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 static RAND_DRBG rand_drbg; /* The default global DRBG. */
  19 static RAND_DRBG priv_drbg; /* The global private-key DRBG. */
  20
  21 /*
  22  * Support framework for NIST SP 800-90A DRBG, AES-CTR mode.
  23  * The RAND_DRBG is OpenSSL's pointer to an instance of the DRBG.
  24  *
  25  * The OpenSSL model is to have new and free functions, and that new
  26  * does all initialization.  That is not the NIST model, which has
  27  * instantiation and un-instantiate, and re-use within a new/free
  28  * lifecycle.  (No doubt this comes from the desire to support hardware
  29  * DRBG, where allocation of resources on something like an HSM is
  30  * a much bigger deal than just re-setting an allocated resource.)
  31  */
  32
  33 static CRYPTO_ONCE rand_init_drbg = CRYPTO_ONCE_STATIC_INIT;
  34
  35 /*
  36  * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
  37  * Return -2 if the type is not supported, 1 on success and -1 on
  38  * failure.
  39  */
  40 int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
  41 {
  42     int ret = 1;
  43
  44     drbg->state = DRBG_UNINITIALISED;
  45     drbg->flags = flags;
  46     drbg->nid = nid;
  47
  48     switch (nid) {
  49     default:
  50         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
  51         return -2;
  52     case 0:
  53         /* Uninitialized; that's okay. */
  54         return 1;
  55     case NID_aes_128_ctr:
  56     case NID_aes_192_ctr:
  57     case NID_aes_256_ctr:
  58         ret = ctr_init(drbg);
  59         break;
  60     }
  61
  62     if (ret < 0)
  63         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
  64     return ret;
  65 }
  66
  67 /*
  68  * Allocate memory and initialize a new DRBG.  The |parent|, if not
  69  * NULL, will be used to auto-seed this RAND_DRBG as needed.
  70  */
  71 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
  72 {
  73     RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
  74
  75     if (drbg == NULL) {
  76         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
  77         goto err;
  78     }
  79     drbg->size = RANDOMNESS_NEEDED;
  80     drbg->fork_count = rand_fork_count;
  81     drbg->parent = parent;
  82     if (RAND_DRBG_set(drbg, type, flags) < 0)
  83         goto err;
  84
  85     if (parent != NULL) {
  86         if (!RAND_DRBG_set_callbacks(drbg, drbg_entropy_from_parent,
  87                                      drbg_release_entropy,
  88                                      NULL, NULL))
  89             goto err;
  90     }
  91
  92     return drbg;
  93
  94 err:
  95     OPENSSL_free(drbg);
  96     return NULL;
  97 }
  98
  99 /*
 100  * Uninstantiate |drbg| and free all memory.
 101  */
 102 void RAND_DRBG_free(RAND_DRBG *drbg)
 103 {
 104     /* The global DRBG is free'd by rand_cleanup_drbg_int() */
 105     if (drbg == NULL || drbg == &rand_drbg)
 106         return;
 107
 108     ctr_uninstantiate(drbg);
 109     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 110     OPENSSL_clear_free(drbg, sizeof(*drbg));
 111 }
 112
 113 /*
 114  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 115  * |perslen| as prediction-resistance input.
 116  */
 117 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 118                           const unsigned char *pers, size_t perslen)
 119 {
 120     unsigned char *nonce = NULL, *entropy = NULL;
 121     size_t noncelen = 0, entropylen = 0;
 122
 123     if (perslen > drbg->max_perslen) {
 124         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 125                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 126         goto end;
 127     }
 128     if (drbg->state != DRBG_UNINITIALISED) {
 129         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 130                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 131                                           : RAND_R_ALREADY_INSTANTIATED);
 132         goto end;
 133     }
 134
 135     drbg->state = DRBG_ERROR;
 136     if (drbg->get_entropy != NULL)
 137         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 138                                    drbg->min_entropylen, drbg->max_entropylen);
 139     if (entropylen < drbg->min_entropylen || entropylen > drbg->max_entropylen) {
 140         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 141         goto end;
 142     }
 143
 144     if (drbg->max_noncelen > 0 && drbg->get_nonce != NULL) {
 145         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 146                                    drbg->min_noncelen, drbg->max_noncelen);
 147         if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
 148             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_NONCE);
 149             goto end;
 150         }
 151     }
 152
 153     if (!ctr_instantiate(drbg, entropy, entropylen,
 154                          nonce, noncelen, pers, perslen)) {
 155         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 156         goto end;
 157     }
 158
 159     drbg->state = DRBG_READY;
 160     drbg->reseed_counter = 1;
 161
 162 end:
 163     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 164         drbg->cleanup_entropy(drbg, entropy, entropylen);
 165     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 166         drbg->cleanup_nonce(drbg, nonce, noncelen);
 167     if (drbg->state == DRBG_READY)
 168         return 1;
 169     return 0;
 170 }
 171
 172 /*
 173  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 174  */
 175 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 176 {
 177     int ret = ctr_uninstantiate(drbg);
 178
 179     OPENSSL_cleanse(&drbg->ctr, sizeof(drbg->ctr));
 180     drbg->state = DRBG_UNINITIALISED;
 181     return ret;
 182 }
 183
 184 /*
 185  * Mix in the specified data to reseed |drbg|.
 186  */
 187 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 188                      const unsigned char *adin, size_t adinlen)
 189 {
 190     unsigned char *entropy = NULL;
 191     size_t entropylen = 0;
 192
 193     if (drbg->state == DRBG_ERROR) {
 194         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 195         return 0;
 196     }
 197     if (drbg->state == DRBG_UNINITIALISED) {
 198         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 199         return 0;
 200     }
 201
 202     if (adin == NULL)
 203         adinlen = 0;
 204     else if (adinlen > drbg->max_adinlen) {
 205         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 206         return 0;
 207     }
 208
 209     drbg->state = DRBG_ERROR;
 210     if (drbg->get_entropy != NULL)
 211         entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 212                                    drbg->min_entropylen, drbg->max_entropylen);
 213     if (entropylen < drbg->min_entropylen || entropylen > drbg->max_entropylen) {
 214         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 215         goto end;
 216     }
 217
 218     if (!ctr_reseed(drbg, entropy, entropylen, adin, adinlen))
 219         goto end;
 220     drbg->state = DRBG_READY;
 221     drbg->reseed_counter = 1;
 222
 223 end:
 224     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 225         drbg->cleanup_entropy(drbg, entropy, entropylen);
 226     if (drbg->state == DRBG_READY)
 227         return 1;
 228     return 0;
 229 }
 230
 231 /*
 232  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 233  * to or if |prediction_resistance| is set.  Additional input can be
 234  * sent in |adin| and |adinlen|.
 235  */
 236 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 237                        int prediction_resistance,
 238                        const unsigned char *adin, size_t adinlen)
 239 {
 240     if (drbg->state == DRBG_ERROR) {
 241         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 242         return 0;
 243     }
 244     if (drbg->state == DRBG_UNINITIALISED) {
 245         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 246         return 0;
 247     }
 248     if (outlen > drbg->max_request) {
 249         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 250         return 0;
 251     }
 252     if (adinlen > drbg->max_adinlen) {
 253         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 254         return 0;
 255     }
 256
 257     if (drbg->fork_count != rand_fork_count) {
 258         drbg->fork_count = rand_fork_count;
 259         drbg->state = DRBG_RESEED;
 260     }
 261
 262     if (drbg->reseed_counter >= drbg->reseed_interval)
 263         drbg->state = DRBG_RESEED;
 264
 265     if (drbg->state == DRBG_RESEED || prediction_resistance) {
 266         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 267             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 268             return 0;
 269         }
 270         adin = NULL;
 271         adinlen = 0;
 272     }
 273
 274     if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
 275         drbg->state = DRBG_ERROR;
 276         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 277         return 0;
 278     }
 279
 280     if (drbg->reseed_counter >= drbg->reseed_interval)
 281         drbg->state = DRBG_RESEED;
 282     else
 283         drbg->reseed_counter++;
 284     return 1;
 285 }
 286
 287 /*
 288  * Set the callbacks for entropy and nonce.  We currently don't use
 289  * the nonce; that's mainly for the KATs
 290  */
 291 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 292                             RAND_DRBG_get_entropy_fn cb_get_entropy,
 293                             RAND_DRBG_cleanup_entropy_fn cb_cleanup_entropy,
 294                             RAND_DRBG_get_nonce_fn cb_get_nonce,
 295                             RAND_DRBG_cleanup_nonce_fn cb_cleanup_nonce)
 296 {
 297     if (drbg->state != DRBG_UNINITIALISED)
 298         return 0;
 299     drbg->get_entropy = cb_get_entropy;
 300     drbg->cleanup_entropy = cb_cleanup_entropy;
 301     drbg->get_nonce = cb_get_nonce;
 302     drbg->cleanup_nonce = cb_cleanup_nonce;
 303     return 1;
 304 }
 305
 306 /*
 307  * Set the reseed interval.
 308  */
 309 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, int interval)
 310 {
 311     if (interval < 0 || interval > MAX_RESEED)
 312         return 0;
 313     drbg->reseed_interval = interval;
 314     return 1;
 315 }
 316
 317 /*
 318  * Get and set the EXDATA
 319  */
 320 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 321 {
 322     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 323 }
 324
 325 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 326 {
 327     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 328 }
 329
 330
 331 /*
 332  * The following functions provide a RAND_METHOD that works on the
 333  * global DRBG.  They lock.
 334  */
 335
 336 /*
 337  * Creates a global DRBG with default settings.
 338  * Returns 1 on success, 0 on failure
 339  */
 340 static int setup_drbg(RAND_DRBG *drbg)
 341 {
 342     int ret = 1;
 343
 344     drbg->lock = CRYPTO_THREAD_lock_new();
 345     ret &= drbg->lock != NULL;
 346     drbg->size = RANDOMNESS_NEEDED;
 347     drbg->secure = CRYPTO_secure_malloc_initialized();
 348     /* If you change these parameters, see RANDOMNESS_NEEDED */
 349     ret &= RAND_DRBG_set(drbg,
 350                          NID_aes_128_ctr, RAND_DRBG_FLAG_CTR_USE_DF) == 1;
 351     ret &= RAND_DRBG_set_callbacks(drbg, drbg_entropy_from_system,
 352                                    drbg_release_entropy, NULL, NULL) == 1;
 353     ret &= RAND_DRBG_instantiate(drbg, NULL, 0) == 1;
 354     return ret;
 355 }
 356
 357 /*
 358  * Initialize the global DRBGs on first use.
 359  * Returns 1 on success, 0 on failure.
 360  */
 361 DEFINE_RUN_ONCE_STATIC(do_rand_init_drbg)
 362 {
 363     int ret = 1;
 364
 365     ret &= setup_drbg(&rand_drbg);
 366     ret &= setup_drbg(&priv_drbg);
 367
 368     return ret;
 369 }
 370
 371 /* Clean up a DRBG and free it */
 372 static void free_drbg(RAND_DRBG *drbg)
 373 {
 374     CRYPTO_THREAD_lock_free(drbg->lock);
 375     RAND_DRBG_uninstantiate(drbg);
 376 }
 377
 378 /* Clean up the global DRBGs before exit */
 379 void rand_cleanup_drbg_int(void)
 380 {
 381     free_drbg(&rand_drbg);
 382     free_drbg(&priv_drbg);
 383 }
 384
 385 static int drbg_bytes(unsigned char *out, int count)
 386 {
 387     int ret = 0;
 388     size_t chunk;
 389     RAND_DRBG *drbg = RAND_DRBG_get0_global();
 390
 391     if (drbg == NULL)
 392         return 0;
 393
 394     CRYPTO_THREAD_write_lock(drbg->lock);
 395     if (drbg->state == DRBG_UNINITIALISED)
 396         goto err;
 397
 398     for ( ; count > 0; count -= chunk, out += chunk) {
 399         chunk = count;
 400         if (chunk > drbg->max_request)
 401             chunk = drbg->max_request;
 402         ret = RAND_DRBG_generate(drbg, out, chunk, 0, NULL, 0);
 403         if (!ret)
 404             goto err;
 405     }
 406     ret = 1;
 407
 408 err:
 409     CRYPTO_THREAD_unlock(drbg->lock);
 410     return ret;
 411 }
 412
 413 static int drbg_add(const void *buf, int num, double randomness)
 414 {
 415     unsigned char *in = (unsigned char *)buf;
 416     unsigned char *out, *end;
 417
 418     CRYPTO_THREAD_write_lock(rand_bytes.lock);
 419     out = &rand_bytes.buff[rand_bytes.curr];
 420     end = &rand_bytes.buff[rand_bytes.size];
 421
 422     /* Copy whatever fits into the end of the buffer. */
 423     for ( ; --num >= 0 && out < end; rand_bytes.curr++)
 424         *out++ = *in++;
 425
 426     /* XOR any the leftover. */
 427     while (num > 0) {
 428         for (out = rand_bytes.buff; --num >= 0 && out < end; )
 429             *out++ ^= *in++;
 430     }
 431
 432     CRYPTO_THREAD_unlock(rand_bytes.lock);
 433     return 1;
 434 }
 435
 436 static int drbg_seed(const void *buf, int num)
 437 {
 438     return drbg_add(buf, num, num);
 439 }
 440
 441 static int drbg_status(void)
 442 {
 443     int ret;
 444     RAND_DRBG *drbg = RAND_DRBG_get0_global();
 445
 446     if (drbg == NULL)
 447         return 0;
 448
 449     CRYPTO_THREAD_write_lock(drbg->lock);
 450     ret = drbg->state == DRBG_READY ? 1 : 0;
 451     CRYPTO_THREAD_unlock(drbg->lock);
 452     return ret;
 453 }
 454
 455 /*
 456  * Get the global public DRBG.
 457  * Returns pointer to the DRBG on success, NULL on failure.
 458  */
 459 RAND_DRBG *RAND_DRBG_get0_global(void)
 460 {
 461     if (!RUN_ONCE(&rand_init_drbg, do_rand_init_drbg))
 462         return NULL;
 463
 464     return &rand_drbg;
 465 }
 466
 467 /*
 468  * Get the global private DRBG.
 469  * Returns pointer to the DRBG on success, NULL on failure.
 470  */
 471 RAND_DRBG *RAND_DRBG_get0_priv_global(void)
 472 {
 473     if (!RUN_ONCE(&rand_init_drbg, do_rand_init_drbg))
 474         return NULL;
 475
 476     return &priv_drbg;
 477 }
 478
 479 RAND_METHOD rand_meth = {
 480     drbg_seed,
 481     drbg_bytes,
 482     NULL,
 483     drbg_add,
 484     drbg_bytes,
 485     drbg_status
 486 };
 487
 488 RAND_METHOD *RAND_OpenSSL(void)
 489 {
 490     return &rand_meth;
 491 }