13236757158

Committed 10 Feb 2025 08:39AM UTC coverage: 57.649% (-1.2%) from 58.815%

Build # 13236757158

Build Type

Pull #9493

github

Committed by

ziggie1984

Commit Message

lncli: for some cmds we don't replace the data of the response.

For some cmds it is not very practical to replace the json output
because we might pipe it into other commands. For example when
creating the route we want to pipe it into sendtoRoute.

Pull Request Pull Request #9493: For some lncli cmds we should not replace the content with other data

Run Details

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Source File
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82.87

/lnwallet/commitment.go

package lnwallet

import (
        "bytes"
        "fmt"

        "github.com/btcsuite/btcd/blockchain"
        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/fn/v2"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/lntypes"
        "github.com/lightningnetwork/lnd/lnwallet/chainfee"
        "github.com/lightningnetwork/lnd/lnwire"
)

// AnchorSize is the constant anchor output size.
const AnchorSize = btcutil.Amount(330)

// DefaultAnchorsCommitMaxFeeRateSatPerVByte is the default max fee rate in
// sat/vbyte the initiator will use for anchor channels. This should be enough
// to ensure propagation before anchoring down the commitment transaction.
const DefaultAnchorsCommitMaxFeeRateSatPerVByte = 10

// CommitmentKeyRing holds all derived keys needed to construct commitment and
// HTLC transactions. The keys are derived differently depending whether the
// commitment transaction is ours or the remote peer's. Private keys associated
// with each key may belong to the commitment owner or the "other party" which
// is referred to in the field comments, regardless of which is local and which
// is remote.
type CommitmentKeyRing struct {
        // CommitPoint is the "per commitment point" used to derive the tweak
        // for each base point.
        CommitPoint *btcec.PublicKey

        // LocalCommitKeyTweak is the tweak used to derive the local public key
        // from the local payment base point or the local private key from the
        // base point secret. This may be included in a SignDescriptor to
        // generate signatures for the local payment key.
        //
        // NOTE: This will always refer to "our" local key, regardless of
        // whether this is our commit or not.
        LocalCommitKeyTweak []byte

        // TODO(roasbeef): need delay tweak as well?

        // LocalHtlcKeyTweak is the tweak used to derive the local HTLC key
        // from the local HTLC base point. This value is needed in order to
        // derive the final key used within the HTLC scripts in the commitment
        // transaction.
        //
        // NOTE: This will always refer to "our" local HTLC key, regardless of
        // whether this is our commit or not.
        LocalHtlcKeyTweak []byte

        // LocalHtlcKey is the key that will be used in any clause paying to
        // our node of any HTLC scripts within the commitment transaction for
        // this key ring set.
        //
        // NOTE: This will always refer to "our" local HTLC key, regardless of
        // whether this is our commit or not.
        LocalHtlcKey *btcec.PublicKey

        // RemoteHtlcKey is the key that will be used in clauses within the
        // HTLC script that send money to the remote party.
        //
        // NOTE: This will always refer to "their" remote HTLC key, regardless
        // of whether this is our commit or not.
        RemoteHtlcKey *btcec.PublicKey

        // ToLocalKey is the commitment transaction owner's key which is
        // included in HTLC success and timeout transaction scripts. This is
        // the public key used for the to_local output of the commitment
        // transaction.
        //
        // NOTE: Who's key this is depends on the current perspective. If this
        // is our commitment this will be our key.
        ToLocalKey *btcec.PublicKey

        // ToRemoteKey is the non-owner's payment key in the commitment tx.
        // This is the key used to generate the to_remote output within the
        // commitment transaction.
        //
        // NOTE: Who's key this is depends on the current perspective. If this
        // is our commitment this will be their key.
        ToRemoteKey *btcec.PublicKey

        // RevocationKey is the key that can be used by the other party to
        // redeem outputs from a revoked commitment transaction if it were to
        // be published.
        //
        // NOTE: Who can sign for this key depends on the current perspective.
        // If this is our commitment, it means the remote node can sign for
        // this key in case of a breach.
        RevocationKey *btcec.PublicKey
}

// DeriveCommitmentKeys generates a new commitment key set using the base points
// and commitment point. The keys are derived differently depending on the type
// of channel, and whether the commitment transaction is ours or the remote
// peer's.
func DeriveCommitmentKeys(commitPoint *btcec.PublicKey,
        whoseCommit lntypes.ChannelParty, chanType channeldb.ChannelType,
        localChanCfg, remoteChanCfg *channeldb.ChannelConfig) *CommitmentKeyRing {

        tweaklessCommit := chanType.IsTweakless()

        // Depending on if this is our commit or not, we'll choose the correct
        // base point.
        localBasePoint := localChanCfg.PaymentBasePoint
        if whoseCommit.IsLocal() {
                localBasePoint = localChanCfg.DelayBasePoint
        }

        // First, we'll derive all the keys that don't depend on the context of
        // whose commitment transaction this is.
        keyRing := &CommitmentKeyRing{
                CommitPoint: commitPoint,

                LocalCommitKeyTweak: input.SingleTweakBytes(
                        commitPoint, localBasePoint.PubKey,
                ),
                LocalHtlcKeyTweak: input.SingleTweakBytes(
                        commitPoint, localChanCfg.HtlcBasePoint.PubKey,
                ),
                LocalHtlcKey: input.TweakPubKey(
                        localChanCfg.HtlcBasePoint.PubKey, commitPoint,
                ),
                RemoteHtlcKey: input.TweakPubKey(
                        remoteChanCfg.HtlcBasePoint.PubKey, commitPoint,
                ),
        }

        // We'll now compute the to_local, to_remote, and revocation key based
        // on the current commitment point. All keys are tweaked each state in
        // order to ensure the keys from each state are unlinkable. To create
        // the revocation key, we take the opposite party's revocation base
        // point and combine that with the current commitment point.
        var (
                toLocalBasePoint    *btcec.PublicKey
                toRemoteBasePoint   *btcec.PublicKey
                revocationBasePoint *btcec.PublicKey
        )
        if whoseCommit.IsLocal() {
                toLocalBasePoint = localChanCfg.DelayBasePoint.PubKey
                toRemoteBasePoint = remoteChanCfg.PaymentBasePoint.PubKey
                revocationBasePoint = remoteChanCfg.RevocationBasePoint.PubKey
        } else {
                toLocalBasePoint = remoteChanCfg.DelayBasePoint.PubKey
                toRemoteBasePoint = localChanCfg.PaymentBasePoint.PubKey
                revocationBasePoint = localChanCfg.RevocationBasePoint.PubKey
        }

        // With the base points assigned, we can now derive the actual keys
        // using the base point, and the current commitment tweak.
        keyRing.ToLocalKey = input.TweakPubKey(toLocalBasePoint, commitPoint)
        keyRing.RevocationKey = input.DeriveRevocationPubkey(
                revocationBasePoint, commitPoint,
        )

        // If this commitment should omit the tweak for the remote point, then
        // we'll use that directly, and ignore the commitPoint tweak.
        if tweaklessCommit {
                keyRing.ToRemoteKey = toRemoteBasePoint

                // If this is not our commitment, the above ToRemoteKey will be
                // ours, and we blank out the local commitment tweak to
                // indicate that the key should not be tweaked when signing.
                if whoseCommit.IsRemote() {
                        keyRing.LocalCommitKeyTweak = nil
                }
        } else {
                keyRing.ToRemoteKey = input.TweakPubKey(
                        toRemoteBasePoint, commitPoint,
                )
        }

        return keyRing
}

// WitnessScriptDesc holds the output script and the witness script for p2wsh
// outputs.
type WitnessScriptDesc struct {
        // OutputScript is the output's PkScript.
        OutputScript []byte

        // WitnessScript is the full script required to properly redeem the
        // output. This field should be set to the full script if a p2wsh
        // output is being signed. For p2wkh it should be set equal to the
        // PkScript.
        WitnessScript []byte
}

// PkScript is the public key script that commits to the final
// contract.
func (w *WitnessScriptDesc) PkScript() []byte {
        return w.OutputScript
}

// WitnessScriptToSign returns the witness script that we'll use when signing
// for the remote party, and also verifying signatures on our transactions. As
// an example, when we create an outgoing HTLC for the remote party, we want to
// sign their success path.
func (w *WitnessScriptDesc) WitnessScriptToSign() []byte {
        return w.WitnessScript
}

// WitnessScriptForPath returns the witness script for the given spending path.
// An error is returned if the path is unknown. This is useful as when
// constructing a control block for a given path, one also needs witness script
// being signed.
func (w *WitnessScriptDesc) WitnessScriptForPath(
        _ input.ScriptPath) ([]byte, error) {

        return w.WitnessScript, nil
}

// CommitScriptToSelf constructs the public key script for the output on the
// commitment transaction paying to the "owner" of said commitment transaction.
// The `initiator` argument should correspond to the owner of the commitment
// transaction which we are generating the to_local script for. If the other
// party learns of the preimage to the revocation hash, then they can claim all
// the settled funds in the channel, plus the unsettled funds.
func CommitScriptToSelf(chanType channeldb.ChannelType, initiator bool,
        selfKey, revokeKey *btcec.PublicKey, csvDelay, leaseExpiry uint32,
        auxLeaf input.AuxTapLeaf) (input.ScriptDescriptor, error) {

        switch {
        // For taproot scripts, we'll need to make a slightly modified script
        // where a NUMS key is used to force a script path reveal of either the
        // revocation or the CSV timeout.
        //
        // Our "redeem" script here is just the taproot witness program.
        case chanType.IsTaproot():
                return input.NewLocalCommitScriptTree(
                        csvDelay, selfKey, revokeKey, auxLeaf,
                )

        // If we are the initiator of a leased channel, then we have an
        // additional CLTV requirement in addition to the usual CSV
        // requirement.
        case initiator && chanType.HasLeaseExpiration():
                toLocalRedeemScript, err := input.LeaseCommitScriptToSelf(
                        selfKey, revokeKey, csvDelay, leaseExpiry,
                )
                if err != nil {
                        return nil, err
                }

                toLocalScriptHash, err := input.WitnessScriptHash(
                        toLocalRedeemScript,
                )
                if err != nil {
                        return nil, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  toLocalScriptHash,
                        WitnessScript: toLocalRedeemScript,
                }, nil

        default:
                toLocalRedeemScript, err := input.CommitScriptToSelf(
                        csvDelay, selfKey, revokeKey,
                )
                if err != nil {
                        return nil, err
                }

                toLocalScriptHash, err := input.WitnessScriptHash(
                        toLocalRedeemScript,
                )
                if err != nil {
                        return nil, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  toLocalScriptHash,
                        WitnessScript: toLocalRedeemScript,
                }, nil
        }
}

// CommitScriptToRemote derives the appropriate to_remote script based on the
// channel's commitment type. The `initiator` argument should correspond to the
// owner of the commitment transaction which we are generating the to_remote
// script for. The second return value is the CSV delay of the output script,
// what must be satisfied in order to spend the output.
func CommitScriptToRemote(chanType channeldb.ChannelType, initiator bool,
        remoteKey *btcec.PublicKey, leaseExpiry uint32,
        auxLeaf input.AuxTapLeaf) (input.ScriptDescriptor, uint32, error) {

        switch {
        // If we are not the initiator of a leased channel, then the remote
        // party has an additional CLTV requirement in addition to the 1 block
        // CSV requirement.
        case chanType.HasLeaseExpiration() && !initiator:
                script, err := input.LeaseCommitScriptToRemoteConfirmed(
                        remoteKey, leaseExpiry,
                )
                if err != nil {
                        return nil, 0, err
                }

                p2wsh, err := input.WitnessScriptHash(script)
                if err != nil {
                        return nil, 0, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  p2wsh,
                        WitnessScript: script,
                }, 1, nil

        // For taproot channels, we'll use a slightly different format, where
        // we use a NUMS key to force the remote party to take a script path,
        // with the sole tap leaf enforcing the 1 CSV delay.
        case chanType.IsTaproot():
                toRemoteScriptTree, err := input.NewRemoteCommitScriptTree(
                        remoteKey, auxLeaf,
                )
                if err != nil {
                        return nil, 0, err
                }

                return toRemoteScriptTree, 1, nil

        // If this channel type has anchors, we derive the delayed to_remote
        // script.
        case chanType.HasAnchors():
                script, err := input.CommitScriptToRemoteConfirmed(remoteKey)
                if err != nil {
                        return nil, 0, err
                }

                p2wsh, err := input.WitnessScriptHash(script)
                if err != nil {
                        return nil, 0, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  p2wsh,
                        WitnessScript: script,
                }, 1, nil

        default:
                // Otherwise the to_remote will be a simple p2wkh.
                p2wkh, err := input.CommitScriptUnencumbered(remoteKey)
                if err != nil {
                        return nil, 0, err
                }

                // Since this is a regular P2WKH, the WitnessScipt and PkScript
                // should both be set to the script hash.
                return &WitnessScriptDesc{
                        OutputScript:  p2wkh,
                        WitnessScript: p2wkh,
                }, 0, nil
        }
}

// HtlcSigHashType returns the sighash type to use for HTLC success and timeout
// transactions given the channel type.
func HtlcSigHashType(chanType channeldb.ChannelType) txscript.SigHashType {
        if chanType.HasAnchors() {
                return txscript.SigHashSingle | txscript.SigHashAnyOneCanPay
        }

        return txscript.SigHashAll
}

// HtlcSignDetails converts the passed parameters to a SignDetails valid for
// this channel type. For non-anchor channels this will return nil.
func HtlcSignDetails(chanType channeldb.ChannelType, signDesc input.SignDescriptor,
        sigHash txscript.SigHashType, peerSig input.Signature) *input.SignDetails {

        // Non-anchor channels don't need sign details, as the HTLC second
        // level cannot be altered.
        if !chanType.HasAnchors() {
                return nil
        }

        return &input.SignDetails{
                SignDesc:    signDesc,
                SigHashType: sigHash,
                PeerSig:     peerSig,
        }
}

// HtlcSecondLevelInputSequence dictates the sequence number we must use on the
// input to a second level HTLC transaction.
func HtlcSecondLevelInputSequence(chanType channeldb.ChannelType) uint32 {
        if chanType.HasAnchors() {
                return 1
        }

        return 0
}

// sweepSigHash returns the sign descriptor to use when signing a sweep
// transaction. For taproot channels, we'll use this to always sweep with
// sighash default.
func sweepSigHash(chanType channeldb.ChannelType) txscript.SigHashType {
        if chanType.IsTaproot() {
                return txscript.SigHashDefault
        }

        return txscript.SigHashAll
}

// SecondLevelHtlcScript derives the appropriate second level HTLC script based
// on the channel's commitment type. It is the uniform script that's used as the
// output for the second-level HTLC transactions. The second level transaction
// act as a sort of covenant, ensuring that a 2-of-2 multi-sig output can only
// be spent in a particular way, and to a particular output. The `initiator`
// argument should correspond to the owner of the commitment transaction which
// we are generating the to_local script for.
func SecondLevelHtlcScript(chanType channeldb.ChannelType, initiator bool,
        revocationKey, delayKey *btcec.PublicKey, csvDelay, leaseExpiry uint32,
        auxLeaf input.AuxTapLeaf) (input.ScriptDescriptor, error) {

        switch {
        // For taproot channels, the pkScript is a segwit v1 p2tr output.
        case chanType.IsTaproot():
                return input.TaprootSecondLevelScriptTree(
                        revocationKey, delayKey, csvDelay, auxLeaf,
                )

        // If we are the initiator of a leased channel, then we have an
        // additional CLTV requirement in addition to the usual CSV
        // requirement.
        case initiator && chanType.HasLeaseExpiration():
                witnessScript, err := input.LeaseSecondLevelHtlcScript(
                        revocationKey, delayKey, csvDelay, leaseExpiry,
                )
                if err != nil {
                        return nil, err
                }

                pkScript, err := input.WitnessScriptHash(witnessScript)
                if err != nil {
                        return nil, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  pkScript,
                        WitnessScript: witnessScript,
                }, nil

        default:
                witnessScript, err := input.SecondLevelHtlcScript(
                        revocationKey, delayKey, csvDelay,
                )
                if err != nil {
                        return nil, err
                }

                pkScript, err := input.WitnessScriptHash(witnessScript)
                if err != nil {
                        return nil, err
                }

                return &WitnessScriptDesc{
                        OutputScript:  pkScript,
                        WitnessScript: witnessScript,
                }, nil
        }
}

// CommitWeight returns the base commitment weight before adding HTLCs.
func CommitWeight(chanType channeldb.ChannelType) lntypes.WeightUnit {
        switch {
        case chanType.IsTaproot():
                return input.TaprootCommitWeight

        // If this commitment has anchors, it will be slightly heavier.
        case chanType.HasAnchors():
                return input.AnchorCommitWeight

        default:
                return input.CommitWeight
        }
}

// HtlcTimeoutFee returns the fee in satoshis required for an HTLC timeout
// transaction based on the current fee rate.
func HtlcTimeoutFee(chanType channeldb.ChannelType,
        feePerKw chainfee.SatPerKWeight) btcutil.Amount {

        switch {
        // For zero-fee HTLC channels, this will always be zero, regardless of
        // feerate.
        case chanType.ZeroHtlcTxFee() || chanType.IsTaproot():
                return 0

        case chanType.HasAnchors():
                return feePerKw.FeeForWeight(input.HtlcTimeoutWeightConfirmed)

        default:
                return feePerKw.FeeForWeight(input.HtlcTimeoutWeight)
        }
}

// HtlcSuccessFee returns the fee in satoshis required for an HTLC success
// transaction based on the current fee rate.
func HtlcSuccessFee(chanType channeldb.ChannelType,
        feePerKw chainfee.SatPerKWeight) btcutil.Amount {

        switch {
        // For zero-fee HTLC channels, this will always be zero, regardless of
        // feerate.
        case chanType.ZeroHtlcTxFee() || chanType.IsTaproot():
                return 0

        case chanType.HasAnchors():
                return feePerKw.FeeForWeight(input.HtlcSuccessWeightConfirmed)

        default:
                return feePerKw.FeeForWeight(input.HtlcSuccessWeight)
        }
}

// CommitScriptAnchors return the scripts to use for the local and remote
// anchor.
func CommitScriptAnchors(chanType channeldb.ChannelType,
        localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
        keyRing *CommitmentKeyRing) (
        input.ScriptDescriptor, input.ScriptDescriptor, error) {

        var (
                anchorScript func(
                        key *btcec.PublicKey) (input.ScriptDescriptor, error)

                keySelector func(*channeldb.ChannelConfig,
                        bool) *btcec.PublicKey
        )

        switch {
        // For taproot channels, the anchor is slightly different: the top
        // level key is now the (relative) local delay and remote public key,
        // since these are fully revealed once the commitment hits the chain.
        case chanType.IsTaproot():
                anchorScript = func(
                        key *btcec.PublicKey) (input.ScriptDescriptor, error) {

                        return input.NewAnchorScriptTree(key)
                }

                keySelector = func(cfg *channeldb.ChannelConfig,
                        local bool) *btcec.PublicKey {

                        if local {
                                return keyRing.ToLocalKey
                        }

                        return keyRing.ToRemoteKey
                }

        // For normal channels we'll use the multi-sig keys since those are
        // revealed when the channel closes
        default:
                // For normal channels, we'll create a p2wsh script based on
                // the target key.
                anchorScript = func(
                        key *btcec.PublicKey) (input.ScriptDescriptor, error) {

                        script, err := input.CommitScriptAnchor(key)
                        if err != nil {
                                return nil, err
                        }

                        scriptHash, err := input.WitnessScriptHash(script)
                        if err != nil {
                                return nil, err
                        }

                        return &WitnessScriptDesc{
                                OutputScript:  scriptHash,
                                WitnessScript: script,
                        }, nil
                }

                // For the existing channels, we'll always select the multi-sig
                // key from the party's channel config.
                keySelector = func(cfg *channeldb.ChannelConfig,
                        _ bool) *btcec.PublicKey {

                        return cfg.MultiSigKey.PubKey
                }
        }

        // Get the script used for the anchor output spendable by the local
        // node.
        localAnchor, err := anchorScript(keySelector(localChanCfg, true))
        if err != nil {
                return nil, nil, err
        }

        // And the anchor spendable by the remote node.
        remoteAnchor, err := anchorScript(keySelector(remoteChanCfg, false))
        if err != nil {
                return nil, nil, err
        }

        return localAnchor, remoteAnchor, nil
}

// CommitmentBuilder is a type that wraps the type of channel we are dealing
// with, and abstracts the various ways of constructing commitment
// transactions.
type CommitmentBuilder struct {
        // chanState is the underlying channel's state struct, used to
        // determine the type of channel we are dealing with, and relevant
        // parameters.
        chanState *channeldb.OpenChannel

        // obfuscator is a 48-bit state hint that's used to obfuscate the
        // current state number on the commitment transactions.
        obfuscator [StateHintSize]byte

        // auxLeafStore is an interface that allows us to fetch auxiliary
        // tapscript leaves for the commitment output.
        auxLeafStore fn.Option[AuxLeafStore]
}

// NewCommitmentBuilder creates a new CommitmentBuilder from chanState.
func NewCommitmentBuilder(chanState *channeldb.OpenChannel,
        leafStore fn.Option[AuxLeafStore]) *CommitmentBuilder {

        // The anchor channel type MUST be tweakless.
        if chanState.ChanType.HasAnchors() && !chanState.ChanType.IsTweakless() {
                panic("invalid channel type combination")
        }

        return &CommitmentBuilder{
                chanState:    chanState,
                obfuscator:   createStateHintObfuscator(chanState),
                auxLeafStore: leafStore,
        }
}

// createStateHintObfuscator derives and assigns the state hint obfuscator for
// the channel, which is used to encode the commitment height in the sequence
// number of commitment transaction inputs.
func createStateHintObfuscator(state *channeldb.OpenChannel) [StateHintSize]byte {
        if state.IsInitiator {
                return DeriveStateHintObfuscator(
                        state.LocalChanCfg.PaymentBasePoint.PubKey,
                        state.RemoteChanCfg.PaymentBasePoint.PubKey,
                )
        }

        return DeriveStateHintObfuscator(
                state.RemoteChanCfg.PaymentBasePoint.PubKey,
                state.LocalChanCfg.PaymentBasePoint.PubKey,
        )
}

// unsignedCommitmentTx is the final commitment created from evaluating an HTLC
// view at a given height, along with some meta data.
type unsignedCommitmentTx struct {
        // txn is the final, unsigned commitment transaction for this view.
        txn *wire.MsgTx

        // fee is the total fee of the commitment transaction.
        fee btcutil.Amount

        // ourBalance is our balance on this commitment *after* subtracting
        // commitment fees and anchor outputs. This can be different than the
        // balances before creating the commitment transaction as one party must
        // pay the commitment fee.
        ourBalance lnwire.MilliSatoshi

        // theirBalance is their balance of this commitment *after* subtracting
        // commitment fees and anchor outputs. This can be different than the
        // balances before creating the commitment transaction as one party must
        // pay the commitment fee.
        theirBalance lnwire.MilliSatoshi

        // cltvs is a sorted list of CLTV deltas for each HTLC on the commitment
        // transaction. Any non-htlc outputs will have a CLTV delay of zero.
        cltvs []uint32
}

// createUnsignedCommitmentTx generates the unsigned commitment transaction for
// a commitment view and returns it as part of the unsignedCommitmentTx. The
// passed in balances should be balances *before* subtracting any commitment
// fees, but after anchor outputs.
func (cb *CommitmentBuilder) createUnsignedCommitmentTx(ourBalance,
        theirBalance lnwire.MilliSatoshi, whoseCommit lntypes.ChannelParty,
        feePerKw chainfee.SatPerKWeight, height uint64, originalHtlcView,
        filteredHTLCView *HtlcView, keyRing *CommitmentKeyRing,
        prevCommit *commitment) (*unsignedCommitmentTx, error) {

        dustLimit := cb.chanState.LocalChanCfg.DustLimit
        if whoseCommit.IsRemote() {
                dustLimit = cb.chanState.RemoteChanCfg.DustLimit
        }

        numHTLCs := int64(0)
        for _, htlc := range filteredHTLCView.Updates.Local {
                if HtlcIsDust(
                        cb.chanState.ChanType, false, whoseCommit, feePerKw,
                        htlc.Amount.ToSatoshis(), dustLimit,
                ) {

                        continue
                }

                numHTLCs++
        }
        for _, htlc := range filteredHTLCView.Updates.Remote {
                if HtlcIsDust(
                        cb.chanState.ChanType, true, whoseCommit, feePerKw,
                        htlc.Amount.ToSatoshis(), dustLimit,
                ) {

                        continue
                }

                numHTLCs++
        }

        // Next, we'll calculate the fee for the commitment transaction based
        // on its total weight. Once we have the total weight, we'll multiply
        // by the current fee-per-kw, then divide by 1000 to get the proper
        // fee.
        totalCommitWeight := CommitWeight(cb.chanState.ChanType) +
                lntypes.WeightUnit(input.HTLCWeight*numHTLCs)

        // With the weight known, we can now calculate the commitment fee,
        // ensuring that we account for any dust outputs trimmed above.
        commitFee := feePerKw.FeeForWeight(totalCommitWeight)
        commitFeeMSat := lnwire.NewMSatFromSatoshis(commitFee)

        // Currently, within the protocol, the initiator always pays the fees.
        // So we'll subtract the fee amount from the balance of the current
        // initiator. If the initiator is unable to pay the fee fully, then
        // their entire output is consumed.
        switch {
        case cb.chanState.IsInitiator && commitFee > ourBalance.ToSatoshis():
                ourBalance = 0

        case cb.chanState.IsInitiator:
                ourBalance -= commitFeeMSat

        case !cb.chanState.IsInitiator && commitFee > theirBalance.ToSatoshis():
                theirBalance = 0

        case !cb.chanState.IsInitiator:
                theirBalance -= commitFeeMSat
        }

        var commitTx *wire.MsgTx

        // Before we create the commitment transaction below, we'll try to see
        // if there're any aux leaves that need to be a part of the tapscript
        // tree. We'll only do this if we have a custom blob defined though.
        auxResult, err := fn.MapOptionZ(
                cb.auxLeafStore,
                func(s AuxLeafStore) fn.Result[CommitDiffAuxResult] {
                        return auxLeavesFromView(
                                s, cb.chanState, prevCommit.customBlob,
                                originalHtlcView, whoseCommit, ourBalance,
                                theirBalance, *keyRing,
                        )
                },
        ).Unpack()
        if err != nil {
                return nil, fmt.Errorf("unable to fetch aux leaves: %w", err)
        }

        // Depending on whether the transaction is ours or not, we call
        // CreateCommitTx with parameters matching the perspective, to generate
        // a new commitment transaction with all the latest unsettled/un-timed
        // out HTLCs.
        var leaseExpiry uint32
        if cb.chanState.ChanType.HasLeaseExpiration() {
                leaseExpiry = cb.chanState.ThawHeight
        }
        if whoseCommit.IsLocal() {
                commitTx, err = CreateCommitTx(
                        cb.chanState.ChanType, fundingTxIn(cb.chanState), keyRing,
                        &cb.chanState.LocalChanCfg, &cb.chanState.RemoteChanCfg,
                        ourBalance.ToSatoshis(), theirBalance.ToSatoshis(),
                        numHTLCs, cb.chanState.IsInitiator, leaseExpiry,
                        auxResult.AuxLeaves,
                )
        } else {
                commitTx, err = CreateCommitTx(
                        cb.chanState.ChanType, fundingTxIn(cb.chanState), keyRing,
                        &cb.chanState.RemoteChanCfg, &cb.chanState.LocalChanCfg,
                        theirBalance.ToSatoshis(), ourBalance.ToSatoshis(),
                        numHTLCs, !cb.chanState.IsInitiator, leaseExpiry,
                        auxResult.AuxLeaves,
                )
        }
        if err != nil {
                return nil, err
        }

        // Similarly, we'll now attempt to extract the set of aux leaves for
        // the set of incoming and outgoing HTLCs.
        incomingAuxLeaves := fn.MapOption(
                func(leaves CommitAuxLeaves) input.HtlcAuxLeaves {
                        return leaves.IncomingHtlcLeaves
                },
        )(auxResult.AuxLeaves)
        outgoingAuxLeaves := fn.MapOption(
                func(leaves CommitAuxLeaves) input.HtlcAuxLeaves {
                        return leaves.OutgoingHtlcLeaves
                },
        )(auxResult.AuxLeaves)

        // We'll now add all the HTLC outputs to the commitment transaction.
        // Each output includes an off-chain 2-of-2 covenant clause, so we'll
        // need the objective local/remote keys for this particular commitment
        // as well. For any non-dust HTLCs that are manifested on the commitment
        // transaction, we'll also record its CLTV which is required to sort the
        // commitment transaction below. The slice is initially sized to the
        // number of existing outputs, since any outputs already added are
        // commitment outputs and should correspond to zero values for the
        // purposes of sorting.
        cltvs := make([]uint32, len(commitTx.TxOut))
        htlcIndexes := make([]input.HtlcIndex, len(commitTx.TxOut))
        for _, htlc := range filteredHTLCView.Updates.Local {
                if HtlcIsDust(
                        cb.chanState.ChanType, false, whoseCommit, feePerKw,
                        htlc.Amount.ToSatoshis(), dustLimit,
                ) {

                        continue
                }

                auxLeaf := fn.FlatMapOption(
                        func(leaves input.HtlcAuxLeaves) input.AuxTapLeaf {
                                return leaves[htlc.HtlcIndex].AuxTapLeaf
                        },
                )(outgoingAuxLeaves)

                err := addHTLC(
                        commitTx, whoseCommit, false, htlc, keyRing,
                        cb.chanState.ChanType, auxLeaf,
                )
                if err != nil {
                        return nil, err
                }

                // We want to add the CLTV and HTLC index to their respective
                // slices, even if we already pre-allocated them.
                cltvs = append(cltvs, htlc.Timeout)               //nolint
                htlcIndexes = append(htlcIndexes, htlc.HtlcIndex) //nolint
        }
        for _, htlc := range filteredHTLCView.Updates.Remote {
                if HtlcIsDust(
                        cb.chanState.ChanType, true, whoseCommit, feePerKw,
                        htlc.Amount.ToSatoshis(), dustLimit,
                ) {

                        continue
                }

                auxLeaf := fn.FlatMapOption(
                        func(leaves input.HtlcAuxLeaves) input.AuxTapLeaf {
                                return leaves[htlc.HtlcIndex].AuxTapLeaf
                        },
                )(incomingAuxLeaves)

                err := addHTLC(
                        commitTx, whoseCommit, true, htlc, keyRing,
                        cb.chanState.ChanType, auxLeaf,
                )
                if err != nil {
                        return nil, err
                }

                // We want to add the CLTV and HTLC index to their respective
                // slices, even if we already pre-allocated them.
                cltvs = append(cltvs, htlc.Timeout)               //nolint
                htlcIndexes = append(htlcIndexes, htlc.HtlcIndex) //nolint
        }

        // Set the state hint of the commitment transaction to facilitate
        // quickly recovering the necessary penalty state in the case of an
        // uncooperative broadcast.
        err = SetStateNumHint(commitTx, height, cb.obfuscator)
        if err != nil {
                return nil, err
        }

        // Sort the transactions according to the agreed upon canonical
        // ordering (which might be customized for custom channel types, but
        // deterministic and both parties will arrive at the same result). This
        // lets us skip sending the entire transaction over, instead we'll just
        // send signatures.
        commitSort := auxResult.CommitSortFunc.UnwrapOr(DefaultCommitSort)
        err = commitSort(commitTx, cltvs, htlcIndexes)
        if err != nil {
                return nil, fmt.Errorf("unable to sort commitment "+
                        "transaction: %w", err)
        }

        // Next, we'll ensure that we don't accidentally create a commitment
        // transaction which would be invalid by consensus.
        uTx := btcutil.NewTx(commitTx)
        if err := blockchain.CheckTransactionSanity(uTx); err != nil {
                return nil, err
        }

        // Finally, we'll assert that were not attempting to draw more out of
        // the channel that was originally placed within it.
        var totalOut btcutil.Amount
        for _, txOut := range commitTx.TxOut {
                totalOut += btcutil.Amount(txOut.Value)
        }
        if totalOut+commitFee > cb.chanState.Capacity {
                return nil, fmt.Errorf("height=%v, for ChannelPoint(%v) "+
                        "attempts to consume %v while channel capacity is %v",
                        height, cb.chanState.FundingOutpoint,
                        totalOut+commitFee, cb.chanState.Capacity)
        }

        return &unsignedCommitmentTx{
                txn:          commitTx,
                fee:          commitFee,
                ourBalance:   ourBalance,
                theirBalance: theirBalance,
                cltvs:        cltvs,
        }, nil
}

// CreateCommitTx creates a commitment transaction, spending from specified
// funding output. The commitment transaction contains two outputs: one local
// output paying to the "owner" of the commitment transaction which can be
// spent after a relative block delay or revocation event, and a remote output
// paying the counterparty within the channel, which can be spent immediately
// or after a delay depending on the commitment type. The `initiator` argument
// should correspond to the owner of the commitment transaction we are creating.
func CreateCommitTx(chanType channeldb.ChannelType,
        fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
        localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
        amountToLocal, amountToRemote btcutil.Amount,
        numHTLCs int64, initiator bool, leaseExpiry uint32,
        auxLeaves fn.Option[CommitAuxLeaves]) (*wire.MsgTx, error) {

        // First, we create the script for the delayed "pay-to-self" output.
        // This output has 2 main redemption clauses: either we can redeem the
        // output after a relative block delay, or the remote node can claim
        // the funds with the revocation key if we broadcast a revoked
        // commitment transaction.
        localAuxLeaf := fn.MapOption(func(l CommitAuxLeaves) input.AuxTapLeaf {
                return l.LocalAuxLeaf
        })(auxLeaves)
        toLocalScript, err := CommitScriptToSelf(
                chanType, initiator, keyRing.ToLocalKey, keyRing.RevocationKey,
                uint32(localChanCfg.CsvDelay), leaseExpiry,
                fn.FlattenOption(localAuxLeaf),
        )
        if err != nil {
                return nil, err
        }

        // Next, we create the script paying to the remote.
        remoteAuxLeaf := fn.MapOption(func(l CommitAuxLeaves) input.AuxTapLeaf {
                return l.RemoteAuxLeaf
        })(auxLeaves)
        toRemoteScript, _, err := CommitScriptToRemote(
                chanType, initiator, keyRing.ToRemoteKey, leaseExpiry,
                fn.FlattenOption(remoteAuxLeaf),
        )
        if err != nil {
                return nil, err
        }

        // Now that both output scripts have been created, we can finally create
        // the transaction itself. We use a transaction version of 2 since CSV
        // will fail unless the tx version is >= 2.
        commitTx := wire.NewMsgTx(2)
        commitTx.AddTxIn(&fundingOutput)

        // Avoid creating dust outputs within the commitment transaction.
        localOutput := amountToLocal >= localChanCfg.DustLimit
        if localOutput {
                commitTx.AddTxOut(&wire.TxOut{
                        PkScript: toLocalScript.PkScript(),
                        Value:    int64(amountToLocal),
                })
        }

        remoteOutput := amountToRemote >= localChanCfg.DustLimit
        if remoteOutput {
                commitTx.AddTxOut(&wire.TxOut{
                        PkScript: toRemoteScript.PkScript(),
                        Value:    int64(amountToRemote),
                })
        }

        // If this channel type has anchors, we'll also add those.
        if chanType.HasAnchors() {
                localAnchor, remoteAnchor, err := CommitScriptAnchors(
                        chanType, localChanCfg, remoteChanCfg, keyRing,
                )
                if err != nil {
                        return nil, err
                }

                // Add local anchor output only if we have a commitment output
                // or there are HTLCs.
                if localOutput || numHTLCs > 0 {
                        commitTx.AddTxOut(&wire.TxOut{
                                PkScript: localAnchor.PkScript(),
                                Value:    int64(AnchorSize),
                        })
                }

                // Add anchor output to remote only if they have a commitment
                // output or there are HTLCs.
                if remoteOutput || numHTLCs > 0 {
                        commitTx.AddTxOut(&wire.TxOut{
                                PkScript: remoteAnchor.PkScript(),
                                Value:    int64(AnchorSize),
                        })
                }
        }

        return commitTx, nil
}

// CoopCloseBalance returns the final balances that should be used to create
// the cooperative close tx, given the channel type and transaction fee.
func CoopCloseBalance(chanType channeldb.ChannelType, isInitiator bool,
        coopCloseFee, ourBalance, theirBalance, commitFee btcutil.Amount,
        feePayer fn.Option[lntypes.ChannelParty],
) (btcutil.Amount, btcutil.Amount, error) {

        // We'll make sure we account for the complete balance by adding the
        // current dangling commitment fee to the balance of the initiator.
        initiatorDelta := commitFee

        // Since the initiator's balance also is stored after subtracting the
        // anchor values, add that back in case this was an anchor commitment.
        if chanType.HasAnchors() {
                initiatorDelta += 2 * AnchorSize
        }

        // To start with, we'll add the anchor and/or commitment fee to the
        // balance of the initiator.
        if isInitiator {
                ourBalance += initiatorDelta
        } else {
                theirBalance += initiatorDelta
        }

        // With the initiator's balance credited, we'll now subtract the closing
        // fee from the closing party. By default, the initiator pays the full
        // amount, but this can be overridden by the feePayer option.
        defaultPayer := func() lntypes.ChannelParty {
                if isInitiator {
                        return lntypes.Local
                }

                return lntypes.Remote
        }()
        payer := feePayer.UnwrapOr(defaultPayer)

        // Based on the payer computed above, we'll subtract the closing fee.
        switch payer {
        case lntypes.Local:
                ourBalance -= coopCloseFee
        case lntypes.Remote:
                theirBalance -= coopCloseFee
        }

        // During fee negotiation it should always be verified that the
        // initiator can pay the proposed fee, but we do a sanity check just to
        // be sure here.
        if ourBalance < 0 || theirBalance < 0 {
                return 0, 0, fmt.Errorf("initiator cannot afford proposed " +
                        "coop close fee")
        }

        return ourBalance, theirBalance, nil
}

// genSegwitV0HtlcScript generates the HTLC scripts for a normal segwit v0
// channel.
func genSegwitV0HtlcScript(chanType channeldb.ChannelType,
        isIncoming bool, whoseCommit lntypes.ChannelParty, timeout uint32,
        rHash [32]byte, keyRing *CommitmentKeyRing,
) (*WitnessScriptDesc, error) {

        var (
                witnessScript []byte
                err           error
        )

        // Choose scripts based on channel type.
        confirmedHtlcSpends := false
        if chanType.HasAnchors() {
                confirmedHtlcSpends = true
        }

        // Generate the proper redeem scripts for the HTLC output modified by
        // two-bits denoting if this is an incoming HTLC, and if the HTLC is
        // being applied to their commitment transaction or ours.
        switch {
        // The HTLC is paying to us, and being applied to our commitment
        // transaction. So we need to use the receiver's version of the HTLC
        // script.
        case isIncoming && whoseCommit.IsLocal():
                witnessScript, err = input.ReceiverHTLCScript(
                        timeout, keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
                        keyRing.RevocationKey, rHash[:], confirmedHtlcSpends,
                )

        // We're being paid via an HTLC by the remote party, and the HTLC is
        // being added to their commitment transaction, so we use the sender's
        // version of the HTLC script.
        case isIncoming && whoseCommit.IsRemote():
                witnessScript, err = input.SenderHTLCScript(
                        keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
                        keyRing.RevocationKey, rHash[:], confirmedHtlcSpends,
                )

        // We're sending an HTLC which is being added to our commitment
        // transaction. Therefore, we need to use the sender's version of the
        // HTLC script.
        case !isIncoming && whoseCommit.IsLocal():
                witnessScript, err = input.SenderHTLCScript(
                        keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
                        keyRing.RevocationKey, rHash[:], confirmedHtlcSpends,
                )

        // Finally, we're paying the remote party via an HTLC, which is being
        // added to their commitment transaction. Therefore, we use the
        // receiver's version of the HTLC script.
        case !isIncoming && whoseCommit.IsRemote():
                witnessScript, err = input.ReceiverHTLCScript(
                        timeout, keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
                        keyRing.RevocationKey, rHash[:], confirmedHtlcSpends,
                )
        }
        if err != nil {
                return nil, err
        }

        // Now that we have the redeem scripts, create the P2WSH public key
        // script for the output itself.
        htlcP2WSH, err := input.WitnessScriptHash(witnessScript)
        if err != nil {
                return nil, err
        }

        return &WitnessScriptDesc{
                OutputScript:  htlcP2WSH,
                WitnessScript: witnessScript,
        }, nil
}

// GenTaprootHtlcScript generates the HTLC scripts for a taproot+musig2
// channel.
func GenTaprootHtlcScript(isIncoming bool, whoseCommit lntypes.ChannelParty,
        timeout uint32, rHash [32]byte, keyRing *CommitmentKeyRing,
        auxLeaf input.AuxTapLeaf) (*input.HtlcScriptTree, error) {

        var (
                htlcScriptTree *input.HtlcScriptTree
                err            error
        )

        // Generate the proper redeem scripts for the HTLC output modified by
        // two-bits denoting if this is an incoming HTLC, and if the HTLC is
        // being applied to their commitment transaction or ours.
        switch {
        // The HTLC is paying to us, and being applied to our commitment
        // transaction. So we need to use the receiver's version of HTLC the
        // script.
        case isIncoming && whoseCommit.IsLocal():
                htlcScriptTree, err = input.ReceiverHTLCScriptTaproot(
                        timeout, keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
                        keyRing.RevocationKey, rHash[:], whoseCommit, auxLeaf,
                )

        // We're being paid via an HTLC by the remote party, and the HTLC is
        // being added to their commitment transaction, so we use the sender's
        // version of the HTLC script.
        case isIncoming && whoseCommit.IsRemote():
                htlcScriptTree, err = input.SenderHTLCScriptTaproot(
                        keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
                        keyRing.RevocationKey, rHash[:], whoseCommit, auxLeaf,
                )

        // We're sending an HTLC which is being added to our commitment
        // transaction. Therefore, we need to use the sender's version of the
        // HTLC script.
        case !isIncoming && whoseCommit.IsLocal():
                htlcScriptTree, err = input.SenderHTLCScriptTaproot(
                        keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
                        keyRing.RevocationKey, rHash[:], whoseCommit, auxLeaf,
                )

        // Finally, we're paying the remote party via an HTLC, which is being
        // added to their commitment transaction. Therefore, we use the
        // receiver's version of the HTLC script.
        case !isIncoming && whoseCommit.IsRemote():
                htlcScriptTree, err = input.ReceiverHTLCScriptTaproot(
                        timeout, keyRing.LocalHtlcKey, keyRing.RemoteHtlcKey,
                        keyRing.RevocationKey, rHash[:], whoseCommit, auxLeaf,
                )
        }

        return htlcScriptTree, err
}

// genHtlcScript generates the proper P2WSH public key scripts for the HTLC
// output modified by two-bits denoting if this is an incoming HTLC, and if the
// HTLC is being applied to their commitment transaction or ours. A script
// multiplexer for the various spending paths is returned. The script path that
// we need to sign for the remote party (2nd level HTLCs) is also returned
// along side the multiplexer.
func genHtlcScript(chanType channeldb.ChannelType, isIncoming bool,
        whoseCommit lntypes.ChannelParty, timeout uint32, rHash [32]byte,
        keyRing *CommitmentKeyRing,
        auxLeaf input.AuxTapLeaf) (input.ScriptDescriptor, error) {

        if !chanType.IsTaproot() {
                return genSegwitV0HtlcScript(
                        chanType, isIncoming, whoseCommit, timeout, rHash,
                        keyRing,
                )
        }

        return GenTaprootHtlcScript(
                isIncoming, whoseCommit, timeout, rHash, keyRing, auxLeaf,
        )
}

// addHTLC adds a new HTLC to the passed commitment transaction. One of four
// full scripts will be generated for the HTLC output depending on if the HTLC
// is incoming and if it's being applied to our commitment transaction or that
// of the remote node's. Additionally, in order to be able to efficiently
// locate the added HTLC on the commitment transaction from the
// paymentDescriptor that generated it, the generated script is stored within
// the descriptor itself.
func addHTLC(commitTx *wire.MsgTx, whoseCommit lntypes.ChannelParty,
        isIncoming bool, paymentDesc *paymentDescriptor,
        keyRing *CommitmentKeyRing, chanType channeldb.ChannelType,
        auxLeaf input.AuxTapLeaf) error {

        timeout := paymentDesc.Timeout
        rHash := paymentDesc.RHash

        scriptInfo, err := genHtlcScript(
                chanType, isIncoming, whoseCommit, timeout, rHash, keyRing,
                auxLeaf,
        )
        if err != nil {
                return err
        }

        pkScript := scriptInfo.PkScript()

        // Add the new HTLC outputs to the respective commitment transactions.
        amountPending := int64(paymentDesc.Amount.ToSatoshis())
        commitTx.AddTxOut(wire.NewTxOut(amountPending, pkScript))

        // Store the pkScript of this particular paymentDescriptor so we can
        // quickly locate it within the commitment transaction later.
        if whoseCommit.IsLocal() {
                paymentDesc.ourPkScript = pkScript

                paymentDesc.ourWitnessScript = scriptInfo.WitnessScriptToSign()
        } else {
                paymentDesc.theirPkScript = pkScript

                //nolint:ll
                paymentDesc.theirWitnessScript = scriptInfo.WitnessScriptToSign()
        }

        return nil
}

// findOutputIndexesFromRemote finds the index of our and their outputs from
// the remote commitment transaction. It derives the key ring to compute the
// output scripts and compares them against the outputs inside the commitment
// to find the match.
func findOutputIndexesFromRemote(revocationPreimage *chainhash.Hash,
        chanState *channeldb.OpenChannel,
        leafStore fn.Option[AuxLeafStore]) (uint32, uint32, error) {

        // Init the output indexes as empty.
        ourIndex := uint32(channeldb.OutputIndexEmpty)
        theirIndex := uint32(channeldb.OutputIndexEmpty)

        chanCommit := chanState.RemoteCommitment
        _, commitmentPoint := btcec.PrivKeyFromBytes(revocationPreimage[:])

        // With the commitment point generated, we can now derive the king ring
        // which will be used to generate the output scripts.
        keyRing := DeriveCommitmentKeys(
                commitmentPoint, lntypes.Remote, chanState.ChanType,
                &chanState.LocalChanCfg, &chanState.RemoteChanCfg,
        )

        // Since it's remote commitment chain, we'd used the mirrored values.
        //
        // We use the remote's channel config for the csv delay.
        theirDelay := uint32(chanState.RemoteChanCfg.CsvDelay)

        // If we are the initiator of this channel, then it's be false from the
        // remote's PoV.
        isRemoteInitiator := !chanState.IsInitiator

        var leaseExpiry uint32
        if chanState.ChanType.HasLeaseExpiration() {
                leaseExpiry = chanState.ThawHeight
        }

        // If we have a custom blob, then we'll attempt to fetch the aux leaves
        // for this state.
        auxResult, err := fn.MapOptionZ(
                leafStore, func(a AuxLeafStore) fn.Result[CommitDiffAuxResult] {
                        return a.FetchLeavesFromCommit(
                                NewAuxChanState(chanState), chanCommit,
                                *keyRing, lntypes.Remote,
                        )
                },
        ).Unpack()
        if err != nil {
                return ourIndex, theirIndex, fmt.Errorf("unable to fetch aux "+
                        "leaves: %w", err)
        }

        // Map the scripts from our PoV. When facing a local commitment, the
        // to_local output belongs to us and the to_remote output belongs to
        // them. When facing a remote commitment, the to_local output belongs to
        // them and the to_remote output belongs to us.

        // Compute the to_local script. From our PoV, when facing a remote
        // commitment, the to_local output belongs to them.
        localAuxLeaf := fn.FlatMapOption(
                func(l CommitAuxLeaves) input.AuxTapLeaf {
                        return l.LocalAuxLeaf
                },
        )(auxResult.AuxLeaves)
        theirScript, err := CommitScriptToSelf(
                chanState.ChanType, isRemoteInitiator, keyRing.ToLocalKey,
                keyRing.RevocationKey, theirDelay, leaseExpiry, localAuxLeaf,
        )
        if err != nil {
                return ourIndex, theirIndex, err
        }

        // Compute the to_remote script. From our PoV, when facing a remote
        // commitment, the to_remote output belongs to us.
        remoteAuxLeaf := fn.FlatMapOption(
                func(l CommitAuxLeaves) input.AuxTapLeaf {
                        return l.RemoteAuxLeaf
                },
        )(auxResult.AuxLeaves)
        ourScript, _, err := CommitScriptToRemote(
                chanState.ChanType, isRemoteInitiator, keyRing.ToRemoteKey,
                leaseExpiry, remoteAuxLeaf,
        )
        if err != nil {
                return ourIndex, theirIndex, err
        }

        // Now compare the scripts to find our/their output index.
        for i, txOut := range chanCommit.CommitTx.TxOut {
                switch {
                case bytes.Equal(txOut.PkScript, ourScript.PkScript()):
                        ourIndex = uint32(i)
                case bytes.Equal(txOut.PkScript, theirScript.PkScript()):
                        theirIndex = uint32(i)
                }
        }

        return ourIndex, theirIndex, nil
}

lightningnetwork / lnd / 13236757158

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