Method x11Handler

agent/agentssh/x11.go:87–135

x11Handler is called when a session has requested X11 forwarding. It listens for X11 connections and forwards them to the client.

(sshCtx ssh.Context, sshSession ssh.Session)

// x11Handler is called when a session has requested X11 forwarding.
// It listens for X11 connections and forwards them to the client.
func (x *x11Forwarder) x11Handler(sshCtx ssh.Context, sshSession ssh.Session) (displayNumber int, handled bool) {
	x11, hasX11 := sshSession.X11()
	if !hasX11 {
		return -1, false
	}
	serverConn, valid := sshCtx.Value(ssh.ContextKeyConn).(*gossh.ServerConn)
	if !valid {
		x.logger.Warn(sshCtx, "failed to get server connection")
		return -1, false
	}
	ctx := slog.With(sshCtx, slog.F("session_id", fmt.Sprintf("%x", serverConn.SessionID())))

	hostname, err := os.Hostname()
	if err != nil {
		x.logger.Warn(ctx, "failed to get hostname", slog.Error(err))
		x.x11HandlerErrors.WithLabelValues("hostname").Add(1)
		return -1, false
	}

	x11session, err := x.createX11Session(ctx, sshSession)
	if err != nil {
		x.logger.Warn(ctx, "failed to create X11 listener", slog.Error(err))
		x.x11HandlerErrors.WithLabelValues("listen").Add(1)
		return -1, false
	}
	defer func() {
		if !handled {
			x.closeAndRemoveSession(x11session)
		}
	}()

	err = addXauthEntry(ctx, x.fs, hostname, strconv.Itoa(x11session.display), x11.AuthProtocol, x11.AuthCookie)
	if err != nil {
		x.logger.Warn(ctx, "failed to add Xauthority entry", slog.Error(err))
		x.x11HandlerErrors.WithLabelValues("xauthority").Add(1)
		return -1, false
	}

	// clean up the X11 session if the SSH session completes.
	go func() {
		<-ctx.Done()
		x.closeAndRemoveSession(x11session)
	}()

	go x.listenForConnections(ctx, x11session, serverConn, x11)
	x.logger.Debug(ctx, "X11 forwarding started", slog.F("display", x11session.display))

	return x11session.display, true
}

func (x *x11Forwarder) trackGoroutine() (closing bool, done func()) {
	x.mu.Lock()