hMailserver is an open source Window e-mail server. For incoming e-mail it supports
STARTTLS with the help of OpenSSL 1.1.1.
It allows configuring the cipher suites, the default is:
ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384: ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256: kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA: ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384: ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA: DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA: AES128-GCM-SHA256:AES256-GCM-SHA384:ECDHE-RSA-RC4-SHA:ECDHE-ECDSA-RC4-SHA: AES128:AES256:RC4-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!3DES:!MD5:!PSK;
I wanted to disable
AES256-GCM-SHA384 but after removing it, the cipher suite was still offered for
STARTTLS (according to test site https://internet.nl)
In the end I had to remove
HIGH to stop
AES256-GCM-SHA384 from appearing on
How should I read this OpenSSL configuration setting? On the last line
AES256 are mentioned standalone. Doesn't this mean that any cipher with
AES256 will be allowed making the long list before that quite redundant?
The same goes for the
HIGH, doesn't that make mentioning a lot of the other cipher suites redundant?
In response to questions why I want to remove
ES256-GCM-SHA384: for a Dutch government contract they expect our e-mail server to score excellent at the https://internet.nl test site. On
AES256-GCM-SHA384 it tells:
At least one of your mail servers supports one or more ciphers that have a phase out status, because they are known to be fragile and are at risk of becoming insufficiently secure.
That is why I am trying to disable it.