Date: Wed, 29 May 2002 15:41:13 -0700 From: "Crist J. Clark" <crist.clark@attbi.com> To: "Jacques A. Vidrine" <nectar@freebsd.org> Cc: security@freebsd.org Subject: Re: FreeBSD Security Advisory FreeBSD-SA-02:27.rc Message-ID: <20020529154113.D12700@blossom.cjclark.org> In-Reply-To: <20020529210334.GA5544@madman.nectar.cc>; from nectar@freebsd.org on Wed, May 29, 2002 at 04:03:34PM -0500 References: <200205291636.g4TGaZX40801@freefall.freebsd.org> <20020529133852.B12700@blossom.cjclark.org> <20020529210334.GA5544@madman.nectar.cc>
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On Wed, May 29, 2002 at 04:03:34PM -0500, Jacques A. Vidrine wrote:
> On Wed, May 29, 2002 at 01:38:52PM -0700, Crist J. Clark wrote:
> > > /bin/sh -c 'echo -e "/.X11-unix/s/^/#/\nw\nq\n" | /bin/ed -s /etc/rc'
> >
> > Ick. How about,
> >
> > # /usr/bin/printf "/.X11-unix/s/^/#/\nw\nq\n" | /bin/ed -s /etc/rc
> >
> > Next time?
>
> *shrug* One could prescribe any number of alternatives to achieve the
> modification. I chose this way, because /bin/sh and /bin/ed are both
> statically linked and should always be available on all systems in
> single user mode. It seems unlikely that this will be an issue for
> anyone, but hey - you never know.
I guess I should have explained my concern more. I'm thinking some
l33t kid out there is going to look at that and say, "I can just do,
# echo -e "/.X11-unix/s/^/#/\nw\nq\n" | /bin/ed -s /etc/rc
And not have to worry about all of that /bin/sh stuff at the front..."
and thus outsmart himself. He wouldn't realize you are counting on
features of the echo builtin in sh(1) and not /bin/echo or the csh(1)
echo builtin. The above commands don't work as desired for a
non-sh(1)-ish shell.
I'm curious to see how many posts to the list might appear as people
do just that.
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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