Re: [netmod] Eric Rescorla's Discuss on draft-ietf-netmod-schema-mount-11: (with DISCUSS)

Eric Rescorla <ekr@rtfm.com> Tue, 16 October 2018 13:01 UTC

Return-Path: <ekr@rtfm.com>
X-Original-To: netmod@ietfa.amsl.com
Delivered-To: netmod@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 0BB6A130DE4 for <netmod@ietfa.amsl.com>; Tue, 16 Oct 2018 06:01:13 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001] autolearn=unavailable autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=rtfm-com.20150623.gappssmtp.com
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 4bCuf0SS-nWp for <netmod@ietfa.amsl.com>; Tue, 16 Oct 2018 06:01:06 -0700 (PDT)
Received: from mail-lf1-x12c.google.com (mail-lf1-x12c.google.com [IPv6:2a00:1450:4864:20::12c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id BDFD0130DEA for <netmod@ietf.org>; Tue, 16 Oct 2018 06:00:57 -0700 (PDT)
Received: by mail-lf1-x12c.google.com with SMTP id o21-v6so16867178lfe.0 for <netmod@ietf.org>; Tue, 16 Oct 2018 06:00:57 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rtfm-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5ECC8bNKU5bfg/6BBibCPR8ABG3AyrFNYpLu20hbVxs=; b=bx3FNqswjvDMIpi4XSCn9KlNvjk1Ik/UNGjWVt+QuzCFfooR0YR0kD4SfQUGK9xkWT L7G2cSreEIWfxqoOagZ3BzmFQ2WaaW5suDOyTWe2sO8jOa4KqXk16P02GvyY+28FIN6P VoZqcI/a+vBaXzG5h0N5/LPeGpJXwm9LP0rwzwKu6mvW77xBJ81tOsdVEP8qEkipF1cV jmxPDnm0ZZV6PuCv2AV0qVIqQHy9WO41EYOwK0ouRc1CIFlhNlKYPhU8F+5k0lMQ3Qwg kbqgZ3oAvEGliIMCRd1YnIMVPfjgXrZLOx68pXw0yPLYWYTWUsIYO2zVw8D5KIU5FZ0k Qw7g==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5ECC8bNKU5bfg/6BBibCPR8ABG3AyrFNYpLu20hbVxs=; b=O0f69va7XvEw0TdJM8Vv1TbKEHme5fM+xDsxJ/JrZnxnGRJj1VLhOA8SRtjYbDcrLn g0u2VOMu5FrqgToBqljKnaPDLXsXpcZR6AB5revbe1wNNO2ICIQfypOvhYA4PE0enK9O nY6mIBLdTT++j9hQFX0bR6dec4fRru8VPAmHd7EMLv9Pk1wBkntKbvXypJk+UiOG+jZg GsPOqobGPhmQj4bfqd/fz/K5vORi0uOVI3Xk+n2kE/yyMjGWp7D8W0eGpXfBq6a/YHm2 ER9ZW5EDf3ooQQBZ6w4HI9tRzWiT5TTzHx2TKG5BDp4mRFOgxzCYoAkokRZYwDRq9LAC phwA==
X-Gm-Message-State: ABuFfohl/22JMzhhRiQPQb+e9C6+cX0lm85rgWaLTB4F5/vhSA2NdZSW CtORsZ1trFEZvbZb40YWxgw94kOiInkWB2PzusAF7w==
X-Google-Smtp-Source: ACcGV61NLNoGi1bytnEfjxkI/FL4lsmFyitfv8l8UN89fuelYcYQ5BTX1gx/Y8aOJDviRAOkZdrWC7/2n2ek2JPyong=
X-Received: by 2002:ac2:434d:: with SMTP id o13-v6mr13173301lfl.129.1539694855832; Tue, 16 Oct 2018 06:00:55 -0700 (PDT)
MIME-Version: 1.0
References: <CABcZeBMJmM_NaRY3GzcV4HO+BB14ooqxJ9oGrrer6nx3ZAqMxw@mail.gmail.com> <20181011.091817.1727547509052700274.mbj@tail-f.com> <CABcZeBNZ+AMXXNu7C5nvxie6NmJdJ_6FbHJXtdkxnMAN3rNGHQ@mail.gmail.com> <20181016.144545.1184951335260453665.mbj@tail-f.com>
In-Reply-To: <20181016.144545.1184951335260453665.mbj@tail-f.com>
From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 16 Oct 2018 06:00:18 -0700
Message-ID: <CABcZeBPaFXsven2XOC9+CdNqEfxvO4n0RivYuWCLXu9KGFYgDw@mail.gmail.com>
To: =?UTF-8?Q?martin_bj=C3=B6rklund?= <mbj@tail-f.com>
Cc: IESG <iesg@ietf.org>, NetMod WG Chairs <netmod-chairs@ietf.org>, NetMod WG <netmod@ietf.org>, joel jaeggli <joelja@gmail.com>, draft-ietf-netmod-schema-mount@ietf.org, Kent Watsen <kwatsen@juniper.net>, Lou Berger <lberger@labn.net>
Content-Type: multipart/alternative; boundary="000000000000f20b6f0578582470"
Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/MHaaR1U0Qw9hbOO7Ofc_Xzw-1bg>
Subject: Re: [netmod] Eric Rescorla's Discuss on draft-ietf-netmod-schema-mount-11: (with DISCUSS)
X-BeenThere: netmod@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: NETMOD WG list <netmod.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/netmod>, <mailto:netmod-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/netmod/>
List-Post: <mailto:netmod@ietf.org>
List-Help: <mailto:netmod-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/netmod>, <mailto:netmod-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 16 Oct 2018 13:01:13 -0000

I'm sorry, but I still don't think I understand the security impacts of
this well enough to know if this text is OK.

Can you provide a more detailed explanation of what XPath expressions can
and cannot do here? Happy to discuss live either on the phone or in BKK

-Ekr


On Tue, Oct 16, 2018 at 5:45 AM Martin Bjorklund <mbj@tail-f.com> wrote:

> Hi,
>
> Eric Rescorla <ekr@rtfm.com> wrote:
> > That seems like it's going to have some pretty surprising consequences
> and
> > at minimum needs more information in the Security Considerations.
>
> Ok.  Howabout we add a paragraph to the end of the Security
> Considerations section:
>
>   Care must be taken when the "parent-reference" XPath expressions are
>   constructed, since the result of the evaluation of these expressions
>   is added to the accessible tree for any XPath expression found in
>   the mounted schema.
>
>
> /martin
>
> > On Thu, Oct 11, 2018 at 12:18 AM Martin Bjorklund <mbj@tail-f.com>
> wrote:
> >
> > > Eric Rescorla <ekr@rtfm.com> wrote:
> > > > I'm sorry but I don't understand this.
> > > >
> > > > Does the externally visible behavior of any mounted module depend in
> any
> > > > way on these XPATH references
> > >
> > > Yes, but note that these XPath expressions ("parent-reference") are
> > > read-only (config false in the YANG model).  Thus they are set by the
> > > implementation, and used to inform the operator about the environment
> > > in which other XPath expressions are evaluated.
> > >
> > >
> > > /martin
> > >
> > >
> > > >
> > > > -Ekr
> > > >
> > > >
> > > >
> > > >
> > > > On Wed, Oct 10, 2018 at 6:38 AM Martin Bjorklund <mbj@tail-f.com>
> wrote:
> > > >
> > > > > Eric Rescorla <ekr@rtfm.com> wrote:
> > > > > > On Wed, Oct 10, 2018 at 5:32 AM Martin Bjorklund <mbj@tail-f.com
> >
> > > wrote:
> > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > Eric Rescorla <ekr@rtfm.com> wrote:
> > > > > > > > Eric Rescorla has entered the following ballot position for
> > > > > > > > draft-ietf-netmod-schema-mount-11: Discuss
> > > > > > > >
> > > > > > > > When responding, please keep the subject line intact and
> reply
> > > to all
> > > > > > > > email addresses included in the To and CC lines. (Feel free
> to
> > > cut
> > > > > this
> > > > > > > > introductory paragraph, however.)
> > > > > > > >
> > > > > > > >
> > > > > > > > Please refer to
> > > > > > > https://www.ietf.org/iesg/statement/discuss-criteria.html
> > > > > > > > for more information about IESG DISCUSS and COMMENT
> positions.
> > > > > > > >
> > > > > > > >
> > > > > > > > The document, along with other ballot positions, can be found
> > > here:
> > > > > > > >
> https://datatracker.ietf.org/doc/draft-ietf-netmod-schema-mount/
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > >
> ----------------------------------------------------------------------
> > > > > > > > DISCUSS:
> > > > > > > >
> > > > >
> ----------------------------------------------------------------------
> > > > > > > >
> > > > > > > > Rich version of this review at:
> > > > > > > > https://mozphab-ietf.devsvcdev.mozaws.net/D3506
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > DETAIL
> > > > > > > > S 4.
> > > > > > > > >
> > > > > > > > >      It is worth emphasizing that the nodes specified in
> > > > > > > > >      "parent-reference" leaf-list are available in the
> mounted
> > > > > schema
> > > > > > > only
> > > > > > > > >      for XPath evaluations.  In particular, they cannot be
> > > accessed
> > > > > > > there
> > > > > > > > >      via network management protocols such as NETCONF
> > > [RFC6241] or
> > > > > > > > >      RESTCONF [RFC8040].
> > > > > > > >
> > > > > > > > What are the security implications of this XPath reference
> > > outside
> > > > > the
> > > > > > > > mount jail? Specifically, how does it interact with the
> access
> > > > > control
> > > > > > > > for the enclosing module.
> > > > > > >
> > > > > > > There is no such interaction, since access control comes into
> play
> > > > > > > when some external entity accesses the data through some
> management
> > > > > > > protocol, and the nodes from the "parent-reference" expressions
> > > cannot
> > > > > > > be accessed via management protocols.
> > > > > > >
> > > > > > > The last sentence of the quoted paragraph was supposed to make
> this
> > > > > > > clear, but it seems we might need some additional explanation?
> > > > > > >
> > > > > >
> > > > > > Yes, I think so. I guess I'm not clear on what the XPath
> expressions
> > > are
> > > > > > for if they
> > > > > > can't be accessed via the management protocols. How can they be
> used?
> > > > >
> > > > > These are XPath expressions defined in the YANG models themselves,
> > > > > such as "must" expressions or "leafrefs".   The description of
> > > > > "parent-reference" refer to them as:
> > > > >
> > > > >                [...] XPath
> > > > >                expressions whose context nodes are defined in the
> > > > >                mounted schema
> > > > >
> > > > >
> > > > >
> > > > > /martin
> > > > >
> > >
>