A local copy of OpenSSL from GitHub
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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_RDCPU
# if defined(OPENSSL_SYS_TANDEM) && defined(_TNS_X_TARGET)
# include <builtin.h> /* _rdrand64 */
# include <string.h> /* memcpy */
# else
size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
# endif
static size_t get_hardware_random_value(unsigned char *buf, size_t len);
/*
* Acquire entropy using Intel-specific cpu instructions
*
* Uses the RDSEED instruction if available, otherwise uses
* RDRAND if available.
*
* For the differences between RDSEED and RDRAND, and why RDSEED
* is the preferred choice, see https://goo.gl/oK3KcN
*
* 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_cpu(RAND_POOL *pool)
{
size_t bytes_needed;
unsigned char *buffer;
bytes_needed = ossl_rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
if (bytes_needed > 0) {
buffer = ossl_rand_pool_add_begin(pool, bytes_needed);
if (buffer != NULL) {
if (get_hardware_random_value(buffer, bytes_needed) == bytes_needed) {
ossl_rand_pool_add_end(pool, bytes_needed, 8 * bytes_needed);
} else {
ossl_rand_pool_add_end(pool, 0, 0);
}
}
}
return ossl_rand_pool_entropy_available(pool);
}
#if defined(OPENSSL_SYS_TANDEM) && defined(_TNS_X_TARGET)
/* Obtain random bytes from the x86 hardware random function in 64 bit chunks */
static size_t get_hardware_random_value(unsigned char *buf, size_t len)
{
size_t bytes_remaining = len;
while (bytes_remaining > 0) {
/* Always use 64 bit fetch, then use the lower bytes as needed. */
/* The platform is big-endian. */
uint64_t random_value = 0;
if (_rdrand64(&random_value) != 0) {
unsigned char *random_buffer = (unsigned char *)&random_value;
if (bytes_remaining >= sizeof(random_value)) {
memcpy(buf, random_buffer, sizeof(random_value));
bytes_remaining -= sizeof(random_value);
buf += sizeof(random_value);
} else {
memcpy(buf,
random_buffer + (sizeof(random_value) - bytes_remaining),
bytes_remaining);
bytes_remaining = 0; /* This will terminate the loop */
}
} else
break;
}
if (bytes_remaining == 0)
return len;
return 0;
}
#else
static size_t get_hardware_random_value(unsigned char *buf, size_t len) {
/* Whichever comes first, use RDSEED, RDRAND or nothing */
if ((OPENSSL_ia32cap_P[2] & (1 << 18)) != 0) {
if (OPENSSL_ia32_rdseed_bytes(buf, len) != len)
return 0;
} else if ((OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) != 0) {
if (OPENSSL_ia32_rdrand_bytes(buf, len) != len)
return 0;
} else
return 0;
return len;
}
#endif
#else
NON_EMPTY_TRANSLATION_UNIT
#endif