Re: Tempfile vulnerabilities

From: Theo de Raadt (deraadtat_private)
Date: Wed Feb 02 2000 - 13:36:20 PST

  • Next message: Michal Zalewski: "Re: no comment"

    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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