Re: Concurrent access to /dev/urandom

Adam Heath
2004-12-11T19:58:58Z

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?