OSEC

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Subject: Re: Tempfile vulnerabilities
From: antirez (antirezINVECE.ORG)
Date: Sat Feb 05 2000 - 05:16:09 CST

On Wed, Feb 02, 2000 at 02:36:20PM -0700, Theo de Raadt wrote:
> 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
[snip]

Sure but there is another problem, while evil user exec 'cat /dev/random >
 /dev/null &' maybe that the following results in an infinite loop:

while(there_are_enougt_entropy() == 0)
        sleep(1);
/* race -- what if the evil user starts to deplate the entropy pool here? */
get_entropy_from_randomdev();

Can be so easy to DoS cryptographic software?

Of course all insecure cgi scripts or daemons may be used to pool from
/dev/random remotely. An example? the old TERM="../../../bla" problem.

antirez