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lnwallet+sweep: extend the WitnessGenerator type to return an InputScript

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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.
This commit is contained in:
Olaoluwa Osuntokun 2018-11-17 20:48:41 -08:00
parent bd9ebbd5af
commit c18e166e03
No known key found for this signature in database
GPG Key ID: CE58F7F8E20FD9A2
4 changed files with 132 additions and 47 deletions
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13
breacharbiter.go
View File

@ -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
}

98
lnwallet/witnessgen.go
View File

@ -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)

52
sweep/input.go
View File

@ -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

16
sweep/txgenerator.go
View File

@ -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
}
}