tapfreighter+tapsend: check input uniqueness

In this commit, we check for input asset uniqueness for parcels in the
PreBroadcast state, before being converted to a Transfer. This prevents
invalid transfers from being published and logged via RPC.

tapfreighter/parcel.go

@@ -529,6 +529,11 @@ func ConvertToTransfer(currentHeight uint32, activeTransfers []*tappsbt.VPacket,
 		PassiveAssetsAnchor: passiveAssetAnchor,
 	}
 
+	allPackets := append(activeTransfers, passiveAssets...)
+	if err := tapsend.AssertInputsUnique(allPackets); err != nil {
+		return nil, fmt.Errorf("unable to convert to transfer: %w", err)
+	}
+
 	for pIdx := range activeTransfers {
 		vPkt := activeTransfers[pIdx]
 

tapsend/send.go

@@ -27,6 +27,7 @@ import (
 	"github.com/lightninglabs/taproot-assets/fn"
 	"github.com/lightninglabs/taproot-assets/tappsbt"
 	"github.com/lightninglabs/taproot-assets/tapscript"
+	lfn "github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"golang.org/x/exp/maps"
@@ -1030,9 +1031,10 @@ func addKeyTweaks(unknowns []*psbt.Unknown, desc *lndclient.SignDescriptor) {
 func CreateOutputCommitments(
 	packets []*tappsbt.VPacket) (tappsbt.OutputCommitments, error) {
 
-	// We create an empty output commitment map, keyed by the anchor output
-	// index.
-	outputCommitments := make(tappsbt.OutputCommitments)
+	// Inputs must be unique.
+	if err := AssertInputsUnique(packets); err != nil {
+		return nil, err
+	}
 
 	// We require all outputs that reference the same anchor output to be
 	// identical, otherwise some assumptions in the code below don't hold.
@@ -1052,6 +1054,10 @@ func CreateOutputCommitments(
 		return nil, err
 	}
 
+	// We create an empty output commitment map, keyed by the anchor output
+	// index.
+	outputCommitments := make(tappsbt.OutputCommitments)
+
 	// And now we commit each packet to the respective anchor output
 	// commitments.
 	for _, vPkt := range packets {
@@ -1544,6 +1550,26 @@ func AssertInputAnchorsEqual(packets []*tappsbt.VPacket) error {
 	return nil
 }
 
+// AssertInputsUnique makes sure that every input across all virtual packets is
+// referencing a unique input asset, which is identified by the input PrevID.
+func AssertInputsUnique(packets []*tappsbt.VPacket) error {
+	// PrevIDs are comparable enough to serve as a map key without hashing.
+	inputs := make(lfn.Set[asset.PrevID])
+
+	for _, vPkt := range packets {
+		for _, vIn := range vPkt.Inputs {
+			if inputs.Contains(vIn.PrevID) {
+				return fmt.Errorf("input %v is duplicated",
+					vIn.PrevID)
+			}
+
+			inputs.Add(vIn.PrevID)
+		}
+	}
+
+	return nil
+}
+
 // ExtractUnSpendable extracts all tombstones and burns from the active input
 // commitment.
 func ExtractUnSpendable(c *commitment.TapCommitment) []*asset.Asset {