Fix handling of xattrs with symlinks

Fix Linux, Darwin, and other BSD (untested) to allow proper
handling of xattrs with symlinks. On Linux we cannot use the f*
syscalls for symlinks because symlinks cannot be opened.
File flags must be handled differently on darwin and other BSD due
to the lack of the LCHFLAGS syscall on darwin, and the fact that it
is emulated in libc. However, we do have O_SYMLINK on darwin.

src/duplicacy_utils_bsd.go

@@ -1,53 +0,0 @@
-// Copyright (c) Acrosync LLC. All rights reserved.
-// Free for personal use and commercial trial
-// Commercial use requires per-user licenses available from https://duplicacy.com
-
-//go:build freebsd || netbsd || darwin
-// +build freebsd netbsd darwin
-
-package duplicacy
-
-import (
-	"encoding/binary"
-	"os"
-	"syscall"
-)
-
-const bsdFileFlagsKey = "\x00bf"
-
-func (entry *Entry) ReadFileFlags(f *os.File) error {
-	fileInfo, err := f.Stat()
-	if err != nil {
-		return err
-	}
-	stat, ok := fileInfo.Sys().(*syscall.Stat_t)
-	if ok && stat.Flags != 0 {
-		if entry.Attributes == nil {
-			entry.Attributes = &map[string][]byte{}
-		}
-		v := make([]byte, 4)
-		binary.LittleEndian.PutUint32(v, stat.Flags)
-		(*entry.Attributes)[bsdFileFlagsKey] = v
-		LOG_DEBUG("ATTR_READ", "Read flags 0x%x for %s", stat.Flags, entry.Path)
-	}
-	return nil
-}
-
-func (entry *Entry) RestoreEarlyDirFlags(path string) error {
-	return nil
-}
-
-func (entry *Entry) RestoreEarlyFileFlags(f *os.File) error {
-	return nil
-}
-
-func (entry *Entry) RestoreLateFileFlags(f *os.File) error {
-	if entry.Attributes == nil {
-		return nil
-	}
-	if v, have := (*entry.Attributes)[bsdFileFlagsKey]; have {
-		LOG_DEBUG("ATTR_RESTORE", "Restore flags 0x%x for %s", binary.LittleEndian.Uint32(v), entry.Path)
-		return syscall.Fchflags(int(f.Fd()), int(binary.LittleEndian.Uint32(v)))
-	}
-	return nil
-}

src/duplicacy_utils_bsd_common.go

@@ -0,0 +1,90 @@
+// Copyright (c) Acrosync LLC. All rights reserved.
+// Free for personal use and commercial trial
+// Commercial use requires per-user licenses available from https://duplicacy.com
+
+//go:build freebsd || netbsd || darwin
+// +build freebsd netbsd darwin
+
+package duplicacy
+
+import (
+	"encoding/binary"
+	"os"
+	"path/filepath"
+	"bytes"
+	"syscall"
+
+	"github.com/pkg/xattr"
+)
+
+const bsdFileFlagsKey = "\x00bf"
+
+func (entry *Entry) ReadAttributes(top string) {
+	fullPath := filepath.Join(top, entry.Path)
+	fileInfo, err := os.Lstat(fullPath)
+	if err != nil {
+		return
+	}
+	attributes, _ := xattr.LList(fullPath)
+	if len(attributes) > 0 {
+		entry.Attributes = &map[string][]byte{}
+		for _, name := range attributes {
+			attribute, err := xattr.LGet(fullPath, name)
+			if err == nil {
+				(*entry.Attributes)[name] = attribute
+			}
+		}
+	}
+	if err := entry.readFileFlags(fileInfo); err != nil {
+		LOG_INFO("ATTR_BACKUP", "Could not backup flags for file %s: %v", fullPath, err)
+	}
+}
+
+func (entry *Entry) SetAttributesToFile(fullPath string) {
+	names, _ := xattr.LList(fullPath)
+	for _, name := range names {
+		newAttribute, found := (*entry.Attributes)[name]
+		if found {
+			oldAttribute, _ := xattr.LGet(fullPath, name)
+			if !bytes.Equal(oldAttribute, newAttribute) {
+				xattr.LSet(fullPath, name, newAttribute)
+			}
+			delete(*entry.Attributes, name)
+		} else {
+			xattr.LRemove(fullPath, name)
+		}
+	}
+
+	for name, attribute := range *entry.Attributes {
+		if len(name) > 0 && name[0] == '\x00' {
+			continue
+		}
+		xattr.LSet(fullPath, name, attribute)
+	}
+	if err := entry.restoreLateFileFlags(fullPath); err != nil {
+		LOG_DEBUG("ATTR_RESTORE", "Could not restore flags for file %s: %v", fullPath, err)
+	}
+}
+
+func (entry *Entry) readFileFlags(fileInfo os.FileInfo) error {
+	stat, ok := fileInfo.Sys().(*syscall.Stat_t)
+	if ok && stat.Flags != 0 {
+		if entry.Attributes == nil {
+			entry.Attributes = &map[string][]byte{}
+		}
+		v := make([]byte, 4)
+		binary.LittleEndian.PutUint32(v, stat.Flags)
+		(*entry.Attributes)[bsdFileFlagsKey] = v
+		LOG_DEBUG("ATTR_READ", "Read flags 0x%x for %s", stat.Flags, entry.Path)
+	}
+	return nil
+}
+
+func (entry *Entry) RestoreEarlyDirFlags(path string) error {
+	return nil
+}
+
+func (entry *Entry) RestoreEarlyFileFlags(f *os.File) error {
+	return nil
+}
+

src/duplicacy_utils_darwin.go

@@ -5,10 +5,29 @@
 package duplicacy
 
 import (
+	"os"
+	"syscall"
 	"strings"
+	"encoding/binary"
 )
 
 func excludedByAttribute(attributes map[string][]byte) bool {
 	value, ok := attributes["com.apple.metadata:com_apple_backup_excludeItem"]
 	return ok && strings.Contains(string(value), "com.apple.backupd")
 }
+
+func (entry *Entry) restoreLateFileFlags(path string) error {
+	if entry.Attributes == nil {
+		return nil
+	}
+	if v, have := (*entry.Attributes)[bsdFileFlagsKey]; have {
+		f, err := os.OpenFile(path, os.O_RDONLY|syscall.O_SYMLINK, 0)
+		if err != nil {
+			return err
+		}
+		err = syscall.Fchflags(int(f.Fd()), int(binary.LittleEndian.Uint32(v)))
+		f.Close()
+		return err
+	}
+	return nil
+}

src/duplicacy_utils_linux.go

@@ -5,10 +5,14 @@
 package duplicacy
 
 import (
+	"bytes"
 	"encoding/binary"
 	"os"
 	"syscall"
 	"unsafe"
+	"path/filepath"
+
+	"github.com/pkg/xattr"
 )
 
 const (
@@ -47,10 +51,116 @@ func ioctl(f *os.File, request uintptr, attrp *uint32) error {
 	return nil
 }
 
-func (entry *Entry) ReadFileFlags(f *os.File) error {
-	if entry.IsSpecial() {
-		return nil
+type xattrHandle struct {
+	f *os.File
+	fullPath string
+}
+
+func (x xattrHandle) list() ([]string, error) {
+	if x.f != nil {
+		return xattr.FList(x.f)
+	} else {
+		return xattr.LList(x.fullPath)
 	}
+}
+
+func (x xattrHandle) get(name string) ([]byte, error) {
+	if x.f != nil {
+		return xattr.FGet(x.f, name)
+	} else {
+		return xattr.LGet(x.fullPath, name)
+	}
+}
+
+func (x xattrHandle) set(name string, value []byte) error {
+	if x.f != nil {
+		return xattr.FSet(x.f, name, value)
+	} else {
+		return xattr.LSet(x.fullPath, name, value)
+	}
+}
+
+func (x xattrHandle) remove(name string) error {
+	if x.f != nil {
+		return xattr.FRemove(x.f, name)
+	} else {
+		return xattr.LRemove(x.fullPath, name)
+	}
+}
+
+func (entry *Entry) ReadAttributes(top string) {
+	fullPath := filepath.Join(top, entry.Path)
+	x := xattrHandle{nil, fullPath}
+
+	if !entry.IsLink() {
+		var err error
+		x.f, err = os.OpenFile(fullPath, os.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0)
+		if err != nil {
+			// FIXME: We really should return errors for failure to read
+			return
+		}
+	}
+
+	attributes, _ := x.list()
+
+	if len(attributes) > 0 {
+		entry.Attributes = &map[string][]byte{}
+	}
+	for _, name := range attributes {
+		attribute, err := x.get(name)
+		if err == nil {
+			(*entry.Attributes)[name] = attribute
+		}
+	}
+
+	if entry.IsFile() || entry.IsDir() {
+		if err := entry.readFileFlags(x.f); err != nil {
+			LOG_INFO("ATTR_BACKUP", "Could not backup flags for file %s: %v", fullPath, err)
+		}
+	}
+	x.f.Close()
+}
+
+func (entry *Entry) SetAttributesToFile(fullPath string) {
+	x := xattrHandle{nil, fullPath}
+	if !entry.IsLink() {
+		var err error
+		x.f, err = os.OpenFile(fullPath, os.O_RDONLY|syscall.O_NOFOLLOW, 0)
+		if err != nil {
+			return
+		}
+	}
+
+	names, _ := x.list()
+
+	for _, name := range names {
+		newAttribute, found := (*entry.Attributes)[name]
+		if found {
+			oldAttribute, _ := x.get(name)
+			if !bytes.Equal(oldAttribute, newAttribute) {
+				x.set(name, newAttribute)
+			}
+			delete(*entry.Attributes, name)
+		} else {
+			x.remove(name)
+		}
+	}
+
+	for name, attribute := range *entry.Attributes {
+		if len(name) > 0 && name[0] == '\x00' {
+			continue
+		}
+		x.set(name, attribute)
+	}
+	if entry.IsFile() || entry.IsDir() {
+		if err := entry.restoreLateFileFlags(x.f); err != nil {
+			LOG_DEBUG("ATTR_RESTORE", "Could not restore flags for file %s: %v", fullPath, err)
+		}
+	}
+	x.f.Close()
+}
+
+func (entry *Entry) readFileFlags(f *os.File) error {
 	var flags uint32
 	if err := ioctl(f, linux_FS_IOC_GETFLAGS, &flags); err != nil {
 		return err
@@ -97,7 +207,7 @@ func (entry *Entry) RestoreEarlyFileFlags(f *os.File) error {
 	return nil
 }
 
-func (entry *Entry) RestoreLateFileFlags(f *os.File) error {
+func (entry *Entry) restoreLateFileFlags(f *os.File) error {
 	if entry.Attributes == nil {
 		return nil
 	}

src/duplicacy_utils_others.go

@@ -2,18 +2,15 @@
 // Free for personal use and commercial trial
 // Commercial use requires per-user licenses available from https://duplicacy.com
 
+//go:build !windows
 // +build !windows
 
 package duplicacy
 
 import (
-	"bytes"
 	"os"
 	"path"
-	"path/filepath"
 	"syscall"
-
-	"github.com/pkg/xattr"
 )
 
 func Readlink(path string) (isRegular bool, s string, err error) {
@@ -47,60 +44,6 @@ func SetOwner(fullPath string, entry *Entry, fileInfo *os.FileInfo) bool {
 	return true
 }
 
-func (entry *Entry) ReadAttributes(top string) {
-	fullPath := filepath.Join(top, entry.Path)
-	f, err := os.OpenFile(fullPath, os.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0)
-	if err != nil {
-		return
-	}
-	attributes, _ := xattr.FList(f)
-	if len(attributes) > 0 {
-		entry.Attributes = &map[string][]byte{}
-		for _, name := range attributes {
-			attribute, err := xattr.Get(fullPath, name)
-			if err == nil {
-				(*entry.Attributes)[name] = attribute
-			}
-		}
-	}
-	if err := entry.ReadFileFlags(f); err != nil {
-		LOG_INFO("ATTR_BACKUP", "Could not backup flags for file %s: %v", fullPath, err)
-	}
-	f.Close()
-}
-
-func (entry *Entry) SetAttributesToFile(fullPath string) {
-	f, err := os.OpenFile(fullPath, os.O_RDONLY|syscall.O_NOFOLLOW, 0)
-	if err != nil {
-		return
-	}
-
-	names, _ := xattr.FList(f)
-	for _, name := range names {
-		newAttribute, found := (*entry.Attributes)[name]
-		if found {
-			oldAttribute, _ := xattr.FGet(f, name)
-			if !bytes.Equal(oldAttribute, newAttribute) {
-				xattr.FSet(f, name, newAttribute)
-			}
-			delete(*entry.Attributes, name)
-		} else {
-			xattr.FRemove(f, name)
-		}
-	}
-
-	for name, attribute := range *entry.Attributes {
-		if len(name) > 0 && name[0] == '\x00' {
-			continue
-		}
-		xattr.FSet(f, name, attribute)
-	}
-	if err := entry.RestoreLateFileFlags(f); err != nil {
-		LOG_DEBUG("ATTR_RESTORE", "Could not restore flags for file %s: %v", fullPath, err)
-	}
-	f.Close()
-}
-
 func (entry *Entry) ReadSpecial(fileInfo os.FileInfo) bool {
 	if fileInfo.Mode() & (os.ModeDevice | os.ModeCharDevice) == 0 {
 		return true
@@ -117,19 +60,18 @@ func (entry *Entry) ReadSpecial(fileInfo os.FileInfo) bool {
 }
 
 func (entry *Entry) RestoreSpecial(fullPath string) error {
-	if entry.Mode & uint32(os.ModeDevice | os.ModeCharDevice) != 0 {
-		mode := entry.Mode & uint32(fileModeMask)
-		if entry.Mode & uint32(os.ModeCharDevice) != 0 {
-			mode |= syscall.S_IFCHR
-		} else {
-			mode |= syscall.S_IFBLK
-		}
-		rdev := uint64(entry.StartChunk) | uint64(entry.StartOffset) << 32
-		return syscall.Mknod(fullPath, mode, int(rdev))
-	} else if entry.Mode & uint32(os.ModeNamedPipe) != 0 {
-		return syscall.Mkfifo(fullPath, uint32(entry.Mode))
+	mode := entry.Mode & uint32(fileModeMask)
+
+	if entry.Mode & uint32(os.ModeNamedPipe) != 0 {
+		mode |= syscall.S_IFIFO
+	} else if entry.Mode & uint32(os.ModeCharDevice) != 0 {
+		mode |= syscall.S_IFCHR
+	} else if entry.Mode & uint32(os.ModeDevice) != 0 {
+		mode |= syscall.S_IFBLK
+	} else {
+		return nil
 	}
-	return nil
+	return syscall.Mknod(fullPath, mode, int(uint64(entry.StartChunk) | uint64(entry.StartOffset) << 32))
 }
 
 func joinPath(components ...string) string {

src/duplicacy_utils_xbsd.go

@@ -0,0 +1,30 @@
+// Copyright (c) Acrosync LLC. All rights reserved.
+// Free for personal use and commercial trial
+// Commercial use requires per-user licenses available from https://duplicacy.com
+
+//go:build freebsd || netbsd
+// +build freebsd netbsd
+
+package duplicacy
+
+import (
+	"bytes"
+	"encoding/binary"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/pkg/xattr"
+)
+
+func (entry *Entry) restoreLateFileFlags(path string) error {
+	if entry.Attributes == nil {
+		return nil
+	}
+	if v, have := (*entry.Attributes)[bsdFileFlagsKey]; have {
+		if _, _, errno := syscall.Syscall(syscall.SYS_LCHFLAGS, uintptr(unsafe.Pointer(syscall.StringBytePtr(path))), uintptr(v), 0); errno != 0 {
+			return os.NewSyscallError("lchflags", errno)
+		}
+	}
+	return nil
+}