package lnwallet import ( "encoding/hex" "errors" "fmt" "math" "sync" "sync/atomic" "github.com/btcsuite/btcd/btcjson" "github.com/lightningnetwork/lnd/chainntfs" "github.com/lightningnetwork/lnd/chainntfs/btcdnotify" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/elkrem" "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/txscript" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcrpcclient" "github.com/btcsuite/btcutil" "github.com/btcsuite/btcutil/coinset" "github.com/btcsuite/btcutil/txsort" "github.com/btcsuite/btcwallet/chain" "github.com/btcsuite/btcwallet/waddrmgr" btcwallet "github.com/btcsuite/btcwallet/wallet" ) const ( // The size of the buffered queue of requests to the wallet from the // outside word. msgBufferSize = 100 ) var ( // Error types ErrInsufficientFunds = errors.New("not enough available outputs to " + "create funding transaction") // Namespace bucket keys. lightningNamespaceKey = []byte("ln-wallet") waddrmgrNamespaceKey = []byte("waddrmgr") wtxmgrNamespaceKey = []byte("wtxmgr") ) // initFundingReserveReq is the first message sent to initiate the workflow // required to open a payment channel with a remote peer. The initial required // paramters are configurable accross channels. These paramters are to be chosen // depending on the fee climate within the network, and time value of funds to // be locked up within the channel. Upon success a ChannelReservation will be // created in order to track the lifetime of this pending channel. Outputs // selected will be 'locked', making them unavailable, for any other pending // reservations. Therefore, all channels in reservation limbo will be periodically // after a timeout period in order to avoid "exhaustion" attacks. // NOTE: The workflow currently assumes fully balanced symmetric channels. // Meaning both parties must encumber the same amount of funds. // TODO(roasbeef): zombie reservation sweeper goroutine. type initFundingReserveMsg struct { // The amount of funds requested for this channel. fundingAmount btcutil.Amount // The minimum accepted satoshis/KB fee for the funding transaction. In // order to ensure timely confirmation, it is recomened that this fee // should be generous, paying some multiple of the accepted base fee // rate of the network. // TODO(roasbeef): integrate fee estimation project... minFeeRate btcutil.Amount // The ID of the remote node we would like to open a channel with. nodeID [32]byte // The delay on the "pay-to-self" output(s) of the commitment transaction. csvDelay uint32 // A channel in which all errors will be sent accross. Will be nil if // this initial set is succesful. // NOTE: In order to avoid deadlocks, this channel MUST be buffered. err chan error // A ChannelReservation with our contributions filled in will be sent // accross this channel in the case of a succesfully reservation // initiation. In the case of an error, this will read a nil pointer. // NOTE: In order to avoid deadlocks, this channel MUST be buffered. resp chan *ChannelReservation } // fundingReserveCancelMsg is a message reserved for cancelling an existing // channel reservation identified by its reservation ID. Cancelling a reservation // frees its locked outputs up, for inclusion within further reservations. type fundingReserveCancelMsg struct { pendingFundingID uint64 // NOTE: In order to avoid deadlocks, this channel MUST be buffered. err chan error // Buffered } // addContributionMsg represents a message executing the second phase of the // channel reservation workflow. This message carries the counterparty's // "contribution" to the payment channel. In the case that this message is // processed without generating any errors, then channel reservation will then // be able to construct the funding tx, both commitment transactions, and // finally generate signatures for all our inputs to the funding transaction, // and for the remote node's version of the commitment transaction. type addContributionMsg struct { pendingFundingID uint64 // TODO(roasbeef): Should also carry SPV proofs in we're in SPV mode contribution *ChannelContribution // NOTE: In order to avoid deadlocks, this channel MUST be buffered. err chan error } // addCounterPartySigsMsg represents the final message required to complete, // and 'open' a payment channel. This message carries the counterparty's // signatures for each of their inputs to the funding transaction, and also a // signature allowing us to spend our version of the commitment transaction. // If we're able to verify all the signatures are valid, the funding transaction // will be broadcast to the network. After the funding transaction gains a // configurable number of confirmations, the channel is officially considered // 'open'. type addCounterPartySigsMsg struct { pendingFundingID uint64 // Should be order of sorted inputs that are theirs. Sorting is done // in accordance to BIP-69: // https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki. theirFundingInputScripts []*InputScript // This should be 1/2 of the signatures needed to succesfully spend our // version of the commitment transaction. theirCommitmentSig []byte // NOTE: In order to avoid deadlocks, this channel MUST be buffered. err chan error } // LightningWallet is a domain specific, yet general Bitcoin wallet capable of // executing workflow required to interact with the Lightning Network. It is // domain specific in the sense that it understands all the fancy scripts used // within the Lightning Network, channel lifetimes, etc. However, it embedds a // general purpose Bitcoin wallet within it. Therefore, it is also able to serve // as a regular Bitcoin wallet which uses HD keys. The wallet is highly concurrent // internally. All communication, and requests towards the wallet are // dispatched as messages over channels, ensuring thread safety across all // operations. Interaction has been designed independant of any peer-to-peer // communication protocol, allowing the wallet to be self-contained and embeddable // within future projects interacting with the Lightning Network. // NOTE: At the moment the wallet requires a btcd full node, as it's dependant // on btcd's websockets notifications as even triggers during the lifetime of // a channel. However, once the chainntnfs package is complete, the wallet // will be compatible with multiple RPC/notification services such as Electrum, // Bitcoin Core + ZeroMQ, etc. Eventually, the wallet won't require a full-node // at all, as SPV support is integrated inot btcwallet. type LightningWallet struct { // This mutex is to be held when generating external keys to be used // as multi-sig, and commitment keys within the channel. KeyGenMtx sync.RWMutex // This mutex MUST be held when performing coin selection in order to // avoid inadvertently creating multiple funding transaction which // double spend inputs accross each other. coinSelectMtx sync.RWMutex // A wrapper around a namespace within boltdb reserved for ln-based // wallet meta-data. See the 'channeldb' package for further // information. channelDB *channeldb.DB // Used by in order to obtain notifications about funding transaction // reaching a specified confirmation depth, and to catch // counterparty's broadcasting revoked commitment states. chainNotifier chainntnfs.ChainNotifier // The core wallet, all non Lightning Network specific interaction is // proxied to the internal wallet. *btcwallet.Wallet // An active RPC connection to a full-node. In the case of a btcd node, // websockets are used for notifications. If using Bitcoin Core, // notifications are either generated via long-polling or the usage of // ZeroMQ. // TODO(roasbeef): make into interface need: getrawtransaction + gettxout // * getrawtransaction -> verify proof of channel links // * gettxout -> verify inputs to funding tx exist and are unspent rpc *chain.RPCClient // All messages to the wallet are to be sent accross this channel. msgChan chan interface{} // Incomplete payment channels are stored in the map below. An intent // to create a payment channel is tracked as a "reservation" within // limbo. Once the final signatures have been exchanged, a reservation // is removed from limbo. Each reservation is tracked by a unique // monotonically integer. All requests concerning the channel MUST // carry a valid, active funding ID. fundingLimbo map[uint64]*ChannelReservation nextFundingID uint64 limboMtx sync.RWMutex // TODO(roasbeef): zombie garbage collection routine to solve // lost-object/starvation problem/attack. cfg *Config started int32 shutdown int32 quit chan struct{} wg sync.WaitGroup // TODO(roasbeef): handle wallet lock/unlock } // NewLightningWallet creates/opens and initializes a LightningWallet instance. // If the wallet has never been created (according to the passed dataDir), first-time // setup is executed. // TODO(roasbeef): fin...add config func NewLightningWallet(config *Config, cdb *channeldb.DB) (*LightningWallet, error) { // Ensure the wallet exists or create it when the create flag is set. netDir := networkDir(config.DataDir, config.NetParams) var pubPass []byte if config.PublicPass == nil { pubPass = defaultPubPassphrase } else { pubPass = config.PublicPass } loader := btcwallet.NewLoader(config.NetParams, netDir) walletExists, err := loader.WalletExists() if err != nil { return nil, err } var createID bool var wallet *btcwallet.Wallet if !walletExists { // Wallet has never been created, perform initial set up. wallet, err = loader.CreateNewWallet(pubPass, config.PrivatePass, config.HdSeed) if err != nil { return nil, err } createID = true } else { // Wallet has been created and been initialized at this point, open it // along with all the required DB namepsaces, and the DB itself. wallet, err = loader.OpenExistingWallet(pubPass, false) if err != nil { return nil, err } } if err := wallet.Manager.Unlock(config.PrivatePass); err != nil { return nil, err } // If we just created the wallet, then reserve, and store a key for // our ID within the Lightning Network. if createID { account := uint32(waddrmgr.DefaultAccountNum) adrs, err := wallet.Manager.NextInternalAddresses(account, 1, waddrmgr.WitnessPubKey) if err != nil { return nil, err } idPubkeyHash := adrs[0].Address().ScriptAddress() if err := cdb.PutIdKey(idPubkeyHash); err != nil { return nil, err } log.Infof("stored identity key pubkey hash in channeldb") } // Create a special websockets rpc client for btcd which will be used // by the wallet for notifications, calls, etc. rpcc, err := chain.NewRPCClient(config.NetParams, config.RpcHost, config.RpcUser, config.RpcPass, config.CACert, false, 20) if err != nil { return nil, err } // Using the same authentication info, create a config for a second // rpcclient which will be used by the current default chain // notifier implemenation. rpcConfig := &btcrpcclient.ConnConfig{ Host: config.RpcHost, Endpoint: "ws", User: config.RpcUser, Pass: config.RpcPass, Certificates: config.CACert, DisableTLS: false, DisableConnectOnNew: true, DisableAutoReconnect: false, } chainNotifier, err := btcdnotify.NewBtcdNotifier(rpcConfig) if err != nil { return nil, err } // TODO(roasbeef): logging return &LightningWallet{ chainNotifier: chainNotifier, rpc: rpcc, Wallet: wallet, channelDB: cdb, msgChan: make(chan interface{}, msgBufferSize), // TODO(roasbeef): make this atomic.Uint32 instead? Which is // faster, locks or CAS? I'm guessing CAS because assembly: // * https://golang.org/src/sync/atomic/asm_amd64.s nextFundingID: 0, cfg: config, fundingLimbo: make(map[uint64]*ChannelReservation), quit: make(chan struct{}), }, nil } // Startup establishes a connection to the RPC source, and spins up all // goroutines required to handle incoming messages. func (l *LightningWallet) Startup() error { // Already started? if atomic.AddInt32(&l.started, 1) != 1 { return nil } // Establish an RPC connection in additino to starting the goroutines // in the underlying wallet. if err := l.rpc.Start(); err != nil { return err } l.Start() // Start the notification server. This is used so channel managment // goroutines can be notified when a funding transaction reaches a // sufficient number of confirmations, or when the input for the funding // transaction is spent in an attempt at an uncooperative close by the // counter party. if err := l.chainNotifier.Start(); err != nil { return err } // Pass the rpc client into the wallet so it can sync up to the current // main chain. l.SynchronizeRPC(l.rpc) l.wg.Add(1) // TODO(roasbeef): multiple request handlers? go l.requestHandler() return nil } // Shutdown gracefully stops the wallet, and all active goroutines. func (l *LightningWallet) Shutdown() error { if atomic.AddInt32(&l.shutdown, 1) != 1 { return nil } // Signal the underlying wallet controller to shutdown, waiting until // all active goroutines have been shutdown. l.Stop() l.WaitForShutdown() l.rpc.Shutdown() l.chainNotifier.Stop() close(l.quit) l.wg.Wait() return nil } // requestHandler is the primary goroutine(s) resposible for handling, and // dispatching relies to all messages. func (l *LightningWallet) requestHandler() { out: for { select { case m := <-l.msgChan: switch msg := m.(type) { case *initFundingReserveMsg: l.handleFundingReserveRequest(msg) case *fundingReserveCancelMsg: l.handleFundingCancelRequest(msg) case *addContributionMsg: l.handleContributionMsg(msg) case *addCounterPartySigsMsg: l.handleFundingCounterPartySigs(msg) } case <-l.quit: // TODO: do some clean up break out } } l.wg.Done() } // InitChannelReservation kicks off the 3-step workflow required to succesfully // open a payment channel with a remote node. As part of the funding // reservation, the inputs selected for the funding transaction are 'locked'. // This ensures that multiple channel reservations aren't double spending the // same inputs in the funding transaction. If reservation initialization is // succesful, a ChannelReservation containing our completed contribution is // returned. Our contribution contains all the items neccessary to allow the // counter party to build the funding transaction, and both versions of the // commitment transaction. Otherwise, an error occured a nil pointer along with // an error are returned. // // Once a ChannelReservation has been obtained, two // additional steps must be processed before a payment channel can be considered // 'open'. The second step validates, and processes the counterparty's channel // contribution. The third, and final step verifies all signatures for the inputs // of the funding transaction, and that the signature we records for our version // of the commitment transaction is valid. func (l *LightningWallet) InitChannelReservation(a btcutil.Amount, theirID [32]byte, csvDelay uint32) (*ChannelReservation, error) { errChan := make(chan error, 1) respChan := make(chan *ChannelReservation, 1) l.msgChan <- &initFundingReserveMsg{ fundingAmount: a, csvDelay: csvDelay, nodeID: theirID, err: errChan, resp: respChan, } return <-respChan, <-errChan } // handleFundingReserveRequest processes a message intending to create, and // validate a funding reservation request. func (l *LightningWallet) handleFundingReserveRequest(req *initFundingReserveMsg) { // Create a limbo and record entry for this newly pending funding request. l.limboMtx.Lock() id := l.nextFundingID reservation := newChannelReservation(req.fundingAmount, req.minFeeRate, l, id) l.nextFundingID++ l.fundingLimbo[id] = reservation l.limboMtx.Unlock() // Grab the mutex on the ChannelReservation to ensure thead-safety reservation.Lock() defer reservation.Unlock() reservation.partialState.TheirLNID = req.nodeID ourContribution := reservation.ourContribution ourContribution.CsvDelay = req.csvDelay reservation.partialState.LocalCsvDelay = req.csvDelay // We hold the coin select mutex while querying for outputs, and // performing coin selection in order to avoid inadvertent double spends // accross funding transactions. // NOTE: We don't use defer her so we can properly release the lock // when we encounter an error condition. l.coinSelectMtx.Lock() // TODO(roasbeef): check if balance is insufficient, if so then select // on two channels, one is a time.After that will bail out with // insuffcient funds, the other is a notification that the balance has // been updated make(chan struct{}, 1). // Find all unlocked unspent witness outputs with greater than 6 // confirmations. // TODO(roasbeef): make 6 a config paramter? unspentOutputs, err := l.ListUnspentWitness(6) if err != nil { l.coinSelectMtx.Unlock() req.err <- err req.resp <- nil return } // Convert the outputs to coins for coin selection below. coins, err := outputsToCoins(unspentOutputs) if err != nil { l.coinSelectMtx.Unlock() req.err <- err req.resp <- nil return } // Peform coin selection over our available, unlocked unspent outputs // in order to find enough coins to meet the funding amount requirements. // // TODO(roasbeef): Should extend coinset with optimal coin selection // heuristics for our use case. // TODO(roasbeef): factor in fees.. // TODO(roasbeef): possibly integrate the fee prediction project? if // results hold up... // NOTE: this current selection assumes "priority" is still a thing. selector := &coinset.MaxValueAgeCoinSelector{ MaxInputs: 10, MinChangeAmount: 10000, } selectedCoins, err := selector.CoinSelect(req.fundingAmount, coins) if err != nil { l.coinSelectMtx.Unlock() req.err <- err req.resp <- nil return } // Lock the selected coins. These coins are now "reserved", this // prevents concurrent funding requests from referring to and this // double-spending the same set of coins. ourContribution.Inputs = make([]*wire.TxIn, len(selectedCoins.Coins())) for i, coin := range selectedCoins.Coins() { txout := wire.NewOutPoint(coin.Hash(), coin.Index()) l.LockOutpoint(*txout) // Empty sig script, we'll actually sign if this reservation is // queued up to be completed (the other side accepts). outPoint := wire.NewOutPoint(coin.Hash(), coin.Index()) ourContribution.Inputs[i] = wire.NewTxIn(outPoint, nil, nil) } l.coinSelectMtx.Unlock() // Create some possibly neccessary change outputs. selectedTotalValue := coinset.NewCoinSet(selectedCoins.Coins()).TotalValue() if selectedTotalValue > req.fundingAmount { ourContribution.ChangeOutputs = make([]*wire.TxOut, 1) // Change is necessary. Query for an available change address to // send the remainder to. changeAddr, err := l.NewChangeAddress(waddrmgr.DefaultAccountNum, waddrmgr.WitnessPubKey) if err != nil { req.err <- err req.resp <- nil return } changeAddrScript, err := txscript.PayToAddrScript(changeAddr) if err != nil { req.err <- err req.resp <- nil return } changeAmount := selectedTotalValue - req.fundingAmount ourContribution.ChangeOutputs[0] = wire.NewTxOut(int64(changeAmount), changeAddrScript) } // TODO(roasbeef): re-calculate fees here to minFeePerKB, may need more inputs // Grab two fresh keys from out HD chain, one will be used for the // multi-sig funding transaction, and the other for the commitment // transaction. multiSigKey, err := l.getNextRawKey() if err != nil { req.err <- err req.resp <- nil return } commitKey, err := l.getNextRawKey() if err != nil { req.err <- err req.resp <- nil return } reservation.partialState.MultiSigKey = multiSigKey ourContribution.MultiSigKey = multiSigKey.PubKey() reservation.partialState.OurCommitKey = commitKey ourContribution.CommitKey = commitKey.PubKey() // Generate a fresh address to be used in the case of a cooperative // channel close. deliveryAddress, err := l.NewAddress(waddrmgr.DefaultAccountNum, waddrmgr.WitnessPubKey) if err != nil { req.err <- err req.resp <- nil return } deliveryScript, err := txscript.PayToAddrScript(deliveryAddress) if err != nil { req.err <- err req.resp <- nil return } reservation.partialState.OurDeliveryScript = deliveryScript ourContribution.DeliveryAddress = deliveryAddress // Create a new elkrem for verifiable transaction revocations. This // will be used to generate revocation hashes for our past/current // commitment transactions once we start to make payments within the // channel. // TODO(roabeef): should be HMAC based...REMOVE BEFORE ALPHA var zero wire.ShaHash elkremSender := elkrem.NewElkremSender(63, zero) reservation.partialState.LocalElkrem = &elkremSender firstPrimage, err := elkremSender.AtIndex(0) if err != nil { req.err <- err req.resp <- nil return } copy(ourContribution.RevocationHash[:], btcutil.Hash160(firstPrimage[:])) // Funding reservation request succesfully handled. The funding inputs // will be marked as unavailable until the reservation is either // completed, or cancecled. req.resp <- reservation req.err <- nil } // handleFundingReserveCancel cancels an existing channel reservation. As part // of the cancellation, outputs previously selected as inputs for the funding // transaction via coin selection are freed allowing future reservations to // include them. func (l *LightningWallet) handleFundingCancelRequest(req *fundingReserveCancelMsg) { // TODO(roasbeef): holding lock too long // RLOCK? l.limboMtx.Lock() defer l.limboMtx.Unlock() pendingReservation, ok := l.fundingLimbo[req.pendingFundingID] if !ok { // TODO(roasbeef): make new error, "unkown funding state" or something req.err <- fmt.Errorf("attempted to cancel non-existant funding state") return } // Grab the mutex on the ChannelReservation to ensure thead-safety pendingReservation.Lock() defer pendingReservation.Unlock() // Mark all previously locked outpoints as usuable for future funding // requests. for _, unusedInput := range pendingReservation.ourContribution.Inputs { l.UnlockOutpoint(unusedInput.PreviousOutPoint) } // TODO(roasbeef): is it even worth it to keep track of unsed keys? // TODO(roasbeef): Is it possible to mark the unused change also as // available? delete(l.fundingLimbo, req.pendingFundingID) req.err <- nil } // handleFundingCounterPartyFunds processes the second workflow step for the // lifetime of a channel reservation. Upon completion, the reservation will // carry a completed funding transaction (minus the counterparty's input // signatures), both versions of the commitment transaction, and our signature // for their version of the commitment transaction. func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) { l.limboMtx.Lock() pendingReservation, ok := l.fundingLimbo[req.pendingFundingID] l.limboMtx.Unlock() if !ok { req.err <- fmt.Errorf("attempted to update non-existant funding state") return } // Grab the mutex on the ChannelReservation to ensure thead-safety pendingReservation.Lock() defer pendingReservation.Unlock() // Create a blank, fresh transaction. Soon to be a complete funding // transaction which will allow opening a lightning channel. pendingReservation.partialState.FundingTx = wire.NewMsgTx() fundingTx := pendingReservation.partialState.FundingTx // Some temporary variables to cut down on the resolution verbosity. pendingReservation.theirContribution = req.contribution theirContribution := req.contribution ourContribution := pendingReservation.ourContribution // Add all multi-party inputs and outputs to the transaction. for _, ourInput := range ourContribution.Inputs { fundingTx.AddTxIn(ourInput) } for _, theirInput := range theirContribution.Inputs { fundingTx.AddTxIn(theirInput) } for _, ourChangeOutput := range ourContribution.ChangeOutputs { fundingTx.AddTxOut(ourChangeOutput) } for _, theirChangeOutput := range theirContribution.ChangeOutputs { fundingTx.AddTxOut(theirChangeOutput) } ourKey := pendingReservation.partialState.MultiSigKey theirKey := theirContribution.MultiSigKey // Finally, add the 2-of-2 multi-sig output which will set up the lightning // channel. channelCapacity := int64(pendingReservation.partialState.Capacity) redeemScript, multiSigOut, err := genFundingPkScript(ourKey.PubKey().SerializeCompressed(), theirKey.SerializeCompressed(), channelCapacity) if err != nil { req.err <- err return } // Register intent for notifications related to the funding output. // This'll allow us to properly track the number of confirmations the // funding tx has once it has been broadcasted. lastBlock := l.Manager.SyncedTo() scriptAddr, err := l.Manager.ImportScript(redeemScript, &lastBlock) if err != nil { req.err <- err return } if err := l.rpc.NotifyReceived([]btcutil.Address{scriptAddr.Address()}); err != nil { req.err <- err return } pendingReservation.partialState.FundingRedeemScript = redeemScript fundingTx.AddTxOut(multiSigOut) // Sort the transaction. Since both side agree to a cannonical // ordering, by sorting we no longer need to send the entire // transaction. Only signatures will be exchanged. txsort.InPlaceSort(pendingReservation.partialState.FundingTx) // Next, sign all inputs that are ours, collecting the signatures in // order of the inputs. pendingReservation.ourFundingInputScripts = make([]*InputScript, 0, len(ourContribution.Inputs)) hashCache := txscript.NewTxSigHashes(fundingTx) for i, txIn := range fundingTx.TxIn { // Does the wallet know about the txin? txDetail, _ := l.TxStore.TxDetails(&txIn.PreviousOutPoint.Hash) if txDetail == nil { continue } // Is this our txin? prevIndex := txIn.PreviousOutPoint.Index prevOut := txDetail.TxRecord.MsgTx.TxOut[prevIndex] _, addrs, _, _ := txscript.ExtractPkScriptAddrs(prevOut.PkScript, l.cfg.NetParams) apkh := addrs[0] ai, err := l.Manager.Address(apkh) if err != nil { req.err <- fmt.Errorf("cannot get address info: %v", err) return } pka := ai.(waddrmgr.ManagedPubKeyAddress) privKey, err := pka.PrivKey() if err != nil { req.err <- fmt.Errorf("cannot get private key: %v", err) return } var witnessProgram []byte inputScript := &InputScript{} // If we're spending p2wkh output nested within a p2sh output, // then we'll need to attach a sigScript in addition to witness // data. if pka.IsNestedWitness() { witnessProgram, err = txscript.PayToAddrScript(pka.Address()) if err != nil { req.err <- fmt.Errorf("unable to create witness program: %v", err) return } bldr := txscript.NewScriptBuilder() bldr.AddData(witnessProgram) scriptSig, err := bldr.Script() if err != nil { req.err <- fmt.Errorf("unable to create scriptsig: %v", err) return } txIn.SignatureScript = scriptSig inputScript.ScriptSig = scriptSig } else { witnessProgram = prevOut.PkScript } // Generate a valid witness stack for the input. inputValue := prevOut.Value witnessScript, err := txscript.WitnessScript(fundingTx, hashCache, i, inputValue, witnessProgram, txscript.SigHashAll, privKey, true) if err != nil { req.err <- fmt.Errorf("cannot create witnessscript: %s", err) return } txIn.Witness = witnessScript inputScript.Witness = witnessScript pendingReservation.ourFundingInputScripts = append( pendingReservation.ourFundingInputScripts, inputScript, ) } // Initialize an empty sha-chain for them, tracking the current pending // revocation hash (we don't yet know the pre-image so we can't add it // to the chain). e := elkrem.NewElkremReceiver(63) // TODO(roasbeef): this is incorrect!! fix before lnstate integration var zero wire.ShaHash if err := e.AddNext(&zero); err != nil { req.err <- nil return } pendingReservation.partialState.RemoteElkrem = &e pendingReservation.partialState.TheirCurrentRevocation = theirContribution.RevocationHash // Grab the hash of the current pre-image in our chain, this is needed // for our commitment tx. // TODO(roasbeef): grab partial state above to avoid long attr chain ourCurrentRevokeHash := pendingReservation.ourContribution.RevocationHash // Create the txIn to our commitment transaction. In the process, we // need to locate the index of the multi-sig output on the funding tx // since the outputs are cannonically sorted. fundingNTxid := fundingTx.TxSha() // NOTE: assumes testnet-L _, multiSigIndex := findScriptOutputIndex(fundingTx, multiSigOut.PkScript) fundingTxIn := wire.NewTxIn(wire.NewOutPoint(&fundingNTxid, multiSigIndex), nil, nil) // With the funding tx complete, create both commitment transactions. initialBalance := ourContribution.FundingAmount pendingReservation.fundingLockTime = theirContribution.CsvDelay ourCommitKey := ourContribution.CommitKey theirCommitKey := theirContribution.CommitKey ourCommitTx, err := createCommitTx(fundingTxIn, ourCommitKey, theirCommitKey, ourCurrentRevokeHash[:], theirContribution.CsvDelay, initialBalance, initialBalance) if err != nil { req.err <- err return } theirCommitTx, err := createCommitTx(fundingTxIn, theirCommitKey, ourCommitKey, theirContribution.RevocationHash[:], theirContribution.CsvDelay, initialBalance, initialBalance) if err != nil { req.err <- err return } // Sort both transactions according to the agreed upon cannonical // ordering. This lets us skip sending the entire transaction over, // instead we'll just send signatures. txsort.InPlaceSort(ourCommitTx) txsort.InPlaceSort(theirCommitTx) deliveryScript, err := txscript.PayToAddrScript(theirContribution.DeliveryAddress) if err != nil { req.err <- err return } // Record newly available information witin the open channel state. pendingReservation.partialState.RemoteCsvDelay = theirContribution.CsvDelay pendingReservation.partialState.TheirDeliveryScript = deliveryScript pendingReservation.partialState.ChanID = fundingNTxid pendingReservation.partialState.TheirCommitKey = theirCommitKey pendingReservation.partialState.TheirCommitTx = theirCommitTx pendingReservation.partialState.OurCommitTx = ourCommitTx // Generate a signature for their version of the initial commitment // transaction. sigTheirCommit, err := txscript.RawTxInSignature(theirCommitTx, 0, redeemScript, txscript.SigHashAll, ourKey) if err != nil { req.err <- err return } pendingReservation.ourCommitmentSig = sigTheirCommit req.err <- nil } // handleFundingCounterPartySigs is the final step in the channel reservation // workflow. During this setp, we validate *all* the received signatures for // inputs to the funding transaction. If any of these are invalid, we bail, // and forcibly cancel this funding request. Additionally, we ensure that the // signature we received from the counterparty for our version of the commitment // transaction allows us to spend from the funding output with the addition of // our signature. func (l *LightningWallet) handleFundingCounterPartySigs(msg *addCounterPartySigsMsg) { l.limboMtx.RLock() pendingReservation, ok := l.fundingLimbo[msg.pendingFundingID] l.limboMtx.RUnlock() if !ok { msg.err <- fmt.Errorf("attempted to update non-existant funding state") return } // Grab the mutex on the ChannelReservation to ensure thead-safety pendingReservation.Lock() defer pendingReservation.Unlock() // Now we can complete the funding transaction by adding their // signatures to their inputs. pendingReservation.theirFundingInputScripts = msg.theirFundingInputScripts fundingTx := pendingReservation.partialState.FundingTx sigIndex := 0 fundingHashCache := txscript.NewTxSigHashes(fundingTx) for i, txin := range fundingTx.TxIn { if len(txin.Witness) == 0 { // Attach the input scripts so we can verify it below. inputScripts := pendingReservation.theirFundingInputScripts txin.Witness = inputScripts[sigIndex].Witness txin.SignatureScript = inputScripts[sigIndex].ScriptSig // Fetch the alleged previous output along with the // pkscript referenced by this input. prevOut := txin.PreviousOutPoint output, err := l.rpc.GetTxOut(&prevOut.Hash, prevOut.Index, false) if output == nil { msg.err <- fmt.Errorf("input to funding tx does not exist: %v", err) return } pkScript, err := hex.DecodeString(output.ScriptPubKey.Hex) if err != nil { msg.err <- err return } // Sadly, gettxout returns the output value in BTC // instead of satoshis. inputValue := int64(output.Value) * 1e8 // Ensure that the witness+sigScript combo is valid. vm, err := txscript.NewEngine(pkScript, fundingTx, i, txscript.StandardVerifyFlags, nil, fundingHashCache, inputValue) if err != nil { // TODO(roasbeef): cancel at this stage if invalid sigs? msg.err <- fmt.Errorf("cannot create script engine: %s", err) return } if err = vm.Execute(); err != nil { msg.err <- fmt.Errorf("cannot validate transaction: %s", err) return } sigIndex++ } } // At this point, we can also record and verify their signature for our // commitment transaction. pendingReservation.theirCommitmentSig = msg.theirCommitmentSig commitTx := pendingReservation.partialState.OurCommitTx theirKey := pendingReservation.theirContribution.MultiSigKey ourKey := pendingReservation.partialState.MultiSigKey // Re-generate both the redeemScript and p2sh output. We sign the // redeemScript script, but include the p2sh output as the subscript // for verification. redeemScript := pendingReservation.partialState.FundingRedeemScript p2wsh, err := witnessScriptHash(redeemScript) if err != nil { msg.err <- err return } // First, we sign our copy of the commitment transaction ourselves. channelValue := int64(pendingReservation.partialState.Capacity) hashCache := txscript.NewTxSigHashes(commitTx) ourCommitSig, err := txscript.RawTxInWitnessSignature(commitTx, hashCache, 0, channelValue, redeemScript, txscript.SigHashAll, ourKey) if err != nil { msg.err <- err return } // Next, create the spending scriptSig, and then verify that the script // is complete, allowing us to spend from the funding transaction. theirCommitSig := msg.theirCommitmentSig ourKeySer := ourKey.PubKey().SerializeCompressed() theirKeySer := theirKey.SerializeCompressed() witness := spendMultiSig(redeemScript, ourKeySer, ourCommitSig, theirKeySer, theirCommitSig) // Finally, create an instance of a Script VM, and ensure that the // Script executes succesfully. inputValue := pendingReservation.partialState.Capacity fmt.Println(inputValue) commitTx.TxIn[0].Witness = witness vm, err := txscript.NewEngine(p2wsh, commitTx, 0, txscript.StandardVerifyFlags, nil, nil, int64(inputValue)) if err != nil { msg.err <- err return } if err := vm.Execute(); err != nil { msg.err <- fmt.Errorf("counterparty's commitment signature is invalid: %v", err) return } // Funding complete, this entry can be removed from limbo. l.limboMtx.Lock() delete(l.fundingLimbo, pendingReservation.reservationID) // TODO(roasbeef): unlock outputs here, Store.InsertTx will handle marking // input in unconfirmed tx, so future coin selects don't pick it up // * also record location of change address so can use AddCredit l.limboMtx.Unlock() // Add the complete funding transaction to the DB, in it's open bucket // which will be used for the lifetime of this channel. if err := pendingReservation.partialState.FullSync(); err != nil { msg.err <- err return } // Create a goroutine to watch the chain so we can open the channel once // the funding tx has enough confirmations. // TODO(roasbeef): add number of confs to the confi go l.openChannelAfterConfirmations(pendingReservation, 3) msg.err <- nil } // openChannelAfterConfirmations creates, and opens a payment channel after // the funding transaction created within the passed channel reservation // obtains the specified number of confirmations. func (l *LightningWallet) openChannelAfterConfirmations(res *ChannelReservation, numConfs uint32) { // Register with the ChainNotifier for a notification once the funding // transaction reaches `numConfs` confirmations. txid := res.partialState.FundingTx.TxSha() confNtfn, _ := l.chainNotifier.RegisterConfirmationsNtfn(&txid, numConfs) // Wait until the specified number of confirmations has been reached, // or the wallet signals a shutdown. out: select { case <-confNtfn.Confirmed: break out case <-l.quit: res.chanOpen <- nil return } // Finally, create and officially open the payment channel! // TODO(roasbeef): CreationTime once tx is 'open' channel, _ := newLightningChannel(l, l.chainNotifier, l.channelDB, res.partialState) res.chanOpen <- channel } // getNextRawKey retrieves the next key within our HD key-chain for use within // as a multi-sig key within the funding transaction, or within the commitment // transaction's outputs. // TODO(roasbeef): on shutdown, write state of pending keys, then read back? func (l *LightningWallet) getNextRawKey() (*btcec.PrivateKey, error) { l.KeyGenMtx.Lock() defer l.KeyGenMtx.Unlock() nextAddr, err := l.Manager.NextExternalAddresses(waddrmgr.DefaultAccountNum, 1, waddrmgr.WitnessPubKey) if err != nil { return nil, err } pkAddr := nextAddr[0].(waddrmgr.ManagedPubKeyAddress) return pkAddr.PrivKey() } // ListUnspentWitness returns a slice of all the unspent outputs the wallet // controls which pay to witness programs either directly or indirectly. func (l *LightningWallet) ListUnspentWitness(minConfs int32) ([]*btcjson.ListUnspentResult, error) { // First, grab all the unfiltered currently unspent outputs. maxConfs := int32(math.MaxInt32) unspentOutputs, err := l.ListUnspent(minConfs, maxConfs, nil) if err != nil { return nil, err } // Next, we'll run through all the regular outputs, only saving those // which are p2wkh outputs or a p2wsh output nested within a p2sh output. witnessOutputs := make([]*btcjson.ListUnspentResult, 0, len(unspentOutputs)) for _, output := range unspentOutputs { pkScript, err := hex.DecodeString(output.ScriptPubKey) if err != nil { return nil, err } // TODO(roasbeef): this assumes all p2sh outputs returned by // the wallet are nested p2sh... if txscript.IsPayToWitnessPubKeyHash(pkScript) || txscript.IsPayToScriptHash(pkScript) { witnessOutputs = append(witnessOutputs, output) } } return witnessOutputs, nil } type WaddrmgrEncryptorDecryptor struct { M *waddrmgr.Manager } func (w *WaddrmgrEncryptorDecryptor) Encrypt(p []byte) ([]byte, error) { return w.M.Encrypt(waddrmgr.CKTPrivate, p) } func (w *WaddrmgrEncryptorDecryptor) Decrypt(c []byte) ([]byte, error) { return w.M.Decrypt(waddrmgr.CKTPrivate, c) } func (w *WaddrmgrEncryptorDecryptor) OverheadSize() uint32 { return 24 }