fix!: prevent 0 gas txs (#12416)

## Description

Update `DeductFeeDecorator` to prevent 0-gas txs.

closes: #12415

---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -62,6 +62,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* [#12416](https://github.com/cosmos/cosmos-sdk/pull/12416) Prevent zero gas transactions in the `DeductFeeDecorator` AnteHandler decorator.
 * (x/mint) [#12384](https://github.com/cosmos/cosmos-sdk/pull/12384) Ensure `GoalBonded` must be positive when performing `x/mint` parameter validation.
 * (x/auth) [#12261](https://github.com/cosmos/cosmos-sdk/pull/12261) Deprecate pagination in GetTxsEventRequest/Response in favor of page and limit to align with tendermint `SignClient.TxSearch`
 * (vesting) [#12190](https://github.com/cosmos/cosmos-sdk/pull/12190) Replace https://github.com/cosmos/cosmos-sdk/pull/12190 to use `NewBaseAccountWithAddress` in all vesting account message handlers.

types/errors/errors.go

@@ -161,6 +161,10 @@ var (
 	// ErrAppConfig defines an error occurred if min-gas-prices field in BaseConfig is empty.
 	ErrAppConfig = Register(RootCodespace, 40, "error in app.toml")
 
+	// ErrInvalidGasLimit defines an error when an invalid GasWanted value is
+	// supplied.
+	ErrInvalidGasLimit = Register(RootCodespace, 41, "invalid gas limit")
+
 	// ErrPanic should only be set when we recovering from a panic
 	ErrPanic = errorsmod.ErrPanic
 )

x/auth/ante/fee.go

@@ -37,6 +37,15 @@ func NewDeductFeeDecorator(ak AccountKeeper, bk types.BankKeeper, fk FeegrantKee
 }
 
 func (dfd DeductFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (sdk.Context, error) {
+	feeTx, ok := tx.(sdk.FeeTx)
+	if !ok {
+		return ctx, sdkerrors.Wrap(sdkerrors.ErrTxDecode, "Tx must be a FeeTx")
+	}
+
+	if ctx.BlockHeight() > 0 && feeTx.GetGas() == 0 {
+		return ctx, sdkerrors.Wrap(sdkerrors.ErrInvalidGasLimit, "must provide positive gas")
+	}
+
 	fee, priority, err := dfd.txFeeChecker(ctx, tx)
 	if err != nil {
 		return ctx, err

x/auth/ante/fee_test.go

@@ -8,66 +8,96 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/bank/testutil"
 )
 
-func (suite *AnteTestSuite) TestEnsureMempoolFees() {
-	suite.SetupTest(true) // setup
-	suite.txBuilder = suite.clientCtx.TxConfig.NewTxBuilder()
+func (s *AnteTestSuite) TestDeductFeeDecorator_ZeroGas() {
+	s.SetupTest(true) // setup
+	s.txBuilder = s.clientCtx.TxConfig.NewTxBuilder()
 
-	mfd := ante.NewDeductFeeDecorator(suite.accountKeeper, suite.bankKeeper, suite.feeGrantKeeper, nil)
+	mfd := ante.NewDeductFeeDecorator(s.accountKeeper, s.bankKeeper, s.feeGrantKeeper, nil)
 	antehandler := sdk.ChainAnteDecorators(mfd)
 
 	// keys and addresses
 	priv1, _, addr1 := testdata.KeyTestPubAddr()
 	coins := sdk.NewCoins(sdk.NewCoin("atom", sdk.NewInt(300)))
-	testutil.FundAccount(suite.bankKeeper, suite.ctx, addr1, coins)
+	testutil.FundAccount(s.bankKeeper, s.ctx, addr1, coins)
+
+	// msg and signatures
+	msg := testdata.NewTestMsg(addr1)
+	s.Require().NoError(s.txBuilder.SetMsgs(msg))
+
+	// set zero gas
+	s.txBuilder.SetGasLimit(0)
+
+	privs, accNums, accSeqs := []cryptotypes.PrivKey{priv1}, []uint64{0}, []uint64{0}
+	tx, err := s.CreateTestTx(privs, accNums, accSeqs, s.ctx.ChainID())
+	s.Require().NoError(err)
+
+	// Set IsCheckTx to true
+	s.ctx = s.ctx.WithIsCheckTx(true)
+
+	_, err = antehandler(s.ctx, tx, false)
+	s.Require().Error(err)
+}
+
+func (s *AnteTestSuite) TestEnsureMempoolFees() {
+	s.SetupTest(true) // setup
+	s.txBuilder = s.clientCtx.TxConfig.NewTxBuilder()
+
+	mfd := ante.NewDeductFeeDecorator(s.accountKeeper, s.bankKeeper, s.feeGrantKeeper, nil)
+	antehandler := sdk.ChainAnteDecorators(mfd)
+
+	// keys and addresses
+	priv1, _, addr1 := testdata.KeyTestPubAddr()
+	coins := sdk.NewCoins(sdk.NewCoin("atom", sdk.NewInt(300)))
+	testutil.FundAccount(s.bankKeeper, s.ctx, addr1, coins)
 
 	// msg and signatures
 	msg := testdata.NewTestMsg(addr1)
 	feeAmount := testdata.NewTestFeeAmount()
 	gasLimit := testdata.NewTestGasLimit()
-	suite.Require().NoError(suite.txBuilder.SetMsgs(msg))
-	suite.txBuilder.SetFeeAmount(feeAmount)
-	suite.txBuilder.SetGasLimit(gasLimit)
+	s.Require().NoError(s.txBuilder.SetMsgs(msg))
+	s.txBuilder.SetFeeAmount(feeAmount)
+	s.txBuilder.SetGasLimit(gasLimit)
 
 	privs, accNums, accSeqs := []cryptotypes.PrivKey{priv1}, []uint64{0}, []uint64{0}
-	tx, err := suite.CreateTestTx(privs, accNums, accSeqs, suite.ctx.ChainID())
-	suite.Require().NoError(err)
+	tx, err := s.CreateTestTx(privs, accNums, accSeqs, s.ctx.ChainID())
+	s.Require().NoError(err)
 
 	// Set high gas price so standard test fee fails
 	atomPrice := sdk.NewDecCoinFromDec("atom", sdk.NewDec(200).Quo(sdk.NewDec(100000)))
 	highGasPrice := []sdk.DecCoin{atomPrice}
-	suite.ctx = suite.ctx.WithMinGasPrices(highGasPrice)
+	s.ctx = s.ctx.WithMinGasPrices(highGasPrice)
 
 	// Set IsCheckTx to true
-	suite.ctx = suite.ctx.WithIsCheckTx(true)
+	s.ctx = s.ctx.WithIsCheckTx(true)
 
 	// antehandler errors with insufficient fees
-	_, err = antehandler(suite.ctx, tx, false)
-	suite.Require().NotNil(err, "Decorator should have errored on too low fee for local gasPrice")
+	_, err = antehandler(s.ctx, tx, false)
+	s.Require().NotNil(err, "Decorator should have errored on too low fee for local gasPrice")
 
 	// Set IsCheckTx to false
-	suite.ctx = suite.ctx.WithIsCheckTx(false)
+	s.ctx = s.ctx.WithIsCheckTx(false)
 
 	// antehandler should not error since we do not check minGasPrice in DeliverTx
-	_, err = antehandler(suite.ctx, tx, false)
-	suite.Require().Nil(err, "MempoolFeeDecorator returned error in DeliverTx")
+	_, err = antehandler(s.ctx, tx, false)
+	s.Require().Nil(err, "MempoolFeeDecorator returned error in DeliverTx")
 
 	// Set IsCheckTx back to true for testing sufficient mempool fee
-	suite.ctx = suite.ctx.WithIsCheckTx(true)
+	s.ctx = s.ctx.WithIsCheckTx(true)
 
 	atomPrice = sdk.NewDecCoinFromDec("atom", sdk.NewDec(0).Quo(sdk.NewDec(100000)))
 	lowGasPrice := []sdk.DecCoin{atomPrice}
-	suite.ctx = suite.ctx.WithMinGasPrices(lowGasPrice)
+	s.ctx = s.ctx.WithMinGasPrices(lowGasPrice)
 
-	newCtx, err := antehandler(suite.ctx, tx, false)
-	suite.Require().Nil(err, "Decorator should not have errored on fee higher than local gasPrice")
+	newCtx, err := antehandler(s.ctx, tx, false)
+	s.Require().Nil(err, "Decorator should not have errored on fee higher than local gasPrice")
 	// Priority is the smallest amount in any denom. Since we have only 1 fee
 	// of 150atom, the priority here is 150.
-	suite.Require().Equal(feeAmount.AmountOf("atom").Int64(), newCtx.Priority())
+	s.Require().Equal(feeAmount.AmountOf("atom").Int64(), newCtx.Priority())
 }
 
-func (suite *AnteTestSuite) TestDeductFees() {
-	suite.SetupTest(false) // setup
-	suite.txBuilder = suite.clientCtx.TxConfig.NewTxBuilder()
+func (s *AnteTestSuite) TestDeductFees() {
+	s.SetupTest(false) // setup
+	s.txBuilder = s.clientCtx.TxConfig.NewTxBuilder()
 
 	// keys and addresses
 	priv1, _, addr1 := testdata.KeyTestPubAddr()
@@ -76,34 +106,34 @@ func (suite *AnteTestSuite) TestDeductFees() {
 	msg := testdata.NewTestMsg(addr1)
 	feeAmount := testdata.NewTestFeeAmount()
 	gasLimit := testdata.NewTestGasLimit()
-	suite.Require().NoError(suite.txBuilder.SetMsgs(msg))
-	suite.txBuilder.SetFeeAmount(feeAmount)
-	suite.txBuilder.SetGasLimit(gasLimit)
+	s.Require().NoError(s.txBuilder.SetMsgs(msg))
+	s.txBuilder.SetFeeAmount(feeAmount)
+	s.txBuilder.SetGasLimit(gasLimit)
 
 	privs, accNums, accSeqs := []cryptotypes.PrivKey{priv1}, []uint64{0}, []uint64{0}
-	tx, err := suite.CreateTestTx(privs, accNums, accSeqs, suite.ctx.ChainID())
-	suite.Require().NoError(err)
+	tx, err := s.CreateTestTx(privs, accNums, accSeqs, s.ctx.ChainID())
+	s.Require().NoError(err)
 
 	// Set account with insufficient funds
-	acc := suite.accountKeeper.NewAccountWithAddress(suite.ctx, addr1)
-	suite.accountKeeper.SetAccount(suite.ctx, acc)
+	acc := s.accountKeeper.NewAccountWithAddress(s.ctx, addr1)
+	s.accountKeeper.SetAccount(s.ctx, acc)
 	coins := sdk.NewCoins(sdk.NewCoin("atom", sdk.NewInt(10)))
-	err = testutil.FundAccount(suite.bankKeeper, suite.ctx, addr1, coins)
-	suite.Require().NoError(err)
+	err = testutil.FundAccount(s.bankKeeper, s.ctx, addr1, coins)
+	s.Require().NoError(err)
 
-	dfd := ante.NewDeductFeeDecorator(suite.accountKeeper, suite.bankKeeper, nil, nil)
+	dfd := ante.NewDeductFeeDecorator(s.accountKeeper, s.bankKeeper, nil, nil)
 	antehandler := sdk.ChainAnteDecorators(dfd)
 
-	_, err = antehandler(suite.ctx, tx, false)
+	_, err = antehandler(s.ctx, tx, false)
 
-	suite.Require().NotNil(err, "Tx did not error when fee payer had insufficient funds")
+	s.Require().NotNil(err, "Tx did not error when fee payer had insufficient funds")
 
 	// Set account with sufficient funds
-	suite.accountKeeper.SetAccount(suite.ctx, acc)
-	err = testutil.FundAccount(suite.bankKeeper, suite.ctx, addr1, sdk.NewCoins(sdk.NewCoin("atom", sdk.NewInt(200))))
-	suite.Require().NoError(err)
+	s.accountKeeper.SetAccount(s.ctx, acc)
+	err = testutil.FundAccount(s.bankKeeper, s.ctx, addr1, sdk.NewCoins(sdk.NewCoin("atom", sdk.NewInt(200))))
+	s.Require().NoError(err)
 
-	_, err = antehandler(suite.ctx, tx, false)
+	_, err = antehandler(s.ctx, tx, false)
 
-	suite.Require().Nil(err, "Tx errored after account has been set with sufficient funds")
+	s.Require().Nil(err, "Tx errored after account has been set with sufficient funds")
 }

x/auth/ante/testutil_test.go

@@ -50,6 +50,10 @@ type AnteTestSuite struct {
 	feeGrantKeeper    feegrantkeeper.Keeper
 }
 
+func TestAnteTestSuite(t *testing.T) {
+	suite.Run(t, new(AnteTestSuite))
+}
+
 // SetupTest setups a new test, with new app, context, and anteHandler.
 func (suite *AnteTestSuite) SetupTest(isCheckTx bool) {
 	var (
@@ -209,7 +213,3 @@ func (suite *AnteTestSuite) RunTestCase(privs []cryptotypes.PrivKey, msgs []sdk.
 		}
 	})
 }
-
-func TestAnteTestSuite(t *testing.T) {
-	suite.Run(t, new(AnteTestSuite))
-}