Date: Tue, 22 Jun 1999 01:08:04 -0400 (EDT) From: "Brian F. Feldman" <green@unixhelp.org> To: Kris Kennaway <kkennawa@physics.adelaide.edu.au> Cc: Peter Wemm <peter@netplex.com.au>, Jean-Marc Zucconi <jmz@freebsd.org>, hoek@freebsd.org, cvs-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/kern imgact_gzip.c Message-ID: <Pine.BSF.4.10.9906220107400.60297-200000@janus.syracuse.net> In-Reply-To: <Pine.OSF.4.10.9906221242200.4351-100000@bragg>
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On Tue, 22 Jun 1999, Kris Kennaway wrote:
> On Tue, 22 Jun 1999, Peter Wemm wrote:
>
> > Ahh yes, I forgot that / was read-write for MFS boots. However:
> >
> > #!/bin/sh
> > skip=18
> > if /usr/bin/tail +$skip $0 | gzip -cd > /tmp/gztmp$$; then
> > chmod 700 /tmp/gztmp$$
> > prog="`echo $0 | sed 's|^.*/||'`"
> > if /bin/ln /tmp/gztmp$$ "/tmp/$prog" 2>/dev/null; then
> > trap '/bin/rm -f /tmp/gztmp$$ "/tmp/$prog"; exit $res' 0
> > (/bin/sleep 5; /bin/rm -f /tmp/gztmp$$ "/tmp/$prog") 2>/dev/null &
> > /tmp/"$prog" ${1+"$@"}; res=$?
> > else
> > trap '/bin/rm -f /tmp/gztmp$$; exit $res' 0
> > (/bin/sleep 5; /bin/rm -f /tmp/gztmp$$) 2>/dev/null &
> > /tmp/gztmp$$ ${1+"$@"}; res=$?
> > fi
> > else
> > echo Cannot decompress $0; exit 1
> > fi; exit $res
>
> This is the unpatched (insecure) version of gzexe (all the /tmp/gztmp$$'s),
> but it's functionally the same.
>
> > Now, if tail, sh, gzip, chmod, ln, sleep, rm, etc are all in the gzexe'd
> > crunched linked binary, how is it supposed to decompress itself? "sh" itself
> > is part of the crunched binary, so what is going to decode sh when sh itself
> > is a shell script?
>
> Yes, that seems to be a problem - gzexe depends on those executables. However
> it shouldn't be too hard to recode this decompressor in C to perform the same
> job without any external dependencies. The question is whether that would be
> easier than fixing the kernel to handle gzipped ELF binaries transparently -
> almost certainly it would be.
How's what I attached?
>
> Kris
>
> > Cheers,
> > -Peter
>
> -----
> "Never criticize anybody until you have walked a mile in their shoes,
> because by that time you will be a mile away and have their shoes."
> -- Unknown
>
>
Brian Fundakowski Feldman _ __ ___ ____ ___ ___ ___
green@FreeBSD.org _ __ ___ | _ ) __| \
FreeBSD: The Power to Serve! _ __ | _ \._ \ |) |
http://www.FreeBSD.org/ _ |___/___/___/
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