x/auth: auth fee nil guard

x/auth/tx/builder.go

@@ -180,14 +180,25 @@ func (w *wrapper) GetPubKeys() ([]cryptotypes.PubKey, error) {
 }
 
 func (w *wrapper) GetGas() uint64 {
+	if w.tx.AuthInfo.Fee == nil {
+		return 0
+	}
 	return w.tx.AuthInfo.Fee.GasLimit
 }
 
 func (w *wrapper) GetFee() sdk.Coins {
+	if w.tx.AuthInfo.Fee == nil {
+		return nil
+	}
 	return w.tx.AuthInfo.Fee.Amount
 }
 
 func (w *wrapper) FeePayer() []byte {
+	// A fee-less decoded tx has no payer; short-circuit before the GetSigners
+	// fallback, which dereferences AuthInfo.Fee.Payer without a nil guard.
+	if w.tx.AuthInfo.Fee == nil {
+		return nil
+	}
 	feePayer := w.tx.AuthInfo.Fee.Payer
 	if feePayer != "" {
 		feePayerAddr, err := w.cdc.InterfaceRegistry().SigningContext().AddressCodec().StringToBytes(feePayer)
@@ -207,6 +218,9 @@ func (w *wrapper) FeePayer() []byte {
 }
 
 func (w *wrapper) FeeGranter() []byte {
+	if w.tx.AuthInfo.Fee == nil {
+		return nil
+	}
 	return w.tx.FeeGranter(w.cdc)
 }
 

x/auth/tx/nilfee_repro_test.go

@@ -0,0 +1,59 @@
+package tx
+
+import (
+	"testing"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/tx"
+	"github.com/stretchr/testify/require"
+)
+
+// decodeAuthInfo builds and decodes a tx with the given AuthInfo, leaving the
+// body minimal, and returns it as an sdk.FeeTx. It mirrors what a decoded
+// wire tx looks like when the fee field is present or omitted.
+func decodeAuthInfo(t *testing.T, authInfo *tx.AuthInfo) sdk.FeeTx {
+	t.Helper()
+	cdc := codec.NewProtoCodec(codectypes.NewInterfaceRegistry())
+
+	bodyBz, err := (&tx.TxBody{Memo: "foo"}).Marshal()
+	require.NoError(t, err)
+	authInfoBz, err := authInfo.Marshal()
+	require.NoError(t, err)
+	txBz, err := (&tx.TxRaw{BodyBytes: bodyBz, AuthInfoBytes: authInfoBz}).Marshal()
+	require.NoError(t, err)
+
+	decoded, err := DefaultTxDecoder(cdc)(txBz)
+	require.NoError(t, err)
+	feeTx, ok := decoded.(sdk.FeeTx)
+	require.True(t, ok)
+	return feeTx
+}
+
+// A tx whose AuthInfo omits the Fee field (proto field 2) decodes with
+// AuthInfo.Fee == nil. The fee accessors — reached first by the ante chain's
+// SetUpContextDecorator — must return zero values instead of dereferencing nil.
+func TestNilFeeAccessorsDoNotPanic(t *testing.T) {
+	feeTx := decodeAuthInfo(t, &tx.AuthInfo{})
+
+	require.NotPanics(t, func() {
+		require.Equal(t, uint64(0), feeTx.GetGas())
+		require.Nil(t, feeTx.GetFee())
+		require.Nil(t, feeTx.FeePayer())
+		require.Nil(t, feeTx.FeeGranter())
+	})
+}
+
+// An empty (but present) Fee — what newBuilder always sets — must keep working.
+func TestEmptyFeeStillWorks(t *testing.T) {
+	feeTx := decodeAuthInfo(t, &tx.AuthInfo{Fee: &tx.Fee{}})
+	require.Equal(t, uint64(0), feeTx.GetGas())
+	require.Nil(t, feeTx.GetFee())
+}
+
+// A populated Fee returns its values unchanged.
+func TestPopulatedFeeUnchanged(t *testing.T) {
+	feeTx := decodeAuthInfo(t, &tx.AuthInfo{Fee: &tx.Fee{GasLimit: 21000}})
+	require.Equal(t, uint64(21000), feeTx.GetGas())
+}