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trezor-firmware/legacy/bootloader/usb.c
tychovrahe daf566a260 fix(legacy): fix v2 signature validation
2023-02-06 10:03:27 +01:00

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/*
* This file is part of the Trezor project, https://trezor.io/
*
* Copyright (C) 2014 Pavol Rusnak <stick@satoshilabs.com>
*
* This library is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This library 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libopencm3/stm32/flash.h>
#include <libopencm3/usb/usbd.h>
#include <vendor/libopencm3/include/libopencmsis/core_cm3.h>
#include <string.h>
#include "bootloader.h"
#include "buttons.h"
#include "ecdsa.h"
#include "fw_signatures.h"
#include "layout.h"
#include "memory.h"
#include "memzero.h"
#include "oled.h"
#include "rng.h"
#include "secbool.h"
#include "secp256k1.h"
#include "sha2.h"
#include "usb.h"
#include "util.h"
#include "usb21_standard.h"
#include "webusb.h"
#include "winusb.h"
#include "usb_desc.h"
#include "usb_send.h"
enum {
STATE_READY,
STATE_OPEN,
STATE_FLASHSTART,
STATE_FLASHING,
STATE_CHECK,
STATE_END,
};
static uint32_t flash_pos = 0, flash_len = 0;
static uint32_t chunk_idx = 0;
static char flash_state = STATE_READY;
static uint32_t FW_HEADER[FLASH_FWHEADER_LEN / sizeof(uint32_t)];
static uint32_t FW_CHUNK[FW_CHUNK_SIZE / sizeof(uint32_t)];
static void flash_enter(void) {
flash_wait_for_last_operation();
flash_clear_status_flags();
flash_unlock();
}
static void flash_exit(void) {
flash_wait_for_last_operation();
flash_lock();
}
#include "usb_erase.h"
static void check_and_write_chunk(void) {
uint32_t offset = (chunk_idx == 0) ? FLASH_FWHEADER_LEN : 0;
uint32_t chunk_pos = flash_pos % FW_CHUNK_SIZE;
if (chunk_pos == 0) {
chunk_pos = FW_CHUNK_SIZE;
}
uint8_t hash[32] = {0};
SHA256_CTX ctx = {0};
sha256_Init(&ctx);
sha256_Update(&ctx, (const uint8_t *)FW_CHUNK + offset, chunk_pos - offset);
if (chunk_pos < 64 * 1024) {
// pad with FF
for (uint32_t i = chunk_pos; i < 64 * 1024; i += 4) {
sha256_Update(&ctx, (const uint8_t *)"\xFF\xFF\xFF\xFF", 4);
}
}
sha256_Final(&ctx, hash);
const image_header *hdr = (const image_header *)FW_HEADER;
// invalid chunk sent
if (0 != memcmp(hash, hdr->hashes + chunk_idx * 32, 32)) {
// erase storage
erase_storage();
flash_state = STATE_END;
show_halt("Error installing", "firmware.");
return;
}
flash_enter();
for (uint32_t i = offset / sizeof(uint32_t); i < chunk_pos / sizeof(uint32_t);
i++) {
flash_program_word(
FLASH_FWHEADER_START + chunk_idx * FW_CHUNK_SIZE + i * sizeof(uint32_t),
FW_CHUNK[i]);
}
flash_exit();
// all done
if (flash_len == flash_pos) {
// check remaining chunks if any
for (uint32_t i = chunk_idx + 1; i < 16; i++) {
// hash should be empty if the chunk is unused
if (!mem_is_empty(hdr->hashes + 32 * i, 32)) {
flash_state = STATE_END;
show_halt("Error installing", "firmware.");
return;
}
}
}
memzero(FW_CHUNK, sizeof(FW_CHUNK));
chunk_idx++;
}
// read protobuf integer and advance pointer
static secbool readprotobufint(const uint8_t **ptr, uint32_t *result) {
*result = 0;
for (int i = 0; i <= 3; ++i) {
*result += (**ptr & 0x7F) << (7 * i);
if ((**ptr & 0x80) == 0) {
(*ptr)++;
return sectrue;
}
(*ptr)++;
}
if (**ptr & 0xF0) {
// result does not fit into uint32_t
*result = 0;
// skip over the rest of the integer
while (**ptr & 0x80) (*ptr)++;
(*ptr)++;
return secfalse;
}
*result += (uint32_t)(**ptr) << 28;
(*ptr)++;
return sectrue;
}
/** Reverse-endian version comparison
*
* Versions are loaded from the header via a packed struct image_header. A
* version is represented as a single uint32_t. Arm is natively little-endian,
* but the version is actually stored as four bytes in major-minor-patch-build
* order. This function implements `cmp` with "lowest" byte first.
*/
static int version_compare(const uint32_t vera, const uint32_t verb) {
int a, b; // signed temp values so that we can safely return a signed result
a = vera & 0xFF;
b = verb & 0xFF;
if (a != b) return a - b;
a = (vera >> 8) & 0xFF;
b = (verb >> 8) & 0xFF;
if (a != b) return a - b;
a = (vera >> 16) & 0xFF;
b = (verb >> 16) & 0xFF;
if (a != b) return a - b;
a = (vera >> 24) & 0xFF;
b = (verb >> 24) & 0xFF;
return a - b;
}
static int should_keep_storage(int old_was_signed,
uint32_t fix_version_current) {
// if the current firmware is unsigned, always erase storage
if (SIG_OK != old_was_signed) return SIG_FAIL;
const image_header *new_hdr = (const image_header *)FW_HEADER;
// new header must be signed by v3 signmessage/verifymessage scheme
if (SIG_OK != signatures_ok(new_hdr, NULL, sectrue)) return SIG_FAIL;
// if the new header hashes don't match flash contents, erase storage
if (SIG_OK != check_firmware_hashes(new_hdr)) return SIG_FAIL;
// if the current fix_version is higher than the new one, erase storage
if (version_compare(new_hdr->version, fix_version_current) < 0) {
return SIG_FAIL;
}
return SIG_OK;
}
static void rx_callback(usbd_device *dev, uint8_t ep) {
(void)ep;
static uint16_t msg_id = 0xFFFF;
static uint8_t buf[64] __attribute__((aligned(4)));
static uint32_t w;
static int wi;
static int old_was_signed;
static uint32_t fix_version_current = 0xffffffff;
if (usbd_ep_read_packet(dev, ENDPOINT_ADDRESS_OUT, buf, 64) != 64) return;
if (flash_state == STATE_END) {
return;
}
if (flash_state == STATE_READY || flash_state == STATE_OPEN ||
flash_state == STATE_FLASHSTART || flash_state == STATE_CHECK) {
if (buf[0] != '?' || buf[1] != '#' ||
buf[2] != '#') { // invalid start - discard
return;
}
// struct.unpack(">HL") => msg, size
msg_id = (buf[3] << 8) + buf[4];
}
if (flash_state == STATE_READY || flash_state == STATE_OPEN) {
if (msg_id == 0x0000) { // Initialize message (id 0)
send_msg_features(dev);
flash_state = STATE_OPEN;
return;
}
if (msg_id == 0x0037) { // GetFeatures message (id 55)
send_msg_features(dev);
return;
}
if (msg_id == 0x0001) { // Ping message (id 1)
send_msg_success(dev);
return;
}
if (msg_id == 0x0005) { // WipeDevice message (id 5)
layoutDialog(&bmp_icon_question, "Cancel", "Confirm", NULL,
"Do you really want to", "wipe the device?", NULL,
"All data will be lost.", NULL, NULL);
bool but = get_button_response();
if (but) {
erase_storage_code_progress();
flash_state = STATE_END;
show_unplug("Device", "successfully wiped.");
send_msg_success(dev);
} else {
flash_state = STATE_END;
show_unplug("Device wipe", "aborted.");
send_msg_failure(dev, 4); // Failure_ActionCancelled
}
return;
}
if (msg_id != 0x0006) {
send_msg_failure(dev, 1); // Failure_UnexpectedMessage
return;
}
}
if (flash_state == STATE_OPEN) {
if (msg_id == 0x0006) { // FirmwareErase message (id 6)
bool proceed = false;
if (firmware_present_new()) {
layoutDialog(&bmp_icon_question, "Abort", "Continue", NULL,
"Install new", "firmware?", NULL, "Never do this without",
"your recovery card!", NULL);
proceed = get_button_response();
} else {
proceed = true;
}
if (proceed) {
// check whether the current firmware is signed (old or new method)
if (firmware_present_new()) {
const image_header *hdr =
(const image_header *)FLASH_PTR(FLASH_FWHEADER_START);
// previous firmware was signed either v2 or v3 scheme
old_was_signed =
signatures_match(hdr, NULL) & check_firmware_hashes(hdr);
fix_version_current = hdr->fix_version;
} else {
old_was_signed = SIG_FAIL;
fix_version_current = 0xffffffff;
}
erase_code_progress();
send_msg_success(dev);
flash_state = STATE_FLASHSTART;
} else {
send_msg_failure(dev, 4); // Failure_ActionCancelled
flash_state = STATE_END;
show_unplug("Firmware installation", "aborted.");
}
return;
}
send_msg_failure(dev, 1); // Failure_UnexpectedMessage
return;
}
if (flash_state == STATE_FLASHSTART) {
if (msg_id == 0x0007) { // FirmwareUpload message (id 7)
if (buf[9] != 0x0a) { // invalid contents
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Error installing", "firmware.");
return;
}
// read payload length
const uint8_t *p = buf + 10;
if (readprotobufint(&p, &flash_len) != sectrue) { // integer too large
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Firmware is", "too big.");
return;
}
if (flash_len <= FLASH_FWHEADER_LEN) { // firmware is too small
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Firmware is", "too small.");
return;
}
if (flash_len >
FLASH_FWHEADER_LEN + FLASH_APP_LEN) { // firmware is too big
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Firmware is", "too big.");
return;
}
// check firmware magic
if (memcmp(p, &FIRMWARE_MAGIC_NEW, 4) != 0) {
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Wrong firmware", "header.");
return;
}
memzero(FW_HEADER, sizeof(FW_HEADER));
memzero(FW_CHUNK, sizeof(FW_CHUNK));
flash_state = STATE_FLASHING;
flash_pos = 0;
chunk_idx = 0;
w = 0;
while (p < buf + 64) {
// assign byte to first byte of uint32_t w
w = (w >> 8) | (((uint32_t)*p) << 24);
wi++;
if (wi == 4) {
FW_HEADER[flash_pos / 4] = w;
flash_pos += 4;
wi = 0;
}
p++;
}
return;
}
send_msg_failure(dev, 1); // Failure_UnexpectedMessage
return;
}
if (flash_state == STATE_FLASHING) {
if (buf[0] != '?') { // invalid contents
send_msg_failure(dev, 9); // Failure_ProcessError
flash_state = STATE_END;
show_halt("Error installing", "firmware.");
return;
}
static uint8_t flash_anim = 0;
if (flash_anim % 32 == 4) {
layoutProgress("INSTALLING ... Please wait",
1000 * flash_pos / flash_len);
}
flash_anim++;
const uint8_t *p = buf + 1;
while (p < buf + 64 && flash_pos < flash_len) {
// assign byte to first byte of uint32_t w
w = (w >> 8) | (((uint32_t)*p) << 24);
wi++;
if (wi == 4) {
if (flash_pos < FLASH_FWHEADER_LEN) {
FW_HEADER[flash_pos / 4] = w;
} else {
FW_CHUNK[(flash_pos % FW_CHUNK_SIZE) / 4] = w;
}
flash_pos += 4;
wi = 0;
// finished the whole chunk
if (flash_pos % FW_CHUNK_SIZE == 0) {
check_and_write_chunk();
}
}
p++;
}
// flashing done
if (flash_pos == flash_len) {
// flush remaining data in the last chunk
if (flash_pos % FW_CHUNK_SIZE > 0) {
check_and_write_chunk();
}
flash_state = STATE_CHECK;
const image_header *hdr = (const image_header *)FW_HEADER;
// allow only v3 signmessage/verifymessage signature for new FW
if (SIG_OK != signatures_ok(hdr, NULL, sectrue)) {
send_msg_buttonrequest_firmwarecheck(dev);
return;
}
} else {
return;
}
}
if (flash_state == STATE_CHECK) {
// use the firmware header from RAM
image_header *hdr = (image_header *)FW_HEADER;
bool hash_check_ok;
// show fingerprint of unsigned firmware
// allow only v3 signmessage/verifymessage signatures
if (SIG_OK != signatures_ok(hdr, NULL, sectrue)) {
// clear invalid signatures
hdr->sigindex1 = 0;
hdr->sigindex2 = 0;
hdr->sigindex3 = 0;
memset(hdr->sig1, 0, sizeof(hdr->sig1));
memset(hdr->sig2, 0, sizeof(hdr->sig2));
memset(hdr->sig3, 0, sizeof(hdr->sig3));
if (msg_id != 0x001B) { // ButtonAck message (id 27)
return;
}
uint8_t hash[32] = {0};
compute_firmware_fingerprint(hdr, hash);
layoutFirmwareFingerprint(hash);
hash_check_ok = get_button_response();
} else {
hash_check_ok = true;
}
layoutProgress("INSTALLING ... Please wait", 1000);
// wipe storage if:
// 1) old firmware was unsigned or not present
// 2) signatures are not OK
// 3) hashes are not OK
if (SIG_OK != should_keep_storage(old_was_signed, fix_version_current)) {
// erase storage
erase_storage();
// check erasure
uint8_t hash[32] = {0};
sha256_Raw(FLASH_PTR(FLASH_STORAGE_START), FLASH_STORAGE_LEN, hash);
if (memcmp(hash,
"\x2d\x86\x4c\x0b\x78\x9a\x43\x21\x4e\xee\x85\x24\xd3\x18\x20"
"\x75\x12\x5e\x5c\xa2\xcd\x52\x7f\x35\x82\xec\x87\xff\xd9\x40"
"\x76\xbc",
32) != 0) {
send_msg_failure(dev, 9); // Failure_ProcessError
show_halt("Error installing", "firmware.");
return;
}
}
flash_enter();
// write firmware header only when hash was confirmed
if (hash_check_ok) {
for (size_t i = 0; i < FLASH_FWHEADER_LEN / sizeof(uint32_t); i++) {
flash_program_word(FLASH_FWHEADER_START + i * sizeof(uint32_t),
FW_HEADER[i]);
}
} else {
for (size_t i = 0; i < FLASH_FWHEADER_LEN / sizeof(uint32_t); i++) {
flash_program_word(FLASH_FWHEADER_START + i * sizeof(uint32_t), 0);
}
}
flash_exit();
flash_state = STATE_END;
if (hash_check_ok) {
send_msg_success(dev);
__disable_irq();
// wait 3 seconds
char line[] = "will be restarted in _ s.";
for (int i = 3; i > 0; i--) {
line[21] = '0' + i;
layoutDialog(&bmp_icon_ok, NULL, NULL, NULL, "New firmware",
"successfully installed.", NULL, "Your Trezor", line,
NULL);
delay(30000 * 1000);
}
scb_reset_system();
} else {
layoutDialog(&bmp_icon_warning, NULL, NULL, NULL, "Firmware installation",
"aborted.", NULL, "You need to repeat", "the procedure with",
"the correct firmware.");
send_msg_failure(dev, 9); // Failure_ProcessError
shutdown();
}
return;
}
}
static void set_config(usbd_device *dev, uint16_t wValue) {
(void)wValue;
usbd_ep_setup(dev, ENDPOINT_ADDRESS_IN, USB_ENDPOINT_ATTR_INTERRUPT, 64, 0);
usbd_ep_setup(dev, ENDPOINT_ADDRESS_OUT, USB_ENDPOINT_ATTR_INTERRUPT, 64,
rx_callback);
}
static usbd_device *usbd_dev;
static uint8_t usbd_control_buffer[256] __attribute__((aligned(2)));
static const struct usb_device_capability_descriptor *capabilities_landing[] = {
(const struct usb_device_capability_descriptor
*)&webusb_platform_capability_descriptor_landing,
};
static const struct usb_device_capability_descriptor
*capabilities_no_landing[] = {
(const struct usb_device_capability_descriptor
*)&webusb_platform_capability_descriptor_no_landing,
};
static const struct usb_bos_descriptor bos_descriptor_landing = {
.bLength = USB_DT_BOS_SIZE,
.bDescriptorType = USB_DT_BOS,
.bNumDeviceCaps =
sizeof(capabilities_landing) / sizeof(capabilities_landing[0]),
.capabilities = capabilities_landing};
static const struct usb_bos_descriptor bos_descriptor_no_landing = {
.bLength = USB_DT_BOS_SIZE,
.bDescriptorType = USB_DT_BOS,
.bNumDeviceCaps =
sizeof(capabilities_no_landing) / sizeof(capabilities_no_landing[0]),
.capabilities = capabilities_no_landing};
static void usbInit(bool firmware_present) {
usbd_dev = usbd_init(&otgfs_usb_driver, &dev_descr, &config, usb_strings,
sizeof(usb_strings) / sizeof(const char *),
usbd_control_buffer, sizeof(usbd_control_buffer));
usbd_register_set_config_callback(usbd_dev, set_config);
usb21_setup(usbd_dev, firmware_present ? &bos_descriptor_no_landing
: &bos_descriptor_landing);
webusb_setup(usbd_dev, "trezor.io/start");
winusb_setup(usbd_dev, USB_INTERFACE_INDEX_MAIN);
}
static void checkButtons(void) {
static bool btn_left = false, btn_right = false, btn_final = false;
if (btn_final) {
return;
}
uint16_t state = gpio_port_read(BTN_PORT);
if ((state & (BTN_PIN_YES | BTN_PIN_NO)) != (BTN_PIN_YES | BTN_PIN_NO)) {
if ((state & BTN_PIN_NO) != BTN_PIN_NO) {
btn_left = true;
}
if ((state & BTN_PIN_YES) != BTN_PIN_YES) {
btn_right = true;
}
}
if (btn_left) {
oledBox(0, 0, 3, 3, true);
}
if (btn_right) {
oledBox(OLED_WIDTH - 4, 0, OLED_WIDTH - 1, 3, true);
}
if (btn_left || btn_right) {
oledRefresh();
}
if (btn_left && btn_right) {
btn_final = true;
}
}
void usbLoop(void) {
bool firmware_present = firmware_present_new();
usbInit(firmware_present);
for (;;) {
usbd_poll(usbd_dev);
if (!firmware_present &&
(flash_state == STATE_READY || flash_state == STATE_OPEN)) {
checkButtons();
}
}
}
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