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Add ability to mount everything read-only.
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Adds a new read-only flag that prevents the fuseftp client from making
any kind of modifications to the mounted file system.

The winfsp fuse implementation doesn't provide a "ro" option, so this
addition is implemented by letting all methods that modify the file
system return an error. See winfsp/cgofuse#15
for more info.

This is a client-only implementation. It does not require any additional
features from the server.

Signed-off-by: Thomas Hallgren <[email protected]>
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@thallgren
thallgren committed Nov 14, 2024
1 parent 5b8d2ac commit a4f84ea
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Showing 5 changed files with 264 additions and 66 deletions.
60 changes: 47 additions & 13 deletions pkg/fs/ftp.go
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,9 @@ type fuseImpl struct {
// current maps file handles to info structs
current map[uint64]*info

// readOnly will prohibit all create, open with write access, and writes when set to true.
readOnly bool

// shuttingDown prevent that new handles are added
shuttingDown bool
}
Expand Down Expand Up @@ -111,11 +114,12 @@ type FTPClient interface {
// NewFTPClient returns an implementation of the fuse.FileSystemInterface that is backed by
// an FTP server connection tp the address. The dir parameter is the directory that the
// FTP server changes to when connecting.
func NewFTPClient(ctx context.Context, addr netip.AddrPort, dir string, readTimeout time.Duration) (FTPClient, error) {
func NewFTPClient(ctx context.Context, addr netip.AddrPort, dir string, ro bool, readTimeout time.Duration) (FTPClient, error) {
ctx, cancel := context.WithCancel(ctx)
f := &fuseImpl{
cancel: cancel,
current: make(map[uint64]*info),
cancel: cancel,
current: make(map[uint64]*info),
readOnly: ro,
pool: connPool{
dir: dir,
timeout: readTimeout,
Expand Down Expand Up @@ -148,6 +152,9 @@ func (f *fuseImpl) SetAddress(addr netip.AddrPort) error {
// The third argument, the mode bits, are currently ignored
func (f *fuseImpl) Create(path string, flags int, _ uint32) (int, uint64) {
log.Debugf("Create(%s, %#x)", path, flags)
if f.readOnly {
return -fuse.EROFS, 0
}
fe, _, errCode := f.openHandle(path, flags|fuse.O_CREAT)
if errCode < 0 {
return errCode, 0
Expand Down Expand Up @@ -213,7 +220,7 @@ func (f *fuseImpl) Getattr(path string, s *fuse.Stat_t, fh uint64) int {
e, errCode = f.getEntry(path)
}
if errCode == 0 {
toStat(e, s)
toStat(e, s, f.readOnly)
}
return errCode
}
Expand All @@ -226,6 +233,9 @@ func (f *fuseImpl) Init() {

func (f *fuseImpl) Mkdir(path string, mode uint32) int {
log.Debugf("Mkdir(%s, %O)", path, mode)
if f.readOnly {
return -fuse.EROFS
}
err := f.withConn(func(conn *ftp.ServerConn) error {
return conn.MakeDir(relpath(path))
})
Expand Down Expand Up @@ -343,7 +353,7 @@ func (f *fuseImpl) Readdir(path string, fill func(name string, stat *fuse.Stat_t
}
for _, e := range es {
s := &fuse.Stat_t{}
toStat(e, s)
toStat(e, s, f.readOnly)
if !fill(e.Name, s, 0) {
break
}
Expand All @@ -368,6 +378,9 @@ func (f *fuseImpl) Releasedir(path string, fh uint64) int {
// Rename will rename or move oldpath to newpath
func (f *fuseImpl) Rename(oldpath string, newpath string) int {
log.Debugf("Rename(%s, %s)", oldpath, newpath)
if f.readOnly {
return -fuse.EROFS
}
if oldpath == newpath {
return 0
}
Expand All @@ -380,6 +393,9 @@ func (f *fuseImpl) Rename(oldpath string, newpath string) int {
// Rmdir removes the directory at path. The directory must be empty
func (f *fuseImpl) Rmdir(path string) int {
log.Debugf("Rmdir(%s)", path)
if f.readOnly {
return -fuse.EROFS
}
err := f.withConn(func(conn *ftp.ServerConn) error {
e, err := conn.GetEntry(relpath(path))
if err != nil {
Expand Down Expand Up @@ -415,6 +431,9 @@ func (f *fuseImpl) Rmdir(path string) int {
// with zero bytes and an offset. This behavior will only work with some servers.
func (f *fuseImpl) Truncate(path string, size int64, fh uint64) int {
log.Debugf("Truncate(%s, sz=%d, %d)", path, size, fh)
if f.readOnly {
return -fuse.EROFS
}
var fe *info
var errCode int
if fh == math.MaxUint64 {
Expand All @@ -439,6 +458,9 @@ func (f *fuseImpl) Truncate(path string, size int64, fh uint64) int {
// Unlink will remove the path from the file system.
func (f *fuseImpl) Unlink(path string) int {
log.Debugf("Unlink(%s)", path)
if f.readOnly {
return -fuse.EROFS
}
return f.errToFuseErr(f.withConn(func(conn *ftp.ServerConn) error {
if err := conn.Delete(relpath(path)); err != nil {
return err
Expand Down Expand Up @@ -476,6 +498,9 @@ func (i *info) pipeCopy(of uint64) int {
// until the handle is released by a call to Release
func (f *fuseImpl) Write(path string, buf []byte, ofst int64, fh uint64) int {
log.Debugf("Write(%s, sz=%d, off=%d, %d)", path, len(buf), ofst, fh)
if f.readOnly {
return -fuse.EROFS
}
fe, errCode := f.loadHandle(fh)
if errCode < 0 {
return errCode
Expand Down Expand Up @@ -597,9 +622,10 @@ func (f *fuseImpl) errToFuseErr(err error) int {
return -fuse.EEXIST
default:
// TODO
buf := make([]byte, 0x10000)
n := runtime.Stack(buf, false)
log.Printf("%T %v\n%s", err, err, string(buf[:n]))
// buf := make([]byte, 0x10000)
// n := runtime.Stack(buf, false)
// log.Printf("%T %v\n%s", err, err, string(buf[:n]))
log.Printf("%T, %v\n", err, err)
return -fuse.EIO
}
}
Expand Down Expand Up @@ -642,6 +668,9 @@ func (f *fuseImpl) loadHandle(fh uint64) (*info, int) {
}

func (f *fuseImpl) openHandle(path string, flags int) (nfe *info, e *ftp.Entry, errCode int) {
if f.readOnly && flags&(fuse.O_CREAT|fuse.O_TRUNC|fuse.O_APPEND|fuse.O_WRONLY|fuse.O_RDWR) != 0 {
return nil, nil, -fuse.EROFS
}
f.RLock()
shuttingDown := f.shuttingDown
f.RUnlock()
Expand Down Expand Up @@ -718,16 +747,22 @@ func containsAny(str string, ss ...string) bool {
return false
}

func toStat(e *ftp.Entry, s *fuse.Stat_t) {
func toStat(e *ftp.Entry, s *fuse.Stat_t, ro bool) {
// TODO: ftp actually returns a line similar to what 'ls -l' produces. It is
// possible to parse the mode from that but the client we use here doesn't do that.
switch e.Type {
case ftp.EntryTypeFolder:
s.Mode = fuse.S_IFDIR | 0755
s.Mode = fuse.S_IFDIR | 0o555
case ftp.EntryTypeLink:
s.Mode = fuse.S_IFLNK | 0755
s.Mode = fuse.S_IFLNK | 0o555
default:
s.Mode = fuse.S_IFREG | 0644
s.Mode = fuse.S_IFREG | 0o444
}
if !ro {
s.Mode |= 0o200
s.Flags = 0
} else {
s.Flags = fuse.UF_READONLY
}
tm := fuse.NewTimespec(e.Time)
s.Size = int64(e.Size)
Expand All @@ -738,5 +773,4 @@ func toStat(e *ftp.Entry, s *fuse.Stat_t) {
s.Uid = uint32(os.Getuid())
s.Gid = uint32(os.Getgid())
s.Nlink = 1
s.Flags = 0
}
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