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feat(agent/agentssh): use tcp for X11 forwarding#14560
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15 changes: 8 additions & 7 deletionsagent/agentssh/agentssh.go
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141 changes: 88 additions & 53 deletionsagent/agentssh/x11.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -7,6 +7,7 @@ import ( | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
| "math" | ||
| "net" | ||
| "os" | ||
| "path/filepath" | ||
| @@ -22,102 +23,136 @@ import ( | ||
| "cdr.dev/slog" | ||
| ) | ||
| const ( | ||
| // X11StartPort is the starting port for X11 forwarding, this is the | ||
| // port used for "DISPLAY=localhost:0". | ||
| X11StartPort = 6000 | ||
| // X11DefaultDisplayOffset is the default offset for X11 forwarding. | ||
| X11DefaultDisplayOffset = 10 | ||
| ) | ||
| // x11Callback is called when the client requests X11 forwarding. | ||
| func (*Server) x11Callback(_ ssh.Context, _ ssh.X11) bool { | ||
| // Always allow. | ||
| return true | ||
| } | ||
| // x11Handler is called when a session has requested X11 forwarding. | ||
| // It listens for X11 connections and forwards them to the client. | ||
| func (s *Server) x11Handler(ctx ssh.Context, x11 ssh.X11) (displayNumber int, handled bool) { | ||
| serverConn, valid := ctx.Value(ssh.ContextKeyConn).(*gossh.ServerConn) | ||
| if !valid { | ||
| s.logger.Warn(ctx, "failed to get server connection") | ||
| return -1, false | ||
| } | ||
| hostname, err := os.Hostname() | ||
johnstcn marked this conversation as resolved. Show resolvedHide resolvedUh oh!There was an error while loading.Please reload this page. | ||
| if err != nil { | ||
| s.logger.Warn(ctx, "failed to get hostname", slog.Error(err)) | ||
| s.metrics.x11HandlerErrors.WithLabelValues("hostname").Add(1) | ||
| return-1,false | ||
| } | ||
| ln, display,err:= createX11Listener(ctx, *s.config.X11DisplayOffset) | ||
| if err != nil { | ||
| s.logger.Warn(ctx, "failed to create X11 listener", slog.Error(err)) | ||
| s.metrics.x11HandlerErrors.WithLabelValues("listen").Add(1) | ||
| return -1, false | ||
| } | ||
| s.trackListener(ln, true) | ||
| defer func() { | ||
| if !handled { | ||
| s.trackListener(ln, false) | ||
| _ = ln.Close() | ||
| } | ||
| }() | ||
| err = addXauthEntry(ctx, s.fs, hostname, strconv.Itoa(display), x11.AuthProtocol, x11.AuthCookie) | ||
| if err != nil { | ||
| s.logger.Warn(ctx, "failed to add Xauthority entry", slog.Error(err)) | ||
| s.metrics.x11HandlerErrors.WithLabelValues("xauthority").Add(1) | ||
| return-1,false | ||
| } | ||
| go func() { | ||
| // Don't leave the listener open after the session is gone. | ||
| <-ctx.Done() | ||
| _ = ln.Close() | ||
johnstcn marked this conversation as resolved. Show resolvedHide resolvedUh oh!There was an error while loading.Please reload this page. | ||
| }() | ||
| go func() { | ||
| defer ln.Close() | ||
| defer s.trackListener(ln, false) | ||
| for { | ||
| conn, err :=ln.Accept() | ||
| if err != nil { | ||
| if errors.Is(err, net.ErrClosed) { | ||
| return | ||
| } | ||
| s.logger.Warn(ctx, "failed to accept X11 connection", slog.Error(err)) | ||
| return | ||
| } | ||
| if x11.SingleConnection { | ||
| s.logger.Debug(ctx, "single connection requested, closing X11 listener") | ||
| _ = ln.Close() | ||
| } | ||
| tcpConn, ok := conn.(*net.TCPConn) | ||
| if !ok { | ||
| s.logger.Warn(ctx, fmt.Sprintf("failed to cast connection to TCPConn. got: %T", conn)) | ||
| _ = conn.Close() | ||
| continue | ||
| } | ||
| tcpAddr, ok :=tcpConn.LocalAddr().(*net.TCPAddr) | ||
| if !ok { | ||
| s.logger.Warn(ctx, fmt.Sprintf("failed to cast local address to TCPAddr. got: %T", tcpConn.LocalAddr())) | ||
| _ = conn.Close() | ||
| continue | ||
mafredri marked this conversation as resolved. Show resolvedHide resolvedUh oh!There was an error while loading.Please reload this page. | ||
| } | ||
| channel, reqs, err := serverConn.OpenChannel("x11", gossh.Marshal(struct { | ||
| OriginatorAddress string | ||
| OriginatorPort uint32 | ||
| }{ | ||
| OriginatorAddress:tcpAddr.IP.String(), | ||
| OriginatorPort:uint32(tcpAddr.Port), | ||
| })) | ||
| if err != nil { | ||
| s.logger.Warn(ctx, "failed to open X11 channel", slog.Error(err)) | ||
| _ = conn.Close() | ||
| continue | ||
| } | ||
| go gossh.DiscardRequests(reqs) | ||
| if !s.trackConn(ln, conn, true) { | ||
| s.logger.Warn(ctx, "failed to track X11 connection") | ||
| _ = conn.Close() | ||
| continue | ||
| } | ||
| go func() { | ||
| defer s.trackConn(ln, conn, false) | ||
| Bicopy(ctx, conn, channel) | ||
| }() | ||
| } | ||
| }() | ||
| return display, true | ||
| } | ||
| // createX11Listener creates a listener for X11 forwarding, it will use | ||
| // the next available port starting from X11StartPort and displayOffset. | ||
| func createX11Listener(ctx context.Context, displayOffset int) (ln net.Listener, display int, err error) { | ||
| var lc net.ListenConfig | ||
| // Look for an open port to listen on. | ||
| for port := X11StartPort + displayOffset; port < math.MaxUint16; port++ { | ||
| ln, err = lc.Listen(ctx, "tcp", fmt.Sprintf("localhost:%d", port)) | ||
| if err == nil { | ||
| display = port - X11StartPort | ||
| return ln, display, nil | ||
| } | ||
| } | ||
| return nil, -1, xerrors.Errorf("failed to find open port for X11 listener: %w", err) | ||
| } | ||
| // addXauthEntry adds an Xauthority entry to the Xauthority file. | ||
40 changes: 33 additions & 7 deletionsagent/agentssh/x11_test.go
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