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From: David Brown <david.brown@linaro.org>
To: kernel-hardening@lists.openwall.com
Cc: Andrew Morton <akpm@linux-foundation.org>,
	pageexec@freemail.hu, spender@grsecurity.net, mmarek@suse.com,
	keescook@chromium.org, linux-kernel@vger.kernel.org,
	yamada.masahiro@socionext.com, linux-kbuild@vger.kernel.org,
	tytso@mit.edu, linux-mm@kvack.org, axboe@kernel.dk,
	viro@zeniv.linux.org.uk, paulmck@linux.vnet.ibm.com,
	mingo@redhat.com, tglx@linutronix.de, bart.vanassche@sandisk.com,
	davem@davemloft.net
Subject: Re: [kernel-hardening] Re: [PATCH v2 1/3] Add the latent_entropy gcc plugin
Date: Mon, 6 Jun 2016 07:38:01 -0600	[thread overview]
Message-ID: <20160606133801.GA6136@davidb.org> (raw)
In-Reply-To: <20160603194252.91064b8e682ad988283fc569@gmail.com>

On Fri, Jun 03, 2016 at 07:42:52PM +0200, Emese Revfy wrote:
>On Wed, 1 Jun 2016 12:42:27 -0700
>Andrew Morton <akpm@linux-foundation.org> wrote:
>
>> On Tue, 31 May 2016 01:31:45 +0200 Emese Revfy <re.emese@gmail.com> wrote:
>>
>> > This plugin mitigates the problem of the kernel having too little entropy during
>> > and after boot for generating crypto keys.
>> >
>> > It creates a local variable in every marked function. The value of this variable is
>> > modified by randomly chosen operations (add, xor and rol) and
>> > random values (gcc generates them at compile time and the stack pointer at runtime).
>> > It depends on the control flow (e.g., loops, conditions).
>> >
>> > Before the function returns the plugin writes this local variable
>> > into the latent_entropy global variable. The value of this global variable is
>> > added to the kernel entropy pool in do_one_initcall() and _do_fork().
>>
>> I don't think I'm really understanding.  Won't this produce the same
>> value on each and every boot?
>
>No, because of interrupts and intentional data races.

Wouldn't that result in the value having one of a small number of
values, then?  Even if it was just one of thousands or millions of
values, it would make the search space quite small.

David

  reply	other threads:[~2016-06-06 13:38 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       ` David Brown [this message]
2016-06-06 15:50         ` [kernel-hardening] " 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
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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