Re: Concurrent access to /dev/urandom

[Adam Heath]

On Sat, 11 Dec 2004, Theodore Ts'o wrote:

> On Fri, Dec 10, 2004 at 06:22:37PM -0600, Adam Heath wrote:
> >
> > Actually, I think this is a security issue.  Since any plain old program can
> > read from /dev/urandom at any time, an attacker could attempt to read from
> > that device at the same moment some other program is doing so, and thereby
> > gain some knowledge as to the other program's state.
>
> It could be a potential exploit, but....
>
> 	(a) it only applies on SMP machines
> 	(b) it's not a remote exploit; the attacker needs to have
> 		the ability to run arbitrary programs on the local
> 		machine
> 	(c) the attacker won't get all of other programs' reads of
> 		/dev/urandom, and
> 	(d) the attacker would have to have a program continuously
> 		reading from /dev/urandom, which would take up enough
> 		CPU time that it would be rather hard to hide.
>
> That's not to say that we shouldn't fix it at our earliest
> convenience, and I'd urge Andrew to push this to Linus for 2.6.10 ---
> but I don't think we need to move heaven and earth to try to
> accelerate the 2.6.10 release process, either.

Is it a problem for other kernel versions?  2.4?  Shouldn't this patch be
pushed out separately to distributions?
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