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Change keystore to version 3

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* Change password protection crypto in keystore to version 3
* Update KeyStoreTests/basic_tests.json
* Add support for PBKDF2 with HMAC-SHA256
* Change MAC and encryption key to avoid unnecessary hashing
* Add tests for test vectors in new wiki page defining version 3
* Add tests for new keystore tests in ethereum/tests repo
* Move JSON loading util to common for use in both tests and
  crypto packages
* Add backwards compatibility with key store version 1
This commit is contained in:
Gustav Simonsson
2015-05-24 03:42:10 +02:00
parent 22c7ce0162
commit d23ec6c419
8 changed files with 385 additions and 95 deletions
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199
crypto/key_store_passphrase.go
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@@ -26,40 +26,7 @@
This key store behaves as KeyStorePlain with the difference that
the private key is encrypted and on disk uses another JSON encoding.
Cryptography:
1. Encryption key is first 16 bytes of scrypt derived key
from user passphrase. Scrypt parameters
(work factors) [1][2] are defined as constants below.
2. Scrypt salt is 32 random bytes from CSPRNG.
It's stored in plain next in the key file.
3. MAC is SHA3-256 of concatenation of ciphertext and
last 16 bytes of scrypt derived key.
4. Plaintext is the EC private key bytes.
5. Encryption algo is AES 128 CBC [3][4]
6. CBC IV is 16 random bytes from CSPRNG.
It's stored in plain next in the key file.
7. Plaintext padding is PKCS #7 [5][6]
Encoding:
1. On disk, the ciphertext, MAC, salt and IV are encoded in a JSON object.
cat a key file to see the structure.
2. byte arrays are base64 JSON strings.
3. The EC private key bytes are in uncompressed form [7].
They are a big-endian byte slice of the absolute value of D [8][9].
References:
1. http://www.tarsnap.com/scrypt/scrypt-slides.pdf
2. http://stackoverflow.com/questions/11126315/what-are-optimal-scrypt-work-factors
3. http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
4. http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_.28CBC.29
5. https://leanpub.com/gocrypto/read#leanpub-auto-block-cipher-modes
6. http://tools.ietf.org/html/rfc2315
7. http://bitcoin.stackexchange.com/questions/3059/what-is-a-compressed-bitcoin-key
8. http://golang.org/pkg/crypto/ecdsa/#PrivateKey
9. https://golang.org/pkg/math/big/#Int.Bytes
The crypto is documented at https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition
*/
@@ -68,23 +35,25 @@ package crypto
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"reflect"
"code.google.com/p/go-uuid/uuid"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto/randentropy"
"golang.org/x/crypto/pbkdf2"
"golang.org/x/crypto/scrypt"
)
const (
keyHeaderVersion = "1"
keyHeaderKDF = "scrypt"
keyHeaderKDF = "scrypt"
// 2^18 / 8 / 1 uses 256MB memory and approx 1s CPU time on a modern CPU.
scryptN = 1 << 18
scryptr = 8
@@ -105,7 +74,7 @@ func (ks keyStorePassphrase) GenerateNewKey(rand io.Reader, auth string) (key *K
}
func (ks keyStorePassphrase) GetKey(keyAddr common.Address, auth string) (key *Key, err error) {
keyBytes, keyId, err := DecryptKey(ks, keyAddr, auth)
keyBytes, keyId, err := DecryptKeyFromFile(ks, keyAddr, auth)
if err != nil {
return nil, err
}
@@ -129,51 +98,43 @@ func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
return err
}
encryptKey := Sha3(derivedKey[:16])[:16]
encryptKey := derivedKey[:16]
keyBytes := FromECDSA(key.PrivateKey)
toEncrypt := PKCS7Pad(keyBytes)
AES128Block, err := aes.NewCipher(encryptKey)
iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
cipherText, err := aesCTRXOR(encryptKey, keyBytes, iv)
if err != nil {
return err
}
iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
AES128CBCEncrypter := cipher.NewCBCEncrypter(AES128Block, iv)
cipherText := make([]byte, len(toEncrypt))
AES128CBCEncrypter.CryptBlocks(cipherText, toEncrypt)
mac := Sha3(derivedKey[16:32], cipherText)
scryptParamsJSON := scryptParamsJSON{
N: scryptN,
R: scryptr,
P: scryptp,
DkLen: scryptdkLen,
Salt: hex.EncodeToString(salt),
}
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-cbc",
Cipher: "aes-128-ctr",
CipherText: hex.EncodeToString(cipherText),
CipherParams: cipherParamsJSON,
KDF: "scrypt",
KDFParams: scryptParamsJSON,
MAC: hex.EncodeToString(mac),
Version: "1",
}
encryptedKeyJSON := encryptedKeyJSON{
encryptedKeyJSONV3 := encryptedKeyJSONV3{
hex.EncodeToString(key.Address[:]),
cryptoStruct,
key.Id.String(),
version,
}
keyJSON, err := json.Marshal(encryptedKeyJSON)
keyJSON, err := json.Marshal(encryptedKeyJSONV3)
if err != nil {
return err
}
@@ -183,7 +144,7 @@ func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
func (ks keyStorePassphrase) DeleteKey(keyAddr common.Address, auth string) (err error) {
// only delete if correct passphrase is given
_, _, err = DecryptKey(ks, keyAddr, auth)
_, _, err = DecryptKeyFromFile(ks, keyAddr, auth)
if err != nil {
return err
}
@@ -192,17 +153,43 @@ func (ks keyStorePassphrase) DeleteKey(keyAddr common.Address, auth string) (err
return os.RemoveAll(keyDirPath)
}
func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (keyBytes []byte, keyId []byte, err error) {
func DecryptKeyFromFile(ks keyStorePassphrase, keyAddr common.Address, auth string) (keyBytes []byte, keyId []byte, err error) {
fileContent, err := GetKeyFile(ks.keysDirPath, keyAddr)
if err != nil {
return nil, nil, err
}
keyProtected := new(encryptedKeyJSON)
err = json.Unmarshal(fileContent, keyProtected)
m := make(map[string]interface{})
err = json.Unmarshal(fileContent, &m)
v := reflect.ValueOf(m["version"])
if v.Kind() == reflect.String && v.String() == "1" {
k := new(encryptedKeyJSONV1)
err := json.Unmarshal(fileContent, k)
if err != nil {
return nil, nil, err
}
return decryptKeyV1(k, auth)
} else {
k := new(encryptedKeyJSONV3)
err := json.Unmarshal(fileContent, k)
if err != nil {
return nil, nil, err
}
return decryptKeyV3(k, auth)
}
}
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
@@ -218,27 +205,49 @@ func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (key
return nil, nil, err
}
salt, err := hex.DecodeString(keyProtected.Crypto.KDFParams.Salt)
if err != nil {
return nil, nil, err
}
n := keyProtected.Crypto.KDFParams.N
r := keyProtected.Crypto.KDFParams.R
p := keyProtected.Crypto.KDFParams.P
dkLen := keyProtected.Crypto.KDFParams.DkLen
authArray := []byte(auth)
derivedKey, err := scrypt.Key(authArray, salt, n, r, p, dkLen)
derivedKey, err := getKDFKey(keyProtected.Crypto, auth)
if err != nil {
return nil, nil, err
}
calculatedMAC := Sha3(derivedKey[16:32], cipherText)
if !bytes.Equal(calculatedMAC, mac) {
err = errors.New("Decryption failed: MAC mismatch")
return nil, nil, errors.New("Decryption failed: MAC mismatch")
}
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 := Sha3(derivedKey[16:32], cipherText)
if !bytes.Equal(calculatedMAC, mac) {
return nil, nil, errors.New("Decryption failed: MAC mismatch")
}
plainText, err := aesCBCDecrypt(Sha3(derivedKey[:16])[:16], cipherText, iv)
if err != nil {
@@ -246,3 +255,41 @@ func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (key
}
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: ", prf)
}
key := pbkdf2.Key(authArray, salt, c, dkLen, sha256.New)
return key, nil
}
return nil, fmt.Errorf("Unsupported KDF: ", 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
}