cli/pkg/cmd/codespace/ssh.go

package codespace

// This file defines the 'gh cs ssh' and 'gh cs cp' subcommands.

import (
	"context"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"os"
	"path/filepath"
	"strings"
	"text/template"

	"github.com/MakeNowJust/heredoc"
	"github.com/cli/cli/v2/internal/codespaces"
	"github.com/cli/cli/v2/internal/codespaces/api"
	"github.com/cli/cli/v2/pkg/cmdutil"
	"github.com/cli/cli/v2/pkg/liveshare"
	"github.com/spf13/cobra"
)

type sshOptions struct {
	codespace  string
	profile    string
	serverPort int
	debug      bool
	debugFile  string
	stdio      bool
	scpArgs    []string // scp arguments, for 'cs cp' (nil for 'cs ssh')
}

func newSSHCmd(app *App) *cobra.Command {
	var opts sshOptions

	sshCmd := &cobra.Command{
		Use:   "ssh [<flags>...] [-- <ssh-flags>...] [<command>]",
		Short: "SSH into a codespace",
		PreRunE: func(c *cobra.Command, args []string) error {
			if opts.stdio {
				if opts.codespace == "" {
					return errors.New("`--stdio` requires explicit `--codespace`")
				}
				if opts.serverPort != 0 {
					return errors.New("cannot use `--stdio` with `--server-port`")
				}
				if opts.profile != "" {
					return errors.New("cannot use `--stdio` with `--profile`")
				}
			}
			return nil
		},
		RunE: func(cmd *cobra.Command, args []string) error {
			return app.SSH(cmd.Context(), args, opts)
		},
		DisableFlagsInUseLine: true,
	}

	sshCmd.Flags().StringVarP(&opts.profile, "profile", "", "", "Name of the SSH profile to use")
	sshCmd.Flags().IntVarP(&opts.serverPort, "server-port", "", 0, "SSH server port number (0 => pick unused)")
	sshCmd.Flags().StringVarP(&opts.codespace, "codespace", "c", "", "Name of the codespace")
	sshCmd.Flags().BoolVarP(&opts.debug, "debug", "d", false, "Log debug data to a file")
	sshCmd.Flags().StringVarP(&opts.debugFile, "debug-file", "", "", "Path of the file log to")
	sshCmd.Flags().BoolVar(&opts.stdio, "stdio", false, "Proxy sshd connection to stdio")
	sshCmd.Flags().MarkHidden("stdio")

	sshCmd.AddCommand(newConfigCmd(app))

	return sshCmd
}

// SSH opens an ssh session or runs an ssh command in a codespace.
func (a *App) SSH(ctx context.Context, sshArgs []string, opts sshOptions) (err error) {
	// Ensure all child tasks (e.g. port forwarding) terminate before return.
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	liveshareLogger := noopLogger()
	if opts.debug {
		debugLogger, err := newFileLogger(opts.debugFile)
		if err != nil {
			return fmt.Errorf("error creating debug logger: %w", err)
		}
		defer safeClose(debugLogger, &err)

		liveshareLogger = debugLogger.Logger
		a.errLogger.Printf("Debug file located at: %s", debugLogger.Name())
	}

	codespace, err := getOrChooseCodespace(ctx, a.apiClient, opts.codespace)
	if err != nil {
		return fmt.Errorf("get or choose codespace: %w", err)
	}

	// While connecting, ensure in the background that the user has keys installed.
	// That lets us report a more useful error message if they don't.
	authkeys := make(chan error, 1)
	go func() {
		authkeys <- a.ensureAuthorizedKeys(ctx)
	}()

	session, err := a.openSSHSession(ctx, codespace, liveshareLogger)
	if err != nil {
		if authErr := <-authkeys; authErr != nil {
			return authErr
		}
		return fmt.Errorf("error connecting to codespace: %w", err)
	}
	defer safeClose(session, &err)

	a.StartProgressIndicatorWithLabel("Fetching SSH Details")
	remoteSSHServerPort, sshUser, err := session.StartSSHServer(ctx)
	a.StopProgressIndicator()
	if err != nil {
		return fmt.Errorf("error getting ssh server details: %w", err)
	}

	if opts.stdio {
		fwd := liveshare.NewPortForwarder(session, "sshd", remoteSSHServerPort, true)
		stdio := newReadWriteCloser(os.Stdin, os.Stdout)
		err := fwd.Forward(ctx, stdio) // always non-nil
		return fmt.Errorf("tunnel closed: %w", err)
	}

	localSSHServerPort := opts.serverPort
	usingCustomPort := localSSHServerPort != 0 // suppress log of command line in Shell

	// Ensure local port is listening before client (Shell) connects.
	// Unless the user specifies a server port, localSSHServerPort is 0
	// and thus the client will pick a random port.
	listen, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", localSSHServerPort))
	if err != nil {
		return err
	}
	defer listen.Close()
	localSSHServerPort = listen.Addr().(*net.TCPAddr).Port

	connectDestination := opts.profile
	if connectDestination == "" {
		connectDestination = fmt.Sprintf("%s@localhost", sshUser)
	}

	tunnelClosed := make(chan error, 1)
	go func() {
		fwd := liveshare.NewPortForwarder(session, "sshd", remoteSSHServerPort, true)
		tunnelClosed <- fwd.ForwardToListener(ctx, listen) // always non-nil
	}()

	shellClosed := make(chan error, 1)
	go func() {
		var err error
		if opts.scpArgs != nil {
			err = codespaces.Copy(ctx, opts.scpArgs, localSSHServerPort, connectDestination)
		} else {
			err = codespaces.Shell(ctx, a.errLogger, sshArgs, localSSHServerPort, connectDestination, usingCustomPort)
		}
		shellClosed <- err
	}()

	select {
	case err := <-tunnelClosed:
		return fmt.Errorf("tunnel closed: %w", err)
	case err := <-shellClosed:
		if err != nil {
			return fmt.Errorf("shell closed: %w", err)
		}
		return nil // success
	}
}

func (a *App) printOpenSSHConfig(ctx context.Context, opts configOptions) error {
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	var err error
	var codespaces []*api.Codespace
	if opts.codespace == "" {
		a.StartProgressIndicatorWithLabel("Fetching codespaces")
		codespaces, err = a.apiClient.ListCodespaces(ctx, -1)
		a.StopProgressIndicator()
	} else {
		var codespace *api.Codespace
		codespace, err = getOrChooseCodespace(ctx, a.apiClient, opts.codespace)
		codespaces = []*api.Codespace{codespace}
	}
	if err != nil {
		return fmt.Errorf("error getting codespace info: %w", err)
	}

	sshUsers := make(chan sshResult)
	fetches := 0
	var status error
	for _, cs := range codespaces {
		if cs.State != "Available" {
			fmt.Fprintf(os.Stderr, "skipping unavailable codespace %s: %s\n", cs.Name, cs.State)
			status = cmdutil.SilentError
			continue
		}

		cs := cs
		fetches += 1
		go func() {
			result := sshResult{}
			defer func() {
				select {
				case sshUsers <- result:
				case <-ctx.Done():
				}
			}()

			session, err := a.openSSHSession(ctx, cs, nil)
			if err != nil {
				result.err = fmt.Errorf("error connecting to codespace: %w", err)
				return
			}
			defer session.Close()

			//a.StartProgressIndicatorWithLabel(fmt.Sprintf("Fetching SSH Details for %s", cs.Name))
			_, result.user, err = session.StartSSHServer(ctx)
			//a.StopProgressIndicator()
			if err != nil {
				result.err = fmt.Errorf("error getting ssh server details: %w", err)
				return
			}

			result.codespace = cs
		}()
	}

	// While the above fetches are running, ensure that the user has keys installed.
	// That lets us report a more useful error message if they don't.
	if err = a.ensureAuthorizedKeys(ctx); err != nil {
		return err
	}

	ghexec, err := os.Executable()
	if err != nil {
		return err
	}

	t, err := template.New("ssh_config").Parse(`Host cs.{{.Name}}.{{.EscapedRef}}
	User {{.SSHUser}}
	ProxyCommand {{.GHExec}} cs ssh -c {{.Name}} --stdio
	UserKnownHostsFile=/dev/null
	StrictHostKeyChecking no
	LogLevel quiet
	ControlMaster auto

`)
	if err != nil {
		return fmt.Errorf("error formatting template: %w", err)
	}

	for i := 0; i < fetches; i++ {
		result := <-sshUsers
		if result.err != nil {
			fmt.Fprintf(os.Stderr, "%v\n", result.err)
			status = cmdutil.SilentError
			continue
		}

		conf := codespaceSSHConfig{
			Name:       result.codespace.Name,
			EscapedRef: strings.ReplaceAll(result.codespace.GitStatus.Ref, "/", "-"),
			SSHUser:    result.user,
			GHExec:     ghexec,
		}
		if err := t.Execute(a.io.Out, conf); err != nil {
			return err
		}
	}

	return status
}

type sshResult struct {
	codespace *api.Codespace
	user      string // on success, the remote ssh username; else nil
	err       error
}

// codespaceSSHConfig contains values needed to write an OpenSSH host
// configuration for a single codespace. For example:
//
// Host {{Name}}.{{EscapedRef}
//   User {{SSHUser}
//   ProxyCommand {{GHExec}} cs ssh -c {{Name}} --stdio
//
// EscapedRef is included in the name to help distinguish between codespaces
// when tab-completing ssh hostnames. '/' characters in EscapedRef are
// flattened to '-' to prevent problems with tab completion or when the
// hostname appears in ControlMaster socket paths.
type codespaceSSHConfig struct {
	Name       string // the codespace name, passed to `ssh -c`
	EscapedRef string // the currently checked-out branch
	SSHUser    string // the remote ssh username
	GHExec     string // path used for invoking the current `gh` binary
}

func (a *App) openSSHSession(ctx context.Context, codespace *api.Codespace, liveshareLogger *log.Logger) (*liveshare.Session, error) {
	if liveshareLogger == nil {
		liveshareLogger = noopLogger()
	}

	session, err := codespaces.ConnectToLiveshare(ctx, a, liveshareLogger, a.apiClient, codespace)
	if err != nil {
		return nil, fmt.Errorf("error connecting to codespace: %w", err)
	}

	return session, nil
}

func (a *App) ensureAuthorizedKeys(ctx context.Context) error {
	user, err := a.apiClient.GetUser(ctx)
	if err != nil {
		return fmt.Errorf("error getting user: %w", err)
	}

	return checkAuthorizedKeys(ctx, a.apiClient, user.Login)
}

type cpOptions struct {
	sshOptions
	recursive bool // -r
	expand    bool // -e
}

func newCpCmd(app *App) *cobra.Command {
	var opts cpOptions

	cpCmd := &cobra.Command{
		Use:   "cp [-e] [-r] <sources>... <dest>",
		Short: "Copy files between local and remote file systems",
		Long: heredoc.Docf(`
			The cp command copies files between the local and remote file systems.

			As with the UNIX %[1]scp%[1]s command, the first argument specifies the source and the last
			specifies the destination; additional sources may be specified after the first,
			if the destination is a directory.

			The %[1]s--recursive%[1]s flag is required if any source is a directory.

			A "remote:" prefix on any file name argument indicates that it refers to
			the file system of the remote (Codespace) machine. It is resolved relative
			to the home directory of the remote user.

			By default, remote file names are interpreted literally. With the %[1]s--expand%[1]s flag,
			each such argument is treated in the manner of %[1]sscp%[1]s, as a Bash expression to
			be evaluated on the remote machine, subject to expansion of tildes, braces, globs,
			environment variables, and backticks. For security, do not use this flag with arguments
			provided by untrusted users; see <https://lwn.net/Articles/835962/> for discussion.
		`, "`"),
		Example: heredoc.Doc(`
			$ gh codespace cp -e README.md 'remote:/workspaces/$RepositoryName/'
			$ gh codespace cp -e 'remote:~/*.go' ./gofiles/
			$ gh codespace cp -e 'remote:/workspaces/myproj/go.{mod,sum}' ./gofiles/
		`),
		RunE: func(cmd *cobra.Command, args []string) error {
			return app.Copy(cmd.Context(), args, opts)
		},
		DisableFlagsInUseLine: true,
	}

	// We don't expose all sshOptions.
	cpCmd.Flags().BoolVarP(&opts.recursive, "recursive", "r", false, "Recursively copy directories")
	cpCmd.Flags().BoolVarP(&opts.expand, "expand", "e", false, "Expand remote file names on remote shell")
	cpCmd.Flags().StringVarP(&opts.codespace, "codespace", "c", "", "Name of the codespace")
	return cpCmd
}

// Copy copies files between the local and remote file systems.
// The mechanics are similar to 'ssh' but using 'scp'.
func (a *App) Copy(ctx context.Context, args []string, opts cpOptions) error {
	if len(args) < 2 {
		return fmt.Errorf("cp requires source and destination arguments")
	}
	if opts.recursive {
		opts.scpArgs = append(opts.scpArgs, "-r")
	}
	opts.scpArgs = append(opts.scpArgs, "--")
	hasRemote := false
	for _, arg := range args {
		if rest := strings.TrimPrefix(arg, "remote:"); rest != arg {
			hasRemote = true
			// scp treats each filename argument as a shell expression,
			// subjecting it to expansion of environment variables, braces,
			// tilde, backticks, globs and so on. Because these present a
			// security risk (see https://lwn.net/Articles/835962/), we
			// disable them by shell-escaping the argument unless the user
			// provided the -e flag.
			if !opts.expand {
				arg = `remote:'` + strings.Replace(rest, `'`, `'\''`, -1) + `'`
			}

		} else if !filepath.IsAbs(arg) {
			// scp treats a colon in the first path segment as a host identifier.
			// Escape it by prepending "./".
			// TODO(adonovan): test on Windows, including with a c:\\foo path.
			const sep = string(os.PathSeparator)
			first := strings.Split(filepath.ToSlash(arg), sep)[0]
			if strings.Contains(first, ":") {
				arg = "." + sep + arg
			}
		}
		opts.scpArgs = append(opts.scpArgs, arg)
	}
	if !hasRemote {
		return cmdutil.FlagErrorf("at least one argument must have a 'remote:' prefix")
	}
	return a.SSH(ctx, nil, opts.sshOptions)
}

type configOptions struct {
	codespace string
}

func newConfigCmd(app *App) *cobra.Command {
	var opts configOptions

	configCmd := &cobra.Command{
		Use:   "config [-c codespace]",
		Short: "Write OpenSSH configuration to stdout",
		Long: heredoc.Docf(`
			The config command generates per-codespace ssh configuration in OpenSSH format.

			Including this configuration in ~/.ssh/config improves the user experience of other
			tools that integrate with OpenSSH, such as bash/zsh completion of ssh hostnames,
			remote path completion for scp/rsync/sshfs, git ssh remotes, and so on.

			If -c/--codespace is specified, configuration is generated for that codespace
			only. Otherwise configuration is emitted for all available codespaces.

			Codespaces that aren't in "Available" state are skipped because it's necessary to
			connect to the running codespace to determine the required remote ssh username.
		`, "`"),
		Example: heredoc.Doc(`
			$ gh codespace config > ~/.ssh/codespaces
			$ echo 'include ~/.ssh/codespaces' >> ~/.ssh/config'
		`),
		RunE: func(cmd *cobra.Command, args []string) error {
			return app.printOpenSSHConfig(cmd.Context(), opts)
		},
		DisableFlagsInUseLine: true,
	}

	configCmd.Flags().StringVarP(&opts.codespace, "codespace", "c", "", "Name of a codespace")

	return configCmd
}

// fileLogger is a wrapper around an log.Logger configured to write
// to a file. It exports two additional methods to get the log file name
// and close the file handle when the operation is finished.
type fileLogger struct {
	*log.Logger

	f *os.File
}

// newFileLogger creates a new fileLogger. It returns an error if the file
// cannot be created. The file is created on the specified path, if the path
// is empty it is created in the temporary directory.
func newFileLogger(file string) (fl *fileLogger, err error) {
	var f *os.File
	if file == "" {
		f, err = ioutil.TempFile("", "")
		if err != nil {
			return nil, fmt.Errorf("failed to create tmp file: %w", err)
		}
	} else {
		f, err = os.Create(file)
		if err != nil {
			return nil, err
		}
	}

	return &fileLogger{
		Logger: log.New(f, "", log.LstdFlags),
		f:      f,
	}, nil
}

func (fl *fileLogger) Name() string {
	return fl.f.Name()
}

func (fl *fileLogger) Close() error {
	return fl.f.Close()
}

type combinedReadWriteCloser struct {
	io.ReadCloser
	io.WriteCloser
}

func newReadWriteCloser(reader io.ReadCloser, writer io.WriteCloser) io.ReadWriteCloser {
	return &combinedReadWriteCloser{reader, writer}
}

func (crwc *combinedReadWriteCloser) Close() error {
	werr := crwc.WriteCloser.Close()
	rerr := crwc.ReadCloser.Close()
	if werr != nil {
		return werr
	}
	return rerr
}