From: Juergen Strobel <strobel@...>
Date: 2006-06-23T05:27:02+09:00
Subject: Re: Achieve pure object oriented design in Ruby

--8GpibOaaTibBMecb
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed, Jun 21, 2006 at 08:19:15PM +0900, Robert Dober wrote:
> On 6/21/06, Juergen Strobel <strobel@secure.at> wrote:
> >
> ><snip>
>=20
> In no language private/protected (or final) is a fool proof security
>=20
>=20
> I doubt this strongly, Ada springs into mind.

Disassemblers/source extractors. Debuggers. Special kernel
modules. Running in a VM with outside tracing mechanisms
attached. Need I continue? This may take the attacker to an
outside-the-language level, but is still very practical.

The best feature of Ada is probably its obscurity outside some special
user groups.

> measure. It is there to provide some safety nets against errors, and
> >to help design, not for security. It is quite easy in C++ to get at
> >any function in memory via pointers. In Java people can use AOP to
> >accomplish this.
>=20
>=20
> In theory I hate it, in practice it is frequently sufficent.
> Ruby is not doing that bad either, in practice I will often not care if
> somebody redefines the access rights of my methods, I feel that this is a
> theoretical discussion, though, right ?

Yes. But practical work is not far behind, and it usually suffices if
*one* of your users breaks your defenses and distributes a "crack"
around. You sit on the wrong side of a long lever here, hence my
advice to not waste effort in a lost battle.

> Your most economical bet is to just document the class (or whatever)
> >to be "private, not to be used directly" in Ruby. Sometimes the
> >low-tech effort is simply the best, especially if any high-tech effort
> >is going to put *you* to much more troubles than the attacker, who will
> >circumvent it fast any way.
>=20
>=20
> I appreciate your defence of ruby ;) but the ability  to completely hide
> implementation from the interface user is a feature not a bug.

Most people who would consider this a feature would also consider
static typing a feature -- ruby is different. It is a feature of ruby
to be dynamic and reflective. Don't misunderstand me, I am all for
encapsulation, but as a design not a security/obscurity device.

I dare you to show me a system that manages to completely hide away,
apart from secure hardware (like smartcards).

> It does not seem a good idea to me to allow everything with the perfect
> excuse of following the "enabeling approach", because it does not allow me
> to implement some of the more basic principles of modern Software Design
> (Data Hiding for instance).

Encapsulation <> data hiding, and the former counts IMHO. I'd contend
that hiding in your sense is a basic software design principle, that
is a not so uncommon misunderstanding about OOP.

> All this is on a philosophical base, in practice Ruby gives me what *I* n=
eed
> However, *I* is not the world, as has been pointed out to me frequently a=
nd
> recently, quite a rude message BTW ;)
>=20
> Cheers
> Robert

I hope that wasn't me. I am opiniated, but I never intended to be rude.

-J=FCrgen

--=20
 The box said it requires Windows 95 or better so I installed Linux

--8GpibOaaTibBMecb
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature
Content-Disposition: inline

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.3 (GNU/Linux)

iQEVAwUBRJr9D/y64gyiEfXtAQJlAgf/dKUhTblspd1WoT7hluCu/WbOYwYyRrhP
5r1WNNWlgIjpsmZD7kp2RM2wq4Hj6Ic/TqKrMpUIcdHF4TssV3tgqhSPB4CMTj5j
Xy5A0KI7996mIsTgKyreFYEtp8ewOkBKZPBy+UgwB4tnjjzyhcEN/XrMS+C7f+UM
cC0kcTK1I4aOix970KI32+HKHIDdbl9zE9sHXmPYc+kqYQRcZ3QuXNFS8NE4901R
JuyqdUwC9aZrpSjl/ohwwreRdEvFOArSpd/vWhpFKqX6XbLJgVdNZEhiLEjaOuSO
qSIdRLszxILf2r2tCIP6piDL92eOKv7+r37xE/jkP8Mc5aP+D8JjBA==
=vtUr
-----END PGP SIGNATURE-----

--8GpibOaaTibBMecb--