From ddf0571031092d9c5e1aad305127a4e186d16b72 Mon Sep 17 00:00:00 2001
From: Andras Banki-Horvath <bhandras@gmail.com>
Date: Fri, 6 May 2022 12:29:12 +0200
Subject: [PATCH 1/3] itest: cover musig2 combine without all signatures ready

---
 lntest/itest/lnd_taproot_test.go | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lntest/itest/lnd_taproot_test.go b/lntest/itest/lnd_taproot_test.go
index 589b75e8e..4492bf973 100644
--- a/lntest/itest/lnd_taproot_test.go
+++ b/lntest/itest/lnd_taproot_test.go
@@ -902,6 +902,20 @@ func testTaprootMuSig2CombinedLeafKeySpend(ctxt context.Context, t *harnessTest,
 	)
 	require.NoError(t.t, err)
 
+	// Before we have all partial signatures, we shouldn't get a final
+	// signature back.
+	combineSigResp, err := alice.SignerClient.MuSig2CombineSig(
+		ctxt, &signrpc.MuSig2CombineSigRequest{
+			SessionId: sessResp1.SessionId,
+			OtherPartialSignatures: [][]byte{
+				signResp2.LocalPartialSignature,
+			},
+		},
+	)
+	require.NoError(t.t, err)
+	require.False(t.t, combineSigResp.HaveAllSignatures)
+	require.Empty(t.t, combineSigResp.FinalSignature)
+
 	signResp3, err := alice.SignerClient.MuSig2Sign(
 		ctxt, &signrpc.MuSig2SignRequest{
 			SessionId:     sessResp3.SessionId,
@@ -935,7 +949,6 @@ func testTaprootMuSig2CombinedLeafKeySpend(ctxt context.Context, t *harnessTest,
 		ctxt, &signrpc.MuSig2CombineSigRequest{
 			SessionId: sessResp1.SessionId,
 			OtherPartialSignatures: [][]byte{
-				signResp2.LocalPartialSignature,
 				signResp3.LocalPartialSignature,
 			},
 		},

From c4c188f6d9f85a92cb4a423a9d99402892b9a991 Mon Sep 17 00:00:00 2001
From: Andras Banki-Horvath <bhandras@gmail.com>
Date: Thu, 5 May 2022 20:20:03 +0200
Subject: [PATCH 2/3] signer: fix crash when musig combine doesn't have final
 sig

---
 lnrpc/signrpc/signer_server.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lnrpc/signrpc/signer_server.go b/lnrpc/signrpc/signer_server.go
index ba98f276d..36a9de6fa 100644
--- a/lnrpc/signrpc/signer_server.go
+++ b/lnrpc/signrpc/signer_server.go
@@ -938,10 +938,15 @@ func (s *Server) MuSig2CombineSig(_ context.Context,
 		return nil, fmt.Errorf("error combining signatures: %v", err)
 	}
 
-	return &MuSig2CombineSigResponse{
+	resp := &MuSig2CombineSigResponse{
 		HaveAllSignatures: haveAllSigs,
-		FinalSignature:    finalSig.Serialize(),
-	}, nil
+	}
+
+	if haveAllSigs {
+		resp.FinalSignature = finalSig.Serialize()
+	}
+
+	return resp, err
 }
 
 // MuSig2Cleanup removes a session from memory to free up resources.

From bbe953d70dcd9911510f71deb6fc977953703eff Mon Sep 17 00:00:00 2001
From: Andras Banki-Horvath <bhandras@gmail.com>
Date: Thu, 5 May 2022 20:21:36 +0200
Subject: [PATCH 3/3] docs: update release notes 0.15.0

---
 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 658ee46fd..d7485c7d8 100644
--- a/docs/release-notes/release-notes-0.15.0.md
+++ b/docs/release-notes/release-notes-0.15.0.md
@@ -85,6 +85,8 @@ to Bitcoin nodes that advertise a Tor v3 onion service address.
 * [Fixed an edge case where the lnd might be stuck at starting due to channel
   arbitrator relying on htlcswitch to be started
   first](https://github.com/lightningnetwork/lnd/pull/6214).
+
+* [Fixed crash in MuSig2Combine](https://github.com/lightningnetwork/lnd/pull/6502)
   
 ## Neutrino