SSL Configuration

[kylebryan]

Hello everyone.  I'd like to poll the group and see what SSL configurations you recommend using in ESA.  Currently i'm running mine at "MEDIUM:HIGH:-SSLv2:-SSLv3:-aNULL:-EXPORT:@STRENGTH" on inbound SMTP but we are having quite a few complaints with senders unable to send us mail.  Thanks in advance for your help.  

[Ken Stieers]

I'm using that string too...

My guess is that they're using low bit encryption or SSLV3.

Grep your logs for 'TLS fail.' , you'll get a list of message ICIDs that failed, and then grep for that ICID and that will show you all of the logs for that message.



You can try educating your business partners...

[Paul Thomas Cyblue]

You have turned off TLSv1.0 - first turn this back on.
You need to perform an analysis of traffic before turning this off.  Working with the critical business partners still using this.

A good check against your system is using checktls.com using SSL Probe option

I believe the below cipher string is from a 'recommendation' - but who is recommending I say.  You need to balance support v security, that is why the big providers provide so much backwards compatibility to low encryption levels, as they don't want to turn business away. 

EDH+TLSv1.2:EDH+HIGH:HIGH:!MEDIUM:!ECDH:!ECDSA:!LOW:!EXP:!aNULL:!DSS:!IDEA:!PSK:!3DES:!SRP:@STRENGTH:!EXPORT:-aNULL:-EXPORT

Analyse the traffic, when low enough, on v11+ then turn off TLSv1.0 + tune weaker ciphers from the above cipher string.  A good time to reassess tuning is when upgrading to the next ESA version.