/*

  *  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.myfaces.shared_impl.util;

 import java.io.ByteArrayInputStream;

 import java.io.ByteArrayOutputStream;

 import java.io.IOException;

 import java.io.ObjectInputStream;

 import java.io.ObjectOutputStream;

 import java.io.UnsupportedEncodingException;

 import java.security.AccessController;

 import java.security.NoSuchAlgorithmException;

 import java.security.PrivilegedActionException;

 import java.security.PrivilegedExceptionAction;

 import java.util.Random;

 import java.util.zip.GZIPInputStream;

 import java.util.zip.GZIPOutputStream;

 import javax.crypto.Cipher;

 import javax.crypto.KeyGenerator;

 import javax.crypto.Mac;

 import javax.crypto.SecretKey;

 import javax.crypto.spec.IvParameterSpec;

 import javax.crypto.spec.SecretKeySpec;

 import javax.faces.FacesException;

 import javax.faces.application.ViewExpiredException;

 import javax.faces.context.ExternalContext;

 import javax.servlet.ServletContext;

 import org.apache.commons.codec.binary.Base64;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;

 import org.apache.myfaces.shared_impl.util.serial.SerialFactory;

 /**

  * <p>This Class exposes a handful of methods related to encryption,

  * compression and serialization.</p>

  * 

  * <ul>

  * <li>ISO-8859-1 is the character set used.</li>

  * <li>GZIP is used for all compression/decompression.</li>

  * <li>Base64 is used for all encoding and decoding.</li>

  * <li>DES is the default encryption algorithm</li>

  * <li>ECB is the default mode</li>

  * <li>PKCS5Padding is the default padding</li>

  * <li>HmacSHA1 is the default MAC algorithm</li>

  * <li>The default algorithm can be overridden using the

  * <i>org.apache.myfaces.ALGORITHM</i> parameter</li>

  * <li>The default mode and padding can be overridden using the

  * <i>org.apache.myfaces.ALGORITHM.PARAMETERS</i> parameter</li>

  * <li>This class has not been tested with modes other than ECB and CBC</li>

  * <li>An initialization vector can be specified via the

  * <i>org.apache.myfaces.ALGORITHM.IV</i> parameter</li>

  * <li>The default MAC algorithm can be overridden using the

  * <i>org.apache.myfaces.MAC_ALGORITHM</i> parameter</li>

  * </ul>

  *

  * <p>The secret is interpretted as base 64 encoded.  In other

  * words, if your secret is "76543210", you would put "NzY1NDMyMTA=" in

  * the deployment descriptor.  This is needed so that key values are not

  * limited to just values composed of printable characters.</p>

  *

  * <p>If you are using CBC mode encryption, you <b>must</b> specify an

  * initialization vector.</p>

  *

  * <p>If you are using the AES algorithm and getting a SecurityException

  * complaining about keysize, you most likely need to get the unlimited

  * strength jurisdiction policy files from a place like

  * http://java.sun.com/j2se/1.4.2/download.html .</p>

  *

  * @author Dennis C. Byrne

  * @see org.apache.myfaces.webapp.StartupServletContextListener

  */

 public final class StateUtils {

     private static final Log log = LogFactory.getLog(StateUtils.class);

     public static final String ZIP_CHARSET = "ISO-8859-1";

     public static final String DEFAULT_ALGORITHM = "DES";

     public static final String DEFAULT_ALGORITHM_PARAMS = "ECB/PKCS5Padding";

     public static final String INIT_PREFIX = "org.apache.myfaces.";

     /**

      * Indicate if the view state is encrypted or not. By default, encryption is enabled.

      */

     @JSFWebConfigParam(name="org.apache.myfaces.USE_ENCRYPTION",since="1.1",defaultValue="true",expectedValues="true,false")

     public static final String USE_ENCRYPTION = INIT_PREFIX + "USE_ENCRYPTION";

     /**

      * Defines the secret (Base64 encoded) used to initialize the secret key

      * for encryption algorithm. See MyFaces wiki/web site documentation 

      * for instructions on how to configure an application for 

      * different encryption strengths.

      */

     @JSFWebConfigParam(name="org.apache.myfaces.SECRET",since="1.1")

     public static final String INIT_SECRET = INIT_PREFIX + "SECRET";

     /**

      * Indicate the encryption algorithm used for encrypt the view state.

      */

     @JSFWebConfigParam(name="org.apache.myfaces.ALGORITHM",since="1.1",defaultValue="DES")

     public static final String INIT_ALGORITHM = INIT_PREFIX + "ALGORITHM";

     /**

      * If is set to "false", the secret key used for encryption algorithm is not cached. This is used

      * when the returned SecretKey for encryption algorithm is not thread safe. 

      */

     @JSFWebConfigParam(name="org.apache.myfaces.SECRET.CACHE",since="1.1")

     public static final String INIT_SECRET_KEY_CACHE = INIT_SECRET + ".CACHE";

     /**

      * Defines the initialization vector (Base64 encoded) used for the encryption algorithm

      */

     @JSFWebConfigParam(name="org.apache.myfaces.ALGORITHM.IV",since="1.1")

     public static final String INIT_ALGORITHM_IV = INIT_ALGORITHM + ".IV";

     /**

      * Defines the default mode and padding used for the encryption algorithm

      */

     @JSFWebConfigParam(name="org.apache.myfaces.ALGORITHM.PARAMETERS",since="1.1",defaultValue="ECB/PKCS5Padding")

     public static final String INIT_ALGORITHM_PARAM = INIT_ALGORITHM + ".PARAMETERS";

     /**

      * Defines the factory class name using for serialize/deserialize the view state returned 

      * by state manager into a byte array. The expected class must implement

      * org.apache.myfaces.shared_impl.util.serial.SerialFactory interface.

      */

     @JSFWebConfigParam(name="org.apache.myfaces.SERIAL_FACTORY", since="1.1")

     public static final String SERIAL_FACTORY = INIT_PREFIX + "SERIAL_FACTORY";

     /**

      * Indicate if the view state should be compressed before encrypted(optional) and encoded

      */

     @JSFWebConfigParam(name="org.apache.myfaces.COMPRESS_STATE_IN_CLIENT",since="1.1",defaultValue="false",expectedValues="true,false")

     public static final String COMPRESS_STATE_IN_CLIENT = INIT_PREFIX + "COMPRESS_STATE_IN_CLIENT";

     public static final String DEFAULT_MAC_ALGORITHM = "HmacSHA1";

     /**

      * Indicate the algorithm used to calculate the Message Authentication Code that is

      * added to the view state.

      */

     @JSFWebConfigParam(name="org.apache.myfaces.MAC_ALGORITHM",defaultValue="HmacSHA1")

     public static final String INIT_MAC_ALGORITHM = "org.apache.myfaces.MAC_ALGORITHM";

     /**

      * Define the initialization code that are used to initialize the secret key used

      * on the Message Authentication Code algorithm

      */

     @JSFWebConfigParam(name="org.apache.myfaces.MAC_SECRET")

     public static final String INIT_MAC_SECRET = "org.apache.myfaces.MAC_SECRET";

     /**

      * If is set to "false", the secret key used for MAC algorithm is not cached. This is used

      * when the returned SecretKey for mac algorithm is not thread safe. 

      */

     @JSFWebConfigParam(name="org.apache.myfaces.MAC_SECRET.CACHE")

     public static final String INIT_MAC_SECRET_KEY_CACHE = "org.apache.myfaces.MAC_SECRET.CACHE";

     /** Utility class, do not instatiate */

     private StateUtils()

     {

         //nope

     }

     private static void testConfiguration(ExternalContext ctx){

         String algorithmParams = ctx.getInitParameter(INIT_ALGORITHM_PARAM);

         if (algorithmParams == null)

         {

             algorithmParams = ctx.getInitParameter(INIT_ALGORITHM_PARAM.toLowerCase());

         }

         String iv = ctx.getInitParameter(INIT_ALGORITHM_IV);

         if (iv == null)

         {

             iv = ctx.getInitParameter(INIT_ALGORITHM_IV.toLowerCase());

         }

         if (algorithmParams != null && algorithmParams.startsWith("CBC") )

         {

             if(iv == null)

                 throw new FacesException(INIT_ALGORITHM_PARAM +

                                     " parameter has been set with CBC mode," +

                                     " but no initialization vector has been set " +

                                     " with " + INIT_ALGORITHM_IV);

         }

     }

     public static boolean enableCompression(ExternalContext ctx)

     {

         if(ctx == null)

             throw new NullPointerException("ExternalContext ctx");

         return "true".equals(ctx.getInitParameter(COMPRESS_STATE_IN_CLIENT));

     }

     public static boolean isSecure(ExternalContext ctx)

     {

         if(ctx == null)

             throw new NullPointerException("ExternalContext ctx");

         return ! "false".equals(ctx.getInitParameter(USE_ENCRYPTION));

     }

     /**

      * This fires during the Render Response phase, saving state.

      */

     public static final String construct(Object object, ExternalContext ctx){

         byte[] bytes = getAsByteArray(object, ctx);

         if( enableCompression(ctx) )

                 bytes = compress(bytes);

         if(isSecure(ctx))

                 bytes = encrypt(bytes, ctx);

         bytes = encode(bytes);

         try

         {

             return new String(bytes, ZIP_CHARSET);

         }

         catch (UnsupportedEncodingException e)

         {

             throw new FacesException(e);

         }

     }

     /**

      * Performs serialization with the serialization provider created by the 

      * SerialFactory.  

      * 

      * @param object

      * @param ctx

      * @return

      */

     public static final byte[] getAsByteArray(Object object, ExternalContext ctx)

     {

         ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

         // get the Factory that was instantiated @ startup

         SerialFactory serialFactory = (SerialFactory) ctx.getApplicationMap().get(SERIAL_FACTORY);

         if(serialFactory == null)

             throw new NullPointerException("serialFactory");

         try

         {

             ObjectOutputStream writer = serialFactory.getObjectOutputStream(outputStream);

             writer.writeObject(object);

             byte[] bytes = outputStream.toByteArray();

             writer.close();

             outputStream.close();

             writer = null;

             outputStream = null;

             return bytes;

         }

         catch (IOException e)

         {

             throw new FacesException(e);

         }

     }

     public static byte[] encrypt(byte[] insecure, ExternalContext ctx)

     {

         if (ctx == null)

             throw new NullPointerException("ExternalContext ctx");

         testConfiguration(ctx);

         SecretKey secretKey = (SecretKey) getSecret(ctx);

         String algorithm = findAlgorithm(ctx);

         String algorithmParams = findAlgorithmParams(ctx);

         byte[] iv = findInitializationVector(ctx);

         SecretKey macSecretKey = (SecretKey) getMacSecret(ctx);

         String macAlgorithm = findMacAlgorithm(ctx);

         try

         {

             // keep local to avoid threading issue

             Mac mac = Mac.getInstance(macAlgorithm);

             mac.init(macSecretKey);

             Cipher cipher = Cipher.getInstance(algorithm + "/" + algorithmParams);

             if (iv != null)

             {

                 IvParameterSpec ivSpec = new IvParameterSpec(iv);

                 cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);

             }

             else

             {

                 cipher.init(Cipher.ENCRYPT_MODE, secretKey);

             }

             if (log.isDebugEnabled())

             {

                 log.debug("encrypting w/ " + algorithm + "/" + algorithmParams);

             }

             //EtM Composition Approach

             int macLenght = mac.getMacLength();

             byte[] secure = new byte[cipher.getOutputSize(insecure.length)+ macLenght];

             int secureCount = cipher.doFinal(insecure,0,insecure.length,secure);

             mac.update(secure, 0, secureCount);

             mac.doFinal(secure, secureCount);

             return secure;

         }

         catch (Exception e)

         {

             throw new FacesException(e);

         }

     }

     public static final byte[] compress(byte[] bytes)

     {

         ByteArrayOutputStream baos = new ByteArrayOutputStream();

         try

         {

             GZIPOutputStream gzip = new GZIPOutputStream(baos);

             gzip.write(bytes, 0, bytes.length);

             gzip.finish();

             byte[] fewerBytes = baos.toByteArray();

             gzip.close();

             baos.close();

             gzip = null;

             baos = null;

             return fewerBytes;

         }

         catch (IOException e)

         {

             throw new FacesException(e);

         }

     }

     public static final byte[] encode(byte[] bytes)

     {

           return new Base64().encode(bytes);

     }

     /**

      * This fires during the Restore View phase, restoring state.

      */

     public static final Object reconstruct(String string, ExternalContext ctx)

     {

         byte[] bytes;

         try

         {

             if(log.isDebugEnabled())

                 log.debug("Processing state : "+string);

             bytes = string.getBytes(ZIP_CHARSET);

             bytes = decode(bytes);

             if(isSecure(ctx))

                 bytes = decrypt(bytes, ctx);

             if( enableCompression(ctx) )

                 bytes = decompress(bytes);

             return getAsObject(bytes, ctx);

         }

         catch (Throwable e)

         {

             if (log.isErrorEnabled())

             {

                 log.error("View State cannot be reconstructed", e);

             }

             return null;

         }

     }

     public static final byte[] decode(byte[] bytes)

     {

           return new Base64().decode(bytes);

     }

     public static final byte[] decompress(byte[] bytes)

     {

         if(bytes == null)

             throw new NullPointerException("byte[] bytes");

         ByteArrayInputStream bais = new ByteArrayInputStream(bytes);

         ByteArrayOutputStream baos = new ByteArrayOutputStream();

         byte[] buffer = new byte[bytes.length];

         int length;

         try

         {

             GZIPInputStream gis = new GZIPInputStream(bais);

             while ((length = gis.read(buffer)) != -1)

             {

                 baos.write(buffer, 0, length);

             }

             byte[] moreBytes = baos.toByteArray();

             baos.close();

             bais.close();

             gis.close();

             baos = null;

             bais = null;

             gis = null;

             return moreBytes;

         }

         catch (IOException e)

         {

             throw new FacesException(e);

         }

     }

     public static byte[] decrypt(byte[] secure, ExternalContext ctx)

     {

         if (ctx == null)

             throw new NullPointerException("ExternalContext ctx");

         testConfiguration(ctx);

         SecretKey secretKey = (SecretKey) getSecret(ctx);

         String algorithm = findAlgorithm(ctx);

         String algorithmParams = findAlgorithmParams(ctx);

         byte[] iv = findInitializationVector(ctx);

         SecretKey macSecretKey = (SecretKey) getMacSecret(ctx);

         String macAlgorithm = findMacAlgorithm(ctx);

         try

         {

             // keep local to avoid threading issue

             Mac mac = Mac.getInstance(macAlgorithm);

             mac.init(macSecretKey);

             Cipher cipher = Cipher.getInstance(algorithm + "/"

                     + algorithmParams);

             if (iv != null)

             {

                 IvParameterSpec ivSpec = new IvParameterSpec(iv);

                 cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);

             }

             else

             {

                 cipher.init(Cipher.DECRYPT_MODE, secretKey);

             }

             if (log.isDebugEnabled())

             {

                 log.debug("decrypting w/ " + algorithm + "/" + algorithmParams);

             }

             //EtM Composition Approach

             int macLenght = mac.getMacLength();

             mac.update(secure, 0, secure.length-macLenght);

             byte[] signedDigestHash = mac.doFinal();

             boolean isMacEqual = true;

             for (int i = 0; i < signedDigestHash.length; i++)

             {

                 if (signedDigestHash[i] != secure[secure.length-macLenght+i])

                 {

                     isMacEqual = false;

                     break;

                 }

             }

             if (!isMacEqual)

             {

                 throw new ViewExpiredException();

             }

             return cipher.doFinal(secure, 0, secure.length-macLenght);

         }

         catch (Exception e)

         {

             throw new FacesException(e);

         }

     }

     /**

      * Performs deserialization with the serialization provider created from the

      * SerialFactory.

      * 

      * @param bytes

      * @param ctx

      * @return

      */

     public static final Object getAsObject(byte[] bytes, ExternalContext ctx)

     {

         ByteArrayInputStream input = null;

         try

         {

             input = new ByteArrayInputStream(bytes);

             // get the Factory that was instantiated @ startup

             SerialFactory serialFactory = (SerialFactory) ctx.getApplicationMap().get(SERIAL_FACTORY);

             if(serialFactory == null)

                 throw new NullPointerException("serialFactory");

             ObjectInputStream s = null;

             Exception pendingException = null;

             try

             {

                 s = serialFactory.getObjectInputStream(input); 

                 Object object = null;

                 if (System.getSecurityManager() != null)

                 {

                     final ObjectInputStream ois = s;

                     object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>()

                     {

                         //Put IOException and ClassNotFoundException as "checked" exceptions,

                         //so AccessController wrap them in a PrivilegedActionException

                         public Object run() throws  PrivilegedActionException, IOException, ClassNotFoundException

                         {

                             return ois.readObject();

                         }

                     });

                     // Since s has the same instance as ois,

                     // we don't need to close it here, rather

                     // close it on the finally block related to s

                     // and avoid duplicate close exceptions

                     // finally

                     // {

                     //    ois.close();

                     // }

                 }

                 else

                 {

                     object = s.readObject();

                 }

                 return object;

             }

             catch (Exception e)

             {

                 pendingException = e;

                 throw new FacesException(e);

             }

             finally

             {

                 if (s != null)

                 {

                     try

                     {

                         s.close();

                     }

                     catch (IOException e)

                     {

                         // If a previous exception is thrown 

                         // ignore this, but if not, wrap it in a

                         // FacesException and throw it. In this way

                         // we preserve the original semantic of this

                         // method, but we handle correctly the case

                         // when we close a stream. Obviously, the 

                         // information about this exception is lost,

                         // but note that the interesting information 

                         // is always on pendingException, since we

                         // only do a readObject() on the outer try block.

                         if (pendingException == null)

                         {

                             throw new FacesException(e);

                         }                        

                     }

                     finally

                     {

                         s = null;

                     }

                 }

             }

         }

         finally

         {

             if (input != null)

             {

                 try

                 {

                     input.close();

                 }

                 catch (IOException e)

                 {

                     //ignore it, because ByteArrayInputStream.close has

                     //no effect, but it is better to call close and preserve

                     //semantic from previous code.

                 }

                 finally

                 {

                     input = null;

                 }

             }

         }

     }

     /**

      * Utility method for generating base 64 encoded strings.

      * 

      * @param args

      * @throws UnsupportedEncodingException

      */

     public static void main (String[] args) throws UnsupportedEncodingException

     {

         byte[] bytes = encode(args[0].getBytes(ZIP_CHARSET));

           System.out.println(new String(bytes, ZIP_CHARSET));

     }

     private static byte[] findInitializationVector(ExternalContext ctx) {

         byte[] iv = null;

         String _iv = ctx.getInitParameter(INIT_ALGORITHM_IV);

         if(_iv == null)

         {

             _iv = ctx.getInitParameter(INIT_ALGORITHM_IV.toLowerCase());

         }

         if (_iv != null)

             iv = new Base64().decode(_iv.getBytes());

         return iv;

     }

     private static String findAlgorithmParams(ExternalContext ctx) {

         String algorithmParams = ctx.getInitParameter(INIT_ALGORITHM_PARAM);

         if (algorithmParams == null)

         {

             algorithmParams = ctx.getInitParameter(INIT_ALGORITHM_PARAM.toLowerCase());

         }

         if (algorithmParams == null)

         {

             algorithmParams = DEFAULT_ALGORITHM_PARAMS;

         }

         if (log.isDebugEnabled())

         {

             log.debug("Using algorithm paramaters " + algorithmParams);

         }

         return algorithmParams;

     }

     private static String findAlgorithm(ExternalContext ctx) {

         String algorithm = ctx.getInitParameter(INIT_ALGORITHM);

         if (algorithm == null)

         {

             algorithm = ctx.getInitParameter(INIT_ALGORITHM.toLowerCase());

         }

         return findAlgorithm( algorithm );

     }

     private static String findAlgorithm(ServletContext ctx) {

         String algorithm = ctx.getInitParameter(INIT_ALGORITHM);

         if (algorithm == null)

         {

             algorithm = ctx.getInitParameter(INIT_ALGORITHM.toLowerCase());

         }

         return findAlgorithm( algorithm );

     }

     private static String findAlgorithm(String initParam) {

         if (initParam == null)

         {

             initParam = DEFAULT_ALGORITHM;

         }

         if (log.isDebugEnabled())

         {

             log.debug("Using algorithm " + initParam);

         }

         return initParam;

     }

     /**

      * Does nothing if the user has disabled the SecretKey cache. This is

      * useful when dealing with a JCA provider whose SecretKey 

      * implementation is not thread safe.

      * 

      * Instantiates a SecretKey instance based upon what the user has 

      * specified in the deployment descriptor.  The SecretKey is then 

      * stored in application scope where it can be used for all requests.

      */

     public static void initSecret(ServletContext ctx){

         if(ctx == null)

             throw new NullPointerException("ServletContext ctx");

         if (log.isDebugEnabled())

             log.debug("Storing SecretKey @ " + INIT_SECRET_KEY_CACHE);

         // Create and store SecretKey on application scope

         String cache = ctx.getInitParameter(INIT_SECRET_KEY_CACHE);

         if(cache == null)

         {

             cache = ctx.getInitParameter(INIT_SECRET_KEY_CACHE.toLowerCase());

         }

         if (!"false".equals(cache))

         {

             String algorithm = findAlgorithm(ctx);

             // you want to create this as few times as possible

             ctx.setAttribute(INIT_SECRET_KEY_CACHE, new SecretKeySpec(findSecret(ctx, algorithm), algorithm));

         }

         if (log.isDebugEnabled())

             log.debug("Storing SecretKey @ " + INIT_MAC_SECRET_KEY_CACHE);

         String macCache = ctx.getInitParameter(INIT_MAC_SECRET_KEY_CACHE);

         if(macCache == null)

         {

             macCache = ctx.getInitParameter(INIT_MAC_SECRET_KEY_CACHE.toLowerCase());

         }

         if (!"false".equals(macCache))

         {

             String macAlgorithm = findMacAlgorithm(ctx);

             // init mac secret and algorithm 

             ctx.setAttribute(INIT_MAC_SECRET_KEY_CACHE, new SecretKeySpec(findMacSecret(ctx, macAlgorithm), macAlgorithm));

         }

     }

     private static SecretKey getSecret(ExternalContext ctx)

     {

         Object secretKey = (SecretKey) ctx.getApplicationMap().get(INIT_SECRET_KEY_CACHE);

         if (secretKey == null)

         {

             String cache = ctx.getInitParameter(INIT_SECRET_KEY_CACHE);

             if(cache == null)

             {

                 cache = ctx.getInitParameter(INIT_SECRET_KEY_CACHE.toLowerCase());

             }

             if ("false".equals(cache))

             {

                 // No cache is used. This option is activated

                 String secret = ctx.getInitParameter(INIT_SECRET);

                 if (secret == null)

                 {

                     secret = ctx.getInitParameter(INIT_SECRET.toLowerCase());

                 }

                 if (secret == null)

                 {

                     throw new NullPointerException("Could not find secret using key '" + INIT_SECRET + "'");

                 }

                 String algorithm = findAlgorithm(ctx);

                 secretKey = new SecretKeySpec(findSecret(ctx, algorithm), algorithm);

             }

             else

             {

                 throw new NullPointerException("Could not find SecretKey in application scope using key '" 

                         + INIT_SECRET_KEY_CACHE + "'");

             }

         }

         if( ! ( secretKey instanceof SecretKey ) )

             throw new ClassCastException("Did not find an instance of SecretKey "

                     + "in application scope using the key '" + INIT_SECRET_KEY_CACHE + "'");

         return (SecretKey) secretKey;

     }

     private static byte[] findSecret(ExternalContext ctx, String algorithm)

     {

         String secret = ctx.getInitParameter(INIT_SECRET);

         if (secret == null)

         {

             secret = ctx.getInitParameter(INIT_SECRET.toLowerCase());

         }

         return findSecret(secret, algorithm);

     }    

     private static byte[] findSecret(ServletContext ctx, String algorithm)

     {

         String secret = ctx.getInitParameter(INIT_SECRET);

         if (secret == null)

         {

             secret = ctx.getInitParameter(INIT_SECRET.toLowerCase());

         }

         return findSecret(secret, algorithm);

     }

     private static byte[] findSecret(String secret, String algorithm) {

         byte[] bytes = null;

         if(secret == null)

         {

             try

             {

                 KeyGenerator kg = KeyGenerator.getInstance(algorithm);

                 bytes = kg.generateKey().getEncoded();

                 if(log.isDebugEnabled())

                     log.debug("generated random password of length " + bytes.length);

             }

             catch (NoSuchAlgorithmException e)

             {

                 // Generate random password length 8, 

                 int length = 8;

                 bytes = new byte[length];

                 new Random().nextBytes(bytes);

                 if(log.isDebugEnabled())

                     log.debug("generated random password of length " + length);

             }

         }

         else 

         {

             bytes = new Base64().decode(secret.getBytes());

         }

         return bytes;

     }

     private static String findMacAlgorithm(ExternalContext ctx) {

         String algorithm = ctx.getInitParameter(INIT_MAC_ALGORITHM);

         if (algorithm == null)

         {

             algorithm = ctx.getInitParameter(INIT_MAC_ALGORITHM.toLowerCase());

         }

         return findMacAlgorithm( algorithm );

     }

     private static String findMacAlgorithm(ServletContext ctx) {

         String algorithm = ctx.getInitParameter(INIT_MAC_ALGORITHM);

         if (algorithm == null)

         {

             algorithm = ctx.getInitParameter(INIT_MAC_ALGORITHM.toLowerCase());

         }

         return findMacAlgorithm( algorithm );

     }

     private static String findMacAlgorithm(String initParam) {

         if (initParam == null)

         {

             initParam = DEFAULT_MAC_ALGORITHM;

         }

         if (log.isDebugEnabled())

         {

             log.debug("Using algorithm " + initParam);

         }

         return initParam;

     }

     private static SecretKey getMacSecret(ExternalContext ctx)

     {

         Object secretKey = (SecretKey) ctx.getApplicationMap().get(INIT_MAC_SECRET_KEY_CACHE);

         if (secretKey == null)

         {

             String cache = ctx.getInitParameter(INIT_MAC_SECRET_KEY_CACHE);

             if(cache == null)

             {

                 cache = ctx.getInitParameter(INIT_MAC_SECRET_KEY_CACHE.toLowerCase());

             }

             if ("false".equals(cache))

             {

                 // No cache is used. This option is activated

                 String secret = ctx.getInitParameter(INIT_MAC_SECRET);

                 if (secret == null)

                 {

                     secret = ctx.getInitParameter(INIT_MAC_SECRET.toLowerCase());

                 }

                 if (secret == null)

                 {

                     throw new NullPointerException("Could not find secret using key '" + INIT_MAC_SECRET + "'");

                 }

                 String macAlgorithm = findMacAlgorithm(ctx);

                 secretKey = new SecretKeySpec(findMacSecret(ctx, macAlgorithm), macAlgorithm);

             }

             else

             {

                 throw new NullPointerException("Could not find SecretKey in application scope using key '" 

                         + INIT_MAC_SECRET_KEY_CACHE + "'");

             }

         }

         if( ! ( secretKey instanceof SecretKey ) )

             throw new ClassCastException("Did not find an instance of SecretKey "

                     + "in application scope using the key '" + INIT_MAC_SECRET_KEY_CACHE + "'");

         return (SecretKey) secretKey;

     }

     private static byte[] findMacSecret(ExternalContext ctx, String algorithm)

     {

         String secret = ctx.getInitParameter(INIT_MAC_SECRET);

         if (secret == null)

         {

             secret = ctx.getInitParameter(INIT_MAC_SECRET.toLowerCase());

         }

         return findMacSecret(secret, algorithm);

     }    

     private static byte[] findMacSecret(ServletContext ctx, String algorithm)

     {

         String secret = ctx.getInitParameter(INIT_MAC_SECRET);

         if (secret == null)

         {

             secret = ctx.getInitParameter(INIT_MAC_SECRET.toLowerCase());

         }

         return findMacSecret(secret, algorithm);

     }

     private static byte[] findMacSecret(String secret, String algorithm) {

         byte[] bytes = null;

         if(secret == null)

         {

             try

             {

                 KeyGenerator kg = KeyGenerator.getInstance(algorithm);

                 bytes = kg.generateKey().getEncoded();

                 if(log.isDebugEnabled())

                     log.debug("generated random mac password of length " + bytes.length);

             }

             catch (NoSuchAlgorithmException e)

             {

                 // Generate random password length 8, 

                 int length = 8;

                 bytes = new byte[length];

                 new Random().nextBytes(bytes);

                 if(log.isDebugEnabled())

                     log.debug("generated random mac password of length " + length);

             }

         }

         else 

         {

             bytes = new Base64().decode(secret.getBytes());

         }

         return bytes;

     }

 }