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I'd like to know if any certificates support a double wildcard like *.*.example.com? I've just been on the phone with my current SSL provider (register.com) and the girl there said they don't offer anything like that and that she didn't think it was possible anyway.

Can anyone tell me if this is possible, and if browsers support this?

Thanks! Rob

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3 Answers

up vote 4 down vote

RFC2818 states:

If more than one identity of a given type is present in the certificate (e.g., more than one dNSName name, a match in any one of the set is considered acceptable.) Names may contain the wildcard character * which is considered to match any single domain name component or component fragment. E.g., *.a.com matches foo.a.com but not bar.foo.a.com. f*.com matches foo.com but not bar.com.

Internet Explorer behaves in the way outlined by the RFC, where each level needs its own wildcarded certificate. Firefox is happy with a single *.domain.com where * matches anything in front of domain.com, including other.levels.domain.com, but will also handle the *.*.domain.com types as well.

So, to answer your question: it is possible, and supported by browsers.

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Thank you! Testing on FF 3.5.7 this morning showed that it is now RFC compliant in the same way as IE. It rejected my .example.com cert for foo.bar.example.com. So just to clarify all I need is another wildcard cert that has *..example.com as the Common Name? – Rob Long Jan 19 '10 at 17:04
correct, based on that you would need a *.*.example.com – Alex Jan 19 '10 at 18:41
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I just tested in FF 3.5 and IE 8 and neither would accept a certificate for ..example.com. I think the only solution is to use multiple wildcard certificates. – Robert Jan 21 '10 at 1:16
Who wrote this standard? This is worthless. Also a waste of money if you ask me. What does it protect? – Brent Pabst Apr 2 at 23:15
If double-wildcards cause problems, do specific subdomains around wildcards work? ala SubjectAltName: DNS:foo.*.example.com, DNS:bar.*.example.com – rcoup May 1 at 21:19
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up vote 2 down vote

Just to confirm FF and IE 8 will NOT accept certificates in the form *.*.example.com although it is technically possible to create them.

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up vote 0 down vote

there is no need for double wildcard as the single wildcard can accommodate any subdomains under the domain.com domain.

http://www.mail-archive.com/plug@lists.linux.org.ph/msg17605.html

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I have done some testing on this in the past with self-signed certs. Firefox behaved as you suggest, where one *.domain.com covered it all. Internet Explorer, on the other hand, treats the wildcard ONLY for that portion of the domain. So you would need to have 2 wildcarded certs to secure both www.domain.com (*.domain.com) and secure.mail.domain.com (*.*.domain.com) as the original question is stated. – Alex Jan 19 '10 at 15:18
@Alex is right, see his answer! – Stefano May 10 '11 at 10:06
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