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// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package accounts
import (
"crypto/aes"
"crypto/cipher"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"github.com/ethereum/go-ethereum/crypto"
"github.com/pborman/uuid"
"golang.org/x/crypto/pbkdf2"
)
// creates a Key and stores that in the given KeyStore by decrypting a presale key JSON
func importPreSaleKey(keyStore keyStore, keyJSON []byte, password string) (Account, *Key, error) {
key, err := decryptPreSaleKey(keyJSON, password)
if err != nil {
return Account{}, nil, err
}
key.Id = uuid.NewRandom()
a := Account{Address: key.Address, File: keyStore.JoinPath(keyFileName(key.Address))}
err = keyStore.StoreKey(a.File, key, password)
return a, key, err
}
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 := crypto.Keccak256(plainText)
ecKey := crypto.ToECDSA(ethPriv)
key = &Key{
Id: nil,
Address: crypto.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
}
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 {
err = errors.New("Decryption failed: PKCS7Unpad failed after AES decryption")
}
return plaintext, err
}
// From https://leanpub.com/gocrypto/read#leanpub-auto-block-cipher-modes
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)]
}
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