Re: [TLS] Enforcing Protocol Invariants

Patrick Mevzek <> Fri, 09 November 2018 14:38 UTC

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From: Patrick Mevzek <>
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Date: Fri, 09 Nov 2018 09:38:20 -0500
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Subject: Re: [TLS] Enforcing Protocol Invariants
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On 2018-11-08 20:41 -0500, Jim Reid wrote:
> On 8 Nov 2018, at 08:44, Ryan Carboni <> wrote:
>> This might be a radical proposal, but maybe the certificate hash could be placed in a DNS TXT record.


> If you need to put this hash in the DNS, you might as well get a type code assigned for a specifc RR to do that.

Which is exactly what TLSA records are for (RFC 6698), and its type 3:

3 -- Certificate usage 3 is used to specify a certificate, or the
       public key of such a certificate, that MUST match the end entity
       certificate given by the server in TLS.  This certificate usage is
       sometimes referred to as "domain-issued certificate" because it
       allows for a domain name administrator to issue certificates for a
       domain without involving a third-party CA.  The target certificate
       MUST match the TLSA record.  The difference between certificate
       usage 1 and certificate usage 3 is that certificate usage 1
       requires that the certificate pass PKIX validation, but PKIX
       validation is not tested for certificate usage 3.
Patrick Mevzek