/* * This file is part of the TREZOR project, https://trezor.io/ * * Copyright (c) SatoshiLabs * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include STM32_HAL_H #include "rng.h" #pragma GCC optimize( \ "no-stack-protector") // applies to all functions in this file void rng_init(void) { // enable TRNG peripheral clock // use the HAL version due to section 2.1.6 of STM32F42xx Errata sheet // "Delay after an RCC peripheral clock enabling" __HAL_RCC_RNG_CLK_ENABLE(); RNG->CR = RNG_CR_RNGEN; // enable TRNG } uint32_t rng_read(const uint32_t previous, const uint32_t compare_previous) { uint32_t temp = previous; do { while ((RNG->SR & (RNG_SR_SECS | RNG_SR_CECS | RNG_SR_DRDY)) != RNG_SR_DRDY) ; // wait until TRNG is ready temp = RNG->DR; // read the data from the TRNG } while (compare_previous && (temp == previous)); // RM0090 section 24.3.1 FIPS continuous random // number generator test return temp; } uint32_t rng_get(void) { // reason for keeping history: RM0090 section 24.3.1 FIPS continuous random // number generator test static uint32_t previous = 0, current = 0; if (previous == current) { previous = rng_read(previous, 0); } else { previous = current; } current = rng_read(previous, 1); return current; }