Real-world use case
You need to secure webmail access to your Zimbra server: here's how to easily install a Gandi commercial certificate.
Installing a Gandi certificate on Zimbra
An SSL certificate validated by a certificate authority is essential, especially to guarantee a sufficient level of trust to your users. For a Zimbra server accessible over https on the front end, we'll use a commercial certificate provided by Gandi. Setup is very quick and very simple.
Info: The Zimbra server already has a self-signed certificate, so we'll replace it with Gandi's.
Creating the commercial certificate on Zimbra
To start, we'll need the following certificates:
- Gandi's commercial certificate: certificate-205432.crt.
- Gandi's SHA2 intermediate certificate: GandiStandardSSLCA2.pem.
- The authority's root certificate: addtrustexternalcaroot.crt.
Once we have all the certificates, let's go to:
bash
cd /opt/zimbra/ssl/zimbra/commercial/
Let's create our first commercial.crt certificate for Zimbra (paste in the content of your Gandi certificate: certificate-205432.crt).
bash
nano commercial.crt
Then we'll now create a second file:
bash
touch commercial_ca.crt
Here, in order: the GandiStandardSSLCA2.pem certificate, then the addtrustexternalcaroot.crt certificate, like this:
bash
-----BEGIN CERTIFICATE-----
MIIF6TCCA9GgAwIBAgIQBeTcO5Q4qzuFl8umoZhQ4zANBgkqhkiG9w0BAQwFADCB
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-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIFdzCCBF+gAwIBAgIQE+oocFv07O0MNmMJgGFDNjANBgkqhkiG9w0BAQwFADBv
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0fKtirOMxyHNwu8=
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIENjCCAx6gAwIBAgIBATANBgkqhkiG9w0BAQUFADBvMQswCQYDVQQGEwJTRTEU
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-----END CERTIFICATE-----
We've now done the hardest part, our two certificates are in place:
bash
commercial_ca.crt commercial.crt
The next step validates our certificate:
bash
/opt/zimbra/openssl/bin/openssl verify -CAfile commercial_ca.crt commercial.crt
The result should look like this:
bash
commercial.crt
commercial.crt: OK
Then deployment is done like this:
bash
/opt/zimbra/bin/zmcertmgr deploycrt comm commercial.crt commercial_ca.crt
The result then appears:
yaml
Valid Certificate: commercial.crt: OK
** Copying commercial.crt to /opt/zimbra/ssl/zimbra/commercial/commercial.crt
cp: 'commercial.crt' and '/opt/zimbra/ssl/zimbra/commercial/commercial.crt' are the same file
** Appending ca chain commercial_ca.crt to /opt/zimbra/ssl/zimbra/commercial/commercial.crt
cp: 'commercial_ca.crt' and '/opt/zimbra/ssl/zimbra/commercial/commercial_ca.crt' are the same file
** Importing certificate /opt/zimbra/ssl/zimbra/commercial/commercial_ca.crt to CACERTS as zcs-user-commercial_ca...done.
** NOTE: mailboxd must be restarted in order to use the imported certificate.
** Saving server config key zimbraSSLCertificate...done.
** Saving server config key zimbraSSLPrivateKey...done.
** Installing mta certificate and key...done.
** Installing slapd certificate and key...done.
** Installing proxy certificate and key...done.
** Creating pkcs12 file /opt/zimbra/ssl/zimbra/jetty.pkcs12...done.
** Creating keystore file /opt/zimbra/mailboxd/etc/keystore...done.
** Installing CA to /opt/zimbra/conf/ca...done.
Once in place, let's restart our server:
bash
zmcontrol restart
The "openssl" command can also be used to check our certificate's validity by emulating a client:
bash
openssl s_client -showcerts -connect your_zimbra_server:465
Your certificate is working.
