[cabfpub] Definition of an SSL certificate

Jeremy Rowley jeremy.rowley at digicert.com
Wed Jan 8 18:13:24 UTC 2014

I don’t think anyone disagrees that server certs should have the serverAuth EKU.  However, this discussion is primarily about how to address the anyEKU and omission of EKU issue.  Both types are treated like serverAuth certs by browsers.


From: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] On Behalf Of Chema López González
Sent: Wednesday, January 08, 2014 5:15 AM
To: Rob Stradling
Cc: Mads Egil Henriksveen; public at cabforum.org; Brown, Wendy (10421)
Subject: Re: [cabfpub] Definition of an SSL certificate


First things first:


But BR also accepts that only the clientAuth EKU bit is set, and this sounds strange to me when the BR scope is ‘authenticating servers’.




Are CAs that issue QCs audited by some ETSI audit equivalent to BRs, in which the auditors check that the CA verified any domain names that appear in QCs?


I have to disagree with Moudrick but this is not consistent across European Countries and this is not mandatory at all.


On the other hand, the European Directive on Electronic Signature <http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31999L0093:EN:HTML>  states (ANNEX II) that:


(d) verify, by appropriate means in accordance with national law, the identity and, if applicable, any specific attributes of the person to which a qualified certificate is issued;


but the Spanish law on electronic signature <https://www.boe.es/buscar/act.php?id=BOE-A-2003-23399>  (ES) is a little bit more restrictive, and states (Art. 12):


"b) Verify that the information contained in the certificate is accurate and contains all the details prescribed for a qualified certificate."


So we can not expect that a Certification Services Provider that issues QC (Qualified Trust Services Provider) is audited by some ETSI. Nevertheless, at the end, the majority of CSP is audited either WebTrust for CA or ETSI TS 101456/102042/102023.


Said that, I can not imagine a certificate authenticating a server without the serverAuth EKU.



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Chema López González
AC Firmaprofesional S.A.


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Tel: 93.477.42.45 / 666.429.224


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On Mon, Jan 6, 2014 at 11:05 AM, Rob Stradling <rob.stradling at comodo.com> wrote:

On 06/01/14 09:54, Moudrick M. Dadashov wrote:
> On 1/3/2014 11:58 PM, Rob Stradling wrote:
>> On 03/01/14 21:09, Moudrick M. Dadashov wrote:


>>> Jeremy, to my understanding RFC 5280 accepts anyEKU only in combination
>>> with any other EKU but not as the only EKU:
>>> “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.
>> But RFC5280 also says:
>>   "Applications that require the presence of a
>>    particular purpose MAY reject certificates that include the
>>    anyExtendedKeyUsage OID but not the particular OID expected for the
>>    application.
>> That's MAY, not MUST.
> Rob, that's right, but isn't about application behavior only?

Yes, that's correct.

> The reference below explains when/why CA may need anyEKU and it says "CA
> can include...".
> I may have missed something though..


>>> 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***.

I don't read that "If" as an "Iff" (If and only if).  In other words, I
don't think this statement limits when anyEKU can be used.  It simply
points out one scenario where it might be useful to use anyEKU.

>>> So based on this:
>>> SSL server: = SAN + serverAuth + [anyEKU+EKU]
>>> SSL client:= [SAN] +clientAuth + [anyEKU+EKU]
>>> Thanks,
>>> M.D.
>>>> Although the definition needs word smithing, it captures the
>>>> certificates of primary concern (those containing domain names)
>>>> without excluding internal server name certs. Thoughts?
>>>> Jeremy
>>>> *From:*Brown, Wendy (10421) [mailto:wendy.brown at protiviti.com]
>>>> *Sent:* Friday, January 03, 2014 12:08 PM
>>>> *To:* Jeremy Rowley; 'Mads Egil Henriksveen'; 'Moudrick M. Dadashov';
>>>> public at cabforum.org
>>>> *Subject:* RE: [cabfpub] Definition of an SSL certificate
>>>> The requirement to verify is in the CP – the details of How goes in
>>>> the CPS.
>>>> *From:*Jeremy Rowley [mailto:jeremy.rowley at digicert.com]
>>>> *Sent:* Friday, January 03, 2014 2:03 PM
>>>> *To:* Brown, Wendy (10421); 'Mads Egil Henriksveen'; 'Moudrick M.
>>>> Dadashov'; public at cabforum.org <mailto:public at cabforum.org>
>>>> *Subject:* RE: [cabfpub] Definition of an SSL certificate
>>>> Thanks Wendy for the clarification.  However, I didn’t see anything
>>>> specifying how the CA is supposed to verify the domain.
>>>> *From:*Brown, Wendy (10421) [mailto:wendy.brown at protiviti.com]
>>>> *Sent:* Friday, January 03, 2014 11:55 AM
>>>> *To:* Jeremy Rowley; 'Mads Egil Henriksveen'; 'Moudrick M. Dadashov';
>>>> public at cabforum.org <mailto:public at cabforum.org>
>>>> *Subject:* RE: [cabfpub] Definition of an SSL certificate
>>>> The FBCA and Common Policy CPs actually require all information
>>>> included in a certificate to be verified – so that would include any
>>>> domain names, see 3.2.4.
>>>> Thanks,
>>>> Wendy
>>>> Wendy Brown
>>>> FPKIMA Technical Liaison
>>>> Protiviti Government Services
>>>> 703-299-4705 (office)    703-965-2990 (cell)
>>>> wendy.brown at fpki.gov <mailto:wendy.brown at fpki.gov>
>>>> wendy.brown at protiviti.com <mailto:wendy.brown at protiviti.com>
>>>> *From:*public-bounces at cabforum.org
>>>> <mailto:public-bounces at cabforum.org>
>>>> [mailto:public-bounces at cabforum.org] *On Behalf Of *Jeremy Rowley
>>>> *Sent:* Friday, January 03, 2014 11:19 AM
>>>> *To:* 'Mads Egil Henriksveen'; 'Moudrick M. Dadashov';
>>>> public at cabforum.org <mailto:public at cabforum.org>
>>>> *Subject:* Re: [cabfpub] Definition of an SSL certificate
>>>> Many of the trusted QC issuers (and other community issuers) are not
>>>> involved in the CAB Forum.  Although you are aware of the
>>>> requirements, I don’t think this knowledge is global. For example, I
>>>> don’t think the NIST CP or FBCA CP ever mentions domain validation. A
>>>> CA following either CP for client certs wouldn’t necessarily validate
>>>> an included domain.
>>>> Jeremy
>>>> *From:*public-bounces at cabforum.org
>>>> <mailto:public-bounces at cabforum.org>
>>>> [mailto:public-bounces at cabforum.org] *On Behalf Of *Mads Egil
>>>> Henriksveen
>>>> *Sent:* Friday, January 03, 2014 4:52 AM
>>>> *To:* Moudrick M. Dadashov; Jeremy Rowley; public at cabforum.org
>>>> <mailto:public at cabforum.org>
>>>> *Subject:* Re: [cabfpub] Definition of an SSL certificate
>>>> Hi Moudrick
>>>> There might not be a real use case for including a domain name in a
>>>> QC, but as a trusted CA we take the responsibility for the accuracy of
>>>> information in all certs we issue. And that was my point and why I am
>>>> not very concerned about the described attack scenario.
>>>> Regards
>>>> Mads
>>>> *From:*public-bounces at cabforum.org
>>>> <mailto:public-bounces at cabforum.org>
>>>> [mailto:public-bounces at cabforum.org] *On Behalf Of *Moudrick M.
>>>> Dadashov
>>>> *Sent:* 3. januar 2014 11:51
>>>> *To:* Mads Egil Henriksveen; Jeremy Rowley; public at cabforum.org
>>>> <mailto:public at cabforum.org>
>>>> *Subject:* Re: [cabfpub] Definition of an SSL certificate
>>>> Mads,
>>>> On 1/3/2014 11:49 AM, Mads Egil Henriksveen wrote:
>>>>     The attack scenario assumes that the QC can be chained to a root
>>>>     cert in a trusted CA root store. This means that the CA should
>>>>     know the root store requirements and should be aware of the risk
>>>>     issuing any cert that could be used as an SSL certificate.
>>>>     Buypass do issue both QC and SSL certificates and with the
>>>>     DigiNotar attack back in 2011 we realized that the browsers do
>>>>     accept a lot of certificates as SSL certificates. Since then we
>>>>     have had strict controls to ensure that no certificate is issued
>>>>     with an unverified domain name. I guess most of the trusted QC
>>>>     issuers who also issue SSL certificates are aware of this, I would
>>>>     not be very concerned about this attack scenario.
>>>> What is the use case when in a QC we'd need a [any/unverified] domain
>>>> name? (aren't CAs responsible for the accuracy of information in the
>>>> QCs they issue?).
>>>> However, I do support the idea of a technical definition of an SSL
>>>> certificate and I like the proposal from Ryan Hurst requiring the
>>>> BR/EV OIDs.
>>>> Under ETSI framework compliance assumes two things: compliance with
>>>> the corresponding requirements plus certificate profile compliance.
>>>> These two categories exist as separate documents (under their own ETSI
>>>> IDs).
>>>> Ryan's proposal is definitely a  good step forward, I'd vote with my
>>>> both hands if we go even further, and like ETSI, have separate BR/EV
>>>> profile specifications.
>>>> Thanks,
>>>> M.D.
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Rob Stradling
Senior Research & Development Scientist
COMODO - Creating Trust Online
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