On Fri, Dec 12, 2003 at 04:20:04PM -0700, Brett Glass wrote: > At 11:19 AM 12/12/2003, Barney Wolff wrote: > > >How is this problem confined to NAT? Seems to me that any system > >connecting to the Internet would have the same issue, if it's actually > >a problem at all. > > Well, yes and no. A system behind a firewall that uses a port that's > commonly used by a worm could find a session blocked, because the > firewall can't trust it not to be infected just because it's inside. > But hopefully, it'd retry and would get another port the next time. > With NAT, there's a bigger problem: the firewall that's doing NAT may > give it the same port again and again, locking it out. (I've seen > this happen.)
This *should* not happen if the end-host uses different source ports on each try, at least as I read the alias_db.c code. Have you tried the -same_ports option? > >So if I were going to solve it (which I'm not) I would expose the kernel's >>"pick a high port" function, add hitlist capability, and have libalias use it. > > Not a bad way to go, actually. It'd be nice to restrict which ports the OS > allowed apps to use, not only so that they don't get blocked by a firewall > but so that a worm that's gotten into the system is detected. (You could set > off an alarm if it tried to bind a "forbidden" port.) For most systems, the coarse granularity of sysctl net.inet.ip.portrange would seem sufficient. I have a real philosophical problem with ceding ports to worms, viruses and trojans. Where will it stop? Portno is a finite resource. -- Barney Wolff http://www.databus.com/bwresume.pdf I'm available by contract or FT, in the NYC metro area or via the 'Net. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
