shared, but used only by a
  59  * single thread at every time, for example the DRBGs which are owned by
  60  * an SSL context. All DRBGs are organized in a hierarchical fashion
  61  * with the <master> DRBG as root.
  62  *
  63  * This gives the following overall picture:
  64  *
  65  *                  <os entropy sources>
  66  *                         |
  67  *    RAND_add() ==>    <master>          \
  68  *                       /   \            | shared DRBGs (with locking)
  69  *                 <public>  <private>    /
  70  *                     |
  71  *                   <ssl>  owned by an SSL context
  72  *
  73  * AUTOMATIC RESEEDING
  74  *
  75  * Before satisfying a generate request, a DRBG reseeds itself automatically,
  76  * if one of the following two conditions holds:
  77  *
  78  * - the number of generate requests since the last reseeding exceeds a
  79  *   certain threshold, the so called |reseed_interval|. This behaviour
  80  *   can be disabled by setting the |reseed_interval| to 0.
  81  *
  82  * - the time elapsed since the last reseeding exceeds a certain time
  83  *   interval, the so called |reseed_time_interval|. This behaviour
  84  *   can be disabled by setting the |reseed_time_interval| to 0.
  85  *
  86  * MANUAL RESEEDING
  87  *
  88  * For the three shared DRBGs (and only for these) there is another way to
  89  * reseed them manually by calling RAND_seed() (or RAND_add() with a positive
  90  * |randomness| argument). This will immediately reseed the <master> DRBG.
  91  * The <public> and <private> DRBG will detect this on their next generate
  92  * call and reseed, pulling randomness from <master>.
  93  */
  94
  95
  96 /* NIST SP 800-90A DRBG recommends the use of a personalization string. */
  97 static const char ossl_pers_string[] = "OpenSSL NIST SP 800-90A DRBG";
  98
  99 static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;
 100
 101 static RAND_DRBG *drbg_setup(RAND_DRBG *parent);
 102 static void drbg_cleanup(RAND_DRBG *drbg);
 103
 104 /*
 105  * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
 106  *
 107  * Returns 1 on success, 0 on failure.
 108  */
 109 int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
 110 {
 111     int ret = 1;
 112
 113     drbg->state = DRBG_UNINITIALISED;
 114     drbg->flags = flags;
 115     drbg->nid = nid;
 116
 117     switch (nid) {
 118     default:
 119         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
 120         return 0;
 121     case 0:
 122         /* Uninitialized; that's okay. */
 123         return 1;
 124     case NID_aes_128_ctr:
 125     case NID_aes_192_ctr:
 126     case NID_aes_256_ctr:
 127         ret = drbg_ctr_init(drbg);
 128         break;
 129     }
 130
 131     if (ret == 0)
 132         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
 133     return ret;
 134 }
 135
 136 /*
 137  * Allocate memory and initialize a new DRBG.  The |parent|, if not
 138  * NULL, will be used to auto-seed this RAND_DRBG as needed.
 139  *
 140  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 141  */
 142 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
 143 {
 144     RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
 145
 146     if (drbg == NULL) {
 147         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
 148         goto err;
 149     }
 150     drbg->fork_count = rand_fork_count;
 151     drbg->parent = parent;
 152     if (RAND_DRBG_set(drbg, type, flags) == 0)
 153         goto err;
 154
 155     if (!RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 156                                  rand_drbg_cleanup_entropy,
 157                                  NULL, NULL))
 158         goto err;
 159
 160     return drbg;
 161
 162 err:
 163     OPENSSL_free(drbg);
 164     return NULL;
 165 }
 166
 167 /*
 168  * Uninstantiate |drbg| and free all memory.
 169  */
 170 void RAND_DRBG_free(RAND_DRBG *drbg)
 171 {
 172     if (drbg == NULL)
 173         return;
 174
 175     if (drbg->meth != NULL)
 176         drbg->meth->uninstantiate(drbg);
 177     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 178     OPENSSL_clear_free(drbg, sizeof(*drbg));
 179 }
 180
 181 /*
 182  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 183  * |perslen| as prediction-resistance input.
 184  *
 185  * Requires that drbg->lock is already locked for write, if non-null.
 186  *
 187  * Returns 1 on success, 0 on failure.
 188  */
 189 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 190                           const unsigned char *pers, size_t perslen)
 191 {
 192     unsigned char *nonce = NULL, *entropy = NULL;
 193     size_t noncelen = 0, entropylen = 0;
 194
 195     if (perslen > drbg->max_perslen) {
 196         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 197                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 198         goto end;
 199     }
 200
 201     if (drbg->meth == NULL)
 202     {
 203         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 204                 RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
 205         goto end;
 206     }
 207
 208     if (drbg->state != DRBG_UNINITIALISED) {
 209         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 210                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 211                                           : RAND_R_ALREADY_INSTANTIATED);
 212         goto end;
 213     }
 214
 215     drbg->state = DRBG_ERROR;
 216     if (drbg->get_entropy != NULL)
 217         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 218                                    drbg->min_entropylen, drbg->max_entropylen);
 219     if (entropylen < drbg->min_entropylen
 220         || entropylen > drbg->max_entropylen) {
 221         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 222         goto end;
 223     }
 224
 225     if (drbg->max_noncelen > 0 && drbg->get_nonce != NULL) {
 226         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 227                                    drbg->min_noncelen, drbg->max_noncelen);
 228         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
 229             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 230                     RAND_R_ERROR_RETRIEVING_NONCE);
 231             goto end;
 232         }
 233     }
 234
 235     if (!drbg->meth->instantiate(drbg, entropy, entropylen,
 236                          nonce, noncelen, pers, perslen)) {
 237         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 238         goto end;
 239     }
 240
 241     drbg->state = DRBG_READY;
 242     drbg->generate_counter = 0;
 243     drbg->reseed_time = time(NULL);
 244     if (drbg->reseed_counter > 0) {
 245         if (drbg->parent == NULL)
 246             drbg->reseed_counter++;
 247         else
 248             drbg->reseed_counter = drbg->parent->reseed_counter;
 249     }
 250
 251 end:
 252     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 253         drbg->cleanup_entropy(drbg, entropy, entropylen);
 254     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 255         drbg->cleanup_nonce(drbg, nonce, noncelen);
 256     if (drbg->pool != NULL) {
 257         if (drbg->state == DRBG_READY) {
 258             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 259                     RAND_R_ERROR_ENTROPY_POOL_WAS_IGNORED);
 260             drbg->state = DRBG_ERROR;
 261         }
 262         RAND_POOL_free(drbg->pool);
 263         drbg->pool = NULL;
 264     }
 265     if (drbg->state == DRBG_READY)
 266         return 1;
 267     return 0;
 268 }
 269
 270 /*
 271  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 272  *
 273  * Requires that drbg->lock is already locked for write, if non-null.
 274  *
 275  * Returns 1 on success, 0 on failure.
 276  */
 277 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 278 {
 279     if (drbg->meth == NULL)
 280     {
 281         RANDerr(RAND_F_RAND_DRBG_UNINSTANTIATE,
 282                 RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
 283         return 0;
 284     }
 285
 286     /* Clear the entire drbg->ctr struct, then reset some important
 287      * members of the drbg->ctr struct (e.g. keysize, df_ks) to their
 288      * initial values.
 289      */
 290     drbg->meth->uninstantiate(drbg);
 291     return RAND_DRBG_set(drbg, drbg->nid, drbg->flags);
 292 }
 293
 294 /*
 295  * Reseed |drbg|, mixing in the specified data
 296  *
 297  * Requires that drbg->lock is already locked for write, if non-null.
 298  *
 299  * Returns 1 on success, 0 on failure.
 300  */
 301 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 302                      const unsigned char *adin, size_t adinlen)
 303 {
 304     unsigned char *entropy = NULL;
 305     size_t entropylen = 0;
 306
 307     if (drbg->state == DRBG_ERROR) {
 308         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 309         return 0;
 310     }
 311     if (drbg->state == DRBG_UNINITIALISED) {
 312         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 313         return 0;
 314     }
 315
 316     if (adin == NULL)
 317         adinlen = 0;
 318     else if (adinlen > drbg->max_adinlen) {
 319         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 320         return 0;
 321     }
 322
 323     drbg->state = DRBG_ERROR;
 324     if (drbg->get_entropy != NULL)
 325         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 326                                    drbg->min_entropylen, drbg->max_entropylen);
 327     if (entropylen < drbg->min_entropylen
 328         || entropylen > drbg->max_entropylen) {
 329         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 330         goto end;
 331     }
 332
 333     if (!drbg->meth->reseed(drbg, entropy, entropylen, adin, adinlen))
 334         goto end;
 335
 336     drbg->state = DRBG_READY;
 337     drbg->generate_counter = 0;
 338     drbg->reseed_time = time(NULL);
 339     if (drbg->reseed_counter > 0) {
 340         if (drbg->parent == NULL)
 341             drbg->reseed_counter++;
 342         else
 343             drbg->reseed_counter = drbg->parent->reseed_counter;
 344     }
 345
 346 end:
 347     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 348         drbg->cleanup_entropy(drbg, entropy, entropylen);
 349     if (drbg->state == DRBG_READY)
 350         return 1;
 351     return 0;
 352 }
 353
 354 /*
 355  * Restart |drbg|, using the specified entropy or additional input
 356  *
 357  * Tries its best to get the drbg instantiated by all means,
 358  * regardless of its current state.
 359  *
 360  * Optionally, a |buffer| of |len| random bytes can be passed,
 361  * which is assumed to contain at least |entropy| bits of entropy.
 362  *
 363  * If |entropy| > 0, the buffer content is used as entropy input.
 364  *
 365  * If |entropy| == 0, the buffer content is used as additional input
 366  *
 367  * Returns 1 on success, 0 on failure.
 368  *
 369  * This function is used internally only.
 370  */
 371 int rand_drbg_restart(RAND_DRBG *drbg,
 372                       const unsigned char *buffer, size_t len, size_t entropy)
 373 {
 374     int reseeded = 0;
 375     const unsigned char *adin = NULL;
 376     size_t adinlen = 0;
 377
 378     if (drbg->pool != NULL) {
 379         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 380         RAND_POOL_free(drbg->pool);
 381         drbg->pool = NULL;
 382     }
 383
 384     if (buffer != NULL) {
 385         if (entropy > 0) {
 386             if (drbg->max_entropylen < len) {
 387                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 388                     RAND_R_ENTROPY_INPUT_TOO_LONG);
 389                 return 0;
 390             }
 391
 392             if (entropy > 8 * len) {
 393                 RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
 394                 return 0;
 395             }
 396
 397             /* will be picked up by the rand_drbg_get_entropy() callback */
 398             drbg->pool = RAND_POOL_new(entropy, len, len);
 399             if (drbg->pool == NULL)
 400                 return 0;
 401
 402             RAND_POOL_add(drbg->pool, buffer, len, entropy);
 403         } else {
 404             if (drbg->max_adinlen < len) {
 405                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 406                         RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 407                 return 0;
 408             }
 409             adin = buffer;
 410             adinlen = len;
 411         }
 412     }
 413
 414     /* repair error state */
 415     if (drbg->state == DRBG_ERROR)
 416         RAND_DRBG_uninstantiate(drbg);
 417
 418     /* repair uninitialized state */
 419     if (drbg->state == DRBG_UNINITIALISED) {
 420         /* reinstantiate drbg */
 421         RAND_DRBG_instantiate(drbg,
 422                               (const unsigned char *) ossl_pers_string,
 423                               sizeof(ossl_pers_string) - 1);
 424         /* already reseeded. prevent second reseeding below */
 425         reseeded = (drbg->state == DRBG_READY);
 426     }
 427
 428     /* refresh current state if entropy or additional input has been provided */
 429     if (drbg->state == DRBG_READY) {
 430         if (adin != NULL) {
 431             /*
 432              * mix in additional input without reseeding
 433              *
 434              * Similar to RAND_DRBG_reseed(), but the provided additional
 435              * data |adin| is mixed into the current state without pulling
 436              * entropy from the trusted entropy source using get_entropy().
 437              * This is not a reseeding in the strict sense of NIST SP 800-90A.
 438              */
 439             drbg->meth->reseed(drbg, adin, adinlen, NULL, 0);
 440         } else if (reseeded == 0) {
 441             /* do a full reseeding if it has not been done yet above */
 442             RAND_DRBG_reseed(drbg, NULL, 0);
 443         }
 444     }
 445
 446     /* check whether a given entropy pool was cleared properly during reseed */
 447     if (drbg->pool != NULL) {
 448         drbg->state = DRBG_ERROR;
 449         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 450         RAND_POOL_free(drbg->pool);
 451         drbg->pool = NULL;
 452         return 0;
 453     }
 454
 455     return drbg->state == DRBG_READY;
 456 }
 457
 458 /*
 459  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 460  * to or if |prediction_resistance| is set.  Additional input can be
 461  * sent in |adin| and |adinlen|.
 462  *
 463  * Requires that drbg->lock is already locked for write, if non-null.
 464  *
 465  * Returns 1 on success, 0 on failure.
 466  *
 467  */
 468 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 469                        int prediction_resistance,
 470                        const unsigned char *adin, size_t adinlen)
 471 {
 472     int reseed_required = 0;
 473
 474     if (drbg->state != DRBG_READY) {
 475         /* try to recover from previous errors */
 476         rand_drbg_restart(drbg, NULL, 0, 0);
 477
 478         if (drbg->state == DRBG_ERROR) {
 479             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 480             return 0;
 481         }
 482         if (drbg->state == DRBG_UNINITIALISED) {
 483             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 484             return 0;
 485         }
 486     }
 487
 488     if (outlen > drbg->max_request) {
 489         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 490         return 0;
 491     }
 492     if (adinlen > drbg->max_adinlen) {
 493         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 494         return 0;
 495     }
 496
 497     if (drbg->fork_count != rand_fork_count) {
 498         drbg->fork_count = rand_fork_count;
 499         reseed_required = 1;
 500     }
 501
 502     if (drbg->reseed_interval > 0) {
 503         if (drbg->generate_counter >= drbg->reseed_interval)
 504             reseed_required = 1;
 505     }
 506     if (drbg->reseed_time_interval > 0) {
 507         time_t now = time(NULL);
 508         if (now < drbg->reseed_time
 509             || now - drbg->reseed_time >= drbg->reseed_time_interval)
 510             reseed_required = 1;
 511     }
 512     if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
 513         if (drbg->reseed_counter != drbg->parent->reseed_counter)
 514             reseed_required = 1;
 515     }
 516
 517     if (reseed_required || prediction_resistance) {
 518         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 519             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 520             return 0;
 521         }
 522         adin = NULL;
 523         adinlen = 0;
 524     }
 525
 526     if (!drbg->meth->generate(drbg, out, outlen, adin, adinlen)) {
 527         drbg->state = DRBG_ERROR;
 528         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 529         return 0;
 530     }
 531
 532     drbg->generate_counter++;
 533
 534     return 1;
 535 }
 536
 537 /*
 538  * Generates |outlen| random bytes and stores them in |out|. It will
 539  * using the given |drbg| to generate the bytes.
 540  *
 541  * Requires that drbg->lock is already locked for write, if non-null.
 542  *
 543  * Returns 1 on success 0 on failure.
 544  */
 545 int RAND_DRBG_bytes(RAND_DRBG *drbg, unsigned char *out, size_t outlen)
 546 {
 547     unsigned char *additional = NULL;
 548     size_t additional_len;
 549     size_t chunk;
 550     size_t ret;
 551
 552     additional_len = rand_drbg_get_additional_data(&additional, drbg->max_adinlen);
 553
 554     for ( ; outlen > 0; outlen -= chunk, out += chunk) {
 555         chunk = outlen;
 556         if (chunk > drbg->max_request)
 557             chunk = drbg->max_request;
 558         ret = RAND_DRBG_generate(drbg, out, chunk, 0, additional, additional_len);
 559         if (!ret)
 560             goto err;
 561     }
 562     ret = 1;
 563
 564 err:
 565     if (additional_len != 0)
 566         OPENSSL_secure_clear_free(additional, additional_len);
 567
 568     return ret;
 569 }
 570
 571 /*
 572  * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
 573  *
 574  * In the following, the signature and the semantics of the
 575  * get_entropy() and cleanup_entropy() callbacks are explained.
 576  *
 577  * GET_ENTROPY
 578  *
 579  *     size_t get_entropy(RAND_DRBG *ctx,
 580  *                        unsigned char **pout,
 581  *                        int entropy,
 582  *                        size_t min_len, size_t max_len);
 583  *
 584  * This is a request to allocate and fill a buffer of size
 585  * |min_len| <= size <= |max_len| (in bytes) which contains
 586  * at least |entropy| bits of randomness. The buffer's address is
 587  * to be returned in |*pout| and the number of collected
 588  * randomness bytes (which may be less than the allocated size
 589  * of the buffer) as return value.
 590  *
 591  * If the callback fails to acquire at least |entropy| bits of
 592  * randomness, it shall return a buffer length of 0.
 593  *
 594  * CLEANUP_ENTROPY
 595  *
 596  *     void cleanup_entropy(RAND_DRBG *ctx,
 597  *                          unsigned char *out, size_t outlen);
 598  *
 599  * A request to clear and free the buffer allocated by get_entropy().
 600  * The values |out| and |outlen| are expected to be the random buffer's
 601  * address and length, as returned by the get_entropy() callback.
 602  *
 603  * GET_NONCE, CLEANUP_NONCE
 604  *
 605  * Signature and semantics of the get_nonce() and cleanup_nonce()
 606  * callbacks are analogous to get_entropy() and cleanup_entropy().
 607  * Currently, the nonce is used only for the known answer tests.
 608  */
 609 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 610                             RAND_DRBG_get_entropy_fn get_entropy,
 611                             RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
 612                             RAND_DRBG_get_nonce_fn get_nonce,
 613                             RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
 614 {
 615     if (drbg->state != DRBG_UNINITIALISED)
 616         return 0;
 617     drbg->get_entropy = get_entropy;
 618     drbg->cleanup_entropy = cleanup_entropy;
 619     drbg->get_nonce = get_nonce;
 620     drbg->cleanup_nonce = cleanup_nonce;
 621     return 1;
 622 }
 623
 624 /*
 625  * Set the reseed interval.
 626  *
 627  * The drbg will reseed automatically whenever the number of generate
 628  * requests exceeds the given reseed interval. If the reseed interval
 629  * is 0, then this feature is disabled.
 630  *
 631  * Returns 1 on success, 0 on failure.
 632  */
 633 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
 634 {
 635     if (interval > MAX_RESEED_INTERVAL)
 636         return 0;
 637     drbg->reseed_interval = interval;
 638     return 1;
 639 }
 640
 641 /*
 642  * Set the reseed time interval.
 643  *
 644  * The drbg will reseed automatically whenever the time elapsed since
 645  * the last reseeding exceeds the given reseed time interval. For safety,
 646  * a reseeding will also occur if the clock has been reset to a smaller
 647  * value.
 648  *
 649  * Returns 1 on success, 0 on failure.
 650  */
 651 int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
 652 {
 653     if (interval > MAX_RESEED_TIME_INTERVAL)
 654         return 0;
 655     drbg->reseed_time_interval = interval;
 656     return 1;
 657 }
 658
 659 /*
 660  * Get and set the EXDATA
 661  */
 662 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 663 {
 664     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 665 }
 666
 667 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 668 {
 669     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 670 }
 671
 672
 673 /*
 674  * The following functions provide a RAND_METHOD that works on the
 675  * global DRBG.  They lock.
 676  */
 677
 678 /*
 679  * Allocates a new global DRBG on the secure heap (if enabled) and
 680  * initializes it with default settings.
 681  *
 682  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 683  */
 684 static RAND_DRBG *drbg_setup(RAND_DRBG *parent)
 685 {
 686     RAND_DRBG *drbg;
 687
 688     drbg = OPENSSL_secure_zalloc(sizeof(RAND_DRBG));
 689     if (drbg == NULL)
 690         return NULL;
 691
 692     drbg->lock = CRYPTO_THREAD_lock_new();
 693     if (drbg->lock == NULL) {
 694         RANDerr(RAND_F_DRBG_SETUP, RAND_R_FAILED_TO_CREATE_LOCK);
 695         goto err;
 696     }
 697
 698     if (RAND_DRBG_set(drbg,
 699                       RAND_DRBG_NID, RAND_DRBG_FLAG_CTR_USE_DF) != 1)
 700         goto err;
 701     if (RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 702                                 rand_drbg_cleanup_entropy, NULL, NULL) != 1)
 703         goto err;
 704
 705     if (parent == NULL) {
 706         drbg->reseed_interval = MASTER_RESEED_INTERVAL;
 707         drbg->reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
 708     } else {
 709         drbg->parent = parent;
 710         drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
 711         drbg->reseed_time_interval = SLAVE_RESEED_TIME_INTERVAL;
 712     }
 713
 714     /* enable seed propagation */
 715     drbg->reseed_counter = 1;
 716
 717     /*
 718      * Ignore instantiation error so support just-in-time instantiation.
 719      *
 720      * The state of the drbg will be checked in RAND_DRBG_generate() and
 721      * an automatic recovery is attempted.
 722      */
 723     RAND_DRBG_instantiate(drbg,
 724                           (const unsigned char *) ossl_pers_string,
 725                           sizeof(ossl_pers_string) - 1);
 726     return drbg;
 727
 728 err:
 729     drbg_cleanup(drbg);
 730     return NULL;
 731 }
 732
 733 /*
 734  * Initialize the global DRBGs on first use.
 735  * Returns 1 on success, 0 on failure.
 736  */
 737 DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
 738 {
 739     /*
 740      * ensure that libcrypto is initialized, otherwise the
 741      * DRBG locks are not cleaned up properly
 742      */
 743     if (!OPENSSL_init_crypto(0, NULL))
 744         return 0;
 745
 746     drbg_master = drbg_setup(NULL);
 747     drbg_public = drbg_setup(drbg_master);
 748     drbg_private = drbg_setup(drbg_master);
 749
 750     if (drbg_master == NULL || drbg_public == NULL || drbg_private == NULL)
 751         return 0;
 752
 753     return 1;
 754 }
 755
 756 /* Cleans up the given global DRBG  */
 757 static void drbg_cleanup(RAND_DRBG *drbg)
 758 {
 759     if (drbg != NULL) {
 760         RAND_DRBG_uninstantiate(drbg);
 761         CRYPTO_THREAD_lock_free(drbg->lock);
 762         OPENSSL_secure_clear_free(drbg, sizeof(RAND_DRBG));
 763     }
 764 }
 765
 766 /* Clean up the global DRBGs before exit */
 767 void rand_drbg_cleanup_int(void)
 768 {
 769     drbg_cleanup(drbg_private);
 770     drbg_cleanup(drbg_public);
 771     drbg_cleanup(drbg_master);
 772
 773     drbg_private = drbg_public = drbg_master = NULL;
 774 }
 775
 776 /* Implements the default OpenSSL RAND_bytes() method */
 777 static int drbg_bytes(unsigned char *out, int count)
 778 {
 779     int ret = 0;
 780     size_t chunk;
 781     RAND_DRBG *drbg = RAND_DRBG_get0_public();
 782
 783     if (drbg == NULL)
 784         return 0;
 785
 786     CRYPTO_THREAD_write_lock(drbg->lock);
 787     for ( ; count > 0; count -= chunk, out += chunk) {
 788         chunk = count;
 789         if (chunk > drbg->max_request)
 790             chunk = drbg->max_request;
 791         ret = RAND_DRBG_generate(drbg, out, chunk, 0, NULL, 0);
 792         if (!ret)
 793             goto err;
 794     }
 795     ret = 1;
 796
 797 err:
 798     CRYPTO_THREAD_unlock(drbg->lock);
 799     return ret;
 800 }
 801
 802 /* Implements the default OpenSSL RAND_add() method */
 803 static int drbg_add(const void *buf, int num, double randomness)
 804 {
 805     int ret = 0;
 806     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 807
 808     if (drbg == NULL)
 809         return 0;
 810
 811     if (num < 0 || randomness < 0.0)
 812         return 0;
 813
 814     if (randomness > (double)drbg->max_entropylen) {
 815         /*
 816          * The purpose of this check is to bound |randomness| by a
 817          * relatively small value in order to prevent an integer
 818          * overflow when multiplying by 8 in the rand_drbg_restart()
 819          * call below.
 820          */
 821         return 0;
 822     }
 823
 824     CRYPTO_THREAD_write_lock(drbg->lock);
 825     ret = rand_drbg_restart(drbg, buf,
 826                             (size_t)(unsigned int)num,
 827                             (size_t)(8*randomness));
 828     CRYPTO_THREAD_unlock(drbg->lock);
 829
 830     return ret;
 831 }
 832
 833 /* Implements the default OpenSSL RAND_seed() method */
 834 static int drbg_seed(const void *buf, int num)
 835 {
 836     return drbg_add(buf, num, num);
 837 }
 838
 839 /* Implements the default OpenSSL RAND_status() method */
 840 static int drbg_status(void)
 841 {
 842     int ret;
 843     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 844
 845     if (drbg == NULL)
 846         return 0;
 847
 848     CRYPTO_THREAD_write_lock(drbg->lock);
 849     ret = drbg->state == DRBG_READY ? 1 : 0;
 850     CRYPTO_THREAD_unlock(drbg->lock);
 851     return ret;
 852 }
 853
 854 /*
 855  * Get the master DRBG.
 856  * Returns pointer to the DRBG on success, NULL on failure.
 857  *
 858  */
 859 RAND_DRBG *RAND_DRBG_get0_master(void)
 860 {
 861     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 862         return NULL;
 863
 864     return drbg_master;
 865 }
 866
 867 /*
 868  * Get the public DRBG.
 869  * Returns pointer to the DRBG on success, NULL on failure.
 870  */
 871 RAND_DRBG *RAND_DRBG_get0_public(void)
 872 {
 873     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 874         return NULL;
 875
 876     return drbg_public;
 877 }
 878
 879 /*
 880  * Get the private DRBG.
 881  * Returns pointer to the DRBG on success, NULL on failure.
 882  */
 883 RAND_DRBG *RAND_DRBG_get0_private(void)
 884 {
 885     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 886         return NULL;
 887
 888     return drbg_private;
 889 }
 890
 891 RAND_METHOD rand_meth = {
 892     drbg_seed,
 893     drbg_bytes,
 894     NULL,
 895     drbg_add,
 896     drbg_bytes,
 897     drbg_status
 898 };
 899
 900 RAND_METHOD *RAND_OpenSSL(void)
 901 {
 902     return &rand_meth;
 903 }