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
mbedtls_entropy_init(mbedtls_entropy_context * ctx)60 void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
61 {
62 ctx->source_count = 0;
63 memset( ctx->source, 0, sizeof( ctx->source ) );
64
65 #if defined(MBEDTLS_THREADING_C)
66 mbedtls_mutex_init( &ctx->mutex );
67 #endif
68
69 ctx->accumulator_started = 0;
70 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
71 mbedtls_sha512_init( &ctx->accumulator );
72 #else
73 mbedtls_sha256_init( &ctx->accumulator );
74 #endif
75 #if defined(MBEDTLS_HAVEGE_C)
76 mbedtls_havege_init( &ctx->havege_data );
77 #endif
78
79 /* Reminder: Update ENTROPY_HAVE_STRONG in the test files
80 * when adding more strong entropy sources here. */
81
82 #if defined(MBEDTLS_TEST_NULL_ENTROPY)
83 mbedtls_entropy_add_source( ctx, mbedtls_null_entropy_poll, NULL,
84 1, MBEDTLS_ENTROPY_SOURCE_STRONG );
85 #endif
86
87 #if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
88 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
89 mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,
90 MBEDTLS_ENTROPY_MIN_PLATFORM,
91 MBEDTLS_ENTROPY_SOURCE_STRONG );
92 #endif
93 #if defined(MBEDTLS_TIMING_C)
94 mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL,
95 MBEDTLS_ENTROPY_MIN_HARDCLOCK,
96 MBEDTLS_ENTROPY_SOURCE_WEAK );
97 #endif
98 #if defined(MBEDTLS_HAVEGE_C)
99 mbedtls_entropy_add_source( ctx, mbedtls_havege_poll, &ctx->havege_data,
100 MBEDTLS_ENTROPY_MIN_HAVEGE,
101 MBEDTLS_ENTROPY_SOURCE_STRONG );
102 #endif
103 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
104 mbedtls_entropy_add_source( ctx, mbedtls_hardware_poll, NULL,
105 MBEDTLS_ENTROPY_MIN_HARDWARE,
106 MBEDTLS_ENTROPY_SOURCE_STRONG );
107 #endif
108 #if defined(MBEDTLS_ENTROPY_NV_SEED)
109 mbedtls_entropy_add_source( ctx, mbedtls_nv_seed_poll, NULL,
110 MBEDTLS_ENTROPY_BLOCK_SIZE,
111 MBEDTLS_ENTROPY_SOURCE_STRONG );
112 ctx->initial_entropy_run = 0;
113 #endif
114 #endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
115 }
116
mbedtls_entropy_free(mbedtls_entropy_context * ctx)117 void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
118 {
119 #if defined(MBEDTLS_HAVEGE_C)
120 mbedtls_havege_free( &ctx->havege_data );
121 #endif
122 #if defined(MBEDTLS_THREADING_C)
123 mbedtls_mutex_free( &ctx->mutex );
124 #endif
125 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
126 mbedtls_sha512_free( &ctx->accumulator );
127 #else
128 mbedtls_sha256_free( &ctx->accumulator );
129 #endif
130 #if defined(MBEDTLS_ENTROPY_NV_SEED)
131 ctx->initial_entropy_run = 0;
132 #endif
133 ctx->source_count = 0;
134 mbedtls_platform_zeroize( ctx->source, sizeof( ctx->source ) );
135 ctx->accumulator_started = 0;
136 }
137
mbedtls_entropy_add_source(mbedtls_entropy_context * ctx,mbedtls_entropy_f_source_ptr f_source,void * p_source,size_t threshold,int strong)138 int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
139 mbedtls_entropy_f_source_ptr f_source, void *p_source,
140 size_t threshold, int strong )
141 {
142 int idx, ret = 0;
143
144 #if defined(MBEDTLS_THREADING_C)
145 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
146 return( ret );
147 #endif
148
149 idx = ctx->source_count;
150 if( idx >= MBEDTLS_ENTROPY_MAX_SOURCES )
151 {
152 ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;
153 goto exit;
154 }
155
156 ctx->source[idx].f_source = f_source;
157 ctx->source[idx].p_source = p_source;
158 ctx->source[idx].threshold = threshold;
159 ctx->source[idx].strong = strong;
160
161 ctx->source_count++;
162
163 exit:
164 #if defined(MBEDTLS_THREADING_C)
165 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
166 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
167 #endif
168
169 return( ret );
170 }
171
172 /*
173 * Entropy accumulator update
174 */
entropy_update(mbedtls_entropy_context * ctx,unsigned char source_id,const unsigned char * data,size_t len)175 static int entropy_update( mbedtls_entropy_context *ctx, unsigned char source_id,
176 const unsigned char *data, size_t len )
177 {
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 {
186 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
187 if( ( ret = mbedtls_sha512_ret( data, len, tmp, 0 ) ) != 0 )
188 goto cleanup;
189 #else
190 if( ( ret = mbedtls_sha256_ret( data, len, tmp, 0 ) ) != 0 )
191 goto cleanup;
192 #endif
193 p = tmp;
194 use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
195 }
196
197 header[0] = source_id;
198 header[1] = use_len & 0xFF;
199
200 /*
201 * Start the accumulator if this has not already happened. Note that
202 * it is sufficient to start the accumulator here only because all calls to
203 * gather entropy eventually execute this code.
204 */
205 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
206 if( ctx->accumulator_started == 0 &&
207 ( ret = mbedtls_sha512_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
208 goto cleanup;
209 else
210 ctx->accumulator_started = 1;
211 if( ( ret = mbedtls_sha512_update_ret( &ctx->accumulator, header, 2 ) ) != 0 )
212 goto cleanup;
213 ret = mbedtls_sha512_update_ret( &ctx->accumulator, p, use_len );
214 #else
215 if( ctx->accumulator_started == 0 &&
216 ( ret = mbedtls_sha256_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
217 goto cleanup;
218 else
219 ctx->accumulator_started = 1;
220 if( ( ret = mbedtls_sha256_update_ret( &ctx->accumulator, header, 2 ) ) != 0 )
221 goto cleanup;
222 ret = mbedtls_sha256_update_ret( &ctx->accumulator, p, use_len );
223 #endif
224
225 cleanup:
226 mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
227
228 return( ret );
229 }
230
mbedtls_entropy_update_manual(mbedtls_entropy_context * ctx,const unsigned char * data,size_t len)231 int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
232 const unsigned char *data, size_t len )
233 {
234 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
235
236 #if defined(MBEDTLS_THREADING_C)
237 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
238 return( ret );
239 #endif
240
241 ret = entropy_update( ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len );
242
243 #if defined(MBEDTLS_THREADING_C)
244 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
245 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
246 #endif
247
248 return( ret );
249 }
250
251 /*
252 * Run through the different sources to add entropy to our accumulator
253 */
entropy_gather_internal(mbedtls_entropy_context * ctx)254 static int entropy_gather_internal( mbedtls_entropy_context *ctx )
255 {
256 int ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
257 int i;
258 int have_one_strong = 0;
259 unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
260 size_t olen;
261
262 if( ctx->source_count == 0 )
263 return( MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED );
264
265 /*
266 * Run through our entropy sources
267 */
268 for( i = 0; i < ctx->source_count; i++ )
269 {
270 if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
271 have_one_strong = 1;
272
273 olen = 0;
274 if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
275 buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen ) ) != 0 )
276 {
277 goto cleanup;
278 }
279
280 /*
281 * Add if we actually gathered something
282 */
283 if( olen > 0 )
284 {
285 if( ( ret = entropy_update( ctx, (unsigned char) i,
286 buf, olen ) ) != 0 )
287 return( ret );
288 ctx->source[i].size += olen;
289 }
290 }
291
292 if( have_one_strong == 0 )
293 ret = MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE;
294
295 cleanup:
296 mbedtls_platform_zeroize( buf, sizeof( buf ) );
297
298 return( ret );
299 }
300
301 /*
302 * Thread-safe wrapper for entropy_gather_internal()
303 */
mbedtls_entropy_gather(mbedtls_entropy_context * ctx)304 int mbedtls_entropy_gather( mbedtls_entropy_context *ctx )
305 {
306 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
307
308 #if defined(MBEDTLS_THREADING_C)
309 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
310 return( ret );
311 #endif
312
313 ret = entropy_gather_internal( ctx );
314
315 #if defined(MBEDTLS_THREADING_C)
316 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
317 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
318 #endif
319
320 return( ret );
321 }
322
mbedtls_entropy_func(void * data,unsigned char * output,size_t len)323 int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
324 {
325 int ret, count = 0, i, thresholds_reached;
326 size_t strong_size;
327 mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
328 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
329
330 if( len > MBEDTLS_ENTROPY_BLOCK_SIZE )
331 return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
332
333 #if defined(MBEDTLS_ENTROPY_NV_SEED)
334 /* Update the NV entropy seed before generating any entropy for outside
335 * use.
336 */
337 if( ctx->initial_entropy_run == 0 )
338 {
339 ctx->initial_entropy_run = 1;
340 if( ( ret = mbedtls_entropy_update_nv_seed( ctx ) ) != 0 )
341 return( ret );
342 }
343 #endif
344
345 #if defined(MBEDTLS_THREADING_C)
346 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
347 return( ret );
348 #endif
349
350 /*
351 * Always gather extra entropy before a call
352 */
353 do
354 {
355 if( count++ > ENTROPY_MAX_LOOP )
356 {
357 ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
358 goto exit;
359 }
360
361 if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
362 goto exit;
363
364 thresholds_reached = 1;
365 strong_size = 0;
366 for( i = 0; i < ctx->source_count; i++ )
367 {
368 if( ctx->source[i].size < ctx->source[i].threshold )
369 thresholds_reached = 0;
370 if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
371 strong_size += ctx->source[i].size;
372 }
373 }
374 while( ! thresholds_reached || strong_size < MBEDTLS_ENTROPY_BLOCK_SIZE );
375
376 memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
377
378 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
379 /*
380 * Note that at this stage it is assumed that the accumulator was started
381 * in a previous call to entropy_update(). If this is not guaranteed, the
382 * code below will fail.
383 */
384 if( ( ret = mbedtls_sha512_finish_ret( &ctx->accumulator, buf ) ) != 0 )
385 goto exit;
386
387 /*
388 * Reset accumulator and counters and recycle existing entropy
389 */
390 mbedtls_sha512_free( &ctx->accumulator );
391 mbedtls_sha512_init( &ctx->accumulator );
392 if( ( ret = mbedtls_sha512_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
393 goto exit;
394 if( ( ret = mbedtls_sha512_update_ret( &ctx->accumulator, buf,
395 MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
396 goto exit;
397
398 /*
399 * Perform second SHA-512 on entropy
400 */
401 if( ( ret = mbedtls_sha512_ret( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
402 buf, 0 ) ) != 0 )
403 goto exit;
404 #else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
405 if( ( ret = mbedtls_sha256_finish_ret( &ctx->accumulator, buf ) ) != 0 )
406 goto exit;
407
408 /*
409 * Reset accumulator and counters and recycle existing entropy
410 */
411 mbedtls_sha256_free( &ctx->accumulator );
412 mbedtls_sha256_init( &ctx->accumulator );
413 if( ( ret = mbedtls_sha256_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
414 goto exit;
415 if( ( ret = mbedtls_sha256_update_ret( &ctx->accumulator, buf,
416 MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
417 goto exit;
418
419 /*
420 * Perform second SHA-256 on entropy
421 */
422 if( ( ret = mbedtls_sha256_ret( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
423 buf, 0 ) ) != 0 )
424 goto exit;
425 #endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
426
427 for( i = 0; i < ctx->source_count; i++ )
428 ctx->source[i].size = 0;
429
430 memcpy( output, buf, len );
431
432 ret = 0;
433
434 exit:
435 mbedtls_platform_zeroize( buf, sizeof( buf ) );
436
437 #if defined(MBEDTLS_THREADING_C)
438 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
439 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
440 #endif
441
442 return( ret );
443 }
444
445 #if defined(MBEDTLS_ENTROPY_NV_SEED)
mbedtls_entropy_update_nv_seed(mbedtls_entropy_context * ctx)446 int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx )
447 {
448 int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
449 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
450
451 /* Read new seed and write it to NV */
452 if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
453 return( ret );
454
455 if( mbedtls_nv_seed_write( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
456 return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
457
458 /* Manually update the remaining stream with a separator value to diverge */
459 memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
460 ret = mbedtls_entropy_update_manual( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
461
462 return( ret );
463 }
464 #endif /* MBEDTLS_ENTROPY_NV_SEED */
465
466 #if defined(MBEDTLS_FS_IO)
mbedtls_entropy_write_seed_file(mbedtls_entropy_context * ctx,const char * path)467 int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path )
468 {
469 int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
470 FILE *f;
471 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
472
473 if( ( f = fopen( path, "wb" ) ) == NULL )
474 return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
475
476 if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
477 goto exit;
478
479 if( fwrite( buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f ) != MBEDTLS_ENTROPY_BLOCK_SIZE )
480 {
481 ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
482 goto exit;
483 }
484
485 ret = 0;
486
487 exit:
488 mbedtls_platform_zeroize( buf, sizeof( buf ) );
489
490 fclose( f );
491 return( ret );
492 }
493
mbedtls_entropy_update_seed_file(mbedtls_entropy_context * ctx,const char * path)494 int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path )
495 {
496 int ret = 0;
497 FILE *f;
498 size_t n;
499 unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
500
501 if( ( f = fopen( path, "rb" ) ) == NULL )
502 return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
503
504 fseek( f, 0, SEEK_END );
505 n = (size_t) ftell( f );
506 fseek( f, 0, SEEK_SET );
507
508 if( n > MBEDTLS_ENTROPY_MAX_SEED_SIZE )
509 n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
510
511 if( fread( buf, 1, n, f ) != n )
512 ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
513 else
514 ret = mbedtls_entropy_update_manual( ctx, buf, n );
515
516 fclose( f );
517
518 mbedtls_platform_zeroize( buf, sizeof( buf ) );
519
520 if( ret != 0 )
521 return( ret );
522
523 return( mbedtls_entropy_write_seed_file( ctx, path ) );
524 }
525 #endif /* MBEDTLS_FS_IO */
526
527 #if defined(MBEDTLS_SELF_TEST)
528 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
529 /*
530 * Dummy source function
531 */
entropy_dummy_source(void * data,unsigned char * output,size_t len,size_t * olen)532 static int entropy_dummy_source( void *data, unsigned char *output,
533 size_t len, size_t *olen )
534 {
535 ((void) data);
536
537 memset( output, 0x2a, len );
538 *olen = len;
539
540 return( 0 );
541 }
542 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
543
544 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
545
mbedtls_entropy_source_self_test_gather(unsigned char * buf,size_t buf_len)546 static int mbedtls_entropy_source_self_test_gather( unsigned char *buf, size_t buf_len )
547 {
548 int ret = 0;
549 size_t entropy_len = 0;
550 size_t olen = 0;
551 size_t attempts = buf_len;
552
553 while( attempts > 0 && entropy_len < buf_len )
554 {
555 if( ( ret = mbedtls_hardware_poll( NULL, buf + entropy_len,
556 buf_len - entropy_len, &olen ) ) != 0 )
557 return( ret );
558
559 entropy_len += olen;
560 attempts--;
561 }
562
563 if( entropy_len < buf_len )
564 {
565 ret = 1;
566 }
567
568 return( ret );
569 }
570
571
mbedtls_entropy_source_self_test_check_bits(const unsigned char * buf,size_t buf_len)572 static int mbedtls_entropy_source_self_test_check_bits( const unsigned char *buf,
573 size_t buf_len )
574 {
575 unsigned char set= 0xFF;
576 unsigned char unset = 0x00;
577 size_t i;
578
579 for( i = 0; i < buf_len; i++ )
580 {
581 set &= buf[i];
582 unset |= buf[i];
583 }
584
585 return( set == 0xFF || unset == 0x00 );
586 }
587
588 /*
589 * A test to ensure hat the entropy sources are functioning correctly
590 * and there is no obvious failure. The test performs the following checks:
591 * - The entropy source is not providing only 0s (all bits unset) or 1s (all
592 * bits set).
593 * - The entropy source is not providing values in a pattern. Because the
594 * hardware could be providing data in an arbitrary length, this check polls
595 * the hardware entropy source twice and compares the result to ensure they
596 * are not equal.
597 * - The error code returned by the entropy source is not an error.
598 */
mbedtls_entropy_source_self_test(int verbose)599 int mbedtls_entropy_source_self_test( int verbose )
600 {
601 int ret = 0;
602 unsigned char buf0[2 * sizeof( unsigned long long int )];
603 unsigned char buf1[2 * sizeof( unsigned long long int )];
604
605 if( verbose != 0 )
606 mbedtls_printf( " ENTROPY_BIAS test: " );
607
608 memset( buf0, 0x00, sizeof( buf0 ) );
609 memset( buf1, 0x00, sizeof( buf1 ) );
610
611 if( ( ret = mbedtls_entropy_source_self_test_gather( buf0, sizeof( buf0 ) ) ) != 0 )
612 goto cleanup;
613 if( ( ret = mbedtls_entropy_source_self_test_gather( buf1, sizeof( buf1 ) ) ) != 0 )
614 goto cleanup;
615
616 /* Make sure that the returned values are not all 0 or 1 */
617 if( ( ret = mbedtls_entropy_source_self_test_check_bits( buf0, sizeof( buf0 ) ) ) != 0 )
618 goto cleanup;
619 if( ( ret = mbedtls_entropy_source_self_test_check_bits( buf1, sizeof( buf1 ) ) ) != 0 )
620 goto cleanup;
621
622 /* Make sure that the entropy source is not returning values in a
623 * pattern */
624 ret = memcmp( buf0, buf1, sizeof( buf0 ) ) == 0;
625
626 cleanup:
627 if( verbose != 0 )
628 {
629 if( ret != 0 )
630 mbedtls_printf( "failed\n" );
631 else
632 mbedtls_printf( "passed\n" );
633
634 mbedtls_printf( "\n" );
635 }
636
637 return( ret != 0 );
638 }
639
640 #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
641
642 /*
643 * The actual entropy quality is hard to test, but we can at least
644 * test that the functions don't cause errors and write the correct
645 * amount of data to buffers.
646 */
mbedtls_entropy_self_test(int verbose)647 int mbedtls_entropy_self_test( int verbose )
648 {
649 int ret = 1;
650 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
651 mbedtls_entropy_context ctx;
652 unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
653 unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
654 size_t i, j;
655 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
656
657 if( verbose != 0 )
658 mbedtls_printf( " ENTROPY test: " );
659
660 #if !defined(MBEDTLS_TEST_NULL_ENTROPY)
661 mbedtls_entropy_init( &ctx );
662
663 /* First do a gather to make sure we have default sources */
664 if( ( ret = mbedtls_entropy_gather( &ctx ) ) != 0 )
665 goto cleanup;
666
667 ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16,
668 MBEDTLS_ENTROPY_SOURCE_WEAK );
669 if( ret != 0 )
670 goto cleanup;
671
672 if( ( ret = mbedtls_entropy_update_manual( &ctx, buf, sizeof buf ) ) != 0 )
673 goto cleanup;
674
675 /*
676 * To test that mbedtls_entropy_func writes correct number of bytes:
677 * - use the whole buffer and rely on ASan to detect overruns
678 * - collect entropy 8 times and OR the result in an accumulator:
679 * any byte should then be 0 with probably 2^(-64), so requiring
680 * each of the 32 or 64 bytes to be non-zero has a false failure rate
681 * of at most 2^(-58) which is acceptable.
682 */
683 for( i = 0; i < 8; i++ )
684 {
685 if( ( ret = mbedtls_entropy_func( &ctx, buf, sizeof( buf ) ) ) != 0 )
686 goto cleanup;
687
688 for( j = 0; j < sizeof( buf ); j++ )
689 acc[j] |= buf[j];
690 }
691
692 for( j = 0; j < sizeof( buf ); j++ )
693 {
694 if( acc[j] == 0 )
695 {
696 ret = 1;
697 goto cleanup;
698 }
699 }
700
701 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
702 if( ( ret = mbedtls_entropy_source_self_test( 0 ) ) != 0 )
703 goto cleanup;
704 #endif
705
706 cleanup:
707 mbedtls_entropy_free( &ctx );
708 #endif /* !MBEDTLS_TEST_NULL_ENTROPY */
709
710 if( verbose != 0 )
711 {
712 if( ret != 0 )
713 mbedtls_printf( "failed\n" );
714 else
715 mbedtls_printf( "passed\n" );
716
717 mbedtls_printf( "\n" );
718 }
719
720 return( ret != 0 );
721 }
722 #endif /* MBEDTLS_SELF_TEST */
723
724 #endif /* MBEDTLS_ENTROPY_C */
725
