path: root/crypto/key_store_passphrase.go

// Copyright 2014 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum 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.
//
// go-ethereum 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 go-ethereum.  If not, see <http://www.gnu.org/licenses/>.

/*

This key store behaves as KeyStorePlain with the difference that
the private key is encrypted and on disk uses another JSON encoding.

The crypto is documented at https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition

*/

package crypto

import (
    "bytes"
    "crypto/aes"
    "crypto/sha256"
    "encoding/hex"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "reflect"

    "code.google.com/p/go-uuid/uuid"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto/randentropy"
    "golang.org/x/crypto/pbkdf2"
    "golang.org/x/crypto/scrypt"
)

const (
    keyHeaderKDF = "scrypt"
    // 2^18 / 8 / 1 uses 256MB memory and approx 1s CPU time on a modern CPU.
    scryptN     = 1 << 18
    scryptr     = 8
    scryptp     = 1
    scryptdkLen = 32
)

type keyStorePassphrase struct {
    keysDirPath string
}

func NewKeyStorePassphrase(path string) KeyStore {
    return &keyStorePassphrase{path}
}

func (ks keyStorePassphrase) GenerateNewKey(rand io.Reader, auth string) (key *Key, err error) {
    return GenerateNewKeyDefault(ks, rand, auth)
}

func (ks keyStorePassphrase) GetKey(keyAddr common.Address, auth string) (key *Key, err error) {
    keyBytes, keyId, err := decryptKeyFromFile(ks.keysDirPath, keyAddr, auth)
    if err == nil {
        key = &Key{
            Id:         uuid.UUID(keyId),
            Address:    keyAddr,
            PrivateKey: ToECDSA(keyBytes),
        }
    }
    return
}

func (ks keyStorePassphrase) Cleanup(keyAddr common.Address) (err error) {
    return cleanup(ks.keysDirPath, keyAddr)
}

func (ks keyStorePassphrase) GetKeyAddresses() (addresses []common.Address, err error) {
    return getKeyAddresses(ks.keysDirPath)
}

func (ks keyStorePassphrase) StoreKey(key *Key, auth string) (err error) {
    authArray := []byte(auth)
    salt := randentropy.GetEntropyCSPRNG(32)
    derivedKey, err := scrypt.Key(authArray, salt, scryptN, scryptr, scryptp, scryptdkLen)
    if err != nil {
        return err
    }

    encryptKey := derivedKey[:16]
    keyBytes := FromECDSA(key.PrivateKey)

    iv := randentropy.GetEntropyCSPRNG(aes.BlockSize) // 16
    cipherText, err := aesCTRXOR(encryptKey, keyBytes, iv)
    if err != nil {
        return err
    }

    mac := Sha3(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:          "scrypt",
        KDFParams:    scryptParamsJSON,
        MAC:          hex.EncodeToString(mac),
    }
    encryptedKeyJSONV3 := encryptedKeyJSONV3{
        hex.EncodeToString(key.Address[:]),
        cryptoStruct,
        key.Id.String(),
        version,
    }
    keyJSON, err := json.Marshal(encryptedKeyJSONV3)
    if err != nil {
        return err
    }

    return writeKeyFile(key.Address, ks.keysDirPath, keyJSON)
}

func (ks keyStorePassphrase) DeleteKey(keyAddr common.Address, auth string) (err error) {
    // only delete if correct passphrase is given
    _, _, err = decryptKeyFromFile(ks.keysDirPath, keyAddr, auth)
    if err != nil {
        return err
    }

    return deleteKey(ks.keysDirPath, keyAddr)
}

func decryptKeyFromFile(keysDirPath string, keyAddr common.Address, auth string) (keyBytes []byte, keyId []byte, err error) {
    m := make(map[string]interface{})
    err = getKey(keysDirPath, keyAddr, &m)
    if err != nil {
        return
    }

    v := reflect.ValueOf(m["version"])
    if v.Kind() == reflect.String && v.String() == "1" {
        k := new(encryptedKeyJSONV1)
        err = getKey(keysDirPath, keyAddr, &k)
        if err != nil {
            return
        }
        return decryptKeyV1(k, auth)
    } else {
        k := new(encryptedKeyJSONV3)
        err = getKey(keysDirPath, keyAddr, &k)
        if err != nil {
            return
        }
        return decryptKeyV3(k, auth)
    }
}

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 := Sha3(derivedKey[16:32], cipherText)
    if !bytes.Equal(calculatedMAC, mac) {
        return nil, nil, errors.New("Decryption failed: MAC mismatch")
    }

    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 := Sha3(derivedKey[16:32], cipherText)
    if !bytes.Equal(calculatedMAC, mac) {
        return nil, nil, errors.New("Decryption failed: MAC mismatch")
    }

    plainText, err := aesCBCDecrypt(Sha3(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 == "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)
}

// TODO: can we do without this when unmarshalling dynamic JSON?
// why do integers in KDF params end up as float64 and not int after
// unmarshal?
func ensureInt(x interface{}) int {
    res, ok := x.(int)
    if !ok {
        res = int(x.(float64))
    }
    return res
}