pkg/archive/diff.go
package archive // import "github.com/docker/docker/pkg/archive"
import (
"archive/tar"
"context"
"fmt"
"io"
"os"
"path/filepath"
"runtime"
"strings"
"github.com/containerd/log"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/system"
)
// UnpackLayer unpack `layer` to a `dest`. The stream `layer` can be
// compressed or uncompressed.
// Returns the size in bytes of the contents of the layer.
func UnpackLayer(dest string, layer io.Reader, options *TarOptions) (size int64, err error) {
tr := tar.NewReader(layer)
trBuf := pools.BufioReader32KPool.Get(tr)
defer pools.BufioReader32KPool.Put(trBuf)
var dirs []*tar.Header
unpackedPaths := make(map[string]struct{})
if options == nil {
options = &TarOptions{}
}
if options.ExcludePatterns == nil {
options.ExcludePatterns = []string{}
}
aufsTempdir := ""
aufsHardlinks := make(map[string]*tar.Header)
// Iterate through the files in the archive.
for {
hdr, err := tr.Next()
if err == io.EOF {
// end of tar archive
break
}
if err != nil {
return 0, err
}
size += hdr.Size
// Normalize name, for safety and for a simple is-root check
hdr.Name = filepath.Clean(hdr.Name)
// Windows does not support filenames with colons in them. Ignore
// these files. This is not a problem though (although it might
// appear that it is). Let's suppose a client is running docker pull.
// The daemon it points to is Windows. Would it make sense for the
// client to be doing a docker pull Ubuntu for example (which has files
// with colons in the name under /usr/share/man/man3)? No, absolutely
// not as it would really only make sense that they were pulling a
// Windows image. However, for development, it is necessary to be able
// to pull Linux images which are in the repository.
//
// TODO Windows. Once the registry is aware of what images are Windows-
// specific or Linux-specific, this warning should be changed to an error
// to cater for the situation where someone does manage to upload a Linux
// image but have it tagged as Windows inadvertently.
if runtime.GOOS == "windows" {
if strings.Contains(hdr.Name, ":") {
log.G(context.TODO()).Warnf("Windows: Ignoring %s (is this a Linux image?)", hdr.Name)
continue
}
}
// Ensure that the parent directory exists.
err = createImpliedDirectories(dest, hdr, options)
if err != nil {
return 0, err
}
// Skip AUFS metadata dirs
if strings.HasPrefix(hdr.Name, WhiteoutMetaPrefix) {
// Regular files inside /.wh..wh.plnk can be used as hardlink targets
// We don't want this directory, but we need the files in them so that
// such hardlinks can be resolved.
if strings.HasPrefix(hdr.Name, WhiteoutLinkDir) && hdr.Typeflag == tar.TypeReg {
basename := filepath.Base(hdr.Name)
aufsHardlinks[basename] = hdr
if aufsTempdir == "" {
if aufsTempdir, err = os.MkdirTemp(dest, "dockerplnk"); err != nil {
return 0, err
}
defer os.RemoveAll(aufsTempdir)
}
if err := createTarFile(filepath.Join(aufsTempdir, basename), dest, hdr, tr, options); err != nil {
return 0, err
}
}
if hdr.Name != WhiteoutOpaqueDir {
continue
}
}
//#nosec G305 -- The joined path is guarded against path traversal.
path := filepath.Join(dest, hdr.Name)
rel, err := filepath.Rel(dest, path)
if err != nil {
return 0, err
}
// Note as these operations are platform specific, so must the slash be.
if strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
return 0, breakoutError(fmt.Errorf("%q is outside of %q", hdr.Name, dest))
}
base := filepath.Base(path)
if strings.HasPrefix(base, WhiteoutPrefix) {
dir := filepath.Dir(path)
if base == WhiteoutOpaqueDir {
_, err := os.Lstat(dir)
if err != nil {
return 0, err
}
err = filepath.WalkDir(dir, func(path string, info os.DirEntry, err error) error {
if err != nil {
if os.IsNotExist(err) {
err = nil // parent was deleted
}
return err
}
if path == dir {
return nil
}
if _, exists := unpackedPaths[path]; !exists {
return os.RemoveAll(path)
}
return nil
})
if err != nil {
return 0, err
}
} else {
originalBase := base[len(WhiteoutPrefix):]
originalPath := filepath.Join(dir, originalBase)
if err := os.RemoveAll(originalPath); err != nil {
return 0, err
}
}
} else {
// If path exits we almost always just want to remove and replace it.
// The only exception is when it is a directory *and* the file from
// the layer is also a directory. Then we want to merge them (i.e.
// just apply the metadata from the layer).
if fi, err := os.Lstat(path); err == nil {
if !(fi.IsDir() && hdr.Typeflag == tar.TypeDir) {
if err := os.RemoveAll(path); err != nil {
return 0, err
}
}
}
trBuf.Reset(tr)
srcData := io.Reader(trBuf)
srcHdr := hdr
// Hard links into /.wh..wh.plnk don't work, as we don't extract that directory, so
// we manually retarget these into the temporary files we extracted them into
if hdr.Typeflag == tar.TypeLink && strings.HasPrefix(filepath.Clean(hdr.Linkname), WhiteoutLinkDir) {
linkBasename := filepath.Base(hdr.Linkname)
srcHdr = aufsHardlinks[linkBasename]
if srcHdr == nil {
return 0, fmt.Errorf("Invalid aufs hardlink")
}
tmpFile, err := os.Open(filepath.Join(aufsTempdir, linkBasename))
if err != nil {
return 0, err
}
defer tmpFile.Close()
srcData = tmpFile
}
if err := remapIDs(options.IDMap, srcHdr); err != nil {
return 0, err
}
if err := createTarFile(path, dest, srcHdr, srcData, options); err != nil {
return 0, err
}
// 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)
}
unpackedPaths[path] = struct{}{}
}
}
for _, hdr := range dirs {
//#nosec G305 -- The header was checked for path traversal before it was appended to the dirs slice.
path := filepath.Join(dest, hdr.Name)
if err := system.Chtimes(path, hdr.AccessTime, hdr.ModTime); err != nil {
return 0, err
}
}
return size, nil
}
// ApplyLayer parses a diff in the standard layer format from `layer`,
// and applies it to the directory `dest`. The stream `layer` can be
// compressed or uncompressed.
// Returns the size in bytes of the contents of the layer.
func ApplyLayer(dest string, layer io.Reader) (int64, error) {
return applyLayerHandler(dest, layer, &TarOptions{}, true)
}
// ApplyUncompressedLayer parses a diff in the standard layer format from
// `layer`, and applies it to the directory `dest`. The stream `layer`
// can only be uncompressed.
// Returns the size in bytes of the contents of the layer.
func ApplyUncompressedLayer(dest string, layer io.Reader, options *TarOptions) (int64, error) {
return applyLayerHandler(dest, layer, options, false)
}
// IsEmpty checks if the tar archive is empty (doesn't contain any entries).
func IsEmpty(rd io.Reader) (bool, error) {
decompRd, err := DecompressStream(rd)
if err != nil {
return true, fmt.Errorf("failed to decompress archive: %v", err)
}
defer decompRd.Close()
tarReader := tar.NewReader(decompRd)
if _, err := tarReader.Next(); err != nil {
if err == io.EOF {
return true, nil
}
return false, fmt.Errorf("failed to read next archive header: %v", err)
}
return false, nil
}
// do the bulk load of ApplyLayer, but allow for not calling DecompressStream
func applyLayerHandler(dest string, layer io.Reader, options *TarOptions, decompress bool) (int64, error) {
dest = filepath.Clean(dest)
// We need to be able to set any perms
restore := overrideUmask(0)
defer restore()
if decompress {
decompLayer, err := DecompressStream(layer)
if err != nil {
return 0, err
}
defer decompLayer.Close()
layer = decompLayer
}
return UnpackLayer(dest, layer, options)
}