139 lines
3.3 KiB
Go
139 lines
3.3 KiB
Go
// Copyright (C) 2014 The Syncthing Authors.
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//
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// This program is free software: you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by the Free
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// Software Foundation, either version 3 of the License, or (at your option)
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// any later version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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// more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with this program. If not, see <http://www.gnu.org/licenses/>.
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package symlinks
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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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"github.com/syncthing/syncthing/internal/osutil"
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"github.com/syncthing/syncthing/internal/protocol"
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)
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var (
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Supported = false
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ErrUnsupported = errors.New("symlinks not supported")
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)
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func init() {
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Supported = symlinksSupported()
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}
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func Read(path string) (string, uint32, error) {
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if !Supported {
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return "", 0, ErrUnsupported
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}
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var mode uint32
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stat, err := os.Stat(path)
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if err != nil {
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mode = protocol.FlagSymlinkMissingTarget
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} else if stat.IsDir() {
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mode = protocol.FlagDirectory
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}
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path, err = os.Readlink(path)
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return osutil.NormalizedFilename(path), mode, err
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}
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func IsSymlink(path string) (bool, error) {
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if !Supported {
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return false, ErrUnsupported
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}
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lstat, err := os.Lstat(path)
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if err != nil {
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return false, err
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}
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return lstat.Mode()&os.ModeSymlink != 0, nil
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}
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func Create(target, source string, flags uint32) error {
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if !Supported {
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return ErrUnsupported
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}
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return os.Symlink(osutil.NativeFilename(target), source)
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}
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func ChangeType(path string, flags uint32) error {
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if runtime.GOOS != "windows" {
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// This is a Windows-only concept.
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return nil
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}
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if !Supported {
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return ErrUnsupported
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}
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target, cflags, err := Read(path)
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if err != nil {
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return err
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}
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// If it's the same type, nothing to do.
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if cflags&protocol.SymlinkTypeMask == flags&protocol.SymlinkTypeMask {
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return nil
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}
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// If the actual type is unknown, but the new type is file, nothing to do
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if cflags&protocol.FlagSymlinkMissingTarget != 0 && flags&protocol.FlagDirectory == 0 {
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return nil
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}
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return osutil.InWritableDir(func(path string) error {
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// It should be a symlink as well hence no need to change permissions
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// on the file.
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os.Remove(path)
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return Create(target, path, flags)
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}, path)
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}
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func symlinksSupported() bool {
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if runtime.GOOS != "windows" {
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// Symlinks are supported. In practice there may be deviations (FAT
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// filesystems etc), but these get handled and reported as the errors
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// they are when they happen.
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return true
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}
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// We try to create a symlink and verify that it looks like we expected.
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// Needs administrator priviledges and a version higher than XP.
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base := os.TempDir()
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path := filepath.Join(base, "syncthing-symlink-test")
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defer os.Remove(path)
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err := Create(base, path, protocol.FlagDirectory)
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if err != nil {
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return false
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}
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isLink, err := IsSymlink(path)
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if err != nil || !isLink {
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return false
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}
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target, flags, err := Read(path)
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if err != nil || osutil.NativeFilename(target) != base || flags&protocol.FlagDirectory == 0 {
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return false
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}
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return true
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}
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