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watchtower: introduce CommitmentType

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In this commit a new enum, CommitmentType, is introduced and initially
there are 3 CommitmentTypes: Legacy, LegacyTweakless and Anchor.

Then, various methods are added to `CommitmentType`. This allows us to
remove a bunch of "if-else" chains from the `wtclient` and `lookout`
code. This will also make things easier to extend when a new commitment
type (like Taproot) is added.
This commit is contained in:
Elle Mouton
2023-05-30 17:13:11 +02:00
parent 4d8fa349ca
commit 204ca6cb0f
6 changed files with 305 additions and 161 deletions
Download Patch File Download Diff File Expand all files Collapse all files

118
watchtower/wtclient/backup_task.go
View File

@@ -12,7 +12,6 @@ import (
"github.com/btcsuite/btcd/wire"
"github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/watchtower/blob"
"github.com/lightningnetwork/lnd/watchtower/wtdb"
)
@@ -37,8 +36,9 @@ import (
// necessary components are stripped out and encrypted before being sent to
// the tower in a StateUpdate.
type backupTask struct {
id wtdb.BackupID
breachInfo *lnwallet.BreachRetribution
id wtdb.BackupID
breachInfo *lnwallet.BreachRetribution
commitmentType blob.CommitmentType
// state-dependent variables
@@ -127,6 +127,11 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
return err
}
commitType, err := session.Policy.BlobType.CommitmentType(&chanType)
if err != nil {
return err
}
// Parse the non-dust outputs from the breach transaction,
// simultaneously computing the total amount contained in the inputs
// present. We can't compute the exact output values at this time
@@ -147,48 +152,23 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
// to that output as local, though relative to their commitment, it is
// paying to-the-remote party (which is us).
if breachInfo.RemoteOutputSignDesc != nil {
toLocalInput = input.NewBaseInput(
&breachInfo.RemoteOutpoint,
input.CommitmentRevoke,
breachInfo.RemoteOutputSignDesc,
0,
)
toLocalInput, err = commitType.ToLocalInput(breachInfo)
if err != nil {
return err
}
totalAmt += breachInfo.RemoteOutputSignDesc.Output.Value
}
if breachInfo.LocalOutputSignDesc != nil {
var witnessType input.WitnessType
switch {
case chanType.HasAnchors():
witnessType = input.CommitmentToRemoteConfirmed
case chanType.IsTweakless():
witnessType = input.CommitSpendNoDelayTweakless
default:
witnessType = input.CommitmentNoDelay
}
// Anchor channels have a CSV-encumbered to-remote output. We'll
// construct a CSV input in that case and assign the proper CSV
// delay of 1, otherwise we fallback to the a regular P2WKH
// to-remote output for tweaked or tweakless channels.
if chanType.HasAnchors() {
toRemoteInput = input.NewCsvInput(
&breachInfo.LocalOutpoint,
witnessType,
breachInfo.LocalOutputSignDesc,
0, 1,
)
} else {
toRemoteInput = input.NewBaseInput(
&breachInfo.LocalOutpoint,
witnessType,
breachInfo.LocalOutputSignDesc,
0,
)
toRemoteInput, err = commitType.ToRemoteInput(breachInfo)
if err != nil {
return err
}
totalAmt += breachInfo.LocalOutputSignDesc.Output.Value
}
t.commitmentType = commitType
t.breachInfo = breachInfo
t.toLocalInput = toLocalInput
t.toRemoteInput = toRemoteInput
@@ -202,34 +182,20 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
// Next, add the contribution from the inputs that are present on this
// breach transaction.
if t.toLocalInput != nil {
// An older ToLocalPenaltyWitnessSize constant used to
// underestimate the size by one byte. The diferrence in weight
// can cause different output values on the sweep transaction,
// so we mimic the original bug and create signatures using the
// original weight estimate. For anchor channels we'll go ahead
// an use the correct penalty witness when signing our justice
// transactions.
if chanType.HasAnchors() {
weightEstimate.AddWitnessInput(
input.ToLocalPenaltyWitnessSize,
)
} else {
weightEstimate.AddWitnessInput(
input.ToLocalPenaltyWitnessSize - 1,
)
toLocalWitnessSize, err := commitType.ToLocalWitnessSize()
if err != nil {
return err
}
weightEstimate.AddWitnessInput(toLocalWitnessSize)
}
if t.toRemoteInput != nil {
// Legacy channels (both tweaked and non-tweaked) spend from
// P2WKH output. Anchor channels spend a to-remote confirmed
// P2WSH output.
if chanType.HasAnchors() {
weightEstimate.AddWitnessInput(
input.ToRemoteConfirmedWitnessSize,
)
} else {
weightEstimate.AddWitnessInput(input.P2WKHWitnessSize)
toRemoteWitnessSize, err := commitType.ToRemoteWitnessSize()
if err != nil {
return err
}
weightEstimate.AddWitnessInput(toRemoteWitnessSize)
}
// All justice transactions will either use segwit v0 (p2wkh + p2wsh)
@@ -349,6 +315,7 @@ func (t *backupTask) craftSessionPayload(
// Now, iterate through the list of inputs that were initially added to
// the transaction and store the computed witness within the justice
// kit.
commitType := t.commitmentType
for _, inp := range inputs {
// Lookup the input's new post-sort position.
i := inputIndex[*inp.OutPoint()]
@@ -361,17 +328,17 @@ func (t *backupTask) craftSessionPayload(
return hint, nil, err
}
// Parse the DER-encoded signature from the first position of
// the resulting witness. We trim an extra byte to remove the
// sighash flag.
witness := inputScript.Witness
rawSignature := witness[0][:len(witness[0])-1]
signature, err := commitType.ParseRawSig(inputScript.Witness)
if err != nil {
return hint, nil, err
}
// Re-encode the DER signature into a fixed-size 64 byte
// signature.
signature, err := lnwire.NewSigFromECDSARawSignature(
rawSignature,
)
toLocalWitnessType, err := commitType.ToLocalWitnessType()
if err != nil {
return hint, nil, err
}
toRemoteWitnessType, err := commitType.ToRemoteWitnessType()
if err != nil {
return hint, nil, err
}
@@ -380,14 +347,9 @@ func (t *backupTask) craftSessionPayload(
// using the input's witness type to select the appropriate
// field
switch inp.WitnessType() {
case input.CommitmentRevoke:
case toLocalWitnessType:
justiceKit.CommitToLocalSig = signature
case input.CommitSpendNoDelayTweakless:
fallthrough
case input.CommitmentNoDelay:
fallthrough
case input.CommitmentToRemoteConfirmed:
case toRemoteWitnessType:
justiceKit.CommitToRemoteSig = signature
default:
return hint, nil, fmt.Errorf("invalid witness type: %v",

64
watchtower/wtclient/backup_task_internal_test.go
View File

@@ -72,6 +72,7 @@ type backupTaskTest struct {
// corresponding BreachInfo, as well as setting the wtpolicy.Policy of the given
// session.
func genTaskTest(
t *testing.T,
name string,
stateNum uint64,
toLocalAmt int64,
@@ -91,15 +92,12 @@ func genTaskTest(
}
// Parse the key pairs for all keys used in the test.
revSK, revPK := btcec.PrivKeyFromBytes(
revPrivBytes,
)
_, toLocalPK := btcec.PrivKeyFromBytes(
toLocalPrivBytes,
)
toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(
toRemotePrivBytes,
)
revSK, revPK := btcec.PrivKeyFromBytes(revPrivBytes)
_, toLocalPK := btcec.PrivKeyFromBytes(toLocalPrivBytes)
toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(toRemotePrivBytes)
commitType, err := blobType.CommitmentType(&chanType)
require.NoError(t, err)
// Create the signer, and add the revocation and to-remote privkeys.
signer := wtmock.NewMockSigner()
@@ -174,12 +172,9 @@ func genTaskTest(
Hash: txid,
Index: index,
}
toLocalInput = input.NewBaseInput(
&breachInfo.RemoteOutpoint,
input.CommitmentRevoke,
breachInfo.RemoteOutputSignDesc,
0,
)
toLocalInput, err = commitType.ToLocalInput(breachInfo)
require.NoError(t, err)
index++
}
if toRemoteAmt > 0 {
@@ -188,31 +183,8 @@ func genTaskTest(
Index: index,
}
var witnessType input.WitnessType
switch {
case chanType.HasAnchors():
witnessType = input.CommitmentToRemoteConfirmed
case chanType.IsTweakless():
witnessType = input.CommitSpendNoDelayTweakless
default:
witnessType = input.CommitmentNoDelay
}
if chanType.HasAnchors() {
toRemoteInput = input.NewCsvInput(
&breachInfo.LocalOutpoint,
witnessType,
breachInfo.LocalOutputSignDesc,
0, 1,
)
} else {
toRemoteInput = input.NewBaseInput(
&breachInfo.LocalOutpoint,
witnessType,
breachInfo.LocalOutputSignDesc,
0,
)
}
toRemoteInput, err = commitType.ToRemoteInput(breachInfo)
require.NoError(t, err)
}
return backupTaskTest{
@@ -312,6 +284,7 @@ func TestBackupTask(t *testing.T) {
backupTaskTests = append(backupTaskTests, []backupTaskTest{
genTaskTest(
t,
"commit no-reward, both outputs",
100, // stateNum
200000, // toLocalAmt
@@ -325,6 +298,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit no-reward, to-local output only",
1000, // stateNum
200000, // toLocalAmt
@@ -338,6 +312,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit no-reward, to-remote output only",
1, // stateNum
0, // toLocalAmt
@@ -351,6 +326,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit no-reward, to-remote output only, creates dust",
1, // stateNum
0, // toLocalAmt
@@ -364,6 +340,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit no-reward, no outputs, fee rate exceeds inputs",
300, // stateNum
0, // toLocalAmt
@@ -377,6 +354,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit no-reward, no outputs, fee rate of 0 creates dust",
300, // stateNum
0, // toLocalAmt
@@ -390,6 +368,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, both outputs",
100, // stateNum
200000, // toLocalAmt
@@ -403,6 +382,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, to-local output only",
1000, // stateNum
200000, // toLocalAmt
@@ -416,6 +396,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, to-remote output only",
1, // stateNum
0, // toLocalAmt
@@ -429,6 +410,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, to-remote output only, creates dust",
1, // stateNum
0, // toLocalAmt
@@ -442,6 +424,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, no outputs, fee rate exceeds inputs",
300, // stateNum
0, // toLocalAmt
@@ -455,6 +438,7 @@ func TestBackupTask(t *testing.T) {
chanType,
),
genTaskTest(
t,
"commit reward, no outputs, fee rate of 0 creates dust",
300, // stateNum
0, // toLocalAmt