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// SPDX-License-Identifier: BSD-2-Clause
/*
* Copyright (c) 2014, STMicroelectronics International N.V.
*/
#include "mpa.h"
#include <tee_api_types.h>
/*
* This code is compiled for both kernel and user mode. How to obtain
* random differs since the RNG resides in kernel mode.
*/
#ifdef __KERNEL__
#include <crypto/crypto.h>
static TEE_Result get_rng_array(void *buf, size_t blen)
{
return crypto_rng_read(buf, blen);
}
#else
#include "utee_syscalls.h"
static TEE_Result get_rng_array(void *buf, size_t blen)
{
return utee_cryp_random_number_generate(buf, blen);
}
#endif
static uint8_t get_random_byte(void)
{
uint8_t buf;
while (get_rng_array(&buf, 1) != TEE_SUCCESS)
;
return buf;
}
/*------------------------------------------------------------
*
* mpa_get_random
*
*/
void mpa_get_random(mpanum dest, mpanum limit)
{
int done = 0;
mpa_wipe(dest);
if (__mpanum_alloced(dest) < __mpanum_size(limit))
dest->size = __mpanum_alloced(dest);
else
dest->size = __mpanum_size(limit);
while (!done) {
for (int idx = 0; idx < dest->size; idx++) {
mpa_word_t w = 0;
for (int j = 0; j < BYTES_PER_WORD; j++)
w = (w << 8) ^ get_random_byte();
dest->d[idx] = w;
}
if (dest->size < __mpanum_size(limit)) {
done = 1;
} else {
mpa_word_t hbi =
(mpa_word_t) mpa_highest_bit_index(limit);
/* 1 <= hbi <= WORD_SIZE */
hbi = (hbi % WORD_SIZE) + 1;
if (hbi < WORD_SIZE) {
hbi = (1 << hbi) - 1;
dest->d[dest->size - 1] &= hbi;
}
done = (mpa_cmp(dest, limit) < 0) ? 1 : 0;
}
}
}
int mpa_get_random_digits(mpanum dest, mpa_usize_t size)
{
mpa_wipe(dest);
if (size > __mpanum_alloced(dest))
return 0;
dest->size = size;
if (get_rng_array(&dest->d, WORDS_TO_BYTES(__mpanum_size(dest))))
return 0;
return __mpanum_size(dest);
}
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