Official Go implementation of the Ethereum protocol
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go-ethereum/crypto/signature_nocgo.go

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6.0 KiB

// Copyright 2017 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/>.
//go:build nacl || js || !cgo || gofuzz
// +build nacl js !cgo gofuzz
package crypto
import (
"crypto/ecdsa"
"errors"
"fmt"
"math/big"
"github.com/btcsuite/btcd/btcec/v2"
btc_ecdsa "github.com/btcsuite/btcd/btcec/v2/ecdsa"
)
// Ecrecover returns the uncompressed public key that created the given signature.
func Ecrecover(hash, sig []byte) ([]byte, error) {
pub, err := sigToPub(hash, sig)
if err != nil {
return nil, err
}
bytes := pub.SerializeUncompressed()
return bytes, err
}
func sigToPub(hash, sig []byte) (*btcec.PublicKey, error) {
if len(sig) != SignatureLength {
return nil, errors.New("invalid signature")
}
// Convert to btcec input format with 'recovery id' v at the beginning.
btcsig := make([]byte, SignatureLength)
btcsig[0] = sig[RecoveryIDOffset] + 27
copy(btcsig[1:], sig)
pub, _, err := btc_ecdsa.RecoverCompact(btcsig, hash)
return pub, err
}
// SigToPub returns the public key that created the given signature.
func SigToPub(hash, sig []byte) (*ecdsa.PublicKey, error) {
pub, err := sigToPub(hash, sig)
if err != nil {
return nil, err
}
// We need to explicitly set the curve here, because we're wrapping
// the original curve to add (un-)marshalling
return &ecdsa.PublicKey{
Curve: S256(),
X: pub.X(),
Y: pub.Y(),
}, nil
}
// Sign calculates an ECDSA signature.
//
// This function is susceptible to chosen plaintext attacks that can leak
// information about the private key that is used for signing. Callers must
// be aware that the given hash cannot be chosen by an adversary. Common
// solution is to hash any input before calculating the signature.
//
// The produced signature is in the [R || S || V] format where V is 0 or 1.
func Sign(hash []byte, prv *ecdsa.PrivateKey) ([]byte, error) {
if len(hash) != 32 {
return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
}
if prv.Curve != S256() {
return nil, errors.New("private key curve is not secp256k1")
}
// ecdsa.PrivateKey -> btcec.PrivateKey
var priv btcec.PrivateKey
if overflow := priv.Key.SetByteSlice(prv.D.Bytes()); overflow || priv.Key.IsZero() {
return nil, errors.New("invalid private key")
}
defer priv.Zero()
sig := btc_ecdsa.SignCompact(&priv, hash, false) // ref uncompressed pubkey
// Convert to Ethereum signature format with 'recovery id' v at the end.
v := sig[0] - 27
copy(sig, sig[1:])
sig[RecoveryIDOffset] = v
return sig, nil
}
// VerifySignature checks that the given public key created signature over hash.
// The public key should be in compressed (33 bytes) or uncompressed (65 bytes) format.
// The signature should have the 64 byte [R || S] format.
func VerifySignature(pubkey, hash, signature []byte) bool {
if len(signature) != 64 {
return false
}
var r, s btcec.ModNScalar
if r.SetByteSlice(signature[:32]) {
return false // overflow
}
if s.SetByteSlice(signature[32:]) {
return false
}
sig := btc_ecdsa.NewSignature(&r, &s)
key, err := btcec.ParsePubKey(pubkey)
if err != nil {
return false
}
// Reject malleable signatures. libsecp256k1 does this check but btcec doesn't.
if s.IsOverHalfOrder() {
return false
}
return sig.Verify(hash, key)
}
// DecompressPubkey parses a public key in the 33-byte compressed format.
func DecompressPubkey(pubkey []byte) (*ecdsa.PublicKey, error) {
if len(pubkey) != 33 {
return nil, errors.New("invalid compressed public key length")
}
key, err := btcec.ParsePubKey(pubkey)
if err != nil {
return nil, err
}
// We need to explicitly set the curve here, because we're wrapping
// the original curve to add (un-)marshalling
return &ecdsa.PublicKey{
Curve: S256(),
X: key.X(),
Y: key.Y(),
}, nil
}
// CompressPubkey encodes a public key to the 33-byte compressed format. The
// provided PublicKey must be valid. Namely, the coordinates must not be larger
// than 32 bytes each, they must be less than the field prime, and it must be a
// point on the secp256k1 curve. This is the case for a PublicKey constructed by
// elliptic.Unmarshal (see UnmarshalPubkey), or by ToECDSA and ecdsa.GenerateKey
// when constructing a PrivateKey.
func CompressPubkey(pubkey *ecdsa.PublicKey) []byte {
// NOTE: the coordinates may be validated with
// btcec.ParsePubKey(FromECDSAPub(pubkey))
var x, y btcec.FieldVal
x.SetByteSlice(pubkey.X.Bytes())
y.SetByteSlice(pubkey.Y.Bytes())
return btcec.NewPublicKey(&x, &y).SerializeCompressed()
}
// S256 returns an instance of the secp256k1 curve.
func S256() EllipticCurve {
return btCurve{btcec.S256()}
}
type btCurve struct {
*btcec.KoblitzCurve
}
// Marshal converts a point given as (x, y) into a byte slice.
func (curve btCurve) Marshal(x, y *big.Int) []byte {
byteLen := (curve.Params().BitSize + 7) / 8
ret := make([]byte, 1+2*byteLen)
ret[0] = 4 // uncompressed point
x.FillBytes(ret[1 : 1+byteLen])
y.FillBytes(ret[1+byteLen : 1+2*byteLen])
return ret
}
// Unmarshal converts a point, serialised by Marshal, into an x, y pair. On
// error, x = nil.
func (curve btCurve) Unmarshal(data []byte) (x, y *big.Int) {
byteLen := (curve.Params().BitSize + 7) / 8
if len(data) != 1+2*byteLen {
return nil, nil
}
if data[0] != 4 { // uncompressed form
return nil, nil
}
x = new(big.Int).SetBytes(data[1 : 1+byteLen])
y = new(big.Int).SetBytes(data[1+byteLen:])
return
}