Comment 2 for bug 1783610

Copying from what I wrote on the openconnect-devel mailing list…

Nikos's proposed fix is to change "-VERS-TLS-ALL:+VERS-TLS1.0" to
"-VERS-SSL3.0".

It's useful to consider the total set of possible effects of this change on Ubuntu 14.04's openconnect:

1) Good: Fixes the incompatibility reported here, allowing it to
connect to gateways that require TLS1.1 or TLS1.2.
2) Neutral: No effect on ancient gateways that only support SSLv3
(insecure, already locked out).
3) Neutral: No effect on ancient gateways that only support TLS1.0
(still possible to connect).
4) Bad: May prevent connections to TLS-version-intolerant (aka
"broken") servers and middleboxes which support TLS1.0 but fail to
correctly negotiate down to it when presented with TLS1.1/1.2
ClientHellos.

The upside (1) is pretty obvious and clear, because lots of newer
gateways simply refuse TLS1.0 these days.

The downside (4) is harder to estimate… I don't think there are too many
TLS1.0-only version-intolerant middleboxes out there these days
because they would be breaking pretty much all the modern clients with
the misfortune to go through them. And I don't think I've ever seen a
report on the mailing list of a TLS1.0-only version-intolerant Cisco
ASA.

Basically, this change would vastly improve compatibility with newer gateways that refuse TLS1.0… and it would *only* reduce compatibility with really obsolete middleboxes that are intolerant to TLS1.1 and newer. I doubt that many such middleboxes still exist on the public Internet, because they would be breaking most modern clients.

So I'm in favor.