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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

WARNING: multiple messages have this Message-ID (diff)
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

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WARNING: multiple messages have this Message-ID (diff)
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: [kernel-hardening] 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

  reply	other threads:[~2016-06-14 22:24 UTC|newest]

Thread overview: 62+ 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 23:30 ` [kernel-hardening] " Emese Revfy
2016-05-30 23:30 ` Emese Revfy
2016-05-30 23:31 ` [PATCH v2 1/3] Add " Emese Revfy
2016-05-30 23:31   ` [kernel-hardening] " Emese Revfy
2016-05-30 23:31   ` Emese Revfy
2016-06-01 19:42   ` Andrew Morton
2016-06-01 19:42     ` [kernel-hardening] " Andrew Morton
2016-06-01 19:42     ` Andrew Morton
2016-06-03 17:42     ` Emese Revfy
2016-06-03 17:42       ` [kernel-hardening] " Emese Revfy
2016-06-03 17:42       ` Emese Revfy
2016-06-06 13:38       ` [kernel-hardening] " David Brown
2016-06-06 13:38         ` David Brown
2016-06-06 15:50         ` Kees Cook
2016-06-06 15:50           ` Kees Cook
2016-06-06 15:50           ` Kees Cook
2016-06-06 19:30         ` PaX Team
2016-06-06 19:30           ` PaX Team
2016-06-06 23:13           ` Theodore Ts'o
2016-06-06 23:13             ` Theodore Ts'o
2016-06-07 12:19             ` PaX Team
2016-06-07 12:19               ` PaX Team
2016-06-07 13:58               ` Theodore Ts'o
2016-06-07 13:58                 ` Theodore Ts'o
2016-06-09 17:22                 ` PaX Team
2016-06-09 17:22                   ` PaX Team
2016-06-09 19:55                   ` Theodore Ts'o
2016-06-09 19:55                     ` Theodore Ts'o
2016-06-09 20:08                     ` Kees Cook
2016-06-09 20:08                       ` Kees Cook
2016-06-09 20:08                       ` Kees Cook
2016-06-09 21:51   ` Kees Cook
2016-06-09 21:51     ` [kernel-hardening] " Kees Cook
2016-06-09 21:51     ` Kees Cook
2016-06-09 21:51     ` Kees Cook
2016-06-13 21:49     ` Emese Revfy
2016-06-13 21:49       ` [kernel-hardening] " Emese Revfy
2016-06-13 21:49       ` Emese Revfy
2016-06-13 21:49       ` Emese Revfy
2016-06-14 18:27       ` Kees Cook
2016-06-14 18:27         ` [kernel-hardening] " Kees Cook
2016-06-14 18:27         ` Kees Cook
2016-06-14 18:27         ` Kees Cook
2016-06-14 22:31         ` Emese Revfy [this message]
2016-06-14 22:31           ` [kernel-hardening] " Emese Revfy
2016-06-14 22:31           ` Emese Revfy
2016-06-14 22:31           ` Emese Revfy
2016-05-30 23:32 ` [PATCH v2 2/3] Mark functions with the latent_entropy attribute Emese Revfy
2016-05-30 23:32   ` [kernel-hardening] " Emese Revfy
2016-05-30 23:32   ` Emese Revfy
2016-05-30 23:34 ` [PATCH v2 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy
2016-05-30 23:34   ` [kernel-hardening] " Emese Revfy
2016-05-30 23:34   ` Emese Revfy
2016-06-09 21:18 ` [PATCH v2 0/3] Introduce the latent_entropy gcc plugin Kees Cook
2016-06-09 21:18   ` [kernel-hardening] " Kees Cook
2016-06-09 21:18   ` Kees Cook
2016-06-09 21:18   ` Kees Cook
2016-06-09 23:33   ` Emese Revfy
2016-06-09 23:33     ` [kernel-hardening] " Emese Revfy
2016-06-09 23:33     ` Emese Revfy
2016-06-09 23:33     ` Emese Revfy

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