libgocryptfs/internal/fusefrontend/xattr_linux.go
Sebastian Lackner 5055f39bd5 fusefrontend: Allow to set/remove xattr on directory without read permission.
Setting/removing extended attributes on directories was partially fixed with
commit eff35e60b6. However, on most file systems
it is also possible to do these operations without read access (see tests).

Since we cannot open a write-access fd to a directory, we have to use the
/proc/self/fd trick (already used for ListXAttr) for the other operations aswell.
For simplicity, let's separate the Linux and Darwin code again (basically revert
commit f320b76fd1), and always use the
/proc/self/fd trick on Linux. On Darwin we use the best-effort approach with
openBackingFile() as a fallback.

More discussion about the available options is available in
https://github.com/rfjakob/gocryptfs/issues/308.
2019-01-05 12:34:40 +01:00

84 lines
2.2 KiB
Go

// +build linux
// Package fusefrontend interfaces directly with the go-fuse library.
package fusefrontend
import (
"fmt"
"strings"
"syscall"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
)
// Only allow the "user" namespace, block "trusted" and "security", as
// these may be interpreted by the system, and we don't want to cause
// trouble with our encrypted garbage.
const xattrUserPrefix = "user."
func disallowedXAttrName(attr string) bool {
return !strings.HasPrefix(attr, xattrUserPrefix)
}
func filterXattrSetFlags(flags int) int {
return flags
}
func (fs *FS) getXAttr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
dirfd, cName, err := fs.openBackingDir(relPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
procPath := fmt.Sprintf("/proc/self/fd/%d/%s", dirfd, cName)
cData, err := syscallcompat.Lgetxattr(procPath, cAttr)
if err != nil {
return nil, fuse.ToStatus(err)
}
return cData, fuse.OK
}
func (fs *FS) setXAttr(relPath string, cAttr string, cData []byte, flags int, context *fuse.Context) fuse.Status {
dirfd, cName, err := fs.openBackingDir(relPath)
if err != nil {
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
procPath := fmt.Sprintf("/proc/self/fd/%d/%s", dirfd, cName)
err = unix.Lsetxattr(procPath, cAttr, cData, flags)
return fuse.ToStatus(err)
}
func (fs *FS) removeXAttr(relPath string, cAttr string, context *fuse.Context) fuse.Status {
dirfd, cName, err := fs.openBackingDir(relPath)
if err != nil {
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
procPath := fmt.Sprintf("/proc/self/fd/%d/%s", dirfd, cName)
err = unix.Lremovexattr(procPath, cAttr)
return fuse.ToStatus(err)
}
func (fs *FS) listXAttr(relPath string, context *fuse.Context) ([]string, fuse.Status) {
dirfd, cName, err := fs.openBackingDir(relPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
procPath := fmt.Sprintf("/proc/self/fd/%d/%s", dirfd, cName)
cNames, err := syscallcompat.Llistxattr(procPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
return cNames, fuse.OK
}