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