Generate CSR certificate signing request via command line and with OpenSSL

[Sandeep B.]

In this tutorial we’ll learn how you can use openssl to generate CSR and RSA Private key. CSR is needed when you issue paid SSL certificate.

A CSR (Certificate Signing Request) is a specially formatted encrypted message sent from a Secure Sockets Layer (SSL) digital certificate applicant to a certificate authority (CA). The CSR validates the information the CA requires to issue a certificate.

RSA key is a private key based on RSA algorithm. Private Key is used for authentication and a symmetric key exchange during establishment of an SSL/TLS session. It is a part of the public key infrastructure that is generally used in case of SSL certificates. RSA keys are of 2 types for ssl certs i.e. the lengths are 2048 and 4096.

This command will generate CSR and RSA private key within seconds

For 2048 Key length :

openssl req -nodes -newkey rsa:2048 -sha256 -keyout domainname.key -out domainname.csr

For 4096 key length :

openssl req -nodes -newkey rsa:4096 -sha256 -keyout domainname.key -out domainname.csr

After you completed below form the 2 files are created domainname.key and domainname.csr in the same dir you’ve currently use pwd to get the current dir path

you’ll be asked below questions :

root@server:~# openssl req -nodes -newkey rsa:4096 -sha256 -keyout domainname.key -out domainname.csr
Generating a RSA private key
.....................................................................................................................................................................................................................................................................................++++
........++++
writing new private key to 'domainname.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:IN
State or Province Name (full name) [Some-State]:IN
Locality Name (eg, city) []:IN
Organization Name (eg, company) [Internet Widgits Pty Ltd]:WORDPRESS
Organizational Unit Name (eg, section) []:BLOG
Common Name (e.g. server FQDN or YOUR name) []:alphagnu.com
Email Address []:emailid@gmail.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:alphagnu
**A challenge password should be empty hit enter key

Type ls command to list if the files are generated :

root@server:~# ls
domainname.csr   domainname.key