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Security practices
From: Roeland Meyer <rmeyer () mhsc com>
Date: Tue, 15 May 2001 09:46:08 -0700


From: Adam McKenna [mailto:adam () flounder net]
Sent: Monday, May 14, 2001 11:18 PM

On Mon, May 14, 2001 at 05:27:09PM -0400, Christopher A. 
Woodfield wrote:

I didn't intend to imply that matching forward/reverse DNS 
was a security 
measure I'd trust by itself, but it certainly doesn't hurt 
to implement as 
a "outer perimeter" measure in conjunction with IP-based rules and 
secure authentication...

It does hurt.  It causes non-obvious problems.  Forcing 
hostnames and PTR's
to match (commonly referred to as PARANOID checking) does not 
provide extra
security, it just prevents people with badly configured DNS 
from accessing
your servers.

IOW, it lets lazy/incompetent ISPs and SysAdms get away with not being
thourough. Actually, basic security isn't that bad, if you tighten up the
ship such that, you are doing what you are supposed to be doing
...exactly... and no more. Cut out the slop and most things work better,
with fewer holes. This is on the principle that memcpy, strcmp, and strcpy
are the biggest (only?) security holes on the net (and why open-source is
the only acceptable source of security related code).

Reverse checks work if you run your own zone servers and control your own
in-addr.arpa entries and they are all on the same LAN/net-block. Clone a
[RFC 2870] root zone server into this and you are almost spoof proof. When
accessing your own hosts, you shouldn't be going outside your LAN for any
authentication or host reference data (the single reason spoofs work at all)
nor should your packets leave your LAN.


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