common/mbedtls/entropy.c

   1 /*
   2  *  Entropy accumulator implementation
   3  *
   4  *  Copyright The Mbed TLS Contributors
   5  *  SPDX-License-Identifier: Apache-2.0
   6  *
   7  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
   8  *  not use this file except in compliance with the License.
   9  *  You may obtain a copy of the License at
  10  *
  11  *  http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  *  Unless required by applicable law or agreed to in writing, software
  14  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  15  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  *  See the License for the specific language governing permissions and
  17  *  limitations under the License.
  18  */
  19
  20 #include "common.h"
  21
  22 #if defined(MBEDTLS_ENTROPY_C)
  23
  24 #if defined(MBEDTLS_TEST_NULL_ENTROPY)
  25 #warning "**** WARNING!  MBEDTLS_TEST_NULL_ENTROPY defined! "
  26 #warning "**** THIS BUILD HAS NO DEFINED ENTROPY SOURCES "
  27 #warning "**** THIS BUILD IS *NOT* SUITABLE FOR PRODUCTION USE "
  28 #endif
  29
  30 #include "mbedtls/entropy.h"
  31 #include "mbedtls/entropy_poll.h"
  32 #include "mbedtls/platform_util.h"
  33 #include "mbedtls/error.h"
  34
  35 #include <string.h>
  36
  37 #if defined(MBEDTLS_FS_IO)
  38 #include <stdio.h>
  39 #endif
  40
  41 #if defined(MBEDTLS_ENTROPY_NV_SEED)
  42 #include "mbedtls/platform.h"
  43 #endif
  44
  45 #if defined(MBEDTLS_SELF_TEST)
  46 #if defined(MBEDTLS_PLATFORM_C)
  47 #include "mbedtls/platform.h"
  48 #else
  49 #include <stdio.h>
  50 #define mbedtls_printf     printf
  51 #endif /* MBEDTLS_PLATFORM_C */
  52 #endif /* MBEDTLS_SELF_TEST */
  53
  54 #if defined(MBEDTLS_HAVEGE_C)
  55 #include "mbedtls/havege.h"
  56 #endif
  57
  58 #define ENTROPY_MAX_LOOP    256     /**< Maximum amount to loop before error */
  59
  60 void mbedtls_entropy_init(mbedtls_entropy_context *ctx) {
  61     ctx->source_count = 0;
  62     memset(ctx->source, 0, sizeof(ctx->source));
  63
  64 #if defined(MBEDTLS_THREADING_C)
  65     mbedtls_mutex_init(&ctx->mutex);
  66 #endif
  67
  68     ctx->accumulator_started = 0;
  69 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
  70     mbedtls_sha512_init(&ctx->accumulator);
  71 #else
  72     mbedtls_sha256_init(&ctx->accumulator);
  73 #endif
  74 #if defined(MBEDTLS_HAVEGE_C)
  75     mbedtls_havege_init(&ctx->havege_data);
  76 #endif
  77
  78     /* Reminder: Update ENTROPY_HAVE_STRONG in the test files
  79      *           when adding more strong entropy sources here. */
  80
  81 #if defined(MBEDTLS_TEST_NULL_ENTROPY)
  82     mbedtls_entropy_add_source(ctx, mbedtls_null_entropy_poll, NULL,
  83                                1, MBEDTLS_ENTROPY_SOURCE_STRONG);
  84 #endif
  85
  86 #if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
  87 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
  88     mbedtls_entropy_add_source(ctx, mbedtls_platform_entropy_poll, NULL,
  89                                MBEDTLS_ENTROPY_MIN_PLATFORM,
  90                                MBEDTLS_ENTROPY_SOURCE_STRONG);
  91 #endif
  92 #if defined(MBEDTLS_TIMING_C)
  93     mbedtls_entropy_add_source(ctx, mbedtls_hardclock_poll, NULL,
  94                                MBEDTLS_ENTROPY_MIN_HARDCLOCK,
  95                                MBEDTLS_ENTROPY_SOURCE_WEAK);
  96 #endif
  97 #if defined(MBEDTLS_HAVEGE_C)
  98     mbedtls_entropy_add_source(ctx, mbedtls_havege_poll, &ctx->havege_data,
  99                                MBEDTLS_ENTROPY_MIN_HAVEGE,
 100                                MBEDTLS_ENTROPY_SOURCE_STRONG);
 101 #endif
 102 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
 103     mbedtls_entropy_add_source(ctx, mbedtls_hardware_poll, NULL,
 104                                MBEDTLS_ENTROPY_MIN_HARDWARE,
 105                                MBEDTLS_ENTROPY_SOURCE_STRONG);
 106 #endif
 107 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 108     mbedtls_entropy_add_source(ctx, mbedtls_nv_seed_poll, NULL,
 109                                MBEDTLS_ENTROPY_BLOCK_SIZE,
 110                                MBEDTLS_ENTROPY_SOURCE_STRONG);
 111     ctx->initial_entropy_run = 0;
 112 #endif
 113 #endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
 114 }
 115
 116 void mbedtls_entropy_free(mbedtls_entropy_context *ctx) {
 117     /* If the context was already free, don't call free() again.
 118      * This is important for mutexes which don't allow double-free. */
 119     if (ctx->accumulator_started == -1)
 120         return;
 121
 122 #if defined(MBEDTLS_HAVEGE_C)
 123     mbedtls_havege_free(&ctx->havege_data);
 124 #endif
 125 #if defined(MBEDTLS_THREADING_C)
 126     mbedtls_mutex_free(&ctx->mutex);
 127 #endif
 128 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
 129     mbedtls_sha512_free(&ctx->accumulator);
 130 #else
 131     mbedtls_sha256_free(&ctx->accumulator);
 132 #endif
 133 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 134     ctx->initial_entropy_run = 0;
 135 #endif
 136     ctx->source_count = 0;
 137     mbedtls_platform_zeroize(ctx->source, sizeof(ctx->source));
 138     ctx->accumulator_started = -1;
 139 }
 140
 141 int mbedtls_entropy_add_source(mbedtls_entropy_context *ctx,
 142                                mbedtls_entropy_f_source_ptr f_source, void *p_source,
 143                                size_t threshold, int strong) {
 144     int idx, ret = 0;
 145
 146 #if defined(MBEDTLS_THREADING_C)
 147     if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
 148         return (ret);
 149 #endif
 150
 151     idx = ctx->source_count;
 152     if (idx >= MBEDTLS_ENTROPY_MAX_SOURCES) {
 153         ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;
 154         goto exit;
 155     }
 156
 157     ctx->source[idx].f_source  = f_source;
 158     ctx->source[idx].p_source  = p_source;
 159     ctx->source[idx].threshold = threshold;
 160     ctx->source[idx].strong    = strong;
 161
 162     ctx->source_count++;
 163
 164 exit:
 165 #if defined(MBEDTLS_THREADING_C)
 166     if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
 167         return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
 168 #endif
 169
 170     return (ret);
 171 }
 172
 173 /*
 174  * Entropy accumulator update
 175  */
 176 static int entropy_update(mbedtls_entropy_context *ctx, unsigned char source_id,
 177                           const unsigned char *data, size_t len) {
 178     unsigned char header[2];
 179     unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];
 180     size_t use_len = len;
 181     const unsigned char *p = data;
 182     int ret = 0;
 183
 184     if (use_len > MBEDTLS_ENTROPY_BLOCK_SIZE) {
 185 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
 186         if ((ret = mbedtls_sha512_ret(data, len, tmp, 0)) != 0)
 187             goto cleanup;
 188 #else
 189         if ((ret = mbedtls_sha256_ret(data, len, tmp, 0)) != 0)
 190             goto cleanup;
 191 #endif
 192         p = tmp;
 193         use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
 194     }
 195
 196     header[0] = source_id;
 197     header[1] = use_len & 0xFF;
 198
 199     /*
 200      * Start the accumulator if this has not already happened. Note that
 201      * it is sufficient to start the accumulator here only because all calls to
 202      * gather entropy eventually execute this code.
 203      */
 204 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
 205     if (ctx->accumulator_started == 0 &&
 206             (ret = mbedtls_sha512_starts_ret(&ctx->accumulator, 0)) != 0)
 207         goto cleanup;
 208     else
 209         ctx->accumulator_started = 1;
 210     if ((ret = mbedtls_sha512_update_ret(&ctx->accumulator, header, 2)) != 0)
 211         goto cleanup;
 212     ret = mbedtls_sha512_update_ret(&ctx->accumulator, p, use_len);
 213 #else
 214     if (ctx->accumulator_started == 0 &&
 215             (ret = mbedtls_sha256_starts_ret(&ctx->accumulator, 0)) != 0)
 216         goto cleanup;
 217     else
 218         ctx->accumulator_started = 1;
 219     if ((ret = mbedtls_sha256_update_ret(&ctx->accumulator, header, 2)) != 0)
 220         goto cleanup;
 221     ret = mbedtls_sha256_update_ret(&ctx->accumulator, p, use_len);
 222 #endif
 223
 224 cleanup:
 225     mbedtls_platform_zeroize(tmp, sizeof(tmp));
 226
 227     return (ret);
 228 }
 229
 230 int mbedtls_entropy_update_manual(mbedtls_entropy_context *ctx,
 231                                   const unsigned char *data, size_t len) {
 232     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 233
 234 #if defined(MBEDTLS_THREADING_C)
 235     if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
 236         return (ret);
 237 #endif
 238
 239     ret = entropy_update(ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len);
 240
 241 #if defined(MBEDTLS_THREADING_C)
 242     if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
 243         return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
 244 #endif
 245
 246     return (ret);
 247 }
 248
 249 /*
 250  * Run through the different sources to add entropy to our accumulator
 251  */
 252 static int entropy_gather_internal(mbedtls_entropy_context *ctx) {
 253     int ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
 254     int i;
 255     int have_one_strong = 0;
 256     unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
 257     size_t olen;
 258
 259     if (ctx->source_count == 0)
 260         return (MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED);
 261
 262     /*
 263      * Run through our entropy sources
 264      */
 265     for (i = 0; i < ctx->source_count; i++) {
 266         if (ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG)
 267             have_one_strong = 1;
 268
 269         olen = 0;
 270         if ((ret = ctx->source[i].f_source(ctx->source[i].p_source,
 271                                            buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen)) != 0) {
 272             goto cleanup;
 273         }
 274
 275         /*
 276          * Add if we actually gathered something
 277          */
 278         if (olen > 0) {
 279             if ((ret = entropy_update(ctx, (unsigned char) i,
 280                                       buf, olen)) != 0)
 281                 return (ret);
 282             ctx->source[i].size += olen;
 283         }
 284     }
 285
 286     if (have_one_strong == 0)
 287         ret = MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE;
 288
 289 cleanup:
 290     mbedtls_platform_zeroize(buf, sizeof(buf));
 291
 292     return (ret);
 293 }
 294
 295 /*
 296  * Thread-safe wrapper for entropy_gather_internal()
 297  */
 298 int mbedtls_entropy_gather(mbedtls_entropy_context *ctx) {
 299     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 300
 301 #if defined(MBEDTLS_THREADING_C)
 302     if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
 303         return (ret);
 304 #endif
 305
 306     ret = entropy_gather_internal(ctx);
 307
 308 #if defined(MBEDTLS_THREADING_C)
 309     if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
 310         return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
 311 #endif
 312
 313     return (ret);
 314 }
 315
 316 int mbedtls_entropy_func(void *data, unsigned char *output, size_t len) {
 317     int ret, count = 0, i, thresholds_reached;
 318     size_t strong_size;
 319     mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
 320     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
 321
 322     if (len > MBEDTLS_ENTROPY_BLOCK_SIZE)
 323         return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
 324
 325 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 326     /* Update the NV entropy seed before generating any entropy for outside
 327      * use.
 328      */
 329     if (ctx->initial_entropy_run == 0) {
 330         ctx->initial_entropy_run = 1;
 331         if ((ret = mbedtls_entropy_update_nv_seed(ctx)) != 0)
 332             return (ret);
 333     }
 334 #endif
 335
 336 #if defined(MBEDTLS_THREADING_C)
 337     if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
 338         return (ret);
 339 #endif
 340
 341     /*
 342      * Always gather extra entropy before a call
 343      */
 344     do {
 345         if (count++ > ENTROPY_MAX_LOOP) {
 346             ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
 347             goto exit;
 348         }
 349
 350         if ((ret = entropy_gather_internal(ctx)) != 0)
 351             goto exit;
 352
 353         thresholds_reached = 1;
 354         strong_size = 0;
 355         for (i = 0; i < ctx->source_count; i++) {
 356             if (ctx->source[i].size < ctx->source[i].threshold)
 357                 thresholds_reached = 0;
 358             if (ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG)
 359                 strong_size += ctx->source[i].size;
 360         }
 361     } while (! thresholds_reached || strong_size < MBEDTLS_ENTROPY_BLOCK_SIZE);
 362
 363     memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
 364
 365 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
 366     /*
 367      * Note that at this stage it is assumed that the accumulator was started
 368      * in a previous call to entropy_update(). If this is not guaranteed, the
 369      * code below will fail.
 370      */
 371     if ((ret = mbedtls_sha512_finish_ret(&ctx->accumulator, buf)) != 0)
 372         goto exit;
 373
 374     /*
 375      * Reset accumulator and counters and recycle existing entropy
 376      */
 377     mbedtls_sha512_free(&ctx->accumulator);
 378     mbedtls_sha512_init(&ctx->accumulator);
 379     if ((ret = mbedtls_sha512_starts_ret(&ctx->accumulator, 0)) != 0)
 380         goto exit;
 381     if ((ret = mbedtls_sha512_update_ret(&ctx->accumulator, buf,
 382                                          MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0)
 383         goto exit;
 384
 385     /*
 386      * Perform second SHA-512 on entropy
 387      */
 388     if ((ret = mbedtls_sha512_ret(buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
 389                                   buf, 0)) != 0)
 390         goto exit;
 391 #else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
 392     if ((ret = mbedtls_sha256_finish_ret(&ctx->accumulator, buf)) != 0)
 393         goto exit;
 394
 395     /*
 396      * Reset accumulator and counters and recycle existing entropy
 397      */
 398     mbedtls_sha256_free(&ctx->accumulator);
 399     mbedtls_sha256_init(&ctx->accumulator);
 400     if ((ret = mbedtls_sha256_starts_ret(&ctx->accumulator, 0)) != 0)
 401         goto exit;
 402     if ((ret = mbedtls_sha256_update_ret(&ctx->accumulator, buf,
 403                                          MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0)
 404         goto exit;
 405
 406     /*
 407      * Perform second SHA-256 on entropy
 408      */
 409     if ((ret = mbedtls_sha256_ret(buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
 410                                   buf, 0)) != 0)
 411         goto exit;
 412 #endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
 413
 414     for (i = 0; i < ctx->source_count; i++)
 415         ctx->source[i].size = 0;
 416
 417     memcpy(output, buf, len);
 418
 419     ret = 0;
 420
 421 exit:
 422     mbedtls_platform_zeroize(buf, sizeof(buf));
 423
 424 #if defined(MBEDTLS_THREADING_C)
 425     if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
 426         return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
 427 #endif
 428
 429     return (ret);
 430 }
 431
 432 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 433 int mbedtls_entropy_update_nv_seed(mbedtls_entropy_context *ctx) {
 434     int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
 435     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
 436
 437     /* Read new seed  and write it to NV */
 438     if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0)
 439         return (ret);
 440
 441     if (mbedtls_nv_seed_write(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0)
 442         return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
 443
 444     /* Manually update the remaining stream with a separator value to diverge */
 445     memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
 446     ret = mbedtls_entropy_update_manual(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);
 447
 448     return (ret);
 449 }
 450 #endif /* MBEDTLS_ENTROPY_NV_SEED */
 451
 452 #if defined(MBEDTLS_FS_IO)
 453 int mbedtls_entropy_write_seed_file(mbedtls_entropy_context *ctx, const char *path) {
 454     int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
 455     FILE *f;
 456     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
 457
 458     if ((f = fopen(path, "wb")) == NULL)
 459         return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
 460
 461     if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0)
 462         goto exit;
 463
 464     if (fwrite(buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f) != MBEDTLS_ENTROPY_BLOCK_SIZE) {
 465         ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
 466         goto exit;
 467     }
 468
 469     ret = 0;
 470
 471 exit:
 472     mbedtls_platform_zeroize(buf, sizeof(buf));
 473
 474     fclose(f);
 475     return (ret);
 476 }
 477
 478 int mbedtls_entropy_update_seed_file(mbedtls_entropy_context *ctx, const char *path) {
 479     int ret = 0;
 480     FILE *f;
 481     size_t n;
 482     unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
 483
 484     if ((f = fopen(path, "rb")) == NULL)
 485         return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
 486
 487     fseek(f, 0, SEEK_END);
 488     n = (size_t) ftell(f);
 489     fseek(f, 0, SEEK_SET);
 490
 491     if (n > MBEDTLS_ENTROPY_MAX_SEED_SIZE)
 492         n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
 493
 494     if (fread(buf, 1, n, f) != n)
 495         ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
 496     else
 497         ret = mbedtls_entropy_update_manual(ctx, buf, n);
 498
 499     fclose(f);
 500
 501     mbedtls_platform_zeroize(buf, sizeof(buf));
 502
 503     if (ret != 0)
 504         return (ret);
 505
 506     return (mbedtls_entropy_write_seed_file(ctx, path));
 507 }
 508 #endif /* MBEDTLS_FS_IO */
 509
 510 #if defined(MBEDTLS_SELF_TEST)
 511 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
 512 /*
 513  * Dummy source function
 514  */
 515 static int entropy_dummy_source(void *data, unsigned char *output,
 516                                 size_t len, size_t *olen) {
 517     ((void) data);
 518
 519     memset(output, 0x2a, len);
 520     *olen = len;
 521
 522     return (0);
 523 }
 524 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
 525
 526 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
 527
 528 static int mbedtls_entropy_source_self_test_gather(unsigned char *buf, size_t buf_len) {
 529     int ret = 0;
 530     size_t entropy_len = 0;
 531     size_t olen = 0;
 532     size_t attempts = buf_len;
 533
 534     while (attempts > 0 && entropy_len < buf_len) {
 535         if ((ret = mbedtls_hardware_poll(NULL, buf + entropy_len,
 536                                          buf_len - entropy_len, &olen)) != 0)
 537             return (ret);
 538
 539         entropy_len += olen;
 540         attempts--;
 541     }
 542
 543     if (entropy_len < buf_len) {
 544         ret = 1;
 545     }
 546
 547     return (ret);
 548 }
 549
 550
 551 static int mbedtls_entropy_source_self_test_check_bits(const unsigned char *buf,
 552                                                        size_t buf_len) {
 553     unsigned char set = 0xFF;
 554     unsigned char unset = 0x00;
 555     size_t i;
 556
 557     for (i = 0; i < buf_len; i++) {
 558         set &= buf[i];
 559         unset |= buf[i];
 560     }
 561
 562     return (set == 0xFF || unset == 0x00);
 563 }
 564
 565 /*
 566  * A test to ensure hat the entropy sources are functioning correctly
 567  * and there is no obvious failure. The test performs the following checks:
 568  *  - The entropy source is not providing only 0s (all bits unset) or 1s (all
 569  *    bits set).
 570  *  - The entropy source is not providing values in a pattern. Because the
 571  *    hardware could be providing data in an arbitrary length, this check polls
 572  *    the hardware entropy source twice and compares the result to ensure they
 573  *    are not equal.
 574  *  - The error code returned by the entropy source is not an error.
 575  */
 576 int mbedtls_entropy_source_self_test(int verbose) {
 577     int ret = 0;
 578     unsigned char buf0[2 * sizeof(unsigned long long int)];
 579     unsigned char buf1[2 * sizeof(unsigned long long int)];
 580
 581     if (verbose != 0)
 582         mbedtls_printf("  ENTROPY_BIAS test: ");
 583
 584     memset(buf0, 0x00, sizeof(buf0));
 585     memset(buf1, 0x00, sizeof(buf1));
 586
 587     if ((ret = mbedtls_entropy_source_self_test_gather(buf0, sizeof(buf0))) != 0)
 588         goto cleanup;
 589     if ((ret = mbedtls_entropy_source_self_test_gather(buf1, sizeof(buf1))) != 0)
 590         goto cleanup;
 591
 592     /* Make sure that the returned values are not all 0 or 1 */
 593     if ((ret = mbedtls_entropy_source_self_test_check_bits(buf0, sizeof(buf0))) != 0)
 594         goto cleanup;
 595     if ((ret = mbedtls_entropy_source_self_test_check_bits(buf1, sizeof(buf1))) != 0)
 596         goto cleanup;
 597
 598     /* Make sure that the entropy source is not returning values in a
 599      * pattern */
 600     ret = memcmp(buf0, buf1, sizeof(buf0)) == 0;
 601
 602 cleanup:
 603     if (verbose != 0) {
 604         if (ret != 0)
 605             mbedtls_printf("failed\n");
 606         else
 607             mbedtls_printf("passed\n");
 608
 609         mbedtls_printf("\n");
 610     }
 611
 612     return (ret != 0);
 613 }
 614
 615 #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
 616
 617 /*
 618  * The actual entropy quality is hard to test, but we can at least
 619  * test that the functions don't cause errors and write the correct
 620  * amount of data to buffers.
 621  */
 622 int mbedtls_entropy_self_test(int verbose) {
 623     int ret = 1;
 624 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
 625     mbedtls_entropy_context ctx;
 626     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
 627     unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
 628     size_t i, j;
 629 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
 630
 631     if (verbose != 0)
 632         mbedtls_printf("  ENTROPY test: ");
 633
 634 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
 635     mbedtls_entropy_init(&ctx);
 636
 637     /* First do a gather to make sure we have default sources */
 638     if ((ret = mbedtls_entropy_gather(&ctx)) != 0)
 639         goto cleanup;
 640
 641     ret = mbedtls_entropy_add_source(&ctx, entropy_dummy_source, NULL, 16,
 642                                      MBEDTLS_ENTROPY_SOURCE_WEAK);
 643     if (ret != 0)
 644         goto cleanup;
 645
 646     if ((ret = mbedtls_entropy_update_manual(&ctx, buf, sizeof buf)) != 0)
 647         goto cleanup;
 648
 649     /*
 650      * To test that mbedtls_entropy_func writes correct number of bytes:
 651      * - use the whole buffer and rely on ASan to detect overruns
 652      * - collect entropy 8 times and OR the result in an accumulator:
 653      *   any byte should then be 0 with probably 2^(-64), so requiring
 654      *   each of the 32 or 64 bytes to be non-zero has a false failure rate
 655      *   of at most 2^(-58) which is acceptable.
 656      */
 657     for (i = 0; i < 8; i++) {
 658         if ((ret = mbedtls_entropy_func(&ctx, buf, sizeof(buf))) != 0)
 659             goto cleanup;
 660
 661         for (j = 0; j < sizeof(buf); j++)
 662             acc[j] |= buf[j];
 663     }
 664
 665     for (j = 0; j < sizeof(buf); j++) {
 666         if (acc[j] == 0) {
 667             ret = 1;
 668             goto cleanup;
 669         }
 670     }
 671
 672 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
 673     if ((ret = mbedtls_entropy_source_self_test(0)) != 0)
 674         goto cleanup;
 675 #endif
 676
 677 cleanup:
 678     mbedtls_entropy_free(&ctx);
 679 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
 680
 681     if (verbose != 0) {
 682         if (ret != 0)
 683             mbedtls_printf("failed\n");
 684         else
 685             mbedtls_printf("passed\n");
 686
 687         mbedtls_printf("\n");
 688     }
 689
 690     return (ret != 0);
 691 }
 692 #endif /* MBEDTLS_SELF_TEST */
 693
 694 #endif /* MBEDTLS_ENTROPY_C */