| 1 | /*
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| 2 | * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/cryptlib.h"
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| 11 | #include <openssl/opensslconf.h>
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| 12 | #include "crypto/rand_pool.h"
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| 13 | #include "prov/seeding.h"
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| 14 |
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| 15 | #ifdef OPENSSL_RAND_SEED_RDTSC
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| 16 | /*
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| 17 | * IMPORTANT NOTE: It is not currently possible to use this code
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| 18 | * because we are not sure about the amount of randomness it provides.
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| 19 | * Some SP800-90B tests have been run, but there is internal skepticism.
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| 20 | * So for now this code is not used.
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| 21 | */
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| 22 | # error "RDTSC enabled? Should not be possible!"
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| 23 |
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| 24 | /*
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| 25 | * Acquire entropy from high-speed clock
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| 26 | *
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| 27 | * Since we get some randomness from the low-order bits of the
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| 28 | * high-speed clock, it can help.
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| 29 | *
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| 30 | * Returns the total entropy count, if it exceeds the requested
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| 31 | * entropy count. Otherwise, returns an entropy count of 0.
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| 32 | */
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| 33 | size_t ossl_prov_acquire_entropy_from_tsc(RAND_POOL *pool)
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| 34 | {
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| 35 | unsigned char c;
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| 36 | int i;
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| 37 |
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| 38 | if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) {
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| 39 | for (i = 0; i < TSC_READ_COUNT; i++) {
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| 40 | c = (unsigned char)(OPENSSL_rdtsc() & 0xFF);
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| 41 | ossl_rand_pool_add(pool, &c, 1, 4);
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| 42 | }
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| 43 | }
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| 44 | return ossl_rand_pool_entropy_available(pool);
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| 45 | }
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| 46 | #else
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| 47 | NON_EMPTY_TRANSLATION_UNIT
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| 48 | #endif
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