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domainaware / checkdmarc

A parser for SPF and DMARC DNS records
https://domainaware.github.io/checkdmarc
Apache License 2.0
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Wildcard DMARC report destination #142

Open kazet opened 1 month ago

kazet commented 1 month ago

Hello,

The RFC says that:

A Report Receiver that is willing to receive reports for any domain can use a wildcard DNS record. For example, a TXT resource record at "*._report._dmarc.example.com" containing at least "v=DMARC1" confirms that example.com is willing to receive DMARC reports for any domain.

There are two possible interpretations of this paragraph. One is that to allow receiving reports from all domains the recipient domain should add a wildcard DNS record (not with a literal asterisk in the domain name) so that a query for any domain under _report._dmarc will return the same.

The second interpretation is that a DNS record with a literal asterisk should be added. Checkdmarc (and opendmarc) is checking for a domain with a literal asterisk. Are you sure this is a correct behavior?

seanthegeek commented 1 month ago

The Wikipedia article on wildcard DNS records states that a wildcard DNS record has a * at the leftmost part of the hostname, which is the same as what we are checking with .*_report._dmarc.example.com, so I don't see the distinction you are making,

kazet commented 1 month ago

Hello,

In my understanding: yes, you configure the record on the DNS server by providing in the zone file, but the DNS server interprets such setting as "whatever domains get queried, return the following data: ". So this will result in all subdomains returning the configured result - you don't have to query for a subdomain separately.

What do you think?

czw., 1 sie 2024, 17:38 użytkownik Sean Whalen @.***> napisał:

The Wikipedia article https://en.wikipedia.org/wiki/Wildcard_DNS_record on wildcard DNS records states that a wildcard DNS record has a at the leftmost part of the hostname, which is the same as what we are checking with ._report._dmarc.example.com, so I don't see the distinction you are making,

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