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Path: utzoo!mnetor!seismo!munnari!kre
From: kre@munnari.oz (Robert Elz)
Newsgroups: comp.unix.wizards
Subject: Re: /etc/rc, security ...
Message-ID: <1573@munnari.oz>
Date: Wed, 22-Apr-87 09:55:35 EST
Article-I.D.: munnari.1573
Posted: Wed Apr 22 09:55:35 1987
Date-Received: Fri, 24-Apr-87 01:13:16 EST
References: <623@rna.UUCP> <439@uhccux.UUCP>
Organization: Comp Sci, Melbourne Uni, Australia
Lines: 47

In article <623@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes:
>	I did a PS on our 4.2BSD system today and found extra copies of
> /etc/update, cron and a few other running, owned by one of our users.

In article <439@uhccux.UUCP>, todd@uhccux.UUCP (The Perplexed Wiz) replies:
> It seems that BSD releases are full of weird security holes as delivered.

I'm not sure what your definition of a "security hole" is, but
this doesn't fit mine.  Its just a slightly silly setup, it
doesn't allow anything at all that users couldn't do anyway.

If I have an inclination to run /etc/update, but /etc/update is
700 mode (or similar), I just

	cp /usr/src/etc/update.c .; cc update.c; ./a.out

and it runs.  If I can do it that way (so the system staff
can't even see that its update that's running easily) I can't
see why I shouldn't just be able to do /etc/update.

Its a bit of a dumb thing to want to do, but not a security hole.

If the source is protected incidentally, then I just do

	cat <<! >update.c
	main() {
		for (;;)
			sleep(60), sync();
	}
	!

instead of the copy, and then continue.

Exactly the same applies to cron .. having a user run it is a bit
dumb, but not any kind of security hole.  You might want to protect
crontab rather than cron, so users can't see what processes you have
cron run, but that's just obscurity security, and is only marginally
useful.

I should say that even given all that, I do recommend protecting
cron, update, etc .. the type of user dumb enough to actually run
one of those things is usually also dumb enough not to know any
of the above techniques to get around the protection, and it does
save wasting system resourses (an extra few copies of update running
can limit the effectiveness of the buffer cache).

kre