Re: [netmod] Eric Rescorla's Discuss on draft-ietf-netmod-schema-mount-11: (with DISCUSS)
Eric Rescorla <ekr@rtfm.com> Tue, 16 October 2018 21:52 UTC
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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> <CABcZeBPaFXsven2XOC9+CdNqEfxvO4n0RivYuWCLXu9KGFYgDw@mail.gmail.com> <68a6fced-b67d-633e-fbbc-6b3d3fe4240d@gmail.com>
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From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 16 Oct 2018 14:51:41 -0700
Message-ID: <CABcZeBOkEYC7Y_8KB_O3VwX8KPMxKfdByqwtmYRRDA8=JY4p2Q@mail.gmail.com>
To: joel jaeggli <joelja@gmail.com>
Cc: martin björklund <mbj@tail-f.com>, IESG <iesg@ietf.org>, NetMod WG Chairs <netmod-chairs@ietf.org>, NetMod WG <netmod@ietf.org>, draft-ietf-netmod-schema-mount@ietf.org, Kent Watsen <kwatsen@juniper.net>, Lou Berger <lberger@labn.net>
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Subject: Re: [netmod] Eric Rescorla's Discuss on draft-ietf-netmod-schema-mount-11: (with DISCUSS)
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OK, after reading your explanation and the example, I think I am clearer on the use case and the text you propose seems appropriate. Why don't you provide a new ID and I'll clear my DISCUSS -Ekr On Tue, Oct 16, 2018 at 9:05 AM joel jaeggli <joelja@gmail.com> wrote: > On 10/16/18 06:00, Eric Rescorla wrote: > > 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 > I'm probably grossly simplifying the goal here, but. > > xpath statement allow for referencing another path or applying > constraints e.g. when / must (rfc 6020) > > the canonical example in 6020 being something like > > container interface { > leaf ifType { > type enumeration { > enum ethernet; > enum atm; > } > } > leaf ifMTU { > type uint32; > } > must "ifType != 'ethernet' or " + > "(ifType = 'ethernet' and ifMTU = 1500)" { > error-message "An ethernet MTU must be 1500"; > } > must "ifType != 'atm' or " + > "(ifType = 'atm' and ifMTU <= 17966 and ifMTU >= 64)" { > error-message "An atm MTU must be 64 .. 17966"; > } > > http://www.yang-central.org/twiki/pub/Main/YangDocuments/rfc6020.html#xpath > > Imposing constraints using nodes in mounted modules is kind of a key > application of schema-mount. > > > -Ekr > > > > > > On Tue, Oct 16, 2018 at 5:45 AM Martin Bjorklund <mbj@tail-f.com > > <mailto:mbj@tail-f.com>> wrote: > > > > Hi, > > > > Eric Rescorla <ekr@rtfm.com <mailto: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 > > <mailto:mbj@tail-f.com>> wrote: > > > > > > > Eric Rescorla <ekr@rtfm.com <mailto: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 <mailto:mbj@tail-f.com>> wrote: > > > > > > > > > > > Eric Rescorla <ekr@rtfm.com <mailto:ekr@rtfm.com>> wrote: > > > > > > > On Wed, Oct 10, 2018 at 5:32 AM Martin Bjorklund > > <mbj@tail-f.com <mailto:mbj@tail-f.com>> > > > > wrote: > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > Eric Rescorla <ekr@rtfm.com <mailto: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 > > > > > > > > > > > > > > >
- [netmod] Eric Rescorla's Discuss on draft-ietf-ne… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Martin Bjorklund
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Martin Bjorklund
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Martin Bjorklund
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Martin Bjorklund
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… joel jaeggli
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Eric Rescorla
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… joel jaeggli
- Re: [netmod] Eric Rescorla's Discuss on draft-iet… Martin Bjorklund