Don't pass password around as a pointer to a slice

A slice can be nil, so there is no reason for extra indirection to
represent the lack of a password.

router/crypto.go

@@ -19,11 +19,11 @@ func GenerateKeyPair() (publicKey, privateKey *[32]byte, err error) {
 	return box.GenerateKey(rand.Reader)
 }
 
-func FormSessionKey(remotePublicKey, localPrivateKey *[32]byte, secretKey *[]byte) *[32]byte {
+func FormSessionKey(remotePublicKey, localPrivateKey *[32]byte, secretKey []byte) *[32]byte {
 	var sharedKey [32]byte
 	box.Precompute(&sharedKey, remotePublicKey, localPrivateKey)
 	sharedKeySlice := sharedKey[:]
-	sharedKeySlice = append(sharedKeySlice, *secretKey...)
+	sharedKeySlice = append(sharedKeySlice, secretKey...)
 	sessionKey := sha256.Sum256(sharedKeySlice)
 	return &sessionKey
 }

router/router.go

@@ -27,7 +27,7 @@ type Router struct {
 	GossipChannels  map[uint32]*GossipChannel
 	TopologyGossip  Gossip
 	UDPListener     *net.UDPConn
-	Password        *[]byte
+	Password        []byte
 	ConnLimit       int
 	BufSz           int
 	LogFrame        func(string, []byte, *layers.Ethernet)
@@ -50,12 +50,10 @@ func NewRouter(iface *net.Interface, name PeerName, nickName string, password []
 	router := &Router{
 		Iface:          iface,
 		GossipChannels: make(map[uint32]*GossipChannel),
+		Password:       password,
 		ConnLimit:      connLimit,
 		BufSz:          bufSz,
 		LogFrame:       logFrame}
-	if len(password) > 0 {
-		router.Password = &password
-	}
 	onMacExpiry := func(mac net.HardwareAddr, peer *Peer) {
 		log.Println("Expired MAC", mac, "at", peer.Name)
 	}

weaver/main.go

@@ -104,9 +104,12 @@ func main() {
 	if password == "" {
 		password = os.Getenv("WEAVE_PASSWORD")
 	}
+
+	var pwSlice []byte
 	if password == "" {
 		log.Println("Communication between peers is unencrypted.")
 	} else {
+		pwSlice = []byte(password)
 		log.Println("Communication between peers is encrypted.")
 	}
 
@@ -130,7 +133,7 @@ func main() {
 		defer profile.Start(&p).Stop()
 	}
 
-	router := weave.NewRouter(iface, ourName, nickName, []byte(password), connLimit, bufSz*1024*1024, logFrame)
+	router := weave.NewRouter(iface, ourName, nickName, pwSlice, connLimit, bufSz*1024*1024, logFrame)
 	log.Println("Our name is", router.Ourself.Name, "("+router.Ourself.NickName+")")
 	router.Start()
 	for _, peer := range peers {
@@ -146,7 +149,7 @@ func main() {
 
 func handleHttp(router *weave.Router) {
 	encryption := "off"
-	if router.Password != nil && len(*router.Password) > 0 {
+	if router.Password != nil {
 		encryption = "on"
 	}
 	http.HandleFunc("/status", func(w http.ResponseWriter, r *http.Request) {