From: Pavel Machek <pavel@ucw.cz>
To: Kees Cook <kees.cook@canonical.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [Security] proactive defense: using read-only memory
Date: Sun, 2 Jan 2011 10:09:11 +0100 [thread overview]
Message-ID: <20110102090911.GU32469@atrey.karlin.mff.cuni.cz> (raw)
In-Reply-To: <20101117221443.GR13854@outflux.net>
Hi!
> > > - Pointers to function table also need to be marked read-only after
> > > they are set. An example of this is the security_ops table pointer. It
> > > gets set once at boot, and never changes again. These need to be handled
> > > so it isn't possible to just trivially reaim the entire security_ops
> > > table lookup somewhere else.
> >
> > But there are too many of those. You can't block them all...
>
> Well, I don't think "too many" is a good reason. And I think it is possible
> to block them all if we're careful and diligent. Maybe I'm naive;
> we'll see.
I believe "too many" is very good reason -- you do not want to uglify
the kernel too badly.
It is not like anything that makes attackers life harder is a good
thing... for example deleting all the comments would clearly make
attacking linux harder, but it is also clearly bad idea.
> > > - Entry points to set_kernel_text_rw() and similar need to be blockable.
> > > Having these symbols available make kernel memory modification trivial;
> >
> > What prevents attacker to just inlining those functions in the
> > exploit?
>
> The goal is to make it harder for an attacker to create, change, or hide
> kernel code in memory. If they're able to already execute arbitrary code,
> then yes, it's doesn't change anything. But the point is to make it harder
> to get to that point to start with.
So... what do you assume attacker _can_ do? What is it you are trying
to protect against?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2011-01-02 9:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-07 19:35 [Security] proactive defense: using read-only memory Kees Cook
2010-11-08 6:13 ` [Security] proactive defense: using read-only memory, RO/NX modules Ingo Molnar
2010-11-08 10:03 ` Alan Cox
2010-11-08 21:42 ` Kees Cook
2010-11-10 9:04 ` Ingo Molnar
2010-11-11 6:56 ` Kees Cook
2010-11-11 9:07 ` Ingo Molnar
2010-11-13 19:59 ` matthieu castet
2010-11-14 9:56 ` Ingo Molnar
2010-11-17 10:00 ` [Security] proactive defense: using read-only memory Pavel Machek
2010-11-17 22:14 ` Kees Cook
2011-01-02 9:09 ` Pavel Machek [this message]
2010-11-18 0:12 ` Valdis.Kletnieks
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