Momentum-Apps/apps_source_code/FlipBIP/lib/crypto/rand.c

/**
 * Copyright (c) 2013-2014 Tomas Dzetkulic
 * Copyright (c) 2013-2014 Pavol Rusnak
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
 * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

// NOTE:
// random32() and random_buffer() have been replaced in this implementation
// with Flipper Zero specific code. The original code is commented out below.

#include "rand.h"

// Flipper Zero RNG code:
#include <furi_hal_random.h>

#ifndef RAND_PLATFORM_INDEPENDENT

// Original code:
// #pragma message("NOT SUITABLE FOR PRODUCTION USE! Replace random32() function with your own secure code.")

// The following code is not supposed to be used in a production environment.
// It's included only to make the library testable.
// The message above tries to prevent any accidental use outside of the test
// environment.
//
// You are supposed to replace the random8() and random32() function with your
// own secure code. There is also a possibility to replace the random_buffer()
// function as it is defined as a weak symbol.

static uint32_t seed = 0;

void random_reseed(const uint32_t value) {
    seed = value;
}

// Original code:
// uint32_t random32(void) {
//   // Linear congruential generator from Numerical Recipes
//   // https://en.wikipedia.org/wiki/Linear_congruential_generator
//   seed = 1664525 * seed + 1013904223;
//   return seed;
// }

// Flipper Zero RNG code:
uint32_t random32(void) {
    return furi_hal_random_get();
}

// Flipper Zero RNG code:
void random_buffer(uint8_t* buf, size_t len) {
    furi_hal_random_fill_buf(buf, len);
}

#endif /* RAND_PLATFORM_INDEPENDENT */

//
// The following code is platform independent
//

// Original code:
// void __attribute__((weak)) random_buffer(uint8_t *buf, size_t len) {
//   uint32_t r = 0;
//   for (size_t i = 0; i < len; i++) {
//     if (i % 4 == 0) {
//       r = random32();
//     }
//     buf[i] = (r >> ((i % 4) * 8)) & 0xFF;
//   }
// }

uint32_t random_uniform(uint32_t n) {
    uint32_t x = 0, max = 0xFFFFFFFF - (0xFFFFFFFF % n);
    while((x = random32()) >= max)
        ;
    return x / (max / n);
}

void random_permute(char* str, size_t len) {
    for(int i = len - 1; i >= 1; i--) {
        int j = random_uniform(i + 1);
        char t = str[j];
        str[j] = str[i];
        str[i] = t;
    }
}