backup: Ignore xattr.list permission error for parent directories

On FreeBSD, limited users may not be able to even list xattrs for the
parent directories above the snapshot source paths. As this can cause
the backup to fail, just ignore those errors.

changelog/unreleased/issue-3600

@@ -0,0 +1,11 @@
+Bugfix: `backup` works if xattrs above the backup target cannot be read
+
+When backup targets are specified using absolute paths, then `backup` also
+includes information about the parent folders of the backup targets in the
+snapshot. If the extended attributes for some of these folders could not be
+read due to missing permissions, this caused the backup to fail. This has been
+fixed.
+
+https://github.com/restic/restic/issues/3600
+https://github.com/restic/restic/pull/4668
+https://forum.restic.net/t/parent-directories-above-the-snapshot-source-path-fatal-error-permission-denied/7216

internal/archiver/archiver.go

@@ -237,8 +237,8 @@ func (arch *Archiver) trackItem(item string, previous, current *restic.Node, s I
 }
 
 // nodeFromFileInfo returns the restic node from an os.FileInfo.
-func (arch *Archiver) nodeFromFileInfo(snPath, filename string, fi os.FileInfo) (*restic.Node, error) {
+func (arch *Archiver) nodeFromFileInfo(snPath, filename string, fi os.FileInfo, ignoreXattrListError bool) (*restic.Node, error) {
-	node, err := restic.NodeFromFileInfo(filename, fi)
+	node, err := restic.NodeFromFileInfo(filename, fi, ignoreXattrListError)
 	if !arch.WithAtime {
 		node.AccessTime = node.ModTime
 	}
@@ -289,7 +289,7 @@ func (arch *Archiver) wrapLoadTreeError(id restic.ID, err error) error {
 func (arch *Archiver) saveDir(ctx context.Context, snPath string, dir string, fi os.FileInfo, previous *restic.Tree, complete CompleteFunc) (d FutureNode, err error) {
 	debug.Log("%v %v", snPath, dir)
 
-	treeNode, err := arch.nodeFromFileInfo(snPath, dir, fi)
+	treeNode, err := arch.nodeFromFileInfo(snPath, dir, fi, false)
 	if err != nil {
 		return FutureNode{}, err
 	}
@@ -444,7 +444,7 @@ func (arch *Archiver) save(ctx context.Context, snPath, target string, previous
 				debug.Log("%v hasn't changed, using old list of blobs", target)
 				arch.trackItem(snPath, previous, previous, ItemStats{}, time.Since(start))
 				arch.CompleteBlob(previous.Size)
-				node, err := arch.nodeFromFileInfo(snPath, target, fi)
+				node, err := arch.nodeFromFileInfo(snPath, target, fi, false)
 				if err != nil {
 					return FutureNode{}, false, err
 				}
@@ -540,7 +540,7 @@ func (arch *Archiver) save(ctx context.Context, snPath, target string, previous
 	default:
 		debug.Log("  %v other", target)
 
-		node, err := arch.nodeFromFileInfo(snPath, target, fi)
+		node, err := arch.nodeFromFileInfo(snPath, target, fi, false)
 		if err != nil {
 			return FutureNode{}, false, err
 		}
@@ -623,7 +623,9 @@ func (arch *Archiver) saveTree(ctx context.Context, snPath string, atree *Tree,
 		}
 
 		debug.Log("%v, dir node data loaded from %v", snPath, atree.FileInfoPath)
-		node, err = arch.nodeFromFileInfo(snPath, atree.FileInfoPath, fi)
+		// in some cases reading xattrs for directories above the backup target is not allowed
+		// thus ignore errors for such folders.
+		node, err = arch.nodeFromFileInfo(snPath, atree.FileInfoPath, fi, true)
 		if err != nil {
 			return FutureNode{}, 0, err
 		}

internal/archiver/archiver_test.go

@@ -556,7 +556,7 @@ func rename(t testing.TB, oldname, newname string) {
 }
 
 func nodeFromFI(t testing.TB, filename string, fi os.FileInfo) *restic.Node {
-	node, err := restic.NodeFromFileInfo(filename, fi)
+	node, err := restic.NodeFromFileInfo(filename, fi, false)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -2230,7 +2230,7 @@ func TestMetadataChanged(t *testing.T) {
 
 	// get metadata
 	fi := lstat(t, "testfile")
-	want, err := restic.NodeFromFileInfo("testfile", fi)
+	want, err := restic.NodeFromFileInfo("testfile", fi, false)
 	if err != nil {
 		t.Fatal(err)
 	}

internal/archiver/archiver_unix_test.go

@@ -48,7 +48,7 @@ func wrapFileInfo(fi os.FileInfo) os.FileInfo {
 
 func statAndSnapshot(t *testing.T, repo restic.Repository, name string) (*restic.Node, *restic.Node) {
 	fi := lstat(t, name)
-	want, err := restic.NodeFromFileInfo(name, fi)
+	want, err := restic.NodeFromFileInfo(name, fi, false)
 	rtest.OK(t, err)
 
 	_, node := snapshot(t, repo, fs.Local{}, nil, name)

internal/archiver/file_saver.go

@@ -29,7 +29,7 @@ type FileSaver struct {
 
 	CompleteBlob func(bytes uint64)
 
-	NodeFromFileInfo func(snPath, filename string, fi os.FileInfo) (*restic.Node, error)
+	NodeFromFileInfo func(snPath, filename string, fi os.FileInfo, ignoreXattrListError bool) (*restic.Node, error)
 }
 
 // NewFileSaver returns a new file saver. A worker pool with fileWorkers is
@@ -156,7 +156,7 @@ func (s *FileSaver) saveFile(ctx context.Context, chnker *chunker.Chunker, snPat
 
 	debug.Log("%v", snPath)
 
-	node, err := s.NodeFromFileInfo(snPath, f.Name(), fi)
+	node, err := s.NodeFromFileInfo(snPath, f.Name(), fi, false)
 	if err != nil {
 		_ = f.Close()
 		completeError(err)

internal/archiver/file_saver_test.go

@@ -49,8 +49,8 @@ func startFileSaver(ctx context.Context, t testing.TB) (*FileSaver, context.Cont
 	}
 
 	s := NewFileSaver(ctx, wg, saveBlob, pol, workers, workers)
-	s.NodeFromFileInfo = func(snPath, filename string, fi os.FileInfo) (*restic.Node, error) {
+	s.NodeFromFileInfo = func(snPath, filename string, fi os.FileInfo, ignoreXattrListError bool) (*restic.Node, error) {
-		return restic.NodeFromFileInfo(filename, fi)
+		return restic.NodeFromFileInfo(filename, fi, ignoreXattrListError)
 	}
 
 	return s, ctx, wg

internal/restic/node.go

@@ -134,7 +134,7 @@ func (node Node) String() string {
 
 // NodeFromFileInfo returns a new node from the given path and FileInfo. It
 // returns the first error that is encountered, together with a node.
-func NodeFromFileInfo(path string, fi os.FileInfo) (*Node, error) {
+func NodeFromFileInfo(path string, fi os.FileInfo, ignoreXattrListError bool) (*Node, error) {
 	mask := os.ModePerm | os.ModeType | os.ModeSetuid | os.ModeSetgid | os.ModeSticky
 	node := &Node{
 		Path:    path,
@@ -148,7 +148,7 @@ func NodeFromFileInfo(path string, fi os.FileInfo) (*Node, error) {
 		node.Size = uint64(fi.Size())
 	}
 
-	err := node.fillExtra(path, fi)
+	err := node.fillExtra(path, fi, ignoreXattrListError)
 	return node, err
 }
 
@@ -675,7 +675,7 @@ func lookupGroup(gid uint32) string {
 	return group
 }
 
-func (node *Node) fillExtra(path string, fi os.FileInfo) error {
+func (node *Node) fillExtra(path string, fi os.FileInfo, ignoreXattrListError bool) error {
 	stat, ok := toStatT(fi.Sys())
 	if !ok {
 		// fill minimal info with current values for uid, gid
@@ -719,7 +719,7 @@ func (node *Node) fillExtra(path string, fi os.FileInfo) error {
 	allowExtended, err := node.fillGenericAttributes(path, fi, stat)
 	if allowExtended {
 		// Skip processing ExtendedAttributes if allowExtended is false.
-		errEx := node.fillExtendedAttributes(path)
+		errEx := node.fillExtendedAttributes(path, ignoreXattrListError)
 		if err == nil {
 			err = errEx
 		} else {
@@ -729,10 +729,13 @@ func (node *Node) fillExtra(path string, fi os.FileInfo) error {
 	return err
 }
 
-func (node *Node) fillExtendedAttributes(path string) error {
+func (node *Node) fillExtendedAttributes(path string, ignoreListError bool) error {
 	xattrs, err := Listxattr(path)
 	debug.Log("fillExtendedAttributes(%v) %v %v", path, xattrs, err)
 	if err != nil {
+		if ignoreListError && IsListxattrPermissionError(err) {
+			return nil
+		}
 		return err
 	}
 

internal/restic/node_aix.go

@@ -33,6 +33,10 @@ func Listxattr(path string) ([]string, error) {
 	return nil, nil
 }
 
+func IsListxattrPermissionError(_ error) bool {
+	return false
+}
+
 // Setxattr is a no-op on AIX.
 func Setxattr(path, name string, data []byte) error {
 	return nil

internal/restic/node_netbsd.go

@@ -23,6 +23,10 @@ func Listxattr(path string) ([]string, error) {
 	return nil, nil
 }
 
+func IsListxattrPermissionError(_ error) bool {
+	return false
+}
+
 // Setxattr is a no-op on netbsd.
 func Setxattr(path, name string, data []byte) error {
 	return nil

internal/restic/node_openbsd.go

@@ -23,6 +23,10 @@ func Listxattr(path string) ([]string, error) {
 	return nil, nil
 }
 
+func IsListxattrPermissionError(_ error) bool {
+	return false
+}
+
 // Setxattr is a no-op on openbsd.
 func Setxattr(path, name string, data []byte) error {
 	return nil

internal/restic/node_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/restic/restic/internal/test"
 	rtest "github.com/restic/restic/internal/test"
 )
@@ -31,7 +32,7 @@ func BenchmarkNodeFillUser(t *testing.B) {
 	t.ResetTimer()
 
 	for i := 0; i < t.N; i++ {
-		_, err := NodeFromFileInfo(path, fi)
+		_, err := NodeFromFileInfo(path, fi, false)
 		rtest.OK(t, err)
 	}
 
@@ -55,7 +56,7 @@ func BenchmarkNodeFromFileInfo(t *testing.B) {
 	t.ResetTimer()
 
 	for i := 0; i < t.N; i++ {
-		_, err := NodeFromFileInfo(path, fi)
+		_, err := NodeFromFileInfo(path, fi, false)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -227,8 +228,11 @@ func TestNodeRestoreAt(t *testing.T) {
 			fi, err := os.Lstat(nodePath)
 			rtest.OK(t, err)
 
-			n2, err := NodeFromFileInfo(nodePath, fi)
+			n2, err := NodeFromFileInfo(nodePath, fi, false)
 			rtest.OK(t, err)
+			n3, err := NodeFromFileInfo(nodePath, fi, true)
+			rtest.OK(t, err)
+			rtest.Assert(t, n2.Equals(*n3), "unexpected node info mismatch %v", cmp.Diff(n2, n3))
 
 			rtest.Assert(t, test.Name == n2.Name,
 				"%v: name doesn't match (%v != %v)", test.Type, test.Name, n2.Name)

internal/restic/node_unix_test.go

@@ -128,7 +128,7 @@ func TestNodeFromFileInfo(t *testing.T) {
 				return
 			}
 
-			node, err := NodeFromFileInfo(test.filename, fi)
+			node, err := NodeFromFileInfo(test.filename, fi, false)
 			if err != nil {
 				t.Fatal(err)
 			}

internal/restic/node_windows.go

@@ -78,6 +78,10 @@ func Listxattr(path string) ([]string, error) {
 	return nil, nil
 }
 
+func IsListxattrPermissionError(_ error) bool {
+	return false
+}
+
 // Setxattr associates name and data together as an attribute of path.
 func Setxattr(path, name string, data []byte) error {
 	return nil

internal/restic/node_windows_test.go

@@ -165,7 +165,7 @@ func restoreAndGetNode(t *testing.T, tempDir string, testNode Node, warningExpec
 	fi, err := os.Lstat(testPath)
 	test.OK(t, errors.Wrapf(err, "Could not Lstat for path: %s", testPath))
 
-	nodeFromFileInfo, err := NodeFromFileInfo(testPath, fi)
+	nodeFromFileInfo, err := NodeFromFileInfo(testPath, fi, false)
 	test.OK(t, errors.Wrapf(err, "Could not get NodeFromFileInfo for path: %s", testPath))
 
 	return testPath, nodeFromFileInfo

internal/restic/node_xattr.go

@@ -25,6 +25,14 @@ func Listxattr(path string) ([]string, error) {
 	return l, handleXattrErr(err)
 }
 
+func IsListxattrPermissionError(err error) bool {
+	var xerr *xattr.Error
+	if errors.As(err, &xerr) {
+		return xerr.Op == "xattr.list" && errors.Is(xerr.Err, os.ErrPermission)
+	}
+	return false
+}
+
 // Setxattr associates name and data together as an attribute of path.
 func Setxattr(path, name string, data []byte) error {
 	return handleXattrErr(xattr.LSet(path, name, data))

internal/restic/node_xattr_test.go

@@ -0,0 +1,28 @@
+//go:build darwin || freebsd || linux || solaris
+// +build darwin freebsd linux solaris
+
+package restic
+
+import (
+	"os"
+	"testing"
+
+	"github.com/pkg/xattr"
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func TestIsListxattrPermissionError(t *testing.T) {
+	xerr := &xattr.Error{
+		Op:   "xattr.list",
+		Name: "test",
+		Err:  os.ErrPermission,
+	}
+	err := handleXattrErr(xerr)
+	rtest.Assert(t, err != nil, "missing error")
+	rtest.Assert(t, IsListxattrPermissionError(err), "expected IsListxattrPermissionError to return true for %v", err)
+
+	xerr.Err = os.ErrNotExist
+	err = handleXattrErr(xerr)
+	rtest.Assert(t, err != nil, "missing error")
+	rtest.Assert(t, !IsListxattrPermissionError(err), "expected IsListxattrPermissionError to return false for %v", err)
+}

internal/restic/tree_test.go

@@ -86,7 +86,7 @@ func TestNodeComparison(t *testing.T) {
 	fi, err := os.Lstat("tree_test.go")
 	rtest.OK(t, err)
 
-	node, err := restic.NodeFromFileInfo("tree_test.go", fi)
+	node, err := restic.NodeFromFileInfo("tree_test.go", fi, false)
 	rtest.OK(t, err)
 
 	n2 := *node
@@ -127,7 +127,7 @@ func TestTreeEqualSerialization(t *testing.T) {
 		for _, fn := range files[:i] {
 			fi, err := os.Lstat(fn)
 			rtest.OK(t, err)
-			node, err := restic.NodeFromFileInfo(fn, fi)
+			node, err := restic.NodeFromFileInfo(fn, fi, false)
 			rtest.OK(t, err)
 
 			rtest.OK(t, tree.Insert(node))