mirror of
https://github.com/trezor/trezor-firmware.git
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92 lines
2.8 KiB
C
92 lines
2.8 KiB
C
/**
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* Copyright (c) 2013-2014 Tomas Dzetkulic
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* Copyright (c) 2013-2014 Pavol Rusnak
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "rand.h"
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#ifdef USE_INSECURE_PRNG
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#pragma message( \
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"NOT SUITABLE FOR PRODUCTION USE! Replace random32() function with your own secure code.")
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// The following code is not supposed to be used in a production environment.
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// It's included only to make the library testable.
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// The message above tries to prevent any accidental use outside of the test
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// environment.
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//
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// You are supposed to replace the random8() and random32() function with your
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// own secure code. There is also a possibility to replace the random_buffer()
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// function as it is defined as a weak symbol.
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static uint32_t seed = 0;
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void random_reseed(const uint32_t value) { seed = value; }
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uint32_t random32(void) {
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// Linear congruential generator from Numerical Recipes
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// https://en.wikipedia.org/wiki/Linear_congruential_generator
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seed = 1664525 * seed + 1013904223;
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return seed;
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}
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#endif /* USE_INSECURE_PRNG */
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//
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// The following code is platform independent
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//
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void __attribute__((weak)) random_buffer(uint8_t *buf, size_t len) {
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uint32_t r = 0;
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for (size_t 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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}
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void random_xor(uint8_t *buf, size_t len) {
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uint8_t r[4] = {0};
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for (size_t i = 0; i < len; i++) {
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if (i % sizeof(r) == 0) {
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random_buffer(r, sizeof(r));
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}
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buf[i] ^= r[i % sizeof(r)];
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}
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}
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uint32_t random_uniform(uint32_t n) {
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uint32_t x = 0, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
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while ((x = random32()) >= max)
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;
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return x / (max / n);
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}
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void random_permute(char *str, size_t len) {
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for (int i = len - 1; i >= 1; i--) {
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int j = random_uniform(i + 1);
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char t = str[j];
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str[j] = str[i];
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str[i] = t;
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}
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}
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