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scprng.c
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scprng.c
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/**
* MIT License
*
* Copyright 2024 PE Stanislav Yahniukov <pe@yahniukov.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this
* software and associated documentation files (the “Software”), to deal in the Software
* without restriction, including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
* to whom the Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
* FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#include <stdlib.h>
#include <string.h>
#include "mbedtls/sha3.h"
#include "mbedtls/chacha20.h"
#include "scprng.h"
#define _RESEED_LIMIT_BYTES (512) // reseed every 512 bytes
static int _scprng_seed(uint8_t key[64],
uint8_t nonce[12],
uint8_t counter[4],
uint8_t encryption_key[32])
{
uint8_t seed[48] = {0};
memset(seed, 0, 48);
int err = mbedtls_sha3(MBEDTLS_SHA3_384,
key, 64,
seed, 48);
if (err)
return -1;
memcpy(encryption_key, seed, 32);
memcpy(counter, seed + 44, 4);
memcpy(nonce, seed + 32, 12);
return 0;
}
int scprng_rand_numbers(uint32_t *numbers,
uint32_t numbers_count,
uint8_t key[64])
{
int err = 0;
uint32_t counter = 0;
uint8_t rand[64] = {0};
uint8_t nonce[12] = {0};
uint8_t encryption_key[32] = {0};
uint32_t idx = 0, idx_from_reseed = 0;
if (!numbers || !numbers_count || !key)
return -1;
memset(nonce, 0, 12);
memcpy(rand, key, 64);
memset(encryption_key, 0, 32);
if (_scprng_seed(key, nonce, (uint8_t *)&counter, encryption_key))
return -1;
while (idx < numbers_count)
{
err = mbedtls_chacha20_crypt((const unsigned char *)encryption_key,
(const unsigned char *)nonce,
counter, 64,
(const unsigned char *)rand,
(unsigned char *)rand);
if (err)
return -1;
size_t copy_cnt = (idx + 16) < numbers_count ? 16 :
numbers_count - idx;
memcpy(&numbers[idx], rand, copy_cnt * sizeof(uint32_t));
idx += copy_cnt;
idx_from_reseed += copy_cnt;
if ((idx_from_reseed * sizeof(uint32_t)) > _RESEED_LIMIT_BYTES)
{
if (_scprng_seed(rand, nonce, (uint8_t *)&counter, encryption_key))
return -1;
else
idx_from_reseed = 0;
}
++counter;
}
return 0;
}