title: using openssl to generate a self signed certificate from pem file
body: <p>I have a pem file with a public key (also have the private key in pkcs8 file)</p>
  <p>I want to create a self signed certificate from it and can't find a way using openssl</p>
  <p>how can I do it?
  thanks</p>
  <p>I searched a lot but only answers that creates a new keys</p>