Subject: [Uta] Using TLS with NNTP

From: Julien ÉLIE <[email-masked]>
Date: Mon, 2 Nov 2015 11:12:04 +0100

Hi all,

Since the publication of RFC 7465 "Prohibiting RC4 Cipher Suites", there 
has been a discrepancy with the requirements of Section 5 of RFC 4642 
"Using Transport Layer Security (TLS) with Network News Transfer 
Protocol (NNTP)":

    NNTP client and server implementations MUST implement the
    TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite and SHOULD implement the
    TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite.  This is
    important, as it assures that any two compliant implementations can
    be configured to interoperate.  All other cipher suites are OPTIONAL.

Another point is the fact that TLS 1.3 will remove support for 
compression.  The NNTP protocol is currently relying on that feature of 
TLS, as we can see in the abstract and the description of the STARTTLS 
command in RFC 4642:

    The STARTTLS command is usually used to initiate session security,
    although it can also be used for client and/or server certificate
    authentication and/or data compression.

A huge thread of more than a thousand messages has just been held in the 
TLS IETF working group. The chairs agreed to remove compression from TLS 
1.3:
     https://www.ietf.org/mail-archive/web/tls/current/msg17941.html

Basically, it is not the role of a security layer to provide a facility 
(compression) that is known to cause security issues (CRIME attack for 
instance).
If compression with TLS is wanted for NNTP, then clients and servers 
will have to use TLS 1.2 (or more ancient).

I was advised in the TLS mailing-list to contact the UTA WG.  (The NNTP 
WG is no longer an active IETF WG.)

The questions are:

- what move should be done about RFC 4642?
The good news is that Stephen Farrell, an IETF/IESG chairman, is willing 
to shepherd us on refreshing RFC 4642.  We have to decide the best move 
to do between a new RFC that obsoletes RFC 4642 or a short RFC that 
updates RFC 4242.
     http://www.ietf.org/mail-archive/web/tls/current/msg17562.html

- what should we say in that refresh?
An idea is that we could just refer to RFC 7525 (Recommendations for 
Secure Use of Transport Layer Security (TLS) and Datagram Transport 
Layer Security (DTLS)), that is a Best Current Practice:
     https://tools.ietf.org/html/bcp195

- do you see other things that should be improved at the same time in 
RFC 4642?

- as for compression, there is a draft for a COMPRESS command:
     http://tools.ietf.org/id/draft-murchison-nntp-compress-01.html
Is it the right move to do for Applications that are currently relying 
on the compression provided by TLS?

P.-S. : Maybe in the wiki of UTA, the NNTP protocol could be mentioned :)
     http://trac.tools.ietf.org/wg/uta/trac/wiki

Thanks beforehand,

-- 
Julien ÉLIE

« Aut bibas aut abeas. »

---

From: Julien ÉLIE <[email-masked]>
Date: Thu, 12 Nov 2015 21:50:34 +0100

Hi all,

What would you recommend to refresh RFC 4642 so that it can be 
consistent with the latest published RFCs about TLS and its best practices?

A new RFC obsoleting it, or only an update like RFC 7590 is for XMPP?

And is UTA the right WG to work on that refresh?

You'll find more background about that in my mail below.
I've CC: the original authors of RFC 4642.

Thanks beforehand,

-- 
Julien

---

From: Leif Johansson <[email-masked]>
Date: Fri, 13 Nov 2015 10:29:20 +0100

> I've CC: the original authors of RFC 4642.

UTA could definitely be the right place for this work. In Yokohama last
week Orit stood up at the mic in SAAG to ask for those able and willing
to turn up and help out with this.

My suggestion is that you publish an individual submission with the
updates to NNTP and other language around TLS in NTTP you and the
NNTP community consider appropriate and then we'll just have to see
if there is enough traction in the UTA wg to take this on as a WG
item.

I would also suggest that if you or others have contacts in the NNTP
community then please ask them to gather on this list and volunteer
to work on this. This would significantly increase the chance that
UTA will be successful in taking this work on.

	Cheers Leif

---

From: Julien ÉLIE <[email-masked]>
Date: Tue, 24 Nov 2015 22:36:33 +0100

Hi Leif,

> to turn up and help out with this.

Thanks for your details about what happened in Yokohama.  I'm also 
grateful to Orit for having asked.

> updates to NNTP and other language around TLS in NNTP you and the

That sounds good.  I'll have a look at it in the first few months of 
2016, and propose the draft to the UTA WG.

> UTA will be successful in taking this work on.

Sure.  I know a few active people in the NNTP community that should be 
interested in reviewing the draft and participating to subsequent 
discussion.

Have a nice week,

-- 
Julien ÉLIE

« Aequum est ut cuius participauit lucrum, participet et damnun. »