How to convert PKCS#8 plain private key to hex string to use with KEYUTIL.getKey?

[fgsalomon]

Hello,

I have a RSA private key generated with OpenSSL in PKCS#8 format.

I know I can load the key using from the PEM string with KEYUTIL.getKey(pemString), but I'd like to load it from a hex string using KEYUTIL.getKey(hexString, null, "pkcs5prv");

Does anyone know how to convert the PEM file to a hex string?

I've tried changing the headers -----BEGIN PRIVATE KEY----- to -----BEGIN RSA PRIVATE KEY-----, etc. and then generate the string with:

xxd -p private-key.pem | tr -d '\n'

but the generated hex string it's not valid for jsrasign (Error: unsupported PKCS#1/5 hexadecimal key).

Thank you.