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100 lines
2.3 KiB
C
100 lines
2.3 KiB
C
/**
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* Copyright (C) 2016-2018 Bas Stottelaar <basstottelaar@gmail.com>
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup sys_random
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* @{
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* @file
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*
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* @brief Glue-code for Fortuna PRNG.
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*
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* @author Bas Stottelaar <basstottelaar@gmail.com>
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* @}
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*/
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#include <string.h>
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#include "log.h"
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#include "mutex.h"
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#include "fortuna/fortuna.h"
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/**
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* @brief This holds the PRNG state.
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*/
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static fortuna_state_t fortuna_state;
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/**
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* @brief Initialize the PRNG with a given number of bytes.
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*/
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static void _init(uint8_t *in, size_t bytes)
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{
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fortuna_seed_t seed;
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/* ensure a seed of proper length is available, which may not be the case
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with a small input */
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memset(seed, 0, sizeof(seed));
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for (int i = 0; i < (int) bytes; i++) {
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seed[i % sizeof(seed)] ^= in[i];
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}
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/* initialize the PRNG state */
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fortuna_init(&fortuna_state);
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/* update the PRNG seed (seed will be overwritten by design!) */
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fortuna_update_seed(&fortuna_state, &seed);
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}
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/**
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* @brief Wrapper for fortuna_random_data that supports reading more than
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* FORTUNA_RESEED_LIMIT and also checks the result.
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*/
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static void _read(uint8_t *out, size_t bytes)
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{
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do {
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/* read at most chunk bytes to not exhaust the state at once */
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size_t chunk = (bytes < FORTUNA_RESEED_LIMIT) ?
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bytes : FORTUNA_RESEED_LIMIT;
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int res = fortuna_random_data(&fortuna_state, out, chunk);
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if (res == -1) {
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LOG_ERROR("random: reading more bytes than allowed.\n");
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}
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else if (res == -2) {
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LOG_ERROR("random: PRNG not initialized.\n");
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}
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else if (res == -3) {
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LOG_ERROR("random: unknown error.\n");
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}
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/* advance bytes and buffer */
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bytes -= chunk;
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out += chunk;
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} while (bytes > FORTUNA_RESEED_LIMIT);
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}
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void random_init_by_array(uint32_t init_key[], int key_length)
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{
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_init((uint8_t *) init_key, sizeof(uint32_t) * key_length);
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}
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void random_init(uint32_t s)
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{
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_init((uint8_t *) &s, sizeof(s));
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}
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uint32_t random_uint32(void)
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{
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uint32_t data;
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_read((uint8_t *) &data, sizeof(data));
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return data;
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}
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