Re: [netconf] Latest ietf-netconf-server draft and related modules

Michal Vaško <mvasko@cesnet.cz> Fri, 02 April 2021 19:33 UTC

Return-Path: <mvasko@cesnet.cz>
X-Original-To: netconf@ietfa.amsl.com
Delivered-To: netconf@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 4A2683A2112 for <netconf@ietfa.amsl.com>; Fri, 2 Apr 2021 12:33:26 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Level:
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cesnet.cz
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tgI7EkaLPYad for <netconf@ietfa.amsl.com>; Fri, 2 Apr 2021 12:33:21 -0700 (PDT)
Received: from kalendar.cesnet.cz (kalendar.cesnet.cz [78.128.211.34]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 403213A20F2 for <netconf@ietf.org>; Fri, 2 Apr 2021 12:33:18 -0700 (PDT)
Received: by kalendar.cesnet.cz (Postfix, from userid 110) id C4C3160088; Fri, 2 Apr 2021 21:33:07 +0200 (CEST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cesnet.cz; s=kalendar; t=1617391987; bh=77Tfvzv1IlpXQHs2oHAEwC4bfT18ZeOIm/0QvNyUd/I=; h=From:In-Reply-To:Date:Cc:To:Subject; b=AM2G9QibEzcoVYxY4vRQVSqa+IUTpMEMYtcwPRg4nJ4NzRh8PFTeFAHKS0+wmlxzB zUZItsQFtNPqbgOgIgY0EvO5qjui6Muv9Nped6YsS/9FsFpXBHH5nhl0JTmLgydd87 A2z+6CbaZFrEfPHlZd2Q8gLsxuBf/NFsFpVRodHg=
From: =?utf-8?q?Michal_Va=C5=A1ko?= <mvasko@cesnet.cz>
In-Reply-To: <0100017804af516b-fff3cc4f-3806-4108-a448-db4249a437a4-000000@email.amazonses.com>
Content-Type: text/plain; charset="utf-8"
X-Forward: 84.42.188.124
Date: Fri, 02 Apr 2021 21:33:07 +0200
Cc: "netconf@ietf.org" <netconf@ietf.org>
To: "Kent Watsen" <kent@watsen.net>
MIME-Version: 1.0
Message-ID: <5303-60677180-31-62233d80@261934540>
User-Agent: SOGoMail 5.0.1
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://mailarchive.ietf.org/arch/msg/netconf/TX90roHsSQyzTlDSIr1o55E4Wcg>
Subject: Re: [netconf] =?utf-8?q?Latest_ietf-netconf-server_draft_and_related?= =?utf-8?q?_modules?=
X-BeenThere: netconf@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: NETCONF WG list <netconf.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/netconf>, <mailto:netconf-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/netconf/>
List-Post: <mailto:netconf@ietf.org>
List-Help: <mailto:netconf-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/netconf>, <mailto:netconf-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 02 Apr 2021 19:33:32 -0000

Hi Kent,

firstly I am sorry, somehow I missed this reply, my bad :(

> > I had a chance to look at these modules again and have 2 questions regarding some recent changes.
> > 
> > - ietf-ssh-server, ssh-server-grouping/client-authentication/supported-authentication-methods> 
> > Since the "other" leaf-list was removed there is no way to support some other methods than those specified. I am not sure whether this was the intention and if so, what is the reason for it? If nothing else, we support "interactive" authentication method but there are some others that I see no reason why they could not be used.
> 
> It took me a bit to determine that this change happened in ssh-client-server-18.
> 
> The motivation behind the change was to align the values with those defined in RFCs 4252 and 4250.
> 
> You mention an “interactive” and “some other” methods - where are they defined?

That is a good question. It seems no other methods are standardized but that does not mean they are not used.

> > For a robust and extendible solution, why not use an identityref leaf-list with all the methods as identities? One could then simply add new ones with specific "if-feature" statements.
> 
> An identityref seems reasonable, could you propose a snippet of YANG for it?
> 
> That said, it seems equally possible for a future module to augment-in a new leaf under the "supported-authentication-methods” container...

Right, that would solve the problem, too. So you can keep it the way it is, up to you which solution you prefer. Not sure why I did not think of augments first but identityrefs. But identityrefs are much more general so the implementation should probably depend on whether these authentication methods are to be used only for this single purpose or not.

> > - ietf-netconf-server, grouping netconf-server-grouping/client-identity-mappings
> > 
> > The "if-feature" on this container is strange. The practical problem is that if one wants to support certificates only for TLS, both one of the TLS features and "ssh-x509-certs" must be enabled. This then results in the container being defined for both SSH and TLS so there is no way to support it only for TLS or SSH.
> 
> Yes, granular features would be nice.  This issue is tracked here: https://github.com/netmod-wg/yang-next/issues/82 <https://github.com/netmod-wg/yang-next/issues/82>.  A possible fix would be to enable features on a per-XPath basis, perhaps using the “node-tags” draft going on in NETMOD.   Do you have a proposal?
> 
> BTW, shouldn’t the “if-feature” statement have an “or” (not an “and”) between the two major expressions?

Yes, I think "or" fits much better. I just was not sure whether there is not a specific reason why "and" was chosen.

Regards,
Michal