keystore_passphrase.go

//<developer>
//    <name>linapex 曹一峰</name>
//    <email>linapex@163.com</email>
//    <wx>superexc</wx>
//    <qqgroup>128148617</qqgroup>
//    <url>https://jsq.ink</url>
//    <role>pku engineer</role>
//    <date>2019-03-16 12:09:26</date>
//</624342585237835776>


/*

此密钥存储区的行为与密钥存储区的区别在于
私钥是加密的，在磁盘上使用另一个JSON编码。

密码记录在https://github.com/ethereum/wiki/wiki/web3-secret-storage-definition上。

**/


package keystore

import (
	"bytes"
	"crypto/aes"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"path/filepath"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/pborman/uuid"
	"golang.org/x/crypto/pbkdf2"
	"golang.org/x/crypto/scrypt"
)

const (
	keyHeaderKDF = "scrypt"

//标准加密是加密算法的n个参数，使用256MB
//在现代处理器上占用大约1秒的CPU时间。
	StandardScryptN = 1 << 18

//StandardScryptP是加密算法的P参数，使用256MB
//在现代处理器上占用大约1秒的CPU时间。
	StandardScryptP = 1

//lightscryptn是加密算法的n个参数，使用4MB
//在现代处理器上占用大约100毫秒的CPU时间。
	LightScryptN = 1 << 12

//lightscryptp是加密算法的p参数，使用4MB
//在现代处理器上占用大约100毫秒的CPU时间。
	LightScryptP = 6

	scryptR     = 8
	scryptDKLen = 32
)

type keyStorePassphrase struct {
	keysDirPath string
	scryptN     int
	scryptP     int
}

func (ks keyStorePassphrase) GetKey(addr common.Address, filename, auth string) (*Key, error) {
//从密钥库加载密钥并解密其内容
	keyjson, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	key, err := DecryptKey(keyjson, auth)
	if err != nil {
		return nil, err
	}
//确保我们确实在使用请求的密钥（没有交换攻击）
	if key.Address != addr {
		return nil, fmt.Errorf("key content mismatch: have account %x, want %x", key.Address, addr)
	}
	return key, nil
}

//storekey生成一个密钥，用auth加密并存储在给定的目录中
func StoreKey(dir, auth string, scryptN, scryptP int) (common.Address, error) {
	_, a, err := storeNewKey(&keyStorePassphrase{dir, scryptN, scryptP}, rand.Reader, auth)
	return a.Address, err
}

func (ks keyStorePassphrase) StoreKey(filename string, key *Key, auth string) error {
	keyjson, err := EncryptKey(key, auth, ks.scryptN, ks.scryptP)
	if err != nil {
		return err
	}
	return writeKeyFile(filename, keyjson)
}

func (ks keyStorePassphrase) JoinPath(filename string) string {
	if filepath.IsAbs(filename) {
		return filename
	}
	return filepath.Join(ks.keysDirPath, filename)
}

//encryptkey使用指定的scrypt参数将密钥加密到JSON中
//稍后可以解密的blob。
func EncryptKey(key *Key, auth string, scryptN, scryptP int) ([]byte, error) {
	authArray := []byte(auth)

	salt := make([]byte, 32)
	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
		panic("reading from crypto/rand failed: " + err.Error())
	}
	derivedKey, err := scrypt.Key(authArray, salt, scryptN, scryptR, scryptP, scryptDKLen)
	if err != nil {
		return nil, err
	}
	encryptKey := derivedKey[:16]
	keyBytes := math.PaddedBigBytes(key.PrivateKey.D, 32)

iv := make([]byte, aes.BlockSize) //十六
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic("reading from crypto/rand failed: " + err.Error())
	}
	cipherText, err := aesCTRXOR(encryptKey, keyBytes, iv)
	if err != nil {
		return nil, err
	}
	mac := crypto.Keccak256(derivedKey[16:32], cipherText)

	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-ctr",
		CipherText:   hex.EncodeToString(cipherText),
		CipherParams: cipherParamsJSON,
		KDF:          keyHeaderKDF,
		KDFParams:    scryptParamsJSON,
		MAC:          hex.EncodeToString(mac),
	}
	encryptedKeyJSONV3 := encryptedKeyJSONV3{
		hex.EncodeToString(key.Address[:]),
		cryptoStruct,
		key.Id.String(),
		version,
	}
	return json.Marshal(encryptedKeyJSONV3)
}

//decryptkey从JSON blob中解密密钥，返回私钥本身。
func DecryptKey(keyjson []byte, auth string) (*Key, error) {
//将JSON解析为一个简单的映射以获取密钥版本
	m := make(map[string]interface{})
	if err := json.Unmarshal(keyjson, &m); err != nil {
		return nil, err
	}
//根据版本，尝试以某种方式分析
	var (
		keyBytes, keyId []byte
		err             error
	)
	if version, ok := m["version"].(string); ok && version == "1" {
		k := new(encryptedKeyJSONV1)
		if err := json.Unmarshal(keyjson, k); err != nil {
			return nil, err
		}
		keyBytes, keyId, err = decryptKeyV1(k, auth)
	} else {
		k := new(encryptedKeyJSONV3)
		if err := json.Unmarshal(keyjson, k); err != nil {
			return nil, err
		}
		keyBytes, keyId, err = decryptKeyV3(k, auth)
	}
//处理任何解密错误并返回密钥
	if err != nil {
		return nil, err
	}
	key := crypto.ToECDSAUnsafe(keyBytes)

	return &Key{
		Id:         uuid.UUID(keyId),
		Address:    crypto.PubkeyToAddress(key.PublicKey),
		PrivateKey: key,
	}, nil
}

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
	}

	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 := crypto.Keccak256(derivedKey[16:32], cipherText)
	if !bytes.Equal(calculatedMAC, mac) {
		return nil, nil, ErrDecrypt
	}

	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 := crypto.Keccak256(derivedKey[16:32], cipherText)
	if !bytes.Equal(calculatedMAC, mac) {
		return nil, nil, ErrDecrypt
	}

	plainText, err := aesCBCDecrypt(crypto.Keccak256(derivedKey[:16])[:16], cipherText, iv)
	if err != nil {
		return nil, nil, err
	}
	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 == keyHeaderKDF {
		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: %s", prf)
		}
		key := pbkdf2.Key(authArray, salt, c, dkLen, sha256.New)
		return key, nil
	}

	return nil, fmt.Errorf("Unsupported KDF: %s", cryptoJSON.KDF)
}

//TODO:在解组动态JSON时，我们可以不这样做吗？
//为什么kdf参数中的整数以float64结尾，而不是后面的int
//元帅？
func ensureInt(x interface{}) int {
	res, ok := x.(int)
	if !ok {
		res = int(x.(float64))
	}
	return res
}