From e11c41ba8f71766f74a9fe201a60a2d64e80ad52 Mon Sep 17 00:00:00 2001
From: Liviu <liviu.ln@protonmail.com>
Date: Sun, 30 Jan 2022 21:37:32 -0800
Subject: [PATCH 1/2] walletrpc: return an error when finalizing an already
 complete PSBT Return an error to the client if attempting to finalize a PSBS
 with no missing signatures.

---
 lnrpc/walletrpc/walletkit_server.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lnrpc/walletrpc/walletkit_server.go b/lnrpc/walletrpc/walletkit_server.go
index d0e807c6d..71f192537 100644
--- a/lnrpc/walletrpc/walletkit_server.go
+++ b/lnrpc/walletrpc/walletkit_server.go
@@ -1254,8 +1254,7 @@ func (w *WalletKit) FinalizePsbt(_ context.Context,
 		account = req.Account
 	}
 
-	// Parse the funded PSBT. No additional checks are required at this
-	// level as the wallet will perform all of them.
+	// Parse the funded PSBT.
 	packet, err := psbt.NewFromRawBytes(
 		bytes.NewReader(req.FundedPsbt), false,
 	)
@@ -1263,6 +1262,12 @@ func (w *WalletKit) FinalizePsbt(_ context.Context,
 		return nil, fmt.Errorf("error parsing PSBT: %v", err)
 	}
 
+	// The only check done at this level is to validate that the PSBT is
+	// not complete. The wallet performs all other checks.
+	if packet.IsComplete() {
+		return nil, fmt.Errorf("PSBT is already fully signed")
+	}
+
 	// Let the wallet do the heavy lifting. This will sign all inputs that
 	// we have the UTXO for. If some inputs can't be signed and don't have
 	// witness data attached, this will fail.

From 78ee332f96c9013fb7f5e86d9258672a9e309398 Mon Sep 17 00:00:00 2001
From: liviu-ln <96348901+liviu-ln@users.noreply.github.com>
Date: Sun, 30 Jan 2022 22:33:39 -0800
Subject: [PATCH 2/2] docs: update release notes

---
 docs/release-notes/release-notes-0.15.0.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/release-notes/release-notes-0.15.0.md b/docs/release-notes/release-notes-0.15.0.md
index 9f6000be2..a852f5e4a 100644
--- a/docs/release-notes/release-notes-0.15.0.md
+++ b/docs/release-notes/release-notes-0.15.0.md
@@ -65,6 +65,8 @@
 * [Add dev only RPC subserver and the devrpc.ImportGraph
   call](https://github.com/lightningnetwork/lnd/pull/6149)
 
+* [Improve validation of a PSBT packet when handling a request to finalize it.](https://github.com/lightningnetwork/lnd/pull/6217)
+
 ## Documentation
 
 * Improved instructions on [how to build lnd for mobile](https://github.com/lightningnetwork/lnd/pull/6085).