1 /* 2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (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 "internal/cryptlib.h" 11 #include <openssl/opensslconf.h> 12 #include "crypto/rand_pool.h" 13 #include "prov/seeding.h" 14 15 #ifdef OPENSSL_RAND_SEED_RDTSC 16 /* 17 * IMPORTANT NOTE: It is not currently possible to use this code 18 * because we are not sure about the amount of randomness it provides. 19 * Some SP800-90B tests have been run, but there is internal skepticism. 20 * So for now this code is not used. 21 */ 22 # error "RDTSC enabled? Should not be possible!" 23 24 /* 25 * Acquire entropy from high-speed clock 26 * 27 * Since we get some randomness from the low-order bits of the 28 * high-speed clock, it can help. 29 * 30 * Returns the total entropy count, if it exceeds the requested 31 * entropy count. Otherwise, returns an entropy count of 0. 32 */ ossl_prov_acquire_entropy_from_tsc(RAND_POOL * pool)33size_t ossl_prov_acquire_entropy_from_tsc(RAND_POOL *pool) 34 { 35 unsigned char c; 36 int i; 37 38 if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) { 39 for (i = 0; i < TSC_READ_COUNT; i++) { 40 c = (unsigned char)(OPENSSL_rdtsc() & 0xFF); 41 ossl_rand_pool_add(pool, &c, 1, 4); 42 } 43 } 44 return ossl_rand_pool_entropy_available(pool); 45 } 46 #else 47 NON_EMPTY_TRANSLATION_UNIT 48 #endif 49