This adds a folder option "CopyOwnershipFromParent" which, when set, makes Syncthing attempt to retain the owner/group information when syncing files. Specifically, at the finisher stage we look at the parent dir to get owner/group and then attempt a Lchown call on the temp file. For this to succeed Syncthing must be running with the appropriate permissions. On Linux this is CAP_FOWNER, which can be granted by the service manager on startup or set on the binary in the filesystem. Other operating systems do other things, but often it's not required to run as full "root". On Windows this patch does nothing - ownership works differently there and is generally less of a deal, as permissions are inherited as ACLs anyway. There are unit tests on the Lchown functionality, which requires the above permissions to run. There is also a unit test on the folder which uses the fake filesystem and hence does not need special permissions.
337 lines
7.9 KiB
Go
337 lines
7.9 KiB
Go
// Copyright (C) 2016 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package fs
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import (
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"errors"
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"os"
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"path/filepath"
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"runtime"
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"strings"
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"time"
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"github.com/calmh/du"
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)
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var (
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ErrInvalidFilename = errors.New("filename is invalid")
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ErrNotRelative = errors.New("not a relative path")
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)
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// The BasicFilesystem implements all aspects by delegating to package os.
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// All paths are relative to the root and cannot (should not) escape the root directory.
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type BasicFilesystem struct {
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root string
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}
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func newBasicFilesystem(root string) *BasicFilesystem {
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// The reason it's done like this:
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// C: -> C:\ -> C:\ (issue that this is trying to fix)
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// C:\somedir -> C:\somedir\ -> C:\somedir
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// C:\somedir\ -> C:\somedir\\ -> C:\somedir
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// This way in the tests, we get away without OS specific separators
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// in the test configs.
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sep := string(filepath.Separator)
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root = filepath.Dir(root + sep)
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// Attempt tilde expansion; leave unchanged in case of error
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if path, err := ExpandTilde(root); err == nil {
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root = path
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}
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// Attempt absolutification; leave unchanged in case of error
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if !filepath.IsAbs(root) {
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// Abs() looks like a fairly expensive syscall on Windows, while
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// IsAbs() is a whole bunch of string mangling. I think IsAbs() may be
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// somewhat faster in the general case, hence the outer if...
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if path, err := filepath.Abs(root); err == nil {
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root = path
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}
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}
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// Attempt to enable long filename support on Windows. We may still not
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// have an absolute path here if the previous steps failed.
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if runtime.GOOS == "windows" {
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root = longFilenameSupport(root)
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}
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return &BasicFilesystem{root}
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}
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// rooted expands the relative path to the full path that is then used with os
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// package. If the relative path somehow causes the final path to escape the root
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// directory, this returns an error, to prevent accessing files that are not in the
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// shared directory.
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func (f *BasicFilesystem) rooted(rel string) (string, error) {
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return rooted(rel, f.root)
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}
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func rooted(rel, root string) (string, error) {
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// The root must not be empty.
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if root == "" {
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return "", ErrInvalidFilename
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}
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var err error
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// Takes care that rel does not try to escape
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rel, err = Canonicalize(rel)
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if err != nil {
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return "", err
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}
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return filepath.Join(root, rel), nil
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}
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func (f *BasicFilesystem) unrooted(path string) string {
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return rel(path, f.root)
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}
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func (f *BasicFilesystem) Chmod(name string, mode FileMode) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.Chmod(name, os.FileMode(mode))
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}
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func (f *BasicFilesystem) Lchown(name string, uid, gid int) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.Lchown(name, uid, gid)
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}
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func (f *BasicFilesystem) Chtimes(name string, atime time.Time, mtime time.Time) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.Chtimes(name, atime, mtime)
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}
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func (f *BasicFilesystem) Mkdir(name string, perm FileMode) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.Mkdir(name, os.FileMode(perm))
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}
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// MkdirAll creates a directory named path, along with any necessary parents,
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// and returns nil, or else returns an error.
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// The permission bits perm are used for all directories that MkdirAll creates.
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// If path is already a directory, MkdirAll does nothing and returns nil.
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func (f *BasicFilesystem) MkdirAll(path string, perm FileMode) error {
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path, err := f.rooted(path)
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if err != nil {
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return err
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}
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return f.mkdirAll(path, os.FileMode(perm))
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}
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func (f *BasicFilesystem) Lstat(name string) (FileInfo, error) {
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name, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fi, err := underlyingLstat(name)
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if err != nil {
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return nil, err
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}
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return fsFileInfo{fi}, err
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}
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func (f *BasicFilesystem) Remove(name string) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.Remove(name)
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}
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func (f *BasicFilesystem) RemoveAll(name string) error {
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name, err := f.rooted(name)
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if err != nil {
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return err
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}
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return os.RemoveAll(name)
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}
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func (f *BasicFilesystem) Rename(oldpath, newpath string) error {
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oldpath, err := f.rooted(oldpath)
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if err != nil {
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return err
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}
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newpath, err = f.rooted(newpath)
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if err != nil {
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return err
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}
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return os.Rename(oldpath, newpath)
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}
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func (f *BasicFilesystem) Stat(name string) (FileInfo, error) {
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name, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fi, err := os.Stat(name)
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if err != nil {
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return nil, err
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}
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return fsFileInfo{fi}, err
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}
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func (f *BasicFilesystem) DirNames(name string) ([]string, error) {
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name, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fd, err := os.OpenFile(name, OptReadOnly, 0777)
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if err != nil {
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return nil, err
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}
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defer fd.Close()
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names, err := fd.Readdirnames(-1)
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if err != nil {
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return nil, err
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}
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return names, nil
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}
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func (f *BasicFilesystem) Open(name string) (File, error) {
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rootedName, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fd, err := os.Open(rootedName)
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if err != nil {
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return nil, err
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}
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return fsFile{fd, name}, err
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}
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func (f *BasicFilesystem) OpenFile(name string, flags int, mode FileMode) (File, error) {
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rootedName, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fd, err := os.OpenFile(rootedName, flags, os.FileMode(mode))
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if err != nil {
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return nil, err
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}
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return fsFile{fd, name}, err
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}
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func (f *BasicFilesystem) Create(name string) (File, error) {
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rootedName, err := f.rooted(name)
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if err != nil {
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return nil, err
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}
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fd, err := os.Create(rootedName)
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if err != nil {
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return nil, err
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}
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return fsFile{fd, name}, err
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}
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func (f *BasicFilesystem) Walk(root string, walkFn WalkFunc) error {
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// implemented in WalkFilesystem
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return errors.New("not implemented")
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}
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func (f *BasicFilesystem) Glob(pattern string) ([]string, error) {
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pattern, err := f.rooted(pattern)
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if err != nil {
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return nil, err
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}
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files, err := filepath.Glob(pattern)
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unrooted := make([]string, len(files))
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for i := range files {
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unrooted[i] = f.unrooted(files[i])
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}
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return unrooted, err
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}
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func (f *BasicFilesystem) Usage(name string) (Usage, error) {
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name, err := f.rooted(name)
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if err != nil {
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return Usage{}, err
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}
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u, err := du.Get(name)
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return Usage{
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Free: u.FreeBytes,
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Total: u.TotalBytes,
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}, err
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}
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func (f *BasicFilesystem) Type() FilesystemType {
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return FilesystemTypeBasic
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}
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func (f *BasicFilesystem) URI() string {
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return strings.TrimPrefix(f.root, `\\?\`)
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}
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func (f *BasicFilesystem) SameFile(fi1, fi2 FileInfo) bool {
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// Like os.SameFile, we always return false unless fi1 and fi2 were created
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// by this package's Stat/Lstat method.
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f1, ok1 := fi1.(fsFileInfo)
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f2, ok2 := fi2.(fsFileInfo)
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if !ok1 || !ok2 {
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return false
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}
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return os.SameFile(f1.FileInfo, f2.FileInfo)
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}
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// fsFile implements the fs.File interface on top of an os.File
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type fsFile struct {
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*os.File
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name string
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}
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func (f fsFile) Name() string {
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return f.name
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}
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func (f fsFile) Stat() (FileInfo, error) {
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info, err := f.File.Stat()
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if err != nil {
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return nil, err
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}
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return fsFileInfo{info}, nil
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}
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// fsFileInfo implements the fs.FileInfo interface on top of an os.FileInfo.
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type fsFileInfo struct {
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os.FileInfo
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}
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func (e fsFileInfo) IsSymlink() bool {
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// Must use fsFileInfo.Mode() because it may apply magic.
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return e.Mode()&ModeSymlink != 0
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}
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func (e fsFileInfo) IsRegular() bool {
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// Must use fsFileInfo.Mode() because it may apply magic.
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return e.Mode()&ModeType == 0
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}
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// longFilenameSupport adds the necessary prefix to the path to enable long
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// filename support on windows if necessary.
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// This does NOT check the current system, i.e. will also take effect on unix paths.
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func longFilenameSupport(path string) string {
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if filepath.IsAbs(path) && !strings.HasPrefix(path, `\\`) {
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return `\\?\` + path
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}
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return path
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}
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