Moves files

internal/backend/sftp/sftp.go

@@ -0,0 +1,497 @@
+package sftp
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path"
+	"restic"
+	"strings"
+	"time"
+
+	"restic/errors"
+
+	"restic/backend"
+	"restic/debug"
+
+	"github.com/pkg/sftp"
+)
+
+// SFTP is a backend in a directory accessed via SFTP.
+type SFTP struct {
+	c *sftp.Client
+	p string
+
+	cmd    *exec.Cmd
+	result <-chan error
+
+	backend.Layout
+	Config
+}
+
+var _ restic.Backend = &SFTP{}
+
+const defaultLayout = "default"
+
+func startClient(program string, args ...string) (*SFTP, error) {
+	debug.Log("start client %v %v", program, args)
+	// Connect to a remote host and request the sftp subsystem via the 'ssh'
+	// command.  This assumes that passwordless login is correctly configured.
+	cmd := exec.Command(program, args...)
+
+	// prefix the errors with the program name
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return nil, errors.Wrap(err, "cmd.StderrPipe")
+	}
+
+	go func() {
+		sc := bufio.NewScanner(stderr)
+		for sc.Scan() {
+			fmt.Fprintf(os.Stderr, "subprocess %v: %v\n", program, sc.Text())
+		}
+	}()
+
+	// ignore signals sent to the parent (e.g. SIGINT)
+	cmd.SysProcAttr = ignoreSigIntProcAttr()
+
+	// get stdin and stdout
+	wr, err := cmd.StdinPipe()
+	if err != nil {
+		return nil, errors.Wrap(err, "cmd.StdinPipe")
+	}
+	rd, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, errors.Wrap(err, "cmd.StdoutPipe")
+	}
+
+	// start the process
+	if err := cmd.Start(); err != nil {
+		return nil, errors.Wrap(err, "cmd.Start")
+	}
+
+	// wait in a different goroutine
+	ch := make(chan error, 1)
+	go func() {
+		err := cmd.Wait()
+		debug.Log("ssh command exited, err %v", err)
+		ch <- errors.Wrap(err, "cmd.Wait")
+	}()
+
+	// open the SFTP session
+	client, err := sftp.NewClientPipe(rd, wr)
+	if err != nil {
+		return nil, errors.Errorf("unable to start the sftp session, error: %v", err)
+	}
+
+	return &SFTP{c: client, cmd: cmd, result: ch}, nil
+}
+
+// clientError returns an error if the client has exited. Otherwise, nil is
+// returned immediately.
+func (r *SFTP) clientError() error {
+	select {
+	case err := <-r.result:
+		debug.Log("client has exited with err %v", err)
+		return err
+	default:
+	}
+
+	return nil
+}
+
+// Open opens an sftp backend as described by the config by running
+// "ssh" with the appropriate arguments (or cfg.Command, if set).
+func Open(cfg Config) (*SFTP, error) {
+	debug.Log("open backend with config %#v", cfg)
+
+	cmd, args, err := buildSSHCommand(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	sftp, err := startClient(cmd, args...)
+	if err != nil {
+		debug.Log("unable to start program: %v", err)
+		return nil, err
+	}
+
+	sftp.Layout, err = backend.ParseLayout(sftp, cfg.Layout, defaultLayout, cfg.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	debug.Log("layout: %v\n", sftp.Layout)
+
+	if err := sftp.checkDataSubdirs(); err != nil {
+		debug.Log("checkDataSubdirs returned %v", err)
+		return nil, err
+	}
+
+	sftp.Config = cfg
+	sftp.p = cfg.Path
+	return sftp, nil
+}
+
+func (r *SFTP) checkDataSubdirs() error {
+	datadir := r.Dirname(restic.Handle{Type: restic.DataFile})
+
+	// check if all paths for data/ exist
+	entries, err := r.c.ReadDir(datadir)
+	if err != nil {
+		return err
+	}
+
+	subdirs := make(map[string]struct{}, len(entries))
+	for _, entry := range entries {
+		subdirs[entry.Name()] = struct{}{}
+	}
+
+	for i := 0; i < 256; i++ {
+		subdir := fmt.Sprintf("%02x", i)
+		if _, ok := subdirs[subdir]; !ok {
+			debug.Log("subdir %v is missing, creating", subdir)
+			err := r.mkdirAll(path.Join(datadir, subdir), backend.Modes.Dir)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func (r *SFTP) mkdirAllDataSubdirs() error {
+	for _, d := range r.Paths() {
+		err := r.mkdirAll(d, backend.Modes.Dir)
+		debug.Log("mkdirAll %v -> %v", d, err)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Join combines path components with slashes (according to the sftp spec).
+func (r *SFTP) Join(p ...string) string {
+	return path.Join(p...)
+}
+
+// ReadDir returns the entries for a directory.
+func (r *SFTP) ReadDir(dir string) ([]os.FileInfo, error) {
+	return r.c.ReadDir(dir)
+}
+
+// IsNotExist returns true if the error is caused by a not existing file.
+func (r *SFTP) IsNotExist(err error) bool {
+	if os.IsNotExist(err) {
+		return true
+	}
+
+	statusError, ok := err.(*sftp.StatusError)
+	if !ok {
+		return false
+	}
+
+	return statusError.Error() == `sftp: "No such file" (SSH_FX_NO_SUCH_FILE)`
+}
+
+func buildSSHCommand(cfg Config) (cmd string, args []string, err error) {
+	if cfg.Command != "" {
+		return SplitShellArgs(cfg.Command)
+	}
+
+	cmd = "ssh"
+
+	hostport := strings.Split(cfg.Host, ":")
+	args = []string{hostport[0]}
+	if len(hostport) > 1 {
+		args = append(args, "-p", hostport[1])
+	}
+	if cfg.User != "" {
+		args = append(args, "-l")
+		args = append(args, cfg.User)
+	}
+	args = append(args, "-s")
+	args = append(args, "sftp")
+	return cmd, args, nil
+}
+
+// Create creates an sftp backend as described by the config by running
+// "ssh" with the appropriate arguments (or cfg.Command, if set).
+func Create(cfg Config) (*SFTP, error) {
+	cmd, args, err := buildSSHCommand(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	sftp, err := startClient(cmd, args...)
+	if err != nil {
+		debug.Log("unable to start program: %v", err)
+		return nil, err
+	}
+
+	sftp.Layout, err = backend.ParseLayout(sftp, cfg.Layout, defaultLayout, cfg.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	// test if config file already exists
+	_, err = sftp.c.Lstat(Join(cfg.Path, backend.Paths.Config))
+	if err == nil {
+		return nil, errors.New("config file already exists")
+	}
+
+	// create paths for data and refs
+	if err = sftp.mkdirAllDataSubdirs(); err != nil {
+		return nil, err
+	}
+
+	err = sftp.Close()
+	if err != nil {
+		return nil, errors.Wrap(err, "Close")
+	}
+
+	// open backend
+	return Open(cfg)
+}
+
+// Location returns this backend's location (the directory name).
+func (r *SFTP) Location() string {
+	return r.p
+}
+
+func (r *SFTP) mkdirAll(dir string, mode os.FileMode) error {
+	// check if directory already exists
+	fi, err := r.c.Lstat(dir)
+	if err == nil {
+		if fi.IsDir() {
+			return nil
+		}
+
+		return errors.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
+	}
+
+	// create parent directories
+	errMkdirAll := r.mkdirAll(path.Dir(dir), backend.Modes.Dir)
+
+	// create directory
+	errMkdir := r.c.Mkdir(dir)
+
+	// test if directory was created successfully
+	fi, err = r.c.Lstat(dir)
+	if err != nil {
+		// return previous errors
+		return errors.Errorf("mkdirAll(%s): unable to create directories: %v, %v", dir, errMkdirAll, errMkdir)
+	}
+
+	if !fi.IsDir() {
+		return errors.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
+	}
+
+	// set mode
+	return r.c.Chmod(dir, mode)
+}
+
+// Join joins the given paths and cleans them afterwards. This always uses
+// forward slashes, which is required by sftp.
+func Join(parts ...string) string {
+	return path.Clean(path.Join(parts...))
+}
+
+// Save stores data in the backend at the handle.
+func (r *SFTP) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err error) {
+	debug.Log("Save %v", h)
+	if err := r.clientError(); err != nil {
+		return err
+	}
+
+	if err := h.Valid(); err != nil {
+		return err
+	}
+
+	filename := r.Filename(h)
+
+	// create new file
+	f, err := r.c.OpenFile(filename, os.O_CREATE|os.O_EXCL|os.O_WRONLY)
+	if r.IsNotExist(errors.Cause(err)) {
+		// create the locks dir, then try again
+		err = r.mkdirAll(r.Dirname(h), backend.Modes.Dir)
+		if err != nil {
+			return errors.Wrap(err, "MkdirAll")
+		}
+
+		return r.Save(ctx, h, rd)
+	}
+
+	if err != nil {
+		return errors.Wrap(err, "OpenFile")
+	}
+
+	// save data
+	_, err = io.Copy(f, rd)
+	if err != nil {
+		_ = f.Close()
+		return errors.Wrap(err, "Write")
+	}
+
+	err = f.Close()
+	if err != nil {
+		return errors.Wrap(err, "Close")
+	}
+
+	// set mode to read-only
+	fi, err := r.c.Lstat(filename)
+	if err != nil {
+		return errors.Wrap(err, "Lstat")
+	}
+
+	err = r.c.Chmod(filename, fi.Mode()&os.FileMode(^uint32(0222)))
+	return errors.Wrap(err, "Chmod")
+}
+
+// Load returns a reader that yields the contents of the file at h at the
+// given offset. If length is nonzero, only a portion of the file is
+// returned. rd must be closed after use.
+func (r *SFTP) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
+	debug.Log("Load %v, length %v, offset %v", h, length, offset)
+	if err := h.Valid(); err != nil {
+		return nil, err
+	}
+
+	if offset < 0 {
+		return nil, errors.New("offset is negative")
+	}
+
+	f, err := r.c.Open(r.Filename(h))
+	if err != nil {
+		return nil, err
+	}
+
+	if offset > 0 {
+		_, err = f.Seek(offset, 0)
+		if err != nil {
+			_ = f.Close()
+			return nil, err
+		}
+	}
+
+	if length > 0 {
+		return backend.LimitReadCloser(f, int64(length)), nil
+	}
+
+	return f, nil
+}
+
+// Stat returns information about a blob.
+func (r *SFTP) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
+	debug.Log("Stat(%v)", h)
+	if err := r.clientError(); err != nil {
+		return restic.FileInfo{}, err
+	}
+
+	if err := h.Valid(); err != nil {
+		return restic.FileInfo{}, err
+	}
+
+	fi, err := r.c.Lstat(r.Filename(h))
+	if err != nil {
+		return restic.FileInfo{}, errors.Wrap(err, "Lstat")
+	}
+
+	return restic.FileInfo{Size: fi.Size()}, nil
+}
+
+// Test returns true if a blob of the given type and name exists in the backend.
+func (r *SFTP) Test(ctx context.Context, h restic.Handle) (bool, error) {
+	debug.Log("Test(%v)", h)
+	if err := r.clientError(); err != nil {
+		return false, err
+	}
+
+	_, err := r.c.Lstat(r.Filename(h))
+	if os.IsNotExist(errors.Cause(err)) {
+		return false, nil
+	}
+
+	if err != nil {
+		return false, errors.Wrap(err, "Lstat")
+	}
+
+	return true, nil
+}
+
+// Remove removes the content stored at name.
+func (r *SFTP) Remove(ctx context.Context, h restic.Handle) error {
+	debug.Log("Remove(%v)", h)
+	if err := r.clientError(); err != nil {
+		return err
+	}
+
+	return r.c.Remove(r.Filename(h))
+}
+
+// List returns a channel that yields all names of blobs of type t. A
+// goroutine is started for this. If the channel done is closed, sending
+// stops.
+func (r *SFTP) List(ctx context.Context, t restic.FileType) <-chan string {
+	debug.Log("List %v", t)
+
+	ch := make(chan string)
+
+	go func() {
+		defer close(ch)
+
+		walker := r.c.Walk(r.Basedir(t))
+		for walker.Step() {
+			if walker.Err() != nil {
+				continue
+			}
+
+			if !walker.Stat().Mode().IsRegular() {
+				continue
+			}
+
+			select {
+			case ch <- path.Base(walker.Path()):
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return ch
+
+}
+
+var closeTimeout = 2 * time.Second
+
+// Close closes the sftp connection and terminates the underlying command.
+func (r *SFTP) Close() error {
+	debug.Log("")
+	if r == nil {
+		return nil
+	}
+
+	err := r.c.Close()
+	debug.Log("Close returned error %v", err)
+
+	// wait for closeTimeout before killing the process
+	select {
+	case err := <-r.result:
+		return err
+	case <-time.After(closeTimeout):
+	}
+
+	if err := r.cmd.Process.Kill(); err != nil {
+		return err
+	}
+
+	// get the error, but ignore it
+	<-r.result
+	return nil
+}