/* * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy * in the file LICENSE in the source distribution or at * https://www.openssl.org/source/license.html */ #include "internal/cryptlib.h" #include <openssl/opensslconf.h> #include "crypto/rand_pool.h" #include "prov/seeding.h" #ifdef OPENSSL_RAND_SEED_RDTSC /* * IMPORTANT NOTE: It is not currently possible to use this code * because we are not sure about the amount of randomness it provides. * Some SP800-90B tests have been run, but there is internal skepticism. * So for now this code is not used. */ # error "RDTSC enabled? Should not be possible!" /* * Acquire entropy from high-speed clock * * Since we get some randomness from the low-order bits of the * high-speed clock, it can help. * * Returns the total entropy count, if it exceeds the requested * entropy count. Otherwise, returns an entropy count of 0. */ size_t ossl_prov_acquire_entropy_from_tsc(RAND_POOL *pool) { unsigned char c; int i; if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) { for (i = 0; i < TSC_READ_COUNT; i++) { c = (unsigned char)(OPENSSL_rdtsc() & 0xFF); ossl_rand_pool_add(pool, &c, 1, 4); } } return ossl_rand_pool_entropy_available(pool); } #else NON_EMPTY_TRANSLATION_UNIT #endif |