feat: transient (per-block) counter that increments on each zero-gas EVM tx during DeliverTx

Author: matthiasmatt

evm-e2e/.gitignore

@@ -2,3 +2,8 @@ types
 artifacts
 cache
 .env
+
+# local e2e chain data
+.nibid-testnet2/
+.passkey-testnet2-wallet.json
+.passkey-testnet2-privkey.txt

x/evm/const.go

@@ -126,6 +126,8 @@ const (
 	NamespaceBlockTxIndex collections.Namespace = 2
 	NamespaceBlockLogSize collections.Namespace = 3
 	NamespaceBlockGasUsed collections.Namespace = 4
+	// NamespaceBlockZeroGasTxCount: number of zero-gas EVM txs in the current block.
+	NamespaceBlockZeroGasTxCount collections.Namespace = 5
 )
 
 var KeyPrefixBzAccState = KeyPrefixAccState.Prefix()

x/evm/errors.go

@@ -25,6 +25,7 @@ const (
 	codeErrInvalidBaseFee
 	codeErrInvalidAccount
 	codeErrInactivePrecompile
+	codeErrZeroGasBlockQuotaExceeded
 )
 
 var (
@@ -55,6 +56,9 @@ var (
 	// ErrInvalidAccount returns an error if the account is not an EVM compatible account
 	ErrInvalidAccount = sdkioerrors.Register(ModuleName, codeErrInvalidAccount, "account type is not a valid ethereum account")
 
+	// ErrZeroGasBlockQuotaExceeded returns an error when the per-block quota for zero-gas EVM txs is exceeded.
+	ErrZeroGasBlockQuotaExceeded = sdkioerrors.Register(ModuleName, codeErrZeroGasBlockQuotaExceeded, "zero-gas block quota exceeded")
+
 	ErrCanonicalWnibi = "canonical WNIBI address in state is a not a smart contract"
 )
 

x/evm/evmante/all_evmante.go

@@ -31,6 +31,7 @@ func NewAnteHandlerEvm(
 		EthSigVerification,
 		AnteStepValidateBasic,
 		AnteStepDetectZeroGas, // must run before MempoolGasPrice, VerifyEthAcc, CanTransfer, DeductGas
+		AnteStepZeroGasBlockQuota,
 		AnteStepMempoolGasPrice,
 		AnteStepBlockGasMeter,
 		AnteStepVerifyEthAcc,

x/evm/evmante/evmante_zero_gas_quota.go

@@ -0,0 +1,60 @@
+package evmante
+
+// Copyright (c) 2023-2024 Nibi, Inc.
+//
+// evmante_zero_gas_quota.go: Per-block quota enforcement for zero-gas EVM txs.
+
+import (
+	sdkioerrors "cosmossdk.io/errors"
+
+	"github.com/NibiruChain/nibiru/v2/x/evm"
+	evmstate "github.com/NibiruChain/nibiru/v2/x/evm/evmstate"
+)
+
+var _ AnteStep = AnteStepZeroGasBlockQuota
+
+// maxZeroGasTxsPerBlock is a consensus-critical constant.
+//
+// Set to 0 to disable quota enforcement.
+//
+// Note: For production, making this governance-controlled (e.g. via x/sudo state
+// or x/evm params) is preferable to a hardcoded constant.
+const maxZeroGasTxsPerBlock uint64 = 100
+
+// AnteStepZeroGasBlockQuota enforces a per-block cap on the number of zero-gas
+// EVM transactions that can be included. It uses the EVM transient store, which
+// is reset at Commit (end of block).
+//
+// Rationale: Zero-gas txs bypass fee-based spam controls. A quota provides a
+// deterministic backstop against free blockspace consumption.
+//
+// Enforcement:
+//   - DeliverTx only. (CheckTx/mempool admission is intentionally unaffected.)
+func AnteStepZeroGasBlockQuota(
+	sdb *evmstate.SDB,
+	k *evmstate.Keeper,
+	msgEthTx *evm.MsgEthereumTx,
+	simulate bool,
+	opts AnteOptionsEVM,
+) (err error) {
+	if maxZeroGasTxsPerBlock == 0 {
+		return nil
+	}
+	if !evmstate.IsDeliverTx(sdb.Ctx()) {
+		return nil
+	}
+	if !evm.IsZeroGasEthTx(sdb.Ctx()) {
+		return nil
+	}
+
+	count := k.EvmState.BlockZeroGasTxCount.GetOr(sdb.Ctx(), 0)
+	if count >= maxZeroGasTxsPerBlock {
+		return sdkioerrors.Wrapf(
+			evm.ErrZeroGasBlockQuotaExceeded,
+			"max=%d", maxZeroGasTxsPerBlock,
+		)
+	}
+
+	k.EvmState.BlockZeroGasTxCount.Set(sdb.Ctx(), count+1)
+	return nil
+}

x/evm/evmante/evmante_zero_gas_quota_test.go

@@ -0,0 +1,68 @@
+package evmante_test
+
+import (
+	"math/big"
+	"testing"
+
+	gethcommon "github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
+
+	"github.com/NibiruChain/nibiru/v2/x/evm"
+	"github.com/NibiruChain/nibiru/v2/x/evm/evmante"
+	"github.com/NibiruChain/nibiru/v2/x/evm/evmtest"
+	"github.com/NibiruChain/nibiru/v2/x/sudo"
+)
+
+func TestAnteStepZeroGasBlockQuota_PerBlockTxCount(t *testing.T) {
+	deps := evmtest.NewTestDeps()
+
+	// Configure ZeroGasActors with an always_zero_gas_contracts entry.
+	targetAddr := gethcommon.HexToAddress("0x2222222222222222222222222222222222222222")
+	deps.App.SudoKeeper.ZeroGasActors.Set(deps.Ctx(), sudo.ZeroGasActors{
+		AlwaysZeroGasContracts: []string{targetAddr.Hex()},
+	})
+
+	// Create a tx that targets the allowlisted contract with zero value.
+	to := targetAddr
+	tx := evm.NewTx(&evm.EvmTxArgs{
+		ChainID:  deps.App.EvmKeeper.EthChainID(deps.Ctx()),
+		Nonce:    0,
+		GasLimit: 50_000,
+		GasPrice: big.NewInt(0),
+		To:       &to,
+		Amount:   big.NewInt(0),
+	})
+	tx.From = deps.Sender.EthAddr.Hex()
+
+	// Fill the quota within the same block.
+	for i := uint64(0); i < 100; i++ {
+		sdb := deps.NewStateDB()
+		err := evmante.AnteStepDetectZeroGas(
+			sdb, sdb.Keeper(), tx, false, ANTE_OPTIONS_UNUSED,
+		)
+		require.NoError(t, err)
+		require.True(t, evm.IsZeroGasEthTx(sdb.Ctx()))
+
+		err = evmante.AnteStepZeroGasBlockQuota(
+			sdb, sdb.Keeper(), tx, false, ANTE_OPTIONS_UNUSED,
+		)
+		require.NoError(t, err)
+		deps.Commit()
+	}
+
+	// The next zero-gas tx in the same block should fail.
+	{
+		sdb := deps.NewStateDB()
+		err := evmante.AnteStepDetectZeroGas(
+			sdb, sdb.Keeper(), tx, false, ANTE_OPTIONS_UNUSED,
+		)
+		require.NoError(t, err)
+		require.True(t, evm.IsZeroGasEthTx(sdb.Ctx()))
+
+		err = evmante.AnteStepZeroGasBlockQuota(
+			sdb, sdb.Keeper(), tx, false, ANTE_OPTIONS_UNUSED,
+		)
+		require.Error(t, err)
+		require.ErrorContains(t, err, "zero-gas block quota exceeded")
+	}
+}

x/evm/evmstate/evm_state.go

@@ -47,6 +47,8 @@ type EvmState struct {
 	BlockTxIndex collections.ItemTransient[uint64]
 	// BlockBloom: Bloom filters.
 	BlockBloom collections.ItemTransient[[]byte]
+	// BlockZeroGasTxCount: number of zero-gas EVM txs in the current block (transient).
+	BlockZeroGasTxCount collections.ItemTransient[uint64]
 
 	NetWeiBlockDelta collections.Item[sdkmath.Int]
 }
@@ -88,6 +90,11 @@ func NewEvmState(
 			evm.NamespaceBlockTxIndex,
 			collections.Uint64ValueEncoder,
 		),
+		BlockZeroGasTxCount: collections.NewItemTransient(
+			storeKeyTransient,
+			evm.NamespaceBlockZeroGasTxCount,
+			collections.Uint64ValueEncoder,
+		),
 		NetWeiBlockDelta: collections.NewItem(
 			storeKey,
 			evm.KeyPrefixNetWeiBlockDelta,