>>>>> "IF" == Ian Fette (イアンフェッティ) <[email protected]> writes:

IF> Let's say that you want to know a-priori if an email will be sent over TLS.

IF> (2) gives you a signal that you could potentially pass on to a user,
IF> and then the user can potentially make a decision about whether or
IF> not they want to send the email.

The idea of using the existence of an unsecured tlsa rr as a hint that
tls must be used was, IIRC, discussed in the early days of this wg.

There wasn't consensus to include that -- or anything dealing with
unsecured rr sets -- in the rfc due (again, IIRC) to the ease with
which a mitm also can mitm the dns.

Doing MX+TLSA queries as soon as the destination(s) are known so as to
indicate the possibility of TLS (Trusted, Untrusted or Verified) can be
a good idea.

There is a risk of leaking information when the client is not the same
system which will do the outgoing smtp, though, so the lookups may need
securely to be proxied, depending on how the mail is to be submitted.

But it tlsa existance is to be the key, it does seem best to demand that
it be secured.

But please do publish the tlsa sooner rather than later.  Even though
they likely will not get used in practice until the zones are signed,
tests can still be done to ensure accuracy, and there won't have to be
any delays post-signing.

-JimC
-- 
James Cloos <[email protected]>         OpenPGP: 1024D/ED7DAEA6
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