12199391122

Committed 06 Dec 2024 01:10PM UTC coverage: 49.807% (-9.1%) from 58.933%

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Merge pull request #9337 from Guayaba221/patch-1

chore: fix typo in ruby.md

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/watchtower/wtclient/backup_task.go

package wtclient

import (
        "fmt"

        "github.com/btcsuite/btcd/blockchain"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/btcutil/txsort"
        "github.com/btcsuite/btcd/chaincfg"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/watchtower/blob"
        "github.com/lightningnetwork/lnd/watchtower/wtdb"
)

// backupTask is an internal struct for computing the justice transaction for a
// particular revoked state. A backupTask functions as a scratch pad for storing
// computing values of the transaction itself, such as the final split in
// balance if the justice transaction will give a reward to the tower. The
// backup task has three primary phases:
//  1. Init: Determines which inputs from the breach transaction will be spent,
//     and the total amount contained in the inputs.
//  2. Bind: Asserts that the revoked state is eligible under a given session's
//     parameters. Certain states may be ineligible due to fee rates, too little
//     input amount, etc. Backup of these states can be deferred to a later time
//     or session with more favorable parameters. If the session is bound
//     successfully, the final session-dependent values to the justice
//     transaction are solidified.
//  3. Send: Once the task is bound, it will be queued to send to a specific
//     tower corresponding to the session in which it was bound. The justice
//     transaction will be assembled by examining the parameters left as a
//     result of the binding. After the justice transaction is signed, the
//     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
        commitmentType blob.CommitmentType

        // state-dependent variables

        toLocalInput  input.Input
        toRemoteInput input.Input
        totalAmt      btcutil.Amount
        sweepPkScript []byte

        // session-dependent variables

        blobType blob.Type
        outputs  []*wire.TxOut
}

// newBackupTask initializes a new backupTask.
func newBackupTask(id wtdb.BackupID, sweepPkScript []byte) *backupTask {
        return &backupTask{
                id:            id,
                sweepPkScript: sweepPkScript,
        }
}

// inputs returns all non-dust inputs that we will attempt to spend from.
//
// NOTE: Ordering of the inputs is not critical as we sort the transaction with
// BIP69 in a later stage.
func (t *backupTask) inputs() map[wire.OutPoint]input.Input {
        inputs := make(map[wire.OutPoint]input.Input)
        if t.toLocalInput != nil {
                inputs[t.toLocalInput.OutPoint()] = t.toLocalInput
        }
        if t.toRemoteInput != nil {
                inputs[t.toRemoteInput.OutPoint()] = t.toRemoteInput
        }

        return inputs
}

// addrType returns the type of an address after parsing it and matching it to
// the set of known script templates.
func addrType(pkScript []byte) txscript.ScriptClass {
        // We pass in a set of dummy chain params here as they're only needed
        // to make the address struct, which we're ignoring anyway (scripts are
        // always the same, it's addresses that change across chains).
        scriptClass, _, _, _ := txscript.ExtractPkScriptAddrs(
                pkScript, &chaincfg.MainNetParams,
        )

        return scriptClass
}

// addScriptWeight parses the passed pkScript and adds the computed weight cost
// were the script to be added to the justice transaction.
func addScriptWeight(weightEstimate *input.TxWeightEstimator,
        pkScript []byte) error {

        switch addrType(pkScript) {
        case txscript.WitnessV0PubKeyHashTy:
                weightEstimate.AddP2WKHOutput()

        case txscript.WitnessV0ScriptHashTy:
                weightEstimate.AddP2WSHOutput()

        case txscript.WitnessV1TaprootTy:
                weightEstimate.AddP2TROutput()

        default:
                return fmt.Errorf("invalid addr type: %v", addrType(pkScript))
        }

        return nil
}

// bindSession first populates all state-dependent variables of the task. Then
// it determines if the backupTask is compatible with the passed SessionInfo's
// policy. If no error is returned, the task has been bound to the session and
// can be queued to upload to the tower. Otherwise, the bind failed and should
// be rescheduled with a different session.
func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
        newBreachRetribution BreachRetributionBuilder) error {

        breachInfo, chanType, err := newBreachRetribution(
                t.id.ChanID, t.id.CommitHeight,
        )
        if err != nil {
                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
        // since the task has not been assigned to a session, at which point
        // parameters such as fee rate, number of outputs, and reward rate will
        // be finalized.
        var (
                totalAmt      int64
                toLocalInput  input.Input
                toRemoteInput input.Input
        )

        // Add the sign descriptors and outputs corresponding to the to-local
        // and to-remote outputs, respectively, if either input amount is
        // non-dust. Note that the naming here seems reversed, but both are
        // correct. For example, the to-remote output on the remote party's
        // commitment is an output that pays to us. Hence the retribution refers
        // 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, err = commitType.ToLocalInput(breachInfo)
                if err != nil {
                        return err
                }

                totalAmt += breachInfo.RemoteOutputSignDesc.Output.Value
        }
        if breachInfo.LocalOutputSignDesc != nil {
                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
        t.totalAmt = btcutil.Amount(totalAmt)

        // First we'll begin by deriving a weight estimate for the justice
        // transaction. The final weight can be different depending on whether
        // the watchtower is taking a reward.
        var weightEstimate input.TxWeightEstimator

        // Next, add the contribution from the inputs that are present on this
        // breach transaction.
        if t.toLocalInput != nil {
                toLocalWitnessSize, err := commitType.ToLocalWitnessSize()
                if err != nil {
                        return err
                }

                weightEstimate.AddWitnessInput(toLocalWitnessSize)
        }
        if t.toRemoteInput != nil {
                toRemoteWitnessSize, err := commitType.ToRemoteWitnessSize()
                if err != nil {
                        return err
                }

                weightEstimate.AddWitnessInput(toRemoteWitnessSize)
        }

        // All justice transactions will either use segwit v0 (p2wkh + p2wsh)
        // or segwit v1 (p2tr).
        err = addScriptWeight(&weightEstimate, t.sweepPkScript)
        if err != nil {
                return err
        }

        // If the justice transaction has a reward output, add the output's
        // contribution to the weight estimate.
        if session.Policy.BlobType.Has(blob.FlagReward) {
                err := addScriptWeight(&weightEstimate, session.RewardPkScript)
                if err != nil {
                        return err
                }
        }

        // Now, compute the output values depending on whether FlagReward is set
        // in the current session's policy.
        outputs, err := session.Policy.ComputeJusticeTxOuts(
                t.totalAmt, weightEstimate.Weight(),
                t.sweepPkScript, session.RewardPkScript,
        )
        if err != nil {
                return err
        }

        t.blobType = session.Policy.BlobType
        t.outputs = outputs

        return nil
}

// craftSessionPayload is the final stage for a backupTask, and generates the
// encrypted payload and breach hint that should be sent to the tower. This
// method computes the final justice transaction using the bound
// session-dependent variables, and signs the resulting transaction. The
// required pieces from signatures, witness scripts, etc are then packaged into
// a JusticeKit and encrypted using the breach transaction's key.
func (t *backupTask) craftSessionPayload(
        signer input.Signer) (blob.BreachHint, []byte, error) {

        var hint blob.BreachHint

        justiceKit, err := t.commitmentType.NewJusticeKit(
                t.sweepPkScript, t.breachInfo, t.toRemoteInput != nil,
        )
        if err != nil {
                return hint, nil, err
        }

        // Now, begin construction of the justice transaction. We'll start with
        // a version 2 transaction.
        justiceTxn := wire.NewMsgTx(2)

        // Next, add the non-dust inputs that were derived from the breach
        // information. This will either be contain both the to-local and
        // to-remote outputs, or only be the to-local output.
        inputs := t.inputs()
        prevOutputFetcher := txscript.NewMultiPrevOutFetcher(nil)
        for prevOutPoint, inp := range inputs {
                prevOutputFetcher.AddPrevOut(
                        prevOutPoint, inp.SignDesc().Output,
                )
                justiceTxn.AddTxIn(&wire.TxIn{
                        PreviousOutPoint: prevOutPoint,
                        Sequence:         inp.BlocksToMaturity(),
                })
        }

        // Add the sweep output paying directly to the user and possibly a
        // reward output, using the outputs computed when the task was bound.
        justiceTxn.TxOut = t.outputs

        // Sort the justice transaction according to BIP69.
        txsort.InPlaceSort(justiceTxn)

        // Check that the justice transaction meets basic validity requirements
        // before attempting to attach the witnesses.
        btx := btcutil.NewTx(justiceTxn)
        if err := blockchain.CheckTransactionSanity(btx); err != nil {
                return hint, nil, err
        }

        // Construct a sighash cache to improve signing performance.
        hashCache := txscript.NewTxSigHashes(justiceTxn, prevOutputFetcher)

        // Since the transaction inputs could have been reordered as a result of
        // the BIP69 sort, create an index mapping each prevout to it's new
        // index.
        inputIndex := make(map[wire.OutPoint]int)
        for i, txIn := range justiceTxn.TxIn {
                inputIndex[txIn.PreviousOutPoint] = i
        }

        // 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()]

                // Construct the full witness required to spend this input.
                inputScript, err := inp.CraftInputScript(
                        signer, justiceTxn, hashCache, prevOutputFetcher, i,
                )
                if err != nil {
                        return hint, nil, err
                }

                signature, err := commitType.ParseRawSig(inputScript.Witness)
                if err != nil {
                        return hint, nil, err
                }

                toLocalWitnessType, err := commitType.ToLocalWitnessType()
                if err != nil {
                        return hint, nil, err
                }

                toRemoteWitnessType, err := commitType.ToRemoteWitnessType()
                if err != nil {
                        return hint, nil, err
                }

                // Finally, copy the serialized signature into the justice kit,
                // using the input's witness type to select the appropriate
                // field
                switch inp.WitnessType() {
                case toLocalWitnessType:
                        justiceKit.AddToLocalSig(signature)

                case toRemoteWitnessType:
                        justiceKit.AddToRemoteSig(signature)
                default:
                        return hint, nil, fmt.Errorf("invalid witness type: %v",
                                inp.WitnessType())
                }
        }

        breachTxID := t.breachInfo.BreachTxHash

        // Compute the breach hint as SHA256(txid)[:16] and breach key as
        // SHA256(txid || txid).
        hint, key := blob.NewBreachHintAndKeyFromHash(&breachTxID)

        // Then, we'll encrypt the computed justice kit using the full breach
        // transaction id, which will allow the tower to recover the contents
        // after the transaction is seen in the chain or mempool.
        encBlob, err := blob.Encrypt(justiceKit, key)
        if err != nil {
                return hint, nil, err
        }

        return hint, encBlob, nil
}

1	package wtclient
2
3	import (
4	"fmt"
5
6	"github.com/btcsuite/btcd/blockchain"
7	"github.com/btcsuite/btcd/btcutil"
8	"github.com/btcsuite/btcd/btcutil/txsort"
9	"github.com/btcsuite/btcd/chaincfg"
10	"github.com/btcsuite/btcd/txscript"
11	"github.com/btcsuite/btcd/wire"
12	"github.com/lightningnetwork/lnd/input"
13	"github.com/lightningnetwork/lnd/lnwallet"
14	"github.com/lightningnetwork/lnd/watchtower/blob"
15	"github.com/lightningnetwork/lnd/watchtower/wtdb"
16	)
17
18	// backupTask is an internal struct for computing the justice transaction for a
19	// particular revoked state. A backupTask functions as a scratch pad for storing
20	// computing values of the transaction itself, such as the final split in
21	// balance if the justice transaction will give a reward to the tower. The
22	// backup task has three primary phases:
23	// 1. Init: Determines which inputs from the breach transaction will be spent,
24	// and the total amount contained in the inputs.
25	// 2. Bind: Asserts that the revoked state is eligible under a given session's
26	// parameters. Certain states may be ineligible due to fee rates, too little
27	// input amount, etc. Backup of these states can be deferred to a later time
28	// or session with more favorable parameters. If the session is bound
29	// successfully, the final session-dependent values to the justice
30	// transaction are solidified.
31	// 3. Send: Once the task is bound, it will be queued to send to a specific
32	// tower corresponding to the session in which it was bound. The justice
33	// transaction will be assembled by examining the parameters left as a
34	// result of the binding. After the justice transaction is signed, the
35	// necessary components are stripped out and encrypted before being sent to
36	// the tower in a StateUpdate.
37	type backupTask struct {
38	id wtdb.BackupID
39	breachInfo *lnwallet.BreachRetribution
40	commitmentType blob.CommitmentType
41
42	// state-dependent variables
43
44	toLocalInput input.Input
45	toRemoteInput input.Input
46	totalAmt btcutil.Amount
47	sweepPkScript []byte
48
49	// session-dependent variables
50
51	blobType blob.Type
52	outputs []*wire.TxOut
53	}
54
55	// newBackupTask initializes a new backupTask.
56	func newBackupTask(id wtdb.BackupID, sweepPkScript []byte) *backupTask {	4✔
57	return &backupTask{	4✔
58	id: id,	4✔
59	sweepPkScript: sweepPkScript,	4✔
60	}	4✔
61	}	4✔
62
63	// inputs returns all non-dust inputs that we will attempt to spend from.
64	//
65	// NOTE: Ordering of the inputs is not critical as we sort the transaction with
66	// BIP69 in a later stage.
67	func (t *backupTask) inputs() map[wire.OutPoint]input.Input {	4✔
68	inputs := make(map[wire.OutPoint]input.Input)	4✔
69	if t.toLocalInput != nil {	8✔
70	inputs[t.toLocalInput.OutPoint()] = t.toLocalInput	4✔
71	}	4✔
72	if t.toRemoteInput != nil {	8✔
73	inputs[t.toRemoteInput.OutPoint()] = t.toRemoteInput	4✔
74	}	4✔
75
76	return inputs	4✔
77	}
78
79	// addrType returns the type of an address after parsing it and matching it to
80	// the set of known script templates.
81	func addrType(pkScript []byte) txscript.ScriptClass {	4✔
82	// We pass in a set of dummy chain params here as they're only needed	4✔
83	// to make the address struct, which we're ignoring anyway (scripts are	4✔
84	// always the same, it's addresses that change across chains).	4✔
85	scriptClass, _, _, _ := txscript.ExtractPkScriptAddrs(	4✔
86	pkScript, &chaincfg.MainNetParams,	4✔
87	)	4✔
88		4✔
89	return scriptClass	4✔
90	}	4✔
91
92	// addScriptWeight parses the passed pkScript and adds the computed weight cost
93	// were the script to be added to the justice transaction.
94	func addScriptWeight(weightEstimate *input.TxWeightEstimator,
95	pkScript []byte) error {	4✔
96		4✔
97	switch addrType(pkScript) {	4✔
98	case txscript.WitnessV0PubKeyHashTy:	×
99	weightEstimate.AddP2WKHOutput()	×
100
101	case txscript.WitnessV0ScriptHashTy:	×
102	weightEstimate.AddP2WSHOutput()	×
103
104	case txscript.WitnessV1TaprootTy:	4✔
105	weightEstimate.AddP2TROutput()	4✔
106
107	default:	×
108	return fmt.Errorf("invalid addr type: %v", addrType(pkScript))	×
109	}
110
111	return nil	4✔
112	}
113
114	// bindSession first populates all state-dependent variables of the task. Then
115	// it determines if the backupTask is compatible with the passed SessionInfo's
116	// policy. If no error is returned, the task has been bound to the session and
117	// can be queued to upload to the tower. Otherwise, the bind failed and should
118	// be rescheduled with a different session.
119	func (t backupTask) bindSession(session wtdb.ClientSessionBody,
120	newBreachRetribution BreachRetributionBuilder) error {	4✔
121		4✔
122	breachInfo, chanType, err := newBreachRetribution(	4✔
123	t.id.ChanID, t.id.CommitHeight,	4✔
124	)	4✔
125	if err != nil {	4✔
126	return err	×
127	}	×
128
129	commitType, err := session.Policy.BlobType.CommitmentType(&chanType)	4✔
130	if err != nil {	4✔
131	return err	×
132	}	×
133
134	// Parse the non-dust outputs from the breach transaction,
135	// simultaneously computing the total amount contained in the inputs
136	// present. We can't compute the exact output values at this time
137	// since the task has not been assigned to a session, at which point
138	// parameters such as fee rate, number of outputs, and reward rate will
139	// be finalized.
140	var (	4✔
141	totalAmt int64	4✔
142	toLocalInput input.Input	4✔
143	toRemoteInput input.Input	4✔
144	)	4✔
145		4✔
146	// Add the sign descriptors and outputs corresponding to the to-local	4✔
147	// and to-remote outputs, respectively, if either input amount is	4✔
148	// non-dust. Note that the naming here seems reversed, but both are	4✔
149	// correct. For example, the to-remote output on the remote party's	4✔
150	// commitment is an output that pays to us. Hence the retribution refers	4✔
151	// to that output as local, though relative to their commitment, it is	4✔
152	// paying to-the-remote party (which is us).	4✔
153	if breachInfo.RemoteOutputSignDesc != nil {	8✔
154	toLocalInput, err = commitType.ToLocalInput(breachInfo)	4✔
155	if err != nil {	4✔
156	return err	×
157	}	×
158
159	totalAmt += breachInfo.RemoteOutputSignDesc.Output.Value	4✔
160	}
161	if breachInfo.LocalOutputSignDesc != nil {	8✔
162	toRemoteInput, err = commitType.ToRemoteInput(breachInfo)	4✔
163	if err != nil {	4✔
164	return err	×
165	}	×
166
167	totalAmt += breachInfo.LocalOutputSignDesc.Output.Value	4✔
168	}
169
170	t.commitmentType = commitType	4✔
171	t.breachInfo = breachInfo	4✔
172	t.toLocalInput = toLocalInput	4✔
173	t.toRemoteInput = toRemoteInput	4✔
174	t.totalAmt = btcutil.Amount(totalAmt)	4✔
175		4✔
176	// First we'll begin by deriving a weight estimate for the justice	4✔
177	// transaction. The final weight can be different depending on whether	4✔
178	// the watchtower is taking a reward.	4✔
179	var weightEstimate input.TxWeightEstimator	4✔
180		4✔
181	// Next, add the contribution from the inputs that are present on this	4✔
182	// breach transaction.	4✔
183	if t.toLocalInput != nil {	8✔
184	toLocalWitnessSize, err := commitType.ToLocalWitnessSize()	4✔
185	if err != nil {	4✔
186	return err	×
187	}	×
188
189	weightEstimate.AddWitnessInput(toLocalWitnessSize)	4✔
190	}
191	if t.toRemoteInput != nil {	8✔
192	toRemoteWitnessSize, err := commitType.ToRemoteWitnessSize()	4✔
193	if err != nil {	4✔
194	return err	×
195	}	×
196
197	weightEstimate.AddWitnessInput(toRemoteWitnessSize)	4✔
198	}
199
200	// All justice transactions will either use segwit v0 (p2wkh + p2wsh)
201	// or segwit v1 (p2tr).
202	err = addScriptWeight(&weightEstimate, t.sweepPkScript)	4✔
203	if err != nil {	4✔
204	return err	×
205	}	×
206
207	// If the justice transaction has a reward output, add the output's
208	// contribution to the weight estimate.
209	if session.Policy.BlobType.Has(blob.FlagReward) {	4✔
210	err := addScriptWeight(&weightEstimate, session.RewardPkScript)	×
211	if err != nil {	×
212	return err	×
213	}	×
214	}
215
216	// Now, compute the output values depending on whether FlagReward is set
217	// in the current session's policy.
218	outputs, err := session.Policy.ComputeJusticeTxOuts(	4✔
219	t.totalAmt, weightEstimate.Weight(),	4✔
220	t.sweepPkScript, session.RewardPkScript,	4✔
221	)	4✔
222	if err != nil {	4✔
223	return err	×
224	}	×
225
226	t.blobType = session.Policy.BlobType	4✔
227	t.outputs = outputs	4✔
228		4✔
229	return nil	4✔
230	}
231
232	// craftSessionPayload is the final stage for a backupTask, and generates the
233	// encrypted payload and breach hint that should be sent to the tower. This
234	// method computes the final justice transaction using the bound
235	// session-dependent variables, and signs the resulting transaction. The
236	// required pieces from signatures, witness scripts, etc are then packaged into
237	// a JusticeKit and encrypted using the breach transaction's key.
238	func (t *backupTask) craftSessionPayload(
239	signer input.Signer) (blob.BreachHint, []byte, error) {	4✔
240		4✔
241	var hint blob.BreachHint	4✔
242		4✔
243	justiceKit, err := t.commitmentType.NewJusticeKit(	4✔
244	t.sweepPkScript, t.breachInfo, t.toRemoteInput != nil,	4✔
245	)	4✔
246	if err != nil {	4✔
247	return hint, nil, err	×
248	}	×
249
250	// Now, begin construction of the justice transaction. We'll start with
251	// a version 2 transaction.
252	justiceTxn := wire.NewMsgTx(2)	4✔
253		4✔
254	// Next, add the non-dust inputs that were derived from the breach	4✔
255	// information. This will either be contain both the to-local and	4✔
256	// to-remote outputs, or only be the to-local output.	4✔
257	inputs := t.inputs()	4✔
258	prevOutputFetcher := txscript.NewMultiPrevOutFetcher(nil)	4✔
259	for prevOutPoint, inp := range inputs {	8✔
260	prevOutputFetcher.AddPrevOut(	4✔
261	prevOutPoint, inp.SignDesc().Output,	4✔
262	)	4✔
263	justiceTxn.AddTxIn(&wire.TxIn{	4✔
264	PreviousOutPoint: prevOutPoint,	4✔
265	Sequence: inp.BlocksToMaturity(),	4✔
266	})	4✔
267	}	4✔
268
269	// Add the sweep output paying directly to the user and possibly a
270	// reward output, using the outputs computed when the task was bound.
271	justiceTxn.TxOut = t.outputs	4✔
272		4✔
273	// Sort the justice transaction according to BIP69.	4✔
274	txsort.InPlaceSort(justiceTxn)	4✔
275		4✔
276	// Check that the justice transaction meets basic validity requirements	4✔
277	// before attempting to attach the witnesses.	4✔
278	btx := btcutil.NewTx(justiceTxn)	4✔
279	if err := blockchain.CheckTransactionSanity(btx); err != nil {	4✔
280	return hint, nil, err	×
281	}	×
282
283	// Construct a sighash cache to improve signing performance.
284	hashCache := txscript.NewTxSigHashes(justiceTxn, prevOutputFetcher)	4✔
285		4✔
286	// Since the transaction inputs could have been reordered as a result of	4✔
287	// the BIP69 sort, create an index mapping each prevout to it's new	4✔
288	// index.	4✔
289	inputIndex := make(map[wire.OutPoint]int)	4✔
290	for i, txIn := range justiceTxn.TxIn {	8✔
291	inputIndex[txIn.PreviousOutPoint] = i	4✔
292	}	4✔
293
294	// Now, iterate through the list of inputs that were initially added to
295	// the transaction and store the computed witness within the justice
296	// kit.
297	commitType := t.commitmentType	4✔
298	for _, inp := range inputs {	8✔
299	// Lookup the input's new post-sort position.	4✔
300	i := inputIndex[inp.OutPoint()]	4✔
301		4✔
302	// Construct the full witness required to spend this input.	4✔
303	inputScript, err := inp.CraftInputScript(	4✔
304	signer, justiceTxn, hashCache, prevOutputFetcher, i,	4✔
305	)	4✔
306	if err != nil {	4✔
307	return hint, nil, err	×
308	}	×
309
310	signature, err := commitType.ParseRawSig(inputScript.Witness)	4✔
311	if err != nil {	4✔
312	return hint, nil, err	×
313	}	×
314
315	toLocalWitnessType, err := commitType.ToLocalWitnessType()	4✔
316	if err != nil {	4✔
317	return hint, nil, err	×
318	}	×
319
320	toRemoteWitnessType, err := commitType.ToRemoteWitnessType()	4✔
321	if err != nil {	4✔
322	return hint, nil, err	×
323	}	×
324
325	// Finally, copy the serialized signature into the justice kit,
326	// using the input's witness type to select the appropriate
327	// field
328	switch inp.WitnessType() {	4✔
329	case toLocalWitnessType:	4✔
330	justiceKit.AddToLocalSig(signature)	4✔
331
332	case toRemoteWitnessType:	4✔
333	justiceKit.AddToRemoteSig(signature)	4✔
334	default:	×
335	return hint, nil, fmt.Errorf("invalid witness type: %v",	×
336	inp.WitnessType())	×
337	}
338	}
339
340	breachTxID := t.breachInfo.BreachTxHash	4✔
341		4✔
342	// Compute the breach hint as SHA256(txid)[:16] and breach key as	4✔
343	// SHA256(txid \|\| txid).	4✔
344	hint, key := blob.NewBreachHintAndKeyFromHash(&breachTxID)	4✔
345		4✔
346	// Then, we'll encrypt the computed justice kit using the full breach	4✔
347	// transaction id, which will allow the tower to recover the contents	4✔
348	// after the transaction is seen in the chain or mempool.	4✔
349	encBlob, err := blob.Encrypt(justiceKit, key)	4✔
350	if err != nil {	4✔
351	return hint, nil, err	×
352	}	×
353
354	return hint, encBlob, nil	4✔
355	}

lightningnetwork / lnd / 12199391122

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