presto-hive/src/main/java/io/prestosql/plugin/hive/authentication/KerberosHiveMetastoreAuthentication.java/KerberosHiveMetastoreAuthentication/SaslClientCallbackHandler
class KerberosHiveMetastoreAuthentication:        SaslClientCallbackHandler(Token<DelegationTokenIdentifier> token)
        {
            this.username = Base64.getEncoder().encodeToString(token.getIdentifier());
            this.password = Base64.getEncoder().encodeToString(token.getPassword());
        }