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 * distributed with this work for additional information
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 * to you 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
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package org.apache.ofbiz.base.html;

import java.util.regex.Pattern;

import org.owasp.html.HtmlPolicyBuilder;
import org.owasp.html.PolicyFactory;

import com.google.common.base.Predicate;

/**
 * Based on the <a href=
 * "http://www.owasp.org/index.php/Category:OWASP_AntiSamy_Project#Stage_2_-_Choosing_a_base_policy_file">AntiSamy
 * EBay example</a>. eBay (http://www.ebay.com/) is the most
 * popular online auction site in the universe, as far as I can tell. It is a
 * public site so anyone is allowed to post listings with rich HTML content.
 * It's not surprising that given the attractiveness of eBay as a target that it
 * has been subject to a few complex XSS attacks. Listings are allowed to
 * contain much more rich content than, say, Slashdot- so it's attack surface is
 * considerably larger. The following tags appear to be accepted by eBay (they
 * don't publish rules): {@code <a>},...
 */
public class CustomPermissivePolicy implements SanitizerCustomPolicy {

    // Some common regular expression definitions.

    // The 16 colors defined by the HTML Spec (also used by the CSS Spec)
    private static final Pattern COLOR_NAME = Pattern.compile(
            "(?:aqua|black|blue|fuchsia|gray|grey|green|lime|maroon|navy|olive|purple"
                    + "|red|silver|teal|white|yellow)");

    // HTML/CSS Spec allows 3 or 6 digit hex to specify color
    private static final Pattern COLOR_CODE = Pattern.compile(
            "(?:#(?:[0-9a-fA-F]{3}(?:[0-9a-fA-F]{3})?))");

    private static final Pattern NUMBER_OR_PERCENT = Pattern.compile(
            "[0-9]+%?");
    private static final Pattern PARAGRAPH = Pattern.compile(
            "(?:[\\p{L}\\p{N},'\\.\\s\\-_\\(\\)]|&[0-9]{2};)*");
    private static final Pattern HTML_ID = Pattern.compile(
            "[a-zA-Z0-9\\:\\-_\\.]+");
    // force non-empty with a '+' at the end instead of '*'
    private static final Pattern HTML_TITLE = Pattern.compile(
            "[\\p{L}\\p{N}\\s\\-_',:\\[\\]!\\./\\\\\\(\\)&]*");
    private static final Pattern HTML_CLASS = Pattern.compile(
            "[a-zA-Z0-9\\s,\\-_]+");

    private static final Pattern ONSITE_URL = Pattern.compile(
            "(?:[\\p{L}\\p{N}\\\\\\.\\#@\\$%\\+&;\\-_~,\\?=/!]+|\\#(\\w)+)");
    private static final Pattern OFFSITE_URL = Pattern.compile(
            "\\s*(?:(?:ht|f)tps?://|mailto:)[\\p{L}\\p{N}]"
                    + "[\\p{L}\\p{N}\\p{Zs}\\.\\#@\\$%\\+&;:\\-_~,\\?=/!\\(\\)]*+\\s*");

    private static final Pattern NUMBER = Pattern.compile(
            "[+-]?(?:(?:[0-9]+(?:\\.[0-9]*)?)|\\.[0-9]+)");

    private static final Pattern NAME = Pattern.compile("[a-zA-Z0-9\\-_\\$]+");

    private static final Pattern ALIGN = Pattern.compile(
            "(?i)center|left|right|justify|char");

    private static final Pattern VALIGN = Pattern.compile(
            "(?i)baseline|bottom|middle|top");

    private static final Predicate<String> COLOR_NAME_OR_COLOR_CODE = matchesEither(COLOR_NAME, COLOR_CODE);

    private static final Predicate<String> ONSITE_OR_OFFSITE_URL = matchesEither(ONSITE_URL, OFFSITE_URL);

    private static final Pattern HISTORY_BACK = Pattern.compile(
            "(?:javascript:)?\\Qhistory.go(-1)\\E");

    private static final Pattern ONE_CHAR = Pattern.compile(
            ".?", Pattern.DOTALL);

    /**
     * A policy that can be used to produce policies that sanitize to HTML sinks via
     * {@link PolicyFactory#apply}.
     */
    public static final PolicyFactory POLICY_DEFINITION = new HtmlPolicyBuilder()
            .allowAttributes("id").matching(HTML_ID).globally()
            .allowAttributes("class").matching(HTML_CLASS).globally()
            .allowAttributes("lang").matching(Pattern.compile("[a-zA-Z]{2,20}"))
            .globally()
            .allowAttributes("title").matching(HTML_TITLE).globally()
            .allowStyling()
            .allowAttributes("align").matching(ALIGN).onElements("p")
            .allowAttributes("for").matching(HTML_ID).onElements("label")
            .allowAttributes("color").matching(COLOR_NAME_OR_COLOR_CODE)
            .onElements("font")
            .allowAttributes("face")
            .matching(Pattern.compile("[\\w;, \\-]+"))
            .onElements("font")
            .allowAttributes("size").matching(NUMBER).onElements("font")
            .allowAttributes("href").matching(ONSITE_OR_OFFSITE_URL)
            .onElements("a")
            .allowStandardUrlProtocols()
            .allowAttributes("nohref").onElements("a")
            .allowAttributes("target").matching(NAME).onElements("a")
            .allowAttributes("name").matching(NAME).onElements("a")
            .allowAttributes("onfocus", "onblur", "onclick", "onmousedown", "onmouseup")
            .matching(HISTORY_BACK).onElements("a")
            .requireRelNofollowOnLinks()
            .allowAttributes("src").matching(ONSITE_OR_OFFSITE_URL)
            .onElements("img")
            .allowAttributes("name").matching(NAME)
            .onElements("img")
            .allowAttributes("alt").matching(PARAGRAPH)
            .onElements("img")
            .allowAttributes("border", "hspace", "vspace").matching(NUMBER)
            .onElements("img")
            .allowAttributes("border", "cellpadding", "cellspacing")
            .matching(NUMBER).onElements("table")
            .allowAttributes("bgcolor").matching(COLOR_NAME_OR_COLOR_CODE)
            .onElements("table")
            .allowAttributes("background").matching(ONSITE_URL)
            .onElements("table")
            .allowAttributes("background").matching(ONSITE_URL)
            .onElements("td", "th", "tr")
            .allowAttributes("align").matching(ALIGN)
            .onElements("table")
            .allowAttributes("noresize").matching(Pattern.compile("(?i)noresize"))
            .onElements("table")
            .allowAttributes("bgcolor").matching(COLOR_NAME_OR_COLOR_CODE)
            .onElements("td", "th")
            .allowAttributes("abbr").matching(PARAGRAPH)
            .onElements("td", "th")
            .allowAttributes("axis", "headers").matching(NAME)
            .onElements("td", "th")
            .allowAttributes("scope")
            .matching(Pattern.compile("(?i)(?:row|col)(?:group)?"))
            .onElements("td", "th")
            .allowAttributes("nowrap")
            .onElements("td", "th")
            .allowAttributes("height", "width").matching(NUMBER_OR_PERCENT)
            .onElements("table", "td", "th", "tr", "img")
            .allowAttributes("align").matching(ALIGN)
            .onElements("thead", "tbody", "tfoot", "img", "td", "th", "tr", "colgroup", "col")
            .allowAttributes("valign").matching(VALIGN)
            .onElements("thead", "tbody", "tfoot", "td", "th", "tr", "colgroup", "col")
            .allowAttributes("charoff").matching(NUMBER_OR_PERCENT)
            .onElements("td", "th", "tr", "colgroup", "col", "thead", "tbody", "tfoot")
            .allowAttributes("char").matching(ONE_CHAR)
            .onElements("td", "th", "tr", "colgroup", "col", "thead", "tbody", "tfoot")
            .allowAttributes("colspan", "rowspan").matching(NUMBER)
            .onElements("td", "th")
            .allowAttributes("span", "width").matching(NUMBER_OR_PERCENT)
            .onElements("colgroup", "col")
            .allowElements(
                    "a", "label", "noscript", "h1", "h2", "h3", "h4", "h5", "h6", "hr",
                    "p", "i", "b", "u", "strong", "em", "small", "big", "pre", "code",
                    "cite", "samp", "sub", "sup", "strike", "center", "blockquote",
                    "hr", "br", "col", "font", "map", "span", "div", "img",
                    "ul", "ol", "li", "dd", "dt", "dl", "tbody", "thead", "tfoot",
                    "table", "td", "th", "tr", "colgroup", "fieldset", "legend", "header",
                    "picture", "source", "section", "nav", "footer")
            .toFactory();

    /**
     * Constructs a predicate checking if a string matches any of the two provided patterns.
     * @param a  the first pattern
     * @param b  the second pattern
     * @return a predicate checking if a string matches either {@code a} or {@code b}
     */
    private static Predicate<String> matchesEither(Pattern a, Pattern b) {
        return str -> a.matcher(str).matches() || b.matcher(str).matches();
    }

    @Override
    public PolicyFactory getSanitizerPolicy() {
        return POLICY_DEFINITION;
    }
}
