mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-11-23 07:58:09 +00:00
71 lines
1.2 KiB
C
71 lines
1.2 KiB
C
#include <string.h>
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#include "rand.h"
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#ifdef UNIX
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#include <stdio.h>
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#include <assert.h>
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static FILE *frand = NULL;
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#else
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uint32_t rng_get(void);
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#endif
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uint32_t random32(void)
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{
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#ifdef UNIX
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uint32_t r;
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size_t len = sizeof(r);
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if (!frand) {
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frand = fopen("/dev/urandom", "r");
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}
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size_t len_read = fread(&r, 1, len, frand);
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(void)len_read;
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assert(len_read == len);
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return r;
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#else
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return rng_get();
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#endif
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}
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uint32_t random_uniform(uint32_t n)
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{
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uint32_t x, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
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while ((x = random32()) >= max);
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return x / (max / n);
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}
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void random_buffer(uint8_t *buf, size_t len)
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{
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#ifdef UNIX
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if (!frand) {
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frand = fopen("/dev/urandom", "r");
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}
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size_t len_read = fread(buf, 1, len, frand);
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(void)len_read;
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assert(len_read == len);
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#else
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size_t i;
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uint32_t r = 0;
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for (i = 0; i < len; i++) {
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if (i % 4 == 0) {
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r = random32();
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}
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buf[i] = (r >> ((i % 4) * 8)) & 0xFF;
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}
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#endif
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}
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void random_permute(void *buf, size_t size, size_t count)
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{
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if (count < 1 || size < 1) {
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return;
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}
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uint8_t *d = (uint8_t *)buf;
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uint8_t t[size];
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for (size_t i = count - 1; i >= 1; i--) {
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size_t j = random_uniform(i + 1);
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memcpy(t, d + j * size, size);
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memcpy(d + j * size, d + i * size, size);
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memcpy(d + i * size, t, size);
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}
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}
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