Create a DER encoded X509 certificate

Two types of X509 certificates

There are base64 encoded certificates which look like

-----BEGIN CERTIFICATE-----
 MIIFcDCCA1gCAhAAMA0GCSqGSIb3DQEBCwUAMHExCzAJBgNVBAYTAkdCMRAwDgYD
 (...)
 lcH2kxKqa1CWUQGz3S9raNtesOI7jbO9d2HRVPPTPVTliHukS8tlBouq5tU6IFgH
 I61lVg==
 -----END CERTIFICATE-----

Then there are DER encoded certificates which look like

To convert base64 to DER

openssl x509 -outform der -in certificate.crt -out certificate.der