Re: [TLS] supported_versions in TLS 1.2

[Peter Gutmann <[e-mail]>]

Salz, Rich <[e-mail]> writes:

>Peter has forgotten more about long-term embedded applications than the rest
>of us have experience. I’ll leave it to him to say why it’s important.

I was making a more general point about not assuming that the only thing that
matters is TLS 1.3 vs. TLS 1.2, and that that's all that needs to be
accommodated.  Because of the TLS family A vs. family B protocol fork, there
will be family A around more or less forever.  For example just a few days ago
I was part of a long conference call with a major global user who was looking
at a minimum 15-year (but in practice I expect more like 20-30 year) support
plan for an upcoming rollout of family A TLS.  So just because TLS 1.3 exists
doesn't mean all work on, and accommodation of, earlier versions should stop.
In particular that's why I wrote the TLS-LTS doc, because that explains how to
apply family A in the safest manner possible for the foreseeable future.

In the specific case of supported_versions, there's no reason why the same
thing can't be used to deal with e.g. TLS 1.0 -> TLS 1.2 version intolerance,
which is still a thing.  That's one thing that SSH did right (alongside a lot
of stuff that TLS does much better), you can fingerprint a server via its ID
string and work around problems when you connect without needing to change the
code on the server you're connecting to.

Peter.