class Acme::Client::CertificateRequest

def generate
  OpenSSL::X509::Request.new.tap do |csr|
    if @private_key.is_a?(OpenSSL::PKey::EC) && RbConfig::CONFIG['MAJOR'] == '2' &&
       RbConfig::CONFIG['MINOR'].to_i < 4
      # OpenSSL::PKey::EC does not respect classic PKey interface (as defined by
      # PKey::RSA and PKey::DSA) until ruby 2.4.
      # Supporting this interface needs monkey patching of OpenSSL:PKey::EC, or
      # subclassing it. Here, use a subclass.
      @private_key = ECKeyPatch.new(@private_key)
    end
    csr.public_key = @private_key
    csr.subject = generate_subject
    csr.version = 0
    add_extension(csr)
    csr.sign @private_key, @digest
  end
end