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lnwallet: move methods to commitment.go
PURE CODE MOVE: Moving createCommitmentTx, CreateCommitTx, createStateHintObfuscator, CommitmentKeyRing, DeriveCommitmentKeys, addHTLC, genHtlcScripts We move the methods and structs to a new file commitment.go in preparation for defining all the logic that is dependent on the channel type in this new file.
This commit is contained in:
Johan T. Halseth
parent
fff9dbe6f3
commit
83e0d47ba3
@ -937,121 +937,6 @@ func (lc *LightningChannel) diskCommitToMemCommit(isLocal bool,
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return commit, nil
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}
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// CommitmentKeyRing holds all derived keys needed to construct commitment and
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// HTLC transactions. The keys are derived differently depending whether the
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// commitment transaction is ours or the remote peer's. Private keys associated
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// with each key may belong to the commitment owner or the "other party" which
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// is referred to in the field comments, regardless of which is local and which
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// is remote.
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type CommitmentKeyRing struct {
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// commitPoint is the "per commitment point" used to derive the tweak
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// for each base point.
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CommitPoint *btcec.PublicKey
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// LocalCommitKeyTweak is the tweak used to derive the local public key
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// from the local payment base point or the local private key from the
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// base point secret. This may be included in a SignDescriptor to
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// generate signatures for the local payment key.
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LocalCommitKeyTweak []byte
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// TODO(roasbeef): need delay tweak as well?
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// LocalHtlcKeyTweak is the teak used to derive the local HTLC key from
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// the local HTLC base point. This value is needed in order to
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// derive the final key used within the HTLC scripts in the commitment
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// transaction.
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LocalHtlcKeyTweak []byte
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// LocalHtlcKey is the key that will be used in the "to self" clause of
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// any HTLC scripts within the commitment transaction for this key ring
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// set.
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LocalHtlcKey *btcec.PublicKey
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// RemoteHtlcKey is the key that will be used in clauses within the
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// HTLC script that send money to the remote party.
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RemoteHtlcKey *btcec.PublicKey
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// DelayKey is the commitment transaction owner's key which is included
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// in HTLC success and timeout transaction scripts.
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DelayKey *btcec.PublicKey
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// NoDelayKey is the other party's payment key in the commitment tx.
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// This is the key used to generate the unencumbered output within the
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// commitment transaction.
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NoDelayKey *btcec.PublicKey
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// RevocationKey is the key that can be used by the other party to
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// redeem outputs from a revoked commitment transaction if it were to
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// be published.
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RevocationKey *btcec.PublicKey
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}
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// DeriveCommitmentKey generates a new commitment key set using the base points
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// and commitment point. The keys are derived differently depending whether the
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// commitment transaction is ours or the remote peer's.
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func DeriveCommitmentKeys(commitPoint *btcec.PublicKey,
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isOurCommit, tweaklessCommit bool,
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localChanCfg, remoteChanCfg *channeldb.ChannelConfig) *CommitmentKeyRing {
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// First, we'll derive all the keys that don't depend on the context of
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// whose commitment transaction this is.
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keyRing := &CommitmentKeyRing{
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CommitPoint: commitPoint,
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LocalCommitKeyTweak: input.SingleTweakBytes(
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commitPoint, localChanCfg.PaymentBasePoint.PubKey,
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),
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LocalHtlcKeyTweak: input.SingleTweakBytes(
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commitPoint, localChanCfg.HtlcBasePoint.PubKey,
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),
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LocalHtlcKey: input.TweakPubKey(
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localChanCfg.HtlcBasePoint.PubKey, commitPoint,
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),
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RemoteHtlcKey: input.TweakPubKey(
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remoteChanCfg.HtlcBasePoint.PubKey, commitPoint,
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),
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}
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// We'll now compute the delay, no delay, and revocation key based on
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// the current commitment point. All keys are tweaked each state in
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// order to ensure the keys from each state are unlinkable. To create
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// the revocation key, we take the opposite party's revocation base
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// point and combine that with the current commitment point.
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var (
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delayBasePoint *btcec.PublicKey
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noDelayBasePoint *btcec.PublicKey
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revocationBasePoint *btcec.PublicKey
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)
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if isOurCommit {
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delayBasePoint = localChanCfg.DelayBasePoint.PubKey
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noDelayBasePoint = remoteChanCfg.PaymentBasePoint.PubKey
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revocationBasePoint = remoteChanCfg.RevocationBasePoint.PubKey
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} else {
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delayBasePoint = remoteChanCfg.DelayBasePoint.PubKey
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noDelayBasePoint = localChanCfg.PaymentBasePoint.PubKey
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revocationBasePoint = localChanCfg.RevocationBasePoint.PubKey
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}
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// With the base points assigned, we can now derive the actual keys
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// using the base point, and the current commitment tweak.
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keyRing.DelayKey = input.TweakPubKey(delayBasePoint, commitPoint)
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keyRing.RevocationKey = input.DeriveRevocationPubkey(
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revocationBasePoint, commitPoint,
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)
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// If this commitment should omit the tweak for the remote point, then
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// we'll use that directly, and ignore the commitPoint tweak.
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if tweaklessCommit {
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keyRing.NoDelayKey = noDelayBasePoint
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} else {
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keyRing.NoDelayKey = input.TweakPubKey(
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noDelayBasePoint, commitPoint,
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)
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}
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return keyRing
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}
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// commitmentChain represents a chain of unrevoked commitments. The tail of the
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// chain is the latest fully signed, yet unrevoked commitment. Two chains are
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// tracked, one for the local node, and another for the remote node. New
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@ -1473,24 +1358,6 @@ func (lc *LightningChannel) createSignDesc() error {
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return nil
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}
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// createStateHintObfuscator derives and assigns the state hint obfuscator for
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// the channel, which is used to encode the commitment height in the sequence
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// number of commitment transaction inputs.
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func (lc *LightningChannel) createStateHintObfuscator() {
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state := lc.channelState
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if state.IsInitiator {
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lc.stateHintObfuscator = DeriveStateHintObfuscator(
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state.LocalChanCfg.PaymentBasePoint.PubKey,
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state.RemoteChanCfg.PaymentBasePoint.PubKey,
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)
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} else {
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lc.stateHintObfuscator = DeriveStateHintObfuscator(
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state.RemoteChanCfg.PaymentBasePoint.PubKey,
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state.LocalChanCfg.PaymentBasePoint.PubKey,
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)
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}
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}
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// ResetState resets the state of the channel back to the default state. This
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// ensures that any active goroutines which need to act based on on-chain
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// events do so properly.
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@ -2370,164 +2237,6 @@ func (lc *LightningChannel) fundingTxIn() wire.TxIn {
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return *wire.NewTxIn(&lc.channelState.FundingOutpoint, nil, nil)
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}
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// createCommitmentTx generates the unsigned commitment transaction for a
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// commitment view and assigns to txn field.
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func (lc *LightningChannel) createCommitmentTx(c *commitment,
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filteredHTLCView *htlcView, keyRing *CommitmentKeyRing) error {
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ourBalance := c.ourBalance
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theirBalance := c.theirBalance
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numHTLCs := int64(0)
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for _, htlc := range filteredHTLCView.ourUpdates {
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if htlcIsDust(false, c.isOurs, c.feePerKw,
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htlc.Amount.ToSatoshis(), c.dustLimit) {
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continue
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}
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numHTLCs++
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}
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for _, htlc := range filteredHTLCView.theirUpdates {
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if htlcIsDust(true, c.isOurs, c.feePerKw,
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htlc.Amount.ToSatoshis(), c.dustLimit) {
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continue
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}
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numHTLCs++
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}
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// Next, we'll calculate the fee for the commitment transaction based
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// on its total weight. Once we have the total weight, we'll multiply
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// by the current fee-per-kw, then divide by 1000 to get the proper
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// fee.
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totalCommitWeight := input.CommitWeight + (input.HtlcWeight * numHTLCs)
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// With the weight known, we can now calculate the commitment fee,
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// ensuring that we account for any dust outputs trimmed above.
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commitFee := c.feePerKw.FeeForWeight(totalCommitWeight)
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commitFeeMSat := lnwire.NewMSatFromSatoshis(commitFee)
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// Currently, within the protocol, the initiator always pays the fees.
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// So we'll subtract the fee amount from the balance of the current
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// initiator. If the initiator is unable to pay the fee fully, then
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// their entire output is consumed.
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switch {
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case lc.channelState.IsInitiator && commitFee > ourBalance.ToSatoshis():
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ourBalance = 0
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case lc.channelState.IsInitiator:
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ourBalance -= commitFeeMSat
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case !lc.channelState.IsInitiator && commitFee > theirBalance.ToSatoshis():
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theirBalance = 0
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case !lc.channelState.IsInitiator:
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theirBalance -= commitFeeMSat
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}
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var (
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commitTx *wire.MsgTx
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err error
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)
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// Depending on whether the transaction is ours or not, we call
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// CreateCommitTx with parameters mathcing the perspective, to generate
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// a new commitment transaction with all the latest unsettled/un-timed
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// out HTLCs.
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if c.isOurs {
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commitTx, err = CreateCommitTx(
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lc.fundingTxIn(), keyRing, &lc.channelState.LocalChanCfg,
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&lc.channelState.RemoteChanCfg, ourBalance.ToSatoshis(),
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theirBalance.ToSatoshis(),
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)
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} else {
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commitTx, err = CreateCommitTx(
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lc.fundingTxIn(), keyRing, &lc.channelState.RemoteChanCfg,
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&lc.channelState.LocalChanCfg, theirBalance.ToSatoshis(),
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ourBalance.ToSatoshis(),
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)
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}
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if err != nil {
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return err
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}
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// We'll now add all the HTLC outputs to the commitment transaction.
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// Each output includes an off-chain 2-of-2 covenant clause, so we'll
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// need the objective local/remote keys for this particular commitment
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// as well. For any non-dust HTLCs that are manifested on the commitment
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// transaction, we'll also record its CLTV which is required to sort the
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// commitment transaction below. The slice is initially sized to the
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// number of existing outputs, since any outputs already added are
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// commitment outputs and should correspond to zero values for the
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// purposes of sorting.
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cltvs := make([]uint32, len(commitTx.TxOut))
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for _, htlc := range filteredHTLCView.ourUpdates {
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if htlcIsDust(false, c.isOurs, c.feePerKw,
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htlc.Amount.ToSatoshis(), c.dustLimit) {
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continue
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}
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err := addHTLC(commitTx, c.isOurs, false, htlc, keyRing)
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if err != nil {
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return err
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}
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cltvs = append(cltvs, htlc.Timeout)
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}
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for _, htlc := range filteredHTLCView.theirUpdates {
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if htlcIsDust(true, c.isOurs, c.feePerKw,
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htlc.Amount.ToSatoshis(), c.dustLimit) {
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continue
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}
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err := addHTLC(commitTx, c.isOurs, true, htlc, keyRing)
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if err != nil {
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return err
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}
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cltvs = append(cltvs, htlc.Timeout)
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}
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// Set the state hint of the commitment transaction to facilitate
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// quickly recovering the necessary penalty state in the case of an
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// uncooperative broadcast.
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err = SetStateNumHint(commitTx, c.height, lc.stateHintObfuscator)
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if err != nil {
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return err
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}
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// Sort the transactions according to the agreed upon canonical
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// ordering. This lets us skip sending the entire transaction over,
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// instead we'll just send signatures.
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InPlaceCommitSort(commitTx, cltvs)
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// Next, we'll ensure that we don't accidentally create a commitment
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// transaction which would be invalid by consensus.
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uTx := btcutil.NewTx(commitTx)
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if err := blockchain.CheckTransactionSanity(uTx); err != nil {
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return err
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}
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// Finally, we'll assert that were not attempting to draw more out of
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// the channel that was originally placed within it.
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var totalOut btcutil.Amount
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for _, txOut := range commitTx.TxOut {
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totalOut += btcutil.Amount(txOut.Value)
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}
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if totalOut > lc.channelState.Capacity {
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return fmt.Errorf("height=%v, for ChannelPoint(%v) attempts "+
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"to consume %v while channel capacity is %v",
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c.height, lc.channelState.FundingOutpoint,
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totalOut, lc.channelState.Capacity)
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}
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c.txn = commitTx
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c.fee = commitFee
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c.ourBalance = ourBalance
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c.theirBalance = theirBalance
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return nil
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}
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// evaluateHTLCView processes all update entries in both HTLC update logs,
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// producing a final view which is the result of properly applying all adds,
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// settles, timeouts and fee updates found in both logs. The resulting view
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@ -4933,101 +4642,6 @@ func (lc *LightningChannel) RemoteUpfrontShutdownScript() lnwire.DeliveryAddress
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return lc.channelState.RemoteShutdownScript
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}
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// genHtlcScript generates the proper P2WSH public key scripts for the HTLC
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// output modified by two-bits denoting if this is an incoming HTLC, and if the
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// HTLC is being applied to their commitment transaction or ours.
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func genHtlcScript(isIncoming, ourCommit bool, timeout uint32, rHash [32]byte,
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keyRing *CommitmentKeyRing) ([]byte, []byte, error) {
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var (
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witnessScript []byte
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err error
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)
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// Generate the proper redeem scripts for the HTLC output modified by
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// two-bits denoting if this is an incoming HTLC, and if the HTLC is
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// being applied to their commitment transaction or ours.
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switch {
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// The HTLC is paying to us, and being applied to our commitment
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// transaction. So we need to use the receiver's version of HTLC the
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// script.
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case isIncoming && ourCommit:
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witnessScript, err = input.ReceiverHTLCScript(timeout,
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keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
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keyRing.RevocationKey, rHash[:])
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// We're being paid via an HTLC by the remote party, and the HTLC is
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// being added to their commitment transaction, so we use the sender's
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// version of the HTLC script.
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case isIncoming && !ourCommit:
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witnessScript, err = input.SenderHTLCScript(keyRing.RemoteHtlcKey,
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keyRing.LocalHtlcKey, keyRing.RevocationKey, rHash[:])
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// We're sending an HTLC which is being added to our commitment
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// transaction. Therefore, we need to use the sender's version of the
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// HTLC script.
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case !isIncoming && ourCommit:
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witnessScript, err = input.SenderHTLCScript(keyRing.LocalHtlcKey,
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keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
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// Finally, we're paying the remote party via an HTLC, which is being
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// added to their commitment transaction. Therefore, we use the
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// receiver's version of the HTLC script.
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case !isIncoming && !ourCommit:
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witnessScript, err = input.ReceiverHTLCScript(timeout, keyRing.LocalHtlcKey,
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keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
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}
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if err != nil {
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return nil, nil, err
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}
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// Now that we have the redeem scripts, create the P2WSH public key
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// script for the output itself.
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htlcP2WSH, err := input.WitnessScriptHash(witnessScript)
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if err != nil {
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return nil, nil, err
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}
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return htlcP2WSH, witnessScript, nil
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}
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// addHTLC adds a new HTLC to the passed commitment transaction. One of four
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// full scripts will be generated for the HTLC output depending on if the HTLC
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// is incoming and if it's being applied to our commitment transaction or that
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// of the remote node's. Additionally, in order to be able to efficiently
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// locate the added HTLC on the commitment transaction from the
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// PaymentDescriptor that generated it, the generated script is stored within
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// the descriptor itself.
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func addHTLC(commitTx *wire.MsgTx, ourCommit bool,
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isIncoming bool, paymentDesc *PaymentDescriptor,
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keyRing *CommitmentKeyRing) error {
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timeout := paymentDesc.Timeout
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rHash := paymentDesc.RHash
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p2wsh, witnessScript, err := genHtlcScript(isIncoming, ourCommit,
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timeout, rHash, keyRing)
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if err != nil {
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return err
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}
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// Add the new HTLC outputs to the respective commitment transactions.
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amountPending := int64(paymentDesc.Amount.ToSatoshis())
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commitTx.AddTxOut(wire.NewTxOut(amountPending, p2wsh))
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// Store the pkScript of this particular PaymentDescriptor so we can
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// quickly locate it within the commitment transaction later.
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if ourCommit {
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paymentDesc.ourPkScript = p2wsh
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paymentDesc.ourWitnessScript = witnessScript
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} else {
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paymentDesc.theirPkScript = p2wsh
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paymentDesc.theirWitnessScript = witnessScript
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}
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return nil
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}
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// getSignedCommitTx function take the latest commitment transaction and
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// populate it with witness data.
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func (lc *LightningChannel) getSignedCommitTx() (*wire.MsgTx, error) {
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@ -6219,67 +5833,6 @@ func (lc *LightningChannel) generateRevocation(height uint64) (*lnwire.RevokeAnd
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return revocationMsg, nil
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}
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// CreateCommitTx creates a commitment transaction, spending from specified
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// funding output. The commitment transaction contains two outputs: one local
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// output paying to the "owner" of the commitment transaction which can be
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// spent after a relative block delay or revocation event, and a remote output
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// paying the counterparty within the channel, which can be spent immediately
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// or after a delay depending on the commitment type..
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func CreateCommitTx(fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
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localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
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amountToLocal, amountToRemote btcutil.Amount) (*wire.MsgTx, error) {
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// First, we create the script for the delayed "pay-to-self" output.
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// This output has 2 main redemption clauses: either we can redeem the
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// output after a relative block delay, or the remote node can claim
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// the funds with the revocation key if we broadcast a revoked
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// commitment transaction.
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toLocalRedeemScript, err := input.CommitScriptToSelf(
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uint32(localChanCfg.CsvDelay), keyRing.DelayKey,
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keyRing.RevocationKey,
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)
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if err != nil {
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return nil, err
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}
|
||||
toLocalScriptHash, err := input.WitnessScriptHash(
|
||||
toLocalRedeemScript,
|
||||
)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
// Next, we create the script paying to the remote. This is just a
|
||||
// regular P2WPKH output, without any added CSV delay.
|
||||
toRemoteWitnessKeyHash, err := input.CommitScriptUnencumbered(
|
||||
keyRing.NoDelayKey,
|
||||
)
|
||||
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.
|
||||
if amountToLocal >= localChanCfg.DustLimit {
|
||||
commitTx.AddTxOut(&wire.TxOut{
|
||||
PkScript: toLocalScriptHash,
|
||||
Value: int64(amountToLocal),
|
||||
})
|
||||
}
|
||||
if amountToRemote >= localChanCfg.DustLimit {
|
||||
commitTx.AddTxOut(&wire.TxOut{
|
||||
PkScript: toRemoteWitnessKeyHash,
|
||||
Value: int64(amountToRemote),
|
||||
})
|
||||
}
|
||||
|
||||
return commitTx, nil
|
||||
}
|
||||
|
||||
// CreateCooperativeCloseTx creates a transaction which if signed by both
|
||||
// parties, then broadcast cooperatively closes an active channel. The creation
|
||||
// of the closure transaction is modified by a boolean indicating if the party
|
||||
|
||||
460
lnwallet/commitment.go
Normal file
460
lnwallet/commitment.go
Normal file
@ -0,0 +1,460 @@
|
||||
package lnwallet
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
|
||||
"github.com/btcsuite/btcd/blockchain"
|
||||
"github.com/btcsuite/btcd/btcec"
|
||||
"github.com/btcsuite/btcd/wire"
|
||||
"github.com/btcsuite/btcutil"
|
||||
"github.com/lightningnetwork/lnd/channeldb"
|
||||
"github.com/lightningnetwork/lnd/input"
|
||||
"github.com/lightningnetwork/lnd/lnwire"
|
||||
)
|
||||
|
||||
// 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.
|
||||
LocalCommitKeyTweak []byte
|
||||
|
||||
// TODO(roasbeef): need delay tweak as well?
|
||||
|
||||
// LocalHtlcKeyTweak is the teak 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.
|
||||
LocalHtlcKeyTweak []byte
|
||||
|
||||
// LocalHtlcKey is the key that will be used in the "to self" clause of
|
||||
// any HTLC scripts within the commitment transaction for this key ring
|
||||
// set.
|
||||
LocalHtlcKey *btcec.PublicKey
|
||||
|
||||
// RemoteHtlcKey is the key that will be used in clauses within the
|
||||
// HTLC script that send money to the remote party.
|
||||
RemoteHtlcKey *btcec.PublicKey
|
||||
|
||||
// DelayKey is the commitment transaction owner's key which is included
|
||||
// in HTLC success and timeout transaction scripts.
|
||||
DelayKey *btcec.PublicKey
|
||||
|
||||
// NoDelayKey is the other party's payment key in the commitment tx.
|
||||
// This is the key used to generate the unencumbered output within the
|
||||
// commitment transaction.
|
||||
NoDelayKey *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.
|
||||
RevocationKey *btcec.PublicKey
|
||||
}
|
||||
|
||||
// DeriveCommitmentKey generates a new commitment key set using the base points
|
||||
// and commitment point. The keys are derived differently depending whether the
|
||||
// commitment transaction is ours or the remote peer's.
|
||||
func DeriveCommitmentKeys(commitPoint *btcec.PublicKey,
|
||||
isOurCommit, tweaklessCommit bool,
|
||||
localChanCfg, remoteChanCfg *channeldb.ChannelConfig) *CommitmentKeyRing {
|
||||
|
||||
// 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, localChanCfg.PaymentBasePoint.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 delay, no delay, 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 (
|
||||
delayBasePoint *btcec.PublicKey
|
||||
noDelayBasePoint *btcec.PublicKey
|
||||
revocationBasePoint *btcec.PublicKey
|
||||
)
|
||||
if isOurCommit {
|
||||
delayBasePoint = localChanCfg.DelayBasePoint.PubKey
|
||||
noDelayBasePoint = remoteChanCfg.PaymentBasePoint.PubKey
|
||||
revocationBasePoint = remoteChanCfg.RevocationBasePoint.PubKey
|
||||
} else {
|
||||
delayBasePoint = remoteChanCfg.DelayBasePoint.PubKey
|
||||
noDelayBasePoint = 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.DelayKey = input.TweakPubKey(delayBasePoint, 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.NoDelayKey = noDelayBasePoint
|
||||
} else {
|
||||
keyRing.NoDelayKey = input.TweakPubKey(
|
||||
noDelayBasePoint, commitPoint,
|
||||
)
|
||||
}
|
||||
|
||||
return keyRing
|
||||
}
|
||||
|
||||
// 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 (lc *LightningChannel) createStateHintObfuscator() {
|
||||
state := lc.channelState
|
||||
if state.IsInitiator {
|
||||
lc.stateHintObfuscator = DeriveStateHintObfuscator(
|
||||
state.LocalChanCfg.PaymentBasePoint.PubKey,
|
||||
state.RemoteChanCfg.PaymentBasePoint.PubKey,
|
||||
)
|
||||
} else {
|
||||
lc.stateHintObfuscator = DeriveStateHintObfuscator(
|
||||
state.RemoteChanCfg.PaymentBasePoint.PubKey,
|
||||
state.LocalChanCfg.PaymentBasePoint.PubKey,
|
||||
)
|
||||
}
|
||||
}
|
||||
|
||||
// createCommitmentTx generates the unsigned commitment transaction for a
|
||||
// commitment view and assigns to txn field.
|
||||
func (lc *LightningChannel) createCommitmentTx(c *commitment,
|
||||
filteredHTLCView *htlcView, keyRing *CommitmentKeyRing) error {
|
||||
|
||||
ourBalance := c.ourBalance
|
||||
theirBalance := c.theirBalance
|
||||
|
||||
numHTLCs := int64(0)
|
||||
for _, htlc := range filteredHTLCView.ourUpdates {
|
||||
if htlcIsDust(false, c.isOurs, c.feePerKw,
|
||||
htlc.Amount.ToSatoshis(), c.dustLimit) {
|
||||
|
||||
continue
|
||||
}
|
||||
|
||||
numHTLCs++
|
||||
}
|
||||
for _, htlc := range filteredHTLCView.theirUpdates {
|
||||
if htlcIsDust(true, c.isOurs, c.feePerKw,
|
||||
htlc.Amount.ToSatoshis(), c.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 := input.CommitWeight + (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 := c.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 lc.channelState.IsInitiator && commitFee > ourBalance.ToSatoshis():
|
||||
ourBalance = 0
|
||||
|
||||
case lc.channelState.IsInitiator:
|
||||
ourBalance -= commitFeeMSat
|
||||
|
||||
case !lc.channelState.IsInitiator && commitFee > theirBalance.ToSatoshis():
|
||||
theirBalance = 0
|
||||
|
||||
case !lc.channelState.IsInitiator:
|
||||
theirBalance -= commitFeeMSat
|
||||
}
|
||||
|
||||
var (
|
||||
commitTx *wire.MsgTx
|
||||
err error
|
||||
)
|
||||
|
||||
// Depending on whether the transaction is ours or not, we call
|
||||
// CreateCommitTx with parameters mathcing the perspective, to generate
|
||||
// a new commitment transaction with all the latest unsettled/un-timed
|
||||
// out HTLCs.
|
||||
if c.isOurs {
|
||||
commitTx, err = CreateCommitTx(
|
||||
lc.fundingTxIn(), keyRing, &lc.channelState.LocalChanCfg,
|
||||
&lc.channelState.RemoteChanCfg, ourBalance.ToSatoshis(),
|
||||
theirBalance.ToSatoshis(),
|
||||
)
|
||||
} else {
|
||||
commitTx, err = CreateCommitTx(
|
||||
lc.fundingTxIn(), keyRing, &lc.channelState.RemoteChanCfg,
|
||||
&lc.channelState.LocalChanCfg, theirBalance.ToSatoshis(),
|
||||
ourBalance.ToSatoshis(),
|
||||
)
|
||||
}
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
// 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))
|
||||
for _, htlc := range filteredHTLCView.ourUpdates {
|
||||
if htlcIsDust(false, c.isOurs, c.feePerKw,
|
||||
htlc.Amount.ToSatoshis(), c.dustLimit) {
|
||||
continue
|
||||
}
|
||||
|
||||
err := addHTLC(commitTx, c.isOurs, false, htlc, keyRing)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
cltvs = append(cltvs, htlc.Timeout)
|
||||
}
|
||||
for _, htlc := range filteredHTLCView.theirUpdates {
|
||||
if htlcIsDust(true, c.isOurs, c.feePerKw,
|
||||
htlc.Amount.ToSatoshis(), c.dustLimit) {
|
||||
continue
|
||||
}
|
||||
|
||||
err := addHTLC(commitTx, c.isOurs, true, htlc, keyRing)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
cltvs = append(cltvs, htlc.Timeout)
|
||||
}
|
||||
|
||||
// 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, c.height, lc.stateHintObfuscator)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
// Sort the transactions according to the agreed upon canonical
|
||||
// ordering. This lets us skip sending the entire transaction over,
|
||||
// instead we'll just send signatures.
|
||||
InPlaceCommitSort(commitTx, cltvs)
|
||||
|
||||
// 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 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 > lc.channelState.Capacity {
|
||||
return fmt.Errorf("height=%v, for ChannelPoint(%v) attempts "+
|
||||
"to consume %v while channel capacity is %v",
|
||||
c.height, lc.channelState.FundingOutpoint,
|
||||
totalOut, lc.channelState.Capacity)
|
||||
}
|
||||
|
||||
c.txn = commitTx
|
||||
c.fee = commitFee
|
||||
c.ourBalance = ourBalance
|
||||
c.theirBalance = theirBalance
|
||||
return 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..
|
||||
func CreateCommitTx(fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
|
||||
localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
|
||||
amountToLocal, amountToRemote btcutil.Amount) (*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.
|
||||
toLocalRedeemScript, err := input.CommitScriptToSelf(
|
||||
uint32(localChanCfg.CsvDelay), keyRing.DelayKey,
|
||||
keyRing.RevocationKey,
|
||||
)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
toLocalScriptHash, err := input.WitnessScriptHash(
|
||||
toLocalRedeemScript,
|
||||
)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
// Next, we create the script paying to the remote. This is just a
|
||||
// regular P2WPKH output, without any added CSV delay.
|
||||
toRemoteWitnessKeyHash, err := input.CommitScriptUnencumbered(
|
||||
keyRing.NoDelayKey,
|
||||
)
|
||||
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.
|
||||
if amountToLocal >= localChanCfg.DustLimit {
|
||||
commitTx.AddTxOut(&wire.TxOut{
|
||||
PkScript: toLocalScriptHash,
|
||||
Value: int64(amountToLocal),
|
||||
})
|
||||
}
|
||||
if amountToRemote >= localChanCfg.DustLimit {
|
||||
commitTx.AddTxOut(&wire.TxOut{
|
||||
PkScript: toRemoteWitnessKeyHash,
|
||||
Value: int64(amountToRemote),
|
||||
})
|
||||
}
|
||||
|
||||
return commitTx, nil
|
||||
}
|
||||
|
||||
// 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.
|
||||
func genHtlcScript(isIncoming, ourCommit bool, timeout uint32, rHash [32]byte,
|
||||
keyRing *CommitmentKeyRing) ([]byte, []byte, error) {
|
||||
|
||||
var (
|
||||
witnessScript []byte
|
||||
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 && ourCommit:
|
||||
witnessScript, err = input.ReceiverHTLCScript(timeout,
|
||||
keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
|
||||
keyRing.RevocationKey, rHash[:])
|
||||
|
||||
// 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 && !ourCommit:
|
||||
witnessScript, err = input.SenderHTLCScript(keyRing.RemoteHtlcKey,
|
||||
keyRing.LocalHtlcKey, keyRing.RevocationKey, rHash[:])
|
||||
|
||||
// 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 && ourCommit:
|
||||
witnessScript, err = input.SenderHTLCScript(keyRing.LocalHtlcKey,
|
||||
keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
|
||||
|
||||
// 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 && !ourCommit:
|
||||
witnessScript, err = input.ReceiverHTLCScript(timeout, keyRing.LocalHtlcKey,
|
||||
keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
|
||||
}
|
||||
if err != nil {
|
||||
return nil, 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, nil, err
|
||||
}
|
||||
|
||||
return htlcP2WSH, witnessScript, nil
|
||||
}
|
||||
|
||||
// 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, ourCommit bool,
|
||||
isIncoming bool, paymentDesc *PaymentDescriptor,
|
||||
keyRing *CommitmentKeyRing) error {
|
||||
|
||||
timeout := paymentDesc.Timeout
|
||||
rHash := paymentDesc.RHash
|
||||
|
||||
p2wsh, witnessScript, err := genHtlcScript(isIncoming, ourCommit,
|
||||
timeout, rHash, keyRing)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
// Add the new HTLC outputs to the respective commitment transactions.
|
||||
amountPending := int64(paymentDesc.Amount.ToSatoshis())
|
||||
commitTx.AddTxOut(wire.NewTxOut(amountPending, p2wsh))
|
||||
|
||||
// Store the pkScript of this particular PaymentDescriptor so we can
|
||||
// quickly locate it within the commitment transaction later.
|
||||
if ourCommit {
|
||||
paymentDesc.ourPkScript = p2wsh
|
||||
paymentDesc.ourWitnessScript = witnessScript
|
||||
} else {
|
||||
paymentDesc.theirPkScript = p2wsh
|
||||
paymentDesc.theirWitnessScript = witnessScript
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user