package lnwallet import ( "bytes" "container/list" "crypto/sha256" "fmt" "runtime" "sort" "sync" "sync/atomic" "github.com/davecgh/go-spew/spew" "github.com/lightningnetwork/lnd/chainntnfs" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwire" "github.com/roasbeef/btcd/blockchain" "github.com/roasbeef/btcd/chaincfg/chainhash" "github.com/roasbeef/btcd/btcec" "github.com/roasbeef/btcd/txscript" "github.com/roasbeef/btcd/wire" "github.com/roasbeef/btcutil" "github.com/roasbeef/btcutil/txsort" ) var zeroHash chainhash.Hash var ( // ErrChanClosing is returned when a caller attempts to close a channel // that has already been closed or is in the process of being closed. ErrChanClosing = fmt.Errorf("channel is being closed, operation disallowed") // ErrNoWindow is returned when revocation window is exausted. ErrNoWindow = fmt.Errorf("unable to sign new commitment, the current" + " revocation window is exhausted") // ErrMaxWeightCost is returned when the cost/weight (see segwit) // exceeds the widely used maximum allowed policy weight limit. In this // case the commitment transaction can't be propagated through the // network. ErrMaxWeightCost = fmt.Errorf("commitment transaction exceed max " + "available cost") // ErrMaxHTLCNumber is returned when a proposed HTLC would exceed the // maximum number of allowed HTLC's if committed in a state transition ErrMaxHTLCNumber = fmt.Errorf("commitment transaction exceed max " + "htlc number") // ErrInsufficientBalance is returned when a proposed HTLC would // exceed the available balance. ErrInsufficientBalance = fmt.Errorf("insufficient local balance") // ErrCannotSyncCommitChains is returned if, upon receiving a ChanSync // message, the state machine deems that is unable to properly // synchronize states with the remote peer. ErrCannotSyncCommitChains = fmt.Errorf("unable to sync commit chains") // ErrInvalidLastCommitSecret is returned in the case that the // commitment secret sent by the remote party in their // ChannelReestablish message doesn't match the last secret we sent. ErrInvalidLastCommitSecret = fmt.Errorf("commit secret is incorrect") // ErrCommitSyncDataLoss is returned in the case that we receive a // valid commit secret within the ChannelReestablish message from the // remote node AND they advertise a RemoteCommitTailHeight higher than // our current known height. ErrCommitSyncDataLoss = fmt.Errorf("possible commitment state data " + "loss") ) // channelState is an enum like type which represents the current state of a // particular channel. // TODO(roasbeef): actually update state type channelState uint8 const ( // channelPending indicates this channel is still going through the // funding workflow, and isn't yet open. channelPending channelState = iota // channelOpen represents an open, active channel capable of // sending/receiving HTLCs. channelOpen // channelClosing represents a channel which is in the process of being // closed. channelClosing // channelClosed represents a channel which has been fully closed. Note // that before a channel can be closed, ALL pending HTLCs must be // settled/removed. channelClosed // channelDispute indicates that an un-cooperative closure has been // detected within the channel. channelDispute // channelPendingPayment indicates that there a currently outstanding // HTLCs within the channel. channelPendingPayment ) // PaymentHash represents the sha256 of a random value. This hash is used to // uniquely track incoming/outgoing payments within this channel, as well as // payments requested by the wallet/daemon. type PaymentHash [32]byte // updateType is the exact type of an entry within the shared HTLC log. type updateType uint8 const ( // Add is an update type that adds a new HTLC entry into the log. // Either side can add a new pending HTLC by adding a new Add entry // into their update log. Add updateType = iota // Fail is an update type which removes a prior HTLC entry from the // log. Adding a Fail entry to ones log will modify the _remote_ // parties update log once a new commitment view has been evaluated // which contains the Fail entry. Fail // MalformedFail is an update type which removes a prior HTLC entry // from the log. Adding a MalformedFail entry to ones log will modify // the _remote_ parties update log once a new commitment view has been // evaluated which contains the MalformedFail entry. The difference // from Fail type lie in // the different data we have to store. MalformedFail // Settle is an update type which settles a prior HTLC crediting the // balance of the receiving node. Adding a Settle entry to a log will // result in the settle entry being removed on the log as well as the // original add entry from the remote party's log after the next state // transition. Settle ) // String returns a human readable string that uniquely identifies the target // update type. func (u updateType) String() string { switch u { case Add: return "Add" case Fail: return "Fail" case MalformedFail: return "MalformedFail" case Settle: return "Settle" default: return "" } } // PaymentDescriptor represents a commitment state update which either adds, // settles, or removes an HTLC. PaymentDescriptors encapsulate all necessary // metadata w.r.t to an HTLC, and additional data pairing a settle message to // the original added HTLC. // // TODO(roasbeef): LogEntry interface?? // * need to separate attrs for cancel/add/settle type PaymentDescriptor struct { // RHash is the payment hash for this HTLC. The HTLC can be settled iff // the preimage to this hash is presented. RHash PaymentHash // RPreimage is the preimage that settles the HTLC pointed to within the // log by the ParentIndex. RPreimage PaymentHash // Timeout is the absolute timeout in blocks, after which this HTLC // expires. Timeout uint32 // Amount is the HTLC amount in milli-satoshis. Amount lnwire.MilliSatoshi // LogIndex is the log entry number that his HTLC update has within the // log. Depending on if IsIncoming is true, this is either an entry the // remote party added, or one that we added locally. LogIndex uint64 // HtlcIndex is the index within the main update log for this HTLC. // Entries within the log of type Add will have this field populated, // as other entries will point to the entry via this counter. // // NOTE: This field will only be populate if EntryType is Add. HtlcIndex uint64 // ParentIndex is the HTLC index of the entry that this update settles or // times out. // // NOTE: This field will only be populate if EntryType is Fail or // Settle. ParentIndex uint64 // localOutputIndex is the output index of this HTLc output in the // commitment transaction of the local node. // // NOTE: If the output is dust from the PoV of the local commitment // chain, then this value will be -1. localOutputIndex int32 // remoteOutputIndex is the output index of this HTLC output in the // commitment transaction of the remote node. // // NOTE: If the output is dust from the PoV of the remote commitment // chain, then this value will be -1. remoteOutputIndex int32 // sig is the signature for the second-level HTLC transaction that // spends the version of this HTLC on the commitment transaction of the // local node. This signature is generated by the remote node and // stored by the local node in the case that local node needs to // broadcast their commitment transaction. sig *btcec.Signature // addCommitHeight[Remote|Local] encodes the height of the commitment // which included this HTLC on either the remote or local commitment // chain. This value is used to determine when an HTLC is fully // "locked-in". addCommitHeightRemote uint64 addCommitHeightLocal uint64 // removeCommitHeight[Remote|Local] encodes the height of the // commitment which removed the parent pointer of this // PaymentDescriptor either due to a timeout or a settle. Once both // these heights are below the tail of both chains, the log entries can // safely be removed. removeCommitHeightRemote uint64 removeCommitHeightLocal uint64 // OnionBlob is an opaque blob which is used to complete multi-hop // routing. // // NOTE: Populated only on add payment descriptor entry types. OnionBlob []byte // ShaOnionBlob is a sha of the onion blob. // // NOTE: Populated only in payment descriptor with MalfromedFail type. ShaOnionBlob [sha256.Size]byte // FailReason stores the reason why a particular payment was cancelled. // // NOTE: Populate only in fail payment descriptor entry types. FailReason []byte // FailCode stores the code why a particular payment was cancelled. // // NOTE: Populated only in payment descriptor with MalfromedFail type. FailCode lnwire.FailCode // [our|their|]PkScript are the raw public key scripts that encodes the // redemption rules for this particular HTLC. These fields will only be // populated iff the EntryType of this PaymentDescriptor is Add. // ourPkScript is the ourPkScript from the context of our local // commitment chain. theirPkScript is the latest pkScript from the // context of the remote commitment chain. // // NOTE: These values may change within the logs themselves, however, // they'll stay consistent within the commitment chain entries // themselves. ourPkScript []byte ourWitnessScript []byte theirPkScript []byte theirWitnessScript []byte // EntryType denotes the exact type of the PaymentDescriptor. In the // case of a Timeout, or Settle type, then the Parent field will point // into the log to the HTLC being modified. EntryType updateType // isForwarded denotes if an incoming HTLC has been forwarded to any // possible upstream peers in the route. isForwarded bool } // commitment represents a commitment to a new state within an active channel. // New commitments can be initiated by either side. Commitments are ordered // into a commitment chain, with one existing for both parties. Each side can // independently extend the other side's commitment chain, up to a certain // "revocation window", which once reached, disallows new commitments until // the local nodes receives the revocation for the remote node's chain tail. type commitment struct { // height represents the commitment height of this commitment, or the // update number of this commitment. height uint64 // isOurs indicates whether this is the local or remote node's version // of the commitment. isOurs bool // [our|their]MessageIndex are indexes into the HTLC log, up to which // this commitment transaction includes. These indexes allow both sides // to independently, and concurrent send create new commitments. Each // new commitment sent to the remote party includes an index in the // shared log which details which of their updates we're including in // this new commitment. ourMessageIndex uint64 theirMessageIndex uint64 // [our|their]HtlcIndex are the current running counters for the HTLC's // offered by either party. This value is incremented each time a party // offers a new HTLC. The log update methods that consume HTLC's will // reference these counters, rather than the running cumulative message // counters. ourHtlcIndex uint64 theirHtlcIndex uint64 // txn is the commitment transaction generated by including any HTLC // updates whose index are below the two indexes listed above. If this // commitment is being added to the remote chain, then this txn is // their version of the commitment transactions. If the local commit // chain is being modified, the opposite is true. txn *wire.MsgTx // sig is a signature for the above commitment transaction. sig []byte // [our|their]Balance represents the settled balances at this point // within the commitment chain. This balance is computed by properly // evaluating all the add/remove/settle log entries before the listed // indexes. ourBalance lnwire.MilliSatoshi theirBalance lnwire.MilliSatoshi // fee is the amount that will be paid as fees for this commitment // transaction. The fee is recorded here so that it can be added back // and recalculated for each new update to the channel state. fee btcutil.Amount // feePerKw is the fee per kw used to calculate this commitment // transaction's fee. feePerKw btcutil.Amount // dustLimit is the limit on the commitment transaction such that no // output values should be below this amount. dustLimit btcutil.Amount // outgoingHTLCs is a slice of all the outgoing HTLC's (from our PoV) // on this commitment transaction. outgoingHTLCs []PaymentDescriptor // incomingHTLCs is a slice of all the incoming HTLC's (from our PoV) // on this commitment transaction. incomingHTLCs []PaymentDescriptor // [outgoing|incoming]HTLCIndex is an index that maps an output index // on the commitment transaction to the payment descriptor that // represents the HTLC output. // // NOTE: that these fields are only populated if this commitment state // belongs to the local node. These maps are used when validating any // HTLC signatures which are part of the local commitment state. We use // this map in order to locate the details needed to validate an HTLC // signature while iterating of the outputs in the local commitment // view. outgoingHTLCIndex map[int32]*PaymentDescriptor incomingHTLCIndex map[int32]*PaymentDescriptor } // locateOutputIndex is a small helper function to locate the output index of a // particular HTLC within the current commitment transaction. The duplicate map // massed in is to be retained for each output within the commitment // transition. This ensures that we don't assign multiple HTLC's to the same // index within the commitment transaction. func locateOutputIndex(p *PaymentDescriptor, tx *wire.MsgTx, ourCommit bool, dups map[PaymentHash][]int32) (int32, error) { // Checks to see if element (e) exists in slice (s). contains := func(s []int32, e int32) bool { for _, a := range s { if a == e { return true } } return false } // If this their commitment transaction, we'll be trying to locate // their pkScripts, otherwise we'll be looking for ours. This is // required as the commitment states are asymmetric in order to ascribe // blame in the case of a contract breach. pkScript := p.theirPkScript if ourCommit { pkScript = p.ourPkScript } for i, txOut := range tx.TxOut { if bytes.Equal(txOut.PkScript, pkScript) && txOut.Value == int64(p.Amount.ToSatoshis()) { // If this payment hash and index has already been // found, then we'll continue in order to avoid any // duplicate indexes. if contains(dups[p.RHash], int32(i)) { continue } idx := int32(i) dups[p.RHash] = append(dups[p.RHash], idx) return idx, nil } } return 0, fmt.Errorf("unable to find htlc: script=%x, value=%v", pkScript, p.Amount) } // populateHtlcIndexes modifies the set of HTLC's locked-into the target view // to have full indexing information populated. This information is required as // we need to keep track of the indexes of each HTLC in order to properly write // the current state to disk, and also to locate the PaymentDescriptor // corresponding to HTLC outputs in the commitment transaction. func (c *commitment) populateHtlcIndexes() error { // First, we'll set up some state to allow us to locate the output // index of the all the HTLC's within the commitment transaction. We // must keep this index so we can validate the HTLC signatures sent to // us. dups := make(map[PaymentHash][]int32) c.outgoingHTLCIndex = make(map[int32]*PaymentDescriptor) c.incomingHTLCIndex = make(map[int32]*PaymentDescriptor) // populateIndex is a helper function that populates the necessary // indexes within the commitment view for a particular HTLC. populateIndex := func(htlc *PaymentDescriptor, incoming bool) error { isDust := htlcIsDust(incoming, c.isOurs, c.feePerKw, htlc.Amount.ToSatoshis(), c.dustLimit) var err error switch { // If this is our commitment transaction, and this is a dust // output then we mark it as such using a -1 index. case c.isOurs && isDust: htlc.localOutputIndex = -1 // If this is the commitment transaction of the remote party, // and this is a dust output then we mark it as such using a -1 // index. case !c.isOurs && isDust: htlc.remoteOutputIndex = -1 // If this is our commitment transaction, then we'll need to // locate the output and the index so we can verify an HTLC // signatures. case c.isOurs: htlc.localOutputIndex, err = locateOutputIndex( htlc, c.txn, c.isOurs, dups, ) if err != nil { return err } // As this is our commitment transactions, we need to // keep track of the locations of each output on the // transaction so we can verify any HTLC signatures // sent to us after we construct the HTLC view. if incoming { c.incomingHTLCIndex[htlc.localOutputIndex] = htlc } else { c.outgoingHTLCIndex[htlc.localOutputIndex] = htlc } // Otherwise, this is there remote party's commitment // transaction and we only need to populate the remote output // index within the HTLC index. case !c.isOurs: htlc.remoteOutputIndex, err = locateOutputIndex( htlc, c.txn, c.isOurs, dups, ) if err != nil { return err } default: return fmt.Errorf("invalid commitment configuration") } return nil } // Finally, we'll need to locate the index within the commitment // transaction of all the HTLC outputs. This index will be required // later when we write the commitment state to disk, and also when // generating signatures for each of the HTLC transactions. for i := 0; i < len(c.outgoingHTLCs); i++ { htlc := &c.outgoingHTLCs[i] if err := populateIndex(htlc, false); err != nil { return nil } } for i := 0; i < len(c.incomingHTLCs); i++ { htlc := &c.incomingHTLCs[i] if err := populateIndex(htlc, true); err != nil { return nil } } return nil } // toDiskCommit converts the target commitment into a format suitable to be // written to disk after an accepted state transition. func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment { numHtlcs := len(c.outgoingHTLCs) + len(c.incomingHTLCs) commit := &channeldb.ChannelCommitment{ CommitHeight: c.height, LocalLogIndex: c.ourMessageIndex, LocalHtlcIndex: c.ourHtlcIndex, RemoteLogIndex: c.theirMessageIndex, RemoteHtlcIndex: c.theirHtlcIndex, LocalBalance: c.ourBalance, RemoteBalance: c.theirBalance, CommitFee: c.fee, FeePerKw: c.feePerKw, CommitTx: c.txn, CommitSig: c.sig, Htlcs: make([]channeldb.HTLC, 0, numHtlcs), } for _, htlc := range c.outgoingHTLCs { outputIndex := htlc.localOutputIndex if !ourCommit { outputIndex = htlc.remoteOutputIndex } h := channeldb.HTLC{ RHash: htlc.RHash, Amt: htlc.Amount, RefundTimeout: htlc.Timeout, OutputIndex: outputIndex, HtlcIndex: htlc.HtlcIndex, LogIndex: htlc.LogIndex, Incoming: false, } h.OnionBlob = make([]byte, len(htlc.OnionBlob)) copy(h.OnionBlob[:], htlc.OnionBlob) if ourCommit && htlc.sig != nil { h.Signature = htlc.sig.Serialize() } commit.Htlcs = append(commit.Htlcs, h) } for _, htlc := range c.incomingHTLCs { outputIndex := htlc.localOutputIndex if !ourCommit { outputIndex = htlc.remoteOutputIndex } h := channeldb.HTLC{ RHash: htlc.RHash, Amt: htlc.Amount, RefundTimeout: htlc.Timeout, OutputIndex: outputIndex, HtlcIndex: htlc.HtlcIndex, LogIndex: htlc.LogIndex, Incoming: true, } h.OnionBlob = make([]byte, len(htlc.OnionBlob)) copy(h.OnionBlob[:], htlc.OnionBlob) if ourCommit && htlc.sig != nil { h.Signature = htlc.sig.Serialize() } commit.Htlcs = append(commit.Htlcs, h) } return commit } // diskHtlcToPayDesc converts an HTLC previously written to disk within a // commitment state to the form required to manipulate in memory within the // commitment struct and updateLog. This function is used when we need to // restore commitment state written do disk back into memory once we need to // restart a channel session. func (lc *LightningChannel) diskHtlcToPayDesc(feeRate btcutil.Amount, commitHeight uint64, isPendingCommit bool, htlc *channeldb.HTLC, localCommitKeys, remoteCommitKeys *commitmentKeyRing) (PaymentDescriptor, error) { // The proper pkScripts for this PaymentDescriptor must be // generated so we can easily locate them within the commitment // transaction in the future. var ( ourP2WSH, theirP2WSH []byte ourWitnessScript, theirWitnessScript []byte pd PaymentDescriptor err error ) // If the either outputs is dust from the local or remote node's // perspective, then we don't need to generate the scripts as we only // generate them in order to locate the outputs within the commitment // transaction. As we'll mark dust with a special output index in the // on-disk state snapshot. isDustLocal := htlcIsDust(htlc.Incoming, true, feeRate, htlc.Amt.ToSatoshis(), lc.channelState.LocalChanCfg.DustLimit) if !isDustLocal && localCommitKeys != nil { ourP2WSH, ourWitnessScript, err = genHtlcScript( htlc.Incoming, true, htlc.RefundTimeout, htlc.RHash, localCommitKeys) if err != nil { return pd, err } } isDustRemote := htlcIsDust(htlc.Incoming, false, feeRate, htlc.Amt.ToSatoshis(), lc.channelState.RemoteChanCfg.DustLimit) if !isDustRemote && remoteCommitKeys != nil { theirP2WSH, theirWitnessScript, err = genHtlcScript( htlc.Incoming, false, htlc.RefundTimeout, htlc.RHash, remoteCommitKeys) if err != nil { return pd, err } } // With the scripts reconstructed (depending on if this is our commit // vs theirs or a pending commit for the remote party), we can now // re-create the original payment descriptor. pd = PaymentDescriptor{ RHash: htlc.RHash, Timeout: htlc.RefundTimeout, Amount: htlc.Amt, EntryType: Add, HtlcIndex: htlc.HtlcIndex, LogIndex: htlc.LogIndex, OnionBlob: htlc.OnionBlob, ourPkScript: ourP2WSH, ourWitnessScript: ourWitnessScript, theirPkScript: theirP2WSH, theirWitnessScript: theirWitnessScript, } // If this is a pending commit, then the HTLC was only included in the // commitment of the remote party, so we only set that commit height. // Otherwise, we'll set the commit height for both chains as the HTLC // was written to disk after it was fully locked in. if isPendingCommit { pd.addCommitHeightRemote = commitHeight } else { pd.addCommitHeightRemote = commitHeight pd.addCommitHeightLocal = commitHeight } return pd, nil } // extractPayDescs will convert all HTLC's present within a disk commit state // to a set of incoming and outgoing payment descriptors. Once reconstructed, // these payment descriptors can be re-inserted into the in-memory updateLog // for each side. func (lc *LightningChannel) extractPayDescs(commitHeight uint64, isPendingCommit bool, feeRate btcutil.Amount, htlcs []channeldb.HTLC, localCommitKeys *commitmentKeyRing, remoteCommitKeys *commitmentKeyRing) ([]PaymentDescriptor, []PaymentDescriptor, error) { var ( incomingHtlcs []PaymentDescriptor outgoingHtlcs []PaymentDescriptor ) // For each included HTLC within this commitment state, we'll convert // the disk format into our in memory PaymentDescriptor format, // partitioning based on if we offered or received the HTLC. for _, htlc := range htlcs { // TODO(roasbeef): set isForwarded to false for all? need to // persist state w.r.t to if forwarded or not, or can // inadvertently trigger replays payDesc, err := lc.diskHtlcToPayDesc( feeRate, commitHeight, isPendingCommit, &htlc, localCommitKeys, remoteCommitKeys, ) if err != nil { return incomingHtlcs, outgoingHtlcs, err } if htlc.Incoming { incomingHtlcs = append(incomingHtlcs, payDesc) } else { outgoingHtlcs = append(outgoingHtlcs, payDesc) } } return incomingHtlcs, outgoingHtlcs, nil } // diskCommitToMemCommit converts tthe on-disk commitment format to our // in-memory commitment format which is needed in order to properly resume // channel operations after a restart. func (lc *LightningChannel) diskCommitToMemCommit(isLocal, isPendingCommit bool, diskCommit *channeldb.ChannelCommitment, localCommitPoint, remoteCommitPoint *btcec.PublicKey) (*commitment, error) { // First, we'll need to re-derive the commitment key ring for each // party used within this particular state. If this is a pending commit // (we extended but weren't able to complete the commitment dance // before shutdown), then the localCommitPoint won't be set as we // haven't yet received a responding commitment from the remote party. var localCommitKeys, remoteCommitKeys *commitmentKeyRing if localCommitPoint != nil { localCommitKeys = deriveCommitmentKeys(localCommitPoint, true, lc.localChanCfg, lc.remoteChanCfg) } if remoteCommitPoint != nil { remoteCommitKeys = deriveCommitmentKeys(remoteCommitPoint, false, lc.localChanCfg, lc.remoteChanCfg) } // With the key rings re-created, we'll now convert all the on-disk // HTLC"s into PaymentDescriptor's so we can re-insert them into our // update log. incomingHtlcs, outgoingHtlcs, err := lc.extractPayDescs( diskCommit.CommitHeight, isPendingCommit, diskCommit.FeePerKw, diskCommit.Htlcs, localCommitKeys, remoteCommitKeys, ) if err != nil { return nil, err } // With the necessary items generated, we'll now re-construct the // commitment state as it was originally present in memory. commit := &commitment{ height: diskCommit.CommitHeight, isOurs: isLocal, ourBalance: diskCommit.LocalBalance, theirBalance: diskCommit.RemoteBalance, ourMessageIndex: diskCommit.LocalLogIndex, ourHtlcIndex: diskCommit.LocalHtlcIndex, theirMessageIndex: diskCommit.RemoteLogIndex, theirHtlcIndex: diskCommit.RemoteHtlcIndex, txn: diskCommit.CommitTx, sig: diskCommit.CommitSig, fee: diskCommit.CommitFee, feePerKw: diskCommit.FeePerKw, incomingHTLCs: incomingHtlcs, outgoingHTLCs: outgoingHtlcs, } if isLocal { commit.dustLimit = lc.channelState.LocalChanCfg.DustLimit } else { commit.dustLimit = lc.channelState.RemoteChanCfg.DustLimit } // Finally, we'll re-populate the HTLC index for this state so we can // properly locate each HTLC within the commitment transaction. if err := commit.populateHtlcIndexes(); err != nil { return nil, err } return commit, nil } // 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 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 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: SingleTweakBytes(commitPoint, localChanCfg.PaymentBasePoint), localHtlcKeyTweak: SingleTweakBytes(commitPoint, localChanCfg.HtlcBasePoint), localHtlcKey: TweakPubKey(localChanCfg.HtlcBasePoint, commitPoint), remoteHtlcKey: TweakPubKey(remoteChanCfg.HtlcBasePoint, 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 noDelayBasePoint = remoteChanCfg.PaymentBasePoint revocationBasePoint = remoteChanCfg.RevocationBasePoint } else { delayBasePoint = remoteChanCfg.DelayBasePoint noDelayBasePoint = localChanCfg.PaymentBasePoint revocationBasePoint = localChanCfg.RevocationBasePoint } // With the base points assigned, we can now derive the actual keys // using the base point, and the current commitment tweak. keyRing.delayKey = TweakPubKey(delayBasePoint, commitPoint) keyRing.noDelayKey = TweakPubKey(noDelayBasePoint, commitPoint) keyRing.revocationKey = DeriveRevocationPubkey( revocationBasePoint, commitPoint, ) return keyRing } // commitmentChain represents a chain of unrevoked commitments. The tail of the // chain is the latest fully signed, yet unrevoked commitment. Two chains are // tracked, one for the local node, and another for the remote node. New // commitments we create locally extend the remote node's chain, and vice // versa. Commitment chains are allowed to grow to a bounded length, after // which the tail needs to be "dropped" before new commitments can be received. // The tail is "dropped" when the owner of the chain sends a revocation for the // previous tail. type commitmentChain struct { // commitments is a linked list of commitments to new states. New // commitments are added to the end of the chain with increase height. // Once a commitment transaction is revoked, the tail is incremented, // freeing up the revocation window for new commitments. commitments *list.List // startingHeight is the starting height of this commitment chain on a // session basis. startingHeight uint64 } // newCommitmentChain creates a new commitment chain from an initial height. func newCommitmentChain(initialHeight uint64) *commitmentChain { return &commitmentChain{ commitments: list.New(), startingHeight: initialHeight, } } // addCommitment extends the commitment chain by a single commitment. This // added commitment represents a state update proposed by either party. Once // the commitment prior to this commitment is revoked, the commitment becomes // the new defacto state within the channel. func (s *commitmentChain) addCommitment(c *commitment) { s.commitments.PushBack(c) } // advanceTail reduces the length of the commitment chain by one. The tail of // the chain should be advanced once a revocation for the lowest unrevoked // commitment in the chain is received. func (s *commitmentChain) advanceTail() { s.commitments.Remove(s.commitments.Front()) } // tip returns the latest commitment added to the chain. func (s *commitmentChain) tip() *commitment { return s.commitments.Back().Value.(*commitment) } // tail returns the lowest unrevoked commitment transaction in the chain. func (s *commitmentChain) tail() *commitment { return s.commitments.Front().Value.(*commitment) } // hasUnackedCommitment returns true if the commitment chain has more than one // entry. The tail of the commitment chain has been ACKed by revoking all prior // commitments, but any subsequent commitments have not yet been ACKed. func (s *commitmentChain) hasUnackedCommitment() bool { return s.commitments.Front() != s.commitments.Back() } // updateLog is an append-only log that stores updates to a node's commitment // chain. This structure can be seen as the "mempool" within Lightning where // changes are stored before they're committed to the chain. Once an entry has // been committed in both the local and remote commitment chain, then it can be // removed from this log. // // TODO(roasbeef): create lightning package, move commitment and update to // package? // * also move state machine, separate from lnwallet package // * possible embed updateLog within commitmentChain. type updateLog struct { // logIndex is a monotonically increasing integer that tracks the total // number of update entries ever applied to the log. When sending new // commitment states, we include all updates up to this index. logIndex uint64 // htlcCounter is a monotonically increasing integer that tracks the // total number of offered HTLC's by the owner of this update log. We // use a distinct index for this purpose, as update's that remove // entires from the log will be indexed using this counter. htlcCounter uint64 // List is the updatelog itself, we embed this value so updateLog has // access to all the method of a list.List. *list.List // updateIndex is an index that maps a particular entries index to the // list element within the list.List above. updateIndex map[uint64]*list.Element // offerIndex is an index that maps the counter for offered HTLC's to // their list elemtn within the main list.List. htlcIndex map[uint64]*list.Element } // newUpdateLog creates a new updateLog instance. func newUpdateLog(logIndex, htlcCounter uint64) *updateLog { return &updateLog{ List: list.New(), updateIndex: make(map[uint64]*list.Element), htlcIndex: make(map[uint64]*list.Element), logIndex: logIndex, htlcCounter: htlcCounter, } } // restoreHtlc will "restore" a prior HTLC to the updateLog. We say restore as // this method is intended to be used when re-covering a prior commitment // state. This function differs from appendHtlc in that it won't increment // either of log's counters. If the HTLC is already present, then it is // ignored. func (u *updateLog) restoreHtlc(pd *PaymentDescriptor) { if _, ok := u.htlcIndex[pd.HtlcIndex]; ok { return } u.htlcIndex[pd.HtlcIndex] = u.PushBack(pd) } // appendUpdate appends a new update to the tip of the updateLog. The entry is // also added to index accordingly. func (u *updateLog) appendUpdate(pd *PaymentDescriptor) { u.updateIndex[u.logIndex] = u.PushBack(pd) u.logIndex++ } // appendHtlc appends a new HTLC offer to the tip of the update log. The entry // is also added to the offer index accordingly. func (u *updateLog) appendHtlc(pd *PaymentDescriptor) { u.htlcIndex[u.htlcCounter] = u.PushBack(pd) u.htlcCounter++ u.logIndex++ } // lookupHtlc attempts to look up an offered HTLC according to it's offer // index. If the entry isn't found, then a nil pointer is returned. func (u *updateLog) lookupHtlc(i uint64) *PaymentDescriptor { htlc, ok := u.htlcIndex[i] if !ok { return nil } return htlc.Value.(*PaymentDescriptor) } // remove attempts to remove an entry from the update log. If the entry is // found, then the entry will be removed from the update log and index. func (u *updateLog) removeUpdate(i uint64) { entry := u.updateIndex[i] u.Remove(entry) delete(u.updateIndex, i) } // removeHtlc attempts to remove an HTLC offer form the update log. If the // entry is found, then the entry will be removed from both the main log and // the offer index. func (u *updateLog) removeHtlc(i uint64) { entry := u.htlcIndex[i] u.Remove(entry) delete(u.htlcIndex, i) } // compactLogs performs garbage collection within the log removing HTLCs which // have been removed from the point-of-view of the tail of both chains. The // entries which timeout/settle HTLCs are also removed. func compactLogs(ourLog, theirLog *updateLog, localChainTail, remoteChainTail uint64) { compactLog := func(logA, logB *updateLog) { var nextA *list.Element for e := logA.Front(); e != nil; e = nextA { // Assign next iteration element at top of loop because // we may remove the current element from the list, // which can change the iterated sequence. nextA = e.Next() htlc := e.Value.(*PaymentDescriptor) if htlc.EntryType == Add { continue } // If the HTLC hasn't yet been removed from either // chain, the skip it. if htlc.removeCommitHeightRemote == 0 || htlc.removeCommitHeightLocal == 0 { continue } // Otherwise if the height of the tail of both chains // is at least the height in which the HTLC was // removed, then evict the settle/timeout entry along // with the original add entry. if remoteChainTail >= htlc.removeCommitHeightRemote && localChainTail >= htlc.removeCommitHeightLocal { logA.removeUpdate(htlc.LogIndex) logB.removeHtlc(htlc.ParentIndex) } } } compactLog(ourLog, theirLog) compactLog(theirLog, ourLog) } // LightningChannel implements the state machine which corresponds to the // current commitment protocol wire spec. The state machine implemented allows // for asynchronous fully desynchronized, batched+pipelined updates to // commitment transactions allowing for a high degree of non-blocking // bi-directional payment throughput. // // In order to allow updates to be fully non-blocking, either side is able to // create multiple new commitment states up to a pre-determined window size. // This window size is encoded within InitialRevocationWindow. Before the start // of a session, both side should send out revocation messages with nil // preimages in order to populate their revocation window for the remote party. // // The state machine has for main methods: // * .SignNextCommitment() // * Called one one wishes to sign the next commitment, either initiating a // new state update, or responding to a received commitment. // * .ReceiveNewCommitment() // * Called upon receipt of a new commitment from the remote party. If the // new commitment is valid, then a revocation should immediately be // generated and sent. // * .RevokeCurrentCommitment() // * Revokes the current commitment. Should be called directly after // receiving a new commitment. // * .ReceiveRevocation() // * Processes a revocation from the remote party. If successful creates a // new defacto broadcastable state. // // See the individual comments within the above methods for further details. type LightningChannel struct { // signer is the main signer instances that will be responsible for // signing any HTLC and commitment transaction generated by the state // machine. signer Signer // signDesc is the primary sign descriptor that is capable of signing // the commitment transaction that spends the multi-sig output. signDesc *SignDescriptor channelEvents chainntnfs.ChainNotifier status channelState // ChanPoint is the funding outpoint of this channel. ChanPoint *wire.OutPoint // sigPool is a pool of workers that are capable of signing and // validating signatures in parallel. This is utilized as an // optimization to void serially signing or validating the HTLC // signatures, of which there may be hundreds. sigPool *sigPool // feeEstimator is used to calculate the fee rate for the channel's // commitment and cooperative close transactions. feeEstimator FeeEstimator // Capacity is the total capacity of this channel. Capacity btcutil.Amount // stateHintObfuscator is a 48-bit state hint that's used to obfsucate // the current state number on the commitment transactions. stateHintObfuscator [StateHintSize]byte // currentHeight is the current height of our local commitment chain. // This is also the same as the number of updates to the channel we've // accepted. currentHeight uint64 // remoteCommitChain is the remote node's commitment chain. Any new // commitments we initiate are added to the tip of this chain. remoteCommitChain *commitmentChain // localCommitChain is our local commitment chain. Any new commitments // received are added to the tip of this chain. The tail (or lowest // height) in this chain is our current accepted state, which we are // able to broadcast safely. localCommitChain *commitmentChain channelState *channeldb.OpenChannel localChanCfg *channeldb.ChannelConfig remoteChanCfg *channeldb.ChannelConfig // [local|remote]Log is a (mostly) append-only log storing all the HTLC // updates to this channel. The log is walked backwards as HTLC updates // are applied in order to re-construct a commitment transaction from a // commitment. The log is compacted once a revocation is received. localUpdateLog *updateLog remoteUpdateLog *updateLog // pendingFeeUpdate is set to the fee-per-kw we last sent (if we are // channel initiator) or received (if non-initiator) in an update fee // message, which haven't yet been included in a commitment. It will // be nil if no fee update is un-committed. pendingFeeUpdate *btcutil.Amount // pendingAckFeeUpdate is set to the last committed fee update which is // not yet ACKed. This value will be nil if a fee update hasn't been // initiated. pendingAckFeeUpdate *btcutil.Amount // FundingWitnessScript is the witness script for the 2-of-2 multi-sig // that opened the channel. FundingWitnessScript []byte fundingTxIn wire.TxIn fundingP2WSH []byte // ForceCloseSignal is a channel that is closed to indicate that a // local system has initiated a force close by broadcasting the current // commitment transaction directly on-chain. ForceCloseSignal chan struct{} // UnilateralCloseSignal is a channel that is closed to indicate that // the remote party has performed a unilateral close by broadcasting // their version of the commitment transaction on-chain. UnilateralCloseSignal chan struct{} // UnilateralClose is a channel that will be sent upon by the close // observer once the unilateral close of a channel is detected. UnilateralClose chan *UnilateralCloseSummary // ContractBreach is a channel that is used to communicate the data // necessary to fully resolve the channel in the case that a contract // breach is detected. A contract breach occurs it is detected that the // counterparty has broadcast a prior *revoked* state. ContractBreach chan *BreachRetribution // LocalFundingKey is the public key under control by the wallet that // was used for the 2-of-2 funding output which created this channel. LocalFundingKey *btcec.PublicKey // RemoteFundingKey is the public key for the remote channel counter // party which used for the 2-of-2 funding output which created this // channel. RemoteFundingKey *btcec.PublicKey sync.RWMutex cowg sync.WaitGroup wg sync.WaitGroup shutdown int32 quit chan struct{} observerFin int32 observerQuit chan struct{} } // NewLightningChannel creates a new, active payment channel given an // implementation of the chain notifier, channel database, and the current // settled channel state. Throughout state transitions, then channel will // automatically persist pertinent state to the database in an efficient // manner. func NewLightningChannel(signer Signer, events chainntnfs.ChainNotifier, fe FeeEstimator, state *channeldb.OpenChannel) (*LightningChannel, error) { localKey := state.LocalChanCfg.MultiSigKey.SerializeCompressed() remoteKey := state.RemoteChanCfg.MultiSigKey.SerializeCompressed() multiSigScript, err := genMultiSigScript(localKey, remoteKey) if err != nil { return nil, err } var stateHint [StateHintSize]byte if state.IsInitiator { stateHint = deriveStateHintObfuscator( state.LocalChanCfg.PaymentBasePoint, state.RemoteChanCfg.PaymentBasePoint, ) } else { stateHint = deriveStateHintObfuscator( state.RemoteChanCfg.PaymentBasePoint, state.LocalChanCfg.PaymentBasePoint, ) } localCommit := state.LocalCommitment remoteCommit := state.RemoteCommitment // First, initialize the update logs with their current counter values // from the local and remote commitments. localUpdateLog := newUpdateLog( localCommit.LocalLogIndex, localCommit.LocalHtlcIndex, ) remoteUpdateLog := newUpdateLog( remoteCommit.RemoteLogIndex, remoteCommit.RemoteHtlcIndex, ) lc := &LightningChannel{ // TODO(roasbeef): tune num sig workers? sigPool: newSigPool(runtime.NumCPU(), signer), signer: signer, channelEvents: events, feeEstimator: fe, stateHintObfuscator: stateHint, currentHeight: localCommit.CommitHeight, remoteCommitChain: newCommitmentChain(remoteCommit.CommitHeight), localCommitChain: newCommitmentChain(localCommit.CommitHeight), channelState: state, localChanCfg: &state.LocalChanCfg, remoteChanCfg: &state.RemoteChanCfg, localUpdateLog: localUpdateLog, remoteUpdateLog: remoteUpdateLog, ChanPoint: &state.FundingOutpoint, Capacity: state.Capacity, FundingWitnessScript: multiSigScript, ForceCloseSignal: make(chan struct{}), UnilateralClose: make(chan *UnilateralCloseSummary, 1), UnilateralCloseSignal: make(chan struct{}), ContractBreach: make(chan *BreachRetribution, 1), LocalFundingKey: state.LocalChanCfg.MultiSigKey, RemoteFundingKey: state.RemoteChanCfg.MultiSigKey, quit: make(chan struct{}), observerQuit: make(chan struct{}), } // With the main channel struct reconstructed, we'll now restore the // commitment state in memory and also the update logs themselves. err = lc.restoreCommitState( &localCommit, &remoteCommit, localUpdateLog, remoteUpdateLog, ) if err != nil { return nil, err } // Create the sign descriptor which we'll be using very frequently to // request a signature for the 2-of-2 multi-sig from the signer in // order to complete channel state transitions. fundingPkScript, err := witnessScriptHash(multiSigScript) if err != nil { return nil, err } lc.fundingTxIn = *wire.NewTxIn(&state.FundingOutpoint, nil, nil) lc.fundingP2WSH = fundingPkScript lc.signDesc = &SignDescriptor{ PubKey: lc.localChanCfg.MultiSigKey, WitnessScript: multiSigScript, Output: &wire.TxOut{ PkScript: lc.fundingP2WSH, Value: int64(lc.channelState.Capacity), }, HashType: txscript.SigHashAll, InputIndex: 0, } // We'll only launch a close observer if the ChainNotifier // implementation is non-nil. Passing a nil value indicates that the // channel shouldn't be actively watched for. if lc.channelEvents != nil { // Register for a notification to be dispatched if the funding // outpoint has been spent. This indicates that either us or // the remote party has broadcast a commitment transaction // on-chain. fundingOut := &lc.fundingTxIn.PreviousOutPoint // As a height hint, we'll try to use the opening height, but // if the channel isn't yet open, then we'll use the height it // was broadcast at. heightHint := lc.channelState.ShortChanID.BlockHeight if heightHint == 0 { heightHint = lc.channelState.FundingBroadcastHeight } channelCloseNtfn, err := lc.channelEvents.RegisterSpendNtfn( fundingOut, heightHint, ) if err != nil { return nil, err } // Launch the close observer which will vigilantly watch the // network for any broadcasts the current or prior commitment // transactions, taking action accordingly. lc.cowg.Add(1) go lc.closeObserver(channelCloseNtfn) } // Finally, we'll kick of the signature job pool to handle any upcoming // commitment state generation and validation. if err := lc.sigPool.Start(); err != nil { return nil, err } return lc, nil } // Stop gracefully shuts down any active goroutines spawned by the // LightningChannel during regular duties. func (lc *LightningChannel) Stop() { if !atomic.CompareAndSwapInt32(&lc.shutdown, 0, 1) { return } lc.sigPool.Stop() close(lc.quit) } // CancelObserver signals the active goroutines watching for on-chain channel // closes that they can exit safely. func (lc *LightningChannel) CancelObserver() { if !atomic.CompareAndSwapInt32(&lc.observerFin, 0, 1) { return } close(lc.observerQuit) } // WaitForClose blocks until the channel's close observer has terminated. func (lc *LightningChannel) WaitForClose() { lc.cowg.Wait() } // ResetState resets the state of the channel back to the default state. This // ensures that any active goroutines which need to act based on on-chain // events do so properly. func (lc *LightningChannel) ResetState() { lc.Lock() lc.status = channelOpen lc.Unlock() } // logUpdateToPayDesc converts a LogUpdate into a matching PaymentDescriptor // entry that can be re-inserted into the update log. This method is used when // we extended a state to the remote party, but the connection was obstructed // before we could finish the commitment dance. In this case, we need to // re-insert the original entries back into the update log so we can resume as // if nothing happened. func (lc *LightningChannel) logUpdateToPayDesc(logUpdate *channeldb.LogUpdate, remoteUpdateLog *updateLog, commitHeight uint64, feeRate btcutil.Amount, remoteCommitKeys *commitmentKeyRing, remoteDustLimit btcutil.Amount) (*PaymentDescriptor, error) { // Depending on the type of update message we'll map that to a distinct // PaymentDescriptor instance. var pd *PaymentDescriptor switch wireMsg := logUpdate.UpdateMsg.(type) { // For offered HTLC's, we'll map that to a PaymentDescriptor with the // type Add, ensuring we restore the necessary fields. From the PoV of // the commitment chain, this HTLC was included in the remote chain, // but not the local chain. case *lnwire.UpdateAddHTLC: // First, we'll map all the relevant fields in the // UpdateAddHTLC message to their corresponding fields in the // PaymentDescriptor struct. We also set addCommitHeightRemote // as we've included this HTLC in our local commitment chain // for the remote party. pd = &PaymentDescriptor{ RHash: wireMsg.PaymentHash, Timeout: wireMsg.Expiry, Amount: wireMsg.Amount, EntryType: Add, HtlcIndex: wireMsg.ID, LogIndex: logUpdate.LogIndex, addCommitHeightRemote: commitHeight, } pd.OnionBlob = make([]byte, len(wireMsg.OnionBlob)) copy(pd.OnionBlob[:], wireMsg.OnionBlob[:]) isDustRemote := htlcIsDust(false, false, feeRate, wireMsg.Amount.ToSatoshis(), remoteDustLimit) if !isDustRemote { theirP2WSH, theirWitnessScript, err := genHtlcScript( false, false, wireMsg.Expiry, wireMsg.PaymentHash, remoteCommitKeys) if err != nil { return nil, err } pd.theirPkScript = theirP2WSH pd.theirWitnessScript = theirWitnessScript } // For HTLC's we we're offered we'll fetch the original offered HTLc // from the remote party's update log so we can retrieve the same // PaymentDescriptor that SettleHTLC would produce. case *lnwire.UpdateFufillHTLC: ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID) pd = &PaymentDescriptor{ Amount: ogHTLC.Amount, RPreimage: wireMsg.PaymentPreimage, LogIndex: logUpdate.LogIndex, ParentIndex: ogHTLC.HtlcIndex, EntryType: Settle, removeCommitHeightRemote: commitHeight, } // If we sent a failure for a prior incoming HTLC, then we'll consult // the update log of the remote party so we can retrieve the // information of the original HTLC we're failing. We also set the // removal height for the remote commitment. case *lnwire.UpdateFailHTLC: ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID) pd = &PaymentDescriptor{ Amount: ogHTLC.Amount, RHash: ogHTLC.RHash, ParentIndex: ogHTLC.HtlcIndex, LogIndex: logUpdate.LogIndex, EntryType: Fail, FailReason: wireMsg.Reason[:], removeCommitHeightRemote: commitHeight, } // HTLC fails due to malformed onion blobs are treated the exact same // way as regular HTLC fails. case *lnwire.UpdateFailMalformedHTLC: ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID) // TODO(roasbeef): err if nil? pd = &PaymentDescriptor{ Amount: ogHTLC.Amount, RHash: ogHTLC.RHash, ParentIndex: ogHTLC.HtlcIndex, LogIndex: logUpdate.LogIndex, EntryType: MalformedFail, FailCode: wireMsg.FailureCode, ShaOnionBlob: wireMsg.ShaOnionBlob, removeCommitHeightRemote: commitHeight, } } return pd, nil } // restoreCommitState will restore the local commitment chain and updateLog // state to a consistent in-memory representation of the passed dis commitment. // This method is to be used upon reconnection to our channel counter party. // Once the connection has been established, we'll prepare our in memory state // to re-sync states with the remote party, and also verify/extend new proposed // commitment states. func (lc *LightningChannel) restoreCommitState( localCommitState, remoteCommitState *channeldb.ChannelCommitment, localUpdateLog, remoteUpdateLog *updateLog) error { // In order to reconstruct the pkScripts on each of the pending HTLC // outputs (if any) we'll need to regenerate the current revocation for // this current un-revoked state as well as retrieve the current // revocation for the remote party. ourRevPreImage, err := lc.channelState.RevocationProducer.AtIndex( lc.currentHeight, ) if err != nil { return err } localCommitPoint := ComputeCommitmentPoint(ourRevPreImage[:]) remoteCommitPoint := lc.channelState.RemoteCurrentRevocation // With the revocation state reconstructed, we can now convert the disk // commitment into our in-memory commitment format, inserting it into // the local commitment chain. localCommit, err := lc.diskCommitToMemCommit( true, false, localCommitState, localCommitPoint, remoteCommitPoint, ) if err != nil { return err } lc.localCommitChain.addCommitment(localCommit) walletLog.Debugf("ChannelPoint(%v), starting local commitment: %v", lc.channelState.FundingOutpoint, newLogClosure(func() string { return spew.Sdump(lc.localCommitChain.tail()) }), ) // We'll also do the same for the remote commitment chain. remoteCommit, err := lc.diskCommitToMemCommit( false, false, remoteCommitState, localCommitPoint, remoteCommitPoint, ) if err != nil { return err } lc.remoteCommitChain.addCommitment(remoteCommit) walletLog.Debugf("ChannelPoint(%v), starting remote commitment: %v", lc.channelState.FundingOutpoint, newLogClosure(func() string { return spew.Sdump(lc.remoteCommitChain.tail()) }), ) var ( pendingRemoteCommit *commitment pendingRemoteCommitDiff *channeldb.CommitDiff pendingRemoteKeyChain *commitmentKeyRing ) // Next, we'll check to see if we have an un-acked commitment state we // extended to the remote party but which was never ACK'd. pendingRemoteCommitDiff, err = lc.channelState.RemoteCommitChainTip() if err != nil && err != channeldb.ErrNoPendingCommit { return nil } if pendingRemoteCommitDiff != nil { // If we have a pending remote commitment, then we'll also // reconstruct the original commitment for that state, // inserting it into the remote party's commitment chain. We // don't pass our commit point as we don't have the // corresponding state for the local commitment chain. pendingCommitPoint := lc.channelState.RemoteNextRevocation pendingRemoteCommit, err = lc.diskCommitToMemCommit( false, true, &pendingRemoteCommitDiff.Commitment, nil, pendingCommitPoint, ) if err != nil { return err } lc.remoteCommitChain.addCommitment(pendingRemoteCommit) // We'll also re-create the set of commitment keys needed to // fully re-derive the state. pendingRemoteKeyChain = deriveCommitmentKeys( pendingCommitPoint, false, lc.localChanCfg, lc.remoteChanCfg, ) } // Finally, with the commitment states restored, we'll now restore the // state logs based on the current local+remote commit, and any pending // remote commit that exists. err = lc.restoreStateLogs(localCommit, remoteCommit, pendingRemoteCommit, pendingRemoteCommitDiff, pendingRemoteKeyChain, ) if err != nil { return err } return nil } // restoreStateLogs runs through the current locked-in HTLCs from the point of // view of the channel and insert corresponding log entries (both local and // remote) for each HTLC read from disk. This method is required to sync the // in-memory state of the state machine with that read from persistent storage. func (lc *LightningChannel) restoreStateLogs( localCommitment, remoteCommitment, pendingRemoteCommit *commitment, pendingRemoteCommitDiff *channeldb.CommitDiff, pendingRemoteKeys *commitmentKeyRing) error { // For each HTLC within the local commitment, we add it to the relevant // update logc based on if it's incoming vs outgoing. For any incoming // HTLC's, we also re-add it to the rHashMap so we can quickly look it // up. for i := range localCommitment.incomingHTLCs { htlc := localCommitment.incomingHTLCs[i] lc.remoteUpdateLog.restoreHtlc(&htlc) } for i := range localCommitment.outgoingHTLCs { htlc := localCommitment.outgoingHTLCs[i] lc.localUpdateLog.restoreHtlc(&htlc) } // We'll also do the same for the HTLC"s within the remote commitment // party. We also insert these HTLC's as it's possible our state has // diverged slightly in the case of a congruent update from both sides. // The restoreHtlc method will de-dup the HTLC's to handle this case. for i := range remoteCommitment.incomingHTLCs { htlc := remoteCommitment.incomingHTLCs[i] lc.remoteUpdateLog.restoreHtlc(&htlc) } for i := range remoteCommitment.outgoingHTLCs { htlc := remoteCommitment.outgoingHTLCs[i] lc.localUpdateLog.restoreHtlc(&htlc) } // If we didn't have a dangling (un-acked) commit for the remote party, // then we can exit here. if pendingRemoteCommit == nil { return nil } // If we do have a dangling commitment for the remote party, then we'll // also restore into the log any incoming HTLC's offered by them. Any // outgoing HTLC's that were initially committed in this new state will // be restored below. for i := range pendingRemoteCommit.incomingHTLCs { htlc := pendingRemoteCommit.incomingHTLCs[i] lc.remoteUpdateLog.restoreHtlc(&htlc) } // We'll also update the log counters to match the latest known // counters in this dangling commitment. Otherwise, our updateLog would // have dated counters as it was initially created using their lowest // unrevoked commitment. lc.remoteUpdateLog.logIndex = pendingRemoteCommit.theirMessageIndex lc.remoteUpdateLog.htlcCounter = pendingRemoteCommit.theirHtlcIndex pendingCommit := pendingRemoteCommitDiff.Commitment pendingHeight := pendingCommit.CommitHeight // If we did have a dangling commit, then we'll examine which updates // we included in that state and re-insert them into our update log. for _, logUpdate := range pendingRemoteCommitDiff.LogUpdates { // If the log update is a fee update, then it doesn't need an // entry within the updateLog, so we'll just apply it and move // on. if feeUpdate, ok := logUpdate.UpdateMsg.(*lnwire.UpdateFee); ok { newFeeRate := btcutil.Amount(feeUpdate.FeePerKw) lc.pendingAckFeeUpdate = &newFeeRate continue } payDesc, err := lc.logUpdateToPayDesc( &logUpdate, lc.remoteUpdateLog, pendingHeight, pendingCommit.FeePerKw, pendingRemoteKeys, lc.channelState.RemoteChanCfg.DustLimit, ) if err != nil { return err } if payDesc.EntryType == Add { lc.localUpdateLog.appendHtlc(payDesc) } else { lc.localUpdateLog.appendUpdate(payDesc) } } return nil } // HtlcRetribution contains all the items necessary to seep a revoked HTLC // transaction from a revoked commitment transaction broadcast by the remote // party. type HtlcRetribution struct { // SignDesc is a design descriptor capable of generating the necessary // signatures to satisfy the revocation clause of the HTLC's public key // script. SignDesc SignDescriptor // OutPoint is the target outpoint of this HTLC pointing to the // breached commitment transaction. OutPoint wire.OutPoint // IsIncoming is a boolean flag that indicates whether or not this // HTLC was accepted from the counterparty. A false value indicates that // this HTLC was offered by us. This flag is used determine the exact // witness type should be used to sweep the output. IsIncoming bool } // BreachRetribution contains all the data necessary to bring a channel // counterparty to justice claiming ALL lingering funds within the channel in // the scenario that they broadcast a revoked commitment transaction. A // BreachRetribution is created by the closeObserver if it detects an // uncooperative close of the channel which uses a revoked commitment // transaction. The BreachRetribution is then sent over the ContractBreach // channel in order to allow the subscriber of the channel to dispatch justice. type BreachRetribution struct { // BreachTransaction is the transaction which breached the channel // contract by spending from the funding multi-sig with a revoked // commitment transaction. BreachTransaction *wire.MsgTx // BreachHeight records the block height confirming the breach // transaction, used as a height hint when registering for // confirmations. BreachHeight uint32 // ChainHash is the chain that the contract beach was identified // within. This is also the resident chain of the contract (the chain // the contract was created on). ChainHash chainhash.Hash // RevokedStateNum is the revoked state number which was broadcast. RevokedStateNum uint64 // PendingHTLCs is a slice of the HTLCs which were pending at this // point within the channel's history transcript. PendingHTLCs []channeldb.HTLC // LocalOutputSignDesc is a SignDescriptor which is capable of // generating the signature necessary to sweep the output within the // BreachTransaction that pays directly us. // // NOTE: A nil value indicates that the local output is considered dust // according to the remote party's dust limit. LocalOutputSignDesc *SignDescriptor // LocalOutpoint is the outpoint of the output paying to us (the local // party) within the breach transaction. LocalOutpoint wire.OutPoint // RemoteOutputSignDesc is a SignDescriptor which is capable of // generating the signature required to claim the funds as described // within the revocation clause of the remote party's commitment // output. // // NOTE: A nil value indicates that the local output is considered dust // according to the remote party's dust limit. RemoteOutputSignDesc *SignDescriptor // RemoteOutpoint is the outpoint of the output paying to the remote // party within the breach transaction. RemoteOutpoint wire.OutPoint // HtlcRetributions is a slice of HTLC retributions for each output // active HTLC output within the breached commitment transaction. HtlcRetributions []HtlcRetribution // Err is used to reliably hand-off the breach retribution to the breach // arbiter. Err chan error } // newBreachRetribution creates a new fully populated BreachRetribution for the // passed channel, at a particular revoked state number, and one which targets // the passed commitment transaction. func newBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64, broadcastCommitment *wire.MsgTx, breachHeight uint32) (*BreachRetribution, error) { commitHash := broadcastCommitment.TxHash() // Query the on-disk revocation log for the snapshot which was recorded // at this particular state num. revokedSnapshot, err := chanState.FindPreviousState(stateNum) if err != nil { return nil, err } // With the state number broadcast known, we can now derive/restore the // proper revocation preimage necessary to sweep the remote party's // output. revocationPreimage, err := chanState.RevocationStore.LookUp(stateNum) if err != nil { return nil, err } commitmentSecret, commitmentPoint := btcec.PrivKeyFromBytes(btcec.S256(), revocationPreimage[:]) // With the commitment point generated, we can now generate the four // keys we'll need to reconstruct the commitment state, keyRing := deriveCommitmentKeys(commitmentPoint, false, &chanState.LocalChanCfg, &chanState.RemoteChanCfg) // Next, reconstruct the scripts as they were present at this state // number so we can have the proper witness script to sign and include // within the final witness. remoteDelay := uint32(chanState.RemoteChanCfg.CsvDelay) remotePkScript, err := commitScriptToSelf(remoteDelay, keyRing.delayKey, keyRing.revocationKey) if err != nil { return nil, err } remoteWitnessHash, err := witnessScriptHash(remotePkScript) if err != nil { return nil, err } localPkScript, err := commitScriptUnencumbered(keyRing.noDelayKey) if err != nil { return nil, err } // In order to fully populate the breach retribution struct, we'll need // to find the exact index of the local+remote commitment outputs. localOutpoint := wire.OutPoint{ Hash: commitHash, } remoteOutpoint := wire.OutPoint{ Hash: commitHash, } for i, txOut := range broadcastCommitment.TxOut { switch { case bytes.Equal(txOut.PkScript, localPkScript): localOutpoint.Index = uint32(i) case bytes.Equal(txOut.PkScript, remoteWitnessHash): remoteOutpoint.Index = uint32(i) } } // Conditionally instantiate a sign descriptor for each of the // commitment outputs. If either is considered dust using the remote // party's dust limit, the respective sign descriptor will be nil. var ( localSignDesc *SignDescriptor remoteSignDesc *SignDescriptor ) // Compute the local and remote balances in satoshis. localAmt := revokedSnapshot.LocalBalance.ToSatoshis() remoteAmt := revokedSnapshot.RemoteBalance.ToSatoshis() // If the local balance exceeds the remote party's dust limit, // instantiate the local sign descriptor. if localAmt >= chanState.RemoteChanCfg.DustLimit { localSignDesc = &SignDescriptor{ SingleTweak: keyRing.localCommitKeyTweak, PubKey: chanState.LocalChanCfg.PaymentBasePoint, WitnessScript: localPkScript, Output: &wire.TxOut{ PkScript: localPkScript, Value: int64(localAmt), }, HashType: txscript.SigHashAll, } } // Similarly, if the remote balance exceeds the remote party's dust // limit, assemble the remote sign descriptor. if remoteAmt >= chanState.RemoteChanCfg.DustLimit { remoteSignDesc = &SignDescriptor{ PubKey: chanState.LocalChanCfg.RevocationBasePoint, DoubleTweak: commitmentSecret, WitnessScript: remotePkScript, Output: &wire.TxOut{ PkScript: remoteWitnessHash, Value: int64(remoteAmt), }, HashType: txscript.SigHashAll, } } // With the commitment outputs located, we'll now generate all the // retribution structs for each of the HTLC transactions active on the // remote commitment transaction. htlcRetributions := make([]HtlcRetribution, len(revokedSnapshot.Htlcs)) for i, htlc := range revokedSnapshot.Htlcs { var ( htlcScript []byte err error ) // If this is an incoming HTLC, then this means that they were // the sender of the HTLC (relative to us). So we'll // re-generate the sender HTLC script. if htlc.Incoming { htlcScript, err = senderHTLCScript( keyRing.localHtlcKey, keyRing.remoteHtlcKey, keyRing.revocationKey, htlc.RHash[:], ) if err != nil { return nil, err } // Otherwise, is this was an outgoing HTLC that we sent, then // from the PoV of the remote commitment state, they're the // receiver of this HTLC. } else { htlcScript, err = receiverHTLCScript( htlc.RefundTimeout, keyRing.localHtlcKey, keyRing.remoteHtlcKey, keyRing.revocationKey, htlc.RHash[:], ) if err != nil { return nil, err } } htlcRetributions[i] = HtlcRetribution{ SignDesc: SignDescriptor{ PubKey: chanState.LocalChanCfg.RevocationBasePoint, DoubleTweak: commitmentSecret, WitnessScript: htlcScript, Output: &wire.TxOut{ Value: int64(htlc.Amt.ToSatoshis()), }, HashType: txscript.SigHashAll, }, OutPoint: wire.OutPoint{ Hash: commitHash, Index: uint32(htlc.OutputIndex), }, IsIncoming: htlc.Incoming, } } // Finally, with all the necessary data constructed, we can create the // BreachRetribution struct which houses all the data necessary to // swiftly bring justice to the cheating remote party. return &BreachRetribution{ ChainHash: chanState.ChainHash, BreachTransaction: broadcastCommitment, BreachHeight: breachHeight, RevokedStateNum: stateNum, PendingHTLCs: revokedSnapshot.Htlcs, LocalOutpoint: localOutpoint, LocalOutputSignDesc: localSignDesc, RemoteOutpoint: remoteOutpoint, RemoteOutputSignDesc: remoteSignDesc, HtlcRetributions: htlcRetributions, Err: make(chan error, 1), }, nil } // closeObserver is a goroutine which watches the network for any spends of the // multi-sig funding output. A spend from the multi-sig output may occur under // the following three scenarios: a cooperative close, a unilateral close, and // a uncooperative contract breaching close. In the case of the last scenario a // BreachRetribution struct is created and sent over the ContractBreach channel // notifying subscribers that the counterparty has violated the condition of // the channel by broadcasting a revoked prior state. // // NOTE: This MUST be run as a goroutine. func (lc *LightningChannel) closeObserver(channelCloseNtfn *chainntnfs.SpendEvent) { defer lc.cowg.Done() walletLog.Infof("Close observer for ChannelPoint(%v) active", lc.channelState.FundingOutpoint) var ( commitSpend *chainntnfs.SpendDetail spendHeight uint32 ok bool ) select { // If the daemon is shutting down, then this notification channel will // be closed, so check the second read-value to avoid a false positive. case commitSpend, ok = <-channelCloseNtfn.Spend: if !ok { return } spendHeight = uint32(commitSpend.SpendingHeight) // Otherwise, we've been signalled to bail out early by the // caller/maintainer of this channel. case <-lc.observerQuit: // As we're exiting before the spend notification has been // triggered, we'll cancel the notification intent so the // ChainNotiifer can free up the resources. channelCloseNtfn.Cancel() return } // If we've already initiated a local cooperative or unilateral close // locally, then we have nothing more to do. lc.RLock() if lc.status == channelClosed || lc.status == channelDispute || lc.status == channelClosing { // TODO(roasbeef): if seq+lockno are zero, then is cooperative closure lc.RUnlock() return } lc.RUnlock() // Otherwise, the remote party might have broadcast a prior revoked // state...!!! commitTxBroadcast := commitSpend.SpendingTx // If this is our commitment transaction, then we can exit here as we // don't have any further processing we need to do (we can't cheat // ourselves :p). commitmentHash := lc.channelState.LocalCommitment.CommitTx.TxHash() isOurCommitment := commitSpend.SpenderTxHash.IsEqual(&commitmentHash) if isOurCommitment { return } lc.Lock() defer lc.Unlock() walletLog.Warnf("Unprompted commitment broadcast for ChannelPoint(%v) "+ "detected!", lc.channelState.FundingOutpoint) // Decode the state hint encoded within the commitment transaction to // determine if this is a revoked state or not. obfuscator := lc.stateHintObfuscator broadcastStateNum := GetStateNumHint(commitTxBroadcast, obfuscator) remoteStateNum := lc.channelState.RemoteCommitment.CommitHeight // TODO(roasbeef): track heights distinctly? switch { // If state number spending transaction matches the current latest // state, then they've initiated a unilateral close. So we'll trigger // the unilateral close signal so subscribers can clean up the state as // necessary. // // We'll also handle the case of the remote party broadcasting their // commitment transaction which is one height above ours. This case can // arise when we initiate a state transition, but the remote party has // a fail crash _after_ accepting the new state, but _before_ sending // their signature to us. case broadcastStateNum >= remoteStateNum: walletLog.Infof("Unilateral close of ChannelPoint(%v) "+ "detected", lc.channelState.FundingOutpoint) // As we've detected that the channel has been closed, // immediately delete the state from disk, creating a close // summary for future usage by related sub-systems. // // TODO(roasbeef): include HTLC's // * and time-locked balance, NEED TO??? closeSummary := channeldb.ChannelCloseSummary{ ChanPoint: lc.channelState.FundingOutpoint, ChainHash: lc.channelState.ChainHash, ClosingTXID: *commitSpend.SpenderTxHash, CloseHeight: spendHeight, RemotePub: lc.channelState.IdentityPub, Capacity: lc.Capacity, SettledBalance: lc.channelState.LocalCommitment.LocalBalance.ToSatoshis(), CloseType: channeldb.ForceClose, IsPending: true, } if err := lc.DeleteState(&closeSummary); err != nil { walletLog.Errorf("unable to delete channel state: %v", err) return } // TODO(roasbeef): need to handle case of if > // First, we'll generate the commitment point and the // revocation point so we can re-construct the HTLC state and // also our payment key. commitPoint := lc.channelState.RemoteCurrentRevocation keyRing := deriveCommitmentKeys(commitPoint, false, lc.localChanCfg, lc.remoteChanCfg) // Next, we'll obtain HTLC resolutions for all the outgoing // HTLC's we had on their commitment transaction. htlcResolutions, err := extractHtlcResolutions( lc.channelState.LocalCommitment.FeePerKw, false, lc.signer, lc.channelState.LocalCommitment.Htlcs, keyRing, lc.localChanCfg, lc.remoteChanCfg, *commitSpend.SpenderTxHash) if err != nil { walletLog.Errorf("unable to create htlc "+ "resolutions: %v", err) return } // Before we can generate the proper sign descriptor, we'll // need to locate the output index of our non-delayed output on // the commitment transaction. selfP2WKH, err := commitScriptUnencumbered(keyRing.noDelayKey) if err != nil { walletLog.Errorf("unable to create self commit "+ "script: %v", err) return } var selfPoint *wire.OutPoint for outputIndex, txOut := range commitTxBroadcast.TxOut { if bytes.Equal(txOut.PkScript, selfP2WKH) { selfPoint = &wire.OutPoint{ Hash: *commitSpend.SpenderTxHash, Index: uint32(outputIndex), } break } } // With the HTLC's taken care of, we'll generate the sign // descriptor necessary to sweep our commitment output, but // only if we had a non-trimmed balance. var selfSignDesc *SignDescriptor if selfPoint != nil { localPayBase := lc.localChanCfg.PaymentBasePoint localBalance := lc.channelState.LocalCommitment.LocalBalance.ToSatoshis() selfSignDesc = &SignDescriptor{ PubKey: localPayBase, SingleTweak: keyRing.localCommitKeyTweak, WitnessScript: selfP2WKH, Output: &wire.TxOut{ Value: int64(localBalance), PkScript: selfP2WKH, }, HashType: txscript.SigHashAll, } } // We'll also send all the details necessary to re-claim funds // that are suspended within any contracts. unilateralCloseSummary := &UnilateralCloseSummary{ SpendDetail: commitSpend, ChannelCloseSummary: closeSummary, SelfOutPoint: selfPoint, SelfOutputSignDesc: selfSignDesc, MaturityDelay: uint32(lc.remoteChanCfg.CsvDelay), HtlcResolutions: htlcResolutions, } // TODO(roasbeef): send msg before writing to disk // * need to ensure proper fault tolerance in all cases // * get ACK from the consumer of the ntfn before writing to disk? // * no harm in repeated ntfns: at least once semantics // Notify any subscribers that we've detected a unilateral // commitment transaction broadcast. close(lc.UnilateralCloseSignal) select { case lc.UnilateralClose <- unilateralCloseSummary: case <-lc.observerQuit: walletLog.Errorf("channel shutting down") return } // If the state number broadcast is lower than the remote node's // current un-revoked height, then THEY'RE ATTEMPTING TO VIOLATE THE // CONTRACT LAID OUT WITHIN THE PAYMENT CHANNEL. Therefore we close // the signal indicating a revoked broadcast to allow subscribers to // swiftly dispatch justice!!! case broadcastStateNum < remoteStateNum: walletLog.Warnf("Remote peer has breached the channel "+ "contract for ChannelPoint(%v). Revoked state #%v was "+ "broadcast!!!", lc.channelState.FundingOutpoint, remoteStateNum) if err := lc.channelState.MarkBorked(); err != nil { walletLog.Errorf("unable to mark channel as borked: %v", err) return } // Create a new reach retribution struct which contains all the // data needed to swiftly bring the cheating peer to justice. retribution, err := newBreachRetribution(lc.channelState, broadcastStateNum, commitTxBroadcast, spendHeight) if err != nil { walletLog.Errorf("unable to create breach retribution: %v", err) return } walletLog.Debugf("Punishment breach retribution created: %v", spew.Sdump(retribution)) // Finally, send the retribution struct over the contract beach // channel to allow the observer the use the breach retribution // to sweep ALL funds. select { case lc.ContractBreach <- retribution: case <-lc.observerQuit: walletLog.Errorf("channel shutting down") return } // Wait for the breach arbiter to ACK the handoff before marking // the channel as pending force closed in channeldb. select { case err := <-retribution.Err: // Bail if the handoff failed. if err != nil { walletLog.Errorf("unable to handoff "+ "retribution info: %v", err) return } case <-lc.observerQuit: walletLog.Errorf("channel shutting down") return } // At this point, we've successfully received an ack for the // breach close. We now construct and persist the close // summary, marking the channel as pending force closed. settledBalance := lc.channelState.LocalCommitment. LocalBalance.ToSatoshis() closeSummary := channeldb.ChannelCloseSummary{ ChanPoint: lc.channelState.FundingOutpoint, ChainHash: lc.channelState.ChainHash, ClosingTXID: *commitSpend.SpenderTxHash, CloseHeight: spendHeight, RemotePub: lc.channelState.IdentityPub, Capacity: lc.Capacity, SettledBalance: settledBalance, CloseType: channeldb.BreachClose, IsPending: true, } err = lc.DeleteState(&closeSummary) if err != nil { walletLog.Errorf("unable to delete channel state: %v", err) return } walletLog.Infof("Breached channel=%v marked pending-closed", lc.channelState.FundingOutpoint) } } // htlcTimeoutFee returns the fee in satoshis required for an HTLC timeout // transaction based on the current fee rate. func htlcTimeoutFee(feePerKw btcutil.Amount) btcutil.Amount { return (feePerKw * HtlcTimeoutWeight) / 1000 } // htlcSuccessFee returns the fee in satoshis required for an HTLC success // transaction based on the current fee rate. func htlcSuccessFee(feePerKw btcutil.Amount) btcutil.Amount { return (feePerKw * HtlcSuccessWeight) / 1000 } // htlcIsDust determines if an HTLC output is dust or not depending on two // bits: if the HTLC is incoming and if the HTLC will be placed on our // commitment transaction, or theirs. These two pieces of information are // require as we currently used second-level HTLC transactions ass off-chain // covenants. Depending on the two bits, we'll either be using a timeout or // success transaction which have different weights. func htlcIsDust(incoming, ourCommit bool, feePerKw, htlcAmt, dustLimit btcutil.Amount) bool { // First we'll determine the fee required for this HTLC based on if this is // an incoming HTLC or not, and also on whose commitment transaction it // will be placed on. var htlcFee btcutil.Amount switch { // If this is an incoming HTLC on our commitment transaction, then the // second-level transaction will be a success transaction. case incoming && ourCommit: htlcFee = htlcSuccessFee(feePerKw) // If this is an incoming HTLC on their commitment transaction, then // we'll be using a second-level timeout transaction as they've added // this HTLC. case incoming && !ourCommit: htlcFee = htlcTimeoutFee(feePerKw) // If this is an outgoing HTLC on our commitment transaction, then // we'll be using a timeout transaction as we're the sender of the // HTLC. case !incoming && ourCommit: htlcFee = htlcTimeoutFee(feePerKw) // If this is an outgoing HTLC on their commitment transaction, then // we'll be using an HTLC success transaction as they're the receiver // of this HTLC. case !incoming && !ourCommit: htlcFee = htlcSuccessFee(feePerKw) } return (htlcAmt - htlcFee) < dustLimit } // htlcView represents the "active" HTLCs at a particular point within the // history of the HTLC update log. type htlcView struct { ourUpdates []*PaymentDescriptor theirUpdates []*PaymentDescriptor } // fetchHTLCView returns all the candidate HTLC updates which should be // considered for inclusion within a commitment based on the passed HTLC log // indexes. func (lc *LightningChannel) fetchHTLCView(theirLogIndex, ourLogIndex uint64) *htlcView { var ourHTLCs []*PaymentDescriptor for e := lc.localUpdateLog.Front(); e != nil; e = e.Next() { htlc := e.Value.(*PaymentDescriptor) // This HTLC is active from this point-of-view iff the log // index of the state update is below the specified index in // our update log. if htlc.LogIndex < ourLogIndex { ourHTLCs = append(ourHTLCs, htlc) } } var theirHTLCs []*PaymentDescriptor for e := lc.remoteUpdateLog.Front(); e != nil; e = e.Next() { htlc := e.Value.(*PaymentDescriptor) // If this is an incoming HTLC, then it is only active from // this point-of-view if the index of the HTLC addition in // their log is below the specified view index. if htlc.LogIndex < theirLogIndex { theirHTLCs = append(theirHTLCs, htlc) } } return &htlcView{ ourUpdates: ourHTLCs, theirUpdates: theirHTLCs, } } // fetchCommitmentView returns a populated commitment which expresses the state // of the channel from the point of view of a local or remote chain, evaluating // the HTLC log up to the passed indexes. This function is used to construct // both local and remote commitment transactions in order to sign or verify new // commitment updates. A fully populated commitment is returned which reflects // the proper balances for both sides at this point in the commitment chain. func (lc *LightningChannel) fetchCommitmentView(remoteChain bool, ourLogIndex, ourHtlcIndex, theirLogIndex, theirHtlcIndex uint64, keyRing *commitmentKeyRing) (*commitment, error) { commitChain := lc.localCommitChain if remoteChain { commitChain = lc.remoteCommitChain } ourBalance := commitChain.tip().ourBalance theirBalance := commitChain.tip().theirBalance // Add the fee from the previous commitment state back to the // initiator's balance, so that the fee can be recalculated and // re-applied in case fee estimation parameters have changed or the // number of outstanding HTLCs has changed. if lc.channelState.IsInitiator { ourBalance += lnwire.NewMSatFromSatoshis(commitChain.tip().fee) } else if !lc.channelState.IsInitiator { theirBalance += lnwire.NewMSatFromSatoshis(commitChain.tip().fee) } nextHeight := commitChain.tip().height + 1 // Run through all the HTLCs that will be covered by this transaction // in order to update their commitment addition height, and to adjust // the balances on the commitment transaction accordingly. htlcView := lc.fetchHTLCView(theirLogIndex, ourLogIndex) filteredHTLCView := lc.evaluateHTLCView(htlcView, &ourBalance, &theirBalance, nextHeight, remoteChain) // Initiate feePerKw to the last committed fee for this chain as we'll // need this to determine which HTLC's are dust, and also the final fee // rate. feePerKw := commitChain.tail().feePerKw // Check if any fee updates have taken place since that last // commitment. if lc.channelState.IsInitiator { switch { // We've sent an update_fee message since our last commitment, // and now are now creating a commitment that reflects the new // fee update. case remoteChain && lc.pendingFeeUpdate != nil: feePerKw = *lc.pendingFeeUpdate // We've created a new commitment for the remote chain that // includes a fee update, and have not received a commitment // after the fee update has been ACKed. case !remoteChain && lc.pendingAckFeeUpdate != nil: feePerKw = *lc.pendingAckFeeUpdate } } else { switch { // We've received a fee update since the last local commitment, // so we'll include the fee update in the current view. case !remoteChain && lc.pendingFeeUpdate != nil: feePerKw = *lc.pendingFeeUpdate // Earlier we received a commitment that signed an earlier fee // update, and now we must ACK that update. case remoteChain && lc.pendingAckFeeUpdate != nil: feePerKw = *lc.pendingAckFeeUpdate } } // Determine how many current HTLCs are over the dust limit, and should // be counted for the purpose of fee calculation. var dustLimit btcutil.Amount if remoteChain { dustLimit = lc.remoteChanCfg.DustLimit } else { dustLimit = lc.localChanCfg.DustLimit } c := &commitment{ ourBalance: ourBalance, theirBalance: theirBalance, ourMessageIndex: ourLogIndex, ourHtlcIndex: ourHtlcIndex, theirMessageIndex: theirLogIndex, theirHtlcIndex: theirHtlcIndex, height: nextHeight, feePerKw: feePerKw, dustLimit: dustLimit, isOurs: !remoteChain, } // Actually generate unsigned commitment transaction for this view. if err := lc.createCommitmentTx(c, filteredHTLCView, keyRing); err != nil { return nil, err } // In order to ensure _none_ of the HTLC's associated with this new // commitment are mutated, we'll manually copy over each HTLC to its // respective slice. c.outgoingHTLCs = make([]PaymentDescriptor, len(filteredHTLCView.ourUpdates)) for i, htlc := range filteredHTLCView.ourUpdates { c.outgoingHTLCs[i] = *htlc } c.incomingHTLCs = make([]PaymentDescriptor, len(filteredHTLCView.theirUpdates)) for i, htlc := range filteredHTLCView.theirUpdates { c.incomingHTLCs[i] = *htlc } // Finally, we'll populate all the HTLC indexes so we can track the // locations of each HTLC in the commitment state. if err := c.populateHtlcIndexes(); err != nil { return nil, err } return c, nil } // 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 := CommitWeight + (HtlcWeight * numHTLCs) // With the weight known, we can now calculate the commitment fee, // ensuring that we account for any dust outputs trimmed above. commitFee := btcutil.Amount((int64(c.feePerKw) * totalCommitWeight) / 1000) // 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 lc.channelState.IsInitiator { ourBalance -= lnwire.NewMSatFromSatoshis(commitFee) } else if !lc.channelState.IsInitiator { theirBalance -= lnwire.NewMSatFromSatoshis(commitFee) } var ( delay uint32 delayBalance, p2wkhBalance btcutil.Amount ) if c.isOurs { delay = uint32(lc.localChanCfg.CsvDelay) delayBalance = ourBalance.ToSatoshis() p2wkhBalance = theirBalance.ToSatoshis() } else { delay = uint32(lc.remoteChanCfg.CsvDelay) delayBalance = theirBalance.ToSatoshis() p2wkhBalance = ourBalance.ToSatoshis() } // Generate a new commitment transaction with all the latest // unsettled/un-timed out HTLCs. commitTx, err := CreateCommitTx(lc.fundingTxIn, keyRing, delay, delayBalance, p2wkhBalance, c.dustLimit) 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 _, htlc := range filteredHTLCView.ourUpdates { if htlcIsDust(false, c.isOurs, c.feePerKw, htlc.Amount.ToSatoshis(), c.dustLimit) { continue } err := lc.addHTLC(commitTx, c.isOurs, false, htlc, keyRing) if err != nil { return err } } for _, htlc := range filteredHTLCView.theirUpdates { if htlcIsDust(true, c.isOurs, c.feePerKw, htlc.Amount.ToSatoshis(), c.dustLimit) { continue } err := lc.addHTLC(commitTx, c.isOurs, true, htlc, keyRing) if err != nil { return err } } // 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. txsort.InPlaceSort(commitTx) c.txn = commitTx c.fee = commitFee c.ourBalance = ourBalance c.theirBalance = theirBalance return nil } // evaluateHTLCView processes all update entries in both HTLC update logs, // producing a final view which is the result of properly applying all adds, // settles, and timeouts found in both logs. The resulting view returned // reflects the current state of HTLCs within the remote or local commitment // chain. func (lc *LightningChannel) evaluateHTLCView(view *htlcView, ourBalance, theirBalance *lnwire.MilliSatoshi, nextHeight uint64, remoteChain bool) *htlcView { newView := &htlcView{} // We use two maps, one for the local log and one for the remote log to // keep track of which entries we need to skip when creating the final // htlc view. We skip an entry whenever we find a settle or a timeout // modifying an entry. skipUs := make(map[uint64]struct{}) skipThem := make(map[uint64]struct{}) // First we run through non-add entries in both logs, populating the // skip sets and mutating the current chain state (crediting balances, // etc) to reflect the settle/timeout entry encountered. for _, entry := range view.ourUpdates { if entry.EntryType == Add { continue } // If we're settling an inbound HTLC, and it hasn't been // processed yet, then increment our state tracking the total // number of satoshis we've received within the channel. if entry.EntryType == Settle && !remoteChain && entry.removeCommitHeightLocal == 0 { lc.channelState.TotalMSatReceived += entry.Amount } addEntry := lc.remoteUpdateLog.lookupHtlc(entry.ParentIndex) skipThem[addEntry.HtlcIndex] = struct{}{} processRemoveEntry(entry, ourBalance, theirBalance, nextHeight, remoteChain, true) } for _, entry := range view.theirUpdates { if entry.EntryType == Add { continue } // If the remote party is settling one of our outbound HTLC's, // and it hasn't been processed, yet, the increment our state // tracking the total number of satoshis we've sent within the // channel. if entry.EntryType == Settle && !remoteChain && entry.removeCommitHeightLocal == 0 { lc.channelState.TotalMSatSent += entry.Amount } addEntry := lc.localUpdateLog.lookupHtlc(entry.ParentIndex) skipUs[addEntry.HtlcIndex] = struct{}{} processRemoveEntry(entry, ourBalance, theirBalance, nextHeight, remoteChain, false) } // Next we take a second pass through all the log entries, skipping any // settled HTLCs, and debiting the chain state balance due to any newly // added HTLCs. for _, entry := range view.ourUpdates { isAdd := entry.EntryType == Add if _, ok := skipUs[entry.HtlcIndex]; !isAdd || ok { continue } processAddEntry(entry, ourBalance, theirBalance, nextHeight, remoteChain, false) newView.ourUpdates = append(newView.ourUpdates, entry) } for _, entry := range view.theirUpdates { isAdd := entry.EntryType == Add if _, ok := skipThem[entry.HtlcIndex]; !isAdd || ok { continue } processAddEntry(entry, ourBalance, theirBalance, nextHeight, remoteChain, true) newView.theirUpdates = append(newView.theirUpdates, entry) } return newView } // processAddEntry evaluates the effect of an add entry within the HTLC log. // If the HTLC hasn't yet been committed in either chain, then the height it // was committed is updated. Keeping track of this inclusion height allows us to // later compact the log once the change is fully committed in both chains. func processAddEntry(htlc *PaymentDescriptor, ourBalance, theirBalance *lnwire.MilliSatoshi, nextHeight uint64, remoteChain bool, isIncoming bool) { // If we're evaluating this entry for the remote chain (to create/view // a new commitment), then we'll may be updating the height this entry // was added to the chain. Otherwise, we may be updating the entry's // height w.r.t the local chain. var addHeight *uint64 if remoteChain { addHeight = &htlc.addCommitHeightRemote } else { addHeight = &htlc.addCommitHeightLocal } if *addHeight != 0 { return } if isIncoming { // If this is a new incoming (un-committed) HTLC, then we need // to update their balance accordingly by subtracting the // amount of the HTLC that are funds pending. *theirBalance -= htlc.Amount } else { // Similarly, we need to debit our balance if this is an out // going HTLC to reflect the pending balance. *ourBalance -= htlc.Amount } *addHeight = nextHeight } // processRemoveEntry processes a log entry which settles or times out a // previously added HTLC. If the removal entry has already been processed, it // is skipped. func processRemoveEntry(htlc *PaymentDescriptor, ourBalance, theirBalance *lnwire.MilliSatoshi, nextHeight uint64, remoteChain bool, isIncoming bool) { var removeHeight *uint64 if remoteChain { removeHeight = &htlc.removeCommitHeightRemote } else { removeHeight = &htlc.removeCommitHeightLocal } // Ignore any removal entries which have already been processed. if *removeHeight != 0 { return } switch { // If an incoming HTLC is being settled, then this means that we've // received the preimage either from another subsystem, or the // upstream peer in the route. Therefore, we increase our balance by // the HTLC amount. case isIncoming && htlc.EntryType == Settle: *ourBalance += htlc.Amount // Otherwise, this HTLC is being failed out, therefore the value of the // HTLC should return to the remote party. case isIncoming && (htlc.EntryType == Fail || htlc.EntryType == MalformedFail): *theirBalance += htlc.Amount // If an outgoing HTLC is being settled, then this means that the // downstream party resented the preimage or learned of it via a // downstream peer. In either case, we credit their settled value with // the value of the HTLC. case !isIncoming && htlc.EntryType == Settle: *theirBalance += htlc.Amount // Otherwise, one of our outgoing HTLC's has timed out, so the value of // the HTLC should be returned to our settled balance. case !isIncoming && (htlc.EntryType == Fail || htlc.EntryType == MalformedFail): *ourBalance += htlc.Amount } *removeHeight = nextHeight } // generateRemoteHtlcSigJobs generates a series of HTLC signature jobs for the // sig pool, along with a channel that if closed, will cancel any jobs after // they have been submitted to the sigPool. This method is to be used when // generating a new commitment for the remote party. The jobs generated by the // signature can be submitted to the sigPool to generate all the signatures // asynchronously and in parallel. func genRemoteHtlcSigJobs(keyRing *commitmentKeyRing, localChanCfg, remoteChanCfg *channeldb.ChannelConfig, remoteCommitView *commitment) ([]signJob, chan struct{}, error) { txHash := remoteCommitView.txn.TxHash() dustLimit := localChanCfg.DustLimit feePerKw := remoteCommitView.feePerKw // With the keys generated, we'll make a slice with enough capacity to // hold potentially all the HTLC's. The actual slice may be a bit // smaller (than its total capacity) an some HTLC's may be dust. numSigs := (len(remoteCommitView.incomingHTLCs) + len(remoteCommitView.outgoingHTLCs)) sigBatch := make([]signJob, 0, numSigs) var err error cancelChan := make(chan struct{}) // For ech outgoing and incoming HTLC, if the HTLC isn't considered a // dust output after taking into account second-level HTLC fees, then a // sigJob will be generated and appended to the current batch. for _, htlc := range remoteCommitView.incomingHTLCs { if htlcIsDust(true, false, feePerKw, htlc.Amount.ToSatoshis(), dustLimit) { continue } // If the HTLC isn't dust, then we'll create an empty sign job // to add to the batch momentarily. sigJob := signJob{} sigJob.cancel = cancelChan sigJob.resp = make(chan signJobResp, 1) // As this is an incoming HTLC and we're sinning the commitment // transaction of the remote node, we'll need to generate an // HTLC timeout transaction for them. The output of the timeout // transaction needs to account for fees, so we'll compute the // required fee and output now. htlcFee := htlcTimeoutFee(feePerKw) outputAmt := htlc.Amount.ToSatoshis() - htlcFee // With the fee calculate, we can properly create the HTLC // timeout transaction using the HTLC amount minus the fee. op := wire.OutPoint{ Hash: txHash, Index: uint32(htlc.remoteOutputIndex), } sigJob.tx, err = createHtlcTimeoutTx(op, outputAmt, htlc.Timeout, uint32(remoteChanCfg.CsvDelay), keyRing.revocationKey, keyRing.delayKey) if err != nil { return nil, nil, err } // Finally, we'll generate a sign descriptor to generate a // signature to give to the remote party for this commitment // transaction. Note we use the raw HTLC amount. sigJob.signDesc = SignDescriptor{ PubKey: localChanCfg.HtlcBasePoint, SingleTweak: keyRing.localHtlcKeyTweak, WitnessScript: htlc.theirWitnessScript, Output: &wire.TxOut{ Value: int64(htlc.Amount.ToSatoshis()), }, HashType: txscript.SigHashAll, SigHashes: txscript.NewTxSigHashes(sigJob.tx), InputIndex: 0, } sigJob.outputIndex = htlc.remoteOutputIndex sigBatch = append(sigBatch, sigJob) } for _, htlc := range remoteCommitView.outgoingHTLCs { if htlcIsDust(false, false, feePerKw, htlc.Amount.ToSatoshis(), dustLimit) { continue } sigJob := signJob{} sigJob.cancel = cancelChan sigJob.resp = make(chan signJobResp, 1) // As this is an outgoing HTLC and we're signing the commitment // transaction of the remote node, we'll need to generate an // HTLC success transaction for them. The output of the timeout // transaction needs to account for fees, so we'll compute the // required fee and output now. htlcFee := htlcSuccessFee(feePerKw) outputAmt := htlc.Amount.ToSatoshis() - htlcFee // With the proper output amount calculated, we can now // generate the success transaction using the remote party's // CSV delay. op := wire.OutPoint{ Hash: txHash, Index: uint32(htlc.remoteOutputIndex), } sigJob.tx, err = createHtlcSuccessTx(op, outputAmt, uint32(remoteChanCfg.CsvDelay), keyRing.revocationKey, keyRing.delayKey) if err != nil { return nil, nil, err } // Finally, we'll generate a sign descriptor to generate a // signature to give to the remote party for this commitment // transaction. Note we use the raw HTLC amount. sigJob.signDesc = SignDescriptor{ PubKey: localChanCfg.HtlcBasePoint, SingleTweak: keyRing.localHtlcKeyTweak, WitnessScript: htlc.theirWitnessScript, Output: &wire.TxOut{ Value: int64(htlc.Amount.ToSatoshis()), }, HashType: txscript.SigHashAll, SigHashes: txscript.NewTxSigHashes(sigJob.tx), InputIndex: 0, } sigJob.outputIndex = htlc.remoteOutputIndex sigBatch = append(sigBatch, sigJob) } return sigBatch, cancelChan, nil } // createCommitDiff will create a commit diff given a new pending commitment // for the remote party and the necessary signatures for the remote party to // validate this new state. This function is called right before sending the // new commitment to the remote party. The commit diff returned contains all // information necessary for retransmission. func (lc *LightningChannel) createCommitDiff( newCommit *commitment, commitSig *btcec.Signature, htlcSigs []*btcec.Signature) (*channeldb.CommitDiff, error) { // First, we need to convert the funding outpoint into the ID that's // used on the wire to identify this channel. We'll use this shortly // when recording the exact CommitSig message that we'll be sending // out. chanID := lnwire.NewChanIDFromOutPoint(&lc.channelState.FundingOutpoint) // If we have a fee update that we're waiting on an ACK of, then we'll // create an entry so this is properly retransmitted. Note that we can // only send an UpdateFee message if we're the initiator of the // channel. var logUpdates []channeldb.LogUpdate if lc.channelState.IsInitiator && lc.pendingFeeUpdate != nil { logUpdates = append(logUpdates, channeldb.LogUpdate{ UpdateMsg: &lnwire.UpdateFee{ ChanID: chanID, FeePerKw: uint32(*lc.pendingFeeUpdate), }, }) } // We'll now run through our local update log to locate the items which // were only just committed within this pending state. This will be the // set of items we need to retransmit if we reconnect and find that // they didn't process this new state fully. for e := lc.localUpdateLog.Front(); e != nil; e = e.Next() { pd := e.Value.(*PaymentDescriptor) // If this entry wasn't committed at the exact height of this // remote commitment, then we'll skip it as it was already // lingering in the log. if pd.addCommitHeightRemote != newCommit.height && pd.removeCommitHeightRemote != newCommit.height { continue } // Knowing that this update is a part of this new commitment, // we'll create a log update and not it's index in the log so // we can later restore it properly if a restart occurs. logUpdate := channeldb.LogUpdate{ LogIndex: pd.LogIndex, } // We'll map the type of the PaymentDescriptor to one of the // four messages that it corresponds to. With this set of // messages obtained, we can simply read from disk and re-send // them in the case of a needed channel sync. switch pd.EntryType { case Add: htlc := &lnwire.UpdateAddHTLC{ ChanID: chanID, ID: pd.HtlcIndex, Amount: pd.Amount, Expiry: pd.Timeout, PaymentHash: pd.RHash, } copy(htlc.OnionBlob[:], pd.OnionBlob) logUpdate.UpdateMsg = htlc case Settle: logUpdate.UpdateMsg = &lnwire.UpdateFufillHTLC{ ChanID: chanID, ID: pd.ParentIndex, PaymentPreimage: pd.RPreimage, } case Fail: logUpdate.UpdateMsg = &lnwire.UpdateFailHTLC{ ChanID: chanID, ID: pd.ParentIndex, Reason: pd.FailReason, } case MalformedFail: logUpdate.UpdateMsg = &lnwire.UpdateFailMalformedHTLC{ ChanID: chanID, ID: pd.ParentIndex, ShaOnionBlob: pd.ShaOnionBlob, FailureCode: pd.FailCode, } } logUpdates = append(logUpdates, logUpdate) } // With the set of log updates mapped into wire messages, we'll now // convert the in-memory commit into a format suitable for writing to // disk. diskCommit := newCommit.toDiskCommit(false) return &channeldb.CommitDiff{ Commitment: *diskCommit, CommitSig: &lnwire.CommitSig{ ChanID: lnwire.NewChanIDFromOutPoint( &lc.channelState.FundingOutpoint, ), CommitSig: commitSig, HtlcSigs: htlcSigs, }, LogUpdates: logUpdates, }, nil } // SignNextCommitment signs a new commitment which includes any previous // unsettled HTLCs, any new HTLCs, and any modifications to prior HTLCs // committed in previous commitment updates. Signing a new commitment // decrements the available revocation window by 1. After a successful method // call, the remote party's commitment chain is extended by a new commitment // which includes all updates to the HTLC log prior to this method invocation. // The first return parameter is the signature for the commitment transaction // itself, while the second parameter is a slice of all HTLC signatures (if // any). The HTLC signatures are sorted according to the BIP 69 order of the // HTLC's on the commitment transaction. func (lc *LightningChannel) SignNextCommitment() (*btcec.Signature, []*btcec.Signature, error) { lc.Lock() defer lc.Unlock() // If we're awaiting for an ACK to a commitment signature, or if we // don't yet have the initial next revocation point of the remote // party, then we're unable to create new states. Each time we create a // new state, we consume a prior revocation point. commitPoint := lc.channelState.RemoteNextRevocation if lc.remoteCommitChain.hasUnackedCommitment() || commitPoint == nil { return nil, nil, ErrNoWindow } // Determine the last update on the remote log that has been locked in. remoteACKedIndex := lc.localCommitChain.tail().theirMessageIndex remoteHtlcIndex := lc.localCommitChain.tail().theirHtlcIndex // Before we extend this new commitment to the remote commitment chain, // ensure that we aren't violating any of the constraints the remote // party set up when we initially set up the channel. If we are, then // we'll abort this state transition. err := lc.validateCommitmentSanity(remoteACKedIndex, lc.localUpdateLog.logIndex, false, true, true) if err != nil { return nil, nil, err } // Grab the next commitment point for the remote party. This will be // used within fetchCommitmentView to derive all the keys necessary to // construct the commitment state. keyRing := deriveCommitmentKeys(commitPoint, false, lc.localChanCfg, lc.remoteChanCfg) // Create a new commitment view which will calculate the evaluated // state of the remote node's new commitment including our latest added // HTLCs. The view includes the latest balances for both sides on the // remote node's chain, and also update the addition height of any new // HTLC log entries. When we creating a new remote view, we include // _all_ of our changes (pending or committed) but only the remote // node's changes up to the last change we've ACK'd. newCommitView, err := lc.fetchCommitmentView( true, lc.localUpdateLog.logIndex, lc.localUpdateLog.htlcCounter, remoteACKedIndex, remoteHtlcIndex, keyRing, ) if err != nil { return nil, nil, err } walletLog.Tracef("ChannelPoint(%v): extending remote chain to height %v, "+ "local_log=%v, remote_log=%v", lc.channelState.FundingOutpoint, newCommitView.height, lc.localUpdateLog.logIndex, remoteACKedIndex) walletLog.Tracef("ChannelPoint(%v): remote chain: our_balance=%v, "+ "their_balance=%v, commit_tx: %v", lc.channelState.FundingOutpoint, newCommitView.ourBalance, newCommitView.theirBalance, newLogClosure(func() string { return spew.Sdump(newCommitView.txn) }), ) // With the commitment view constructed, if there are any HTLC's, we'll // need to generate signatures of each of them for the remote party's // commitment state. We do so in two phases: first we generate and // submit the set of signature jobs to the worker pool. sigBatch, cancelChan, err := genRemoteHtlcSigJobs(keyRing, lc.localChanCfg, lc.remoteChanCfg, newCommitView, ) if err != nil { return nil, nil, err } lc.sigPool.SubmitSignBatch(sigBatch) // While the jobs are being carried out, we'll Sign their version of // the new commitment transaction while we're waiting for the rest of // the HTLC signatures to be processed. lc.signDesc.SigHashes = txscript.NewTxSigHashes(newCommitView.txn) rawSig, err := lc.signer.SignOutputRaw(newCommitView.txn, lc.signDesc) if err != nil { close(cancelChan) return nil, nil, err } sig, err := btcec.ParseSignature(rawSig, btcec.S256()) if err != nil { close(cancelChan) return nil, nil, err } // We'll need to send over the signatures to the remote party in the // order as they appear on the commitment transaction after BIP 69 // sorting. sort.Slice(sigBatch, func(i, j int) bool { return sigBatch[i].outputIndex < sigBatch[j].outputIndex }) // With the jobs sorted, we'll now iterate through all the responses to // gather each of the signatures in order. htlcSigs := make([]*btcec.Signature, 0, len(sigBatch)) for _, htlcSigJob := range sigBatch { select { case jobResp := <-htlcSigJob.resp: // If an error occurred, then we'll cancel any other // active jobs. if jobResp.err != nil { close(cancelChan) return nil, nil, err } htlcSigs = append(htlcSigs, jobResp.sig) case <-lc.quit: return nil, nil, fmt.Errorf("channel shutting down") } } // As we're about to proposer a new commitment state for the remote // party, we'll write this pending state to disk before we exit, so we // can retransmit it if necessary. commitDiff, err := lc.createCommitDiff(newCommitView, sig, htlcSigs) if err != nil { return nil, nil, err } if lc.channelState.AppendRemoteCommitChain(commitDiff); err != nil { return nil, nil, err } // TODO(roasbeef): check that one eclair bug // * need to retransmit on first state still? // * after initial reconnect // Extend the remote commitment chain by one with the addition of our // latest commitment update. lc.remoteCommitChain.addCommitment(newCommitView) // If we are the channel initiator then we would have signed any sent // fee update at this point, so mark this update as pending ACK, and // set pendingFeeUpdate to nil. We can do this since we know we won't // sign any new commitment before receiving a RevokeAndAck, because of // the revocation window of 1. if lc.channelState.IsInitiator { lc.pendingAckFeeUpdate = lc.pendingFeeUpdate lc.pendingFeeUpdate = nil } return sig, htlcSigs, nil } // ProcessChanSyncMsg processes a ChannelReestablish message sent by the remote // connection upon re establishment of our connection with them. This method // will return a single message if we are currently out of sync, otherwise a // nil lnwire.Message will be returned. If it is decided that our level of // de-synchronization is irreconcilable, then an error indicating the issue // will be returned. In this case that an error is returned, the channel should // be force closed, as we cannot continue updates. // // One of two message sets will be returned: // // * CommitSig+Updates: if we have a pending remote commit which they claim to // have not received // * RevokeAndAck: if we sent a revocation message that they claim to have // not received func (lc *LightningChannel) ProcessChanSyncMsg(msg *lnwire.ChannelReestablish) ([]lnwire.Message, error) { // We owe them a commitment if they have an un-acked commitment and the // tip of their chain (from our Pov) is equal to what they think their // next commit height should be. remoteChainTip := lc.remoteCommitChain.tip() oweCommitment := (lc.remoteCommitChain.hasUnackedCommitment() && msg.NextLocalCommitHeight == remoteChainTip.height) // We owe them a revocation if the tail of our current commitment is // one greater than what they _think_ our commitment tail is. localChainTail := lc.localCommitChain.tail() oweRevocation := localChainTail.height == msg.RemoteCommitTailHeight+1 // Now we'll examine the state we have, vs what was contained in the // chain sync message. If we're de-synchronized, then we'll send a // batch of messages which when applied will kick start the chain // resync. var updates []lnwire.Message // If the remote party included the optional fields, then we'll verify // their correctness first, as it will influence our decisions below. hasRecoveryOptions := msg.LocalUnrevokedCommitPoint != nil commitSecretCorrect := true if hasRecoveryOptions && msg.RemoteCommitTailHeight != 0 { // We'll check that they've really sent a valid commit // secret from our shachain for our prior height, but only if // this isn't the first state. heightSecret, err := lc.channelState.RevocationProducer.AtIndex( msg.RemoteCommitTailHeight - 1, ) if err != nil { return nil, err } commitSecretCorrect = bytes.Equal( heightSecret[:], msg.LastRemoteCommitSecret[:], ) } // TODO(roasbeef): check validity of commitment point after the fact // If the commit secret they sent is incorrect then we'll fail the // channel as the remote node has an inconsistent state. if !commitSecretCorrect { // In this case, we'll return an error to indicate the remote // node sent us the wrong values. This will let the caller act // accordingly. return nil, ErrInvalidLastCommitSecret } switch { // If we owe the remote party a revocation message, then we'll re-send // the last revocation message that we sent. This will be the // revocation message for our prior chain tail. case oweRevocation: revocationMsg, err := lc.generateRevocation( localChainTail.height - 1, ) if err != nil { return nil, err } updates = append(updates, revocationMsg) // Next, as a precaution, we'll check a special edge case. If // they initiated a state transition, we sent the revocation, // but died before the signature was sent. We re-transmit our // revocation, but also initiate a state transition to re-sync // them. if lc.localCommitChain.tip().height > lc.remoteCommitChain.tip().height { commitSig, htlcSigs, err := lc.SignNextCommitment() switch { // If we signed this state, then we'll accumulate // another update to send over. case err == nil: updates = append(updates, &lnwire.CommitSig{ ChanID: lnwire.NewChanIDFromOutPoint( &lc.channelState.FundingOutpoint, ), CommitSig: commitSig, HtlcSigs: htlcSigs, }) // If we get a failure due to not knowing their next // point, then this is fine as they'll either send // FundingLocked, or revoke their next state to allow // us to continue forwards. case err == ErrNoWindow: // Otherwise, this is an error and we'll treat it as // such. default: return nil, err } } // If we don't owe the remote party a revocation, but their value for // what our remote chain tail should be doesn't match up, and their // purported commitment secrete matches up, then we'll behind! case (msg.RemoteCommitTailHeight > localChainTail.height && hasRecoveryOptions && commitSecretCorrect): // In this case, we've likely lost data and shouldn't proceed // with channel updates. So we'll return the appropriate error // to signal to the caller the current state. return nil, ErrCommitSyncDataLoss // If we don't owe them a revocation, and the height of our commitment // chain reported by the remote party is not equal to our chain tail, // then we cannot sync. case !oweRevocation && localChainTail.height != msg.RemoteCommitTailHeight: if err := lc.channelState.MarkBorked(); err != nil { return nil, err } return nil, ErrCannotSyncCommitChains } // If we owe them a commitment, then we'll read from disk our // commitment diff, so we can re-send them to the remote party. if oweCommitment { // Grab the current remote chain tip from the database. This // commit diff contains all the information required to re-sync // our states. commitDiff, err := lc.channelState.RemoteCommitChainTip() if err != nil { return nil, err } // Next, we'll need to send over any updates we sent as part of // this new proposed commitment state. for _, logUpdate := range commitDiff.LogUpdates { updates = append(updates, logUpdate.UpdateMsg) } // With the batch of updates accumulated, we'll now re-send the // original CommitSig message required to re-sync their remote // commitment chain with our local version of their chain. updates = append(updates, commitDiff.CommitSig) } else if !oweCommitment && remoteChainTip.height+1 != msg.NextLocalCommitHeight { if err := lc.channelState.MarkBorked(); err != nil { return nil, err } // If we don't owe them a commitment, yet the tip of their // chain isn't one more than the next local commit height they // report, we'll fail the channel. return nil, ErrCannotSyncCommitChains } return updates, nil } // ChanSyncMsg returns the ChannelReestablish message that should be sent upon // reconnection with the remote peer that we're maintaining this channel with. // The information contained within this message is necessary to re-sync our // commitment chains in the case of a last or only partially processed message. // When the remote party receiver this message one of three things may happen: // // 1. We're fully synced and no messages need to be sent. // 2. We didn't get the last CommitSig message they sent, to they'll re-send // it. // 3. We didn't get the last RevokeAndAck message they sent, so they'll // re-send it. func (lc *LightningChannel) ChanSyncMsg() (*lnwire.ChannelReestablish, error) { // The remote commitment height that we we'll send in the // ChannelReestablish message is our current commitment height plus // one. If the receiver thinks that our commitment height is actually // *equal* to this value, then they'll re-send the last commitment that // they sent but we never fully processed. localHeight := lc.localCommitChain.tip().height nextLocalCommitHeight := localHeight + 1 // The second value we'll send is the height of the remote commitment // from our PoV. If the receiver thinks that their height is actually // *one plus* this value, then they'll re-send their last revocation. remoteChainTipHeight := lc.remoteCommitChain.tail().height // If this channel has undergone a commitment update, then in order to // prove to the remote party our knowledge of their prior commitment // state, we'll also send over the last commitment secret that the // remote party sent. var lastCommitSecret [32]byte if remoteChainTipHeight != 0 { remoteSecret, err := lc.channelState.RevocationStore.LookUp( remoteChainTipHeight - 1, ) if err != nil { return nil, err } lastCommitSecret = [32]byte(*remoteSecret) } // Additionally, we'll send over the current unrevoked commitment on // our local commitment transaction. currentCommitSecret, err := lc.channelState.RevocationProducer.AtIndex( localHeight, ) if err != nil { return nil, err } return &lnwire.ChannelReestablish{ ChanID: lnwire.NewChanIDFromOutPoint( &lc.channelState.FundingOutpoint, ), NextLocalCommitHeight: nextLocalCommitHeight, RemoteCommitTailHeight: remoteChainTipHeight, LastRemoteCommitSecret: lastCommitSecret, LocalUnrevokedCommitPoint: ComputeCommitmentPoint( currentCommitSecret[:], ), }, nil } // validateCommitmentSanity is used to validate that on current state the commitment // transaction is valid in terms of propagating it over Bitcoin network, and // also that all outputs are meet Bitcoin spec requirements and they are // spendable. func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter, ourLogCounter uint64, prediction bool, local bool, remote bool) error { // TODO(roasbeef): verify remaining sanity requirements htlcCount := 0 // If we adding or receiving the htlc we increase the number of htlcs // by one in order to not overflow the commitment transaction by // insertion. if prediction { htlcCount++ } // TODO(roasbeef): call availableBalance in here re-using htlcView // Run through all the HTLCs that will be covered by this transaction // in order to calculate theirs count. view := lc.fetchHTLCView(theirLogCounter, ourLogCounter) if remote { for _, entry := range view.theirUpdates { if entry.EntryType == Add { htlcCount++ } } for _, entry := range view.ourUpdates { if entry.EntryType != Add { htlcCount-- } } } if local { for _, entry := range view.ourUpdates { if entry.EntryType == Add { htlcCount++ } } for _, entry := range view.theirUpdates { if entry.EntryType != Add { htlcCount-- } } } // If we're validating the commitment sanity for HTLC _log_ update by a // particular side, then we'll only consider half of the available HTLC // bandwidth. However, if we're validating the _creation_ of a new // commitment state, then we'll use the full value as the sum of the // contribution of both sides shouldn't exceed the max number. var maxHTLCNumber int if local && remote { maxHTLCNumber = MaxHTLCNumber } else { maxHTLCNumber = MaxHTLCNumber / 2 } if htlcCount > maxHTLCNumber { return ErrMaxHTLCNumber } return nil } // genHtlcSigValidationJobs generates a series of signatures verification jobs // meant to verify all the signatures for HTLC's attached to a newly created // commitment state. The jobs generated are fully populated, and can be sent // directly into the pool of workers. func genHtlcSigValidationJobs(localCommitmentView *commitment, keyRing *commitmentKeyRing, htlcSigs []*btcec.Signature, localChanCfg, remoteChanCfg *channeldb.ChannelConfig) []verifyJob { // If this new commitment state doesn't have any HTLC's that are to be // signed, then we'll return a nil slice. if len(htlcSigs) == 0 { return nil } txHash := localCommitmentView.txn.TxHash() feePerKw := localCommitmentView.feePerKw // With the required state generated, we'll create a slice with large // enough capacity to hold verification jobs for all HTLC's in this // view. In the case that we have some dust outputs, then the actual // length will be smaller than the total capacity. numHtlcs := (len(localCommitmentView.incomingHTLCs) + len(localCommitmentView.outgoingHTLCs)) verifyJobs := make([]verifyJob, 0, numHtlcs) // We'll iterate through each output in the commitment transaction, // populating the sigHash closure function if it's detected to be an // HLTC output. Given the sighash, and the signing key, we'll be able // to validate each signature within the worker pool. i := 0 for index := range localCommitmentView.txn.TxOut { var sigHash func() ([]byte, error) outputIndex := int32(index) switch { // If this output index is found within the incoming HTLC index, // then this means that we need to generate an HTLC success // transaction in order to validate the signature. case localCommitmentView.incomingHTLCIndex[outputIndex] != nil: htlc := localCommitmentView.incomingHTLCIndex[outputIndex] sigHash = func() ([]byte, error) { op := wire.OutPoint{ Hash: txHash, Index: uint32(htlc.localOutputIndex), } htlcFee := htlcSuccessFee(feePerKw) outputAmt := htlc.Amount.ToSatoshis() - htlcFee successTx, err := createHtlcSuccessTx(op, outputAmt, uint32(localChanCfg.CsvDelay), keyRing.revocationKey, keyRing.delayKey) if err != nil { return nil, err } hashCache := txscript.NewTxSigHashes(successTx) sigHash, err := txscript.CalcWitnessSigHash( htlc.ourWitnessScript, hashCache, txscript.SigHashAll, successTx, 0, int64(htlc.Amount.ToSatoshis()), ) if err != nil { return nil, err } return sigHash, nil } // With the sighash generated, we'll also store the // signature so it can be written to disk if this state // is valid. htlc.sig = htlcSigs[i] // Otherwise, if this is an outgoing HTLC, then we'll need to // generate a timeout transaction so we can verify the // signature presented. case localCommitmentView.outgoingHTLCIndex[outputIndex] != nil: htlc := localCommitmentView.outgoingHTLCIndex[outputIndex] sigHash = func() ([]byte, error) { op := wire.OutPoint{ Hash: txHash, Index: uint32(htlc.localOutputIndex), } htlcFee := htlcTimeoutFee(feePerKw) outputAmt := htlc.Amount.ToSatoshis() - htlcFee timeoutTx, err := createHtlcTimeoutTx(op, outputAmt, htlc.Timeout, uint32(localChanCfg.CsvDelay), keyRing.revocationKey, keyRing.delayKey, ) if err != nil { return nil, err } hashCache := txscript.NewTxSigHashes(timeoutTx) sigHash, err := txscript.CalcWitnessSigHash( htlc.ourWitnessScript, hashCache, txscript.SigHashAll, timeoutTx, 0, int64(htlc.Amount.ToSatoshis()), ) if err != nil { return nil, err } return sigHash, nil } // With the sighash generated, we'll also store the // signature so it can be written to disk if this state // is valid. htlc.sig = htlcSigs[i] default: continue } verifyJobs = append(verifyJobs, verifyJob{ pubKey: keyRing.remoteHtlcKey, sig: htlcSigs[i], sigHash: sigHash, }) i++ } return verifyJobs } // InvalidCommitSigError is a struct that implements the error interface to // report a failure to validation a commitment signature for a remote peer. // We'll use the items in this struct to generate a rich error message for the // remote peer when we receive an invalid signature from it. Doing so can // greatly aide in debugging cross implementation issues. type InvalidCommitSigError struct { commitHeight uint64 commitSig []byte sigHash []byte commitTx []byte } // Error returns a detailed error string including the exact transaction that // caused an invalid commitment signature. func (i *InvalidCommitSigError) Error() string { return fmt.Sprintf("rejected commitment: commit_height=%v, "+ "invalid_sig=%x, commit_tx=%x, sig_hash=%x", i.commitHeight, i.commitSig[:], i.commitTx, i.sigHash[:]) } // A compile time flag to ensure that InvalidCommitSigError implements the // error interface. var _ error = (*InvalidCommitSigError)(nil) // ReceiveNewCommitment process a signature for a new commitment state sent by // the remote party. This method should be called in response to the // remote party initiating a new change, or when the remote party sends a // signature fully accepting a new state we've initiated. If we are able to // successfully validate the signature, then the generated commitment is added // to our local commitment chain. Once we send a revocation for our prior // state, then this newly added commitment becomes our current accepted channel // state. func (lc *LightningChannel) ReceiveNewCommitment(commitSig *btcec.Signature, htlcSigs []*btcec.Signature) error { lc.Lock() defer lc.Unlock() // Determine the last update on the local log that has been locked in. localACKedIndex := lc.remoteCommitChain.tail().ourMessageIndex localHtlcIndex := lc.remoteCommitChain.tail().ourHtlcIndex // Ensure that this new local update from the remote node respects all // the constraints we specified during initial channel setup. If not, // then we'll abort the channel as they've violated our constraints. err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex, localACKedIndex, false, true, true) if err != nil { return err } // We're receiving a new commitment which attempts to extend our local // commitment chain height by one, so fetch the proper commitment point // as this will be needed to derive the keys required to construct the // commitment. nextHeight := lc.currentHeight + 1 commitSecret, err := lc.channelState.RevocationProducer.AtIndex(nextHeight) if err != nil { return err } commitPoint := ComputeCommitmentPoint(commitSecret[:]) keyRing := deriveCommitmentKeys(commitPoint, true, lc.localChanCfg, lc.remoteChanCfg) // With the current commitment point re-calculated, construct the new // commitment view which includes all the entries we know of in their // HTLC log, and up to ourLogIndex in our HTLC log. localCommitmentView, err := lc.fetchCommitmentView( false, localACKedIndex, localHtlcIndex, lc.remoteUpdateLog.logIndex, lc.remoteUpdateLog.htlcCounter, keyRing, ) if err != nil { return err } walletLog.Tracef("ChannelPoint(%v): extending local chain to height %v, "+ "local_log=%v, remote_log=%v", lc.channelState.FundingOutpoint, localCommitmentView.height, localACKedIndex, lc.remoteUpdateLog.logIndex) walletLog.Tracef("ChannelPoint(%v): local chain: our_balance=%v, "+ "their_balance=%v, commit_tx: %v", lc.channelState.FundingOutpoint, localCommitmentView.ourBalance, localCommitmentView.theirBalance, newLogClosure(func() string { return spew.Sdump(localCommitmentView.txn) }), ) // Construct the sighash of the commitment transaction corresponding to // this newly proposed state update. localCommitTx := localCommitmentView.txn multiSigScript := lc.FundingWitnessScript hashCache := txscript.NewTxSigHashes(localCommitTx) sigHash, err := txscript.CalcWitnessSigHash(multiSigScript, hashCache, txscript.SigHashAll, localCommitTx, 0, int64(lc.channelState.Capacity)) if err != nil { // TODO(roasbeef): fetchview has already mutated the HTLCs... // * need to either roll-back, or make pure return err } // As an optimization, we'll generate a series of jobs for the worker // pool to verify each of the HTLc signatures presented. Once // generated, we'll submit these jobs to the worker pool. verifyJobs := genHtlcSigValidationJobs(localCommitmentView, keyRing, htlcSigs, lc.localChanCfg, lc.remoteChanCfg) cancelChan := make(chan struct{}) verifyResps := lc.sigPool.SubmitVerifyBatch(verifyJobs, cancelChan) // While the HTLC verification jobs are proceeding asynchronously, // we'll ensure that the newly constructed commitment state has a valid // signature. verifyKey := btcec.PublicKey{ X: lc.remoteChanCfg.MultiSigKey.X, Y: lc.remoteChanCfg.MultiSigKey.Y, Curve: btcec.S256(), } if !commitSig.Verify(sigHash, &verifyKey) { close(cancelChan) // If we fail to validate their commitment signature, we'll // generate a special error to send over the protocol. We'll // include the exact signature and commitment we failed to // verify against in order to aide debugging. var txBytes bytes.Buffer localCommitTx.Serialize(&txBytes) return &InvalidCommitSigError{ commitHeight: nextHeight, commitSig: commitSig.Serialize(), sigHash: sigHash, commitTx: txBytes.Bytes(), } } // With the primary commitment transaction validated, we'll check each // of the HTLC validation jobs. for i := 0; i < len(verifyJobs); i++ { // In the case that a single signature is invalid, we'll exit // early and cancel all the outstanding verification jobs. select { case err := <-verifyResps: if err != nil { close(cancelChan) return fmt.Errorf("invalid htlc signature: %v", err) } case <-lc.quit: return fmt.Errorf("channel shutting down") } } // The signature checks out, so we can now add the new commitment to // our local commitment chain. localCommitmentView.sig = commitSig.Serialize() lc.localCommitChain.addCommitment(localCommitmentView) // If we are not channel initiator, then the commitment just received // would've signed any received fee update since last commitment. Mark // any such fee update as pending ACK (so we remember to ACK it on our // next commitment), and set pendingFeeUpdate to nil. We can do this // since we won't receive any new commitment before ACKing. if !lc.channelState.IsInitiator { lc.pendingAckFeeUpdate = lc.pendingFeeUpdate lc.pendingFeeUpdate = nil } return nil } // FullySynced returns a boolean value reflecting if both commitment chains // (remote+local) are fully in sync. Both commitment chains are fully in sync // if the tip of each chain includes the latest committed changes from both // sides. func (lc *LightningChannel) FullySynced() bool { lc.RLock() defer lc.RUnlock() lastLocalCommit := lc.localCommitChain.tip() lastRemoteCommit := lc.remoteCommitChain.tip() oweCommitment := lastLocalCommit.height > lastRemoteCommit.height localUpdatesSynced := (lastLocalCommit.ourMessageIndex == lastRemoteCommit.ourMessageIndex) remoteUpdatesSynced := (lastLocalCommit.theirMessageIndex == lastRemoteCommit.theirMessageIndex) return !oweCommitment && localUpdatesSynced && remoteUpdatesSynced } // RevokeCurrentCommitment revokes the next lowest unrevoked commitment // transaction in the local commitment chain. As a result the edge of our // revocation window is extended by one, and the tail of our local commitment // chain is advanced by a single commitment. This now lowest unrevoked // commitment becomes our currently accepted state within the channel. func (lc *LightningChannel) RevokeCurrentCommitment() (*lnwire.RevokeAndAck, error) { lc.Lock() defer lc.Unlock() revocationMsg, err := lc.generateRevocation(lc.currentHeight) if err != nil { return nil, err } walletLog.Tracef("ChannelPoint(%v): revoking height=%v, now at height=%v", lc.channelState.FundingOutpoint, lc.localCommitChain.tail().height, lc.currentHeight+1) // Advance our tail, as we've revoked our previous state. lc.localCommitChain.advanceTail() lc.currentHeight++ // Additionally, generate a channel delta for this state transition for // persistent storage. chainTail := lc.localCommitChain.tail() newCommitment := chainTail.toDiskCommit(true) err = lc.channelState.UpdateCommitment(newCommitment) if err != nil { return nil, err } walletLog.Tracef("ChannelPoint(%v): state transition accepted: "+ "our_balance=%v, their_balance=%v", lc.channelState.FundingOutpoint, chainTail.ourBalance, chainTail.theirBalance) revocationMsg.ChanID = lnwire.NewChanIDFromOutPoint( &lc.channelState.FundingOutpoint, ) return revocationMsg, nil } // ReceiveRevocation processes a revocation sent by the remote party for the // lowest unrevoked commitment within their commitment chain. We receive a // revocation either during the initial session negotiation wherein revocation // windows are extended, or in response to a state update that we initiate. If // successful, then the remote commitment chain is advanced by a single // commitment, and a log compaction is attempted. In addition, a slice of // HTLC's which can be forwarded upstream are returned. func (lc *LightningChannel) ReceiveRevocation(revMsg *lnwire.RevokeAndAck) ([]*PaymentDescriptor, error) { lc.Lock() defer lc.Unlock() // Ensure that the new pre-image can be placed in preimage store. store := lc.channelState.RevocationStore revocation, err := chainhash.NewHash(revMsg.Revocation[:]) if err != nil { return nil, err } if err := store.AddNextEntry(revocation); err != nil { return nil, err } // Verify that if we use the commitment point computed based off of the // revealed secret to derive a revocation key with our revocation base // point, then it matches the current revocation of the remote party. currentCommitPoint := lc.channelState.RemoteCurrentRevocation derivedCommitPoint := ComputeCommitmentPoint(revMsg.Revocation[:]) if !derivedCommitPoint.IsEqual(currentCommitPoint) { return nil, fmt.Errorf("revocation key mismatch") } // Now that we've verified that the prior commitment has been properly // revoked, we'll advance the revocation state we track for the remote // party: the new current revocation is what was previously the next // revocation, and the new next revocation is set to the key included // in the message. lc.channelState.RemoteCurrentRevocation = lc.channelState.RemoteNextRevocation lc.channelState.RemoteNextRevocation = revMsg.NextRevocationKey walletLog.Tracef("ChannelPoint(%v): remote party accepted state transition, "+ "revoked height %v, now at %v", lc.channelState.FundingOutpoint, lc.remoteCommitChain.tail().height, lc.remoteCommitChain.tail().height+1) // At this point, the revocation has been accepted, and we've rotated // the current revocation key+hash for the remote party. Therefore we // sync now to ensure the revocation producer state is consistent with // the current commitment height and also to advance the on-disk // commitment chain. if err := lc.channelState.AdvanceCommitChainTail(); err != nil { return nil, err } // Since they revoked the current lowest height in their commitment // chain, we can advance their chain by a single commitment. lc.remoteCommitChain.advanceTail() remoteChainTail := lc.remoteCommitChain.tail().height localChainTail := lc.localCommitChain.tail().height // Now that we've verified the revocation update the state of the HTLC // log as we may be able to prune portions of it now, and update their // balance. var htlcsToForward []*PaymentDescriptor for e := lc.remoteUpdateLog.Front(); e != nil; e = e.Next() { htlc := e.Value.(*PaymentDescriptor) if htlc.isForwarded { continue } uncomitted := (htlc.addCommitHeightRemote == 0 || htlc.addCommitHeightLocal == 0) if htlc.EntryType == Add && uncomitted { continue } if htlc.EntryType == Add && remoteChainTail >= htlc.addCommitHeightRemote && localChainTail >= htlc.addCommitHeightLocal { htlc.isForwarded = true htlcsToForward = append(htlcsToForward, htlc) } else if htlc.EntryType != Add && remoteChainTail >= htlc.removeCommitHeightRemote && localChainTail >= htlc.removeCommitHeightLocal { htlc.isForwarded = true htlcsToForward = append(htlcsToForward, htlc) } } // As we've just completed a new state transition, attempt to see if we // can remove any entries from the update log which have been removed // from the PoV of both commitment chains. compactLogs(lc.localUpdateLog, lc.remoteUpdateLog, localChainTail, remoteChainTail) return htlcsToForward, nil } // NextRevocationKey returns the commitment point for the _next_ commitment // height. The pubkey returned by this function is required by the remote party // along with their revocation base to to extend our commitment chain with a // new commitment. func (lc *LightningChannel) NextRevocationKey() (*btcec.PublicKey, error) { lc.RLock() defer lc.RUnlock() nextHeight := lc.currentHeight + 1 revocation, err := lc.channelState.RevocationProducer.AtIndex(nextHeight) if err != nil { return nil, err } return ComputeCommitmentPoint(revocation[:]), nil } // InitNextRevocation inserts the passed commitment point as the _next_ // revocation to be used when creating a new commitment state for the remote // party. This function MUST be called before the channel can accept or propose // any new states. func (lc *LightningChannel) InitNextRevocation(revKey *btcec.PublicKey) error { lc.Lock() defer lc.Unlock() return lc.channelState.InsertNextRevocation(revKey) } // AddHTLC adds an HTLC to the state machine's local update log. This method // should be called when preparing to send an outgoing HTLC. func (lc *LightningChannel) AddHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, error) { lc.Lock() defer lc.Unlock() if err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex, lc.localUpdateLog.logIndex, true, true, false); err != nil { return 0, err } // To ensure that we can actually fully accept this new HTLC, we'll // calculate the current available bandwidth, and subtract the value of // the HTLC from it. initialBalance, _ := lc.availableBalance() availableBalance := initialBalance availableBalance -= htlc.Amount feePerKw := lc.channelState.LocalCommitment.FeePerKw dustLimit := lc.channelState.LocalChanCfg.DustLimit htlcIsDust := htlcIsDust( false, true, feePerKw, htlc.Amount.ToSatoshis(), dustLimit, ) // If this HTLC is not dust, and we're the initiator, then we'll also // subtract the amount we'll need to pay in fees for this HTLC. if !htlcIsDust && lc.channelState.IsInitiator { htlcFee := lnwire.NewMSatFromSatoshis( btcutil.Amount((int64(feePerKw) * HtlcWeight) / 1000), ) availableBalance -= htlcFee } // If this value is negative, then we can't accept the HTLC, so we'll // reject it with an error. if availableBalance < 0 { // TODO(roasbeef): also needs to respect reservation // * expand to add context err msg walletLog.Errorf("Unable to carry added HTLC: amt=%v, bal=%v", htlc.Amount, availableBalance) return 0, ErrInsufficientBalance } pd := &PaymentDescriptor{ EntryType: Add, RHash: PaymentHash(htlc.PaymentHash), Timeout: htlc.Expiry, Amount: htlc.Amount, LogIndex: lc.localUpdateLog.logIndex, HtlcIndex: lc.localUpdateLog.htlcCounter, OnionBlob: htlc.OnionBlob[:], } lc.localUpdateLog.appendHtlc(pd) return pd.HtlcIndex, nil } // ReceiveHTLC adds an HTLC to the state machine's remote update log. This // method should be called in response to receiving a new HTLC from the remote // party. func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, error) { lc.Lock() defer lc.Unlock() if htlc.ID != lc.remoteUpdateLog.htlcCounter { return 0, fmt.Errorf("ID %d on HTLC add does not match expected next "+ "ID %d", htlc.ID, lc.remoteUpdateLog.htlcCounter) } if err := lc.validateCommitmentSanity(lc.remoteUpdateLog.logIndex, lc.localUpdateLog.logIndex, true, false, true); err != nil { return 0, err } pd := &PaymentDescriptor{ EntryType: Add, RHash: PaymentHash(htlc.PaymentHash), Timeout: htlc.Expiry, Amount: htlc.Amount, LogIndex: lc.remoteUpdateLog.logIndex, HtlcIndex: lc.remoteUpdateLog.htlcCounter, OnionBlob: htlc.OnionBlob[:], } lc.remoteUpdateLog.appendHtlc(pd) return pd.HtlcIndex, nil } // SettleHTLC attempts to settle an existing outstanding received HTLC. The // remote log index of the HTLC settled is returned in order to facilitate // creating the corresponding wire message. In the case the supplied preimage // is invalid, an error is returned. Additionally, the value of the settled // HTLC is also returned. func (lc *LightningChannel) SettleHTLC(preimage [32]byte, htlcIndex uint64, ) error { lc.Lock() defer lc.Unlock() htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex) if htlc == nil { return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex, lc.channelState.ShortChanID) } if htlc.RHash != sha256.Sum256(preimage[:]) { return fmt.Errorf("Invalid payment preimage %x for hash %x", preimage[:], htlc.RHash[:]) } pd := &PaymentDescriptor{ Amount: htlc.Amount, RPreimage: preimage, LogIndex: lc.localUpdateLog.logIndex, ParentIndex: htlcIndex, EntryType: Settle, } lc.localUpdateLog.appendUpdate(pd) return nil } // ReceiveHTLCSettle attempts to settle an existing outgoing HTLC indexed by an // index into the local log. If the specified index doesn't exist within the // log, and error is returned. Similarly if the preimage is invalid w.r.t to // the referenced of then a distinct error is returned. func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, htlcIndex uint64) error { lc.Lock() defer lc.Unlock() htlc := lc.localUpdateLog.lookupHtlc(htlcIndex) if htlc == nil { return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex, lc.channelState.ShortChanID) } if htlc.RHash != sha256.Sum256(preimage[:]) { return fmt.Errorf("Invalid payment preimage %x for hash %x", preimage[:], htlc.RHash[:]) } pd := &PaymentDescriptor{ Amount: htlc.Amount, RPreimage: preimage, ParentIndex: htlc.HtlcIndex, RHash: htlc.RHash, LogIndex: lc.remoteUpdateLog.logIndex, EntryType: Settle, } lc.remoteUpdateLog.appendUpdate(pd) return nil } // FailHTLC attempts to fail a targeted HTLC by its payment hash, inserting an // entry which will remove the target log entry within the next commitment // update. This method is intended to be called in order to cancel in // _incoming_ HTLC. func (lc *LightningChannel) FailHTLC(htlcIndex uint64, reason []byte) error { lc.Lock() defer lc.Unlock() htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex) if htlc == nil { return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex, lc.channelState.ShortChanID) } pd := &PaymentDescriptor{ Amount: htlc.Amount, RHash: htlc.RHash, ParentIndex: htlcIndex, LogIndex: lc.localUpdateLog.logIndex, EntryType: Fail, FailReason: reason, } lc.localUpdateLog.appendUpdate(pd) return nil } // MalformedFailHTLC attempts to fail a targeted HTLC by its payment hash, // inserting an entry which will remove the target log entry within the next // commitment update. This method is intended to be called in order to cancel // in _incoming_ HTLC. func (lc *LightningChannel) MalformedFailHTLC(htlcIndex uint64, failCode lnwire.FailCode, shaOnionBlob [sha256.Size]byte) error { lc.Lock() defer lc.Unlock() htlc := lc.remoteUpdateLog.lookupHtlc(htlcIndex) if htlc == nil { return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex, lc.channelState.ShortChanID) } pd := &PaymentDescriptor{ Amount: htlc.Amount, RHash: htlc.RHash, ParentIndex: htlcIndex, LogIndex: lc.localUpdateLog.logIndex, EntryType: MalformedFail, FailCode: failCode, ShaOnionBlob: shaOnionBlob, } lc.localUpdateLog.appendUpdate(pd) return nil } // ReceiveFailHTLC attempts to cancel a targeted HTLC by its log index, // inserting an entry which will remove the target log entry within the next // commitment update. This method should be called in response to the upstream // party cancelling an outgoing HTLC. The value of the failed HTLC is returned // along with an error indicating success. func (lc *LightningChannel) ReceiveFailHTLC(htlcIndex uint64, reason []byte, ) error { lc.Lock() defer lc.Unlock() htlc := lc.localUpdateLog.lookupHtlc(htlcIndex) if htlc == nil { return fmt.Errorf("No HTLC with ID %d in channel %v", htlcIndex, lc.channelState.ShortChanID) } pd := &PaymentDescriptor{ Amount: htlc.Amount, RHash: htlc.RHash, ParentIndex: htlc.HtlcIndex, LogIndex: lc.remoteUpdateLog.logIndex, EntryType: Fail, FailReason: reason, } lc.remoteUpdateLog.appendUpdate(pd) return nil } // ChannelPoint returns the outpoint of the original funding transaction which // created this active channel. This outpoint is used throughout various // subsystems to uniquely identify an open channel. func (lc *LightningChannel) ChannelPoint() *wire.OutPoint { lc.RLock() defer lc.RUnlock() return &lc.channelState.FundingOutpoint } // ShortChanID returns the short channel ID for the channel. The short channel // ID encodes the exact location in the main chain that the original // funding output can be found. func (lc *LightningChannel) ShortChanID() lnwire.ShortChannelID { lc.RLock() defer lc.RUnlock() return lc.channelState.ShortChanID } // 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 = 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 = 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 = 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 = 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 := 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 (lc *LightningChannel) 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 } // getSignedCommitTx function take the latest commitment transaction and // populate it with witness data. func (lc *LightningChannel) getSignedCommitTx() (*wire.MsgTx, error) { // Fetch the current commitment transaction, along with their signature // for the transaction. localCommit := lc.channelState.LocalCommitment commitTx := localCommit.CommitTx theirSig := append(localCommit.CommitSig, byte(txscript.SigHashAll)) // With this, we then generate the full witness so the caller can // broadcast a fully signed transaction. lc.signDesc.SigHashes = txscript.NewTxSigHashes(commitTx) ourSigRaw, err := lc.signer.SignOutputRaw(commitTx, lc.signDesc) if err != nil { return nil, err } ourSig := append(ourSigRaw, byte(txscript.SigHashAll)) // With the final signature generated, create the witness stack // required to spend from the multi-sig output. ourKey := lc.localChanCfg.MultiSigKey.SerializeCompressed() theirKey := lc.remoteChanCfg.MultiSigKey.SerializeCompressed() commitTx.TxIn[0].Witness = SpendMultiSig( lc.FundingWitnessScript, ourKey, ourSig, theirKey, theirSig, ) return commitTx, nil } // UnilateralCloseSummary describes the details of a detected unilateral // channel closure. This includes the information about with which // transactions, and block the channel was unilaterally closed, as well as // summarization details concerning the _state_ of the channel at the point of // channel closure. Additionally, if we had a commitment output above dust on // the remote party's commitment transaction, the necessary a SignDescriptor // with the material necessary to seep the output are returned. Finally, if we // had any outgoing HTLC's within the commitment transaction, then an // OutgoingHtlcResolution for each output will included. type UnilateralCloseSummary struct { // SpendDetail is a struct that describes how and when the commitment // output was spent. *chainntnfs.SpendDetail // ChannelCloseSummary is a struct describing the final state of the // channel and in which state is was closed. channeldb.ChannelCloseSummary // SelfOutPoint is the full outpoint that points to our non-delayed // pay-to-self output within the commitment transaction of the remote // party. SelfOutPoint *wire.OutPoint // SelfOutputSignDesc is a fully populated sign descriptor capable of // generating a valid signature to sweep the output paying to us SelfOutputSignDesc *SignDescriptor // MaturityDelay is the relative time-lock, in blocks for all outputs // that pay to the local party within the broadcast commitment // transaction. MaturityDelay uint32 // HtlcResolutions is a slice of HTLC resolutions which allows the // local node to sweep any outgoing HTLC"s after the timeout period has // passed. HtlcResolutions []OutgoingHtlcResolution } // OutgoingHtlcResolution houses the information necessary to sweep any outgoing // HTLC's after their contract has expired. This struct will be needed in one // of two cases: the local party force closes the commitment transaction or the // remote party unilaterally closes with their version of the commitment // transaction. type OutgoingHtlcResolution struct { // Expiry the absolute timeout of the HTLC. This value is expressed in // block height, meaning after this height the HLTC can be swept. Expiry uint32 // SignedTimeoutTx is the fully signed HTLC timeout transaction. This // must be broadcast immediately after timeout has passed. Once this // has been confirmed, the HTLC output will transition into the // delay+claim state. SignedTimeoutTx *wire.MsgTx // SweepSignDesc is a sign descriptor that has been populated with the // necessary items required to spend the sole output of the above // transaction. SweepSignDesc SignDescriptor } // newHtlcResolution generates a new HTLC resolution capable of allowing the // caller to sweep an outgoing HTLC present on either their, or the remote // party's commitment transaction. func newHtlcResolution(signer Signer, localChanCfg *channeldb.ChannelConfig, commitHash chainhash.Hash, htlc *channeldb.HTLC, keyRing *commitmentKeyRing, feePewKw, dustLimit btcutil.Amount, csvDelay uint32, ) (*OutgoingHtlcResolution, error) { op := wire.OutPoint{ Hash: commitHash, Index: uint32(htlc.OutputIndex), } // In order to properly reconstruct the HTLC transaction, we'll need to // re-calculate the fee required at this state, so we can add the // correct output value amount to the transaction. htlcFee := htlcTimeoutFee(feePewKw) secondLevelOutputAmt := htlc.Amt.ToSatoshis() - htlcFee // With the fee calculated, re-construct the second level timeout // transaction. timeoutTx, err := createHtlcTimeoutTx( op, secondLevelOutputAmt, htlc.RefundTimeout, csvDelay, keyRing.revocationKey, keyRing.delayKey, ) if err != nil { return nil, err } // TODO(roasbeef): branch based on local vs remote commit // With the transaction created, we can generate a sign descriptor // that's capable of generating the signature required to spend the // HTLC output using the timeout transaction. htlcCreationScript, err := senderHTLCScript(keyRing.localHtlcKey, keyRing.remoteHtlcKey, keyRing.revocationKey, htlc.RHash[:]) if err != nil { return nil, err } timeoutSignDesc := SignDescriptor{ PubKey: localChanCfg.HtlcBasePoint, SingleTweak: keyRing.localHtlcKeyTweak, WitnessScript: htlcCreationScript, Output: &wire.TxOut{ Value: int64(htlc.Amt.ToSatoshis()), }, HashType: txscript.SigHashAll, SigHashes: txscript.NewTxSigHashes(timeoutTx), InputIndex: 0, } // With the sign desc created, we can now construct the full witness // for the timeout transaction, and populate it as well. timeoutWitness, err := senderHtlcSpendTimeout( htlc.Signature, signer, &timeoutSignDesc, timeoutTx) if err != nil { return nil, err } timeoutTx.TxIn[0].Witness = timeoutWitness // Finally, we'll generate the script output that the timeout // transaction creates so we can generate the signDesc required to // complete the claim process after a delay period. htlcSweepScript, err := secondLevelHtlcScript( keyRing.revocationKey, keyRing.delayKey, csvDelay, ) if err != nil { return nil, err } htlcScriptHash, err := witnessScriptHash(htlcSweepScript) if err != nil { return nil, err } // TODO(roasbeef): signing with the delay key is wrong for remote // commitments // * would instead be signing with local htlc key localDelayTweak := SingleTweakBytes(keyRing.commitPoint, localChanCfg.DelayBasePoint) return &OutgoingHtlcResolution{ Expiry: htlc.RefundTimeout, SignedTimeoutTx: timeoutTx, SweepSignDesc: SignDescriptor{ PubKey: localChanCfg.DelayBasePoint, SingleTweak: localDelayTweak, WitnessScript: htlcSweepScript, Output: &wire.TxOut{ PkScript: htlcScriptHash, Value: int64(secondLevelOutputAmt), }, HashType: txscript.SigHashAll, }, }, nil } // extractHtlcResolutions creates a series of outgoing HTLC resolutions, and // the local key used when generating the HTLC scrips. This function is to be // used in two cases: force close, or a unilateral close. func extractHtlcResolutions(feePerKw btcutil.Amount, ourCommit bool, signer Signer, htlcs []channeldb.HTLC, keyRing *commitmentKeyRing, localChanCfg, remoteChanCfg *channeldb.ChannelConfig, commitHash chainhash.Hash) ([]OutgoingHtlcResolution, error) { dustLimit := remoteChanCfg.DustLimit csvDelay := remoteChanCfg.CsvDelay if ourCommit { dustLimit = localChanCfg.DustLimit csvDelay = localChanCfg.CsvDelay } htlcResolutions := make([]OutgoingHtlcResolution, 0, len(htlcs)) for _, htlc := range htlcs { // Skip any incoming HTLC's, as unless we have the pre-image to // spend them, they'll eventually be swept by the party that // offered the HTLC after the timeout. if htlc.Incoming { continue } // We'll also skip any HTLC's which were dust on the commitment // transaction, as these don't have a corresponding output // within the commitment transaction. if htlcIsDust(htlc.Incoming, ourCommit, feePerKw, htlc.Amt.ToSatoshis(), dustLimit) { continue } ohr, err := newHtlcResolution( signer, localChanCfg, commitHash, &htlc, keyRing, feePerKw, dustLimit, uint32(csvDelay), ) if err != nil { return nil, err } // TODO(roasbeef): needs to point to proper amount including htlcResolutions = append(htlcResolutions, *ohr) } return htlcResolutions, nil } // ForceCloseSummary describes the final commitment state before the channel is // locked-down to initiate a force closure by broadcasting the latest state // on-chain. The summary includes all the information required to claim all // rightfully owned outputs. type ForceCloseSummary struct { // ChanPoint is the outpoint that created the channel which has been // force closed. ChanPoint wire.OutPoint // SelfOutpoint is the output created by the above close tx which is // spendable by us after a relative time delay. SelfOutpoint wire.OutPoint // CloseTx is the transaction which closed the channel on-chain. If we // initiate the force close, then this'll be our latest commitment // state. Otherwise, this'll be the state that the remote peer // broadcasted on-chain. CloseTx *wire.MsgTx // SelfOutputSignDesc is a fully populated sign descriptor capable of // generating a valid signature to sweep the self output. // // NOTE: If the commitment delivery output of the force closing party // is below the dust limit, then this will be nil. SelfOutputSignDesc *SignDescriptor // SelfOutputMaturity is the relative maturity period before the above // output can be claimed. SelfOutputMaturity uint32 // HtlcResolutions is a slice of HTLC resolutions which allows the // local node to sweep any outgoing HTLC"s after the timeout period has // passed. HtlcResolutions []OutgoingHtlcResolution } // ForceClose executes a unilateral closure of the transaction at the current // lowest commitment height of the channel. Following a force closure, all // state transitions, or modifications to the state update logs will be // rejected. Additionally, this function also returns a ForceCloseSummary which // includes the necessary details required to sweep all the time-locked within // the commitment transaction. // // TODO(roasbeef): all methods need to abort if in dispute state // TODO(roasbeef): method to generate CloseSummaries for when the remote peer // does a unilateral close func (lc *LightningChannel) ForceClose() (*ForceCloseSummary, error) { lc.Lock() defer lc.Unlock() // Set the channel state to indicate that the channel is now in a // contested state. lc.status = channelDispute commitTx, err := lc.getSignedCommitTx() if err != nil { return nil, err } // Re-derive the original pkScript for to-self output within the // commitment transaction. We'll need this to find the corresponding // output in the commitment transaction and potentially for creating // the sign descriptor. csvTimeout := uint32(lc.localChanCfg.CsvDelay) unusedRevocation, err := lc.channelState.RevocationProducer.AtIndex( lc.currentHeight, ) if err != nil { return nil, err } commitPoint := ComputeCommitmentPoint(unusedRevocation[:]) keyRing := deriveCommitmentKeys(commitPoint, true, lc.localChanCfg, lc.remoteChanCfg) selfScript, err := commitScriptToSelf(csvTimeout, keyRing.delayKey, keyRing.revocationKey) if err != nil { return nil, err } payToUsScriptHash, err := witnessScriptHash(selfScript) if err != nil { return nil, err } // Locate the output index of the delayed commitment output back to us. // We'll return the details of this output to the caller so they can // sweep it once it's mature. var ( delayIndex uint32 delayScript []byte selfSignDesc *SignDescriptor ) for i, txOut := range commitTx.TxOut { if !bytes.Equal(payToUsScriptHash, txOut.PkScript) { continue } delayIndex = uint32(i) delayScript = txOut.PkScript break } localCommitment := lc.channelState.LocalCommitment // With the necessary information gathered above, create a new sign // descriptor which is capable of generating the signature the caller // needs to sweep this output. The hash cache, and input index are not // set as the caller will decide these values once sweeping the output. // If the output is non-existent (dust), have the sign descriptor be // nil. if len(delayScript) != 0 { singleTweak := SingleTweakBytes(commitPoint, lc.localChanCfg.DelayBasePoint) localBalance := localCommitment.LocalBalance selfSignDesc = &SignDescriptor{ PubKey: lc.localChanCfg.DelayBasePoint, SingleTweak: singleTweak, WitnessScript: selfScript, Output: &wire.TxOut{ PkScript: delayScript, Value: int64(localBalance.ToSatoshis()), }, HashType: txscript.SigHashAll, } } // Once the delay output has been found (if it exists), then we'll also // need to create a series of sign descriptors for any lingering // outgoing HTLC's that we'll need to claim as well. txHash := commitTx.TxHash() htlcResolutions, err := extractHtlcResolutions( localCommitment.FeePerKw, true, lc.signer, localCommitment.Htlcs, keyRing, lc.localChanCfg, lc.remoteChanCfg, txHash) if err != nil { return nil, err } // Finally, close the channel force close signal which notifies any // subscribers that the channel has now been forcibly closed. This // allows callers to begin to carry out any post channel closure // activities. close(lc.ForceCloseSignal) return &ForceCloseSummary{ ChanPoint: lc.channelState.FundingOutpoint, SelfOutpoint: wire.OutPoint{ Hash: commitTx.TxHash(), Index: delayIndex, }, CloseTx: commitTx, SelfOutputSignDesc: selfSignDesc, SelfOutputMaturity: csvTimeout, HtlcResolutions: htlcResolutions, }, nil } // CreateCloseProposal is used by both parties in a cooperative channel close // workflow to generate proposed close transactions and signatures. This method // should only be executed once all pending HTLCs (if any) on the channel have // been cleared/removed. Upon completion, the source channel will shift into // the "closing" state, which indicates that all incoming/outgoing HTLC // requests should be rejected. A signature for the closing transaction is // returned. // // TODO(roasbeef): caller should initiate signal to reject all incoming HTLCs, // settle any in flight. func (lc *LightningChannel) CreateCloseProposal(proposedFee btcutil.Amount, localDeliveryScript, remoteDeliveryScript []byte) ([]byte, error) { lc.Lock() defer lc.Unlock() // If we've already closed the channel, then ignore this request. if lc.status == channelClosed { // TODO(roasbeef): check to ensure no pending payments return nil, ErrChanClosing } // Subtract the proposed fee from the appropriate balance, taking care // not to persist the adjusted balance, as the feeRate may change // during the channel closing process. localCommit := lc.channelState.LocalCommitment ourBalance := localCommit.LocalBalance.ToSatoshis() theirBalance := localCommit.RemoteBalance.ToSatoshis() // We'll make sure we account for the complete balance by adding the // current dangling commitment fee to the balance of the initiator. commitFee := localCommit.CommitFee if lc.channelState.IsInitiator { ourBalance = ourBalance - proposedFee + commitFee } else { theirBalance = theirBalance - proposedFee + commitFee } closeTx := CreateCooperativeCloseTx(lc.fundingTxIn, lc.localChanCfg.DustLimit, lc.remoteChanCfg.DustLimit, ourBalance, theirBalance, localDeliveryScript, remoteDeliveryScript, lc.channelState.IsInitiator) // Ensure that the transaction doesn't explicitly violate any // consensus rules such as being too big, or having any value with a // negative output. tx := btcutil.NewTx(closeTx) if err := blockchain.CheckTransactionSanity(tx); err != nil { return nil, err } // Finally, sign the completed cooperative closure transaction. As the // initiator we'll simply send our signature over to the remote party, // using the generated txid to be notified once the closure transaction // has been confirmed. lc.signDesc.SigHashes = txscript.NewTxSigHashes(closeTx) sig, err := lc.signer.SignOutputRaw(closeTx, lc.signDesc) if err != nil { return nil, err } // As everything checks out, indicate in the channel status that a // channel closure has been initiated. lc.status = channelClosing return sig, nil } // CompleteCooperativeClose completes the cooperative closure of the target // active lightning channel. A fully signed closure transaction as well as the // signature itself are returned. Additionally, we also return our final // settled balance, which reflects any fees we may have paid. // // NOTE: The passed local and remote sigs are expected to be fully complete // signatures including the proper sighash byte. func (lc *LightningChannel) CompleteCooperativeClose(localSig, remoteSig []byte, localDeliveryScript, remoteDeliveryScript []byte, proposedFee btcutil.Amount) (*wire.MsgTx, btcutil.Amount, error) { lc.Lock() defer lc.Unlock() // If the channel is already closed, then ignore this request. if lc.status == channelClosed { // TODO(roasbeef): check to ensure no pending payments return nil, 0, ErrChanClosing } // Subtract the proposed fee from the appropriate balance, taking care // not to persist the adjusted balance, as the feeRate may change // during the channel closing process. localCommit := lc.channelState.LocalCommitment ourBalance := localCommit.LocalBalance.ToSatoshis() theirBalance := localCommit.RemoteBalance.ToSatoshis() // We'll make sure we account for the complete balance by adding the // current dangling commitment fee to the balance of the initiator. commitFee := localCommit.CommitFee if lc.channelState.IsInitiator { ourBalance = ourBalance - proposedFee + commitFee } else { theirBalance = theirBalance - proposedFee + commitFee } // Create the transaction used to return the current settled balance // on this active channel back to both parties. In this current model, // the initiator pays full fees for the cooperative close transaction. closeTx := CreateCooperativeCloseTx(lc.fundingTxIn, lc.localChanCfg.DustLimit, lc.remoteChanCfg.DustLimit, ourBalance, theirBalance, localDeliveryScript, remoteDeliveryScript, lc.channelState.IsInitiator) // Ensure that the transaction doesn't explicitly validate any // consensus rules such as being too big, or having any value with a // negative output. tx := btcutil.NewTx(closeTx) if err := blockchain.CheckTransactionSanity(tx); err != nil { return nil, 0, err } hashCache := txscript.NewTxSigHashes(closeTx) // Finally, construct the witness stack minding the order of the // pubkeys+sigs on the stack. ourKey := lc.localChanCfg.MultiSigKey.SerializeCompressed() theirKey := lc.remoteChanCfg.MultiSigKey.SerializeCompressed() witness := SpendMultiSig(lc.signDesc.WitnessScript, ourKey, localSig, theirKey, remoteSig) closeTx.TxIn[0].Witness = witness // Validate the finalized transaction to ensure the output script is // properly met, and that the remote peer supplied a valid signature. vm, err := txscript.NewEngine(lc.fundingP2WSH, closeTx, 0, txscript.StandardVerifyFlags, nil, hashCache, int64(lc.channelState.Capacity)) if err != nil { return nil, 0, err } if err := vm.Execute(); err != nil { return nil, 0, err } // As the transaction is sane, and the scripts are valid we'll mark the // channel now as closed as the closure transaction should get into the // chain in a timely manner and possibly be re-broadcast by the wallet. lc.status = channelClosed return closeTx, ourBalance, nil } // DeleteState deletes all state concerning the channel from the underlying // database, only leaving a small summary describing metadata of the // channel's lifetime. func (lc *LightningChannel) DeleteState(c *channeldb.ChannelCloseSummary) error { return lc.channelState.CloseChannel(c) } // AvailableBalance returns the current available balance within the channel. // By available balance, we mean that if at this very instance s new commitment // were to be created which evals all the log entries, what would our available // balance me. This method is useful when deciding if a given channel can // accept an HTLC in the multi-hop forwarding scenario. func (lc *LightningChannel) AvailableBalance() lnwire.MilliSatoshi { lc.RLock() defer lc.RUnlock() bal, _ := lc.availableBalance() return bal } // availableBalance is the private, non mutexed version of AvailableBalance. // This method is provided so methods that already hold the lock can access // this method. Additionally, the total weight of the next to be created // commitment is returned for accounting purposes. func (lc *LightningChannel) availableBalance() (lnwire.MilliSatoshi, int64) { // First, we'll grab the current local balance. If we're the initiator // of the channel then we paid the fees on the last commitment state, // so we'll re-apply those. settledBalance := lc.channelState.LocalCommitment.LocalBalance if lc.channelState.IsInitiator { settledBalance += lnwire.NewMSatFromSatoshis( lc.localCommitChain.tip().fee, ) } // Next we'll grab the current set of log updates that are still active // and haven't been garbage collected. htlcView := lc.fetchHTLCView(lc.remoteUpdateLog.logIndex, lc.localUpdateLog.logIndex) feePerKw := lc.channelState.LocalCommitment.FeePerKw dustLimit := lc.channelState.LocalChanCfg.DustLimit // We'll now re-compute the current weight of all the active HTLC's. We // make sure to skip any HTLC's that would be dust on our version of // the commitment transaction. var totalHtlcWeight int64 for _, htlc := range lc.channelState.LocalCommitment.Htlcs { if htlcIsDust(false, true, feePerKw, htlc.Amt.ToSatoshis(), dustLimit) { continue } totalHtlcWeight += HtlcWeight } // Next we'll run through our set of updates and modify the // settledBalance and totalHtlcWeight fields accordingly. for _, entry := range htlcView.ourUpdates { switch { // For any new HTLC's added as a part of this state, we'll // subtract the total balance, and tally the weight increase if // it isn't dust. case entry.EntryType == Add && entry.addCommitHeightLocal == 0: settledBalance -= entry.Amount if htlcIsDust(false, true, feePerKw, entry.Amount.ToSatoshis(), dustLimit) { continue } totalHtlcWeight += HtlcWeight // For any new HTLC's we newly settled as part of this state, // we'll subtract the HTLC weight and increase our balance // accordingly. case entry.EntryType == Settle && entry.removeCommitHeightLocal == 0: totalHtlcWeight -= HtlcWeight settledBalance += entry.Amount // For any new fails added as a part of this state, we'll // subtract the weight of the HTLC we're failing. case entry.EntryType == Fail && entry.removeCommitHeightLocal == 0: fallthrough case entry.EntryType == MalformedFail && entry.removeCommitHeightLocal == 0: totalHtlcWeight -= HtlcWeight } } for _, entry := range htlcView.theirUpdates { switch { // If the remote party has an HTLC that will be included as // part of this state, then we'll account for the additional // weight of the HTLC. case entry.EntryType == Add && entry.addCommitHeightLocal == 0: if htlcIsDust(true, true, feePerKw, entry.Amount.ToSatoshis(), dustLimit) { continue } totalHtlcWeight += HtlcWeight // If the remote party is settling one of our HTLC's for the // first time as part of this state, then we'll subtract the // weight of the HTLC. case entry.EntryType == Settle && entry.removeCommitHeightLocal == 0: totalHtlcWeight -= HtlcWeight // For any HTLC's that they're failing as a part of the next, // state, we'll subtract the weight of the HTLC and also credit // ourselves back the value of the HTLC. case entry.EntryType == Fail && entry.removeCommitHeightLocal == 0: fallthrough case entry.EntryType == MalformedFail && entry.removeCommitHeightLocal == 0: totalHtlcWeight -= HtlcWeight settledBalance += entry.Amount } } // If we subtracted dust HTLC's, then we'll need to reset the weight of // the HTLCs back to zero. if totalHtlcWeight < 0 { totalHtlcWeight = 0 } // If we're the initiator then we need to pay fees for this state, so // taking into account the number of active HTLC's we'll calculate the // fee that must be paid. totalCommitWeight := CommitWeight + totalHtlcWeight if lc.channelState.IsInitiator { additionalFee := lnwire.NewMSatFromSatoshis( btcutil.Amount((int64(feePerKw) * totalCommitWeight) / 1000), ) settledBalance -= additionalFee } return settledBalance, totalCommitWeight } // StateSnapshot returns a snapshot of the current fully committed state within // the channel. func (lc *LightningChannel) StateSnapshot() *channeldb.ChannelSnapshot { lc.RLock() defer lc.RUnlock() return lc.channelState.Snapshot() } // validateFeeRate ensures that if the passed fee is applied to the channel, // and a new commitment is created (which evaluates this fee), then the // initiator of the channel does not dip below their reserve. func (lc *LightningChannel) validateFeeRate(feePerKw btcutil.Amount) error { // We'll ensure that we can accommodate this new fee change, yet still // be above our reserve balance. Otherwise, we'll reject the fee // update. availableBalance, txWeight := lc.availableBalance() // Using the weight of the commitment transaction if we were to create // a commitment now, we'll compute our remaining balance if we apply // this new fee update. newFee := lnwire.NewMSatFromSatoshis( btcutil.Amount((int64(feePerKw) * txWeight) / 1000), ) balanceAfterFee := availableBalance - newFee // If this new balance is below our reserve, then we can't accommodate // the fee change, so we'll reject it. if balanceAfterFee.ToSatoshis() < lc.channelState.LocalChanCfg.ChanReserve { return fmt.Errorf("cannot apply fee_update=%v sat/kw, "+ "insufficient balance: start=%v, end=%v", int64(feePerKw), availableBalance, balanceAfterFee) } // TODO(halseth): should fail if fee update is unreasonable, // as specified in BOLT#2. // * COMMENT(roasbeef): can cross-check with our ideal fee rate return nil } // UpdateFee initiates a fee update for this channel. Must only be called by // the channel initiator, and must be called before sending update_fee to // the remote. func (lc *LightningChannel) UpdateFee(feePerKw btcutil.Amount) error { lc.Lock() defer lc.Unlock() // Only initiator can send fee update, so trying to send one as // non-initiator will fail. if !lc.channelState.IsInitiator { return fmt.Errorf("local fee update as non-initiator") } // Ensure that the passed fee rate meets our current requirements. if err := lc.validateFeeRate(feePerKw); err != nil { return err } lc.pendingFeeUpdate = &feePerKw return nil } // ReceiveUpdateFee handles an updated fee sent from remote. This method will // return an error if called as channel initiator. func (lc *LightningChannel) ReceiveUpdateFee(feePerKw btcutil.Amount) error { lc.Lock() defer lc.Unlock() // Only initiator can send fee update, and we must fail if we receive // fee update as initiator if lc.channelState.IsInitiator { return fmt.Errorf("received fee update as initiator") } // TODO(roasbeef): or just modify to use the other balance? lc.pendingFeeUpdate = &feePerKw return nil } // generateRevocation generates the revocation message for a given height. func (lc *LightningChannel) generateRevocation(height uint64) (*lnwire.RevokeAndAck, error) { // Now that we've accept a new state transition, we send the remote // party the revocation for our current commitment state. revocationMsg := &lnwire.RevokeAndAck{} commitSecret, err := lc.channelState.RevocationProducer.AtIndex(height) if err != nil { return nil, err } copy(revocationMsg.Revocation[:], commitSecret[:]) // Along with this revocation, we'll also send the _next_ commitment // point that the remote party should use to create our next commitment // transaction. We use a +2 here as we already gave them a look ahead // of size one after the FundingLocked message was sent: // // 0: current revocation, 1: their "next" revocation, 2: this revocation // // We're revoking the current revocation. Once they receive this // message they'll set the "current" revocation for us to their stored // "next" revocation, and this revocation will become their new "next" // revocation. // // Put simply in the window slides to the left by one. nextCommitSecret, err := lc.channelState.RevocationProducer.AtIndex( height + 2, ) if err != nil { return nil, err } revocationMsg.NextRevocationKey = ComputeCommitmentPoint(nextCommitSecret[:]) revocationMsg.ChanID = lnwire.NewChanIDFromOutPoint( &lc.channelState.FundingOutpoint) return revocationMsg, nil } // CreateCommitTx creates a commitment transaction, spending from specified // funding output. The commitment transaction contains two outputs: one paying // to the "owner" of the commitment transaction which can be spent after a // relative block delay or revocation event, and the other paying the // counterparty within the channel, which can be spent immediately. func CreateCommitTx(fundingOutput wire.TxIn, keyRing *commitmentKeyRing, csvTimeout uint32, amountToSelf, amountToThem, dustLimit 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. ourRedeemScript, err := commitScriptToSelf(csvTimeout, keyRing.delayKey, keyRing.revocationKey) if err != nil { return nil, err } payToUsScriptHash, err := witnessScriptHash(ourRedeemScript) if err != nil { return nil, err } // Next, we create the script paying to them. This is just a regular // P2WPKH output, without any added CSV delay. theirWitnessKeyHash, err := 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 amountToSelf >= dustLimit { commitTx.AddTxOut(&wire.TxOut{ PkScript: payToUsScriptHash, Value: int64(amountToSelf), }) } if amountToThem >= dustLimit { commitTx.AddTxOut(&wire.TxOut{ PkScript: theirWitnessKeyHash, Value: int64(amountToThem), }) } 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 // constructing the channel is the initiator of the closure. Currently it is // expected that the initiator pays the transaction fees for the closing // transaction in full. func CreateCooperativeCloseTx(fundingTxIn wire.TxIn, localDust, remoteDust, ourBalance, theirBalance btcutil.Amount, ourDeliveryScript, theirDeliveryScript []byte, initiator bool) *wire.MsgTx { // Construct the transaction to perform a cooperative closure of the // channel. In the event that one side doesn't have any settled funds // within the channel then a refund output for that particular side can // be omitted. closeTx := wire.NewMsgTx(2) closeTx.AddTxIn(&fundingTxIn) // Create both cooperative closure outputs, properly respecting the // dust limits of both parties. if ourBalance >= localDust { closeTx.AddTxOut(&wire.TxOut{ PkScript: ourDeliveryScript, Value: int64(ourBalance), }) } if theirBalance >= remoteDust { closeTx.AddTxOut(&wire.TxOut{ PkScript: theirDeliveryScript, Value: int64(theirBalance), }) } txsort.InPlaceSort(closeTx) return closeTx } // CalcFee returns the commitment fee to use for the given // fee rate (fee-per-kw). func (lc *LightningChannel) CalcFee(feeRate uint64) uint64 { return (feeRate * uint64(CommitWeight)) / 1000 } // RemoteNextRevocation returns the channelState's RemoteNextRevocation. func (lc *LightningChannel) RemoteNextRevocation() *btcec.PublicKey { lc.RLock() defer lc.RUnlock() return lc.channelState.RemoteNextRevocation } // IsInitiator returns true if we were the ones that initiated the funding // workflow which led to the creation of this channel. Otherwise, it returns // false. func (lc *LightningChannel) IsInitiator() bool { lc.RLock() defer lc.RUnlock() return lc.channelState.IsInitiator } // CommitFeeRate returns the current fee rate of the commitment transaction in // units of sat-per-kw. func (lc *LightningChannel) CommitFeeRate() btcutil.Amount { lc.RLock() defer lc.RUnlock() return lc.channelState.LocalCommitment.FeePerKw } // IsPending returns true if the channel's funding transaction has been fully // confirmed, and false otherwise. func (lc *LightningChannel) IsPending() bool { lc.RLock() defer lc.RUnlock() return lc.channelState.IsPending } // State provides access to the channel's internal state for testing. func (lc *LightningChannel) State() *channeldb.OpenChannel { return lc.channelState } // ObserverQuit returns the quit channel used to coordinate the shutdown of the // close observer. func (lc *LightningChannel) ObserverQuit() chan struct{} { return lc.observerQuit }