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)
}
// Key derives a key from the password, salt, and cost parameters, returning
// a byte slice of length keyLen that can be used as cryptographic key.
//
// N is a CPU/memory cost parameter, which must be a power of two greater than 1.
// r and p must satisfy r * p < 2³⁰. If the parameters do not satisfy the
// limits, the function returns a nil byte slice and an error.
//
// For example, you can get a derived key for e.g. AES-256 (which needs a
// 32-byte key) by doing:
//
// dk := scrypt.Key([]byte("some password"), salt, 16384, 8, 1, 32)
//
// The recommended parameters for interactive logins as of 2009 are N=16384,
// r=8, p=1. They should be increased as memory latency and CPU parallelism
// increases. Remember to get a good random salt.
func Key(password, salt []byte, N, r, p, keyLen int) ([]byte, error) {
if N <= 1 || N&(N-1) != 0 {
return nil, errors.New("scrypt: N must be > 1 and a power of 2")
}
if uint64(r)*uint64(p) >= 1<<30 || r > maxInt/128/p || r > maxInt/256 || N > maxInt/128/r {
return nil, errors.New("scrypt: parameters are too large")
}
xy := make([]uint32, 64*r)
v := make([]uint32, 32*N*r)
b := pbkdf2.Key(password, salt, 1, p*128*r, sha256.New)
for i := 0; i < p; i++ {
smix(b[i*128*r:], r, N, v, xy)
}
return pbkdf2.Key(password, b, 1, keyLen, sha256.New), nil
}
func decryptPreSaleKey(fileContent []byte, password string) (key *Key, err error) {
preSaleKeyStruct := struct {
EncSeed string
EthAddr string
Email string
BtcAddr string
}{}
err = json.Unmarshal(fileContent, &preSaleKeyStruct)
if err != nil {
return nil, err
}
encSeedBytes, err := hex.DecodeString(preSaleKeyStruct.EncSeed)
iv := encSeedBytes[:16]
cipherText := encSeedBytes[16:]
/*
See https://github.com/ethereum/pyethsaletool
pyethsaletool generates the encryption key from password by
2000 rounds of PBKDF2 with HMAC-SHA-256 using password as salt (:().
16 byte key length within PBKDF2 and resulting key is used as AES key
*/
passBytes := []byte(password)
derivedKey := pbkdf2.Key(passBytes, passBytes, 2000, 16, sha256.New)
plainText, err := aesCBCDecrypt(derivedKey, cipherText, iv)
if err != nil {
return nil, err
}
ethPriv := Sha3(plainText)
ecKey := ToECDSA(ethPriv)
key = &Key{
Id: nil,
Address: PubkeyToAddress(ecKey.PublicKey),
PrivateKey: ecKey,
}
derivedAddr := hex.EncodeToString(key.Address.Bytes()) // needed because .Hex() gives leading "0x"
expectedAddr := preSaleKeyStruct.EthAddr
if derivedAddr != expectedAddr {
err = fmt.Errorf("decrypted addr '%s' not equal to expected addr '%s'", derivedAddr, expectedAddr)
}
return key, err
}