CAA Question - issue / issuewild

Issuance Policy
1

Hi,

I have read through a lot of material but can't see a clear answer anywhere. I think to understand CAA fully you have to read a lot of RFC material. Question:

If I wanted to allow absolutely all certificates to be issued for example.com from both LetsEncrypt & Digicert do I need both 'issue' and 'issuewild' records for both LetsEncrypt & Digicert? I.e.

example.com 0 issue letsencrypt.org
example.com 0 issuewild letsencrypt.org
example.com 0 issue digicert.com
example.com 0 issuewild digicert.com

Some reference material I'm finding seems to suggest 'issue' allows for both wildcard and non-wildcard certificates to be issued?

Would the CAA setup above allow certificates to be issued / validated for "example.com", "wildcard.example.com", "subdomain.example.com" & "subdomain.subdomain.example.com", "wildcard.subdomain.example.com"

Many thanks.

2

yes. unless you override it with a more specific CAA record on a subdomain.

Also yes. If you want to forbid wildcard issuance you can use

example.com 0 issue "letsencrypt.org"
example.com 0 issue "digicert.com"
example.com 0 issuewild ";"
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3

Thank you. So in other words I can allow absolutely everything for LetsEncrypt & Digicert with the following records:

example.com 0 issue "letsencrypt.org"
example.com 0 issue "digicert.com"

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4

I think you didn't quite say what you meant, if you want only Digicert & Sectigo then you wouldn't be including Let's Encrypt.

If there are no issuewild entries, then wildcards follow the issue entries. That is, if you have any issuewild at all, then a wildcard has to match them, but if you only have issue entries, then they apply for both wildcard and non-wildcard certs.

Agreed, it (like many things relating to certificates) seems a lot more confusing than it has to be, with lots of cross-references to lots of documents. In this case, the paragraph I think you're looking for is in RFC 8659, section 4.3,

If at least one issuewild Property is specified in the Relevant RRset for a Wildcard Domain Name, each issue Property MUST be ignored when processing a request for that Wildcard Domain Name.

Which is trying to say that wildcards use the issuewild instead of issue, only if there is at least one issuewild property in existance.

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5

Okay thanks. It was my mistake on the first bit. A typo. I meant to say LetsEncrypt & Digicert. I have edited the original post.

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6

Yes, that will allow both those CAs to issue any certificates for example.com, regardless of whether it's a wildcard or not.

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7

Thank you both! Very clear and helpful answers.

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8

the edge case might be this one: RFC 8659: DNS Certification Authority Authorization (CAA) Resource Record

wild3.example.com         CAA 0 issuewild "ca2.example.org"
wild3.example.com         CAA 0 issue ";"
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9

The previous posts were all helpful. Also, from this page

Is a link to this CAA generator.
https://sslmate.com/caa/

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