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recoverloopin.go
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recoverloopin.go
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package main
import (
"bytes"
"context"
"encoding/hex"
"errors"
"fmt"
"path/filepath"
"time"
"github.com/btcsuite/btcd/btcutil"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/lightninglabs/chantools/lnd"
"github.com/lightninglabs/loop"
"github.com/lightninglabs/loop/loopdb"
"github.com/lightninglabs/loop/swap"
"github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/keychain"
"github.com/lightningnetwork/lnd/lnrpc"
"github.com/lightningnetwork/lnd/lnwallet/chainfee"
"github.com/spf13/cobra"
)
var (
errSwapNotFound = fmt.Errorf("loop in swap not found")
)
type recoverLoopInCommand struct {
TxID string
Vout uint32
SwapHash string
SweepAddr string
OutputAmt uint64
FeeRate uint32
StartKeyIndex int
NumTries int
APIURL string
Publish bool
LoopDbDir string
SqliteFile string
rootKey *rootKey
cmd *cobra.Command
}
func newRecoverLoopInCommand() *cobra.Command {
cc := &recoverLoopInCommand{}
cc.cmd = &cobra.Command{
Use: "recoverloopin",
Short: "Recover a loop in swap that the loop daemon " +
"is not able to sweep",
Example: `chantools recoverloopin \
--txid abcdef01234... \
--vout 0 \
--swap_hash abcdef01234... \
--loop_db_dir /path/to/loop/db/dir \
--sweep_addr bc1pxxxxxxx \
--feerate 10`,
RunE: cc.Execute,
}
cc.cmd.Flags().StringVar(
&cc.TxID, "txid", "", "transaction id of the on-chain "+
"transaction that created the HTLC",
)
cc.cmd.Flags().Uint32Var(
&cc.Vout, "vout", 0, "output index of the on-chain "+
"transaction that created the HTLC",
)
cc.cmd.Flags().StringVar(
&cc.SwapHash, "swap_hash", "", "swap hash of the loop in "+
"swap",
)
cc.cmd.Flags().StringVar(
&cc.LoopDbDir, "loop_db_dir", "", "path to the loop "+
"database directory, where the loop.db file is located",
)
cc.cmd.Flags().StringVar(
&cc.SweepAddr, "sweepaddr", "", "address to recover the funds "+
"to; specify '"+lnd.AddressDeriveFromWallet+"' to "+
"derive a new address from the seed automatically",
)
cc.cmd.Flags().Uint32Var(
&cc.FeeRate, "feerate", 0, "fee rate to "+
"use for the sweep transaction in sat/vByte",
)
cc.cmd.Flags().IntVar(
&cc.NumTries, "num_tries", 1000, "number of tries to "+
"try to find the correct key index",
)
cc.cmd.Flags().IntVar(
&cc.StartKeyIndex, "start_key_index", 0, "start key index "+
"to try to find the correct key index",
)
cc.cmd.Flags().StringVar(
&cc.APIURL, "apiurl", defaultAPIURL, "API URL to use (must "+
"be esplora compatible)",
)
cc.cmd.Flags().BoolVar(
&cc.Publish, "publish", false, "publish sweep TX to the chain "+
"API instead of just printing the TX",
)
cc.cmd.Flags().Uint64Var(
&cc.OutputAmt, "output_amt", 0, "amount of the output to sweep",
)
cc.cmd.Flags().StringVar(
&cc.SqliteFile, "sqlite_file", "", "optional path to the loop "+
"sqlite database file, if not specified, the default "+
"location will be loaded from --loop_db_dir",
)
cc.rootKey = newRootKey(cc.cmd, "deriving starting key")
return cc.cmd
}
func (c *recoverLoopInCommand) Execute(_ *cobra.Command, _ []string) error {
extendedKey, err := c.rootKey.read()
if err != nil {
return fmt.Errorf("error reading root key: %w", err)
}
if c.TxID == "" {
return fmt.Errorf("txid is required")
}
if c.SwapHash == "" {
return fmt.Errorf("swap_hash is required")
}
if c.LoopDbDir == "" {
return fmt.Errorf("loop_db_dir is required")
}
err = lnd.CheckAddress(
c.SweepAddr, chainParams, true, "sweep", lnd.AddrTypeP2WKH,
lnd.AddrTypeP2TR,
)
if err != nil {
return err
}
api := newExplorerAPI(c.APIURL)
ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
defer cancel()
signer := &lnd.Signer{
ExtendedKey: extendedKey,
ChainParams: chainParams,
}
// Try to fetch the swap from the boltdb.
var (
store loopdb.SwapStore
loopIn *loopdb.LoopIn
)
// First check if a boltdb file exists.
if lnrpc.FileExists(filepath.Join(c.LoopDbDir, "loop.db")) {
store, err = loopdb.NewBoltSwapStore(c.LoopDbDir, chainParams)
if err != nil {
return err
}
defer store.Close()
loopIn, err = findLoopInSwap(ctx, store, c.SwapHash)
if err != nil && !errors.Is(err, errSwapNotFound) {
return err
}
}
// If the loopin is not found yet, try to fetch it from the sqlite db.
if loopIn == nil {
if c.SqliteFile == "" {
c.SqliteFile = filepath.Join(
c.LoopDbDir, "loop_sqlite.db",
)
}
sqliteDb, err := loopdb.NewSqliteStore(
&loopdb.SqliteConfig{
DatabaseFileName: c.SqliteFile,
SkipMigrations: true,
}, chainParams,
)
if err != nil {
return err
}
defer sqliteDb.Close()
loopIn, err = findLoopInSwap(ctx, sqliteDb, c.SwapHash)
if err != nil && !errors.Is(err, errSwapNotFound) {
return err
}
}
// If the loopin is still not found, return an error.
if loopIn == nil {
return errSwapNotFound
}
// If the swap is an external htlc, we require the output amount to be
// set, as a lot of failure cases steam from the output amount being
// wrong.
if loopIn.Contract.ExternalHtlc && c.OutputAmt == 0 {
return fmt.Errorf("output_amt is required for external htlc")
}
fmt.Println("Loop expires at block height", loopIn.Contract.CltvExpiry)
outputValue := loopIn.Contract.AmountRequested
if c.OutputAmt != 0 {
outputValue = btcutil.Amount(c.OutputAmt)
}
// Get the swaps htlc.
htlc, err := loop.GetHtlc(
loopIn.Hash, &loopIn.Contract.SwapContract, chainParams,
)
if err != nil {
return err
}
// Get the destination address.
var estimator input.TxWeightEstimator
sweepScript, err := lnd.PrepareWalletAddress(
c.SweepAddr, chainParams, &estimator, extendedKey, "sweep",
)
if err != nil {
return err
}
// Calculate the sweep fee.
err = htlc.AddTimeoutToEstimator(&estimator)
if err != nil {
return err
}
feeRateKWeight := chainfee.SatPerKVByte(
1000 * c.FeeRate,
).FeePerKWeight()
fee := feeRateKWeight.FeeForWeight(int64(estimator.Weight()))
txID, err := chainhash.NewHashFromStr(c.TxID)
if err != nil {
return err
}
// Get the htlc outpoint.
htlcOutpoint := wire.OutPoint{
Hash: *txID,
Index: c.Vout,
}
// Compose tx.
sweepTx := wire.NewMsgTx(2)
sweepTx.LockTime = uint32(loopIn.Contract.CltvExpiry)
// Add HTLC input.
sweepTx.AddTxIn(&wire.TxIn{
PreviousOutPoint: htlcOutpoint,
Sequence: 0,
})
// Add output for the destination address.
sweepTx.AddTxOut(&wire.TxOut{
PkScript: sweepScript,
Value: int64(outputValue) - int64(fee),
})
// If the htlc is version 2, we need to brute force the key locator, as
// it is not stored in the database.
var rawTx []byte
if htlc.Version == swap.HtlcV2 {
fmt.Println("Brute forcing key index...")
for i := c.StartKeyIndex; i < c.StartKeyIndex+c.NumTries; i++ {
rawTx, err = getSignedTx(
signer, sweepTx, htlc,
keychain.KeyFamily(swap.KeyFamily), uint32(i),
outputValue,
)
if err == nil {
break
}
}
if rawTx == nil {
return fmt.Errorf("failed to brute force key index, " +
"please try again with a higher start key " +
"index")
}
} else {
rawTx, err = getSignedTx(
signer, sweepTx, htlc,
loopIn.Contract.HtlcKeys.ClientScriptKeyLocator.Family,
loopIn.Contract.HtlcKeys.ClientScriptKeyLocator.Index,
outputValue,
)
if err != nil {
return err
}
}
// Publish TX.
if c.Publish {
response, err := api.PublishTx(
hex.EncodeToString(rawTx),
)
if err != nil {
return err
}
log.Infof("Published TX %s, response: %s",
sweepTx.TxHash().String(), response)
} else {
fmt.Printf("Success, we successfully created the sweep "+
"transaction. Please publish this using any bitcoin "+
"node:\n\n%x\n\n", rawTx)
}
return nil
}
func getSignedTx(signer *lnd.Signer, sweepTx *wire.MsgTx, htlc *swap.Htlc,
keyFamily keychain.KeyFamily, keyIndex uint32,
outputValue btcutil.Amount) ([]byte, error) {
// Create the sign descriptor.
prevTxOut := &wire.TxOut{
PkScript: htlc.PkScript,
Value: int64(outputValue),
}
prevOutputFetcher := txscript.NewCannedPrevOutputFetcher(
prevTxOut.PkScript, prevTxOut.Value,
)
signDesc := &input.SignDescriptor{
KeyDesc: keychain.KeyDescriptor{
KeyLocator: keychain.KeyLocator{
Family: keyFamily,
Index: keyIndex,
},
},
WitnessScript: htlc.TimeoutScript(),
HashType: htlc.SigHash(),
InputIndex: 0,
PrevOutputFetcher: prevOutputFetcher,
Output: prevTxOut,
}
switch htlc.Version {
case swap.HtlcV2:
signDesc.SignMethod = input.WitnessV0SignMethod
case swap.HtlcV3:
signDesc.SignMethod = input.TaprootScriptSpendSignMethod
}
sig, err := signer.SignOutputRaw(sweepTx, signDesc)
if err != nil {
return nil, err
}
witness, err := htlc.GenTimeoutWitness(sig.Serialize())
if err != nil {
return nil, err
}
sweepTx.TxIn[0].Witness = witness
rawTx, err := encodeTx(sweepTx)
if err != nil {
return nil, err
}
sigHashes := txscript.NewTxSigHashes(sweepTx, prevOutputFetcher)
// Verify the signature. This will throw an error if the signature is
// invalid and allows us to bruteforce the key index.
vm, err := txscript.NewEngine(
prevTxOut.PkScript, sweepTx, 0, txscript.StandardVerifyFlags,
nil, sigHashes, prevTxOut.Value, prevOutputFetcher,
)
if err != nil {
return nil, err
}
err = vm.Execute()
if err != nil {
return nil, err
}
return rawTx, nil
}
func findLoopInSwap(ctx context.Context, store loopdb.SwapStore,
swapHash string) (*loopdb.LoopIn, error) {
swaps, err := store.FetchLoopInSwaps(ctx)
if err != nil {
return nil, err
}
for _, s := range swaps {
if s.Hash.String() == swapHash {
return s, nil
}
}
return nil, errSwapNotFound
}
// encodeTx encodes a tx to raw bytes.
func encodeTx(tx *wire.MsgTx) ([]byte, error) {
var buffer bytes.Buffer
err := tx.BtcEncode(&buffer, 0, wire.WitnessEncoding)
if err != nil {
return nil, err
}
rawTx := buffer.Bytes()
return rawTx, nil
}