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unpack.go

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package runtime

import (

"archive/tar"

"compress/gzip"

"fmt"

"io"

"os"

"path/filepath"

"strings"

"time"

"github.com/containers/image/types"

"github.com/pkg/errors"

)

func UnpackImage(src types.Image, target string) error {

ref := src.Reference()

unpackLayer, err := getLayerUnpacker(ref)

if err != nil {

return err

}

raw, err := ref.NewImageSource(nil)

if err != nil {

return err

}

for _, layer := range src.LayerInfos() {

rc, _, err := raw.GetBlob(layer)

if err != nil {

return err

}

if err := unpackLayer(target, rc); err != nil {

return err

}

}

return nil

}

func getLayerUnpacker(ref types.ImageReference) (func(string, io.Reader) error, error) {

transport := ref.Transport().Name()

switch transport {

case "docker-daemon":

return untar, nil

case "docker":

return untarGzip, nil

default:

return nil, fmt.Errorf("unsupported transport: %s", transport)

}

}

func untarGzip(dest string, r io.Reader) error {

gz, err := gzip.NewReader(r)

if err != nil {

return errors.Wrap(err, "error creating gzip reader")

}

defer gz.Close()

return untar(dest, gz)

}

func untar(dest string, r io.Reader) error {

entries := make(map[string]bool)

var dirs []*tar.Header

tr := tar.NewReader(r)

loop:

for {

hdr, err := tr.Next()

switch err {

case io.EOF:

break loop

case nil:

// success, continue below

default:

return errors.Wrapf(err, "error advancing tar stream")

}

hdr.Name = filepath.Clean(hdr.Name)

if !strings.HasSuffix(hdr.Name, string(os.PathSeparator)) {

// Not the root directory, ensure that the parent directory exists

parent := filepath.Dir(hdr.Name)

parentPath := filepath.Join(dest, parent)

if _, err2 := os.Lstat(parentPath); err2 != nil && os.IsNotExist(err2) {

if err3 := os.MkdirAll(parentPath, 0755); err3 != nil {

return err3

}

}

}

path := filepath.Join(dest, hdr.Name)

if entries[path] {

return fmt.Errorf("duplicate entry for %s", path)

}

entries[path] = true

rel, err := filepath.Rel(dest, path)

if err != nil {

return err

}

info := hdr.FileInfo()

if strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {

return fmt.Errorf("%q is outside of %q", hdr.Name, dest)

}

if strings.HasPrefix(info.Name(), ".wh.") {

path = strings.Replace(path, ".wh.", "", 1)

if err := os.RemoveAll(path); err != nil {

return errors.Wrap(err, "unable to delete whiteout path")

}

continue loop

}

switch hdr.Typeflag {

case tar.TypeDir:

if fi, err := os.Lstat(path); !(err == nil && fi.IsDir()) {

if err2 := os.MkdirAll(path, info.Mode()); err2 != nil {

return errors.Wrap(err2, "error creating directory")

}

}

case tar.TypeReg, tar.TypeRegA:

f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, info.Mode())

if err != nil {

return errors.Wrap(err, "unable to open file")

}

if _, err := io.Copy(f, tr); err != nil {

f.Close()

return errors.Wrap(err, "unable to copy")

}

f.Close()

case tar.TypeLink:

target := filepath.Join(dest, hdr.Linkname)

trueTarget, err := filepath.EvalSymlinks(target)

if err != nil {

return err

}

if !strings.HasPrefix(trueTarget, dest) {

return fmt.Errorf("hardlink %q -> %q outside destination", target, hdr.Linkname)

}

if !strings.HasPrefix(target, dest) {

return fmt.Errorf("invalid hardlink %q -> %q", target, hdr.Linkname)

}

if err := os.Link(target, path); err != nil {

return err

}

case tar.TypeSymlink:

target := filepath.Join(filepath.Dir(path), hdr.Linkname)

trueTarget, err := filepath.EvalSymlinks(target)

if err != nil {

return err

}

if !strings.HasPrefix(trueTarget, dest) {

return fmt.Errorf("hardlink %q -> %q outside destination", target, hdr.Linkname)

}

if !strings.HasPrefix(target, dest) {

return fmt.Errorf("invalid symlink %q -> %q", path, hdr.Linkname)

}

err := os.Symlink(hdr.Linkname, path)

if err != nil {

if os.IsExist(err) {

if err := os.Remove(path); err != nil {

return err

}

if err := os.Symlink(hdr.Linkname, path); err != nil {

return err

}

}

}

case tar.TypeXGlobalHeader:

return nil

}

// Directory mtimes must be handled at the end to avoid further

// file creation in them to modify the directory mtime

if hdr.Typeflag == tar.TypeDir {

dirs = append(dirs, hdr)

}

}

for _, hdr := range dirs {

path := filepath.Join(dest, hdr.Name)

finfo := hdr.FileInfo()

// I believe the old version was using time.Now().UTC() to overcome an

// invalid error from chtimes.....but here we lose hdr.AccessTime like this...

if err := os.Chtimes(path, time.Now().UTC(), finfo.ModTime()); err != nil {

return errors.Wrap(err, "error changing time")

}

}

return nil

}