11166428937

Committed 03 Oct 2024 05:07PM UTC coverage: 58.738% (-0.08%) from 58.817%

Build # 11166428937

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push

github

Committed by

web-flow

Commit Message

Merge pull request #8960 from lightningnetwork/0-19-staging-rebased

[custom channels 5/5]: merge custom channel staging branch into master

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80.17

/contractcourt/htlc_incoming_contest_resolver.go

package contractcourt

import (
        "bytes"
        "encoding/binary"
        "errors"
        "fmt"
        "io"

        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/txscript"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/channeldb/models"
        "github.com/lightningnetwork/lnd/fn"
        "github.com/lightningnetwork/lnd/htlcswitch/hop"
        "github.com/lightningnetwork/lnd/invoices"
        "github.com/lightningnetwork/lnd/lntypes"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/queue"
)

// htlcIncomingContestResolver is a ContractResolver that's able to resolve an
// incoming HTLC that is still contested. An HTLC is still contested, if at the
// time of commitment broadcast, we don't know of the preimage for it yet, and
// it hasn't expired. In this case, we can resolve the HTLC if we learn of the
// preimage, otherwise the remote party will sweep it after it expires.
//
// TODO(roasbeef): just embed the other resolver?
type htlcIncomingContestResolver struct {
        // htlcExpiry is the absolute expiry of this incoming HTLC. We use this
        // value to determine if we can exit early as if the HTLC times out,
        // before we learn of the preimage then we can't claim it on chain
        // successfully.
        htlcExpiry uint32

        // htlcSuccessResolver is the inner resolver that may be utilized if we
        // learn of the preimage.
        *htlcSuccessResolver
}

// newIncomingContestResolver instantiates a new incoming htlc contest resolver.
func newIncomingContestResolver(
        res lnwallet.IncomingHtlcResolution, broadcastHeight uint32,
        htlc channeldb.HTLC, resCfg ResolverConfig) *htlcIncomingContestResolver {

        success := newSuccessResolver(
                res, broadcastHeight, htlc, resCfg,
        )

        return &htlcIncomingContestResolver{
                htlcExpiry:          htlc.RefundTimeout,
                htlcSuccessResolver: success,
        }
}

func (h *htlcIncomingContestResolver) processFinalHtlcFail() error {
        // Mark the htlc as final failed.
        err := h.ChainArbitratorConfig.PutFinalHtlcOutcome(
                h.ChannelArbitratorConfig.ShortChanID, h.htlc.HtlcIndex, false,
        )
        if err != nil {
                return err
        }

        // Send notification.
        h.ChainArbitratorConfig.HtlcNotifier.NotifyFinalHtlcEvent(
                models.CircuitKey{
                        ChanID: h.ShortChanID,
                        HtlcID: h.htlc.HtlcIndex,
                },
                channeldb.FinalHtlcInfo{
                        Settled:  false,
                        Offchain: false,
                },
        )

        return nil
}

// Resolve attempts to resolve this contract. As we don't yet know of the
// preimage for the contract, we'll wait for one of two things to happen:
//
//  1. We learn of the preimage! In this case, we can sweep the HTLC incoming
//     and ensure that if this was a multi-hop HTLC we are made whole. In this
//     case, an additional ContractResolver will be returned to finish the
//     job.
//
//  2. The HTLC expires. If this happens, then the contract is fully resolved
//     as we have no remaining actions left at our disposal.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Resolve(
        _ bool) (ContractResolver, error) {

        // If we're already full resolved, then we don't have anything further
        // to do.
        if h.resolved {
                return nil, nil
        }

        // If the HTLC has custom records, then for now we'll pause resolution.
        //
        // TODO(roasbeef): Implement resolving HTLCs with custom records
        // (follow-up PR).
        if len(h.htlc.CustomRecords) != 0 {
                select { //nolint:gosimple
                case <-h.quit:
                        return nil, errResolverShuttingDown
                }
        }

        // First try to parse the payload. If that fails, we can stop resolution
        // now.
        payload, nextHopOnionBlob, err := h.decodePayload()
        if err != nil {
                log.Debugf("ChannelArbitrator(%v): cannot decode payload of "+
                        "htlc %v", h.ChanPoint, h.HtlcPoint())

                // If we've locked in an htlc with an invalid payload on our
                // commitment tx, we don't need to resolve it. The other party
                // will time it out and get their funds back. This situation
                // can present itself when we crash before processRemoteAdds in
                // the link has ran.
                h.resolved = true

                if err := h.processFinalHtlcFail(); err != nil {
                        return nil, err
                }

                // We write a report to disk that indicates we could not decode
                // the htlc.
                resReport := h.report().resolverReport(
                        nil, channeldb.ResolverTypeIncomingHtlc,
                        channeldb.ResolverOutcomeAbandoned,
                )
                return nil, h.PutResolverReport(nil, resReport)
        }

        // Register for block epochs. After registration, the current height
        // will be sent on the channel immediately.
        blockEpochs, err := h.Notifier.RegisterBlockEpochNtfn(nil)
        if err != nil {
                return nil, err
        }
        defer blockEpochs.Cancel()

        var currentHeight int32
        select {
        case newBlock, ok := <-blockEpochs.Epochs:
                if !ok {
                        return nil, errResolverShuttingDown
                }
                currentHeight = newBlock.Height
        case <-h.quit:
                return nil, errResolverShuttingDown
        }

        log.Debugf("%T(%v): Resolving incoming HTLC(expiry=%v, height=%v)", h,
                h.htlcResolution.ClaimOutpoint, h.htlcExpiry, currentHeight)

        // We'll first check if this HTLC has been timed out, if so, we can
        // return now and mark ourselves as resolved. If we're past the point of
        // expiry of the HTLC, then at this point the sender can sweep it, so
        // we'll end our lifetime. Here we deliberately forego the chance that
        // the sender doesn't sweep and we already have or will learn the
        // preimage. Otherwise the resolver could potentially stay active
        // indefinitely and the channel will never close properly.
        if uint32(currentHeight) >= h.htlcExpiry {
                // TODO(roasbeef): should also somehow check if outgoing is
                // resolved or not
                //  * may need to hook into the circuit map
                //  * can't timeout before the outgoing has been

                log.Infof("%T(%v): HTLC has timed out (expiry=%v, height=%v), "+
                        "abandoning", h, h.htlcResolution.ClaimOutpoint,
                        h.htlcExpiry, currentHeight)
                h.resolved = true

                if err := h.processFinalHtlcFail(); err != nil {
                        return nil, err
                }

                // Finally, get our report and checkpoint our resolver with a
                // timeout outcome report.
                report := h.report().resolverReport(
                        nil, channeldb.ResolverTypeIncomingHtlc,
                        channeldb.ResolverOutcomeTimeout,
                )
                return nil, h.Checkpoint(h, report)
        }

        // applyPreimage is a helper function that will populate our internal
        // resolver with the preimage we learn of. This should be called once
        // the preimage is revealed so the inner resolver can properly complete
        // its duties. The error return value indicates whether the preimage
        // was properly applied.
        applyPreimage := func(preimage lntypes.Preimage) error {
                // Sanity check to see if this preimage matches our htlc. At
                // this point it should never happen that it does not match.
                if !preimage.Matches(h.htlc.RHash) {
                        return errors.New("preimage does not match hash")
                }

                // Update htlcResolution with the matching preimage.
                h.htlcResolution.Preimage = preimage

                log.Infof("%T(%v): applied preimage=%v", h,
                        h.htlcResolution.ClaimOutpoint, preimage)

                isSecondLevel := h.htlcResolution.SignedSuccessTx != nil

                // If we didn't have to go to the second level to claim (this
                // is the remote commitment transaction), then we don't need to
                // modify our canned witness.
                if !isSecondLevel {
                        return nil
                }

                isTaproot := txscript.IsPayToTaproot(
                        h.htlcResolution.SignedSuccessTx.TxOut[0].PkScript,
                )

                // If this is our commitment transaction, then we'll need to
                // populate the witness for the second-level HTLC transaction.
                switch {
                // For taproot channels, the witness for sweeping with success
                // looks like:
                //   - <sender sig> <receiver sig> <preimage> <success_script>
                //     <control_block>
                //
                // So we'll insert it at the 3rd index of the witness.
                case isTaproot:
                        //nolint:lll
                        h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[2] = preimage[:]

                // Within the witness for the success transaction, the
                // preimage is the 4th element as it looks like:
                //
                //  * <0> <sender sig> <recvr sig> <preimage> <witness script>
                //
                // We'll populate it within the witness, as since this
                // was a "contest" resolver, we didn't yet know of the
                // preimage.
                case !isTaproot:
                        h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[3] = preimage[:]
                }

                return nil
        }

        // Define a closure to process htlc resolutions either directly or
        // triggered by future notifications.
        processHtlcResolution := func(e invoices.HtlcResolution) (
                ContractResolver, error) {

                // Take action based on the type of resolution we have
                // received.
                switch resolution := e.(type) {
                // If the htlc resolution was a settle, apply the
                // preimage and return a success resolver.
                case *invoices.HtlcSettleResolution:
                        err := applyPreimage(resolution.Preimage)
                        if err != nil {
                                return nil, err
                        }

                        return h.htlcSuccessResolver, nil

                // If the htlc was failed, mark the htlc as
                // resolved.
                case *invoices.HtlcFailResolution:
                        log.Infof("%T(%v): Exit hop HTLC canceled "+
                                "(expiry=%v, height=%v), abandoning", h,
                                h.htlcResolution.ClaimOutpoint,
                                h.htlcExpiry, currentHeight)

                        h.resolved = true

                        if err := h.processFinalHtlcFail(); err != nil {
                                return nil, err
                        }

                        // Checkpoint our resolver with an abandoned outcome
                        // because we take no further action on this htlc.
                        report := h.report().resolverReport(
                                nil, channeldb.ResolverTypeIncomingHtlc,
                                channeldb.ResolverOutcomeAbandoned,
                        )
                        return nil, h.Checkpoint(h, report)

                // Error if the resolution type is unknown, we are only
                // expecting settles and fails.
                default:
                        return nil, fmt.Errorf("unknown resolution"+
                                " type: %v", e)
                }
        }

        var (
                hodlChan       <-chan interface{}
                witnessUpdates <-chan lntypes.Preimage
        )
        if payload.FwdInfo.NextHop == hop.Exit {
                // Create a buffered hodl chan to prevent deadlock.
                hodlQueue := queue.NewConcurrentQueue(10)
                hodlQueue.Start()

                hodlChan = hodlQueue.ChanOut()

                // Notify registry that we are potentially resolving as an exit
                // hop on-chain. If this HTLC indeed pays to an existing
                // invoice, the invoice registry will tell us what to do with
                // the HTLC. This is identical to HTLC resolution in the link.
                circuitKey := models.CircuitKey{
                        ChanID: h.ShortChanID,
                        HtlcID: h.htlc.HtlcIndex,
                }

                resolution, err := h.Registry.NotifyExitHopHtlc(
                        h.htlc.RHash, h.htlc.Amt, h.htlcExpiry, currentHeight,
                        circuitKey, hodlQueue.ChanIn(), nil, payload,
                )
                if err != nil {
                        return nil, err
                }

                defer func() {
                        h.Registry.HodlUnsubscribeAll(hodlQueue.ChanIn())

                        hodlQueue.Stop()
                }()

                // Take action based on the resolution we received. If the htlc
                // was settled, or a htlc for a known invoice failed we can
                // resolve it directly. If the resolution is nil, the htlc was
                // neither accepted nor failed, so we cannot take action yet.
                switch res := resolution.(type) {
                case *invoices.HtlcFailResolution:
                        // In the case where the htlc failed, but the invoice
                        // was known to the registry, we can directly resolve
                        // the htlc.
                        if res.Outcome != invoices.ResultInvoiceNotFound {
                                return processHtlcResolution(resolution)
                        }

                // If we settled the htlc, we can resolve it.
                case *invoices.HtlcSettleResolution:
                        return processHtlcResolution(resolution)

                // If the resolution is nil, the htlc was neither settled nor
                // failed so we cannot take action at present.
                case nil:

                default:
                        return nil, fmt.Errorf("unknown htlc resolution type: %T",
                                resolution)
                }
        } else {
                // If the HTLC hasn't expired yet, then we may still be able to
                // claim it if we learn of the pre-image, so we'll subscribe to
                // the preimage database to see if it turns up, or the HTLC
                // times out.
                //
                // NOTE: This is done BEFORE opportunistically querying the db,
                // to ensure the preimage can't be delivered between querying
                // and registering for the preimage subscription.
                preimageSubscription, err := h.PreimageDB.SubscribeUpdates(
                        h.htlcSuccessResolver.ShortChanID, &h.htlc,
                        payload, nextHopOnionBlob,
                )
                if err != nil {
                        return nil, err
                }
                defer preimageSubscription.CancelSubscription()

                // With the epochs and preimage subscriptions initialized, we'll
                // query to see if we already know the preimage.
                preimage, ok := h.PreimageDB.LookupPreimage(h.htlc.RHash)
                if ok {
                        // If we do, then this means we can claim the HTLC!
                        // However, we don't know how to ourselves, so we'll
                        // return our inner resolver which has the knowledge to
                        // do so.
                        if err := applyPreimage(preimage); err != nil {
                                return nil, err
                        }

                        return h.htlcSuccessResolver, nil
                }

                witnessUpdates = preimageSubscription.WitnessUpdates
        }

        for {
                select {
                case preimage := <-witnessUpdates:
                        // We received a new preimage, but we need to ignore
                        // all except the preimage we are waiting for.
                        if !preimage.Matches(h.htlc.RHash) {
                                continue
                        }

                        if err := applyPreimage(preimage); err != nil {
                                return nil, err
                        }

                        // We've learned of the preimage and this information
                        // has been added to our inner resolver. We return it so
                        // it can continue contract resolution.
                        return h.htlcSuccessResolver, nil

                case hodlItem := <-hodlChan:
                        htlcResolution := hodlItem.(invoices.HtlcResolution)
                        return processHtlcResolution(htlcResolution)

                case newBlock, ok := <-blockEpochs.Epochs:
                        if !ok {
                                return nil, errResolverShuttingDown
                        }

                        // If this new height expires the HTLC, then this means
                        // we never found out the preimage, so we can mark
                        // resolved and exit.
                        newHeight := uint32(newBlock.Height)
                        if newHeight >= h.htlcExpiry {
                                log.Infof("%T(%v): HTLC has timed out "+
                                        "(expiry=%v, height=%v), abandoning", h,
                                        h.htlcResolution.ClaimOutpoint,
                                        h.htlcExpiry, currentHeight)
                                h.resolved = true

                                if err := h.processFinalHtlcFail(); err != nil {
                                        return nil, err
                                }

                                report := h.report().resolverReport(
                                        nil,
                                        channeldb.ResolverTypeIncomingHtlc,
                                        channeldb.ResolverOutcomeTimeout,
                                )
                                return nil, h.Checkpoint(h, report)
                        }

                case <-h.quit:
                        return nil, errResolverShuttingDown
                }
        }
}

// report returns a report on the resolution state of the contract.
func (h *htlcIncomingContestResolver) report() *ContractReport {
        // No locking needed as these values are read-only.

        finalAmt := h.htlc.Amt.ToSatoshis()
        if h.htlcResolution.SignedSuccessTx != nil {
                finalAmt = btcutil.Amount(
                        h.htlcResolution.SignedSuccessTx.TxOut[0].Value,
                )
        }

        return &ContractReport{
                Outpoint:       h.htlcResolution.ClaimOutpoint,
                Type:           ReportOutputIncomingHtlc,
                Amount:         finalAmt,
                MaturityHeight: h.htlcExpiry,
                LimboBalance:   finalAmt,
                Stage:          1,
        }
}

// Stop signals the resolver to cancel any current resolution processes, and
// suspend.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Stop() {
        close(h.quit)
}

// IsResolved returns true if the stored state in the resolve is fully
// resolved. In this case the target output can be forgotten.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) IsResolved() bool {
        return h.resolved
}

// Encode writes an encoded version of the ContractResolver into the passed
// Writer.
//
// NOTE: Part of the ContractResolver interface.
func (h *htlcIncomingContestResolver) Encode(w io.Writer) error {
        // We'll first write out the one field unique to this resolver.
        if err := binary.Write(w, endian, h.htlcExpiry); err != nil {
                return err
        }

        // Then we'll write out our internal resolver.
        return h.htlcSuccessResolver.Encode(w)
}

// newIncomingContestResolverFromReader attempts to decode an encoded ContractResolver
// from the passed Reader instance, returning an active ContractResolver
// instance.
func newIncomingContestResolverFromReader(r io.Reader, resCfg ResolverConfig) (
        *htlcIncomingContestResolver, error) {

        h := &htlcIncomingContestResolver{}

        // We'll first read the one field unique to this resolver.
        if err := binary.Read(r, endian, &h.htlcExpiry); err != nil {
                return nil, err
        }

        // Then we'll decode our internal resolver.
        successResolver, err := newSuccessResolverFromReader(r, resCfg)
        if err != nil {
                return nil, err
        }
        h.htlcSuccessResolver = successResolver

        return h, nil
}

// Supplement adds additional information to the resolver that is required
// before Resolve() is called.
//
// NOTE: Part of the htlcContractResolver interface.
func (h *htlcIncomingContestResolver) Supplement(htlc channeldb.HTLC) {
        h.htlc = htlc
}

// SupplementDeadline does nothing for an incoming htlc resolver.
//
// NOTE: Part of the htlcContractResolver interface.
func (h *htlcIncomingContestResolver) SupplementDeadline(_ fn.Option[int32]) {
}

// decodePayload (re)decodes the hop payload of a received htlc.
func (h *htlcIncomingContestResolver) decodePayload() (*hop.Payload,
        []byte, error) {

        blindingInfo := hop.ReconstructBlindingInfo{
                IncomingAmt:    h.htlc.Amt,
                IncomingExpiry: h.htlc.RefundTimeout,
                BlindingKey:    h.htlc.BlindingPoint,
        }

        onionReader := bytes.NewReader(h.htlc.OnionBlob[:])
        iterator, err := h.OnionProcessor.ReconstructHopIterator(
                onionReader, h.htlc.RHash[:], blindingInfo,
        )
        if err != nil {
                return nil, nil, err
        }

        payload, _, err := iterator.HopPayload()
        if err != nil {
                return nil, nil, err
        }

        // Transform onion blob for the next hop.
        var onionBlob [lnwire.OnionPacketSize]byte
        buf := bytes.NewBuffer(onionBlob[0:0])
        err = iterator.EncodeNextHop(buf)
        if err != nil {
                return nil, nil, err
        }

        return payload, onionBlob[:], nil
}

// A compile time assertion to ensure htlcIncomingContestResolver meets the
// ContractResolver interface.
var _ htlcContractResolver = (*htlcIncomingContestResolver)(nil)

1	package contractcourt
2
3	import (
4	"bytes"
5	"encoding/binary"
6	"errors"
7	"fmt"
8	"io"
9
10	"github.com/btcsuite/btcd/btcutil"
11	"github.com/btcsuite/btcd/txscript"
12	"github.com/lightningnetwork/lnd/channeldb"
13	"github.com/lightningnetwork/lnd/channeldb/models"
14	"github.com/lightningnetwork/lnd/fn"
15	"github.com/lightningnetwork/lnd/htlcswitch/hop"
16	"github.com/lightningnetwork/lnd/invoices"
17	"github.com/lightningnetwork/lnd/lntypes"
18	"github.com/lightningnetwork/lnd/lnwallet"
19	"github.com/lightningnetwork/lnd/lnwire"
20	"github.com/lightningnetwork/lnd/queue"
21	)
22
23	// htlcIncomingContestResolver is a ContractResolver that's able to resolve an
24	// incoming HTLC that is still contested. An HTLC is still contested, if at the
25	// time of commitment broadcast, we don't know of the preimage for it yet, and
26	// it hasn't expired. In this case, we can resolve the HTLC if we learn of the
27	// preimage, otherwise the remote party will sweep it after it expires.
28	//
29	// TODO(roasbeef): just embed the other resolver?
30	type htlcIncomingContestResolver struct {
31	// htlcExpiry is the absolute expiry of this incoming HTLC. We use this
32	// value to determine if we can exit early as if the HTLC times out,
33	// before we learn of the preimage then we can't claim it on chain
34	// successfully.
35	htlcExpiry uint32
36
37	// htlcSuccessResolver is the inner resolver that may be utilized if we
38	// learn of the preimage.
39	*htlcSuccessResolver
40	}
41
42	// newIncomingContestResolver instantiates a new incoming htlc contest resolver.
43	func newIncomingContestResolver(
44	res lnwallet.IncomingHtlcResolution, broadcastHeight uint32,
45	htlc channeldb.HTLC, resCfg ResolverConfig) *htlcIncomingContestResolver {	3✔
46		3✔
47	success := newSuccessResolver(	3✔
48	res, broadcastHeight, htlc, resCfg,	3✔
49	)	3✔
50		3✔
51	return &htlcIncomingContestResolver{	3✔
52	htlcExpiry: htlc.RefundTimeout,	3✔
53	htlcSuccessResolver: success,	3✔
54	}	3✔
55	}	3✔
56
57	func (h *htlcIncomingContestResolver) processFinalHtlcFail() error {	8✔
58	// Mark the htlc as final failed.	8✔
59	err := h.ChainArbitratorConfig.PutFinalHtlcOutcome(	8✔
60	h.ChannelArbitratorConfig.ShortChanID, h.htlc.HtlcIndex, false,	8✔
61	)	8✔
62	if err != nil {	8✔
63	return err	×
64	}	×
65
66	// Send notification.
67	h.ChainArbitratorConfig.HtlcNotifier.NotifyFinalHtlcEvent(	8✔
68	models.CircuitKey{	8✔
69	ChanID: h.ShortChanID,	8✔
70	HtlcID: h.htlc.HtlcIndex,	8✔
71	},	8✔
72	channeldb.FinalHtlcInfo{	8✔
73	Settled: false,	8✔
74	Offchain: false,	8✔
75	},	8✔
76	)	8✔
77		8✔
78	return nil	8✔
79	}
80
81	// Resolve attempts to resolve this contract. As we don't yet know of the
82	// preimage for the contract, we'll wait for one of two things to happen:
83	//
84	// 1. We learn of the preimage! In this case, we can sweep the HTLC incoming
85	// and ensure that if this was a multi-hop HTLC we are made whole. In this
86	// case, an additional ContractResolver will be returned to finish the
87	// job.
88	//
89	// 2. The HTLC expires. If this happens, then the contract is fully resolved
90	// as we have no remaining actions left at our disposal.
91	//
92	// NOTE: Part of the ContractResolver interface.
93	func (h *htlcIncomingContestResolver) Resolve(
94	_ bool) (ContractResolver, error) {	12✔
95		12✔
96	// If we're already full resolved, then we don't have anything further	12✔
97	// to do.	12✔
98	if h.resolved {	12✔
99	return nil, nil	×
100	}	×
101
102	// If the HTLC has custom records, then for now we'll pause resolution.
103	//
104	// TODO(roasbeef): Implement resolving HTLCs with custom records
105	// (follow-up PR).
106	if len(h.htlc.CustomRecords) != 0 {	12✔
NEW 107	select { //nolint:gosimple	×
NEW 108	case <-h.quit:	×
NEW 109	return nil, errResolverShuttingDown	×
110	}
111	}
112
113	// First try to parse the payload. If that fails, we can stop resolution
114	// now.
115	payload, nextHopOnionBlob, err := h.decodePayload()	12✔
116	if err != nil {	12✔
117	log.Debugf("ChannelArbitrator(%v): cannot decode payload of "+	×
118	"htlc %v", h.ChanPoint, h.HtlcPoint())	×
119		×
120	// If we've locked in an htlc with an invalid payload on our	×
121	// commitment tx, we don't need to resolve it. The other party	×
122	// will time it out and get their funds back. This situation	×
123	// can present itself when we crash before processRemoteAdds in	×
124	// the link has ran.	×
125	h.resolved = true	×
126		×
127	if err := h.processFinalHtlcFail(); err != nil {	×
128	return nil, err	×
129	}	×
130
131	// We write a report to disk that indicates we could not decode
132	// the htlc.
133	resReport := h.report().resolverReport(	×
134	nil, channeldb.ResolverTypeIncomingHtlc,	×
135	channeldb.ResolverOutcomeAbandoned,	×
136	)	×
137	return nil, h.PutResolverReport(nil, resReport)	×
138	}
139
140	// Register for block epochs. After registration, the current height
141	// will be sent on the channel immediately.
142	blockEpochs, err := h.Notifier.RegisterBlockEpochNtfn(nil)	12✔
143	if err != nil {	12✔
144	return nil, err	×
145	}	×
146	defer blockEpochs.Cancel()	12✔
147		12✔
148	var currentHeight int32	12✔
149	select {	12✔
150	case newBlock, ok := <-blockEpochs.Epochs:	12✔
151	if !ok {	12✔
152	return nil, errResolverShuttingDown	×
153	}	×
154	currentHeight = newBlock.Height	12✔
155	case <-h.quit:	×
156	return nil, errResolverShuttingDown	×
157	}
158
159	log.Debugf("%T(%v): Resolving incoming HTLC(expiry=%v, height=%v)", h,	12✔
160	h.htlcResolution.ClaimOutpoint, h.htlcExpiry, currentHeight)	12✔
161		12✔
162	// We'll first check if this HTLC has been timed out, if so, we can	12✔
163	// return now and mark ourselves as resolved. If we're past the point of	12✔
164	// expiry of the HTLC, then at this point the sender can sweep it, so	12✔
165	// we'll end our lifetime. Here we deliberately forego the chance that	12✔
166	// the sender doesn't sweep and we already have or will learn the	12✔
167	// preimage. Otherwise the resolver could potentially stay active	12✔
168	// indefinitely and the channel will never close properly.	12✔
169	if uint32(currentHeight) >= h.htlcExpiry {	16✔
170	// TODO(roasbeef): should also somehow check if outgoing is	4✔
171	// resolved or not	4✔
172	// * may need to hook into the circuit map	4✔
173	// * can't timeout before the outgoing has been	4✔
174		4✔
175	log.Infof("%T(%v): HTLC has timed out (expiry=%v, height=%v), "+	4✔
176	"abandoning", h, h.htlcResolution.ClaimOutpoint,	4✔
177	h.htlcExpiry, currentHeight)	4✔
178	h.resolved = true	4✔
179		4✔
180	if err := h.processFinalHtlcFail(); err != nil {	4✔
181	return nil, err	×
182	}	×
183
184	// Finally, get our report and checkpoint our resolver with a
185	// timeout outcome report.
186	report := h.report().resolverReport(	4✔
187	nil, channeldb.ResolverTypeIncomingHtlc,	4✔
188	channeldb.ResolverOutcomeTimeout,	4✔
189	)	4✔
190	return nil, h.Checkpoint(h, report)	4✔
191	}
192
193	// applyPreimage is a helper function that will populate our internal
194	// resolver with the preimage we learn of. This should be called once
195	// the preimage is revealed so the inner resolver can properly complete
196	// its duties. The error return value indicates whether the preimage
197	// was properly applied.
198	applyPreimage := func(preimage lntypes.Preimage) error {	18✔
199	// Sanity check to see if this preimage matches our htlc. At	7✔
200	// this point it should never happen that it does not match.	7✔
201	if !preimage.Matches(h.htlc.RHash) {	7✔
202	return errors.New("preimage does not match hash")	×
203	}	×
204
205	// Update htlcResolution with the matching preimage.
206	h.htlcResolution.Preimage = preimage	7✔
207		7✔
208	log.Infof("%T(%v): applied preimage=%v", h,	7✔
209	h.htlcResolution.ClaimOutpoint, preimage)	7✔
210		7✔
211	isSecondLevel := h.htlcResolution.SignedSuccessTx != nil	7✔
212		7✔
213	// If we didn't have to go to the second level to claim (this	7✔
214	// is the remote commitment transaction), then we don't need to	7✔
215	// modify our canned witness.	7✔
216	if !isSecondLevel {	14✔
217	return nil	7✔
218	}	7✔
219
220	isTaproot := txscript.IsPayToTaproot(	3✔
221	h.htlcResolution.SignedSuccessTx.TxOut[0].PkScript,	3✔
222	)	3✔
223		3✔
224	// If this is our commitment transaction, then we'll need to	3✔
225	// populate the witness for the second-level HTLC transaction.	3✔
226	switch {	3✔
227	// For taproot channels, the witness for sweeping with success
228	// looks like:
229	// - <sender sig> <receiver sig> <preimage> <success_script>
230	// <control_block>
231	//
232	// So we'll insert it at the 3rd index of the witness.
233	case isTaproot:	3✔
234	//nolint:lll	3✔
235	h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[2] = preimage[:]	3✔
236
237	// Within the witness for the success transaction, the
238	// preimage is the 4th element as it looks like:
239	//
240	// * <0> <sender sig> <recvr sig> <preimage> <witness script>
241	//
242	// We'll populate it within the witness, as since this
243	// was a "contest" resolver, we didn't yet know of the
244	// preimage.
245	case !isTaproot:	3✔
246	h.htlcResolution.SignedSuccessTx.TxIn[0].Witness[3] = preimage[:]	3✔
247	}
248
249	return nil	3✔
250	}
251
252	// Define a closure to process htlc resolutions either directly or
253	// triggered by future notifications.
254	processHtlcResolution := func(e invoices.HtlcResolution) (	11✔
255	ContractResolver, error) {	18✔
256		7✔
257	// Take action based on the type of resolution we have	7✔
258	// received.	7✔
259	switch resolution := e.(type) {	7✔
260	// If the htlc resolution was a settle, apply the
261	// preimage and return a success resolver.
262	case *invoices.HtlcSettleResolution:	5✔
263	err := applyPreimage(resolution.Preimage)	5✔
264	if err != nil {	5✔
265	return nil, err	×
266	}	×
267
268	return h.htlcSuccessResolver, nil	5✔
269
270	// If the htlc was failed, mark the htlc as
271	// resolved.
272	case *invoices.HtlcFailResolution:	5✔
273	log.Infof("%T(%v): Exit hop HTLC canceled "+	5✔
274	"(expiry=%v, height=%v), abandoning", h,	5✔
275	h.htlcResolution.ClaimOutpoint,	5✔
276	h.htlcExpiry, currentHeight)	5✔
277		5✔
278	h.resolved = true	5✔
279		5✔
280	if err := h.processFinalHtlcFail(); err != nil {	5✔
281	return nil, err	×
282	}	×
283
284	// Checkpoint our resolver with an abandoned outcome
285	// because we take no further action on this htlc.
286	report := h.report().resolverReport(	5✔
287	nil, channeldb.ResolverTypeIncomingHtlc,	5✔
288	channeldb.ResolverOutcomeAbandoned,	5✔
289	)	5✔
290	return nil, h.Checkpoint(h, report)	5✔
291
292	// Error if the resolution type is unknown, we are only
293	// expecting settles and fails.
294	default:	×
295	return nil, fmt.Errorf("unknown resolution"+	×
296	" type: %v", e)	×
297	}
298	}
299
300	var (	11✔
301	hodlChan <-chan interface{}	11✔
302	witnessUpdates <-chan lntypes.Preimage	11✔
303	)	11✔
304	if payload.FwdInfo.NextHop == hop.Exit {	19✔
305	// Create a buffered hodl chan to prevent deadlock.	8✔
306	hodlQueue := queue.NewConcurrentQueue(10)	8✔
307	hodlQueue.Start()	8✔
308		8✔
309	hodlChan = hodlQueue.ChanOut()	8✔
310		8✔
311	// Notify registry that we are potentially resolving as an exit	8✔
312	// hop on-chain. If this HTLC indeed pays to an existing	8✔
313	// invoice, the invoice registry will tell us what to do with	8✔
314	// the HTLC. This is identical to HTLC resolution in the link.	8✔
315	circuitKey := models.CircuitKey{	8✔
316	ChanID: h.ShortChanID,	8✔
317	HtlcID: h.htlc.HtlcIndex,	8✔
318	}	8✔
319		8✔
320	resolution, err := h.Registry.NotifyExitHopHtlc(	8✔
321	h.htlc.RHash, h.htlc.Amt, h.htlcExpiry, currentHeight,	8✔
322	circuitKey, hodlQueue.ChanIn(), nil, payload,	8✔
323	)	8✔
324	if err != nil {	8✔
325	return nil, err	×
326	}	×
327
328	defer func() {	16✔
329	h.Registry.HodlUnsubscribeAll(hodlQueue.ChanIn())	8✔
330		8✔
331	hodlQueue.Stop()	8✔
332	}()	8✔
333
334	// Take action based on the resolution we received. If the htlc
335	// was settled, or a htlc for a known invoice failed we can
336	// resolve it directly. If the resolution is nil, the htlc was
337	// neither accepted nor failed, so we cannot take action yet.
338	switch res := resolution.(type) {	8✔
339	case *invoices.HtlcFailResolution:	4✔
340	// In the case where the htlc failed, but the invoice	4✔
341	// was known to the registry, we can directly resolve	4✔
342	// the htlc.	4✔
343	if res.Outcome != invoices.ResultInvoiceNotFound {	5✔
344	return processHtlcResolution(resolution)	1✔
345	}	1✔
346
347	// If we settled the htlc, we can resolve it.
348	case *invoices.HtlcSettleResolution:	4✔
349	return processHtlcResolution(resolution)	4✔
350
351	// If the resolution is nil, the htlc was neither settled nor
352	// failed so we cannot take action at present.
353	case nil:	6✔
354
355	default:	×
356	return nil, fmt.Errorf("unknown htlc resolution type: %T",	×
357	resolution)	×
358	}
359	} else {	6✔
360	// If the HTLC hasn't expired yet, then we may still be able to	6✔
361	// claim it if we learn of the pre-image, so we'll subscribe to	6✔
362	// the preimage database to see if it turns up, or the HTLC	6✔
363	// times out.	6✔
364	//	6✔
365	// NOTE: This is done BEFORE opportunistically querying the db,	6✔
366	// to ensure the preimage can't be delivered between querying	6✔
367	// and registering for the preimage subscription.	6✔
368	preimageSubscription, err := h.PreimageDB.SubscribeUpdates(	6✔
369	h.htlcSuccessResolver.ShortChanID, &h.htlc,	6✔
370	payload, nextHopOnionBlob,	6✔
371	)	6✔
372	if err != nil {	6✔
373	return nil, err	×
374	}	×
375	defer preimageSubscription.CancelSubscription()	6✔
376		6✔
377	// With the epochs and preimage subscriptions initialized, we'll	6✔
378	// query to see if we already know the preimage.	6✔
379	preimage, ok := h.PreimageDB.LookupPreimage(h.htlc.RHash)	6✔
380	if ok {	10✔
381	// If we do, then this means we can claim the HTLC!	4✔
382	// However, we don't know how to ourselves, so we'll	4✔
383	// return our inner resolver which has the knowledge to	4✔
384	// do so.	4✔
385	if err := applyPreimage(preimage); err != nil {	4✔
386	return nil, err	×
387	}	×
388
389	return h.htlcSuccessResolver, nil	4✔
390	}
391
392	witnessUpdates = preimageSubscription.WitnessUpdates	5✔
393	}
394
395	for {	17✔
396	select {	9✔
397	case preimage := <-witnessUpdates:	4✔
398	// We received a new preimage, but we need to ignore	4✔
399	// all except the preimage we are waiting for.	4✔
400	if !preimage.Matches(h.htlc.RHash) {	7✔
401	continue	3✔
402	}
403
404	if err := applyPreimage(preimage); err != nil {	4✔
405	return nil, err	×
406	}	×
407
408	// We've learned of the preimage and this information
409	// has been added to our inner resolver. We return it so
410	// it can continue contract resolution.
411	return h.htlcSuccessResolver, nil	4✔
412
413	case hodlItem := <-hodlChan:	5✔
414	htlcResolution := hodlItem.(invoices.HtlcResolution)	5✔
415	return processHtlcResolution(htlcResolution)	5✔
416
417	case newBlock, ok := <-blockEpochs.Epochs:	6✔
418	if !ok {	6✔
419	return nil, errResolverShuttingDown	×
420	}	×
421
422	// If this new height expires the HTLC, then this means
423	// we never found out the preimage, so we can mark
424	// resolved and exit.
425	newHeight := uint32(newBlock.Height)	6✔
426	if newHeight >= h.htlcExpiry {	11✔
427	log.Infof("%T(%v): HTLC has timed out "+	5✔
428	"(expiry=%v, height=%v), abandoning", h,	5✔
429	h.htlcResolution.ClaimOutpoint,	5✔
430	h.htlcExpiry, currentHeight)	5✔
431	h.resolved = true	5✔
432		5✔
433	if err := h.processFinalHtlcFail(); err != nil {	5✔
434	return nil, err	×
435	}	×
436
437	report := h.report().resolverReport(	5✔
438	nil,	5✔
439	channeldb.ResolverTypeIncomingHtlc,	5✔
440	channeldb.ResolverOutcomeTimeout,	5✔
441	)	5✔
442	return nil, h.Checkpoint(h, report)	5✔
443	}
444
445	case <-h.quit:	3✔
446	return nil, errResolverShuttingDown	3✔
447	}
448	}
449	}
450
451	// report returns a report on the resolution state of the contract.
452	func (h htlcIncomingContestResolver) report() ContractReport {	8✔
453	// No locking needed as these values are read-only.	8✔
454		8✔
455	finalAmt := h.htlc.Amt.ToSatoshis()	8✔
456	if h.htlcResolution.SignedSuccessTx != nil {	11✔
457	finalAmt = btcutil.Amount(	3✔
458	h.htlcResolution.SignedSuccessTx.TxOut[0].Value,	3✔
459	)	3✔
460	}	3✔
461
462	return &ContractReport{	8✔
463	Outpoint: h.htlcResolution.ClaimOutpoint,	8✔
464	Type: ReportOutputIncomingHtlc,	8✔
465	Amount: finalAmt,	8✔
466	MaturityHeight: h.htlcExpiry,	8✔
467	LimboBalance: finalAmt,	8✔
468	Stage: 1,	8✔
469	}	8✔
470	}
471
472	// Stop signals the resolver to cancel any current resolution processes, and
473	// suspend.
474	//
475	// NOTE: Part of the ContractResolver interface.
476	func (h *htlcIncomingContestResolver) Stop() {	3✔
477	close(h.quit)	3✔
478	}	3✔
479
480	// IsResolved returns true if the stored state in the resolve is fully
481	// resolved. In this case the target output can be forgotten.
482	//
483	// NOTE: Part of the ContractResolver interface.
484	func (h *htlcIncomingContestResolver) IsResolved() bool {	3✔
485	return h.resolved	3✔
486	}	3✔
487
488	// Encode writes an encoded version of the ContractResolver into the passed
489	// Writer.
490	//
491	// NOTE: Part of the ContractResolver interface.
492	func (h *htlcIncomingContestResolver) Encode(w io.Writer) error {	4✔
493	// We'll first write out the one field unique to this resolver.	4✔
494	if err := binary.Write(w, endian, h.htlcExpiry); err != nil {	4✔
495	return err	×
496	}	×
497
498	// Then we'll write out our internal resolver.
499	return h.htlcSuccessResolver.Encode(w)	4✔
500	}
501
502	// newIncomingContestResolverFromReader attempts to decode an encoded ContractResolver
503	// from the passed Reader instance, returning an active ContractResolver
504	// instance.
505	func newIncomingContestResolverFromReader(r io.Reader, resCfg ResolverConfig) (
506	*htlcIncomingContestResolver, error) {	4✔
507		4✔
508	h := &htlcIncomingContestResolver{}	4✔
509		4✔
510	// We'll first read the one field unique to this resolver.	4✔
511	if err := binary.Read(r, endian, &h.htlcExpiry); err != nil {	4✔
512	return nil, err	×
513	}	×
514
515	// Then we'll decode our internal resolver.
516	successResolver, err := newSuccessResolverFromReader(r, resCfg)	4✔
517	if err != nil {	4✔
518	return nil, err	×
519	}	×
520	h.htlcSuccessResolver = successResolver	4✔
521		4✔
522	return h, nil	4✔
523	}
524
525	// Supplement adds additional information to the resolver that is required
526	// before Resolve() is called.
527	//
528	// NOTE: Part of the htlcContractResolver interface.
529	func (h *htlcIncomingContestResolver) Supplement(htlc channeldb.HTLC) {	3✔
530	h.htlc = htlc	3✔
531	}	3✔
532
533	// SupplementDeadline does nothing for an incoming htlc resolver.
534	//
535	// NOTE: Part of the htlcContractResolver interface.
536	func (h *htlcIncomingContestResolver) SupplementDeadline(_ fn.Option[int32]) {	×
537	}	×
538
539	// decodePayload (re)decodes the hop payload of a received htlc.
540	func (h htlcIncomingContestResolver) decodePayload() (hop.Payload,
541	[]byte, error) {	12✔
542		12✔
543	blindingInfo := hop.ReconstructBlindingInfo{	12✔
544	IncomingAmt: h.htlc.Amt,	12✔
545	IncomingExpiry: h.htlc.RefundTimeout,	12✔
546	BlindingKey: h.htlc.BlindingPoint,	12✔
547	}	12✔
548		12✔
549	onionReader := bytes.NewReader(h.htlc.OnionBlob[:])	12✔
550	iterator, err := h.OnionProcessor.ReconstructHopIterator(	12✔
551	onionReader, h.htlc.RHash[:], blindingInfo,	12✔
552	)	12✔
553	if err != nil {	12✔
554	return nil, nil, err	×
555	}	×
556
557	payload, _, err := iterator.HopPayload()	12✔
558	if err != nil {	12✔
559	return nil, nil, err	×
560	}	×
561
562	// Transform onion blob for the next hop.
563	var onionBlob [lnwire.OnionPacketSize]byte	12✔
564	buf := bytes.NewBuffer(onionBlob[0:0])	12✔
565	err = iterator.EncodeNextHop(buf)	12✔
566	if err != nil {	12✔
567	return nil, nil, err	×
568	}	×
569
570	return payload, onionBlob[:], nil	12✔
571	}
572
573	// A compile time assertion to ensure htlcIncomingContestResolver meets the
574	// ContractResolver interface.
575	var _ htlcContractResolver = (*htlcIncomingContestResolver)(nil)

lightningnetwork / lnd / 11166428937

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