<div dir="ltr"><div>Hi Dimitris,</div><div><br></div><div>I've been thinking about your email all night, and I want to figure out where our reasoning about the integrity of DCV via WHOIS-1932 or HTTP-nonce (3.2.2.5.1) diverge. I was quite surprised by your statements about the properties of internet security, the responsibility of TLS and SCWG, and the limitations that should be accepted in performing DCV. I'm hoping that your new responsibilities as Chair (congratulations!) will still leave you a bit of time to point out where my reasoning doesn't connect. :)<br></div><div><br></div><div>Because I'm not sure where we diverge, I'm going to walk through my understanding of the principles underlying the DCV methods used historically by CA/BF (and CAs in the dark days of private deals with individual browsers), and the direction towards which the SCWG and root programs seem to be headed in terms of those principles. Please, *please* do not take this as me implying that you don't know these things: I'm not trying to lecture, but to be as explicit as reasonable in explaining my thinking, so that it's easiest for yourself or others to help me correct error in it. I would be quite grateful for such generosity, honestly! I also apologize in advance for the length of this message. I lack the wisdom to make it smaller, perhaps.<br></div><div><br></div><div>(Some of this is entangled with "what is this even for?" sorts of discussion about who the web PKI should ultimately benefit, but I've tried to keep that separate.)<br></div><div><br></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Sep 18, 2024 at 12:18 PM Dimitris Zacharopoulos (HARICA) <<a href="mailto:dzacharo@harica.gr">dzacharo@harica.gr</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>We don't need Domain Name Registrars to go through WebTrust or ETSI
audits suitable for Trust Service Providers. These Registrars are
the source of truth for the DNS on which all Internet connections,
and the WebPKI relies on. It's so fundamental to the ecosystem that
IMO it doesn't make sense to ask ourselves how this Forum can make
them better. Other authorities should be working on that.<br></div></blockquote><div><br></div><div>A recurring theme throughout web PKI operations has been that a participant in the ecosystem thinks that they are doing a good job, and perhaps indeed are doing a good job of some kind, but are not providing the guarantees or protections that others are assuming are in place. I don't mean "good job" in the sense of competence or ethics, but rather "meeting the requirements through actions". The farther that the participant is from the core of the web PKI ecosystem, which is to say the less likely they are to evaluate all their actions by the effects of those actions on the trustworthiness of web certificates and server authentication. This means, IMO, that this group and other stewards of the PKI should be very conservative, and very explicit, when depending on another participant of the ecosystem to maintain certain properties. Otherwise, those dependency-bearing organizations may not even know what is being expected of them.<br></div><div><br></div><div>I am not suggesting that CA/BF in any way place requirements on what an organization must do in order to be a domain registrar, and reporter of that registry. As you say, that is beyond both the scope and the expertise of this group, and this group has plenty to keep it busy! I am, rather, suggesting that SCWG should establish criteria against which it will determine if a registrar's publication of domain information should be considered to be reliable enough to accomplish DCV. Similarly, the group does not put any requirements forcing public DNS servers to strictly check DNSSEC, but if a CA is going to use a DNS server for checking CAA records or doing 3.2.2.4.7 "DNS Change" validation, then that's only acceptable if the DNS server enforces DNSSEC in the presence of a validation chain. (I think that might only be in Bugzilla and not yet captured in the BRs, but it's well-enough understood that failure to adhere to it has required reissuance.)<br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>
If a ".cookoo" TLD operator is not functioning properly, then the
entire TLD is in jeopardy and every Domain owner under that TLD is
at risk. Certificates are the least of people's problems when
relying parties connect to websites operated under that unsafe TLD
operator.<br></div></blockquote><div><br></div><div>As above, this depends very much on exactly what form "not functioning properly" takes. If their systems are broken such that it's impossible to make changes to registrations, or to look up registrations, I think we would all agree that the TLD operator is not functioning properly, but that would not have as much risk to the integrity of the web PKI as those systems being broken such that *anyone* can change any TLD.</div><div><br></div><div>For CAs to rely on email address information from registrars for issuance of certificates, I think it's only appropriate that they ensure that the information is "fit for purpose" and that it's managed (and accessed) in a way consistent with the level of trust placed in it.</div><div><br></div><div>This means making sure that the integrity of the response is maintained, which is a role that WHOIS-3912 simply cannot perform.<br></div><div> <br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
No, the SCWG and TLS is not here to solve the unencrypted nature of
the DNS protocol. IETF and DNSSEC is. There is a great number of
Domain Names in the DNS without DNSSEC, and there is still heavy
reliance on the unencrypted DNS protocol in almost EVERY Domain
Validation under 3.2.2.4.<br></blockquote><div><br></div><div>DNS being unencrypted is not a problem, and indeed even DNSSEC doesn't encrypt traffic. DNS results being *unauthenticated* is a problem for clients who wish to be certain that they have been given an authorized address in response to their lookup, but even with DNSSEC that leaves the issue of ensuring that the unauthenticated IP layer reached the "real" home of that address (thus DANE).<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
Even the Agreed-upon change to website method, 3.2.2.4.18, relies on
"Authorized Ports that are offered via non-encrypted channels (ports
80, 25, 22).<br></blockquote><div><br></div><div>Again, encryption during validation is not necessary for there to be a reliable chain of trust from the browser to the site certificate, via CA-operated root certificates. We need authentication, but only authentication, of every step of the delegation of trust.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
I would go as far as to say that even the ACME methods connecting to
https URLs are untrusted, because the endpoints are not protected by
publicly trusted certificates and anyone could launch a MiTM attack.</blockquote>
</div><div><br></div><div>
This is a part that really got stuck in my head. Are you saying that ALPN-1 is vulnerable to a MITM attack during validation? That would be a pretty shocking situation, in my opinion!</div><div><br></div><div>How would the attacker get access to the key material needed to complete the challenge? It never leaves the subscriber machine from what I can tell. Similarly, the ACME account key is used in HTTP-01 to render MITM attacks ineffective.<br></div><div><br></div><div>This is how the trust in that connection is bootstrapped based on the trust in the connection between subscriber and CA when the certificate is requested. Presumably publicly-trusted certificates are used when the subscriber connects to the CA's server to make that request and obtain the account key!<br></div><div><br></div><div>This transitivity of trust goes to the issue with WHOIS. Even if the registrar is maximally diligent in their key ceremonies and internal processes and generating certificates correctly, WHOIS-3912 puts a *maximum* trustworthiness on the entire operation, which is that of unauthenticated TCP. In my opinion, that is not appropriate for web PKI, and is a relic of a time before this community took technical registration-time attacks as seriously as we do now.<br></div><div><br></div><div><blockquote> In order for
the SCWG measures to be proportionate, we should not blame the
entire WHOIS protocol but work on additional controls to minimize
the risk of CAs using those problematic WHOIS libraries.<br><br></blockquote>Could you describe how a non-problematic WHOIS-3912 library could provide assurance of the validity of the data returned, equivalent to the integrity of the results from HTTP-01/DNS-01/ALPN-01?<br></div><div><blockquote type="cite"><div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> Instead, we could focus on requiring
immediate/emergency measures for CAs to use the WHOIS
protocol securely</div></blockquote><div><br></div></div></div></blockquote><div dir="ltr"><div class="gmail_quote"><div>This is definitely one place that our reasoning diverges: I don't see a way to use WHOIS-3912 securely, where by "securely" I mean "in such a way as to not weaken the DCV guarantees that the web PKI wishes to make".<br></div></div></div><blockquote type="cite"><div dir="ltr"><div class="gmail_quote"><div> </div>I disagree. We are trying to move from "http" to a "trustworthy
https" (note: "trustworthy https" in the sense that it doesn't use
untrusted certificates). At some point, CAs need to rely on
unencrypted communication to achieve that.</div><div class="gmail_quote"><br></div></div></blockquote><div dir="ltr"><div class="gmail_quote">Why do CAs need to rely on unauthenticated communication to achieve that? If we were establishing the very first root, someone would have to carry the key physically to the browser developer as a form of IRL authentication, but we have sufficient systems in place now to inductively create a completely authenticated chain of validation if we should want to.</div><div class="gmail_quote"><br></div><div class="gmail_quote">Where is that chain impossible to authenticate, in your opinion?<br></div></div></div><div><br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
I'm confused by this statement. Is this a plea to the CAs to stop
using what you think is an insecure method?</blockquote></div><div><br></div><div>Yes, it is exactly that. I don't know how anyone can seriously claim that WHOIS-3912 is a secure method, regardless of how high quality the data on the other side is.<br></div><div><blockquote type="cite"><div dir="ltr"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Domain Registries for validation of domain contacts:
domain registry information should, IMO, only be used at
*all*, independent of protocol, if the SCWG can be confident
that IANA or another trusted body will be able to ensure
that all those registries, for all domains present and
future, will meet the SCWG's requirements for reliability.<br>
</blockquote>
</div>
</div>
</blockquote><blockquote>
This is like saying that the Registrars, the main stewards assigned
to run the DNS which is fundamental for how the Internet works and
practically the World Wide Web, need to meet the SCWG requirements
for reliability.</blockquote></div><div><br></div><div>As above, domain registrars do not need to meet any SCWG requirements. CAs need to meet the SCWG requirements, and I think that those requirements should include minimum properties that must hold of a registrar's data management practices, and the means of accessing it, if such data is to be used as authoritative proof of domain control.<br></div><div><br></div><div>An example: do registrars inform registrants that anyone who can receive email at the listed contact address can be issued a certificate for their domain? I think that the significance of that address as used for DCV is not well-understood by most registrants, and that many will send that email to ticket/CS lists composed of people who are *not* authorized to make changes to DNS, and are not assumed to have the same authority for requesting certificates. Similarly, I don't think that registrants understand that someone popping a domain-privacy provider not only gets their email and contact information, but could plausibly also silently have certificates issued against their domain.</div><div><br></div><div>If these participants in the ecosystem (registrar and registrants) don't regard the email contact field as having such immense security significance, then it is unlikely that they will manage it with appropriate care. Given that, as you correctly point out, the SCWG is in no position to put requirements on registrars or registrants, all that we can do is say that CAs must not use registrar data unless it is managed to an appropriate standard, and accessed in an appropriate way. That is *well* within the mandate of the SCWG, and consistent with all of its other activities in defining validation standards.<br></div><div><blockquote type="cite">
<div dir="ltr">
<div class="gmail_quote">
<div> </div>I believe the WHOIS
deprecation could follow a similar pattern but for sure the SCWG
should urgently focus on requiring CAs to use WHOIS libraries that
query the proper Registrar endpoints, IF they are using the WHOIS
method to query Domain Contact information</div><div class="gmail_quote"><br></div></div></blockquote><div dir="ltr"><div class="gmail_quote">If CAs are going to continue to use WHOIS-3912, I think that the SCWG should require that the traffic be carried over an authenticated TLS channel, or that the response be signed. Anything less doesn't address the fundamental insecurity of the *access protocol*, whatever the truth of the data returned in the request. Do you feel that unauthenticated requests over the public internet really have a place in DCV?<br></div><div class="gmail_quote"><br></div><div class="gmail_quote">Saying that the internet is fundamentally insecure is like saying that electricity is fundamentally insecure, to me. The base protocols of the internet, like IP, don't provide sufficient security properties given the importance of the modern web. But just as TCP provides in-order delivery over un-ordered IP, and TLS provides privacy and integrity over TCP (which features neither of those, save a trivial attempt at integrity aimed at signalling errors and not malicious interception), the web PKI can provide authentication of domain ownership and connection validity by layering appropriate protocols (computer and human) atop the less-capable lower layers. That to me is the essence of the mandate of the SCWG. We are to TLS what ICANN is to DNS: ICANN doesn't say that you can't return arbitrary nonsense in a DNS response from your server on a private network, but it *does* say that if you want to operate a DNS server on behalf of a gTLD, you need to meet certain requirements or ICANN simply won't point traffic at you. We should "stop pointing traffic" at certificates that were validated using WHOIS-3912 DCV, and I wish I'd pushed to do so multiple decades ago.</div><div class="gmail_quote"><br></div><div class="gmail_quote">Mike</div><div class="gmail_quote"><br></div></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
</blockquote></div></div>