Remove exchange rate calculation for non CELO denominated txs in state_transition (#2299)

Fix state_transition producing invalid gas used values for pre-H fork transactions.

Specifically the fix is ensuring that non CIP-66 transactions do not call GetExchangeRate
on the fee currency in the debitFee function, since calling GetExchangeRate can hit some
memory locations which can result in lower gas costs for accesses for the rest of the transaction.

Author: hbandura

core/state_transition.go

@@ -217,12 +217,12 @@ func IntrinsicGas(data []byte, accessList types.AccessList, isContractCreation b
 func NewStateTransition(evm *vm.EVM, msg Message, gp *GasPool, vmRunner vm.EVMRunner, sysCtx *SysContractCallCtx) *StateTransition {
 	var gasPriceMinimum *big.Int
 	if evm.ChainConfig().IsEspresso(evm.Context.BlockNumber) {
-		var feeCurrency *common.Address = msg.FeeCurrency()
 		if msg.MaxFeeInFeeCurrency() != nil {
 			// Celo denominated tx
-			feeCurrency = nil
+			gasPriceMinimum = sysCtx.GetGasPriceMinimum(nil)
+		} else {
+			gasPriceMinimum = sysCtx.GetGasPriceMinimum(msg.FeeCurrency())
 		}
-		gasPriceMinimum = sysCtx.GetGasPriceMinimum(feeCurrency)
 	} else {
 		gasPriceMinimum, _ = gpm.GetBaseFeeForCurrency(vmRunner, msg.FeeCurrency(), nil)
 	}
@@ -264,7 +264,7 @@ func (st *StateTransition) to() common.Address {
 }
 
 // payFees deducts gas and gateway fees from sender balance and adds the purchased amount of gas to the state.
-func (st *StateTransition) payFees(espresso bool, feeCurrencyRate *currency.ExchangeRate) error {
+func (st *StateTransition) payFees(espresso bool, denominatedCurrencyRate *currency.ExchangeRate) error {
 	var isWhiteListed bool
 	if espresso {
 		isWhiteListed = st.sysCtx.IsWhitelisted(st.msg.FeeCurrency())
@@ -275,7 +275,7 @@ func (st *StateTransition) payFees(espresso bool, feeCurrencyRate *currency.Exch
 		log.Trace("Fee currency not whitelisted", "fee currency address", st.msg.FeeCurrency())
 		return ErrNonWhitelistedFeeCurrency
 	}
-	if err := st.canPayFee(st.msg.From(), st.msg.FeeCurrency(), espresso, feeCurrencyRate); err != nil {
+	if err := st.canPayFee(st.msg.From(), st.msg.FeeCurrency(), espresso, denominatedCurrencyRate); err != nil {
 		return err
 	}
 	if err := st.gp.SubGas(st.msg.Gas()); err != nil {
@@ -284,7 +284,7 @@ func (st *StateTransition) payFees(espresso bool, feeCurrencyRate *currency.Exch
 
 	st.initialGas = st.msg.Gas()
 	st.gas += st.msg.Gas()
-	err := st.debitFee(st.msg.From(), st.msg.FeeCurrency(), feeCurrencyRate)
+	err := st.debitFee(st.msg.From(), st.msg.FeeCurrency(), denominatedCurrencyRate)
 	return err
 }
 
@@ -297,7 +297,7 @@ func (st *StateTransition) payFees(espresso bool, feeCurrencyRate *currency.Exch
 // For non-native tokens(cUSD, cEUR, ...) as feeCurrency:
 //   - Pre-Espresso: it ensures balance > GasPrice * gas + gatewayFee (3)
 //   - Post-Espresso: it ensures balance >= GasFeeCap * gas + gatewayFee (4)
-func (st *StateTransition) canPayFee(accountOwner common.Address, feeCurrency *common.Address, espresso bool, feeCurrencyRate *currency.ExchangeRate) error {
+func (st *StateTransition) canPayFee(accountOwner common.Address, feeCurrency *common.Address, espresso bool, denominatedCurrencyRate *currency.ExchangeRate) error {
 	if feeCurrency == nil {
 		balance := st.state.GetBalance(st.msg.From())
 		if espresso {
@@ -340,7 +340,7 @@ func (st *StateTransition) canPayFee(accountOwner common.Address, feeCurrency *c
 			if st.msg.MaxFeeInFeeCurrency() != nil {
 				// Celo Denominated Tx: max fee is a tx field
 				// Translate fees to feeCurrency
-				feeGap = feeCurrencyRate.FromBase(feeGap)
+				feeGap = denominatedCurrencyRate.FromBase(feeGap)
 				// Check that fee <= MaxFeeInFeeCurrency
 				if feeGap.Cmp(st.msg.MaxFeeInFeeCurrency()) > 0 {
 					return ErrDenominatedLowMaxFee
@@ -363,7 +363,7 @@ func (st *StateTransition) canPayFee(accountOwner common.Address, feeCurrency *c
 	return nil
 }
 
-func (st *StateTransition) debitFee(from common.Address, feeCurrency *common.Address, feeCurrencyRate *currency.ExchangeRate) (err error) {
+func (st *StateTransition) debitFee(from common.Address, feeCurrency *common.Address, denominatedCurrencyRate *currency.ExchangeRate) (err error) {
 	if st.evm.Config.SkipDebitCredit {
 		return nil
 	}
@@ -378,16 +378,12 @@ func (st *StateTransition) debitFee(from common.Address, feeCurrency *common.Add
 		st.state.SubBalance(from, effectiveFee)
 		return nil
 	} else {
-		var currencyFee *big.Int
-		if st.msg.MaxFeeInFeeCurrency() == nil {
-			// Normal feeCurrency tx
-			currencyFee = effectiveFee
+		if st.msg.MaxFeeInFeeCurrency() != nil {
+			st.erc20FeeDebited = denominatedCurrencyRate.FromBase(effectiveFee)
 		} else {
-			// Celo denominated tx
-			currencyFee = feeCurrencyRate.FromBase(effectiveFee)
+			st.erc20FeeDebited = effectiveFee
 		}
-		st.erc20FeeDebited = currencyFee
-		return erc20gas.DebitFees(st.evm, from, currencyFee, feeCurrency)
+		return erc20gas.DebitFees(st.evm, from, st.erc20FeeDebited, feeCurrency)
 	}
 }
 
@@ -482,9 +478,14 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 	if st.msg.FeeCurrency() == nil && st.msg.MaxFeeInFeeCurrency() != nil {
 		return nil, ErrDenominatedNoCurrency
 	}
-	feeCurrencyRate, err := currency.GetExchangeRate(st.vmRunner, st.msg.FeeCurrency())
-	if err != nil {
-		return nil, err
+	var denominatedCurrencyRate *currency.ExchangeRate
+	// Get rate only for CELO denominated txs (H fork)
+	if st.msg.MaxFeeInFeeCurrency() != nil {
+		var err error
+		denominatedCurrencyRate, err = currency.GetExchangeRate(st.vmRunner, st.msg.FeeCurrency())
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	// Check clauses 1-2
@@ -517,7 +518,7 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 		return nil, fmt.Errorf("%w: have %d, want %d", ErrIntrinsicGas, st.msg.Gas(), gas)
 	}
 	// Check clauses 3-4, pay the fees (which buys gas), and subtract the intrinsic gas
-	err = st.payFees(espresso, feeCurrencyRate)
+	err = st.payFees(espresso, denominatedCurrencyRate)
 	if err != nil {
 		log.Error("Transaction failed to buy gas", "err", err, "gas", gas)
 		return nil, err
@@ -553,7 +554,7 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 		st.refundGas(params.RefundQuotientEIP3529)
 	}
 
-	err = st.creditTxFees(feeCurrencyRate)
+	err = st.creditTxFees(denominatedCurrencyRate)
 	if err != nil {
 		return nil, err
 	}
@@ -565,7 +566,7 @@ func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
 }
 
 // creditTxFees calculates the amounts and recipients of transaction fees and credits the accounts.
-func (st *StateTransition) creditTxFees(feeCurrencyRate *currency.ExchangeRate) error {
+func (st *StateTransition) creditTxFees(denominatedCurrencyRate *currency.ExchangeRate) error {
 	if st.evm.Config.SkipDebitCredit {
 		return nil
 	}
@@ -596,8 +597,8 @@ func (st *StateTransition) creditTxFees(feeCurrencyRate *currency.ExchangeRate)
 		// conversions have limited accuracy, the only way to achieve this
 		// is to calculate one of the three credit values based on the two
 		// others after the exchange rate conversion.
-		tipTxFee = feeCurrencyRate.FromBase(tipTxFee)
-		baseTxFee = feeCurrencyRate.FromBase(baseTxFee)
+		tipTxFee = denominatedCurrencyRate.FromBase(tipTxFee)
+		baseTxFee = denominatedCurrencyRate.FromBase(baseTxFee)
 		totalTxFee.Add(tipTxFee, baseTxFee)
 		refund.Sub(st.erc20FeeDebited, totalTxFee) // refund = debited - tip - basefee
 		// No need to exchange gateway fee since it's it's deprecated on G fork,