all: Support syncing ownership (fixes #1329) (#8434)

This adds support for syncing ownership on Unixes and on Windows. The
scanner always picks up ownership information, but it is not applied
unless the new folder option "Sync Ownership" is set.

Ownership data is stored in a new FileInfo field called "platform data". This
is intended to hold further platform-specific data in the future
(specifically, extended attributes), which is why the whole design is a
bit overkill for just ownership.

lib/model/folder_sendrecv.go

@@ -13,6 +13,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
@@ -627,8 +628,8 @@ func (f *sendReceiveFolder) handleDir(file protocol.FileInfo, snap *db.Snapshot,
 				return err
 			}
 
-			// Copy the parent owner and group, if we are supposed to do that.
-			if err := f.maybeCopyOwner(path); err != nil {
+			// Adjust the ownership, if we are supposed to do that.
+			if err := f.maybeAdjustOwnership(&file, path); err != nil {
 				return err
 			}
 
@@ -754,7 +755,7 @@ func (f *sendReceiveFolder) handleSymlink(file protocol.FileInfo, snap *db.Snaps
 		if err := f.mtimefs.CreateSymlink(file.SymlinkTarget, path); err != nil {
 			return err
 		}
-		return f.maybeCopyOwner(path)
+		return f.maybeAdjustOwnership(&file, path)
 	}
 
 	if err = f.inWritableDir(createLink, file.Name); err == nil {
@@ -989,7 +990,13 @@ func (f *sendReceiveFolder) renameFile(cur, source, target protocol.FileInfo, sn
 	default:
 		var fi protocol.FileInfo
 		if fi, err = scanner.CreateFileInfo(stat, target.Name, f.mtimefs); err == nil {
-			if !fi.IsEquivalentOptional(curTarget, f.modTimeWindow, f.IgnorePerms, true, protocol.LocalAllFlags) {
+			if !fi.IsEquivalentOptional(curTarget, protocol.FileInfoComparison{
+				ModTimeWindow:   f.modTimeWindow,
+				IgnorePerms:     f.IgnorePerms,
+				IgnoreBlocks:    true,
+				IgnoreFlags:     protocol.LocalAllFlags,
+				IgnoreOwnership: !f.SyncOwnership,
+			}) {
 				// Target changed
 				scanChan <- target.Name
 				err = errModified
@@ -1227,6 +1234,11 @@ func (f *sendReceiveFolder) shortcutFile(file protocol.FileInfo, dbUpdateChan ch
 		}
 	}
 
+	if err := f.maybeAdjustOwnership(&file, file.Name); err != nil {
+		f.newPullError(file.Name, err)
+		return
+	}
+
 	// Still need to re-write the trailer with the new encrypted fileinfo.
 	if f.Type == config.FolderTypeReceiveEncrypted {
 		err = inWritableDir(func(path string) error {
@@ -1592,8 +1604,8 @@ func (f *sendReceiveFolder) performFinish(file, curFile protocol.FileInfo, hasCu
 		}
 	}
 
-	// Copy the parent owner and group, if we are supposed to do that.
-	if err := f.maybeCopyOwner(tempName); err != nil {
+	// Set ownership based on file metadata or parent, maybe.
+	if err := f.maybeAdjustOwnership(&file, tempName); err != nil {
 		return err
 	}
 
@@ -1972,7 +1984,13 @@ func (f *sendReceiveFolder) deleteDirOnDiskHandleChildren(dir string, snap *db.S
 			hasToBeScanned = true
 			return nil
 		}
-		if !cf.IsEquivalentOptional(diskFile, f.modTimeWindow, f.IgnorePerms, true, protocol.LocalAllFlags) {
+		if !cf.IsEquivalentOptional(diskFile, protocol.FileInfoComparison{
+			ModTimeWindow:   f.modTimeWindow,
+			IgnorePerms:     f.IgnorePerms,
+			IgnoreBlocks:    true,
+			IgnoreFlags:     protocol.LocalAllFlags,
+			IgnoreOwnership: !f.SyncOwnership,
+		}) {
 			// File on disk changed compared to what we have in db
 			// -> schedule scan.
 			scanChan <- path
@@ -2041,7 +2059,13 @@ func (f *sendReceiveFolder) scanIfItemChanged(name string, stat fs.FileInfo, ite
 		return errors.Wrap(err, "comparing item on disk to db")
 	}
 
-	if !statItem.IsEquivalentOptional(item, f.modTimeWindow, f.IgnorePerms, true, protocol.LocalAllFlags) {
+	if !statItem.IsEquivalentOptional(item, protocol.FileInfoComparison{
+		ModTimeWindow:   f.modTimeWindow,
+		IgnorePerms:     f.IgnorePerms,
+		IgnoreBlocks:    true,
+		IgnoreFlags:     protocol.LocalAllFlags,
+		IgnoreOwnership: !f.SyncOwnership,
+	}) {
 		return errModified
 	}
 
@@ -2074,11 +2098,23 @@ func (f *sendReceiveFolder) checkToBeDeleted(file, cur protocol.FileInfo, hasCur
 	return f.scanIfItemChanged(file.Name, stat, cur, hasCur, scanChan)
 }
 
-func (f *sendReceiveFolder) maybeCopyOwner(path string) error {
-	if !f.CopyOwnershipFromParent {
-		// Not supposed to do anything.
-		return nil
+func (f *sendReceiveFolder) maybeAdjustOwnership(file *protocol.FileInfo, name string) error {
+	if f.SyncOwnership {
+		// Set ownership based on file metadata.
+		if err := f.syncOwnership(file, name); err != nil {
+			return err
+		}
+	} else if f.CopyOwnershipFromParent {
+		// Copy the parent owner and group.
+		if err := f.copyOwnershipFromParent(name); err != nil {
+			return err
+		}
 	}
+	// Nothing to do
+	return nil
+}
+
+func (f *sendReceiveFolder) copyOwnershipFromParent(path string) error {
 	if runtime.GOOS == "windows" {
 		// Can't do anything.
 		return nil
@@ -2088,7 +2124,7 @@ func (f *sendReceiveFolder) maybeCopyOwner(path string) error {
 	if err != nil {
 		return errors.Wrap(err, "copy owner from parent")
 	}
-	if err := f.mtimefs.Lchown(path, info.Owner(), info.Group()); err != nil {
+	if err := f.mtimefs.Lchown(path, strconv.Itoa(info.Owner()), strconv.Itoa(info.Group())); err != nil {
 		return errors.Wrap(err, "copy owner from parent")
 	}
 	return nil