trezor-firmware/bootloader/usb.c

/*
 * 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/usb/usbd.h>
#include <libopencm3/stm32/flash.h>

#include <string.h>

#include "buttons.h"
#include "bootloader.h"
#include "oled.h"
#include "rng.h"
#include "usb.h"
#include "layout.h"
#include "util.h"
#include "signatures.h"
#include "sha2.h"
#include "ecdsa.h"
#include "secp256k1.h"
#include "memzero.h"
#include "memory.h"

#include "usb21_standard.h"
#include "webusb.h"
#include "winusb.h"

#include "usb_desc.h"
#include "usb_send.h"
#include "usb_erase.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 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];
	SHA256_CTX ctx;
	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_wait_for_last_operation();
	flash_clear_status_flags();
	flash_unlock();
	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_wait_for_last_operation();
	flash_lock();

	// 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++;
}

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;

	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;
				layoutDialog(&bmp_icon_ok, NULL, NULL, NULL, "Device", "successfully wiped.", NULL, "You may now", "unplug your TREZOR.", NULL);
				send_msg_success(dev);
			} else {
				flash_state = STATE_END;
				layoutDialog(&bmp_icon_warning, NULL, NULL, NULL, "Device wipe", "aborted.", NULL, "You may now", "unplug your TREZOR.", NULL);
				send_msg_failure(dev);
			}
			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);
					old_was_signed = signatures_new_ok(hdr, NULL) & check_firmware_hashes(hdr);
				} else if (firmware_present_old()) {
					old_was_signed = signatures_old_ok();
				} else {
					old_was_signed = SIG_FAIL;
				}
				erase_code_progress();
				send_msg_success(dev);
				flash_state = STATE_FLASHSTART;
			} else {
				send_msg_failure(dev);
				flash_state = STATE_END;
				layoutDialog(&bmp_icon_warning, NULL, NULL, NULL, "Firmware installation", "aborted.", NULL, "You may now", "unplug your TREZOR.", NULL);
			}
			return;
		}
		return;
	}

	if (flash_state == STATE_FLASHSTART) {
		if (msg_id == 0x0007) {		// FirmwareUpload message (id 7)
			if (buf[9] != 0x0a) { // invalid contents
				send_msg_failure(dev);
				flash_state = STATE_END;
				show_halt("Error installing", "firmware.");
				return;
			}
			// read payload length
			const uint8_t *p = buf + 10;
			flash_len = readprotobufint(&p);
			if (flash_len <= FLASH_FWHEADER_LEN) { // firmware is too small
				send_msg_failure(dev);
				flash_state = STATE_END;
				show_halt("Firmware is too small.", NULL);
				return;
			}
			if (flash_len > FLASH_FWHEADER_LEN + FLASH_APP_LEN) { // firmware is too big
				send_msg_failure(dev);
				flash_state = STATE_END;
				show_halt("Firmware is too big.", NULL);
				return;
			}
			// check firmware magic
			if (memcmp(p, &FIRMWARE_MAGIC_NEW, 4) != 0) {
				send_msg_failure(dev);
				flash_state = STATE_END;
				show_halt("Wrong firmware header.", NULL);
				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) {
				w = (w >> 8) | (*p << 24); // assign byte to first byte of uint32_t w
				wi++;
				if (wi == 4) {
					FW_HEADER[flash_pos / 4] = w;
					flash_pos += 4;
					wi = 0;
				}
				p++;
			}
			return;
		}
		return;
	}

	if (flash_state == STATE_FLASHING) {
		if (buf[0] != '?') {	// invalid contents
			send_msg_failure(dev);
			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) {
			w = (w >> 8) | (*p << 24); // assign byte to first byte of uint32_t w
			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;
			if (SIG_OK != signatures_new_ok(hdr, NULL)) {
				send_msg_buttonrequest_firmwarecheck(dev);
				return;
			}
		} else {
			return;
		}
	}

	if (flash_state == STATE_CHECK) {

		// use the firmware header from RAM
		const image_header *hdr = (const image_header *)FW_HEADER;

		bool hash_check_ok;
		// show fingerprint of unsigned firmware
		if (SIG_OK != signatures_new_ok(hdr, NULL)) {
			if (msg_id != 0x001B) {	// ButtonAck message (id 27)
				return;
			}
			uint8_t hash[32];
			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 != old_was_signed || SIG_OK != signatures_new_ok(hdr, NULL) || SIG_OK != check_firmware_hashes(hdr)) {
			// erase storage
			erase_storage();
			// check erasure
			uint8_t hash[32];
			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);
				show_halt("Error installing", "firmware.");
				return;
			}
		}
		flash_wait_for_last_operation();
		flash_clear_status_flags();
		flash_unlock();
		// 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_wait_for_last_operation();
		flash_lock();

		flash_state = STATE_END;
		if (hash_check_ok) {
			layoutDialog(&bmp_icon_ok, NULL, NULL, NULL, "New firmware", "successfully installed.", NULL, "You may now", "unplug your TREZOR.", NULL);
			send_msg_success(dev);
			shutdown();
		} 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);
			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[] = {
	(const struct usb_device_capability_descriptor*)&webusb_platform_capability_descriptor,
};

static const struct usb_bos_descriptor bos_descriptor = {
	.bLength = USB_DT_BOS_SIZE,
	.bDescriptorType = USB_DT_BOS,
	.bNumDeviceCaps = sizeof(capabilities)/sizeof(capabilities[0]),
	.capabilities = capabilities
};

static void usbInit(void)
{
	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, &bos_descriptor);
	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();
	for (;;) {
		usbd_poll(usbd_dev);
		if (!firmware_present && (flash_state == STATE_READY || flash_state == STATE_OPEN)) {
			checkButtons();
		}
	}
}