trezor-firmware/firmware/recovery.c

/*
 * This file is part of the TREZOR project, https://trezor.io/
 *
 * Copyright (C) 2014 Pavol Rusnak <stick@satoshilabs.com>
 * Copyright (C) 2016 Jochen Hoenicke <hoenicke@gmail.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 <ctype.h>
#include "recovery.h"
#include "fsm.h"
#include "storage.h"
#include "layout2.h"
#include "protect.h"
#include "messages.h"
#include "rng.h"
#include "bip39.h"
#include "oled.h"
#include "usb.h"
#include "gettext.h"
#include "recovery-table.h"
#include "memzero.h"
#include "messages.pb.h"

/* number of words expected in the new seed */
static uint32_t word_count;

/* recovery mode:
 * 0: not recovering
 * 1: recover by scrambled plain text words
 * 2: recover by matrix entry
 */
static int awaiting_word = 0;

/* True if we should not write anything back to storage
 * (can be used for testing seed for correctness).
 */
static bool dry_run;

/* True if we should check that seed corresponds to bip39.
 */
static bool enforce_wordlist;

/* For scrambled recovery Trezor may ask for faked words if
 * seed is short.  This contains the fake word.
 */
static char fake_word[12];

/* Word position in the seed that we are currently asking for.
 * This is 0 if we ask for a fake word.  Only for scrambled recovery.
 */
static uint32_t word_pos;

/* Scrambled recovery:  How many words has the user already entered.
 * Matrix recovery: How many digits has the user already entered.
 */
static uint32_t word_index;

/* Order in which we ask for the words.  It holds that
 * word_order[word_index] == word_pos.  Only for scrambled recovery.
 */
static char word_order[24];

/* The recovered seed.  This is filled during the recovery process.
 */
static char words[24][12];

/* The "pincode" of the current word.  This is basically the "pin"
 * that the user would have entered for the current word if the words
 * were displayed in alphabetical order.  Note that it is base 9, not
 * base 10.  Only for matrix recovery.
 */
static uint16_t word_pincode;

/* The pinmatrix currently displayed on screen.
 * Only for matrix recovery.
 */
static uint8_t word_matrix[9];

/* The words are stored in two tables.
 *
 * The low bits of the first table (TABLE1) store the index into the
 * second table, for each of the 81 choices for the first two levels
 * of the matrix.  The final entry points to the final entry of the
 * second table.  The difference TABLE1(idx+1)-TABLE1(idx) gives the
 * number of choices for the third level.  The value
 * TABLE2(TABLE1(idx)) gives the index of the first word in the range
 * and TABLE2(TABLE1(idx+1))-1 gives the index of the last word.
 *
 * The low bits of the second table (TABLE2) store the index into the
 * word list for each of the choices for the first three levels.  The
 * final entry stores the value 2048 (number of bip39 words).  table.
 * The difference TABLE2(idx+1)-TABLE2(idx) gives the number of
 * choices for the last level.  The value TABLE2(idx) gives the index
 * of the first word in the range and TABLE2(idx)-1 gives the index of
 * the last word.
 *
 * The high bits in each table is the "prefix length", i.e. the number
 * of significant letters for the corresponding choice.  There is no
 * prefix length or table for the very first level, as the prefix length
 * is always one and there are always nine choices on the second level.
 */
#define MASK_IDX(x) ((x) & 0xfff)
#define TABLE1(x) MASK_IDX(word_table1[x])
#define TABLE2(x) MASK_IDX(word_table2[x])

/* Helper function to format a two digit number.
 * Parameter dest is buffer containing the string. It should already
 * start with "##th".  The number is written in place.
 * Parameter number gives the number that we should format.
 */
static void format_number(char *dest, int number) {
	if (number < 10) {
		dest[0] = ' ';
	} else {
		dest[0] = '0' + number / 10;
	}
	dest[1] = '0' + number % 10;
	if (number == 1 || number == 21) {
		dest[2] = 's'; dest[3] = 't';
	} else if (number == 2 || number == 22) {
		dest[2] = 'n'; dest[3] = 'd';
	} else if (number == 3 || number == 23) {
		dest[2] = 'r'; dest[3] = 'd';
	}
}

/* Send a request for a new word/matrix code to the PC.
 */
static void recovery_request(void) {
	WordRequest resp;
	memset(&resp, 0, sizeof(WordRequest));
	resp.has_type = true;
	resp.type = awaiting_word == 1 ? WordRequestType_WordRequestType_Plain
		: (word_index % 4 == 3) ? WordRequestType_WordRequestType_Matrix6
		: WordRequestType_WordRequestType_Matrix9;
	msg_write(MessageType_MessageType_WordRequest, &resp);
}

/* Called when the last word was entered.
 * Check mnemonic and send success/failure.
 */
static void recovery_done(void) {
	char new_mnemonic[241] = {0}; // TODO: remove constant

	strlcpy(new_mnemonic, words[0], sizeof(new_mnemonic));
	for (uint32_t i = 1; i < word_count; i++) {
		strlcat(new_mnemonic, " ", sizeof(new_mnemonic));
		strlcat(new_mnemonic, words[i], sizeof(new_mnemonic));
	}
	if (!enforce_wordlist || mnemonic_check(new_mnemonic)) {
		// New mnemonic is valid.
		if (!dry_run) {
			// Update mnemonic on storage.
			storage_setMnemonic(new_mnemonic);
			memzero(new_mnemonic, sizeof(new_mnemonic));
			if (!enforce_wordlist) {
				// not enforcing => mark storage as imported
				storage_setImported(true);
			}
			storage_update();
			fsm_sendSuccess(_("Device recovered"));
		} else {
			// Inform the user about new mnemonic correctness (as well as whether it is the same as the current one).
			bool match = (storage_isInitialized() && storage_containsMnemonic(new_mnemonic));
			memzero(new_mnemonic, sizeof(new_mnemonic));
			if (match) {
				layoutDialog(&bmp_icon_ok, NULL, _("Confirm"), NULL,
					_("The seed is valid"),
					_("and MATCHES"),
					_("the one in the device."), NULL, NULL, NULL);
				protectButton(ButtonRequestType_ButtonRequest_Other, true);
				fsm_sendSuccess(_("The seed is valid and matches the one in the device"));
			} else {
				layoutDialog(&bmp_icon_error, NULL, _("Confirm"), NULL,
					_("The seed is valid"),
					_("but does NOT MATCH"),
					_("the one in the device."), NULL, NULL, NULL);
				protectButton(ButtonRequestType_ButtonRequest_Other, true);
				fsm_sendFailure(FailureType_Failure_DataError,
					_("The seed is valid but does not match the one in the device"));
			}
		}
	} else {
		// New mnemonic is invalid.
		memzero(new_mnemonic, sizeof(new_mnemonic));
		if (!dry_run) {
			session_clear(true);
		} else {
			layoutDialog(&bmp_icon_error, NULL, _("Confirm"), NULL,
				_("The seed is"), _("INVALID!"), NULL, NULL, NULL, NULL);
			protectButton(ButtonRequestType_ButtonRequest_Other, true);
		}
		fsm_sendFailure(FailureType_Failure_DataError, _("Invalid seed, are words in correct order?"));
	}
	awaiting_word = 0;
	layoutHome();
}

/* Helper function for matrix recovery:
 * Formats a string describing the word range from first to last where
 * prefixlen gives the number of characters in first and last that are
 * significant, i.e. the word before first or the word after last differ
 * exactly at the prefixlen-th character.
 *
 * Invariants:
 *  memcmp("first - 1", first, prefixlen) != 0
 *  memcmp(last, "last + 1", prefixlen) != 0
 *  first[prefixlen-2] == last[prefixlen-2]  except for range WI-Z.
 */
static void add_choice(char choice[12], int prefixlen, const char *first, const char *last) {
	// assert 1 <= prefixlen <= 4
	char *dest = choice;
	for (int i = 0; i < prefixlen; i++) {
		*dest++ = toupper((int) first[i]);
	}
	if (first[0] != last[0]) {
		/* special case WI-Z; also used for T-Z, etc. */
		*dest++ = '-';
		*dest++ = toupper((int) last[0]);
	} else if (last[prefixlen-1] == first[prefixlen-1]) {
		/* single prefix */
	} else if (prefixlen < 3) {
		/* AB-AC, etc. */
		*dest++ = '-';
		for (int i = 0; i < prefixlen; i++) {
			*dest++ = toupper((int) last[i]);
		}
	} else {
		/* RE[A-M] etc. */
		/* remove last and replace with space */
		dest[-1] = ' ';
		if (first[prefixlen - 1]) {
			/* handle special case: CAN[-D] */
			*dest++ = toupper((int)first[prefixlen - 1]);
		}
		*dest++ = '-';
		*dest++ = toupper((int) last[prefixlen - 1]);
	}
	*dest++ = 0;
}

/* Helper function for matrix recovery:
 * Display the recovery matrix given in choices.  If twoColumn is set
 * use 2x3 layout, otherwise 3x3 layout.  Also generates a random
 * scrambling and stores it in word_matrix.
 */
static void display_choices(bool twoColumn, char choices[9][12], int num)
{
	const int nColumns = twoColumn ? 2 : 3;
	const int displayedChoices = nColumns * 3;
	for (int i = 0; i < displayedChoices; i++) {
		word_matrix[i] = i;
	}
	/* scramble matrix */
	random_permute((char*)word_matrix, displayedChoices);

	if (word_index % 4 == 0) {
		char desc[] = "##th word";
		int nr = (word_index / 4) + 1;
		format_number(desc, nr);
		layoutDialogSwipe(&bmp_icon_info, NULL, NULL, NULL, _("Please enter the"), (nr < 10 ? desc + 1 : desc), _("of your mnemonic"), NULL, NULL, NULL);
	} else {
		oledBox(0, 27, 127, 63, false);
	}

	for (int row = 0; row < 3; row ++) {
		int y = 55 - row * 11;
		for (int col = 0; col < nColumns; col++) {
			int x = twoColumn ? 64 * col + 32 : 42 * col + 22;
			int choice = word_matrix[nColumns*row + col];
			const char *text = choice < num ? choices[choice] : "-";
			oledDrawString(x - oledStringWidth(text, FONT_STANDARD)/2, y, text, FONT_STANDARD);
			if (twoColumn) {
				oledInvert(x - 32 + 1, y - 1, x - 32 + 63 - 1, y + 8);
			} else {
				oledInvert(x - 22 + 1, y - 1, x - 22 + 41 - 1, y + 8);
			}
		}
	}
	oledRefresh();

	/* avoid picking out of range numbers */
	for (int i = 0; i < displayedChoices; i++) {
		if (word_matrix[i] >= num)
			word_matrix[i] = 0;
	}
	/* two column layout: middle column = right column */
	if (twoColumn) {
		static const uint8_t twolayout[9] = { 0, 1, 1, 2, 3, 3, 4, 5, 5 };
		for (int i = 8; i >= 2; i--) {
			word_matrix[i] = word_matrix[twolayout[i]];
		}
	}
}

/* Helper function for matrix recovery:
 * Generates a new matrix and requests the next pin.
 */
static void next_matrix(void) {
	const char * const *wl = mnemonic_wordlist();
	char word_choices[9][12];
	uint32_t idx, num;
	bool last = (word_index % 4) == 3;

	/* Build the matrix:
	 * num: number of choices
	 * word_choices[][]: the strings containing the choices
	 */
	switch (word_index % 4) {
	case 3:
		/* last level: show up to six words */
		/* idx: index in table2 for the entered choice. */
		/* first: the first word. */
		/* num: the number of words to choose from. */
		idx = TABLE1(word_pincode / 9) + word_pincode % 9;
		const uint32_t first = TABLE2(idx);
		num = TABLE2(idx + 1) - first;
		for (uint32_t i = 0; i < num; i++) {
			strlcpy(word_choices[i], wl[first + i], sizeof(word_choices[i]));
		}
		break;

	case 2:
		/* third level: show up to nine ranges (using table2) */
		/* idx: first index in table2 corresponding to pin code. */
		/* num: the number of choices. */
		idx = TABLE1(word_pincode);
		num = TABLE1(word_pincode + 1) - idx;
		for (uint32_t i = 0; i < num; i++) {
			add_choice(word_choices[i], (word_table2[idx + i] >> 12),
					   wl[TABLE2(idx + i)],
					   wl[TABLE2(idx + i + 1) - 1]);
		}
		break;

	case 1:
		/* second level: exactly nine ranges (using table1) */
		/* idx: first index in table1 corresponding to pin code. */
		/* num: the number of choices. */
		idx = word_pincode * 9;
		num = 9;
		for (uint32_t i = 0; i < num; i++) {
			add_choice(word_choices[i], (word_table1[idx + i] >> 12),
					   wl[TABLE2(TABLE1(idx + i))],
					   wl[TABLE2(TABLE1(idx + i + 1)) - 1]);
		}
		break;

	case 0:
		/* first level: exactly nine ranges */
		/* num: the number of choices. */
		num = 9;
		for (uint32_t i = 0; i < num; i++) {
			add_choice(word_choices[i], 1,
					   wl[TABLE2(TABLE1(9*i))],
					   wl[TABLE2(TABLE1(9*(i+1)))-1]);
		}
		break;
	}
	display_choices(last, word_choices, num);

	recovery_request();
}

/* Function called when a digit was entered by user.
 * digit: ascii code of the entered digit ('1'-'9') or
 * '\x08' for backspace.
 */
static void recovery_digit(const char digit) {
	if (digit == 8) {
		/* backspace: undo */
		if ((word_index % 4) == 0) {
			/* undo complete word */
			if (word_index > 0)
				word_index -= 4;
		} else {
			word_index--;
			word_pincode /= 9;
		}
		next_matrix();
		return;
	}

	if (digit < '1' || digit > '9') {
		recovery_request();
		return;
	}

	int choice = word_matrix[digit - '1'];
	if ((word_index % 4) == 3) {
		/* received final word */

		/* Mark the chosen word for 250 ms */
		int y = 54 - ((digit - '1') / 3) * 11;
		int x = 64 * (((digit - '1') % 3) > 0);
		oledInvert(x + 1, y, x + 62, y + 9);
		oledRefresh();
		usbTiny(1);
		usbSleep(250);
		usbTiny(0);

		/* index of the chosen word */
		int idx = TABLE2(TABLE1(word_pincode / 9) + (word_pincode % 9)) + choice;
		uint32_t widx = word_index / 4;

		word_pincode = 0;
		strlcpy(words[widx], mnemonic_wordlist()[idx], sizeof(words[widx]));
		if (widx + 1 == word_count) {
			recovery_done();
			return;
		}
		/* next word */
	} else {
		word_pincode = word_pincode * 9 + choice;
	}
	word_index++;
	next_matrix();
}

/* Helper function for scrambled recovery:
 * Ask the user for the next word.
 */
void next_word(void) {
	word_pos = word_order[word_index];
	if (word_pos == 0) {
		const char * const *wl = mnemonic_wordlist();
		strlcpy(fake_word, wl[random_uniform(2048)], sizeof(fake_word));
		layoutDialogSwipe(&bmp_icon_info, NULL, NULL, NULL, _("Please enter the word"), NULL, fake_word, NULL, _("on your computer"), NULL);
	} else {
		fake_word[0] = 0;
		char desc[] = "##th word";
		format_number(desc, word_pos);
		layoutDialogSwipe(&bmp_icon_info, NULL, NULL, NULL, _("Please enter the"), NULL, (word_pos < 10 ? desc + 1 : desc), NULL, _("of your mnemonic"), NULL);
	}
	recovery_request();
}

void recovery_init(uint32_t _word_count, bool passphrase_protection, bool pin_protection, const char *language, const char *label, bool _enforce_wordlist, uint32_t type, uint32_t u2f_counter, bool _dry_run)
{
	if (_word_count != 12 && _word_count != 18 && _word_count != 24) return;

	word_count = _word_count;
	enforce_wordlist = _enforce_wordlist;
	dry_run = _dry_run;

	if (!dry_run) {
		layoutDialogSwipe(&bmp_icon_question, _("Cancel"), _("Confirm"), NULL, _("Do you really want to"), _("recover the device?"), NULL, NULL, NULL, NULL);
		if (!protectButton(ButtonRequestType_ButtonRequest_ProtectCall, false)) {
			fsm_sendFailure(FailureType_Failure_ActionCancelled, NULL);
			layoutHome();
			return;
		}
	}

	if (!dry_run) {
		if (pin_protection && !protectChangePin()) {
			fsm_sendFailure(FailureType_Failure_PinMismatch, NULL);
			layoutHome();
			return;
		}

		storage_setPassphraseProtection(passphrase_protection);
		storage_setLanguage(language);
		storage_setLabel(label);
		storage_setU2FCounter(u2f_counter);
		storage_update();
	}

	if ((type & RecoveryDeviceType_RecoveryDeviceType_Matrix) != 0) {
		awaiting_word = 2;
		word_index = 0;
		word_pincode = 0;
		next_matrix();
	} else {
		for (uint32_t i = 0; i < word_count; i++) {
			word_order[i] = i + 1;
		}
		for (uint32_t i = word_count; i < 24; i++) {
			word_order[i] = 0;
		}
		random_permute(word_order, 24);
		awaiting_word = 1;
		word_index = 0;
		next_word();
	}
}

static void recovery_scrambledword(const char *word)
{
	if (word_pos == 0) { // fake word
		if (strcmp(word, fake_word) != 0) {
			if (!dry_run) {
				session_clear(true);
			}
			fsm_sendFailure(FailureType_Failure_ProcessError, _("Wrong word retyped"));
			layoutHome();
			return;
		}
	} else { // real word
		if (enforce_wordlist) { // check if word is valid
			const char * const *wl = mnemonic_wordlist();
			bool found = false;
			while (*wl) {
				if (strcmp(word, *wl) == 0) {
					found = true;
					break;
				}
				wl++;
			}
			if (!found) {
				if (!dry_run) {
					session_clear(true);
				}
				fsm_sendFailure(FailureType_Failure_DataError, _("Word not found in a wordlist"));
				layoutHome();
				return;
			}
		}
		strlcpy(words[word_pos - 1], word, sizeof(words[word_pos - 1]));
	}

	if (word_index + 1 == 24) { // last one
		recovery_done();
	} else {
		word_index++;
		next_word();
	}
}

/* Function called when a word was entered by user. Used
 * for scrambled recovery.
 */
void recovery_word(const char *word)
{
	switch (awaiting_word) {
	case 2:
		recovery_digit(word[0]);
		break;
	case 1:
		recovery_scrambledword(word);
		break;
	default:
		fsm_sendFailure(FailureType_Failure_UnexpectedMessage, _("Not in Recovery mode"));
		break;
	}
}

/* Abort recovery.
 */
void recovery_abort(void)
{
	if (awaiting_word) {
		layoutHome();
		awaiting_word = 0;
	}
}

#if DEBUG_LINK

const char *recovery_get_fake_word(void)
{
	return fake_word;
}

uint32_t recovery_get_word_pos(void)
{
	return word_pos;
}

#endif