Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!nrl-cmf!cmcl2!adm!xadmx!mcvax!kernel.co.uk!mjh@uunet.uu.net
From: mcvax!kernel.co.uk!mjh@uunet.uu.net (Mark J. Hewitt)
Newsgroups: comp.unix.wizards
Subject: What reason should /dev/kmem not be world-readable?
Message-ID: <17488@adm.BRL.MIL>
Date: 11 Nov 88 21:10:35 GMT
Sender: news@adm.BRL.MIL
Lines: 19

>  ...reading clists...

Int the good old days, we acheived this by adding a little code to the
tty interrupt routine - when it placed a character on the output queue,
it looked to see if there was a second tty to receive the character
(from a kernel variable poked by a runnable by root only program called
`spy'!), and stuffed it on that queue too.  This was on UNIX Ed. 6.
Later versions are a little harder because the queue is written in one
of several places (multiplexer files, line disciplines, probably
streams, etc...), but I did the same thing on a 4.2bsd system despite
this.  

Mark J. Hewitt

usenet:	...!{mcvax,uunet}!ukc!kernel!mjh	JANET:	mjh@uk.co.kernel
voice:	(+44) 532 444566			other:	mjh@kernel.co.uk
fax:	(+44) 532 425456	   old style: mjh%uk.co.kernel@uk.ac.ukc
paper:	Kernel Technology Ltd, Development Centre, 46 The Calls, Leeds,
	LS2 7EY, West Yorkshire, UK