Merge pull request #5539 from Kixunil/no-psbt-midstep-enforce-new-reserved-value

Do not enforce new reserved value in PSBT midstep

docs/release-notes/release-notes-0.14.2.md

@@ -5,6 +5,15 @@
 * [Return the nearest known fee rate when a given conf target cannot be found
   from Web API fee estimator.](https://github.com/lightningnetwork/lnd/pull/6062)
 
+## Wallet
+
+* A bug that prevented opening anchor-based channels from external wallets when
+  the internal wallet was empty even though the transaction contained a
+  sufficiently large output belonging to the internal wallet
+  [was fixed](https://github.com/lightningnetwork/lnd/pull/5539)
+  In other words, freshly-installed LND can now be initailized with multiple
+  channels from an external (e.g. hardware) wallet *in a single transaction*.
+
 ## Build System
 
 * [Clean up Makefile by using go
@@ -35,6 +44,7 @@
 
 * Andras Banki-Horvath
 * Harsha Goli
+* Martin Habovštiak
 * Naveen Srinivasan
 * Oliver Gugger
 * Yong Yu

lntest/itest/lnd_psbt_test.go

@@ -6,8 +6,10 @@ import (
 	"crypto/rand"
 	"fmt"
 
+	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/btcsuite/btcutil/psbt"
 	"github.com/lightningnetwork/lnd/funding"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
@@ -466,6 +468,189 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	closeChannelAndAssert(t, net, carol, chanPoint2, false)
 }
 
+// testPsbtChanFundingSingleStep checks whether PSBT funding works also when the
+// wallet of both nodes are empty and one of them uses PSBT and an external
+// wallet to fund the channel while creating reserve output in the same
+// transaction.
+func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
+	ctxb := context.Background()
+	const chanSize = funding.MaxBtcFundingAmount
+
+	args := nodeArgsForCommitType(lnrpc.CommitmentType_ANCHORS)
+
+	// First, we'll create two new nodes that we'll use to open channels
+	// between for this test. But in this case both nodes have an empty
+	// wallet.
+	carol := net.NewNode(t.t, "carol", args)
+	defer shutdownAndAssert(net, t, carol)
+
+	dave := net.NewNode(t.t, "dave", args)
+	defer shutdownAndAssert(net, t, dave)
+
+	net.SendCoins(t.t, btcutil.SatoshiPerBitcoin, net.Alice)
+
+	// Get new address for anchor reserve.
+	reserveAddrReq := &lnrpc.NewAddressRequest{
+		Type: lnrpc.AddressType_WITNESS_PUBKEY_HASH,
+	}
+	addrResp, err := carol.NewAddress(ctxb, reserveAddrReq)
+	require.NoError(t.t, err)
+	reserveAddr, err := btcutil.DecodeAddress(addrResp.Address, harnessNetParams)
+	require.NoError(t.t, err)
+	reserveAddrScript, err := txscript.PayToAddrScript(reserveAddr)
+	require.NoError(t.t, err)
+
+	// Before we start the test, we'll ensure both sides are connected so
+	// the funding flow can be properly executed.
+	net.EnsureConnected(t.t, carol, dave)
+
+	// At this point, we can begin our PSBT channel funding workflow. We'll
+	// start by generating a pending channel ID externally that will be used
+	// to track this new funding type.
+	var pendingChanID [32]byte
+	_, err = rand.Read(pendingChanID[:])
+	require.NoError(t.t, err)
+
+	// Now that we have the pending channel ID, Carol will open the channel
+	// by specifying a PSBT shim.
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+	chanUpdates, tempPsbt, err := openChannelPsbt(
+		ctxt, carol, dave, lntest.OpenChannelParams{
+			Amt: chanSize,
+			FundingShim: &lnrpc.FundingShim{
+				Shim: &lnrpc.FundingShim_PsbtShim{
+					PsbtShim: &lnrpc.PsbtShim{
+						PendingChanId: pendingChanID[:],
+						NoPublish:     false,
+					},
+				},
+			},
+		},
+	)
+	require.NoError(t.t, err)
+
+	decodedPsbt, err := psbt.NewFromRawBytes(bytes.NewReader(tempPsbt), false)
+	require.NoError(t.t, err)
+
+	reserveTxOut := wire.TxOut{
+		Value:    10000,
+		PkScript: reserveAddrScript,
+	}
+
+	decodedPsbt.UnsignedTx.TxOut = append(
+		decodedPsbt.UnsignedTx.TxOut, &reserveTxOut,
+	)
+	decodedPsbt.Outputs = append(decodedPsbt.Outputs, psbt.POutput{})
+
+	var psbtBytes bytes.Buffer
+	err = decodedPsbt.Serialize(&psbtBytes)
+	require.NoError(t.t, err)
+
+	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+	fundReq := &walletrpc.FundPsbtRequest{
+		Template: &walletrpc.FundPsbtRequest_Psbt{
+			Psbt: psbtBytes.Bytes(),
+		},
+		Fees: &walletrpc.FundPsbtRequest_SatPerVbyte{
+			SatPerVbyte: 2,
+		},
+	}
+	fundResp, err := net.Alice.WalletKitClient.FundPsbt(ctxt, fundReq)
+	require.NoError(t.t, err)
+
+	// Make sure the wallets are actually empty
+	unspentCarol, err := carol.ListUnspent(ctxb, &lnrpc.ListUnspentRequest{})
+	require.NoError(t.t, err)
+	require.Len(t.t, unspentCarol.Utxos, 0)
+
+	unspentDave, err := dave.ListUnspent(ctxb, &lnrpc.ListUnspentRequest{})
+	require.NoError(t.t, err)
+	require.Len(t.t, unspentDave.Utxos, 0)
+
+	// We have a PSBT that has no witness data yet, which is exactly what we
+	// need for the next step: Verify the PSBT with the funding intents.
+	_, err = carol.FundingStateStep(ctxb, &lnrpc.FundingTransitionMsg{
+		Trigger: &lnrpc.FundingTransitionMsg_PsbtVerify{
+			PsbtVerify: &lnrpc.FundingPsbtVerify{
+				PendingChanId: pendingChanID[:],
+				FundedPsbt:    fundResp.FundedPsbt,
+			},
+		},
+	})
+	require.NoError(t.t, err)
+
+	// Now we'll ask Alice's wallet to sign the PSBT so we can finish the
+	// funding flow.
+	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+	finalizeReq := &walletrpc.FinalizePsbtRequest{
+		FundedPsbt: fundResp.FundedPsbt,
+	}
+	finalizeRes, err := net.Alice.WalletKitClient.FinalizePsbt(ctxt, finalizeReq)
+	require.NoError(t.t, err)
+
+	// We've signed our PSBT now, let's pass it to the intent again.
+	_, err = carol.FundingStateStep(ctxb, &lnrpc.FundingTransitionMsg{
+		Trigger: &lnrpc.FundingTransitionMsg_PsbtFinalize{
+			PsbtFinalize: &lnrpc.FundingPsbtFinalize{
+				PendingChanId: pendingChanID[:],
+				SignedPsbt:    finalizeRes.SignedPsbt,
+			},
+		},
+	})
+	require.NoError(t.t, err)
+
+	// Consume the "channel pending" update. This waits until the funding
+	// transaction was fully compiled.
+	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+	updateResp, err := receiveChanUpdate(ctxt, chanUpdates)
+	require.NoError(t.t, err)
+	upd, ok := updateResp.Update.(*lnrpc.OpenStatusUpdate_ChanPending)
+	require.True(t.t, ok)
+	chanPoint := &lnrpc.ChannelPoint{
+		FundingTxid: &lnrpc.ChannelPoint_FundingTxidBytes{
+			FundingTxidBytes: upd.ChanPending.Txid,
+		},
+		OutputIndex: upd.ChanPending.OutputIndex,
+	}
+
+	var finalTx wire.MsgTx
+	err = finalTx.Deserialize(bytes.NewReader(finalizeRes.RawFinalTx))
+	require.NoError(t.t, err)
+
+	txHash := finalTx.TxHash()
+	block := mineBlocks(t, net, 6, 1)[0]
+	assertTxInBlock(t, block, &txHash)
+	err = carol.WaitForNetworkChannelOpen(chanPoint)
+	require.NoError(t.t, err)
+
+	// Next, to make sure the channel functions as normal, we'll make some
+	// payments within the channel.
+	payAmt := btcutil.Amount(100000)
+	invoice := &lnrpc.Invoice{
+		Memo:  "new chans",
+		Value: int64(payAmt),
+	}
+	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+	resp, err := dave.AddInvoice(ctxt, invoice)
+	require.NoError(t.t, err)
+	err = completePaymentRequests(
+		carol, carol.RouterClient, []string{resp.PaymentRequest},
+		true,
+	)
+	require.NoError(t.t, err)
+
+	// To conclude, we'll close the newly created channel between Carol and
+	// Dave. This function will also block until the channel is closed and
+	// will additionally assert the relevant channel closing post
+	// conditions.
+	closeChannelAndAssert(t, net, carol, chanPoint, false)
+}
+
 // openChannelPsbt attempts to open a channel between srcNode and destNode with
 // the passed channel funding parameters. If the passed context has a timeout,
 // then if the timeout is reached before the channel pending notification is

lntest/itest/lnd_test_list_on_test.go

@@ -287,6 +287,10 @@ var allTestCases = []*testCase{
 		name: "batch channel funding",
 		test: testBatchChanFunding,
 	},
+	{
+		name: "psbt channel funding single step",
+		test: testPsbtChanFundingSingleStep,
+	},
 	{
 		name: "sendtoroute multi path payment",
 		test: testSendToRouteMultiPath,

lnwallet/wallet.go

@@ -706,6 +706,12 @@ func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg
 		return
 	}
 
+	// We need to avoid enforcing reserved value in the middle of PSBT
+	// funding because some of the following steps may add UTXOs funding
+	// the on-chain wallet.
+	// The enforcement still happens at the last step - in PsbtFundingVerify
+	enforceNewReservedValue := true
+
 	// If no chanFunder was provided, then we'll assume the default
 	// assembler, which is backed by the wallet's internal coin selection.
 	if req.ChanFunder == nil {
@@ -720,6 +726,9 @@ func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg
 			DustLimit:        DustLimitForSize(input.P2WSHSize),
 		}
 		req.ChanFunder = chanfunding.NewWalletAssembler(cfg)
+	} else {
+		_, isPsbtFunder := req.ChanFunder.(*chanfunding.PsbtAssembler)
+		enforceNewReservedValue = !isPsbtFunder
 	}
 
 	localFundingAmt := req.LocalFundingAmt
@@ -819,13 +828,15 @@ func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg
 	// when the PSBT has been verified.
 	isPublic := req.Flags&lnwire.FFAnnounceChannel != 0
 	hasAnchors := req.CommitType.HasAnchors()
-	err = l.enforceNewReservedValue(fundingIntent, isPublic, hasAnchors)
-	if err != nil {
-		fundingIntent.Cancel()
+	if enforceNewReservedValue {
+		err = l.enforceNewReservedValue(fundingIntent, isPublic, hasAnchors)
+		if err != nil {
+			fundingIntent.Cancel()
 
-		req.err <- err
-		req.resp <- nil
-		return
+			req.err <- err
+			req.resp <- nil
+			return
+		}
 	}
 
 	// The total channel capacity will be the size of the funding output we