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storage: pin checking in c proof of concept

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TODO: move out of modtrezorconfig
TODO: flash unix mock
pull/25/head
Jan Pochyla 7 years ago
parent 2ebd2b1b6b
commit 4cabe40220
3 changed files with 175 additions and 1 deletions
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151
embed/extmod/modtrezorconfig/modtrezorconfig.c
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@ -1,19 +1,140 @@
/*
* Copyright (c) Pavol Rusnak, SatoshiLabs
* Copyright (c) Pavol Rusnak, Jan Pochyla, SatoshiLabs
*
* Licensed under TREZOR License
* see LICENSE file for details
*/
#include "py/runtime.h"
#include "py/mphal.h"
#if MICROPY_PY_TREZORCONFIG
#include <stdint.h>
#include <string.h>
#include "norcow.h"
#include "flash.h"
#define MAX_WRONG_PINS 15
#define FAIL_SECTOR_LEN 16 * 1024
#define STORAGE_KEY_PIN 0x00
static void pin_fails_reset(uint32_t ofs)
{
if (ofs + sizeof(uint32_t) >= FAIL_SECTOR_LEN) {
// ofs points to the last word of the PIN fails area. Because there is
// no space left, we recycle the sector (set all words to 0xffffffff).
// On next unlock attempt, we start counting from the the first word.
flash_erase_sectors(FLASH_SECTOR_PIN_AREA, FLASH_SECTOR_PIN_AREA, NULL);
} else {
// Mark this counter as exhausted. On next unlock attempt, pinfails_get
// seeks to the next word.
flash_unlock();
flash_write_word_rel(FLASH_SECTOR_PIN_AREA, ofs, 0);
flash_lock();
}
}
static bool pin_fails_increase(uint32_t ofs)
{
uint32_t ctr = ~MAX_WRONG_PINS;
if (!flash_read_word_rel(FLASH_SECTOR_PIN_AREA, ofs, &ctr)) {
return false;
}
ctr = ctr << 1;
flash_unlock();
if (!flash_write_word_rel(FLASH_SECTOR_PIN_AREA, ofs, ctr)) {
flash_lock();
return false;
}
flash_lock();
uint32_t check = 0;
if (!flash_read_word_rel(FLASH_SECTOR_PIN_AREA, ofs, &check)) {
return false;
}
return ctr == check;
}
static bool pin_fails_check_max(uint32_t ctr)
{
if (~ctr >= 1 << MAX_WRONG_PINS) {
norcow_wipe();
// TODO: shutdown
return false;
}
return true;
}
static bool pin_fails_get(uint32_t *ofs, uint32_t *ctr)
{
if (!ofs || !ctr) {
return false;
}
for (uint32_t o = 0; o < FAIL_SECTOR_LEN; o += sizeof(uint32_t)) {
uint32_t c = 0;
if (!flash_read_word_rel(FLASH_SECTOR_PIN_AREA, o, &c)) {
return false;
}
if (c != 0) {
*ofs = o;
*ctr = c;
return true;
}
}
return false;
}
static bool const_cmp(const uint8_t *pub, size_t publen, const uint8_t *sec, size_t seclen)
{
size_t diff = seclen - publen;
for (size_t i = 0; i < publen; i++) {
diff |= pub[i] ^ sec[i];
}
return diff == 0;
}
static bool pin_check(const uint8_t *pin, size_t pinlen)
{
const void *st_pin;
uint16_t st_pinlen;
if (!norcow_get(STORAGE_KEY_PIN, &st_pin, &st_pinlen)) {
return false;
}
return const_cmp(pin, pinlen, st_pin, (size_t)st_pinlen);
}
static bool pin_unlock(const uint8_t *pin, size_t pinlen)
{
uint32_t ofs;
uint32_t ctr;
if (!pin_fails_get(&ofs, &ctr)) {
return false;
}
pin_fails_check_max(ctr);
// Sleep for ~ctr seconds before checking the PIN.
for (uint32_t wait = ~ctr; wait > 0; wait--) {
mp_hal_delay_ms(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 (!pin_fails_increase(ofs)) {
return false;
}
if (!pin_check(pin, pinlen)) {
pin_fails_check_max(ctr << 1);
return false;
}
pin_fails_reset(ofs);
return true;
}
static bool initialized = false;
static bool unlocked = false;
/// def init() -> None:
/// '''
@ -25,10 +146,29 @@ STATIC mp_obj_t mod_trezorconfig_init(void) {
mp_raise_msg(&mp_type_RuntimeError, "Could not initialize config module");
}
initialized = true;
unlocked = false;
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorconfig_init_obj, mod_trezorconfig_init);
/// def unlock(pin: str) -> None:
/// '''
/// Tries to unlock the storage with given PIN key.
/// '''
STATIC mp_obj_t mod_trezorconfig_unlock(mp_obj_t pin) {
if (!initialized) {
mp_raise_msg(&mp_type_RuntimeError, "Config module not initialized");
}
mp_buffer_info_t pinbuf;
mp_get_buffer_raise(pin, &pinbuf, MP_BUFFER_READ);
bool r = pin_unlock(pinbuf.buf, pinbuf.len);
if (!r) {
return mp_const_false;
}
return mp_const_true;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorconfig_unlock_obj, mod_trezorconfig_unlock);
/// def get(app: int, key: int) -> bytes:
/// '''
/// Gets a value of given key for given app (or empty bytes if not set).
@ -37,6 +177,10 @@ STATIC mp_obj_t mod_trezorconfig_get(mp_obj_t app, mp_obj_t key) {
if (!initialized) {
mp_raise_msg(&mp_type_RuntimeError, "Config module not initialized");
}
if (!unlocked) {
mp_raise_msg(&mp_type_RuntimeError, "Config module locked");
// TODO: shutdown?
}
uint8_t a = mp_obj_get_int(app);
uint8_t k = mp_obj_get_int(key);
uint16_t appkey = a << 8 | k, len;
@ -60,6 +204,10 @@ STATIC mp_obj_t mod_trezorconfig_set(mp_obj_t app, mp_obj_t key, mp_obj_t value)
if (!initialized) {
mp_raise_msg(&mp_type_RuntimeError, "Config module not initialized");
}
if (!unlocked) {
mp_raise_msg(&mp_type_RuntimeError, "Config module locked");
// TODO: shutdown?
}
uint8_t a = mp_obj_get_int(app);
uint8_t k = mp_obj_get_int(key);
uint16_t appkey = a << 8 | k;
@ -92,6 +240,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(mod_trezorconfig_wipe_obj, mod_trezorconfig_wip
STATIC const mp_rom_map_elem_t mp_module_trezorconfig_globals_table[] = {
{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_trezorconfig) },
{ MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&mod_trezorconfig_init_obj) },
{ MP_ROM_QSTR(MP_QSTR_unlock), MP_ROM_PTR(&mod_trezorconfig_unlock_obj) },
{ MP_ROM_QSTR(MP_QSTR_get), MP_ROM_PTR(&mod_trezorconfig_get_obj) },
{ MP_ROM_QSTR(MP_QSTR_set), MP_ROM_PTR(&mod_trezorconfig_set_obj) },
{ MP_ROM_QSTR(MP_QSTR_wipe), MP_ROM_PTR(&mod_trezorconfig_wipe_obj) },

22
embed/trezorhal/flash.c
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@ -91,6 +91,28 @@ secbool flash_write_word(uint32_t address, uint32_t data)
return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, address, data));
}
bool flash_write_byte_rel(uint32_t sector, uint32_t offset, uint8_t data)
{
return HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_BYTE, SECTOR_TABLE[sector] + offset, data);
}
bool flash_write_word_rel(uint32_t sector, uint32_t offset, uint32_t data)
{
if (offset % 4 != 0) {
return false;
}
return HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, SECTOR_TABLE[sector] + offset, data);
}
bool flash_read_word_rel(uint32_t sector, uint32_t offset, uint32_t *data)
{
if (offset % 4 != 0) {
return false;
}
*data = *((uint32_t *) SECTOR_TABLE[sector] + offset);
return true;
}
#define FLASH_OTP_LOCK_BASE 0x1FFF7A00U
secbool flash_otp_read(uint8_t block, uint8_t offset, uint8_t *data, uint8_t datalen)

3
embed/trezorhal/flash.h
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@ -51,6 +51,9 @@ secbool flash_lock(void);
secbool flash_erase_sectors(const uint8_t *sectors, int len, void (*progress)(int pos, int len));
secbool flash_write_byte(uint32_t address, uint8_t data);
secbool flash_write_word(uint32_t address, uint32_t data);
secbool flash_write_byte_rel(uint32_t sector, uint32_t offset, uint8_t data);
secbool flash_write_word_rel(uint32_t sector, uint32_t offset, uint32_t data);
secbool flash_read_word_rel(uint32_t sector, uint32_t offset, uint32_t *data);
#define FLASH_OTP_NUM_BLOCKS 16
#define FLASH_OTP_BLOCK_SIZE 32

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