fix: MinGasPFB decorator check for nested authz messages (backport #4465) (#4468)

Previously the MinGasPFB decorator was not looking inside authz
`MsgExec`s.<hr>This is an automatic backport of pull request #4465 done
by [Mergify](https://mergify.com).

Co-authored-by: Rootul P <[email protected]>

Author: mergify[bot]

x/blob/ante/ante.go

@@ -8,6 +8,7 @@ import (
 	"cosmossdk.io/errors"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+	"github.com/cosmos/cosmos-sdk/x/authz"
 )
 
 // MinGasPFBDecorator helps to prevent a PFB from being included in a block
@@ -29,27 +30,62 @@ func (d MinGasPFBDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool
 		return next(ctx, tx, simulate)
 	}
 
-	var gasPerByte uint32
+	// Skip gas checks during genesis initialization
+	if ctx.BlockHeight() == 0 {
+		return next(ctx, tx, simulate)
+	}
+
+	gasPerByte := d.getGasPerByte(ctx)
 	txGas := ctx.GasMeter().GasRemaining()
-	for _, m := range tx.GetMsgs() {
-		// NOTE: here we assume only one PFB per transaction
-		if pfb, ok := m.(*types.MsgPayForBlobs); ok {
-			if gasPerByte == 0 {
-				if ctx.BlockHeader().Version.App <= v2.Version {
-					// lazily fetch the gas per byte param
-					gasPerByte = d.k.GasPerBlobByte(ctx)
-				} else {
-					gasPerByte = appconsts.GasPerBlobByte(ctx.BlockHeader().Version.App)
-				}
+	err := d.validatePFBHasEnoughGas(tx.GetMsgs(), gasPerByte, txGas)
+	if err != nil {
+		return ctx, err
+	}
+
+	return next(ctx, tx, simulate)
+}
+
+// validatePFBHasEnoughGas iterates through all the msgs and nested msgs to find
+// a MsgPayForBlobs. If found, it validates that the txGas is enough to pay for
+// the blobs.
+func (d MinGasPFBDecorator) validatePFBHasEnoughGas(msgs []sdk.Msg, gasPerByte uint32, txGas uint64) error {
+	for _, m := range msgs {
+		if execMsg, ok := m.(*authz.MsgExec); ok {
+			// Recursively look for PFBs in nested authz messages.
+			nestedMsgs, err := execMsg.GetMessages()
+			if err != nil {
+				return err
 			}
-			gasToConsume := pfb.Gas(gasPerByte)
-			if gasToConsume > txGas {
-				return ctx, errors.Wrapf(sdkerrors.ErrInsufficientFee, "not enough gas to pay for blobs (minimum: %d, got: %d)", gasToConsume, txGas)
+			err = d.validatePFBHasEnoughGas(nestedMsgs, gasPerByte, txGas)
+			if err != nil {
+				return err
+			}
+		}
+		if pfb, ok := m.(*types.MsgPayForBlobs); ok {
+			err := validateEnoughGas(pfb, gasPerByte, txGas)
+			if err != nil {
+				return err
 			}
 		}
 	}
+	return nil
+}
 
-	return next(ctx, tx, simulate)
+func (d MinGasPFBDecorator) getGasPerByte(ctx sdk.Context) uint32 {
+	if ctx.BlockHeader().Version.App <= v2.Version {
+		return d.k.GasPerBlobByte(ctx)
+	}
+	return appconsts.GasPerBlobByte(ctx.BlockHeader().Version.App)
+}
+
+// validateEnoughGas returns an error if the gas needed to pay for the blobs is
+// greater than the txGas.
+func validateEnoughGas(msg *types.MsgPayForBlobs, gasPerByte uint32, txGas uint64) error {
+	gasToConsume := msg.Gas(gasPerByte)
+	if gasToConsume > txGas {
+		return errors.Wrapf(sdkerrors.ErrInsufficientFee, "not enough gas to pay for blobs (minimum: %d, got: %d)", gasToConsume, txGas)
+	}
+	return nil
 }
 
 type BlobKeeper interface {

x/blob/ante/ante_test.go

@@ -2,6 +2,7 @@ package ante_test
 
 import (
 	"fmt"
+	"math"
 	"testing"
 
 	"github.com/celestiaorg/celestia-app/v3/app"
@@ -12,6 +13,8 @@ import (
 	blob "github.com/celestiaorg/celestia-app/v3/x/blob/types"
 	"github.com/celestiaorg/go-square/v2/share"
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
+	"github.com/cosmos/cosmos-sdk/x/authz"
 	"github.com/stretchr/testify/require"
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 	"github.com/tendermint/tendermint/proto/tendermint/version"
@@ -124,6 +127,7 @@ func TestPFBAnteHandler(t *testing.T) {
 					Version: version.Consensus{
 						App: currentVersion,
 					},
+					Height: 1,
 				}, true, nil).WithGasMeter(sdk.NewGasMeter(uint64(tc.txGas(gasPerBlobByte)))).WithIsCheckTx(true)
 
 				ctx.GasMeter().ConsumeGas(tc.gasConsumed, "test")
@@ -141,6 +145,49 @@ func TestPFBAnteHandler(t *testing.T) {
 	}
 }
 
+// TestMinGasPFBDecoratorWithMsgExec tests that the MinGasPFBDecorator rejects a
+// MsgExec that contains a MsgExec with a MsgPayForBlob where the MsgPayForBlob
+// gas cost is greater than the tx's gas limit.
+func TestMinGasPFBDecoratorWithMsgExec(t *testing.T) {
+	anteHandler := ante.NewMinGasPFBDecorator(mockBlobKeeper{})
+	txConfig := encoding.MakeConfig(app.ModuleEncodingRegisters...).TxConfig
+
+	// Create a context with a gas meter with a high gas limit
+	gasLimit := uint64(100_000_000)
+	ctx := sdk.NewContext(nil, tmproto.Header{
+		Version: version.Consensus{
+			App: appconsts.LatestVersion,
+		},
+		Height: 1,
+	}, true, nil).WithGasMeter(sdk.NewGasMeter(gasLimit)).WithIsCheckTx(true)
+
+	// Build a tx with a MsgExec containing a MsgPayForBlobs with a huge gas cost
+	txBuilder := txConfig.NewTxBuilder()
+	msgExec := authz.NewMsgExec(sdk.AccAddress{}, []sdk.Msg{
+		&blob.MsgPayForBlobs{
+			Signer:    "celestia...",
+			BlobSizes: []uint32{uint32(math.MaxUint32)},
+		},
+	})
+	require.NoError(t, txBuilder.SetMsgs(&msgExec))
+	tx := txBuilder.GetTx()
+
+	// Run the ante handler
+	_, err := anteHandler.AnteHandle(ctx, tx, false, mockNext)
+	require.Error(t, err)
+	require.ErrorIs(t, err, sdkerrors.ErrInsufficientFee)
+
+	// Create a MsgExec that wraps a MsgExec that contains a MsgPayForBlobs with a huge gas cost
+	nestedMsgExec := authz.NewMsgExec(sdk.AccAddress{}, []sdk.Msg{&msgExec})
+	require.NoError(t, txBuilder.SetMsgs(&nestedMsgExec))
+	tx = txBuilder.GetTx()
+
+	// Run the ante handler
+	_, err = anteHandler.AnteHandle(ctx, tx, false, mockNext)
+	require.Error(t, err)
+	require.ErrorIs(t, err, sdkerrors.ErrInsufficientFee)
+}
+
 type mockBlobKeeper struct{}
 
 func (mockBlobKeeper) GasPerBlobByte(_ sdk.Context) uint32 {