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// +build linux
// Package fusefrontend interfaces directly with the go-fuse library.
package fusefrontend
import (
"fmt"
"strings"
"syscall"
"github.com/hanwen/go-fuse/fuse"
"github.com/pkg/xattr"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// 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
}
// procFd returns the path to file descriptor "fd" in /proc/self/fd.
func procFd(fd int) string {
return fmt.Sprintf("/proc/self/fd/%d", fd)
}
// getFileFd calls fs.Open() on relative plaintext path "relPath" and returns
// the resulting fusefrontend.*File along with the underlying fd. The caller
// MUST call file.Release() when done with the file. The O_NONBLOCK flag is
// used to not block on FIFOs.
//
// Used by xattrGet() and friends.
func (fs *FS) getFileFd(relPath string, context *fuse.Context) (*File, int, fuse.Status) {
fuseFile, status := fs.Open(relPath, syscall.O_RDONLY|syscall.O_NONBLOCK, context)
if !status.Ok() {
return nil, -1, status
}
file, ok := fuseFile.(*File)
if !ok {
tlog.Warn.Printf("BUG: xattrGet: cast to *File failed")
fuseFile.Release()
return nil, -1, fuse.EIO
}
return file, file.intFd(), fuse.OK
}
// getXattr - read encrypted xattr name "cAttr" from relative
// plaintext path "relPath". Returns the encrypted xattr value.
//
// This function is symlink-safe by using /proc/self/fd.
func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
file, fd, status := fs.getFileFd(relPath, context)
if !status.Ok() {
return nil, status
}
defer file.Release()
cData, err := xattr.Get(procFd(fd), cAttr)
if err != nil {
return nil, unpackXattrErr(err)
}
return cData, fuse.OK
}
// setXattr - set encrypted xattr name "cAttr" to value "cData" on plaintext
// path "relPath".
//
// This function is symlink-safe by using /proc/self/fd.
func (fs *FS) setXattr(relPath string, cAttr string, cData []byte, flags int, context *fuse.Context) fuse.Status {
file, fd, status := fs.getFileFd(relPath, context)
if !status.Ok() {
return status
}
defer file.Release()
err := xattr.SetWithFlags(procFd(fd), cAttr, cData, flags)
return unpackXattrErr(err)
}
// removeXAttr - remove encrypted xattr name "cAttr" from
// plaintext path "relPath".
//
// This function is symlink-safe on Linux by using /proc/self/fd.
func (fs *FS) removeXAttr(relPath string, cAttr string, context *fuse.Context) fuse.Status {
file, fd, status := fs.getFileFd(relPath, context)
if !status.Ok() {
return status
}
defer file.Release()
err := xattr.Remove(procFd(fd), cAttr)
return unpackXattrErr(err)
}
// listXAttr - list encrypted xattr names on plaintext path "relPath".
//
// This function is symlink-safe on Linux by using /proc/self/fd.
func (fs *FS) listXAttr(relPath string, context *fuse.Context) ([]string, fuse.Status) {
file, fd, status := fs.getFileFd(relPath, context)
if !status.Ok() {
// If relPath is a symlink, getFileFd fails with ELOOP. As setXattr()
// also fails with ELOOP, there is no way to set xattrs on symlinks,
// and we can assume that the file does not have any.
if status == fuse.Status(syscall.ELOOP) {
return nil, fuse.OK
}
return nil, status
}
defer file.Release()
cNames, err := xattr.List(procFd(fd))
if err != nil {
status := unpackXattrErr(err)
return nil, status
}
return cNames, fuse.OK
}
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