Subject: Re: [PATCH] drivers/net: remove network drivers' last few uses of IRQF_SAMPLE_RANDOM

From: Glen Turner <[email-masked]>
Date: Mon, 26 May 2008 00:39:49 +0930

On Fri, 2008-05-16 at 21:55 -0700, Chris Peterson wrote:
> * network drivers could use IRQF_SAMPLE_URANDOM

Is it permissable for /dev/urandom to degrade to be externally
influenced
by a hostile party?

For example, /dev/random has run out. So the output of /dev/urandom is
now
determined by previous values of /dev/random.  I then send in a stack of
network packets at regular intervals. So the output of /dev/urandom is
now greatly determined by those packets.  My search space for the
resulting
key is small since /dev/urandom appears to be random, but in fact is
periodic.

I'll also note that there is a huge number of periodic packets seen by
hosts on quiet networks -- such as a preparation VLAN where a system
administrator might choose to run up a new machine.