Deploying Diffie-Hellman for TLS

Jerry jerry at seibercom.net
Mon Mar 20 13:49:55 EET 2017


I have been reading up on TLS and Dovecot and came across this URL:
https://www.weakdh.org/sysadmin.html which recommended these settings
for Dovecot. I would like to know if they are correct? Some much
documentation on the web is pure garbage.

Dovecot

These changes should be made in /etc/dovecot.conf

Cipher Suites

ssl_cipher_list=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:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA

ssl_prefer_server_ciphers = yes (Dovecot 2.2.6 or greater)

DH parameters

#regenerates every week
ssl_dh_parameters_length = 2048

Contrary to what the site recommends, I would have thought that changes
should be made in the "10-ssl.conf" file. I am running "Dovecot 2.2.28"
on a FreeBSD-11 machine with OpenSSL 1.0.2k, if that makes any
difference.

Thanks

-- 
Jerry


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