1 files changed, 260 insertions, 0 deletions
diff --git a/core/types/transaction_signing.go b/core/types/transaction_signing.go
new file mode 100644
index 0000000..cb556eb
--- /dev/null
+++ b/core/types/transaction_signing.go
@@ -0,0 +1,260 @@
+// Copyright 2016 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 types
+
+import (
+	"crypto/ecdsa"
+	"errors"
+	"fmt"
+	"math/big"
+
+	"github.com/ava-labs/coreth/params"
+	"github.com/ava-labs/go-ethereum/common"
+	"github.com/ava-labs/go-ethereum/crypto"
+)
+
+var (
+	ErrInvalidChainId = errors.New("invalid chain id for signer")
+)
+
+// sigCache is used to cache the derived sender and contains
+// the signer used to derive it.
+type sigCache struct {
+	signer Signer
+	from   common.Address
+}
+
+// MakeSigner returns a Signer based on the given chain config and block number.
+func MakeSigner(config *params.ChainConfig, blockNumber *big.Int) Signer {
+	var signer Signer
+	switch {
+	case config.IsEIP155(blockNumber):
+		signer = NewEIP155Signer(config.ChainID)
+	case config.IsHomestead(blockNumber):
+		signer = HomesteadSigner{}
+	default:
+		signer = FrontierSigner{}
+	}
+	return signer
+}
+
+// SignTx signs the transaction using the given signer and private key
+func SignTx(tx *Transaction, s Signer, prv *ecdsa.PrivateKey) (*Transaction, error) {
+	h := s.Hash(tx)
+	sig, err := crypto.Sign(h[:], prv)
+	if err != nil {
+		return nil, err
+	}
+	return tx.WithSignature(s, sig)
+}
+
+// Sender returns the address derived from the signature (V, R, S) using secp256k1
+// elliptic curve and an error if it failed deriving or upon an incorrect
+// signature.
+//
+// Sender may cache the address, allowing it to be used regardless of
+// signing method. The cache is invalidated if the cached signer does
+// not match the signer used in the current call.
+func Sender(signer Signer, tx *Transaction) (common.Address, error) {
+	if sc := tx.from.Load(); sc != nil {
+		sigCache := sc.(sigCache)
+		// If the signer used to derive from in a previous
+		// call is not the same as used current, invalidate
+		// the cache.
+		if sigCache.signer.Equal(signer) {
+			return sigCache.from, nil
+		}
+	}
+
+	addr, err := signer.Sender(tx)
+	if err != nil {
+		return common.Address{}, err
+	}
+	tx.from.Store(sigCache{signer: signer, from: addr})
+	return addr, nil
+}
+
+// Signer encapsulates transaction signature handling. Note that this interface is not a
+// stable API and may change at any time to accommodate new protocol rules.
+type Signer interface {
+	// Sender returns the sender address of the transaction.
+	Sender(tx *Transaction) (common.Address, error)
+	// SignatureValues returns the raw R, S, V values corresponding to the
+	// given signature.
+	SignatureValues(tx *Transaction, sig []byte) (r, s, v *big.Int, err error)
+	// Hash returns the hash to be signed.
+	Hash(tx *Transaction) common.Hash
+	// Equal returns true if the given signer is the same as the receiver.
+	Equal(Signer) bool
+}
+
+// EIP155Transaction implements Signer using the EIP155 rules.
+type EIP155Signer struct {
+	chainId, chainIdMul *big.Int
+}
+
+func NewEIP155Signer(chainId *big.Int) EIP155Signer {
+	if chainId == nil {
+		chainId = new(big.Int)
+	}
+	return EIP155Signer{
+		chainId:    chainId,
+		chainIdMul: new(big.Int).Mul(chainId, big.NewInt(2)),
+	}
+}
+
+func (s EIP155Signer) Equal(s2 Signer) bool {
+	eip155, ok := s2.(EIP155Signer)
+	return ok && eip155.chainId.Cmp(s.chainId) == 0
+}
+
+var big8 = big.NewInt(8)
+
+func (s EIP155Signer) Sender(tx *Transaction) (common.Address, error) {
+	if !tx.Protected() {
+		return HomesteadSigner{}.Sender(tx)
+	}
+	if tx.ChainId().Cmp(s.chainId) != 0 {
+		return common.Address{}, ErrInvalidChainId
+	}
+	V := new(big.Int).Sub(tx.data.V, s.chainIdMul)
+	V.Sub(V, big8)
+	return recoverPlain(s.Hash(tx), tx.data.R, tx.data.S, V, true)
+}
+
+// SignatureValues returns signature values. This signature
+// needs to be in the [R || S || V] format where V is 0 or 1.
+func (s EIP155Signer) SignatureValues(tx *Transaction, sig []byte) (R, S, V *big.Int, err error) {
+	R, S, V, err = HomesteadSigner{}.SignatureValues(tx, sig)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	if s.chainId.Sign() != 0 {
+		V = big.NewInt(int64(sig[64] + 35))
+		V.Add(V, s.chainIdMul)
+	}
+	return R, S, V, nil
+}
+
+// Hash returns the hash to be signed by the sender.
+// It does not uniquely identify the transaction.
+func (s EIP155Signer) Hash(tx *Transaction) common.Hash {
+	return rlpHash([]interface{}{
+		tx.data.AccountNonce,
+		tx.data.Price,
+		tx.data.GasLimit,
+		tx.data.Recipient,
+		tx.data.Amount,
+		tx.data.Payload,
+		s.chainId, uint(0), uint(0),
+	})
+}
+
+// HomesteadTransaction implements TransactionInterface using the
+// homestead rules.
+type HomesteadSigner struct{ FrontierSigner }
+
+func (s HomesteadSigner) Equal(s2 Signer) bool {
+	_, ok := s2.(HomesteadSigner)
+	return ok
+}
+
+// SignatureValues returns signature values. This signature
+// needs to be in the [R || S || V] format where V is 0 or 1.
+func (hs HomesteadSigner) SignatureValues(tx *Transaction, sig []byte) (r, s, v *big.Int, err error) {
+	return hs.FrontierSigner.SignatureValues(tx, sig)
+}
+
+func (hs HomesteadSigner) Sender(tx *Transaction) (common.Address, error) {
+	return recoverPlain(hs.Hash(tx), tx.data.R, tx.data.S, tx.data.V, true)
+}
+
+type FrontierSigner struct{}
+
+func (s FrontierSigner) Equal(s2 Signer) bool {
+	_, ok := s2.(FrontierSigner)
+	return ok
+}
+
+// SignatureValues returns signature values. This signature
+// needs to be in the [R || S || V] format where V is 0 or 1.
+func (fs FrontierSigner) SignatureValues(tx *Transaction, sig []byte) (r, s, v *big.Int, err error) {
+	if len(sig) != crypto.SignatureLength {
+		panic(fmt.Sprintf("wrong size for signature: got %d, want %d", len(sig), crypto.SignatureLength))
+	}
+	r = new(big.Int).SetBytes(sig[:32])
+	s = new(big.Int).SetBytes(sig[32:64])
+	v = new(big.Int).SetBytes([]byte{sig[64] + 27})
+	return r, s, v, nil
+}
+
+// Hash returns the hash to be signed by the sender.
+// It does not uniquely identify the transaction.
+func (fs FrontierSigner) Hash(tx *Transaction) common.Hash {
+	return rlpHash([]interface{}{
+		tx.data.AccountNonce,
+		tx.data.Price,
+		tx.data.GasLimit,
+		tx.data.Recipient,
+		tx.data.Amount,
+		tx.data.Payload,
+	})
+}
+
+func (fs FrontierSigner) Sender(tx *Transaction) (common.Address, error) {
+	return recoverPlain(fs.Hash(tx), tx.data.R, tx.data.S, tx.data.V, false)
+}
+
+func recoverPlain(sighash common.Hash, R, S, Vb *big.Int, homestead bool) (common.Address, error) {
+	if Vb.BitLen() > 8 {
+		return common.Address{}, ErrInvalidSig
+	}
+	V := byte(Vb.Uint64() - 27)
+	if !crypto.ValidateSignatureValues(V, R, S, homestead) {
+		return common.Address{}, ErrInvalidSig
+	}
+	// encode the signature in uncompressed format
+	r, s := R.Bytes(), S.Bytes()
+	sig := make([]byte, crypto.SignatureLength)
+	copy(sig[32-len(r):32], r)
+	copy(sig[64-len(s):64], s)
+	sig[64] = V
+	// recover the public key from the signature
+	pub, err := crypto.Ecrecover(sighash[:], sig)
+	if err != nil {
+		return common.Address{}, err
+	}
+	if len(pub) == 0 || pub[0] != 4 {
+		return common.Address{}, errors.New("invalid public key")
+	}
+	var addr common.Address
+	copy(addr[:], crypto.Keccak256(pub[1:])[12:])
+	return addr, nil
+}
+
+// deriveChainId derives the chain id from the given v parameter
+func deriveChainId(v *big.Int) *big.Int {
+	if v.BitLen() <= 64 {
+		v := v.Uint64()
+		if v == 27 || v == 28 {
+			return new(big.Int)
+		}
+		return new(big.Int).SetUint64((v - 35) / 2)
+	}
+	v = new(big.Int).Sub(v, big.NewInt(35))
+	return v.Div(v, big.NewInt(2))
+}