pkg/archive/copy.go
package archive // import "github.com/docker/docker/pkg/archive"
import (
"archive/tar"
"context"
"errors"
"io"
"os"
"path/filepath"
"strings"
"github.com/containerd/log"
"github.com/docker/docker/pkg/system"
)
// Errors used or returned by this file.
var (
ErrNotDirectory = errors.New("not a directory")
ErrDirNotExists = errors.New("no such directory")
ErrCannotCopyDir = errors.New("cannot copy directory")
ErrInvalidCopySource = errors.New("invalid copy source content")
)
// PreserveTrailingDotOrSeparator returns the given cleaned path (after
// processing using any utility functions from the path or filepath stdlib
// packages) and appends a trailing `/.` or `/` if its corresponding original
// path (from before being processed by utility functions from the path or
// filepath stdlib packages) ends with a trailing `/.` or `/`. If the cleaned
// path already ends in a `.` path segment, then another is not added. If the
// clean path already ends in a path separator, then another is not added.
func PreserveTrailingDotOrSeparator(cleanedPath string, originalPath string) string {
// Ensure paths are in platform semantics
cleanedPath = normalizePath(cleanedPath)
originalPath = normalizePath(originalPath)
if !specifiesCurrentDir(cleanedPath) && specifiesCurrentDir(originalPath) {
if !hasTrailingPathSeparator(cleanedPath) {
// Add a separator if it doesn't already end with one (a cleaned
// path would only end in a separator if it is the root).
cleanedPath += string(filepath.Separator)
}
cleanedPath += "."
}
if !hasTrailingPathSeparator(cleanedPath) && hasTrailingPathSeparator(originalPath) {
cleanedPath += string(filepath.Separator)
}
return cleanedPath
}
// assertsDirectory returns whether the given path is
// asserted to be a directory, i.e., the path ends with
// a trailing '/' or `/.`, assuming a path separator of `/`.
func assertsDirectory(path string) bool {
return hasTrailingPathSeparator(path) || specifiesCurrentDir(path)
}
// hasTrailingPathSeparator returns whether the given
// path ends with the system's path separator character.
func hasTrailingPathSeparator(path string) bool {
return len(path) > 0 && path[len(path)-1] == filepath.Separator
}
// specifiesCurrentDir returns whether the given path specifies
// a "current directory", i.e., the last path segment is `.`.
func specifiesCurrentDir(path string) bool {
return filepath.Base(path) == "."
}
// SplitPathDirEntry splits the given path between its directory name and its
// basename by first cleaning the path but preserves a trailing "." if the
// original path specified the current directory.
func SplitPathDirEntry(path string) (dir, base string) {
cleanedPath := filepath.Clean(filepath.FromSlash(path))
if specifiesCurrentDir(path) {
cleanedPath += string(os.PathSeparator) + "."
}
return filepath.Dir(cleanedPath), filepath.Base(cleanedPath)
}
// TarResource archives the resource described by the given CopyInfo to a Tar
// archive. A non-nil error is returned if sourcePath does not exist or is
// asserted to be a directory but exists as another type of file.
//
// This function acts as a convenient wrapper around TarWithOptions, which
// requires a directory as the source path. TarResource accepts either a
// directory or a file path and correctly sets the Tar options.
func TarResource(sourceInfo CopyInfo) (content io.ReadCloser, err error) {
return TarResourceRebase(sourceInfo.Path, sourceInfo.RebaseName)
}
// TarResourceRebase is like TarResource but renames the first path element of
// items in the resulting tar archive to match the given rebaseName if not "".
func TarResourceRebase(sourcePath, rebaseName string) (content io.ReadCloser, err error) {
sourcePath = normalizePath(sourcePath)
if _, err = os.Lstat(sourcePath); err != nil {
// Catches the case where the source does not exist or is not a
// directory if asserted to be a directory, as this also causes an
// error.
return
}
// Separate the source path between its directory and
// the entry in that directory which we are archiving.
sourceDir, sourceBase := SplitPathDirEntry(sourcePath)
opts := TarResourceRebaseOpts(sourceBase, rebaseName)
log.G(context.TODO()).Debugf("copying %q from %q", sourceBase, sourceDir)
return TarWithOptions(sourceDir, opts)
}
// TarResourceRebaseOpts does not preform the Tar, but instead just creates the rebase
// parameters to be sent to TarWithOptions (the TarOptions struct)
func TarResourceRebaseOpts(sourceBase string, rebaseName string) *TarOptions {
filter := []string{sourceBase}
return &TarOptions{
Compression: Uncompressed,
IncludeFiles: filter,
IncludeSourceDir: true,
RebaseNames: map[string]string{
sourceBase: rebaseName,
},
}
}
// CopyInfo holds basic info about the source
// or destination path of a copy operation.
type CopyInfo struct {
Path string
Exists bool
IsDir bool
RebaseName string
}
// CopyInfoSourcePath stats the given path to create a CopyInfo
// struct representing that resource for the source of an archive copy
// operation. The given path should be an absolute local path. A source path
// has all symlinks evaluated that appear before the last path separator ("/"
// on Unix). As it is to be a copy source, the path must exist.
func CopyInfoSourcePath(path string, followLink bool) (CopyInfo, error) {
// normalize the file path and then evaluate the symbol link
// we will use the target file instead of the symbol link if
// followLink is set
path = normalizePath(path)
resolvedPath, rebaseName, err := ResolveHostSourcePath(path, followLink)
if err != nil {
return CopyInfo{}, err
}
stat, err := os.Lstat(resolvedPath)
if err != nil {
return CopyInfo{}, err
}
return CopyInfo{
Path: resolvedPath,
Exists: true,
IsDir: stat.IsDir(),
RebaseName: rebaseName,
}, nil
}
// CopyInfoDestinationPath stats the given path to create a CopyInfo
// struct representing that resource for the destination of an archive copy
// operation. The given path should be an absolute local path.
func CopyInfoDestinationPath(path string) (info CopyInfo, err error) {
maxSymlinkIter := 10 // filepath.EvalSymlinks uses 255, but 10 already seems like a lot.
path = normalizePath(path)
originalPath := path
stat, err := os.Lstat(path)
if err == nil && stat.Mode()&os.ModeSymlink == 0 {
// The path exists and is not a symlink.
return CopyInfo{
Path: path,
Exists: true,
IsDir: stat.IsDir(),
}, nil
}
// While the path is a symlink.
for n := 0; err == nil && stat.Mode()&os.ModeSymlink != 0; n++ {
if n > maxSymlinkIter {
// Don't follow symlinks more than this arbitrary number of times.
return CopyInfo{}, errors.New("too many symlinks in " + originalPath)
}
// The path is a symbolic link. We need to evaluate it so that the
// destination of the copy operation is the link target and not the
// link itself. This is notably different than CopyInfoSourcePath which
// only evaluates symlinks before the last appearing path separator.
// Also note that it is okay if the last path element is a broken
// symlink as the copy operation should create the target.
var linkTarget string
linkTarget, err = os.Readlink(path)
if err != nil {
return CopyInfo{}, err
}
if !system.IsAbs(linkTarget) {
// Join with the parent directory.
dstParent, _ := SplitPathDirEntry(path)
linkTarget = filepath.Join(dstParent, linkTarget)
}
path = linkTarget
stat, err = os.Lstat(path)
}
if err != nil {
// It's okay if the destination path doesn't exist. We can still
// continue the copy operation if the parent directory exists.
if !os.IsNotExist(err) {
return CopyInfo{}, err
}
// Ensure destination parent dir exists.
dstParent, _ := SplitPathDirEntry(path)
parentDirStat, err := os.Stat(dstParent)
if err != nil {
return CopyInfo{}, err
}
if !parentDirStat.IsDir() {
return CopyInfo{}, ErrNotDirectory
}
return CopyInfo{Path: path}, nil
}
// The path exists after resolving symlinks.
return CopyInfo{
Path: path,
Exists: true,
IsDir: stat.IsDir(),
}, nil
}
// PrepareArchiveCopy prepares the given srcContent archive, which should
// contain the archived resource described by srcInfo, to the destination
// described by dstInfo. Returns the possibly modified content archive along
// with the path to the destination directory which it should be extracted to.
func PrepareArchiveCopy(srcContent io.Reader, srcInfo, dstInfo CopyInfo) (dstDir string, content io.ReadCloser, err error) {
// Ensure in platform semantics
srcInfo.Path = normalizePath(srcInfo.Path)
dstInfo.Path = normalizePath(dstInfo.Path)
// Separate the destination path between its directory and base
// components in case the source archive contents need to be rebased.
dstDir, dstBase := SplitPathDirEntry(dstInfo.Path)
_, srcBase := SplitPathDirEntry(srcInfo.Path)
switch {
case dstInfo.Exists && dstInfo.IsDir:
// The destination exists as a directory. No alteration
// to srcContent is needed as its contents can be
// simply extracted to the destination directory.
return dstInfo.Path, io.NopCloser(srcContent), nil
case dstInfo.Exists && srcInfo.IsDir:
// The destination exists as some type of file and the source
// content is a directory. This is an error condition since
// you cannot copy a directory to an existing file location.
return "", nil, ErrCannotCopyDir
case dstInfo.Exists:
// The destination exists as some type of file and the source content
// is also a file. The source content entry will have to be renamed to
// have a basename which matches the destination path's basename.
if len(srcInfo.RebaseName) != 0 {
srcBase = srcInfo.RebaseName
}
return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
case srcInfo.IsDir:
// The destination does not exist and the source content is an archive
// of a directory. The archive should be extracted to the parent of
// the destination path instead, and when it is, the directory that is
// created as a result should take the name of the destination path.
// The source content entries will have to be renamed to have a
// basename which matches the destination path's basename.
if len(srcInfo.RebaseName) != 0 {
srcBase = srcInfo.RebaseName
}
return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
case assertsDirectory(dstInfo.Path):
// The destination does not exist and is asserted to be created as a
// directory, but the source content is not a directory. This is an
// error condition since you cannot create a directory from a file
// source.
return "", nil, ErrDirNotExists
default:
// The last remaining case is when the destination does not exist, is
// not asserted to be a directory, and the source content is not an
// archive of a directory. It this case, the destination file will need
// to be created when the archive is extracted and the source content
// entry will have to be renamed to have a basename which matches the
// destination path's basename.
if len(srcInfo.RebaseName) != 0 {
srcBase = srcInfo.RebaseName
}
return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
}
}
// RebaseArchiveEntries rewrites the given srcContent archive replacing
// an occurrence of oldBase with newBase at the beginning of entry names.
func RebaseArchiveEntries(srcContent io.Reader, oldBase, newBase string) io.ReadCloser {
if oldBase == string(os.PathSeparator) {
// If oldBase specifies the root directory, use an empty string as
// oldBase instead so that newBase doesn't replace the path separator
// that all paths will start with.
oldBase = ""
}
rebased, w := io.Pipe()
go func() {
srcTar := tar.NewReader(srcContent)
rebasedTar := tar.NewWriter(w)
for {
hdr, err := srcTar.Next()
if err == io.EOF {
// Signals end of archive.
rebasedTar.Close()
w.Close()
return
}
if err != nil {
w.CloseWithError(err)
return
}
// srcContent tar stream, as served by TarWithOptions(), is
// definitely in PAX format, but tar.Next() mistakenly guesses it
// as USTAR, which creates a problem: if the newBase is >100
// characters long, WriteHeader() returns an error like
// "archive/tar: cannot encode header: Format specifies USTAR; and USTAR cannot encode Name=...".
//
// To fix, set the format to PAX here. See docker/for-linux issue #484.
hdr.Format = tar.FormatPAX
hdr.Name = strings.Replace(hdr.Name, oldBase, newBase, 1)
if hdr.Typeflag == tar.TypeLink {
hdr.Linkname = strings.Replace(hdr.Linkname, oldBase, newBase, 1)
}
if err = rebasedTar.WriteHeader(hdr); err != nil {
w.CloseWithError(err)
return
}
// Ignoring GoSec G110. See https://github.com/securego/gosec/pull/433
// and https://cure53.de/pentest-report_opa.pdf, which recommends to
// replace io.Copy with io.CopyN7. The latter allows to specify the
// maximum number of bytes that should be read. By properly defining
// the limit, it can be assured that a GZip compression bomb cannot
// easily cause a Denial-of-Service.
// After reviewing with @tonistiigi and @cpuguy83, this should not
// affect us, because here we do not read into memory, hence should
// not be vulnerable to this code consuming memory.
//nolint:gosec // G110: Potential DoS vulnerability via decompression bomb (gosec)
if _, err = io.Copy(rebasedTar, srcTar); err != nil {
w.CloseWithError(err)
return
}
}
}()
return rebased
}
// CopyResource performs an archive copy from the given source path to the
// given destination path. The source path MUST exist and the destination
// path's parent directory must exist.
func CopyResource(srcPath, dstPath string, followLink bool) error {
var (
srcInfo CopyInfo
err error
)
// Ensure in platform semantics
srcPath = normalizePath(srcPath)
dstPath = normalizePath(dstPath)
// Clean the source and destination paths.
srcPath = PreserveTrailingDotOrSeparator(filepath.Clean(srcPath), srcPath)
dstPath = PreserveTrailingDotOrSeparator(filepath.Clean(dstPath), dstPath)
if srcInfo, err = CopyInfoSourcePath(srcPath, followLink); err != nil {
return err
}
content, err := TarResource(srcInfo)
if err != nil {
return err
}
defer content.Close()
return CopyTo(content, srcInfo, dstPath)
}
// CopyTo handles extracting the given content whose
// entries should be sourced from srcInfo to dstPath.
func CopyTo(content io.Reader, srcInfo CopyInfo, dstPath string) error {
// The destination path need not exist, but CopyInfoDestinationPath will
// ensure that at least the parent directory exists.
dstInfo, err := CopyInfoDestinationPath(normalizePath(dstPath))
if err != nil {
return err
}
dstDir, copyArchive, err := PrepareArchiveCopy(content, srcInfo, dstInfo)
if err != nil {
return err
}
defer copyArchive.Close()
options := &TarOptions{
NoLchown: true,
NoOverwriteDirNonDir: true,
}
return Untar(copyArchive, dstDir, options)
}
// ResolveHostSourcePath decides real path need to be copied with parameters such as
// whether to follow symbol link or not, if followLink is true, resolvedPath will return
// link target of any symbol link file, else it will only resolve symlink of directory
// but return symbol link file itself without resolving.
func ResolveHostSourcePath(path string, followLink bool) (resolvedPath, rebaseName string, err error) {
if followLink {
resolvedPath, err = filepath.EvalSymlinks(path)
if err != nil {
return
}
resolvedPath, rebaseName = GetRebaseName(path, resolvedPath)
} else {
dirPath, basePath := filepath.Split(path)
// if not follow symbol link, then resolve symbol link of parent dir
var resolvedDirPath string
resolvedDirPath, err = filepath.EvalSymlinks(dirPath)
if err != nil {
return
}
// resolvedDirPath will have been cleaned (no trailing path separators) so
// we can manually join it with the base path element.
resolvedPath = resolvedDirPath + string(filepath.Separator) + basePath
if hasTrailingPathSeparator(path) &&
filepath.Base(path) != filepath.Base(resolvedPath) {
rebaseName = filepath.Base(path)
}
}
return resolvedPath, rebaseName, nil
}
// GetRebaseName normalizes and compares path and resolvedPath,
// return completed resolved path and rebased file name
func GetRebaseName(path, resolvedPath string) (string, string) {
// linkTarget will have been cleaned (no trailing path separators and dot) so
// we can manually join it with them
var rebaseName string
if specifiesCurrentDir(path) &&
!specifiesCurrentDir(resolvedPath) {
resolvedPath += string(filepath.Separator) + "."
}
if hasTrailingPathSeparator(path) &&
!hasTrailingPathSeparator(resolvedPath) {
resolvedPath += string(filepath.Separator)
}
if filepath.Base(path) != filepath.Base(resolvedPath) {
// In the case where the path had a trailing separator and a symlink
// evaluation has changed the last path component, we will need to
// rebase the name in the archive that is being copied to match the
// originally requested name.
rebaseName = filepath.Base(path)
}
return resolvedPath, rebaseName
}