Merge pull request #4708 from zmanda/windows-securitydesc

Back up and restore SecurityDescriptors on Windows

changelog/unreleased/pull-4611

@@ -1,7 +1,7 @@
 Enhancement: Back up windows created time and file attributes like hidden flag
 
 Restic did not back up windows-specific meta-data like created time and file attributes like hidden flag.
-Restic now backs up file created time and file attributes like hidden, readonly and encrypted flag when backing up files and folders on windows.
+Restic now backs up file created time and file attributes like hidden, readonly and encrypted flag when backing up files and folders on Windows.
 
 https://github.com/restic/restic/pull/4611
 

changelog/unreleased/pull-4708

@@ -0,0 +1,11 @@
+Enhancement: Back up and restore SecurityDescriptors on Windows
+
+Restic now backs up and restores SecurityDescriptors when backing up files and folders 
+on Windows which includes owner, group, discretionary access control list (DACL), 
+system access control list (SACL). This requires the user to be a member of backup 
+operators or the application must be run as admin.
+If that is not the case, only the current user's owner, group and DACL will be backed up 
+and during restore only the DACL of the backed file will be restored while the current 
+user's owner and group will be set during the restore.
+
+https://github.com/restic/restic/pull/4708

doc/040_backup.rst

@@ -514,12 +514,17 @@ written, and the next backup needs to write new metadata again. If you really
 want to save the access time for files and directories, you can pass the
 ``--with-atime`` option to the ``backup`` command.
 
+Backing up full security descriptors on Windows is only possible when the user 
+has ``SeBackupPrivilege``privilege or is running as admin. This is a restriction 
+of Windows not restic.
+If either of these conditions are not met, only the owner, group and DACL will 
+be backed up.
+
 Note that ``restic`` does not back up some metadata associated with files. Of
 particular note are:
 
 * File creation date on Unix platforms
 * Inode flags on Unix platforms
-* File ownership and ACLs on Windows
 
 Reading data from a command
 ***************************

doc/050_restore.rst

@@ -72,6 +72,11 @@ Restoring symbolic links on windows is only possible when the user has
 ``SeCreateSymbolicLinkPrivilege`` privilege or is running as admin. This is a
 restriction of windows not restic.
 
+Restoring full security descriptors on Windows is only possible when the user has
+``SeRestorePrivilege``, ``SeSecurityPrivilege`` and ``SeTakeOwnershipPrivilege`` 
+privilege or is running as admin. This is a restriction of Windows not restic.
+If either of these conditions are not met, only the DACL will be restored.
+
 By default, restic does not restore files as sparse. Use ``restore --sparse`` to
 enable the creation of sparse files if supported by the filesystem. Then restic
 will restore long runs of zero bytes as holes in the corresponding files.

internal/debug/debug.go

@@ -8,8 +8,6 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
-
-	"github.com/restic/restic/internal/fs"
 )
 
 var opts struct {
@@ -46,7 +44,7 @@ func initDebugLogger() {
 
 	fmt.Fprintf(os.Stderr, "debug log file %v\n", debugfile)
 
-	f, err := fs.OpenFile(debugfile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
+	f, err := os.OpenFile(debugfile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "unable to open debug log file: %v\n", err)
 		os.Exit(2)

internal/errors/errors.go

@@ -43,22 +43,28 @@ func Is(x, y error) bool { return stderrors.Is(x, y) }
 // unwrap errors returned by [Join].
 func Unwrap(err error) error { return stderrors.Unwrap(err) }
 
-// CombineErrors combines multiple errors into a single error.
-func CombineErrors(errors ...error) error {
+// CombineErrors combines multiple errors into a single error after filtering out any nil values.
+// If no errors are passed, it returns nil.
+// If one error is passed, it simply returns that same error.
+func CombineErrors(errors ...error) (err error) {
 	var combinedErrorMsg string
-
-	for _, err := range errors {
-		if err != nil {
+	var multipleErrors bool
+	for _, errVal := range errors {
+		if errVal != nil {
 			if combinedErrorMsg != "" {
 				combinedErrorMsg += "; " // Separate error messages with a delimiter
+				multipleErrors = true
+			} else {
+				// Set the first error
+				err = errVal
 			}
-			combinedErrorMsg += err.Error()
+			combinedErrorMsg += errVal.Error()
 		}
 	}
-
 	if combinedErrorMsg == "" {
-		return nil // No errors, return nil
+		return nil // If no errors, return nil
+	} else if !multipleErrors {
+		return err // If only one error, return that first error
 	}
-
 	return fmt.Errorf("multiple errors occurred: [%s]", combinedErrorMsg)
 }

internal/fs/sd_windows.go

@@ -0,0 +1,439 @@
+package fs
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"unicode/utf16"
+	"unsafe"
+
+	"github.com/restic/restic/internal/debug"
+	"golang.org/x/sys/windows"
+)
+
+var (
+	onceBackup  sync.Once
+	onceRestore sync.Once
+
+	// SeBackupPrivilege allows the application to bypass file and directory ACLs to back up files and directories.
+	SeBackupPrivilege = "SeBackupPrivilege"
+	// SeRestorePrivilege allows the application to bypass file and directory ACLs to restore files and directories.
+	SeRestorePrivilege = "SeRestorePrivilege"
+	// SeSecurityPrivilege allows read and write access to all SACLs.
+	SeSecurityPrivilege = "SeSecurityPrivilege"
+	// SeTakeOwnershipPrivilege allows the application to take ownership of files and directories, regardless of the permissions set on them.
+	SeTakeOwnershipPrivilege = "SeTakeOwnershipPrivilege"
+
+	lowerPrivileges atomic.Bool
+)
+
+// Flags for backup and restore with admin permissions
+var highSecurityFlags windows.SECURITY_INFORMATION = windows.OWNER_SECURITY_INFORMATION | windows.GROUP_SECURITY_INFORMATION | windows.DACL_SECURITY_INFORMATION | windows.SACL_SECURITY_INFORMATION | windows.LABEL_SECURITY_INFORMATION | windows.ATTRIBUTE_SECURITY_INFORMATION | windows.SCOPE_SECURITY_INFORMATION | windows.BACKUP_SECURITY_INFORMATION | windows.PROTECTED_DACL_SECURITY_INFORMATION | windows.PROTECTED_SACL_SECURITY_INFORMATION | windows.UNPROTECTED_DACL_SECURITY_INFORMATION | windows.UNPROTECTED_SACL_SECURITY_INFORMATION
+
+// Flags for backup without admin permissions. If there are no admin permissions, only the current user's owner, group and DACL will be backed up.
+var lowBackupSecurityFlags windows.SECURITY_INFORMATION = windows.OWNER_SECURITY_INFORMATION | windows.GROUP_SECURITY_INFORMATION | windows.DACL_SECURITY_INFORMATION | windows.LABEL_SECURITY_INFORMATION | windows.ATTRIBUTE_SECURITY_INFORMATION | windows.SCOPE_SECURITY_INFORMATION | windows.PROTECTED_DACL_SECURITY_INFORMATION | windows.UNPROTECTED_DACL_SECURITY_INFORMATION
+
+// Flags for restore without admin permissions. If there are no admin permissions, only the DACL from the SD can be restored and owner and group will be set based on the current user.
+var lowRestoreSecurityFlags windows.SECURITY_INFORMATION = windows.DACL_SECURITY_INFORMATION | windows.ATTRIBUTE_SECURITY_INFORMATION | windows.PROTECTED_DACL_SECURITY_INFORMATION
+
+// GetSecurityDescriptor takes the path of the file and returns the SecurityDescriptor for the file.
+// This needs admin permissions or SeBackupPrivilege for getting the full SD.
+// If there are no admin permissions, only the current user's owner, group and DACL will be got.
+func GetSecurityDescriptor(filePath string) (securityDescriptor *[]byte, err error) {
+	onceBackup.Do(enableBackupPrivilege)
+
+	var sd *windows.SECURITY_DESCRIPTOR
+
+	if lowerPrivileges.Load() {
+		sd, err = getNamedSecurityInfoLow(filePath)
+	} else {
+		sd, err = getNamedSecurityInfoHigh(filePath)
+	}
+	if err != nil {
+		if !lowerPrivileges.Load() && isHandlePrivilegeNotHeldError(err) {
+			// If ERROR_PRIVILEGE_NOT_HELD is encountered, fallback to backups/restores using lower non-admin privileges.
+			lowerPrivileges.Store(true)
+			sd, err = getNamedSecurityInfoLow(filePath)
+			if err != nil {
+				return nil, fmt.Errorf("get low-level named security info failed with: %w", err)
+			}
+		} else {
+			return nil, fmt.Errorf("get named security info failed with: %w", err)
+		}
+	}
+
+	sdBytes, err := securityDescriptorStructToBytes(sd)
+	if err != nil {
+		return nil, fmt.Errorf("convert security descriptor to bytes failed: %w", err)
+	}
+	return &sdBytes, nil
+}
+
+// SetSecurityDescriptor sets the SecurityDescriptor for the file at the specified path.
+// This needs admin permissions or SeRestorePrivilege, SeSecurityPrivilege and SeTakeOwnershipPrivilege
+// for setting the full SD.
+// If there are no admin permissions/required privileges, only the DACL from the SD can be set and
+// owner and group will be set based on the current user.
+func SetSecurityDescriptor(filePath string, securityDescriptor *[]byte) error {
+	onceRestore.Do(enableRestorePrivilege)
+	// Set the security descriptor on the file
+	sd, err := SecurityDescriptorBytesToStruct(*securityDescriptor)
+	if err != nil {
+		return fmt.Errorf("error converting bytes to security descriptor: %w", err)
+	}
+
+	owner, _, err := sd.Owner()
+	if err != nil {
+		//Do not set partial values.
+		owner = nil
+	}
+	group, _, err := sd.Group()
+	if err != nil {
+		//Do not set partial values.
+		group = nil
+	}
+	dacl, _, err := sd.DACL()
+	if err != nil {
+		//Do not set partial values.
+		dacl = nil
+	}
+	sacl, _, err := sd.SACL()
+	if err != nil {
+		//Do not set partial values.
+		sacl = nil
+	}
+
+	if lowerPrivileges.Load() {
+		err = setNamedSecurityInfoLow(filePath, dacl)
+	} else {
+		err = setNamedSecurityInfoHigh(filePath, owner, group, dacl, sacl)
+	}
+
+	if err != nil {
+		if !lowerPrivileges.Load() && isHandlePrivilegeNotHeldError(err) {
+			// If ERROR_PRIVILEGE_NOT_HELD is encountered, fallback to backups/restores using lower non-admin privileges.
+			lowerPrivileges.Store(true)
+			err = setNamedSecurityInfoLow(filePath, dacl)
+			if err != nil {
+				return fmt.Errorf("set low-level named security info failed with: %w", err)
+			}
+		} else {
+			return fmt.Errorf("set named security info failed with: %w", err)
+		}
+	}
+	return nil
+}
+
+// getNamedSecurityInfoHigh gets the higher level SecurityDescriptor which requires admin permissions.
+func getNamedSecurityInfoHigh(filePath string) (*windows.SECURITY_DESCRIPTOR, error) {
+	return windows.GetNamedSecurityInfo(filePath, windows.SE_FILE_OBJECT, highSecurityFlags)
+}
+
+// getNamedSecurityInfoLow gets the lower level SecurityDescriptor which requires no admin permissions.
+func getNamedSecurityInfoLow(filePath string) (*windows.SECURITY_DESCRIPTOR, error) {
+	return windows.GetNamedSecurityInfo(filePath, windows.SE_FILE_OBJECT, lowBackupSecurityFlags)
+}
+
+// setNamedSecurityInfoHigh sets the higher level SecurityDescriptor which requires admin permissions.
+func setNamedSecurityInfoHigh(filePath string, owner *windows.SID, group *windows.SID, dacl *windows.ACL, sacl *windows.ACL) error {
+	return windows.SetNamedSecurityInfo(filePath, windows.SE_FILE_OBJECT, highSecurityFlags, owner, group, dacl, sacl)
+}
+
+// setNamedSecurityInfoLow sets the lower level SecurityDescriptor which requires no admin permissions.
+func setNamedSecurityInfoLow(filePath string, dacl *windows.ACL) error {
+	return windows.SetNamedSecurityInfo(filePath, windows.SE_FILE_OBJECT, lowRestoreSecurityFlags, nil, nil, dacl, nil)
+}
+
+// enableBackupPrivilege enables privilege for backing up security descriptors
+func enableBackupPrivilege() {
+	err := enableProcessPrivileges([]string{SeBackupPrivilege})
+	if err != nil {
+		debug.Log("error enabling backup privilege: %v", err)
+	}
+}
+
+// enableBackupPrivilege enables privilege for restoring security descriptors
+func enableRestorePrivilege() {
+	err := enableProcessPrivileges([]string{SeRestorePrivilege, SeSecurityPrivilege, SeTakeOwnershipPrivilege})
+	if err != nil {
+		debug.Log("error enabling restore/security privilege: %v", err)
+	}
+}
+
+// isHandlePrivilegeNotHeldError checks if the error is ERROR_PRIVILEGE_NOT_HELD
+func isHandlePrivilegeNotHeldError(err error) bool {
+	// Use a type assertion to check if the error is of type syscall.Errno
+	if errno, ok := err.(syscall.Errno); ok {
+		// Compare the error code to the expected value
+		return errno == windows.ERROR_PRIVILEGE_NOT_HELD
+	}
+	return false
+}
+
+// SecurityDescriptorBytesToStruct converts the security descriptor bytes representation
+// into a pointer to windows SECURITY_DESCRIPTOR.
+func SecurityDescriptorBytesToStruct(sd []byte) (*windows.SECURITY_DESCRIPTOR, error) {
+	if l := int(unsafe.Sizeof(windows.SECURITY_DESCRIPTOR{})); len(sd) < l {
+		return nil, fmt.Errorf("securityDescriptor (%d) smaller than expected (%d): %w", len(sd), l, windows.ERROR_INCORRECT_SIZE)
+	}
+	s := (*windows.SECURITY_DESCRIPTOR)(unsafe.Pointer(&sd[0]))
+	return s, nil
+}
+
+// securityDescriptorStructToBytes converts the pointer to windows SECURITY_DESCRIPTOR
+// into a security descriptor bytes representation.
+func securityDescriptorStructToBytes(sd *windows.SECURITY_DESCRIPTOR) ([]byte, error) {
+	b := unsafe.Slice((*byte)(unsafe.Pointer(sd)), sd.Length())
+	return b, nil
+}
+
+// The code below was adapted from
+// https://github.com/microsoft/go-winio/blob/3c9576c9346a1892dee136329e7e15309e82fb4f/privilege.go
+// under MIT license.
+
+// The MIT License (MIT)
+
+// Copyright (c) 2015 Microsoft
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+var (
+	modadvapi32 = windows.NewLazySystemDLL("advapi32.dll")
+
+	procLookupPrivilegeValueW       = modadvapi32.NewProc("LookupPrivilegeValueW")
+	procAdjustTokenPrivileges       = modadvapi32.NewProc("AdjustTokenPrivileges")
+	procLookupPrivilegeDisplayNameW = modadvapi32.NewProc("LookupPrivilegeDisplayNameW")
+	procLookupPrivilegeNameW        = modadvapi32.NewProc("LookupPrivilegeNameW")
+)
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoErrorIOPending = 997
+
+	//revive:disable-next-line:var-naming ALL_CAPS
+	SE_PRIVILEGE_ENABLED = windows.SE_PRIVILEGE_ENABLED
+
+	//revive:disable-next-line:var-naming ALL_CAPS
+	ERROR_NOT_ALL_ASSIGNED windows.Errno = windows.ERROR_NOT_ALL_ASSIGNED
+)
+
+var (
+	errErrorIOPending error = syscall.Errno(errnoErrorIOPending)
+	errErrorEinval    error = syscall.EINVAL
+
+	privNames     = make(map[string]uint64)
+	privNameMutex sync.Mutex
+)
+
+// PrivilegeError represents an error enabling privileges.
+type PrivilegeError struct {
+	privileges []uint64
+}
+
+// Error returns the string message for the error.
+func (e *PrivilegeError) Error() string {
+	s := "Could not enable privilege "
+	if len(e.privileges) > 1 {
+		s = "Could not enable privileges "
+	}
+	for i, p := range e.privileges {
+		if i != 0 {
+			s += ", "
+		}
+		s += `"`
+		s += getPrivilegeName(p)
+		s += `"`
+	}
+	return s
+}
+
+func mapPrivileges(names []string) ([]uint64, error) {
+	privileges := make([]uint64, 0, len(names))
+	privNameMutex.Lock()
+	defer privNameMutex.Unlock()
+	for _, name := range names {
+		p, ok := privNames[name]
+		if !ok {
+			err := lookupPrivilegeValue("", name, &p)
+			if err != nil {
+				return nil, err
+			}
+			privNames[name] = p
+		}
+		privileges = append(privileges, p)
+	}
+	return privileges, nil
+}
+
+// enableProcessPrivileges enables privileges globally for the process.
+func enableProcessPrivileges(names []string) error {
+	return enableDisableProcessPrivilege(names, SE_PRIVILEGE_ENABLED)
+}
+
+func enableDisableProcessPrivilege(names []string, action uint32) error {
+	privileges, err := mapPrivileges(names)
+	if err != nil {
+		return err
+	}
+
+	p := windows.CurrentProcess()
+	var token windows.Token
+	err = windows.OpenProcessToken(p, windows.TOKEN_ADJUST_PRIVILEGES|windows.TOKEN_QUERY, &token)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		_ = token.Close()
+	}()
+	return adjustPrivileges(token, privileges, action)
+}
+
+func adjustPrivileges(token windows.Token, privileges []uint64, action uint32) error {
+	var b bytes.Buffer
+	_ = binary.Write(&b, binary.LittleEndian, uint32(len(privileges)))
+	for _, p := range privileges {
+		_ = binary.Write(&b, binary.LittleEndian, p)
+		_ = binary.Write(&b, binary.LittleEndian, action)
+	}
+	prevState := make([]byte, b.Len())
+	reqSize := uint32(0)
+	success, err := adjustTokenPrivileges(token, false, &b.Bytes()[0], uint32(len(prevState)), &prevState[0], &reqSize)
+	if !success {
+		return err
+	}
+	if err == ERROR_NOT_ALL_ASSIGNED { //nolint:errorlint // err is Errno
+		debug.Log("Not all requested privileges were fully set: %v. AdjustTokenPrivileges returned warning: %v", privileges, err)
+	}
+	return nil
+}
+
+func getPrivilegeName(luid uint64) string {
+	var nameBuffer [256]uint16
+	bufSize := uint32(len(nameBuffer))
+	err := lookupPrivilegeName("", &luid, &nameBuffer[0], &bufSize)
+	if err != nil {
+		return fmt.Sprintf("<unknown privilege %d>", luid)
+	}
+
+	var displayNameBuffer [256]uint16
+	displayBufSize := uint32(len(displayNameBuffer))
+	var langID uint32
+	err = lookupPrivilegeDisplayName("", &nameBuffer[0], &displayNameBuffer[0], &displayBufSize, &langID)
+	if err != nil {
+		return fmt.Sprintf("<unknown privilege %s>", string(utf16.Decode(nameBuffer[:bufSize])))
+	}
+
+	return string(utf16.Decode(displayNameBuffer[:displayBufSize]))
+}
+
+// The functions below are copied over from https://github.com/microsoft/go-winio/blob/main/zsyscall_windows.go
+
+// This windows api always returns an error even in case of success, warnings (partial success) and error cases.
+//
+// Full success - When we call this with admin permissions, it returns DNS_ERROR_RCODE_NO_ERROR (0).
+// This gets translated to errErrorEinval and ultimately in adjustTokenPrivileges, it gets ignored.
+//
+// Partial success - If we call this api without admin privileges, privileges related to SACLs do not get set and
+// though the api returns success, it returns an error - golang.org/x/sys/windows.ERROR_NOT_ALL_ASSIGNED (1300)
+func adjustTokenPrivileges(token windows.Token, releaseAll bool, input *byte, outputSize uint32, output *byte, requiredSize *uint32) (success bool, err error) {
+	var _p0 uint32
+	if releaseAll {
+		_p0 = 1
+	}
+	r0, _, e1 := syscall.SyscallN(procAdjustTokenPrivileges.Addr(), uintptr(token), uintptr(_p0), uintptr(unsafe.Pointer(input)), uintptr(outputSize), uintptr(unsafe.Pointer(output)), uintptr(unsafe.Pointer(requiredSize)))
+	success = r0 != 0
+	if true {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func lookupPrivilegeDisplayName(systemName string, name *uint16, buffer *uint16, size *uint32, languageID *uint32) (err error) {
+	var _p0 *uint16
+	_p0, err = syscall.UTF16PtrFromString(systemName)
+	if err != nil {
+		return
+	}
+	return _lookupPrivilegeDisplayName(_p0, name, buffer, size, languageID)
+}
+
+func _lookupPrivilegeDisplayName(systemName *uint16, name *uint16, buffer *uint16, size *uint32, languageID *uint32) (err error) {
+	r1, _, e1 := syscall.SyscallN(procLookupPrivilegeDisplayNameW.Addr(), uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(name)), uintptr(unsafe.Pointer(buffer)), uintptr(unsafe.Pointer(size)), uintptr(unsafe.Pointer(languageID)))
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func lookupPrivilegeName(systemName string, luid *uint64, buffer *uint16, size *uint32) (err error) {
+	var _p0 *uint16
+	_p0, err = syscall.UTF16PtrFromString(systemName)
+	if err != nil {
+		return
+	}
+	return _lookupPrivilegeName(_p0, luid, buffer, size)
+}
+
+func _lookupPrivilegeName(systemName *uint16, luid *uint64, buffer *uint16, size *uint32) (err error) {
+	r1, _, e1 := syscall.SyscallN(procLookupPrivilegeNameW.Addr(), uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(luid)), uintptr(unsafe.Pointer(buffer)), uintptr(unsafe.Pointer(size)))
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func lookupPrivilegeValue(systemName string, name string, luid *uint64) (err error) {
+	var _p0 *uint16
+	_p0, err = syscall.UTF16PtrFromString(systemName)
+	if err != nil {
+		return
+	}
+	var _p1 *uint16
+	_p1, err = syscall.UTF16PtrFromString(name)
+	if err != nil {
+		return
+	}
+	return _lookupPrivilegeValue(_p0, _p1, luid)
+}
+
+func _lookupPrivilegeValue(systemName *uint16, name *uint16, luid *uint64) (err error) {
+	r1, _, e1 := syscall.SyscallN(procLookupPrivilegeValueW.Addr(), uintptr(unsafe.Pointer(systemName)), uintptr(unsafe.Pointer(name)), uintptr(unsafe.Pointer(luid)))
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// The code below was copied from https://github.com/microsoft/go-winio/blob/main/tools/mkwinsyscall/mkwinsyscall.go
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errErrorEinval
+	case errnoErrorIOPending:
+		return errErrorIOPending
+	}
+	return e
+}

internal/fs/sd_windows_test.go

@@ -0,0 +1,60 @@
+//go:build windows
+// +build windows
+
+package fs
+
+import (
+	"encoding/base64"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/test"
+)
+
+func TestSetGetFileSecurityDescriptors(t *testing.T) {
+	tempDir := t.TempDir()
+	testfilePath := filepath.Join(tempDir, "testfile.txt")
+	// create temp file
+	testfile, err := os.Create(testfilePath)
+	if err != nil {
+		t.Fatalf("failed to create temporary file: %s", err)
+	}
+	defer func() {
+		err := testfile.Close()
+		if err != nil {
+			t.Logf("Error closing file %s: %v\n", testfilePath, err)
+		}
+	}()
+
+	testSecurityDescriptors(t, TestFileSDs, testfilePath)
+}
+
+func TestSetGetFolderSecurityDescriptors(t *testing.T) {
+	tempDir := t.TempDir()
+	testfolderPath := filepath.Join(tempDir, "testfolder")
+	// create temp folder
+	err := os.Mkdir(testfolderPath, os.ModeDir)
+	if err != nil {
+		t.Fatalf("failed to create temporary file: %s", err)
+	}
+
+	testSecurityDescriptors(t, TestDirSDs, testfolderPath)
+}
+
+func testSecurityDescriptors(t *testing.T, testSDs []string, testPath string) {
+	for _, testSD := range testSDs {
+		sdInputBytes, err := base64.StdEncoding.DecodeString(testSD)
+		test.OK(t, errors.Wrapf(err, "Error decoding SD: %s", testPath))
+
+		err = SetSecurityDescriptor(testPath, &sdInputBytes)
+		test.OK(t, errors.Wrapf(err, "Error setting file security descriptor for: %s", testPath))
+
+		var sdOutputBytes *[]byte
+		sdOutputBytes, err = GetSecurityDescriptor(testPath)
+		test.OK(t, errors.Wrapf(err, "Error getting file security descriptor for: %s", testPath))
+
+		CompareSecurityDescriptors(t, testPath, sdInputBytes, *sdOutputBytes)
+	}
+}

internal/fs/sd_windows_test_helpers.go

@@ -0,0 +1,126 @@
+//go:build windows
+// +build windows
+
+package fs
+
+import (
+	"os/user"
+	"testing"
+
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/test"
+	"golang.org/x/sys/windows"
+)
+
+var (
+	TestFileSDs = []string{"AQAUvBQAAAAwAAAAAAAAAEwAAAABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvqAwAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIAfAAEAAAAAAAkAKkAEgABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvtAwAAABAUAP8BHwABAQAAAAAABRIAAAAAEBgA/wEfAAECAAAAAAAFIAAAACACAAAAECQA/wEfAAEFAAAAAAAFFQAAAIifWK5WoILqzL0mq+oDAAA=",
+		"AQAUvBQAAAAwAAAAAAAAAEwAAAABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvqAwAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIAyAAHAAAAAAAUAKkAEgABAQAAAAAABQcAAAAAABQAiQASAAEBAAAAAAAFBwAAAAAAJACpABIAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSar7QMAAAAAJAC/ARMAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSar6gMAAAAAFAD/AR8AAQEAAAAAAAUSAAAAAAAYAP8BHwABAgAAAAAABSAAAAAgAgAAAAAkAP8BHwABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvqAwAA",
+		"AQAUvBQAAAAwAAAA7AAAAEwAAAABBQAAAAAABRUAAAAvr7t03PyHGk2FokNHCAAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIAoAAFAAAAAAAkAP8BHwABBQAAAAAABRUAAAAvr7t03PyHGk2FokNHCAAAAAAkAKkAEgABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvtAwAAABAUAP8BHwABAQAAAAAABRIAAAAAEBgA/wEfAAECAAAAAAAFIAAAACACAAAAECQA/wEfAAEFAAAAAAAFFQAAAIifWK5WoILqzL0mq+oDAAACAHQAAwAAAAKAJAC/AQIAAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDtgQAAALAJAC/AQMAAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDPgkAAAJAJAD/AQ8AAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDtQQAAA==",
+	}
+	TestDirSDs = []string{"AQAUvBQAAAAwAAAAAAAAAEwAAAABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvqAwAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIAfAAEAAAAAAAkAKkAEgABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvtAwAAABMUAP8BHwABAQAAAAAABRIAAAAAExgA/wEfAAECAAAAAAAFIAAAACACAAAAEyQA/wEfAAEFAAAAAAAFFQAAAIifWK5WoILqzL0mq+oDAAA=",
+		"AQAUvBQAAAAwAAAAAAAAAEwAAAABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvqAwAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIA3AAIAAAAAAIUAKkAEgABAQAAAAAABQcAAAAAAxQAiQASAAEBAAAAAAAFBwAAAAAAJACpABIAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSar7QMAAAAAJAC/ARMAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSar6gMAAAALFAC/ARMAAQEAAAAAAAMAAAAAABMUAP8BHwABAQAAAAAABRIAAAAAExgA/wEfAAECAAAAAAAFIAAAACACAAAAEyQA/wEfAAEFAAAAAAAFFQAAAIifWK5WoILqzL0mq+oDAAA=",
+		"AQAUvBQAAAAwAAAA7AAAAEwAAAABBQAAAAAABRUAAAAvr7t03PyHGk2FokNHCAAAAQUAAAAAAAUVAAAAiJ9YrlaggurMvSarAQIAAAIAoAAFAAAAAAAkAP8BHwABBQAAAAAABRUAAAAvr7t03PyHGk2FokNHCAAAAAAkAKkAEgABBQAAAAAABRUAAACIn1iuVqCC6sy9JqvtAwAAABMUAP8BHwABAQAAAAAABRIAAAAAExgA/wEfAAECAAAAAAAFIAAAACACAAAAEyQA/wEfAAEFAAAAAAAFFQAAAIifWK5WoILqzL0mq+oDAAACAHQAAwAAAAKAJAC/AQIAAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDtgQAAALAJAC/AQMAAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDPgkAAAJAJAD/AQ8AAQUAAAAAAAUVAAAAL6+7dNz8hxpNhaJDtQQAAA==",
+	}
+)
+
+// IsAdmin checks if current user is an administrator.
+func IsAdmin() (isAdmin bool, err error) {
+	var sid *windows.SID
+	err = windows.AllocateAndInitializeSid(&windows.SECURITY_NT_AUTHORITY, 2, windows.SECURITY_BUILTIN_DOMAIN_RID, windows.DOMAIN_ALIAS_RID_ADMINS,
+		0, 0, 0, 0, 0, 0, &sid)
+	if err != nil {
+		return false, errors.Errorf("sid error: %s", err)
+	}
+	windows.GetCurrentProcessToken()
+	token := windows.Token(0)
+	member, err := token.IsMember(sid)
+	if err != nil {
+		return false, errors.Errorf("token membership error: %s", err)
+	}
+	return member, nil
+}
+
+// CompareSecurityDescriptors runs tests for comparing 2 security descriptors in []byte format.
+func CompareSecurityDescriptors(t *testing.T, testPath string, sdInputBytes, sdOutputBytes []byte) {
+	sdInput, err := SecurityDescriptorBytesToStruct(sdInputBytes)
+	test.OK(t, errors.Wrapf(err, "Error converting SD to struct for: %s", testPath))
+
+	sdOutput, err := SecurityDescriptorBytesToStruct(sdOutputBytes)
+	test.OK(t, errors.Wrapf(err, "Error converting SD to struct for: %s", testPath))
+
+	isAdmin, err := IsAdmin()
+	test.OK(t, errors.Wrapf(err, "Error checking if user is admin: %s", testPath))
+
+	var ownerExpected *windows.SID
+	var defaultedOwnerExpected bool
+	var groupExpected *windows.SID
+	var defaultedGroupExpected bool
+	var daclExpected *windows.ACL
+	var defaultedDaclExpected bool
+	var saclExpected *windows.ACL
+	var defaultedSaclExpected bool
+
+	// The Dacl is set correctly whether or not application is running as admin.
+	daclExpected, defaultedDaclExpected, err = sdInput.DACL()
+	test.OK(t, errors.Wrapf(err, "Error getting input dacl for: %s", testPath))
+
+	if isAdmin {
+		// If application is running as admin, all sd values including owner, group, dacl, sacl are set correctly during restore.
+		// Hence we will use the input values for comparison with the output values.
+		ownerExpected, defaultedOwnerExpected, err = sdInput.Owner()
+		test.OK(t, errors.Wrapf(err, "Error getting input owner for: %s", testPath))
+		groupExpected, defaultedGroupExpected, err = sdInput.Group()
+		test.OK(t, errors.Wrapf(err, "Error getting input group for: %s", testPath))
+		saclExpected, defaultedSaclExpected, err = sdInput.SACL()
+		test.OK(t, errors.Wrapf(err, "Error getting input sacl for: %s", testPath))
+	} else {
+		// If application is not running as admin, owner and group are set as current user's SID/GID during restore and sacl is empty.
+		// Get the current user
+		user, err := user.Current()
+		test.OK(t, errors.Wrapf(err, "Could not get current user for: %s", testPath))
+		// Get current user's SID
+		currentUserSID, err := windows.StringToSid(user.Uid)
+		test.OK(t, errors.Wrapf(err, "Error getting output group for: %s", testPath))
+		// Get current user's Group SID
+		currentGroupSID, err := windows.StringToSid(user.Gid)
+		test.OK(t, errors.Wrapf(err, "Error getting output group for: %s", testPath))
+
+		// Set owner and group as current user's SID and GID during restore.
+		ownerExpected = currentUserSID
+		defaultedOwnerExpected = false
+		groupExpected = currentGroupSID
+		defaultedGroupExpected = false
+
+		// If application is not running as admin, SACL is returned empty.
+		saclExpected = nil
+		defaultedSaclExpected = false
+	}
+	// Now do all the comparisons
+	// Get owner SID from output file
+	ownerOut, defaultedOwnerOut, err := sdOutput.Owner()
+	test.OK(t, errors.Wrapf(err, "Error getting output owner for: %s", testPath))
+	// Compare owner SIDs. We must use the Equals method for comparison as a syscall is made for comparing SIDs.
+	test.Assert(t, ownerExpected.Equals(ownerOut), "Owner from SDs read from test path don't match: %s, cur:%s, exp: %s", testPath, ownerExpected.String(), ownerOut.String())
+	test.Equals(t, defaultedOwnerExpected, defaultedOwnerOut, "Defaulted for owner from SDs read from test path don't match: %s", testPath)
+
+	// Get group SID from output file
+	groupOut, defaultedGroupOut, err := sdOutput.Group()
+	test.OK(t, errors.Wrapf(err, "Error getting output group for: %s", testPath))
+	// Compare group SIDs. We must use the Equals method for comparison as a syscall is made for comparing SIDs.
+	test.Assert(t, groupExpected.Equals(groupOut), "Group from SDs read from test path don't match: %s, cur:%s, exp: %s", testPath, groupExpected.String(), groupOut.String())
+	test.Equals(t, defaultedGroupExpected, defaultedGroupOut, "Defaulted for group from SDs read from test path don't match: %s", testPath)
+
+	// Get dacl from output file
+	daclOut, defaultedDaclOut, err := sdOutput.DACL()
+	test.OK(t, errors.Wrapf(err, "Error getting output dacl for: %s", testPath))
+	// Compare dacls
+	test.Equals(t, daclExpected, daclOut, "DACL from SDs read from test path don't match: %s", testPath)
+	test.Equals(t, defaultedDaclExpected, defaultedDaclOut, "Defaulted for DACL from SDs read from test path don't match: %s", testPath)
+
+	// Get sacl from output file
+	saclOut, defaultedSaclOut, err := sdOutput.SACL()
+	test.OK(t, errors.Wrapf(err, "Error getting output sacl for: %s", testPath))
+	// Compare sacls
+	test.Equals(t, saclExpected, saclOut, "DACL from SDs read from test path don't match: %s", testPath)
+	test.Equals(t, defaultedSaclExpected, defaultedSaclOut, "Defaulted for SACL from SDs read from test path don't match: %s", testPath)
+}

internal/restic/node.go

@@ -48,13 +48,15 @@ const (
 	TypeCreationTime GenericAttributeType = "windows.creation_time"
 	// TypeFileAttributes is the GenericAttributeType used for storing file attributes for windows files within the generic attributes map.
 	TypeFileAttributes GenericAttributeType = "windows.file_attributes"
+	// TypeSecurityDescriptor is the GenericAttributeType used for storing security descriptors including owner, group, discretionary access control list (DACL), system access control list (SACL)) for windows files within the generic attributes map.
+	TypeSecurityDescriptor GenericAttributeType = "windows.security_descriptor"
 
 	// Generic Attributes for other OS types should be defined here.
 )
 
 // init is called when the package is initialized. Any new GenericAttributeTypes being created must be added here as well.
 func init() {
-	storeGenericAttributeType(TypeCreationTime, TypeFileAttributes)
+	storeGenericAttributeType(TypeCreationTime, TypeFileAttributes, TypeSecurityDescriptor)
 }
 
 // genericAttributesForOS maintains a map of known genericAttributesForOS to the OSType
@@ -719,12 +721,7 @@ func (node *Node) fillExtra(path string, fi os.FileInfo, ignoreXattrListError bo
 	allowExtended, err := node.fillGenericAttributes(path, fi, stat)
 	if allowExtended {
 		// Skip processing ExtendedAttributes if allowExtended is false.
-		errEx := node.fillExtendedAttributes(path, ignoreXattrListError)
-		if err == nil {
-			err = errEx
-		} else {
-			debug.Log("Error filling extended attributes for %v at %v : %v", node.Name, path, errEx)
-		}
+		err = errors.CombineErrors(err, node.fillExtendedAttributes(path, ignoreXattrListError))
 	}
 	return err
 }

internal/restic/node_windows.go

@@ -23,6 +23,9 @@ type WindowsAttributes struct {
 	CreationTime *syscall.Filetime `generic:"creation_time"`
 	// FileAttributes is used for storing file attributes for windows files.
 	FileAttributes *uint32 `generic:"file_attributes"`
+	// SecurityDescriptor is used for storing security descriptors which includes
+	// owner, group, discretionary access control list (DACL), system access control list (SACL)
+	SecurityDescriptor *[]byte `generic:"security_descriptor"`
 }
 
 var (
@@ -118,7 +121,7 @@ func (s statT) mtim() syscall.Timespec {
 
 func (s statT) ctim() syscall.Timespec {
 	// Windows does not have the concept of a "change time" in the sense Unix uses it, so we're using the LastWriteTime here.
-	return syscall.NsecToTimespec(s.LastWriteTime.Nanoseconds())
+	return s.mtim()
 }
 
 // restoreGenericAttributes restores generic attributes for Windows
@@ -141,6 +144,11 @@ func (node Node) restoreGenericAttributes(path string, warn func(msg string)) (e
 			errs = append(errs, fmt.Errorf("error restoring file attributes for: %s : %v", path, err))
 		}
 	}
+	if windowsAttributes.SecurityDescriptor != nil {
+		if err := fs.SetSecurityDescriptor(path, windowsAttributes.SecurityDescriptor); err != nil {
+			errs = append(errs, fmt.Errorf("error restoring security descriptor for: %s : %v", path, err))
+		}
+	}
 
 	HandleUnknownGenericAttributesFound(unknownAttribs, warn)
 	return errors.CombineErrors(errs...)
@@ -274,11 +282,18 @@ func (node *Node) fillGenericAttributes(path string, fi os.FileInfo, stat *statT
 		// Do not process file attributes and created time for windows directories like
 		// C:, D:
 		// Filepath.Clean(path) ends with '\' for Windows root drives only.
+		var sd *[]byte
+		if node.Type == "file" || node.Type == "dir" {
+			if sd, err = fs.GetSecurityDescriptor(path); err != nil {
+				return true, err
+			}
+		}
 
 		// Add Windows attributes
 		node.GenericAttributes, err = WindowsAttrsToGenericAttributes(WindowsAttributes{
-			CreationTime:   getCreationTime(fi, path),
-			FileAttributes: &stat.FileAttributes,
+			CreationTime:       getCreationTime(fi, path),
+			FileAttributes:     &stat.FileAttributes,
+			SecurityDescriptor: sd,
 		})
 	}
 	return true, err

internal/restic/node_windows_test.go

@@ -4,6 +4,7 @@
 package restic
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -12,10 +13,66 @@ import (
 	"testing"
 
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/fs"
 	"github.com/restic/restic/internal/test"
 	"golang.org/x/sys/windows"
 )
 
+func TestRestoreSecurityDescriptors(t *testing.T) {
+	t.Parallel()
+	tempDir := t.TempDir()
+	for i, sd := range fs.TestFileSDs {
+		testRestoreSecurityDescriptor(t, sd, tempDir, "file", fmt.Sprintf("testfile%d", i))
+	}
+	for i, sd := range fs.TestDirSDs {
+		testRestoreSecurityDescriptor(t, sd, tempDir, "dir", fmt.Sprintf("testdir%d", i))
+	}
+}
+
+func testRestoreSecurityDescriptor(t *testing.T, sd string, tempDir, fileType, fileName string) {
+	// Decode the encoded string SD to get the security descriptor input in bytes.
+	sdInputBytes, err := base64.StdEncoding.DecodeString(sd)
+	test.OK(t, errors.Wrapf(err, "Error decoding SD for: %s", fileName))
+	// Wrap the security descriptor bytes in windows attributes and convert to generic attributes.
+	genericAttributes, err := WindowsAttrsToGenericAttributes(WindowsAttributes{CreationTime: nil, FileAttributes: nil, SecurityDescriptor: &sdInputBytes})
+	test.OK(t, errors.Wrapf(err, "Error constructing windows attributes for: %s", fileName))
+	// Construct a Node with the generic attributes.
+	expectedNode := getNode(fileName, fileType, genericAttributes)
+
+	// Restore the file/dir and restore the meta data including the security descriptors.
+	testPath, node := restoreAndGetNode(t, tempDir, expectedNode, false)
+	// Get the security descriptor from the node constructed from the file info of the restored path.
+	sdByteFromRestoredNode := getWindowsAttr(t, testPath, node).SecurityDescriptor
+
+	// Get the security descriptor for the test path after the restore.
+	sdBytesFromRestoredPath, err := fs.GetSecurityDescriptor(testPath)
+	test.OK(t, errors.Wrapf(err, "Error while getting the security descriptor for: %s", testPath))
+
+	// Compare the input SD and the SD got from the restored file.
+	fs.CompareSecurityDescriptors(t, testPath, sdInputBytes, *sdBytesFromRestoredPath)
+	// Compare the SD got from node constructed from the restored file info and the SD got directly from the restored file.
+	fs.CompareSecurityDescriptors(t, testPath, *sdByteFromRestoredNode, *sdBytesFromRestoredPath)
+}
+
+func getNode(name string, fileType string, genericAttributes map[GenericAttributeType]json.RawMessage) Node {
+	return Node{
+		Name:              name,
+		Type:              fileType,
+		Mode:              0644,
+		ModTime:           parseTime("2024-02-21 6:30:01.111"),
+		AccessTime:        parseTime("2024-02-22 7:31:02.222"),
+		ChangeTime:        parseTime("2024-02-23 8:32:03.333"),
+		GenericAttributes: genericAttributes,
+	}
+}
+
+func getWindowsAttr(t *testing.T, testPath string, node *Node) WindowsAttributes {
+	windowsAttributes, unknownAttribs, err := genericAttributesToWindowsAttrs(node.GenericAttributes)
+	test.OK(t, errors.Wrapf(err, "Error getting windows attr from generic attr: %s", testPath))
+	test.Assert(t, len(unknownAttribs) == 0, "Unkown attribs found: %s for: %s", unknownAttribs, testPath)
+	return windowsAttributes
+}
+
 func TestRestoreCreationTime(t *testing.T) {
 	t.Parallel()
 	path := t.TempDir()