Do we want a few sentences in Security Considerations that references https://www.rfc-editor.org/rfc/rfc9460.html#section-3.1 to call this out?
This seems like something that became less clear when we split these two docs apart. Most of draft-ietf-tls-svcb-ech used to be a section of what is now rfc9460 but got split out due to publication timelines. It may be that some non-normative references back to rfc9460 might help readers not miss things like this which might have been more clear when they were a single document. Erik On Fri, Mar 29, 2024 at 11:31 PM Ted Lemon <mel...@fugue.com> wrote: > Yes, that fully addresses my concern. Thanks! > > Op vr 29 mrt 2024 om 22:54 schreef Eric Rescorla <e...@rtfm.com> > >> >> Hi Ted, >> >> Doesn't this section of RFC 9460 address this case and say what you are >> recommending: >> >> https://www.rfc-editor.org/rfc/rfc9460.html#section-3.1 >> >> -Ekr >> >> >> >> On Fri, Mar 29, 2024 at 6:49 PM Ted Lemon <mel...@fugue.com> wrote: >> >>> Okay, I think I see the disconnect, maybe. The issue I'm pointing to is >>> that you may or may not be doing DNSSEC validation. And you may or may not >>> be /able/ to do DNSSEC validation if the infrastructure breaks it >>> accidentally or deliberately. >>> >>> The document says: "The SVCB-optional client behavior specified in >>> (Section 3 of [SVCB]) permits clients to fall back to a direct connection >>> if all SVCB options fail. This behavior is not suitable for ECH, because >>> fallback would negate the privacy benefits of ECH." >>> >>> So it's saying that the default handling of SVCB is incorrect and would >>> fail open, and overriding that behavior. Given that this is the case, that >>> implies that it matters whether the data has been validated, but nowhere in >>> the document, certainly not in Security Considerations, is any mention made >>> of this issue. So that's what I'm pointing out. >>> >>> It is absolutely not the case in practice that all stub resolvers do >>> validation. You are making a security decision about trust based on data >>> the trustworthiness of which you've not discussed, in a situation where the >>> implementor has meaningful choices to make with respect to validating that >>> trustworthiness. So it's worth mentioning that if the policy is not to >>> validate, this vulnerability exists. >>> >>> I'm a DNS guy, not a TLS guy, so I don't know the history of this >>> work—I'm just making this observation about the document I was asked to >>> review. The fact that (apparently) no DNSDIR review ever raised this issue >>> about the other documents you mentioned is of no interest to me—I'm not >>> reviewing those documents.Whether you take this advice is between you and >>> the IESG. I'm not even claiming to be right—just pointing out the issue I >>> see. >>> >>> On Fri, Mar 29, 2024 at 7:21 PM Rob Sayre <say...@gmail.com> wrote: >>> >>>> I don't think it relates to DNSSEC. You can fail at DNS (DNSSEC >>>> failure) or you can fail during ECH (unless you want to use non-ECH, which >>>> is not ECH, and not part of this draft). >>>> >>>> It makes sense to me: one can reject a request unless the requirements >>>> embedded in the SVCB are met (the server chooses those, which can include >>>> many aspects of the request). I don't understand why one would insert >>>> DNSSEC here. That seems to be the whole point--it works without it. >>>> >>>> thanks, >>>> Rob >>>> >>>> >>>> On Fri, Mar 29, 2024 at 3:57 PM Ted Lemon <mel...@fugue.com> wrote: >>>> >>>>> I'm not telling you that you have to require DNSSEC. I'm saying the >>>>> document is incomplete if you don't talk about how it relates to DNSSEC. I >>>>> think EKR got the point, so maybe go with his approach? >>>>> >>>>> On Fri, Mar 29, 2024 at 6:27 PM Rob Sayre <say...@gmail.com> wrote: >>>>> >>>>>> It's a policy choice, though, right? I think ekr hinted at this issue >>>>>> as well. >>>>>> >>>>>> It's that one might also view requests that reveal the SNI as >>>>>> insecure. If that's the case, DNSSEC doesn't help. There will certainly >>>>>> be >>>>>> a transition period where that will be impractical for many servers. I >>>>>> think these are separate problems, though. >>>>>> >>>>>> thanks, >>>>>> Rob >>>>>> >>>>>> >>>>>> On Fri, Mar 29, 2024 at 3:10 PM Ted Lemon <mel...@fugue.com> wrote: >>>>>> >>>>>>> It looks like if you can't get the SCVB you're going to fail >>>>>>> insecure, so being able to use DNSSEC to prevent that for signed domains >>>>>>> seems worthwhile. >>>>>>> >>>>>>> On Fri, Mar 29, 2024 at 4:41 PM Rob Sayre <say...@gmail.com> wrote: >>>>>>> >>>>>>>> On Fri, Mar 29, 2024 at 1:02 PM Ted Lemon via Datatracker < >>>>>>>> nore...@ietf.org> wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> I don't think it's reasonable to specify the privacy properties of >>>>>>>>> SVCB and >>>>>>>>> /not/ talk about DNSSEC validation. >>>>>>>>> >>>>>>>> >>>>>>>> Could you explain more about this part? I think DNSSEC doesn't add >>>>>>>> much here, unless you want to accept non-ECH traffic. For example, >>>>>>>> many of >>>>>>>> the test servers will bounce you to some other site if you don't send >>>>>>>> ECH >>>>>>>> or screw it up in some way (speaking as someone who has screwed it up >>>>>>>> many >>>>>>>> times...). >>>>>>>> >>>>>>>> I think there might be a DoS attack here, where someone messes with >>>>>>>> the response, but they can also turn off the DNSSEC bit unless it's >>>>>>>> DoT/DoH/DoQ etc. So, if using those, it's just the trustworthiness of >>>>>>>> the >>>>>>>> DNS server itself, right? Sorry if I'm missing something. >>>>>>>> >>>>>>>> thanks, >>>>>>>> Rob >>>>>>>> >>>>>>>> _______________________________________________ >>> TLS mailing list >>> TLS@ietf.org >>> https://www.ietf.org/mailman/listinfo/tls >>> >>
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