Introduction

Create Root CA Certificate

The first step includes to create a private key (root-ca.key) and self-signed certificate (root-ca.crt) for the Root CA both in PEM format. This step is performed just once.

# step 1 Generate Certificate Authority (CA) Private Key
openssl ecparam -name prime256v1 -genkey -noout -out root-ca.key

# step 2: Generate Certificate Authority Certificate
openssl req -new -x509 -sha256 -key root-ca.key -out root-ca.crt

Create Server Certificate

The second step includes to create for a given server a private key and certificate request (CSR). The resulting server certificate will be signed. 

This step is performed for each server certificate that should be created.

Run the following commands from a bash shell and replace the value of the SERVER variable with the hostname or FQDN for which the certificate should be created:

# Specify server for which the certificate should be created
SERVER=somehost

# Step 1 - Generate Private Key and Certificate Signing Request
openssl req -new -config openssl-cert.config -extensions 'standard exts' -nodes \
    -days 7300 -newkey rsa:4096 -keyout ${SERVER}.key -out ${SERVER}.csr

# Step 2 - Generate and Sign the Server Certificate
openssl x509 -req \
    -in ${SERVER}.csr \
    -CA root-ca.crt \
    -CAkey root-ca.key \
    -CAcreateserial \
    -out ${SERVER}.crt -days 7300 \
    -extfile <(printf "subjectAltName=DNS:${SERVER}\nnsCertType = client, server\nkeyUsage = digitalSignature, keyEncipherment\nextendedKeyUsage = serverAuth, clientAuth\n")

In order to run the script successfully the following openssl-cert.config file has to be present. To create a server certificate the CommonName attribute has to be adjusted. The attribute holds the hostname of the server for which the certificate should be created:

[ req ]
prompt             = no
distinguished_name = standard dn

[ standard dn ]
            commonName = somehost
           countryName = DE
          localityName = Berlin
      organizationName = SOS
organizationalUnitName = JS7
   stateOrProvinceName = Berlin

[ standard exts ]
extendedKeyUsage = serverAuth,clientAuth

Resources

Links

• JS7 - How to add SSL TLS Certificates to Keystore and Truststore

Shell Scripts

As an alternative to running OpenSSL commands in an interactive shell some scripts are provided that perform this task.

The below scripts assume the following directory layout:

• <ca>  The directory <ca> is a placeholder. Any directory can be used.
  • create_root_ca.sh
  • create_certificate.sh
  • certs
  • csr
  • private

The sub-directories certs, csr and private will be created from the below scripts should they not exist.

Create Root CA Certificate

The following files will be created:

• <ca>/certs/root-ca.crt
• <ca>/private/root-ca.key

This step is performed just once. In case of repeated execution a new Root CA Certificate will be created and server certificates will have to be renewed.

• Download: create_root_ca.sh
• The shell script is executed without arguments.
  
  

./create_root_ca.sh

Create Certificate from Shell Script

The following files will be created with <server> being a placeholder for the hostname of the indicated server.

• <ca>/certs/<server>.crt
• <ca>/certs/<server>.csr
• <ca>/private/<server>.key

This step is performed for each server certificate that should be created.

• Download: create_certificate.sh
• The shell script is executed with two arguments:
  • The DNS hostname of the server that should receive the certificate. A server can be assigned more than one DNS hostname, for example its FQDN can be different. All DNS hostnames have to be added to the certificate in order to secure connections.
  • The lifetime of the certificate specified by the number of days.
    
    

./create_certificate.sh --dns=<server-hostname>[,<server-hostname>]> --days=<number-of-days>