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Re: [Acme] Handling non-conformant CAA property names in ACME-CAA

Jacob Hoffman-Andrews <jsha@eff.org> Tue, 10 July 2018 00:57 UTC

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From: Jacob Hoffman-Andrews <jsha@eff.org>
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Subject: Re: [Acme] Handling non-conformant CAA property names in ACME-CAA
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There's a similar issue for parameters: RFC 6844 section 3 says each 
name-value pair is separated by a semicolon:

https://tools.ietf.org/html/rfc6844#section-3
 >    issue <Issuer Domain Name> [; <name>=<value> ]* :  The issue property

RFC 6844 section 5.2 says each name-value pair is separated by a space:

https://tools.ietf.org/html/rfc6844#section-5.2
 >    issuevalue  = space [domain] space [";" *(space parameter) space]


For 6844-bis, in the LAMPS WG, we concluded that the latter was most 
likely an error in the ABNF, and that semicolons were preferable:

https://tools.ietf.org/html/draft-ietf-lamps-rfc6844bis-00#section-5.2
 >    parameters = (parameter *WSP ";" *WSP parameters) / parameter


ACME-CAA's examples use semicolons:

https://tools.ietf.org/html/draft-ietf-acme-caa-03#appendix-A
 > example.com. IN CAA 0 issue "example.net; \
 >     account-uri=https://example.net/account/1234; \
 >     validation-methods=dns-01"


We resolved the hyphen question on the basis of interoperability: Some 
DNS UIs rejected setting CAA records with hyphens in property names, so 
we did the simple thing and removed them.

The semicolon question is not so easily solved. There is no unambiguous 
reading of RFC 6844, no reason to consider section 3 more normative than 
section 5.2 or vice versa.

I have one piece of interop data: While Route53 rejected hyphens in 
property names, it accepts semicolons separating name-value pairs.

My preference is for ACME-CAA to continue follow the RFC 6844bis 
interpretation. What are others' thoughts?

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