From b3f14d66f0423a8512d1c55e2b5233fc77425bd7 Mon Sep 17 00:00:00 2001
From: eugene <elzeigel@gmail.com>
Date: Thu, 22 Apr 2021 12:18:04 -0400
Subject: [PATCH] lnwallet/chanfunding: assert PSBT Inputs have WitnessUtxo

---
 lnwallet/chanfunding/psbt_assembler.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lnwallet/chanfunding/psbt_assembler.go b/lnwallet/chanfunding/psbt_assembler.go
index 4d15ff53..75b0e708 100644
--- a/lnwallet/chanfunding/psbt_assembler.go
+++ b/lnwallet/chanfunding/psbt_assembler.go
@@ -249,6 +249,15 @@ func (i *PsbtIntent) Verify(packet *psbt.Packet) error {
 			"output amount sum")
 	}
 
+	// SumUtxoInputValues checks that packet.Inputs is non-empty. Here we
+	// check that each Input has a WitnessUtxo field, to avoid possible
+	// malleability.
+	for _, in := range packet.Inputs {
+		if in.WitnessUtxo == nil {
+			return fmt.Errorf("not all inputs are segwit spends")
+		}
+	}
+
 	i.PendingPsbt = packet
 	i.State = PsbtVerified
 	return nil