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/*
* 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
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