How to configure Dovecot to disable NIST's curves and still rertain EECDH?

[Tributh]

Am 19.12.18 um 07:10 schrieb Kurt Fitzner:
> My opinion is that security by RFC is not security, it's mommy
> medicine.  Standards have had a terrible time keeping up with security
> realities.
> 
> NITS's curves leak side channel information all over the place.  I don't
> have details on what implementations are set to calculate the NIST
> curves in constant time, and that's not an easy feat to do anyway so I
> don't want to depend on implementations that say they are actually doing
> it the right way.  Frankly I can't be bothered to keep up with that. 
> There are better curves *today*, so yes I intend to use them if I can
> find a way.  Otherwise, I'll just keep EECDH disabled.
> 
> I have EDH now, and I've not yet run into a client that doesn't support
> it.  I want EECDH, but I won't use it without safe curves.  I'm
> confident that EECDH with safe curves and a second choice of EDH will
> support any clients that are worth using.  OpenSSL supports X25519, and
> that is half the battle.
> 
> Is there a way to change the curve selection in Dovecot?

Yes. Try:

ssl_curve_list = X448:X25519

Tested and works with openssl 1.1.1a