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Re: Tempfile vulnerabilities
From: deraadt () CVS OPENBSD ORG (Theo de Raadt)
Date: Wed, 2 Feb 2000 14:36:20 -0700


The terrible /tmp race handling aside...

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 &

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

On Mon, 31 Jan 2000, Grant Taylor wrote:

       open RAN, "/dev/random" || die;
       read(RAN,$foo,16);
       close RAN;
       $file = '/tmp/autobuse' . unpack('H16',$foo);

Please, never use /dev/random or /dev/urandom for such purposes.

Aside the fact, that it does not help much in what you want to achieve
it is a desaster to system performance because it empties the system's
entropy pool and wastes precious entropy for unneeded things.

Crypto software _really_ needs these random numbers.


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

     Boycott Amazon!  -  http://www.gnu.org/philosophy/amazon.html


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