Charsets.java

/*
 *Copyright 2014 Google Inc. All rights reserved.
 *
 * 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 com.google.testing.security.firingrange.tests.reflected;

import com.google.common.base.Splitter;
import com.google.common.base.Strings;
import com.google.testing.security.firingrange.utils.Responses;
import com.google.testing.security.firingrange.utils.Templates;

import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Handles reflected XSS on parameters on any method, but applies filtering based on
 * restricted charsets.
 */
public class Charsets extends HttpServlet {
  private static final String ECHOED_PARAM = "q";
  
  @Override
  public void service(HttpServletRequest request, HttpServletResponse response) throws IOException {
    String echoedParam = Strings.nullToEmpty(request.getParameter(ECHOED_PARAM));
    String template = Templates.getTemplate(request, getClass());
    String restrictedCharsets = Splitter.on('/').splitToList(request.getPathInfo()).get(2);
    switch(restrictedCharsets) {
      case "SpaceDoubleQuoteSlashEquals":
        if (containsChars(echoedParam, '=', '\\', '"', ' ')) {
          Responses.sendError(response, "Invalid param.", 400);
          return;
        }
        break;
      case "DoubleQuoteSinglequote":
        if (containsChars(echoedParam, '"', '\'')) {
          Responses.sendError(response, "Invalid param.", 400);
          return;
        }
        break;
      default:
        Responses.sendError(response, "Invalid charset.", 400);
        return;
    }
    Responses.sendXssed(response, Templates.replacePayload(template, echoedParam));
  }

  private boolean containsChars(String echoedParam, Character... chars) {
    for (Character character : chars) {
      if (echoedParam.contains(character.toString())) {
        return true;
      }
    }
    return false;
  }
}