[Servercert-wg] Ballot SC33: TLS Using ALPN Method

Wayne Thayer wthayer at gmail.com
Fri Jul 31 09:50:01 MST 2020

This begins the discussion period for ballot SC33: TLS Using ALPN Method

Purpose of Ballot:

In January 2018, a vulnerability affecting the ACME TLS-SNI-01 method of
domain validation was disclosed [1]. That method is an implementation of BR, which is still permitted by the BRs despite the vulnerability.
Some Browsers have banned the use of method 10 unless mitigations for the
vulnerability have been put into place, and one approach to mitigation -
using application-layer protocol negotiation (ALPN) - has now been
standardized by the IETF as RFC 8737. This ballot replaces the poorly
specified and potentially insecure 'method 10' with a new 'method 20' based
on RFC 8737.

The ballot proposed no transition period during which method 10, or
validations performed using method 10 may continue to be relied upon. The
only known current use of method 10 is an implementation of RFC 8737 that
would remain compliant (although it may require changes to the CA's CPS and
the identifier of the method that is being logged when performing

This ballot also limits the use of the new method to the specific FQDN that
was validated - different subdomains require new validations, and wildcards
are not permitted. This requirement is not the result of a specific known
risk but rather stems from a belief that DNS-based validation methods are
more appropriate for verifying control over an entire subdomain.


The following motion has been proposed by Wayne Thayer of Mozilla and
endorsed by Roland Shoemaker of Let's Encrypt and Tim Hollebeek of DigiCert.


This ballot modifies the “Baseline Requirements for the Issuance and
Management of Publicly-Trusted Certificates” as follows, based on Version

MODIFY section as defined in the following redline:


This ballot proposes a Final Maintenance Guideline.

The procedure for approval of this ballot is as follows:

Discussion (7+ days)

Start Time: 31-July, 2020 17:00 UTC

End Time: not before 7-August, 2020 17:00 UTC

Vote for approval (7 days)

Start Time: TBD

End Time: TBD
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