crypto/rand/rand_lib.c

   1 /*
   2  * Copyright 1995-2017 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 <stdio.h>
  11 #include <time.h>
  12 #include "internal/cryptlib.h"
  13 #include <openssl/opensslconf.h>
  14 #include "internal/rand_int.h"
  15 #include <openssl/engine.h>
  16 #include "internal/thread_once.h"
  17 #include "rand_lcl.h"
  18
  19 #ifndef OPENSSL_NO_ENGINE
  20 /* non-NULL if default_RAND_meth is ENGINE-provided */
  21 static ENGINE *funct_ref;
  22 static CRYPTO_RWLOCK *rand_engine_lock;
  23 #endif
  24 static CRYPTO_RWLOCK *rand_meth_lock;
  25 static const RAND_METHOD *default_RAND_meth;
  26 static CRYPTO_ONCE rand_init = CRYPTO_ONCE_STATIC_INIT;
  27
  28 int rand_fork_count;
  29
  30 #ifdef OPENSSL_RAND_SEED_RDTSC
  31 /*
  32  * IMPORTANT NOTE:  It is not currently possible to use this code
  33  * because we are not sure about the amount of randomness it provides.
  34  * Some SP900 tests have been run, but there is internal skepticism.
  35  * So for now this code is not used.
  36  */
  37 # error "RDTSC enabled?  Should not be possible!"
  38
  39 /*
  40  * Acquire entropy from high-speed clock
  41  *
  42  * Since we get some randomness from the low-order bits of the
  43  * high-speed clock, it can help.
  44  *
  45  * Returns the total entropy count, if it exceeds the requested
  46  * entropy count. Otherwise, returns an entropy count of 0.
  47  */
  48 size_t rand_acquire_entropy_from_tsc(RAND_POOL *pool)
  49 {
  50     unsigned char c;
  51     int i;
  52
  53     if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) {
  54         for (i = 0; i < TSC_READ_COUNT; i++) {
  55             c = (unsigned char)(OPENSSL_rdtsc() & 0xFF);
  56             RAND_POOL_add(pool, &c, 1, 4);
  57         }
  58     }
  59     return RAND_POOL_entropy_available(pool);
  60 }
  61 #endif
  62
  63 #ifdef OPENSSL_RAND_SEED_RDCPU
  64 size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
  65 size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
  66
  67 extern unsigned int OPENSSL_ia32cap_P[];
  68
  69 /*
  70  * Acquire entropy using Intel-specific cpu instructions
  71  *
  72  * Uses the RDSEED instruction if available, otherwise uses
  73  * RDRAND if available.
  74  *
  75  * For the differences between RDSEED and RDRAND, and why RDSEED
  76  * is the preferred choice, see https://goo.gl/oK3KcN
  77  *
  78  * Returns the total entropy count, if it exceeds the requested
  79  * entropy count. Otherwise, returns an entropy count of 0.
  80  */
  81 size_t rand_acquire_entropy_from_cpu(RAND_POOL *pool)
  82 {
  83     size_t bytes_needed;
  84     unsigned char *buffer;
  85
  86     bytes_needed = RAND_POOL_bytes_needed(pool, 8 /*entropy_per_byte*/);
  87     if (bytes_needed > 0) {
  88         buffer = RAND_POOL_add_begin(pool, bytes_needed);
  89
  90         if (buffer != NULL) {
  91
  92             /* If RDSEED is available, use that. */
  93             if ((OPENSSL_ia32cap_P[2] & (1 << 18)) != 0) {
  94                 if (OPENSSL_ia32_rdseed_bytes(buffer, bytes_needed)
  95                     == bytes_needed)
  96                     return RAND_POOL_add_end(pool,
  97                                              bytes_needed,
  98                                              8 * bytes_needed);
  99             }
 100
 101             /* Second choice is RDRAND. */
 102             if ((OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) != 0) {
 103                 if (OPENSSL_ia32_rdrand_bytes(buffer, bytes_needed)
 104                     == bytes_needed)
 105                     return RAND_POOL_add_end(pool,
 106                                              bytes_needed,
 107                                              8 * bytes_needed);
 108             }
 109
 110             return RAND_POOL_add_end(pool, 0, 0);
 111         }
 112     }
 113
 114     return RAND_POOL_entropy_available(pool);
 115 }
 116 #endif
 117
 118
 119 /*
 120  * Implements the get_entropy() callback (see RAND_DRBG_set_callbacks())
 121  *
 122  * If the DRBG has a parent, then the required amount of entropy input
 123  * is fetched using the parent's RAND_DRBG_generate().
 124  *
 125  * Otherwise, the entropy is polled from the system entropy sources
 126  * using RAND_POOL_acquire_entropy().
 127  *
 128  * If a random pool has been added to the DRBG using RAND_add(), then
 129  * its entropy will be used up first.
 130  */
 131 size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
 132                         unsigned char **pout,
 133                         int entropy, size_t min_len, size_t max_len)
 134 {
 135     size_t ret = 0;
 136     size_t entropy_available = 0;
 137     RAND_POOL *pool = RAND_POOL_new(entropy, min_len, max_len);
 138
 139     if (pool == NULL)
 140         return 0;
 141
 142     if (drbg->pool) {
 143         RAND_POOL_add(pool,
 144                       RAND_POOL_buffer(drbg->pool),
 145                       RAND_POOL_length(drbg->pool),
 146                       RAND_POOL_entropy(drbg->pool));
 147         RAND_POOL_free(drbg->pool);
 148         drbg->pool = NULL;
 149     }
 150
 151     if (drbg->parent) {
 152         size_t bytes_needed = RAND_POOL_bytes_needed(pool, 8);
 153         unsigned char *buffer = RAND_POOL_add_begin(pool, bytes_needed);
 154
 155         if (buffer != NULL) {
 156             size_t bytes = 0;
 157
 158             /* Get entropy from parent, include our state as additional input */
 159             if (RAND_DRBG_generate(drbg->parent,
 160                                    buffer, bytes_needed,
 161                                    0,
 162                                    (unsigned char *)drbg, sizeof(*drbg)) != 0)
 163                 bytes = bytes_needed;
 164
 165             entropy_available = RAND_POOL_add_end(pool, bytes, 8 * bytes);
 166         }
 167
 168     } else {
 169         /* Get entropy by polling system entropy sources. */
 170         entropy_available = RAND_POOL_acquire_entropy(pool);
 171     }
 172
 173     if (entropy_available > 0) {
 174         ret   = RAND_POOL_length(pool);
 175         *pout = RAND_POOL_detach(pool);
 176     }
 177
 178     RAND_POOL_free(pool);
 179     return ret;
 180 }
 181
 182
 183 /*
 184  * Implements the cleanup_entropy() callback (see RAND_DRBG_set_callbacks())
 185  *
 186  */
 187 void rand_drbg_cleanup_entropy(RAND_DRBG *drbg,
 188                                unsigned char *out, size_t outlen)
 189 {
 190     OPENSSL_secure_clear_free(out, outlen);
 191 }
 192
 193 void rand_fork()
 194 {
 195     rand_fork_count++;
 196 }
 197
 198 DEFINE_RUN_ONCE_STATIC(do_rand_init)
 199 {
 200     int ret = 1;
 201
 202 #ifndef OPENSSL_NO_ENGINE
 203     rand_engine_lock = CRYPTO_THREAD_glock_new("rand_engine");
 204     ret &= rand_engine_lock != NULL;
 205 #endif
 206     rand_meth_lock = CRYPTO_THREAD_glock_new("rand_meth");
 207     ret &= rand_meth_lock != NULL;
 208
 209     return ret;
 210 }
 211
 212 void rand_cleanup_int(void)
 213 {
 214     const RAND_METHOD *meth = default_RAND_meth;
 215
 216     if (meth != NULL && meth->cleanup != NULL)
 217         meth->cleanup();
 218     RAND_set_rand_method(NULL);
 219 #ifndef OPENSSL_NO_ENGINE
 220     CRYPTO_THREAD_lock_free(rand_engine_lock);
 221 #endif
 222     CRYPTO_THREAD_lock_free(rand_meth_lock);
 223 }
 224
 225 /*
 226  * RAND_poll() reseeds the default RNG using random input
 227  *
 228  * The random input is obtained from polling various entropy
 229  * sources which depend on the operating system and are
 230  * configurable via the --with-rand-seed configure option.
 231  */
 232 int RAND_poll(void)
 233 {
 234     int ret = 0;
 235
 236     RAND_POOL *pool = NULL;
 237
 238     const RAND_METHOD *meth = RAND_get_rand_method();
 239
 240     if (meth == RAND_OpenSSL()) {
 241         /* fill random pool and seed the default DRBG */
 242         RAND_DRBG *drbg = RAND_DRBG_get0_global();
 243
 244         if (drbg == NULL)
 245             return 0;
 246
 247         CRYPTO_THREAD_write_lock(drbg->lock);
 248         ret = rand_drbg_restart(drbg, NULL, 0, 0);
 249         CRYPTO_THREAD_unlock(drbg->lock);
 250
 251         return ret;
 252
 253     } else {
 254         /* fill random pool and seed the current legacy RNG */
 255         pool = RAND_POOL_new(RAND_DRBG_STRENGTH,
 256                              RAND_DRBG_STRENGTH / 8,
 257                              DRBG_MINMAX_FACTOR * (RAND_DRBG_STRENGTH / 8));
 258         if (pool == NULL)
 259             return 0;
 260
 261         if (RAND_POOL_acquire_entropy(pool) == 0)
 262             goto err;
 263
 264         if (meth->add == NULL
 265             || meth->add(RAND_POOL_buffer(pool),
 266                          RAND_POOL_length(pool),
 267                          (RAND_POOL_entropy(pool) / 8.0)) == 0)
 268             goto err;
 269
 270         ret = 1;
 271     }
 272
 273 err:
 274     RAND_POOL_free(pool);
 275     return ret;
 276 }
 277
 278 /*
 279  * The 'random pool' acts as a dumb container for collecting random
 280  * input from various entropy sources. The pool has no knowledge about
 281  * whether its randomness is fed into a legacy RAND_METHOD via RAND_add()
 282  * or into a new style RAND_DRBG. It is the callers duty to 1) initialize the
 283  * random pool, 2) pass it to the polling callbacks, 3) seed the RNG, and
 284  * 4) cleanup the random pool again.
 285  *
 286  * The random pool contains no locking mechanism because its scope and
 287  * lifetime is intended to be restricted to a single stack frame.
 288  */
 289 struct rand_pool_st {
 290     unsigned char *buffer;  /* points to the beginning of the random pool */
 291     size_t len; /* current number of random bytes contained in the pool */
 292
 293     size_t min_len; /* minimum number of random bytes requested */
 294     size_t max_len; /* maximum number of random bytes (allocated buffer size) */
 295     size_t entropy; /* current entropy count in bits */
 296     size_t requested_entropy; /* requested entropy count in bits */
 297 };
 298
 299 /*
 300  * Allocate memory and initialize a new random pool
 301  */
 302
 303 RAND_POOL *RAND_POOL_new(int entropy, size_t min_len, size_t max_len)
 304 {
 305     RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
 306
 307     if (pool == NULL) {
 308         RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
 309         goto err;
 310     }
 311
 312     pool->min_len = min_len;
 313     pool->max_len = max_len;
 314
 315     pool->buffer = OPENSSL_secure_zalloc(pool->max_len);
 316     if (pool->buffer == NULL) {
 317         RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
 318         goto err;
 319     }
 320
 321     pool->requested_entropy = entropy;
 322
 323     return pool;
 324
 325 err:
 326     OPENSSL_free(pool);
 327     return NULL;
 328 }
 329
 330 /*
 331  * Free |pool|, securely erasing its buffer.
 332  */
 333 void RAND_POOL_free(RAND_POOL *pool)
 334 {
 335     if (pool == NULL)
 336         return;
 337
 338     OPENSSL_secure_clear_free(pool->buffer, pool->max_len);
 339     OPENSSL_free(pool);
 340 }
 341
 342 /*
 343  * Return the |pool|'s buffer to the caller (readonly).
 344  */
 345 const unsigned char *RAND_POOL_buffer(RAND_POOL *pool)
 346 {
 347     return pool->buffer;
 348 }
 349
 350 /*
 351  * Return the |pool|'s entropy to the caller.
 352  */
 353 size_t RAND_POOL_entropy(RAND_POOL *pool)
 354 {
 355     return pool->entropy;
 356 }
 357
 358 /*
 359  * Return the |pool|'s buffer length to the caller.
 360  */
 361 size_t RAND_POOL_length(RAND_POOL *pool)
 362 {
 363     return pool->len;
 364 }
 365
 366 /*
 367  * Detach the |pool| buffer and return it to the caller.
 368  * It's the responsibility of the caller to free the buffer
 369  * using OPENSSL_secure_clear_free().
 370  */
 371 unsigned char *RAND_POOL_detach(RAND_POOL *pool)
 372 {
 373     unsigned char *ret = pool->buffer;
 374     pool->buffer = NULL;
 375     return ret;
 376 }
 377
 378
 379 /*
 380  * If every byte of the input contains |entropy_per_bytes| bits of entropy,
 381  * how many bytes does one need to obtain at least |bits| bits of entropy?
 382  */
 383 #define ENTROPY_TO_BYTES(bits, entropy_per_bytes) \
 384     (((bits) + ((entropy_per_bytes) - 1))/(entropy_per_bytes))
 385
 386
 387 /*
 388  * Checks whether the |pool|'s entropy is available to the caller.
 389  * This is the case when entropy count and buffer length are high enough.
 390  * Returns
 391  *
 392  *  |entropy|  if the entropy count and buffer size is large enough
 393  *      0      otherwise
 394  */
 395 size_t RAND_POOL_entropy_available(RAND_POOL *pool)
 396 {
 397     if (pool->entropy < pool->requested_entropy)
 398         return 0;
 399
 400     if (pool->len < pool->min_len)
 401         return 0;
 402
 403     return pool->entropy;
 404 }
 405
 406 /*
 407  * Returns the (remaining) amount of entropy needed to fill
 408  * the random pool.
 409  */
 410
 411 size_t RAND_POOL_entropy_needed(RAND_POOL *pool)
 412 {
 413     if (pool->entropy < pool->requested_entropy)
 414         return pool->requested_entropy - pool->entropy;
 415
 416     return 0;
 417 }
 418
 419 /*
 420  * Returns the number of bytes needed to fill the pool, assuming
 421  * the input has 'entropy_per_byte' entropy bits per byte.
 422  * In case of an error, 0 is returned.
 423  */
 424
 425 size_t RAND_POOL_bytes_needed(RAND_POOL *pool, unsigned int entropy_per_byte)
 426 {
 427     size_t bytes_needed;
 428     size_t entropy_needed = RAND_POOL_entropy_needed(pool);
 429
 430     if (entropy_per_byte < 1 || entropy_per_byte > 8) {
 431         RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_ARGUMENT_OUT_OF_RANGE);
 432         return 0;
 433     }
 434
 435     bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_per_byte);
 436
 437     if (bytes_needed > pool->max_len - pool->len) {
 438         /* not enough space left */
 439         RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_RANDOM_POOL_OVERFLOW);
 440         return 0;
 441     }
 442
 443     if (pool->len < pool->min_len &&
 444         bytes_needed < pool->min_len - pool->len)
 445         /* to meet the min_len requirement */
 446         bytes_needed = pool->min_len - pool->len;
 447
 448     return bytes_needed;
 449 }
 450
 451 /* Returns the remaining number of bytes available */
 452 size_t RAND_POOL_bytes_remaining(RAND_POOL *pool)
 453 {
 454     return pool->max_len - pool->len;
 455 }
 456
 457 /*
 458  * Add random bytes to the random pool.
 459  *
 460  * It is expected that the |buffer| contains |len| bytes of
 461  * random input which contains at least |entropy| bits of
 462  * randomness.
 463  *
 464  * Return available amount of entropy after this operation.
 465  * (see RAND_POOL_entropy_available(pool))
 466  */
 467 size_t RAND_POOL_add(RAND_POOL *pool,
 468                      const unsigned char *buffer, size_t len, size_t entropy)
 469 {
 470     if (len > pool->max_len - pool->len) {
 471         RANDerr(RAND_F_RAND_POOL_ADD, RAND_R_ENTROPY_INPUT_TOO_LONG);
 472         return 0;
 473     }
 474
 475     if (len > 0) {
 476         memcpy(pool->buffer + pool->len, buffer, len);
 477         pool->len += len;
 478         pool->entropy += entropy;
 479     }
 480
 481     return RAND_POOL_entropy_available(pool);
 482 }
 483
 484 /*
 485  * Start to add random bytes to the random pool in-place.
 486  *
 487  * Reserves the next |len| bytes for adding random bytes in-place
 488  * and returns a pointer to the buffer.
 489  * The caller is allowed to copy up to |len| bytes into the buffer.
 490  * If |len| == 0 this is considered a no-op and a NULL pointer
 491  * is returned without producing an error message.
 492  *
 493  * After updating the buffer, RAND_POOL_add_end() needs to be called
 494  * to finish the udpate operation (see next comment).
 495  */
 496 unsigned char *RAND_POOL_add_begin(RAND_POOL *pool, size_t len)
 497 {
 498     if (len == 0)
 499         return NULL;
 500
 501     if (len > pool->max_len - pool->len) {
 502         RANDerr(RAND_F_RAND_POOL_ADD_BEGIN, RAND_R_RANDOM_POOL_OVERFLOW);
 503         return NULL;
 504     }
 505
 506     return pool->buffer + pool->len;
 507 }
 508
 509 /*
 510  * Finish to add random bytes to the random pool in-place.
 511  *
 512  * Finishes an in-place update of the random pool started by
 513  * RAND_POOL_add_begin() (see previous comment).
 514  * It is expected that |len| bytes of random input have been added
 515  * to the buffer which contain at least |entropy| bits of randomness.
 516  * It is allowed to add less bytes than originally reserved.
 517  */
 518 size_t RAND_POOL_add_end(RAND_POOL *pool, size_t len, size_t entropy)
 519 {
 520     if (len > pool->max_len - pool->len) {
 521         RANDerr(RAND_F_RAND_POOL_ADD_END, RAND_R_RANDOM_POOL_OVERFLOW);
 522         return 0;
 523     }
 524
 525     if (len > 0) {
 526         pool->len += len;
 527         pool->entropy += entropy;
 528     }
 529
 530     return RAND_POOL_entropy_available(pool);
 531 }
 532
 533 int RAND_set_rand_method(const RAND_METHOD *meth)
 534 {
 535     if (!RUN_ONCE(&rand_init, do_rand_init))
 536         return 0;
 537
 538     CRYPTO_THREAD_write_lock(rand_meth_lock);
 539 #ifndef OPENSSL_NO_ENGINE
 540     ENGINE_finish(funct_ref);
 541     funct_ref = NULL;
 542 #endif
 543     default_RAND_meth = meth;
 544     CRYPTO_THREAD_unlock(rand_meth_lock);
 545     return 1;
 546 }
 547
 548 const RAND_METHOD *RAND_get_rand_method(void)
 549 {
 550     const RAND_METHOD *tmp_meth = NULL;
 551
 552     if (!RUN_ONCE(&rand_init, do_rand_init))
 553         return NULL;
 554
 555     CRYPTO_THREAD_write_lock(rand_meth_lock);
 556     if (default_RAND_meth == NULL) {
 557 #ifndef OPENSSL_NO_ENGINE
 558         ENGINE *e;
 559
 560         /* If we have an engine that can do RAND, use it. */
 561         if ((e = ENGINE_get_default_RAND()) != NULL
 562                 && (tmp_meth = ENGINE_get_RAND(e)) != NULL) {
 563             funct_ref = e;
 564             default_RAND_meth = tmp_meth;
 565         } else {
 566             ENGINE_finish(e);
 567             default_RAND_meth = &rand_meth;
 568         }
 569 #else
 570         default_RAND_meth = &rand_meth;
 571 #endif
 572     }
 573     tmp_meth = default_RAND_meth;
 574     CRYPTO_THREAD_unlock(rand_meth_lock);
 575     return tmp_meth;
 576 }
 577
 578 #ifndef OPENSSL_NO_ENGINE
 579 int RAND_set_rand_engine(ENGINE *engine)
 580 {
 581     const RAND_METHOD *tmp_meth = NULL;
 582
 583     if (!RUN_ONCE(&rand_init, do_rand_init))
 584         return 0;
 585
 586     if (engine != NULL) {
 587         if (!ENGINE_init(engine))
 588             return 0;
 589         tmp_meth = ENGINE_get_RAND(engine);
 590         if (tmp_meth == NULL) {
 591             ENGINE_finish(engine);
 592             return 0;
 593         }
 594     }
 595     CRYPTO_THREAD_write_lock(rand_engine_lock);
 596     /* This function releases any prior ENGINE so call it first */
 597     RAND_set_rand_method(tmp_meth);
 598     funct_ref = engine;
 599     CRYPTO_THREAD_unlock(rand_engine_lock);
 600     return 1;
 601 }
 602 #endif
 603
 604 void RAND_seed(const void *buf, int num)
 605 {
 606     const RAND_METHOD *meth = RAND_get_rand_method();
 607
 608     if (meth->seed != NULL)
 609         meth->seed(buf, num);
 610 }
 611
 612 void RAND_add(const void *buf, int num, double randomness)
 613 {
 614     const RAND_METHOD *meth = RAND_get_rand_method();
 615
 616     if (meth->add != NULL)
 617         meth->add(buf, num, randomness);
 618 }
 619
 620 /*
 621  * This function is not part of RAND_METHOD, so if we're not using
 622  * the default method, then just call RAND_bytes().  Otherwise make
 623  * sure we're instantiated and use the private DRBG.
 624  */
 625 int RAND_priv_bytes(unsigned char *buf, int num)
 626 {
 627     const RAND_METHOD *meth = RAND_get_rand_method();
 628     RAND_DRBG *drbg;
 629
 630     if (meth != RAND_OpenSSL())
 631         return RAND_bytes(buf, num);
 632
 633     drbg = RAND_DRBG_get0_priv_global();
 634     if (drbg == NULL)
 635         return 0;
 636
 637     return RAND_DRBG_generate(drbg, buf, num, 0, NULL, 0);
 638 }
 639
 640 int RAND_bytes(unsigned char *buf, int num)
 641 {
 642     const RAND_METHOD *meth = RAND_get_rand_method();
 643
 644     if (meth->bytes != NULL)
 645         return meth->bytes(buf, num);
 646     RANDerr(RAND_F_RAND_BYTES, RAND_R_FUNC_NOT_IMPLEMENTED);
 647     return -1;
 648 }
 649
 650 #if OPENSSL_API_COMPAT < 0x10100000L
 651 int RAND_pseudo_bytes(unsigned char *buf, int num)
 652 {
 653     const RAND_METHOD *meth = RAND_get_rand_method();
 654
 655     if (meth->pseudorand != NULL)
 656         return meth->pseudorand(buf, num);
 657     return -1;
 658 }
 659 #endif
 660
 661 int RAND_status(void)
 662 {
 663     const RAND_METHOD *meth = RAND_get_rand_method();
 664
 665     if (meth->status != NULL)
 666         return meth->status();
 667     return 0;
 668 }