On Tue, May 20, 2014 at 02:35:04PM +0100, Colin Fowler wrote:
> BTW, this whole thing came about from me testing using
> https://starttls.info/ which scored what I thought was a well secured server
> quite badly. I see now that the testing site is itself the problem, not my
> original config.
Yep, the site is clueless. My DNSSEC + DANE validated domain scores a "D":
mx1.dukhovni.org: Grade: D (43.5%)
Certificate:
* The certificate is not valid for the server's hostname.
* There is a self-signed certificate in the trust chain. It may be a
configuration problem.
* There are one or more fatal problems which causes the
certificate not to be trusted.
There are validity issues for the certificate. Certificates
are seldom verified for SMTP servers, so this doesn't mean that
STARTTLS won't be used.
[ Actually, I have one of the few SMTP domains whose certificate can be
used for MiTM-resistant authentication. ]
Generally speaking it's a bad practice not to have a valid
certificate, and an even worse practice not to verify them.
Any attempted encrypted communication is left all but wide open
to Man-in-the-Middle attacks.
[ Except that not authenticating certificates is exactly what one
needs to do with SMTP. ]
Protocol:
* Supports SSLV3.
* Supports TLSV1.
* Supports TLSV1.1.
Key exchange:
* Anonymous Diffie-Hellman is accepted. This is suspectible to
Man-in-the-Middle attacks.
[ But DANE clients won't offer this. And server support of aNULL ciphers
is always harmless, and makes it easier to determine which clients are
not authenticating the server. Pretending client offers of aNULL ciphers
did not happen does not improve security. ]
* Key size is 1024 bits; that's somewhat insecure.
[ Fine, will be changed when the server is upgraded... ]
Cipher:
* Weakest accepted cipher: 0.
* Strongest accepted cipher: 256.
[ Scoring aNULL as "0" is simply wrong. ]
This site is useless.
--
Viktor.
