class Acme::Client::SelfSignCertificate

def certificate
  @certificate ||= begin
    certificate = generate_certificate
    extension_factory = generate_extension_factory(certificate)
    subject_alt_name_entry = subject_alt_names.map { |d| "DNS: #{d}" }.join(',')
    subject_alt_name_extension = extension_factory.create_extension('subjectAltName', subject_alt_name_entry)
    certificate.add_extension(subject_alt_name_extension)
    certificate.sign(private_key, digest)
  end
end