trezor-firmware/storage/tests/c0/storage.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 <string.h>

#include "common.h"
#include "norcow.h"
#include "storage.h"

// Norcow storage key of configured PIN.
#define PIN_KEY 0x0000

// Maximum PIN length.
#define PIN_MAXLEN 32

// Byte-length of flash section containing fail counters.
#define PIN_FAIL_KEY 0x0001
#define PIN_FAIL_SECTOR_SIZE 32

// Maximum number of failed unlock attempts.
#define PIN_MAX_TRIES 15

static secbool initialized = secfalse;
static secbool unlocked = secfalse;
static PIN_UI_WAIT_CALLBACK ui_callback = NULL;

void storage_init(PIN_UI_WAIT_CALLBACK callback) {
  initialized = secfalse;
  unlocked = secfalse;
  norcow_init();
  initialized = sectrue;
  ui_callback = callback;
}

static secbool pin_fails_reset(uint16_t ofs) {
  return norcow_update(PIN_FAIL_KEY, ofs, 0);
}

static secbool pin_fails_increase(const uint32_t *ptr, uint16_t ofs) {
  uint32_t ctr = *ptr;
  ctr = ctr << 1;

  if (sectrue != norcow_update(PIN_FAIL_KEY, ofs, ctr)) {
    return secfalse;
  }

  uint32_t check = *ptr;
  if (ctr != check) {
    return secfalse;
  }
  return sectrue;
}

static void pin_fails_check_max(uint32_t ctr) {
  if (~ctr >= (1 << PIN_MAX_TRIES)) {
    norcow_wipe();
    ensure(secfalse, "pin_fails_check_max");
  }
}

static secbool pin_cmp(const uint32_t pin) {
  const void *spin = NULL;
  uint16_t spinlen = 0;
  norcow_get(PIN_KEY, &spin, &spinlen);
  if (NULL != spin && spinlen == sizeof(uint32_t)) {
    return sectrue * (pin == *(const uint32_t *)spin);
  } else {
    return sectrue * (1 == pin);
  }
}

static secbool pin_get_fails(const uint32_t **pinfail, uint32_t *pofs) {
  const void *vpinfail;
  uint16_t pinfaillen;
  unsigned int ofs;
  // The PIN_FAIL_KEY points to an area of words, initialized to
  // 0xffffffff (meaning no pin failures).  The first non-zero word
  // in this area is the current pin failure counter.  If  PIN_FAIL_KEY
  // has no configuration or is empty, the pin failure counter is 0.
  // We rely on the fact that flash allows to clear bits and we clear one
  // bit to indicate pin failure.  On success, the word is set to 0,
  // indicating that the next word is the pin failure counter.

  // Find the current pin failure counter
  if (secfalse != norcow_get(PIN_FAIL_KEY, &vpinfail, &pinfaillen)) {
    *pinfail = vpinfail;
    for (ofs = 0; ofs < pinfaillen / sizeof(uint32_t); ofs++) {
      if (((const uint32_t *)vpinfail)[ofs]) {
        *pinfail = vpinfail;
        *pofs = ofs;
        return sectrue;
      }
    }
  }

  // No pin failure section, or all entries used -> create a new one.
  uint32_t pinarea[PIN_FAIL_SECTOR_SIZE];
  memset(pinarea, 0xff, sizeof(pinarea));
  if (sectrue != norcow_set(PIN_FAIL_KEY, pinarea, sizeof(pinarea))) {
    return secfalse;
  }
  if (sectrue != norcow_get(PIN_FAIL_KEY, &vpinfail, &pinfaillen)) {
    return secfalse;
  }
  *pinfail = vpinfail;
  *pofs = 0;
  return sectrue;
}

secbool storage_check_pin(const uint32_t pin) {
  const uint32_t *pinfail = NULL;
  uint32_t ofs;
  uint32_t ctr;

  // Get the pin failure counter
  if (pin_get_fails(&pinfail, &ofs) != sectrue) {
    return secfalse;
  }

  // Read current failure counter
  ctr = pinfail[ofs];
  // Wipe storage if too many failures
  pin_fails_check_max(ctr);

  // Sleep for ~ctr seconds before checking the PIN.
  uint32_t progress;
  for (uint32_t wait = ~ctr; wait > 0; wait--) {
    for (int i = 0; i < 10; i++) {
      if (ui_callback) {
        if ((~ctr) > 1000000) {  // precise enough
          progress = (~ctr - wait) / ((~ctr) / 1000);
        } else {
          progress = ((~ctr - wait) * 10 + i) * 100 / (~ctr);
        }
        ui_callback(wait, progress);
      }
      hal_delay(100);
    }
  }
  // Show last frame if we were waiting
  if ((~ctr > 0) && ui_callback) {
    ui_callback(0, 1000);
  }

  // First, we increase PIN fail counter in storage, even before checking the
  // PIN.  If the PIN is correct, we reset the counter afterwards.  If not, we
  // check if this is the last allowed attempt.
  if (sectrue != pin_fails_increase(pinfail + ofs, ofs * sizeof(uint32_t))) {
    return secfalse;
  }
  if (sectrue != pin_cmp(pin)) {
    // Wipe storage if too many failures
    pin_fails_check_max(ctr << 1);
    return secfalse;
  }
  // Finally set the counter to 0 to indicate success.
  return pin_fails_reset(ofs * sizeof(uint32_t));
}

secbool storage_unlock(const uint32_t pin) {
  unlocked = secfalse;
  if (sectrue == initialized && sectrue == storage_check_pin(pin)) {
    unlocked = sectrue;
  }
  return unlocked;
}

secbool storage_get(const uint16_t key, const void **val, uint16_t *len) {
  const uint8_t app = key >> 8;
  // APP == 0 is reserved for PIN related values
  if (sectrue != initialized || app == 0) {
    return secfalse;
  }
  // top bit of APP set indicates the value can be read from unlocked device
  if (sectrue != unlocked && ((app & 0x80) == 0)) {
    return secfalse;
  }
  return norcow_get(key, val, len);
}

secbool storage_set(const uint16_t key, const void *val, uint16_t len) {
  const uint8_t app = key >> 8;
  // APP == 0 is reserved for PIN related values
  if (sectrue != initialized || sectrue != unlocked || app == 0) {
    return secfalse;
  }
  return norcow_set(key, val, len);
}

secbool storage_has_pin(void) {
  if (sectrue != initialized) {
    return secfalse;
  }
  return sectrue == pin_cmp(1) ? secfalse : sectrue;
}

secbool storage_change_pin(const uint32_t oldpin, const uint32_t newpin) {
  if (sectrue != initialized || sectrue != unlocked) {
    return secfalse;
  }
  if (sectrue != storage_check_pin(oldpin)) {
    return secfalse;
  }
  return norcow_set(PIN_KEY, &newpin, sizeof(uint32_t));
}

void storage_wipe(void) { norcow_wipe(); }