linux-kernel - Re: [PATCH 05/12] usb: feed USB device information to the /dev/random driver

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Date:	Fri, 6 Jul 2012 20:08:22 -0500
From:	Jonathan Nieder <jrnieder@...il.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	ewust@...ch.edu, zakir@...ch.edu, nadiah@...ucsd.edu,
	jhalderm@...ch.edu, Linus Torvalds <torvalds@...ux-foundation.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH 05/12] usb: feed USB device information to the
 /dev/random driver

Hi,

Theodore Ts'o wrote:
> On Fri, Jul 06, 2012 at 06:02:18PM -0500, Jonathan Nieder wrote:

>> Why cc: stable@?  Does this fix a build error, oops, hang, data
>> corruption, real security issue, or other critical "oh, that's not
>> good" bug?
>
> All of the /dev/random patches in this patch series that were marked
> for the stable backports are to address a security issue.  See:
> https://factorable.net/

Thanks for explaining.  If there's occasion for a reroll (I'm guessing
there won't be) then it would be nice to mention this in the commit
messages.

[...]
> While these patches are designed to do as much as we can without
> assuming any fixes in userspace, and the weak kea vulnerabilities are
> much more obviously detectable in embedded devices with close to zero
> available entropy, ideally there are improvements that can and should
> be done in upstream userspace packages as well as in the packaging and
> installation scripts for more general-purpose server and workstation
> distributions.
>
> For example, ssh key generation should happen as late as possible;
> ideally, some time *after* the networking has been brought up.
[...]
>               The same is true for the generation of remote
> administration keys for ntpd and bind.

Very much agreed.  These patches look like an improvement but on
diskless systems without a hardware RNG it still seems possible for
someone with knowledge of the hardware configuration to predict the
generator state.

Except that patch 2 improves matters a lot.

Thanks for your work and kindness,
Jonathan
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