linux-kernel - Re: [PATCH] random: add blocking facility to urandom

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 7 Sep 2011 17:18:58 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Steve Grubb <sgrubb@...hat.com>
Cc:	Jarod Wilson <jarod@...hat.com>,
	Sasha Levin <levinsasha928@...il.com>,
	linux-crypto@...r.kernel.org, Matt Mackall <mpm@...enic.com>,
	Neil Horman <nhorman@...hat.com>,
	Herbert Xu <herbert.xu@...hat.com>,
	Stephan Mueller <stephan.mueller@...ec.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] random: add blocking facility to urandom

On Wed, Sep 07, 2011 at 04:02:24PM -0400, Steve Grubb wrote:
> 
> When a system is underattack, do you really want to be using a PRNG
> for anything like seeding openssl?  Because a PRNG is what urandom
> degrades into when its attacked.

This is not technically true.  urandom degrades into a CRNG
(cryptographic random number generator).  In fact what most security
experts recommend is to take a small amount of security, and then use
that to seed a CRNG.

> If enough bytes are read that an
> attacker can guess the internal state of the RNG, do you really want
> it seeding a openssh session?

In a cryptographic random number generator, there is a either a
cryptographic hash or a encryption algorithm at the core.  So you
would need a huge amounts of bytes, and then you would have to carry
out an attack on the cryptographic core.

If this is the basis for the patch, then we should definitely NACK it.
It sounds like snake oil fear mongering.

					- Ted

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/