blob: ab6c675ec8b352e845785850daa37a82b789d73c [file] [log] [blame]
package sftp
// This serves as an example of how to implement the request server handler as
// well as a dummy backend for testing. It implements an in-memory backend that
// works as a very simple filesystem with simple flat key-value lookup system.
import (
"errors"
"io"
"os"
"path"
"sort"
"strings"
"sync"
"syscall"
"time"
)
const maxSymlinkFollows = 5
var errTooManySymlinks = errors.New("too many symbolic links")
// InMemHandler returns a Hanlders object with the test handlers.
func InMemHandler() Handlers {
root := &root{
rootFile: &memFile{name: "/", modtime: time.Now(), isdir: true},
files: make(map[string]*memFile),
}
return Handlers{root, root, root, root}
}
// Example Handlers
func (fs *root) Fileread(r *Request) (io.ReaderAt, error) {
flags := r.Pflags()
if !flags.Read {
// sanity check
return nil, os.ErrInvalid
}
return fs.OpenFile(r)
}
func (fs *root) Filewrite(r *Request) (io.WriterAt, error) {
flags := r.Pflags()
if !flags.Write {
// sanity check
return nil, os.ErrInvalid
}
return fs.OpenFile(r)
}
func (fs *root) OpenFile(r *Request) (WriterAtReaderAt, error) {
if fs.mockErr != nil {
return nil, fs.mockErr
}
_ = r.WithContext(r.Context()) // initialize context for deadlock testing
fs.mu.Lock()
defer fs.mu.Unlock()
return fs.openfile(r.Filepath, r.Flags)
}
func (fs *root) putfile(pathname string, file *memFile) error {
pathname, err := fs.canonName(pathname)
if err != nil {
return err
}
if !strings.HasPrefix(pathname, "/") {
return os.ErrInvalid
}
if _, err := fs.lfetch(pathname); err != os.ErrNotExist {
return os.ErrExist
}
file.name = pathname
fs.files[pathname] = file
return nil
}
func (fs *root) openfile(pathname string, flags uint32) (*memFile, error) {
pflags := newFileOpenFlags(flags)
file, err := fs.fetch(pathname)
if err == os.ErrNotExist {
if !pflags.Creat {
return nil, os.ErrNotExist
}
var count int
// You can create files through dangling symlinks.
link, err := fs.lfetch(pathname)
for err == nil && link.symlink != "" {
if pflags.Excl {
// unless you also passed in O_EXCL
return nil, os.ErrInvalid
}
if count++; count > maxSymlinkFollows {
return nil, errTooManySymlinks
}
pathname = link.symlink
link, err = fs.lfetch(pathname)
}
file := &memFile{
modtime: time.Now(),
}
if err := fs.putfile(pathname, file); err != nil {
return nil, err
}
return file, nil
}
if err != nil {
return nil, err
}
if pflags.Creat && pflags.Excl {
return nil, os.ErrExist
}
if file.IsDir() {
return nil, os.ErrInvalid
}
if pflags.Trunc {
if err := file.Truncate(0); err != nil {
return nil, err
}
}
return file, nil
}
func (fs *root) Filecmd(r *Request) error {
if fs.mockErr != nil {
return fs.mockErr
}
_ = r.WithContext(r.Context()) // initialize context for deadlock testing
fs.mu.Lock()
defer fs.mu.Unlock()
switch r.Method {
case "Setstat":
file, err := fs.openfile(r.Filepath, sshFxfWrite)
if err != nil {
return err
}
if r.AttrFlags().Size {
return file.Truncate(int64(r.Attributes().Size))
}
return nil
case "Rename":
// SFTP-v2: "It is an error if there already exists a file with the name specified by newpath."
// This varies from the POSIX specification, which allows limited replacement of target files.
if fs.exists(r.Target) {
return os.ErrExist
}
return fs.rename(r.Filepath, r.Target)
case "Rmdir":
return fs.rmdir(r.Filepath)
case "Remove":
// IEEE 1003.1 remove explicitly can unlink files and remove empty directories.
// We use instead here the semantics of unlink, which is allowed to be restricted against directories.
return fs.unlink(r.Filepath)
case "Mkdir":
return fs.mkdir(r.Filepath)
case "Link":
return fs.link(r.Filepath, r.Target)
case "Symlink":
// NOTE: r.Filepath is the target, and r.Target is the linkpath.
return fs.symlink(r.Filepath, r.Target)
}
return errors.New("unsupported")
}
func (fs *root) rename(oldpath, newpath string) error {
file, err := fs.lfetch(oldpath)
if err != nil {
return err
}
newpath, err = fs.canonName(newpath)
if err != nil {
return err
}
if !strings.HasPrefix(newpath, "/") {
return os.ErrInvalid
}
target, err := fs.lfetch(newpath)
if err != os.ErrNotExist {
if target == file {
// IEEE 1003.1: if oldpath and newpath are the same directory entry,
// then return no error, and perform no further action.
return nil
}
switch {
case file.IsDir():
// IEEE 1003.1: if oldpath is a directory, and newpath exists,
// then newpath must be a directory, and empty.
// It is to be removed prior to rename.
if err := fs.rmdir(newpath); err != nil {
return err
}
case target.IsDir():
// IEEE 1003.1: if oldpath is not a directory, and newpath exists,
// then newpath may not be a directory.
return syscall.EISDIR
}
}
fs.files[newpath] = file
if file.IsDir() {
dirprefix := file.name + "/"
for name, file := range fs.files {
if strings.HasPrefix(name, dirprefix) {
newname := path.Join(newpath, strings.TrimPrefix(name, dirprefix))
fs.files[newname] = file
file.name = newname
delete(fs.files, name)
}
}
}
file.name = newpath
delete(fs.files, oldpath)
return nil
}
func (fs *root) PosixRename(r *Request) error {
if fs.mockErr != nil {
return fs.mockErr
}
_ = r.WithContext(r.Context()) // initialize context for deadlock testing
fs.mu.Lock()
defer fs.mu.Unlock()
return fs.rename(r.Filepath, r.Target)
}
func (fs *root) StatVFS(r *Request) (*StatVFS, error) {
if fs.mockErr != nil {
return nil, fs.mockErr
}
return getStatVFSForPath(r.Filepath)
}
func (fs *root) mkdir(pathname string) error {
dir := &memFile{
modtime: time.Now(),
isdir: true,
}
return fs.putfile(pathname, dir)
}
func (fs *root) rmdir(pathname string) error {
// IEEE 1003.1: If pathname is a symlink, then rmdir should fail with ENOTDIR.
dir, err := fs.lfetch(pathname)
if err != nil {
return err
}
if !dir.IsDir() {
return syscall.ENOTDIR
}
// use the dir‘s internal name not the pathname we passed in.
// the dir.name is always the canonical name of a directory.
pathname = dir.name
for name := range fs.files {
if path.Dir(name) == pathname {
return errors.New("directory not empty")
}
}
delete(fs.files, pathname)
return nil
}
func (fs *root) link(oldpath, newpath string) error {
file, err := fs.lfetch(oldpath)
if err != nil {
return err
}
if file.IsDir() {
return errors.New("hard link not allowed for directory")
}
return fs.putfile(newpath, file)
}
// symlink() creates a symbolic link named `linkpath` which contains the string `target`.
// NOTE! This would be called with `symlink(req.Filepath, req.Target)` due to different semantics.
func (fs *root) symlink(target, linkpath string) error {
link := &memFile{
modtime: time.Now(),
symlink: target,
}
return fs.putfile(linkpath, link)
}
func (fs *root) unlink(pathname string) error {
// does not follow symlinks!
file, err := fs.lfetch(pathname)
if err != nil {
return err
}
if file.IsDir() {
// IEEE 1003.1: implementations may opt out of allowing the unlinking of directories.
// SFTP-v2: SSH_FXP_REMOVE may not remove directories.
return os.ErrInvalid
}
// DO NOT use the file’s internal name.
// because of hard-links files cannot have a single canonical name.
delete(fs.files, pathname)
return nil
}
type listerat []os.FileInfo
// Modeled after strings.Reader's ReadAt() implementation
func (f listerat) ListAt(ls []os.FileInfo, offset int64) (int, error) {
var n int
if offset >= int64(len(f)) {
return 0, io.EOF
}
n = copy(ls, f[offset:])
if n < len(ls) {
return n, io.EOF
}
return n, nil
}
func (fs *root) Filelist(r *Request) (ListerAt, error) {
if fs.mockErr != nil {
return nil, fs.mockErr
}
_ = r.WithContext(r.Context()) // initialize context for deadlock testing
fs.mu.Lock()
defer fs.mu.Unlock()
switch r.Method {
case "List":
files, err := fs.readdir(r.Filepath)
if err != nil {
return nil, err
}
return listerat(files), nil
case "Stat":
file, err := fs.fetch(r.Filepath)
if err != nil {
return nil, err
}
return listerat{file}, nil
case "Readlink":
symlink, err := fs.readlink(r.Filepath)
if err != nil {
return nil, err
}
// SFTP-v2: The server will respond with a SSH_FXP_NAME packet containing only
// one name and a dummy attributes value.
return listerat{
&memFile{
name: symlink,
err: os.ErrNotExist, // prevent accidental use as a reader/writer.
},
}, nil
}
return nil, errors.New("unsupported")
}
func (fs *root) readdir(pathname string) ([]os.FileInfo, error) {
dir, err := fs.fetch(pathname)
if err != nil {
return nil, err
}
if !dir.IsDir() {
return nil, syscall.ENOTDIR
}
var files []os.FileInfo
for name, file := range fs.files {
if path.Dir(name) == dir.name {
files = append(files, file)
}
}
sort.Slice(files, func(i, j int) bool { return files[i].Name() < files[j].Name() })
return files, nil
}
func (fs *root) readlink(pathname string) (string, error) {
file, err := fs.lfetch(pathname)
if err != nil {
return "", err
}
if file.symlink == "" {
return "", os.ErrInvalid
}
return file.symlink, nil
}
// implements LstatFileLister interface
func (fs *root) Lstat(r *Request) (ListerAt, error) {
if fs.mockErr != nil {
return nil, fs.mockErr
}
_ = r.WithContext(r.Context()) // initialize context for deadlock testing
fs.mu.Lock()
defer fs.mu.Unlock()
file, err := fs.lfetch(r.Filepath)
if err != nil {
return nil, err
}
return listerat{file}, nil
}
// In memory file-system-y thing that the Hanlders live on
type root struct {
rootFile *memFile
mockErr error
mu sync.Mutex
files map[string]*memFile
}
// Set a mocked error that the next handler call will return.
// Set to nil to reset for no error.
func (fs *root) returnErr(err error) {
fs.mockErr = err
}
func (fs *root) lfetch(path string) (*memFile, error) {
if path == "/" {
return fs.rootFile, nil
}
file, ok := fs.files[path]
if file == nil {
if ok {
delete(fs.files, path)
}
return nil, os.ErrNotExist
}
return file, nil
}
// canonName returns the “canonical” name of a file, that is:
// if the directory of the pathname is a symlink, it follows that symlink to the valid directory name.
// this is relatively easy, since `dir.name` will be the only valid canonical path for a directory.
func (fs *root) canonName(pathname string) (string, error) {
dirname, filename := path.Dir(pathname), path.Base(pathname)
dir, err := fs.fetch(dirname)
if err != nil {
return "", err
}
if !dir.IsDir() {
return "", syscall.ENOTDIR
}
return path.Join(dir.name, filename), nil
}
func (fs *root) exists(path string) bool {
path, err := fs.canonName(path)
if err != nil {
return false
}
_, err = fs.lfetch(path)
return err != os.ErrNotExist
}
func (fs *root) fetch(path string) (*memFile, error) {
file, err := fs.lfetch(path)
if err != nil {
return nil, err
}
var count int
for file.symlink != "" {
if count++; count > maxSymlinkFollows {
return nil, errTooManySymlinks
}
file, err = fs.lfetch(file.symlink)
if err != nil {
return nil, err
}
}
return file, nil
}
// Implements os.FileInfo, io.ReaderAt and io.WriterAt interfaces.
// These are the 3 interfaces necessary for the Handlers.
// Implements the optional interface TransferError.
type memFile struct {
name string
modtime time.Time
symlink string
isdir bool
mu sync.RWMutex
content []byte
err error
}
// These are helper functions, they must be called while holding the memFile.mu mutex
func (f *memFile) size() int64 { return int64(len(f.content)) }
func (f *memFile) grow(n int64) { f.content = append(f.content, make([]byte, n)...) }
// Have memFile fulfill os.FileInfo interface
func (f *memFile) Name() string { return path.Base(f.name) }
func (f *memFile) Size() int64 {
f.mu.Lock()
defer f.mu.Unlock()
return f.size()
}
func (f *memFile) Mode() os.FileMode {
if f.isdir {
return os.FileMode(0755) | os.ModeDir
}
if f.symlink != "" {
return os.FileMode(0777) | os.ModeSymlink
}
return os.FileMode(0644)
}
func (f *memFile) ModTime() time.Time { return f.modtime }
func (f *memFile) IsDir() bool { return f.isdir }
func (f *memFile) Sys() interface{} {
return fakeFileInfoSys()
}
func (f *memFile) ReadAt(b []byte, off int64) (int, error) {
f.mu.Lock()
defer f.mu.Unlock()
if f.err != nil {
return 0, f.err
}
if off < 0 {
return 0, errors.New("memFile.ReadAt: negative offset")
}
if off >= f.size() {
return 0, io.EOF
}
n := copy(b, f.content[off:])
if n < len(b) {
return n, io.EOF
}
return n, nil
}
func (f *memFile) WriteAt(b []byte, off int64) (int, error) {
// fmt.Println(string(p), off)
// mimic write delays, should be optional
time.Sleep(time.Microsecond * time.Duration(len(b)))
f.mu.Lock()
defer f.mu.Unlock()
if f.err != nil {
return 0, f.err
}
grow := int64(len(b)) + off - f.size()
if grow > 0 {
f.grow(grow)
}
return copy(f.content[off:], b), nil
}
func (f *memFile) Truncate(size int64) error {
f.mu.Lock()
defer f.mu.Unlock()
if f.err != nil {
return f.err
}
grow := size - f.size()
if grow <= 0 {
f.content = f.content[:size]
} else {
f.grow(grow)
}
return nil
}
func (f *memFile) TransferError(err error) {
f.mu.Lock()
defer f.mu.Unlock()
f.err = err
}