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/*
 * Copyright 2022 Red Hat, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.wildfly.common.xml;

import org.wildfly.common.annotation.NotNull;

import static javax.xml.XMLConstants.FEATURE_SECURE_PROCESSING;
import static javax.xml.XMLConstants.ACCESS_EXTERNAL_DTD;
import static javax.xml.XMLConstants.ACCESS_EXTERNAL_STYLESHEET;
import static org.wildfly.common.xml.Log.XML_FACTORY_LOGGER;

import javax.xml.XMLConstants;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Factory provides {@link TransformerFactory} with secure defaults set. Properties not supported generate a warning, but the
 * factory process creation will continue and return a result.
 * Settings based on recommendations of
 * Sonarcloud RSPEC-2755 and
 * OWASP XML
 * External Entity Prevention Cheatsheet.
 * 
 *
 * 

 * {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} is set to true.
 * {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_DTD} is set to empty.
 * {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_STYLESHEET} is set to empty.
 * 
 *
 * @author Boris Unckel
 * @since 1.6.0.Final
 */
public final class TransformerFactoryUtil {

    /*
     * Prevent recurring log messages (per classloader).
     */
    private static final AtomicBoolean TO_BE_LOGGED = new AtomicBoolean(true);

    @NotNull
    public static TransformerFactory create() {
        final TransformerFactory instance = TransformerFactory.newInstance();
        final boolean toBeLogged = TO_BE_LOGGED.compareAndSet(true, false);

        try {
            instance.setFeature(FEATURE_SECURE_PROCESSING, true);
        } catch (TransformerConfigurationException e) {
            if (toBeLogged) {
                XML_FACTORY_LOGGER.xmlFactoryPropertyNotSupported(e, FEATURE_SECURE_PROCESSING,
                        instance.getClass().getCanonicalName());
            }
        }

        try {
            instance.setAttribute(ACCESS_EXTERNAL_DTD, "");
        } catch (IllegalArgumentException e) {
            if (toBeLogged) {
                XML_FACTORY_LOGGER.xmlFactoryPropertyNotSupported(e, ACCESS_EXTERNAL_DTD,
                        instance.getClass().getCanonicalName());
            }
        }

        try {
            instance.setAttribute(ACCESS_EXTERNAL_STYLESHEET, "");
        } catch (IllegalArgumentException e) {
            if (toBeLogged) {
                XML_FACTORY_LOGGER.xmlFactoryPropertyNotSupported(e, ACCESS_EXTERNAL_STYLESHEET,
                        instance.getClass().getCanonicalName());
            }
        }

        return instance;
    }

    /**
     * No instance.
     */
    private TransformerFactoryUtil() {
        throw new IllegalStateException("No instance");
    }

}