lnd.xprv/cmd/lncli/cmd_open_channel.go

package main

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strconv"
	"strings"

	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
	"github.com/lightningnetwork/lnd/lnrpc"
	"github.com/lightningnetwork/lnd/lnwallet/chanfunding"
	"github.com/urfave/cli"
)

const (
	userMsgFund = `PSBT funding initiated with peer %x.
Please create a PSBT that sends %v (%d satoshi) to the funding address %s.

Note: The whole process should be completed within 10 minutes, otherwise there
is a risk of the remote node timing out and canceling the funding process.

Example with bitcoind:
	bitcoin-cli walletcreatefundedpsbt [] '[{"%s":%.8f}]'

If you are using a wallet that can fund a PSBT directly (currently not possible
with bitcoind), you can use this PSBT that contains the same address and amount:
%s

!!! WARNING !!!
DO NOT PUBLISH the finished transaction by yourself or with another tool.
lnd MUST publish it in the proper funding flow order OR THE FUNDS CAN BE LOST!

Paste the funded PSBT here to continue the funding flow.
If your PSBT is very long (specifically, more than 4096 characters), please save
it to a file and paste the full file path here instead as some terminals will
truncate the pasted text if it's too long.
Base64 encoded PSBT (or path to text file): `

	userMsgSign = `
PSBT verified by lnd, please continue the funding flow by signing the PSBT by
all required parties/devices. Once the transaction is fully signed, paste it
again here either in base64 PSBT or hex encoded raw wire TX format.

Signed base64 encoded PSBT or hex encoded raw wire TX (or path to text file): `

	// psbtMaxFileSize is the maximum file size we allow a PSBT file to be
	// in case we want to read a PSBT from a file. This is mainly to protect
	// the user from choosing a large file by accident and running into out
	// of memory issues or other weird errors.
	psbtMaxFileSize = 1024 * 1024
)

// TODO(roasbeef): change default number of confirmations
var openChannelCommand = cli.Command{
	Name:     "openchannel",
	Category: "Channels",
	Usage:    "Open a channel to a node or an existing peer.",
	Description: `
	Attempt to open a new channel to an existing peer with the key node-key
	optionally blocking until the channel is 'open'.

	One can also connect to a node before opening a new channel to it by
	setting its host:port via the --connect argument. For this to work,
	the node_key must be provided, rather than the peer_id. This is optional.

	The channel will be initialized with local-amt satoshis local and push-amt
	satoshis for the remote node. Note that specifying push-amt means you give that
	amount to the remote node as part of the channel opening. Once the channel is open,
	a channelPoint (txid:vout) of the funding output is returned.

	If the remote peer supports the option upfront shutdown feature bit (query
	listpeers to see their supported feature bits), an address to enforce
	payout of funds on cooperative close can optionally be provided. Note that
	if you set this value, you will not be able to cooperatively close out to
	another address.

	One can manually set the fee to be used for the funding transaction via either
	the --conf_target or --sat_per_byte arguments. This is optional.`,
	ArgsUsage: "node-key local-amt push-amt",
	Flags: []cli.Flag{
		cli.StringFlag{
			Name: "node_key",
			Usage: "the identity public key of the target node/peer " +
				"serialized in compressed format",
		},
		cli.StringFlag{
			Name:  "connect",
			Usage: "(optional) the host:port of the target node",
		},
		cli.IntFlag{
			Name:  "local_amt",
			Usage: "the number of satoshis the wallet should commit to the channel",
		},
		cli.IntFlag{
			Name: "push_amt",
			Usage: "the number of satoshis to give the remote side " +
				"as part of the initial commitment state, " +
				"this is equivalent to first opening a " +
				"channel and sending the remote party funds, " +
				"but done all in one step",
		},
		cli.BoolFlag{
			Name:  "block",
			Usage: "block and wait until the channel is fully open",
		},
		cli.Int64Flag{
			Name: "conf_target",
			Usage: "(optional) the number of blocks that the " +
				"transaction *should* confirm in, will be " +
				"used for fee estimation",
		},
		cli.Int64Flag{
			Name: "sat_per_byte",
			Usage: "(optional) a manual fee expressed in " +
				"sat/byte that should be used when crafting " +
				"the transaction",
		},
		cli.BoolFlag{
			Name: "private",
			Usage: "make the channel private, such that it won't " +
				"be announced to the greater network, and " +
				"nodes other than the two channel endpoints " +
				"must be explicitly told about it to be able " +
				"to route through it",
		},
		cli.Int64Flag{
			Name: "min_htlc_msat",
			Usage: "(optional) the minimum value we will require " +
				"for incoming HTLCs on the channel",
		},
		cli.Uint64Flag{
			Name: "remote_csv_delay",
			Usage: "(optional) the number of blocks we will require " +
				"our channel counterparty to wait before accessing " +
				"its funds in case of unilateral close. If this is " +
				"not set, we will scale the value according to the " +
				"channel size",
		},
		cli.Uint64Flag{
			Name: "max_local_csv",
			Usage: "(optional) the maximum number of blocks that " +
				"we will allow the remote peer to require we " +
				"wait before accessing our funds in the case " +
				"of a unilateral close.",
		},
		cli.Uint64Flag{
			Name: "min_confs",
			Usage: "(optional) the minimum number of confirmations " +
				"each one of your outputs used for the funding " +
				"transaction must satisfy",
			Value: defaultUtxoMinConf,
		},
		cli.StringFlag{
			Name: "close_address",
			Usage: "(optional) an address to enforce payout of our " +
				"funds to on cooperative close. Note that if this " +
				"value is set on channel open, you will *not* be " +
				"able to cooperatively close to a different address.",
		},
		cli.BoolFlag{
			Name: "psbt",
			Usage: "start an interactive mode that initiates " +
				"funding through a partially signed bitcoin " +
				"transaction (PSBT), allowing the channel " +
				"funds to be added and signed from a hardware " +
				"or other offline device.",
		},
		cli.StringFlag{
			Name: "base_psbt",
			Usage: "when using the interactive PSBT mode to open " +
				"a new channel, use this base64 encoded PSBT " +
				"as a base and add the new channel output to " +
				"it instead of creating a new, empty one.",
		},
		cli.BoolFlag{
			Name: "no_publish",
			Usage: "when using the interactive PSBT mode to open " +
				"multiple channels in a batch, this flag " +
				"instructs lnd to not publish the full batch " +
				"transaction just yet. For safety reasons " +
				"this flag should be set for each of the " +
				"batch's transactions except the very last",
		},
		cli.Uint64Flag{
			Name: "remote_max_value_in_flight_msat",
			Usage: "(optional) the maximum value in msat that " +
				"can be pending within the channel at any given time",
		},
	},
	Action: actionDecorator(openChannel),
}

func openChannel(ctx *cli.Context) error {
	// TODO(roasbeef): add deadline to context
	ctxc := getContext()
	client, cleanUp := getClient(ctx)
	defer cleanUp()

	args := ctx.Args()
	var err error

	// Show command help if no arguments provided
	if ctx.NArg() == 0 && ctx.NumFlags() == 0 {
		_ = cli.ShowCommandHelp(ctx, "openchannel")
		return nil
	}

	minConfs := int32(ctx.Uint64("min_confs"))
	req := &lnrpc.OpenChannelRequest{
		TargetConf:                 int32(ctx.Int64("conf_target")),
		SatPerByte:                 ctx.Int64("sat_per_byte"),
		MinHtlcMsat:                ctx.Int64("min_htlc_msat"),
		RemoteCsvDelay:             uint32(ctx.Uint64("remote_csv_delay")),
		MinConfs:                   minConfs,
		SpendUnconfirmed:           minConfs == 0,
		CloseAddress:               ctx.String("close_address"),
		RemoteMaxValueInFlightMsat: ctx.Uint64("remote_max_value_in_flight_msat"),
		MaxLocalCsv:                uint32(ctx.Uint64("max_local_csv")),
	}

	switch {
	case ctx.IsSet("node_key"):
		nodePubHex, err := hex.DecodeString(ctx.String("node_key"))
		if err != nil {
			return fmt.Errorf("unable to decode node public key: %v", err)
		}
		req.NodePubkey = nodePubHex

	case args.Present():
		nodePubHex, err := hex.DecodeString(args.First())
		if err != nil {
			return fmt.Errorf("unable to decode node public key: %v", err)
		}
		args = args.Tail()
		req.NodePubkey = nodePubHex
	default:
		return fmt.Errorf("node id argument missing")
	}

	// As soon as we can confirm that the node's node_key was set, rather
	// than the peer_id, we can check if the host:port was also set to
	// connect to it before opening the channel.
	if req.NodePubkey != nil && ctx.IsSet("connect") {
		addr := &lnrpc.LightningAddress{
			Pubkey: hex.EncodeToString(req.NodePubkey),
			Host:   ctx.String("connect"),
		}

		req := &lnrpc.ConnectPeerRequest{
			Addr: addr,
			Perm: false,
		}

		// Check if connecting to the node was successful.
		// We discard the peer id returned as it is not needed.
		_, err := client.ConnectPeer(ctxc, req)
		if err != nil &&
			!strings.Contains(err.Error(), "already connected") {
			return err
		}
	}

	switch {
	case ctx.IsSet("local_amt"):
		req.LocalFundingAmount = int64(ctx.Int("local_amt"))
	case args.Present():
		req.LocalFundingAmount, err = strconv.ParseInt(args.First(), 10, 64)
		if err != nil {
			return fmt.Errorf("unable to decode local amt: %v", err)
		}
		args = args.Tail()
	default:
		return fmt.Errorf("local amt argument missing")
	}

	if ctx.IsSet("push_amt") {
		req.PushSat = int64(ctx.Int("push_amt"))
	} else if args.Present() {
		req.PushSat, err = strconv.ParseInt(args.First(), 10, 64)
		if err != nil {
			return fmt.Errorf("unable to decode push amt: %v", err)
		}
	}

	req.Private = ctx.Bool("private")

	// PSBT funding is a more involved, interactive process that is too
	// large to also fit into this already long function.
	if ctx.Bool("psbt") {
		return openChannelPsbt(ctxc, ctx, client, req)
	}
	if !ctx.Bool("psbt") && ctx.Bool("no_publish") {
		return fmt.Errorf("the --no_publish flag can only be used in " +
			"combination with the --psbt flag")
	}

	stream, err := client.OpenChannel(ctxc, req)
	if err != nil {
		return err
	}

	for {
		resp, err := stream.Recv()
		if err == io.EOF {
			return nil
		} else if err != nil {
			return err
		}

		switch update := resp.Update.(type) {
		case *lnrpc.OpenStatusUpdate_ChanPending:
			err := printChanPending(update)
			if err != nil {
				return err
			}

			if !ctx.Bool("block") {
				return nil
			}

		case *lnrpc.OpenStatusUpdate_ChanOpen:
			return printChanOpen(update)
		}
	}
}

// openChannelPsbt starts an interactive channel open protocol that uses a
// partially signed bitcoin transaction (PSBT) to fund the channel output. The
// protocol involves several steps between the RPC server and the CLI client:
//
// RPC server                           CLI client
//     |                                    |
//     |  |<------open channel (stream)-----|
//     |  |-------ready for funding----->|  |
//     |  |<------PSBT verify------------|  |
//     |  |-------ready for signing----->|  |
//     |  |<------PSBT finalize----------|  |
//     |  |-------channel pending------->|  |
//     |  |-------channel open------------->|
//     |                                    |
func openChannelPsbt(rpcCtx context.Context, ctx *cli.Context,
	client lnrpc.LightningClient,
	req *lnrpc.OpenChannelRequest) error {

	var (
		pendingChanID [32]byte
		shimPending   = true
		basePsbtBytes []byte
		quit          = make(chan struct{})
		srvMsg        = make(chan *lnrpc.OpenStatusUpdate, 1)
		srvErr        = make(chan error, 1)
		ctxc, cancel  = context.WithCancel(rpcCtx)
	)
	defer cancel()

	// Make sure the user didn't supply any command line flags that are
	// incompatible with PSBT funding.
	err := checkPsbtFlags(req)
	if err != nil {
		return err
	}

	// If the user supplied a base PSBT, only make sure it's valid base64.
	// The RPC server will make sure it's also a valid PSBT.
	basePsbt := ctx.String("base_psbt")
	if basePsbt != "" {
		basePsbtBytes, err = base64.StdEncoding.DecodeString(basePsbt)
		if err != nil {
			return fmt.Errorf("error parsing base PSBT: %v", err)
		}
	}

	// Generate a new, random pending channel ID that we'll use as the main
	// identifier when sending update messages to the RPC server.
	if _, err := rand.Read(pendingChanID[:]); err != nil {
		return fmt.Errorf("unable to generate random chan ID: %v", err)
	}
	fmt.Printf("Starting PSBT funding flow with pending channel ID %x.\n",
		pendingChanID)

	// maybeCancelShim is a helper function that cancels the funding shim
	// with the RPC server in case we end up aborting early.
	maybeCancelShim := func() {
		// If the user canceled while there was still a shim registered
		// with the wallet, release the resources now.
		if shimPending {
			fmt.Printf("Canceling PSBT funding flow for pending "+
				"channel ID %x.\n", pendingChanID)
			cancelMsg := &lnrpc.FundingTransitionMsg{
				Trigger: &lnrpc.FundingTransitionMsg_ShimCancel{
					ShimCancel: &lnrpc.FundingShimCancel{
						PendingChanId: pendingChanID[:],
					},
				},
			}
			err := sendFundingState(ctxc, ctx, cancelMsg)
			if err != nil {
				fmt.Printf("Error canceling shim: %v\n", err)
			}
			shimPending = false
		}

		// Abort the stream connection to the server.
		cancel()
	}
	defer maybeCancelShim()

	// Create the PSBT funding shim that will tell the funding manager we
	// want to use a PSBT.
	req.FundingShim = &lnrpc.FundingShim{
		Shim: &lnrpc.FundingShim_PsbtShim{
			PsbtShim: &lnrpc.PsbtShim{
				PendingChanId: pendingChanID[:],
				BasePsbt:      basePsbtBytes,
				NoPublish:     ctx.Bool("no_publish"),
			},
		},
	}

	// Start the interactive process by opening the stream connection to the
	// daemon. If the user cancels by pressing <Ctrl+C> we need to cancel
	// the shim. To not just kill the process on interrupt, we need to
	// explicitly capture the signal.
	stream, err := client.OpenChannel(ctxc, req)
	if err != nil {
		return fmt.Errorf("opening stream to server failed: %v", err)
	}

	// We also need to spawn a goroutine that reads from the server. This
	// will copy the messages to the channel as long as they come in or add
	// exactly one error to the error stream and then bail out.
	go func() {
		for {
			// Recv blocks until a message or error arrives.
			resp, err := stream.Recv()
			if err == io.EOF {
				srvErr <- fmt.Errorf("lnd shutting down: %v",
					err)
				return
			} else if err != nil {
				srvErr <- fmt.Errorf("got error from server: "+
					"%v", err)
				return
			}

			// Don't block on sending in case of shutting down.
			select {
			case srvMsg <- resp:
			case <-quit:
				return
			}
		}
	}()

	// Spawn another goroutine that only handles abort from user or errors
	// from the server. Both will trigger an attempt to cancel the shim with
	// the server.
	go func() {
		select {
		case <-rpcCtx.Done():
			fmt.Printf("\nInterrupt signal received.\n")
			close(quit)

		case err := <-srvErr:
			fmt.Printf("\nError received: %v\n", err)

			// If the remote peer canceled on us, the reservation
			// has already been deleted. We don't need to try to
			// remove it again, this would just produce another
			// error.
			cancelErr := chanfunding.ErrRemoteCanceled.Error()
			if err != nil && strings.Contains(err.Error(), cancelErr) {
				shimPending = false
			}
			close(quit)

		case <-quit:
		}
	}()

	// Our main event loop where we wait for triggers
	for {
		var srvResponse *lnrpc.OpenStatusUpdate
		select {
		case srvResponse = <-srvMsg:
		case <-quit:
			return nil
		}

		switch update := srvResponse.Update.(type) {
		case *lnrpc.OpenStatusUpdate_PsbtFund:
			// First tell the user how to create the PSBT with the
			// address and amount we now know.
			amt := btcutil.Amount(update.PsbtFund.FundingAmount)
			addr := update.PsbtFund.FundingAddress
			fmt.Printf(
				userMsgFund, req.NodePubkey, amt, amt, addr,
				addr, amt.ToBTC(),
				base64.StdEncoding.EncodeToString(
					update.PsbtFund.Psbt,
				),
			)

			// Read the user's response and send it to the server to
			// verify everything's correct before anything is
			// signed.
			psbtBase64, err := readTerminalOrFile(quit)
			if err == io.EOF {
				return nil
			}
			if err != nil {
				return fmt.Errorf("reading from terminal or "+
					"file failed: %v", err)
			}
			fundedPsbt, err := base64.StdEncoding.DecodeString(
				strings.TrimSpace(psbtBase64),
			)
			if err != nil {
				return fmt.Errorf("base64 decode failed: %v",
					err)
			}
			verifyMsg := &lnrpc.FundingTransitionMsg{
				Trigger: &lnrpc.FundingTransitionMsg_PsbtVerify{
					PsbtVerify: &lnrpc.FundingPsbtVerify{
						FundedPsbt:    fundedPsbt,
						PendingChanId: pendingChanID[:],
					},
				},
			}
			err = sendFundingState(ctxc, ctx, verifyMsg)
			if err != nil {
				return fmt.Errorf("verifying PSBT by lnd "+
					"failed: %v", err)
			}

			// Now that we know the PSBT looks good, we can let it
			// be signed by the user.
			fmt.Print(userMsgSign)

			// Read the signed PSBT and send it to lnd.
			finalTxStr, err := readTerminalOrFile(quit)
			if err == io.EOF {
				return nil
			}
			if err != nil {
				return fmt.Errorf("reading from terminal or "+
					"file failed: %v", err)
			}
			finalizeMsg, err := finalizeMsgFromString(
				finalTxStr, pendingChanID[:],
			)
			if err != nil {
				return err
			}
			transitionMsg := &lnrpc.FundingTransitionMsg{
				Trigger: finalizeMsg,
			}
			err = sendFundingState(ctxc, ctx, transitionMsg)
			if err != nil {
				return fmt.Errorf("finalizing PSBT funding "+
					"flow failed: %v", err)
			}

		case *lnrpc.OpenStatusUpdate_ChanPending:
			// As soon as the channel is pending, there is no more
			// shim that needs to be canceled. If the user
			// interrupts now, we don't need to clean up anything.
			shimPending = false

			err := printChanPending(update)
			if err != nil {
				return err
			}

			if !ctx.Bool("block") {
				return nil
			}

		case *lnrpc.OpenStatusUpdate_ChanOpen:
			return printChanOpen(update)
		}
	}
}

// printChanOpen prints the channel point of the channel open message.
func printChanOpen(update *lnrpc.OpenStatusUpdate_ChanOpen) error {
	channelPoint := update.ChanOpen.ChannelPoint

	// A channel point's funding txid can be get/set as a
	// byte slice or a string. In the case it is a string,
	// decode it.
	var txidHash []byte
	switch channelPoint.GetFundingTxid().(type) {
	case *lnrpc.ChannelPoint_FundingTxidBytes:
		txidHash = channelPoint.GetFundingTxidBytes()
	case *lnrpc.ChannelPoint_FundingTxidStr:
		s := channelPoint.GetFundingTxidStr()
		h, err := chainhash.NewHashFromStr(s)
		if err != nil {
			return err
		}

		txidHash = h[:]
	}

	txid, err := chainhash.NewHash(txidHash)
	if err != nil {
		return err
	}

	index := channelPoint.OutputIndex
	printJSON(struct {
		ChannelPoint string `json:"channel_point"`
	}{
		ChannelPoint: fmt.Sprintf("%v:%v", txid, index),
	})
	return nil
}

// printChanPending prints the funding transaction ID of the channel pending
// message.
func printChanPending(update *lnrpc.OpenStatusUpdate_ChanPending) error {
	txid, err := chainhash.NewHash(update.ChanPending.Txid)
	if err != nil {
		return err
	}

	printJSON(struct {
		FundingTxid string `json:"funding_txid"`
	}{
		FundingTxid: txid.String(),
	})
	return nil
}

// readTerminalOrFile reads a single line from the terminal. If the line read is
// short enough to be a file and a file with that exact name exists, the content
// of that file is read and returned as a string. If the content is longer or no
// file exists, the string read from the terminal is returned directly. This
// function can be used to circumvent the N_TTY_BUF_SIZE kernel parameter that
// prevents pasting more than 4096 characters (on most systems) into a terminal.
func readTerminalOrFile(quit chan struct{}) (string, error) {
	maybeFile, err := readLine(quit)
	if err != nil {
		return "", err
	}

	// Absolute file paths normally can't be longer than 255 characters so
	// we don't even check if it's a file in that case.
	if len(maybeFile) > 255 {
		return maybeFile, nil
	}

	// It might be a file since the length is small enough. Calling os.Stat
	// should be safe with any arbitrary input as it will only query info
	// about the file, not open or execute it directly.
	stat, err := os.Stat(maybeFile)

	// The file doesn't exist, we must assume this wasn't a file path after
	// all.
	if err != nil && os.IsNotExist(err) {
		return maybeFile, nil
	}

	// Some other error, perhaps access denied or something similar, let's
	// surface that to the user.
	if err != nil {
		return "", err
	}

	// Make sure we don't read a huge file by accident which might lead to
	// undesired side effects. Even very large PSBTs should still only be a
	// few hundred kilobytes so it makes sense to put a cap here.
	if stat.Size() > psbtMaxFileSize {
		return "", fmt.Errorf("error reading file %s: size of %d "+
			"bytes exceeds max PSBT file size of %d", maybeFile,
			stat.Size(), psbtMaxFileSize)
	}

	// If it's a path to an existing file and it's small enough, let's try
	// to read its content now.
	content, err := ioutil.ReadFile(maybeFile)
	if err != nil {
		return "", err
	}

	return string(content), nil
}

// readLine reads a line from standard in but does not block in case of a
// system interrupt like syscall.SIGINT (Ctrl+C).
func readLine(quit chan struct{}) (string, error) {
	msg := make(chan string, 1)

	// In a normal console, reading from stdin won't signal EOF when the
	// user presses Ctrl+C. That's why we need to put this in a separate
	// goroutine so it doesn't block.
	go func() {
		for {
			var str string
			_, _ = fmt.Scan(&str)
			msg <- str
			return
		}
	}()
	for {
		select {
		case <-quit:
			return "", io.EOF

		case str := <-msg:
			return str, nil
		}
	}
}

// checkPsbtFlags make sure a request to open a channel doesn't set any
// parameters that are incompatible with the PSBT funding flow.
func checkPsbtFlags(req *lnrpc.OpenChannelRequest) error {
	if req.MinConfs != defaultUtxoMinConf || req.SpendUnconfirmed {
		return fmt.Errorf("specifying minimum confirmations for PSBT " +
			"funding is not supported")
	}
	if req.TargetConf != 0 || req.SatPerByte != 0 {
		return fmt.Errorf("setting fee estimation parameters not " +
			"supported for PSBT funding")
	}
	return nil
}

// sendFundingState sends a single funding state step message by using a new
// client connection. This is necessary if the whole funding flow takes longer
// than the default macaroon timeout, then we cannot use a single client
// connection.
func sendFundingState(cancelCtx context.Context, cliCtx *cli.Context,
	msg *lnrpc.FundingTransitionMsg) error {

	client, cleanUp := getClient(cliCtx)
	defer cleanUp()

	_, err := client.FundingStateStep(cancelCtx, msg)
	return err
}

// finalizeMsgFromString creates the final message for the PsbtFinalize step
// from either a hex encoded raw wire transaction or a base64 encoded PSBT
// packet.
func finalizeMsgFromString(tx string,
	pendingChanID []byte) (*lnrpc.FundingTransitionMsg_PsbtFinalize, error) {

	rawTx, err := hex.DecodeString(strings.TrimSpace(tx))
	if err == nil {
		// Hex decoding succeeded so we assume we have a raw wire format
		// transaction. Let's submit that instead of a PSBT packet.
		tx := &wire.MsgTx{}
		err := tx.Deserialize(bytes.NewReader(rawTx))
		if err != nil {
			return nil, fmt.Errorf("deserializing as raw wire "+
				"transaction failed: %v", err)
		}
		return &lnrpc.FundingTransitionMsg_PsbtFinalize{
			PsbtFinalize: &lnrpc.FundingPsbtFinalize{
				FinalRawTx:    rawTx,
				PendingChanId: pendingChanID,
			},
		}, nil
	}

	// If the string isn't a hex encoded transaction, we assume it must be
	// a base64 encoded PSBT packet.
	psbtBytes, err := base64.StdEncoding.DecodeString(strings.TrimSpace(tx))
	if err != nil {
		return nil, fmt.Errorf("base64 decode failed: %v", err)
	}
	return &lnrpc.FundingTransitionMsg_PsbtFinalize{
		PsbtFinalize: &lnrpc.FundingPsbtFinalize{
			SignedPsbt:    psbtBytes,
			PendingChanId: pendingChanID,
		},
	}, nil
}