CIP-64 / CIP-66 compatible TransactionArgs (#123)

Fixes #109

Add CIP-66 transaction type
This introduces the CeloDenominatedTx type, which will when implemented allow for the fee-currency to be denominated in cel2 native token.

Make the TransactionArgs CIP-64/CIP-66 compatible
The TransactionArgs are used in some API endpoints to fill incomplete fields of passed in transactions and then
convert this internally to an EVM-message or Transaction. This PR adds code that distinguishes some combination of passed in fields for the TransactionArgs between CIP-64 and CIP-66 transactions in order to create the concrete internal transaction type. The filling of missing required fields now considers wether the transaction is Celo-denominated or not.
Additionally, the new MaxFeeInFeeCurrency field is passed along to the internal transaction representations

Included commits:

* Format comments in TransactionArgs fields

* Add CIP-66 tx type (Celo denominated)

Co-authored-by: bandu

* Fix nil-deref in CIP-66 Transaction getter

* Fix required RLP field for fee-currency in CIP66

* Fix initialize MaxFeePerFeeCurrency value upon copy

* Convert TransactionArgs to CIP-64/66 transaction

Closes #109

* Add MaxFeeInFeeCurrency to EVM Message

* Fix CIP-64/66 related sanity checks

The fee-currency conversion pre-London (legacy-tx) was unneccessary,
since we don't allow celo transactions here.

Additionally some sanity-checks regarding Celo related fields were
missing

* Add tests for CIP-64/66 compatible TransactionArgs

* Fix call-arg naming for currency conversion

* Fix comments and formatting

accounts/external/backend.go

@@ -215,7 +215,7 @@ func (api *ExternalSigner) SignTx(account accounts.Account, tx *types.Transactio
 	switch tx.Type() {
 	case types.LegacyTxType, types.AccessListTxType:
 		args.GasPrice = (*hexutil.Big)(tx.GasPrice())
-	case types.DynamicFeeTxType, types.CeloDynamicFeeTxType:
+	case types.DynamicFeeTxType, types.CeloDynamicFeeTxType, types.CeloDenominatedTxType:
 		args.MaxFeePerGas = (*hexutil.Big)(tx.GasFeeCap())
 		args.MaxPriorityFeePerGas = (*hexutil.Big)(tx.GasTipCap())
 	default:

core/state_transition.go

@@ -182,8 +182,7 @@ type Message struct {
 	// FeeCurrency specifies the currency for gas fees.
 	// `nil` corresponds to Celo Gold (native currency).
 	// All other values should correspond to ERC20 contract addresses.
-	FeeCurrency *common.Address
-
+	FeeCurrency         *common.Address
 	MaxFeeInFeeCurrency *big.Int // MaxFeeInFeeCurrency is the maximum fee that can be charged in the fee currency.
 }
 
@@ -213,7 +212,7 @@ func TransactionToMessage(tx *types.Transaction, s types.Signer, baseFee *big.In
 	}
 	// If baseFee provided, set gasPrice to effectiveGasPrice.
 	if baseFee != nil {
-		if msg.FeeCurrency != nil {
+		if tx.Type() == types.CeloDynamicFeeTxType {
 			var err error
 			baseFee, err = exchange.ConvertGoldToCurrency(exchangeRates, msg.FeeCurrency, baseFee)
 			if err != nil {

core/types/celo_denominated_tx.go

@@ -0,0 +1,121 @@
+package types
+
+import (
+	"bytes"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+type CeloDenominatedTx struct {
+	ChainID    *big.Int
+	Nonce      uint64
+	GasTipCap  *big.Int
+	GasFeeCap  *big.Int
+	Gas        uint64
+	To         *common.Address `rlp:"nil"` // nil means contract creation
+	Value      *big.Int
+	Data       []byte
+	AccessList AccessList
+
+	FeeCurrency         *common.Address
+	MaxFeeInFeeCurrency *big.Int
+
+	// Signature values
+	V *big.Int `json:"v" gencodec:"required"`
+	R *big.Int `json:"r" gencodec:"required"`
+	S *big.Int `json:"s" gencodec:"required"`
+}
+
+// copy creates a deep copy of the transaction data and initializes all fields.
+func (tx *CeloDenominatedTx) copy() TxData {
+	cpy := &CeloDenominatedTx{
+		Nonce:       tx.Nonce,
+		To:          copyAddressPtr(tx.To),
+		Data:        common.CopyBytes(tx.Data),
+		Gas:         tx.Gas,
+		FeeCurrency: copyAddressPtr(tx.FeeCurrency),
+		// These are copied below.
+		MaxFeeInFeeCurrency: new(big.Int),
+		AccessList:          make(AccessList, len(tx.AccessList)),
+		Value:               new(big.Int),
+		ChainID:             new(big.Int),
+		GasTipCap:           new(big.Int),
+		GasFeeCap:           new(big.Int),
+		V:                   new(big.Int),
+		R:                   new(big.Int),
+		S:                   new(big.Int),
+	}
+	if tx.MaxFeeInFeeCurrency != nil {
+		cpy.MaxFeeInFeeCurrency.Set(tx.MaxFeeInFeeCurrency)
+	}
+	copy(cpy.AccessList, tx.AccessList)
+	if tx.Value != nil {
+		cpy.Value.Set(tx.Value)
+	}
+	if tx.ChainID != nil {
+		cpy.ChainID.Set(tx.ChainID)
+	}
+	if tx.GasTipCap != nil {
+		cpy.GasTipCap.Set(tx.GasTipCap)
+	}
+	if tx.GasFeeCap != nil {
+		cpy.GasFeeCap.Set(tx.GasFeeCap)
+	}
+	if tx.V != nil {
+		cpy.V.Set(tx.V)
+	}
+	if tx.R != nil {
+		cpy.R.Set(tx.R)
+	}
+	if tx.S != nil {
+		cpy.S.Set(tx.S)
+	}
+	return cpy
+}
+
+// accessors for innerTx.
+func (tx *CeloDenominatedTx) txType() byte           { return CeloDenominatedTxType }
+func (tx *CeloDenominatedTx) chainID() *big.Int      { return tx.ChainID }
+func (tx *CeloDenominatedTx) accessList() AccessList { return tx.AccessList }
+func (tx *CeloDenominatedTx) data() []byte           { return tx.Data }
+func (tx *CeloDenominatedTx) gas() uint64            { return tx.Gas }
+func (tx *CeloDenominatedTx) gasFeeCap() *big.Int    { return tx.GasFeeCap }
+func (tx *CeloDenominatedTx) gasTipCap() *big.Int    { return tx.GasTipCap }
+func (tx *CeloDenominatedTx) gasPrice() *big.Int     { return tx.GasFeeCap }
+func (tx *CeloDenominatedTx) value() *big.Int        { return tx.Value }
+func (tx *CeloDenominatedTx) nonce() uint64          { return tx.Nonce }
+func (tx *CeloDenominatedTx) to() *common.Address    { return tx.To }
+func (tx *CeloDenominatedTx) isSystemTx() bool       { return false }
+
+func (tx *CeloDenominatedTx) effectiveGasPrice(dst *big.Int, baseFee *big.Int) *big.Int {
+	if baseFee == nil {
+		return dst.Set(tx.GasFeeCap)
+	}
+	tip := dst.Sub(tx.GasFeeCap, baseFee)
+	if tip.Cmp(tx.GasTipCap) > 0 {
+		tip.Set(tx.GasTipCap)
+	}
+	return tip.Add(tip, baseFee)
+}
+
+func (tx *CeloDenominatedTx) rawSignatureValues() (v, r, s *big.Int) {
+	return tx.V, tx.R, tx.S
+}
+
+func (tx *CeloDenominatedTx) setSignatureValues(chainID, v, r, s *big.Int) {
+	tx.ChainID, tx.V, tx.R, tx.S = chainID, v, r, s
+}
+
+func (tx *CeloDenominatedTx) encode(b *bytes.Buffer) error {
+	return rlp.Encode(b, tx)
+}
+
+func (tx *CeloDenominatedTx) decode(input []byte) error {
+	return rlp.DecodeBytes(input, tx)
+}
+
+func (tx *CeloDenominatedTx) feeCurrency() *common.Address { return tx.FeeCurrency }
+
+func (tx *CeloDenominatedTx) maxFeeInFeeCurrency() *big.Int { return tx.MaxFeeInFeeCurrency }

core/types/celo_dynamic_fee_tx.go

@@ -114,4 +114,5 @@ func (tx *CeloDynamicFeeTx) decode(input []byte) error {
 	return rlp.DecodeBytes(input, tx)
 }
 
-func (tx *CeloDynamicFeeTx) feeCurrency() *common.Address { return tx.FeeCurrency }
+func (tx *CeloDynamicFeeTx) feeCurrency() *common.Address  { return tx.FeeCurrency }
+func (tx *CeloDynamicFeeTx) maxFeeInFeeCurrency() *big.Int { return nil }

core/types/celo_transaction_signing.go

@@ -36,7 +36,7 @@ func NewCel2Signer(chainId *big.Int) Signer {
 }
 
 func (s cel2Signer) Sender(tx *Transaction) (common.Address, error) {
-	if tx.Type() != CeloDynamicFeeTxType {
+	if tx.Type() != CeloDynamicFeeTxType && tx.Type() != CeloDenominatedTxType {
 		return s.londonSigner.Sender(tx)
 	}
 	V, R, S := tx.RawSignatureValues()
@@ -55,13 +55,14 @@ func (s cel2Signer) Equal(s2 Signer) bool {
 }
 
 func (s cel2Signer) SignatureValues(tx *Transaction, sig []byte) (R, S, V *big.Int, err error) {
-	txdata, ok := tx.inner.(*CeloDynamicFeeTx)
-	if !ok {
+	if tx.Type() != CeloDynamicFeeTxType && tx.Type() != CeloDenominatedTxType {
 		return s.londonSigner.SignatureValues(tx, sig)
 	}
+
 	// Check that chain ID of tx matches the signer. We also accept ID zero here,
 	// because it indicates that the chain ID was not specified in the tx.
-	if txdata.ChainID.Sign() != 0 && txdata.ChainID.Cmp(s.chainId) != 0 {
+	chainID := tx.inner.chainID()
+	if chainID.Sign() != 0 && chainID.Cmp(s.chainId) != 0 {
 		return nil, nil, nil, ErrInvalidChainId
 	}
 	R, S, _ = decodeSignature(sig)
@@ -88,5 +89,22 @@ func (s cel2Signer) Hash(tx *Transaction) common.Hash {
 				tx.FeeCurrency(),
 			})
 	}
+	if tx.Type() == CeloDenominatedTxType {
+		return prefixedRlpHash(
+			tx.Type(),
+			[]interface{}{
+				s.chainId,
+				tx.Nonce(),
+				tx.GasTipCap(),
+				tx.GasFeeCap(),
+				tx.Gas(),
+				tx.To(),
+				tx.Value(),
+				tx.Data(),
+				tx.AccessList(),
+				tx.FeeCurrency(),
+				tx.MaxFeeInFeeCurrency(),
+			})
+	}
 	return s.londonSigner.Hash(tx)
 }

core/types/deposit_tx.go

@@ -102,4 +102,5 @@ func (tx *DepositTx) decode(input []byte) error {
 	return rlp.DecodeBytes(input, tx)
 }
 
-func (tx *DepositTx) feeCurrency() *common.Address { return nil }
+func (tx *DepositTx) feeCurrency() *common.Address  { return nil }
+func (tx *DepositTx) maxFeeInFeeCurrency() *big.Int { return nil }

core/types/transaction.go

@@ -51,7 +51,8 @@ const (
 	DynamicFeeTxType = 0x02
 	BlobTxType       = 0x03
 	// CeloDynamicFeeTxType = 0x7c  old Celo tx type with gateway fee
-	CeloDynamicFeeTxType = 0x7b
+	CeloDynamicFeeTxType  = 0x7b
+	CeloDenominatedTxType = 0x7a
 )
 
 // Transaction is an Ethereum transaction.
@@ -110,6 +111,7 @@ type TxData interface {
 
 	// Celo specific fields
 	feeCurrency() *common.Address
+	maxFeeInFeeCurrency() *big.Int
 }
 
 // EncodeRLP implements rlp.Encoder
@@ -216,6 +218,8 @@ func (tx *Transaction) decodeTyped(b []byte) (TxData, error) {
 		inner = new(DynamicFeeTx)
 	case CeloDynamicFeeTxType:
 		inner = new(CeloDynamicFeeTx)
+	case CeloDenominatedTxType:
+		inner = new(CeloDenominatedTx)
 	case BlobTxType:
 		inner = new(BlobTx)
 	case DepositTxType:
@@ -628,6 +632,16 @@ func (tx *Transaction) FeeCurrency() *common.Address {
 	return copyAddressPtr(tx.inner.feeCurrency())
 }
 
+// MaxFeeInFeeCurrency is only used to guard against very quickly changing exchange rates.
+// Txs must be discarded if MaxFeeInFeeCurrency is exceeded.
+func (tx *Transaction) MaxFeeInFeeCurrency() *big.Int {
+	mfifc := tx.inner.maxFeeInFeeCurrency()
+	if mfifc == nil {
+		return nil
+	}
+	return new(big.Int).Set(mfifc)
+}
+
 // Transactions implements DerivableList for transactions.
 type Transactions []*Transaction
 

core/types/tx_access_list.go

@@ -129,4 +129,5 @@ func (tx *AccessListTx) decode(input []byte) error {
 	return rlp.DecodeBytes(input, tx)
 }
 
-func (tx *AccessListTx) feeCurrency() *common.Address { return nil }
+func (tx *AccessListTx) feeCurrency() *common.Address  { return nil }
+func (tx *AccessListTx) maxFeeInFeeCurrency() *big.Int { return nil }

core/types/tx_blob.go

@@ -238,4 +238,5 @@ func (tx *BlobTx) decode(input []byte) error {
 	return nil
 }
 
-func (tx *BlobTx) feeCurrency() *common.Address { return nil }
+func (tx *BlobTx) feeCurrency() *common.Address  { return nil }
+func (tx *BlobTx) maxFeeInFeeCurrency() *big.Int { return nil }

core/types/tx_dynamic_fee.go

@@ -125,4 +125,5 @@ func (tx *DynamicFeeTx) decode(input []byte) error {
 	return rlp.DecodeBytes(input, tx)
 }
 
-func (tx *DynamicFeeTx) feeCurrency() *common.Address { return nil }
+func (tx *DynamicFeeTx) feeCurrency() *common.Address  { return nil }
+func (tx *DynamicFeeTx) maxFeeInFeeCurrency() *big.Int { return nil }

core/types/tx_legacy.go

@@ -125,4 +125,5 @@ func (tx *LegacyTx) decode([]byte) error {
 	panic("decode called on LegacyTx)")
 }
 
-func (tx *LegacyTx) feeCurrency() *common.Address { return nil }
+func (tx *LegacyTx) feeCurrency() *common.Address  { return nil }
+func (tx *LegacyTx) maxFeeInFeeCurrency() *big.Int { return nil }

internal/celoapi/backend.go

@@ -60,18 +60,18 @@ func (b *CeloAPIBackend) GetExchangeRates(ctx context.Context, blockNumOrHash rp
 	return er, nil
 }
 
-func (b *CeloAPIBackend) ConvertToCurrency(ctx context.Context, blockNumOrHash rpc.BlockNumberOrHash, value *big.Int, fromFeeCurrency *common.Address) (*big.Int, error) {
+func (b *CeloAPIBackend) ConvertToCurrency(ctx context.Context, blockNumOrHash rpc.BlockNumberOrHash, goldAmount *big.Int, toFeeCurrency *common.Address) (*big.Int, error) {
 	er, err := b.GetExchangeRates(ctx, blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}
-	return exchange.ConvertGoldToCurrency(er, fromFeeCurrency, value)
+	return exchange.ConvertGoldToCurrency(er, toFeeCurrency, goldAmount)
 }
 
-func (b *CeloAPIBackend) ConvertToGold(ctx context.Context, blockNumOrHash rpc.BlockNumberOrHash, value *big.Int, toFeeCurrency *common.Address) (*big.Int, error) {
+func (b *CeloAPIBackend) ConvertToGold(ctx context.Context, blockNumOrHash rpc.BlockNumberOrHash, currencyAmount *big.Int, fromFeeCurrency *common.Address) (*big.Int, error) {
 	er, err := b.GetExchangeRates(ctx, blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}
-	return exchange.ConvertCurrencyToGold(er, value, toFeeCurrency)
+	return exchange.ConvertCurrencyToGold(er, currencyAmount, fromFeeCurrency)
 }

internal/ethapi/api.go

@@ -1477,7 +1477,8 @@ type RPCTransaction struct {
 	DepositReceiptVersion *hexutil.Uint64 `json:"depositReceiptVersion,omitempty"`
 
 	// Celo
-	FeeCurrency *common.Address `json:"feeCurrency,omitempty"`
+	FeeCurrency         *common.Address `json:"feeCurrency,omitempty"`
+	MaxFeeInFeeCurrency *hexutil.Big    `json:"maxFeeInFeeCurrency,omitempty"`
 }
 
 // newRPCTransaction returns a transaction that will serialize to the RPC
@@ -1500,7 +1501,8 @@ func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber
 		R:        (*hexutil.Big)(r),
 		S:        (*hexutil.Big)(s),
 		// Celo
-		FeeCurrency: tx.FeeCurrency(),
+		FeeCurrency:         tx.FeeCurrency(),
+		MaxFeeInFeeCurrency: (*hexutil.Big)(tx.MaxFeeInFeeCurrency()),
 	}
 	if blockHash != (common.Hash{}) {
 		result.BlockHash = &blockHash
@@ -1542,7 +1544,7 @@ func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber
 		result.ChainID = (*hexutil.Big)(tx.ChainId())
 		result.YParity = &yparity
 
-	case types.DynamicFeeTxType, types.CeloDynamicFeeTxType:
+	case types.DynamicFeeTxType, types.CeloDynamicFeeTxType, types.CeloDenominatedTxType:
 		al := tx.AccessList()
 		yparity := hexutil.Uint64(v.Sign())
 		result.Accesses = &al