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
  16 /*
  17  * Support framework for NIST SP 800-90A DRBG, AES-CTR mode.
  18  * The RAND_DRBG is OpenSSL's pointer to an instance of the DRBG.
  19  *
  20  * The OpenSSL model is to have new and free functions, and that new
  21  * does all initialization.  That is not the NIST model, which has
  22  * instantiation and un-instantiate, and re-use within a new/free
  23  * lifecycle.  (No doubt this comes from the desire to support hardware
  24  * DRBG, where allocation of resources on something like an HSM is
  25  * a much bigger deal than just re-setting an allocated resource.)
  26  */
  27
  28 /*
  29  * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
  30  * Return -2 if the type is not supported, 1 on success and -1 on
  31  * failure.
  32  */
  33 int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
  34 {
  35     int ret = 1;
  36
  37     drbg->state = DRBG_UNINITIALISED;
  38     drbg->flags = flags;
  39     drbg->nid = nid;
  40
  41     switch (nid) {
  42     default:
  43         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
  44         return -2;
  45     case 0:
  46         /* Uninitialized; that's okay. */
  47         return 1;
  48     case NID_aes_128_ctr:
  49     case NID_aes_192_ctr:
  50     case NID_aes_256_ctr:
  51         ret = ctr_init(drbg);
  52         break;
  53     }
  54
  55     if (ret < 0)
  56         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
  57     return ret;
  58 }
  59
  60 /*
  61  * Allocate memory and initialize a new DRBG.  The |parent|, if not
  62  * NULL, will be used to auto-seed this RAND_DRBG as needed.
  63  */
  64 RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
  65 {
  66     RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
  67     unsigned char *ucp = OPENSSL_zalloc(RANDOMNESS_NEEDED);
  68
  69     if (drbg == NULL || ucp == NULL) {
  70         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
  71         goto err;
  72     }
  73     drbg->size = RANDOMNESS_NEEDED;
  74     drbg->randomness = ucp;
  75     drbg->fork_count = rand_fork_count;
  76     drbg->parent = parent;
  77     if (RAND_DRBG_set(drbg, type, flags) < 0)
  78         goto err;
  79
  80     if (parent != NULL) {
  81         if (parent->state == DRBG_UNINITIALISED
  82                 && RAND_DRBG_instantiate(parent, NULL, 0) == 0)
  83             goto err;
  84         if (!RAND_DRBG_set_callbacks(drbg, drbg_entropy_from_parent,
  85                                      drbg_release_entropy,
  86                                      NULL, NULL)
  87                 /*
  88                  * Add in our address.  Note we are adding the pointer
  89                  * itself, not its contents!
  90                  */
  91                 || !RAND_DRBG_instantiate(drbg,
  92                                           (unsigned char*)&drbg, sizeof(drbg)))
  93             goto err;
  94     }
  95
  96     return drbg;
  97
  98 err:
  99     OPENSSL_free(ucp);
 100     OPENSSL_free(drbg);
 101     return NULL;
 102 }
 103
 104 RAND_DRBG *RAND_DRBG_get0_global(void)
 105 {
 106     return &rand_drbg;
 107 }
 108
 109 /*
 110  * Uninstantiate |drbg| and free all memory.
 111  */
 112 void RAND_DRBG_free(RAND_DRBG *drbg)
 113 {
 114     /* The global DRBG is free'd by rand_cleanup_int() */
 115     if (drbg == NULL || drbg == &rand_drbg)
 116         return;
 117
 118     ctr_uninstantiate(drbg);
 119     OPENSSL_cleanse(drbg->randomness, drbg->size);
 120     OPENSSL_free(drbg->randomness);
 121     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
 122     OPENSSL_clear_free(drbg, sizeof(*drbg));
 123 }
 124
 125 /*
 126  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
 127  * |perslen| as prediction-resistance input.
 128  */
 129 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
 130                           const unsigned char *pers, size_t perslen)
 131 {
 132     unsigned char *nonce = NULL, *entropy = NULL;
 133     size_t noncelen = 0, entlen = 0;
 134
 135     if (perslen > drbg->max_pers) {
 136         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 137                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
 138         goto end;
 139     }
 140     if (drbg->state != DRBG_UNINITIALISED) {
 141         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
 142                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
 143                                           : RAND_R_ALREADY_INSTANTIATED);
 144         goto end;
 145     }
 146
 147     drbg->state = DRBG_ERROR;
 148     if (drbg->get_entropy != NULL)
 149         entlen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 150                                    drbg->min_entropy, drbg->max_entropy);
 151     if (entlen < drbg->min_entropy || entlen > drbg->max_entropy) {
 152         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
 153         goto end;
 154     }
 155
 156     if (drbg->max_nonce > 0 && drbg->get_nonce != NULL) {
 157         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
 158                                    drbg->min_nonce, drbg->max_nonce);
 159         if (noncelen < drbg->min_nonce || noncelen > drbg->max_nonce) {
 160             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_NONCE);
 161             goto end;
 162         }
 163     }
 164
 165     if (!ctr_instantiate(drbg, entropy, entlen,
 166                          nonce, noncelen, pers, perslen)) {
 167         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
 168         goto end;
 169     }
 170
 171     drbg->state = DRBG_READY;
 172     drbg->reseed_counter = 1;
 173
 174 end:
 175     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 176         drbg->cleanup_entropy(drbg, entropy);
 177     if (nonce != NULL && drbg->cleanup_nonce!= NULL )
 178         drbg->cleanup_nonce(drbg, nonce);
 179     if (drbg->state == DRBG_READY)
 180         return 1;
 181     return 0;
 182 }
 183
 184 /*
 185  * Uninstantiate |drbg|. Must be instantiated before it can be used.
 186  */
 187 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 188 {
 189     int ret = ctr_uninstantiate(drbg);
 190
 191     OPENSSL_cleanse(&drbg->ctr, sizeof(drbg->ctr));
 192     drbg->state = DRBG_UNINITIALISED;
 193     return ret;
 194 }
 195
 196 /*
 197  * Mix in the specified data to reseed |drbg|.
 198  */
 199 int RAND_DRBG_reseed(RAND_DRBG *drbg,
 200                      const unsigned char *adin, size_t adinlen)
 201 {
 202     unsigned char *entropy = NULL;
 203     size_t entlen = 0;
 204
 205     if (drbg->state == DRBG_ERROR) {
 206         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
 207         return 0;
 208     }
 209     if (drbg->state == DRBG_UNINITIALISED) {
 210         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
 211         return 0;
 212     }
 213
 214     if (adin == NULL)
 215         adinlen = 0;
 216     else if (adinlen > drbg->max_adin) {
 217         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 218         return 0;
 219     }
 220
 221     drbg->state = DRBG_ERROR;
 222     if (drbg->get_entropy != NULL)
 223         entlen = drbg->get_entropy(drbg, &entropy, drbg->strength,
 224                                    drbg->min_entropy, drbg->max_entropy);
 225     if (entlen < drbg->min_entropy || entlen > drbg->max_entropy) {
 226         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
 227         goto end;
 228     }
 229
 230     if (!ctr_reseed(drbg, entropy, entlen, adin, adinlen))
 231         goto end;
 232     drbg->state = DRBG_READY;
 233     drbg->reseed_counter = 1;
 234
 235 end:
 236     if (entropy != NULL && drbg->cleanup_entropy != NULL)
 237         drbg->cleanup_entropy(drbg, entropy);
 238     if (drbg->state == DRBG_READY)
 239         return 1;
 240     return 0;
 241 }
 242
 243 /*
 244  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
 245  * to or if |prediction_resistance| is set.  Additional input can be
 246  * sent in |adin| and |adinlen|.
 247  */
 248 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
 249                        int prediction_resistance,
 250                        const unsigned char *adin, size_t adinlen)
 251 {
 252     if (drbg->state == DRBG_ERROR) {
 253         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
 254         return 0;
 255     }
 256     if (drbg->state == DRBG_UNINITIALISED) {
 257         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
 258         return 0;
 259     }
 260     if (outlen > drbg->max_request) {
 261         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
 262         return 0;
 263     }
 264     if (adinlen > drbg->max_adin) {
 265         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
 266         return 0;
 267     }
 268
 269     if (drbg->fork_count != rand_fork_count) {
 270         drbg->fork_count = rand_fork_count;
 271         drbg->state = DRBG_RESEED;
 272     }
 273
 274     if (drbg->reseed_counter >= drbg->reseed_interval)
 275         drbg->state = DRBG_RESEED;
 276
 277     if (drbg->state == DRBG_RESEED || prediction_resistance) {
 278         if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
 279             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
 280             return 0;
 281         }
 282         adin = NULL;
 283         adinlen = 0;
 284     }
 285
 286     if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
 287         drbg->state = DRBG_ERROR;
 288         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
 289         return 0;
 290     }
 291
 292     if (drbg->reseed_counter >= drbg->reseed_interval)
 293         drbg->state = DRBG_RESEED;
 294     else
 295         drbg->reseed_counter++;
 296     return 1;
 297 }
 298
 299 /*
 300  * Set the callbacks for entropy and nonce.  We currently don't use
 301  * the nonce; that's mainly for the KATs
 302  */
 303 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
 304                             RAND_DRBG_get_entropy_fn cb_get_entropy,
 305                             RAND_DRBG_cleanup_entropy_fn cb_cleanup_entropy,
 306                             RAND_DRBG_get_nonce_fn cb_get_nonce,
 307                             RAND_DRBG_cleanup_nonce_fn cb_cleanup_nonce)
 308 {
 309     if (drbg->state != DRBG_UNINITIALISED)
 310         return 0;
 311     drbg->get_entropy = cb_get_entropy;
 312     drbg->cleanup_entropy = cb_cleanup_entropy;
 313     drbg->get_nonce = cb_get_nonce;
 314     drbg->cleanup_nonce = cb_cleanup_nonce;
 315     return 1;
 316 }
 317
 318 /*
 319  * Set the reseed interval.
 320  */
 321 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, int interval)
 322 {
 323     if (interval < 0 || interval > MAX_RESEED)
 324         return 0;
 325     drbg->reseed_interval = interval;
 326     return 1;
 327 }
 328
 329 /*
 330  * Get and set the EXDATA
 331  */
 332 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
 333 {
 334     return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
 335 }
 336
 337 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
 338 {
 339     return CRYPTO_get_ex_data(&drbg->ex_data, idx);
 340 }
 341
 342
 343 /*
 344  * The following functions provide a RAND_METHOD that works on the
 345  * global DRBG.  They lock.
 346  */
 347
 348 static int drbg_bytes(unsigned char *out, int count)
 349 {
 350     int ret = 0;
 351     size_t chunk;
 352
 353     CRYPTO_THREAD_write_lock(rand_drbg.lock);
 354     if (rand_drbg.state == DRBG_UNINITIALISED
 355             && RAND_DRBG_instantiate(&rand_drbg, NULL, 0) == 0)
 356         goto err;
 357
 358     for ( ; count > 0; count -= chunk, out += chunk) {
 359         chunk = count;
 360         if (chunk > rand_drbg.max_request)
 361             chunk = rand_drbg.max_request;
 362         ret = RAND_DRBG_generate(&rand_drbg, out, chunk, 0, NULL, 0);
 363         if (!ret)
 364             goto err;
 365     }
 366     ret = 1;
 367
 368 err:
 369     CRYPTO_THREAD_unlock(rand_drbg.lock);
 370     return ret;
 371 }
 372
 373 static int drbg_add(const void *buf, int num, double randomness)
 374 {
 375     unsigned char *in = (unsigned char *)buf;
 376     unsigned char *out, *end;
 377
 378     CRYPTO_THREAD_write_lock(rand_bytes.lock);
 379     out = &rand_bytes.buff[rand_bytes.curr];
 380     end = &rand_bytes.buff[rand_bytes.size];
 381
 382     /* Copy whatever fits into the end of the buffer. */
 383     for ( ; --num >= 0 && out < end; rand_bytes.curr++)
 384         *out++ = *in++;
 385
 386     /* XOR any the leftover. */
 387     while (num > 0) {
 388         for (out = rand_bytes.buff; --num >= 0 && out < end; )
 389             *out++ ^= *in++;
 390     }
 391
 392     CRYPTO_THREAD_unlock(rand_bytes.lock);
 393     return 1;
 394 }
 395
 396 static int drbg_seed(const void *buf, int num)
 397 {
 398     return drbg_add(buf, num, num);
 399 }
 400
 401 static int drbg_status(void)
 402 {
 403     int ret;
 404
 405     CRYPTO_THREAD_write_lock(rand_drbg.lock);
 406     ret = rand_drbg.state == DRBG_READY ? 1 : 0;
 407     CRYPTO_THREAD_unlock(rand_drbg.lock);
 408     return ret;
 409 }
 410
 411 RAND_DRBG rand_drbg; /* The default global DRBG. */
 412 RAND_DRBG priv_drbg; /* The global private-key DRBG. */
 413
 414 RAND_METHOD rand_meth = {
 415     drbg_seed,
 416     drbg_bytes,
 417     NULL,
 418     drbg_add,
 419     drbg_bytes,
 420     drbg_status
 421 };
 422
 423 RAND_METHOD *RAND_OpenSSL(void)
 424 {
 425     return &rand_meth;
 426 }