Revision as of 09:36, 21 December 2022

ZCS Certificates Tools

KB 2661	Last updated on 2022-12-21	Last updated by Barry de Graaff	0.00 (0 votes)	Verified in: ZCS 10.0 ZCS 9.0 ZCS 8.8
- This is certified documentation and is protected for editing by Zimbra Employees & Moderators only.

KB 2661	Last updated on 2022-12-21
0.00 (0 votes)
- This is certified documentation and is protected for editing by Zimbra Employees & Moderators only.

A note on CN and subjectAltName

By default ZCS requires valid certificates when communicating with hosts over TLS/SSL. As such, certificates within an install should be valid (not expired and have hostnames matching the certificate).

Per https://tools.ietf.org/html/rfc2818#section-3.1

If a subjectAltName extension of type dNSName is present, that MUST be used as the identity. Otherwise, the (most specific) Common Name field in the Subject field of the certificate MUST be used. Although the use of the Common Name is existing practice, it is deprecated and Certification Authorities are encouraged to use the dNSName instead.

See also RFC2459 section-4.2.1.7 for details on Subject Alternative Name handling and usage.

In short setting subjectAltName, it must include all host names to be trusted, not just "additional" ones beyond what is in CN (by default zmcertmgr will put `zmhostname` in the subjectAltName).

ZCS Administration Console

The ZCS Certificates tools are located in the Navigation pane, under Configure>Certificates

Viewing Certificates

Using the Administration Console, you can view the details of certificates currently deployed. Details include the certificate subject, issuer, validation days, and subject alternative name.

To view a certificate, select a service host name, either under Certificates in the Navigation pane or by selecting a Service host name in the Manage Certificates tab and clicking View Certificate. A Certificates tab for the service host name you selected opens in the Content Pane.

Information about the certificate:

You can refresh the currently displayed details by clicking Refresh at the top of the tab.

Generate a valid CSR (Certificate Signing Request) for a Commercial SSL

Go to Home > Configure > Certificates and click in the settings icon, then click on Install Certificate

Select the target server to generate the SSL files like the CSR and the private key:

In the next step, select the option Generate the CSR for the commercial certificate authorizer

In this window, you need to select the next settings:

Select digest SHA256 or above, not SHA1 as is not longer considered to be secure
Key Length 2048 or above
Common Name (CN) needs to be the FQDN that you want to use, if you are using a Single-Server is recommended that the FQDN and the hostname are the same.
The checkbox about the Wildcard is if you want to use a Wildcard SSL certificate for your Zimbra, and for the rest of you other FQDN in your Company. If the hostname and the FQDN doesn't match, but are in the same domain, use this option and buy a Wildcard Certificate.
In the Subject Alternative Name (SAN), you can select another names if you will use a Multi-SAN SSL certificate, this option is indicated if you want to have mail.customer1.com, mail.customer2.com, etc.

You can download now the CSR file, ready to send to your SSL Certificate Provider, if you miss this step, you can find the csr file in the next path /opt/zimbra/ssl/zimbra/commercial/commercial.csr:

You can check if your CSR is valid and correct using for example https://certlogik.com/decoder/

Installing Certificates

Clicking Install Certificate from either the Manage Certificates tab or a Certificates tab opens the Certificate Installation Wizard. The Certificate Installation Wizard is a tool that will help you quickly create and deploy a certificate.

Generating & Installing a Self-Signed Certificate

Sometimes we want to regenerate the Self-Signed Certificate, we can do it in the Administration Console. We need to click in the Cog>Select Install Certificate and follow the steps:

The first step is select Install the self-signed certificate

Next, we need to mark the checkbox Replace the existing CSR

We need to be sure of select the Key Length at 2048, and the rest of the fields, for now have a Bug Opened in 8.5 and also if you change this values will be the same default values - [1].

We can select also the time that we want to have this SSL validated, remember that is Self-Signed, if we are not planning any future change, we can select more than a year. And then press Install.

The SSL Certificate Self-Signed are now installing in our Zimbra Collaboration Server.

Once the installation has finish, the system request us a restart of the ZCS services.

Trough console by user zimbra we need to execute the next command, and wait until all services are up again:

zmcontrol restart

If we will go again to our https://mail.domain.com we will have the known problem with SSL Certificate in our Web Browser:

Generating Multiple CSRs using the Administration Console

Currently the Administration Console only supports having one Certificate Signing Request (CSR) and private key at a time. Generating a new CSR overrides the existing one and generates a new private key. To generate more than one CSR, move both the CSR and key from the directory it is generated in (e.g. /opt/zimbra/ssl/zimbra/commercial directory/) before generating another CSR.

Maintaining Valid Certificates

It is important to keep your SSL certificates valid to ensure clients and environments work properly, as the ZCS system can become non-functional if certificates are allowed to expire. You can view deployed SSL certificates from the ZCS administrator console, including their validation days. It is suggested that certificates are checked periodically, so you know when they expire and to maintain their validity.

ZCS Certificate CLI

zmcertmgr

This command allows you to manage certificates.

General Guidelines

Follow these guidelines when using this command.

For versions before 8.7, this tool must be run as root. In 8.7+, this tool is run as user zimbra.

Commercial Certificate Guidelines

Follow these guidelines when using this command to generate a commercial certificate.

The private key must exist in the /opt/zimbra/ssl/zimbra/commercial directory, and must be named commercial.key with its permission set to 740 before 8.7, and 640 in 8.7+.
The server certificate and the chain certificate files must exist in a temp directory. (E.g. /tmp/certs/)
The chain certificate files must be concatenated into one file called commercial_ca.crt

Syntax

zmcertmgr [options]

Description

Name	Description
General Options
-help	Displays usage options for zmcertmgr
Self-Signed Certificate Options
createca [-new] [-keysize keysize] [-digest digest] [-subject subject]
	Generates a Certificate Authority (CA).
deployca [-localonly]
	Deploys a Certificate Authority (CA). The -localonly avoids updating any certificate related settings in LDAP.
createcsr <self\|comm> [-new] [-keysize keysize] [-digest digest] [-subject subject] [-subjectAltNames "host1,host2"]
	Creates a certificate signing request (CSR) for either a self or commercially signed certificate authority. By default the CSR subjectAltNames contains the current zmhostname (8.7 only: unless the -noDefaultSubjectAltName argument is used).
createcrt [-new] [-days validation days] [-keysize keysize] [-digest digest] [-subject subject] [-subjectAltNames "host1,host2"]
	Creates a self-signed certificate based on the CSR generated using createcsr.
Where options are:
-new	Force the generation of a new CA/Cert/CSR, overwriting existing data.
-keysize	The RSA keysize in bits, for example "-keysize 4096". Minimum keysize is 2048. Default keysize is 2048. (as of 8.0.7 https://bugzilla.zimbra.com/show_bug.cgi?id=85023)
-subject	The X.500 distinguished name (DN). The default was "/C=US/ST=N\/A/L=N\/A/O=Zimbra Collaboration Suite/OU=Zimbra Collaboration Suite/CN=${zimbra_server_hostname}" before 8.7, and in 8.7+ is "/OU=Zimbra Collaboration Suite/CN=${zimbra_server_hostname}" after.
‑subjectAltNames	Additional host names that may use the certificate other than the one listed in the subject. The alternate names can be specified as comma separate values (or in 8.7+ the -subjectAltNames can be used multiple times).
Self-Signed (self) and Commercial (comm) Certificate Options
deploycrt <<self>\|<comm [certfile ca_chain_file]>> [-allservers] [-localonly] [[-deploy $services] ...]
	Deploys a certificate. For commercial certificates the certificate file and the certificate authority (CA) chain may be specified. For deploycrt, the use of -allservers will cause zmcertmgr to iterate through all servers in the ZCS deployment (zmprov gas, minus the initiating zmcertmgr host).
getcrt <self\|comm> [-allservers]
savecrt <self\|comm> [-allservers]
	Get (or Save) a certificate. For getcrt and savecrt, the use of -allservers causes the configuration keys to be get/set as a global (getConfig/modifyConfig) configuration settings (zimbraSSLCertificate and zimbraSSLPrivateKey) instead of as a per-server setting (getServer/modifyServer).
viewcsr <self\|comm> [csr_file]
	Shows a certificate signing request (CSR). Optionally, the CSR file can be specified.
viewstagedcrt <self\|comm> [certfile]
	Shows a staged certificate. A staged certificate is placed in a staging file, where all files that will be deployed with the certificate are kept. You can use the staging area to verify that you are ready to deploy a certificate.
verifycrt <self\|comm> [[[priv_key] [certfile]] [ca_chain_file]]
	Combines verifycrtkey and verifycrtchain checks (see below).
verifycrtkey <priv_key> <certfile>
	Compares certificate private key and certificate file modulus digests to ensure they match.
verifycrtchain <ca_chain_file> <certfile>
	Verifies a certificate chain.
viewdeployedcrt [all\|ldap\|mailboxd\|mta\|proxy]
	Shows a deployed certificate on the local server.
checkcrtexpiration [all\|ldap\|mailboxd\|mta\|proxy] [-days days]
	Check if certificate(s) expire within -days days

Examples

The following are examples of using the above options for different installation scenarios.

Single-Node Self-Signed Certificate

1. Begin by generating a new Certificate Authority (CA).

 /opt/zimbra/bin/zmcertmgr createca -new

2. Then generate a certificate signed by the CA that expires in 1825 days.

 /opt/zimbra/bin/zmcertmgr createcrt -new -days 1825

3. Next deploy the certificate.

 /opt/zimbra/bin/zmcertmgr deploycrt self

4. Next deploy the CA.

 /opt/zimbra/bin/zmcertmgr deployca

5. To finish, verify the certificate was deployed to all the services.

 /opt/zimbra/bin/zmcertmgr viewdeployedcrt

Multi-Node Self-Signed Certificate

1. Begin by generating a new Certificate Authority (CA).

 /opt/zimbra/bin/zmcertmgr createca -new
 /opt/zimbra/bin/zmcertmgr deployca

2. Then generate a certificate signed by the CA that expires in 365 days with either wild-card or subject altnames.

 /opt/zimbra/bin/zmcertmgr createcrt -new -subjectAltNames "*.example.com"
 /opt/zimbra/bin/zmcertmgr createcrt -new -subject "/C=US/ST=CA/O=Example/CN=*.example.com"
 /opt/zimbra/bin/zmcertmgr createcrt -new -subjectAltNames "host1.example.com,host2.example.come"

3. Next, deploy the certificate to all nodes in the deployment.

 /opt/zimbra/bin/zmcertmgr deploycrt self -allserver

4. To finish, verify the certificate was deployed.

 /opt/zimbra/bin/zmcertmgr viewdeployedcrt

Note: The option viewdeployedcrt only works for the local server.

Alternate Method

The "-allserver" command above doesn't always work as expected, depending on whether the ssh keys are current and working properly. One can also create the new CA first on an LDAP Master node, and then manually deploy the CA and create the self-signed certs on all the other nodes:

On an LDAP Master:

/opt/zimbra/bin/zmcertmgr createca -new
/opt/zimbra/bin/zmcertmgr deployca
/opt/zimbra/bin/zmcertmgr createcrt -new -subject "/C=US/ST=CA/O=Example/CN=*.example.com"
OR
/opt/zimbra/bin/zmcertmgr createcrt -new -subjectAltNames "host1.example.com,host2.example.com"
OR
/opt/zimbra/bin/zmcertmgr createcrt -new -subjectAltNames "*.example.com"
/opt/zimbra/bin/zmcertmgr deploycrt self

On all other systems:

/opt/zimbra/bin/zmcertmgr deployca -localonly
/opt/zimbra/bin/zmcertmgr createcrt -new -subject "/C=US/ST=CA/O=Example/CN=*.example.com"
/opt/zimbra/bin/zmcertmgr deploycrt self

Single-Node Commercial Certificate

We need to take care and ask for the Certificate authority for the Root and Intermediate Keys, we will need it soon.

We will use at least 2048-bit key, is the minimum for all Certificate Authorities: 1. Begin by generating a Certificate Signing Request (CSR).

/opt/zimbra/bin/zmcertmgr createcsr comm -new -subject "/C=US/ST=CA/L=Sunnyvale/O=Zimbra/OU=Zimbra Collaboration Suite/CN=host.example.com" -subjectAltNames host.example.com

2. Next, submit the CSR to the SSL provider and get a commercial certificate in PEM format. Save the new certificate to a temporary file (e.g. /tmp/commercial.crt).

3. Now, download and save the root Certificate Authority (CA) from your provider to a temporary file. (e.g. /tmp/ca.crt)

4. Download any intermediary CAs from your provider to a temporary file. (e.g. /tmp/ca_intermediary.crt)

5. Combine root and intermediary CAs into a temporary file.

cat /tmp/ca_intermediary.crt /tmp/ca.crt > /tmp/ca_chain.crt

6. Verify your commercial certificate.

/opt/zimbra/bin/zmcertmgr verifycrt comm /opt/zimbra/ssl/zimbra/commercial/commercial.key /tmp/commercial.crt /tmp/ca_chain.crt
**Verifying /tmp/commercial.crt against
/opt/zimbra/ssl/zimbra/commercial/commercial.key
Certificate (/tmp/commercial.crt) and private key
(/opt/zimbra/ssl/zimbra/commercial/commercial.key) match.
Valid Certificate: /tmp/commercial.crt: OK

7. Deploy your commercial certificate.

/opt/zimbra/bin/zmcertmgr deploycrt comm /tmp/commercial.crt /tmp/ca_chain.crt
** Verifying /tmp/commercial.crt against
/opt/zimbra/ssl/zimbra/commercial/commercial.key
Certificate (/tmp/commercial.crt) and private key
(/opt/zimbra/ssl/zimbra/commercial/commercial.key) match.
Valid Certificate: /tmpt/commercial.crt: OK
**Copying commercial.crt to /opt/zimbra/ssl/zimbra/commercial/commercial.crt
**Appending CA chain /tmp/ca_chain.crt to
/opt/zimbra/ssl/zimbra/commercial/commercial.crt
**Saving server config key zimbraSSLCeretificate…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/mailbox/etc/keystore…done.
**Installing CA to /opt/zimbra/conf/ca…done.

8. To finish, verify the certificate was deployed.

/opt/zimbra/bin/zmcertmgr viewdeployedcrt

Single-Node Wildcard Commercial Certificate

Using a Wildcard Certificate, you will need the next files, because you probably generated the CSR in other server:

The .key file which you generated the CSR.
The .crt file that you SSL provide to you.
The CA Intermediate and the root files merged into one only file, called for example ca_chain.crt

1.- Backup your actual .key file located in /opt/zimbra/ssl/zimbra/commercial/commercial.key:

mv /opt/zimbra/ssl/zimbra/commercial/commercial.key /opt/zimbra/ssl/zimbra/commercial/commercial.key.backup

2.- Move your actual .key file into the path /opt/zimbra/ssl/zimbra/commercial/ with the name commercial.key:

mv /tmp/wildcard.key /opt/zimbra/ssl/zimbra/commercial/commercial.key

3.- Verify all the files before deploy the SSL certificate with the next command:

/opt/zimbra/bin/zmcertmgr verifycrt comm /opt/zimbra/ssl/zimbra/commercial/commercial.key /tmp/wildcard.crt /tmp/ca_chain.crt

4.- Then as user root (or zimbra for 8.7+) run the next command, please be sure to use the proper path instead /tmp:

/opt/zimbra/bin/zmcertmgr deploycrt comm /tmp/wildcard.crt /tmp/ca_chain.crt

5.- Restart your Zimbra Collaboration server as Zimbra user:

zmcontrol restart

6.- To finish, verify the certificate was deployed.

 /opt/zimbra/bin/zmcertmgr viewdeployedcrt

Multi-Node Commercial Certificate

1. We'll start by assuming you have your Commercial Certificate. If you don't, please see above.

2. Store the certificate and CA Chain on one of your systems:

Signed Certificate: /tmp/commercial.crt
Certificate Key (Private): /tmp/commercial.key
Root Certificate Authority (CA Root): /tmp/ca.crt
Any Intermediate CA Certs: /tmp/ca_intermediary.crt

3. Combine root and intermediary CAs into a temporary file.

 cat /tmp/ca_intermediary.crt /tmp/ca.crt > /tmp/ca_chain.crt

4. [Optional Step] If you previously had an earlier Commercial Certificate on this platform, it may help - make this easier and more consistent - to remove the old ones:

 mv /opt/zimbra/ssl/zimbra /opt/zimbra/ssl/zimbra.old

Then recreate the directories:

 mkdir /opt/zimbra/ssl/zimbra
 mkdir /opt/zimbra/ssl/zimbra/ca
 mkdir /opt/zimbra/ssl/zimbra/commercial
 mkdir /opt/zimbra/ssl/zimbra/server
 chmod 740 /opt/zimbra/ssl/zimbra    # chmod 750 for ZCS 8.7+
 chmod 740 /opt/zimbra/ssl/zimbra/*  # chmod 750 for ZCS 8.7+

4.5 If you go for step 4, copy the contents of /opt/zimbra/ssl/zimbra.old/ca/ directory to /opt/zimbra/ssl/zimbra/ca/

 cp -pr /opt/zimbra/ssl/zimbra.old/ca/* /opt/zimbra/ssl/zimbra/ca/

5. Copy the commercial.key to /opt/zimbra/ssl/zimbra/commercial

 cp /tmp/commercial.key /opt/zimbra/ssl/zimbra/commercial/
 chmod 640 /opt/zimbra/ssl/zimbra/commercial/commercial.key

5. Verify your commercial certificate. (as user root in 8.6- or zimbra in 8.7+):

 /opt/zimbra/bin/zmcertmgr verifycrt comm /opt/zimbra/ssl/zimbra/commercial/commercial.key /tmp/commercial.crt /tmp/ca_chain.crt

6. Deploy your commercial certificate.

 /opt/zimbra/bin/zmcertmgr deploycrt comm /tmp/commercial.crt /tmp/ca_chain.crt

7. To finish, verify the certificate was deployed.

 /opt/zimbra/bin/zmcertmgr viewdeployedcrt

8. In case of any issues in the Java keystore, check that the Intermediate CA was added to the keystore:

 <8.7 # /opt/zimbra/java/bin/keytool -list -keystore \
   /opt/zimbra/java/jre/lib/security/cacerts -storepass changeit
OR
 8.7+ $ keytool -list -keystore \
   /opt/zimbra/common/lib/jvm/java/jre/lib/security/cacerts -storepass changeit

If necessary, import the CA into the keystore:

 <8.7 # /opt/zimbra/java/bin/keytool -import -alias root -keystore \
   /opt/zimbra/java/jre/lib/security/cacerts -storepass changeit -file /opt/zimbra/conf/ca/commercial_ca.pem
OR
 8.7+ $ keytool -import -alias root -keystore \
   /opt/zimbra/common/lib/jvm/java/jre/lib/security/cacerts -storepass changeit -file /opt/zimbra/conf/ca/commercial_ca.pem

9. Copy these files to each of your other nodes, and repeat steps 4-8 on each node:

Signed Certificate: /tmp/commercial.crt
Certificate Key (Private): /tmp/commercial.key
Certificate Chain: /tmp/ca_chain.crt

Verified Against: ZCS 10.0, 9.0, 8.8	Date Created: 9/10/2008
Article ID: https://wiki.zimbra.com/index.php?title=Cipher_suites	Date Modified: 2022-12-21

Cipher suites: Difference between revisions