fix(consensus): validate HTLC tags in v2 signatures

Co-Authored-By: Charon <charon@lethean.io>

consensus/v2sig_test.go

@@ -18,6 +18,18 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func buildSingleZCSigRaw() []byte {
+	var buf bytes.Buffer
+	enc := wire.NewEncoder(&buf)
+	enc.WriteVarint(1)
+	enc.WriteUint8(types.SigTypeZC)
+	enc.WriteBytes(make([]byte, 64))
+	enc.WriteVarint(0)
+	enc.WriteVarint(0)
+	enc.WriteBytes(make([]byte, 64))
+	return buf.Bytes()
+}
+
 // loadTestTx loads and decodes a hex-encoded transaction from testdata.
 func loadTestTx(t *testing.T, filename string) *types.Transaction {
 	t.Helper()
@@ -147,6 +159,20 @@ func TestVerifyV2Signatures_BadSigCount(t *testing.T) {
 	assert.Error(t, err, "should fail with mismatched sig count")
 }
 
+func TestVerifyV2Signatures_HTLCWrongSigTag_Bad(t *testing.T) {
+	tx := &types.Transaction{
+		Version: types.VersionPostHF5,
+		Vin: []types.TxInput{
+			types.TxInputHTLC{Amount: 100, KeyImage: types.KeyImage{1}},
+		},
+		SignaturesRaw: buildSingleZCSigRaw(),
+	}
+
+	err := VerifyTransactionSignatures(tx, config.TestnetForks, 250, nil, nil)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "HTLC")
+}
+
 func TestVerifyV2Signatures_TxHash(t *testing.T) {
 	// Verify the known tx hash matches.
 	tx := loadTestTx(t, "../testdata/v2_spending_tx_mixin0.hex")

consensus/verify.go

@@ -152,7 +152,8 @@ func verifyV2Signatures(tx *types.Transaction, getZCRingOutputs ZCRingOutputsFn)
 		return coreerr.E("verifyV2Signatures", fmt.Sprintf("consensus: V2 signature count %d != input count %d", len(sigEntries), len(tx.Vin)), nil)
 	}
 
-	// Validate that ZC inputs have ZC_sig and vice versa.
+	// Validate that ZC inputs have ZC_sig and that ring-spending inputs use
+	// the ring-signature tags that match their spending model.
 	for i, vin := range tx.Vin {
 		switch vin.(type) {
 		case types.TxInputZC:
@@ -163,6 +164,10 @@ func verifyV2Signatures(tx *types.Transaction, getZCRingOutputs ZCRingOutputsFn)
 			if sigEntries[i].tag != types.SigTypeNLSAG && sigEntries[i].tag != types.SigTypeVoid {
 				return coreerr.E("verifyV2Signatures", fmt.Sprintf("consensus: input %d is to_key but signature tag is 0x%02x", i, sigEntries[i].tag), nil)
 			}
+		case types.TxInputHTLC:
+			if sigEntries[i].tag != types.SigTypeNLSAG && sigEntries[i].tag != types.SigTypeVoid {
+				return coreerr.E("verifyV2Signatures", fmt.Sprintf("consensus: input %d is HTLC but signature tag is 0x%02x", i, sigEntries[i].tag), nil)
+			}
 		}
 	}