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

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

   KB 22051        Last updated on 02/12/2017  




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Purpose

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

Resolution

This wiki requires using the CLI as some options are not available via the Admin Console. Please note: obtaining the best results via the SSL Labs test may not align with your business requirements or environment (e.g. you are still running old equipment like Windows XP, use older Java clients, etc.). Tune your environment according to your needs.

Zimbra Collaboration 8.7.x

ZCS 8.7.x defaults to using a 2048-bit DH parameter (bug 99558) which come from RFC3526 IKE 2048-bit PEM (group 14) for anything in ZCS that utilizes OpenSSL.

Custom or Stronger DH Parameters

In 8.7.x you can generate new/custom DH parameters using a new utility zmdhparam which calls openssl dhparam.

zmdhparam set -new 2048

or

zmdhparam set -new 3072

Tune the Cipher list

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

zmprov mcf 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:!MD5:!PSK:!RC4'

Restart the proxy:

zmproxyctl restart

Strict Transport Security (HSTS) & Session resumption (caching)

Run the next command to add the proper headers to the configuration:

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

Restart the zimbra services

zmcontrol restart

The result

The result in the SSL Labs test will be:

Ssllabs-zimbra-8.7-proxy.png

Zimbra Collaboration 8.6 & 8.5

Using Proxy

Fix the Logjam issue

ZCS 8.6 has a default 1024-bit DH parameter. Best practice is to use at least 2048-bit and that is the minimum for an A+ with Qualys SSL Labs.

As zimbra, create a new 2048 key (it make take several minutes):

openssl dhparam -out /opt/zimbra/conf/dhparam.pem 2048

Edit the following two files:

/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template
/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.template

Add a ssl_dhparam entry before the include so that you end up with something like the following:

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

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

zmprov mcf 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:!MD5:!PSK:!RC4'

Restart the proxy

zmproxyctl restart
Strict Transport Security (HSTS)

As zimbra, edit these files:

/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template
/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.template

and add the following in the server { ... } section:

add_header Strict-Transport-Security "max-age=31536000";
Session resumption (caching)

As zimbra, add the following content after the add_header that you added in the previous step:

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

As zimbra, restart the proxy:

zmproxyctl restart
The result

The result in the SSL Labs test will be:

Zimbra86-aplus-001.png

Without Proxy

Thank you to Alex that wrote these steps months ago.

Fix the Logjam issue

At this moment, Zimbra can't provide any solution to fix Logjam in Zimbra Collaboration 8.5 or above without use Proxy in front, please install the Proxy role. Also you can disable the next Cipher plus the next section to avoid logjam, but all the DHE Cipher will be disabled and can cause some troubles:

zmprov mcf +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA
zmprov mcf +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
zmprov mcf +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
Tune the Cipher list

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

zmprov mcf +zimbraSSLExcludeCipherSuites SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_DSS_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_RC4_40_MD5 \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_MD5 \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_SHA \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_RC4_128_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA256 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_GCM_SHA256 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_DES_CBC_SHA

Restart the mailbox service

zmmailboxdctl restart
Strict Transport Security (HSTS)

As zimbra edit the file /opt/zimbra/jetty/etc/jetty.xml.in and search by:

        <Call name="addRule">
        <Arg>
        <New class="org.eclipse.jetty.rewrite.handler.RewritePatternRule">
            <Set name="pattern">/Microsoft-Server-ActiveSync/*</Set>
            <Set name="replacement">/service/extension/zimbrasync</Set>
        </New>
        </Arg>
        </Call>

Add the following just before that entry:

        <Call name="addRule">
           <Arg>
              <New class="org.eclipse.jetty.rewrite.handler.HeaderPatternRule">
                 <Set name="pattern">*</Set>
                 <Set name="name">Strict-Transport-Security</Set>
                 <Set name="value">max-age=15768000; includeSubDomains</Set>
              </New>
           </Arg>
        </Call>

Restart the mailbox service

zmmailboxdctl restart
The result

The result if you followed all the previous steps in the SSL Labs test will be:

Ssllabs-zimbra-8.6.0-noproxy.png

If the Logjam steps were not performed, you will obtain a B.

Zimbra Collaboration 8.0.9

Generate a SSL Certificate with SHA256

By default, ZCS 8.0.x generated CSRs with SHA1 instead of the now preferred SHA256 hash. Edit /opt/zimbra/bin/zmcertmgr as root to change the default.

Change this line:

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

To the following (adding the -sha256 to the openssl command):

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

Use the Administration Console and CLI Certificate Tools to generate the new CSR (now with a SHA256 hash).

Disable SSLv3 to fix POODLE

Follow How to disable SSLv3 to disable SSLv3 in your ZCS 8.0.x environment.

Disable Client-Initiated SSL renegotiation

Edit the Jetty template and search by org.eclipse.jetty.server.ssl.SslSelectChannelConnector. Before the Set name="Port" line, add a allowRenegotiate False as follows:

            <New id="ssl" class="org.eclipse.jetty.server.ssl.SslSelectChannelConnector">
              <Set name="allowRenegotiate">FALSE</Set>
              <Set name="Port">%%zimbraMailSSLPort%%</Set>

Restart the mailbox service

zmmailboxdctl restart

Strict Transport Security (HSTS)

Add the proper header to the configuration:

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

Restart the zimbra services

zmcontrol restart

Using Proxy

The first step you need to check if you are using the proxy (nginx) or just mailboxd (jetty):

1. Verify if nginx is listening on port 443, in this case you can see that is jetty and not nignx:

lsof -i :443
COMMAND  PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
java    6637 zimbra   96u  IPv4 198165      0t0  TCP *:https (LISTEN)

2. Enable nginx for https, for POP3 and IMAP reverseproxy, as zimbra user:

./libexec/zmproxyconfig -e -w -o -a 8080:80:8443:443 -x https -H `zmhostname`
./libexec/zmproxyconfig -e -m -o -i 7143:143:7993:993 -p 7110:110:7995:995 -H `zmhostname`

3. Sanity check #1

zmprov gs `zmhostname` zimbraMailReferMode
# name zimbra8.zimbra.io
zimbraMailReferMode: reverse-proxied

4. Sanity check #2

lsof -i :443
COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
nginx   31418 zimbra   10u  IPv4 314934      0t0  TCP *:https (LISTEN)
nginx   31419 zimbra   10u  IPv4 314934      0t0  TCP *:https (LISTEN)
nginx   31420 zimbra   10u  IPv4 314934      0t0  TCP *:https (LISTEN)
nginx   31421 zimbra   10u  IPv4 314934      0t0  TCP *:https (LISTEN)

Now you have nginx properly enabled.

Fix the Logjam issue

Zimbra 8.0.x has a default 1024-bit DH parameter. Best practice is to use at least 2048-bit and that is the minimum for an A+ with Qualys SSL Labs.

As zimbra, create a new 2048 key (it make take several minutes):

openssl dhparam -out /opt/zimbra/conf/dhparam.pem 2048

Edit the following two files:

/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template
/opt/zimbra/conf/nginx/templates/nginx.conf.web.https.template

Add a ssl_dhparam entry before the include so that you end up with something like the following:

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

Disable weak Ciphers, thank you to ShanxT. Please note, by eliminating these ciphers, some older clients may stop working:

zmprov mcf +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_256_CBC_SHA \
 +zimbraSSLExcludeCipherSuites DHE-RSA-AES256-SHA  \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 \
 +zimbraSSLExcludeCipherSuites DHE-RSA-AES256-SHA256 \
 +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_256_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_DES_CBC_SHA  \
 +zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_DES_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_DHE_DSS_WITH_DES_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_RC4_40_MD5 \
 +zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_DES40_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_3DES_EDE_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_RSA_EXPORT_WITH_DES40_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_DES_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA \
 +zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 \
 +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA256 \
 +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 \
 +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA \
 +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_256_CBC_SHA256
Tune the Cipher list

Disable RC4 ciphers with the following command:

zmprov mcf +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_MD5 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_MD5 \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_SHA \
+zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_RC4_128_SHA

Restart the mailbox service

zmmailboxdctl restart
The result

The result using a valid SSL commercial certificate, and ZCS 8.0.9 Proxy, in the SSL Labs test will be an A+ if you followed all the steps.

Ssllabs-zimbra-8.0.9-proxyaplus.png

Without Proxy

Fix the Logjam issue

At this moment, Zimbra can't provide any solution to fix Logjam in Zimbra Collaboration 8.0.9, you need to upgrade to Zimbra Collaboration 8.6. But you can disable the following Ciphers, plus the next section to avoid logjam, but all the DHE Cipher will be disabled and can cause some troubles in old computers/clients:

zmprov mcf +zimbraSSLExcludeCipherSuites \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_256_CBC_SHA \
+zimbraSSLExcludeCipherSuites DHE-RSA-AES256-SHA  \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 \
+zimbraSSLExcludeCipherSuites DHE-RSA-AES256-SHA256 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_256_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_DES_CBC_SHA  \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_DSS_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_RC4_40_MD5 \
+zimbraSSLExcludeCipherSuites SSL_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_EXPORT_WITH_DES40_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_DES_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA \
+zimbraSSLExcludeCipherSuites TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_128_CBC_SHA256 \
+zimbraSSLExcludeCipherSuites TLS_RSA_WITH_AES_256_CBC_SHA256
Tune the Cipher list

As zimbra, run the following command to disable RC4 ciphers:

zmprov modifyConfig +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_MD5 \
  +zimbraSSLExcludeCipherSuites TLS_RSA_WITH_RC4_128_SHA \
  +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_MD5 \
  +zimbraSSLExcludeCipherSuites SSL_RSA_WITH_RC4_128_SHA \
  +zimbraSSLExcludeCipherSuites TLS_ECDHE_RSA_WITH_RC4_128_SHA

Restart the mailbox service

zmmailboxdctl restart
The result

The result, using a valid SSL commercial certificate and Zimbra Collaboration Single-Server 8.0.9 without Proxy, in the SSL Labs test will be an A if you followed all the steps. If you want to obtain the A+, please upgrade to Zimbra Collaboration 8.6 with Proxy:

Ssllabs-zimbra-8.0.9-noproxy.png

Additional Content

Verified Against: Zimbra Collaboration 8.7, 8.6, 8.5, 8.0 Date Created: 06/22/2015
Article ID: https://wiki.zimbra.com/index.php?title=How_to_obtain_an_A%2B_in_the_Qualys_SSL_Labs_Security_Test Date Modified: 02/12/2017



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Wiki/KB reviewed by Jorge Phil Gayle B. Last edit by Jorge de la Cruz Mingo
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