From: rseymour@reed.edu (Robert Seymour)
Date: Thu, 8 Dec 94 10:02:38 PST
To: samman@CS.YALE.EDU (Ben)
Subject: Fixing Flash/ANSI Bomb/Terminal Screwup
In-Reply-To: <Pine.3.07.9412081154.E238-a100000@jaguar.zoo.cs.yale.edu>
Message-ID: <m0rFnAL-0001Y9C@vishnu.reed.edu>
MIME-Version: 1.0
Content-Type: text/plain


In the world according to Ben:
> > On Wed, 7 Dec 1994, Roy M. Silvernail wrote:
> > > That person asks that I post instructions for recovering from so heinous
> > > an attack.  All I can suggest is escaping to a shell and doing a 'clear'
> > > (or, under MS-DOS, 'cls').

> > I have found that some attacks that leave your screen doing strange 
> > things can be recoverd from by ussing the talk command. This program, on 
> > UNIX machines seems to reset alot of things that might have gone array 
> > with your screen.

> If you hit the control button with both mouse buttons at the same time in
> twm(an X windows manager) there pops up a menu--choose the 'reset
> terminal' option.

Flash/ANSI Bomb/terminal codes or just general screwups can be quite a pain.
Though the methods suggested above may work in some circumstances, they won't
work all the time. One method I have found to be quick and highly effective
is the following alias (shown from my bash rcfile, but you can easily
translate to other shells):

## This last one is a nifty little way to fix the terminal after being
## flashed or otherwise messed up by some program.  If your terminal is
## really screwed up, it may not be able to parse the return (^M) correctly.
## If so, use linefeed (^J), then type "sanity", then type another linefeed.
alias sanity='stty 500:5:96c:3b:0:3:1c:8:17:4:0:0:0:500:5:96c:8000003b:3:1c:8:17
:4:0:0:0:ff:ff:ff:4:0:1a:11:13:0:0:1a:ff'

(N.B.: make sure that is one line for the alias).  Unfortunately this does
assume that your terminal is at least semi-clued (i.e. minimal vt100 features,
but it should be able to get your back to a sane setup wherein you can re-
source your own rcfiles or set the terminal paramters yourself.  There is
also a script called unflash which will fix basic terminal codes attacks, 
but it is less robust (it just echos {esc}c {esc}0 and clears the screen,
which will end text properties but not neccesarily fix status lines and
other problems).

If you use it, let me know how this generalizes, its been quite stable in
my experience.  The real tough one to deal with is xterm, which can have
font properties set through escape codes, a well designed talk request,
terminal write, or irc bomb can make it entirely unintelligible and very
difficult to recover.  Get you admin to install a good fingerd/talkd
and/or use mesg n to prevent access in the first place.  There are several
around now which disallow terminal codes in the talk requesters id and
check IPs, etc.

|Robert

-- 
Robert Seymour					rseymour@reed.edu
Reed College Artificial Life Project		NeXTmail, MIME, PGP accepted

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