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