netann: let ValidateChannelAnn take the new interface

discovery/gossiper.go

@@ -1890,7 +1890,7 @@ func (d *AuthenticatedGossiper) processRejectedEdge(
 	if err != nil {
 		return nil, err
 	}
-	err = netann.ValidateChannelAnn(chanAnn)
+	err = netann.ValidateChannelAnn(chanAnn, d.fetchPKScript)
 	if err != nil {
 		err := fmt.Errorf("assembled channel announcement proof "+
 			"for shortChanID=%v isn't valid: %v",
@@ -2540,7 +2540,8 @@ func (d *AuthenticatedGossiper) handleChanAnnouncement(nMsg *networkMsg,
 	// the signatures within the proof as it should be well formed.
 	var proof *models.ChannelAuthProof
 	if nMsg.isRemote {
-		if err := netann.ValidateChannelAnn(ann); err != nil {
+		err := netann.ValidateChannelAnn(ann, d.fetchPKScript)
+		if err != nil {
 			err := fmt.Errorf("unable to validate announcement: "+
 				"%v", err)
 
@@ -3434,7 +3435,8 @@ func (d *AuthenticatedGossiper) handleAnnSig(nMsg *networkMsg,
 
 	// With all the necessary components assembled validate the full
 	// channel announcement proof.
-	if err := netann.ValidateChannelAnn(chanAnn); err != nil {
+	err = netann.ValidateChannelAnn(chanAnn, d.fetchPKScript)
+	if err != nil {
 		err := fmt.Errorf("channel announcement proof for "+
 			"short_chan_id=%v isn't valid: %v", shortChanID, err)
 

netann/channel_announcement.go

@@ -3,6 +3,7 @@ package netann
 import (
 	"bytes"
 	"errors"
+	"fmt"
 
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -88,10 +89,25 @@ func CreateChanAnnouncement(chanProof *models.ChannelAuthProof,
 	return chanAnn, edge1Ann, edge2Ann, nil
 }
 
-// ValidateChannelAnn validates the channel announcement message and checks
+// FetchPkScript defines a function that can be used to fetch the output script
+// for the transaction with the given SCID.
+type FetchPkScript func(*lnwire.ShortChannelID) ([]byte, error)
+
+// ValidateChannelAnn validates the channel announcement.
+func ValidateChannelAnn(a lnwire.ChannelAnnouncement, _ FetchPkScript) error {
+	switch ann := a.(type) {
+	case *lnwire.ChannelAnnouncement1:
+		return validateChannelAnn1(ann)
+	default:
+		return fmt.Errorf("unhandled implementation of "+
+			"lnwire.ChannelAnnouncement: %T", a)
+	}
+}
+
+// validateChannelAnn1 validates the channel announcement message and checks
 // that node signatures covers the announcement message, and that the bitcoin
 // signatures covers the node keys.
-func ValidateChannelAnn(a *lnwire.ChannelAnnouncement1) error {
+func validateChannelAnn1(a *lnwire.ChannelAnnouncement1) error {
 	// First, we'll compute the digest (h) which is to be signed by each of
 	// the keys included within the node announcement message. This hash
 	// digest includes all the keys, so the (up to 4 signatures) will