Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ames!apple!oliveb!pyramid!prls!mips!djl
From: djl@mips.COM (Dan Levin)
Newsgroups: comp.sys.mips
Subject: Re: comsat doesn't work in RISC/os 4.0 as distributed
Message-ID: <24049@winchester.mips.COM>
Date: 25 Jul 89 18:56:03 GMT
References: <450@indri.primate.wisc.edu>
Lines: 30

In article <450@indri.primate.wisc.edu>, bin@primate.wisc.edu (Brain in Neutral) writes:
> It would be nice if someone at MIPS could explain just what mcomsat is all
> about, anyway, and why there comsat and mcomsat both exist, rather than just
> comsat.

Well, as the father of this bastard, I suppose I should at least wave my
hands a bit :-)

/bin/mail on RISC/os systems is derived from System V, not from BSD.  The
System V /bin/mail is not setuid root, it is only setgid bin.  Since
/bin/mail is the guy who has to tell comsat that a message has arrived,
and to do that he has to connect to a privileged port, he must be
setuid root to work.

Now, we wanted to have biff, but we didn't want to fix /bin/mail to
be setuid'able, nor did we want to switch over to BSD /bin/mail (for
political and qa reasons).  So, I left the old comsat service in
in case someone wanted to write their own delivery agent that used it,
but I also created a non-privileged service called mcomsat (mips comsat
if you will).  Since our comsat doesn't do anything that could be considered
a security risk, allowing it to be talked to on a non-privileged port
is not a problem.  This allows our setgid /bin/mail to talk to comsat, via
mcomsat, and thus allows biff to work when /bin/mail is the delivery agent.

'Nuff said?

-- 
			***dan

{decwrl,pyramid,ames}!mips!djl         djl@mips.com (No, Really! Trust Me.)