package main import ( "bytes" "encoding/binary" "errors" "fmt" "io" "sync" "sync/atomic" "github.com/boltdb/bolt" "github.com/davecgh/go-spew/spew" "github.com/lightningnetwork/lnd/chainntnfs" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnwallet" "github.com/roasbeef/btcd/btcec" "github.com/roasbeef/btcd/txscript" "github.com/roasbeef/btcd/wire" "github.com/roasbeef/btcutil" ) var ( // preschoolBucket stores outputs from commitment transactions that // have been broadcast, but not yet confirmed. This set of outputs is // persisted in case the system is shut down between the time when the // commitment has been broadcast and the time the transaction has been // confirmed on the blockchain. // TODO(roasbeef): modify schema later to be: // * chanPoint -> // {outpoint1} -> info // {outpoint2} -> info preschoolBucket = []byte("psc") // preschoolIndex is an index that maps original chanPoint that created // the channel to all the active time-locked outpoints for that // channel. preschoolIndex = []byte("preschool-index") // kindergartenBucket stores outputs from commitment transactions that // have received an initial confirmation, but which aren't yet // spendable because they require additional confirmations enforced by // CheckSequenceVerify. Once required additional confirmations have // been reported, a sweep transaction will be created to move the funds // out of these outputs. After a further six confirmations have been // reported, the outputs will be deleted from this bucket. The purpose // of this additional wait time is to ensure that a block // reorganization doesn't result in the sweep transaction getting // re-organized out of the chain. // TODO(roasbeef): modify schema later to be: // * height -> // {chanPoint} -> info kindergartenBucket = []byte("kdg") // contractIndex is an index that maps a contract's channel point to // the current information pertaining to the maturity of outputs within // that contract. Items are inserted into this index once they've been // accepted to pre-school and deleted after the output has been fully // swept. // // mapping: chanPoint -> graduationHeight || byte-offset-in-kindergartenBucket contractIndex = []byte("contract-index") // lastGraduatedHeightKey is used to persist the last block height that // has been checked for graduating outputs. When the nursery is // restarted, lastGraduatedHeightKey is used to determine the point // from which it's necessary to catch up. lastGraduatedHeightKey = []byte("lgh") byteOrder = binary.BigEndian ) // witnessType determines how an output's witness will be generated. The // default commitmentTimeLock type will generate a witness that will allow // spending of a time-locked transaction enforced by CheckSequenceVerify. type witnessType uint16 const ( commitmentTimeLock witnessType = 0 ) // witnessGenerator represents a function which is able to generate the final // witness for a particular public key script. This function acts as an // abstraction layer, hiding the details of the underlying script from the // utxoNursery. type witnessGenerator func(tx *wire.MsgTx, hc *txscript.TxSigHashes, inputIndex int) ([][]byte, error) // generateFunc will return the witnessGenerator function that a kidOutput uses // to generate the witness for a sweep transaction. Currently there is only one // witnessType but this will be expanded. func (wt witnessType) generateFunc(signer *lnwallet.Signer, descriptor *lnwallet.SignDescriptor) witnessGenerator { switch wt { case commitmentTimeLock: return func(tx *wire.MsgTx, hc *txscript.TxSigHashes, inputIndex int) ([][]byte, error) { desc := descriptor desc.SigHashes = hc desc.InputIndex = inputIndex return lnwallet.CommitSpendTimeout(*signer, desc, tx) } } return nil } // utxoNursery is a system dedicated to incubating time-locked outputs created // by the broadcast of a commitment transaction either by us, or the remote // peer. The nursery accepts outputs and "incubates" them until they've reached // maturity, then sweep the outputs into the source wallet. An output is // considered mature after the relative time-lock within the pkScript has // passed. As outputs reach their maturity age, they're swept in batches into // the source wallet, returning the outputs so they can be used within future // channels, or regular Bitcoin transactions. type utxoNursery struct { sync.RWMutex notifier chainntnfs.ChainNotifier wallet *lnwallet.LightningWallet db *channeldb.DB requests chan *incubationRequest started uint32 stopped uint32 quit chan struct{} wg sync.WaitGroup } // newUtxoNursery creates a new instance of the utxoNursery from a // ChainNotifier and LightningWallet instance. func newUtxoNursery(db *channeldb.DB, notifier chainntnfs.ChainNotifier, wallet *lnwallet.LightningWallet) *utxoNursery { return &utxoNursery{ notifier: notifier, wallet: wallet, requests: make(chan *incubationRequest), db: db, quit: make(chan struct{}), } } // Start launches all goroutines the utxoNursery needs to properly carry out // its duties. func (u *utxoNursery) Start() error { if !atomic.CompareAndSwapUint32(&u.started, 0, 1) { return nil } utxnLog.Tracef("Starting UTXO nursery") if err := u.reloadPreschool(); err != nil { return err } // Register with the notifier to receive notifications for each newly // connected block. We register during startup to ensure that no blocks // are missed while we are handling blocks that were missed during the // time the UTXO nursery was unavailable. newBlockChan, err := u.notifier.RegisterBlockEpochNtfn() if err != nil { return err } if err := u.catchUpKindergarten(); err != nil { return err } u.wg.Add(1) go u.incubator(newBlockChan) return nil } // reloadPreschool re-initializes the chain notifier with all of the outputs // that had been saved to the "preschool" database bucket prior to shutdown. func (u *utxoNursery) reloadPreschool() error { return u.db.View(func(tx *bolt.Tx) error { psclBucket := tx.Bucket(preschoolBucket) if psclBucket == nil { return nil } return psclBucket.ForEach(func(outputBytes, kidBytes []byte) error { psclOutput, err := deserializeKidOutput(bytes.NewBuffer(kidBytes)) if err != nil { return err } outpoint := psclOutput.outPoint sourceTxid := outpoint.Hash confChan, err := u.notifier.RegisterConfirmationsNtfn(&sourceTxid, 1) if err != nil { return err } utxnLog.Infof("Preschool outpoint %v re-registered for confirmation "+ "notification.", psclOutput.outPoint) go psclOutput.waitForPromotion(u.db, confChan) return nil }) }) } // catchUpKindergarten handles the graduation of kindergarten outputs from // blocks that were missed while the UTXO Nursery was down or offline. // graduateMissedBlocks is called during the startup of the UTXO Nursery. func (u *utxoNursery) catchUpKindergarten() error { var lastGraduatedHeight uint32 // Query the database for the most recently processed block err := u.db.View(func(tx *bolt.Tx) error { kgtnBucket := tx.Bucket(kindergartenBucket) if kgtnBucket == nil { return nil } heightBytes := kgtnBucket.Get(lastGraduatedHeightKey) if heightBytes == nil { return nil } lastGraduatedHeight = byteOrder.Uint32(heightBytes) return nil }) if err != nil { return err } // Get the most recently mined block _, bestHeight, err := u.wallet.ChainIO.GetBestBlock() if err != nil { return err } // If we haven't yet seen any registered force closes, or we're already // caught up with the current best chain, then we can exit early. if lastGraduatedHeight == 0 || uint32(bestHeight) == lastGraduatedHeight { return nil } utxnLog.Infof("Processing outputs from missed blocks. Starting with "+ "blockHeight: %v, to current blockHeight: %v", lastGraduatedHeight, bestHeight) // Loop through and check for graduating outputs at each of the missed // block heights. for graduationHeight := lastGraduatedHeight + 1; graduationHeight <= uint32(bestHeight); graduationHeight++ { utxnLog.Debugf("Attempting to graduate outputs at height=%v", graduationHeight) if err := u.graduateKindergarten(graduationHeight); err != nil { return err } } utxnLog.Infof("UTXO Nursery is now fully synced") return nil } // Stop gracefully shuts down any lingering goroutines launched during normal // operation of the utxoNursery. func (u *utxoNursery) Stop() error { if !atomic.CompareAndSwapUint32(&u.stopped, 0, 1) { return nil } utxnLog.Infof("UTXO nursery shutting down") close(u.quit) u.wg.Wait() return nil } // kidOutput represents an output that's waiting for a required blockheight // before its funds will be available to be moved into the user's wallet. The // struct includes a witnessGenerator closure which will be used to generate // the witness required to sweep the output once it's mature. // // TODO(roasbeef): rename to immatureOutput? type kidOutput struct { originChanPoint wire.OutPoint amt btcutil.Amount outPoint wire.OutPoint witnessFunc witnessGenerator // TODO(roasbeef): using block timeouts everywhere currently, will need // to modify logic later to account for MTP based timeouts. blocksToMaturity uint32 confHeight uint32 signDescriptor *lnwallet.SignDescriptor witnessType witnessType } // incubationRequest is a request to the utxoNursery to incubate a set of // outputs until their mature, finally sweeping them into the wallet once // available. type incubationRequest struct { outputs []*kidOutput } // incubateOutputs sends a request to utxoNursery to incubate the outputs // defined within the summary of a closed channel. Individually, as all outputs // reach maturity they'll be swept back into the wallet. func (u *utxoNursery) IncubateOutputs(closeSummary *lnwallet.ForceCloseSummary) { var incReq incubationRequest // It could be that our to-self output was below the dust limit. In that // case the SignDescriptor would be nil and we would not have that output // to incubate. if closeSummary.SelfOutputSignDesc != nil { outputAmt := btcutil.Amount(closeSummary.SelfOutputSignDesc.Output.Value) selfOutput := &kidOutput{ originChanPoint: closeSummary.ChanPoint, amt: outputAmt, outPoint: closeSummary.SelfOutpoint, blocksToMaturity: closeSummary.SelfOutputMaturity, signDescriptor: closeSummary.SelfOutputSignDesc, witnessType: commitmentTimeLock, } incReq.outputs = append(incReq.outputs, selfOutput) } // If there are no outputs to incubate, there is nothing to send to the // request channel. if len(incReq.outputs) != 0 { u.requests <- &incReq } } // incubator is tasked with watching over all outputs from channel closes as // they transition from being broadcast (at which point they move into the // "preschool state"), then confirmed and waiting for the necessary number of // blocks to be confirmed (as specified as kidOutput.blocksToMaturity and // enforced by CheckSequenceVerify). When the necessary block height has been // reached, the output has "matured" and the waitForGraduation function will // generate a sweep transaction to move funds from the commitment transaction // into the user's wallet. func (u *utxoNursery) incubator(newBlockChan *chainntnfs.BlockEpochEvent) { defer u.wg.Done() out: for { select { case preschoolRequest := <-u.requests: utxnLog.Infof("Incubating %v new outputs", len(preschoolRequest.outputs)) for _, output := range preschoolRequest.outputs { // We'll skip any zero value'd outputs as this // indicates we don't have a settled balance // within the commitment transaction. if output.amt == 0 { continue } sourceTxid := output.outPoint.Hash if err := output.enterPreschool(u.db); err != nil { utxnLog.Errorf("unable to add kidOutput to preschool: %v, %v ", output, err) continue } // Register for a notification that will // trigger graduation from preschool to // kindergarten when the channel close // transaction has been confirmed. confChan, err := u.notifier.RegisterConfirmationsNtfn(&sourceTxid, 1) if err != nil { utxnLog.Errorf("unable to register output for confirmation: %v", sourceTxid) continue } // Launch a dedicated goroutine that will move // the output from the preschool bucket to the // kindergarten bucket once the channel close // transaction has been confirmed. go output.waitForPromotion(u.db, confChan) } case epoch, ok := <-newBlockChan.Epochs: // If the epoch channel has been closed, then the // ChainNotifier is exiting which means the daemon is // as well. Therefore, we exit early also in order to // ensure the daemon shuts down gracefully, yet // swiftly. if !ok { return } // TODO(roasbeef): if the BlockChainIO is rescanning // will give stale data // A new block has just been connected to the main // chain which means we might be able to graduate some // outputs out of the kindergarten bucket. Graduation // entails successfully sweeping a time-locked output. height := uint32(epoch.Height) if err := u.graduateKindergarten(height); err != nil { utxnLog.Errorf("error while graduating "+ "kindergarten outputs: %v", err) } case <-u.quit: break out } } } // contractMaturityReport is a report that details the maturity progress of a // particular force closed contract. type contractMaturityReport struct { // chanPoint is the channel point of the original contract that is now // awaiting maturity within the utxoNursery. chanPoint wire.OutPoint // limboBalance is the total number of frozen coins within this // contract. limboBalance btcutil.Amount // confirmationHeight is the block height that this output originally // confirmed at. confirmationHeight uint32 // maturityHeight is the input age required for this output to reach // maturity. maturityRequirement uint32 // maturityHeight is the absolute block height that this output will mature // at. maturityHeight uint32 } // NurseryReport attempts to return a nursery report stored for the target // outpoint. A nursery report details the maturity/sweeping progress for a // contract that was previously force closed. If a report entry for the target // chanPoint is unable to be constructed, then an error will be returned. func (u *utxoNursery) NurseryReport(chanPoint *wire.OutPoint) (*contractMaturityReport, error) { var report *contractMaturityReport if err := u.db.View(func(tx *bolt.Tx) error { // First we'll examine the preschool bucket as the target // contract may not yet have been confirmed. psclBucket := tx.Bucket(preschoolBucket) if psclBucket == nil { return nil } psclIndex := tx.Bucket(preschoolIndex) if psclIndex == nil { return nil } var b bytes.Buffer if err := writeOutpoint(&b, chanPoint); err != nil { return err } chanPointBytes := b.Bytes() var outputReader *bytes.Reader // If the target contract hasn't been confirmed yet, then we // can just construct the report from this information. if outPoint := psclIndex.Get(chanPointBytes); outPoint != nil { // The channel entry hasn't yet been fully confirmed // yet, so we'll dig into the preschool bucket to fetch // the channel information. outputBytes := psclBucket.Get(outPoint) if outputBytes == nil { return nil } outputReader = bytes.NewReader(outputBytes) } else { // Otherwise, we'll have to consult out contract index, // so fetch that bucket as well as the kindergarten // bucket. indexBucket := tx.Bucket(contractIndex) if indexBucket == nil { return fmt.Errorf("contract not found, " + "contract index not populated") } kgtnBucket := tx.Bucket(kindergartenBucket) if kgtnBucket == nil { return fmt.Errorf("contract not found, " + "kindergarten bucket not populated") } // Attempt to query the index to see if we have an // entry for this particular contract. indexInfo := indexBucket.Get(chanPointBytes) if indexInfo == nil { return fmt.Errorf("contract not found in index") } // If an entry is found, then using the height store in // the first 4 bytes, we'll fetch the height that this // entry matures at. height := indexInfo[:4] heightRow := kgtnBucket.Get(height) if heightRow == nil { return fmt.Errorf("contract not found") } // Once we have the entry itself, we'll slice of the // last for bytes so we can seek into this row to fetch // the contract's information. offset := byteOrder.Uint32(indexInfo[4:]) outputReader = bytes.NewReader(heightRow[offset:]) } // With the proper set of bytes received, we'll deserialize the // information for this immature output. immatureOutput, err := deserializeKidOutput(outputReader) if err != nil { return err } // TODO(roasbeef): should actually be list of outputs report = &contractMaturityReport{ chanPoint: *chanPoint, limboBalance: immatureOutput.amt, maturityRequirement: immatureOutput.blocksToMaturity, } // If the confirmation height is set, then this means the // contract has been confirmed, and we know the final maturity // height. if immatureOutput.confHeight != 0 { report.confirmationHeight = immatureOutput.confHeight report.maturityHeight = (immatureOutput.blocksToMaturity + immatureOutput.confHeight) } return nil }); err != nil { return nil, err } return report, nil } // enterPreschool is the first stage in the process of transferring funds from // a force closed channel into the user's wallet. When an output is in the // "preschool" stage, the daemon is waiting for the initial confirmation of the // commitment transaction. func (k *kidOutput) enterPreschool(db *channeldb.DB) error { return db.Update(func(tx *bolt.Tx) error { psclBucket, err := tx.CreateBucketIfNotExists(preschoolBucket) if err != nil { return err } psclIndex, err := tx.CreateBucketIfNotExists(preschoolIndex) if err != nil { return err } // Once we have the buckets we can insert the raw bytes of the // immature outpoint into the preschool bucket. var outpointBytes bytes.Buffer if err := writeOutpoint(&outpointBytes, &k.outPoint); err != nil { return err } var kidBytes bytes.Buffer if err := serializeKidOutput(&kidBytes, k); err != nil { return err } err = psclBucket.Put(outpointBytes.Bytes(), kidBytes.Bytes()) if err != nil { return err } // Additionally, we'll populate the preschool index so we can // track all the immature outpoints for a particular channel's // chanPoint. var b bytes.Buffer err = writeOutpoint(&b, &k.originChanPoint) if err != nil { return err } err = psclIndex.Put(b.Bytes(), outpointBytes.Bytes()) if err != nil { return err } utxnLog.Infof("Outpoint %v now in preschool, waiting for "+ "initial confirmation", k.outPoint) return nil }) } // waitForPromotion is intended to be run as a goroutine that will wait until a // channel force close commitment transaction has been included in a confirmed // block. Once the transaction has been confirmed (as reported by the Chain // Notifier), waitForPromotion will delete the output from the "preschool" // database bucket and atomically add it to the "kindergarten" database bucket. // This is the second step in the output incubation process. func (k *kidOutput) waitForPromotion(db *channeldb.DB, confChan *chainntnfs.ConfirmationEvent) { txConfirmation, ok := <-confChan.Confirmed if !ok { utxnLog.Errorf("notification chan "+ "closed, can't advance output %v", k.outPoint) return } utxnLog.Infof("Outpoint %v confirmed in block %v moving to kindergarten", k.outPoint, txConfirmation.BlockHeight) k.confHeight = txConfirmation.BlockHeight // The following block deletes a kidOutput from the preschool database // bucket and adds it to the kindergarten database bucket which is // keyed by block height. Keys and values are serialized into byte // array form prior to database insertion. err := db.Update(func(tx *bolt.Tx) error { var originPoint bytes.Buffer if err := writeOutpoint(&originPoint, &k.originChanPoint); err != nil { return err } psclBucket := tx.Bucket(preschoolBucket) if psclBucket == nil { return errors.New("unable to open preschool bucket") } psclIndex := tx.Bucket(preschoolIndex) if psclIndex == nil { return errors.New("unable to open preschool index") } // Now that the entry has been confirmed, in order to move it // along in the maturity pipeline we first delete the entry // from the preschool bucket, as well as the secondary index. var outpointBytes bytes.Buffer if err := writeOutpoint(&outpointBytes, &k.outPoint); err != nil { return err } if err := psclBucket.Delete(outpointBytes.Bytes()); err != nil { utxnLog.Errorf("unable to delete kindergarten output from "+ "preschool bucket: %v", k.outPoint) return err } if err := psclIndex.Delete(originPoint.Bytes()); err != nil { utxnLog.Errorf("unable to delete kindergarten output from "+ "preschool index: %v", k.outPoint) return err } // Next, fetch the kindergarten bucket. This output will remain // in this bucket until it's fully mature. kgtnBucket, err := tx.CreateBucketIfNotExists(kindergartenBucket) if err != nil { return err } maturityHeight := k.confHeight + k.blocksToMaturity heightBytes := make([]byte, 4) byteOrder.PutUint32(heightBytes, maturityHeight) // If there're any existing outputs for this particular block // height target, then we'll append this new output to the // serialized list of outputs. var existingOutputs []byte if results := kgtnBucket.Get(heightBytes); results != nil { existingOutputs = results } // We'll grab the output's offset in the value for its maturity // height so we can add this to the contract index. outputOffset := len(existingOutputs) b := bytes.NewBuffer(existingOutputs) if err := serializeKidOutput(b, k); err != nil { return err } if err := kgtnBucket.Put(heightBytes, b.Bytes()); err != nil { return err } // Finally, we'll insert a new entry into the contract index. // The entry itself consists of 4 bytes for the height, and 4 // bytes for the offset within the value for the height. var indexEntry [4 + 4]byte copy(indexEntry[:4], heightBytes) byteOrder.PutUint32(indexEntry[4:], uint32(outputOffset)) indexBucket, err := tx.CreateBucketIfNotExists(contractIndex) if err != nil { return err } err = indexBucket.Put(originPoint.Bytes(), indexEntry[:]) if err != nil { return err } utxnLog.Infof("Outpoint %v now in kindergarten, will mature "+ "at height %v (delay of %v)", k.outPoint, maturityHeight, k.blocksToMaturity) return nil }) if err != nil { utxnLog.Errorf("unable to move kid output from preschool bucket "+ "to kindergarten bucket: %v", err) } } // graduateKindergarten handles the steps invoked with moving funds from a // force close commitment transaction into a user's wallet after the output // from the commitment transaction has become spendable. graduateKindergarten // is called both when a new block notification has been received and also at // startup in order to process graduations from blocks missed while the UTXO // nursery was offline. // TODO(roasbeef): single db transaction for the below func (u *utxoNursery) graduateKindergarten(blockHeight uint32) error { // First fetch the set of outputs that we can "graduate" at this // particular block height. We can graduate an output once we've // reached its height maturity. kgtnOutputs, err := fetchGraduatingOutputs(u.db, u.wallet, blockHeight) if err != nil { return err } // If we're able to graduate any outputs, then create a single // transaction which sweeps them all into the wallet. if len(kgtnOutputs) > 0 { err := sweepGraduatingOutputs(u.wallet, kgtnOutputs) if err != nil { return err } // Now that the sweeping transaction has been broadcast, for // each of the immature outputs, we'll mark them as being fully // closed within the database. for _, closedChan := range kgtnOutputs { err := u.db.MarkChanFullyClosed(&closedChan.originChanPoint) if err != nil { return err } } } // Using a re-org safety margin of 6-blocks, delete any outputs which // have graduated 6 blocks ago. deleteHeight := blockHeight - 6 if err := deleteGraduatedOutputs(u.db, deleteHeight); err != nil { return err } // Finally, record the last height at which we graduated outputs so we // can reconcile our state with that of the main-chain during restarts. return putLastHeightGraduated(u.db, blockHeight) } // fetchGraduatingOutputs checks the "kindergarten" database bucket whenever a // new block is received in order to determine if commitment transaction // outputs have become newly spendable. If fetchGraduatingOutputs finds outputs // that are ready for "graduation," it passes them on to be swept. This is the // third step in the output incubation process. func fetchGraduatingOutputs(db *channeldb.DB, wallet *lnwallet.LightningWallet, blockHeight uint32) ([]*kidOutput, error) { var results []byte if err := db.View(func(tx *bolt.Tx) error { // A new block has just been connected, check to see if we have // any new outputs that can be swept into the wallet. kgtnBucket := tx.Bucket(kindergartenBucket) if kgtnBucket == nil { return nil } heightBytes := make([]byte, 4) byteOrder.PutUint32(heightBytes, blockHeight) results = kgtnBucket.Get(heightBytes) return nil }); err != nil { return nil, err } // If no time-locked outputs can be swept at this point, ten we can // exit early. if len(results) == 0 { return nil, nil } // Otherwise, we deserialize the list of kid outputs into their full // forms. kgtnOutputs, err := deserializeKidList(bytes.NewReader(results)) if err != nil { utxnLog.Errorf("error while deserializing list of kidOutputs: %v", err) } // For each of the outputs, we also generate its proper witness // function based on its witness type. This varies if the output is on // our commitment transaction or theirs, and also if it's an HTLC // output or not. for _, kgtnOutput := range kgtnOutputs { kgtnOutput.witnessFunc = kgtnOutput.witnessType.generateFunc( &wallet.Signer, kgtnOutput.signDescriptor, ) } utxnLog.Infof("New block: height=%v, sweeping %v mature outputs", blockHeight, len(kgtnOutputs)) return kgtnOutputs, nil } // sweepGraduatingOutputs generates and broadcasts the transaction that // transfers control of funds from a channel commitment transaction to the // user's wallet. func sweepGraduatingOutputs(wallet *lnwallet.LightningWallet, kgtnOutputs []*kidOutput) error { // Create a transaction which sweeps all the newly mature outputs into // a output controlled by the wallet. // TODO(roasbeef): can be more intelligent about buffering outputs to // be more efficient on-chain. sweepTx, err := createSweepTx(wallet, kgtnOutputs) if err != nil { // TODO(roasbeef): retry logic? utxnLog.Errorf("unable to create sweep tx: %v", err) return err } utxnLog.Infof("Sweeping %v time-locked outputs "+ "with sweep tx (txid=%v): %v", len(kgtnOutputs), sweepTx.TxHash(), newLogClosure(func() string { return spew.Sdump(sweepTx) })) // With the sweep transaction fully signed, broadcast the transaction // to the network. Additionally, we can stop tracking these outputs as // they've just been swept. if err := wallet.PublishTransaction(sweepTx); err != nil { utxnLog.Errorf("unable to broadcast sweep tx: %v, %v", err, spew.Sdump(sweepTx)) return err } return nil } // createSweepTx creates a final sweeping transaction with all witnesses in // place for all inputs. The created transaction has a single output sending // all the funds back to the source wallet. func createSweepTx(wallet *lnwallet.LightningWallet, matureOutputs []*kidOutput) (*wire.MsgTx, error) { pkScript, err := newSweepPkScript(wallet) if err != nil { return nil, err } var totalSum btcutil.Amount for _, o := range matureOutputs { totalSum += o.amt } sweepTx := wire.NewMsgTx(2) sweepTx.AddTxOut(&wire.TxOut{ PkScript: pkScript, Value: int64(totalSum - 5000), }) for _, utxo := range matureOutputs { sweepTx.AddTxIn(&wire.TxIn{ PreviousOutPoint: utxo.outPoint, // TODO(roasbeef): assumes pure block delays Sequence: utxo.blocksToMaturity, }) } // TODO(roasbeef): insert fee calculation // * remove hardcoded fee above // With all the inputs in place, use each output's unique witness // function to generate the final witness required for spending. hashCache := txscript.NewTxSigHashes(sweepTx) for i, txIn := range sweepTx.TxIn { witness, err := matureOutputs[i].witnessFunc(sweepTx, hashCache, i) if err != nil { return nil, err } txIn.Witness = witness } return sweepTx, nil } // deleteGraduatedOutputs removes outputs from the kindergarten database bucket // when six blockchain confirmations have passed since the outputs were swept. // We wait for six confirmations to ensure that the outputs will be swept if a // chain reorganization occurs. This is the final step in the output incubation // process. func deleteGraduatedOutputs(db *channeldb.DB, deleteHeight uint32) error { return db.Update(func(tx *bolt.Tx) error { kgtnBucket := tx.Bucket(kindergartenBucket) if kgtnBucket == nil { return nil } heightBytes := make([]byte, 4) byteOrder.PutUint32(heightBytes, deleteHeight) results := kgtnBucket.Get(heightBytes) if results == nil { return nil } // Delete the row for this height within the kindergarten bucket.k if err := kgtnBucket.Delete(heightBytes); err != nil { return err } sweptOutputs, err := deserializeKidList(bytes.NewBuffer(results)) if err != nil { return err } utxnLog.Infof("Deleting %v swept outputs from kindergarten bucket "+ "at block height: %v", len(sweptOutputs), deleteHeight) // Additionally, for each output that has now been fully swept, // we'll also remove the index entry for that output. indexBucket := tx.Bucket(contractIndex) if indexBucket == nil { return nil } for _, sweptOutput := range sweptOutputs { var chanPoint bytes.Buffer err := writeOutpoint(&chanPoint, &sweptOutput.originChanPoint) if err != nil { return err } if err := indexBucket.Delete(chanPoint.Bytes()); err != nil { return err } } return nil }) } // putLastHeightGraduated persists the most recently processed blockheight // to the database. This blockheight is used during restarts to determine if // blocks were missed while the UTXO Nursery was offline. func putLastHeightGraduated(db *channeldb.DB, blockheight uint32) error { return db.Update(func(tx *bolt.Tx) error { kgtnBucket, err := tx.CreateBucketIfNotExists(kindergartenBucket) if err != nil { return nil } heightBytes := make([]byte, 4) byteOrder.PutUint32(heightBytes, blockheight) return kgtnBucket.Put(lastGraduatedHeightKey, heightBytes) }) } // newSweepPkScript creates a new public key script which should be used to // sweep any time-locked, or contested channel funds into the wallet. // Specifically, the script generated is a version 0, // pay-to-witness-pubkey-hash (p2wkh) output. func newSweepPkScript(wallet lnwallet.WalletController) ([]byte, error) { sweepAddr, err := wallet.NewAddress(lnwallet.WitnessPubKey, false) if err != nil { return nil, err } return txscript.PayToAddrScript(sweepAddr) } // deserializedKidList takes a sequence of serialized kid outputs and returns a // slice of kidOutput structs. func deserializeKidList(r io.Reader) ([]*kidOutput, error) { var kidOutputs []*kidOutput for { kidOutput, err := deserializeKidOutput(r) if err != nil { if err == io.EOF { break } else { return nil, err } } kidOutputs = append(kidOutputs, kidOutput) } return kidOutputs, nil } // serializeKidOutput converts a KidOutput struct into a form // suitable for on-disk database storage. Note that the signDescriptor // struct field is included so that the output's witness can be generated // by createSweepTx() when the output becomes spendable. func serializeKidOutput(w io.Writer, kid *kidOutput) error { var scratch [8]byte byteOrder.PutUint64(scratch[:], uint64(kid.amt)) if _, err := w.Write(scratch[:]); err != nil { return err } if err := writeOutpoint(w, &kid.outPoint); err != nil { return err } if err := writeOutpoint(w, &kid.originChanPoint); err != nil { return err } byteOrder.PutUint32(scratch[:4], kid.blocksToMaturity) if _, err := w.Write(scratch[:4]); err != nil { return err } byteOrder.PutUint32(scratch[:4], kid.confHeight) if _, err := w.Write(scratch[:4]); err != nil { return err } byteOrder.PutUint16(scratch[:2], uint16(kid.witnessType)) if _, err := w.Write(scratch[:2]); err != nil { return err } serializedPubKey := kid.signDescriptor.PubKey.SerializeCompressed() if err := wire.WriteVarBytes(w, 0, serializedPubKey); err != nil { return err } if err := wire.WriteVarBytes(w, 0, kid.signDescriptor.PrivateTweak); err != nil { return err } if err := wire.WriteVarBytes(w, 0, kid.signDescriptor.WitnessScript); err != nil { return err } if err := writeTxOut(w, kid.signDescriptor.Output); err != nil { return err } byteOrder.PutUint32(scratch[:4], uint32(kid.signDescriptor.HashType)) _, err := w.Write(scratch[:4]) return err } // deserializeKidOutput takes a byte array representation of a kidOutput // and converts it to an struct. Note that the witnessFunc method isn't added // during deserialization and must be added later based on the value of the // witnessType field. func deserializeKidOutput(r io.Reader) (*kidOutput, error) { scratch := make([]byte, 8) kid := &kidOutput{} if _, err := r.Read(scratch[:]); err != nil { return nil, err } kid.amt = btcutil.Amount(byteOrder.Uint64(scratch[:])) if err := readOutpoint(io.LimitReader(r, 40), &kid.outPoint); err != nil { return nil, err } if err := readOutpoint(io.LimitReader(r, 40), &kid.originChanPoint); err != nil { return nil, err } if _, err := r.Read(scratch[:4]); err != nil { return nil, err } kid.blocksToMaturity = byteOrder.Uint32(scratch[:4]) if _, err := r.Read(scratch[:4]); err != nil { return nil, err } kid.confHeight = byteOrder.Uint32(scratch[:4]) if _, err := r.Read(scratch[:2]); err != nil { return nil, err } kid.witnessType = witnessType(byteOrder.Uint16(scratch[:2])) kid.signDescriptor = &lnwallet.SignDescriptor{} descKeyBytes, err := wire.ReadVarBytes(r, 0, 34, "descKeyBytes") if err != nil { return nil, err } descKey, err := btcec.ParsePubKey(descKeyBytes, btcec.S256()) if err != nil { return nil, err } kid.signDescriptor.PubKey = descKey descPrivateTweak, err := wire.ReadVarBytes(r, 0, 32, "privateTweak") if err != nil { return nil, err } kid.signDescriptor.PrivateTweak = descPrivateTweak descWitnessScript, err := wire.ReadVarBytes(r, 0, 100, "witnessScript") if err != nil { return nil, err } kid.signDescriptor.WitnessScript = descWitnessScript descTxOut := &wire.TxOut{} if err := readTxOut(r, descTxOut); err != nil { return nil, err } kid.signDescriptor.Output = descTxOut if _, err := r.Read(scratch[:4]); err != nil { return nil, err } kid.signDescriptor.HashType = txscript.SigHashType(byteOrder.Uint32(scratch[:4])) return kid, nil } // TODO(bvu): copied from channeldb, remove repetition func writeOutpoint(w io.Writer, o *wire.OutPoint) error { // TODO(roasbeef): make all scratch buffers on the stack scratch := make([]byte, 4) // TODO(roasbeef): write raw 32 bytes instead of wasting the extra // byte. if err := wire.WriteVarBytes(w, 0, o.Hash[:]); err != nil { return err } byteOrder.PutUint32(scratch, o.Index) _, err := w.Write(scratch) return err } // TODO(bvu): copied from channeldb, remove repetition func readOutpoint(r io.Reader, o *wire.OutPoint) error { scratch := make([]byte, 4) txid, err := wire.ReadVarBytes(r, 0, 32, "prevout") if err != nil { return err } copy(o.Hash[:], txid) if _, err := r.Read(scratch); err != nil { return err } o.Index = byteOrder.Uint32(scratch) return nil } func writeTxOut(w io.Writer, txo *wire.TxOut) error { scratch := make([]byte, 8) byteOrder.PutUint64(scratch, uint64(txo.Value)) if _, err := w.Write(scratch); err != nil { return err } if err := wire.WriteVarBytes(w, 0, txo.PkScript); err != nil { return err } return nil } func readTxOut(r io.Reader, txo *wire.TxOut) error { scratch := make([]byte, 8) if _, err := r.Read(scratch); err != nil { return err } txo.Value = int64(byteOrder.Uint64(scratch)) pkScript, err := wire.ReadVarBytes(r, 0, 80, "pkScript") if err != nil { return err } txo.PkScript = pkScript return nil }