Revision as of 19:05, 14 October 2015 by Plobbes (talk | contribs) (added note on bug 101192)

Security Settings for Zimbra Collaboration 8.7 series

   KB 21837        Last updated on 2015-10-14  

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OpenSSL SSLv3 disabled

  • bug 99886 Along with upgrading to OpenSSL 1.0.1p, ZCS now builds OpenSSL with the "no-ssl3" configure option to completely remove/disable support for SSLv3 in OpenSSL.


DH parameters

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:

See also:


Default zimbraReverseProxySSLCiphers setting in 8.7.0 has been changed to exclude RC4 (ref: bug 96852):


HTTP Strict Transport Security (HSTS)

With bug 98938 it is now possible to set zimbraReverseProxyResponseHeaders and enable HSTS. For example:

 zmprov mcf +zimbraReverseProxyResponseHeaders 'Strict-Transport-Security: "max-age=31536000; includeSubdomains"'

See also:

SSL Session Cache (resumption)

Bug 96544 added, and enabled by default the following:

  • SSL session cache size (zimbraReverseProxySSLSessionCacheSize) of 10 MB
  • SSL session timeout (zimbraReverseProxySSLSessionTimeout) of 10 minutes

zmlookup via HTTPS

  • bug 99279 zmlookup now uses HTTPS instead of HTTP (internal service on port 7072 by default, but now configurable via zimbraExtensionPort bug 99392)

Mailboxd (Jetty)


bug 101192 Disable links within spam (by not looking for 'objects' for Zimlets to handle inside of messages in the Junk/Spam folder)


Default zimbraSSLExcludeCipherSuites setting in 8.7.0 has been changed to exclude RC4 (ref: bug 96921):

zimbraSSLExcludeCipherSuites: .*_RC4_.*

HTTP Strict Transport Security (HSTS)

The configuration key, 'zimbraResponseHeader', can be used to set the HSTS header. For example (ref: bug 84796):

zmprov mcf +zimbraResponseHeader "Strict-Transport-Security: max-age=31536000"

Note: in 8.5 and 8.6 this did not work due to a regression (ref: bug 98495)

saslauthd now on port 7073

As part of bug 97779 the saslauthd service now authenticates against a service listening on port 7073 instead of 7071. This port should be protected (firewall) and not exposed to the internet.

Multi-Domain Installation Enhancements

Enhancements to support limiting the visibility across separate domains in a ZCS installation have been implemented:

  • bug 99825 ability to restrict visibility of public shares
  • bug 100524 ability to restrict sendAs / sendOnBehalfOf
Verified Against: Zimbra Collaboration 8.7 Date Created: 04/22/2015
Article ID: Date Modified: 2015-10-14

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