How to Configure SSL on Jenkins Server

It is very important to secure Jenkins by enabling SSL which runs in a project environment. This article walks you through the step-by-step guide for configuring SSL on a Jenkins server.

Following are the steps involved in configuring SSL on the Jenkins server.

Obtain SSL certificates
Convert SSL keys to PKCS12 format
Convert PKCS12 to JKS format
Add JKS to Jenkins path
Configure Jenkins startup to use the JKS file.
Validate Jenkins SSL

Let's get started with the setup

Step 1: Obtain Domain & SSL Certificates

You should have a valid domain pointing to Jenkins server IP to configure SSL. The domain can be internal or external based on your organization's infrastructure.

SSL certificate can be obtained using the following methods.

In most cases, you will be having Jenkins in a private environment with an internal DNS and you can obtain the internal SSL certificates from the respective organizations.
You can also create self-signed SSL certificates using OpenSSL. Follow create self-signed certificates using OpenSSL
Also, you can use services as Letsencrypt for valid SSL certificates. But these certificates have to be renewed every three months.

Step 2: Convert SSL keys to PKCS12 format

Note: If you already have the certificate in .p12 or .pfx format, you don't have to do this conversion.

The command given below converts SSL certs to intermediate PKCS12 format named jenkins.p12. Make sure you have the following certs with you before executing the command.

ca.crt
server.key
server.crt

Also,

Replace jenkins.devopscube.com in the command with your own alias name
Replace your-strong-password with a strong password.

openssl pkcs12 -export -out jenkins.p12 \
-passout 'pass:your-strong-password' -inkey server.key \
-in server.crt -certfile ca.crt -name jenkins.devopscube.com

Step 3: Convert PKCS12 to JKS format

Use the following keytool command to convert jenkins.p12 file to JKS format.

Replace the following with your own values.

-srcstorepass - Password used in Step 3
-deststorepass - Replace with a strong password.
-srcalias - alias name used in step 2
-destalias - Replace with a destination alias name.

keytool -importkeystore -srckeystore jenkins.p12 \
-srcstorepass 'your-secret-password' -srcstoretype PKCS12 \
-srcalias jenkins.devopscube.com -deststoretype JKS \
-destkeystore jenkins.jks -deststorepass 'your-secret-password' \
-destalias jenkins.devopscube.com

You should see a file named jenkins.jks in you current location.

Step 4: Add JKS to Jenkins path

jenkins.jks file should be saved in a specific location where Jenkins can access it.

Let's create a folder and move the jenkins.jks key to that location.

mkdir -p /etc/jenkins
cp jenkins.jks /etc/jenkins/

Change the permissions of the keys and folder.

chown -R jenkins: /etc/jenkins
chmod 700 /etc/jenkins
chmod 600 /etc/jenkins/jenkins.jks

Step 5: Modify Jenkins Configuration for SSL

All the key Jenkins startup configurations are present in /etc/sysconfig/jenkins file. All the SSL-based configurations go into this file.

Open the file

sudo vi /etc/sysconfig/jenkins

Find and replace the values in the file as shown below.

Note: Replace your-keystore-password with the Keystore password, you set in step 3. Also you can use either 443 or 8443 for ports.

JENKINS_PORT="-1"
JENKINS_HTTPS_PORT="8443"
JENKINS_HTTPS_KEYSTORE="/etc/jenkins/jenkins.jks"
JENKINS_HTTPS_KEYSTORE_PASSWORD="<your-keystore-password>"
JENKINS_HTTPS_LISTEN_ADDRESS="0.0.0.0"

Save the configuration and restart Jenkins.