OpenSSL Generate CSR non-interactive

09-02-2013 | Remy van Elst


Table of Contents


This is a short command to generate a CSR (certificate signing request) with openssl without being prompted for the values which go in the certificate's Subject field.

When you use OpenSSL to generate a CSR and a private key you use the following command:

openssl req -nodes -newkey rsa:2048 -keyout private.key -out CSR.csr

This is the output:

Generating a 2048 bit RSA private key
.................................................................+++
.......................................................................+++
writing new private key to 'private.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]:NL
State or Province Name (full name) [Some-State]:Zuid Holland
Locality Name (eg, city) []:Rotterdam
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Sparkling Network
Organizational Unit Name (eg, section) []:IT Department
Common Name (e.g. server FQDN or YOUR name) []:ssl.raymii.org
Email Address []:

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

You can see that you have to fill in a lot of data during the generation. If you do not want that, maybe because you are using a script to generate a lot of CSR's and private keys, you use the following command. It does the same as the above command, but it has all the data in it:

openssl req -nodes -newkey rsa:2048 -keyout private.key -out CSR.csr -subj "/C=NL/ST=Zuid Holland/L=Rotterdam/O=Sparkling Network/OU=IT Department/CN=ssl.raymii.org"

This is the output:

Generating a 2048 bit RSA private key
.......+++
..............................................................................................................................................+++
writing new private key to 'private.key'
-----

This is what the -subj option does:

  • /C=NL: 2 letter ISO country code (Netherlands)
  • /ST=: State, Zuid Holland (South holland)
  • /L=: Location, city (Rotterdam)
  • /O=: Organization (Sparkling Network)
  • /OU=: Organizational Unit, Department (IT Department, Sales)
  • /CN=: Common Name, for a website certificate this is the FQDN. (ssl.raymii.org)

You can also give a /serialNumber=0123456 with the above option. This is NOT the serial number the issuing Certificate Authority (CA) will use, but a way to give extra information to a certificate. If you have a CN for John Doe, and another one, the serialNumber field can be used to distinguish John Doe 1 from John Doe 2's certificate. Click here for more info.


Tags: certificates, csr, openssl, pki, private-key, public-key, ssl,