path: root/crypto/crypto.go

// Copyright 2014 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 crypto

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    "encoding/hex"
    "errors"
    "io"
    "io/ioutil"
    "math/big"
    "os"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto/sha3"
    "github.com/ethereum/go-ethereum/rlp"
)

var (
    secp256k1_N, _  = new(big.Int).SetString("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141", 16)
    secp256k1_halfN = new(big.Int).Div(secp256k1_N, big.NewInt(2))
)

// Hasher is a repetitive hasher allowing the same hash data structures to be
// reused between hash runs instead of requiring new ones to be created.
type Hasher func(data []byte) []byte

// Keccak256 calculates and returns the Keccak256 hash of the input data.
func Keccak256(data ...[]byte) []byte {
    d := sha3.NewKeccak256()
    for _, b := range data {
        d.Write(b)
    }
    return d.Sum(nil)
}

// Keccak256Hash calculates and returns the Keccak256 hash of the input data,
// converting it to an internal Hash data structure.
func Keccak256Hash(data ...[]byte) (h common.Hash) {
    d := sha3.NewKeccak256()
    for _, b := range data {
        d.Write(b)
    }
    d.Sum(h[:0])
    return h
}

// Keccak256Hasher creates a repetitive Keccak256 hasher, allowing the same hash
// data structures to be reused between hash runs instead of requiring new ones
// to be created.
//
// The returned function is not thread safe!
func Keccak256Hasher() Hasher {
    hasher := sha3.NewKeccak256()

    return func(data []byte) []byte {
        hasher.Write(data)
        result := hasher.Sum(nil)
        hasher.Reset()
        return result
    }
}

// Keccak512 calculates and returns the Keccak512 hash of the input data.
func Keccak512(data ...[]byte) []byte {
    d := sha3.NewKeccak512()
    for _, b := range data {
        d.Write(b)
    }
    return d.Sum(nil)
}

// Keccak512Hasher creates a repetitive Keccak512 hasher, allowing the same hash
// data structures to be reused between hash runs instead of requiring new ones
// to be created.
//
// The returned function is not thread safe!
func Keccak512Hasher() Hasher {
    hasher := sha3.NewKeccak512()

    return func(data []byte) []byte {
        hasher.Write(data)
        result := hasher.Sum(nil)
        hasher.Reset()
        return result
    }
}

// Deprecated: For backward compatibility as other packages depend on these
func Sha3Hash(data ...[]byte) common.Hash { return Keccak256Hash(data...) }

// Creates an ethereum address given the bytes and the nonce
func CreateAddress(b common.Address, nonce uint64) common.Address {
    data, _ := rlp.EncodeToBytes([]interface{}{b, nonce})
    return common.BytesToAddress(Keccak256(data)[12:])
}

// ToECDSA creates a private key with the given D value.
func ToECDSA(prv []byte) *ecdsa.PrivateKey {
    if len(prv) == 0 {
        return nil
    }

    priv := new(ecdsa.PrivateKey)
    priv.PublicKey.Curve = S256()
    priv.D = new(big.Int).SetBytes(prv)
    priv.PublicKey.X, priv.PublicKey.Y = priv.PublicKey.Curve.ScalarBaseMult(prv)
    return priv
}

func FromECDSA(prv *ecdsa.PrivateKey) []byte {
    if prv == nil {
        return nil
    }
    return prv.D.Bytes()
}

func ToECDSAPub(pub []byte) *ecdsa.PublicKey {
    if len(pub) == 0 {
        return nil
    }
    x, y := elliptic.Unmarshal(S256(), pub)
    return &ecdsa.PublicKey{Curve: S256(), X: x, Y: y}
}

func FromECDSAPub(pub *ecdsa.PublicKey) []byte {
    if pub == nil || pub.X == nil || pub.Y == nil {
        return nil
    }
    return elliptic.Marshal(S256(), pub.X, pub.Y)
}

// HexToECDSA parses a secp256k1 private key.
func HexToECDSA(hexkey string) (*ecdsa.PrivateKey, error) {
    b, err := hex.DecodeString(hexkey)
    if err != nil {
        return nil, errors.New("invalid hex string")
    }
    if len(b) != 32 {
        return nil, errors.New("invalid length, need 256 bits")
    }
    return ToECDSA(b), nil
}

// LoadECDSA loads a secp256k1 private key from the given file.
// The key data is expected to be hex-encoded.
func LoadECDSA(file string) (*ecdsa.PrivateKey, error) {
    buf := make([]byte, 64)
    fd, err := os.Open(file)
    if err != nil {
        return nil, err
    }
    defer fd.Close()
    if _, err := io.ReadFull(fd, buf); err != nil {
        return nil, err
    }

    key, err := hex.DecodeString(string(buf))
    if err != nil {
        return nil, err
    }

    return ToECDSA(key), nil
}

// SaveECDSA saves a secp256k1 private key to the given file with
// restrictive permissions. The key data is saved hex-encoded.
func SaveECDSA(file string, key *ecdsa.PrivateKey) error {
    k := hex.EncodeToString(FromECDSA(key))
    return ioutil.WriteFile(file, []byte(k), 0600)
}

func GenerateKey() (*ecdsa.PrivateKey, error) {
    return ecdsa.GenerateKey(S256(), rand.Reader)
}

// ValidateSignatureValues verifies whether the signature values are valid with
// the given chain rules. The v value is assumed to be either 0 or 1.
func ValidateSignatureValues(v byte, r, s *big.Int, homestead bool) bool {
    if r.Cmp(common.Big1) < 0 || s.Cmp(common.Big1) < 0 {
        return false
    }
    // reject upper range of s values (ECDSA malleability)
    // see discussion in secp256k1/libsecp256k1/include/secp256k1.h
    if homestead && s.Cmp(secp256k1_halfN) > 0 {
        return false
    }
    // Frontier: allow s to be in full N range
    return r.Cmp(secp256k1_N) < 0 && s.Cmp(secp256k1_N) < 0 && (v == 0 || v == 1)
}

func PubkeyToAddress(p ecdsa.PublicKey) common.Address {
    pubBytes := FromECDSAPub(&p)
    return common.BytesToAddress(Keccak256(pubBytes[1:])[12:])
}

func zeroBytes(bytes []byte) {
    for i := range bytes {
        bytes[i] = 0
    }
}