syncthing/lib/fs/basicfs.go

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// Copyright (C) 2016 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package fs
import (
"errors"
"os"
"path/filepath"
"runtime"
"strings"
"time"
"github.com/calmh/du"
)
var (
ErrInvalidFilename = errors.New("filename is invalid")
ErrNotRelative = errors.New("not a relative path")
)
// The BasicFilesystem implements all aspects by delegating to package os.
// All paths are relative to the root and cannot (should not) escape the root directory.
type BasicFilesystem struct {
root string
}
func newBasicFilesystem(root string) *BasicFilesystem {
// The reason it's done like this:
// C: -> C:\ -> C:\ (issue that this is trying to fix)
// C:\somedir -> C:\somedir\ -> C:\somedir
// C:\somedir\ -> C:\somedir\\ -> C:\somedir
// This way in the tests, we get away without OS specific separators
// in the test configs.
root = filepath.Dir(root + string(filepath.Separator))
// Attempt tilde expansion; leave unchanged in case of error
if path, err := ExpandTilde(root); err == nil {
root = path
}
// Attempt absolutification; leave unchanged in case of error
if !filepath.IsAbs(root) {
// Abs() looks like a fairly expensive syscall on Windows, while
// IsAbs() is a whole bunch of string mangling. I think IsAbs() may be
// somewhat faster in the general case, hence the outer if...
if path, err := filepath.Abs(root); err == nil {
root = path
}
}
// Attempt to enable long filename support on Windows. We may still not
// have an absolute path here if the previous steps failed.
if runtime.GOOS == "windows" {
if filepath.IsAbs(root) && !strings.HasPrefix(root, `\\`) {
root = `\\?\` + root
}
// If we're not on Windows, we want the path to end with a slash to
// penetrate symlinks. On Windows, paths must not end with a slash.
} else if root[len(root)-1] != filepath.Separator {
root = root + string(filepath.Separator)
}
return &BasicFilesystem{
root: root,
}
}
// rooted expands the relative path to the full path that is then used with os
// package. If the relative path somehow causes the final path to escape the root
// directory, this returns an error, to prevent accessing files that are not in the
// shared directory.
func (f *BasicFilesystem) rooted(rel string) (string, error) {
// The root must not be empty.
if f.root == "" {
return "", ErrInvalidFilename
}
pathSep := string(PathSeparator)
// The expected prefix for the resulting path is the root, with a path
// separator at the end.
expectedPrefix := filepath.FromSlash(f.root)
if !strings.HasSuffix(expectedPrefix, pathSep) {
expectedPrefix += pathSep
}
// The relative path should be clean from internal dotdots and similar
// funkyness.
rel = filepath.FromSlash(rel)
if filepath.Clean(rel) != rel {
return "", ErrInvalidFilename
}
// It is not acceptable to attempt to traverse upwards.
switch rel {
case "..", pathSep:
return "", ErrNotRelative
}
if strings.HasPrefix(rel, ".."+pathSep) {
return "", ErrNotRelative
}
if strings.HasPrefix(rel, pathSep+pathSep) {
// The relative path may pretend to be an absolute path within the
// root, but the double path separator on Windows implies something
// else. It would get cleaned by the Join below, but it's out of
// spec anyway.
return "", ErrNotRelative
}
// The supposedly correct path is the one filepath.Join will return, as
// it does cleaning and so on. Check that one first to make sure no
// obvious escape attempts have been made.
joined := filepath.Join(f.root, rel)
if rel == "." && !strings.HasSuffix(joined, pathSep) {
joined += pathSep
}
if !strings.HasPrefix(joined, expectedPrefix) {
return "", ErrNotRelative
}
return joined, nil
}
func (f *BasicFilesystem) unrooted(path string) string {
return strings.TrimPrefix(strings.TrimPrefix(path, f.root), string(PathSeparator))
}
func (f *BasicFilesystem) Chmod(name string, mode FileMode) error {
name, err := f.rooted(name)
if err != nil {
return err
}
return os.Chmod(name, os.FileMode(mode))
}
func (f *BasicFilesystem) Chtimes(name string, atime time.Time, mtime time.Time) error {
name, err := f.rooted(name)
if err != nil {
return err
}
return os.Chtimes(name, atime, mtime)
}
func (f *BasicFilesystem) Mkdir(name string, perm FileMode) error {
name, err := f.rooted(name)
if err != nil {
return err
}
return os.Mkdir(name, os.FileMode(perm))
}
func (f *BasicFilesystem) Lstat(name string) (FileInfo, error) {
name, err := f.rooted(name)
if err != nil {
return nil, err
}
fi, err := underlyingLstat(name)
if err != nil {
return nil, err
}
return fsFileInfo{fi}, err
}
func (f *BasicFilesystem) Remove(name string) error {
name, err := f.rooted(name)
if err != nil {
return err
}
return os.Remove(name)
}
func (f *BasicFilesystem) RemoveAll(name string) error {
name, err := f.rooted(name)
if err != nil {
return err
}
return os.RemoveAll(name)
}
func (f *BasicFilesystem) Rename(oldpath, newpath string) error {
oldpath, err := f.rooted(oldpath)
if err != nil {
return err
}
newpath, err = f.rooted(newpath)
if err != nil {
return err
}
return os.Rename(oldpath, newpath)
}
func (f *BasicFilesystem) Stat(name string) (FileInfo, error) {
name, err := f.rooted(name)
if err != nil {
return nil, err
}
fi, err := os.Stat(name)
if err != nil {
return nil, err
}
return fsFileInfo{fi}, err
}
func (f *BasicFilesystem) DirNames(name string) ([]string, error) {
name, err := f.rooted(name)
if err != nil {
return nil, err
}
fd, err := os.OpenFile(name, OptReadOnly, 0777)
if err != nil {
return nil, err
}
defer fd.Close()
names, err := fd.Readdirnames(-1)
if err != nil {
return nil, err
}
return names, nil
}
func (f *BasicFilesystem) Open(name string) (File, error) {
rootedName, err := f.rooted(name)
if err != nil {
return nil, err
}
fd, err := os.Open(rootedName)
if err != nil {
return nil, err
}
return fsFile{fd, name}, err
}
func (f *BasicFilesystem) OpenFile(name string, flags int, mode FileMode) (File, error) {
rootedName, err := f.rooted(name)
if err != nil {
return nil, err
}
fd, err := os.OpenFile(rootedName, flags, os.FileMode(mode))
if err != nil {
return nil, err
}
return fsFile{fd, name}, err
}
func (f *BasicFilesystem) Create(name string) (File, error) {
rootedName, err := f.rooted(name)
if err != nil {
return nil, err
}
fd, err := os.Create(rootedName)
if err != nil {
return nil, err
}
return fsFile{fd, name}, err
}
func (f *BasicFilesystem) Walk(root string, walkFn WalkFunc) error {
// implemented in WalkFilesystem
return errors.New("not implemented")
}
func (f *BasicFilesystem) Glob(pattern string) ([]string, error) {
pattern, err := f.rooted(pattern)
if err != nil {
return nil, err
}
files, err := filepath.Glob(pattern)
unrooted := make([]string, len(files))
for i := range files {
unrooted[i] = f.unrooted(files[i])
}
return unrooted, err
}
func (f *BasicFilesystem) Usage(name string) (Usage, error) {
name, err := f.rooted(name)
if err != nil {
return Usage{}, err
}
u, err := du.Get(name)
return Usage{
Free: u.FreeBytes,
Total: u.TotalBytes,
}, err
}
func (f *BasicFilesystem) Type() FilesystemType {
return FilesystemTypeBasic
}
func (f *BasicFilesystem) URI() string {
return strings.TrimPrefix(f.root, `\\?\`)
}
// fsFile implements the fs.File interface on top of an os.File
type fsFile struct {
*os.File
name string
}
func (f fsFile) Name() string {
return f.name
}
func (f fsFile) Stat() (FileInfo, error) {
info, err := f.File.Stat()
if err != nil {
return nil, err
}
return fsFileInfo{info}, nil
}
// fsFileInfo implements the fs.FileInfo interface on top of an os.FileInfo.
type fsFileInfo struct {
os.FileInfo
}
func (e fsFileInfo) Mode() FileMode {
return FileMode(e.FileInfo.Mode())
}
func (e fsFileInfo) IsRegular() bool {
return e.FileInfo.Mode().IsRegular()
}
func (e fsFileInfo) IsSymlink() bool {
return e.FileInfo.Mode()&os.ModeSymlink == os.ModeSymlink
}