accounts, core, crypto, internal: use normalised V during signature handling (#3455)

To address increasing complexity in code that handles signatures, this PR
discards all notion of "different" signature types at the library level. Both
the crypto and accounts package is reduced to only be able to produce plain
canonical secp256k1 signatures. This makes the crpyto APIs much cleaner,
simpler and harder to abuse.

internal/ethapi/api.go

@@ -287,11 +287,19 @@ func signHash(data []byte) []byte {
 // Sign calculates an Ethereum ECDSA signature for:
 // keccack256("\x19Ethereum Signed Message:\n" + len(message) + message))
 //
+// Note, the produced signature conforms to the secp256k1 curve R, S and V values,
+// where the V value will be 27 or 28 for legacy reasons.
+//
 // The key used to calculate the signature is decrypted with the given password.
 //
 // https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_sign
 func (s *PrivateAccountAPI) Sign(ctx context.Context, data hexutil.Bytes, addr common.Address, passwd string) (hexutil.Bytes, error) {
-	return s.b.AccountManager().SignWithPassphrase(addr, passwd, signHash(data))
+	signature, err := s.b.AccountManager().SignWithPassphrase(addr, passwd, signHash(data))
+	if err != nil {
+		return nil, err
+	}
+	signature[64] += 27 // SignWithPassphrase uses canonical secp256k1 signatures (v = 0 or 1), transform to yellow paper
+	return signature, nil
 }
 
 // EcRecover returns the address for the account that was used to create the signature.
@@ -300,15 +308,19 @@ func (s *PrivateAccountAPI) Sign(ctx context.Context, data hexutil.Bytes, addr c
 // hash = keccak256("\x19Ethereum Signed Message:\n"${message length}${message})
 // addr = ecrecover(hash, signature)
 //
+// Note, the signature must conform to the secp256k1 curve R, S and V values, where
+// the V value must be be 27 or 28 for legacy reasons.
+//
 // https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_ecRecover
 func (s *PrivateAccountAPI) EcRecover(ctx context.Context, data, sig hexutil.Bytes) (common.Address, error) {
 	if len(sig) != 65 {
 		return common.Address{}, fmt.Errorf("signature must be 65 bytes long")
 	}
-	// see crypto.Ecrecover description
-	if sig[64] == 27 || sig[64] == 28 {
-		sig[64] -= 27
+	if sig[64] != 27 && sig[64] != 28 {
+		return common.Address{}, fmt.Errorf("invalid Ethereum signature (V is not 27 or 28)")
 	}
+	sig[64] -= 27 // Transform yellow paper signatures to canonical secp256k1 form
+
 	rpk, err := crypto.Ecrecover(signHash(data), sig)
 	if err != nil {
 		return common.Address{}, err
@@ -964,7 +976,7 @@ func (s *PublicTransactionPoolAPI) GetTransactionReceipt(txHash common.Hash) (ma
 func (s *PublicTransactionPoolAPI) sign(addr common.Address, tx *types.Transaction) (*types.Transaction, error) {
 	signer := types.MakeSigner(s.b.ChainConfig(), s.b.CurrentBlock().Number())
 
-	signature, err := s.b.AccountManager().SignEthereum(addr, signer.Hash(tx).Bytes())
+	signature, err := s.b.AccountManager().Sign(addr, signer.Hash(tx).Bytes())
 	if err != nil {
 		return nil, err
 	}
@@ -1046,11 +1058,10 @@ func (s *PublicTransactionPoolAPI) SendTransaction(ctx context.Context, args Sen
 	}
 	tx := args.toTransaction()
 	signer := types.MakeSigner(s.b.ChainConfig(), s.b.CurrentBlock().Number())
-	signature, err := s.b.AccountManager().SignEthereum(args.From, signer.Hash(tx).Bytes())
+	signature, err := s.b.AccountManager().Sign(args.From, signer.Hash(tx).Bytes())
 	if err != nil {
 		return common.Hash{}, err
 	}
-
 	return submitTransaction(ctx, s.b, tx, signature)
 }
 
@@ -1084,11 +1095,19 @@ func (s *PublicTransactionPoolAPI) SendRawTransaction(ctx context.Context, encod
 // Sign calculates an ECDSA signature for:
 // keccack256("\x19Ethereum Signed Message:\n" + len(message) + message).
 //
+// Note, the produced signature conforms to the secp256k1 curve R, S and V values,
+// where the V value will be 27 or 28 for legacy reasons.
+//
 // The account associated with addr must be unlocked.
 //
 // https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign
 func (s *PublicTransactionPoolAPI) Sign(addr common.Address, data hexutil.Bytes) (hexutil.Bytes, error) {
-	return s.b.AccountManager().SignEthereum(addr, signHash(data))
+	signature, err := s.b.AccountManager().Sign(addr, signHash(data))
+	if err == nil {
+		// Sign uses canonical secp256k1 signatures (v = 0 or 1), transform to yellow paper
+		signature[64] += 27
+	}
+	return signature, err
 }
 
 // SignTransactionResult represents a RLP encoded signed transaction.