[nice to have] multisig preventing signing with wrong key

x/auth/client/cli/tx_sign.go

@@ -4,12 +4,14 @@
 	"fmt"
 	"os"
 
+	"github.com/cosmos/cosmos-sdk/crypto/keyring"
 	"github.com/spf13/cobra"
 
 	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/client/flags"
 	"github.com/cosmos/cosmos-sdk/client/tx"
-	sdk "github.com/cosmos/cosmos-sdk/types"
+	kmultisig "github.com/cosmos/cosmos-sdk/crypto/keys/multisig"
+	"github.com/cosmos/cosmos-sdk/types/errors"
 	authclient "github.com/cosmos/cosmos-sdk/x/auth/client"
 )
 
@@ -215,7 +217,7 @@
 			return err
 		}
 
 		txFactory := tx.NewFactoryCLI(clientCtx, cmd.Flags())
 		txCfg := clientCtx.TxConfig
 		txBuilder, err := txCfg.WrapTxBuilder(newTx)
 		if err != nil {
@@ -235,14 +237,33 @@
 
 		overwrite, _ := f.GetBool(flagOverwrite)
 		if multisig != "" {
-			multisigAddr, err := sdk.AccAddressFromBech32(multisig)
+			// Bech32 decode error, maybe it's a name, we try to fetch from keyring
+			multisigAddr, multisigName, _, err := client.GetFromFields(txF.Keybase(), multisig, clientCtx.GenerateOnly)
 			if err != nil {
-				// Bech32 decode error, maybe it's a name, we try to fetch from keyring
-				multisigAddr, _, _, err = client.GetFromFields(txFactory.Keybase(), multisig, clientCtx.GenerateOnly)
-				if err != nil {
-					return fmt.Errorf("error getting account from keybase: %w", err)
+				return fmt.Errorf("error getting account from keybase: %w", err)
+			}
+			multisigkey, err := getMultisigRecord(clientCtx, multisigName)
+			if err != nil {
+				return err
+			}
+			multisigPubKey := multisigkey.GetPubKey()
+			multisigLegacyPub := multisigPubKey.(*kmultisig.LegacyAminoPubKey)
+
+			fromRecord, err := clientCtx.Keyring.Key(fromName)
+			if err != nil {
+				return fmt.Errorf("error getting account from keybase: %w", err)
+			}
+			fromPubKey := fromRecord.GetPubKey()
+
+			var found bool
+			for _, pubkey := range multisigLegacyPub.GetPubKeys() {
+				if pubkey.Equals(fromPubKey) {
+					found = true
 				}
 			}
+			if !found {
+				return fmt.Errorf("signing key is not a part of multisig key")
+			}
 			err = authclient.SignTxWithSignerAddress(
 				txF, clientCtx, multisigAddr, fromName, txBuilder, clientCtx.Offline, overwrite)
 			if err != nil {
@@ -316,3 +337,13 @@
 
 	return txConfig.TxJSONEncoder()(parsedTx)
 }
+
+func getMultisigRecord(clientCtx client.Context, name string) (keyring.Info, error) {
+	kb := clientCtx.Keyring
+	multisigRecord, err := kb.Key(name)
+	if err != nil {
+		return nil, errors.Wrap(err, "error getting keybase multisig account")
+	}
+
+	return multisigRecord, nil
+}

x/auth/client/testutil/suite.go

@@ -60,6 +60,10 @@ func (s *IntegrationTestSuite) SetupSuite() {
 	account2, _, err := kb.NewMnemonic("newAccount2", keyring.English, sdk.FullFundraiserPath, keyring.DefaultBIP39Passphrase, hd.Secp256k1)
 	s.Require().NoError(err)
 
+	// Create a dummy account for testing purpose
+	_, _, err = kb.NewMnemonic("dummyAccount", keyring.English, sdk.FullFundraiserPath, keyring.DefaultBIP39Passphrase, hd.Secp256k1)
+	s.Require().NoError(err)
+
 	multi := kmultisig.NewLegacyAminoPubKey(2, []cryptotypes.PubKey{account1.GetPubKey(), account2.GetPubKey()})
 	_, err = kb.SaveMultisig("multi", multi)
 	s.Require().NoError(err)
@@ -737,6 +741,10 @@ func (s *IntegrationTestSuite) TestCLIMultisignSortSignatures() {
 	multisigInfo, err := val1.ClientCtx.Keyring.Key("multi")
 	s.Require().NoError(err)
 
+	// Generate dummy account which is not a part of multisig.
+	dummyAcc, err := val1.ClientCtx.Keyring.Key("dummyAccount")
+	s.Require().NoError(err)
+
 	resp, err := bankcli.QueryBalancesExec(val1.ClientCtx, multisigInfo.GetAddress())
 	s.Require().NoError(err)
 
@@ -795,6 +803,13 @@ func (s *IntegrationTestSuite) TestCLIMultisignSortSignatures() {
 
 	sign2File := testutil.WriteToNewTempFile(s.T(), account2Signature.String())
 
+	// Sign with dummy account
+	dummyAddr := dummyAcc.GetAddress()
+	s.Require().NoError(err)
+	_, err = TxSignExec(val1.ClientCtx, dummyAddr, multiGeneratedTxFile.Name(), "--multisig", addr.String())
+	s.Require().Error(err)
+	s.Require().Contains(err.Error(), "signing key is not a part of multisig key")
+
 	multiSigWith2Signatures, err := TxMultiSignExec(val1.ClientCtx, multisigInfo.GetName(), multiGeneratedTxFile.Name(), sign1File.Name(), sign2File.Name())
 	s.Require().NoError(err)
 
@@ -849,7 +864,7 @@ func (s *IntegrationTestSuite) TestSignWithMultisig() {
 	// as the main point of this test is to test the `--multisig` flag with an address
 	// that is not in the keyring.
 	_, err = TxSignExec(val1.ClientCtx, addr1, multiGeneratedTx2File.Name(), "--multisig", multisigAddr.String())
-	s.Require().Contains(err.Error(), "tx intended signer does not match the given signer")
+	s.Require().Contains(err.Error(), "error getting account from keybase")
 }
 
 func (s *IntegrationTestSuite) TestCLIMultisign() {