hardcoresushi/libgocryptfs
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fusefrontend: -allow_other: Use MkdiratUser in Mkdir FUSE call.

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Revert commit fcaca5fc94d981aa637beb752edc8cb3c2265e96.

Instead of manually adjusting the user and mode after creating the
directory, adjust effective permissions and let the kernel deal with it.

Related to https://github.com/rfjakob/gocryptfs/issues/338.
This commit is contained in:
Sebastian Lackner 2019-01-12 20:57:31 +01:00
parent 03b9d65cce
commit a525e33eaa
3 changed files with 61 additions and 47 deletions
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81
internal/fusefrontend/fs_dir.go
View File

@ -24,13 +24,13 @@ const dsStoreName = ".DS_Store"
// mkdirWithIv - create a new directory and corresponding diriv file. dirfd
// should be a handle to the parent directory, cName is the name of the new
// directory and mode specifies the access permissions to use.
func (fs *FS) mkdirWithIv(dirfd int, cName string, mode uint32) error {
func (fs *FS) mkdirWithIv(dirfd int, cName string, mode uint32, context *fuse.Context) error {
// Between the creation of the directory and the creation of gocryptfs.diriv
// the directory is inconsistent. Take the lock to prevent other readers
// from seeing it.
fs.dirIVLock.Lock()
defer fs.dirIVLock.Unlock()
err := syscallcompat.Mkdirat(dirfd, cName, mode)
err := syscallcompat.MkdiratUser(dirfd, cName, mode, context)
if err != nil {
return err
}
@ -63,40 +63,20 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
// Don't set the full mode before we have set the correct owner.
// See Create FUSE call for more details.
origMode := mode
if fs.args.PreserveOwner {
mode = 0000
// Make sure context is nil if we don't want to preserve the owner
if !fs.args.PreserveOwner {
context = nil
}
if fs.args.PlaintextNames {
err = syscallcompat.Mkdirat(dirfd, cName, mode)
if err != nil {
return fuse.ToStatus(err)
}
// Set owner
if fs.args.PreserveOwner {
err = syscallcompat.Fchownat(dirfd, cName, int(context.Owner.Uid),
int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchownat %d:%d failed: %v", cName, context.Owner.Uid, context.Owner.Gid, err)
// In case of a failure, we don't want to proceed setting more
// permissive modes.
return fuse.ToStatus(err)
}
}
// Set mode
if origMode != mode {
err = syscallcompat.Fchmodat(dirfd, cName, origMode, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchmodat %#o -> %#o failed: %v", cName, mode, origMode, err)
}
}
return fuse.OK
err = syscallcompat.MkdiratUser(dirfd, cName, mode, context)
return fuse.ToStatus(err)
}
// We need write and execute permissions to create gocryptfs.diriv
mode = mode | 0300
// We need write and execute permissions to create gocryptfs.diriv.
// Also, we need read permissions to open the directory (to avoid
// race-conditions between getting and setting the mode).
origMode := mode
mode = mode | 0700
// Handle long file name
if nametransform.IsLongContent(cName) {
@ -107,33 +87,40 @@ func (fs *FS) Mkdir(newPath string, mode uint32, context *fuse.Context) (code fu
}
// Create directory
err = fs.mkdirWithIv(dirfd, cName, mode)
err = fs.mkdirWithIv(dirfd, cName, mode, context)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
return fuse.ToStatus(err)
}
} else {
err = fs.mkdirWithIv(dirfd, cName, mode)
err = fs.mkdirWithIv(dirfd, cName, mode, context)
if err != nil {
return fuse.ToStatus(err)
}
}
// Set owner
if fs.args.PreserveOwner {
err = syscallcompat.Fchownat(dirfd, cName, int(context.Owner.Uid),
int(context.Owner.Gid), unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchownat %d:%d failed: %v", cName, context.Owner.Uid, context.Owner.Gid, err)
// In case of a failure, we don't want to proceed setting more
// permissive modes.
return fuse.ToStatus(err)
}
}
// Set mode
if origMode != mode {
err = syscallcompat.Fchmodat(dirfd, cName, origMode, unix.AT_SYMLINK_NOFOLLOW)
dirfd2, err := syscallcompat.Openat(dirfd, cName,
syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchmodat %#o -> %#o failed: %v", cName, mode, origMode, err)
tlog.Warn.Printf("Mkdir %q: Openat failed: %v", cName, err)
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd2)
var st syscall.Stat_t
err = syscall.Fstat(dirfd2, &st)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fstat failed: %v", cName, err)
return fuse.ToStatus(err)
}
// Preserve SGID bit if it was set due to inheritance.
origMode = uint32(st.Mode&^0777) | origMode
err = syscall.Fchmod(dirfd2, origMode)
if err != nil {
tlog.Warn.Printf("Mkdir %q: Fchmod %#o -> %#o failed: %v", cName, mode, origMode, err)
return fuse.ToStatus(err)
}
}
return fuse.OK

5
internal/syscallcompat/sys_darwin.go
View File

@ -79,6 +79,11 @@ func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return emulateMkdirat(dirfd, path, mode)
}
func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (err error) {
// FIXME: take into account context.Owner
return Mkdirat(dirfd, path, mode)
}
func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
return emulateFstatat(dirfd, path, stat, flags)
}

22
internal/syscallcompat/sys_linux.go
View File

@ -180,6 +180,28 @@ func Mkdirat(dirfd int, path string, mode uint32) (err error) {
return syscall.Mkdirat(dirfd, path, mode)
}
// MkdiratUser runs the Mkdirat syscall in the context of a different user.
func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (err error) {
if context != nil {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
err = syscall.Setregid(-1, int(context.Owner.Gid))
if err != nil {
return err
}
defer syscall.Setregid(-1, 0)
err = syscall.Setreuid(-1, int(context.Owner.Uid))
if err != nil {
return err
}
defer syscall.Setreuid(-1, 0)
}
return Mkdirat(dirfd, path, mode)
}
// Fstatat syscall.
func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?