ESAPIHelper.java

/*
 Copyright (c) 2012 GFT Appverse, S.L., Sociedad Unipersonal.

 This Source Code Form is subject to the terms of the Appverse Public License
 Version 2.0 (“APL v2.0”). If a copy of the APL was not distributed with this
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 are permitted provided that the conditions of the AppVerse Public License v2.0
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 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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package org.appverse.web.framework.backend.api.helpers.security;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.ws.rs.core.MultivaluedMap;

import org.jsoup.Jsoup;
import org.jsoup.safety.Whitelist;
import org.owasp.esapi.ESAPI;
import org.owasp.esapi.reference.DefaultEncoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ESAPIHelper {
	
	private static Logger logger = LoggerFactory.getLogger(ESAPIHelper.class);
	
    /**
     * Using ESAPI HTML Encoder, encodes the supplied html string.
     * @param html the string to be encoded.
     * @return the encoded string.
     */
    public static String encodeHtml(String html) {    	
        return DefaultEncoder.getInstance().encodeForHTML(html);
    }
	
    /**
     * Apply the XSS filter to the parameters in a MultivaluedMap
     * @param parameters
     */
    public static void cleanParams( MultivaluedMap<String, String> parameters )
    {
        logger.debug("Checking for XSS Vulnerabilities: {}", parameters);

        for( Map.Entry<String, List<String>> params : parameters.entrySet() )
        {
            String key = params.getKey();
            List<String> values = params.getValue();

            List<String> cleanValues = new ArrayList<String>();
            for( String value : values )
            {
                cleanValues.add( stripXSS( value ) );
            }

            parameters.put( key, cleanValues );
        }

        logger.debug( "XSS Vulnerabilities removed: {}", parameters );
    }
    
    /**
     * Apply the XSS filter to the parameters in a Map
     * @param parameters
     */
    public static void cleanParams( Map<String, String> parameters )
    {
        logger.debug("Checking for XSS Vulnerabilities: {}", parameters);

        for( Map.Entry<String, String> params : parameters.entrySet() )
        {
            String key = params.getKey();
            String value = params.getValue();
            parameters.put( key, stripXSS( value ));
        }

        logger.debug( "XSS Vulnerabilities removed: {}", parameters );
    }

    /**
     * Strips any potential XSS threats out of the value
     * @param value
     * @return
     */
    public static String stripXSS( String value )
    {
        if( value != null )
        {
            // Use the ESAPI library to avoid encoded attacks.
            value = ESAPI.encoder().canonicalize( value );

            // Avoid null characters
            value = value.replaceAll("\0", "");

            // Clean out HTML
            // This clean, removes all html tags. so instead of <script>, it simple removes the <script> tag.
            value = Jsoup.clean(value, Whitelist.none());
        }
        return value;
    }
}