Re: Tempfile vulnerabilities

[wk () GNUPG ORG (Werner Koch)]

On Wed, 2 Feb 2000, Theo de Raadt wrote:

> I suppose then that anyone who attacks a machine which relies on
> /dev/random -- a world readable device -- should do the following:
>
>       cat /dev/random > /dev/null &

Yep.

> Crypto software which uses those devices should be doing some kind of
> checking to make sure that they are getting at least good entropy.  I

The good thing is that /dev/random blocks until there is enough entropy
available.  /dev/urandom does not block but continues to return random
bytes by using a PRNG.

> suppose I could even argue that the random devices should make it easy
> for customer software to determine that entropy is low.

There is also an ioctl() to query some statistics.  OpenBSD has some
more kinds of random devices but I don't know much about them.

I have not checked the latest Linux kernels but rumors are that this
device has been enhanced.


--
Werner Koch at guug.de           www.gnupg.org           keyid 621CC013