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Date:      Fri, 25 Oct 2002 19:05:57 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Brooks Davis <brooks@one-eyed-alien.net>
Cc:        Bakul Shah <bakul@bitblocks.com>, freebsd-current@FreeBSD.ORG
Subject:   Re: pppd not working on latest current 2002-10-20
Message-ID:  <3DB9F885.D0A59E87@mindspring.com>
References:  <20021025152221.A8479@Odin.AC.HMC.Edu> <200210260034.UAA03676@tonnant.cnchost.com> <20021025175921.A2761@Odin.AC.HMC.Edu>

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Brooks Davis wrote:
> This isn't going to have an effect on the ability to use kernel ppp for
> other things.  The tty orientation of pppd and the outdated, unmodular
> design on ppp(4) have taken care of that.  This patch gives people
> the functionality they want (pppd just working) without any major
> entanglements (the whole function is <20 lines).  If someone
> wants to make pppd work on arbitrary devices we can deal with that when
> it happens and I frankly doubt it's ever going to since we've got
> netgraph to do that with.

Depending on the value of "sysctl kern.module_path", if the "if_ppp"
module does not exist, and one of the path components is writeable,
then this would permit you to abuse the pppd to load arbitrary modules
into the kernel.

So I understand Bakul's complaint.

But by the same token, "mount" and "ifconfig" have the same problems;
on the other hand, unlike pppd, they are not suid root.

On general principles, loading modules with commands, rather than the
kernel doing it automatically, is a bad idea.  But FreeBSD already
does this in a number of commands, because it lacks a certralized
"feature demand" support facility.

You could also make security arguments on the basis of "what if the
administrator didn't want the machine to be able to be configured
for PPP -- on purpose?"

As long as you control the module path, I don't think this is a real
risk.  There is such a thing as being too paranoid.

As it is, this patch does nothing worse than add to an existing
mess brought about by not having an integrated demand-load facility;
I don't see this as a problem... if there;s a problem, fix it first
in mount and ifconfig, before you complain about this patch.

-- Terry

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