syncthing/lib/osutil/traversessymlink.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 osutil
import (
"fmt"
"path/filepath"
"strings"
"github.com/syncthing/syncthing/lib/fs"
)
// TraversesSymlinkError is an error indicating symlink traversal
type TraversesSymlinkError struct {
path string
}
func (e TraversesSymlinkError) Error() string {
return fmt.Sprintf("traverses symlink: %s", e.path)
}
// NotADirectoryError is an error indicating an expected path is not a directory
type NotADirectoryError struct {
path string
}
func (e NotADirectoryError) Error() string {
return fmt.Sprintf("not a directory: %s", e.path)
}
// TraversesSymlink returns an error if base and any path component of name up to and
// including filepath.Join(base, name) traverses a symlink.
// Base and name must both be clean and name must be relative to base.
func TraversesSymlink(filesystem fs.Filesystem, name string) error {
base := "."
path := base
info, err := filesystem.Lstat(path)
if err != nil {
return err
}
if !info.IsDir() {
return &NotADirectoryError{
path: base,
}
}
if name == "." {
// The result of calling TraversesSymlink("some/where", filepath.Dir("foo"))
return nil
}
parts := strings.Split(name, string(fs.PathSeparator))
for _, part := range parts {
path = filepath.Join(path, part)
info, err := filesystem.Lstat(path)
if err != nil {
if fs.IsNotExist(err) {
return nil
}
return err
}
if info.IsSymlink() {
return &TraversesSymlinkError{
path: strings.TrimPrefix(path, base),
}
}
if !info.IsDir() {
return &NotADirectoryError{
path: strings.TrimPrefix(path, base),
}
}
}
return nil
}