Is there a way to reset the expiry of a self signed X.509 certificate but keep both the public and the private key as they were?
Technically this should be nothing more than a different date for the "Not After" tag and a fresh signature instead of the old. For CA signed certificates this is also very easy as you just have to send in the CSR again. But in this case I don't have any CSR available because the certificate was created with OpenSSL's req command in one step.
Another question would be: Will verifying clients which trusted this stand-alone certificate still think this is the same certificate and accept it?