Change keystore to version 3
* 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
@ -26,40 +26,7 @@
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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 scrypt derived key
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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 in the key file.
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3. MAC is SHA3-256 of concatenation of ciphertext and
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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 in the 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 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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The crypto is documented at https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition
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*/
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@ -68,23 +35,25 @@ 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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"crypto/sha256"
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"encoding/hex"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"reflect"
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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/pbkdf2"
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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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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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@ -105,7 +74,7 @@ func (ks keyStorePassphrase) GenerateNewKey(rand io.Reader, auth string) (key *K
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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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keyBytes, keyId, err := DecryptKeyFromFile(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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@ -129,51 +98,43 @@ func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
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return err
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}
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encryptKey := Sha3(derivedKey[:16])[:16]
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encryptKey := derivedKey[: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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iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
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cipherText, err := aesCTRXOR(encryptKey, keyBytes, iv)
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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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scryptParamsJSON := make(map[string]interface{}, 5)
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scryptParamsJSON["n"] = scryptN
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scryptParamsJSON["r"] = scryptr
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scryptParamsJSON["p"] = scryptp
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scryptParamsJSON["dklen"] = scryptdkLen
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scryptParamsJSON["salt"] = hex.EncodeToString(salt)
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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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Cipher: "aes-128-ctr",
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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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encryptedKeyJSONV3 := encryptedKeyJSONV3{
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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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keyJSON, err := json.Marshal(encryptedKeyJSONV3)
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if err != nil {
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return err
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}
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@ -183,7 +144,7 @@ func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
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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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_, _, err = DecryptKeyFromFile(ks, keyAddr, auth)
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if err != nil {
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return err
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}
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@ -192,17 +153,43 @@ func (ks keyStorePassphrase) DeleteKey(keyAddr common.Address, auth string) (err
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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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func DecryptKeyFromFile(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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m := make(map[string]interface{})
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err = json.Unmarshal(fileContent, &m)
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v := reflect.ValueOf(m["version"])
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if v.Kind() == reflect.String && v.String() == "1" {
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k := new(encryptedKeyJSONV1)
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err := json.Unmarshal(fileContent, k)
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if err != nil {
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return nil, nil, err
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}
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return decryptKeyV1(k, auth)
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} else {
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k := new(encryptedKeyJSONV3)
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err := json.Unmarshal(fileContent, k)
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if err != nil {
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return nil, nil, err
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}
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return decryptKeyV3(k, auth)
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}
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}
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func decryptKeyV3(keyProtected *encryptedKeyJSONV3, auth string) (keyBytes []byte, keyId []byte, err error) {
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if keyProtected.Version != version {
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return nil, nil, fmt.Errorf("Version not supported: %v", keyProtected.Version)
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}
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if keyProtected.Crypto.Cipher != "aes-128-ctr" {
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return nil, nil, fmt.Errorf("Cipher not supported: %v", keyProtected.Crypto.Cipher)
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}
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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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@ -218,27 +205,49 @@ func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (key
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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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derivedKey, err := getKDFKey(keyProtected.Crypto, auth)
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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, errors.New("Decryption failed: MAC mismatch")
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}
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plainText, err := aesCTRXOR(derivedKey[: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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func decryptKeyV1(keyProtected *encryptedKeyJSONV1, auth string) (keyBytes []byte, keyId []byte, err error) {
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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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derivedKey, err := getKDFKey(keyProtected.Crypto, auth)
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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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return nil, nil, errors.New("Decryption failed: MAC mismatch")
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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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@ -246,3 +255,41 @@ func DecryptKey(ks keyStorePassphrase, keyAddr common.Address, auth string) (key
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}
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return plainText, keyId, err
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}
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func getKDFKey(cryptoJSON cryptoJSON, auth string) ([]byte, error) {
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authArray := []byte(auth)
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salt, err := hex.DecodeString(cryptoJSON.KDFParams["salt"].(string))
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if err != nil {
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return nil, err
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}
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dkLen := ensureInt(cryptoJSON.KDFParams["dklen"])
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if cryptoJSON.KDF == "scrypt" {
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n := ensureInt(cryptoJSON.KDFParams["n"])
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r := ensureInt(cryptoJSON.KDFParams["r"])
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p := ensureInt(cryptoJSON.KDFParams["p"])
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return scrypt.Key(authArray, salt, n, r, p, dkLen)
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} else if cryptoJSON.KDF == "pbkdf2" {
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c := ensureInt(cryptoJSON.KDFParams["c"])
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prf := cryptoJSON.KDFParams["prf"].(string)
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if prf != "hmac-sha256" {
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return nil, fmt.Errorf("Unsupported PBKDF2 PRF: ", prf)
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}
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key := pbkdf2.Key(authArray, salt, c, dkLen, sha256.New)
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return key, nil
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}
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return nil, fmt.Errorf("Unsupported KDF: ", cryptoJSON.KDF)
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}
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// TODO: can we do without this when unmarshalling dynamic JSON?
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// why do integers in KDF params end up as float64 and not int after
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// unmarshal?
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func ensureInt(x interface{}) int {
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res, ok := x.(int)
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if !ok {
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res = int(x.(float64))
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}
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return res
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}
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