Merge pull request #822 from yggdrasil-network/sni

TLS Server Name Indication

src/core/link.go

@@ -98,6 +98,22 @@ func (l *links) call(u *url.URL, sintf string) error {
 		l.tcp.call(pathtokens[0], tcpOpts, sintf)
 	case "tls":
 		tcpOpts.upgrade = l.tcp.tls.forDialer
+		// SNI headers must contain hostnames and not IP addresses, so we must make sure
+		// that we do not populate the SNI with an IP literal. We do this by splitting
+		// the host-port combo from the query option and then seeing if it parses to an
+		// IP address successfully or not.
+		if sni := u.Query().Get("sni"); sni != "" {
+			if net.ParseIP(sni) == nil {
+				tcpOpts.tlsSNI = sni
+			}
+		}
+		// If the SNI is not configured still because the above failed then we'll try
+		// again but this time we'll use the host part of the peering URI instead.
+		if tcpOpts.tlsSNI == "" {
+			if host, _, err := net.SplitHostPort(u.Host); err == nil && net.ParseIP(host) == nil {
+				tcpOpts.tlsSNI = host
+			}
+		}
 		l.tcp.call(u.Host, tcpOpts, sintf)
 	default:
 		return errors.New("unknown call scheme: " + u.Scheme)

src/core/tcp.go

@@ -64,6 +64,7 @@ type tcpOptions struct {
 	socksProxyAddr string
 	socksProxyAuth *proxy.Auth
 	socksPeerAddr  string
+	tlsSNI         string
 }
 
 func (l *TcpListener) Stop() {

src/core/tls.go

@@ -78,7 +78,7 @@ func (t *tcptls) init(tcp *tcp) {
 }
 
 func (t *tcptls) configForOptions(options *tcpOptions) *tls.Config {
-	config := *t.config
+	config := t.config.Clone()
 	config.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
 		if len(rawCerts) != 1 {
 			return errors.New("tls not exactly 1 cert")
@@ -103,7 +103,7 @@ func (t *tcptls) configForOptions(options *tcpOptions) *tls.Config {
 		}
 		return nil
 	}
-	return &config
+	return config
 }
 
 func (t *tcptls) upgradeListener(c net.Conn, options *tcpOptions) (net.Conn, error) {
@@ -117,6 +117,7 @@ func (t *tcptls) upgradeListener(c net.Conn, options *tcpOptions) (net.Conn, err
 
 func (t *tcptls) upgradeDialer(c net.Conn, options *tcpOptions) (net.Conn, error) {
 	config := t.configForOptions(options)
+	config.ServerName = options.tlsSNI
 	conn := tls.Client(c, config)
 	if err := conn.Handshake(); err != nil {
 		return c, err