Re: S/Key keyinit(1) authentication (lack thereof) + sudo(1)

From: Wietse Venema (wietseat_private)
Date: Tue Sep 04 2001 - 07:48:39 PDT

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    If an operator leaves his/her terminal unattended, then a miscreant
    can plant any number of trojan horses to gain future root access.
    
    The possibilities for getting future root access are not limited
    to skeyinit + sudo. To begin with, any trojan horse will suffice
    that captures the operator's plain-text password. Then there are
    cron and at, which give the equivalent of operator terminal access.
    
    Therefore, adding a password challenge to skeyinit is not sufficient.
    The fix, at least for today's versions of FreeBSD, is for operators
    not to leave their terminal unattended.
    
    	Wietse
    
    Frank Tobin:
    > Summary: keyinit(1)'s lack of authentication creates severe
    >          authentication issues, especially when used in combination
    >          with programs such as sudo(1).
    > 
    > Affected Systems: FreeBSD-stable (older?), and other systems that use
    >                   S/Key, especially in combination with sudo(1)
    > 
    > Solution Summary: Disable S/Key in favor of OPIE
    >                   or patch keyinit(1) to require authentication
    >                   or do not use sudo(1)
    > 
    > History:
    > 
    > I brought up this matter a few years ago on freebsd-security
    > (http://www.freebsd.org/cgi/getmsg.cgi?fetch=430991+433795+/usr/local/www/db/text/1999/freebsd-security/19990926.freebsd-security),
    > with no response, but at the behest of others during a demonstration I
    > gave recently, I'm prompted to bring this up again.
    



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