Step 1: Install certbot-auto tool
wget https://dl.eff.org/certbot-auto chmod +x certbot-auto
Move the script to directory in your PATH.
sudo mv certbot-auto /usr/local/bin
Confirm it working.
sudo certbot-auto --version
Step 2: Stop Zimbra Proxy Service
We need to stop the jetty or nginx service services before we can configure it to use Let’s Encrypt SSL certificate.
$ sudo su - zimbra -c "zmproxyctl stop" Stopping proxy...done. $ sudo su - zimbra -c "zmmailboxdctl stop" Stopping mailboxd...done.
Step 3: Obtain Let’s Encrypt SSL Certificate
Once the Zimbra proxy and mailboxd services are stopped we can proceed to request for Let’s Encrypt in auto mode. Make sure you pass all the hostnames used by your Mail Server.
# export EMAIL="[email protected]" # certbot-auto certonly --standalone -d mail.computingforgeeks.com --preferred-challenges http --agree-tos -n -m $EMAIL --keep-until-expiring
You can find all your files under /etc/letsencrypt/live/$domain
$ ls -lh /etc/letsencrypt/live/mail.computingforgeeks.com total 4.0K lrwxrwxrwx. 1 root root 50 Jul 5 23:42 cert.pem -> ../../archive/mail.computingforgeeks.com/cert1.pem lrwxrwxrwx. 1 root root 51 Jul 5 23:42 chain.pem -> ../../archive/mail.computingforgeeks.com/chain1.pem lrwxrwxrwx. 1 root root 55 Jul 5 23:42 fullchain.pem -> ../../archive/mail.computingforgeeks.com/fullchain1.pem lrwxrwxrwx. 1 root root 53 Jul 5 23:42 privkey.pem -> ../../archive/mail.computingforgeeks.com/privkey1.pem -rw-r--r--. 1 root root 692 Jul 5 23:42 README
ou’ll see a number of files.
cert.pem: The actual certificate file
chain.pem: The chain file
fullchain.pem: Concatenation of cert.pem + chain.pem
privkey.pem: Private key
Step 4: Secure Zimbra Mail Server with Let’s Encrypt SSL Certificate
Create directory that will hold Let’s Encrypt certificates for Zimbra Server.
sudo mkdir /opt/zimbra/ssl/letsencrypt
Copy Certificate files.
CERTPATH=/etc/letsencrypt/live/mail.computingforgeeks.com sudo cp $CERTPATH/* /opt/zimbra/ssl/letsencrypt/
Confirm files are copied successfully.
$ ls /opt/zimbra/ssl/letsencrypt/ cert.pem chain.pem fullchain.pem privkey.pem README
We now need to build a proper Intermediate CA plus Root CA. You must to use the IdenTrust root Certificate and merge it after the chain.pem.
https://letsencrypt.org/certs/trustid-x3-root.pem.txt
cat $CERTPATH/chain.pem | sudo tee /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem
View the file contents:
$ cat /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem -----BEGIN CERTIFICATE----- MIIEkjCCA3qgAwIBAgIQCgFBQgAAAVOFc2oLheynCDANBgkqhkiG9w0BAQsFADA/ MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT DkRTVCBSb290IENBIFgzMB4XDTE2MDMxNzE2NDA0NloXDTIxMDMxNzE2NDA0Nlow SjELMAkGA1UEBhMCVVMxFjAUBgNVBAoTDUxldCdzIEVuY3J5cHQxIzAhBgNVBAMT GkxldCdzIEVuY3J5cHQgQXV0aG9yaXR5IFgzMIIBIjANBgkqhkiG9w0BAQEFAAOC AQ8AMIIBCgKCAQEAnNMM8FrlLke3cl03g7NoYzDq1zUmGSXhvb418XCSL7e4S0EF q6meNQhY7LEqxGiHC6PjdeTm86dicbp5gWAf15Gan/PQeGdxyGkOlZHP/uaZ6WA8 SMx+yk13EiSdRxta67nsHjcAHJyse6cF6s5K671B5TaYucv9bTyWaN8jKkKQDIZ0 Z8h/pZq4UmEUEz9l6YKHy9v6Dlb2honzhT+Xhq+w3Brvaw2VFn3EK6BlspkENnWA a6xK8xuQSXgvopZPKiAlKQTGdMDQMc2PMTiVFrqoM7hD8bEfwzB/onkxEz0tNvjj /PIzark5McWvxI0NHWQWM6r6hCm21AvA2H3DkwIDAQABo4IBfTCCAXkwEgYDVR0T AQH/BAgwBgEB/wIBADAOBgNVHQ8BAf8EBAMCAYYwfwYIKwYBBQUHAQEEczBxMDIG CCsGAQUFBzABhiZodHRwOi8vaXNyZy50cnVzdGlkLm9jc3AuaWRlbnRydXN0LmNv bTA7BggrBgEFBQcwAoYvaHR0cDovL2FwcHMuaWRlbnRydXN0LmNvbS9yb290cy9k c3Ryb290Y2F4My5wN2MwHwYDVR0jBBgwFoAUxKexpHsscfrb4UuQdf/EFWCFiRAw VAYDVR0gBE0wSzAIBgZngQwBAgEwPwYLKwYBBAGC3xMBAQEwMDAuBggrBgEFBQcC ARYiaHR0cDovL2Nwcy5yb290LXgxLmxldHNlbmNyeXB0Lm9yZzA8BgNVHR8ENTAz MDGgL6AthitodHRwOi8vY3JsLmlkZW50cnVzdC5jb20vRFNUUk9PVENBWDNDUkwu Y3JsMB0GA1UdDgQWBBSoSmpjBH3duubRObemRWXv86jsoTANBgkqhkiG9w0BAQsF AAOCAQEA3TPXEfNjWDjdGBX7CVW+dla5cEilaUcne8IkCJLxWh9KEik3JHRRHGJo uM2VcGfl96S8TihRzZvoroed6ti6WqEBmtzw3Wodatg+VyOeph4EYpr/1wXKtx8/ wApIvJSwtmVi4MFU5aMqrSDE6ea73Mj2tcMyo5jMd6jmeWUHK8so/joWUoHOUgwu X4Po1QYz+3dszkDqMp4fklxBwXRsW10KXzPMTZ+sOPAveyxindmjkW8lGy+QsRlG PfZ+G6Z6h7mjem0Y+iWlkYcV4PIWL1iwBi8saCbGS5jN2p8M+X+Q7UNKEkROb3N6 KOqkqm57TH2H3eDJAkSnh6/DNFu0Qg== -----END CERTIFICATE-----
Combine the chain.pem with the root CA – Order is chain before the root CA.
sudo tee -a /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem<<EOF -----BEGIN CERTIFICATE----- MIIDSjCCAjKgAwIBAgIQRK+wgNajJ7qJMDmGLvhAazANBgkqhkiG9w0BAQUFADA/ MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT DkRTVCBSb290IENBIFgzMB4XDTAwMDkzMDIxMTIxOVoXDTIxMDkzMDE0MDExNVow PzEkMCIGA1UEChMbRGlnaXRhbCBTaWduYXR1cmUgVHJ1c3QgQ28uMRcwFQYDVQQD Ew5EU1QgUm9vdCBDQSBYMzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEB AN+v6ZdQCINXtMxiZfaQguzH0yxrMMpb7NnDfcdAwRgUi+DoM3ZJKuM/IUmTrE4O rz5Iy2Xu/NMhD2XSKtkyj4zl93ewEnu1lcCJo6m67XMuegwGMoOifooUMM0RoOEq OLl5CjH9UL2AZd+3UWODyOKIYepLYYHsUmu5ouJLGiifSKOeDNoJjj4XLh7dIN9b xiqKqy69cK3FCxolkHRyxXtqqzTWMIn/5WgTe1QLyNau7Fqckh49ZLOMxt+/yUFw 7BZy1SbsOFU5Q9D8/RhcQPGX69Wam40dutolucbY38EVAjqr2m7xPi71XAicPNaD aeQQmxkqtilX4+U9m5/wAl0CAwEAAaNCMEAwDwYDVR0TAQH/BAUwAwEB/zAOBgNV HQ8BAf8EBAMCAQYwHQYDVR0OBBYEFMSnsaR7LHH62+FLkHX/xBVghYkQMA0GCSqG SIb3DQEBBQUAA4IBAQCjGiybFwBcqR7uKGY3Or+Dxz9LwwmglSBd49lZRNI+DT69 ikugdB/OEIKcdBodfpga3csTS7MgROSR6cz8faXbauX+5v3gTt23ADq1cEmv8uXr AvHRAosZy5Q6XkjEGB5YGV8eAlrwDPGxrancWYaLbumR9YbK+rlmM6pZW87ipxZz R8srzJmwN0jP41ZL9c8PDHIyh8bwRLtTcm1D9SZImlJnt1ir/md2cXjbDaJWFBM5 JDGFoqgCWjBH4d1QB7wCCZAA62RjYJsWvIjJEubSfZGL+T0yjWW06XyxV3bqxbYo Ob8VZRzI9neWagqNdwvYkQsEjgfbKbYK7p2CNTUQ -----END CERTIFICATE----- EOF
Confirm the resulting file has the two certificates.
$ cat /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem
—–BEGIN CERTIFICATE—–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—–END CERTIFICATE—–
—–BEGIN CERTIFICATE—–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—–END CERTIFICATE—–
Set correct permissions for the directory:
sudo chown -R zimbra:zimbra /opt/zimbra/ssl/letsencrypt/
Confirm the owner is zimbra user.
$ ls -lha /opt/zimbra/ssl/letsencrypt/ total 32K drwxr-xr-x. 2 zimbra zimbra 4.0K Jul 6 00:18 . drwxr-xr-x. 8 zimbra zimbra 4.0K Jul 6 00:13 .. -rw-r--r--. 1 zimbra zimbra 1.9K Jul 6 00:14 cert.pem -rw-r--r--. 1 zimbra zimbra 1.7K Jul 6 00:14 chain.pem -rw-r--r--. 1 zimbra zimbra 3.6K Jul 6 00:14 fullchain.pem -rw-------. 1 zimbra zimbra 1.7K Jul 6 00:14 privkey.pem -rw-r--r--. 1 zimbra zimbra 692 Jul 6 00:14 README -rw-r--r--. 1 zimbra zimbra 2.8K Jul 6 00:23 zimbra_chain.pem
Verify your commercial certificate.
sudo su - zimbra -c '/opt/zimbra/bin/zmcertmgr verifycrt comm /opt/zimbra/ssl/letsencrypt/privkey.pem /opt/zimbra/ssl/letsencrypt/cert.pem /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem'
Output should not give any errors or mismatch.
** Verifying '/opt/zimbra/ssl/letsencrypt/cert.pem' against '/opt/zimbra/ssl/letsencrypt/privkey.pem' Certificate '/opt/zimbra/ssl/letsencrypt/cert.pem' and private key '/opt/zimbra/ssl/letsencrypt/privkey.pem' match. ** Verifying '/opt/zimbra/ssl/letsencrypt/cert.pem' against '/opt/zimbra/ssl/letsencrypt/zimbra_chain.pem' Valid certificate chain: /opt/zimbra/ssl/letsencrypt/cert.pem: OK
Backup current certificate files.
sudo cp -a /opt/zimbra/ssl/zimbra /opt/zimbra/ssl/zimbra.$(date "+%Y%.m%.d-%H.%M")
Copy the private key under Zimbra SSL path.
sudo cp /opt/zimbra/ssl/letsencrypt/privkey.pem /opt/zimbra/ssl/zimbra/commercial/commercial.key sudo chown zimbra:zimbra /opt/zimbra/ssl/zimbra/commercial/commercial.key
Finally deploy the new Let’s Encrypt SSL certificate.
sudo su - zimbra -c '/opt/zimbra/bin/zmcertmgr deploycrt comm /opt/zimbra/ssl/letsencrypt/cert.pem /opt/zimbra/ssl/letsencrypt/zimbra_chain.pem'
My certificate deployment output is as shown below.
** Verifying '/opt/zimbra/ssl/letsencrypt/cert.pem' against '/opt/zimbra/ssl/zimbra/commercial/commercial.key' Certificate '/opt/zimbra/ssl/letsencrypt/cert.pem' and private key '/opt/zimbra/ssl/zimbra/commercial/commercial.key' match. ** Verifying '/opt/zimbra/ssl/letsencrypt/cert.pem' against '/opt/zimbra/ssl/letsencrypt/zimbra_chain.pem' Valid certificate chain: /opt/zimbra/ssl/letsencrypt/cert.pem: OK ** Copying '/opt/zimbra/ssl/letsencrypt/cert.pem' to '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' ** Copying '/opt/zimbra/ssl/letsencrypt/zimbra_chain.pem' to '/opt/zimbra/ssl/zimbra/commercial/commercial_ca.crt' ** Appending ca chain '/opt/zimbra/ssl/letsencrypt/zimbra_chain.pem' to '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' ** Importing cert '/opt/zimbra/ssl/zimbra/commercial/commercial_ca.crt' as 'zcs-user-commercial_ca' into cacerts '/opt/zimbra/common/lib/jvm/java/lib/security/cacerts' ** NOTE: restart mailboxd to use the imported certificate. ** Saving config key 'zimbraSSLCertificate' via zmprov modifyServer mail.computingforgeeks.com...ok ** Saving config key 'zimbraSSLPrivateKey' via zmprov modifyServer mail.computingforgeeks.com...ok ** Installing imapd certificate '/opt/zimbra/conf/imapd.crt' and key '/opt/zimbra/conf/imapd.key' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' to '/opt/zimbra/conf/imapd.crt' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.key' to '/opt/zimbra/conf/imapd.key' ** Creating file '/opt/zimbra/ssl/zimbra/jetty.pkcs12' ** Creating keystore '/opt/zimbra/conf/imapd.keystore' ** Installing ldap certificate '/opt/zimbra/conf/slapd.crt' and key '/opt/zimbra/conf/slapd.key' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' to '/opt/zimbra/conf/slapd.crt' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.key' to '/opt/zimbra/conf/slapd.key' ** Creating file '/opt/zimbra/ssl/zimbra/jetty.pkcs12' ** Creating keystore '/opt/zimbra/mailboxd/etc/keystore' ** Installing mta certificate '/opt/zimbra/conf/smtpd.crt' and key '/opt/zimbra/conf/smtpd.key' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' to '/opt/zimbra/conf/smtpd.crt' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.key' to '/opt/zimbra/conf/smtpd.key' ** Installing proxy certificate '/opt/zimbra/conf/nginx.crt' and key '/opt/zimbra/conf/nginx.key' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' to '/opt/zimbra/conf/nginx.crt' ** Copying '/opt/zimbra/ssl/zimbra/commercial/commercial.key' to '/opt/zimbra/conf/nginx.key' ** NOTE: restart services to use the new certificates. ** Cleaning up 3 files from '/opt/zimbra/conf/ca' ** Removing /opt/zimbra/conf/ca/ca.key ** Removing /opt/zimbra/conf/ca/6703d76b.0 ** Removing /opt/zimbra/conf/ca/ca.pem ** Copying CA to /opt/zimbra/conf/ca ** Copying '/opt/zimbra/ssl/zimbra/ca/ca.key' to '/opt/zimbra/conf/ca/ca.key' ** Copying '/opt/zimbra/ssl/zimbra/ca/ca.pem' to '/opt/zimbra/conf/ca/ca.pem' ** Creating CA hash symlink '6703d76b.0' -> 'ca.pem' ** Creating /opt/zimbra/conf/ca/commercial_ca_1.crt ** Creating CA hash symlink '4f06f81d.0' -> 'commercial_ca_1.crt' ** Creating /opt/zimbra/conf/ca/commercial_ca_2.crt ** Creating CA hash symlink '2e5ac55d.0' -> 'commercial_ca_2.crt'
Restart the nginx or jetty services stopped earlier.
$ sudo su - zimbra -c "zmcontrol restart" Host mail.computingforgeeks.com Stopping zmconfigd...Done. Stopping zimlet webapp...Done. Stopping zimbraAdmin webapp...Done. Stopping zimbra webapp...Done. Stopping service webapp...Done. Stopping stats...Done. Stopping mta...Done. Stopping spell...Done. Stopping snmp...Done. Stopping cbpolicyd...Done. Stopping archiving...Done. Stopping opendkim...Done. Stopping amavis...Done. Stopping antivirus...Done. Stopping antispam...Done. Stopping proxy...Done. Stopping memcached...Done. Stopping mailbox...Done. Stopping logger...Done. Stopping dnscache...Done. Stopping ldap...Done. Host mail.computingforgeeks.com Starting ldap...Done. Starting zmconfigd...Done. Starting dnscache...Done. Starting logger...Done. Starting mailbox...Done. Starting memcached...Done. Starting proxy...Done. Starting amavis...Done. Starting antispam...Done. Starting antivirus...Done. Starting opendkim...Done. Starting snmp...Done. Starting spell...Done. Starting mta...Done. Starting stats...Done. Starting service webapp...Done. Starting zimbra webapp...Done. Starting zimbraAdmin webapp...Done. Starting zimlet webapp...Done.
Step 5: Test Let’s Encrypt SSL Certificate on Zimbra Mail Server
Open the Admin or webmail console of Zimbra collaboration server and check certificate details.
You now have Let’s Encrypt SSL certificate working on your Zimbra Server. For renewal follow below steps.
Stop Zimbra Services
Renew Let’s Encrypt SSL certificate
Then follow the rest of the steps from Step 4
Src:https://computingforgeeks.com/secure-zimbra-mail-server-with-letsencrypt-ssl-certificate/
