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| 1 | +// Package bip39 is the Golang implementation of the BIP39 spec. |
| 2 | +// |
| 3 | +// The official BIP39 spec can be found at |
| 4 | +// https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki |
| 5 | +package bip39 |
| 6 | + |
| 7 | +import ( |
| 8 | + "crypto/rand" |
| 9 | + "crypto/sha256" |
| 10 | + "crypto/sha512" |
| 11 | + "encoding/binary" |
| 12 | + "errors" |
| 13 | + "fmt" |
| 14 | + "math/big" |
| 15 | + "strings" |
| 16 | + |
| 17 | + "github.com/gagliardetto/solana-go/bip39/wordlists" |
| 18 | + "golang.org/x/crypto/pbkdf2" |
| 19 | +) |
| 20 | + |
| 21 | +var ( |
| 22 | + // Some bitwise operands for working with big.Ints |
| 23 | + last11BitsMask = big.NewInt(2047) |
| 24 | + shift11BitsMask = big.NewInt(2048) |
| 25 | + bigOne = big.NewInt(1) |
| 26 | + bigTwo = big.NewInt(2) |
| 27 | + |
| 28 | + // used to isolate the checksum bits from the entropy+checksum byte array |
| 29 | + wordLengthChecksumMasksMapping = map[int]*big.Int{ |
| 30 | + 12: big.NewInt(15), |
| 31 | + 15: big.NewInt(31), |
| 32 | + 18: big.NewInt(63), |
| 33 | + 21: big.NewInt(127), |
| 34 | + 24: big.NewInt(255), |
| 35 | + } |
| 36 | + // used to use only the desired x of 8 available checksum bits. |
| 37 | + // 256 bit (word length 24) requires all 8 bits of the checksum, |
| 38 | + // and thus no shifting is needed for it (we would get a divByZero crash if we did) |
| 39 | + wordLengthChecksumShiftMapping = map[int]*big.Int{ |
| 40 | + 12: big.NewInt(16), |
| 41 | + 15: big.NewInt(8), |
| 42 | + 18: big.NewInt(4), |
| 43 | + 21: big.NewInt(2), |
| 44 | + } |
| 45 | + |
| 46 | + // wordList is the set of words to use |
| 47 | + wordList []string |
| 48 | + |
| 49 | + // wordMap is a reverse lookup map for wordList |
| 50 | + wordMap map[string]int |
| 51 | +) |
| 52 | + |
| 53 | +var ( |
| 54 | + // ErrInvalidMnemonic is returned when trying to use a malformed mnemonic. |
| 55 | + ErrInvalidMnemonic = errors.New("Invalid mnemonic") |
| 56 | + |
| 57 | + // ErrEntropyLengthInvalid is returned when trying to use an entropy set with |
| 58 | + // an invalid size. |
| 59 | + ErrEntropyLengthInvalid = errors.New("Entropy length must be [128, 256] and a multiple of 32") |
| 60 | + |
| 61 | + // ErrValidatedSeedLengthMismatch is returned when a validated seed is not the |
| 62 | + // same size as the given seed. This should never happen is present only as a |
| 63 | + // sanity assertion. |
| 64 | + ErrValidatedSeedLengthMismatch = errors.New("Seed length does not match validated seed length") |
| 65 | + |
| 66 | + // ErrChecksumIncorrect is returned when entropy has the incorrect checksum. |
| 67 | + ErrChecksumIncorrect = errors.New("Checksum incorrect") |
| 68 | +) |
| 69 | + |
| 70 | +func init() { |
| 71 | + SetWordList(wordlists.English) |
| 72 | +} |
| 73 | + |
| 74 | +// SetWordList sets the list of words to use for mnemonics. Currently the list |
| 75 | +// that is set is used package-wide. |
| 76 | +func SetWordList(list []string) { |
| 77 | + wordList = list |
| 78 | + wordMap = map[string]int{} |
| 79 | + for i, v := range wordList { |
| 80 | + wordMap[v] = i |
| 81 | + } |
| 82 | +} |
| 83 | + |
| 84 | +// GetWordList gets the list of words to use for mnemonics. |
| 85 | +func GetWordList() []string { |
| 86 | + return wordList |
| 87 | +} |
| 88 | + |
| 89 | +// GetWordIndex gets word index in wordMap. |
| 90 | +func GetWordIndex(word string) (int, bool) { |
| 91 | + idx, ok := wordMap[word] |
| 92 | + return idx, ok |
| 93 | +} |
| 94 | + |
| 95 | +// NewEntropy will create random entropy bytes |
| 96 | +// so long as the requested size bitSize is an appropriate size. |
| 97 | +// |
| 98 | +// bitSize has to be a multiple 32 and be within the inclusive range of {128, 256} |
| 99 | +func NewEntropy(bitSize int) ([]byte, error) { |
| 100 | + err := validateEntropyBitSize(bitSize) |
| 101 | + if err != nil { |
| 102 | + return nil, err |
| 103 | + } |
| 104 | + |
| 105 | + entropy := make([]byte, bitSize/8) |
| 106 | + _, err = rand.Read(entropy) |
| 107 | + return entropy, err |
| 108 | +} |
| 109 | + |
| 110 | +// EntropyFromMnemonic takes a mnemonic generated by this library, |
| 111 | +// and returns the input entropy used to generate the given mnemonic. |
| 112 | +// An error is returned if the given mnemonic is invalid. |
| 113 | +func EntropyFromMnemonic(mnemonic string) ([]byte, error) { |
| 114 | + mnemonicSlice, isValid := splitMnemonicWords(mnemonic) |
| 115 | + if !isValid { |
| 116 | + return nil, ErrInvalidMnemonic |
| 117 | + } |
| 118 | + |
| 119 | + // Decode the words into a big.Int. |
| 120 | + b := big.NewInt(0) |
| 121 | + for _, v := range mnemonicSlice { |
| 122 | + index, found := wordMap[v] |
| 123 | + if found == false { |
| 124 | + return nil, fmt.Errorf("word `%v` not found in reverse map", v) |
| 125 | + } |
| 126 | + var wordBytes [2]byte |
| 127 | + binary.BigEndian.PutUint16(wordBytes[:], uint16(index)) |
| 128 | + b = b.Mul(b, shift11BitsMask) |
| 129 | + b = b.Or(b, big.NewInt(0).SetBytes(wordBytes[:])) |
| 130 | + } |
| 131 | + |
| 132 | + // Build and add the checksum to the big.Int. |
| 133 | + checksum := big.NewInt(0) |
| 134 | + checksumMask := wordLengthChecksumMasksMapping[len(mnemonicSlice)] |
| 135 | + checksum = checksum.And(b, checksumMask) |
| 136 | + |
| 137 | + b.Div(b, big.NewInt(0).Add(checksumMask, bigOne)) |
| 138 | + |
| 139 | + // The entropy is the underlying bytes of the big.Int. Any upper bytes of |
| 140 | + // all 0's are not returned so we pad the beginning of the slice with empty |
| 141 | + // bytes if necessary. |
| 142 | + entropy := b.Bytes() |
| 143 | + entropy = padByteSlice(entropy, len(mnemonicSlice)/3*4) |
| 144 | + |
| 145 | + // Generate the checksum and compare with the one we got from the mneomnic. |
| 146 | + entropyChecksumBytes := computeChecksum(entropy) |
| 147 | + entropyChecksum := big.NewInt(int64(entropyChecksumBytes[0])) |
| 148 | + if l := len(mnemonicSlice); l != 24 { |
| 149 | + checksumShift := wordLengthChecksumShiftMapping[l] |
| 150 | + entropyChecksum.Div(entropyChecksum, checksumShift) |
| 151 | + } |
| 152 | + |
| 153 | + if checksum.Cmp(entropyChecksum) != 0 { |
| 154 | + return nil, ErrChecksumIncorrect |
| 155 | + } |
| 156 | + |
| 157 | + return entropy, nil |
| 158 | +} |
| 159 | + |
| 160 | +// NewMnemonic will return a string consisting of the mnemonic words for |
| 161 | +// the given entropy. |
| 162 | +// If the provide entropy is invalid, an error will be returned. |
| 163 | +func NewMnemonic(entropy []byte) (string, error) { |
| 164 | + // Compute some lengths for convenience. |
| 165 | + entropyBitLength := len(entropy) * 8 |
| 166 | + checksumBitLength := entropyBitLength / 32 |
| 167 | + sentenceLength := (entropyBitLength + checksumBitLength) / 11 |
| 168 | + |
| 169 | + // Validate that the requested size is supported. |
| 170 | + err := validateEntropyBitSize(entropyBitLength) |
| 171 | + if err != nil { |
| 172 | + return "", err |
| 173 | + } |
| 174 | + |
| 175 | + // Add checksum to entropy. |
| 176 | + entropy = addChecksum(entropy) |
| 177 | + |
| 178 | + // Break entropy up into sentenceLength chunks of 11 bits. |
| 179 | + // For each word AND mask the rightmost 11 bits and find the word at that index. |
| 180 | + // Then bitshift entropy 11 bits right and repeat. |
| 181 | + // Add to the last empty slot so we can work with LSBs instead of MSB. |
| 182 | + |
| 183 | + // Entropy as an int so we can bitmask without worrying about bytes slices. |
| 184 | + entropyInt := new(big.Int).SetBytes(entropy) |
| 185 | + |
| 186 | + // Slice to hold words in. |
| 187 | + words := make([]string, sentenceLength) |
| 188 | + |
| 189 | + // Throw away big.Int for AND masking. |
| 190 | + word := big.NewInt(0) |
| 191 | + |
| 192 | + for i := sentenceLength - 1; i >= 0; i-- { |
| 193 | + // Get 11 right most bits and bitshift 11 to the right for next time. |
| 194 | + word.And(entropyInt, last11BitsMask) |
| 195 | + entropyInt.Div(entropyInt, shift11BitsMask) |
| 196 | + |
| 197 | + // Get the bytes representing the 11 bits as a 2 byte slice. |
| 198 | + wordBytes := padByteSlice(word.Bytes(), 2) |
| 199 | + |
| 200 | + // Convert bytes to an index and add that word to the list. |
| 201 | + words[i] = wordList[binary.BigEndian.Uint16(wordBytes)] |
| 202 | + } |
| 203 | + |
| 204 | + return strings.Join(words, " "), nil |
| 205 | +} |
| 206 | + |
| 207 | +// MnemonicToByteArray takes a mnemonic string and turns it into a byte array |
| 208 | +// suitable for creating another mnemonic. |
| 209 | +// An error is returned if the mnemonic is invalid. |
| 210 | +func MnemonicToByteArray(mnemonic string, raw ...bool) ([]byte, error) { |
| 211 | + var ( |
| 212 | + mnemonicSlice = strings.Split(mnemonic, " ") |
| 213 | + entropyBitSize = len(mnemonicSlice) * 11 |
| 214 | + checksumBitSize = entropyBitSize % 32 |
| 215 | + fullByteSize = (entropyBitSize-checksumBitSize)/8 + 1 |
| 216 | + checksumByteSize = fullByteSize - (fullByteSize % 4) |
| 217 | + ) |
| 218 | + |
| 219 | + // Pre validate that the mnemonic is well formed and only contains words that |
| 220 | + // are present in the word list. |
| 221 | + if !IsMnemonicValid(mnemonic) { |
| 222 | + return nil, ErrInvalidMnemonic |
| 223 | + } |
| 224 | + |
| 225 | + // Convert word indices to a big.Int representing the entropy. |
| 226 | + checksummedEntropy := big.NewInt(0) |
| 227 | + modulo := big.NewInt(2048) |
| 228 | + for _, v := range mnemonicSlice { |
| 229 | + index := big.NewInt(int64(wordMap[v])) |
| 230 | + checksummedEntropy.Mul(checksummedEntropy, modulo) |
| 231 | + checksummedEntropy.Add(checksummedEntropy, index) |
| 232 | + } |
| 233 | + |
| 234 | + // Calculate the unchecksummed entropy so we can validate that the checksum is |
| 235 | + // correct. |
| 236 | + checksumModulo := big.NewInt(0).Exp(bigTwo, big.NewInt(int64(checksumBitSize)), nil) |
| 237 | + rawEntropy := big.NewInt(0).Div(checksummedEntropy, checksumModulo) |
| 238 | + |
| 239 | + // Convert big.Ints to byte padded byte slices. |
| 240 | + rawEntropyBytes := padByteSlice(rawEntropy.Bytes(), checksumByteSize) |
| 241 | + checksummedEntropyBytes := padByteSlice(checksummedEntropy.Bytes(), fullByteSize) |
| 242 | + |
| 243 | + // Validate that the checksum is correct. |
| 244 | + newChecksummedEntropyBytes := padByteSlice(addChecksum(rawEntropyBytes), fullByteSize) |
| 245 | + if !compareByteSlices(checksummedEntropyBytes, newChecksummedEntropyBytes) { |
| 246 | + return nil, ErrChecksumIncorrect |
| 247 | + } |
| 248 | + |
| 249 | + if len(raw) > 0 && raw[0] { |
| 250 | + return rawEntropyBytes, nil |
| 251 | + } |
| 252 | + |
| 253 | + return checksummedEntropyBytes, nil |
| 254 | +} |
| 255 | + |
| 256 | +// NewSeedWithErrorChecking creates a hashed seed output given the mnemonic string and a password. |
| 257 | +// An error is returned if the mnemonic is not convertible to a byte array. |
| 258 | +func NewSeedWithErrorChecking(mnemonic string, password string) ([]byte, error) { |
| 259 | + _, err := MnemonicToByteArray(mnemonic) |
| 260 | + if err != nil { |
| 261 | + return nil, err |
| 262 | + } |
| 263 | + return NewSeed(mnemonic, password), nil |
| 264 | +} |
| 265 | + |
| 266 | +// NewSeed creates a hashed seed output given a provided string and password. |
| 267 | +// No checking is performed to validate that the string provided is a valid mnemonic. |
| 268 | +func NewSeed(mnemonic string, password string) []byte { |
| 269 | + return pbkdf2.Key([]byte(mnemonic), []byte("mnemonic"+password), 2048, 64, sha512.New) |
| 270 | +} |
| 271 | + |
| 272 | +// IsMnemonicValid attempts to verify that the provided mnemonic is valid. |
| 273 | +// Validity is determined by both the number of words being appropriate, |
| 274 | +// and that all the words in the mnemonic are present in the word list. |
| 275 | +func IsMnemonicValid(mnemonic string) bool { |
| 276 | + _, err := EntropyFromMnemonic(mnemonic) |
| 277 | + return err == nil |
| 278 | +} |
| 279 | + |
| 280 | +// Appends to data the first (len(data) / 32)bits of the result of sha256(data) |
| 281 | +// Currently only supports data up to 32 bytes |
| 282 | +func addChecksum(data []byte) []byte { |
| 283 | + // Get first byte of sha256 |
| 284 | + hash := computeChecksum(data) |
| 285 | + firstChecksumByte := hash[0] |
| 286 | + |
| 287 | + // len() is in bytes so we divide by 4 |
| 288 | + checksumBitLength := uint(len(data) / 4) |
| 289 | + |
| 290 | + // For each bit of check sum we want we shift the data one the left |
| 291 | + // and then set the (new) right most bit equal to checksum bit at that index |
| 292 | + // staring from the left |
| 293 | + dataBigInt := new(big.Int).SetBytes(data) |
| 294 | + for i := uint(0); i < checksumBitLength; i++ { |
| 295 | + // Bitshift 1 left |
| 296 | + dataBigInt.Mul(dataBigInt, bigTwo) |
| 297 | + |
| 298 | + // Set rightmost bit if leftmost checksum bit is set |
| 299 | + if uint8(firstChecksumByte&(1<<(7-i))) > 0 { |
| 300 | + dataBigInt.Or(dataBigInt, bigOne) |
| 301 | + } |
| 302 | + } |
| 303 | + |
| 304 | + return dataBigInt.Bytes() |
| 305 | +} |
| 306 | + |
| 307 | +func computeChecksum(data []byte) []byte { |
| 308 | + hasher := sha256.New() |
| 309 | + hasher.Write(data) |
| 310 | + return hasher.Sum(nil) |
| 311 | +} |
| 312 | + |
| 313 | +// validateEntropyBitSize ensures that entropy is the correct size for being a |
| 314 | +// mnemonic. |
| 315 | +func validateEntropyBitSize(bitSize int) error { |
| 316 | + if (bitSize%32) != 0 || bitSize < 128 || bitSize > 256 { |
| 317 | + return ErrEntropyLengthInvalid |
| 318 | + } |
| 319 | + return nil |
| 320 | +} |
| 321 | + |
| 322 | +// padByteSlice returns a byte slice of the given size with contents of the |
| 323 | +// given slice left padded and any empty spaces filled with 0's. |
| 324 | +func padByteSlice(slice []byte, length int) []byte { |
| 325 | + offset := length - len(slice) |
| 326 | + if offset <= 0 { |
| 327 | + return slice |
| 328 | + } |
| 329 | + newSlice := make([]byte, length) |
| 330 | + copy(newSlice[offset:], slice) |
| 331 | + return newSlice |
| 332 | +} |
| 333 | + |
| 334 | +// compareByteSlices returns true of the byte slices have equal contents and |
| 335 | +// returns false otherwise. |
| 336 | +func compareByteSlices(a, b []byte) bool { |
| 337 | + if len(a) != len(b) { |
| 338 | + return false |
| 339 | + } |
| 340 | + for i := range a { |
| 341 | + if a[i] != b[i] { |
| 342 | + return false |
| 343 | + } |
| 344 | + } |
| 345 | + return true |
| 346 | +} |
| 347 | + |
| 348 | +func splitMnemonicWords(mnemonic string) ([]string, bool) { |
| 349 | + // Create a list of all the words in the mnemonic sentence |
| 350 | + words := strings.Fields(mnemonic) |
| 351 | + |
| 352 | + // Get num of words |
| 353 | + numOfWords := len(words) |
| 354 | + |
| 355 | + // The number of words should be 12, 15, 18, 21 or 24 |
| 356 | + if numOfWords%3 != 0 || numOfWords < 12 || numOfWords > 24 { |
| 357 | + return nil, false |
| 358 | + } |
| 359 | + return words, true |
| 360 | +} |
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