Re: [secdir] secdir review of draft-elie-nntp-tls-recommendations-01

[David Mandelberg <[e-mail]>]

On 2016-12-08 16:47, Julien ÉLIE wrote:
> I believe it is OK to take the following text into account for the
> ports to use for NNTP over TLS, but I prefer to share with you the
> wording in case you have any comments about it.  (Maybe it is not
> clear enough!)
> We would then have in Appendix A of the document:
> 
>  The third and fourth paragraphs in Section 1 of [RFC4642] are
>  replaced with the following text:
> 
>   TCP port 563 is dedicated to NNTP over TLS, and registered in the
>   IANA Service Name and Transport Protocol Port Number Registry for
>   that usage.  NNTP implementations using TCP port 563 begin the TLS
>   negotiation immediately upon connection and then continue with the
>   initial steps of an NNTP session.  This use of strict TLS on a
>   separate port is the preferred way of using TLS with NNTP.
> 
>   If a host wishes to offer separate servers for transit and reading
>   clients, TCP port 563 SHOULD be used for the reading server using
>   strict TLS.  If a transit server offers strict TLS, it SHOULD use TCP
>   port 433 if it does not accept unencrypted connections, but can
>   alternatively use another unused port of its choice.  If it accepts
>   dynamic upgrade from unencrypted to TLS-protected traffic, it SHOULD
>   use TCP port 433 for that usage, and another unused port of its
>   choice for strict TLS.  In either case, the port used for strict TLS
>   should be clearly communicated to the client, and specifically that
>   no plain-text communication occurs before the TLS session is
>   negotiated.

 From a security point of view, I have no objection to this text.

I'm a bit surprised that you're using the same port (433) for both plain 
TLS and for STARTTLS, but as long as clients and servers are configured 
correctly, that should work. I assume there's no protocol switching 
attack between TLS and NNTP?


-- 
David Eric Mandelberg / dseomn
http://david.mandelberg.org/