oss-security - Re: DNS vulnerability: other relevant software

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Date: Sat, 12 Jul 2008 23:50:41 +0200
From: Florian Weimer <fw@...eb.enyo.de>
To: oss-security@...ts.openwall.com
Subject: Re: DNS vulnerability: other relevant software

* Eugene Teo:

> Actually, I'm not sure. I'm checking with my colleagues who may be more
> familiar with the implementation of net_random/random32() routine.

Gosh, I must be missing something.  This generator appears to be linear
(but the reduction to the available port range is not).

The comment is pretty clear, too:

 *      A 32 bit pseudo-random number is generated using a fast
 *      algorithm suitable for simulation. This algorithm is NOT
 *      considered safe for cryptographic use.

I haven't written an exploit because I'm not sure how to bypass the
modulo operation.  The modulus is 28233 = 3 * 3 * 3137 by default, so
it's not obvious to me how to recover the internal status without 2**51
effort.

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