evm: fix Chain ID derivation (#579)

* evm: fix Chain ID derivation

* update

* changelog

CHANGELOG.md

@@ -55,6 +55,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (evm) [tharsis#579](https://github.com/tharsis/ethermint/pull/579) Update `DeriveChainID` function to handle `v` signature values `< 35`.
 * (encoding) [tharsis#478](https://github.com/tharsis/ethermint/pull/478) Register `Evidence` to amino codec.
 * (rpc) [tharsis#478](https://github.com/tharsis/ethermint/pull/481) Getting the node configuration when calling the `miner` rpc methods.
 * (cli) [tharsis#561](https://github.com/tharsis/ethermint/pull/561) `Export` and `Start` commands now use the same home directory.

x/evm/types/tx_data.go

@@ -54,9 +54,15 @@ func NewTxDataFromTx(tx *ethtypes.Transaction) TxData {
 	return txData
 }
 
-// DeriveChainID derives the chain id from the given v parameter
+// DeriveChainID derives the chain id from the given v parameter.
+//
+// CONTRACT: v value is either:
+//
+//  - {0,1} + CHAIN_ID * 2 + 35, if EIP155 is used
+//  - {0,1} + 27, otherwise
+// Ref: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md
 func DeriveChainID(v *big.Int) *big.Int {
-	if v == nil {
+	if v == nil || v.Sign() < 1 {
 		return nil
 	}
 
@@ -65,6 +71,12 @@ func DeriveChainID(v *big.Int) *big.Int {
 		if v == 27 || v == 28 {
 			return new(big.Int)
 		}
+
+		if v < 35 {
+			return nil
+		}
+
+		// V MUST be of the form {0,1} + CHAIN_ID * 2 + 35
 		return new(big.Int).SetUint64((v - 35) / 2)
 	}
 	v = new(big.Int).Sub(v, big.NewInt(35))

x/evm/types/tx_data_test.go

@@ -7,9 +7,6 @@ import (
 	"github.com/stretchr/testify/require"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
-	"github.com/ethereum/go-ethereum/common"
-
-	"github.com/tharsis/ethermint/tests"
 )
 
 func TestTxData_chainID(t *testing.T) {
@@ -38,26 +35,49 @@ func TestTxData_chainID(t *testing.T) {
 }
 
 func TestTxData_DeriveChainID(t *testing.T) {
+	bitLen64, ok := new(big.Int).SetString("0x8000000000000000", 0)
+	require.True(t, ok)
+
+	bitLen80, ok := new(big.Int).SetString("0x80000000000000000000", 0)
+	require.True(t, ok)
+
+	expBitLen80, ok := new(big.Int).SetString("302231454903657293676526", 0)
+	require.True(t, ok)
+
 	testCases := []struct {
 		msg        string
 		data       TxData
 		expChainID *big.Int
-		from       common.Address
 	}{
 		{
-			"v = 0", &AccessListTx{V: big.NewInt(0).Bytes()}, nil, tests.GenerateAddress(),
+			"v = -1", &LegacyTx{V: big.NewInt(-1).Bytes()}, nil,
 		},
 		{
-			"v = 1", &AccessListTx{V: big.NewInt(1).Bytes()}, big.NewInt(9223372036854775791), tests.GenerateAddress(),
+			"v = 0", &LegacyTx{V: big.NewInt(0).Bytes()}, nil,
 		},
 		{
-			"v = 27", &AccessListTx{V: big.NewInt(27).Bytes()}, new(big.Int), tests.GenerateAddress(),
+			"v = 1", &LegacyTx{V: big.NewInt(1).Bytes()}, nil,
 		},
 		{
-			"v = 28", &AccessListTx{V: big.NewInt(28).Bytes()}, new(big.Int), tests.GenerateAddress(),
+			"v = 27", &LegacyTx{V: big.NewInt(27).Bytes()}, new(big.Int),
 		},
 		{
-			"v = nil ", &AccessListTx{V: nil}, nil, tests.GenerateAddress(),
+			"v = 28", &LegacyTx{V: big.NewInt(28).Bytes()}, new(big.Int),
+		},
+		{
+			"Ethereum mainnet", &LegacyTx{V: big.NewInt(37).Bytes()}, big.NewInt(1),
+		},
+		{
+			"chain ID 9000", &LegacyTx{V: big.NewInt(18035).Bytes()}, big.NewInt(9000),
+		},
+		{
+			"bit len 64", &LegacyTx{V: bitLen64.Bytes()}, big.NewInt(4611686018427387886),
+		},
+		{
+			"bit len 80", &LegacyTx{V: bitLen80.Bytes()}, expBitLen80,
+		},
+		{
+			"v = nil ", &LegacyTx{V: nil}, nil,
 		},
 	}