Merge pull request #6006 from guggero/remote-signer-no-chain

Allow remote signer to run without chain backend

lntest/itest/lnd_psbt_test.go

@@ -6,12 +6,15 @@ import (
 	"crypto/rand"
 	"fmt"
 
+	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/btcsuite/btcutil/hdkeychain"
 	"github.com/btcsuite/btcutil/psbt"
 	"github.com/lightningnetwork/lnd/funding"
 	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/lntest"
 	"github.com/stretchr/testify/require"
@@ -40,6 +43,12 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	dave *lntest.HarnessNode) {
 
 	ctxb := context.Background()
+
+	// Everything we do here should be done within a second or two, so we
+	// can just keep a single timeout context around for all calls.
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+
 	const chanSize = funding.MaxBtcFundingAmount
 	net.SendCoins(t.t, btcutil.SatoshiPerBitcoin, dave)
 
@@ -63,8 +72,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	// Now that we have the pending channel ID, Carol will open the channel
 	// by specifying a PSBT shim. We use the NoPublish flag here to avoid
 	// publishing the whole batch TX too early.
-	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	chanUpdates, tempPsbt, err := openChannelPsbt(
 		ctxt, carol, dave, lntest.OpenChannelParams{
 			Amt: chanSize,
@@ -83,8 +90,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	// Let's add a second channel to the batch. This time between Carol and
 	// Alice. We will publish the batch TX once this channel funding is
 	// complete.
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	chanUpdates2, psbtBytes2, err := openChannelPsbt(
 		ctxt, carol, net.Alice, lntest.OpenChannelParams{
 			Amt: chanSize,
@@ -104,8 +109,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	// We'll now ask Dave's wallet to fund the PSBT for us. This will return
 	// a packet with inputs and outputs set but without any witness data.
 	// This is exactly what we need for the next step.
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	fundReq := &walletrpc.FundPsbtRequest{
 		Template: &walletrpc.FundPsbtRequest_Psbt{
 			Psbt: psbtBytes2,
@@ -140,8 +143,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 
 	// Now we'll ask Dave'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,
 	}
@@ -161,8 +162,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 
 	// 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)
@@ -195,8 +194,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	// Consume the "channel pending" update for the second channel. This
 	// waits until the funding transaction was fully compiled and in this
 	// case published.
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	updateResp2, err := receiveChanUpdate(ctxt, chanUpdates2)
 	require.NoError(t.t, err)
 	upd2, ok := updateResp2.Update.(*lnrpc.OpenStatusUpdate_ChanPending)
@@ -225,8 +222,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 	// With the channel open, ensure that it is counted towards Carol's
 	// total channel balance.
 	balReq := &lnrpc.ChannelBalanceRequest{}
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	balRes, err := carol.ChannelBalance(ctxt, balReq)
 	require.NoError(t.t, err)
 	require.NotEqual(t.t, int64(0), balRes.LocalBalance.Sat)
@@ -238,7 +233,6 @@ func runPsbtChanFunding(net *lntest.NetworkHarness, t *harnessTest, carol,
 		Memo:  "new chans",
 		Value: int64(payAmt),
 	}
-	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 	resp, err := dave.AddInvoice(ctxt, invoice)
 	require.NoError(t.t, err)
 	err = completePaymentRequests(
@@ -261,6 +255,11 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	ctxb := context.Background()
 	const chanSize = funding.MaxBtcFundingAmount
 
+	// Everything we do here should be done within a second or two, so we
+	// can just keep a single timeout context around for all calls.
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+
 	// First, we'll create two new nodes that we'll use to open channels
 	// between for this test. Both these nodes have an empty wallet as Alice
 	// will be funding the channel.
@@ -290,8 +289,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	// Now that we have the pending channel ID, Carol will open the channel
 	// by specifying a PSBT shim. We use the NoPublish flag here to avoid
 	// publishing the whole batch TX too early.
-	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	chanUpdates, tempPsbt, err := openChannelPsbt(
 		ctxt, carol, dave, lntest.OpenChannelParams{
 			Amt: chanSize,
@@ -310,8 +307,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	// Let's add a second channel to the batch. This time between Carol and
 	// Alice. We will publish the batch TX once this channel funding is
 	// complete.
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	chanUpdates2, psbtBytes2, err := openChannelPsbt(
 		ctxt, carol, net.Alice, lntest.OpenChannelParams{
 			Amt: chanSize,
@@ -331,8 +326,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	// We'll now ask Alice's wallet to fund the PSBT for us. This will
 	// return a packet with inputs and outputs set but without any witness
 	// data. This is exactly what we need for the next step.
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	fundReq := &walletrpc.FundPsbtRequest{
 		Template: &walletrpc.FundPsbtRequest_Psbt{
 			Psbt: psbtBytes2,
@@ -375,8 +368,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// Consume the "channel pending" update. This waits until the funding
 	// transaction was fully compiled for both channels.
-	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)
@@ -403,8 +394,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// 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,
 	}
@@ -439,8 +428,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 	// With the channel open, ensure that it is counted towards Carol's
 	// total channel balance.
 	balReq := &lnrpc.ChannelBalanceRequest{}
-	ctxt, cancel = context.WithTimeout(ctxb, defaultTimeout)
-	defer cancel()
 	balRes, err := carol.ChannelBalance(ctxt, balReq)
 	require.NoError(t.t, err)
 	require.NotEqual(t.t, int64(0), balRes.LocalBalance.Sat)
@@ -452,7 +439,6 @@ func testPsbtChanFundingExternal(net *lntest.NetworkHarness, t *harnessTest) {
 		Memo:  "new chans",
 		Value: int64(payAmt),
 	}
-	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
 	resp, err := dave.AddInvoice(ctxt, invoice)
 	require.NoError(t.t, err)
 	err = completePaymentRequests(
@@ -476,6 +462,11 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 	ctxb := context.Background()
 	const chanSize = funding.MaxBtcFundingAmount
 
+	// Everything we do here should be done within a second or two, so we
+	// can just keep a single timeout context around for all calls.
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+
 	args := nodeArgsForCommitType(lnrpc.CommitmentType_ANCHORS)
 
 	// First, we'll create two new nodes that we'll use to open channels
@@ -513,8 +504,6 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// 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,
@@ -547,8 +536,6 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 	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(),
@@ -583,8 +570,6 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// 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,
 	}
@@ -604,8 +589,6 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 
 	// 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)
@@ -634,8 +617,6 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 		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(
@@ -651,6 +632,182 @@ func testPsbtChanFundingSingleStep(net *lntest.NetworkHarness, t *harnessTest) {
 	closeChannelAndAssert(t, net, carol, chanPoint, false)
 }
 
+// runSignPsbt tests that the SignPsbt RPC works correctly.
+func testSignPsbt(net *lntest.NetworkHarness, t *harnessTest) {
+	runSignPsbt(t, net, net.Alice)
+}
+
+// runSignPsbt tests that the SignPsbt RPC works correctly.
+func runSignPsbt(t *harnessTest, net *lntest.NetworkHarness,
+	alice *lntest.HarnessNode) {
+
+	ctxb := context.Background()
+
+	// Everything we do here should be done within a second or two, so we
+	// can just keep a single timeout context around for all calls.
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+
+	// We test that we can sign a PSBT that spends funds from an input that
+	// the wallet doesn't know about. To set up that test case, we first
+	// derive an address manually that the wallet won't be watching on
+	// chain. We can do that by exporting the account xpub of lnd's main
+	// account.
+	accounts, err := alice.WalletKitClient.ListAccounts(
+		ctxt, &walletrpc.ListAccountsRequest{},
+	)
+	require.NoError(t.t, err)
+	require.NotEmpty(t.t, accounts.Accounts)
+
+	// We also need to parse the accounts, so we have easy access to the
+	// parsed derivation paths.
+	parsedAccounts, err := walletrpc.AccountsToWatchOnly(accounts.Accounts)
+	require.NoError(t.t, err)
+
+	account := parsedAccounts[0]
+	xpub, err := hdkeychain.NewKeyFromString(account.Xpub)
+	require.NoError(t.t, err)
+
+	const (
+		changeIndex = 1
+		addrIndex   = 1337
+	)
+	fullDerivationPath := []uint32{
+		hdkeychain.HardenedKeyStart + account.Purpose,
+		hdkeychain.HardenedKeyStart + account.CoinType,
+		hdkeychain.HardenedKeyStart + account.Account,
+		changeIndex,
+		addrIndex,
+	}
+
+	// Let's simulate a change address.
+	change, err := xpub.DeriveNonStandard(changeIndex) // nolint:staticcheck
+	require.NoError(t.t, err)
+
+	// At an index that we are certainly not watching in the wallet.
+	addrKey, err := change.DeriveNonStandard(addrIndex) // nolint:staticcheck
+	require.NoError(t.t, err)
+
+	addrPubKey, err := addrKey.ECPubKey()
+	require.NoError(t.t, err)
+	pubKeyHash := btcutil.Hash160(addrPubKey.SerializeCompressed())
+	witnessAddr, err := btcutil.NewAddressWitnessPubKeyHash(
+		pubKeyHash, harnessNetParams,
+	)
+	require.NoError(t.t, err)
+
+	pkScript, err := txscript.PayToAddrScript(witnessAddr)
+	require.NoError(t.t, err)
+
+	// Let's send some coins to that address now.
+	utxo := &wire.TxOut{
+		Value:    600_000,
+		PkScript: pkScript,
+	}
+	resp, err := alice.WalletKitClient.SendOutputs(
+		ctxt, &walletrpc.SendOutputsRequest{
+			Outputs: []*signrpc.TxOut{{
+				Value:    utxo.Value,
+				PkScript: utxo.PkScript,
+			}},
+			MinConfs:         0,
+			SpendUnconfirmed: true,
+			SatPerKw:         2500,
+		},
+	)
+	require.NoError(t.t, err)
+
+	prevTx := wire.NewMsgTx(2)
+	err = prevTx.Deserialize(bytes.NewReader(resp.RawTx))
+	require.NoError(t.t, err)
+
+	prevOut := -1
+	for idx, txOut := range prevTx.TxOut {
+		if bytes.Equal(txOut.PkScript, pkScript) {
+			prevOut = idx
+		}
+	}
+	require.Greater(t.t, prevOut, -1)
+
+	// Okay, we have everything we need to create a PSBT now.
+	pendingTx := &wire.MsgTx{
+		Version: 2,
+		TxIn: []*wire.TxIn{{
+			PreviousOutPoint: wire.OutPoint{
+				Hash:  prevTx.TxHash(),
+				Index: uint32(prevOut),
+			},
+		}},
+		// We send to the same address again, but deduct some fees.
+		TxOut: []*wire.TxOut{{
+			Value:    utxo.Value - 600,
+			PkScript: utxo.PkScript,
+		}},
+	}
+	packet, err := psbt.NewFromUnsignedTx(pendingTx)
+	require.NoError(t.t, err)
+
+	// Now let's add the meta information that we need for signing.
+	packet.Inputs[0].Bip32Derivation = []*psbt.Bip32Derivation{{
+		PubKey:    addrPubKey.SerializeCompressed(),
+		Bip32Path: fullDerivationPath,
+	}}
+	packet.Inputs[0].WitnessUtxo = utxo
+	packet.Inputs[0].NonWitnessUtxo = prevTx
+	packet.Inputs[0].SighashType = txscript.SigHashAll
+
+	// That's it, we should be able to sign the PSBT now.
+	var buf bytes.Buffer
+	err = packet.Serialize(&buf)
+	require.NoError(t.t, err)
+
+	signResp, err := alice.WalletKitClient.SignPsbt(
+		ctxt, &walletrpc.SignPsbtRequest{
+			FundedPsbt: buf.Bytes(),
+		},
+	)
+	require.NoError(t.t, err)
+
+	// Let's make sure we have a partial signature.
+	signedPacket, err := psbt.NewFromRawBytes(
+		bytes.NewReader(signResp.SignedPsbt), false,
+	)
+	require.NoError(t.t, err)
+
+	require.Len(t.t, signedPacket.Inputs, 1)
+	require.Len(t.t, signedPacket.Inputs[0].PartialSigs, 1)
+
+	partialSig := signedPacket.Inputs[0].PartialSigs[0]
+	require.Equal(t.t, partialSig.PubKey, addrPubKey.SerializeCompressed())
+	require.Greater(t.t, len(partialSig.Signature), btcec.MinSigLen)
+
+	// We should be able to finalize the PSBT and extract the final TX now.
+	err = psbt.MaybeFinalizeAll(signedPacket)
+	require.NoError(t.t, err)
+
+	finalTx, err := psbt.Extract(signedPacket)
+	require.NoError(t.t, err)
+
+	buf.Reset()
+	err = finalTx.Serialize(&buf)
+	require.NoError(t.t, err)
+
+	// Publish the second transaction and then mine both of them.
+	_, err = alice.WalletKitClient.PublishTransaction(
+		ctxt, &walletrpc.Transaction{
+			TxHex: buf.Bytes(),
+		},
+	)
+	require.NoError(t.t, err)
+
+	// Mine one block which should contain two transactions.
+	block := mineBlocks(t, net, 1, 2)[0]
+	firstTxHash := prevTx.TxHash()
+	secondTxHash := finalTx.TxHash()
+	assertTxInBlock(t, block, &firstTxHash)
+	assertTxInBlock(t, block, &secondTxHash)
+}
+
 // 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_remote_signer_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/btcsuite/btcutil"
+	"github.com/btcsuite/btcutil/hdkeychain"
 	"github.com/btcsuite/btcwallet/waddrmgr"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnrpc"
@@ -39,76 +40,6 @@ var (
 		Xpub: "tpubDDWAWrSLRSFrG1KdqXMQQyTKYGSKLKaY7gxpvK7RdV3e3Dkhvu" +
 			"W2GgsFvsPN4RGmuoYtUgZ1LHZE8oftz7T4mzc1BxGt5rt8zJcVQi" +
 			"KTPPV",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyMultiSig),
-		Xpub: "tpubDDXFHr67Ro2tHKVWG2gNjjijKUH1Lyv5NKFYdJnuaLGVNBVwyV" +
-			"5AbykhR43iy8wYozEMbw2QfmAqZhb8gnuL5mm9sZh8YsR6FjGAbe" +
-			"w1xoT",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyRevocationBase),
-		Xpub: "tpubDDXFHr67Ro2tKkccDqNfDqZpd5wCs2n6XRV2Uh185DzCTbkDaE" +
-			"d9v7P837zZTYBNVfaRriuxgGVgxbGjDui4CKxyzBzwz4aAZxjn2P" +
-			"hNcQy",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyHtlcBase),
-		Xpub: "tpubDDXFHr67Ro2tNH4KH41i4oTsWfRjFigoH1Ee7urvHow51opH9x" +
-			"J7mu1qSPMPVtkVqQZ5tE4NTuFJPrbDqno7TQietyUDmPTwyVviJb" +
-			"GCwXk",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyPaymentBase),
-		Xpub: "tpubDDXFHr67Ro2tQj5Zvav2ALhkU6dRQAhEtNPnYJVBC8hs2U1A9e" +
-			"cqxRY3XTiJKBDD7e8tudhmTRs8aGWJAiAXJN5kXy3Hi6cmiwGWjX" +
-			"K5Cv5",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyDelayBase),
-		Xpub: "tpubDDXFHr67Ro2tSSR2LLBJtotxx2U45cuESLWKA72YT9td3SzVKH" +
-			"AptzDEx5chsUNZ4WRMY5h6HJxRSebjRatxQKX1uUsux1LvKS1wsf" +
-			"NJ2PH",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyRevocationRoot),
-		Xpub: "tpubDDXFHr67Ro2tTwzfWvNoMoPpZbxdMEfe1WhbXJxvXikGixPa4g" +
-			"gSRZeGx6T5yxVHTVT3rjVh35Veqsowj7emX8SZfXKDKDKcLduXCe" +
-			"WPUU3",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyNodeKey),
-		Xpub: "tpubDDXFHr67Ro2tYEDS2EByRedfsUoEwBtrzVbS1qdPrX6sAkUYGL" +
-			"rZWvMmQv8KZDZ4zd9r8WzM9bJ2nGp7XuNVC4w2EBtWg7i76gbrmu" +
-			"EWjQh",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyStaticBackup),
-		Xpub: "tpubDDXFHr67Ro2tYpwnFJEQaM8eAPM2UV5uY6gFgXeSzS5aC5T9Tf" +
-			"zXuawYKBbQMZJn8qHXLafY4tAutoda1aKP5h6Nbgy3swPbnhWbFj" +
-			"S5wnX",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyTowerSession),
-		Xpub: "tpubDDXFHr67Ro2tddKpAjUegXqt7EGxRXnHkeLbUkfuFMGbLJYgRp" +
-			"G4ew5pMmGg2nmcGmHFQ29w3juNhd8N5ZZ8HwJdymC4f5ukQLJ4yg" +
-			"9rEr3",
-	}, {
-		Purpose:  keychain.BIP0043Purpose,
-		CoinType: harnessNetParams.HDCoinType,
-		Account:  uint32(keychain.KeyFamilyTowerID),
-		Xpub: "tpubDDXFHr67Ro2tgE89V8ZdgMytC2Jq1iT9ttGhdzR1X7haQJNBmX" +
-			"t8kau6taC6DGASYzbrjmo9z9w6JQFcaLNqbhS2h2PVSzKf79j265" +
-			"Zi8hF",
 	}}
 )
 
@@ -166,6 +97,7 @@ func testRemoteSigner(net *lntest.NetworkHarness, t *harnessTest) {
 		name: "psbt",
 		fn: func(tt *harnessTest, wo, carol *lntest.HarnessNode) {
 			runPsbtChanFunding(net, tt, carol, wo)
+			runSignPsbt(tt, net, wo)
 		},
 	}}
 
@@ -180,7 +112,7 @@ func testRemoteSigner(net *lntest.NetworkHarness, t *harnessTest) {
 		password := []byte("itestpassword")
 		var (
 			signerNodePubKey  = nodePubKey
-			watchOnlyAccounts = accounts
+			watchOnlyAccounts = deriveCustomScopeAccounts(t.t)
 			signer            *lntest.HarnessNode
 			err               error
 		)
@@ -237,10 +169,6 @@ func testRemoteSigner(net *lntest.NetworkHarness, t *harnessTest) {
 
 		if subTest.sendCoins {
 			net.SendCoins(t.t, btcutil.SatoshiPerBitcoin, watchOnly)
-			assertAccountBalance(
-				t.t, signer, "default",
-				btcutil.SatoshiPerBitcoin, 0,
-			)
 			assertAccountBalance(
 				t.t, watchOnly, "default",
 				btcutil.SatoshiPerBitcoin, 0,
@@ -264,3 +192,55 @@ func testRemoteSigner(net *lntest.NetworkHarness, t *harnessTest) {
 		}
 	}
 }
+
+// deriveCustomScopeAccounts derives the first 255 default accounts of the custom lnd
+// internal key scope.
+func deriveCustomScopeAccounts(t *testing.T) []*lnrpc.WatchOnlyAccount {
+	allAccounts := make([]*lnrpc.WatchOnlyAccount, 0, 255+len(accounts))
+	allAccounts = append(allAccounts, accounts...)
+
+	extendedRootKey, err := hdkeychain.NewKeyFromString(rootKey)
+	require.NoError(t, err)
+
+	path := []uint32{
+		keychain.BIP0043Purpose + hdkeychain.HardenedKeyStart,
+		harnessNetParams.HDCoinType + hdkeychain.HardenedKeyStart,
+	}
+	coinTypeKey, err := derivePath(extendedRootKey, path)
+	require.NoError(t, err)
+	for idx := uint32(0); idx <= 255; idx++ {
+		accountPath := []uint32{idx + hdkeychain.HardenedKeyStart}
+		accountKey, err := derivePath(coinTypeKey, accountPath)
+		require.NoError(t, err)
+
+		accountXPub, err := accountKey.Neuter()
+		require.NoError(t, err)
+
+		allAccounts = append(allAccounts, &lnrpc.WatchOnlyAccount{
+			Purpose:  keychain.BIP0043Purpose,
+			CoinType: harnessNetParams.HDCoinType,
+			Account:  idx,
+			Xpub:     accountXPub.String(),
+		})
+	}
+
+	return allAccounts
+}
+
+// derivePath derives the given path from an extended key.
+func derivePath(key *hdkeychain.ExtendedKey, path []uint32) (
+	*hdkeychain.ExtendedKey, error) {
+
+	var (
+		currentKey = key
+		err        error
+	)
+	for _, pathPart := range path {
+		currentKey, err = currentKey.Derive(pathPart)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return currentKey, nil
+}

lntest/itest/lnd_test_list_on_test.go

@@ -283,6 +283,10 @@ var allTestCases = []*testCase{
 		name: "psbt channel funding external",
 		test: testPsbtChanFundingExternal,
 	},
+	{
+		name: "sign psbt",
+		test: testSignPsbt,
+	},
 	{
 		name: "batch channel funding",
 		test: testBatchChanFunding,

lntest/mock/walletcontroller.go

@@ -53,15 +53,25 @@ func (w *WalletController) FetchInputInfo(
 	return utxo, nil
 }
 
+// ScriptForOutput returns the address, witness program and redeem script for a
+// given UTXO. An error is returned if the UTXO does not belong to our wallet or
+// it is not a managed pubKey address.
+func (w *WalletController) ScriptForOutput(*wire.TxOut) (
+	waddrmgr.ManagedPubKeyAddress, []byte, []byte, error) {
+
+	return nil, nil, nil, nil
+}
+
 // ConfirmedBalance currently returns dummy values.
-func (w *WalletController) ConfirmedBalance(confs int32,
-	_ string) (btcutil.Amount, error) {
+func (w *WalletController) ConfirmedBalance(int32, string) (btcutil.Amount,
+	error) {
+
 	return 0, nil
 }
 
 // NewAddress is called to get new addresses for delivery, change etc.
-func (w *WalletController) NewAddress(addrType lnwallet.AddressType,
-	change bool, _ string) (btcutil.Address, error) {
+func (w *WalletController) NewAddress(lnwallet.AddressType, bool,
+	string) (btcutil.Address, error) {
 
 	addr, _ := btcutil.NewAddressPubKey(
 		w.RootKey.PubKey().SerializeCompressed(), &chaincfg.MainNetParams,
@@ -70,19 +80,21 @@ func (w *WalletController) NewAddress(addrType lnwallet.AddressType,
 }
 
 // LastUnusedAddress currently returns dummy values.
-func (w *WalletController) LastUnusedAddress(addrType lnwallet.AddressType,
-	_ string) (btcutil.Address, error) {
+func (w *WalletController) LastUnusedAddress(lnwallet.AddressType,
+	string) (btcutil.Address, error) {
+
 	return nil, nil
 }
 
 // IsOurAddress currently returns a dummy value.
-func (w *WalletController) IsOurAddress(a btcutil.Address) bool {
+func (w *WalletController) IsOurAddress(btcutil.Address) bool {
 	return false
 }
 
 // ListAccounts currently returns a dummy value.
-func (w *WalletController) ListAccounts(_ string,
-	_ *waddrmgr.KeyScope) ([]*waddrmgr.AccountProperties, error) {
+func (w *WalletController) ListAccounts(string,
+	*waddrmgr.KeyScope) ([]*waddrmgr.AccountProperties, error) {
+
 	return nil, nil
 }
 
@@ -90,33 +102,35 @@ func (w *WalletController) ListAccounts(_ string,
 func (w *WalletController) ImportAccount(string, *hdkeychain.ExtendedKey,
 	uint32, *waddrmgr.AddressType, bool) (*waddrmgr.AccountProperties,
 	[]btcutil.Address, []btcutil.Address, error) {
+
 	return nil, nil, nil, nil
 }
 
 // ImportPublicKey currently returns a dummy value.
 func (w *WalletController) ImportPublicKey(*btcec.PublicKey,
 	waddrmgr.AddressType) error {
+
 	return nil
 }
 
 // SendOutputs currently returns dummy values.
-func (w *WalletController) SendOutputs(outputs []*wire.TxOut,
-	_ chainfee.SatPerKWeight, _ int32, _ string) (*wire.MsgTx, error) {
+func (w *WalletController) SendOutputs([]*wire.TxOut,
+	chainfee.SatPerKWeight, int32, string) (*wire.MsgTx, error) {
 
 	return nil, nil
 }
 
 // CreateSimpleTx currently returns dummy values.
-func (w *WalletController) CreateSimpleTx(outputs []*wire.TxOut,
-	_ chainfee.SatPerKWeight, _ int32, _ bool) (*txauthor.AuthoredTx, error) {
+func (w *WalletController) CreateSimpleTx([]*wire.TxOut,
+	chainfee.SatPerKWeight, int32, bool) (*txauthor.AuthoredTx, error) {
 
 	return nil, nil
 }
 
 // ListUnspentWitness is called by the wallet when doing coin selection. We just
 // need one unspent for the funding transaction.
-func (w *WalletController) ListUnspentWitness(minConfs,
-	maxConfs int32, _ string) ([]*lnwallet.Utxo, error) {
+func (w *WalletController) ListUnspentWitness(int32, int32,
+	string) ([]*lnwallet.Utxo, error) {
 
 	// If the mock already has a list of utxos, return it.
 	if w.Utxos != nil {
@@ -140,8 +154,8 @@ func (w *WalletController) ListUnspentWitness(minConfs,
 }
 
 // ListTransactionDetails currently returns dummy values.
-func (w *WalletController) ListTransactionDetails(_,
-	_ int32, _ string) ([]*lnwallet.TransactionDetail, error) {
+func (w *WalletController) ListTransactionDetails(int32, int32,
+	string) ([]*lnwallet.TransactionDetail, error) {
 
 	return nil, nil
 }
@@ -169,12 +183,17 @@ func (w *WalletController) ListLeasedOutputs() ([]*wtxmgr.LockedOutput, error) {
 }
 
 // FundPsbt currently does nothing.
-func (w *WalletController) FundPsbt(_ *psbt.Packet, _ int32,
-	_ chainfee.SatPerKWeight, _ string) (int32, error) {
+func (w *WalletController) FundPsbt(*psbt.Packet, int32, chainfee.SatPerKWeight,
+	string) (int32, error) {
 
 	return 0, nil
 }
 
+// SignPsbt currently does nothing.
+func (w *WalletController) SignPsbt(*psbt.Packet) error {
+	return nil
+}
+
 // FinalizePsbt currently does nothing.
 func (w *WalletController) FinalizePsbt(_ *psbt.Packet, _ string) error {
 	return nil
@@ -187,8 +206,8 @@ func (w *WalletController) PublishTransaction(tx *wire.MsgTx, _ string) error {
 }
 
 // LabelTransaction currently does nothing.
-func (w *WalletController) LabelTransaction(_ chainhash.Hash, _ string,
-	_ bool) error {
+func (w *WalletController) LabelTransaction(chainhash.Hash, string,
+	bool) error {
 
 	return nil
 }