syscallcompat: check that we get NOFOLLOW wherever possible

...and fix the instances where the AT_SYMLINK_NOFOLLOW /
O_NOFOLLOW / O_EXCL flag was missing.
libgocryptfs
Jakob Unterwurzacher 5 years ago
parent 22282aefe6
commit e97c23e083
  1. 4
      internal/fusefrontend/fs.go
  2. 4
      internal/fusefrontend/fs_dir.go
  3. 3
      internal/nametransform/diriv.go
  4. 4
      internal/syscallcompat/emulate.go
  5. 17
      internal/syscallcompat/sys_linux.go

@ -211,7 +211,7 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
// Create content
var fdRaw int
fdRaw, err = syscallcompat.Openat(int(dirfd.Fd()), cName, newFlags|os.O_CREATE, mode)
fdRaw, err = syscallcompat.Openat(int(dirfd.Fd()), cName, newFlags|os.O_CREATE|os.O_EXCL, mode)
if err != nil {
nametransform.DeleteLongName(dirfd, cName)
return nil, fuse.ToStatus(err)
@ -219,7 +219,7 @@ func (fs *FS) Create(path string, flags uint32, mode uint32, context *fuse.Conte
fd = os.NewFile(uintptr(fdRaw), cName)
} else {
// Normal (short) file name
fd, err = os.OpenFile(cPath, newFlags|os.O_CREATE, os.FileMode(mode))
fd, err = os.OpenFile(cPath, newFlags|os.O_CREATE|os.O_EXCL, os.FileMode(mode))
if err != nil {
return nil, fuse.ToStatus(err)
}

@ -146,7 +146,7 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
cName := filepath.Base(cPath)
dirfdRaw, err := syscallcompat.Openat(int(parentDirFd.Fd()), cName,
syscall.O_RDONLY, 0)
syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
if err == syscall.EACCES {
// We need permission to read and modify the directory
tlog.Debug.Printf("Rmdir: handling EACCESS")
@ -168,7 +168,7 @@ func (fs *FS) Rmdir(path string, context *fuse.Context) (code fuse.Status) {
var st syscall.Stat_t
syscall.Lstat(cPath, &st)
dirfdRaw, err = syscallcompat.Openat(int(parentDirFd.Fd()), cName,
syscall.O_RDONLY, 0)
syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
// Undo the chmod if removing the directory failed
defer func() {
if code != fuse.OK {

@ -36,7 +36,8 @@ func ReadDirIV(dir string) (iv []byte, err error) {
// ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
// Using the dirfd makes it immune to concurrent renames of the directory.
func ReadDirIVAt(dirfd *os.File) (iv []byte, err error) {
fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), DirIVFilename, syscall.O_RDONLY, 0)
fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), DirIVFilename,
syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
if err != nil {
tlog.Warn.Printf("ReadDirIVAt: opening %q in dir %q failed: %v",
DirIVFilename, dirfd.Name(), err)

@ -136,12 +136,12 @@ func emulateFchmodat(dirfd int, path string, mode uint32, flags int) (err error)
}
defer syscall.Fchdir(cwd)
// We also don't have Lchmod, so emulate it (poorly).
if flags&unix.AT_SYMLINK_NOFOLLOW > 0 {
if flags&unix.AT_SYMLINK_NOFOLLOW != 0 {
fi, err := os.Lstat(path)
if err != nil {
return err
}
if fi.Mode()&os.ModeSymlink > 0 {
if fi.Mode()&os.ModeSymlink != 0 {
return nil
}
}

@ -6,6 +6,8 @@ import (
"syscall"
"unsafe"
"golang.org/x/sys/unix"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
@ -46,6 +48,11 @@ func Fallocate(fd int, mode uint32, off int64, len int64) (err error) {
// Openat wraps the Openat syscall.
func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
// Why would we ever want to call this without O_NOFOLLOW and O_EXCL?
if !(flags&syscall.O_CREAT != 0 && flags&syscall.O_EXCL != 0) && flags&syscall.O_NOFOLLOW == 0 {
tlog.Warn.Printf("Openat: adding missing O_NOFOLLOW flag")
flags |= syscall.O_NOFOLLOW
}
return syscall.Openat(dirfd, path, flags, mode)
}
@ -82,11 +89,21 @@ func Dup3(oldfd int, newfd int, flags int) (err error) {
// Fchmodat syscall.
func Fchmodat(dirfd int, path string, mode uint32, flags int) (err error) {
// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?
if flags&unix.AT_SYMLINK_NOFOLLOW == 0 {
tlog.Warn.Printf("Fchmodat: adding missing AT_SYMLINK_NOFOLLOW flag")
flags |= unix.AT_SYMLINK_NOFOLLOW
}
return syscall.Fchmodat(dirfd, path, mode, flags)
}
// Fchownat syscall.
func Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error) {
// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?
if flags&unix.AT_SYMLINK_NOFOLLOW == 0 {
tlog.Warn.Printf("Fchownat: adding missing AT_SYMLINK_NOFOLLOW flag")
flags |= unix.AT_SYMLINK_NOFOLLOW
}
return syscall.Fchownat(dirfd, path, uid, gid, flags)
}

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