248 lines
6.7 KiB
Go
248 lines
6.7 KiB
Go
/*
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This file is part of go-ethereum
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go-ethereum is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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go-ethereum is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* @authors
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* Gustav Simonsson <gustav.simonsson@gmail.com>
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* @date 2015
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*
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*/
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/*
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This key store behaves as KeyStorePlain with the difference that
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the private key is encrypted and on disk uses another JSON encoding.
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Cryptography:
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1. Encryption key is first 16 bytes of SHA3-256 of first 16 bytes of
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scrypt derived key from user passphrase. Scrypt parameters
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(work factors) [1][2] are defined as constants below.
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2. Scrypt salt is 32 random bytes from CSPRNG.
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It's stored in plain next to ciphertext in key file.
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3. MAC is SHA3-256 of concatenation of ciphertext and last 16 bytes of scrypt derived key.
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4. Plaintext is the EC private key bytes.
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5. Encryption algo is AES 128 CBC [3][4]
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6. CBC IV is 16 random bytes from CSPRNG.
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It's stored in plain next to ciphertext in key file.
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7. Plaintext padding is PKCS #7 [5][6]
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Encoding:
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1. On disk, the ciphertext, MAC, salt and IV are encoded in a nested JSON object.
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cat a key file to see the structure.
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2. byte arrays are base64 JSON strings.
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3. The EC private key bytes are in uncompressed form [7].
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They are a big-endian byte slice of the absolute value of D [8][9].
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References:
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1. http://www.tarsnap.com/scrypt/scrypt-slides.pdf
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2. http://stackoverflow.com/questions/11126315/what-are-optimal-scrypt-work-factors
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3. http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
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4. http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_.28CBC.29
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5. https://leanpub.com/gocrypto/read#leanpub-auto-block-cipher-modes
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6. http://tools.ietf.org/html/rfc2315
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7. http://bitcoin.stackexchange.com/questions/3059/what-is-a-compressed-bitcoin-key
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8. http://golang.org/pkg/crypto/ecdsa/#PrivateKey
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9. https://golang.org/pkg/math/big/#Int.Bytes
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*/
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package crypto
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"encoding/hex"
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"encoding/json"
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"errors"
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"io"
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"os"
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"path/filepath"
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"code.google.com/p/go-uuid/uuid"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto/randentropy"
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"golang.org/x/crypto/scrypt"
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)
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const (
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keyHeaderVersion = "1"
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keyHeaderKDF = "scrypt"
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// 2^18 / 8 / 1 uses 256MB memory and approx 1s CPU time on a modern CPU.
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scryptN = 1 << 18
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scryptr = 8
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scryptp = 1
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scryptdkLen = 32
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)
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type keyStorePassphrase struct {
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keysDirPath string
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}
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func NewKeyStorePassphrase(path string) KeyStore2 {
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return &keyStorePassphrase{path}
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}
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func (ks keyStorePassphrase) GenerateNewKey(rand io.Reader, auth string) (key *Key, err error) {
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return GenerateNewKeyDefault(ks, rand, auth)
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}
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func (ks keyStorePassphrase) GetKey(keyAddr common.Address, auth string) (key *Key, err error) {
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keyBytes, keyId, err := DecryptKey(ks, keyAddr, auth)
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if err != nil {
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return nil, err
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}
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key = &Key{
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Id: uuid.UUID(keyId),
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Address: keyAddr,
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PrivateKey: ToECDSA(keyBytes),
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}
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return key, err
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}
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func (ks keyStorePassphrase) GetKeyAddresses() (addresses []common.Address, err error) {
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return GetKeyAddresses(ks.keysDirPath)
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}
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func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
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authArray := []byte(auth)
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salt := randentropy.GetEntropyCSPRNG(32)
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derivedKey, err := scrypt.Key(authArray, salt, scryptN, scryptr, scryptp, scryptdkLen)
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if err != nil {
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return err
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}
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encryptKey := Sha3(derivedKey[:16])[:16]
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keyBytes := FromECDSA(key.PrivateKey)
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toEncrypt := PKCS7Pad(keyBytes)
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AES128Block, err := aes.NewCipher(encryptKey)
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if err != nil {
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return err
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}
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iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
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AES128CBCEncrypter := cipher.NewCBCEncrypter(AES128Block, iv)
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cipherText := make([]byte, len(toEncrypt))
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AES128CBCEncrypter.CryptBlocks(cipherText, toEncrypt)
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mac := Sha3(derivedKey[16:32], cipherText)
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scryptParamsJSON := scryptParamsJSON{
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N: scryptN,
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R: scryptr,
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P: scryptp,
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DkLen: scryptdkLen,
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Salt: hex.EncodeToString(salt),
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}
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cipherParamsJSON := cipherparamsJSON{
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IV: hex.EncodeToString(iv),
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}
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cryptoStruct := cryptoJSON{
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Cipher: "aes-128-cbc",
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CipherText: hex.EncodeToString(cipherText),
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CipherParams: cipherParamsJSON,
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KDF: "scrypt",
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KDFParams: scryptParamsJSON,
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MAC: hex.EncodeToString(mac),
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Version: "1",
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}
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encryptedKeyJSON := encryptedKeyJSON{
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hex.EncodeToString(key.Address[:]),
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cryptoStruct,
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key.Id.String(),
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version,
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}
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keyJSON, err := json.Marshal(encryptedKeyJSON)
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if err != nil {
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return err
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}
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return WriteKeyFile(key.Address, ks.keysDirPath, keyJSON)
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}
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func (ks keyStorePassphrase) DeleteKey(keyAddr common.Address, auth string) (err error) {
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// only delete if correct passphrase is given
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_, _, err = DecryptKey(ks, keyAddr, auth)
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if err != nil {
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return err
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}
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keyDirPath := filepath.Join(ks.keysDirPath, hex.EncodeToString(keyAddr[:]))
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return os.RemoveAll(keyDirPath)
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}
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func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (keyBytes []byte, keyId []byte, err error) {
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fileContent, err := GetKeyFile(ks.keysDirPath, keyAddr)
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if err != nil {
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return nil, nil, err
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}
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keyProtected := new(encryptedKeyJSON)
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err = json.Unmarshal(fileContent, keyProtected)
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keyId = uuid.Parse(keyProtected.Id)
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mac, err := hex.DecodeString(keyProtected.Crypto.MAC)
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if err != nil {
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return nil, nil, err
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}
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iv, err := hex.DecodeString(keyProtected.Crypto.CipherParams.IV)
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if err != nil {
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return nil, nil, err
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}
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cipherText, err := hex.DecodeString(keyProtected.Crypto.CipherText)
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if err != nil {
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return nil, nil, err
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}
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salt, err := hex.DecodeString(keyProtected.Crypto.KDFParams.Salt)
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if err != nil {
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return nil, nil, err
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}
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n := keyProtected.Crypto.KDFParams.N
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r := keyProtected.Crypto.KDFParams.R
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p := keyProtected.Crypto.KDFParams.P
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dkLen := keyProtected.Crypto.KDFParams.DkLen
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authArray := []byte(auth)
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derivedKey, err := scrypt.Key(authArray, salt, n, r, p, dkLen)
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if err != nil {
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return nil, nil, err
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}
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calculatedMAC := Sha3(derivedKey[16:32], cipherText)
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if !bytes.Equal(calculatedMAC, mac) {
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err = errors.New("Decryption failed: MAC mismatch")
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return nil, nil, err
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}
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plainText, err := aesCBCDecrypt(Sha3(derivedKey[:16])[:16], cipherText, iv)
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if err != nil {
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return nil, nil, err
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}
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return plainText, keyId, err
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}
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