One of several problems with that Note is, again, the use of plural where
singular works better. The original text also is overly broad and,
consequentially, ambiguous. So:
<t
hangText="NOTE:"> The use of a wildcard TXT record
that covers a queried DKIM domain name will produce a
response to a DKIM query that is unlikely to be valid
DKIM key record. This problem is not specific to DKIM
and applies to many other types of queries. Client
software that processes DNS responses needs to take
this problem into account.</t>
But note that the final sentence is meaningless, since it provides no guidance
about what it means to "take this problem into account". And the answer isn't
obvious. For example, I have no idea what a DKIM implementer should do to
satisfy this caution.
Not only is it confusing, it's wrong. Wildcard records work just fine
when the wildcard is below the _domainkey label, e.g.
*.foo._domainkey.example. They work less fine in other cases.
The advice is presumably that clients should be prepared to receive and
ignore a TXT key record that isn't syntactically valid, but that's just
good defensive programming with or without wildcards.
R's,
John
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