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 int drbg_setup(RAND_DRBG *drbg, const char *name, RAND_DRBG *parent);
 102
 103 /*
 104  * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
 105  * Return -2 if the type is not supported, 1 on success and -1 on
 106  * failure.
 107  */
 108 int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
 109 {
 110     int ret = 1;
 111
 112     drbg->state = DRBG_UNINITIALISED;
 113     drbg->flags = flags;
 114     drbg->nid = nid;
 115
 116     switch (nid) {
 117     default:
 118         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
 119         return -2;
 120     case 0:
 121         /* Uninitialized; that's okay. */
 122         return 1;
 123     case NID_aes_128_ctr:
 124     case NID_aes_192_ctr:
 125     case NID_aes_256_ctr:
 126         ret = ctr_init(drbg);
 127         break;
 128     }
 129
 130     if (ret < 0)
 131         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
 132     return ret;
 133 }
 134
 135 /*
 136  * Allocate memory and initialize a new DRBG.  The |parent|, if not
 137  * NULL, will be used to auto-seed this RAND_DRBG as needed.
 138  *
 139  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 140  */
 141 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
 142 {
 143     RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
 144
 145     if (drbg == NULL) {
 146         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
 147         goto err;
 148     }
 149     drbg->fork_count = rand_fork_count;
 150     drbg->parent = parent;
 151     if (RAND_DRBG_set(drbg, type, flags) < 0)
 152         goto err;
 153
 154     if (!RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 155                                  rand_drbg_cleanup_entropy,
 156                                  NULL, NULL))
 157         goto err;
 158
 159     return drbg;
 160
 161 err:
 162     OPENSSL_free(drbg);
 163     return NULL;
 164 }
 165
 166 /*
 167  * Uninstantiate |drbg| and free all memory.
 168  */
 169 void RAND_DRBG_free(RAND_DRBG *drbg)
 170 {
 171     if (drbg == NULL)
 172         return;
 173
 174     ctr_uninstantiate(drbg);
 175     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 176     OPENSSL_clear_free(drbg, sizeof(*drbg));
 177 }
 178
 179 /*
 180  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 181  * |perslen| as prediction-resistance input.
 182  *
 183  * Requires that drbg->lock is already locked for write, if non-null.
 184  */
 185 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 186                           const unsigned char *pers, size_t perslen)
 187 {
 188     unsigned char *nonce = NULL, *entropy = NULL;
 189     size_t noncelen = 0, entropylen = 0;
 190
 191     if (perslen > drbg->max_perslen) {
 192         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 193                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 194         goto end;
 195     }
 196     if (drbg->state != DRBG_UNINITIALISED) {
 197         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 198                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 199                                           : RAND_R_ALREADY_INSTANTIATED);
 200         goto end;
 201     }
 202
 203     drbg->state = DRBG_ERROR;
 204     if (drbg->get_entropy != NULL)
 205         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 206                                    drbg->min_entropylen, drbg->max_entropylen);
 207     if (entropylen < drbg->min_entropylen
 208         || entropylen > drbg->max_entropylen) {
 209         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 210         goto end;
 211     }
 212
 213     if (drbg->max_noncelen > 0 && drbg->get_nonce != NULL) {
 214         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 215                                    drbg->min_noncelen, drbg->max_noncelen);
 216         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
 217             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 218                     RAND_R_ERROR_RETRIEVING_NONCE);
 219             goto end;
 220         }
 221     }
 222
 223     if (!ctr_instantiate(drbg, entropy, entropylen,
 224                          nonce, noncelen, pers, perslen)) {
 225         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 226         goto end;
 227     }
 228
 229     drbg->state = DRBG_READY;
 230     drbg->generate_counter = 0;
 231     drbg->reseed_time = time(NULL);
 232     if (drbg->reseed_counter > 0) {
 233         if (drbg->parent == NULL)
 234             drbg->reseed_counter++;
 235         else
 236             drbg->reseed_counter = drbg->parent->reseed_counter;
 237     }
 238
 239 end:
 240     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 241         drbg->cleanup_entropy(drbg, entropy, entropylen);
 242     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 243         drbg->cleanup_nonce(drbg, nonce, noncelen);
 244     if (drbg->pool != NULL) {
 245         if (drbg->state == DRBG_READY) {
 246             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 247                     RAND_R_ERROR_ENTROPY_POOL_WAS_IGNORED);
 248             drbg->state = DRBG_ERROR;
 249         }
 250         RAND_POOL_free(drbg->pool);
 251         drbg->pool = NULL;
 252     }
 253     if (drbg->state == DRBG_READY)
 254         return 1;
 255     return 0;
 256 }
 257
 258 /*
 259  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 260  *
 261  * Requires that drbg->lock is already locked for write, if non-null.
 262  */
 263 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 264 {
 265     int ret = ctr_uninstantiate(drbg);
 266
 267     drbg->state = DRBG_UNINITIALISED;
 268     return ret;
 269 }
 270
 271 /*
 272  * Reseed |drbg|, mixing in the specified data
 273  *
 274  * Requires that drbg->lock is already locked for write, if non-null.
 275  */
 276 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 277                      const unsigned char *adin, size_t adinlen)
 278 {
 279     unsigned char *entropy = NULL;
 280     size_t entropylen = 0;
 281
 282     if (drbg->state == DRBG_ERROR) {
 283         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 284         return 0;
 285     }
 286     if (drbg->state == DRBG_UNINITIALISED) {
 287         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 288         return 0;
 289     }
 290
 291     if (adin == NULL)
 292         adinlen = 0;
 293     else if (adinlen > drbg->max_adinlen) {
 294         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 295         return 0;
 296     }
 297
 298     drbg->state = DRBG_ERROR;
 299     if (drbg->get_entropy != NULL)
 300         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 301                                    drbg->min_entropylen, drbg->max_entropylen);
 302     if (entropylen < drbg->min_entropylen
 303         || entropylen > drbg->max_entropylen) {
 304         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 305         goto end;
 306     }
 307
 308     if (!ctr_reseed(drbg, entropy, entropylen, adin, adinlen))
 309         goto end;
 310
 311     drbg->state = DRBG_READY;
 312     drbg->generate_counter = 0;
 313     drbg->reseed_time = time(NULL);
 314     if (drbg->reseed_counter > 0) {
 315         if (drbg->parent == NULL)
 316             drbg->reseed_counter++;
 317         else
 318             drbg->reseed_counter = drbg->parent->reseed_counter;
 319     }
 320
 321 end:
 322     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 323         drbg->cleanup_entropy(drbg, entropy, entropylen);
 324     if (drbg->state == DRBG_READY)
 325         return 1;
 326     return 0;
 327 }
 328
 329 /*
 330  * Restart |drbg|, using the specified entropy or additional input
 331  *
 332  * Tries its best to get the drbg instantiated by all means,
 333  * regardless of its current state.
 334  *
 335  * Optionally, a |buffer| of |len| random bytes can be passed,
 336  * which is assumed to contain at least |entropy| bits of entropy.
 337  *
 338  * If |entropy| > 0, the buffer content is used as entropy input.
 339  *
 340  * If |entropy| == 0, the buffer content is used as additional input
 341  *
 342  * Returns 1 on success, 0 on failure.
 343  *
 344  * This function is used internally only.
 345  */
 346 int rand_drbg_restart(RAND_DRBG *drbg,
 347                       const unsigned char *buffer, size_t len, size_t entropy)
 348 {
 349     int reseeded = 0;
 350     const unsigned char *adin = NULL;
 351     size_t adinlen = 0;
 352
 353     if (drbg->pool != NULL) {
 354         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 355         RAND_POOL_free(drbg->pool);
 356         drbg->pool = NULL;
 357     }
 358
 359     if (buffer != NULL) {
 360         if (entropy > 0) {
 361             if (drbg->max_entropylen < len) {
 362                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 363                     RAND_R_ENTROPY_INPUT_TOO_LONG);
 364                 return 0;
 365             }
 366
 367             if (entropy > 8 * len) {
 368                 RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
 369                 return 0;
 370             }
 371
 372             /* will be picked up by the rand_drbg_get_entropy() callback */
 373             drbg->pool = RAND_POOL_new(entropy, len, len);
 374             if (drbg->pool == NULL)
 375                 return 0;
 376
 377             RAND_POOL_add(drbg->pool, buffer, len, entropy);
 378         } else {
 379             if (drbg->max_adinlen < len) {
 380                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 381                         RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 382                 return 0;
 383             }
 384             adin = buffer;
 385             adinlen = len;
 386         }
 387     }
 388
 389     /* repair error state */
 390     if (drbg->state == DRBG_ERROR) {
 391         RAND_DRBG_uninstantiate(drbg);
 392         /* The drbg->ctr member needs to be reinitialized before reinstantiation */
 393         RAND_DRBG_set(drbg, drbg->nid, drbg->flags);
 394     }
 395
 396     /* repair uninitialized state */
 397     if (drbg->state == DRBG_UNINITIALISED) {
 398         /* reinstantiate drbg */
 399         RAND_DRBG_instantiate(drbg,
 400                               (const unsigned char *) ossl_pers_string,
 401                               sizeof(ossl_pers_string) - 1);
 402         /* already reseeded. prevent second reseeding below */
 403         reseeded = (drbg->state == DRBG_READY);
 404     }
 405
 406     /* refresh current state if entropy or additional input has been provided */
 407     if (drbg->state == DRBG_READY) {
 408         if (adin != NULL) {
 409             /*
 410              * mix in additional input without reseeding
 411              *
 412              * Similar to RAND_DRBG_reseed(), but the provided additional
 413              * data |adin| is mixed into the current state without pulling
 414              * entropy from the trusted entropy source using get_entropy().
 415              * This is not a reseeding in the strict sense of NIST SP 800-90A.
 416              */
 417             ctr_reseed(drbg, adin, adinlen, NULL, 0);
 418         } else if (reseeded == 0) {
 419             /* do a full reseeding if it has not been done yet above */
 420             RAND_DRBG_reseed(drbg, NULL, 0);
 421         }
 422     }
 423
 424     /* check whether a given entropy pool was cleared properly during reseed */
 425     if (drbg->pool != NULL) {
 426         drbg->state = DRBG_ERROR;
 427         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 428         RAND_POOL_free(drbg->pool);
 429         drbg->pool = NULL;
 430         return 0;
 431     }
 432
 433     return drbg->state == DRBG_READY;
 434 }
 435
 436 /*
 437  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 438  * to or if |prediction_resistance| is set.  Additional input can be
 439  * sent in |adin| and |adinlen|.
 440  *
 441  * Requires that drbg->lock is already locked for write, if non-null.
 442  *
 443  * Returns 1 on success, 0 on failure.
 444  *
 445  */
 446 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 447                        int prediction_resistance,
 448                        const unsigned char *adin, size_t adinlen)
 449 {
 450     int reseed_required = 0;
 451
 452     if (drbg->state != DRBG_READY) {
 453         /* try to recover from previous errors */
 454         rand_drbg_restart(drbg, NULL, 0, 0);
 455
 456         if (drbg->state == DRBG_ERROR) {
 457             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 458             return 0;
 459         }
 460         if (drbg->state == DRBG_UNINITIALISED) {
 461             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 462             return 0;
 463         }
 464     }
 465
 466     if (outlen > drbg->max_request) {
 467         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 468         return 0;
 469     }
 470     if (adinlen > drbg->max_adinlen) {
 471         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 472         return 0;
 473     }
 474
 475     if (drbg->fork_count != rand_fork_count) {
 476         drbg->fork_count = rand_fork_count;
 477         reseed_required = 1;
 478     }
 479
 480     if (drbg->reseed_interval > 0) {
 481         if (drbg->generate_counter >= drbg->reseed_interval)
 482             reseed_required = 1;
 483     }
 484     if (drbg->reseed_time_interval > 0) {
 485         time_t now = time(NULL);
 486         if (now < drbg->reseed_time
 487             || now - drbg->reseed_time >= drbg->reseed_time_interval)
 488             reseed_required = 1;
 489     }
 490     if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
 491         if (drbg->reseed_counter != drbg->parent->reseed_counter)
 492             reseed_required = 1;
 493     }
 494
 495     if (reseed_required || prediction_resistance) {
 496         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 497             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 498             return 0;
 499         }
 500         adin = NULL;
 501         adinlen = 0;
 502     }
 503
 504     if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
 505         drbg->state = DRBG_ERROR;
 506         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 507         return 0;
 508     }
 509
 510     drbg->generate_counter++;
 511
 512     return 1;
 513 }
 514
 515 /*
 516  * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
 517  *
 518  * In the following, the signature and the semantics of the
 519  * get_entropy() and cleanup_entropy() callbacks are explained.
 520  *
 521  * GET_ENTROPY
 522  *
 523  *     size_t get_entropy(RAND_DRBG *ctx,
 524  *                        unsigned char **pout,
 525  *                        int entropy,
 526  *                        size_t min_len, size_t max_len);
 527  *
 528  * This is a request to allocate and fill a buffer of size
 529  * |min_len| <= size <= |max_len| (in bytes) which contains
 530  * at least |entropy| bits of randomness. The buffer's address is
 531  * to be returned in |*pout| and the number of collected
 532  * randomness bytes (which may be less than the allocated size
 533  * of the buffer) as return value.
 534  *
 535  * If the callback fails to acquire at least |entropy| bits of
 536  * randomness, it shall return a buffer length of 0.
 537  *
 538  * CLEANUP_ENTROPY
 539  *
 540  *     void cleanup_entropy(RAND_DRBG *ctx,
 541  *                          unsigned char *out, size_t outlen);
 542  *
 543  * A request to clear and free the buffer allocated by get_entropy().
 544  * The values |out| and |outlen| are expected to be the random buffer's
 545  * address and length, as returned by the get_entropy() callback.
 546  *
 547  * GET_NONCE, CLEANUP_NONCE
 548  *
 549  * Signature and semantics of the get_nonce() and cleanup_nonce()
 550  * callbacks are analogous to get_entropy() and cleanup_entropy().
 551  * Currently, the nonce is used only for the known answer tests.
 552  */
 553 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 554                             RAND_DRBG_get_entropy_fn get_entropy,
 555                             RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
 556                             RAND_DRBG_get_nonce_fn get_nonce,
 557                             RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
 558 {
 559     if (drbg->state != DRBG_UNINITIALISED)
 560         return 0;
 561     drbg->get_entropy = get_entropy;
 562     drbg->cleanup_entropy = cleanup_entropy;
 563     drbg->get_nonce = get_nonce;
 564     drbg->cleanup_nonce = cleanup_nonce;
 565     return 1;
 566 }
 567
 568 /*
 569  * Set the reseed interval.
 570  *
 571  * The drbg will reseed automatically whenever the number of generate
 572  * requests exceeds the given reseed interval. If the reseed interval
 573  * is 0, then this feature is disabled.
 574  *
 575  * Returns 1 on success, 0 on failure.
 576  */
 577 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
 578 {
 579     if (interval > MAX_RESEED_INTERVAL)
 580         return 0;
 581     drbg->reseed_interval = interval;
 582     return 1;
 583 }
 584
 585 /*
 586  * Set the reseed time interval.
 587  *
 588  * The drbg will reseed automatically whenever the time elapsed since
 589  * the last reseeding exceeds the given reseed time interval. For safety,
 590  * a reseeding will also occur if the clock has been reset to a smaller
 591  * value.
 592  *
 593  * Returns 1 on success, 0 on failure.
 594  */
 595 int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
 596 {
 597     if (interval > MAX_RESEED_TIME_INTERVAL)
 598         return 0;
 599     drbg->reseed_time_interval = interval;
 600     return 1;
 601 }
 602
 603 /*
 604  * Get and set the EXDATA
 605  */
 606 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 607 {
 608     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 609 }
 610
 611 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 612 {
 613     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 614 }
 615
 616
 617 /*
 618  * The following functions provide a RAND_METHOD that works on the
 619  * global DRBG.  They lock.
 620  */
 621
 622 /*
 623  * Initializes the given global DRBG with default settings.
 624  * A global lock for the DRBG is created with the given name.
 625  *
 626  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 627  */
 628 static int drbg_setup(RAND_DRBG *drbg, const char *name, RAND_DRBG *parent)
 629 {
 630     int ret = 1;
 631
 632     if (name == NULL || drbg->lock != NULL) {
 633         RANDerr(RAND_F_DRBG_SETUP, ERR_R_INTERNAL_ERROR);
 634         return 0;
 635     }
 636
 637     drbg->lock = CRYPTO_THREAD_glock_new(name);
 638     if (drbg->lock == NULL) {
 639         RANDerr(RAND_F_DRBG_SETUP, RAND_R_FAILED_TO_CREATE_LOCK);
 640         return 0;
 641     }
 642
 643     ret &= RAND_DRBG_set(drbg,
 644                          RAND_DRBG_NID, RAND_DRBG_FLAG_CTR_USE_DF) == 1;
 645     ret &= RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 646                                    rand_drbg_cleanup_entropy, NULL, NULL) == 1;
 647
 648     if (parent == NULL) {
 649         drbg->reseed_interval = MASTER_RESEED_INTERVAL;
 650         drbg->reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
 651     } else {
 652         drbg->parent = parent;
 653         drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
 654         drbg->reseed_time_interval = SLAVE_RESEED_TIME_INTERVAL;
 655     }
 656
 657     /* enable seed propagation */
 658     drbg->reseed_counter = 1;
 659
 660     /*
 661      * Ignore instantiation error so support just-in-time instantiation.
 662      *
 663      * The state of the drbg will be checked in RAND_DRBG_generate() and
 664      * an automatic recovery is attempted.
 665      */
 666     RAND_DRBG_instantiate(drbg,
 667                           (const unsigned char *) ossl_pers_string,
 668                           sizeof(ossl_pers_string) - 1);
 669     return ret;
 670 }
 671
 672 /*
 673  * Initialize the global DRBGs on first use.
 674  * Returns 1 on success, 0 on failure.
 675  */
 676 DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
 677 {
 678     int ret = 1;
 679
 680     ret &= drbg_setup(&drbg_master, "drbg_master", NULL);
 681     ret &= drbg_setup(&drbg_public, "drbg_public", &drbg_master);
 682     ret &= drbg_setup(&drbg_private, "drbg_private", &drbg_master);
 683
 684     return ret;
 685 }
 686
 687 /* Cleans up the given global DRBG  */
 688 static void drbg_cleanup(RAND_DRBG *drbg)
 689 {
 690     CRYPTO_THREAD_lock_free(drbg->lock);
 691     RAND_DRBG_uninstantiate(drbg);
 692 }
 693
 694 /* Clean up the global DRBGs before exit */
 695 void rand_drbg_cleanup_int(void)
 696 {
 697     drbg_cleanup(&drbg_private);
 698     drbg_cleanup(&drbg_public);
 699     drbg_cleanup(&drbg_master);
 700 }
 701
 702 /* Implements the default OpenSSL RAND_bytes() method */
 703 static int drbg_bytes(unsigned char *out, int count)
 704 {
 705     int ret = 0;
 706     size_t chunk;
 707     RAND_DRBG *drbg = RAND_DRBG_get0_public();
 708
 709     if (drbg == NULL)
 710         return 0;
 711
 712     CRYPTO_THREAD_write_lock(drbg->lock);
 713     if (drbg->state == DRBG_UNINITIALISED)
 714         goto err;
 715
 716     for ( ; count > 0; count -= chunk, out += chunk) {
 717         chunk = count;
 718         if (chunk > drbg->max_request)
 719             chunk = drbg->max_request;
 720         ret = RAND_DRBG_generate(drbg, out, chunk, 0, NULL, 0);
 721         if (!ret)
 722             goto err;
 723     }
 724     ret = 1;
 725
 726 err:
 727     CRYPTO_THREAD_unlock(drbg->lock);
 728     return ret;
 729 }
 730
 731 /* Implements the default OpenSSL RAND_add() method */
 732 static int drbg_add(const void *buf, int num, double randomness)
 733 {
 734     int ret = 0;
 735     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 736
 737     if (drbg == NULL)
 738         return 0;
 739
 740     if (num < 0 || randomness < 0.0)
 741         return 0;
 742
 743     if (randomness > (double)drbg->max_entropylen) {
 744         /*
 745          * The purpose of this check is to bound |randomness| by a
 746          * relatively small value in order to prevent an integer
 747          * overflow when multiplying by 8 in the rand_drbg_restart()
 748          * call below.
 749          */
 750         return 0;
 751     }
 752
 753     CRYPTO_THREAD_write_lock(drbg->lock);
 754     ret = rand_drbg_restart(drbg, buf,
 755                             (size_t)(unsigned int)num,
 756                             (size_t)(8*randomness));
 757     CRYPTO_THREAD_unlock(drbg->lock);
 758
 759     return ret;
 760 }
 761
 762 /* Implements the default OpenSSL RAND_seed() method */
 763 static int drbg_seed(const void *buf, int num)
 764 {
 765     return drbg_add(buf, num, num);
 766 }
 767
 768 /* Implements the default OpenSSL RAND_status() method */
 769 static int drbg_status(void)
 770 {
 771     int ret;
 772     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 773
 774     if (drbg == NULL)
 775         return 0;
 776
 777     CRYPTO_THREAD_write_lock(drbg->lock);
 778     ret = drbg->state == DRBG_READY ? 1 : 0;
 779     CRYPTO_THREAD_unlock(drbg->lock);
 780     return ret;
 781 }
 782
 783 /*
 784  * Get the master DRBG.
 785  * Returns pointer to the DRBG on success, NULL on failure.
 786  *
 787  */
 788 RAND_DRBG *RAND_DRBG_get0_master(void)
 789 {
 790     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 791         return NULL;
 792
 793     return &drbg_master;
 794 }
 795
 796 /*
 797  * Get the public DRBG.
 798  * Returns pointer to the DRBG on success, NULL on failure.
 799  */
 800 RAND_DRBG *RAND_DRBG_get0_public(void)
 801 {
 802     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 803         return NULL;
 804
 805     return &drbg_public;
 806 }
 807
 808 /*
 809  * Get the private DRBG.
 810  * Returns pointer to the DRBG on success, NULL on failure.
 811  */
 812 RAND_DRBG *RAND_DRBG_get0_private(void)
 813 {
 814     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 815         return NULL;
 816
 817     return &drbg_private;
 818 }
 819
 820 RAND_METHOD rand_meth = {
 821     drbg_seed,
 822     drbg_bytes,
 823     NULL,
 824     drbg_add,
 825     drbg_bytes,
 826     drbg_status
 827 };
 828
 829 RAND_METHOD *RAND_OpenSSL(void)
 830 {
 831     return &rand_meth;
 832 }