| /* |
| * 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 |