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trezor-firmware/extmod/modtrezorcrypto/rand.c

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/*
* Copyright (c) Pavol Rusnak, SatoshiLabs
*
* Licensed under TREZOR License
* see LICENSE file for details
*/
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#include <string.h>
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#include "rand.h"
#ifdef UNIX
#include <stdio.h>
#include <assert.h>
static FILE *frand = NULL;
#else
uint32_t rng_get(void);
#endif
uint32_t random32(void)
{
#ifdef UNIX
uint32_t r;
size_t len = sizeof(r);
if (!frand) {
frand = fopen("/dev/urandom", "r");
}
size_t len_read = fread(&r, 1, len, frand);
(void)len_read;
assert(len_read == len);
return r;
#else
return rng_get();
#endif
}
uint32_t random_uniform(uint32_t n)
{
uint32_t x, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
while ((x = random32()) >= max);
return x / (max / n);
}
void random_buffer(uint8_t *buf, size_t len)
{
#ifdef UNIX
if (!frand) {
frand = fopen("/dev/urandom", "r");
}
size_t len_read = fread(buf, 1, len, frand);
(void)len_read;
assert(len_read == len);
#else
size_t i;
uint32_t r = 0;
for (i = 0; i < len; i++) {
if (i % 4 == 0) {
r = random32();
}
buf[i] = (r >> ((i % 4) * 8)) & 0xFF;
}
#endif
}
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void random_permute(void *buf, size_t size, size_t count)
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{
if (count < 1 || size < 1) {
return;
}
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uint8_t *d = (uint8_t *)buf;
uint8_t t[size];
for (size_t i = count - 1; i >= 1; i--) {
size_t j = random_uniform(i + 1);
memcpy(t, d + j * size, size);
memcpy(d + j * size, d + i * size, size);
memcpy(d + i * size, t, size);
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}
}