contractcourt: handle sweeping script-enforced leased channel outputs

In order to sweep the commitment and HTLC outputs belonging to a
script-enforced leased channel, each resolver must know whether the
additional CLTV clause on the channel initiator applies to them. To do
so, we retrieve the historical channel state stored within the database
and supplement it to the resolvers to provide them with what's needed in
order to sweep the necessary outputs and resolve their respective
contracts.

contractcourt/commit_sweep_resolver.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"math"
 	"sync"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -43,6 +44,19 @@ type commitSweepResolver struct {
 	// chanPoint is the channel point of the original contract.
 	chanPoint wire.OutPoint
 
+	// channelInitiator denotes whether the party responsible for resolving
+	// the contract initiated the channel.
+	channelInitiator bool
+
+	// leaseExpiry denotes the additional waiting period the contract must
+	// hold until it can be resolved. This waiting period is known as the
+	// expiration of a script-enforced leased channel and only applies to
+	// the channel initiator.
+	//
+	// NOTE: This value should only be set when the contract belongs to a
+	// leased channel.
+	leaseExpiry uint32
+
 	// currentReport stores the current state of the resolver for reporting
 	// over the rpc interface.
 	currentReport ContractReport
@@ -55,8 +69,8 @@ type commitSweepResolver struct {
 
 // newCommitSweepResolver instantiates a new direct commit output resolver.
 func newCommitSweepResolver(res lnwallet.CommitOutputResolution,
-	broadcastHeight uint32,
-	chanPoint wire.OutPoint, resCfg ResolverConfig) *commitSweepResolver {
+	broadcastHeight uint32, chanPoint wire.OutPoint,
+	resCfg ResolverConfig) *commitSweepResolver {
 
 	r := &commitSweepResolver{
 		contractResolverKit: *newContractResolverKit(resCfg),
@@ -181,7 +195,14 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 		return nil, err
 	}
 
+	// Wait up until the CSV expires, unless we also have a CLTV that
+	// expires after.
 	unlockHeight := confHeight + c.commitResolution.MaturityDelay
+	if c.hasCLTV() {
+		unlockHeight = uint32(math.Max(
+			float64(unlockHeight), float64(c.leaseExpiry),
+		))
+	}
 
 	c.log.Debugf("commit conf_height=%v, unlock_height=%v",
 		confHeight, unlockHeight)
@@ -191,14 +212,34 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 	c.currentReport.MaturityHeight = unlockHeight
 	c.reportLock.Unlock()
 
-	// If there is a csv delay, we'll wait for that.
-	if c.commitResolution.MaturityDelay > 0 {
-		c.log.Debugf("waiting for csv lock to expire at height %v",
-			unlockHeight)
+	// If there is a csv/cltv lock, we'll wait for that.
+	if c.commitResolution.MaturityDelay > 0 || c.hasCLTV() {
+		// Determine what height we should wait until for the locks to
+		// expire.
+		var waitHeight uint32
+		switch {
+		// If we have both a csv and cltv lock, we'll need to look at
+		// both and see which expires later.
+		case c.commitResolution.MaturityDelay > 0 && c.hasCLTV():
+			c.log.Debugf("waiting for CSV and CLTV lock to expire "+
+				"at height %v", unlockHeight)
+			// If the CSV expires after the CLTV, or there is no
+			// CLTV, then we can broadcast a sweep a block before.
+			// Otherwise, we need to broadcast at our expected
+			// unlock height.
+			waitHeight = uint32(math.Max(
+				float64(unlockHeight-1), float64(c.leaseExpiry),
+			))
 
-		// We only need to wait for the block before the block that
-		// unlocks the spend path.
-		err := waitForHeight(unlockHeight-1, c.Notifier, c.quit)
+		// If we only have a csv lock, wait for the height before the
+		// lock expires as the spend path should be unlocked by then.
+		case c.commitResolution.MaturityDelay > 0:
+			c.log.Debugf("waiting for CSV lock to expire at "+
+				"height %v", unlockHeight)
+			waitHeight = unlockHeight - 1
+		}
+
+		err := waitForHeight(waitHeight, c.Notifier, c.quit)
 		if err != nil {
 			return nil, err
 		}
@@ -222,10 +263,20 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 	var witnessType input.WitnessType
 	switch {
 
+	// Delayed output to us on our local commitment for a channel lease in
+	// which we are the initiator.
+	case isLocalCommitTx && c.hasCLTV():
+		witnessType = input.LeaseCommitmentTimeLock
+
 	// Delayed output to us on our local commitment.
 	case isLocalCommitTx:
 		witnessType = input.CommitmentTimeLock
 
+	// A confirmed output to us on the remote commitment for a channel lease
+	// in which we are the initiator.
+	case isDelayedOutput && c.hasCLTV():
+		witnessType = input.LeaseCommitmentToRemoteConfirmed
+
 	// A confirmed output to us on the remote commitment.
 	case isDelayedOutput:
 		witnessType = input.CommitmentToRemoteConfirmed
@@ -246,13 +297,21 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 	// We'll craft an input with all the information required for
 	// the sweeper to create a fully valid sweeping transaction to
 	// recover these coins.
-	inp := input.NewCsvInput(
-		&c.commitResolution.SelfOutPoint,
-		witnessType,
-		&c.commitResolution.SelfOutputSignDesc,
-		c.broadcastHeight,
-		c.commitResolution.MaturityDelay,
-	)
+	var inp *input.BaseInput
+	if c.hasCLTV() {
+		inp = input.NewCsvInputWithCltv(
+			&c.commitResolution.SelfOutPoint, witnessType,
+			&c.commitResolution.SelfOutputSignDesc,
+			c.broadcastHeight, c.commitResolution.MaturityDelay,
+			c.leaseExpiry,
+		)
+	} else {
+		inp = input.NewCsvInput(
+			&c.commitResolution.SelfOutPoint, witnessType,
+			&c.commitResolution.SelfOutputSignDesc,
+			c.broadcastHeight, c.commitResolution.MaturityDelay,
+		)
+	}
 
 	// With our input constructed, we'll now offer it to the
 	// sweeper.
@@ -337,6 +396,23 @@ func (c *commitSweepResolver) IsResolved() bool {
 	return c.resolved
 }
 
+// SupplementState allows the user of a ContractResolver to supplement it with
+// state required for the proper resolution of a contract.
+//
+// NOTE: Part of the ContractResolver interface.
+func (c *commitSweepResolver) SupplementState(state *channeldb.OpenChannel) {
+	if state.ChanType.HasLeaseExpiration() {
+		c.leaseExpiry = state.ThawHeight
+	}
+	c.channelInitiator = state.IsInitiator
+}
+
+// hasCLTV denotes whether the resolver must wait for an additional CLTV to
+// expire before resolving the contract.
+func (c *commitSweepResolver) hasCLTV() bool {
+	return c.channelInitiator && c.leaseExpiry > 0
+}
+
 // Encode writes an encoded version of the ContractResolver into the passed
 // Writer.
 //