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142 lines
4.0 KiB
142 lines
4.0 KiB
/**
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* This file is part of the TREZOR project, https://trezor.io/
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*
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* Copyright (c) SatoshiLabs
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "slip39.h"
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#include <stdio.h>
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#include <string.h>
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#include "slip39_wordlist.h"
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static uint16_t find(uint16_t prefix, bool find_index);
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/**
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* Returns word at position `index`.
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*/
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const char* get_word(uint16_t index) {
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if (index >= WORDS_COUNT) {
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return NULL;
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}
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return wordlist[index];
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}
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/**
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* Finds the index of a given word.
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* Returns true on success and stores result in `index`.
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*/
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bool word_index(uint16_t* index, const char* word, uint8_t word_length) {
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uint16_t lo = 0;
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uint16_t hi = WORDS_COUNT;
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uint16_t mid = 0;
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while ((hi - lo) > 1) {
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mid = (hi + lo) / 2;
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if (strncmp(wordlist[mid], word, word_length) > 0) {
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hi = mid;
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} else {
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lo = mid;
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}
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}
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if (strncmp(wordlist[lo], word, word_length) != 0) {
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return false;
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}
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*index = lo;
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return true;
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}
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/**
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* Calculates which buttons on the T9 keyboard can still be pressed after the
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* prefix was entered. Returns a 9-bit bitmask, where each bit specifies which
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* buttons can be pressed (there are still words in this combination). The least
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* significant bit corresponds to the first button.
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*
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* Example: 110000110 - second, third, eighth and ninth button still can be
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* pressed.
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*/
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uint16_t slip39_word_completion_mask(uint16_t prefix) {
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return find(prefix, false);
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}
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/**
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* Returns the first word matching the button sequence prefix or NULL if no
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* match is found.
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*/
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const char* button_sequence_to_word(uint16_t prefix) {
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return get_word(find(prefix, true));
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}
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/**
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* Computes mask if find_index is false.
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* Otherwise finds the first word index that matches the prefix. Returns
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* WORDS_COUNT if no match is found.
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*/
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static uint16_t find(uint16_t prefix, bool find_index) {
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if (prefix == 0) {
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return find_index ? 0 : 0x1ff;
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}
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// Determine the range of sequences [min, max), which have the given prefix.
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uint16_t min = prefix;
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uint16_t max = prefix + 1;
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uint16_t divider = 1;
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while (max <= 1000) {
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min *= 10;
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max *= 10;
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divider *= 10;
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}
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divider /= 10;
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// Four char prefix -> the mask is zero
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if (!divider && !find_index) {
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return 0;
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}
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// We can't use binary search because the numbers are not sorted.
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// They are sorted using the words' alphabet (so we can use the index).
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// Example: axle (1953), beam (1315)
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// The first digit is sorted so we only need to search up to `max_search`.
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uint16_t max_search = min - (min % 1000) + 1000;
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uint16_t bitmap = 0;
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for (uint16_t i = 0; i < WORDS_COUNT; i++) {
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if (words_button_seq[i] >= max_search) {
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break;
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}
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if (words_button_seq[i] >= min && words_button_seq[i] < max) {
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if (find_index) {
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return i;
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}
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uint8_t digit = (words_button_seq[i] / divider) % 10;
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bitmap |= 1 << (digit - 1);
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}
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}
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if (find_index) {
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// Index not found.
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return WORDS_COUNT;
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} else {
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return bitmap;
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}
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}
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