feat: option to have File store preserve permissions when extracting (#891)

This PR takes care of
#886, or rather part of
it.
It adds an option to the File store that's similar to tar's
`--preserve-permissions`.

closes #886
Signed-off-by: Sammy Abed <[email protected]>

Author: sammy-da

content/file/file.go

@@ -108,6 +108,9 @@ type Store struct {
 	// value overrides the [AnnotationUnpack].
 	// Default value: false.
 	SkipUnpack bool
+	// PreservePermissions controls whether to preserve file permissions when unpacking,
+	// disregarding the active umask, similar to tar's `--preserve-permissions`
+	PreservePermissions bool
 
 	workingDir   string   // the working directory of the file store
 	closed       int32    // if the store is closed - 0: false, 1: true.
@@ -499,7 +502,7 @@ func (s *Store) pushDir(name, target string, expected ocispec.Descriptor, conten
 	checksum := expected.Annotations[AnnotationDigest]
 	buf := bufPool.Get().(*[]byte)
 	defer bufPool.Put(buf)
-	if err := extractTarGzip(target, name, gzPath, checksum, *buf); err != nil {
+	if err := extractTarGzip(target, name, gzPath, checksum, *buf, s.PreservePermissions); err != nil {
 		return fmt.Errorf("failed to extract tar to %s: %w", target, err)
 	}
 	return nil

content/file/utils.go

@@ -113,7 +113,7 @@ func tarDirectory(ctx context.Context, root, prefix string, w io.Writer, removeT
 
 // extractTarGzip decompresses the gzip
 // and extracts tar file to a directory specified by the `dir` parameter.
-func extractTarGzip(dirPath, dirName, gzPath, checksum string, buf []byte) (err error) {
+func extractTarGzip(dirPath, dirName, gzPath, checksum string, buf []byte, preservePermissions bool) (err error) {
 	fp, err := os.Open(gzPath)
 	if err != nil {
 		return err
@@ -144,7 +144,7 @@ func extractTarGzip(dirPath, dirName, gzPath, checksum string, buf []byte) (err
 			r = io.TeeReader(r, verifier)
 		}
 	}
-	if err := extractTarDirectory(dirPath, dirName, r, buf); err != nil {
+	if err := extractTarDirectory(dirPath, dirName, r, buf, preservePermissions); err != nil {
 		return err
 	}
 	if verifier != nil && !verifier.Verified() {
@@ -156,7 +156,7 @@ func extractTarGzip(dirPath, dirName, gzPath, checksum string, buf []byte) (err
 // extractTarDirectory extracts tar file to a directory specified by the `dir`
 // parameter. The file name prefix is ensured to be the string specified by the
 // `prefix` parameter and is trimmed.
-func extractTarDirectory(dirPath, dirName string, r io.Reader, buf []byte) error {
+func extractTarDirectory(dirPath, dirName string, r io.Reader, buf []byte, preservePermissions bool) error {
 	tr := tar.NewReader(r)
 	for {
 		header, err := tr.Next()
@@ -214,7 +214,14 @@ func extractTarDirectory(dirPath, dirName string, r io.Reader, buf []byte) error
 		}
 
 		// Change access time and modification time if possible (error ignored)
-		os.Chtimes(filePath, header.AccessTime, header.ModTime)
+		_ = os.Chtimes(filePath, header.AccessTime, header.ModTime)
+
+		// Restore full mode bits
+		if preservePermissions && (header.Typeflag == tar.TypeReg || header.Typeflag == tar.TypeDir) {
+			if err := os.Chmod(filePath, os.FileMode(header.Mode)); err != nil {
+				return err
+			}
+		}
 	}
 }
 

content/file/utils_test.go

@@ -238,7 +238,7 @@ func Test_ensureLinkPath(t *testing.T) {
 
 func Test_extractTarGzip_Error(t *testing.T) {
 	t.Run("Non-existing file", func(t *testing.T) {
-		err := extractTarGzip("", "", "non-existing-file", "", nil)
+		err := extractTarGzip("", "", "non-existing-file", "", nil, false)
 		if err == nil {
 			t.Fatal("expected error, got nil")
 		}
@@ -300,7 +300,7 @@ func Test_extractTarDirectory(t *testing.T) {
 			dirPath := filepath.Join(tempDir, dirName)
 			buf := make([]byte, 1024)
 
-			if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tt.tarData), buf); (err != nil) != tt.wantErr {
+			if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tt.tarData), buf, false); (err != nil) != tt.wantErr {
 				t.Fatalf("extractTarDirectory() error = %v, wantErr %v", err, tt.wantErr)
 			}
 			if !tt.wantErr {
@@ -348,7 +348,7 @@ func Test_extractTarDirectory_HardLink(t *testing.T) {
 			{name: "base/test_hardlink", linkname: linkPath, mode: 0666, isHardLink: true},
 		})
 
-		if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tarData), buf); err != nil {
+		if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tarData), buf, false); err != nil {
 			t.Fatalf("extractTarDirectory() error = %v", err)
 		}
 
@@ -372,7 +372,7 @@ func Test_extractTarDirectory_HardLink(t *testing.T) {
 			{name: "base/test_hardlink", linkname: "whatever", mode: 0666, isHardLink: true},
 		})
 
-		if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tarData), buf); err == nil {
+		if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tarData), buf, false); err == nil {
 			t.Error("extractTarDirectory() error = nil, wantErr = true")
 		}
 	})

content/file/utils_unix_test.go

@@ -0,0 +1,61 @@
+//go:build !windows
+
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package file
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func Test_extractTarDirectory_PreservePermissions(t *testing.T) {
+	fileContent := "hello world"
+	fileMode := os.FileMode(0771)
+	tarData := createTar(t, []tarEntry{
+		{name: "base/", mode: os.ModeDir | 0777},
+		{name: "base/test.txt", content: fileContent, mode: fileMode},
+	})
+
+	tempDir := t.TempDir()
+	dirName := "base"
+	dirPath := filepath.Join(tempDir, dirName)
+	buf := make([]byte, 1024)
+
+	if err := extractTarDirectory(dirPath, dirName, bytes.NewReader(tarData), buf, true); err != nil {
+		t.Fatalf("extractTarDirectory() error = %v", err)
+	}
+
+	filePath := filepath.Join(dirPath, "test.txt")
+	fi, err := os.Lstat(filePath)
+	if err != nil {
+		t.Fatalf("failed to stat file %s: %v", filePath, err)
+	}
+
+	gotContent, err := os.ReadFile(filePath)
+	if err != nil {
+		t.Fatalf("failed to read file %s: %v", filePath, err)
+	}
+	if string(gotContent) != fileContent {
+		t.Errorf("file content = %s, want %s", gotContent, fileContent)
+	}
+
+	if fi.Mode() != fileMode {
+		t.Errorf("file %q mode = %s, want %s", fi.Name(), fi.Mode(), fileMode)
+	}
+}