Re: RSI.0012.12-03-98.SOLARIS.MKCOOKIE

From: Chris Wedgwood (chrisat_private)
Date: Thu Dec 10 1998 - 19:00:50 PST

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    On Mon, Dec 07, 1998 at 01:39:05PM -0500, Readwin, Neil wrote:
    
    > On Solaris mkcookie opens /dev/mem and reads about 8MB of it.
    > mkcookie will run and generate a new cookie if you remove the suid
    > bit, but I guess said cookie will be, umm, less random.
    
    This reminds me (I may have reported this eons ago, I forget).
    
    An old version of util-linux (some years old) also has a hosed
    mcookie program.
    
    You can test this by doing something like;
    
    
       while [ 1 ] ; do mcookie >> file ; done
    
    <pause a few minutes> ^C
    
       sort file | uniq | wc
    
    
    Basically... I was never able to get more that 16384 (2^14) unique
    tokens, a pretty small space compared to the theoretical 2^128.
    <Insert usual bit about birthday attack, blah blah blah>
    
    I don't know which version of util-linux it was, but I'm pretty sure
    2.5 and above use /dev/random and hence don't have this behaviour.
    
    
    
    
    -Chris
    



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