feat: add sign mode direct aux handler (cosmos#9944)

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## Description

Closes: cosmos#9911 

<!-- Add a description of the changes that this PR introduces and the files that
are the most critical to review. -->

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
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/master/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/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/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

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

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)

client/tx/tx.go

@@ -201,11 +201,26 @@ func Sign(txf Factory, name string, txBuilder client.TxBuilder, overwriteSig boo
 	if err != nil {
 		return err
 	}
+
 	pubKey := key.GetPubKey()
+	pubkeys, err := txBuilder.GetTx().GetPubKeys()
+	if err != nil {
+		return err
+	}
+
+	signerIndex := 0
+	for i, p := range pubkeys {
+		if p.Equals(pubKey) {
+			signerIndex = i
+			break
+		}
+	}
+
 	signerData := authsigning.SignerData{
 		ChainID:       txf.chainID,
 		AccountNumber: txf.accountNumber,
 		Sequence:      txf.sequence,
+		SignerIndex:   signerIndex,
 	}
 
 	// For SIGN_MODE_DIRECT, calling SetSignatures calls setSignerInfos on

x/auth/signing/sign_mode_handler.go

@@ -34,4 +34,7 @@ type SignerData struct {
 	// since in SIGN_MODE_DIRECT the account sequence is already in the signer
 	// info.
 	Sequence uint64
+
+	// SignerIndex index of signer in the signer_infos array
+	SignerIndex int
 }

x/auth/tx/direct_aux.go

@@ -0,0 +1,52 @@
+package tx
+
+import (
+	"fmt"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	types "github.com/cosmos/cosmos-sdk/types/tx"
+	signingtypes "github.com/cosmos/cosmos-sdk/types/tx/signing"
+
+	"github.com/cosmos/cosmos-sdk/x/auth/signing"
+)
+
+var _ signing.SignModeHandler = signModeDirectAuxHandler{}
+
+// signModeDirectAuxHandler defines the SIGN_MODE_DIRECT_AUX SignModeHandler
+type signModeDirectAuxHandler struct{}
+
+// DefaultMode implements SignModeHandler.DefaultMode
+func (signModeDirectAuxHandler) DefaultMode() signingtypes.SignMode {
+	return signingtypes.SignMode_SIGN_MODE_DIRECT_AUX
+}
+
+// Modes implements SignModeHandler.Modes
+func (signModeDirectAuxHandler) Modes() []signingtypes.SignMode {
+	return []signingtypes.SignMode{signingtypes.SignMode_SIGN_MODE_DIRECT_AUX}
+}
+
+// GetSignBytes implements SignModeHandler.GetSignBytes
+func (signModeDirectAuxHandler) GetSignBytes(
+	mode signingtypes.SignMode, data signing.SignerData, tx sdk.Tx,
+) ([]byte, error) {
+
+	if mode != signingtypes.SignMode_SIGN_MODE_DIRECT_AUX {
+		return nil, fmt.Errorf("expected %s, got %s", signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, mode)
+	}
+
+	protoTx, ok := tx.(*wrapper)
+	if !ok {
+		return nil, fmt.Errorf("can only handle a protobuf Tx, got %T", tx)
+	}
+
+	signDocDirectAux := types.SignDocDirectAux{
+		BodyBytes:     protoTx.getBodyBytes(),
+		ChainId:       data.ChainID,
+		AccountNumber: data.AccountNumber,
+		Sequence:      data.Sequence,
+		Tip:           protoTx.tx.AuthInfo.Tip,
+		PublicKey:     protoTx.tx.AuthInfo.SignerInfos[data.SignerIndex].PublicKey,
+	}
+
+	return signDocDirectAux.Marshal()
+}

x/auth/tx/direct_aux_test.go

@@ -0,0 +1,140 @@
+package tx
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
+	"github.com/cosmos/cosmos-sdk/testutil/testdata"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	txtypes "github.com/cosmos/cosmos-sdk/types/tx"
+	signingtypes "github.com/cosmos/cosmos-sdk/types/tx/signing"
+	"github.com/cosmos/cosmos-sdk/x/auth/signing"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDirectAuxHandler(t *testing.T) {
+	privKey, pubkey, addr := testdata.KeyTestPubAddr()
+	interfaceRegistry := codectypes.NewInterfaceRegistry()
+	interfaceRegistry.RegisterImplementations((*sdk.Msg)(nil), &testdata.TestMsg{})
+	marshaler := codec.NewProtoCodec(interfaceRegistry)
+
+	txConfig := NewTxConfig(marshaler, []signingtypes.SignMode{signingtypes.SignMode_SIGN_MODE_DIRECT_AUX})
+	txBuilder := txConfig.NewTxBuilder()
+
+	memo := "sometestmemo"
+	msgs := []sdk.Msg{testdata.NewTestMsg(addr)}
+	accSeq := uint64(2) // Arbitrary account sequence
+
+	any, err := codectypes.NewAnyWithValue(pubkey)
+	require.NoError(t, err)
+
+	sigData := &signingtypes.SingleSignatureData{
+		SignMode: signingtypes.SignMode_SIGN_MODE_DIRECT_AUX,
+	}
+
+	sig := signingtypes.SignatureV2{
+		PubKey:   pubkey,
+		Data:     sigData,
+		Sequence: accSeq,
+	}
+
+	fee := txtypes.Fee{Amount: sdk.NewCoins(sdk.NewInt64Coin("atom", 150)), GasLimit: 20000}
+
+	err = txBuilder.SetMsgs(msgs...)
+	require.NoError(t, err)
+	txBuilder.SetMemo(memo)
+	txBuilder.SetFeeAmount(fee.Amount)
+	txBuilder.SetGasLimit(fee.GasLimit)
+
+	err = txBuilder.SetSignatures(sig)
+	require.NoError(t, err)
+
+	signingData := signing.SignerData{
+		ChainID:       "test-chain",
+		AccountNumber: 1,
+	}
+
+	modeHandler := signModeDirectAuxHandler{}
+	signBytes, err := modeHandler.GetSignBytes(signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, signingData, txBuilder.GetTx())
+	require.NoError(t, err)
+	require.NotNil(t, signBytes)
+
+	anys := make([]*codectypes.Any, len(msgs))
+	for i, msg := range msgs {
+		var err error
+		anys[i], err = codectypes.NewAnyWithValue(msg)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	txBody := &txtypes.TxBody{
+		Memo:     memo,
+		Messages: anys,
+	}
+	bodyBytes := marshaler.MustMarshal(txBody)
+
+	t.Log("verify GetSignBytes with generating sign bytes by marshaling signDocDirectAux")
+	signDocDirectAux := txtypes.SignDocDirectAux{
+		AccountNumber: 1,
+		BodyBytes:     bodyBytes,
+		ChainId:       "test-chain",
+		PublicKey:     any,
+	}
+
+	expectedSignBytes, err := signDocDirectAux.Marshal()
+	require.NoError(t, err)
+	require.Equal(t, expectedSignBytes, signBytes)
+
+	t.Log("verify that setting signature doesn't change sign bytes")
+	sigData.Signature, err = privKey.Sign(signBytes)
+	require.NoError(t, err)
+	err = txBuilder.SetSignatures(sig)
+	require.NoError(t, err)
+	signBytes, err = modeHandler.GetSignBytes(signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, signingData, txBuilder.GetTx())
+	require.NoError(t, err)
+	require.Equal(t, expectedSignBytes, signBytes)
+
+	t.Log("verify GetSignBytes with false txBody data")
+	signDocDirectAux.BodyBytes = []byte("dfafdasfds")
+	expectedSignBytes, err = signDocDirectAux.Marshal()
+	require.NoError(t, err)
+	require.NotEqual(t, expectedSignBytes, signBytes)
+}
+
+func TestDirectAuxHandler_DefaultMode(t *testing.T) {
+	handler := signModeDirectAuxHandler{}
+	require.Equal(t, signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, handler.DefaultMode())
+}
+
+func TestDirectAuxModeHandler_nonDIRECT_MODE(t *testing.T) {
+	invalidModes := []signingtypes.SignMode{
+		signingtypes.SignMode_SIGN_MODE_DIRECT,
+		signingtypes.SignMode_SIGN_MODE_DIRECT_JSON,
+		signingtypes.SignMode_SIGN_MODE_TEXTUAL,
+		signingtypes.SignMode_SIGN_MODE_LEGACY_AMINO_JSON,
+		signingtypes.SignMode_SIGN_MODE_UNSPECIFIED,
+	}
+	for _, invalidMode := range invalidModes {
+		t.Run(invalidMode.String(), func(t *testing.T) {
+			var dh signModeDirectAuxHandler
+			var signingData signing.SignerData
+			_, err := dh.GetSignBytes(invalidMode, signingData, nil)
+			require.Error(t, err)
+			wantErr := fmt.Errorf("expected %s, got %s", signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, invalidMode)
+			require.Equal(t, err, wantErr)
+		})
+	}
+}
+
+func TestDirectAuxModeHandler_nonProtoTx(t *testing.T) {
+	var dh signModeDirectAuxHandler
+	var signingData signing.SignerData
+	tx := new(nonProtoTx)
+	_, err := dh.GetSignBytes(signingtypes.SignMode_SIGN_MODE_DIRECT_AUX, signingData, tx)
+	require.Error(t, err)
+	wantErr := fmt.Errorf("can only handle a protobuf Tx, got %T", tx)
+	require.Equal(t, err, wantErr)
+}

x/auth/tx/mode_handler.go

@@ -28,6 +28,8 @@ func makeSignModeHandler(modes []signingtypes.SignMode) signing.SignModeHandler
 			handlers[i] = signModeDirectHandler{}
 		case signingtypes.SignMode_SIGN_MODE_LEGACY_AMINO_JSON:
 			handlers[i] = signModeLegacyAminoJSONHandler{}
+		case signingtypes.SignMode_SIGN_MODE_DIRECT_AUX:
+			handlers[i] = signModeDirectAuxHandler{}
 		default:
 			panic(fmt.Errorf("unsupported sign mode %+v", mode))
 		}