Re: [auth48] *[AD] Re: AUTH48: RFC-to-be 9429 <draft-uberti-rtcweb-rfc8829bis-05> for your review

[Eric Rescorla <[e-mail]>]

This works for me.

On Sat, Feb 24, 2024 at 9:53 AM Cullen Jennings <[e-mail]> wrote:

>
> First, my huge apologies for the ridiculous time I have taken to get back
> to this. I was out sick for a while and then dealing with reorgs at Cisco
> but even with all of that, I should have done this long ago.
>
> I agree with Ekr's reasoning on what we should do here to cite both RFC
> 6347 and 9147 along with the note he proposed for section 5.1.1. I think
> that should acceptable to anyone else too based on Ekr's argument.  I can
> see an argument that the note is not needed but I think it clarifies a
> somewhat confusing situation of what does referencing both 6347 and 9147
> even mean.  I would argue that since 9147 is permitted, not required, in RFC8827
> this could be an information instead of normative reference to 9147.
> However, I think the note clarifies the issue and I am fine with ignoring
> if the ref is normative or not. So I’m fine with both 6347 and 9147
> normative along with the note.
>
> Lynne, can you make the following changes ?
>
> In 5.1.1 add Ekr's note to the bullet point:
>
> OLD
>
> *  DTLS [RFC6347] [RFC9147] or DTLS-SRTP [RFC5763] MUST be used, as
>       appropriate for the media type, as specified in [RFC8827].
>
> NEW
>
> *  DTLS [RFC6347] [RFC9147] or DTLS-SRTP [RFC5763] MUST be used, as
>       appropriate for the media type, as specified in [RFC8827].
>       Note: RFC 8827 requires implementations to support
>       DTLS 1.2 [RFC 6347] and permits the use of DTLS 1.3 [RFC 9147].
>
> (I did not change anything in the old, just added note to end of it).
>
> I think that is only change that comes out of this.
>
> On Jan 15, 2024, at 12:36 PM, Eric Rescorla <[e-mail]> wrote:
>
>
>
> On Mon, Jan 15, 2024 at 11:15 AM Cullen Jennings <[e-mail]> wrote:
>
>>
>> Sorry for the very long delay on this. It’s been an a sort of shitty
>> month for me.
>>
>
> Hi Cullen,
>
> I think we should disentangle two issues.
>
> 1. What we substantively say about what version of DTLS people ought to
> use.
> 2. What we use as a citation where the bare term "DTLS" without a version
> number is used.
>
> As you may recall, JSEP doesn't specify DTLS versions and leaves that to S
> 6.5 or RFC 8827, which has this somewhat labored text encouraging but not
> requiring you to use DTLS 1.2.
>
> All implementations MUST support DTLS 1.2 with the
> TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite and the P-256 curve
> <https://doi.org/10.6028/NIST.FIPS.186-4> [FIPS186
> <https://doi.org/10.6028/NIST.FIPS.186-4>]. Earlier drafts of this
> specification required DTLS 1.0 with the cipher suite
> TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, and at the time of this writing some
> implementations do not support DTLS 1.2; endpoints which support only DTLS
> 1.2 might encounter interoperability issues. The DTLS-SRTP protection
> profile SRTP_AES128_CM_HMAC_SHA1_80 MUST be supported for SRTP.
> Implementations MUST favor cipher suites which support Forward Secrecy
> (FS) over non-FS cipher suites and SHOULD favor Authenticated Encryption
> with Associated Data (AEAD) over non-AEAD cipher suites. Note: the IETF is
> in the process of standardizing DTLS 1.3 [TLS-DTLS13
> <https://tools.ietf.org/html/draft-ietf-tls-dtls13-39>].
>
> If we wanted to say anything normative about DTLS, we would properly do so
> in an 8827 bis, but we haven't done so, and I don't recall there being much
> WG discussion on DTLS versions since DTLS 1.3 was published. So my
> suggestion would be to try to just address point (2) here, which is to say
> to provide reasonable references while not creating new normative facts on
> the ground. I think the text above permits the use of DTLS 1.3,  so the
> current status is your (A), and while I would argue for A'[MUST DTLS 1.2,
> SHOULD DTLS 1.3] I don't think that's for this document.
>
> This leaves us with the question of what references to provide. What I
> suggest here is that we cite both RFC 6347 and 9147 wherever we just say
> "DTLS", except for S 5.1.1, which actually requires the use of DTLS, and
> there add a note something like:
>
> "Note: RFC 8827 requires implementations to support DTLS 1.2 [RFC 6347]
> and permits the use of DTLS 1.3 [RFC 9147]".
>
> How does this sound?
>
>
> Below I do address your substantive points which might go into a
> discussion of an 8827-bis, but if you agree with me here, we don't need to
> reach those here.
>
>
>>
>> > On Dec 11, 2023, at 7:13 AM, Eric Rescorla <[e-mail]> wrote:
>> >
>> > Let's make sure that we agree on the substantive situation first.
>> >
>> > * DTLS 1.3 deprecates DTLS 1.2, so a compliant implementation should be
>> able to use either.
>>
>> I suspect we disagree on what deprecate means but probably not relevant
>> to sort this out.
>
>
> I should have been clear: RFC 9147 obsoletes RFC 6347. As people probably
> know, I'm not a fan of any of these tags, so I'm open to arguments that
> this was wrong, but that's what it says.
>
>
>
>> I want to be careful on use or implement. For sure, I think it is great
>> for an implementation to support both and negotiate the latest thing it
>> can.
>>
>
>>
>> > * DTLS 1.3 is not yet widely deployed, so a compliant implementation
>> should implement 1.2 and 1.3, at least for now.
>>
>> Well, I think I am arguing they need to 1.2 to be a webrtc complaint
>> implantation and it would be very nice if they also do 1.3
>>
>
>> Even worse that adoption, DTLS 1.3 is blocked by a significant fraction
>> of enterprise firewalls. I would like to keep webertc working in those
>> situations for now. I agree there is a point in time where we decide that
>> things that only do 1.2 just get left behind but I don’t think that anyone
>> is arguing we do that in Auth 48 of this doc.
>>
>
> Absolutely not.
>
>
>
>> What I don’t want to be in situation of saying you must use 1.3 to be
>> webrtc compliant because I think that will cause a lot of breakage.
>>
>
> 100% agreed. I also think it is reasonable to argue that we shouldn't have
> MUST implement 1.3 (see below).
>
>
>>
>> >
>> > Neither of these "shoulds" is intended in the 2119 sense, just in terms
>> of what we expect.
>> >
>> > Do you disagree with either of these statements?
>>
>> So just trying to reason my way through this. Look at it from point of
>> view of what we are asking implements to implement if they are compliant
>> with this RFC to be. Some various things we could be asking for are:
>>
>> A. Must implement 1.2 and may implement 1.3
>>
>> B. Must implement both 1.2 and 1.3
>>
>> C. Must implement 1.3 and Must NOT use 1.2
>>
>
>> D. I guess a 4th option is could have a MUST implement 1.3 and but is
>> optional to implement 1.2 or not but that seems pretty much the same as C
>> from an interoperability point of view.
>>
>>
>> I was working on the assumption that we were doing A for this draft
>> because that is the situation for 8829 and we were not changing the TLS
>> version part of things in this draft.
>>
>> I feel very strongly it is too early to do C and it would be bad for
>> WebRTC to do C at this point of time. And this was caused me to think the
>> refs were not right in the draft.
>>
>> On B - I’m just not sure. Part of me feels like mandating this is sort of
>> like mandating webrtc must do both v4 and v6. I have no objections to a
>> very convincing argument either way. I do feel a bit like, is this the
>> right draft for this change.
>>
>> That make sense as way of clarifying a path forward ? I agree with you
>> that as long as we are clear what we are trying to get done, we can figure
>> out how to tweak the reference spices to get that taste.
>>
>
> On the substantive matter, I totally agree that C and D are nonstarters. I
> think it's between A (or maybe A' [MUST TLS 1.2 and SHOULD TLS 1.3]) and B.
>
> -Ekr
>
>
>
>
>