Re: [Dots] AD review of draft-ietf-dots-signal-channel-25 (5th Part)

[<[e-mail]>]

Re-,

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Konda, Tirumaleswar Reddy [mailto:[e-mail]]
> Envoyé : jeudi 17 janvier 2019 11:34
> À : BOUCADAIR Mohamed TGI/OLN; Benjamin Kaduk; draft-ietf-dots-signal-
> [e-mail]
> Cc : [e-mail]
> Objet : RE: AD review of draft-ietf-dots-signal-channel-25 (5th Part)
> 
> > -----Original Message-----
> > From: Dots <[e-mail]> On Behalf Of
> > [e-mail]
> > Sent: Thursday, January 17, 2019 12:21 PM
> > To: Benjamin Kaduk <[e-mail]>; draft-ietf-dots-signal-
> > [e-mail]
> > Cc: [e-mail]
> > Subject: Re: [Dots] AD review of draft-ietf-dots-signal-channel-25 (5th
> Part)
> >
> > This email originated from outside of the organization. Do not click links
> or
> > open attachments unless you recognize the sender and know the content is
> > safe.
> >
> > Hi Ben,
> >
> > Please see inline.
> >
> > Cheers,
> > Med
> >
> > > -----Message d'origine-----
> > > De : Benjamin Kaduk [mailto:[e-mail]] Envoyé : mercredi 16
> > > janvier 2019 01:14 À : [e-mail]
> > > Cc : [e-mail]
> > > Objet : AD review of draft-ietf-dots-signal-channel-25
> > >
> > > Section 7.2
> > >
> > > The TLS 1.3 handshake with 0-RTT diagram needs to be
> > > revisited/refreshed, as RFC 8446 does not look like that.
> > > Additionally, the usage of PSK as well as a certificate is not defined
> > > until draft-housley-tls-tls13-cert-with-extern-psk is published.
> > > I also note that in the diagram as presented, the client is not yet
> > > known to be authenticated when the server sends its initial (0.5-RTT)
> > > DOTS signal message.
> > >
> >
> > [Med] Noted. Thanks.
> 
> The DOTS signal channel draft is discussing PSK with (EC)DHE key
> establishment explained in RFC8446, and I don't see the need to refer to
> draft-housley-tls-tls13-cert-with-extern-psk-00.
> The 0-RTT diagram is a simplified version of 0-RTT just like the Figure 1 in
> https://tools.ietf.org/html/draft-ietf-quic-tls-17.
> 
> The only correction required to the diagram is end_of_early_data must be sent
> along with the client Finished message.
> 
> >
> > > Section 7.3
> > >
> > > This whole section seems to only be relevant for UDP usage, so
> > > probably the "If UDP is used" clause can be dropped and an
> > > introductory statement added earlier on.
> >
> > [Med] Will consider that.
> >
> > >
> > >                               Path MTU MUST be greater than or equal to
> > >    [CoAP message size + DTLS overhead of 13 octets + authentication
> > >    overhead of the negotiated DTLS cipher suite + block padding]
> > >    (Section 4.1.1.1 of [RFC6347]).  If the request size exceeds the path
> > >    MTU then the DOTS client MUST split the DOTS signal into separate
> > >    messages, for example the list of addresses in the 'target-prefix'
> > >    parameter could be split into multiple lists and each list conveyed
> > >    in a new PUT request.
> > >
> > > (DTLS 1.3 will have a short header for some packets, that is less than
> > > 13 octets.)
> >
> > [Med] The text is more about 1.2. We can add a 1.3 note if you think it is
> > useful for the discussion.
> 
> We should say "DTLS 1.2 overhead of 13 octets"
> In DTLS 1.3 DTLSCiphertext structure is variable length (full header is of
> size 6 octets).
> 
> >
> > >
> > > Section 8
> > >
> > > We've got some requirements in here about limiting behavior of
> > > clients/servers when talking to gateways; is knowing about the
> > > presence of a gateway something that's required to happen out of band
> > > or is there an in-band way to identify that the peer is a gateway?
> >
> > [Med] An agent does not necessary know that it peer is gateway. A gateway
> > is seen as a server for the client, and a client for a server.
> >
> > >
> > >    messages from an authorized DOTS gateway, thereby creating a two-link
> > >    chain of transitive authentication between the DOTS client and the
> > >    DOTS server.
> > >
> > > This seems to ignore the possibility of setups that include both
> > > client-domain and server-domain gateways.
> >
> > [Med] I updated the text to mention this is only an example.
> >
> > >
> > >                  DOTS client certificate validation MUST be performed as
> > >    per [RFC5280] and the DOTS client certificate MUST conform to the
> > >    [RFC5280] certificate profile.  [...]
> > >
> > > This seems to duplicate a requirement already stated in Section 7.1;
> > > it's probably best to only have normative language in one location,
> > > even if we need to mention the topic in multiple locations.
> > > Similarly for the mutual authentication requirement, which we
> > > duplicate in the second and fourth paragraphs of this section.
> >
> > [Med] Good point. Fixed.
> >
> > >
> > > If we don't want to use example.com vs. example.net as sample domains,
> > > we can also use whateverwewant.example, per RFC 6761.
> >
> > [Med] Will maintain the ones already in the draft. Thanks.
> >
> > >
> > > Section 9
> > >
> > > We should mention the media-type allocation in the top-level section.
> >
> > [Med] Will fix that.
> >
> > >
> > > "mappings to CBOR" feels confusing to me, since it leaves empty what
> > > we are mapping from.  Perhaps just talking about a registry of "CBOR
> > > map keys" would be better, both here and in the Section 9.3 intro.
> > >
> >
> > [Med] Unless there is an objection, I can use "CBOR Map Keys".
> 
> I don't see "CBOR Map Keys" defined or used anywhere in the draft.
> 

[Med] The proposal was to add it in -17. In my local copy I have implemented "CBOR Key Values". Better? 

> >
> > > Section 9.3
> > >
> > > I suggest being very explicit about whether new requests for
> > > registration should be directed to the mailing list or to IANA, as
> > > we've had some confusion about this elsewhere.
> > >
> > > The criteria used by the experts also just lists things they should
> > > consider, but does not provide full clarity on which answer to the
> > > question is more likely to be approved.  (And yes, I know that this
> > > text is largely copied from already published RFCs, but we can still
> > > do
> > > better.)
> >
> > [Med] Will check this.
> >
> > >
> > > Section 9.3.1
> > >
> > > If we want the value 0 to be reserved we need to say so.
> >
> > [Med] 0 is not part of the allocation range.
> >
> > > Do we want to say anything about the usage of negative integers as map
> > > keys?
> > >
> > > I suggest not mentioning the postal address, given the recent (e.g.)
> > > GDPR requirements.
> >
> > [Med] Good point. Done.
> >
> > >
> > > Section 9.3.2
> > >
> > > It may be worth mentioning Table 4 here as well.
> >
> > [Med] OK.
> >
> > >
> > > Section 9.5.1
> > >
> > > We need to specify which range of values we are asking for an
> > > allocation from.
> >
> > [Med] Added a mention to 0-255 range.
> 
> As per https://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml the allowed
> range is 23-255.

[Med] Ben was referring to 9.5.1 which is now 9.4.1 in -26. So the range I indicated is the correct one. 

> 
> >
> > >
> > > Section 9.6.1
> > >
> > > As above, specify what range we're asking about.
> >
> > [Med] OK.
> 
> The range is already defined in section 9.6.1.1
> 

[Med] Ben was referring to 9.6.1 of -25, which is now 9.5.1 in -26. The comment from Ben is a valid one. 

> Cheers
> -Tiru
> 
> >
> > >
> > > I expect the current text to get some IESG (or directorate) feedback
> > > that the Data Item and Semantics descriptions are repetitive and banal.
> > >
> > > Section 9.7
> > >
> > > IIUC, IANA is going to ask if we want this module to be "maintained by
> > > IANA", so it would be good to have an answer ready even if we don't
> > > put it in the document text.
> >
> > [Med] This is discussed in -26.
> >
> > >
> > >    Rate-limiting DOTS requests, including those with new 'cuid' values,
> > >    from the same DOTS client defends against DoS attacks that would
> > >
> > > With respect to "new" 'cuid' values, is the server required to
> > > remember which ones it has seen in perpetuity, or can it time them out
> > > eventually?
> >
> > [Med] The attack vector is a DOTS client which changes frequently its cuid.
> > The DOTS server can set an interval in which the same client cannot present
> > a new cuid.
> >
> > >
> > > Section 10
> > >
> > > The security considerations seem to be taking a narrow focus on the
> > > requirements for and consequences of specific bits on the wire in the
> > > signal channel protocol.  I think it's appropriate to also include
> > > some high-level thoughts about the functional behavior of the
> > > protocol, allowing to signal that an attack is underway and trigger
> > > mitigation, increasing the availability of services, etc., and the
> > > risks that are posed by the protocol failing to work properly, whether
> > > that means letting attack traffic through or improperly blocking
> > > legitimate traffic.
> >
> > [Med] Would a pointer to the architecture/requirements I-Ds be sufficient
> to
> > cover to high-level aspects?
> >
> > >
> > > Section 13.1
> > >
> > > I think the IANA registries should be listed as Informational and not
> > > Normative references.
> > >
> >
> > [Med] Done.
> >
> > > Section 13.2
> > >
> > > Pending resolution of the question about using
> > > draft-ietf-core-yang-cbor rules or RFC7951+RFC7049, the
> > > draft-ietf-core-yang-cbor reference may need to be Normative.
> >
> > [Med] Please refer to my answer to that question. draft-ietf-core-yang-cbor
> is
> > informative.
> >
> > >
> > > Given that "URI" is a well-known abbreviation, we may be able to get
> > > away with not citing RFC 3986.  On the other hand, it's not causing
> > > any harm to leave it in...
> >
> > [Med] Will leave it.
> >
> > >
> > > RFC 4632 needs to be Normative, since we need to know CIDR to
> > > encode/decode target-prefixes.
> >
> > [Med] Works for me.
> >
> > >
> > > Similarly, I think that RFCs 6234
> >
> > [Med] This one is not listed as normative because other hash algos may be
> > used.
> >
> > , 7413
> > [Med] The support if TFO is not mandatory.
> >
> > , 7589
> > [Med] This is a MAY in the spec. It is just fine to leave it as
> informative..
> >
> > , 7918
> > [Med] Idem as TFO.
> >
> > , 7924
> > [Med] Idem as TFO.
> >
> > , and 7951
> > [Med] this one was not listed as normative because the document lists two
> > ways to do the mapping.
> >
> > > should also be Normative.
> > >
> > >
> > > -Ben
> >
> > _______________________________________________
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> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/dots