Re: [TLS] Last Call: <draft-ietf-tls-dtls-connection-id-10.txt> (Connection Identifiers for DTLS 1.2) to Proposed Standard

Hi Tom, Hannes, Thomas,

"A zero-length value indicates that the server will send with the
client's CID but does not wish the client to include a CID (or again,
alternately, to use a zero-length CID)."

My feeling is, the text in the paragraphs following that seems to
introduce first the idea of a "zero-length CID", and later use that only
to negate the use of tls_cid record. It may be more straight forward, if
the use of a "zero-length CID" is limited to the ClientHello and the
ServerHello extensions. And later the use of a tls_cid record is then
only for negotiated non-empty CID.

WDYT?

best regards
Achim Kraus

Am 12.03.21 um 12:58 schrieb Hannes Tschofenig:
> Hi Tom,
>
> I added a few PRs to address your review (see https://github.com/tlswg/dtls-conn-id/pulls).
>
> Regarding the zero-length CID I believe the current version in the repo at https://github.com/tlswg/dtls-conn-id might have already address your remark.
>
> In general, the zero-length CID in the ClientHello / ServerHello allows us to use CIDs unidirectionally.
>
> Ciao
> Hannes
>
> -----Original Message-----
> From: TLS <tls-bounces@ietf.org> On Behalf Of Thomas Fossati
> Sent: Friday, March 12, 2021 11:58 AM
> To: tom petch <daedulus@btconnect.com>; last-call@ietf.org
> Cc: tls@ietf.org; tls-chairs@ietf.org; draft-ietf-tls-dtls-connection-id@ietf.org
> Subject: Re: [TLS] Last Call: <draft-ietf-tls-dtls-connection-id-10.txt> (Connection Identifiers for DTLS 1.2) to Proposed Standard
>
> Hi Tom,
>
> Thanks very much!
>
> Your review is tracked in the issues below.
>
> On 12/03/2021, 10:39, "tom petch" <daedulus@btconnect.com> wrote:
>>
>> Some editorial quirks
>>
>> s.2
>> lacks the boiler plate of RFC8174
>
> https://github.com/tlswg/dtls-conn-id/issues/88
>
>> s.3
>> I found this unclear until I had understood it all (or perhaps I do
>> not understand it)
>>
>> "...or again, alternately, to use a zero-length CID)."
>> This suggests that a zero length CID is valid in Application Data
>> which later text seems to contradict; otherwise I cannot see what this is saying.
>>
>> "  If DTLS peers have negotiated the use of a CIDs using the
>> ClientHello and the ServerHello messages "
>> arguably sending a zero CID and receiving a zero CID is a successful
>> Hello negotiation perhaps " If DTLS peers have negotiated the use of a
>> non-zero CID in at least one direction, using the ClientHello and the
>> ServerHello messages"
>>
>> "The DTLS peers determine whether incoming and outgoing messages need.."
>> seems not to cater for unidirectional CIDs; perhaps "The DTLS peers
>> determine whether incoming or outgoing, or both, messages need.. "
>
> https://github.com/tlswg/dtls-conn-id/issues/89
>
>> s.4
>> /always recieve CIDs/always receive CIDs/
>>
>>
>> s.5.1
>> "the with Encrypt-then-MAC processing described in [RFC7366]."
>> I do not understand why 'with' is needed
>>
>> s.5.2
>> ditto
>>
>> s.8
>> /this aspects SHOULD refuse/these aspects SHOULD refuse/
>
> https://github.com/tlswg/dtls-conn-id/issues/90
>
>> s.10
>> I would find this clearer as three sections for the three IANA actions
>> 10.1 new column for ExtensionType
>> 10.2 new value for ExtensionType
>> 10.3 new value for ContentType
>>
>> "   IANA is requested to allocate an entry to the existing TLS
>>      "ExtensionType Values" registry, defined in [RFC5246],.."
>> well no; whatever you think of RFC8447 the name has changed
>> "   IANA is requested to allocate an entry to the existing "TLS
>>      ExtensionType Values" registry, defined in [RFC5246],.."
>> or, if you are picky (which I am not),
>>      IANA is requested to allocate an entry to the existing "TLS
>>      "ExtensionType Values" registry, defined in [RFC5246], and
>>      renamed by RFC8447
>>
>> An extra column is added but I cannot see what value should be placed
>> in that column for existing entries.
>>
>> "The tls12_cid ContentType is only applicable to DTLS 1.2."
>> Good information but I struggle to see what IANA will do with it; I
>> see nowhere for it to go.
>
> https://github.com/tlswg/dtls-conn-id/issues/91
>
>
> cheers, t
>
>> Tom Petch
>>
>>
>> On 08/03/2021 11:19, The IESG wrote:
>>
>>
>>>
>>> The IESG has received a request from the Transport Layer Security WG
>>> (tls) to consider the following document: - 'Connection Identifiers for DTLS 1.2'
>>>     <draft-ietf-tls-dtls-connection-id-10.txt> as Proposed Standard
>>>
>>> The IESG plans to make a decision in the next few weeks, and
>>> solicits final comments on this action. Please send substantive
>>> comments to the last-call@ietf.org mailing lists by 2021-03-28.
>>> Exceptionally, comments may be sent to iesg@ietf.org instead. In
>>> either case, please retain the beginning of the Subject line to allow automated sorting.
>>>
>>> Abstract
>>>
>>>
>>>      This document specifies the Connection ID (CID) construct for the
>>>      Datagram Transport Layer Security (DTLS) protocol version 1.2.
>>>
>>>      A CID is an identifier carried in the record layer header that gives
>>>      the recipient additional information for selecting the appropriate
>>>      security association.  In "classical" DTLS, selecting a security
>>>      association of an incoming DTLS record is accomplished with the help
>>>      of the 5-tuple.  If the source IP address and/or source port changes
>>>      during the lifetime of an ongoing DTLS session then the receiver will
>>>      be unable to locate the correct security context.
>>>
>>>
>>>
>>>
>>> The file can be obtained via
>>> https://datatracker.ietf.org/doc/draft-ietf-tls-dtls-connection-id/
>>>
>>>
>>>
>>> No IPR declarations have been submitted directly on this I-D.
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> IETF-Announce mailing list
>>> IETF-Announce@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ietf-announce
>>> .
>>>
>>
>
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