How many SAN entries...?

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How many SAN entries...?

Blumenthal, Uri - 0553 - MITLL

A naïve question. A certificate that contains SAN attribute(s) – is there a limit on how many, say, RFC822 SAN attributes can a valid certificate have?

 

It’s been my understanding that a cert can contain as many SAN attributes as needed, but it appears that Apple believes it has to be only one (because certificates with more than one are not processed properly).

 

Sanity check: please validate – am I correct that having, say, two RFC822 email addresses in one cert is OK?

— 

Regards,

Uri

 


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Re: How many SAN entries...?

OpenSSL - User mailing list
> A naïve question. A certificate that contains SAN attribute(s) – is there a limit on how many, say, RFC822 SAN attributes can a valid certificate have?

No.

> It’s been my understanding that a cert can contain as many SAN attributes as needed, but it appears that Apple believes it has to be only one (because certificates with more than one are not processed properly).

I can guess at, and understand, their reasoning -- it allows mail spoofing and stealing.  And the use of such certs is not common.
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Re: How many SAN entries...?

Viktor Dukhovni
In reply to this post by Blumenthal, Uri - 0553 - MITLL

> On Apr 26, 2017, at 1:03 PM, Blumenthal, Uri - 0553 - MITLL <[hidden email]> wrote:
>
> A naïve question. A certificate that contains SAN attribute(s) – is there a limit
> on how many, say, RFC822 SAN attributes can a valid certificate have?

None of the standard SAN types (DNS, Email, IP, ...) are limited to just one
entry.  If you try to have hundreds of them, eventually the certificate may
become too big for various protocols, but that's an explicit limit on the SAN
multiplicity.

> It’s been my understanding that a cert can contain as many SAN attributes as needed,
> but it appears that Apple believes it has to be only one (because certificates with
> more than one are not processed properly).

Perhaps CAs have rarely issued email certificates with multiple email addresses.

> Sanity check: please validate – am I correct that having, say, two RFC822 email
> addresses in one cert is OK?

OpenSSL will accept multiple email SANs and with email name checks will accept
the certificate as valid so long as one of the addresses is a match.

--
        Viktor.

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Re: How many SAN entries...?

Blumenthal, Uri - 0553 - MITLL
    > It’s been my understanding that a cert can contain as many SAN attributes as needed,
    > but it appears that Apple believes it has to be only one (because certificates with
    > more than one are not processed properly).
   
    Perhaps CAs have rarely issued email certificates with multiple email addresses.
   
:-)

    OpenSSL will accept multiple email SANs and with email name checks will accept
    the certificate as valid so long as *one* of the addresses is a match.
 
Thank you! That’s what I expected and hoped for. Appreciate the help!


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Re: How many SAN entries...?

Alan Buxey-2
confirmed, i've seen dozens on one cert - far more preferable to do
that and have such numbers than a single wildcard cert (which has
issues on all sorts of platforms
for various purposes).

alan

On 26 April 2017 at 18:24, Blumenthal, Uri - 0553 - MITLL
<[hidden email]> wrote:

>     > It’s been my understanding that a cert can contain as many SAN attributes as needed,
>     > but it appears that Apple believes it has to be only one (because certificates with
>     > more than one are not processed properly).
>
>     Perhaps CAs have rarely issued email certificates with multiple email addresses.
>
> :-)
>
>     OpenSSL will accept multiple email SANs and with email name checks will accept
>     the certificate as valid so long as *one* of the addresses is a match.
>
> Thank you! That’s what I expected and hoped for. Appreciate the help!
>
>
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Re: How many SAN entries...?

Jeffrey Walton-3
In reply to this post by Blumenthal, Uri - 0553 - MITLL
On Wed, Apr 26, 2017 at 1:03 PM, Blumenthal, Uri - 0553 - MITLL
<[hidden email]> wrote:
> A naïve question. A certificate that contains SAN attribute(s) – is there a
> limit on how many, say, RFC822 SAN attributes can a valid certificate have?
>
>
>
> It’s been my understanding that a cert can contain as many SAN attributes as
> needed, but it appears that Apple believes it has to be only one (because
> certificates with more than one are not processed properly).

Lol... Apple is notorious for their defective and untested software.
I'm pretty sure they don't have a QA department. Also see
https://news.ycombinator.com/item?id=11034071.

Worse, when a bug is reported through their RADAR, it goes unfixed.
They force users into QA, and then don't fix the bugs that are
reported.

Jeff
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Re: How many SAN entries...?

Jochen Bern
In reply to this post by Blumenthal, Uri - 0553 - MITLL
On 04/26/2017 07:13 PM, Viktor Dukhovni was digested as writing:
> On Apr 26, 2017, at 1:03 PM, Blumenthal, Uri - 0553 - MITLL <[hidden email]> wrote:
>> It?s been my understanding that a cert can contain as many SAN attributes as needed,
>> but it appears that Apple believes it has to be only one (because certificates with
>> more than one are not processed properly).
>
> Perhaps CAs have rarely issued email certificates with multiple email addresses.

The mechanics of verifying - or, if necessary, revoking - every single
one should be ... interesting. Unless, maybe, it's a boatload of
("typo"?) aliases from the same organization.

[Remembers manually splitting others' PGP pubkeys into single-user-ID
ones after signing parties so as to send every freshly-signed ID only to
the *one* address stated in it]

Regards,
--
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Re: How many SAN entries...?

Blumenthal, Uri - 0553 - MITLL
You do not "revoke" a subset of attributes aka SAN emails. When any of the certified attributes changes (i.e., is certification no longer valid), the certificate is revoked and (possibly) re-issued. The process is no different than with any other set of attributes, several of which may be owned/controlled by different organizations.

Regards,
Uri

Sent from my iPhone

> On Apr 27, 2017, at 09:41, Jochen Bern <[hidden email]> wrote:
>
> On 04/26/2017 07:13 PM, Viktor Dukhovni was digested as writing:
>> On Apr 26, 2017, at 1:03 PM, Blumenthal, Uri - 0553 - MITLL <[hidden email]> wrote:
>>> It?s been my understanding that a cert can contain as many SAN attributes as needed,
>>> but it appears that Apple believes it has to be only one (because certificates with
>>> more than one are not processed properly).
>>
>> Perhaps CAs have rarely issued email certificates with multiple email addresses.
>
> The mechanics of verifying - or, if necessary, revoking - every single
> one should be ... interesting. Unless, maybe, it's a boatload of
> ("typo"?) aliases from the same organization.
>
> [Remembers manually splitting others' PGP pubkeys into single-user-ID
> ones after signing parties so as to send every freshly-signed ID only to
> the *one* address stated in it]
>
> Regards,
> --
> Jochen Bern
> Systemingenieur
>
> Fon:    +49 6151 9067-231
> Fax:    +49 6151 9067-290
> E-Mail: [hidden email]
>
> www.binect.de
> www.facebook.de/binect
>
> Binect ist ausgezeichnet:
> Sieger INNOVATIONSPREIS-IT 2017 | Das Büro: Top 100 Büroprodukte 2017
>
> Binect GmbH
>
> Robert-Koch-Straße 9, 64331 Weiterstadt, DE
>
> Geschäftsführung: Christian Ladner, Dr. Frank Wermeyer, Nils Manegold
> Unternehmenssitz: Weiterstadt
> Register:         Amtsgericht Darmstadt, HRB 94685
> Umsatzsteuer-ID:  DE 221 302 264
>
> MAX 21-Unternehmensgruppe
> ✁
> Diese E-Mail kann vertrauliche Informationen enthalten. Wenn Sie nicht
> der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben,
> informieren Sie bitte sofort den Absender und vernichten Sie diese
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Re: How many SAN entries...?

Jochen Bern
In reply to this post by Blumenthal, Uri - 0553 - MITLL
On 04/27/2017 04:09 PM, [hidden email] digested:
> From: "Blumenthal, Uri - 0553 - MITLL" <[hidden email]>
>
> You do not "revoke" a subset of attributes aka SAN emails. When any of
> the certified attributes changes (i.e., is certification no longer valid),
> the certificate is revoked and (possibly) re-issued.

Precisely. Now imagine the cert being used for S/MIME (why would a cert
list several e-mail addresses if it weren't somehow related to e-mails
and the addressee's identity?) and the CA or its procedures insisting on
renewing keypairs when a new cert is issued. I'ld say you'ld get users
and their pitchforks asking for multiple SINGLE-attribute/value certs
real fast.

Regards,
--
Jochen Bern
Systemingenieur

Fon:    +49 6151 9067-231
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Re: How many SAN entries...?

Blumenthal, Uri - 0553 - MITLL
It depends on the CA in question, more so on the number of the attributes that are included, and of course on the set of users. ;-)

So far I assure you I've no concern for pitchforks. ;-)

Regards,
Uri

P.S. Why do you think validating, e.g., three email addresses is any more difficult than one? If that one is not under your direct control, that is? Sure, it may take longer to validate three - but it's the "process" time, not "human/employee" time.

Sent from my iPhone

> On Apr 27, 2017, at 10:28, Jochen Bern <[hidden email]> wrote:
>
> On 04/27/2017 04:09 PM, [hidden email] digested:
>> From: "Blumenthal, Uri - 0553 - MITLL" <[hidden email]>
>>
>> You do not "revoke" a subset of attributes aka SAN emails. When any of
>> the certified attributes changes (i.e., is certification no longer valid),
>> the certificate is revoked and (possibly) re-issued.
>
> Precisely. Now imagine the cert being used for S/MIME (why would a cert
> list several e-mail addresses if it weren't somehow related to e-mails
> and the addressee's identity?) and the CA or its procedures insisting on
> renewing keypairs when a new cert is issued. I'ld say you'ld get users
> and their pitchforks asking for multiple SINGLE-attribute/value certs
> real fast.
>
> Regards,
> --
> Jochen Bern
> Systemingenieur
>
> Fon:    +49 6151 9067-231
> Fax:    +49 6151 9067-290
> E-Mail: [hidden email]
>
> www.binect.de
> www.facebook.de/binect
>
> Binect ist ausgezeichnet:
> Sieger INNOVATIONSPREIS-IT 2017 | Das Büro: Top 100 Büroprodukte 2017
>
> Binect GmbH
>
> Robert-Koch-Straße 9, 64331 Weiterstadt, DE
>
> Geschäftsführung: Christian Ladner, Dr. Frank Wermeyer, Nils Manegold
> Unternehmenssitz: Weiterstadt
> Register:         Amtsgericht Darmstadt, HRB 94685
> Umsatzsteuer-ID:  DE 221 302 264
>
> MAX 21-Unternehmensgruppe
> ✁
> Diese E-Mail kann vertrauliche Informationen enthalten. Wenn Sie nicht
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> Wir schließen, außer für den Fall von Vorsatz oder grober
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> This e-mail may contain confidential and/or privileged information. If
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