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 the number of generate requests since the last reseeding exceeds a
  77  * certain threshold, the so called |reseed_interval|. This automatic
  78  * reseeding  can be disabled by setting the |reseed_interval| to 0.
  79  *
  80  * MANUAL RESEEDING
  81  *
  82  * For the three shared DRBGs (and only for these) there is a way to reseed
  83  * them manually by calling RAND_seed() (or RAND_add() with a positive
  84  * |randomness| argument). This will immediately reseed the <master> DRBG.
  85  * Its immediate children (<public> and <private> DRBG) will detect this
  86  * on their next generate call and reseed, pulling randomness from <master>.
  87  */
  88
  89
  90 /* NIST SP 800-90A DRBG recommends the use of a personalization string. */
  91 static const char ossl_pers_string[] = "OpenSSL NIST SP 800-90A DRBG";
  92
  93 static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;
  94
  95 static int drbg_setup(RAND_DRBG *drbg, const char *name, RAND_DRBG *parent);
  96
  97 /*
  98  * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
  99  * Return -2 if the type is not supported, 1 on success and -1 on
 100  * failure.
 101  */
 102 int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
 103 {
 104     int ret = 1;
 105
 106     drbg->state = DRBG_UNINITIALISED;
 107     drbg->flags = flags;
 108     drbg->nid = nid;
 109
 110     switch (nid) {
 111     default:
 112         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
 113         return -2;
 114     case 0:
 115         /* Uninitialized; that's okay. */
 116         return 1;
 117     case NID_aes_128_ctr:
 118     case NID_aes_192_ctr:
 119     case NID_aes_256_ctr:
 120         ret = ctr_init(drbg);
 121         break;
 122     }
 123
 124     if (ret < 0)
 125         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
 126     return ret;
 127 }
 128
 129 /*
 130  * Allocate memory and initialize a new DRBG.  The |parent|, if not
 131  * NULL, will be used to auto-seed this RAND_DRBG as needed.
 132  *
 133  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 134  */
 135 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
 136 {
 137     RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
 138
 139     if (drbg == NULL) {
 140         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
 141         goto err;
 142     }
 143     drbg->fork_count = rand_fork_count;
 144     drbg->parent = parent;
 145     if (RAND_DRBG_set(drbg, type, flags) < 0)
 146         goto err;
 147
 148     if (!RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 149                                  rand_drbg_cleanup_entropy,
 150                                  NULL, NULL))
 151         goto err;
 152
 153     return drbg;
 154
 155 err:
 156     OPENSSL_free(drbg);
 157     return NULL;
 158 }
 159
 160 /*
 161  * Uninstantiate |drbg| and free all memory.
 162  */
 163 void RAND_DRBG_free(RAND_DRBG *drbg)
 164 {
 165     if (drbg == NULL)
 166         return;
 167
 168     ctr_uninstantiate(drbg);
 169     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 170     OPENSSL_clear_free(drbg, sizeof(*drbg));
 171 }
 172
 173 /*
 174  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 175  * |perslen| as prediction-resistance input.
 176  *
 177  * Requires that drbg->lock is already locked for write, if non-null.
 178  */
 179 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 180                           const unsigned char *pers, size_t perslen)
 181 {
 182     unsigned char *nonce = NULL, *entropy = NULL;
 183     size_t noncelen = 0, entropylen = 0;
 184
 185     if (perslen > drbg->max_perslen) {
 186         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 187                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 188         goto end;
 189     }
 190     if (drbg->state != DRBG_UNINITIALISED) {
 191         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 192                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 193                                           : RAND_R_ALREADY_INSTANTIATED);
 194         goto end;
 195     }
 196
 197     drbg->state = DRBG_ERROR;
 198     if (drbg->get_entropy != NULL)
 199         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 200                                    drbg->min_entropylen, drbg->max_entropylen);
 201     if (entropylen < drbg->min_entropylen
 202         || entropylen > drbg->max_entropylen) {
 203         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 204         goto end;
 205     }
 206
 207     if (drbg->max_noncelen > 0 && drbg->get_nonce != NULL) {
 208         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 209                                    drbg->min_noncelen, drbg->max_noncelen);
 210         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
 211             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 212                     RAND_R_ERROR_RETRIEVING_NONCE);
 213             goto end;
 214         }
 215     }
 216
 217     if (!ctr_instantiate(drbg, entropy, entropylen,
 218                          nonce, noncelen, pers, perslen)) {
 219         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 220         goto end;
 221     }
 222
 223     drbg->state = DRBG_READY;
 224     drbg->generate_counter = 0;
 225
 226     if (drbg->reseed_counter > 0) {
 227         if (drbg->parent == NULL)
 228             drbg->reseed_counter++;
 229         else
 230             drbg->reseed_counter = drbg->parent->reseed_counter;
 231     }
 232
 233 end:
 234     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 235         drbg->cleanup_entropy(drbg, entropy, entropylen);
 236     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 237         drbg->cleanup_nonce(drbg, nonce, noncelen);
 238     if (drbg->pool != NULL) {
 239         if (drbg->state == DRBG_READY) {
 240             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 241                     RAND_R_ERROR_ENTROPY_POOL_WAS_IGNORED);
 242             drbg->state = DRBG_ERROR;
 243         }
 244         RAND_POOL_free(drbg->pool);
 245         drbg->pool = NULL;
 246     }
 247     if (drbg->state == DRBG_READY)
 248         return 1;
 249     return 0;
 250 }
 251
 252 /*
 253  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 254  *
 255  * Requires that drbg->lock is already locked for write, if non-null.
 256  */
 257 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 258 {
 259     int ret = ctr_uninstantiate(drbg);
 260
 261     drbg->state = DRBG_UNINITIALISED;
 262     return ret;
 263 }
 264
 265 /*
 266  * Reseed |drbg|, mixing in the specified data
 267  *
 268  * Requires that drbg->lock is already locked for write, if non-null.
 269  */
 270 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 271                      const unsigned char *adin, size_t adinlen)
 272 {
 273     unsigned char *entropy = NULL;
 274     size_t entropylen = 0;
 275
 276     if (drbg->state == DRBG_ERROR) {
 277         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 278         return 0;
 279     }
 280     if (drbg->state == DRBG_UNINITIALISED) {
 281         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 282         return 0;
 283     }
 284
 285     if (adin == NULL)
 286         adinlen = 0;
 287     else if (adinlen > drbg->max_adinlen) {
 288         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 289         return 0;
 290     }
 291
 292     drbg->state = DRBG_ERROR;
 293     if (drbg->get_entropy != NULL)
 294         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 295                                    drbg->min_entropylen, drbg->max_entropylen);
 296     if (entropylen < drbg->min_entropylen
 297         || entropylen > drbg->max_entropylen) {
 298         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 299         goto end;
 300     }
 301
 302     if (!ctr_reseed(drbg, entropy, entropylen, adin, adinlen))
 303         goto end;
 304
 305     drbg->state = DRBG_READY;
 306     drbg->generate_counter = 0;
 307
 308     if (drbg->reseed_counter > 0) {
 309         if (drbg->parent == NULL)
 310             drbg->reseed_counter++;
 311         else
 312             drbg->reseed_counter = drbg->parent->reseed_counter;
 313     }
 314
 315 end:
 316     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 317         drbg->cleanup_entropy(drbg, entropy, entropylen);
 318     if (drbg->state == DRBG_READY)
 319         return 1;
 320     return 0;
 321 }
 322
 323 /*
 324  * Restart |drbg|, using the specified entropy or additional input
 325  *
 326  * Tries its best to get the drbg instantiated by all means,
 327  * regardless of its current state.
 328  *
 329  * Optionally, a |buffer| of |len| random bytes can be passed,
 330  * which is assumed to contain at least |entropy| bits of entropy.
 331  *
 332  * If |entropy| > 0, the buffer content is used as entropy input.
 333  *
 334  * If |entropy| == 0, the buffer content is used as additional input
 335  *
 336  * Returns 1 on success, 0 on failure.
 337  *
 338  * This function is used internally only.
 339  */
 340 int rand_drbg_restart(RAND_DRBG *drbg,
 341                       const unsigned char *buffer, size_t len, size_t entropy)
 342 {
 343     int reseeded = 0;
 344     const unsigned char *adin = NULL;
 345     size_t adinlen = 0;
 346
 347     if (drbg->pool != NULL) {
 348         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 349         RAND_POOL_free(drbg->pool);
 350         drbg->pool = NULL;
 351     }
 352
 353     if (buffer != NULL) {
 354         if (entropy > 0) {
 355             if (drbg->max_entropylen < len) {
 356                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 357                     RAND_R_ENTROPY_INPUT_TOO_LONG);
 358                 return 0;
 359             }
 360
 361             if (entropy > 8 * len) {
 362                 RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
 363                 return 0;
 364             }
 365
 366             /* will be picked up by the rand_drbg_get_entropy() callback */
 367             drbg->pool = RAND_POOL_new(entropy, len, len);
 368             if (drbg->pool == NULL)
 369                 return 0;
 370
 371             RAND_POOL_add(drbg->pool, buffer, len, entropy);
 372         } else {
 373             if (drbg->max_adinlen < len) {
 374                 RANDerr(RAND_F_RAND_DRBG_RESTART,
 375                         RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 376                 return 0;
 377             }
 378             adin = buffer;
 379             adinlen = len;
 380         }
 381     }
 382
 383     /* repair error state */
 384     if (drbg->state == DRBG_ERROR) {
 385         RAND_DRBG_uninstantiate(drbg);
 386         /* The drbg->ctr member needs to be reinitialized before reinstantiation */
 387         RAND_DRBG_set(drbg, drbg->nid, drbg->flags);
 388     }
 389
 390     /* repair uninitialized state */
 391     if (drbg->state == DRBG_UNINITIALISED) {
 392         /* reinstantiate drbg */
 393         RAND_DRBG_instantiate(drbg,
 394                               (const unsigned char *) ossl_pers_string,
 395                               sizeof(ossl_pers_string) - 1);
 396         /* already reseeded. prevent second reseeding below */
 397         reseeded = (drbg->state == DRBG_READY);
 398     }
 399
 400     /* refresh current state if entropy or additional input has been provided */
 401     if (drbg->state == DRBG_READY) {
 402         if (adin != NULL) {
 403             /*
 404              * mix in additional input without reseeding
 405              *
 406              * Similar to RAND_DRBG_reseed(), but the provided additional
 407              * data |adin| is mixed into the current state without pulling
 408              * entropy from the trusted entropy source using get_entropy().
 409              * This is not a reseeding in the strict sense of NIST SP 800-90A.
 410              */
 411             ctr_reseed(drbg, adin, adinlen, NULL, 0);
 412         } else if (reseeded == 0) {
 413             /* do a full reseeding if it has not been done yet above */
 414             RAND_DRBG_reseed(drbg, NULL, 0);
 415         }
 416     }
 417
 418     /* check whether a given entropy pool was cleared properly during reseed */
 419     if (drbg->pool != NULL) {
 420         drbg->state = DRBG_ERROR;
 421         RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
 422         RAND_POOL_free(drbg->pool);
 423         drbg->pool = NULL;
 424         return 0;
 425     }
 426
 427     return drbg->state == DRBG_READY;
 428 }
 429
 430 /*
 431  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 432  * to or if |prediction_resistance| is set.  Additional input can be
 433  * sent in |adin| and |adinlen|.
 434  *
 435  * Requires that drbg->lock is already locked for write, if non-null.
 436  *
 437  * Returns 1 on success, 0 on failure.
 438  *
 439  */
 440 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 441                        int prediction_resistance,
 442                        const unsigned char *adin, size_t adinlen)
 443 {
 444     int reseed_required = 0;
 445
 446     if (drbg->state != DRBG_READY) {
 447         /* try to recover from previous errors */
 448         rand_drbg_restart(drbg, NULL, 0, 0);
 449
 450         if (drbg->state == DRBG_ERROR) {
 451             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 452             return 0;
 453         }
 454         if (drbg->state == DRBG_UNINITIALISED) {
 455             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 456             return 0;
 457         }
 458     }
 459
 460     if (outlen > drbg->max_request) {
 461         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 462         return 0;
 463     }
 464     if (adinlen > drbg->max_adinlen) {
 465         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 466         return 0;
 467     }
 468
 469     if (drbg->fork_count != rand_fork_count) {
 470         drbg->fork_count = rand_fork_count;
 471         reseed_required = 1;
 472     }
 473
 474     if (drbg->reseed_interval > 0) {
 475         if (drbg->generate_counter >= drbg->reseed_interval)
 476             reseed_required = 1;
 477     }
 478
 479     if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
 480         if (drbg->reseed_counter != drbg->parent->reseed_counter)
 481             reseed_required = 1;
 482     }
 483
 484     if (reseed_required || prediction_resistance) {
 485         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 486             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 487             return 0;
 488         }
 489         adin = NULL;
 490         adinlen = 0;
 491     }
 492
 493     if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
 494         drbg->state = DRBG_ERROR;
 495         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 496         return 0;
 497     }
 498
 499     drbg->generate_counter++;
 500
 501     return 1;
 502 }
 503
 504 /*
 505  * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
 506  *
 507  * In the following, the signature and the semantics of the
 508  * get_entropy() and cleanup_entropy() callbacks are explained.
 509  *
 510  * GET_ENTROPY
 511  *
 512  *     size_t get_entropy(RAND_DRBG *ctx,
 513  *                        unsigned char **pout,
 514  *                        int entropy,
 515  *                        size_t min_len, size_t max_len);
 516  *
 517  * This is a request to allocate and fill a buffer of size
 518  * |min_len| <= size <= |max_len| (in bytes) which contains
 519  * at least |entropy| bits of randomness. The buffer's address is
 520  * to be returned in |*pout| and the number of collected
 521  * randomness bytes (which may be less than the allocated size
 522  * of the buffer) as return value.
 523  *
 524  * If the callback fails to acquire at least |entropy| bits of
 525  * randomness, it shall return a buffer length of 0.
 526  *
 527  * CLEANUP_ENTROPY
 528  *
 529  *     void cleanup_entropy(RAND_DRBG *ctx,
 530  *                          unsigned char *out, size_t outlen);
 531  *
 532  * A request to clear and free the buffer allocated by get_entropy().
 533  * The values |out| and |outlen| are expected to be the random buffer's
 534  * address and length, as returned by the get_entropy() callback.
 535  *
 536  * GET_NONCE, CLEANUP_NONCE
 537  *
 538  * Signature and semantics of the get_nonce() and cleanup_nonce()
 539  * callbacks are analogous to get_entropy() and cleanup_entropy().
 540  * Currently, the nonce is used only for the known answer tests.
 541  */
 542 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 543                             RAND_DRBG_get_entropy_fn get_entropy,
 544                             RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
 545                             RAND_DRBG_get_nonce_fn get_nonce,
 546                             RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
 547 {
 548     if (drbg->state != DRBG_UNINITIALISED)
 549         return 0;
 550     drbg->get_entropy = get_entropy;
 551     drbg->cleanup_entropy = cleanup_entropy;
 552     drbg->get_nonce = get_nonce;
 553     drbg->cleanup_nonce = cleanup_nonce;
 554     return 1;
 555 }
 556
 557 /*
 558  * Set the reseed interval.
 559  *
 560  * The drbg will reseed automatically whenever the number of generate
 561  * requests exceeds the given reseed interval. If the reseed interval
 562  * is 0, then this automatic reseeding is disabled.
 563  *
 564  * Returns 1 on success, 0 on failure.
 565  */
 566 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
 567 {
 568     if (interval > MAX_RESEED_INTERVAL)
 569         return 0;
 570     drbg->reseed_interval = interval;
 571     return 1;
 572 }
 573
 574 /*
 575  * Get and set the EXDATA
 576  */
 577 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 578 {
 579     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 580 }
 581
 582 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 583 {
 584     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 585 }
 586
 587
 588 /*
 589  * The following functions provide a RAND_METHOD that works on the
 590  * global DRBG.  They lock.
 591  */
 592
 593 /*
 594  * Initializes the given global DRBG with default settings.
 595  * A global lock for the DRBG is created with the given name.
 596  *
 597  * Returns a pointer to the new DRBG instance on success, NULL on failure.
 598  */
 599 static int drbg_setup(RAND_DRBG *drbg, const char *name, RAND_DRBG *parent)
 600 {
 601     int ret = 1;
 602
 603     if (name == NULL || drbg->lock != NULL) {
 604         RANDerr(RAND_F_DRBG_SETUP, ERR_R_INTERNAL_ERROR);
 605         return 0;
 606     }
 607
 608     drbg->lock = CRYPTO_THREAD_glock_new(name);
 609     if (drbg->lock == NULL) {
 610         RANDerr(RAND_F_DRBG_SETUP, RAND_R_FAILED_TO_CREATE_LOCK);
 611         return 0;
 612     }
 613
 614     ret &= RAND_DRBG_set(drbg,
 615                          RAND_DRBG_NID, RAND_DRBG_FLAG_CTR_USE_DF) == 1;
 616     ret &= RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
 617                                    rand_drbg_cleanup_entropy, NULL, NULL) == 1;
 618
 619     if (parent == NULL)
 620         drbg->reseed_interval = MASTER_RESEED_INTERVAL;
 621     else {
 622         drbg->parent = parent;
 623         drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
 624     }
 625
 626     /* enable seed propagation */
 627     drbg->reseed_counter = 1;
 628
 629     /*
 630      * Ignore instantiation error so support just-in-time instantiation.
 631      *
 632      * The state of the drbg will be checked in RAND_DRBG_generate() and
 633      * an automatic recovery is attempted.
 634      */
 635     RAND_DRBG_instantiate(drbg,
 636                           (const unsigned char *) ossl_pers_string,
 637                           sizeof(ossl_pers_string) - 1);
 638     return ret;
 639 }
 640
 641 /*
 642  * Initialize the global DRBGs on first use.
 643  * Returns 1 on success, 0 on failure.
 644  */
 645 DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
 646 {
 647     int ret = 1;
 648
 649     ret &= drbg_setup(&drbg_master, "drbg_master", NULL);
 650     ret &= drbg_setup(&drbg_public, "drbg_public", &drbg_master);
 651     ret &= drbg_setup(&drbg_private, "drbg_private", &drbg_master);
 652
 653     return ret;
 654 }
 655
 656 /* Cleans up the given global DRBG  */
 657 static void drbg_cleanup(RAND_DRBG *drbg)
 658 {
 659     CRYPTO_THREAD_lock_free(drbg->lock);
 660     RAND_DRBG_uninstantiate(drbg);
 661 }
 662
 663 /* Clean up the global DRBGs before exit */
 664 void rand_drbg_cleanup_int(void)
 665 {
 666     drbg_cleanup(&drbg_private);
 667     drbg_cleanup(&drbg_public);
 668     drbg_cleanup(&drbg_master);
 669 }
 670
 671 /* Implements the default OpenSSL RAND_bytes() method */
 672 static int drbg_bytes(unsigned char *out, int count)
 673 {
 674     int ret = 0;
 675     size_t chunk;
 676     RAND_DRBG *drbg = RAND_DRBG_get0_public();
 677
 678     if (drbg == NULL)
 679         return 0;
 680
 681     CRYPTO_THREAD_write_lock(drbg->lock);
 682     if (drbg->state == DRBG_UNINITIALISED)
 683         goto err;
 684
 685     for ( ; count > 0; count -= chunk, out += chunk) {
 686         chunk = count;
 687         if (chunk > drbg->max_request)
 688             chunk = drbg->max_request;
 689         ret = RAND_DRBG_generate(drbg, out, chunk, 0, NULL, 0);
 690         if (!ret)
 691             goto err;
 692     }
 693     ret = 1;
 694
 695 err:
 696     CRYPTO_THREAD_unlock(drbg->lock);
 697     return ret;
 698 }
 699
 700 /* Implements the default OpenSSL RAND_add() method */
 701 static int drbg_add(const void *buf, int num, double randomness)
 702 {
 703     int ret = 0;
 704     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 705
 706     if (drbg == NULL)
 707         return 0;
 708
 709     if (num < 0 || randomness < 0.0)
 710         return 0;
 711
 712     if (randomness > (double)drbg->max_entropylen) {
 713         /*
 714          * The purpose of this check is to bound |randomness| by a
 715          * relatively small value in order to prevent an integer
 716          * overflow when multiplying by 8 in the rand_drbg_restart()
 717          * call below.
 718          */
 719         return 0;
 720     }
 721
 722     CRYPTO_THREAD_write_lock(drbg->lock);
 723     ret = rand_drbg_restart(drbg, buf,
 724                             (size_t)(unsigned int)num,
 725                             (size_t)(8*randomness));
 726     CRYPTO_THREAD_unlock(drbg->lock);
 727
 728     return ret;
 729 }
 730
 731 /* Implements the default OpenSSL RAND_seed() method */
 732 static int drbg_seed(const void *buf, int num)
 733 {
 734     return drbg_add(buf, num, num);
 735 }
 736
 737 /* Implements the default OpenSSL RAND_status() method */
 738 static int drbg_status(void)
 739 {
 740     int ret;
 741     RAND_DRBG *drbg = RAND_DRBG_get0_master();
 742
 743     if (drbg == NULL)
 744         return 0;
 745
 746     CRYPTO_THREAD_write_lock(drbg->lock);
 747     ret = drbg->state == DRBG_READY ? 1 : 0;
 748     CRYPTO_THREAD_unlock(drbg->lock);
 749     return ret;
 750 }
 751
 752 /*
 753  * Get the master DRBG.
 754  * Returns pointer to the DRBG on success, NULL on failure.
 755  *
 756  */
 757 RAND_DRBG *RAND_DRBG_get0_master(void)
 758 {
 759     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 760         return NULL;
 761
 762     return &drbg_master;
 763 }
 764
 765 /*
 766  * Get the public DRBG.
 767  * Returns pointer to the DRBG on success, NULL on failure.
 768  */
 769 RAND_DRBG *RAND_DRBG_get0_public(void)
 770 {
 771     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 772         return NULL;
 773
 774     return &drbg_public;
 775 }
 776
 777 /*
 778  * Get the private DRBG.
 779  * Returns pointer to the DRBG on success, NULL on failure.
 780  */
 781 RAND_DRBG *RAND_DRBG_get0_private(void)
 782 {
 783     if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
 784         return NULL;
 785
 786     return &drbg_private;
 787 }
 788
 789 RAND_METHOD rand_meth = {
 790     drbg_seed,
 791     drbg_bytes,
 792     NULL,
 793     drbg_add,
 794     drbg_bytes,
 795     drbg_status
 796 };
 797
 798 RAND_METHOD *RAND_OpenSSL(void)
 799 {
 800     return &rand_meth;
 801 }