tildefriends/src/bip39.c

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#include "bip39.h"
#include "bip39.words.h"
#include "log.h"
#include "util.js.h"
#include "sodium/crypto_hash_sha256.h"
#include <assert.h>
#include <stdio.h>
#include <string.h>
static_assert(k_bip39_words_count == 1 << 11, "Incorrect word count in k_bip39_words.");
bool tf_bip39_bytes_to_words(const uint8_t* bytes, size_t bytes_size, char* out_words, size_t words_size)
{
if (words_size)
{
*out_words = '\0';
}
if (bytes_size != 32)
{
tf_printf("%s expected 32 bytes, got %zd.\n", __func__, bytes_size);
return false;
}
uint8_t data[33];
crypto_hash_sha256(data, bytes, bytes_size);
data[bytes_size] = data[0];
memcpy(data, bytes, bytes_size);
int offset = 0;
for (int i = 0; i < (int)bytes_size * 8; i += 11)
{
uint32_t value = 0;
for (int j = 0; j < 11; j++)
{
value <<= 1;
if ((data[(i + j) / 8] & (1 << (7 - (i + j) % 8))) != 0)
{
value |= 1;
}
}
offset += snprintf(out_words + offset, words_size - offset, i < (int)bytes_size * 8 - 11 ? "%s " : "%s", k_bip39_words[value]);
}
return true;
}
static int _bip39_word_to_index(const char* word)
{
if (!word)
{
return -1;
}
for (int i = 0; i < k_bip39_words_count; i++)
{
if (strcmp(word, k_bip39_words[i]) == 0)
{
return i;
}
}
return -1;
}
bool tf_bip39_words_to_bytes(const char* words, uint8_t* out_bytes, size_t bytes_size)
{
int i = 0;
int word_start = 0;
uint32_t value = 0;
uint32_t value_bits = 0;
int out_index = 0;
uint8_t bytes[33];
while (words[i])
{
for (; words[i] == ' '; i++)
{
word_start = i + 1;
}
for (;; i++)
{
if (words[i] == ' ' || words[i] == '\0')
{
char copy[32] = "";
memcpy(copy, words + word_start, i - word_start);
int index = _bip39_word_to_index(copy);
if (index < 0)
{
tf_printf("%s: Word \"%s\" not found in dictionary.\n", __func__, copy);
return false;
}
value <<= 11;
value |= index;
value_bits += 11;
while (value_bits >= 8 && out_index < (int)sizeof(bytes))
{
bytes[out_index++] = (value >> (value_bits - 8)) & 0xff;
value_bits -= 8;
}
break;
}
}
}
if (out_index != sizeof(bytes))
{
return false;
}
uint8_t data[33];
crypto_hash_sha256(data, bytes, bytes_size);
if (data[0] != bytes[32])
{
tf_printf("%s: Checksum mismatch.\n", __func__);
return false;
}
memcpy(out_bytes, bytes, tf_min(sizeof(bytes), bytes_size));
return true;
}