random_delays.c

/*
 * This file is part of the Trezor project, https://trezor.io/
 *
 * Copyright (c) SatoshiLabs
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "random_delays.h"

#include "common.h"
#include "rng.h"
#include "util.h"

void wait_random(void) {
  int wait = random32() & 0xff;
  volatile int i = 0;
  volatile int j = wait;
  while (i < wait) {
    if (i + j != wait) {
      shutdown();
    }
    ++i;
    --j;
  }
  // Double-check loop completion.
  if (i != wait || j != 0) {
    shutdown();
  }
}