feat(wardend): burn 30% of the tx fee

warden/app/app_config.go

@@ -172,7 +172,7 @@ var (
 
 	// module account permissions
 	moduleAccPerms = []*authmodulev1.ModuleAccountPermission{
-		{Account: authtypes.FeeCollectorName},
+		{Account: authtypes.FeeCollectorName, Permissions: []string{authtypes.Burner}},
 		{Account: distrtypes.ModuleName},
 		{Account: minttypes.ModuleName, Permissions: []string{authtypes.Minter}},
 		{Account: stakingtypes.BondedPoolName, Permissions: []string{authtypes.Burner, stakingtypes.ModuleName}},
@@ -257,8 +257,10 @@ var (
 				Config: appconfig.WrapAny(&paramsmodulev1.Module{}),
 			},
 			{
-				Name:   "tx",
-				Config: appconfig.WrapAny(&txconfigv1.Config{}),
+				Name: "tx",
+				Config: appconfig.WrapAny(&txconfigv1.Config{
+					SkipAnteHandler: true,
+				}),
 			},
 			{
 				Name:   genutiltypes.ModuleName,

warden/x/warden/ante/ante.go

@@ -0,0 +1,61 @@
+package ante
+
+import (
+	errorsmod "cosmossdk.io/errors"
+	"cosmossdk.io/math"
+	storetypes "cosmossdk.io/store/types"
+	txsigning "cosmossdk.io/x/tx/signing"
+	"github.com/warden-protocol/wardenprotocol/warden/x/warden/types"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+	"github.com/cosmos/cosmos-sdk/types/tx/signing"
+	authante "github.com/cosmos/cosmos-sdk/x/auth/ante"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+)
+
+// HandlerOptions are the options required for constructing a default SDK AnteHandler.
+type HandlerOptions struct {
+	AccountKeeper          types.AccountKeeper
+	BankKeeper             types.BankKeeper
+	ExtensionOptionChecker authante.ExtensionOptionChecker
+	FeegrantKeeper         types.FeegrantKeeper
+	SignModeHandler        *txsigning.HandlerMap
+	SigGasConsumer         func(meter storetypes.GasMeter, sig signing.SignatureV2, params authtypes.Params) error
+	FeeBurnRatio           math.LegacyDec
+}
+
+// NewAnteHandler returns an AnteHandler that checks and increments sequence
+// numbers, checks signatures & account numbers, and deducts fees from the first
+// signer.
+func NewAnteHandler(options HandlerOptions) (sdk.AnteHandler, error) {
+	if options.AccountKeeper == nil {
+		return nil, errorsmod.Wrap(sdkerrors.ErrLogic, "account keeper is required for ante builder")
+	}
+
+	if options.BankKeeper == nil {
+		return nil, errorsmod.Wrap(sdkerrors.ErrLogic, "bank keeper is required for ante builder")
+	}
+
+	if options.SignModeHandler == nil {
+		return nil, errorsmod.Wrap(sdkerrors.ErrLogic, "sign mode handler is required for ante builder")
+	}
+
+	anteDecorators := []sdk.AnteDecorator{
+		authante.NewSetUpContextDecorator(), // outermost AnteDecorator. SetUpContext must be called first
+		authante.NewExtensionOptionsDecorator(options.ExtensionOptionChecker),
+		authante.NewValidateBasicDecorator(),
+		authante.NewTxTimeoutHeightDecorator(),
+		authante.NewValidateMemoDecorator(options.AccountKeeper),
+		authante.NewConsumeGasForTxSizeDecorator(options.AccountKeeper),
+		authante.NewDeductFeeDecorator(options.AccountKeeper, options.BankKeeper, options.FeegrantKeeper, nil), // use default sdk FeeChecker
+		NewBurnFeeDecorator(options.BankKeeper, options.FeeBurnRatio),
+		authante.NewSetPubKeyDecorator(options.AccountKeeper), // SetPubKeyDecorator must be called before all signature verification decorators
+		authante.NewValidateSigCountDecorator(options.AccountKeeper),
+		authante.NewSigGasConsumeDecorator(options.AccountKeeper, options.SigGasConsumer),
+		authante.NewSigVerificationDecorator(options.AccountKeeper, options.SignModeHandler),
+		authante.NewIncrementSequenceDecorator(options.AccountKeeper),
+	}
+
+	return sdk.ChainAnteDecorators(anteDecorators...), nil
+}

warden/x/warden/ante/burn_fee.go

@@ -0,0 +1,47 @@
+package ante
+
+import (
+	errorsmod "cosmossdk.io/errors"
+	"cosmossdk.io/math"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+
+	"github.com/warden-protocol/wardenprotocol/warden/x/warden/types"
+)
+
+// BurnFeeDecorator burns specified part of fee collected. This decorator must be called after DeductFeeDecorator
+// because assumes that all fee related checks are already done and does not check anything by itself
+type BurnFeeDecorator struct {
+	bankKeeper types.BankKeeper
+	burnRatio  math.LegacyDec
+}
+
+func NewBurnFeeDecorator(bk types.BankKeeper, br math.LegacyDec) BurnFeeDecorator {
+	return BurnFeeDecorator{
+		bankKeeper: bk,
+		burnRatio:  br,
+	}
+}
+
+func (bfd BurnFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (sdk.Context, error) {
+	feeTx, ok := tx.(sdk.FeeTx)
+	if !ok {
+		return ctx, errorsmod.Wrap(sdkerrors.ErrTxDecode, "Tx must be a FeeTx")
+	}
+
+	// Assume that default sdk FeeChecker is used. It follows that actual fee is always equal to feeTx.GetFee()
+	fee := feeTx.GetFee()
+
+	burnAmount, _ := sdk.NewDecCoinsFromCoins(fee...).MulDec(bfd.burnRatio).TruncateDecimal()
+
+	if !burnAmount.IsZero() {
+		err := bfd.bankKeeper.BurnCoins(ctx, authtypes.FeeCollectorName, burnAmount)
+		if err != nil {
+			return ctx, errorsmod.Wrap(sdkerrors.ErrLogic, "Failed to burn fee")
+		}
+	}
+
+	return next(ctx, tx, simulate)
+}

warden/x/warden/ante/burn_fee_test.go

@@ -0,0 +1,46 @@
+package ante_test
+
+import (
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+	"github.com/warden-protocol/wardenprotocol/warden/x/warden/ante"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/require"
+
+	"cosmossdk.io/math"
+
+	cryptotypes "github.com/cosmos/cosmos-sdk/crypto/types"
+	"github.com/cosmos/cosmos-sdk/testutil/testdata"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/tx/signing"
+)
+
+func TestDeductFees(t *testing.T) {
+	s := SetupTestSuite(t, false)
+	s.txBuilder = s.clientCtx.TxConfig.NewTxBuilder()
+
+	// keys and addresses
+	accs := s.CreateTestAccounts(1)
+
+	// msg and signatures
+	msg := testdata.NewTestMsg(accs[0].acc.GetAddress())
+	feeAmount := sdk.NewCoins(sdk.NewInt64Coin("atom", 150))
+	gasLimit := testdata.NewTestGasLimit()
+	require.NoError(t, s.txBuilder.SetMsgs(msg))
+	s.txBuilder.SetFeeAmount(feeAmount)
+	s.txBuilder.SetGasLimit(gasLimit)
+
+	privs, accNums, accSeqs := []cryptotypes.PrivKey{accs[0].priv}, []uint64{0}, []uint64{0}
+	tx, err := s.CreateTestTx(s.ctx, privs, accNums, accSeqs, s.ctx.ChainID(), signing.SignMode_SIGN_MODE_DIRECT)
+	require.NoError(t, err)
+
+	bfd := ante.NewBurnFeeDecorator(s.bankKeeper, math.LegacyNewDecWithPrec(3, 1))
+	antehandler := sdk.ChainAnteDecorators(bfd)
+
+	burntAmount := sdk.NewCoins(sdk.NewInt64Coin("atom", 45))
+	s.bankKeeper.EXPECT().BurnCoins(gomock.Any(), authtypes.FeeCollectorName, burntAmount).Return(nil)
+	_, err = antehandler(s.ctx, tx, false)
+
+	require.Nil(t, err, "Tx errored after account has been set with sufficient funds")
+}