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