watchtower/wtserver: reject unknown blob types

watchtower/wtserver/server.go

@@ -13,6 +13,7 @@ import (
 	"github.com/btcsuite/btcd/connmgr"
 	"github.com/btcsuite/btcutil"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/watchtower/blob"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
 	"github.com/lightningnetwork/lnd/watchtower/wtwire"
@@ -370,6 +371,15 @@ func (s *Server) handleCreateSession(peer Peer, id *wtdb.SessionID,
 
 	rewardAddrBytes := rewardAddress.ScriptAddress()
 
+	// Ensure that the requested blob type is supported by our tower.
+	if !blob.IsSupportedType(req.BlobType) {
+		log.Debugf("Rejecting CreateSession from %s, unsupported blob "+
+			"type %s", id, req.BlobType)
+		return s.replyCreateSession(
+			peer, id, wtwire.CreateSessionCodeRejectBlobType, nil,
+		)
+	}
+
 	// TODO(conner): create invoice for upfront payment
 
 	// Assemble the session info using the agreed upon parameters, reward

watchtower/wtserver/server_test.go

@@ -170,6 +170,23 @@ var createSessionTests = []createSessionTestCase{
 			Data: []byte(addr.ScriptAddress()),
 		},
 	},
+	{
+		name: "reject unsupported blob type",
+		initMsg: wtwire.NewInitMessage(
+			lnwire.NewRawFeatureVector(),
+			lnwire.NewRawFeatureVector(),
+		),
+		createMsg: &wtwire.CreateSession{
+			BlobType:     0,
+			MaxUpdates:   1000,
+			RewardRate:   0,
+			SweepFeeRate: 1,
+		},
+		expReply: &wtwire.CreateSessionReply{
+			Code: wtwire.CreateSessionCodeRejectBlobType,
+			Data: []byte{},
+		},
+	},
 	// TODO(conner): add policy rejection tests
 }