Tighten TLS - usage of specific ssl_ec-curve

[Aki Tuomi]

On 14.04.2016 20:55, Martin wrote:
> Hi folks, at first: thanks very much for the great piece of software!
>
> I have a proposal to tighten the TLS security: enable the usage of a specific ec-curve in the 10-ssl.conf, e.g.
>
> 	ssl_ec-curve = secp384r1
>
>
> Reason: I use a 384 bit EC server key, but dovecot uses "only" a prime256v1 curve.
>
>
> Keygen was:
> f=dovecot; openssl ecparam -name secp384r1 -genkey -out $f.key
> openssl req -new -x509 -key $f.key -out ${f}.crt -days 2000 -sha512
>
>
> Server check gives:
> prio  ciphersuite                    protocols  pfs                 curves
> 1     ECDHE-ECDSA-AES128-GCM-SHA256  TLSv1.2    ECDH,P-256,256bits  prime256v1
> 2     ECDHE-ECDSA-AES128-SHA256      TLSv1.2    ECDH,P-256,256bits  prime256v1
> 3     ECDHE-ECDSA-AES128-SHA         TLSv1.2    ECDH,P-256,256bits  prime256v1
> 4     ECDHE-ECDSA-AES256-GCM-SHA384  TLSv1.2    ECDH,P-256,256bits  prime256v1
> 5     ECDHE-ECDSA-AES256-SHA384      TLSv1.2    ECDH,P-256,256bits  prime256v1
> 6     ECDHE-ECDSA-AES256-SHA         TLSv1.2    ECDH,P-256,256bits  prime256v1
>
> Certificate: UNTRUSTED, 384 bit, ecdsa-with-SHA512 signature
>
>

Thank you for your suggestion, we will take it under consideration as we 
are improving security settings for next major release.

Aki Tuomi
Dovecot oy