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Don't reflash storage after each PIN entry

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Instead of reflashing the whole storage, we use a designated area
in the second storage block, where we mark each PIN failure by a
single zero bit. This is because one can set bits in flash to zero but
not to one.  If the PIN was entered successfully the whole word is
set to zero and the next word stores the new PIN failure counter.
This commit is contained in:
Jochen Hoenicke 2016-04-27 18:12:03 +02:00
parent e0539f8f8b
commit da98a3a6fd
3 changed files with 128 additions and 92 deletions
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48
firmware/protect.c
View File

@ -142,31 +142,29 @@ const char *requestPin(PinMatrixRequestType type, const char *text)
bool protectPin(bool use_cached) bool protectPin(bool use_cached)
{ {
if (!storage.has_pin || strlen(storage.pin) == 0 || (use_cached && session_isPinCached())) { if (!storage.has_pin || storage.pin[0] == 0 || (use_cached && session_isPinCached())) {
return true; return true;
} }
uint32_t fails = storage_getPinFails(); uint32_t *fails = storage_getPinFailsPtr();
if (fails) { uint32_t wait = ~*fails;
uint32_t wait; while (wait > 0) {
wait = (fails < 32) ? (1u << fails) : 0xFFFFFFFF; // convert wait to secstr string
while (--wait > 0) { char secstrbuf[20];
// convert wait to secstr string strlcpy(secstrbuf, "________0 seconds", sizeof(secstrbuf));
char secstrbuf[20]; char *secstr = secstrbuf + 9;
strlcpy(secstrbuf, "________0 seconds", sizeof(secstrbuf)); uint32_t secs = wait;
char *secstr = secstrbuf + 9; while (secs > 0 && secstr >= secstrbuf) {
uint32_t secs = wait; secstr--;
while (secs > 0 && secstr >= secstrbuf) { *secstr = (secs % 10) + '0';
secstr--; secs /= 10;
*secstr = (secs % 10) + '0';
secs /= 10;
}
if (wait == 1) {
secstrbuf[16] = 0;
}
layoutDialog(DIALOG_ICON_INFO, NULL, NULL, NULL, "Wrong PIN entered", NULL, "Please wait", secstr, "to continue ...", NULL);
// wait one second
usbDelay(840000);
} }
if (wait == 1) {
secstrbuf[16] = 0;
}
layoutDialog(DIALOG_ICON_INFO, NULL, NULL, NULL, "Wrong PIN entered", NULL, "Please wait", secstr, "to continue ...", NULL);
// wait one second
usbDelay(840000);
wait--;
} }
const char *pin; const char *pin;
pin = requestPin(PinMatrixRequestType_PinMatrixRequestType_Current, "Please enter current PIN:"); pin = requestPin(PinMatrixRequestType_PinMatrixRequestType_Current, "Please enter current PIN:");
@ -174,11 +172,9 @@ bool protectPin(bool use_cached)
fsm_sendFailure(FailureType_Failure_PinCancelled, "PIN Cancelled"); fsm_sendFailure(FailureType_Failure_PinCancelled, "PIN Cancelled");
return false; return false;
} }
storage_increasePinFails(); if (storage_increasePinFails(fails) && storage_isPinCorrect(pin)) {
bool increase_failed = (fails >= storage_getPinFails());
if (storage_isPinCorrect(pin) && !increase_failed) {
session_cachePin(); session_cachePin();
storage_resetPinFails(); storage_resetPinFails(fails);
return true; return true;
} else { } else {
fsm_sendFailure(FailureType_Failure_PinInvalid, "Invalid PIN"); fsm_sendFailure(FailureType_Failure_PinInvalid, "Invalid PIN");

166
firmware/storage.c
View File

@ -40,13 +40,38 @@
#include "protect.h" #include "protect.h"
#include "layout2.h" #include "layout2.h"
_Static_assert(sizeof(Storage) <= FLASH_STORAGE_LEN, "Storage struct is too large for TREZOR flash");
Storage storage; Storage storage;
uint8_t storage_uuid[12]; uint8_t storage_uuid[12];
char storage_uuid_str[25]; char storage_uuid_str[25];
/*
storage layout:
offset | type/length | description
--------+-------------+-------------------------------
0x0000 | 4 bytes | magic = 'stor'
0x0004 | 12 bytes | uuid
0x0010 | ? | Storage structure
0x4000 | 4 kbytes | area for pin failures
0x5000 | 12 kbytes | reserved
The area for pin failures looks like this:
0 ... 0 pinfail 0xffffffff .. 0xffffffff
The pinfail is a binary number of the form 1...10...0,
the number of zeros is the number of pin failures.
This layout is used because we can only clear bits without
erasing the flash.
*/
#define FLASH_STORAGE_PINAREA (FLASH_META_START + 0x4000)
#define FLASH_STORAGE_PINAREA_LEN (0x1000)
#define FLASH_STORAGE_REALLEN (4 + sizeof(storage_uuid) + sizeof(Storage))
_Static_assert(FLASH_STORAGE_START + FLASH_STORAGE_REALLEN <= FLASH_STORAGE_PINAREA, "Storage struct is too large for TREZOR flash");
static bool sessionSeedCached; static bool sessionSeedCached;
static uint8_t sessionSeed[64]; static uint8_t sessionSeed[64];
static bool sessionPinCached; static bool sessionPinCached;
@ -54,36 +79,41 @@ static bool sessionPinCached;
static bool sessionPassphraseCached; static bool sessionPassphraseCached;
static char sessionPassphrase[51]; static char sessionPassphrase[51];
/* #define STORAGE_VERSION 6
storage layout:
offset | type/length | description void storage_check_flash_errors(void)
--------+-------------+------------------------------- {
0x0000 | 4 bytes | magic = 'stor' // flash operation failed
0x0004 | 12 bytes | uuid if (FLASH_SR & (FLASH_SR_PGAERR | FLASH_SR_PGPERR | FLASH_SR_PGSERR | FLASH_SR_WRPERR)) {
0x0010 | ? | Storage structure layoutDialog(DIALOG_ICON_ERROR, NULL, NULL, NULL, "Storage failure", "detected.", NULL, "Please unplug", "the device.", NULL);
*/ for (;;) { }
}
#define STORAGE_VERSION 5 }
void storage_from_flash(uint32_t version) void storage_from_flash(uint32_t version)
{ {
switch (version) { // version 1: since 1.0.0
case 1: // copy (since 1.0.0) // version 2: since 1.2.1
memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage)); // version 3: since 1.3.1
break; // version 4: since 1.3.2
case 2: // copy (since 1.2.1) // version 5: since 1.3.3
memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage)); // version 6: since 1.3.6
break; memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage));
case 3: // copy (since 1.3.1) if (version <= 5) {
memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage)); // convert PIN failure counter from version 5 format
break; uint32_t pinctr = storage.has_pin_failed_attempts
case 4: // copy (since 1.3.2) ? storage.pin_failed_attempts : 0;
memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage)); if (pinctr > 31)
break; pinctr = 31;
case 5: // copy (since 1.3.3) flash_clear_status_flags();
memcpy(&storage, (void *)(FLASH_STORAGE_START + 4 + sizeof(storage_uuid)), sizeof(Storage)); flash_unlock();
break; // erase extra storage sector
flash_erase_sector(FLASH_META_SECTOR_LAST, FLASH_CR_PROGRAM_X32);
flash_program_word(FLASH_STORAGE_PINAREA, 0xffffffff << pinctr);
flash_lock();
storage_check_flash_errors();
storage.has_pin_failed_attempts = false;
storage.pin_failed_attempts = 0;
} }
storage.version = STORAGE_VERSION; storage.version = STORAGE_VERSION;
} }
@ -136,35 +166,29 @@ void session_clear(bool clear_pin)
} }
} }
static uint8_t meta_backup[FLASH_META_LEN];
void storage_commit(void) void storage_commit(void)
{ {
int i; int i;
uint32_t *w; uint32_t meta_backup[(FLASH_STORAGE_PINAREA - FLASH_META_START) / 4];
// backup meta // backup meta
memcpy(meta_backup, (void *)FLASH_META_START, FLASH_META_LEN); memcpy((uint8_t*)meta_backup, (uint8_t*)FLASH_META_START, FLASH_META_DESC_LEN);
// modify storage
memcpy((uint8_t*)meta_backup + FLASH_META_DESC_LEN, "stor", 4);
memcpy((uint8_t*)meta_backup + FLASH_META_DESC_LEN + 4, storage_uuid, sizeof(storage_uuid));
memcpy((uint8_t*)meta_backup + FLASH_META_DESC_LEN + 4 + sizeof(storage_uuid), &storage, sizeof(Storage));
memset((uint8_t*)meta_backup + FLASH_META_DESC_LEN + FLASH_STORAGE_REALLEN, 0, sizeof(meta_backup) - FLASH_META_DESC_LEN - FLASH_STORAGE_REALLEN);
flash_clear_status_flags(); flash_clear_status_flags();
flash_unlock(); flash_unlock();
// erase storage // erase storage
for (i = FLASH_META_SECTOR_FIRST; i <= FLASH_META_SECTOR_LAST; i++) { flash_erase_sector(FLASH_META_SECTOR_FIRST, FLASH_CR_PROGRAM_X32);
flash_erase_sector(i, FLASH_CR_PROGRAM_X32);
}
// modify storage
memcpy(meta_backup + FLASH_META_DESC_LEN, "stor", 4);
memcpy(meta_backup + FLASH_META_DESC_LEN + 4, storage_uuid, sizeof(storage_uuid));
memcpy(meta_backup + FLASH_META_DESC_LEN + 4 + sizeof(storage_uuid), &storage, sizeof(Storage));
// copy it back // copy it back
for (i = 0; i < FLASH_META_LEN / 4; i++) { for (i = 0; i < (signed) (sizeof(meta_backup) / 4); i++) {
w = (uint32_t *)(meta_backup + i * 4); flash_program_word(FLASH_META_START + i * 4, meta_backup[i]);
flash_program_word(FLASH_META_START + i * 4, *w);
} }
flash_lock(); flash_lock();
// flash operation failed storage_check_flash_errors();
if (FLASH_SR & (FLASH_SR_PGAERR | FLASH_SR_PGPERR | FLASH_SR_PGSERR | FLASH_SR_WRPERR)) {
layoutDialog(DIALOG_ICON_ERROR, NULL, NULL, NULL, "Storage failure", "detected.", NULL, "Please unplug", "the device.", NULL);
for (;;) { }
}
} }
void storage_loadDevice(LoadDevice *msg) void storage_loadDevice(LoadDevice *msg)
@ -344,7 +368,7 @@ bool storage_hasPin(void)
void storage_setPin(const char *pin) void storage_setPin(const char *pin)
{ {
if (pin && strlen(pin) > 0) { if (pin && pin[0]) {
storage.has_pin = true; storage.has_pin = true;
strlcpy(storage.pin, pin, sizeof(storage.pin)); strlcpy(storage.pin, pin, sizeof(storage.pin));
} else { } else {
@ -376,28 +400,44 @@ bool session_isPinCached(void)
return sessionPinCached; return sessionPinCached;
} }
void storage_resetPinFails(void) void storage_resetPinFails(uint32_t *pinfailsptr)
{ {
storage.has_pin_failed_attempts = true; flash_clear_status_flags();
storage.pin_failed_attempts = 0; flash_unlock();
storage_commit(); if ((uint32_t) (pinfailsptr + 1) - FLASH_STORAGE_PINAREA
} >= FLASH_STORAGE_PINAREA_LEN) {
// erase extra storage sector
void storage_increasePinFails(void) flash_erase_sector(FLASH_META_SECTOR_LAST, FLASH_CR_PROGRAM_X32);
{
if (!storage.has_pin_failed_attempts) {
storage.has_pin_failed_attempts = true;
storage.pin_failed_attempts = 1;
} else { } else {
storage.pin_failed_attempts++; flash_program_word((uint32_t) pinfailsptr, 0);
} }
storage_commit(); flash_lock();
storage_check_flash_errors();
} }
uint32_t storage_getPinFails(void) bool storage_increasePinFails(uint32_t *pinfailsptr)
{ {
storage_from_flash(STORAGE_VERSION); // reload from flash uint32_t newctr = *pinfailsptr << 1;
return storage.has_pin_failed_attempts ? storage.pin_failed_attempts : 0; // counter already at maximum, we do not increase it any more
// return success so that a good pin is accepted
if (!newctr)
return true;
flash_clear_status_flags();
flash_unlock();
flash_program_word((uint32_t) pinfailsptr, newctr);
flash_lock();
storage_check_flash_errors();
return *pinfailsptr == newctr;
}
uint32_t *storage_getPinFailsPtr(void)
{
uint32_t *pinfailsptr = (uint32_t *) FLASH_STORAGE_PINAREA;
while (*pinfailsptr == 0)
pinfailsptr++;
return pinfailsptr;
} }
bool storage_isInitialized(void) bool storage_isInitialized(void)

6
firmware/storage.h
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@ -56,9 +56,9 @@ bool storage_hasPin(void);
void storage_setPin(const char *pin); void storage_setPin(const char *pin);
void session_cachePin(void); void session_cachePin(void);
bool session_isPinCached(void); bool session_isPinCached(void);
void storage_resetPinFails(void); void storage_resetPinFails(uint32_t *pinfailptr);
void storage_increasePinFails(void); bool storage_increasePinFails(uint32_t *pinfailptr);
uint32_t storage_getPinFails(void); uint32_t *storage_getPinFailsPtr(void);
bool storage_isInitialized(void); bool storage_isInitialized(void);