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Date:      Thu, 27 Feb 97 6:55:03 CST
From:      Joe Greco <jgreco@solaria.sol.net>
To:        adrian@obiwan.aceonline.com.au (Adrian Chadd)
Cc:        joerg_wunsch@uriah.heep.sax.de, adrian@cougar.aceonline.com.au, marcs@znep.com, hackers@FreeBSD.ORG, auditors@FreeBSD.ORG
Subject:   Re: disallow setuid root shells?
Message-ID:  <199702271255.GAA22830@solaria.sol.net>
In-Reply-To: <Pine.BSF.3.95q.960111011311.7014A-100000@obiwan.aceonline.com.au> from "Adrian Chadd" at Jan 11, 96 01:18:18 am

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> For the record, I'm mounting/usr/home, /tmp, /var/spool/mail (and anything
> else they have r/w access to) as non-executable, making internal exploits
> run on the local box nearly impossible to run (any ideas how you could
> overflow something in perl / *sh ? :)

This, incidentally, is a pretty good strategy.  Filesystems where there
shouldn't be executables should be mounted nodev,noexec,nosuid (/home should
be at least mounted nodev,nosuid as it may be legit for users to have
executables and shell scripts).

Included, I think, should be all of /var - not just var/spool/mail.

I don't (yet) do this myself, but am thinking of it as I have yet to see
a reason not to do it.  Maybe it could become "standard"...?  Comments?

... Joe

-------------------------------------------------------------------------------
Joe Greco - Systems Administrator			      jgreco@ns.sol.net
Solaria Public Access UNIX - Milwaukee, WI			   414/342-4847



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