Add vnc

Former-commit-id: 825a7f460f

browsergateway/main.go

@@ -51,6 +51,7 @@ func New(cfg Config) *Gateway {
 func (g *Gateway) RegisterHandlers(mux *http.ServeMux) {
 	mux.HandleFunc("/rdp", g.HandleRDP)
 	mux.HandleFunc("/ssh", g.HandleSSH)
+	mux.HandleFunc("/vnc", g.handleVNC)
 }
 
 // HandleRDP is an http.HandlerFunc for RDP-over-WebSocket connections.

browsergateway/vnc.go

@@ -0,0 +1,96 @@
+package browsergateway
+
+import (
+	"context"
+	"crypto/subtle"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/coder/websocket"
+)
+
+const (
+	vncDialTimeout    = 10 * time.Second
+	vncKeepAlive      = 30 * time.Second
+	vncForwardBufSize = 32 * 1024
+)
+
+// handleVNC proxies a noVNC WebSocket connection to a raw TCP VNC backend.
+// It follows the same auth-token-in-query-param pattern as handleSSH.
+//
+// Query parameters:
+//
+//	authToken – shared secret matching the -auth-token flag
+//	host      – VNC backend hostname or IP
+//	port      – VNC backend port (default: 5900)
+func (g *Gateway) handleVNC(w http.ResponseWriter, r *http.Request) {
+	if subtle.ConstantTimeCompare([]byte(r.URL.Query().Get("authToken")), []byte(g.authToken)) != 1 {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	host := r.URL.Query().Get("host")
+	port := r.URL.Query().Get("port")
+	if host == "" {
+		http.Error(w, "missing host", http.StatusBadRequest)
+		return
+	}
+	if port == "" {
+		port = "5900"
+	}
+	target := net.JoinHostPort(host, port)
+
+	// Accept the WebSocket. noVNC negotiates the "binary" subprotocol;
+	// fall back gracefully when the client sends "base64" as well.
+	ws, err := websocket.Accept(w, r, &websocket.AcceptOptions{
+		InsecureSkipVerify: true,
+		Subprotocols:       []string{"binary", "base64"},
+	})
+	if err != nil {
+		log.Printf("vnc: websocket upgrade failed: %v", err)
+		return
+	}
+	ws.SetReadLimit(-1)
+	defer ws.CloseNow() //nolint:errcheck
+
+	ctx := r.Context()
+	if err := serveVNC(ctx, ws, target); err != nil {
+		log.Printf("vnc: session error (%s): %v", target, err)
+	}
+}
+
+func serveVNC(ctx context.Context, ws *websocket.Conn, target string) error {
+	// Dial the VNC backend TCP server.
+	dialer := &net.Dialer{
+		Timeout:   vncDialTimeout,
+		KeepAlive: vncKeepAlive,
+	}
+	conn, err := dialer.DialContext(ctx, "tcp", target)
+	if err != nil {
+		return err
+	}
+	defer conn.Close() //nolint:errcheck
+
+	// Expose the WebSocket as a plain net.Conn byte stream (binary frames).
+	stream := websocket.NetConn(ctx, ws, websocket.MessageBinary)
+	defer stream.Close() //nolint:errcheck
+
+	// Proxy bidirectionally: VNC backend <-> browser.
+	errc := make(chan error, 2)
+	go func() {
+		buf := make([]byte, vncForwardBufSize)
+		_, err := io.CopyBuffer(conn, stream, buf)
+		errc <- err
+	}()
+	go func() {
+		buf := make([]byte, vncForwardBufSize)
+		_, err := io.CopyBuffer(stream, conn, buf)
+		errc <- err
+	}()
+
+	// Return when either direction closes.
+	err = <-errc
+	return err
+}