new command: scbforceclose

cmd/chantools/root.go

@@ -111,6 +111,7 @@ func main() {
 		newFilterBackupCommand(),
 		newFixOldBackupCommand(),
 		newForceCloseCommand(),
+		newScbForceCloseCommand(),
 		newGenImportScriptCommand(),
 		newMigrateDBCommand(),
 		newPullAnchorCommand(),

cmd/chantools/scbforceclose.go

@@ -0,0 +1,335 @@
+package main
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/btcsuite/btcd/btcutil/hdkeychain"
+	"github.com/btcsuite/btcd/txscript"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightninglabs/chantools/btc"
+	"github.com/lightninglabs/chantools/lnd"
+	"github.com/lightningnetwork/lnd/chanbackup"
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/shachain"
+	"github.com/spf13/cobra"
+)
+
+type scbForceCloseCommand struct {
+	APIURL  string
+	Publish bool
+
+	// channel.backup.
+	SingleBackup string
+	SingleFile   string
+	MultiBackup  string
+	MultiFile    string
+
+	rootKey *rootKey
+	cmd     *cobra.Command
+}
+
+func newScbForceCloseCommand() *cobra.Command {
+	cc := &scbForceCloseCommand{}
+	cc.cmd = &cobra.Command{
+		Use:     "scbforceclose",
+		Short:   "Force-close the last state that is in the SCB provided",
+		Long:    forceCloseWarning,
+		Example: `chantools scbforceclose --multi_file channel.backup`,
+		RunE:    cc.Execute,
+	}
+	cc.cmd.Flags().StringVar(
+		&cc.APIURL, "apiurl", defaultAPIURL, "API URL to use (must "+
+			"be esplora compatible)",
+	)
+
+	cc.cmd.Flags().StringVar(
+		&cc.SingleBackup, "single_backup", "", "a hex encoded single channel "+
+			"backup obtained from exportchanbackup for force-closing channels",
+	)
+	cc.cmd.Flags().StringVar(
+		&cc.MultiBackup, "multi_backup", "", "a hex encoded multi-channel "+
+			"backup obtained from exportchanbackup for force-closing channels",
+	)
+	cc.cmd.Flags().StringVar(
+		&cc.SingleFile, "single_file", "", "the path to a single-channel "+
+			"backup file",
+	)
+	cc.cmd.Flags().StringVar(
+		&cc.MultiFile, "multi_file", "", "the path to a single-channel "+
+			"backup file (channel.backup)",
+	)
+
+	cc.cmd.Flags().BoolVar(
+		&cc.Publish, "publish", false, "publish force-closing TX to "+
+			"the chain API instead of just printing the TX",
+	)
+
+	cc.rootKey = newRootKey(cc.cmd, "decrypting the backup and signing tx")
+
+	return cc.cmd
+}
+
+func (c *scbForceCloseCommand) Execute(_ *cobra.Command, _ []string) error {
+	extendedKey, err := c.rootKey.read()
+	if err != nil {
+		return fmt.Errorf("error reading root key: %w", err)
+	}
+
+	api := &btc.ExplorerAPI{BaseURL: c.APIURL}
+	keyRing := &lnd.HDKeyRing{
+		ExtendedKey: extendedKey,
+		ChainParams: chainParams,
+	}
+	var backups []chanbackup.Single
+	if c.SingleBackup != "" || c.SingleFile != "" {
+		if c.SingleBackup != "" && c.SingleFile != "" {
+			return fmt.Errorf("must not pass --single_backup and " +
+				"--single_file together")
+		}
+		var singleBackupBytes []byte
+		if c.SingleBackup != "" {
+			singleBackupBytes, err = hex.DecodeString(c.SingleBackup)
+		} else if c.SingleFile != "" {
+			singleBackupBytes, err = os.ReadFile(c.SingleFile)
+		}
+		if err != nil {
+			return fmt.Errorf("failed to get single backup: %w", err)
+		}
+		var s chanbackup.Single
+		r := bytes.NewReader(singleBackupBytes)
+		if err := s.UnpackFromReader(r, keyRing); err != nil {
+			return fmt.Errorf("failed to unpack single backup: %w", err)
+		}
+		backups = append(backups, s)
+	}
+	if c.MultiBackup != "" || c.MultiFile != "" {
+		if len(backups) != 0 {
+			return fmt.Errorf("must not pass single and multi " +
+				"backups together")
+		}
+		if c.MultiBackup != "" && c.MultiFile != "" {
+			return fmt.Errorf("must not pass --multi_backup and " +
+				"--multi_file together")
+		}
+		var multiBackupBytes []byte
+		if c.MultiBackup != "" {
+			multiBackupBytes, err = hex.DecodeString(c.MultiBackup)
+		} else if c.MultiFile != "" {
+			multiBackupBytes, err = os.ReadFile(c.MultiFile)
+		}
+		if err != nil {
+			return fmt.Errorf("failed to get multi backup: %w", err)
+		}
+		var m chanbackup.Multi
+		r := bytes.NewReader(multiBackupBytes)
+		if err := m.UnpackFromReader(r, keyRing); err != nil {
+			return fmt.Errorf("failed to unpack multi backup: %w", err)
+		}
+		backups = append(backups, m.StaticBackups...)
+	}
+
+	backupsWithInputs := make([]chanbackup.Single, 0, len(backups))
+	for _, s := range backups {
+		if s.CloseTxInputs != nil {
+			backupsWithInputs = append(backupsWithInputs, s)
+		}
+	}
+
+	fmt.Println()
+	fmt.Printf("Found %d channel backups, %d of them have close tx.\n",
+		len(backups), len(backupsWithInputs))
+
+	if len(backupsWithInputs) == 0 {
+		fmt.Println("No channel backups that can be used for force close.")
+		return nil
+	}
+
+	fmt.Println()
+	fmt.Println("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
+	fmt.Println(strings.TrimSpace(forceCloseWarning))
+	fmt.Println("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@")
+	fmt.Println()
+
+	fmt.Printf("Type YES to proceed: ")
+	var userInput string
+	fmt.Scan(&userInput)
+	if strings.TrimSpace(userInput) != "YES" {
+		return fmt.Errorf("cancelled by user")
+	}
+
+	if c.Publish {
+		fmt.Println("Signed transactions will be broadcasted automatically.")
+		fmt.Printf("Type YES again to proceed: ")
+		fmt.Scan(&userInput)
+		if strings.TrimSpace(userInput) != "YES" {
+			return fmt.Errorf("cancelled by user")
+		}
+	}
+
+	for _, s := range backupsWithInputs {
+		signedTx, err := signCloseTx(s, extendedKey)
+		if err != nil {
+			return fmt.Errorf("signCloseTx failed for %s: %w",
+				s.FundingOutpoint, err)
+		}
+		var buf bytes.Buffer
+		if err := signedTx.Serialize(&buf); err != nil {
+			return fmt.Errorf("failed to serialize signed %s: %w",
+				s.FundingOutpoint, err)
+		}
+		txHex := hex.EncodeToString(buf.Bytes())
+		fmt.Println(s.FundingOutpoint)
+		fmt.Println(txHex)
+		fmt.Println()
+
+		// Publish TX.
+		if c.Publish {
+			response, err := api.PublishTx(txHex)
+			if err != nil {
+				return err
+			}
+			log.Infof("Published TX %s, response: %s",
+				signedTx.TxHash(), response)
+		}
+	}
+
+	return nil
+}
+
+func signCloseTx(s chanbackup.Single, extendedKey *hdkeychain.ExtendedKey) (
+	*wire.MsgTx, error) {
+
+	if s.CloseTxInputs == nil {
+		return nil, fmt.Errorf("channel backup does not have data needed " +
+			"to sign force sloe tx")
+	}
+
+	// Each of the keys in our local channel config only have their
+	// locators populate, so we'll re-derive the raw key now.
+	keyRing := &lnd.HDKeyRing{
+		ExtendedKey: extendedKey,
+		ChainParams: chainParams,
+	}
+	var err error
+	s.LocalChanCfg.MultiSigKey, err = keyRing.DeriveKey(
+		s.LocalChanCfg.MultiSigKey.KeyLocator,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("unable to derive multi sig key: %w", err)
+	}
+
+	signDesc, err := createSignDesc(s)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create signDesc: %w", err)
+	}
+
+	inputs := lnwallet.SignedCommitTxInputs{
+		CommitTx:  s.CloseTxInputs.CommitTx,
+		CommitSig: s.CloseTxInputs.CommitSig,
+		OurKey:    s.LocalChanCfg.MultiSigKey,
+		TheirKey:  s.RemoteChanCfg.MultiSigKey,
+		SignDesc:  signDesc,
+	}
+
+	if s.Version == chanbackup.SimpleTaprootVersion {
+		p, err := createTaprootNonceProducer(s, extendedKey)
+		if err != nil {
+			return nil, err
+		}
+		inputs.Taproot = &lnwallet.TaprootSignedCommitTxInputs{
+			CommitHeight:         s.CloseTxInputs.CommitHeight,
+			TaprootNonceProducer: p,
+		}
+	}
+
+	signer := &lnd.Signer{
+		ExtendedKey: extendedKey,
+		ChainParams: chainParams,
+	}
+	musigSessionManager := input.NewMusigSessionManager(signer.FetchPrivKey)
+	signer.MusigSessionManager = musigSessionManager
+
+	return lnwallet.GetSignedCommitTx(inputs, signer)
+}
+
+func createSignDesc(s chanbackup.Single) (*input.SignDescriptor, error) {
+	// See LightningChannel.createSignDesc on how signDesc is produced.
+
+	var fundingPkScript, multiSigScript []byte
+
+	localKey := s.LocalChanCfg.MultiSigKey.PubKey
+	remoteKey := s.RemoteChanCfg.MultiSigKey.PubKey
+
+	var err error
+	if s.Version == chanbackup.SimpleTaprootVersion {
+		fundingPkScript, _, err = input.GenTaprootFundingScript(
+			localKey, remoteKey, int64(s.Capacity),
+		)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		multiSigScript, err = input.GenMultiSigScript(
+			localKey.SerializeCompressed(),
+			remoteKey.SerializeCompressed(),
+		)
+		if err != nil {
+			return nil, err
+		}
+
+		fundingPkScript, err = input.WitnessScriptHash(multiSigScript)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return &input.SignDescriptor{
+		KeyDesc:       s.LocalChanCfg.MultiSigKey,
+		WitnessScript: multiSigScript,
+		Output: &wire.TxOut{
+			PkScript: fundingPkScript,
+			Value:    int64(s.Capacity),
+		},
+		HashType: txscript.SigHashAll,
+		PrevOutputFetcher: txscript.NewCannedPrevOutputFetcher(
+			fundingPkScript, int64(s.Capacity),
+		),
+		InputIndex: 0,
+	}, nil
+}
+
+func createTaprootNonceProducer(
+	s chanbackup.Single,
+	extendedKey *hdkeychain.ExtendedKey,
+) (shachain.Producer, error) {
+
+	revPathStr := fmt.Sprintf("m/1017'/%d'/%d'/0/%d",
+		chainParams.HDCoinType,
+		s.ShaChainRootDesc.KeyLocator.Family,
+		s.ShaChainRootDesc.KeyLocator.Index,
+	)
+	revPath, err := lnd.ParsePath(revPathStr)
+	if err != nil {
+		return nil, err
+	}
+
+	if s.ShaChainRootDesc.PubKey != nil {
+		return nil, fmt.Errorf("taproot channels always use ECDH, " +
+			"but legacy ShaChainRootDesc with pubkey found")
+	}
+	revocationProducer, err := lnd.ShaChainFromPath(
+		extendedKey, revPath, s.LocalChanCfg.MultiSigKey.PubKey,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("lnd.ShaChainFromPath(extendedKey, %v, %v) "+
+			"failed: %w", revPath, s.ShaChainRootDesc.PubKey, err)
+	}
+
+	return channeldb.DeriveMusig2Shachain(revocationProducer)
+}