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Date:      Mon, 23 Aug 1999 22:37:37 +0200
From:      sthaug@nethelp.no
To:        nate@mt.sri.com
Cc:        freebsd@gndrsh.dnsmgr.net, freebsd-security@FreeBSD.ORG
Subject:   Re: IPFW/DNS rules
Message-ID:  <99207.935440657@verdi.nethelp.no>
In-Reply-To: Your message of "Mon, 23 Aug 1999 14:24:01 -0600"
References:  <199908232024.OAA01685@mt.sri.com>

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> > Not a whole lot you can do here, other than keep on top of the latest
> > versions of bind from ISC.  
> 
> *sigh*  Guess Bind is really in the same category as sendmail then.
> Unfortunately, BIND has it's hooks all over the system, including the C
> library.  Can I just install the named and not worry about anything
> else, leaving the system the same?  The box in question is running
> 2.2.8, and I *really* don't want to upgrade it if I can avoid it.

You can install 8.2.1 just fine on a 2.2.8 box. It's a good idea to get
8.2.1 (or newer - 8.2.2 is now in public beta test) because of security
fixes. For one thing, 8.2 and newer lets you randomize query id's -
8.1.2 doesn't.

> > Second since xfers are done via TCP setup rules to allow only your secondaries
> > to ``setup'' connections to your primary, and allow your server to
> > ``setup'' connections to the servers it secondaries for.
> 
> Can I setup firewall rules for this as well?  Do normal queries require
> TCP connections?  I'd like to be able to 'shutoff' TCP access to the box
> except from my secondaries if at all possible.

That would be a pretty bad idea in general:

- A resolver is *allowed* to use TCP for DNS queries.
- The RFC specifies that a resolver *should* retry using TCP if a UDP
answer is too big (and thus gets the TC, Truncated, bit set).

Of course, a for primary which is behind a firewall, and only supposed
to be accessed from the secondaries, the situation is different.

For general DNS info, try http://www.dns.net/dnsrd/. The best book is
the O'Reilly "DNS and BIND" book by Albitz and Liu. Make sure you get
the newest edition.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no



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