builder/dockerfile: ADD with best-effort xattrs

Archives being unpacked by Dockerfiles may have been created on other
OSes with different conventions and semantics for xattrs, making them
impossible to apply when extracting. Restore the old best-effort xattr
behaviour users have come to depend on in the classic builder.

Signed-off-by: Cory Snider <csnider@mirantis.com>

builder/dockerfile/copy.go

@@ -472,7 +472,7 @@ func performCopyForInfo(dest copyInfo, source copyInfo, options copyFileOptions)
 		return copyDirectory(archiver, srcPath, destPath, options.identity)
 	}
 	if options.decompress && archive.IsArchivePath(srcPath) && !source.noDecompress {
-		return archiver.UntarPath(srcPath, destPath)
+		return archiver.UntarPath(srcPath, destPath, archive.WithBestEffortXattrs(true))
 	}
 
 	destExistsAsDir, err := isExistingDirectory(destPath)

pkg/archive/archive.go

@@ -1275,7 +1275,7 @@ func untarHandler(tarArchive io.Reader, dest string, options *TarOptions, decomp
 
 // TarUntar is a convenience function which calls Tar and Untar, with the output of one piped into the other.
 // If either Tar or Untar fails, TarUntar aborts and returns the error.
-func (archiver *Archiver) TarUntar(src, dst string) error {
+func (archiver *Archiver) TarUntar(src, dst string, opts ...func(*TarOptions)) error {
 	archive, err := TarWithOptions(src, &TarOptions{Compression: Uncompressed})
 	if err != nil {
 		return err
@@ -1284,11 +1284,14 @@ func (archiver *Archiver) TarUntar(src, dst string) error {
 	options := &TarOptions{
 		IDMap: archiver.IDMapping,
 	}
+	for _, o := range opts {
+		o(options)
+	}
 	return archiver.Untar(archive, dst, options)
 }
 
 // UntarPath untar a file from path to a destination, src is the source tar file path.
-func (archiver *Archiver) UntarPath(src, dst string) error {
+func (archiver *Archiver) UntarPath(src, dst string, opts ...func(*TarOptions)) error {
 	archive, err := os.Open(src)
 	if err != nil {
 		return err
@@ -1297,20 +1300,23 @@ func (archiver *Archiver) UntarPath(src, dst string) error {
 	options := &TarOptions{
 		IDMap: archiver.IDMapping,
 	}
+	for _, o := range opts {
+		o(options)
+	}
 	return archiver.Untar(archive, dst, options)
 }
 
 // CopyWithTar creates a tar archive of filesystem path `src`, and
 // unpacks it at filesystem path `dst`.
 // The archive is streamed directly with fixed buffering and no
 // intermediary disk IO.
-func (archiver *Archiver) CopyWithTar(src, dst string) error {
+func (archiver *Archiver) CopyWithTar(src, dst string, opts ...func(*TarOptions)) error {
 	srcSt, err := os.Stat(src)
 	if err != nil {
 		return err
 	}
 	if !srcSt.IsDir() {
-		return archiver.CopyFileWithTar(src, dst)
+		return archiver.CopyFileWithTar(src, dst, opts...)
 	}
 
 	// if this Archiver is set up with ID mapping we need to create
@@ -1321,13 +1327,13 @@ func (archiver *Archiver) CopyWithTar(src, dst string) error {
 	if err := idtools.MkdirAllAndChownNew(dst, 0o755, rootIDs); err != nil {
 		return err
 	}
-	return archiver.TarUntar(src, dst)
+	return archiver.TarUntar(src, dst, opts...)
 }
 
 // CopyFileWithTar emulates the behavior of the 'cp' command-line
 // for a single file. It copies a regular file from path `src` to
 // path `dst`, and preserves all its metadata.
-func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
+func (archiver *Archiver) CopyFileWithTar(src, dst string, opts ...func(*TarOptions)) (err error) {
 	srcSt, err := os.Stat(src)
 	if err != nil {
 		return err
@@ -1394,7 +1400,11 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 		}
 	}()
 
-	err = archiver.Untar(r, filepath.Dir(dst), nil)
+	var options TarOptions
+	for _, o := range opts {
+		o(&options)
+	}
+	err = archiver.Untar(r, filepath.Dir(dst), &options)
 	if err != nil {
 		r.CloseWithError(err)
 	}
@@ -1406,6 +1416,13 @@ func (archiver *Archiver) IdentityMapping() idtools.IdentityMapping {
 	return archiver.IDMapping
 }
 
+// WithBestEffortXattrs sets the BestEffortXattrs option for the Archiver operation.
+func WithBestEffortXattrs(v bool) func(*TarOptions) {
+	return func(opts *TarOptions) {
+		opts.BestEffortXattrs = v
+	}
+}
+
 func remapIDs(idMapping idtools.IdentityMapping, hdr *tar.Header) error {
 	ids, err := idMapping.ToHost(idtools.Identity{UID: hdr.Uid, GID: hdr.Gid})
 	hdr.Uid, hdr.Gid = ids.UID, ids.GID