Xref: utzoo alt.security:1626 comp.unix.sysv386:746
Path: utzoo!utgpu!cs.utexas.edu!uunet!mcsun!unido!mikros!mwtech!martin
From: martin@mwtech.UUCP (Martin Weitzel)
Newsgroups: alt.security,comp.unix.sysv386
Subject: Re: Here's how to stop shell escapes from vi
Message-ID: <935@mwtech.UUCP>
Date: 25 Sep 90 18:49:03 GMT
References: <924@mwtech.UUCP> <27387:Sep2320:07:3890@kramden.acf.nyu.edu> <1990Sep24.040745.10454@chinet.chi.il.us> <1038:Sep2414:36:0390@k
Reply-To: martin@mwtech.UUCP (Martin Weitzel)
Organization: MIKROS Systemware, Darmstadt/W-Germany
Lines: 36

In article <1038:Sep2414:36:0390@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:
>In article <1990Sep24.040745.10454@chinet.chi.il.us> les@chinet.chi.il.us (Leslie Mikesell) writes:
>> In article <27387:Sep2320:07:3890@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:
>> >    [ trash the colon with pty -0 tr \: \? | pty vi ]
[...]
>> Umm... Well, there's 'Q' to go to ex mode and stay there while you
>> type sh,
>  [ blah blah blah ]
>
>Read my lips: ``The only thing that you can't completely control from
>within vi is the mapping of the colon---and my solution handles that.''
>You can map Q. You can map @. You can even map !---I didn't realize this
>at first. You can map every single f-ing character the user can type.
>Except the colon.

Dan, calm down. I confess that after your first posting I had not
understood your proposual to map all "dangerous" command from *within*
vi and that mapping Q, @, and ! to <esc> so could effectively disable
these commands. But playing a little with vi, to confirm if it could
work, revealed other interesting things.

If you have two minutes time, please try the following: 2000i-<esc>
This should construct a line of 2000 characters, which is above the
limits at least my vi (386/ix Rel 2.0.2) can handle. Then insert
another character into this line ... and whoops, vi throws you into
ex-mode.

Nice feature - who would ever have thought? Possibly some user which
you carefully tried to keep away from ex-prompts knows this little
"feature" (who said it is a bug?).

Vi wasn't designed for what you have in mind. It MUST be fixed in the
vi-sources, if it should work reliable! I would never trust in any
other solution.
-- 
Martin Weitzel, email: martin@mwtech.UUCP, voice: 49-(0)6151-6 56 83