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