Adding bip39 so I can use it to move around private keys.

git-svn-id: https://www.unprompted.com/svn/projects/tildefriends/trunk@4725 ed5197a5-7fde-0310-b194-c3ffbd925b24

src/bip39.c

@@ -0,0 +1,125 @@
+#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;
+}