[dmarc-ietf] Using CNAME records to DMARC templates causes issues

jbouwh <dmarc-list@jbsoft.nl> Tue, 02 March 2021 07:49 UTC

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Date: Tue, 02 Mar 2021 08:49:27 +0100
From: jbouwh <dmarc-list@jbsoft.nl>
To: dmarc@ietf.org
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Subject: [dmarc-ietf] Using CNAME records to DMARC templates causes issues
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Hi all,
I am new to this list, and will give a short introduction to myself.
I work for the Dutch government as an IT architect. One of my goals is 
improving mail security.
As Dutch government we commit to comply to SPF, DKIM, DMARC, DANE and 
IPv6 standards.
With this we are challenged to keep the technical environment 
manageable.
Some of our government IT partners use CNAME records to refer to DMARC 
templates, and we are planning to use the same technique. Using 
templates makes it more easy to maintain DNS records.

For private purposes I am running my own mail server using opendmarc 
together with postfix, amavis, spamassasin, opendkim and 
postfix-policyd-spf.
During testing mail policies that where published using a CNAME, I 
noticed opendmarc is not handling the published policies, but is acting 
as if no policy was published. To address this issue I have submitted an 
issue to the opendmarc project.

https://github.com/trusteddomainproject/OpenDMARC/issues/103

My questions are:
-	Is it a common practice to use CNAME DNS record to reference DMARC 
templates?
-	Is it a known issue opendmarc does not process the published policies 
when they are published using a CNAME? If this is caused due to a 
software bug, this could be a serious security issue.

Regards,
Jan