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

Martin Bjorklund <mbj@tail-f.com> Tue, 16 October 2018 12:45 UTC

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Date: Tue, 16 Oct 2018 14:45:45 +0200 (CEST)
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] Eric Rescorla's Discuss on draft-ietf-netmod-schema-mount-11: (with DISCUSS)
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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
> > > >
> >