func()

in cmd/coordinator/remote.go [604:765]
143 lines of code
20 McCabe index (conditional complexity)

func (ah *sshHandlers) handleIncomingSSHPostAuth(s ssh.Session) {
	inst := s.User()
	user := userFromGomoteInstanceName(inst)

	requestedMutable := strings.HasPrefix(inst, "mutable-")
	if requestedMutable {
		inst = strings.TrimPrefix(inst, "mutable-")
	}

	ptyReq, winCh, isPty := s.Pty()
	if !isPty {
		fmt.Fprintf(s, "scp etc not yet supported; https://golang.org/issue/21140\n")
		return
	}

	if ah.gomotePublicKey == "" {
		fmt.Fprint(s, "invalid gomote-ssh-public-key")
		return
	}

	remoteBuildlets.Lock()
	rb, ok := remoteBuildlets.m[inst]
	remoteBuildlets.Unlock()
	if !ok {
		fmt.Fprintf(s, "unknown instance %q", inst)
		return
	}

	hostType := rb.HostType
	hostConf, ok := dashboard.Hosts[hostType]
	if !ok {
		fmt.Fprintf(s, "instance %q has unknown host type %q\n", inst, hostType)
		return
	}

	bconf, ok := dashboard.Builders[rb.BuilderType]
	if !ok {
		fmt.Fprintf(s, "instance %q has unknown builder type %q\n", inst, rb.BuilderType)
		return
	}

	ctx, cancel := context.WithCancel(s.Context())
	defer cancel()
	go rb.renew(ctx)

	sshUser := hostConf.SSHUsername
	useLocalSSHProxy := bconf.GOOS() != "plan9"
	if sshUser == "" && useLocalSSHProxy {
		fmt.Fprintf(s, "instance %q host type %q does not have SSH configured\n", inst, hostType)
		return
	}
	if !hostConf.IsHermetic() && !requestedMutable {
		fmt.Fprintf(s, "WARNING: instance %q host type %q is not currently\n", inst, hostType)
		fmt.Fprintf(s, "configured to have a hermetic filesystem per boot.\n")
		fmt.Fprintf(s, "You must be careful not to modify machine state\n")
		fmt.Fprintf(s, "that will affect future builds. Do you agree? If so,\n")
		fmt.Fprintf(s, "run gomote ssh --i-will-not-break-the-host <INST>\n")
		return
	}

	log.Printf("connecting to ssh to instance %q ...", inst)

	fmt.Fprintf(s, "# Welcome to the gomote ssh proxy, %s.\n", user)
	fmt.Fprintf(s, "# Connecting to/starting remote ssh...\n")
	fmt.Fprintf(s, "#\n")

	var localProxyPort int
	if useLocalSSHProxy {
		sshConn, err := rb.buildlet.ConnectSSH(sshUser, ah.gomotePublicKey)
		log.Printf("buildlet(%q).ConnectSSH = %T, %v", inst, sshConn, err)
		if err != nil {
			fmt.Fprintf(s, "failed to connect to ssh on %s: %v\n", inst, err)
			return
		}
		defer sshConn.Close()

		// Now listen on some localhost port that we'll proxy to sshConn.
		// The openssh ssh command line tool will connect to this IP.
		ln, err := net.Listen("tcp", "localhost:0")
		if err != nil {
			fmt.Fprintf(s, "local listen error: %v\n", err)
			return
		}
		localProxyPort = ln.Addr().(*net.TCPAddr).Port
		log.Printf("ssh local proxy port for %s: %v", inst, localProxyPort)
		var lnCloseOnce sync.Once
		lnClose := func() { lnCloseOnce.Do(func() { ln.Close() }) }
		defer lnClose()

		// Accept at most one connection from localProxyPort and proxy
		// it to sshConn.
		go func() {
			c, err := ln.Accept()
			lnClose()
			if err != nil {
				return
			}
			defer c.Close()
			errc := make(chan error, 1)
			go func() {
				_, err := io.Copy(c, sshConn)
				errc <- err
			}()
			go func() {
				_, err := io.Copy(sshConn, c)
				errc <- err
			}()
			err = <-errc
		}()
	}
	workDir, err := rb.buildlet.WorkDir(ctx)
	if err != nil {
		fmt.Fprintf(s, "Error getting WorkDir: %v\n", err)
		return
	}
	ip, _, ipErr := net.SplitHostPort(rb.buildlet.IPPort())

	fmt.Fprintf(s, "# `gomote push` and the builders use:\n")
	fmt.Fprintf(s, "# - workdir: %s\n", workDir)
	fmt.Fprintf(s, "# - GOROOT: %s/go\n", workDir)
	fmt.Fprintf(s, "# - GOPATH: %s/gopath\n", workDir)
	fmt.Fprintf(s, "# - env: %s\n", strings.Join(bconf.Env(), " ")) // TODO: shell quote?
	fmt.Fprintf(s, "# Happy debugging.\n")

	log.Printf("ssh to %s: starting ssh -p %d for %s@localhost", inst, localProxyPort, sshUser)
	var cmd *exec.Cmd
	switch bconf.GOOS() {
	default:
		cmd = exec.Command("ssh",
			"-p", strconv.Itoa(localProxyPort),
			"-o", "UserKnownHostsFile=/dev/null",
			"-o", "StrictHostKeyChecking=no",
			"-i", sshPrivateKeyFile,
			sshUser+"@localhost")
	case "plan9":
		fmt.Fprintf(s, "# Plan9 user/pass: glenda/glenda123\n")
		if ipErr != nil {
			fmt.Fprintf(s, "# Failed to get IP out of %q: %v\n", rb.buildlet.IPPort(), err)
			return
		}
		cmd = exec.Command("/usr/local/bin/drawterm",
			"-a", ip, "-c", ip, "-u", "glenda", "-k", "user=glenda")
	}
	envutil.SetEnv(cmd, "TERM="+ptyReq.Term)
	f, err := pty.Start(cmd)
	if err != nil {
		log.Printf("running ssh client to %s: %v", inst, err)
		return
	}
	defer f.Close()
	go func() {
		for win := range winCh {
			setWinsize(f, win.Width, win.Height)
		}
	}()
	go func() {
		io.Copy(f, s) // stdin
	}()
	io.Copy(s, f) // stdout
	cmd.Process.Kill()
	cmd.Wait()
}