88 "github.com/btcsuite/btcd/btcec/v2"
99 "github.com/btcsuite/btcd/btcec/v2/schnorr"
1010 "github.com/btcsuite/btcd/btcec/v2/schnorr/musig2"
11+ "github.com/btcsuite/btcd/btcutil"
1112 "github.com/btcsuite/btcd/chaincfg/chainhash"
13+ "github.com/btcsuite/btcd/txscript"
1214 "github.com/lightningnetwork/lnd/graph/db/models"
1315 "github.com/lightningnetwork/lnd/lnwire"
1416 "github.com/lightningnetwork/lnd/tlv"
@@ -108,7 +110,8 @@ func CreateChanAnnouncement(chanProof *models.ChannelAuthProof,
108110
109111// FetchPkScript defines a function that can be used to fetch the output script
110112// for the transaction with the given SCID.
111- type FetchPkScript func (lnwire.ShortChannelID ) ([]byte , error )
113+ type FetchPkScript func (lnwire.ShortChannelID ) (txscript.ScriptClass ,
114+ btcutil.Address , error )
112115
113116// ValidateChannelAnn validates the channel announcement.
114117func ValidateChannelAnn (a lnwire.ChannelAnnouncement ,
@@ -202,24 +205,124 @@ func validateChannelAnn1(a *lnwire.ChannelAnnouncement1) error {
202205func validateChannelAnn2 (a * lnwire.ChannelAnnouncement2 ,
203206 fetchPkScript FetchPkScript ) error {
204207
208+ // Next, we fetch the funding transaction's PK script. We need this so
209+ // that we know what type of channel we will be validating: P2WSH or
210+ // P2TR.
211+ scriptClass , scriptAddr , err := fetchPkScript (a .ShortChannelID .Val )
212+ if err != nil {
213+ return err
214+ }
215+
216+ var keys []* btcec.PublicKey
217+
218+ switch scriptClass {
219+ case txscript .WitnessV0ScriptHashTy :
220+ keys , err = chanAnn2P2WSHMuSig2Keys (a )
221+ if err != nil {
222+ return err
223+ }
224+ case txscript .WitnessV1TaprootTy :
225+ keys , err = chanAnn2P2TRMuSig2Keys (a , scriptAddr )
226+ if err != nil {
227+ return err
228+ }
229+ default :
230+ return fmt .Errorf ("invalid on-chain pk script type for " +
231+ "channel_announcement_2: %s" , scriptClass )
232+ }
233+
234+ // Do a MuSig2 aggregation of the keys to obtain the aggregate key that
235+ // the signature will be validated against.
236+ aggKey , _ , _ , err := musig2 .AggregateKeys (keys , true )
237+ if err != nil {
238+ return err
239+ }
240+
241+ // Get the message that the signature should have signed.
205242 dataHash , err := ChanAnn2DigestToSign (a )
206243 if err != nil {
207244 return err
208245 }
209246
247+ // Obtain the signature.
210248 sig , err := a .Signature .Val .ToSignature ()
211249 if err != nil {
212250 return err
213251 }
214252
253+ // Check that the signature is valid for the aggregate key given the
254+ // message digest.
255+ if ! sig .Verify (dataHash .CloneBytes (), aggKey .FinalKey ) {
256+ return fmt .Errorf ("invalid sig" )
257+ }
258+
259+ return nil
260+ }
261+
262+ // chanAnn2P2WSHMuSig2Keys returns the set of keys that should be used to
263+ // construct the aggregate key that the signature in an
264+ // lnwire.ChannelAnnouncement2 message should be verified against in the case
265+ // where the channel being announced is a P2WSH channel.
266+ func chanAnn2P2WSHMuSig2Keys (a * lnwire.ChannelAnnouncement2 ) (
267+ []* btcec.PublicKey , error ) {
268+
215269 nodeKey1 , err := btcec .ParsePubKey (a .NodeID1 .Val [:])
216270 if err != nil {
217- return err
271+ return nil , err
218272 }
219273
220274 nodeKey2 , err := btcec .ParsePubKey (a .NodeID2 .Val [:])
221275 if err != nil {
222- return err
276+ return nil , err
277+ }
278+
279+ btcKeyMissingErrString := "bitcoin key %d missing for announcement " +
280+ "of a P2WSH channel"
281+
282+ btcKey1Bytes , err := a .BitcoinKey1 .UnwrapOrErr (
283+ fmt .Errorf (btcKeyMissingErrString , 1 ),
284+ )
285+ if err != nil {
286+ return nil , err
287+ }
288+
289+ btcKey1 , err := btcec .ParsePubKey (btcKey1Bytes .Val [:])
290+ if err != nil {
291+ return nil , err
292+ }
293+
294+ btcKey2Bytes , err := a .BitcoinKey2 .UnwrapOrErr (
295+ fmt .Errorf (btcKeyMissingErrString , 2 ),
296+ )
297+ if err != nil {
298+ return nil , err
299+ }
300+
301+ btcKey2 , err := btcec .ParsePubKey (btcKey2Bytes .Val [:])
302+ if err != nil {
303+ return nil , err
304+ }
305+
306+ return []* btcec.PublicKey {
307+ nodeKey1 , nodeKey2 , btcKey1 , btcKey2 ,
308+ }, nil
309+ }
310+
311+ // chanAnn2P2TRMuSig2Keys returns the set of keys that should be used to
312+ // construct the aggregate key that the signature in an
313+ // lnwire.ChannelAnnouncement2 message should be verified against in the case
314+ // where the channel being announced is a P2TR channel.
315+ func chanAnn2P2TRMuSig2Keys (a * lnwire.ChannelAnnouncement2 ,
316+ scriptAddr btcutil.Address ) ([]* btcec.PublicKey , error ) {
317+
318+ nodeKey1 , err := btcec .ParsePubKey (a .NodeID1 .Val [:])
319+ if err != nil {
320+ return nil , err
321+ }
322+
323+ nodeKey2 , err := btcec .ParsePubKey (a .NodeID2 .Val [:])
324+ if err != nil {
325+ return nil , err
223326 }
224327
225328 keys := []* btcec.PublicKey {
@@ -240,42 +343,29 @@ func validateChannelAnn2(a *lnwire.ChannelAnnouncement2,
240343
241344 bitcoinKey1 , err := btcec .ParsePubKey (btcKey1 .Val [:])
242345 if err != nil {
243- return err
346+ return nil , err
244347 }
245348
246349 bitcoinKey2 , err := btcec .ParsePubKey (btcKey2 .Val [:])
247350 if err != nil {
248- return err
351+ return nil , err
249352 }
250353
251354 keys = append (keys , bitcoinKey1 , bitcoinKey2 )
252355 } else {
253- // If bitcoin keys are not provided, then we need to get the
254- // on-chain output key since this will be the 3rd key in the
255- // 3-of-3 MuSig2 signature.
256- pkScript , err := fetchPkScript (a .ShortChannelID .Val )
257- if err != nil {
258- return err
259- }
260-
261- outputKey , err := schnorr .ParsePubKey (pkScript [2 :])
356+ // If bitcoin keys are not provided, then the on-chain output
357+ // key is considered the 3rd key in the 3-of-3 MuSig2 signature.
358+ outputKey , err := schnorr .ParsePubKey (
359+ scriptAddr .ScriptAddress (),
360+ )
262361 if err != nil {
263- return err
362+ return nil , err
264363 }
265364
266365 keys = append (keys , outputKey )
267366 }
268367
269- aggKey , _ , _ , err := musig2 .AggregateKeys (keys , true )
270- if err != nil {
271- return err
272- }
273-
274- if ! sig .Verify (dataHash .CloneBytes (), aggKey .FinalKey ) {
275- return fmt .Errorf ("invalid sig" )
276- }
277-
278- return nil
368+ return keys , nil
279369}
280370
281371// ChanAnn2DigestToSign computes the digest of the message to be signed.
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