package lnwallet import ( "net" "sync" "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/chaincfg/chainhash" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwire" ) // ChannelContribution is the primary constituent of the funding workflow // within lnwallet. Each side first exchanges their respective contributions // along with channel specific parameters like the min fee/KB. Once // contributions have been exchanged, each side will then produce signatures // for all their inputs to the funding transactions, and finally a signature // for the other party's version of the commitment transaction. type ChannelContribution struct { // FundingOutpoint is the amount of funds contributed to the funding // transaction. FundingAmount btcutil.Amount // Inputs to the funding transaction. Inputs []*wire.TxIn // ChangeOutputs are the Outputs to be used in the case that the total // value of the funding inputs is greater than the total potential // channel capacity. ChangeOutputs []*wire.TxOut // FirstCommitmentPoint is the first commitment point that will be used // to create the revocation key in the first commitment transaction we // send to the remote party. FirstCommitmentPoint *btcec.PublicKey // ChannelConfig is the concrete contribution that this node is // offering to the channel. This includes all the various constraints // such as the min HTLC, and also all the keys which will be used for // the duration of the channel. *channeldb.ChannelConfig } // toChanConfig returns the raw channel configuration generated by a node's // contribution to the channel. func (c *ChannelContribution) toChanConfig() channeldb.ChannelConfig { return *c.ChannelConfig } // InputScript represents any script inputs required to redeem a previous // output. This struct is used rather than just a witness, or scripSig in // order to accommodate nested p2sh which utilizes both types of input scripts. type InputScript struct { Witness [][]byte ScriptSig []byte } // ChannelReservation represents an intent to open a lightning payment channel // with a counterparty. The funding processes from reservation to channel opening // is a 3-step process. In order to allow for full concurrency during the // reservation workflow, resources consumed by a contribution are "locked" // themselves. This prevents a number of race conditions such as two funding // transactions double-spending the same input. A reservation can also be // cancelled, which removes the resources from limbo, allowing another // reservation to claim them. // // The reservation workflow consists of the following three steps: // 1. lnwallet.InitChannelReservation // * One requests the wallet to allocate the necessary resources for a // channel reservation. These resources are put in limbo for the lifetime // of a reservation. // * Once completed the reservation will have the wallet's contribution // accessible via the .OurContribution() method. This contribution // contains the necessary items to allow the remote party to build both // the funding, and commitment transactions. // 2. ChannelReservation.ProcessContribution/ChannelReservation.ProcessSingleContribution // * The counterparty presents their contribution to the payment channel. // This allows us to build the funding, and commitment transactions // ourselves. // * We're now able to sign our inputs to the funding transactions, and // the counterparty's version of the commitment transaction. // * All signatures crafted by us, are now available via .OurSignatures(). // 3. ChannelReservation.CompleteReservation/ChannelReservation.CompleteReservationSingle // * The final step in the workflow. The counterparty presents the // signatures for all their inputs to the funding transaction, as well // as a signature to our version of the commitment transaction. // * We then verify the validity of all signatures before considering the // channel "open". type ChannelReservation struct { // This mutex MUST be held when either reading or modifying any of the // fields below. sync.RWMutex // fundingTx is the funding transaction for this pending channel. fundingTx *wire.MsgTx // In order of sorted inputs. Sorting is done in accordance // to BIP-69: https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki. ourFundingInputScripts []*InputScript theirFundingInputScripts []*InputScript // Our signature for their version of the commitment transaction. ourCommitmentSig []byte theirCommitmentSig []byte ourContribution *ChannelContribution theirContribution *ChannelContribution partialState *channeldb.OpenChannel nodeAddr net.Addr // The ID of this reservation, used to uniquely track the reservation // throughout its lifetime. reservationID uint64 // pushMSat the amount of milli-satoshis that should be pushed to the // responder of a single funding channel as part of the initial // commitment state. pushMSat lnwire.MilliSatoshi // chanOpen houses a struct containing the channel and additional // confirmation details will be sent on once the channel is considered // 'open'. A channel is open once the funding transaction has reached a // sufficient number of confirmations. chanOpen chan *openChanDetails chanOpenErr chan error wallet *LightningWallet } // NewChannelReservation creates a new channel reservation. This function is // used only internally by lnwallet. In order to concurrent safety, the // creation of all channel reservations should be carried out via the // lnwallet.InitChannelReservation interface. func NewChannelReservation(capacity, fundingAmt btcutil.Amount, commitFeePerKw SatPerKWeight, wallet *LightningWallet, id uint64, pushMSat lnwire.MilliSatoshi, chainHash *chainhash.Hash, flags lnwire.FundingFlag) (*ChannelReservation, error) { var ( ourBalance lnwire.MilliSatoshi theirBalance lnwire.MilliSatoshi initiator bool ) commitFee := commitFeePerKw.FeeForWeight(CommitWeight) fundingMSat := lnwire.NewMSatFromSatoshis(fundingAmt) capacityMSat := lnwire.NewMSatFromSatoshis(capacity) feeMSat := lnwire.NewMSatFromSatoshis(commitFee) // If we're the responder to a single-funder reservation, then we have // no initial balance in the channel unless the remote party is pushing // some funds to us within the first commitment state. if fundingAmt == 0 { ourBalance = pushMSat theirBalance = capacityMSat - feeMSat - pushMSat initiator = false // If the responder doesn't have enough funds to actually pay // the fees, then we'll bail our early. if int64(theirBalance) < 0 { return nil, ErrFunderBalanceDust( int64(commitFee), int64(theirBalance.ToSatoshis()), int64(2*DefaultDustLimit()), ) } } else { // TODO(roasbeef): need to rework fee structure in general and // also when we "unlock" dual funder within the daemon if capacity == fundingAmt { // If we're initiating a single funder workflow, then // we pay all the initial fees within the commitment // transaction. We also deduct our balance by the // amount pushed as part of the initial state. ourBalance = capacityMSat - feeMSat - pushMSat theirBalance = pushMSat } else { // Otherwise, this is a dual funder workflow where both // slides split the amount funded and the commitment // fee. ourBalance = fundingMSat - (feeMSat / 2) theirBalance = capacityMSat - fundingMSat - (feeMSat / 2) + pushMSat } initiator = true // If we, the initiator don't have enough funds to actually pay // the fees, then we'll exit with an error. if int64(ourBalance) < 0 { return nil, ErrFunderBalanceDust( int64(commitFee), int64(ourBalance), int64(2*DefaultDustLimit()), ) } } // If we're the initiator and our starting balance within the channel // after we take account of fees is below 2x the dust limit, then we'll // reject this channel creation request. // // TODO(roasbeef): reject if 30% goes to fees? dust channel if initiator && ourBalance.ToSatoshis() <= 2*DefaultDustLimit() { return nil, ErrFunderBalanceDust( int64(commitFee), int64(ourBalance.ToSatoshis()), int64(2*DefaultDustLimit()), ) } // Next we'll set the channel type based on what we can ascertain about // the balances/push amount within the channel. var chanType channeldb.ChannelType // If either of the balances are zero at this point, or we have a // non-zero push amt (there's no pushing for dual funder), then this is // a single-funder channel. if ourBalance == 0 || theirBalance == 0 || pushMSat != 0 { chanType = channeldb.SingleFunder } else { // Otherwise, this is a dual funder channel, and no side is // technically the "initiator" initiator = false chanType = channeldb.DualFunder } return &ChannelReservation{ ourContribution: &ChannelContribution{ FundingAmount: ourBalance.ToSatoshis(), ChannelConfig: &channeldb.ChannelConfig{}, }, theirContribution: &ChannelContribution{ FundingAmount: theirBalance.ToSatoshis(), ChannelConfig: &channeldb.ChannelConfig{}, }, partialState: &channeldb.OpenChannel{ ChanType: chanType, ChainHash: *chainHash, IsPending: true, IsInitiator: initiator, ChannelFlags: flags, Capacity: capacity, LocalCommitment: channeldb.ChannelCommitment{ LocalBalance: ourBalance, RemoteBalance: theirBalance, FeePerKw: btcutil.Amount(commitFeePerKw), CommitFee: commitFee, }, RemoteCommitment: channeldb.ChannelCommitment{ LocalBalance: ourBalance, RemoteBalance: theirBalance, FeePerKw: btcutil.Amount(commitFeePerKw), CommitFee: commitFee, }, Db: wallet.Cfg.Database, }, pushMSat: pushMSat, reservationID: id, chanOpen: make(chan *openChanDetails, 1), chanOpenErr: make(chan error, 1), wallet: wallet, }, nil } // SetNumConfsRequired sets the number of confirmations that are required for // the ultimate funding transaction before the channel can be considered open. // This is distinct from the main reservation workflow as it allows // implementations a bit more flexibility w.r.t to if the responder of the // initiator sets decides the number of confirmations needed. func (r *ChannelReservation) SetNumConfsRequired(numConfs uint16) { r.Lock() defer r.Unlock() r.partialState.NumConfsRequired = numConfs } // CommitConstraints takes the constraints that the remote party specifies for // the type of commitments that we can generate for them. These constraints // include several parameters that serve as flow control restricting the amount // of satoshis that can be transferred in a single commitment. This function // will also attempt to verify the constraints for sanity, returning an error // if the parameters are seemed unsound. func (r *ChannelReservation) CommitConstraints(c *channeldb.ChannelConstraints) error { r.Lock() defer r.Unlock() // Fail if we consider csvDelay excessively large. // TODO(halseth): find a more scientific choice of value. const maxDelay = 10000 if c.CsvDelay > maxDelay { return ErrCsvDelayTooLarge(c.CsvDelay, maxDelay) } // The dust limit should always be greater or equal to the channel // reserve. The reservation request should be denied if otherwise. if c.DustLimit > c.ChanReserve { return ErrChanReserveTooSmall(c.ChanReserve, c.DustLimit) } // Fail if we consider the channel reserve to be too large. We // currently fail if it is greater than 20% of the channel capacity. maxChanReserve := r.partialState.Capacity / 5 if c.ChanReserve > maxChanReserve { return ErrChanReserveTooLarge(c.ChanReserve, maxChanReserve) } // Fail if the minimum HTLC value is too large. If this is too large, // the channel won't be useful for sending small payments. This limit // is currently set to maxValueInFlight, effectively letting the remote // setting this as large as it wants. if c.MinHTLC > c.MaxPendingAmount { return ErrMinHtlcTooLarge(c.MinHTLC, c.MaxPendingAmount) } // Fail if maxHtlcs is above the maximum allowed number of 483. This // number is specified in BOLT-02. if c.MaxAcceptedHtlcs > uint16(MaxHTLCNumber/2) { return ErrMaxHtlcNumTooLarge( c.MaxAcceptedHtlcs, uint16(MaxHTLCNumber/2), ) } // Fail if we consider maxHtlcs too small. If this is too small we // cannot offer many HTLCs to the remote. const minNumHtlc = 5 if c.MaxAcceptedHtlcs < minNumHtlc { return ErrMaxHtlcNumTooSmall(c.MaxAcceptedHtlcs, minNumHtlc) } // Fail if we consider maxValueInFlight too small. We currently require // the remote to at least allow minNumHtlc * minHtlc in flight. if c.MaxPendingAmount < minNumHtlc*c.MinHTLC { return ErrMaxValueInFlightTooSmall( c.MaxPendingAmount, minNumHtlc*c.MinHTLC, ) } // Our dust limit should always be less than or equal to our proposed // channel reserve. if r.ourContribution.DustLimit > c.ChanReserve { r.ourContribution.DustLimit = c.ChanReserve } r.ourContribution.ChanReserve = c.ChanReserve r.ourContribution.MaxPendingAmount = c.MaxPendingAmount r.ourContribution.MinHTLC = c.MinHTLC r.ourContribution.MaxAcceptedHtlcs = c.MaxAcceptedHtlcs r.ourContribution.CsvDelay = c.CsvDelay return nil } // OurContribution returns the wallet's fully populated contribution to the // pending payment channel. See 'ChannelContribution' for further details // regarding the contents of a contribution. // // NOTE: This SHOULD NOT be modified. // TODO(roasbeef): make copy? func (r *ChannelReservation) OurContribution() *ChannelContribution { r.RLock() defer r.RUnlock() return r.ourContribution } // ProcessContribution verifies the counterparty's contribution to the pending // payment channel. As a result of this incoming message, lnwallet is able to // build the funding transaction, and both commitment transactions. Once this // message has been processed, all signatures to inputs to the funding // transaction belonging to the wallet are available. Additionally, the wallet // will generate a signature to the counterparty's version of the commitment // transaction. func (r *ChannelReservation) ProcessContribution(theirContribution *ChannelContribution) error { errChan := make(chan error, 1) r.wallet.msgChan <- &addContributionMsg{ pendingFundingID: r.reservationID, contribution: theirContribution, err: errChan, } return <-errChan } // ProcessSingleContribution verifies, and records the initiator's contribution // to this pending single funder channel. Internally, no further action is // taken other than recording the initiator's contribution to the single funder // channel. func (r *ChannelReservation) ProcessSingleContribution(theirContribution *ChannelContribution) error { errChan := make(chan error, 1) r.wallet.msgChan <- &addSingleContributionMsg{ pendingFundingID: r.reservationID, contribution: theirContribution, err: errChan, } return <-errChan } // TheirContribution returns the counterparty's pending contribution to the // payment channel. See 'ChannelContribution' for further details regarding the // contents of a contribution. This attribute will ONLY be available after a // call to .ProcessContribution(). // // NOTE: This SHOULD NOT be modified. func (r *ChannelReservation) TheirContribution() *ChannelContribution { r.RLock() defer r.RUnlock() return r.theirContribution } // OurSignatures retrieves the wallet's signatures to all inputs to the funding // transaction belonging to itself, and also a signature for the counterparty's // version of the commitment transaction. The signatures for the wallet's // inputs to the funding transaction are returned in sorted order according to // BIP-69: https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki. // // NOTE: These signatures will only be populated after a call to // .ProcessContribution() func (r *ChannelReservation) OurSignatures() ([]*InputScript, []byte) { r.RLock() defer r.RUnlock() return r.ourFundingInputScripts, r.ourCommitmentSig } // CompleteReservation finalizes the pending channel reservation, transitioning // from a pending payment channel, to an open payment channel. All passed // signatures to the counterparty's inputs to the funding transaction will be // fully verified. Signatures are expected to be passed in sorted order // according to BIP-69: // https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki. // Additionally, verification is performed in order to ensure that the // counterparty supplied a valid signature to our version of the commitment // transaction. Once this method returns, caller's should broadcast the // created funding transaction, then call .WaitForChannelOpen() which will // block until the funding transaction obtains the configured number of // confirmations. Once the method unblocks, a LightningChannel instance is // returned, marking the channel available for updates. func (r *ChannelReservation) CompleteReservation(fundingInputScripts []*InputScript, commitmentSig []byte) (*channeldb.OpenChannel, error) { // TODO(roasbeef): add flag for watch or not? errChan := make(chan error, 1) completeChan := make(chan *channeldb.OpenChannel, 1) r.wallet.msgChan <- &addCounterPartySigsMsg{ pendingFundingID: r.reservationID, theirFundingInputScripts: fundingInputScripts, theirCommitmentSig: commitmentSig, completeChan: completeChan, err: errChan, } return <-completeChan, <-errChan } // CompleteReservationSingle finalizes the pending single funder channel // reservation. Using the funding outpoint of the constructed funding // transaction, and the initiator's signature for our version of the commitment // transaction, we are able to verify the correctness of our commitment // transaction as crafted by the initiator. Once this method returns, our // signature for the initiator's version of the commitment transaction is // available via the .OurSignatures() method. As this method should only be // called as a response to a single funder channel, only a commitment signature // will be populated. func (r *ChannelReservation) CompleteReservationSingle(fundingPoint *wire.OutPoint, commitSig []byte) (*channeldb.OpenChannel, error) { errChan := make(chan error, 1) completeChan := make(chan *channeldb.OpenChannel, 1) r.wallet.msgChan <- &addSingleFunderSigsMsg{ pendingFundingID: r.reservationID, fundingOutpoint: fundingPoint, theirCommitmentSig: commitSig, completeChan: completeChan, err: errChan, } return <-completeChan, <-errChan } // TheirSignatures returns the counterparty's signatures to all inputs to the // funding transaction belonging to them, as well as their signature for the // wallet's version of the commitment transaction. This methods is provided for // additional verification, such as needed by tests. // // NOTE: These attributes will be unpopulated before a call to // .CompleteReservation(). func (r *ChannelReservation) TheirSignatures() ([]*InputScript, []byte) { r.RLock() defer r.RUnlock() return r.theirFundingInputScripts, r.theirCommitmentSig } // FinalFundingTx returns the finalized, fully signed funding transaction for // this reservation. // // NOTE: If this reservation was created as the non-initiator to a single // funding workflow, then the full funding transaction will not be available. // Instead we will only have the final outpoint of the funding transaction. func (r *ChannelReservation) FinalFundingTx() *wire.MsgTx { r.RLock() defer r.RUnlock() return r.fundingTx } // FundingOutpoint returns the outpoint of the funding transaction. // // NOTE: The pointer returned will only be set once the .ProcessContribution() // method is called in the case of the initiator of a single funder workflow, // and after the .CompleteReservationSingle() method is called in the case of // a responder to a single funder workflow. func (r *ChannelReservation) FundingOutpoint() *wire.OutPoint { r.RLock() defer r.RUnlock() return &r.partialState.FundingOutpoint } // Cancel abandons this channel reservation. This method should be called in // the scenario that communications with the counterparty break down. Upon // cancellation, all resources previously reserved for this pending payment // channel are returned to the free pool, allowing subsequent reservations to // utilize the now freed resources. func (r *ChannelReservation) Cancel() error { errChan := make(chan error, 1) r.wallet.msgChan <- &fundingReserveCancelMsg{ pendingFundingID: r.reservationID, err: errChan, } return <-errChan } // OpenChannelDetails wraps the finalized fully confirmed channel which // resulted from a ChannelReservation instance with details concerning exactly // _where_ in the chain the channel was ultimately opened. type OpenChannelDetails struct { // Channel is the active channel created by an instance of a // ChannelReservation and the required funding workflow. Channel *LightningChannel // ConfirmationHeight is the block height within the chain that // included the channel. ConfirmationHeight uint32 // TransactionIndex is the index within the confirming block that the // transaction resides. TransactionIndex uint32 }