title: Write additional properties into a certificate
body: <p>When I'm creating a certificate signing request like below I have to run trough a process and need to enter several properties with individual values per certificate. (see image below)</p>
  
  <pre><code>    openssl req -config ../CA/config/openssl.custom.cnf \
          -key ./private.key.pem \
          -new -sha256 -out ./private.certificate.csr.pem
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/2u4LP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2u4LP.png" alt="enter image description here"></a></p>
  
  <p>Now I want to put additional properties into the cert like a mac address of a device the later validated file is installed on.</p>
  
  <p>I've tried to modify the customized openssl.cnf to write additional properties into the certificate signing request but without any luck and I can't find proper information if it's somehow possible (maybe using the wrong search terms) </p>
  
  <p>My first thought was to use the common name to encode my additional properties in it but I guess that's not good practice — don't know.</p>
  
  <p>I'm happy for any help here.</p>