// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
/*
This key store behaves as KeyStorePlain with the difference that
the private key is encrypted and on disk uses another JSON encoding.
The crypto is documented at https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition
*/
package accounts
import (
"bytes"
"crypto/aes"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"fmt"
"io/ioutil"
"path/filepath"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/randentropy"
"github.com/pborman/uuid"
"golang.org/x/crypto/pbkdf2"
"golang.org/x/crypto/scrypt"
)
const (
keyHeaderKDF = "scrypt"
// n,r,p = 2^18, 8, 1 uses 256MB memory and approx 1s CPU time on a modern CPU.
StandardScryptN = 1 << 18
StandardScryptP = 1
// n,r,p = 2^12, 8, 6 uses 4MB memory and approx 100ms CPU time on a modern CPU.
LightScryptN = 1 << 12
LightScryptP = 6
scryptR = 8
scryptDKLen = 32
)
type keyStorePassphrase struct {
keysDirPath string
scryptN int
scryptP int
}
func (ks keyStorePassphrase) GetKey(addr common.Address, filename, auth string) (*Key, error) {
// Load the key from the keystore and decrypt its contents
keyjson, err := ioutil.ReadFile(filename)
if err != nil {
return nil, err
}
key, err := DecryptKey(keyjson, auth)
if err != nil {
return nil, err
}
// Make sure we're really operating on the requested key (no swap attacks)
if key.Address != addr {
return nil, fmt.Errorf("key content mismatch: have account %x, want %x", key.Address, addr)
}
return key, nil
}
func (ks keyStorePassphrase) StoreKey(filename string, key *Key, auth string) error {
keyjson, err := EncryptKey(key, auth, ks.scryptN, ks.scryptP)
if err != nil {
return err
}
return writeKeyFile(filename, keyjson)
}
func (ks keyStorePassphrase) JoinPath(filename string) string {
if filepath.IsAbs(filename) {
return filename
} else {
return filepath.Join(ks.keysDirPath, filename)
}
}
// EncryptKey encrypts a key using the specified scrypt parameters into a json
// blob that can be decrypted later on.
func EncryptKey(key *Key, auth string, scryptN, scryptP int) ([]byte, error) {
authArray := []byte(auth)
salt := randentropy.GetEntropyCSPRNG(32)
derivedKey, err := scrypt.Key(authArray, salt, scryptN, scryptR, scryptP, scryptDKLen)
if err != nil {
return nil, err
}
encryptKey := derivedKey[:16]
keyBytes := crypto.FromECDSA(key.PrivateKey)
iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
cipherText, err := aesCTRXOR(encryptKey, keyBytes, iv)
if err != nil {
return nil, err
}
mac := crypto.Keccak256(derivedKey[16:32], cipherText)
scryptParamsJSON := make(map[string]interface{}, 5)
scryptParamsJSON["n"] = scryptN
scryptParamsJSON["r"] = scryptR
scryptParamsJSON["p"] = scryptP
scryptParamsJSON["dklen"] = scryptDKLen
scryptParamsJSON["salt"] = hex.EncodeToString(salt)
cipherParamsJSON := cipherparamsJSON{
IV: hex.EncodeToString(iv),
}
cryptoStruct := cryptoJSON{
Cipher: "aes-128-ctr",
CipherText: hex.EncodeToString(cipherText),
CipherParams: cipherParamsJSON,
KDF: "scrypt",
KDFParams: scryptParamsJSON,
MAC: hex.EncodeToString(mac),
}
encryptedKeyJSONV3 := encryptedKeyJSONV3{
hex.EncodeToString(key.Address[:]),
cryptoStruct,
key.Id.String(),
version,
}
return json.Marshal(encryptedKeyJSONV3)
}
// DecryptKey decrypts a key from a json blob, returning the private key itself.
func DecryptKey(keyjson []byte, auth string) (*Key, error) {
// Parse the json into a simple map to fetch the key version
m := make(map[string]interface{})
if err := json.Unmarshal(keyjson, &m); err != nil {
return nil, err
}
// Depending on the version try to parse one way or another
var (
keyBytes, keyId []byte
err error
)
if version, ok := m["version"].(string); ok && version == "1" {
k := new(encryptedKeyJSONV1)
if err := json.Unmarshal(keyjson, k); err != nil {
return nil, err
}
keyBytes, keyId, err = decryptKeyV1(k, auth)
} else {
k := new(encryptedKeyJSONV3)
if err := json.Unmarshal(keyjson, k); err != nil {
return nil, err
}
keyBytes, keyId, err = decryptKeyV3(k, auth)
}
// Handle any decryption errors and return the key
if err != nil {
return nil, err
}
key := crypto.ToECDSA(keyBytes)
return &Key{
Id: uuid.UUID(keyId),
Address: crypto.PubkeyToAddress(key.PublicKey),
PrivateKey: key,
}, nil
}
func decryptKeyV3(keyProtected *encryptedKeyJSONV3, auth string) (keyBytes []byte, keyId []byte, err error) {
if keyProtected.Version != version {
return nil, nil, fmt.Errorf("Version not supported: %v", keyProtected.Version)
}
if keyProtected.Crypto.Cipher != "aes-128-ctr" {
return nil, nil, fmt.Errorf("Cipher not supported: %v", keyProtected.Crypto.Cipher)
}
keyId = uuid.Parse(keyProtected.Id)
mac, err := hex.DecodeString(keyProtected.Crypto.MAC)
if err != nil {
return nil, nil, err
}
iv, err := hex.DecodeString(keyProtected.Crypto.CipherParams.IV)
if err != nil {
return nil, nil, err
}
cipherText, err := hex.DecodeString(keyProtected.Crypto.CipherText)
if err != nil {
return nil, nil, err
}
derivedKey, err := getKDFKey(keyProtected.Crypto, auth)
if err != nil {
return nil, nil, err
}
calculatedMAC := crypto.Keccak256(derivedKey[16:32], cipherText)
if !bytes.Equal(calculatedMAC, mac) {
return nil, nil, ErrDecrypt
}
plainText, err := aesCTRXOR(derivedKey[:16], cipherText, iv)
if err != nil {
return nil, nil, err
}
return plainText, keyId, err
}
func decryptKeyV1(keyProtected *encryptedKeyJSONV1, auth string) (keyBytes []byte, keyId []byte, err error) {
keyId = uuid.Parse(keyProtected.Id)
mac, err := hex.DecodeString(keyProtected.Crypto.MAC)
if err != nil {
return nil, nil, err
}
iv, err := hex.DecodeString(keyProtected.Crypto.CipherParams.IV)
if err != nil {
return nil, nil, err
}
cipherText, err := hex.DecodeString(keyProtected.Crypto.CipherText)
if err != nil {
return nil, nil, err
}
derivedKey, err := getKDFKey(keyProtected.Crypto, auth)
if err != nil {
return nil, nil, err
}
calculatedMAC := crypto.Keccak256(derivedKey[16:32], cipherText)
if !bytes.Equal(calculatedMAC, mac) {
return nil, nil, ErrDecrypt
}
plainText, err := aesCBCDecrypt(crypto.Keccak256(derivedKey[:16])[:16], cipherText, iv)
if err != nil {
return nil, nil, err
}
return plainText, keyId, err
}
func getKDFKey(cryptoJSON cryptoJSON, auth string) ([]byte, error) {
authArray := []byte(auth)
salt, err := hex.DecodeString(cryptoJSON.KDFParams["salt"].(string))
if err != nil {
return nil, err
}
dkLen := ensureInt(cryptoJSON.KDFParams["dklen"])
if cryptoJSON.KDF == "scrypt" {
n := ensureInt(cryptoJSON.KDFParams["n"])
r := ensureInt(cryptoJSON.KDFParams["r"])
p := ensureInt(cryptoJSON.KDFParams["p"])
return scrypt.Key(authArray, salt, n, r, p, dkLen)
} else if cryptoJSON.KDF == "pbkdf2" {
c := ensureInt(cryptoJSON.KDFParams["c"])
prf := cryptoJSON.KDFParams["prf"].(string)
if prf != "hmac-sha256" {
return nil, fmt.Errorf("Unsupported PBKDF2 PRF: %s", prf)
}
key := pbkdf2.Key(authArray, salt, c, dkLen, sha256.New)
return key, nil
}
return nil, fmt.Errorf("Unsupported KDF: %s", cryptoJSON.KDF)
}
// TODO: can we do without this when unmarshalling dynamic JSON?
// why do integers in KDF params end up as float64 and not int after
// unmarshal?
func ensureInt(x interface{}) int {
res, ok := x.(int)
if !ok {
res = int(x.(float64))
}
return res
}
