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feat(core/bootloader): make bootloader more robust against glitches
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@hiviah @TychoVrahe
hiviah authored and TychoVrahe committed Sep 27, 2023
1 parent 660e7f9 commit 77061a8
Showing 1 changed file with 105 additions and 62 deletions.
167 changes: 105 additions & 62 deletions core/embed/bootloader/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,10 @@ typedef enum {
RETURN_TO_MENU = 0x55667788,
} usb_result_t;

volatile secbool dont_optimize_out_true = sectrue;
void failed_jump_to_firmware(void);
volatile void (*firmware_jump_fn)(void) = failed_jump_to_firmware;

static void usb_init_all(secbool usb21_landing) {
usb_dev_info_t dev_info = {
.device_class = 0x00,
Expand Down Expand Up @@ -294,6 +298,79 @@ static void check_bootloader_version(void) {

#endif

void failed_jump_to_firmware(void) {
error_shutdown("INTERNAL ERROR", "(glitch)");
}

void real_jump_to_firmware(void) {
const image_header *hdr = NULL;
vendor_header vhdr = {0};

ensure(read_vendor_header((const uint8_t *)FIRMWARE_START, &vhdr),
"Firmware is corrupted");

ensure(check_vendor_header_keys(&vhdr), "Firmware is corrupted");

ensure(check_vendor_header_lock(&vhdr), "Unauthorized vendor keys");

hdr =
read_image_header((const uint8_t *)(size_t)(FIRMWARE_START + vhdr.hdrlen),
FIRMWARE_IMAGE_MAGIC, FIRMWARE_IMAGE_MAXSIZE);

ensure(hdr == (const image_header *)(size_t)(FIRMWARE_START + vhdr.hdrlen)
? sectrue
: secfalse,
"Firmware is corrupted");

ensure(check_image_model(hdr), "Wrong firmware model");

ensure(check_image_header_sig(hdr, vhdr.vsig_m, vhdr.vsig_n, vhdr.vpub),
"Firmware is corrupted");

ensure(check_image_contents(hdr, IMAGE_HEADER_SIZE + vhdr.hdrlen,
&FIRMWARE_AREA),
"Firmware is corrupted");

#ifdef USE_OPTIGA
if (((vhdr.vtrust & VTRUST_SECRET) != 0) && (sectrue != secret_wiped())) {
ui_screen_install_restricted();
trezor_shutdown();
}
#endif

// if all VTRUST flags are unset = ultimate trust => skip the procedure
if ((vhdr.vtrust & VTRUST_ALL) != VTRUST_ALL) {
ui_fadeout();
ui_screen_boot(&vhdr, hdr);
ui_fadein();

int delay = (vhdr.vtrust & VTRUST_WAIT) ^ VTRUST_WAIT;
if (delay > 1) {
while (delay > 0) {
ui_screen_boot_wait(delay);
hal_delay(1000);
delay--;
}
} else if (delay == 1) {
hal_delay(1000);
}

if ((vhdr.vtrust & VTRUST_CLICK) == 0) {
ui_screen_boot_click();
}

ui_screen_boot_empty(false);
}

ensure_compatible_settings();

// mpu_config_firmware();
// jump_to_unprivileged(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);

mpu_config_off();
jump_to(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);
}

#ifndef TREZOR_EMULATOR
int main(void) {
// grab "stay in bootloader" flag as soon as possible
Expand Down Expand Up @@ -332,6 +409,7 @@ int bootloader_main(void) {
volatile secbool model_ok = secfalse;
volatile secbool header_present = secfalse;
volatile secbool firmware_present = secfalse;
volatile secbool firmware_present_backup = secfalse;

vhdr_present = read_vendor_header((const uint8_t *)FIRMWARE_START, &vhdr);

Expand Down Expand Up @@ -362,6 +440,7 @@ int bootloader_main(void) {
if (sectrue == header_present) {
firmware_present = check_image_contents(
hdr, IMAGE_HEADER_SIZE + vhdr.hdrlen, &FIRMWARE_AREA);
firmware_present_backup = firmware_present;
}

#if defined TREZOR_MODEL_T
Expand Down Expand Up @@ -402,6 +481,9 @@ int bootloader_main(void) {
stay_in_bootloader = sectrue;
}

ensure(dont_optimize_out_true * (firmware_present == firmware_present_backup),
NULL);

// delay to detect touch or skip if we know we are staying in bootloader
// anyway
uint32_t touched = 0;
Expand All @@ -426,6 +508,9 @@ int bootloader_main(void) {
}
#endif

ensure(dont_optimize_out_true * (firmware_present == firmware_present_backup),
NULL);

// start the bootloader ...
// ... if user touched the screen on start
// ... or we have stay_in_bootloader flag to force it
Expand Down Expand Up @@ -455,7 +540,8 @@ int bootloader_main(void) {
}

while (true) {
secbool continue_to_firmware = secfalse;
volatile secbool continue_to_firmware = secfalse;
volatile secbool continue_to_firmware_backup = secfalse;
uint32_t ui_result = 0;

switch (screen) {
Expand All @@ -467,6 +553,7 @@ int bootloader_main(void) {
switch (bootloader_usb_loop(NULL, NULL)) {
case CONTINUE_TO_FIRMWARE:
continue_to_firmware = sectrue;
continue_to_firmware_backup = sectrue;
break;
case RETURN_TO_MENU:
break;
Expand Down Expand Up @@ -494,6 +581,7 @@ int bootloader_main(void) {
if (ui_result == 0x11223344) { // reboot
ui_screen_boot_empty(true);
continue_to_firmware = firmware_present;
continue_to_firmware_backup = firmware_present_backup;
}
if (ui_result == 0x55667788) { // wipe
screen = SCREEN_WIPE_CONFIRM;
Expand Down Expand Up @@ -522,6 +610,7 @@ int bootloader_main(void) {
switch (bootloader_usb_loop(&vhdr, hdr)) {
case CONTINUE_TO_FIRMWARE:
continue_to_firmware = sectrue;
continue_to_firmware_backup = sectrue;
break;
case RETURN_TO_MENU:
screen = SCREEN_INTRO;
Expand All @@ -537,75 +626,29 @@ int bootloader_main(void) {
break;
}

if (continue_to_firmware != continue_to_firmware_backup) {
// erase storage if we saw flips randomly flip, most likely due to
// glitch
ensure(flash_area_erase_bulk(STORAGE_AREAS, STORAGE_AREAS_COUNT, NULL),
NULL);
}
ensure(dont_optimize_out_true *
(continue_to_firmware == continue_to_firmware_backup),
NULL);
if (sectrue == continue_to_firmware) {
firmware_jump_fn = real_jump_to_firmware;
break;
}
}
}

ensure(read_vendor_header((const uint8_t *)FIRMWARE_START, &vhdr),
"Firmware is corrupted");

ensure(check_vendor_header_keys(&vhdr), "Firmware is corrupted");

ensure(check_vendor_header_lock(&vhdr), "Unauthorized vendor keys");

hdr =
read_image_header((const uint8_t *)(size_t)(FIRMWARE_START + vhdr.hdrlen),
FIRMWARE_IMAGE_MAGIC, FIRMWARE_IMAGE_MAXSIZE);

ensure(hdr == (const image_header *)(size_t)(FIRMWARE_START + vhdr.hdrlen)
? sectrue
: secfalse,
"Firmware is corrupted");

ensure(check_image_model(hdr), "Wrong firmware model");

ensure(check_image_header_sig(hdr, vhdr.vsig_m, vhdr.vsig_n, vhdr.vpub),
"Firmware is corrupted");

ensure(check_image_contents(hdr, IMAGE_HEADER_SIZE + vhdr.hdrlen,
&FIRMWARE_AREA),
"Firmware is corrupted");

#ifdef USE_OPTIGA
if (((vhdr.vtrust & VTRUST_SECRET) != 0) && (sectrue != secret_wiped())) {
ui_screen_install_restricted();
return 1;
}
#endif

// if all VTRUST flags are unset = ultimate trust => skip the procedure
if ((vhdr.vtrust & VTRUST_ALL) != VTRUST_ALL) {
ui_fadeout();
ui_screen_boot(&vhdr, hdr);
ui_fadein();

int delay = (vhdr.vtrust & VTRUST_WAIT) ^ VTRUST_WAIT;
if (delay > 1) {
while (delay > 0) {
ui_screen_boot_wait(delay);
hal_delay(1000);
delay--;
}
} else if (delay == 1) {
hal_delay(1000);
}

if ((vhdr.vtrust & VTRUST_CLICK) == 0) {
ui_screen_boot_click();
}

ui_screen_boot_empty(false);
ensure(dont_optimize_out_true * (firmware_present == firmware_present_backup),
NULL);
if (sectrue == firmware_present) {
firmware_jump_fn = real_jump_to_firmware;
}

ensure_compatible_settings();

// mpu_config_firmware();
// jump_to_unprivileged(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);

mpu_config_off();
jump_to(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);
firmware_jump_fn();

return 0;
}
Expand Down

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