SAN stands for “Subject Alternative Names” and this helps you to have a single certificate for multiple CN (Common Name). You might be thinking this is wildcard SSL but let me tell you – it’s slightly different. In the SAN certificate, you can have multiple complete CN. Example:
geekflare.com gf.dev siterelic.com chandan.io
I can have above all and much more in a just single certificate. This means I just have to buy one cert and use in multiple URLs. Sounds interesting? The creation of CSR for SAN is slightly different than traditional OpenSSL command and will explain in a while how to generate CSR for Subject Alternative Names SSL certificate. Let’s take a look at a real-time example of skype.com, which has many SAN in a single certificate.
As you can see the above example – if you are managing multiple https URL, you may consider consolidating into single SSL Cert with SAN and save thousands of dollars. What do you think about this?
Procedure to create CSR with SAN
Login into a server where you have OpenSSL installed Go to /tmp or create any directory Create a file named san.cnf using vi (if on Unix) with the following information
Note: alt_names section is the one you have to change for additional DNS.
Save the file and execute the following OpenSSL command, which will generate CSR and KEY file
This will create sslcert.csr and private.key in the present working directory. You have to send sslcert.csr to certificate signer authority so they can provide you a certificate with SAN.
How to verify CSR for SAN?
It will be a good idea to check if your CSR contains the SAN, which you specified above in san.cnf file. Ex: Once you are happy with the CSR, you can send it to your certificate authority to sign the certificate. Alternatively, you can buy from SSL Store.
