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key.go
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key.go
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package util
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"math/big"
"path/filepath"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/accounts/keystore"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/pborman/uuid"
"github.com/wealdtech/ethereal/v2/cli"
"golang.org/x/crypto/pbkdf2"
"golang.org/x/crypto/scrypt"
)
// PrivateKeyForAccount returns the private key for an account.
func PrivateKeyForAccount(chainID *big.Int, address common.Address, passphrase string) (*ecdsa.PrivateKey, error) {
var account *accounts.Account
_, account, err := cli.ObtainWalletAndAccount(chainID, address)
if err != nil {
return nil, fmt.Errorf("unable to find account %s", address.Hex())
}
ks := keystore.NewKeyStore(filepath.Dir(account.URL.Path), keystore.StandardScryptN, keystore.StandardScryptP)
exported, err := ks.Export(*account, passphrase, passphrase)
if err != nil {
return nil, fmt.Errorf("unable to export keystore for %v", address)
}
m := make(map[string]interface{})
err = json.Unmarshal(exported, &m)
if err != nil {
return nil, fmt.Errorf("unable to unmarshal keystore for %v", address)
}
var keyBytes []byte
if version, ok := m["version"].(string); ok && version == "1" {
k := new(encryptedKeyJSONV1)
err = json.Unmarshal(exported, k)
if err != nil {
return nil, fmt.Errorf("unable to unmarshal keystore for %v", address)
}
keyBytes, _, err = decryptKeyV1(k, passphrase)
} else {
k := new(encryptedKeyJSONV3)
err = json.Unmarshal(exported, k)
if err != nil {
return nil, fmt.Errorf("unable to unmarshal keystore for %v", address)
}
keyBytes, _, err = decryptKeyV3(k, passphrase)
}
if err != nil {
return nil, fmt.Errorf("unable to unmarshal keystore for %v", address)
}
return crypto.ToECDSAUnsafe(keyBytes), nil
}
const (
keyHeaderKDF = "scrypt"
version = 3
)
var errDecrypt = errors.New("could not decrypt key with given passphrase")
func decryptKeyV3(keyProtected *encryptedKeyJSONV3, auth string) ([]byte, []byte, 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) ([]byte, []byte, 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
}
type encryptedKeyJSONV3 struct {
Address string `json:"address"`
Crypto cryptoJSON `json:"crypto"`
ID string `json:"id"`
Version int `json:"version"`
}
type encryptedKeyJSONV1 struct {
Address string `json:"address"`
Crypto cryptoJSON `json:"crypto"`
ID string `json:"id"`
Version string `json:"version"`
}
type cryptoJSON struct {
Cipher string `json:"cipher"`
CipherText string `json:"ciphertext"`
CipherParams cipherparamsJSON `json:"cipherparams"`
KDF string `json:"kdf"`
KDFParams map[string]interface{} `json:"kdfparams"`
MAC string `json:"mac"`
}
type cipherparamsJSON struct {
IV string `json:"iv"`
}
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 == keyHeaderKDF {
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)
}
func ensureInt(x interface{}) int {
res, ok := x.(int)
if !ok {
res = int(x.(float64))
}
return res
}
func aesCTRXOR(key, inText, iv []byte) ([]byte, error) {
// AES-128 is selected due to size of encryptKey.
aesBlock, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
stream := cipher.NewCTR(aesBlock, iv)
outText := make([]byte, len(inText))
stream.XORKeyStream(outText, inText)
return outText, err
}
func aesCBCDecrypt(key, cipherText, iv []byte) ([]byte, error) {
aesBlock, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
decrypter := cipher.NewCBCDecrypter(aesBlock, iv)
paddedPlaintext := make([]byte, len(cipherText))
decrypter.CryptBlocks(paddedPlaintext, cipherText)
plaintext := pkcs7Unpad(paddedPlaintext)
if plaintext == nil {
return nil, errDecrypt
}
return plaintext, err
}
func pkcs7Unpad(in []byte) []byte {
if len(in) == 0 {
return nil
}
padding := in[len(in)-1]
if int(padding) > len(in) || padding > aes.BlockSize {
return nil
} else if padding == 0 {
return nil
}
for i := len(in) - 1; i > len(in)-int(padding)-1; i-- {
if in[i] != padding {
return nil
}
}
return in[:len(in)-int(padding)]
}