165 lines
3.5 KiB
Go
165 lines
3.5 KiB
Go
package wallet
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import (
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"bytes"
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"crypto/sha256"
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"errors"
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"fmt"
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"github.com/CityOfZion/neo-go/pkg/crypto"
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"golang.org/x/crypto/scrypt"
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"golang.org/x/text/unicode/norm"
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)
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// NEP-2 standard implementation for encrypting and decrypting wallets.
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// NEP-2 specified parameters used for cryptography.
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const (
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n = 16384
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r = 8
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p = 8
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keyLen = 64
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nepFlag = 0xe0
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)
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var nepHeader = []byte{0x01, 0x42}
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type scryptParams struct {
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N int `json:"n"`
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R int `json:"r"`
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P int `json:"p"`
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}
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func newScryptParams() scryptParams {
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return scryptParams{
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N: n,
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R: r,
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P: p,
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}
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}
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// NEP2Encrypt encrypts a the PrivateKey using a given passphrase
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// under the NEP-2 standard.
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func NEP2Encrypt(priv *PrivateKey, passphrase string) (s string, err error) {
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address, err := priv.Address()
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if err != nil {
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return s, err
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}
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addrHash := hashAddress(address)[0:4]
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// Normalize the passphrase according to the NFC standard.
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phraseNorm := norm.NFC.Bytes([]byte(passphrase))
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derivedKey, err := scrypt.Key(phraseNorm, addrHash, n, r, p, keyLen)
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if err != nil {
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return s, err
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}
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derivedKey1 := derivedKey[:32]
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derivedKey2 := derivedKey[32:]
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xr := xor(priv.Bytes(), derivedKey1)
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encrypted, err := crypto.AESEncrypt(xr, derivedKey2)
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if err != nil {
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return s, err
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}
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buf := new(bytes.Buffer)
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buf.Write(nepHeader)
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buf.WriteByte(nepFlag)
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buf.Write(addrHash)
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buf.Write(encrypted)
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if buf.Len() != 39 {
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return s, fmt.Errorf("invalid buffer length: expecting 39 bytes got %d", buf.Len())
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}
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return crypto.Base58CheckEncode(buf.Bytes()), nil
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}
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// NEP2Decrypt decrypts an encrypted key using a given passphrase
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// under the NEP-2 standard.
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func NEP2Decrypt(key, passphrase string) (s string, err error) {
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b, err := crypto.Base58CheckDecode(key)
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if err != nil {
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return s, nil
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}
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if err := validateNEP2Format(b); err != nil {
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return s, err
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}
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addrHash := b[3:7]
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// Normalize the passphrase according to the NFC standard.
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phraseNorm := norm.NFC.Bytes([]byte(passphrase))
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derivedKey, err := scrypt.Key(phraseNorm, addrHash, n, r, p, keyLen)
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if err != nil {
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return s, err
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}
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derivedKey1 := derivedKey[:32]
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derivedKey2 := derivedKey[32:]
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encryptedBytes := b[7:]
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decrypted, err := crypto.AESDecrypt(encryptedBytes, derivedKey2)
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if err != nil {
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return s, err
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}
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privBytes := xor(decrypted, derivedKey1)
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// Rebuild the private key.
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privKey, err := NewPrivateKeyFromBytes(privBytes)
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if err != nil {
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return s, err
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}
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if !compareAddressHash(privKey, addrHash) {
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return s, errors.New("password mismatch")
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}
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return privKey.WIF()
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}
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func compareAddressHash(priv *PrivateKey, hash []byte) bool {
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address, err := priv.Address()
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if err != nil {
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return false
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}
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addrHash := hashAddress(address)[0:4]
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return bytes.Compare(addrHash, hash) == 0
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}
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func validateNEP2Format(b []byte) error {
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if len(b) != 39 {
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return fmt.Errorf("invalid length: expecting 39 got %d", len(b))
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}
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if b[0] != 0x01 {
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return fmt.Errorf("invalid byte sequence: expecting 0x01 got 0x%02x", b[0])
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}
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if b[1] != 0x42 {
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return fmt.Errorf("invalid byte sequence: expecting 0x42 got 0x%02x", b[1])
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}
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if b[2] != 0xe0 {
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return fmt.Errorf("invalid byte sequence: expecting 0xe0 got 0x%02x", b[2])
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}
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return nil
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}
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func xor(a, b []byte) []byte {
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if len(a) != len(b) {
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panic("cannot XOR non equal length arrays")
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}
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dst := make([]byte, len(a))
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for i := 0; i < len(dst); i++ {
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dst[i] = a[i] ^ b[i]
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}
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return dst
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}
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func hashAddress(addr string) []byte {
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sha := sha256.New()
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sha.Write([]byte(addr))
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hash := sha.Sum(nil)
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sha.Reset()
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sha.Write(hash)
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return sha.Sum(nil)
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}
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