fix: exempt system txs from min gas check and fee deduction

app/ante/ante.go

@@ -19,19 +19,18 @@ import (
 	"fmt"
 	"runtime/debug"
 
-	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
-	ethante "github.com/evmos/ethermint/app/ante"
-	cctxtypes "github.com/zeta-chain/zetacore/x/crosschain/types"
-
-	tmlog "github.com/tendermint/tendermint/libs/log"
-
 	errorsmod "cosmossdk.io/errors"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	errortypes "github.com/cosmos/cosmos-sdk/types/errors"
 	authante "github.com/cosmos/cosmos-sdk/x/auth/ante"
+	"github.com/cosmos/cosmos-sdk/x/authz"
+	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
+	tmlog "github.com/tendermint/tendermint/libs/log"
+	cctxtypes "github.com/zeta-chain/zetacore/x/crosschain/types"
+	observertypes "github.com/zeta-chain/zetacore/x/observer/types"
 )
 
-func ValidateHandlerOptions(options ethante.HandlerOptions) error {
+func ValidateHandlerOptions(options HandlerOptions) error {
 	if options.AccountKeeper == nil {
 		return errorsmod.Wrap(errortypes.ErrLogic, "account keeper is required for AnteHandler")
 	}
@@ -47,14 +46,17 @@ func ValidateHandlerOptions(options ethante.HandlerOptions) error {
 	if options.EvmKeeper == nil {
 		return errorsmod.Wrap(errortypes.ErrLogic, "evm keeper is required for AnteHandler")
 	}
+	if options.ObserverKeeper == nil {
+		return errorsmod.Wrap(errortypes.ErrLogic, "observer keeper is required for AnteHandler")
+	}
 	return nil
 }
 
 // NewAnteHandler returns an ante handler responsible for attempting to route an
 // Ethereum or SDK transaction to an internal ante handler for performing
 // transaction-level processing (e.g. fee payment, signature verification) before
 // being passed onto it's respective handler.
-func NewAnteHandler(options ethante.HandlerOptions) (sdk.AnteHandler, error) {
+func NewAnteHandler(options HandlerOptions) (sdk.AnteHandler, error) {
 	if err := ValidateHandlerOptions(options); err != nil {
 		return nil, err
 	}
@@ -94,28 +96,26 @@ func NewAnteHandler(options ethante.HandlerOptions) (sdk.AnteHandler, error) {
 		// handle as totally normal Cosmos SDK tx
 		switch tx.(type) {
 		case sdk.Tx:
-			found := false
-			for _, msg := range tx.GetMsgs() {
-				switch msg.(type) {
-				// treat these three msg types differently because they might call EVM which results in massive gas consumption
-				// For these two msg types, we don't check gas limit by using a different ante handler
-				case *cctxtypes.MsgGasPriceVoter, *cctxtypes.MsgVoteOnObservedInboundTx:
-					found = true
-					break
-				case *stakingtypes.MsgCreateValidator:
-					if ctx.BlockHeight() == 0 {
-						found = true
-						break
-					}
-				}
+			// default: handle as normal Cosmos SDK tx
+			anteHandler = newCosmosAnteHandler(options)
+
+			// if tx is a system tx, and singer is authorized, use system tx handler
+
+			isAuthorized := func(creator string) bool {
+				return options.ObserverKeeper.IsAuthorized(ctx, creator)
 			}
-			if len(tx.GetMsgs()) == 1 && found {
-				// this differs newCosmosAnteHandler only in that it doesn't check gas limit
-				// by using an Infinite Gas Meter.
-				anteHandler = newCosmosAnteHandlerNoGasLimit(options)
-			} else {
-				anteHandler = newCosmosAnteHandler(options)
+			if IsSystemTx(tx, isAuthorized) {
+				anteHandler = newCosmosAnteHandlerForSystemTx(options)
 			}
+
+			// if tx is MsgCreatorValidator, use the newCosmosAnteHandlerForSystemTx handler to
+			// exempt gas fee requirement in genesis because it's not possible to pay gas fee in genesis
+			if len(tx.GetMsgs()) == 1 {
+				if _, ok := tx.GetMsgs()[0].(*stakingtypes.MsgCreateValidator); ok && ctx.BlockHeight() == 0 {
+					anteHandler = newCosmosAnteHandlerForSystemTx(options)
+				}
+			}
+
 		default:
 			return ctx, errorsmod.Wrapf(errortypes.ErrUnknownRequest, "invalid transaction type: %T", tx)
 		}
@@ -145,3 +145,41 @@ func Recover(logger tmlog.Logger, err *error) {
 		}
 	}
 }
+
+// IsSystemTx determines whether tx is a system tx that's signed by an authorized signer
+// system tx are special types of txs (see in the switch below), or such txs wrapped inside a MsgExec
+// the parameter isAuthorizedSigner is a caller specified function that determines whether the signer of
+// the tx is authorized.
+func IsSystemTx(tx sdk.Tx, isAuthorizedSigner func(string) bool) bool {
+	// the following determines whether the tx is a system tx which will uses different handler
+	// System txs are always single Msg txs, optionally wrapped by one level of MsgExec
+	if len(tx.GetMsgs()) != 1 { // this is not a system tx
+		return false
+	}
+	msg := tx.GetMsgs()[0]
+
+	// if wrapped inside a MsgExec, unwrap it and reveal the innerMsg.
+	var innerMsg sdk.Msg
+	innerMsg = msg
+	if mm, ok := msg.(*authz.MsgExec); ok { // authz tx; look inside it
+		msgs, err := mm.GetMessages()
+		if err == nil && len(msgs) == 1 {
+			innerMsg = msgs[0]
+		}
+	}
+	switch innerMsg.(type) {
+	case *cctxtypes.MsgGasPriceVoter,
+		*cctxtypes.MsgVoteOnObservedInboundTx,
+		*cctxtypes.MsgVoteOnObservedOutboundTx,
+		*cctxtypes.MsgAddToOutTxTracker,
+		*cctxtypes.MsgCreateTSSVoter,
+		*observertypes.MsgAddBlockHeader,
+		*observertypes.MsgAddBlameVote:
+		signers := innerMsg.GetSigners()
+		if len(signers) == 1 {
+			return isAuthorizedSigner(signers[0].String())
+		}
+	}
+
+	return false
+}

app/ante/ante_test.go

@@ -1,6 +1,19 @@
 package ante_test
 
-import sdk "github.com/cosmos/cosmos-sdk/types"
+import (
+	"testing"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/authz"
+	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
+	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
+	"github.com/stretchr/testify/require"
+	"github.com/zeta-chain/zetacore/app"
+	"github.com/zeta-chain/zetacore/app/ante"
+	"github.com/zeta-chain/zetacore/testutil/sample"
+	crosschaintypes "github.com/zeta-chain/zetacore/x/crosschain/types"
+	observertypes "github.com/zeta-chain/zetacore/x/observer/types"
+)
 
 var _ sdk.AnteHandler = (&MockAnteHandler{}).AnteHandle
 
@@ -16,3 +29,204 @@ func (mah *MockAnteHandler) AnteHandle(ctx sdk.Context, _ sdk.Tx, _ bool) (sdk.C
 	mah.CalledCtx = ctx
 	return ctx, nil
 }
+
+func TestIsSystemTx(t *testing.T) {
+	// system tx types:
+	//      *cctxtypes.MsgGasPriceVoter,
+	//		*cctxtypes.MsgVoteOnObservedInboundTx,
+	//		*cctxtypes.MsgVoteOnObservedOutboundTx,
+	//		*cctxtypes.MsgAddToOutTxTracker,
+	//		*cctxtypes.MsgCreateTSSVoter,
+	//		*observertypes.MsgAddBlockHeader,
+	//		*observertypes.MsgAddBlameVote:
+	buildTxFromMsg := func(msg sdk.Msg) sdk.Tx {
+		txBuilder := app.MakeEncodingConfig().TxConfig.NewTxBuilder()
+		txBuilder.SetMsgs(msg)
+		return txBuilder.GetTx()
+	}
+	buildAuthzTxFromMsg := func(msg sdk.Msg) sdk.Tx {
+		txBuilder := app.MakeEncodingConfig().TxConfig.NewTxBuilder()
+		msgExec := authz.NewMsgExec(sample.Bech32AccAddress(), []sdk.Msg{msg})
+		txBuilder.SetMsgs(&msgExec)
+		return txBuilder.GetTx()
+	}
+	isAuthorized := func(_ string) bool {
+		return true
+	}
+	isAuthorizedFalse := func(_ string) bool {
+		return false
+	}
+
+	tests := []struct {
+		name         string
+		tx           sdk.Tx
+		isAuthorized func(string) bool
+		wantIs       bool
+	}{
+		{
+			"MsgCreateTSSVoter",
+			buildTxFromMsg(&crosschaintypes.MsgCreateTSSVoter{
+				Creator:   sample.AccAddress(),
+				TssPubkey: "pubkey1234",
+			}),
+			isAuthorizedFalse,
+			false,
+		},
+		{
+			"MsgCreateTSSVoter",
+			buildTxFromMsg(&crosschaintypes.MsgCreateTSSVoter{
+				Creator:   sample.AccAddress(),
+				TssPubkey: "pubkey1234",
+			}),
+			isAuthorized,
+			true,
+		},
+		{
+			"MsgExec{MsgCreateTSSVoter}",
+			buildAuthzTxFromMsg(&crosschaintypes.MsgCreateTSSVoter{
+				Creator:   sample.AccAddress(),
+				TssPubkey: "pubkey1234",
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgSend",
+			buildTxFromMsg(&banktypes.MsgSend{}),
+			isAuthorized,
+
+			false,
+		},
+		{
+			"MsgExec{MsgSend}",
+			buildAuthzTxFromMsg(&banktypes.MsgSend{}),
+			isAuthorized,
+
+			false,
+		},
+		{
+			"MsgCreateValidator",
+			buildTxFromMsg(&stakingtypes.MsgCreateValidator{}),
+			isAuthorized,
+
+			false,
+		},
+
+		{
+			"MsgVoteOnObservedInboundTx",
+			buildTxFromMsg(&crosschaintypes.MsgVoteOnObservedInboundTx{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgVoteOnObservedInboundTx}",
+			buildAuthzTxFromMsg(&crosschaintypes.MsgVoteOnObservedInboundTx{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+
+		{
+			"MsgVoteOnObservedOutboundTx",
+			buildTxFromMsg(&crosschaintypes.MsgVoteOnObservedOutboundTx{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgVoteOnObservedOutboundTx}",
+			buildAuthzTxFromMsg(&crosschaintypes.MsgVoteOnObservedOutboundTx{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgAddToOutTxTracker",
+			buildTxFromMsg(&crosschaintypes.MsgAddToOutTxTracker{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgAddToOutTxTracker}",
+			buildAuthzTxFromMsg(&crosschaintypes.MsgAddToOutTxTracker{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgCreateTSSVoter",
+			buildTxFromMsg(&crosschaintypes.MsgCreateTSSVoter{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgCreateTSSVoter}",
+			buildAuthzTxFromMsg(&crosschaintypes.MsgCreateTSSVoter{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgAddBlockHeader",
+			buildTxFromMsg(&observertypes.MsgAddBlockHeader{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgAddBlockHeader}",
+			buildAuthzTxFromMsg(&observertypes.MsgAddBlockHeader{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgAddBlameVote",
+			buildTxFromMsg(&observertypes.MsgAddBlameVote{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+		{
+			"MsgExec{MsgAddBlameVote}",
+			buildAuthzTxFromMsg(&observertypes.MsgAddBlameVote{
+				Creator: sample.AccAddress(),
+			}),
+			isAuthorized,
+
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			is := ante.IsSystemTx(tt.tx, tt.isAuthorized)
+			require.Equal(t, tt.wantIs, is)
+		})
+	}
+}

app/ante/fees.go

@@ -29,6 +29,10 @@ import (
 	evmtypes "github.com/evmos/ethermint/x/evm/types"
 )
 
+var (
+	GasPriceReductionRate = "0.01" // 1% of regular tx gas price for system txs
+)
+
 // MinGasPriceDecorator will check if the transaction's fee is at least as large
 // as the MinGasPrices param. If fee is too low, decorator returns error and tx
 // is rejected. This applies for both CheckTx and DeliverTx
@@ -92,13 +96,16 @@ func (mpd MinGasPriceDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate
 		return next(ctx, tx, simulate)
 	}
 
-	// Short-circuit genesis txs gentx
+	// Short-circuit genesis txs gentx at block 0 (there is no way to pay fee in genesis file)
 	if len(tx.GetMsgs()) == 1 {
-		if _, ok := tx.GetMsgs()[0].(*stakingtypes.MsgCreateValidator); ok {
+		if _, ok := tx.GetMsgs()[0].(*stakingtypes.MsgCreateValidator); ok && ctx.BlockHeight() == 0 {
 			return next(ctx, tx, simulate)
 		}
 	}
 
+	reductionRate := sdk.MustNewDecFromStr(GasPriceReductionRate)
+	minGasPrice = minGasPrice.Mul(reductionRate) // discounts min gas price for system tx
+
 	evmParams := mpd.evmKeeper.GetParams(ctx)
 	evmDenom := evmParams.GetEvmDenom()
 	minGasPrices := sdk.DecCoins{