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chroot_fs.go
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chroot_fs.go
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package syslutil
import (
"errors"
"os"
"path/filepath"
"strings"
"time"
"github.com/spf13/afero"
)
type ChrootFs struct {
fs afero.Fs
root string
}
var _ afero.Fs = &ChrootFs{}
// NewChrootFs returns a filesystem that is rooted at root argument
func NewChrootFs(fs afero.Fs, root string) *ChrootFs {
if !filepath.IsAbs(root) {
var err error
root, err = filepath.Abs(root)
if err != nil {
panic(err)
}
}
return &ChrootFs{fs: fs, root: root}
}
func (fs *ChrootFs) join(name string) (string, error) {
// this is to avoid windows joining volume name twice in a nested fs
volumeName := filepath.VolumeName(name)
if volumeName != "" {
name = strings.TrimLeft(name, volumeName)
}
return filepath.Abs(filepath.Join(fs.root, name))
}
func (fs *ChrootFs) Create(name string) (afero.File, error) {
data, err := fs.wrapCallWithData(name,
func(fixedPath string) (interface{}, error) {
return fs.fs.Create(fixedPath)
})
if err != nil {
return nil, err
}
return data.(afero.File), err
}
func (fs *ChrootFs) Mkdir(name string, perm os.FileMode) error {
return fs.wrapCall(name, func(fixedPath string) error {
return fs.fs.Mkdir(fixedPath, perm)
})
}
func (fs *ChrootFs) MkdirAll(path string, perm os.FileMode) error {
return fs.wrapCall(path, func(fixedPath string) error {
return fs.fs.MkdirAll(fixedPath, perm)
})
}
func (fs *ChrootFs) Open(name string) (afero.File, error) {
data, err := fs.wrapCallWithData(name,
func(fixedPath string) (interface{}, error) {
return fs.fs.Open(fixedPath)
})
if err != nil {
return nil, err
}
return data.(afero.File), err
}
func (fs *ChrootFs) OpenFile(name string, flag int, perm os.FileMode) (afero.File, error) {
data, err := fs.wrapCallWithData(name,
func(fixedPath string) (interface{}, error) {
return fs.fs.OpenFile(fixedPath, flag, perm)
})
if err != nil {
return nil, err
}
return data.(afero.File), err
}
func (fs *ChrootFs) Remove(name string) error {
return fs.wrapCall(name, func(fixedPath string) error {
return fs.fs.Remove(fixedPath)
})
}
func (fs *ChrootFs) RemoveAll(path string) error {
return fs.wrapCall(path, func(fixedPath string) error {
return fs.fs.RemoveAll(fixedPath)
})
}
func (fs *ChrootFs) Rename(oldname, newname string) error {
return fs.wrapCall(oldname, func(fixedPath string) error {
newFile, err := fs.join(newname)
if err != nil {
return err
}
return fs.fs.Rename(fixedPath, newFile)
})
}
func (fs *ChrootFs) Stat(name string) (os.FileInfo, error) {
data, err := fs.wrapCallWithData(name,
func(fixedPath string) (interface{}, error) {
return fs.fs.Stat(fixedPath)
})
if err != nil {
return nil, err
}
return data.(os.FileInfo), err
}
func (fs *ChrootFs) Name() string {
return "ChrootFS"
}
func (fs *ChrootFs) Chmod(name string, mode os.FileMode) error {
return fs.wrapCall(name, func(fixedPath string) error {
return fs.fs.Chmod(fixedPath, mode)
})
}
func (fs *ChrootFs) Chtimes(name string, atime time.Time, mtime time.Time) error {
return fs.wrapCall(name, func(fixedPath string) error {
return fs.fs.Chtimes(fixedPath, atime, mtime)
})
}
func (fs *ChrootFs) openAllowed(fullPath string) error {
relativePath, err := filepath.Rel(fs.root, fullPath)
if err != nil {
return err
}
if relativePath != "" && strings.Split(relativePath, string(os.PathSeparator))[0] == ".." {
return errors.New("permission denied, file outside root")
}
return nil
}
func (fs *ChrootFs) wrapCall(path string, fn func(string) error) error {
filename, err := fs.join(path)
if err != nil {
return err
}
if err := fs.openAllowed(filename); err != nil {
return err
}
return fn(filename)
}
func (fs *ChrootFs) wrapCallWithData(
path string,
fn func(string) (interface{}, error)) (interface{}, error) {
filename, err := fs.join(path)
if err != nil {
return nil, err
}
if err := fs.openAllowed(filename); err != nil {
return nil, err
}
return fn(filename)
}