When configuration "hadoop.security.authorization" is set to false, the system will still try to authorize an RPC and raise AccessDeniedException

if (!authorizeConnection()) {
  // Throw FatalConnectionException wrapping ACE so client does right thing and closes
  // down the connection instead of trying to read non-existent retun.
  throw new AccessDeniedException("Connection from " + this + " for service " +
    connectionHeader.getServiceName() + " is unauthorized for user: " + ugi);
}

if (ugi != null && ugi.getRealUser() != null
    && (authMethod != AuthMethod.DIGEST)) {
  ProxyUsers.authorize(ugi, this.getHostAddress(), conf);
}