From c18e166e032966bc09e7a30acef49bc5eed8b5f0 Mon Sep 17 00:00:00 2001 From: Olaoluwa Osuntokun Date: Sat, 17 Nov 2018 20:48:41 -0800 Subject: [PATCH] lnwallet+sweep: extend the WitnessGenerator type to return an InputScript In this commit, we extend the WitnessGenerator type to now return an InputScript. This allows it to be more encompassing, as now callers can expect a sigScript to be populated if the input being swept requires a sigScript field. Along the way, we've also renamed input.BuildWitness to input.CraftInputScript. We also take a step towards allowing the sweeper to sweep transactions for n2pwkh outputs. We do so by modifying the BuiltWitness method to instead return an InputScript. Additionally, when populating inputs if a sigScript is present, it will now be populated. --- breacharbiter.go | 13 +++--- lnwallet/witnessgen.go | 98 +++++++++++++++++++++++++++++++++++------- sweep/input.go | 52 +++++++++++++--------- sweep/txgenerator.go | 16 ++++--- 4 files changed, 132 insertions(+), 47 deletions(-) diff --git a/breacharbiter.go b/breacharbiter.go index 45c4bafc..269a7b12 100644 --- a/breacharbiter.go +++ b/breacharbiter.go @@ -807,13 +807,13 @@ func (bo *breachedOutput) SignDesc() *lnwallet.SignDescriptor { return &bo.signDesc } -// BuildWitness computes a valid witness that allows us to spend from the +// CraftInputScript computes a valid witness that allows us to spend from the // breached output. It does so by first generating and memoizing the witness // generation function, which parameterized primarily by the witness type and // sign descriptor. The method then returns the witness computed by invoking // this function on the first and subsequent calls. -func (bo *breachedOutput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, - hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) { +func (bo *breachedOutput) CraftInputScript(signer lnwallet.Signer, txn *wire.MsgTx, + hashCache *txscript.TxSigHashes, txinIdx int) (*lnwallet.InputScript, error) { // First, we ensure that the witness generation function has been // initialized for this breached output. @@ -1082,15 +1082,16 @@ func (b *breachArbiter) sweepSpendableOutputsTxn(txWeight int64, // First, we construct a valid witness for this outpoint and // transaction using the SpendableOutput's witness generation // function. - witness, err := so.BuildWitness(b.cfg.Signer, txn, hashCache, - idx) + inputScript, err := so.CraftInputScript( + b.cfg.Signer, txn, hashCache, idx, + ) if err != nil { return err } // Then, we add the witness to the transaction at the // appropriate txin index. - txn.TxIn[idx].Witness = witness + txn.TxIn[idx].Witness = inputScript.Witness return nil } diff --git a/lnwallet/witnessgen.go b/lnwallet/witnessgen.go index 00c3fab0..f2ff9236 100644 --- a/lnwallet/witnessgen.go +++ b/lnwallet/witnessgen.go @@ -110,18 +110,22 @@ func (wt WitnessType) String() string { } // 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. +// witness for a particular public key script. Additionally, if required, this +// function will also return the sigScript for spending nested P2SH witness +// outputs. This function acts as an abstraction layer, hiding the details of +// the underlying script. type WitnessGenerator func(tx *wire.MsgTx, hc *txscript.TxSigHashes, - inputIndex int) ([][]byte, error) + inputIndex int) (*InputScript, error) -// GenWitnessFunc will return a WitnessGenerator function that an output -// uses to generate the witness for a sweep transaction. +// GenWitnessFunc will return a WitnessGenerator function that an output uses +// to generate the witness and optionally the sigScript for a sweep +// transaction. The sigScript will be generated if the witness type warrants +// one for spending, such as the NestedWitnessKeyHash witness type. func (wt WitnessType) GenWitnessFunc(signer Signer, descriptor *SignDescriptor) WitnessGenerator { return func(tx *wire.MsgTx, hc *txscript.TxSigHashes, - inputIndex int) ([][]byte, error) { + inputIndex int) (*InputScript, error) { desc := descriptor desc.SigHashes = hc @@ -129,34 +133,98 @@ func (wt WitnessType) GenWitnessFunc(signer Signer, switch wt { case CommitmentTimeLock: - return CommitSpendTimeout(signer, desc, tx) + witness, err := CommitSpendTimeout(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case CommitmentNoDelay: - return CommitSpendNoDelay(signer, desc, tx) + witness, err := CommitSpendNoDelay(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case CommitmentRevoke: - return CommitSpendRevoke(signer, desc, tx) + witness, err := CommitSpendRevoke(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcOfferedRevoke: - return ReceiverHtlcSpendRevoke(signer, desc, tx) + witness, err := ReceiverHtlcSpendRevoke(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcAcceptedRevoke: - return SenderHtlcSpendRevoke(signer, desc, tx) + witness, err := SenderHtlcSpendRevoke(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcOfferedTimeoutSecondLevel: - return HtlcSecondLevelSpend(signer, desc, tx) + witness, err := HtlcSecondLevelSpend(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcAcceptedSuccessSecondLevel: - return HtlcSecondLevelSpend(signer, desc, tx) + witness, err := HtlcSecondLevelSpend(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcOfferedRemoteTimeout: // We pass in a value of -1 for the timeout, as we // expect the caller to have already set the lock time // value. - return receiverHtlcSpendTimeout(signer, desc, tx, -1) + witness, err := receiverHtlcSpendTimeout(signer, desc, tx, -1) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil case HtlcSecondLevelRevoke: - return htlcSpendRevoke(signer, desc, tx) + witness, err := htlcSpendRevoke(signer, desc, tx) + if err != nil { + return nil, err + } + + return &InputScript{ + Witness: witness, + }, nil + default: return nil, fmt.Errorf("unknown witness type: %v", wt) diff --git a/sweep/input.go b/sweep/input.go index 57ee7939..57a954df 100644 --- a/sweep/input.go +++ b/sweep/input.go @@ -6,7 +6,10 @@ import ( "github.com/lightningnetwork/lnd/lnwallet" ) -// Input contains all data needed to construct a sweep tx input. +// Input represents an abstract UTXO which is to be spent using a sweeping +// transaction. The method provided give the caller all information needed to +// construct a valid input within a sweeping transaction to sweep this +// lingering UTXO. type Input interface { // Outpoint returns the reference to the output being spent, used to // construct the corresponding transaction input. @@ -21,12 +24,14 @@ type Input interface { // that spends this output. SignDesc() *lnwallet.SignDescriptor - // BuildWitness returns a valid witness allowing this output to be - // spent, the witness should be attached to the transaction at the - // location determined by the given `txinIdx`. - BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, + // CraftInputScript returns a valid set of input scripts allowing this + // output to be spent. The returns input scripts should target the + // input at location txIndex within the passed transaction. The input + // scripts generated by this method support spending p2wkh, p2wsh, and + // also nested p2sh outputs. + CraftInputScript(signer lnwallet.Signer, txn *wire.MsgTx, hashCache *txscript.TxSigHashes, - txinIdx int) ([][]byte, error) + txinIdx int) (*lnwallet.InputScript, error) // BlocksToMaturity returns the relative timelock, as a number of // blocks, that must be built on top of the confirmation height before @@ -91,12 +96,12 @@ func MakeBaseInput(outpoint *wire.OutPoint, witnessType lnwallet.WitnessType, } } -// BuildWitness computes a valid witness that allows us to spend from the -// breached output. It does so by generating the witness generation function, -// which is parameterized primarily by the witness type and sign descriptor. -// The method then returns the witness computed by invoking this function. -func (bi *BaseInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, - hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) { +// CraftInputScript returns a valid set of input scripts allowing this output +// to be spent. The returns input scripts should target the input at location +// txIndex within the passed transaction. The input scripts generated by this +// method support spending p2wkh, p2wsh, and also nested p2sh outputs. +func (bi *BaseInput) CraftInputScript(signer lnwallet.Signer, txn *wire.MsgTx, + hashCache *txscript.TxSigHashes, txinIdx int) (*lnwallet.InputScript, error) { witnessFunc := bi.witnessType.GenWitnessFunc( signer, bi.SignDesc(), @@ -138,20 +143,27 @@ func MakeHtlcSucceedInput(outpoint *wire.OutPoint, } } -// BuildWitness computes a valid witness that allows us to spend from the -// breached output. For HtlcSpendInput it will need to make the preimage part -// of the witness. -func (h *HtlcSucceedInput) BuildWitness(signer lnwallet.Signer, txn *wire.MsgTx, - hashCache *txscript.TxSigHashes, txinIdx int) ([][]byte, error) { +// CraftInputScript returns a valid set of input scripts allowing this output +// to be spent. The returns input scripts should target the input at location +// txIndex within the passed transaction. The input scripts generated by this +// method support spending p2wkh, p2wsh, and also nested p2sh outputs. +func (h *HtlcSucceedInput) CraftInputScript(signer lnwallet.Signer, txn *wire.MsgTx, + hashCache *txscript.TxSigHashes, txinIdx int) (*lnwallet.InputScript, error) { desc := h.signDesc desc.SigHashes = hashCache desc.InputIndex = txinIdx - return lnwallet.SenderHtlcSpendRedeem( - signer, &desc, txn, - h.preimage, + witness, err := lnwallet.SenderHtlcSpendRedeem( + signer, &desc, txn, h.preimage, ) + if err != nil { + return nil, err + } + + return &lnwallet.InputScript{ + Witness: witness, + }, nil } // BlocksToMaturity returns the relative timelock, as a number of blocks, that diff --git a/sweep/txgenerator.go b/sweep/txgenerator.go index e173706a..e4ec37df 100644 --- a/sweep/txgenerator.go +++ b/sweep/txgenerator.go @@ -216,25 +216,29 @@ func createSweepTx(inputs []Input, outputPkScript []byte, hashCache := txscript.NewTxSigHashes(sweepTx) - // With all the inputs in place, use each output's unique witness + // With all the inputs in place, use each output's unique input script // function to generate the final witness required for spending. - addWitness := func(idx int, tso Input) error { - witness, err := tso.BuildWitness( + addInputScript := func(idx int, tso Input) error { + inputScript, err := tso.CraftInputScript( signer, sweepTx, hashCache, idx, ) if err != nil { return err } - sweepTx.TxIn[idx].Witness = witness + sweepTx.TxIn[idx].Witness = inputScript.Witness + + if len(inputScript.SigScript) != 0 { + sweepTx.TxIn[idx].SignatureScript = inputScript.SigScript + } return nil } - // Finally we'll attach a valid witness to each csv and cltv input + // Finally we'll attach a valid input script to each csv and cltv input // within the sweeping transaction. for i, input := range inputs { - if err := addWitness(i, input); err != nil { + if err := addInputScript(i, input); err != nil { return nil, err } }