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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