Re: [Acme] DNS challenge spec doesn't support CNAME model

Jacob Hoffman-Andrews <jsha@eff.org> Fri, 18 December 2015 01:17 UTC

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Subject: Re: [Acme] DNS challenge spec doesn't support CNAME model
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> These third party services do have an option that would avoid the need
for their users to add a second CNAME: they could use the HTTP or TLS
SNI challenges. This would require extra engineering work, as they would
need to coordinate the installation/configuration of ACME challenge
responses across a fleet of servers as opposed to changing a DNS record.

Also, Let's Encrypt currently supports HTTP redirects. So a service
provider could set up a static redirect on all their frontends from
/.well-known/validation/<foo> -> acme-validator.serviceprovider.net/foo.
If acme-validator is assumed to be less widely distributed than the
general-purpose frontends, it would be easier to update quickly.