Security/Collab/87

Article Information |
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This article applies to the following ZCS versions. |
Security Settings for Zimbra Collaboration 8.7 series
Proxy
dhparam
Added support for the ssl_dhparam in proxy/nginx. The default DH parameter size is still 1024 bits. With the changes from bug 98852, it is now possible to use a custom (read stronger) key size. However, be aware that some clients may have issues with a size larger than 1024 bits (Java 7 for example, ref: http://httpd.apache.org/docs/trunk/ssl/ssl_faq.html#javadh).
See also:
- http://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_dhparam
- https://www.openssl.org/docs/apps/dhparam.html
- http://www.nginxtips.com/hardening-nginx-ssl-tsl-configuration/
Ciphers
Default zimbraReverseProxySSLCiphers setting in 8.7.0 has been changed to exclude RC4 (ref: bug 96852):
zimbraReverseProxySSLCiphers: 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:AES256:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!3DES:!MD5:!PSK:!RC4
Mailboxd (Jetty)
Ciphers
Default zimbraSSLExcludeCipherSuites setting in 8.7.0 has been changed to exclude RC4 (ref: bug 96921):
zimbraSSLExcludeCipherSuites: .*_RC4_.*