109 lines
2.8 KiB
Go
109 lines
2.8 KiB
Go
package utils
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import (
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"errors"
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"io/fs"
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"os"
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"runtime"
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)
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// DirFS returns a file system (an fs.FS) for the tree of files rooted at the directory dir.
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//
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// Note that DirFS("/prefix") only guarantees that the Open calls it makes to the
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// operating system will begin with "/prefix": DirFS("/prefix").Open("file") is the
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// same as os.Open("/prefix/file"). So if /prefix/file is a symbolic link pointing outside
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// the /prefix tree, then using DirFS does not stop the access any more than using
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// os.Open does. Additionally, the root of the fs.FS returned for a relative path,
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// DirFS("prefix"), will be affected by later calls to Chdir. DirFS is therefore not
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// a general substitute for a chroot-style security mechanism when the directory tree
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// contains arbitrary content.
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//
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// The result implements fs.StatFS AND fs.ReadDirFS because god dammit why not.
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//
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// Implementation copy-pasted from Go 1.20.2.
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func DirFS(dir string) fs.FS {
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return dirFS(dir)
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}
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type dirFS string
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var _ fs.StatFS = dirFS("")
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var _ fs.ReadDirFS = dirFS("")
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func (dir dirFS) Open(name string) (fs.File, error) {
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fullname, err := dir.join(name)
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if err != nil {
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return nil, &os.PathError{Op: "stat", Path: name, Err: err}
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}
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f, err := os.Open(fullname)
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if err != nil {
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// DirFS takes a string appropriate for GOOS,
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// while the name argument here is always slash separated.
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// dir.join will have mixed the two; undo that for
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// error reporting.
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err.(*os.PathError).Path = name
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return nil, err
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}
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return f, nil
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}
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func (dir dirFS) Stat(name string) (fs.FileInfo, error) {
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fullname, err := dir.join(name)
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if err != nil {
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return nil, &os.PathError{Op: "stat", Path: name, Err: err}
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}
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f, err := os.Stat(fullname)
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if err != nil {
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// See comment in dirFS.Open.
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err.(*os.PathError).Path = name
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return nil, err
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}
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return f, nil
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}
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func (dir dirFS) ReadDir(name string) ([]fs.DirEntry, error) {
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fullname, err := dir.join(name)
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if err != nil {
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return nil, &os.PathError{Op: "stat", Path: name, Err: err}
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}
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d, err := os.ReadDir(fullname)
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if err != nil {
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// See comment in dirFS.Open.
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err.(*os.PathError).Path = name
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return nil, err
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}
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return d, nil
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}
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func fromFS(path string) (string, error) {
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if runtime.GOOS == "plan9" {
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if len(path) > 0 && path[0] == '#' {
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return "", os.ErrInvalid
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}
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}
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for i := range path {
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if path[i] == 0 {
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return "", os.ErrInvalid
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}
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}
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return path, nil
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}
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// join returns the path for name in dir.
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func (dir dirFS) join(name string) (string, error) {
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if dir == "" {
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return "", errors.New("os: DirFS with empty root")
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}
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if !fs.ValidPath(name) {
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return "", os.ErrInvalid
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}
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name, err := fromFS(name)
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if err != nil {
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return "", os.ErrInvalid
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}
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if os.IsPathSeparator(dir[len(dir)-1]) {
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return string(dir) + name, nil
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}
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return string(dir) + string(os.PathSeparator) + name, nil
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}
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