sshcode/sshcode.go at master · AlanGreene/sshcode · GitHub

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package main

import (

"context"

"fmt"

"math/rand"

"net"

"net/http"

"os"

"os/exec"

"os/signal"

"path/filepath"

"strconv"

"strings"

"syscall"

"time"

"github.com/pkg/browser"

"go.coder.com/flog"

"golang.org/x/xerrors"

)

const codeServerPath = "~/.cache/sshcode/sshcode-server"

const (

sshDirectory = "~/.ssh"

sshDirectoryUnsafeModeMask = 0022

sshControlPath = sshDirectory + "/control-%h-%p-%r"

)

type options struct {

skipSync bool

syncBack bool

noOpen bool

reuseConnection bool

bindAddr string

remotePort string

sshFlags string

}

func sshCode(host, dir string, o options) error {

host, extraSSHFlags, err := parseHost(host)

if err != nil {

return xerrors.Errorf("failed to parse host IP: %w", err)

}

if extraSSHFlags != "" {

o.sshFlags = strings.Join([]string{extraSSHFlags, o.sshFlags}, " ")

}

o.bindAddr, err = parseBindAddr(o.bindAddr)

if err != nil {

return xerrors.Errorf("failed to parse bind address: %w", err)

}

if o.remotePort == "" {

o.remotePort, err = randomPort()

}

if err != nil {

return xerrors.Errorf("failed to find available remote port: %w", err)

}

// Check the SSH directory's permissions and warn the user if it is not safe.

o.reuseConnection = checkSSHDirectory(sshDirectory, o.reuseConnection)

// Start SSH master connection socket. This prevents multiple password prompts from appearing as authentication

// only happens on the initial connection.

if o.reuseConnection {

flog.Info("starting SSH master connection...")

newSSHFlags, cancel, err := startSSHMaster(o.sshFlags, sshControlPath, host)

defer cancel()

if err != nil {

flog.Error("failed to start SSH master connection: %v", err)

o.reuseConnection = false

} else {

o.sshFlags = newSSHFlags

}

flog.Info("ensuring code-server is updated...")

dlScript := downloadScript(codeServerPath)

// Downloads the latest code-server and allows it to be executed.

sshCmdStr := fmt.Sprintf("ssh %v %v '/usr/bin/env bash -l'", o.sshFlags, host)

sshCmd := exec.Command("sh", "-l", "-c", sshCmdStr)

sshCmd.Stdout = os.Stdout

sshCmd.Stderr = os.Stderr

sshCmd.Stdin = strings.NewReader(dlScript)

err = sshCmd.Run()

if err != nil {

return xerrors.Errorf("failed to update code-server: \n---ssh cmd---\n%s\n---download script---\n%s: %w",

sshCmdStr,

dlScript,

err,

)

}

if !o.skipSync {

start := time.Now()

flog.Info("syncing settings")

err = syncUserSettings(o.sshFlags, host, false)

if err != nil {

return xerrors.Errorf("failed to sync settings: %w", err)

}

flog.Info("synced settings in %s", time.Since(start))

flog.Info("syncing extensions")

err = syncExtensions(o.sshFlags, host, false)

if err != nil {

return xerrors.Errorf("failed to sync extensions: %w", err)

}

flog.Info("synced extensions in %s", time.Since(start))

}

flog.Info("starting code-server...")

flog.Info("Tunneling remote port %v to %v", o.remotePort, o.bindAddr)

sshCmdStr =

fmt.Sprintf("ssh -tt -q -L %v:localhost:%v %v %v 'cd %v; %v --host 127.0.0.1 --allow-http --no-auth --port=%v'",

o.bindAddr, o.remotePort, o.sshFlags, host, dir, codeServerPath, o.remotePort,

)

// Starts code-server and forwards the remote port.

sshCmd = exec.Command("sh", "-l", "-c", sshCmdStr)

sshCmd.Stdin = os.Stdin

sshCmd.Stdout = os.Stdout

sshCmd.Stderr = os.Stderr

err = sshCmd.Start()

if err != nil {

return xerrors.Errorf("failed to start code-server: %w", err)

}

url := fmt.Sprintf("http://%s", o.bindAddr)

ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)

defer cancel()

client := http.Client{

Timeout: time.Second * 3,

}

for {

if ctx.Err() != nil {

return xerrors.Errorf("code-server didn't start in time: %w", ctx.Err())

}

// Waits for code-server to be available before opening the browser.

resp, err := client.Get(url)

if err != nil {

continue

}

resp.Body.Close()

break

}

ctx, cancel = context.WithCancel(context.Background())

if !o.noOpen {

openBrowser(url)

}

go func() {

defer cancel()

sshCmd.Wait()

}()

c := make(chan os.Signal)

signal.Notify(c, os.Interrupt)

select {

case <-ctx.Done():

case <-c:

}

flog.Info("shutting down")

if !o.syncBack || o.skipSync {

return nil

}

flog.Info("synchronizing VS Code back to local")

err = syncExtensions(o.sshFlags, host, true)

if err != nil {

return xerrors.Errorf("failed to sync extensions back: %w", err)

}

err = syncUserSettings(o.sshFlags, host, true)

if err != nil {

return xerrors.Errorf("failed to sync user settings settings back: %w", err)

}

return nil

}

// expandPath returns an expanded version of path.

func expandPath(path string) string {

path = filepath.Clean(os.ExpandEnv(path))

// Replace tilde notation in path with the home directory. You can't replace the first instance of `~` in the

// string with the homedir as having a tilde in the middle of a filename is valid.

homedir := os.Getenv("HOME")

if homedir != "" {

if path == "~" {

path = homedir

} else if strings.HasPrefix(path, "~/") {

path = filepath.Join(homedir, path[2:])

}

return filepath.Clean(path)

}

func parseBindAddr(bindAddr string) (string, error) {

if !strings.Contains(bindAddr, ":") {

bindAddr += ":"

}

host, port, err := net.SplitHostPort(bindAddr)

if err != nil {

return "", err

}

if host == "" {

host = "127.0.0.1"

}

if port == "" {

port, err = randomPort()

}

if err != nil {

return "", err

}

return net.JoinHostPort(host, port), nil

}

func openBrowser(url string) {

var openCmd *exec.Cmd

const (

macPath = "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"

wslPath = "/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe"

)

switch {

case commandExists("google-chrome"):

openCmd = exec.Command("google-chrome", chromeOptions(url)...)

case commandExists("google-chrome-stable"):

openCmd = exec.Command("google-chrome-stable", chromeOptions(url)...)

case commandExists("chromium"):

openCmd = exec.Command("chromium", chromeOptions(url)...)

case commandExists("chromium-browser"):

openCmd = exec.Command("chromium-browser", chromeOptions(url)...)

case pathExists(macPath):

openCmd = exec.Command(macPath, chromeOptions(url)...)

case pathExists(wslPath):

openCmd = exec.Command(wslPath, chromeOptions(url)...)

default:

err := browser.OpenURL(url)

if err != nil {

flog.Error("failed to open browser: %v", err)

}

return

}

// We do not use CombinedOutput because if there is no chrome instance, this will block

// and become the parent process instead of using an existing chrome instance.

err := openCmd.Start()

if err != nil {

flog.Error("failed to open browser: %v", err)

}

func chromeOptions(url string) []string {

return []string{"--app=" + url, "--disable-extensions", "--disable-plugins", "--incognito"}

}

// Checks if a command exists locally.

func commandExists(name string) bool {

_, err := exec.LookPath(name)

return err == nil

}

func pathExists(name string) bool {

_, err := os.Stat(name)

return err == nil

}

// randomPort picks a random port to start code-server on.

func randomPort() (string, error) {

const (

minPort = 1024

maxPort = 65535

maxTries = 10

)

for i := 0; i < maxTries; i++ {

port := rand.Intn(maxPort-minPort+1) + minPort

l, err := net.Listen("tcp", fmt.Sprintf(":%d", port))

if err == nil {

_ = l.Close()

return strconv.Itoa(port), nil

}

flog.Info("port taken: %d", port)

}

return "", xerrors.Errorf("max number of tries exceeded: %d", maxTries)

}

// checkSSHDirectory performs sanity and safety checks on sshDirectory, and

// returns a new value for o.reuseConnection depending on the checks.

func checkSSHDirectory(sshDirectory string, reuseConnection bool) bool {

sshDirectoryMode, err := os.Lstat(expandPath(sshDirectory))

if err != nil {

if reuseConnection {

flog.Info("failed to stat %v directory, disabling connection reuse feature: %v", sshDirectory, err)

}

reuseConnection = false

} else {

if !sshDirectoryMode.IsDir() {

if reuseConnection {

flog.Info("%v is not a directory, disabling connection reuse feature", sshDirectory)

} else {

flog.Info("warning: %v is not a directory", sshDirectory)

}

reuseConnection = false

}

if sshDirectoryMode.Mode().Perm()&sshDirectoryUnsafeModeMask != 0 {

flog.Info("warning: the %v directory has unsafe permissions, they should only be writable by "+

"the owner (and files inside should be set to 0600)", sshDirectory)

}

return reuseConnection

}

// startSSHMaster starts an SSH master connection and waits for it to be ready.

// It returns a new set of SSH flags for child SSH processes to use.

func startSSHMaster(sshFlags string, sshControlPath string, host string) (string, func(), error) {

ctx, cancel := context.WithCancel(context.Background())

newSSHFlags := fmt.Sprintf(`%v -o "ControlPath=%v"`, sshFlags, sshControlPath)

// -MN means "start a master socket and don't open a session, just connect".

sshCmdStr := fmt.Sprintf(`exec ssh %v -MNq %v`, newSSHFlags, host)

sshMasterCmd := exec.CommandContext(ctx, "sh", "-c", sshCmdStr)

sshMasterCmd.Stdin = os.Stdin

sshMasterCmd.Stderr = os.Stderr

// Gracefully stop the SSH master.

stopSSHMaster := func() {

if sshMasterCmd.Process != nil {

if sshMasterCmd.ProcessState != nil && sshMasterCmd.ProcessState.Exited() {

return

}

err := sshMasterCmd.Process.Signal(syscall.SIGTERM)

if err != nil {

flog.Error("failed to send SIGTERM to SSH master process: %v", err)

}

cancel()

}

// Start ssh master and wait. Waiting prevents the process from becoming a zombie process if it dies before

// sshcode does, and allows sshMasterCmd.ProcessState to be populated.

err := sshMasterCmd.Start()

go sshMasterCmd.Wait()

if err != nil {

return "", stopSSHMaster, err

}

err = checkSSHMaster(sshMasterCmd, newSSHFlags, host)

if err != nil {

stopSSHMaster()

return "", stopSSHMaster, xerrors.Errorf("SSH master wasn't ready on time: %w", err)

}

return newSSHFlags, stopSSHMaster, nil

}

// checkSSHMaster polls every second for 30 seconds to check if the SSH master

// is ready.

func checkSSHMaster(sshMasterCmd *exec.Cmd, sshFlags string, host string) error {

var (

maxTries = 30

sleepDur = time.Second

err error

)

for i := 0; i < maxTries; i++ {

// Check if the master is running.

if sshMasterCmd.Process == nil || (sshMasterCmd.ProcessState != nil && sshMasterCmd.ProcessState.Exited()) {

return xerrors.Errorf("SSH master process is not running")

}

// Check if it's ready.

sshCmdStr := fmt.Sprintf(`ssh %v -O check %v`, sshFlags, host)

sshCmd := exec.Command("sh", "-c", sshCmdStr)

err = sshCmd.Run()

if err == nil {

return nil

}

time.Sleep(sleepDur)

}

return xerrors.Errorf("max number of tries exceeded: %d", maxTries)

}

func syncUserSettings(sshFlags string, host string, back bool) error {

localConfDir, err := configDir()

if err != nil {

return err

}

err = ensureDir(localConfDir)

if err != nil {

return err

}

const remoteSettingsDir = "~/.local/share/code-server/User/"

var (

src = localConfDir + "/"

dest = host + ":" + remoteSettingsDir

)

if back {

dest, src = src, dest

}

// Append "/" to have rsync copy the contents of the dir.

return rsync(src, dest, sshFlags, "workspaceStorage", "logs", "CachedData")

}

func syncExtensions(sshFlags string, host string, back bool) error {

localExtensionsDir, err := extensionsDir()

if err != nil {

return err

}

err = ensureDir(localExtensionsDir)

if err != nil {

return err

}

const remoteExtensionsDir = "~/.local/share/code-server/extensions/"

var (

src = localExtensionsDir + "/"

dest = host + ":" + remoteExtensionsDir

)

if back {

dest, src = src, dest

}

return rsync(src, dest, sshFlags)

}

func rsync(src string, dest string, sshFlags string, excludePaths ...string) error {

excludeFlags := make([]string, len(excludePaths))

for i, path := range excludePaths {

excludeFlags[i] = "--exclude=" + path

}

cmd := exec.Command("rsync", append(excludeFlags, "-azvr",

"-e", "ssh "+sshFlags,

// Only update newer directories, and sync times

// to keep things simple.

"-u", "--times",

// This is more unsafe, but it's obnoxious having to enter VS Code

// locally in order to properly delete an extension.

"--delete",

"--copy-unsafe-links",

src, dest,

)...,

)

cmd.Stdout = os.Stdout

cmd.Stderr = os.Stderr

err := cmd.Run()

if err != nil {

return xerrors.Errorf("failed to rsync '%s' to '%s': %w", src, dest, err)

}

return nil

}

func downloadScript(codeServerPath string) string {

return fmt.Sprintf(

`set -euxo pipefail || exit 1

[ "$(uname -m)" != "x86_64" ] && echo "Unsupported server architecture $(uname -m). code-server only has releases for x86_64 systems." && exit 1

pkill -f %v || true

mkdir -p ~/.local/share/code-server %v

cd %v

curlflags="-o latest-linux"

if [ -f latest-linux ]; then

curlflags="$curlflags -z latest-linux"

curl $curlflags https://codesrv-ci.cdr.sh/latest-linux

[ -f %v ] && rm %v

ln latest-linux %v

chmod +x %v`,

codeServerPath,

filepath.Dir(codeServerPath),

codeServerPath,

)

}

// ensureDir creates a directory if it does not exist.

func ensureDir(path string) error {

_, err := os.Stat(path)

if os.IsNotExist(err) {

err = os.MkdirAll(path, 0750)

}

if err != nil {

return err

}

return nil

}

// parseHost parses the host argument. If 'gcp:' is prefixed to the

// host then a lookup is done using gcloud to determine the external IP and any

// additional SSH arguments that should be used for ssh commands. Otherwise, host

// is returned.

func parseHost(host string) (parsedHost string, additionalFlags string, err error) {

host = strings.TrimSpace(host)

switch {

case strings.HasPrefix(host, "gcp:"):

instance := strings.TrimPrefix(host, "gcp:")

return parseGCPSSHCmd(instance)

default:

return host, "", nil

}

// parseGCPSSHCmd parses the IP address and flags used by 'gcloud' when

// ssh'ing to an instance.

func parseGCPSSHCmd(instance string) (ip, sshFlags string, err error) {

dryRunCmd := fmt.Sprintf("gcloud compute ssh --dry-run %v", instance)

out, err := exec.Command("sh", "-l", "-c", dryRunCmd).CombinedOutput()

if err != nil {

return "", "", xerrors.Errorf("%s: %w", out, err)

}

toks := strings.Split(string(out), " ")

if len(toks) < 2 {

return "", "", xerrors.Errorf("unexpected output for '%v' command, %s", dryRunCmd, out)

}

// Slice off the '/usr/bin/ssh' prefix and the '<user>@<ip>' suffix.

sshFlags = strings.Join(toks[1:len(toks)-1], " ")

// E.g. foo@1.2.3.4.

userIP := toks[len(toks)-1]

toks = strings.Split(userIP, "@")

// Assume the '<user>@' is missing.

if len(toks) < 2 {

ip = strings.TrimSpace(toks[0])

} else {

ip = strings.TrimSpace(toks[1])

}

if net.ParseIP(ip) == nil {

return "", "", xerrors.Errorf("parsed invalid ip address %v", ip)

}

return ip, sshFlags, nil

}

sshcode/sshcode.go at master · AlanGreene/sshcode · GitHub

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