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// Copyright 2020 The Swarm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package crypto
import (
"crypto/ecdsa"
"errors"
"fmt"
"math/big"
"github.com/btcsuite/btcd/btcec"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethersphere/bee/pkg/crypto/eip712"
)
var (
ErrInvalidLength = errors.New("invalid signature length")
)
type Signer interface {
// Sign signs data with ethereum prefix (eip191 type 0x45).
Sign(data []byte) ([]byte, error)
// SignTx signs an ethereum transaction.
SignTx(transaction *types.Transaction, chainID *big.Int) (*types.Transaction, error)
// SignTypedData signs data according to eip712.
SignTypedData(typedData *eip712.TypedData) ([]byte, error)
// PublicKey returns the public key this signer uses.
PublicKey() (*ecdsa.PublicKey, error)
// EthereumAddress returns the ethereum address this signer uses.
EthereumAddress() (common.Address, error)
}
// addEthereumPrefix adds the ethereum prefix to the data.
func addEthereumPrefix(data []byte) []byte {
return []byte(fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data))
}
// hashWithEthereumPrefix returns the hash that should be signed for the given data.
func hashWithEthereumPrefix(data []byte) ([]byte, error) {
return LegacyKeccak256(addEthereumPrefix(data))
}
// Recover verifies signature with the data base provided.
// It is using `btcec.RecoverCompact` function.
func Recover(signature, data []byte) (*ecdsa.PublicKey, error) {
if len(signature) != 65 {
return nil, ErrInvalidLength
}
// Convert to btcec input format with 'recovery id' v at the beginning.
btcsig := make([]byte, 65)
btcsig[0] = signature[64]
copy(btcsig[1:], signature)
hash, err := hashWithEthereumPrefix(data)
if err != nil {
return nil, err
}
p, _, err := btcec.RecoverCompact(btcec.S256(), btcsig, hash)
return (*ecdsa.PublicKey)(p), err
}
type defaultSigner struct {
key *ecdsa.PrivateKey
}
func NewDefaultSigner(key *ecdsa.PrivateKey) Signer {
return &defaultSigner{
key: key,
}
}
// PublicKey returns the public key this signer uses.
func (d *defaultSigner) PublicKey() (*ecdsa.PublicKey, error) {
return &d.key.PublicKey, nil
}
// Sign signs data with ethereum prefix (eip191 type 0x45).
func (d *defaultSigner) Sign(data []byte) (signature []byte, err error) {
hash, err := hashWithEthereumPrefix(data)
if err != nil {
return nil, err
}
return d.sign(hash, true)
}
// SignTx signs an ethereum transaction.
func (d *defaultSigner) SignTx(transaction *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
txSigner := types.NewEIP155Signer(chainID)
hash := txSigner.Hash(transaction).Bytes()
// isCompressedKey is false here so we get the expected v value (27 or 28)
signature, err := d.sign(hash, false)
if err != nil {
return nil, err
}
// v value needs to be adjusted by 27 as transaction.WithSignature expects it to be 0 or 1
signature[64] -= 27
return transaction.WithSignature(txSigner, signature)
}
// EthereumAddress returns the ethereum address this signer uses.
func (d *defaultSigner) EthereumAddress() (common.Address, error) {
publicKey, err := d.PublicKey()
if err != nil {
return common.Address{}, err
}
eth, err := NewEthereumAddress(*publicKey)
if err != nil {
return common.Address{}, err
}
var ethAddress common.Address
copy(ethAddress[:], eth)
return ethAddress, nil
}
// SignTypedData signs data according to eip712.
func (d *defaultSigner) SignTypedData(typedData *eip712.TypedData) ([]byte, error) {
rawData, err := eip712.EncodeForSigning(typedData)
if err != nil {
return nil, err
}
sighash, err := LegacyKeccak256(rawData)
if err != nil {
return nil, err
}
return d.sign(sighash, false)
}
// sign the provided hash and convert it to the ethereum (r,s,v) format.
func (d *defaultSigner) sign(sighash []byte, isCompressedKey bool) ([]byte, error) {
signature, err := btcec.SignCompact(btcec.S256(), (*btcec.PrivateKey)(d.key), sighash, false)
if err != nil {
return nil, err
}
// Convert to Ethereum signature format with 'recovery id' v at the end.
v := signature[0]
copy(signature, signature[1:])
signature[64] = v
return signature, nil
}
// RecoverEIP712 recovers the public key for eip712 signed data.
func RecoverEIP712(signature []byte, data *eip712.TypedData) (*ecdsa.PublicKey, error) {
if len(signature) != 65 {
return nil, errors.New("invalid length")
}
// Convert to btcec input format with 'recovery id' v at the beginning.
btcsig := make([]byte, 65)
btcsig[0] = signature[64]
copy(btcsig[1:], signature)
rawData, err := eip712.EncodeForSigning(data)
if err != nil {
return nil, err
}
sighash, err := LegacyKeccak256(rawData)
if err != nil {
return nil, err
}
p, _, err := btcec.RecoverCompact(btcec.S256(), btcsig, sighash)
return (*ecdsa.PublicKey)(p), err
}