[cabfpub] Definition of an SSL certificate

Thu Jan 2 17:40:49 UTC 2014

We are trying to NOT cover QCs in the BR scope.  

Currently, most QCs include the anyEKU, meaning the QC can be used for SSL.  An attacker can an QC certificate with a domain name from a trusted QC issuer.  Since many QC issuers do not provide SSL certificates on a regular basis, they will not realize the certificate must comply with the BRs and fail to properly vet the domain name included in the certificate. After the certificate issues, the attacker can freely use the certificate to MITM everyone on the included domain. This is a real scenario since many of these standards do not require the CA to verify any domain name included in the certificate.

In this example, the CA did nothing wrong from a standard’s perspective. However, this is little comfort to the affected users.  

One proposal (by Ryan Hurst) is to only require compliance if the certs assert the BR/EV CAB Forum OIDs. The browsers can then require the BR/EV OID before trusting the certificate.

An alternative is to expand the definition and include a statement that says any certificate that includes a domain name and the anyEKU, noEKU, or serverAuth  is considered intended for use in SSL.

Jeremy

From: me at chemalogo.com [mailto:me at chemalogo.com] On Behalf Of Chema López González
Sent: Thursday, January 02, 2014 10:26 AM
To: public at cabforum.org
Cc: Jeremy Rowley; i-barreira at izenpe.net; Stephen Davidson
Subject: Re: [cabfpub] Definition of an SSL certificate

Dear all,

Qualified certificates are intended to identify people, not websites nor servers. There are no hard constrains regarding the usage of EKU KU values, but good practices are to use Non-repudiation and only non-repudiation (see RFC3039 <http://www.ietf.org/rfc/rfc3039.txt> , section 3.2.3 in combination with ETSI TS 102 280 <http://www.etsi.org/deliver/etsi_ts/102200_102299/102280/01.01.01_60/ts_102280v010101p.pdf> , section 5.4.3 and taking into account that Qualified Certificates are defined with purpose of creation Qualified Electronic Signatures legally binding!)

In fact any QC contents personal data (or pseudonym but the CSP MUST have the actual personal data bound to the pseudonym) so I do not think any will want to put her personal data authenticating a public website.

Since the purpose of a QC is quite different of the purpose of a SSL certificate and the first is legally constricted I do really think that BR's do not have to cover QC at all. Maybe it exists but I have never seen a QC authenticating a website.

IMHO trying to cover QC is going beyond the purpose of the BR, it will mesh up the whole think without adding security to SSL certificates.

 <http://www.firmaprofesional.com/> AC Firmaprofesional S.A.

Chema López González

AC Firmaprofesional S.A.

Av. Torre Blanca, 57. 
Edificio ESADECREAPOLIS - 1B13

08173 Sant Cugat del Vallès. Barcelona.

Tel: 93.477.42.45 / 666.429.224

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On Thu, Dec 19, 2013 at 5:52 PM, Stephen Davidson <S.Davidson at quovadisglobal.com> wrote:

>  Are qualified certs issued from the same root as BR certs?

Yes.

From: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] On Behalf Of Jeremy Rowley
Sent: Thursday, December 19, 2013 12:51 PM
To: i-barreira at izenpe.net; public at cabforum.org

Subject: Re: [cabfpub] Definition of an SSL certificate

So:

1)      Qualified certs CAN be used for TLS Server Authentication since they may include anyEKU or serverAuth in the EKU extension

2)      Qualified Certs do NOT comply with the BRs, they comply with the appropriate ESTI standard.  

3)      Qualified certs are only distinguishable from BR certs because qualified certs assert a QCStatement

Is this a fair summary? 

From: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] On Behalf Of i-barreira at izenpe.net

Sent: Thursday, December 19, 2013 9:25 AM
To: jeremy.rowley at digicert.com; public at cabforum.org
Subject: Re: [cabfpub] Definition of an SSL certificate

Yes, but with some additional points

-          Mark Jansen is right albeit it depends on national legislation. In Spain, you have to indicate what EKU is to be used.

-          DV or OV will never be considered Qualified certs. EV possibly and will have some impacts

Iñigo Barreira
Responsable del Área técnica
i-barreira at izenpe.net

945067705

Descripción: Descripción: Descripción: firma_izenpe_navid-OK-2

De: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] En nombre de Jeremy Rowley
Enviado el: jueves, 19 de diciembre de 2013 17:06
Para: CABFPub
Asunto: [cabfpub] Definition of an SSL certificate

We are looking to clarify the scope of the BRs.  Right now the BR scope is very loose and subjective: “This version of the Requirements only addresses Certificates intended to be used for authenticating servers  accessible through the Internet.”

This loose definition excludes internal names (which are not typically accessible through the Internet), a type of certificate the BRs are clearly designed to regulate (see 11.1.4).  In addition, a CA could easily issue a certificate outside of the BRs  that could later be used in a TLS/SSL attack simply because the certificate wasn’t intended to be used for SSL.  

Issuance of certificates outside the BRs may not be intentional, especially by CAs who aren’t regularly issuing SSL certificates.  These CAs may not be aware that the BRs apply to their certificates and may not realize their client certificates could be used for SSL since “authenticating servers” is not a well-defined term.  

Clarifying the scope will ensure that every CA is aware of the minimum standards and what they cover.  Originally, the idea was to tie the scope to the values in the EKU.  Unfortunately, there are several obstacles to this approach:

1)      Grid Certificates require serverAuth in the EKU.  It’s unclear whether these certs should be covered.

2)      Per 5280, browsers treat the absence of an EKU and the anyEKU as serverAuth, meaning they are enabled for TLS Server Authentication.

3)      The FBCA requires anyEKU in several certificates.  These are clearly client certificates and are outside the BR scope.

4)      Qualified certificates in the EU have either the anyEKU present or omit the EKU.  They are client certs and clearly not covered by the BRs.  However, they can be used  for server authentication.

For qualified certificates, Moudrick provided the following guidance:

“Certificates using applications MAY require that the extended key usage extension be present and that a particular purpose be indicated in order for the certificate to be acceptable to that application.

If a CA includes extended key usages to satisfy such applications, but does not wish to restrict usages of the key, the CA can include the special KeyPurposeId anyExtendedKeyUsage ***in addition to the particular key purposes required by the applications***.

So a QC pretending to be RFC 5280/BR and ETSI (web server QCs) compliant would have to at least have:

QC + [anyEKU] + id-kp-serverAuth + {DV/OV/EV}

I'm quite confident that the absolute majority of QCs issued so far (that have anyEKU, see Mark Janssen's 08/08/2013 - thank you Stephen) do not contain any DV/OV/EV policy IDs, so why not accept them as BR compliant but not sufficient for TSL/SSL establishment?

In order for a QC to have a TSL/SSL capability, BR may require:

QC + {{id-kp-serverAuth and/or id-kp-clientAuth} + {DV/OV/EV}} (optionally no anyKEY allowed).

A practical interpretation: a WEB server that also does some web site related document/content signing.”

There appears to be a significant conflict between the CAB Forum’s work and the standards set by other bodies.  In particular, their use of the anyEKU or omission of an EKU is permitting the realm of client certs to overlap SSL certs.  Approaching each government body to stop this practice is not feasible and will take a very long time to complete

Hopefully this summary helps inspire ideas on where we can go from here.  I’m looking forward to ideas. 

Thanks!

Jeremy

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