servlets.module.challenge.BrokenCrypto3.java Source code

Introduction

Here is the source code for servlets.module.challenge.BrokenCrypto3.java

Source

package servlets.module.challenge;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;
import java.util.ResourceBundle;

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

import org.apache.log4j.Logger;
import org.owasp.esapi.ESAPI;
import org.owasp.esapi.Encoder;

import utils.ShepherdLogManager;
import utils.Validate;

/**
 * Bad Crypto Challenge Three
 * Really bad crypto algorithm to break. Will reveal key if spaces are submitted
 * <br/><br/>
 * This file is part of the Security Shepherd Project.
 * 
 * The Security Shepherd project is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.<br/>
 * 
 * The Security Shepherd project is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.<br/>
 * 
 * You should have received a copy of the GNU General Public License
 * along with the Security Shepherd project.  If not, see <http://www.gnu.org/licenses/>. 
 * @author Mark Denihan
 *
 */
public class BrokenCrypto3 extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static org.apache.log4j.Logger log = Logger.getLogger(BrokenCrypto3.class);
    private static String levelName = "Broken Crypto Challenge 3";
    public static String levelHash = "2da053b4afb1530a500120a49a14d422ea56705a7e3fc405a77bc269948ccae1";
    public static String levelResult = "thisisthesecurityshepherdabcencryptionkey"; //Is used as encryption key in this level

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //Setting IpAddress To Log and taking header for original IP if forwarded from proxy
        ShepherdLogManager.setRequestIp(request.getRemoteAddr(), request.getHeader("X-Forwarded-For"));

        HttpSession ses = request.getSession(true);
        if (Validate.validateSession(ses)) {
            ShepherdLogManager.setRequestIp(request.getRemoteAddr(), request.getHeader("X-Forwarded-For"),
                    ses.getAttribute("userName").toString());
            log.debug(levelName + " servlet accessed by: " + ses.getAttribute("userName").toString());
            String htmlOutput = new String();

            PrintWriter out = response.getWriter();
            out.print(getServletInfo());

            //Translation Stuff
            Locale locale = new Locale(Validate.validateLanguage(request.getSession()));
            ResourceBundle errors = ResourceBundle.getBundle("i18n.servlets.errors", locale);
            ResourceBundle bundle = ResourceBundle
                    .getBundle("i18n.servlets.challenges.insecureCryptoStorage.insecureCryptoStorage", locale);
            try {
                String userData = request.getParameter("userData");
                log.debug("User Submitted - " + userData);

                log.debug("Decrypting user input");
                //Using level key as encryption key
                String decryptedUserData = decrypt(userData, levelResult);
                log.debug("Decrypted to: " + decryptedUserData);
                Encoder encoder = ESAPI.encoder();
                htmlOutput = "<h2 class='title'>" + bundle.getString("insecureCyrptoStorage.3.plaintextResult")
                        + "</h2><p>" + bundle.getString("insecureCyrptoStorage.3.plaintextResult.message")
                        + "<br/><br/><em>" + encoder.encodeForHTML(decryptedUserData) + "</em></p>";
            } catch (Exception e) {
                log.fatal(levelName + " - " + e.toString());
                htmlOutput = errors.getString("error.funky");
            }
            out.write(htmlOutput);
        } else {
            log.error(levelName + " servlet accessed with no session");
        }
    }

    /**
       * Decrypts the supplied string value using the submitted key
       * @param hash The cipher text to be decrypted
       * @param key The encryption key
       * @return The plain text revealed from the decryption
       * @throws Exception Throws illegal state Exception
       */
    public static String decrypt(String hash, String key) throws Exception {
        try {
            return new String(xor(org.apache.commons.codec.binary.Base64.decodeBase64(hash.getBytes()), key),
                    "UTF-8");
        } catch (java.io.UnsupportedEncodingException ex) {
            throw new IllegalStateException(ex);
        }
    }

    /**
     * XOR Function
     * @param input Byte array to be XOR'd
     * @param key Encryption Key
     * @return
     */
    private static byte[] xor(final byte[] input, String theKey) {
        final byte[] output = new byte[input.length];
        final byte[] secret = theKey.getBytes();
        int spos = 0;
        for (int pos = 0; pos < input.length; pos += 1) {
            output[pos] = (byte) (input[pos] ^ secret[spos]);
            spos += 1;
            if (spos >= secret.length) {
                spos = 0;
            }
        }
        return output;
    }
}