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

Martin Bjorklund <mbj@tail-f.com> Wed, 10 October 2018 13:38 UTC

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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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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