I have a public key in PEM format that was generated with:
ecdsa_public_key = OpenSSL::PKey::EC.new ecdsa_private_key
ecdsa_public_key.private_key = nil
ecdsa_public_key = OpenSSL::PKey.read pem_string
ecdsa_public_key.to_base64 # pseudo code...
you must add your VAPID public key to the Crypto-Key header as a base64 url encoded string with p256ecdsa= prepended to it.
The PEM string actually is base 64 encoded (at least partially), but I don’t think it’s what you want here, it includes other details and I think you want the “raw” public key data.
Here’s one way you can get your key into the format I think you want. It’s a bit long winded but I don’t think Ruby’s OpenSSL bindings provide a more direct method (you’ll need to
require "base64" first):
# Assuming the key is in ecdsa_public_key Base64.urlsafe_encode64(ecdsa_public_key.public_key.to_bn.to_s(2), padding: false)
public_key to get the underlying
OpenSSL::PKey::EC::Point, then converts that to an
OpenSSL::BN in the correct format, and converts that to a binary string. Finally this string is base64 encoded.