Subject: RE: What's in a Name?

From: "Liqiang(Larry) Zhu" <[email-masked]>
Date: Wed, 13 Jul 2005 09:34:16 -0700

The SubjectKeyIdentifier extension is actually REQUIRED for CA certificates. Here is the text in RFC3280. (Martin, RFC3280 is the IETF version of X.509).

   <<cut>> "this extension MUST
   appear in all conforming CA certificates" <<cut>>

I also looped in Stefan to help us interpret the text in RFC3280.

-- Larry

-----Original Message-----
From: Love Hörnquist Åstrand [mailto:[email-masked]] 
Sent: Wednesday, July 13, 2005 12:32 AM
To: Jeffrey Hutzelman
Cc: Liqiang(Larry) Zhu; [email-masked]; [email-masked]
Subject: Re: What's in a Name?

Jeffrey Hutzelman <[email-masked]> writes:

> So, let's go back a step...
> I'm going to try to ask questions in more detail.  Answers from all
> parties are encouraged...

REQUIRE SubjectKeyIdentifier would be unwise given the use of today CA's.

IssuerAndSerialNumber or SubjectKeyIdentifier should be the items that is
used, any of those two uniquely indentifies the certificate. Name might be
used to be friendly to the user/sysadmin, but have not real use for the
protocol/implementations given its non-uniqueness.

Love

---

From: Chaskiel M Grundman <[email-masked]>
Date: Wed, 13 Jul 2005 13:26:03 -0400

--On Wednesday, July 13, 2005 09:34:16 AM -0700 "Liqiang(Larry) Zhu" 
<[email-masked]> wrote:

> The SubjectKeyIdentifier extension is actually REQUIRED for CA
> certificates. Here is the text in RFC3280. (Martin, RFC3280 is the IETF
> version of X.509).

Standards say lots of things. That doesn't mean the deployed 
implementations we have to work with actually follow them. None of the CA 
root certificates from verisign/thawte that are shipped with recent mozilla 
(at least, as extracted by debian into the 'ca-certificates' package. I 
didn't check the actual mozilla sources) include SubjectKeyIdentifier 
extensions.

---

From: Martin Rex <[email-masked]>
Date: Wed, 13 Jul 2005 23:02:43 +0200 (MET DST)

Chaskiel M Grundman wrote:
> 
> --On Wednesday, July 13, 2005 09:34:16 AM -0700 "Liqiang(Larry) Zhu"=20
> Standards say lots of things. That doesn't mean the deployed=20
> implementations we have to work with actually follow them. None of the CA=20
> root certificates from verisign/thawte that are shipped with recent mozilla =
> 
> (at least, as extracted by debian into the 'ca-certificates' package. I=20
> didn't check the actual mozilla sources) include SubjectKeyIdentifier=20
> extensions.

I can confirm this.

RFC3280 (and it's predecessor), the internet certificate and crl profile
are somewhat contorted in a few areas.

There are some "neat ideas", and "SubjectKeyIdentifier in CA certs" is
probably one of them, which are completely unaligned with reality,
and there are some "bad ideas", such as the sugestion "end entity
certificate should not have the cA=FALSE" basic constraint--which
is not the result of common sense, but probably trying to
avoid running into a flaw of installed base PKI implementations
(however the spec doesn't say this).

It would have been a good idea to cover reality (i.e. consider
the facts of installed base, partly documented in Peter Gutmans
X.509 style guide), and to indicate future directions (such
as the SubjectKeyIdentifier).

The (OEM) PKI implementation that we ship entirely ignores
SubjectKeyIdentifier when building certificate chains (at least
in those pieces of the code which I looked at), and, as has been
observed by others, many CA certificates still don't have
SubjectKeyIdentifier.

-Martin