Revision as of 20:21, 9 February 2016 by Plobbes (talk | contribs) (3rd Party Packages of Interest)

Security Settings for Zimbra Collaboration 8.7 series

   KB 21837        Last updated on 2016-02-9  

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SSLv3 Disabled

OpenJDK SSLv3 Disabled

OpenSSL SSLv3 Disabled

Note: OpenSSL is not compiled with the no-ssl3 option due to potential complications during upgrades (ref: OpenSSL configure options).

DH parameters

OpenSSL DH Parameters

The main components utilizing OpenSSL are LDAP, MTA, and Proxy services. In ZCS 8.7, the default DH Parameter uses 2048-bits (ref: bug 99558, bug 99564 - MTA/smtpd_tls_dh1024_param_file, Proxy/ssl_dhparam). The new global configuration parameter to store the PEM formatted DH parameter data is zimbraSSLDHParam. A new utility zmdhparam can be used to create new custom DH parameters.

  • Ability to set DH param file for MTA / Postfix
  • Default to 2048 bit DH Parameters

However, be aware that some clients may have issues with a size larger than 1024 bits (Java 7 for example, ref:

See also:


See also #OpenSSL DH Parameters above.


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)

HTTPS Server Name Indication (SNI) Support

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 (before Patch5) 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

3rd Party Packages of Interest

See for latest

Verified Against: Zimbra Collaboration 8.7 Date Created: 04/22/2015
Article ID: Date Modified: 2016-02-09

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