crypto/rand/drbg_lib.c

   1 /*
   2  * Copyright 2011-2017 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(const char *name, 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  * Return -2 if the type is not supported, 1 on success and -1 on
 107  * 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 -2;
 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 = 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     ctr_uninstantiate(drbg);
 176     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 177     OPENSSL_clear_free(drbg, sizeof(*drbg));
 178 }
 179
 180 /*
 181  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 182  * |perslen| as prediction-resistance input.
 183  *
 184  * Requires that drbg->lock is already locked for write, if non-null.
 185  */
 186 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 187                           const unsigned char *pers, size_t perslen)
 188 {
 189     unsigned char *nonce = NULL, *entropy = NULL;
 190     size_t noncelen = 0, entropylen = 0;
 191
 192     if (perslen > drbg->max_perslen) {
 193         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 194                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 195         goto end;
 196     }
 197     if (drbg->state != DRBG_UNINITIALISED) {
 198         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 199                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 200                                           : RAND_R_ALREADY_INSTANTIATED);
 201         goto end;
 202     }
 203
 204     drbg->state = DRBG_ERROR;
 205     if (drbg->get_entropy != NULL)
 206         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 207                                    drbg->min_entropylen, drbg->max_entropylen);
 208     if (entropylen < drbg->min_entropylen
 209         || entropylen > drbg->max_entropylen) {
 210         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 211         goto end;
 212     }
 213
 214     if (drbg->max_noncelen > 0 && drbg->get_nonce != NULL) {
 215         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 216                                    drbg->min_noncelen, drbg->max_noncelen);
 217         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
 218             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 219                     RAND_R_ERROR_RETRIEVING_NONCE);
 220             goto end;
 221         }
 222     }
 223
 224     if (!ctr_instantiate(drbg, entropy, entropylen,
 225                          nonce, noncelen, pers, perslen)) {
 226         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 227         goto end;
 228     }
 229
 230     drbg->state = DRBG_READY;
 231     drbg->generate_counter = 0;
 232     drbg->reseed_time = time(NULL);
 233     if (drbg->reseed_counter > 0) {
 234         if (drbg->parent == NULL)
 235             drbg->reseed_counter++;
 236         else
 237             drbg->reseed_counter = drbg->parent->reseed_counter;
 238     }
 239
 240 end:
 241     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 242         drbg->cleanup_entropy(drbg, entropy, entropylen);
 243     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 244         drbg->cleanup_nonce(drbg, nonce, noncelen);
 245     if (drbg->pool != NULL) {
 246         if (drbg->state == DRBG_READY) {
 247             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 248                     RAND_R_ERROR_ENTROPY_POOL_WAS_IGNORED);
 249             drbg->state = DRBG_ERROR;
 250         }
 251         RAND_POOL_free(drbg->pool);
 252         drbg->pool = NULL;
 253     }
 254     if (drbg->state == DRBG_READY)
 255         return 1;
 256     return 0;
 257 }
 258
 259 /*
 260  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 261  *
 262  * Requires that drbg->lock is already locked for write, if non-null.
 263  */
 264 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 265 {
 266     int ret = ctr_uninstantiate(drbg);
 267
 268     drbg->state = DRBG_UNINITIALISED;
 269     return ret;
 270 }
 271
 272 /*
 273  * Reseed |drbg|, mixing in the specified data
 274  *
 275  * Requires that drbg->lock is already locked for write, if non-null.
 276  */
 277 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 278                      const unsigned char *adin, size_t adinlen)
 279 {
 280     unsigned char *entropy = NULL;
 281     size_t entropylen = 0;
 282
 283     if (drbg->state == DRBG_ERROR) {
 284         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 285         return 0;
 286     }
 287     if (drbg->state == DRBG_UNINITIALISED) {
 288         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 289         return 0;
 290     }
 291
 292     if (adin == NULL)
 293         adinlen = 0;
 294     else if (adinlen > drbg->max_adinlen) {
 295         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 296         return 0;
 297     }
 298
 299     drbg->state = DRBG_ERROR;
 300     if (drbg->get_entropy != NULL)
 301         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 302                                    drbg->min_entropylen, drbg->max_entropylen);
 303     if (entropylen < drbg->min_entropylen
 304         || entropylen > drbg->max_entropylen) {
 305         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 306         goto end;
 307     }
 308
 309     if (!ctr_reseed(drbg, entropy, entropylen, adin, adinlen))
 310         goto end;
 311
 312     drbg->state = DRBG_READY;
 313     drbg->generate_counter = 0;
 314     drbg->reseed_time = time(NULL);
 315     if (drbg->reseed_counter > 0) {
 316         if (drbg->parent == NULL)
 317             drbg->reseed_counter++;
 318         else
 319             drbg->reseed_counter = drbg->parent->reseed_counter;
 320     }
 321
 322 end:
 323     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 324         drbg->cleanup_entropy(drbg, entropy, entropylen);
 325     if (drbg->state == DRBG_READY)
 326         return 1;
 327     return 0;
 328 }
 329
 330 /*
 331  * Restart |drbg|, using the specified entropy or additional input
 332  *
 333  * Tries its best to get the drbg instantiated by all means,
 334  * regardless of its current state.
 335  *
 336  * Optionally, a |buffer| of |len| random bytes can be passed,
 337  * which is assumed to contain at least |entropy| bits of entropy.
 338  *
 339  * If |entropy| > 0, the buffer content is used as entropy input.
 340  *
 341  * If |entropy| == 0, the buffer content is used as additional input
 342  *
 343  * Returns 1 on success, 0 on failure.
 344  *
 345  * This function is used internally only.
 346  */
 347 int rand_drbg_restart(RAND_DRBG *drbg,
 348                       const unsigned char *buffer, size_t len, size_t entropy)
 349 {
 350     int reseeded = 0;
 351     const unsigned char *adin = NULL;
 352     size_t adinlen = 0;
 353
 354     if (drbg->pool != NULL) {
 355         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 356         RAND_POOL_free(drbg->pool);
 357         drbg->pool = NULL;
 358     }
 359
 360     if (buffer != NULL) {
 361         if (entropy > 0) {
 362             if (drbg->max_entropylen < len) {
 363                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 364                     RAND_R_ENTROPY_INPUT_TOO_LONG);
 365                 return 0;
 366             }
 367
 368             if (entropy > 8 * len) {
 369                 RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
 370                 return 0;
 371             }
 372
 373             /* will be picked up by the rand_drbg_get_entropy() callback */
 374             drbg->pool = RAND_POOL_new(entropy, len, len);
 375             if (drbg->pool == NULL)
 376                 return 0;
 377
 378             RAND_POOL_add(drbg->pool, buffer, len, entropy);
 379         } else {
 380             if (drbg->max_adinlen < len) {
 381                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 382                         RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 383                 return 0;
 384             }
 385             adin = buffer;
 386             adinlen = len;
 387         }
 388     }
 389
 390     /* repair error state */
 391     if (drbg->state == DRBG_ERROR) {
 392         RAND_DRBG_uninstantiate(drbg);
 393         /* The drbg->ctr member needs to be reinitialized before reinstantiation */
 394         RAND_DRBG_set(drbg, drbg->nid, drbg->flags);
 395     }
 396
 397     /* repair uninitialized state */
 398     if (drbg->state == DRBG_UNINITIALISED) {
 399         /* reinstantiate drbg */
 400         RAND_DRBG_instantiate(drbg,
 401                               (const unsigned char *) ossl_pers_string,
 402                               sizeof(ossl_pers_string) - 1);
 403         /* already reseeded. prevent second reseeding below */
 404         reseeded = (drbg->state == DRBG_READY);
 405     }
 406
 407     /* refresh current state if entropy or additional input has been provided */
 408     if (drbg->state == DRBG_READY) {
 409         if (adin != NULL) {
 410             /*
 411              * mix in additional input without reseeding
 412              *
 413              * Similar to RAND_DRBG_reseed(), but the provided additional
 414              * data |adin| is mixed into the current state without pulling
 415              * entropy from the trusted entropy source using get_entropy().
 416              * This is not a reseeding in the strict sense of NIST SP 800-90A.
 417              */
 418             ctr_reseed(drbg, adin, adinlen, NULL, 0);
 419         } else if (reseeded == 0) {
 420             /* do a full reseeding if it has not been done yet above */
 421             RAND_DRBG_reseed(drbg, NULL, 0);
 422         }
 423     }
 424
 425     /* check whether a given entropy pool was cleared properly during reseed */
 426     if (drbg->pool != NULL) {
 427         drbg->state = DRBG_ERROR;
 428         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 429         RAND_POOL_free(drbg->pool);
 430         drbg->pool = NULL;
 431         return 0;
 432     }
 433
 434     return drbg->state == DRBG_READY;
 435 }
 436
 437 /*
 438  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 439  * to or if |prediction_resistance| is set.  Additional input can be
 440  * sent in |adin| and |adinlen|.
 441  *
 442  * Requires that drbg->lock is already locked for write, if non-null.
 443  *
 444  * Returns 1 on success, 0 on failure.
 445  *
 446  */
 447 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 448                        int prediction_resistance,
 449                        const unsigned char *adin, size_t adinlen)
 450 {
 451     int reseed_required = 0;
 452
 453     if (drbg->state != DRBG_READY) {
 454         /* try to recover from previous errors */
 455         rand_drbg_restart(drbg, NULL, 0, 0);
 456
 457         if (drbg->state == DRBG_ERROR) {
 458             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 459             return 0;
 460         }
 461         if (drbg->state == DRBG_UNINITIALISED) {
 462             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 463             return 0;
 464         }
 465     }
 466
 467     if (outlen > drbg->max_request) {
 468         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 469         return 0;
 470     }
 471     if (adinlen > drbg->max_adinlen) {
 472         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 473         return 0;
 474     }
 475
 476     if (drbg->fork_count != rand_fork_count) {
 477         drbg->fork_count = rand_fork_count;
 478         reseed_required = 1;
 479     }
 480
 481     if (drbg->reseed_interval > 0) {
 482         if (drbg->generate_counter >= drbg->reseed_interval)
 483             reseed_required = 1;
 484     }
 485     if (drbg->reseed_time_interval > 0) {
 486         time_t now = time(NULL);
 487         if (now < drbg->reseed_time
 488             || now - drbg->reseed_time >= drbg->reseed_time_interval)
 489             reseed_required = 1;
 490     }
 491     if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
 492         if (drbg->reseed_counter != drbg->parent->reseed_counter)
 493             reseed_required = 1;
 494     }
 495
 496     if (reseed_required || prediction_resistance) {
 497         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 498             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 499             return 0;
 500         }
 501         adin = NULL;
 502         adinlen = 0;
 503     }
 504
 505     if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
 506         drbg->state = DRBG_ERROR;
 507         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 508         return 0;
 509     }
 510
 511     drbg->generate_counter++;
 512
 513     return 1;
 514 }
 515
 516 /*
 517  * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
 518  *
 519  * In the following, the signature and the semantics of the
 520  * get_entropy() and cleanup_entropy() callbacks are explained.
 521  *
 522  * GET_ENTROPY
 523  *
 524  *     size_t get_entropy(RAND_DRBG *ctx,
 525  *                        unsigned char **pout,
 526  *                        int entropy,
 527  *                        size_t min_len, size_t max_len);
 528  *
 529  * This is a request to allocate and fill a buffer of size
 530  * |min_len| <= size <= |max_len| (in bytes) which contains
 531  * at least |entropy| bits of randomness. The buffer's address is
 532  * to be returned in |*pout| and the number of collected
 533  * randomness bytes (which may be less than the allocated size
 534  * of the buffer) as return value.
 535  *
 536  * If the callback fails to acquire at least |entropy| bits of
 537  * randomness, it shall return a buffer length of 0.
 538  *
 539  * CLEANUP_ENTROPY
 540  *
 541  *     void cleanup_entropy(RAND_DRBG *ctx,
 542  *                          unsigned char *out, size_t outlen);
 543  *
 544  * A request to clear and free the buffer allocated by get_entropy().
 545  * The values |out| and |outlen| are expected to be the random buffer's
 546  * address and length, as returned by the get_entropy() callback.
 547  *
 548  * GET_NONCE, CLEANUP_NONCE
 549  *
 550  * Signature and semantics of the get_nonce() and cleanup_nonce()
 551  * callbacks are analogous to get_entropy() and cleanup_entropy().
 552  * Currently, the nonce is used only for the known answer tests.
 553  */
 554 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 555                             RAND_DRBG_get_entropy_fn get_entropy,
 556                             RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
 557                             RAND_DRBG_get_nonce_fn get_nonce,
 558                             RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
 559 {
 560     if (drbg->state != DRBG_UNINITIALISED)
 561         return 0;
 562     drbg->get_entropy = get_entropy;
 563     drbg->cleanup_entropy = cleanup_entropy;
 564     drbg->get_nonce = get_nonce;
 565     drbg->cleanup_nonce = cleanup_nonce;
 566     return 1;
 567 }
 568
 569 /*
 570  * Set the reseed interval.
 571  *
 572  * The drbg will reseed automatically whenever the number of generate
 573  * requests exceeds the given reseed interval. If the reseed interval
 574  * is 0, then this feature is disabled.
 575  *
 576  * Returns 1 on success, 0 on failure.
 577  */
 578 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
 579 {
 580     if (interval > MAX_RESEED_INTERVAL)
 581         return 0;
 582     drbg->reseed_interval = interval;
 583     return 1;
 584 }
 585
 586 /*
 587  * Set the reseed time interval.
 588  *
 589  * The drbg will reseed automatically whenever the time elapsed since
 590  * the last reseeding exceeds the given reseed time interval. For safety,
 591  * a reseeding will also occur if the clock has been reset to a smaller
 592  * value.
 593  *
 594  * Returns 1 on success, 0 on failure.
 595  */
 596 int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
 597 {
 598     if (interval > MAX_RESEED_TIME_INTERVAL)
 599         return 0;
 600     drbg->reseed_time_interval = interval;
 601     return 1;
 602 }
 603
 604 /*
 605  * Get and set the EXDATA
 606  */
 607 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 608 {
 609     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 610 }
 611
 612 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 613 {
 614     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 615 }
 616
 617
 618 /*
 619  * The following functions provide a RAND_METHOD that works on the
 620  * global DRBG.  They lock.
 621  */
 622
 623 /*
 624  * Allocates a new global DRBG on the secure heap (if enabled) and
 625  * initializes it with default settings.
 626  * A global lock for the DRBG is created with the given name.
 627  *
 628  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 629  */
 630 static RAND_DRBG *drbg_setup(const char *name, RAND_DRBG *parent)
 631 {
 632     RAND_DRBG *drbg;
 633
 634     if (name == NULL) {
 635         RANDerr(RAND_F_DRBG_SETUP, ERR_R_INTERNAL_ERROR);
 636         return NULL;
 637     }
 638
 639     drbg = OPENSSL_secure_zalloc(sizeof(RAND_DRBG));
 640     if (drbg == NULL)
 641         return NULL;
 642
 643     drbg->lock = CRYPTO_THREAD_glock_new(name);
 644     if (drbg->lock == NULL) {
 645         RANDerr(RAND_F_DRBG_SETUP, RAND_R_FAILED_TO_CREATE_LOCK);
 646         goto err;
 647     }
 648
 649     if (RAND_DRBG_set(drbg,
 650                       RAND_DRBG_NID, RAND_DRBG_FLAG_CTR_USE_DF) != 1)
 651         goto err;
 652     if (RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 653                                 rand_drbg_cleanup_entropy, NULL, NULL) != 1)
 654         goto err;
 655
 656     if (parent == NULL) {
 657         drbg->reseed_interval = MASTER_RESEED_INTERVAL;
 658         drbg->reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
 659     } else {
 660         drbg->parent = parent;
 661         drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
 662         drbg->reseed_time_interval = SLAVE_RESEED_TIME_INTERVAL;
 663     }
 664
 665     /* enable seed propagation */
 666     drbg->reseed_counter = 1;
 667
 668     /*
 669      * Ignore instantiation error so support just-in-time instantiation.
 670      *
 671      * The state of the drbg will be checked in RAND_DRBG_generate() and
 672      * an automatic recovery is attempted.
 673      */
 674     RAND_DRBG_instantiate(drbg,
 675                           (const unsigned char *) ossl_pers_string,
 676                           sizeof(ossl_pers_string) - 1);
 677     return drbg;
 678
 679 err:
 680     drbg_cleanup(drbg);
 681     return NULL;
 682 }
 683
 684 /*
 685  * Initialize the global DRBGs on first use.
 686  * Returns 1 on success, 0 on failure.
 687  */
 688 DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
 689 {
 690     drbg_master = drbg_setup("drbg_master", NULL);
 691     drbg_public = drbg_setup("drbg_public", drbg_master);
 692     drbg_private = drbg_setup("drbg_private", drbg_master);
 693
 694     if (drbg_master == NULL || drbg_public == NULL || drbg_private == NULL)
 695         return 0;
 696
 697     return 1;
 698 }
 699
 700 /* Cleans up the given global DRBG  */
 701 static void drbg_cleanup(RAND_DRBG *drbg)
 702 {
 703     if (drbg != NULL) {
 704         RAND_DRBG_uninstantiate(drbg);
 705         CRYPTO_THREAD_lock_free(drbg->lock);
 706         OPENSSL_secure_clear_free(drbg, sizeof(RAND_DRBG));
 707     }
 708 }
 709
 710 /* Clean up the global DRBGs before exit */
 711 void rand_drbg_cleanup_int(void)
 712 {
 713     drbg_cleanup(drbg_private);
 714     drbg_cleanup(drbg_public);
 715     drbg_cleanup(drbg_master);
 716
 717     drbg_private = drbg_public = drbg_master = NULL;
 718 }
 719
 720 /* Implements the default OpenSSL RAND_bytes() method */
 721 static int drbg_bytes(unsigned char *out, int count)
 722 {
 723     int ret = 0;
 724     size_t chunk;
 725     RAND_DRBG *drbg = RAND_DRBG_get0_public();
 726
 727     if (drbg == NULL)
 728         return 0;
 729
 730     CRYPTO_THREAD_write_lock(drbg->lock);
 731     if (drbg->state == DRBG_UNINITIALISED)
 732         goto err;
 733
 734     for ( ; count > 0; count -= chunk, out += chunk) {
 735         chunk = count;
 736         if (chunk > drbg->max_request)
 737             chunk = drbg->max_request;
 738         ret = RAND_DRBG_generate(drbg, out, chunk, 0, NULL, 0);
 739         if (!ret)
 740             goto err;
 741     }
 742     ret = 1;
 743
 744 err:
 745     CRYPTO_THREAD_unlock(drbg->lock);
 746     return ret;
 747 }
 748
 749 /* Implements the default OpenSSL RAND_add() method */
 750 static int drbg_add(const void *buf, int num, double randomness)
 751 {
 752     int ret = 0;
 753     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 754
 755     if (drbg == NULL)
 756         return 0;
 757
 758     if (num < 0 || randomness < 0.0)
 759         return 0;
 760
 761     if (randomness > (double)drbg->max_entropylen) {
 762         /*
 763          * The purpose of this check is to bound |randomness| by a
 764          * relatively small value in order to prevent an integer
 765          * overflow when multiplying by 8 in the rand_drbg_restart()
 766          * call below.
 767          */
 768         return 0;
 769     }
 770
 771     CRYPTO_THREAD_write_lock(drbg->lock);
 772     ret = rand_drbg_restart(drbg, buf,
 773                             (size_t)(unsigned int)num,
 774                             (size_t)(8*randomness));
 775     CRYPTO_THREAD_unlock(drbg->lock);
 776
 777     return ret;
 778 }
 779
 780 /* Implements the default OpenSSL RAND_seed() method */
 781 static int drbg_seed(const void *buf, int num)
 782 {
 783     return drbg_add(buf, num, num);
 784 }
 785
 786 /* Implements the default OpenSSL RAND_status() method */
 787 static int drbg_status(void)
 788 {
 789     int ret;
 790     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 791
 792     if (drbg == NULL)
 793         return 0;
 794
 795     CRYPTO_THREAD_write_lock(drbg->lock);
 796     ret = drbg->state == DRBG_READY ? 1 : 0;
 797     CRYPTO_THREAD_unlock(drbg->lock);
 798     return ret;
 799 }
 800
 801 /*
 802  * Get the master DRBG.
 803  * Returns pointer to the DRBG on success, NULL on failure.
 804  *
 805  */
 806 RAND_DRBG *RAND_DRBG_get0_master(void)
 807 {
 808     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 809         return NULL;
 810
 811     return drbg_master;
 812 }
 813
 814 /*
 815  * Get the public DRBG.
 816  * Returns pointer to the DRBG on success, NULL on failure.
 817  */
 818 RAND_DRBG *RAND_DRBG_get0_public(void)
 819 {
 820     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 821         return NULL;
 822
 823     return drbg_public;
 824 }
 825
 826 /*
 827  * Get the private DRBG.
 828  * Returns pointer to the DRBG on success, NULL on failure.
 829  */
 830 RAND_DRBG *RAND_DRBG_get0_private(void)
 831 {
 832     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 833         return NULL;
 834
 835     return drbg_private;
 836 }
 837
 838 RAND_METHOD rand_meth = {
 839     drbg_seed,
 840     drbg_bytes,
 841     NULL,
 842     drbg_add,
 843     drbg_bytes,
 844     drbg_status
 845 };
 846
 847 RAND_METHOD *RAND_OpenSSL(void)
 848 {
 849     return &rand_meth;
 850 }