From: Emese Revfy <re.emese@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: "kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
PaX Team <pageexec@freemail.hu>,
Brad Spengler <spender@grsecurity.net>,
Michal Marek <mmarek@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-kbuild <linux-kbuild@vger.kernel.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>, Jens Axboe <axboe@kernel.dk>,
Al Viro <viro@zeniv.linux.org.uk>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
bart.vanassche@sandisk.com,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v2 1/3] Add the latent_entropy gcc plugin
Date: Wed, 15 Jun 2016 00:31:21 +0200 [thread overview]
Message-ID: <20160615003121.008b63c8152aa60c9c351530@gmail.com> (raw)
In-Reply-To: <CAGXu5j+-owKY_q-0Yow+OEsY3srdv0246H3ob-qRC6O3yg-qkg@mail.gmail.com>
On Tue, 14 Jun 2016 11:27:00 -0700
Kees Cook <keescook@chromium.org> wrote:
> On Mon, Jun 13, 2016 at 2:49 PM, Emese Revfy <re.emese@gmail.com> wrote:
> > On Thu, 9 Jun 2016 14:51:45 -0700
> > Kees Cook <keescook@chromium.org> wrote:
>
> >> > + * gcc plugin to help generate a little bit of entropy from program state,
> >> > + * used throughout the uptime of the kernel
> >>
> >> I think this comment needs a lot of expanding. What are all the ways
> >> that this plugin makes changes to code? Things I think I see are:
> >> pre-filling data variables with randomness, creating a local_entropy
> >> variable (local to what?), mixing stack pointer (into what?), updating
> >> latent_entropy global.
> >
> > I demonstrated the details here:
> > https://github.com/ephox-gcc-plugins/latent_entropy/commit/049acd9f478d47ee6526d8e93ab8cfcc3ff91b13
>
> That helps, thanks. Can you also mention how __latent_entropy changes
> non-functions? (i.e. initializes them with random data.)
>
> Also, I think this isn't accurate:
>
> * local_entropy ^= get_random_long();
>
> Looking at the disassembly, it seems that static random values (i.e.
> randomly chosen at gcc runtime) are added, rather than making calls to
> the kernel's get_random_long() function.
The plugin doesn't insert calls to the kernel's get_random_long().
That was just an example (the plugin instrumentation would look like this in the kernel).
I rewrote these calls to a random constant.
--
Emese
next prev parent reply other threads:[~2016-06-14 22:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 23:30 [PATCH v2 0/3] Introduce the latent_entropy gcc plugin Emese Revfy
2016-05-30 23:31 ` [PATCH v2 1/3] Add " Emese Revfy
2016-06-01 19:42 ` Andrew Morton
2016-06-03 17:42 ` Emese Revfy
2016-06-06 13:38 ` [kernel-hardening] " David Brown
2016-06-06 15:50 ` Kees Cook
2016-06-06 19:30 ` PaX Team
2016-06-06 23:13 ` Theodore Ts'o
2016-06-07 12:19 ` PaX Team
2016-06-07 13:58 ` Theodore Ts'o
2016-06-09 17:22 ` PaX Team
2016-06-09 19:55 ` Theodore Ts'o
2016-06-09 20:08 ` Kees Cook
2016-06-09 21:51 ` Kees Cook
2016-06-13 21:49 ` Emese Revfy
2016-06-14 18:27 ` Kees Cook
2016-06-14 22:31 ` Emese Revfy [this message]
2016-05-30 23:32 ` [PATCH v2 2/3] Mark functions with the latent_entropy attribute Emese Revfy
2016-05-30 23:34 ` [PATCH v2 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy
2016-06-09 21:18 ` [PATCH v2 0/3] Introduce the latent_entropy gcc plugin Kees Cook
2016-06-09 23:33 ` Emese Revfy
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