Can only parse traditional files about acme4j HOT 2 CLOSED

fun readKeyPair(r: Reader): KeyPair {
    PEMParser(r).use { parser ->
        return when(val o = parser.readObject()) {
            is PEMKeyPair -> {
                println("Read old style RSA PRIVATE KEY")
                JcaPEMKeyConverter().getKeyPair(o)
            }
            is PrivateKeyInfo -> {
                println("Read PRIVATE KEY. Assume it is RSA.")
                val privateKey = JcaPEMKeyConverter().getPrivateKey(o) as RSAPrivateCrtKey
                val spec = RSAPublicKeySpec(privateKey.modulus, privateKey.publicExponent)
                val publicKey = KeyFactory.getInstance("RSA").generatePublic(spec)
                return KeyPair(publicKey, privateKey)
            }
            else -> {
                throw IOException("Invalid PEM file")
            }

        }
    }
}