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restic/internal/fs/file_windows.go
Michael Eischer c01b655229 backup: fix reading xattrs on Windows for root disks as regular user
Unprivileged users cannot open the root disks with write permissions for
xattrs. Thus, only request read permissions for reading the xattrs.
2024-06-26 20:13:50 +02:00

126 lines
3.6 KiB
Go

package fs
import (
"math/rand"
"os"
"path/filepath"
"strconv"
"strings"
"time"
"golang.org/x/sys/windows"
)
// fixpath returns an absolute path on windows, so restic can open long file
// names.
func fixpath(name string) string {
abspath, err := filepath.Abs(name)
if err == nil {
// Check if \\?\UNC\ already exist
if strings.HasPrefix(abspath, `\\?\UNC\`) {
return abspath
}
// Check if \\?\ already exist
if strings.HasPrefix(abspath, `\\?\`) {
return abspath
}
// Check if path starts with \\
if strings.HasPrefix(abspath, `\\`) {
return strings.Replace(abspath, `\\`, `\\?\UNC\`, 1)
}
// Normal path
return `\\?\` + abspath
}
return name
}
// TempFile creates a temporary file which is marked as delete-on-close
func TempFile(dir, prefix string) (f *os.File, err error) {
// slightly modified implementation of os.CreateTemp(dir, prefix) to allow us to add
// the FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE flags.
// These provide two large benefits:
// FILE_ATTRIBUTE_TEMPORARY tells Windows to keep the file in memory only if possible
// which reduces the amount of unnecessary disk writes.
// FILE_FLAG_DELETE_ON_CLOSE instructs Windows to automatically delete the file once
// all file descriptors are closed.
if dir == "" {
dir = os.TempDir()
}
access := uint32(windows.GENERIC_READ | windows.GENERIC_WRITE)
creation := uint32(windows.CREATE_NEW)
share := uint32(0) // prevent other processes from accessing the file
flags := uint32(windows.FILE_ATTRIBUTE_TEMPORARY | windows.FILE_FLAG_DELETE_ON_CLOSE)
rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
for i := 0; i < 10000; i++ {
randSuffix := strconv.Itoa(int(1e9 + rnd.Intn(1e9)%1e9))[1:]
path := filepath.Join(dir, prefix+randSuffix)
ptr, err := windows.UTF16PtrFromString(path)
if err != nil {
return nil, err
}
h, err := windows.CreateFile(ptr, access, share, nil, creation, flags, 0)
if os.IsExist(err) {
continue
}
return os.NewFile(uintptr(h), path), err
}
// Proper error handling is still to do
return nil, os.ErrExist
}
// Chmod changes the mode of the named file to mode.
func Chmod(name string, mode os.FileMode) error {
return os.Chmod(fixpath(name), mode)
}
// ClearSystem removes the system attribute from the file.
func ClearSystem(path string) error {
return ClearAttribute(path, windows.FILE_ATTRIBUTE_SYSTEM)
}
// ClearAttribute removes the specified attribute from the file.
func ClearAttribute(path string, attribute uint32) error {
ptr, err := windows.UTF16PtrFromString(path)
if err != nil {
return err
}
fileAttributes, err := windows.GetFileAttributes(ptr)
if err != nil {
return err
}
if fileAttributes&attribute != 0 {
// Clear the attribute
fileAttributes &= ^uint32(attribute)
err = windows.SetFileAttributes(ptr, fileAttributes)
if err != nil {
return err
}
}
return nil
}
// OpenHandleForEA return a file handle for file or dir for setting/getting EAs
func OpenHandleForEA(nodeType, path string, writeAccess bool) (handle windows.Handle, err error) {
path = fixpath(path)
fileAccess := windows.FILE_READ_EA
if writeAccess {
fileAccess = fileAccess | windows.FILE_WRITE_EA
}
switch nodeType {
case "file":
utf16Path := windows.StringToUTF16Ptr(path)
handle, err = windows.CreateFile(utf16Path, uint32(fileAccess), 0, nil, windows.OPEN_EXISTING, windows.FILE_ATTRIBUTE_NORMAL, 0)
case "dir":
utf16Path := windows.StringToUTF16Ptr(path)
handle, err = windows.CreateFile(utf16Path, uint32(fileAccess), 0, nil, windows.OPEN_EXISTING, windows.FILE_ATTRIBUTE_NORMAL|windows.FILE_FLAG_BACKUP_SEMANTICS, 0)
default:
return 0, nil
}
return handle, err
}