Order of protocols in MinProtocol

Matt Caswell matt at openssl.org
Wed Jul 8 16:40:38 UTC 2020

On 08/07/2020 17:21, Viktor Dukhovni wrote:
> On Wed, Jul 08, 2020 at 04:36:55PM +0100, Matt Caswell wrote:
>> On 08/07/2020 16:28, Viktor Dukhovni wrote:
>>>> How could I set the a System default "MinProtocol" for DTLS and TLS to 1.2?
>>> AFAIK, that's not presently possible.  You can specify application
>>> profiles, for applications that specify an application name when
>>> initializing OpenSSL.  Or use the OPENSSL_CONF environment variable to
>>> select an alternative configuration file for DTLS applications.
>> Arguably, that is a bug. You *should* be able to do that - perhaps based
>> on some sensible mapping between TLS protocol versions based on whether
>> we have a DTLS or TLS based SSL_METHOD.
> I agree that the situation with MinProtocol in openssl.cnf is
> unfortunate.  But instead of mappings, I would propose a different
> solution:
>     * Restrict MinProtocol/MaxProtocol to just TLS protocols,
>       i.e. SSL_CTX objects with a TLS-based method.
>     * Introduct new controls: DTLSMinProtocolDTLS, DTLSMaxProtocol,
>       that are similarly restricted to SSL_CTX objects with a DTLS-based
>       method.
>     * Since SSL_CTX_new() takes a required method argument, we are in
>       never in doubt as to which pair of controls to apply to a given
>       context.
> Thoughts?

Yes - that could work. Although it begs the question - would it change
the way SSL_CTX_set_min_proto_version() works? (I assume that currently
works just fine as is)

Another question that throws up is how much of that solution would we
backport to 1.1.1 since DTLS(Min|Max)Protocol would be a new feature.
Should we backport it anyway with the justification that it is a "fix"?
Or do we just backport the bit that means it doesn't get applied to DTLS?


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