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mirror of https://github.com/octoleo/restic.git synced 2024-12-23 03:18:55 +00:00
restic/internal/backend/sftp/sftp.go
Michael Eischer 4b98b5562d
Merge pull request #4075 from greatroar/sftp-enospc
sftp: Fix ENOSPC check
2022-12-09 22:00:13 +01:00

634 lines
15 KiB
Go

package sftp
import (
"bufio"
"context"
"crypto/rand"
"encoding/hex"
"fmt"
"hash"
"io"
"os"
"os/exec"
"path"
"time"
"github.com/restic/restic/internal/backend"
"github.com/restic/restic/internal/backend/layout"
"github.com/restic/restic/internal/backend/sema"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
"github.com/cenkalti/backoff/v4"
"github.com/pkg/sftp"
"golang.org/x/sync/errgroup"
)
// SFTP is a backend in a directory accessed via SFTP.
type SFTP struct {
c *sftp.Client
p string
cmd *exec.Cmd
result <-chan error
posixRename bool
sem sema.Semaphore
layout.Layout
Config
backend.Modes
}
var _ restic.Backend = &SFTP{}
const defaultLayout = "default"
func startClient(cfg Config) (*SFTP, error) {
program, args, err := buildSSHCommand(cfg)
if err != nil {
return nil, err
}
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())
}
}()
// 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")
}
bg, err := backend.StartForeground(cmd)
if err != nil {
if backend.IsErrDot(err) {
return nil, errors.Errorf("cannot implicitly run relative executable %v found in current directory, use -o sftp.command=./<command> to override", cmd.Path)
}
return nil, err
}
// wait in a different goroutine
ch := make(chan error, 1)
go func() {
err := cmd.Wait()
debug.Log("ssh command exited, err %v", err)
for {
ch <- errors.Wrap(err, "ssh command exited")
}
}()
// 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)
}
err = bg()
if err != nil {
return nil, errors.Wrap(err, "bg")
}
_, posixRename := client.HasExtension("posix-rename@openssh.com")
return &SFTP{c: client, cmd: cmd, result: ch, posixRename: posixRename}, 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 backoff.Permanent(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(ctx context.Context, cfg Config) (*SFTP, error) {
debug.Log("open backend with config %#v", cfg)
sftp, err := startClient(cfg)
if err != nil {
debug.Log("unable to start program: %v", err)
return nil, err
}
return open(ctx, sftp, cfg)
}
func open(ctx context.Context, sftp *SFTP, cfg Config) (*SFTP, error) {
sem, err := sema.New(cfg.Connections)
if err != nil {
return nil, err
}
sftp.Layout, err = layout.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
if err != nil {
return nil, err
}
debug.Log("layout: %v\n", sftp.Layout)
fi, err := sftp.c.Stat(sftp.Layout.Filename(restic.Handle{Type: restic.ConfigFile}))
m := backend.DeriveModesFromFileInfo(fi, err)
debug.Log("using (%03O file, %03O dir) permissions", m.File, m.Dir)
sftp.Config = cfg
sftp.p = cfg.Path
sftp.sem = sem
sftp.Modes = m
return sftp, nil
}
func (r *SFTP) mkdirAllDataSubdirs(ctx context.Context, nconn uint) error {
// Run multiple MkdirAll calls concurrently. These involve multiple
// round-trips and we do a lot of them, so this whole operation can be slow
// on high-latency links.
g, _ := errgroup.WithContext(ctx)
// Use errgroup's built-in semaphore, because r.sem is not initialized yet.
g.SetLimit(int(nconn))
for _, d := range r.Paths() {
d := d
g.Go(func() error {
// First try Mkdir. For most directories in Paths, this takes one
// round trip, not counting duplicate parent creations causes by
// concurrency. MkdirAll first does Stat, then recursive MkdirAll
// on the parent, so calls typically take three round trips.
if err := r.c.Mkdir(d); err == nil {
return nil
}
return r.c.MkdirAll(d)
})
}
return g.Wait()
}
// 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(ctx context.Context, dir string) ([]os.FileInfo, error) {
fi, err := r.c.ReadDir(dir)
// sftp client does not specify dir name on error, so add it here
err = errors.Wrapf(err, "(%v)", dir)
return fi, err
}
// IsNotExist returns true if the error is caused by a not existing file.
func (r *SFTP) IsNotExist(err error) bool {
return errors.Is(err, os.ErrNotExist)
}
func buildSSHCommand(cfg Config) (cmd string, args []string, err error) {
if cfg.Command != "" {
args, err := backend.SplitShellStrings(cfg.Command)
if err != nil {
return "", nil, err
}
return args[0], args[1:], nil
}
cmd = "ssh"
host, port := cfg.Host, cfg.Port
args = []string{host}
if port != "" {
args = append(args, "-p", port)
}
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(ctx context.Context, cfg Config) (*SFTP, error) {
sftp, err := startClient(cfg)
if err != nil {
debug.Log("unable to start program: %v", err)
return nil, err
}
sftp.Layout, err = layout.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
if err != nil {
return nil, err
}
sftp.Modes = backend.DefaultModes
// test if config file already exists
_, err = sftp.c.Lstat(sftp.Layout.Filename(restic.Handle{Type: restic.ConfigFile}))
if err == nil {
return nil, errors.New("config file already exists")
}
// create paths for data and refs
if err = sftp.mkdirAllDataSubdirs(ctx, cfg.Connections); err != nil {
return nil, err
}
// repurpose existing connection
return open(ctx, sftp, cfg)
}
func (r *SFTP) Connections() uint {
return r.Config.Connections
}
// Location returns this backend's location (the directory name).
func (r *SFTP) Location() string {
return r.p
}
// Hasher may return a hash function for calculating a content hash for the backend
func (r *SFTP) Hasher() hash.Hash {
return nil
}
// HasAtomicReplace returns whether Save() can atomically replace files
func (r *SFTP) HasAtomicReplace() bool {
return r.posixRename
}
// 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...))
}
// tempSuffix generates a random string suffix that should be sufficiently long
// to avoid accidential conflicts
func tempSuffix() string {
var nonce [16]byte
_, err := rand.Read(nonce[:])
if err != nil {
panic(err)
}
return hex.EncodeToString(nonce[:])
}
// Save stores data in the backend at the handle.
func (r *SFTP) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
debug.Log("Save %v", h)
if err := r.clientError(); err != nil {
return err
}
if err := h.Valid(); err != nil {
return backoff.Permanent(err)
}
filename := r.Filename(h)
tmpFilename := filename + "-restic-temp-" + tempSuffix()
dirname := r.Dirname(h)
r.sem.GetToken()
defer r.sem.ReleaseToken()
// create new file
f, err := r.c.OpenFile(tmpFilename, os.O_CREATE|os.O_EXCL|os.O_WRONLY)
if r.IsNotExist(err) {
// error is caused by a missing directory, try to create it
mkdirErr := r.c.MkdirAll(r.Dirname(h))
if mkdirErr != nil {
debug.Log("error creating dir %v: %v", r.Dirname(h), mkdirErr)
} else {
// try again
f, err = r.c.OpenFile(tmpFilename, os.O_CREATE|os.O_EXCL|os.O_WRONLY)
}
}
// pkg/sftp doesn't allow creating with a mode.
// Chmod while the file is still empty.
if err == nil {
err = f.Chmod(r.Modes.File)
}
if err != nil {
return errors.Wrap(err, "OpenFile")
}
defer func() {
if err == nil {
return
}
// Try not to leave a partial file behind.
rmErr := r.c.Remove(f.Name())
if rmErr != nil {
debug.Log("sftp: failed to remove broken file %v: %v",
f.Name(), rmErr)
}
}()
// save data, make sure to use the optimized sftp upload method
wbytes, err := f.ReadFrom(rd)
if err != nil {
_ = f.Close()
err = r.checkNoSpace(dirname, rd.Length(), err)
return errors.Wrap(err, "Write")
}
// sanity check
if wbytes != rd.Length() {
_ = f.Close()
return errors.Errorf("wrote %d bytes instead of the expected %d bytes", wbytes, rd.Length())
}
err = f.Close()
if err != nil {
return errors.Wrap(err, "Close")
}
// Prefer POSIX atomic rename if available.
if r.posixRename {
err = r.c.PosixRename(tmpFilename, filename)
} else {
err = r.c.Rename(tmpFilename, filename)
}
return errors.Wrap(err, "Rename")
}
// checkNoSpace checks if err was likely caused by lack of available space
// on the remote, and if so, makes it permanent.
func (r *SFTP) checkNoSpace(dir string, size int64, origErr error) error {
// The SFTP protocol has a message for ENOSPC,
// but pkg/sftp doesn't export it and OpenSSH's sftp-server
// sends FX_FAILURE instead.
e, ok := origErr.(*sftp.StatusError)
_, hasExt := r.c.HasExtension("statvfs@openssh.com")
if !ok || e.FxCode() != sftp.ErrSSHFxFailure || !hasExt {
return origErr
}
fsinfo, err := r.c.StatVFS(dir)
if err != nil {
debug.Log("sftp: StatVFS returned %v", err)
return origErr
}
if fsinfo.Favail == 0 || fsinfo.Frsize*fsinfo.Bavail < uint64(size) {
err := errors.New("sftp: no space left on device")
return backoff.Permanent(err)
}
return origErr
}
// Load runs fn with a reader that yields the contents of the file at h at the
// given offset.
func (r *SFTP) Load(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error {
return backend.DefaultLoad(ctx, h, length, offset, r.openReader, fn)
}
// wrapReader wraps an io.ReadCloser to run an additional function on Close.
type wrapReader struct {
io.ReadCloser
io.WriterTo
f func()
}
func (wr *wrapReader) Close() error {
err := wr.ReadCloser.Close()
wr.f()
return err
}
func (r *SFTP) openReader(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, backoff.Permanent(err)
}
if offset < 0 {
return nil, errors.New("offset is negative")
}
r.sem.GetToken()
f, err := r.c.Open(r.Filename(h))
if err != nil {
r.sem.ReleaseToken()
return nil, err
}
if offset > 0 {
_, err = f.Seek(offset, 0)
if err != nil {
r.sem.ReleaseToken()
_ = f.Close()
return nil, err
}
}
// use custom close wrapper to also provide WriteTo() on the wrapper
rd := &wrapReader{
ReadCloser: f,
WriterTo: f,
f: func() {
r.sem.ReleaseToken()
},
}
if length > 0 {
// unlimited reads usually use io.Copy which needs WriteTo support at the underlying reader
// limited reads are usually combined with io.ReadFull which reads all required bytes into a buffer in one go
return backend.LimitReadCloser(rd, int64(length)), nil
}
return rd, 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{}, backoff.Permanent(err)
}
r.sem.GetToken()
defer r.sem.ReleaseToken()
fi, err := r.c.Lstat(r.Filename(h))
if err != nil {
return restic.FileInfo{}, errors.Wrap(err, "Lstat")
}
return restic.FileInfo{Size: fi.Size(), Name: h.Name}, 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
}
r.sem.GetToken()
defer r.sem.ReleaseToken()
return r.c.Remove(r.Filename(h))
}
// List runs fn for each file in the backend which has the type t. When an
// error occurs (or fn returns an error), List stops and returns it.
func (r *SFTP) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
debug.Log("List %v", t)
basedir, subdirs := r.Basedir(t)
walker := r.c.Walk(basedir)
for {
r.sem.GetToken()
ok := walker.Step()
r.sem.ReleaseToken()
if !ok {
break
}
if walker.Err() != nil {
if r.IsNotExist(walker.Err()) {
debug.Log("ignoring non-existing directory")
return nil
}
return walker.Err()
}
if walker.Path() == basedir {
continue
}
if walker.Stat().IsDir() && !subdirs {
walker.SkipDir()
continue
}
fi := walker.Stat()
if !fi.Mode().IsRegular() {
continue
}
debug.Log("send %v\n", path.Base(walker.Path()))
rfi := restic.FileInfo{
Name: path.Base(walker.Path()),
Size: fi.Size(),
}
if ctx.Err() != nil {
return ctx.Err()
}
err := fn(rfi)
if err != nil {
return err
}
if ctx.Err() != nil {
return ctx.Err()
}
}
return ctx.Err()
}
var closeTimeout = 2 * time.Second
// Close closes the sftp connection and terminates the underlying command.
func (r *SFTP) Close() error {
debug.Log("Close")
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
}
func (r *SFTP) deleteRecursive(ctx context.Context, name string) error {
entries, err := r.ReadDir(ctx, name)
if err != nil {
return errors.Wrap(err, "ReadDir")
}
for _, fi := range entries {
itemName := r.Join(name, fi.Name())
if fi.IsDir() {
err := r.deleteRecursive(ctx, itemName)
if err != nil {
return errors.Wrap(err, "ReadDir")
}
err = r.c.RemoveDirectory(itemName)
if err != nil {
return errors.Wrap(err, "RemoveDirectory")
}
continue
}
err := r.c.Remove(itemName)
if err != nil {
return errors.Wrap(err, "ReadDir")
}
}
return nil
}
// Delete removes all data in the backend.
func (r *SFTP) Delete(ctx context.Context) error {
return r.deleteRecursive(ctx, r.p)
}