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.
251 lines
6.3 KiB
Go
251 lines
6.3 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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"context"
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"errors"
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"io"
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"os"
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"path/filepath"
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"strings"
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"time"
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)
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// The Filesystem interface abstracts access to the file system.
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type Filesystem interface {
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Chmod(name string, mode FileMode) error
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Lchown(name string, uid, gid int) error
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Chtimes(name string, atime time.Time, mtime time.Time) error
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Create(name string) (File, error)
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CreateSymlink(target, name string) error
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DirNames(name string) ([]string, error)
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Lstat(name string) (FileInfo, error)
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Mkdir(name string, perm FileMode) error
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MkdirAll(name string, perm FileMode) error
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Open(name string) (File, error)
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OpenFile(name string, flags int, mode FileMode) (File, error)
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ReadSymlink(name string) (string, error)
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Remove(name string) error
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RemoveAll(name string) error
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Rename(oldname, newname string) error
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Stat(name string) (FileInfo, error)
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SymlinksSupported() bool
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Walk(name string, walkFn WalkFunc) error
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Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error)
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Hide(name string) error
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Unhide(name string) error
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Glob(pattern string) ([]string, error)
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Roots() ([]string, error)
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Usage(name string) (Usage, error)
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Type() FilesystemType
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URI() string
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SameFile(fi1, fi2 FileInfo) bool
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}
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// The File interface abstracts access to a regular file, being a somewhat
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// smaller interface than os.File
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type File interface {
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io.Closer
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io.Reader
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io.ReaderAt
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io.Seeker
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io.Writer
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io.WriterAt
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Name() string
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Truncate(size int64) error
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Stat() (FileInfo, error)
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Sync() error
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}
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// The FileInfo interface is almost the same as os.FileInfo, but with the
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// Sys method removed (as we don't want to expose whatever is underlying)
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// and with a couple of convenience methods added.
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type FileInfo interface {
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// Standard things present in os.FileInfo
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Name() string
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Mode() FileMode
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Size() int64
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ModTime() time.Time
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IsDir() bool
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// Extensions
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IsRegular() bool
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IsSymlink() bool
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Owner() int
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Group() int
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}
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// FileMode is similar to os.FileMode
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type FileMode uint32
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func (fm FileMode) String() string {
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return os.FileMode(fm).String()
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}
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// Usage represents filesystem space usage
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type Usage struct {
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Free int64
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Total int64
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}
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type Matcher interface {
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ShouldIgnore(name string) bool
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SkipIgnoredDirs() bool
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}
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type MatchResult interface {
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IsIgnored() bool
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}
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type Event struct {
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Name string
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Type EventType
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}
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type EventType int
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const (
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NonRemove EventType = 1 + iota
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Remove
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Mixed // Should probably not be necessary to be used in filesystem interface implementation
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)
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// Merge returns Mixed, except if evType and other are the same and not Mixed.
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func (evType EventType) Merge(other EventType) EventType {
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return evType | other
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}
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func (evType EventType) String() string {
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switch {
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case evType == NonRemove:
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return "non-remove"
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case evType == Remove:
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return "remove"
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case evType == Mixed:
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return "mixed"
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default:
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panic("bug: Unknown event type")
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}
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}
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var ErrWatchNotSupported = errors.New("watching is not supported")
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// Equivalents from os package.
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const ModePerm = FileMode(os.ModePerm)
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const ModeSetgid = FileMode(os.ModeSetgid)
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const ModeSetuid = FileMode(os.ModeSetuid)
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const ModeSticky = FileMode(os.ModeSticky)
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const ModeSymlink = FileMode(os.ModeSymlink)
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const ModeType = FileMode(os.ModeType)
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const PathSeparator = os.PathSeparator
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const OptAppend = os.O_APPEND
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const OptCreate = os.O_CREATE
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const OptExclusive = os.O_EXCL
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const OptReadOnly = os.O_RDONLY
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const OptReadWrite = os.O_RDWR
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const OptSync = os.O_SYNC
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const OptTruncate = os.O_TRUNC
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const OptWriteOnly = os.O_WRONLY
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// SkipDir is used as a return value from WalkFuncs to indicate that
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// the directory named in the call is to be skipped. It is not returned
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// as an error by any function.
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var SkipDir = filepath.SkipDir
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// IsExist is the equivalent of os.IsExist
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var IsExist = os.IsExist
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// IsNotExist is the equivalent of os.IsNotExist
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var IsNotExist = os.IsNotExist
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// IsPermission is the equivalent of os.IsPermission
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var IsPermission = os.IsPermission
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// IsPathSeparator is the equivalent of os.IsPathSeparator
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var IsPathSeparator = os.IsPathSeparator
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func NewFilesystem(fsType FilesystemType, uri string) Filesystem {
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var fs Filesystem
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switch fsType {
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case FilesystemTypeBasic:
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fs = newBasicFilesystem(uri)
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case FilesystemTypeFake:
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fs = newFakeFilesystem(uri)
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default:
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l.Debugln("Unknown filesystem", fsType, uri)
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fs = &errorFilesystem{
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fsType: fsType,
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uri: uri,
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err: errors.New("filesystem with type " + fsType.String() + " does not exist."),
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}
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}
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if l.ShouldDebug("walkfs") {
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return NewWalkFilesystem(&logFilesystem{fs})
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}
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if l.ShouldDebug("fs") {
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return &logFilesystem{NewWalkFilesystem(fs)}
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}
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return NewWalkFilesystem(fs)
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}
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// IsInternal returns true if the file, as a path relative to the folder
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// root, represents an internal file that should always be ignored. The file
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// path must be clean (i.e., in canonical shortest form).
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func IsInternal(file string) bool {
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// fs cannot import config, so we hard code .stfolder here (config.DefaultMarkerName)
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internals := []string{".stfolder", ".stignore", ".stversions"}
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for _, internal := range internals {
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if file == internal {
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return true
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}
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if IsParent(file, internal) {
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return true
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}
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}
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return false
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}
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// Canonicalize checks that the file path is valid and returns it in the "canonical" form:
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// - /foo/bar -> foo/bar
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// - / -> "."
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func Canonicalize(file string) (string, error) {
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pathSep := string(PathSeparator)
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if strings.HasPrefix(file, pathSep+pathSep) {
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// The relative path may pretend to be an absolute path within
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// the root, but the double path separator on Windows implies
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// something else and is out of spec.
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return "", ErrNotRelative
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}
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// The relative path should be clean from internal dotdots and similar
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// funkyness.
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file = filepath.Clean(file)
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// It is not acceptable to attempt to traverse upwards.
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switch file {
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case "..":
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return "", ErrNotRelative
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}
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if strings.HasPrefix(file, ".."+pathSep) {
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return "", ErrNotRelative
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}
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if strings.HasPrefix(file, pathSep) {
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if file == pathSep {
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return ".", nil
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}
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return file[1:], nil
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}
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return file, nil
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}
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