fix: allow empty public keys when setting signatures (cosmos#19106)

Author: cmwaters

x/auth/CHANGELOG.md

@@ -49,3 +49,5 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [#18817](https://github.com/cosmos/cosmos-sdk/pull/18817) SigVerification, GasConsumption, IncreaseSequence ante decorators have all been joined into one SigVerification decorator. Gas consumption during TX validation flow has reduced.
 
 ### Bug Fixes
+
+* [#19106](https://github.com/cosmos/cosmos-sdk/pull/19106) Allow empty public keys when setting signatures. Public keys aren't needed for every transaction. 

x/auth/tx/builder.go

@@ -352,11 +352,17 @@ func (w *wrapper) SetSignatures(signatures ...signing.SignatureV2) error {
 	rawSigs := make([][]byte, n)
 
 	for i, sig := range signatures {
-		var modeInfo *tx.ModeInfo
+		var (
+			modeInfo *tx.ModeInfo
+			pubKey   *codectypes.Any
+			err      error
+		)
 		modeInfo, rawSigs[i] = SignatureDataToModeInfoAndSig(sig.Data)
-		pubKey, err := codectypes.NewAnyWithValue(sig.PubKey)
-		if err != nil {
-			return err
+		if sig.PubKey != nil {
+			pubKey, err = codectypes.NewAnyWithValue(sig.PubKey)
+			if err != nil {
+				return err
+			}
 		}
 		signerInfos[i] = &tx.SignerInfo{
 			PublicKey: pubKey,

x/auth/tx/builder_test.go

@@ -127,6 +127,20 @@ func TestTxBuilder(t *testing.T) {
 	})
 }
 
+func TestSetSignaturesNoPublicKey(t *testing.T) {
+	_, pubkey, _ := testdata.KeyTestPubAddr()
+	txBuilder := newBuilder(nil)
+	sig2 := signing.SignatureV2{
+		Data: &signing.SingleSignatureData{
+			SignMode:  signing.SignMode_SIGN_MODE_DIRECT,
+			Signature: legacy.Cdc.MustMarshal(pubkey),
+		},
+		Sequence: 1,
+	}
+	err := txBuilder.SetSignatures(sig2)
+	require.NoError(t, err)
+}
+
 func TestBuilderValidateBasic(t *testing.T) {
 	// keys and addresses
 	_, pubKey1, addr1 := testdata.KeyTestPubAddr()