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x/tools/godoc/vfs: adds NewNameSpace() and emptyVFS for better behavior
The existing implementation of NameSpace implicitly assumes that a FileSystem with a directory at the top will be mounted at the root mount point "/" of the NameSpace. If this is not the case, then Stat("/") will fail even if ReadDir("/") succeedes. This is unexpected behavior which breaks directory traversal routines (eg. http.FileServer). This CL adds an unexported implementation of FileSystem called emptyVFS that emulates an empty directory and adds a NewNameSpace() function that binds emptyVFS to "/" so that unexpected behavior does not arise even if the use does not mount anything explicitly at "/". Latest patch set causes the FileInfo of the empty top level emulated directory to return "/" for Name() and Zero Time for ModTime() and removes the related struct state fields being used in the previous implementation. Fixes golang/go#14190 Change-Id: Idce2fc3c9b81206847a33840d76b660059d53d18 Reviewed-on: https://go-review.googlesource.com/19445 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
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85
godoc/vfs/emptyvfs.go
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85
godoc/vfs/emptyvfs.go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package vfs
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import (
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"fmt"
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"os"
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"time"
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)
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// NewNameSpace returns a NameSpace pre-initialized with an empty
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// emulated directory mounted on the root mount point "/". This
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// allows directory traversal routines to work properly even if
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// a folder is not explicitly mounted at root by the user.
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func NewNameSpace() NameSpace {
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ns := NameSpace{}
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ns.Bind("/", &emptyVFS{}, "/", BindReplace)
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return ns
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}
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// type emptyVFS emulates a FileSystem consisting of an empty directory
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type emptyVFS struct{}
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// Open implements Opener. Since emptyVFS is an empty directory, all
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// attempts to open a file should returns errors.
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func (e *emptyVFS) Open(path string) (ReadSeekCloser, error) {
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if path == "/" {
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return nil, fmt.Errorf("open: / is a directory")
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}
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return nil, os.ErrNotExist
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}
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// Stat returns os.FileInfo for an empty directory if the path is
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// is root "/" or error. os.FileInfo is implemented by emptyVFS
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func (e *emptyVFS) Stat(path string) (os.FileInfo, error) {
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if path == "/" {
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return e, nil
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}
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return nil, os.ErrNotExist
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}
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func (e *emptyVFS) Lstat(path string) (os.FileInfo, error) {
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return e.Stat(path)
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}
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// ReadDir returns an empty os.FileInfo slice for "/", else error.
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func (e *emptyVFS) ReadDir(path string) ([]os.FileInfo, error) {
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if path == "/" {
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return []os.FileInfo{}, nil
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}
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return nil, os.ErrNotExist
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}
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func (e *emptyVFS) String() string {
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return "emptyVFS(/)"
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}
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// These functions below implement os.FileInfo for the single
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// empty emulated directory.
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func (e *emptyVFS) Name() string {
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return "/"
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}
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func (e *emptyVFS) Size() int64 {
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return 0
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}
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func (e *emptyVFS) Mode() os.FileMode {
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return os.ModeDir | os.ModePerm
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}
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func (e *emptyVFS) ModTime() time.Time {
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return time.Time{}
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}
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func (e *emptyVFS) IsDir() bool {
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return true
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}
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func (e *emptyVFS) Sys() interface{} {
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return nil
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}
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57
godoc/vfs/emptyvfs_test.go
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57
godoc/vfs/emptyvfs_test.go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package vfs_test
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import (
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"golang.org/x/tools/godoc/vfs"
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"golang.org/x/tools/godoc/vfs/mapfs"
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"testing"
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"time"
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)
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func TestNewNameSpace(t *testing.T) {
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// We will mount this filesystem under /fs1
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mount := mapfs.New(map[string]string{"fs1file": "abcdefgh"})
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// Existing process. This should give error on Stat("/")
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t1 := vfs.NameSpace{}
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t1.Bind("/fs1", mount, "/", vfs.BindReplace)
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// using NewNameSpace. This should work fine.
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t2 := vfs.NewNameSpace()
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t2.Bind("/fs1", mount, "/", vfs.BindReplace)
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testcases := map[string][]bool{
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"/": []bool{false, true},
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"/fs1": []bool{true, true},
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"/fs1/fs1file": []bool{true, true},
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}
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fss := []vfs.FileSystem{t1, t2}
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for j, fs := range fss {
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for k, v := range testcases {
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_, err := fs.Stat(k)
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result := err == nil
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if result != v[j] {
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t.Errorf("fs: %d, testcase: %s, want: %v, got: %v, err: %s", j, k, v[j], result, err)
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}
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}
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}
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fi, err := t2.Stat("/")
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if err != nil {
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t.Fatal(err)
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}
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if fi.Name() != "/" {
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t.Errorf("t2.Name() : want:%s got:%s", "/", fi.Name())
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}
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if !fi.ModTime().IsZero() {
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t.Errorf("t2.Modime() : want:%v got:%v", time.Time{}, fi.ModTime())
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}
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}
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@ -53,6 +53,11 @@ const debugNS = false
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// operate on a path beginning with old, replace that prefix (old) with new
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// operate on a path beginning with old, replace that prefix (old) with new
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// and then pass that path to the FileSystem implementation fs.
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// and then pass that path to the FileSystem implementation fs.
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//
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//
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// If you do not explicitly mount a FileSystem at the root mountpoint "/" of the
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// NameSpace like above, Stat("/") will return a "not found" error which could
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// break typical directory traversal routines. In such cases, use NewNameSpace()
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// to get a NameSpace pre-initialized with an emulated empty directory at root.
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//
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// Given this name space, a ReadDir of /src/pkg/code will check each prefix
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// Given this name space, a ReadDir of /src/pkg/code will check each prefix
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// of the path for a mount point (first /src/pkg/code, then /src/pkg, then /src,
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// of the path for a mount point (first /src/pkg/code, then /src/pkg, then /src,
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// then /), stopping when it finds one. For the above example, /src/pkg/code
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// then /), stopping when it finds one. For the above example, /src/pkg/code
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