Merge pull request #4379 from chenxiaolong/symlink_xattrs

Add support for extended attributes on symlinks

changelog/unreleased/issue-4375

@@ -0,0 +1,8 @@
+Enhancement: Add support for extended attributes on symlinks
+
+Restic now supports extended attributes on symlinks when backing up,
+restoring, or FUSE-mounting snapshots. This includes, for example, the
+`security.selinux` xattr on Linux distributions that use SELinux.
+
+https://github.com/restic/restic/issues/4375
+https://github.com/restic/restic/pull/4379

internal/fuse/dir.go

@@ -222,19 +222,10 @@ func (d *dir) Lookup(ctx context.Context, name string) (fs.Node, error) {
 }
 
 func (d *dir) Listxattr(_ context.Context, req *fuse.ListxattrRequest, resp *fuse.ListxattrResponse) error {
-	debug.Log("Listxattr(%v, %v)", d.node.Name, req.Size)
+	nodeToXattrList(d.node, req, resp)
-	for _, attr := range d.node.ExtendedAttributes {
-		resp.Append(attr.Name)
-	}
 	return nil
 }
 
 func (d *dir) Getxattr(_ context.Context, req *fuse.GetxattrRequest, resp *fuse.GetxattrResponse) error {
-	debug.Log("Getxattr(%v, %v, %v)", d.node.Name, req.Name, req.Size)
+	return nodeGetXattr(d.node, req, resp)
-	attrval := d.node.GetExtendedAttribute(req.Name)
-	if attrval != nil {
-		resp.Xattr = attrval
-		return nil
-	}
-	return fuse.ErrNoXattr
 }

internal/fuse/file.go

@@ -167,19 +167,10 @@ func (f *openFile) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.R
 }
 
 func (f *file) Listxattr(_ context.Context, req *fuse.ListxattrRequest, resp *fuse.ListxattrResponse) error {
-	debug.Log("Listxattr(%v, %v)", f.node.Name, req.Size)
+	nodeToXattrList(f.node, req, resp)
-	for _, attr := range f.node.ExtendedAttributes {
-		resp.Append(attr.Name)
-	}
 	return nil
 }
 
 func (f *file) Getxattr(_ context.Context, req *fuse.GetxattrRequest, resp *fuse.GetxattrResponse) error {
-	debug.Log("Getxattr(%v, %v, %v)", f.node.Name, req.Name, req.Size)
+	return nodeGetXattr(f.node, req, resp)
-	attrval := f.node.GetExtendedAttribute(req.Name)
-	if attrval != nil {
-		resp.Xattr = attrval
-		return nil
-	}
-	return fuse.ErrNoXattr
 }

internal/fuse/fuse_test.go

@@ -271,6 +271,31 @@ func TestInodeFromNode(t *testing.T) {
 	rtest.Assert(t, inoA != inoAbb, "inode(a/b/b) = inode(a)")
 }
 
+func TestLink(t *testing.T) {
+	node := &restic.Node{Name: "foo.txt", Type: "symlink", Links: 1, LinkTarget: "dst", ExtendedAttributes: []restic.ExtendedAttribute{
+		{Name: "foo", Value: []byte("bar")},
+	}}
+
+	lnk, err := newLink(&Root{}, 42, node)
+	rtest.OK(t, err)
+	target, err := lnk.Readlink(context.TODO(), nil)
+	rtest.OK(t, err)
+	rtest.Equals(t, node.LinkTarget, target)
+
+	exp := &fuse.ListxattrResponse{}
+	exp.Append("foo")
+	resp := &fuse.ListxattrResponse{}
+	rtest.OK(t, lnk.Listxattr(context.TODO(), &fuse.ListxattrRequest{}, resp))
+	rtest.Equals(t, exp.Xattr, resp.Xattr)
+
+	getResp := &fuse.GetxattrResponse{}
+	rtest.OK(t, lnk.Getxattr(context.TODO(), &fuse.GetxattrRequest{Name: "foo"}, getResp))
+	rtest.Equals(t, node.ExtendedAttributes[0].Value, getResp.Xattr)
+
+	err = lnk.Getxattr(context.TODO(), &fuse.GetxattrRequest{Name: "invalid"}, nil)
+	rtest.Assert(t, err != nil, "missing error on reading invalid xattr")
+}
+
 var sink uint64
 
 func BenchmarkInode(b *testing.B) {

internal/fuse/link.go

@@ -46,3 +46,12 @@ func (l *link) Attr(_ context.Context, a *fuse.Attr) error {
 
 	return nil
 }
+
+func (l *link) Listxattr(_ context.Context, req *fuse.ListxattrRequest, resp *fuse.ListxattrResponse) error {
+	nodeToXattrList(l.node, req, resp)
+	return nil
+}
+
+func (l *link) Getxattr(_ context.Context, req *fuse.GetxattrRequest, resp *fuse.GetxattrResponse) error {
+	return nodeGetXattr(l.node, req, resp)
+}

internal/fuse/xattr.go

@@ -0,0 +1,24 @@
+package fuse
+
+import (
+	"github.com/anacrolix/fuse"
+	"github.com/restic/restic/internal/debug"
+	"github.com/restic/restic/internal/restic"
+)
+
+func nodeToXattrList(node *restic.Node, req *fuse.ListxattrRequest, resp *fuse.ListxattrResponse) {
+	debug.Log("Listxattr(%v, %v)", node.Name, req.Size)
+	for _, attr := range node.ExtendedAttributes {
+		resp.Append(attr.Name)
+	}
+}
+
+func nodeGetXattr(node *restic.Node, req *fuse.GetxattrRequest, resp *fuse.GetxattrResponse) error {
+	debug.Log("Getxattr(%v, %v, %v)", node.Name, req.Name, req.Size)
+	attrval := node.GetExtendedAttribute(req.Name)
+	if attrval != nil {
+		resp.Xattr = attrval
+		return nil
+	}
+	return fuse.ErrNoXattr
+}

internal/restic/node.go

@@ -609,10 +609,6 @@ func (node *Node) fillExtra(path string, fi os.FileInfo) error {
 }
 
 func (node *Node) fillExtendedAttributes(path string) error {
-	if node.Type == "symlink" {
-		return nil
-	}
-
 	xattrs, err := Listxattr(path)
 	debug.Log("fillExtendedAttributes(%v) %v %v", path, xattrs, err)
 	if err != nil {

internal/restic/node_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"testing"
 	"time"
@@ -163,58 +164,99 @@ var nodeTests = []restic.Node{
 		AccessTime: parseTime("2005-05-14 21:07:04.222"),
 		ChangeTime: parseTime("2005-05-14 21:07:05.333"),
 	},
+	{
+		Name:       "testXattrFile",
+		Type:       "file",
+		Content:    restic.IDs{},
+		UID:        uint32(os.Getuid()),
+		GID:        uint32(os.Getgid()),
+		Mode:       0604,
+		ModTime:    parseTime("2005-05-14 21:07:03.111"),
+		AccessTime: parseTime("2005-05-14 21:07:04.222"),
+		ChangeTime: parseTime("2005-05-14 21:07:05.333"),
+		ExtendedAttributes: []restic.ExtendedAttribute{
+			{"user.foo", []byte("bar")},
+		},
+	},
+	{
+		Name:       "testXattrDir",
+		Type:       "dir",
+		Subtree:    nil,
+		UID:        uint32(os.Getuid()),
+		GID:        uint32(os.Getgid()),
+		Mode:       0750 | os.ModeDir,
+		ModTime:    parseTime("2005-05-14 21:07:03.111"),
+		AccessTime: parseTime("2005-05-14 21:07:04.222"),
+		ChangeTime: parseTime("2005-05-14 21:07:05.333"),
+		ExtendedAttributes: []restic.ExtendedAttribute{
+			{"user.foo", []byte("bar")},
+		},
+	},
 }
 
 func TestNodeRestoreAt(t *testing.T) {
-	tempdir, err := os.MkdirTemp(rtest.TestTempDir, "restic-test-")
+	tempdir := t.TempDir()
-	rtest.OK(t, err)
-
-	defer func() {
-		if rtest.TestCleanupTempDirs {
-			rtest.RemoveAll(t, tempdir)
-		} else {
-			t.Logf("leaving tempdir at %v", tempdir)
-		}
-	}()
 
 	for _, test := range nodeTests {
-		nodePath := filepath.Join(tempdir, test.Name)
+		t.Run("", func(t *testing.T) {
-		rtest.OK(t, test.CreateAt(context.TODO(), nodePath, nil))
+			var nodePath string
-		rtest.OK(t, test.RestoreMetadata(nodePath))
+			if test.ExtendedAttributes != nil {
+				if runtime.GOOS == "windows" {
+					// restic does not support xattrs on windows
+					return
+				}
 
-		if test.Type == "dir" {
+				// tempdir might be backed by a filesystem that does not support
-			rtest.OK(t, test.RestoreTimestamps(nodePath))
+				// extended attributes
-		}
+				nodePath = test.Name
+				defer func() {
+					_ = os.Remove(nodePath)
+				}()
+			} else {
+				nodePath = filepath.Join(tempdir, test.Name)
+			}
+			rtest.OK(t, test.CreateAt(context.TODO(), nodePath, nil))
+			rtest.OK(t, test.RestoreMetadata(nodePath))
 
-		fi, err := os.Lstat(nodePath)
+			if test.Type == "dir" {
-		rtest.OK(t, err)
+				rtest.OK(t, test.RestoreTimestamps(nodePath))
+			}
 
-		n2, err := restic.NodeFromFileInfo(nodePath, fi)
+			fi, err := os.Lstat(nodePath)
-		rtest.OK(t, err)
+			rtest.OK(t, err)
 
-		rtest.Assert(t, test.Name == n2.Name,
+			n2, err := restic.NodeFromFileInfo(nodePath, fi)
-			"%v: name doesn't match (%v != %v)", test.Type, test.Name, n2.Name)
+			rtest.OK(t, err)
-		rtest.Assert(t, test.Type == n2.Type,
-			"%v: type doesn't match (%v != %v)", test.Type, test.Type, n2.Type)
-		rtest.Assert(t, test.Size == n2.Size,
-			"%v: size doesn't match (%v != %v)", test.Size, test.Size, n2.Size)
 
-		if runtime.GOOS != "windows" {
+			rtest.Assert(t, test.Name == n2.Name,
-			rtest.Assert(t, test.UID == n2.UID,
+				"%v: name doesn't match (%v != %v)", test.Type, test.Name, n2.Name)
-				"%v: UID doesn't match (%v != %v)", test.Type, test.UID, n2.UID)
+			rtest.Assert(t, test.Type == n2.Type,
-			rtest.Assert(t, test.GID == n2.GID,
+				"%v: type doesn't match (%v != %v)", test.Type, test.Type, n2.Type)
-				"%v: GID doesn't match (%v != %v)", test.Type, test.GID, n2.GID)
+			rtest.Assert(t, test.Size == n2.Size,
-			if test.Type != "symlink" {
+				"%v: size doesn't match (%v != %v)", test.Size, test.Size, n2.Size)
-				// On OpenBSD only root can set sticky bit (see sticky(8)).
+
-				if runtime.GOOS != "openbsd" && runtime.GOOS != "netbsd" && runtime.GOOS != "solaris" && test.Name == "testSticky" {
+			if runtime.GOOS != "windows" {
-					rtest.Assert(t, test.Mode == n2.Mode,
+				rtest.Assert(t, test.UID == n2.UID,
-						"%v: mode doesn't match (0%o != 0%o)", test.Type, test.Mode, n2.Mode)
+					"%v: UID doesn't match (%v != %v)", test.Type, test.UID, n2.UID)
+				rtest.Assert(t, test.GID == n2.GID,
+					"%v: GID doesn't match (%v != %v)", test.Type, test.GID, n2.GID)
+				if test.Type != "symlink" {
+					// On OpenBSD only root can set sticky bit (see sticky(8)).
+					if runtime.GOOS != "openbsd" && runtime.GOOS != "netbsd" && runtime.GOOS != "solaris" && test.Name == "testSticky" {
+						rtest.Assert(t, test.Mode == n2.Mode,
+							"%v: mode doesn't match (0%o != 0%o)", test.Type, test.Mode, n2.Mode)
+					}
 				}
 			}
-		}
 
-		AssertFsTimeEqual(t, "AccessTime", test.Type, test.AccessTime, n2.AccessTime)
+			AssertFsTimeEqual(t, "AccessTime", test.Type, test.AccessTime, n2.AccessTime)
-		AssertFsTimeEqual(t, "ModTime", test.Type, test.ModTime, n2.ModTime)
+			AssertFsTimeEqual(t, "ModTime", test.Type, test.ModTime, n2.ModTime)
+			if len(n2.ExtendedAttributes) == 0 {
+				n2.ExtendedAttributes = nil
+			}
+			rtest.Assert(t, reflect.DeepEqual(test.ExtendedAttributes, n2.ExtendedAttributes),
+				"%v: xattrs don't match (%v != %v)", test.Name, test.ExtendedAttributes, n2.ExtendedAttributes)
+		})
 	}
 }
 

internal/restic/node_unix_test.go

@@ -5,10 +5,13 @@ package restic
 
 import (
 	"os"
+	"path/filepath"
 	"runtime"
 	"syscall"
 	"testing"
 	"time"
+
+	rtest "github.com/restic/restic/internal/test"
 )
 
 func stat(t testing.TB, filename string) (fi os.FileInfo, ok bool) {
@@ -25,6 +28,7 @@ func stat(t testing.TB, filename string) (fi os.FileInfo, ok bool) {
 }
 
 func checkFile(t testing.TB, stat *syscall.Stat_t, node *Node) {
+	t.Helper()
 	if uint32(node.Mode.Perm()) != uint32(stat.Mode&0777) {
 		t.Errorf("Mode does not match, want %v, got %v", stat.Mode&0777, node.Mode)
 	}
@@ -37,7 +41,7 @@ func checkFile(t testing.TB, stat *syscall.Stat_t, node *Node) {
 		t.Errorf("Dev does not match, want %v, got %v", stat.Dev, node.DeviceID)
 	}
 
-	if node.Size != uint64(stat.Size) {
+	if node.Size != uint64(stat.Size) && node.Type != "symlink" {
 		t.Errorf("Size does not match, want %v, got %v", stat.Size, node.Size)
 	}
 
@@ -83,6 +87,10 @@ func checkDevice(t testing.TB, stat *syscall.Stat_t, node *Node) {
 }
 
 func TestNodeFromFileInfo(t *testing.T) {
+	tmp := t.TempDir()
+	symlink := filepath.Join(tmp, "symlink")
+	rtest.OK(t, os.Symlink("target", symlink))
+
 	type Test struct {
 		filename string
 		canSkip  bool
@@ -90,6 +98,7 @@ func TestNodeFromFileInfo(t *testing.T) {
 	var tests = []Test{
 		{"node_test.go", false},
 		{"/dev/sda", true},
+		{symlink, false},
 	}
 
 	// on darwin, users are not permitted to list the extended attributes of
@@ -125,7 +134,7 @@ func TestNodeFromFileInfo(t *testing.T) {
 			}
 
 			switch node.Type {
-			case "file":
+			case "file", "symlink":
 				checkFile(t, s, node)
 			case "dev", "chardev":
 				checkFile(t, s, node)

internal/restic/node_xattr.go

@@ -13,20 +13,20 @@ import (
 
 // Getxattr retrieves extended attribute data associated with path.
 func Getxattr(path, name string) ([]byte, error) {
-	b, err := xattr.Get(path, name)
+	b, err := xattr.LGet(path, name)
 	return b, handleXattrErr(err)
 }
 
 // Listxattr retrieves a list of names of extended attributes associated with the
 // given path in the file system.
 func Listxattr(path string) ([]string, error) {
-	l, err := xattr.List(path)
+	l, err := xattr.LList(path)
 	return l, handleXattrErr(err)
 }
 
 // Setxattr associates name and data together as an attribute of path.
 func Setxattr(path, name string, data []byte) error {
-	return handleXattrErr(xattr.Set(path, name, data))
+	return handleXattrErr(xattr.LSet(path, name, data))
 }
 
 func handleXattrErr(err error) error {