<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<br>
<br>
<div class="moz-cite-prefix">On 14/5/2024 12:53 μ.μ., Martijn
Katerbarg wrote:<br>
</div>
<blockquote type="cite"
cite="mid:SA1PR17MB650353336B167C8FCB29EA9AE3E32@SA1PR17MB6503.namprd17.prod.outlook.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="Generator"
content="Microsoft Word 15 (filtered medium)">
<style>@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}@font-face
{font-family:Aptos;
panose-1:2 11 0 4 2 2 2 2 2 4;}p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
font-size:12.0pt;
font-family:"Aptos",sans-serif;}a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Aptos",sans-serif;
color:windowtext;}span.apple-converted-space
{mso-style-name:apple-converted-space;}.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;
mso-ligatures:none;}div.WordSection1
{page:WordSection1;}</style>
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">></span><span style="color:#212121">Thoughts?
Disagreements? I know that Apple has already publicly<span
class="apple-converted-space">Â </span></span><a
href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.mozilla.org%2Fshow_bug.cgi%3Fid%3D1886467%23c13&data=05%7C02%7Cmartijn.katerbarg%40sectigo.com%7Ccc5e5bc3c5844518497708dc73f8f6c9%7C0e9c48946caa465d96604b6968b49fb7%7C0%7C0%7C638512760354884136%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=QWqJjIw8XcHlSKQ17G9764glFPOvtujhS%2BwOtvMSuG4%3D&reserved=0"
title="Original URL:
https://bugzilla.mozilla.org/show_bug.cgi?id=1886467#c13
Click to follow link." moz-do-not-send="true"><span
style="color:#0078D7">shared an opinion</span></a><span
class="apple-converted-space"><span style="color:#212121">Â </span></span><span
style="color:#212121">on this matter so I'm hoping to get
more feedback from Members here :)</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="SV"><o:p>Â </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">I do agree with the quoted statement. </span></p>
</div>
</blockquote>
<br>
Are you referring to <i>your</i> quoted statement? I had two quotes
in my first email of the thread :-)<br>
<br>
<blockquote type="cite"
cite="mid:SA1PR17MB650353336B167C8FCB29EA9AE3E32@SA1PR17MB6503.namprd17.prod.outlook.com">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">If compliance is asserted by the inclusion of a
Policy OID, it would come into scope. If not, then indeed it
would seem, it’s not in scope.</span></p>
</div>
</blockquote>
<br>
I already answered that in
<a class="moz-txt-link-freetext" href="https://lists.cabforum.org/pipermail/servercert-wg/2024-May/004575.html">https://lists.cabforum.org/pipermail/servercert-wg/2024-May/004575.html</a>
(apologies for starting the responses in reverse order).<br>
<blockquote type="cite"
cite="mid:SA1PR17MB650353336B167C8FCB29EA9AE3E32@SA1PR17MB6503.namprd17.prod.outlook.com">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p>Â </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">To me this mainly raises the question: What is
a CA allowed to do with a SubCA Private Key. Section 6.1.7
states what a private key corresponding to a Root
Certificate may be used for. Do we need something similar
for private keys corresponding to Subordinate CAs?</span></p>
</div>
</blockquote>
<br>
<blockquote type="cite"
cite="mid:SA1PR17MB650353336B167C8FCB29EA9AE3E32@SA1PR17MB6503.namprd17.prod.outlook.com">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p>Â </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">Such a requirement could then indicate which
type of objects may be signed (such as CRLs, OCSP responses,
TLS certs, precerts. Since the requirements are related to
TLS Certificates, in my opinion it would be in scope to say
that a Subordinate CA capable of issuing TLS Certificates,
may or may not issue clientAuth-only certificates, and if
so, according to which profile.</span></p>
</div>
</blockquote>
<br>
This is an interesting idea, I wouldn't object to it as long as we
reach consensus about the intent related to client authentication
-and other non-server-TLS, non-codeSigning, non-timeStamping,
non-emailProtection-
leaf certificates.<br>
<br>
<br>
Thanks,<br>
Dimitris.<br>
<blockquote type="cite"
cite="mid:SA1PR17MB650353336B167C8FCB29EA9AE3E32@SA1PR17MB6503.namprd17.prod.outlook.com">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US"><o:p>Â </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"
lang="EN-US">Regards,<br>
<br>
Martijn<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p>Â </o:p></span></p>
<div id="mail-editor-reference-message-container">
<div>
<div
style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span
style="color:black">From: </span></b><span
style="color:black">Servercert-wg
<a class="moz-txt-link-rfc2396E" href="mailto:servercert-wg-bounces@cabforum.org"><servercert-wg-bounces@cabforum.org></a> on behalf
of Dimitris Zacharopoulos (HARICA) via Servercert-wg
<a class="moz-txt-link-rfc2396E" href="mailto:servercert-wg@cabforum.org"><servercert-wg@cabforum.org></a><br>
<b>Date: </b>Tuesday, 14 May 2024 at 11:33<br>
<b>To: </b>CA/B Forum Server Certificate WG Public
Discussion List <a class="moz-txt-link-rfc2396E" href="mailto:servercert-wg@cabforum.org"><servercert-wg@cabforum.org></a><br>
<b>Subject: </b>[Servercert-wg] Discussion about
single-purpose client authentication leaf certificates
issued from a server TLS Issuing CA<o:p></o:p></span></p>
</div>
<div
style="border:solid black 1.0pt;padding:2.0pt 2.0pt 2.0pt 2.0pt">
<p class="MsoNormal"
style="line-height:12.0pt;background:#FAFA03"><span
style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black">CAUTION:
This email originated from outside of the
organization. Do not click links or open attachments
unless you recognize the sender and know the content
is safe.<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><o:p>Â </o:p></p>
<div>
<p class="MsoNormal">Dear Members,<br>
<br>
Following-up on an interesting <a
href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.mozilla.org%2Fshow_bug.cgi%3Fid%3D1886467%23c11&data=05%7C02%7Cmartijn.katerbarg%40sectigo.com%7Ccc5e5bc3c5844518497708dc73f8f6c9%7C0e9c48946caa465d96604b6968b49fb7%7C0%7C0%7C638512760354862106%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=WphkYw9Fbr%2FL0dqrFc83nBZLcYw2t7edPk3xMtDIz5Y%3D&reserved=0"
moz-do-not-send="true">public incident</a>, I would
like to have a discussion about the scope of the TLS BRs
as specified in the SCWG Charter and in the actual TLS
BRs, especially when it comes to single-purpose "client
authentication" certificates (i.e. leaf certificates
that include the <i>id-kp-clientAuth</i> and DO NOT
include the<i> id-kp-serverAuth</i> KeyPurposeId in
their extKeyUsage extension).<o:p></o:p></p>
<p>The TLS BRs describe the profiles of Subordinate CA
Certificates issued from a Root that is in-scope for
server TLS authentication, even for the case of
Technically-Constrained non-TLS CA Certificates. There
was a lot of discussion about whether this is permitted
based on the SCWG Charter and there was consensus that
Browsers want to make sure that there are some minimum
expectations about the structure of such non-TLS CA
certificates, especially the adherence to RFC 5280. I
recall that there was also consensus that whatever is
issued off of these TC non-TLS CAs is not in scope of
the TLS BRs.<o:p></o:p></p>
<p><u>Does this seem like a fair statement about intent of
the group on the expectations of TC non-TLS CAs and
their leaf certificates?</u><o:p></o:p></p>
<p>Technically Constrained non-TLS Issuing CAs have a
defined profile in the TLS BRs but IMO it cannot, and
should not mandate the profile of non-TLS leaf
certificates based on the <a
href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcabforum.org%2Fworking-groups%2Fserver%2Fcharter%2F&data=05%7C02%7Cmartijn.katerbarg%40sectigo.com%7Ccc5e5bc3c5844518497708dc73f8f6c9%7C0e9c48946caa465d96604b6968b49fb7%7C0%7C0%7C638512760354875906%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=EE7jB9F8aXgkXT8pAgZExAJsuhFDwBQ%2FEmQP%2BpVxBrc%3D&reserved=0"
moz-do-not-send="true">CA/Browser Forum Server
Certificate Working Group Charter</a> which states
(emphasis mine):<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><i>(a) To specify Baseline
Requirements, Extended Validation Guidelines, and
other acceptable practices for the issuance and
management of <b>TLS server certificates used for
authenticating servers accessible through the
Internet</b></i><o:p></o:p></p>
</blockquote>
<p>It gets more interesting when an Issuing CA that is
technically capable of issuing server authentication TLS
Certificates (by including the<i> id-kp-serverAuth</i>
KeyPurposeId in its extKeyUsage extension), also
includes the <i>id-kp-clientAuth</i> KeyPurposeId, thus
being technically capable of issuing client
authentication TLS Certificates.<o:p></o:p></p>
<p>Please recall that a few years back multi-purpose
Issuing CAs existed, where the EKU was not present, and
even if it was, it allowed the inclusion of various
KeyPurposeIds.<o:p></o:p></p>
<p>Is it ok for such an Issuing CA to create a
single-purpose client authentication TLS Certificate,
one that is structured according to RFC 5280 (thus can
be successfully parsed by Relying Party RFC
5280-conformant software), contains an extKeyUsage
extension which contains the <i>id-kp-clientAuth</i>
and DOES NOT include the <i>id-kp-serverAuth</i>
KeyPurposeId?<o:p></o:p></p>
<p>My understanding is that these particular leaf
certificates are allowed to be issued by a server TLS
capable CA and they are considered out-of-scope of the
BRs, in the sense that <b>they are not TLS Server
Certificates</b>. The SCWG has accepted this "risk"
with the client authentication certificates by allowing
the co-existence of <i>id-kp-clientAuth</i> and<i>
id-kp-serverAuth </i>KeyPurposeIds and the explicit
dis-allowance of <i>id-kp-emailProtection,
id-kp-codeSigning, id-kp-timeStamping,
anyExtendedKeyUsage</i> in the CA Certificate
profiles.<o:p></o:p></p>
<p>The first paragraph of the TLS BRs (section 1.1)
states:<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><i>.....for the issuance and
management of Publicly-Trusted TLS Server
Certificates;</i><o:p></o:p></p>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt">Provided
these certificates follow RFC 5280 and can be properly
parsed, Browsers should never consider such certificates
server TLS certificates. They are by design "technically
constrained".<br>
<br>
Thoughts? Disagreements? I know that Apple has already
publicly <a
href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.mozilla.org%2Fshow_bug.cgi%3Fid%3D1886467%23c13&data=05%7C02%7Cmartijn.katerbarg%40sectigo.com%7Ccc5e5bc3c5844518497708dc73f8f6c9%7C0e9c48946caa465d96604b6968b49fb7%7C0%7C0%7C638512760354884136%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=QWqJjIw8XcHlSKQ17G9764glFPOvtujhS%2BwOtvMSuG4%3D&reserved=0"
moz-do-not-send="true">shared an opinion</a> on this
matter so I'm hoping to get more feedback from Members
here :)<br>
<br>
<br>
Thanks,<br>
Dimitris.<br>
<br>
<o:p></o:p></p>
</div>
</div>
</div>
</div>
</blockquote>
<br>
</body>
</html>