content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * 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 under the License.
   */
  
  package org.apache.hadoop.chukwa.util;
  
  import javax.servlet.http.HttpServletRequest;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.jsoup.Jsoup;
  import org.jsoup.safety.Whitelist;
  import org.owasp.esapi.ESAPI;
  
  public class XssFilter {
      private HttpServletRequest request = null;
      private static Log LOG = LogFactory.getLog(XssFilter.class);
  
      public XssFilter() {
      }
  
      public XssFilter(HttpServletRequest request) {
        // Return the cleansed request
        this.request = request;
      }
      
      public String getParameter(String key) {
        String value=null;
        try {
          value=filter(this.request.getParameter(key));
        } catch (Exception e) {
          LOG.info("XssFilter.getParameter: Cannot get parameter for: "+key);
        }
        return value;
      }
      
      public String[] getParameterValues(String key) {
        String[] values=null;
        try {
  	  values  = this.request.getParameterValues(key);
            int i = 0;
            for(String value : values) {
              values[i] = filter(value);
              i++;
            }
        } catch (Exception e) {
  	  LOG.info("XssFilter.getParameterValues: cannot get parameter for: "+key);
        }
        return values;
      }
  
      /**
       * Strips any potential XSS threats out of the value
       * @param value is a string
       * @return filtered string
       */
      public String filter( String value ) {
        if( value == null )
          return null;
       
        // Use the ESAPI library to avoid encoded attacks.
        value = ESAPI.encoder().canonicalize( value );
   
        // Avoid null characters
        value = value.replaceAll("\0", "");
   
        // Clean out HTML
        value = Jsoup.clean( value, Whitelist.none() );
   
        return value;
      }
  }
  