lib/protocol: Avoid panic in DeviceIDFromBytes (#6714)

cmd/stindex/dump.go

@@ -73,12 +73,16 @@ func dump(ldb backend.Backend) {
 		case db.KeyTypeDeviceIdx:
 			key := binary.BigEndian.Uint32(key[1:])
 			val := it.Value()
-			if len(val) == 0 {
-				fmt.Printf("[deviceidx] K:%d V:<nil>\n", key)
-			} else {
-				dev := protocol.DeviceIDFromBytes(val)
-				fmt.Printf("[deviceidx] K:%d V:%s\n", key, dev)
+			device := "<nil>"
+			if len(val) > 0 {
+				dev, err := protocol.DeviceIDFromBytes(val)
+				if err != nil {
+					device = fmt.Sprintf("<invalid %d bytes>", len(val))
+				} else {
+					device = dev.String()
+				}
 			}
+			fmt.Printf("[deviceidx] K:%d V:%s\n", key, device)
 
 		case db.KeyTypeIndexID:
 			device := binary.BigEndian.Uint32(key[1:])

cmd/strelaysrv/listener.go

@@ -149,7 +149,15 @@ func protocolConnectionHandler(tcpConn net.Conn, config *tls.Config) {
 				protocol.WriteMessage(conn, protocol.ResponseSuccess)
 
 			case protocol.ConnectRequest:
-				requestedPeer := syncthingprotocol.DeviceIDFromBytes(msg.ID)
+				requestedPeer, err := syncthingprotocol.DeviceIDFromBytes(msg.ID)
+				if err != nil {
+					if debug {
+						log.Println(id, "is looking for an invalid peer ID")
+					}
+					protocol.WriteMessage(conn, protocol.ResponseNotFound)
+					conn.Close()
+					continue
+				}
 				outboxesMut.RLock()
 				peerOutbox, ok := outboxes[requestedPeer]
 				outboxesMut.RUnlock()