Introduction
Users have a choice to use CA signed certificates and self-signed certificates:
- CA signed certificates are issued by a know Certificate Authority (CA).
- Self-signed certificates are created by the user and are not related to a known CA.
There is no difference concerning the type of X.509 certificates, the usage for Server Authentication / Client Authentication, or the encryption of connections.
The article explains how to create self-signed certificates by use of OpenSSL. This utility ships with Linux and most Unix environments and is available for Windows environments. The below examples are focused on Unix.
Create Root CA Certificate
The first step includes to create the root-ca.key
private key file and the root-ca.crt
self-signed certificate file 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
For a given server the second step includes to create a private key and Certificate Signing 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")
Explanation:
- The following files will be created for the given server:
<SERVER>
.key
: the Private Key<SERVER>
.csr
: the Certificate Signing Request<SERVER>
.crt
: the Server Certificate
- For operation with JS7 JOC Cockpit, Controller and Agents users can add
- the Private Key and Server Certificate to a keystore.
- the Root CA Certificate to a truststore.
- For details see JS7 - How to add SSL TLS Certificates to Keystore and Truststore
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.
Replace the value of the commonName
attribute with 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
Shell Scripts
As an alternative to running OpenSSL commands in an interactive shell a few 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 by 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 the FQDN can extend the hostname. Only DNS hostnames that are added to the certificate can be used to establish secure connections.
- The lifetime of the certificate is specified by the number of days.
./create_certificate.sh --dns=<server-hostname>[,<server-hostname>]> --days=<number-of-days>