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Re: Tempfile vulnerabilities
From: wk () GNUPG ORG (Werner Koch)
Date: Wed, 2 Feb 2000 23:01:10 +0100


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



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