How to obtain an A+ in the Qualys SSL Labs Security Test

Revision as of 16:05, 23 June 2015 by Jorge de la Cruz (talk | contribs) (Fix the Logjam issue)

Admin Article

Article Information

This article applies to the following ZCS versions.

ZCS 8.7 Article ZCS 8.7ZCS 8.6 Article ZCS 8.6ZCS 8.0 Article ZCS 8.0

How to obtain an A+ in the Qualys SSL Labs security test


List the steps, per release, to obtain an A+ in the Qualys SSL Labs Security Test.


Until have an option in the Admin Console, all of this Wiki is using the CLI.

Zimbra Collaboration 8.7

Work in progress

Zimbra Collaboration 8.6 & 8.5

Fix the Logjam issue

Zimbra 8.6 has per default 1024-bit DH ciphers, as they are secure, the best practice is use at least 2048, and the Qualys SSL Labs test will give us the A+ using the correct ones.

Like root, create a new 2048 key, will take some minutes:

cd /opt/zimbra/conf
openssl dhparam -out dhparams.pem 2048
chown zimbra:zimbra dhparams.pem

Edit the next 2 files:


You need to add the next content, ssl_dhparam /opt/zimbra/conf/dhparams.pem;, before the include, will looks like:

ssl_verify_client       ${ssl.clientcertmode.default};
ssl_verify_depth        ${ssl.clientcertdepth.default};
ssl_dhparam /opt/zimbra/conf/dhparams.pem;
include                 ${core.includes}/${core.cprefix}.web.https.mode-${web.mailmode};

Tune the Cipher list

Like zimbra user, run the next command to tune the Ciphers and disable the RC4, etc:


Restart the proxy

zmproxyctl restart

Strict Transport Security (HSTS)

Like roor user, edit the next file /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template and add in the section server { the next content :

add_header Strict-Transport-Security "max-age=31536000; includeSubdomains;";

Session resumption (caching)

Like roor user, add the next content after the add_header that you added in the previous step:

ssl_session_cache shared:SSL:50m;
ssl_session_timeout 5m;

Then restart the proxy like zimbra user:

zmproxyctl restart

The result

The result in the SSL Labs test will be:


Zimbra Collaboration 8.0.9

Generate a SSL Certiricate with SHA256

Per default, Zimbra Collaboration 8.0.x didn't generate a valid CSR with a 256bit hash. To force it, edit the next file as root:


And change this line:

${openssl} req -new -${DIGEST} -nodes -out ${current_csr} -keyout ${current_key} \

For the next one, adding the -sha256 to the OpenSSL command:

${openssl} req -sha256 -new -${DIGEST} -nodes -out ${current_csr} -keyout ${current_key} \

Then you can generate the new CSR, this time with a SHA256, follow the next Wiki.

Fix the Logjam issue

Zimbra Collaboration 8.0.9 can't fix the issue because the DH Cipher keysize is hardcoded in Java 1.7. You need to upgrade to Zimbra Collaboration 8.6.

Tune the Cipher list

You will want to disable the RC4, run the nex command:

zmprov modifyConfig +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_MD5
zmprov modifyConfig +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_SHA
zmprov modifyConfig +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_MD5
zmprov modifyConfig +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_SHA
zmprov modifyConfig +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_RC4_128_SHA
zmcontrol restart

Disable SSLv3 to fix the Poodle

Follow the next Wiki to disable SSLv3 in your Zimbra Collaboration 8.0.x environment.

The result

The result using a valid SSL commercial certificate, and Zimbra Collaboration 8.0.9 Proxy, in the SSL Labs test will be an F, so you need to think to use a Proxy based in 8.6 if you want to keep your environment secure:

Scenario with Single-Server and a Proxy in Zimbra Collaboration 8.6 on front:


Scenario with Multi-Server and a Proxy in Zimbra Collaboration 8.6 on front:


The result of the test without Proxy in 8.6: Ssllabs-zimbra-8.0.9-002.png

Additional Content

Verified Against: Zimbra Collaboration 8.7, 8.6, 8.5, 8.0 Date Created: 06/22/2015
Article ID: Date Modified: 2015-06-23

Try Zimbra

Try Zimbra Collaboration with a 60-day free trial.
Get it now »

Want to get involved?

You can contribute in the Community, Wiki, Code, or development of Zimlets.
Find out more. »

Looking for a Video?

Visit our YouTube channel to get the latest webinars, technology news, product overviews, and so much more.
Go to the YouTube channel »

Wiki/KB reviewed by SME1 SME2 Copyeditor Last edit by Jorge de la Cruz
Jump to: navigation, search