Date: 28 Jul 1998 15:34:36 +0200 From: Benedikt Stockebrand <benedikt@devnull.ruhr.de> To: sthaug@nethelp.no Cc: marcs@znep.com, ben@rosengart.com, security@FreeBSD.ORG Subject: Re: inetd enhancements (fwd) Message-ID: <87af5um74j.fsf@devnull.ruhr.de> In-Reply-To: sthaug@nethelp.no's message of "Tue, 28 Jul 1998 09:55:12 %2B0200" References: <Pine.GSO.4.00.9807272303400.26598-100000@redfish> <12062.901612512@verdi.nethelp.no>
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sthaug@nethelp.no writes:
> If your box is setup *not* to route (net.inet.ip.forwarding = 0), I can
> certainly see security advantages in not allowing packets to be accepted
> unless they have destination address equal to the interface address. I
> have seen a patch for this floating around on the net, but it would be
> nice to have this configurable.
I'd use a packet filter for that, something like
DENY="/sbin/ipfw add deny"
IF1="ed0"
IP1="192.168.47.11"
IF2="ed1"
IP2="192.168.227.28"
$DENY all from $IP1 to any in via $IF2
$DENY all from $IP2 to any in via $IF1
(this is off my head and a couple months after I've last written a
packet filter set, so YMMV). A similar ruleset that's using networks
instead of individual addresses should be used on any packet filtering
router.
Making this the default behaviour will break a variety of things in
connection with multihomed hosts that have interfaces in multiple
networks (like for performance issues) but leave the actual routing
business to some active network component.
Example: For performance reasons I've got four networks 192.168.1.0 to
192.168.4.0 and a single high-speed NFS server "nfs.example.com" with
an interface in each net on IP addresses 192.168.[1-4].42. If I want
to make use of all these interfaces I can either
- assign different names to the addresses and configure all machines
in the networks to use the proper address for their network
- use some ugly DNS hacking
- announce host routes to the first address on all other addresses.
The first solution involves configuring all client machines, the
second is a bl**dy mess and the third may be somewhat weird. If I'm
dealing with four crowded class C's I'd always go for the third
approach.
So long,
Ben
--
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