11170835610

Committed 03 Oct 2024 10:41PM UTC coverage: 49.188% (-9.6%) from 58.738%

Build # 11170835610

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push

github

Committed by

web-flow

Commit Message

Merge pull request #9154 from ziggie1984/master

multi: bump btcd version.

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83.86

/lnwallet/chanfunding/wallet_assembler.go

package chanfunding

import (
        "fmt"
        "math"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/btcutil/txsort"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/btcsuite/btcwallet/wallet"
        "github.com/btcsuite/btcwallet/wtxmgr"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/keychain"
)

const (
        // DefaultReservationTimeout is the default time we wait until we remove
        // an unfinished (zombiestate) open channel flow from memory.
        DefaultReservationTimeout = 10 * time.Minute

        // DefaultLockDuration is the default duration used to lock outputs.
        DefaultLockDuration = 10 * time.Minute
)

var (
        // LndInternalLockID is the binary representation of the SHA256 hash of
        // the string "lnd-internal-lock-id" and is used for UTXO lock leases to
        // identify that we ourselves are locking an UTXO, for example when
        // giving out a funded PSBT. The ID corresponds to the hex value of
        // ede19a92ed321a4705f8a1cccc1d4f6182545d4bb4fae08bd5937831b7e38f98.
        LndInternalLockID = wtxmgr.LockID{
                0xed, 0xe1, 0x9a, 0x92, 0xed, 0x32, 0x1a, 0x47,
                0x05, 0xf8, 0xa1, 0xcc, 0xcc, 0x1d, 0x4f, 0x61,
                0x82, 0x54, 0x5d, 0x4b, 0xb4, 0xfa, 0xe0, 0x8b,
                0xd5, 0x93, 0x78, 0x31, 0xb7, 0xe3, 0x8f, 0x98,
        }
)

// FullIntent is an intent that is fully backed by the internal wallet. This
// intent differs from the ShimIntent, in that the funding transaction will be
// constructed internally, and will consist of only inputs we wholly control.
// This Intent implements a basic state machine that must be executed in order
// before CompileFundingTx can be called.
//
// Steps to final channel provisioning:
//  1. Call BindKeys to notify the intent which keys to use when constructing
//     the multi-sig output.
//  2. Call CompileFundingTx afterwards to obtain the funding transaction.
//
// If either of these steps fail, then the Cancel method MUST be called.
type FullIntent struct {
        ShimIntent

        // InputCoins are the set of coins selected as inputs to this funding
        // transaction.
        InputCoins []wallet.Coin

        // ChangeOutputs are the set of outputs that the Assembler will use as
        // change from the main funding transaction.
        ChangeOutputs []*wire.TxOut

        // coinLeaser is the Assembler's instance of the OutputLeaser
        // interface.
        coinLeaser OutputLeaser

        // coinSource is the Assembler's instance of the CoinSource interface.
        coinSource CoinSource

        // signer is the Assembler's instance of the Singer interface.
        signer input.Signer
}

// BindKeys is a method unique to the FullIntent variant. This allows the
// caller to decide precisely which keys are used in the final funding
// transaction. This is kept out of the main Assembler as these may may not
// necessarily be under full control of the wallet. Only after this method has
// been executed will CompileFundingTx succeed.
func (f *FullIntent) BindKeys(localKey *keychain.KeyDescriptor,
        remoteKey *btcec.PublicKey) {

        f.localKey = localKey
        f.remoteKey = remoteKey
}

// CompileFundingTx is to be called after BindKeys on the sub-intent has been
// called. This method will construct the final funding transaction, and fully
// sign all inputs that are known by the backing CoinSource. After this method
// returns, the Intent is assumed to be complete, as the output can be created
// at any point.
func (f *FullIntent) CompileFundingTx(extraInputs []*wire.TxIn,
        extraOutputs []*wire.TxOut) (*wire.MsgTx, error) {

        // Create a blank, fresh transaction. Soon to be a complete funding
        // transaction which will allow opening a lightning channel.
        fundingTx := wire.NewMsgTx(2)

        // Add all multi-party inputs and outputs to the transaction.
        for _, coin := range f.InputCoins {
                fundingTx.AddTxIn(&wire.TxIn{
                        PreviousOutPoint: coin.OutPoint,
                })
        }
        for _, theirInput := range extraInputs {
                fundingTx.AddTxIn(theirInput)
        }
        for _, ourChangeOutput := range f.ChangeOutputs {
                fundingTx.AddTxOut(ourChangeOutput)
        }
        for _, theirChangeOutput := range extraOutputs {
                fundingTx.AddTxOut(theirChangeOutput)
        }

        _, fundingOutput, err := f.FundingOutput()
        if err != nil {
                return nil, err
        }

        // Sort the transaction. Since both side agree to a canonical ordering,
        // by sorting we no longer need to send the entire transaction. Only
        // signatures will be exchanged.
        fundingTx.AddTxOut(fundingOutput)
        txsort.InPlaceSort(fundingTx)

        // Now that the funding tx has been fully assembled, we'll locate the
        // index of the funding output so we can create our final channel
        // point.
        _, multiSigIndex := input.FindScriptOutputIndex(
                fundingTx, fundingOutput.PkScript,
        )

        // Next, sign all inputs that are ours, collecting the signatures in
        // order of the inputs.
        prevOutFetcher := NewSegWitV0DualFundingPrevOutputFetcher(
                f.coinSource, extraInputs,
        )
        sigHashes := txscript.NewTxSigHashes(fundingTx, prevOutFetcher)
        for i, txIn := range fundingTx.TxIn {
                signDesc := input.SignDescriptor{
                        SigHashes:         sigHashes,
                        PrevOutputFetcher: prevOutFetcher,
                }
                // We can only sign this input if it's ours, so we'll ask the
                // coin source if it can map this outpoint into a coin we own.
                // If not, then we'll continue as it isn't our input.
                info, err := f.coinSource.CoinFromOutPoint(
                        txIn.PreviousOutPoint,
                )
                if err != nil {
                        continue
                }

                // Now that we know the input is ours, we'll populate the
                // signDesc with the per input unique information.
                signDesc.Output = &wire.TxOut{
                        Value:    info.Value,
                        PkScript: info.PkScript,
                }
                signDesc.InputIndex = i

                // We support spending a p2tr input ourselves. But not as part
                // of their inputs.
                signDesc.HashType = txscript.SigHashAll
                if txscript.IsPayToTaproot(info.PkScript) {
                        signDesc.HashType = txscript.SigHashDefault
                }

                // Finally, we'll sign the input as is, and populate the input
                // with the witness and sigScript (if needed).
                inputScript, err := f.signer.ComputeInputScript(
                        fundingTx, &signDesc,
                )
                if err != nil {
                        return nil, err
                }

                txIn.SignatureScript = inputScript.SigScript
                txIn.Witness = inputScript.Witness
        }

        // Finally, we'll populate the chanPoint now that we've fully
        // constructed the funding transaction.
        f.chanPoint = &wire.OutPoint{
                Hash:  fundingTx.TxHash(),
                Index: multiSigIndex,
        }

        return fundingTx, nil
}

// Inputs returns all inputs to the final funding transaction that we
// know about. Since this funding transaction is created all from our wallet,
// it will be all inputs.
func (f *FullIntent) Inputs() []wire.OutPoint {
        var ins []wire.OutPoint
        for _, coin := range f.InputCoins {
                ins = append(ins, coin.OutPoint)
        }

        return ins
}

// Outputs returns all outputs of the final funding transaction that we
// know about. This will be the funding output and the change outputs going
// back to our wallet.
func (f *FullIntent) Outputs() []*wire.TxOut {
        outs := f.ShimIntent.Outputs()
        outs = append(outs, f.ChangeOutputs...)

        return outs
}

// Cancel allows the caller to cancel a funding Intent at any time.  This will
// return any resources such as coins back to the eligible pool to be used in
// order channel fundings.
//
// NOTE: Part of the chanfunding.Intent interface.
func (f *FullIntent) Cancel() {
        for _, coin := range f.InputCoins {
                err := f.coinLeaser.ReleaseOutput(
                        LndInternalLockID, coin.OutPoint,
                )
                if err != nil {
                        log.Warnf("Failed to release UTXO %s (%v))",
                                coin.OutPoint, err)
                }
        }

        f.ShimIntent.Cancel()
}

// A compile-time check to ensure FullIntent meets the Intent interface.
var _ Intent = (*FullIntent)(nil)

// WalletConfig is the main config of the WalletAssembler.
type WalletConfig struct {
        // CoinSource is what the WalletAssembler uses to list/locate coins.
        CoinSource CoinSource

        // CoinSelectionStrategy is the strategy that is used for selecting
        // coins when funding a transaction.
        CoinSelectionStrategy wallet.CoinSelectionStrategy

        // CoinSelectionLocker allows the WalletAssembler to gain exclusive
        // access to the current set of coins returned by the CoinSource.
        CoinSelectLocker CoinSelectionLocker

        // CoinLeaser is what the WalletAssembler uses to lease coins that may
        // be used as inputs for a new funding transaction.
        CoinLeaser OutputLeaser

        // Signer allows the WalletAssembler to sign inputs on any potential
        // funding transactions.
        Signer input.Signer

        // DustLimit is the current dust limit. We'll use this to ensure that
        // we don't make dust outputs on the funding transaction.
        DustLimit btcutil.Amount
}

// WalletAssembler is an instance of the Assembler interface that is backed by
// a full wallet. This variant of the Assembler interface will produce the
// entirety of the funding transaction within the wallet. This implements the
// typical funding flow that is initiated either on the p2p level or using the
// CLi.
type WalletAssembler struct {
        cfg WalletConfig
}

// NewWalletAssembler creates a new instance of the WalletAssembler from a
// fully populated wallet config.
func NewWalletAssembler(cfg WalletConfig) *WalletAssembler {
        return &WalletAssembler{
                cfg: cfg,
        }
}

// ProvisionChannel is the main entry point to begin a funding workflow given a
// fully populated request. The internal WalletAssembler will perform coin
// selection in a goroutine safe manner, returning an Intent that will allow
// the caller to finalize the funding process.
//
// NOTE: To cancel the funding flow the Cancel() method on the returned Intent,
// MUST be called.
//
// NOTE: This is a part of the chanfunding.Assembler interface.
func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
        var intent Intent

        // We hold the coin select mutex while querying for outputs, and
        // performing coin selection in order to avoid inadvertent double
        // spends across funding transactions.
        err := w.cfg.CoinSelectLocker.WithCoinSelectLock(func() error {
                log.Infof("Performing funding tx coin selection using %v "+
                        "sat/kw as fee rate", int64(r.FeeRate))

                var (
                        // allCoins refers to the entirety of coins in our
                        // wallet that are available for funding a channel.
                        allCoins []wallet.Coin

                        // manuallySelectedCoins refers to the client-side
                        // selected coins that should be considered available
                        // for funding a channel.
                        manuallySelectedCoins []wallet.Coin
                        err                   error
                )

                // Convert manually selected outpoints to coins.
                manuallySelectedCoins, err = outpointsToCoins(
                        r.Outpoints, w.cfg.CoinSource.CoinFromOutPoint,
                )
                if err != nil {
                        return err
                }

                // Find all unlocked unspent witness outputs that satisfy the
                // minimum number of confirmations required. Coin selection in
                // this function currently ignores the configured coin selection
                // strategy.
                allCoins, err = w.cfg.CoinSource.ListCoins(
                        r.MinConfs, math.MaxInt32,
                )
                if err != nil {
                        return err
                }

                // Ensure that all manually selected coins remain unspent.
                unspent := make(map[wire.OutPoint]struct{})
                for _, coin := range allCoins {
                        unspent[coin.OutPoint] = struct{}{}
                }
                for _, coin := range manuallySelectedCoins {
                        if _, ok := unspent[coin.OutPoint]; !ok {
                                return fmt.Errorf("outpoint already spent or "+
                                        "locked by another subsystem: %v",
                                        coin.OutPoint)
                        }
                }

                // The coin selection algorithm requires to know what
                // inputs/outputs are already present in the funding
                // transaction and what a change output would look like. Since
                // a channel funding is always either a P2WSH or P2TR output,
                // we can use just P2WSH here (both of these output types have
                // the same length). And we currently don't support specifying a
                // change output type, so we always use P2TR.
                var fundingOutputWeight input.TxWeightEstimator
                fundingOutputWeight.AddP2WSHOutput()
                changeType := P2TRChangeAddress

                var (
                        coins                []wallet.Coin
                        selectedCoins        []wallet.Coin
                        localContributionAmt btcutil.Amount
                        changeAmt            btcutil.Amount
                )

                // If outputs were specified manually then we'll take the
                // corresponding coins as basis for coin selection. Otherwise,
                // all available coins from our wallet are used.
                coins = allCoins
                if len(manuallySelectedCoins) > 0 {
                        coins = manuallySelectedCoins
                }

                // Perform coin selection over our available, unlocked unspent
                // outputs in order to find enough coins to meet the funding
                // amount requirements.
                switch {
                // If there's no funding amount at all (receiving an inbound
                // single funder request), then we don't need to perform any
                // coin selection at all.
                case r.LocalAmt == 0 && r.FundUpToMaxAmt == 0:
                        break

                // The local funding amount cannot be used in combination with
                // the funding up to some maximum amount. If that is the case
                // we return an error.
                case r.LocalAmt != 0 && r.FundUpToMaxAmt != 0:
                        return fmt.Errorf("cannot use a local funding amount " +
                                "and fundmax parameters")

                // We cannot use the subtract fees flag while using the funding
                // up to some maximum amount. If that is the case we return an
                // error.
                case r.SubtractFees && r.FundUpToMaxAmt != 0:
                        return fmt.Errorf("cannot subtract fees from local " +
                                "amount while using fundmax parameters")

                // In case this request uses funding up to some maximum amount,
                // we will call the specialized coin selection function for
                // that.
                case r.FundUpToMaxAmt != 0 && r.MinFundAmt != 0:
                        // We need to ensure that manually selected coins, which
                        // are spent entirely on the channel funding, leave
                        // enough funds in the wallet to cover for a reserve.
                        reserve := r.WalletReserve
                        if len(manuallySelectedCoins) > 0 {
                                sumCoins := func(
                                        coins []wallet.Coin) btcutil.Amount {

                                        var sum btcutil.Amount
                                        for _, coin := range coins {
                                                sum += btcutil.Amount(
                                                        coin.Value,
                                                )
                                        }

                                        return sum
                                }

                                sumManual := sumCoins(manuallySelectedCoins)
                                sumAll := sumCoins(allCoins)

                                // If sufficient reserve funds are available we
                                // don't have to provide for it during coin
                                // selection. The manually selected coins can be
                                // spent entirely on the channel funding. If
                                // the excess of coins cover the reserve
                                // partially then we have to provide for the
                                // rest during coin selection.
                                excess := sumAll - sumManual
                                if excess >= reserve {
                                        reserve = 0
                                } else {
                                        reserve -= excess
                                }
                        }

                        selectedCoins, localContributionAmt, changeAmt,
                                err = CoinSelectUpToAmount(
                                r.FeeRate, r.MinFundAmt, r.FundUpToMaxAmt,
                                reserve, w.cfg.DustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                        )
                        if err != nil {
                                return err
                        }

                        // Now where the actual channel capacity is determined
                        // we can check for local contribution constraints.
                        //
                        // Ensure that the remote channel reserve does not
                        // exceed 20% of the channel capacity.
                        if r.RemoteChanReserve >= localContributionAmt/5 {
                                return fmt.Errorf("remote channel reserve " +
                                        "must be less than the %%20 of the " +
                                        "channel capacity")
                        }
                        // Ensure that the initial remote balance does not
                        // exceed our local contribution as that would leave a
                        // negative balance on our side.
                        if r.PushAmt >= localContributionAmt {
                                return fmt.Errorf("amount pushed to remote " +
                                        "peer for initial state must be " +
                                        "below the local funding amount")
                        }

                // In case this request want the fees subtracted from the local
                // amount, we'll call the specialized method for that. This
                // ensures that we won't deduct more that the specified balance
                // from our wallet.
                case r.SubtractFees:
                        dustLimit := w.cfg.DustLimit
                        selectedCoins, localContributionAmt, changeAmt,
                                err = CoinSelectSubtractFees(
                                r.FeeRate, r.LocalAmt, dustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                        )
                        if err != nil {
                                return err
                        }

                // Otherwise do a normal coin selection where we target a given
                // funding amount.
                default:
                        dustLimit := w.cfg.DustLimit
                        localContributionAmt = r.LocalAmt
                        selectedCoins, changeAmt, err = CoinSelect(
                                r.FeeRate, r.LocalAmt, dustLimit, coins,
                                w.cfg.CoinSelectionStrategy,
                                fundingOutputWeight, changeType,
                        )
                        if err != nil {
                                return err
                        }
                }

                // Sanity check: The addition of the outputs should not lead to the
                // creation of dust.
                if changeAmt != 0 && changeAmt < w.cfg.DustLimit {
                        return fmt.Errorf("change amount(%v) after coin "+
                                "select is below dust limit(%v)", changeAmt,
                                w.cfg.DustLimit)
                }

                // Record any change output(s) generated as a result of the
                // coin selection.
                var changeOutput *wire.TxOut
                if changeAmt != 0 {
                        changeAddr, err := r.ChangeAddr()
                        if err != nil {
                                return err
                        }
                        changeScript, err := txscript.PayToAddrScript(changeAddr)
                        if err != nil {
                                return err
                        }

                        changeOutput = &wire.TxOut{
                                Value:    int64(changeAmt),
                                PkScript: changeScript,
                        }
                }

                // Lock the selected coins. These coins are now "reserved",
                // this prevents concurrent funding requests from referring to
                // and this double-spending the same set of coins.
                for _, coin := range selectedCoins {
                        outpoint := coin.OutPoint

                        _, err = w.cfg.CoinLeaser.LeaseOutput(
                                LndInternalLockID, outpoint,
                                DefaultReservationTimeout,
                        )
                        if err != nil {
                                return err
                        }
                }

                newIntent := &FullIntent{
                        ShimIntent: ShimIntent{
                                localFundingAmt:  localContributionAmt,
                                remoteFundingAmt: r.RemoteAmt,
                                musig2:           r.Musig2,
                                tapscriptRoot:    r.TapscriptRoot,
                        },
                        InputCoins: selectedCoins,
                        coinLeaser: w.cfg.CoinLeaser,
                        coinSource: w.cfg.CoinSource,
                        signer:     w.cfg.Signer,
                }

                if changeOutput != nil {
                        newIntent.ChangeOutputs = []*wire.TxOut{changeOutput}
                }

                intent = newIntent

                return nil
        })
        if err != nil {
                return nil, err
        }

        return intent, nil
}

// outpointsToCoins maps outpoints to coins in our wallet iff these coins are
// existent and returns an error otherwise.
func outpointsToCoins(outpoints []wire.OutPoint,
        coinFromOutPoint func(wire.OutPoint) (*wallet.Coin, error)) (
        []wallet.Coin, error) {

        var selectedCoins []wallet.Coin
        for _, outpoint := range outpoints {
                coin, err := coinFromOutPoint(
                        outpoint,
                )
                if err != nil {
                        return nil, err
                }
                selectedCoins = append(
                        selectedCoins, *coin,
                )
        }

        return selectedCoins, nil
}

// FundingTxAvailable is an empty method that an assembler can implement to
// signal to callers that its able to provide the funding transaction for the
// channel via the intent it returns.
//
// NOTE: This method is a part of the FundingTxAssembler interface.
func (w *WalletAssembler) FundingTxAvailable() {}

// A compile-time assertion to ensure the WalletAssembler meets the
// FundingTxAssembler interface.
var _ FundingTxAssembler = (*WalletAssembler)(nil)

// SegWitV0DualFundingPrevOutputFetcher is a txscript.PrevOutputFetcher that
// knows about local and remote funding inputs.
//
// TODO(guggero): Support dual funding with p2tr inputs, currently only segwit
// v0 inputs are supported.
type SegWitV0DualFundingPrevOutputFetcher struct {
        local  CoinSource
        remote *txscript.MultiPrevOutFetcher
}

var _ txscript.PrevOutputFetcher = (*SegWitV0DualFundingPrevOutputFetcher)(nil)

// NewSegWitV0DualFundingPrevOutputFetcher creates a new
// txscript.PrevOutputFetcher from the given local and remote inputs.
//
// NOTE: Since the actual pkScript and amounts aren't passed in, this will just
// make sure that nothing will panic when creating a SegWit v0 sighash. But this
// code will NOT WORK for transactions that spend any _remote_ Taproot inputs!
// So basically dual-funding won't work with Taproot inputs unless the UTXO info
// is exchanged between the peers.
func NewSegWitV0DualFundingPrevOutputFetcher(localSource CoinSource,
        remoteInputs []*wire.TxIn) txscript.PrevOutputFetcher {

        remote := txscript.NewMultiPrevOutFetcher(nil)
        for _, inp := range remoteInputs {
                // We add an empty output to prevent the sighash calculation
                // from panicking. But this will always detect the inputs as
                // SegWig v0!
                remote.AddPrevOut(inp.PreviousOutPoint, &wire.TxOut{})
        }
        return &SegWitV0DualFundingPrevOutputFetcher{
                local:  localSource,
                remote: remote,
        }
}

// FetchPrevOutput attempts to fetch the previous output referenced by the
// passed outpoint.
//
// NOTE: This is a part of the txscript.PrevOutputFetcher interface.
func (d *SegWitV0DualFundingPrevOutputFetcher) FetchPrevOutput(
        op wire.OutPoint) *wire.TxOut {

        // Try the local source first. This will return nil if our internal
        // wallet doesn't know the outpoint.
        coin, err := d.local.CoinFromOutPoint(op)
        if err == nil && coin != nil {
                return &coin.TxOut
        }

        // Fall back to the remote
        return d.remote.FetchPrevOutput(op)
}

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