JSF “Error Mac did not verify!” [duplicate]

Question

This question already has answers here:

Getting ViewExpiredException in clustered environment while state saving method is set to client and user session is valid (2 answers)

Closed 3 years ago.

I have been trying to implement some basic push functionality with primefaces in jsf. I have used there counter example http://www.primefaces.org/showcase-labs/push/counter.jsf. Essentially its a button that increments a shared counter. When running this example I always get this error:

ERROR: MAC did not verify!

My understanding is that a mac is generated every session and then checked upon each incoming message to verify that the source hasn't changed (I think). I have not been able to find the cause of this and have looked at other threads such as:

ERROR: MAC did not verify! PrimeFaces

JSF: Mojarra 2.1 to 2.2 migration causing ViewExpiredException

Unfortunately these haven't solved my problem. Both seem to be caused by a ViewExpiredException which I am not getting. The only thing that I have found to stop it is to change the state saving method from client to server in web.xml:

<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>client</param-value>

However when doing this the counter is no longer shared but appears to be per user, which is not what I want. My ultimate goal is to implement a chatroom, which for the most part is there but right now it using short polling which is not very scalable. Having looked at primefaces push I thought it would be ideal but have been struggling to use it.

I have tried on multiple web servers (Tomcat, Jetty and Glassfish) and have tried using different versions of JSF (Mojarra) and versions of primefaces (3.4 and 4.0). I have tested it across multiple browsers and on multiple computers. Sometimes I can increment the counter a few times before I get the error, sometimes it happens straight away. I get no exceptions or servere errors and everything compiles. I'd also like to mention that I have had this error before on other projects, but it has gone away after restarting the server. When using primefaces push it always occurs. Any help will be appreciated.

EDIT

When leaving state saving to server in web.xml to avoid MAC Error, I have noticed that the shared counter works in a per browser basis from the same machine. Meaning if I have multiple tabs or windows, updating the counter in one updates in all of them. But it doesn't work across browsers, a change in the counter in firefox is not reflected in chrome or IE, or the other ways round. It is also not reflected if on two separate computers. I don't know if this helps, but thought I would mention it.

EDIT

After noticing that the bean in the example is session scoped I changed it to application scoped. Of course session scoped means every browser has their own copy. Now the changes are reflected across browser and machines. Back to my original problem, I would still like to know why changing the saving state to server fixes the MAC error, and what the implications of this are ? I assume that the server now has to maintain view states for each session rather than the client, less scalable/more client-server traffic ? From what I've read if you set the saving state to server you can't check for view expired exceptions or stop users from creating views if they already have too many, is this correct ?

Answer 1

Seems your application have dependency problem ViewExpiredException can be handled easily, it is a no problem handle ViewExpiredException

full configured JSF project example JSF2.2 frontend

Answer 2

ByteArrayGuard class randomly outputs "ERROR: MAC did not verify!" messages to the error console. This only occurs when client side viewstate encryption is enabled and that multiple clients are running against the server.

So you must change that class in your Java Server Faces references with...

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 1997-2011 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.faces.renderkit;

import com.sun.faces.util.FacesLogger;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.faces.FacesException;

/**
 * <p>This utility class is to provide both encryption and
 * decryption <code>Ciphers</code> to <code>ResponseStateManager</code>
 * implementations wishing to provide encryption support.</p>
 * 
 * <p>The algorithm used to encrypt byte array is AES with CBC.</p>
 *  
 * <p>Original author Inderjeet Singh, J2EE Blue Prints Team. Modified to suit JSF
 * needs.</p> 
 */
public final class ByteArrayGuard {


     // Log instance for this class
    private static final Logger LOGGER = FacesLogger.RENDERKIT.getLogger();

    private static final int MAC_LENGTH = 32;
    private static final int KEY_LENGTH = 128;
    private static final int IV_LENGTH = 16;

    private static final String KEY_ALGORITHM = "AES";
    private static final String CIPHER_CODE = "AES/CBC/PKCS5Padding";
    private static final String MAC_CODE = "HmacSHA256";
    private SecretKey sk;

    // ------------------------------------------------------------ Constructors

    public ByteArrayGuard() {

        try {
            setupKeyAndMac();
        } catch (Exception e) {
            if (LOGGER.isLoggable(Level.SEVERE)) { 
                LOGGER.log(Level.SEVERE,
                           "Unexpected exception initializing encryption."
                           + "  No encryption will be performed.",
                           e);
            }
            System.err.println("ERROR: Initializing Ciphers");
        }
    }

    // ---------------------------------------------------------- Public Methods    


    /**
     * This method:
     *    Encrypts bytes using a cipher.  
     *    Generates MAC for intialization vector of the cipher
     *    Generates MAC for encrypted data
     *    Returns a byte array consisting of the following concatenated together:
     *       |MAC for cnrypted Data | MAC for Init Vector | Encrypted Data |
     * @param bytes The byte array to be encrypted.
     * @return the encrypted byte array.
     */
    public byte[] encrypt(byte[] bytes) {
        byte[] securedata = null;
        try {
            // Generate IV
            SecureRandom rand = new SecureRandom();
            byte[] iv = new byte[16];
            rand.nextBytes(iv);
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            Cipher encryptCipher = Cipher.getInstance(CIPHER_CODE);
            encryptCipher.init(Cipher.ENCRYPT_MODE, sk, ivspec);
            Mac encryptMac = Mac.getInstance(MAC_CODE);
            encryptMac.init(sk);
            encryptMac.update(iv);
            // encrypt the plaintext
            byte[] encdata = encryptCipher.doFinal(bytes);
            byte[] macBytes = encryptMac.doFinal(encdata);
            byte[] tmp = concatBytes(macBytes, iv);
            securedata = concatBytes(tmp, encdata);
        } catch (Exception e) {
            if (LOGGER.isLoggable(Level.SEVERE)) {
                LOGGER.log(Level.SEVERE,
                           "Unexpected exception initializing encryption."
                           + "  No encryption will be performed.",
                           e);
            }
            return null;
        }
        return securedata;
    }

    /**
     * This method decrypts the provided byte array.
     * The decryption is only performed if the regenerated MAC
     * is the same as the MAC for the received value.
     * @param bytes Encrypted byte array to be decrypted.
     * @return Decrypted byte array.
     */
    public byte[] decrypt(byte[] bytes) {
        try {
            // Extract MAC
            byte[] macBytes = new byte[MAC_LENGTH];
            System.arraycopy(bytes, 0, macBytes, 0, macBytes.length);

            // Extract IV
            byte[] iv = new byte[IV_LENGTH];
            System.arraycopy(bytes, macBytes.length, iv, 0, iv.length);

            // Extract encrypted data
            byte[] encdata = new byte[bytes.length - macBytes.length - iv.length];
            System.arraycopy(bytes, macBytes.length + iv.length, encdata, 0, encdata.length);

            IvParameterSpec ivspec = new IvParameterSpec(iv);
            Cipher decryptCipher = Cipher.getInstance(CIPHER_CODE);
            decryptCipher.init(Cipher.DECRYPT_MODE, sk, ivspec);

            // verify MAC by regenerating it and comparing it with the received value
            Mac decryptMac = Mac.getInstance(MAC_CODE);
            decryptMac.init(sk);
            decryptMac.update(iv);
            decryptMac.update(encdata);
            byte[] macBytesCalculated = decryptMac.doFinal();
            if (Arrays.equals(macBytes, macBytesCalculated)) {
                // continue only if the MAC was valid
                // System.out.println("Valid MAC found!");
                byte[] plaindata = decryptCipher.doFinal(encdata);
                return plaindata;
            } else {
                System.err.println("ERROR: MAC did not verify!");
                return null;
            }
        } catch (Exception e) {
            System.err.println("ERROR: Decrypting:"+e.getCause());
            return null; // Signal to JSF runtime
        }
    }

    // --------------------------------------------------------- Private Methods

    /**
     * Generates secret key.
     * Initializes MAC(s).
     */
    private void setupKeyAndMac() {

        try {
            KeyGenerator kg = KeyGenerator.getInstance(KEY_ALGORITHM);
            kg.init(KEY_LENGTH);   // 256 if you're using the Unlimited Policy Files
            sk = kg.generateKey(); 

        } catch (Exception e) {
            throw new FacesException(e);
        }
    }

    /**
     * This method concatenates two byte arrays
     * @return a byte array of array1||array2
     * @param array1 first byte array to be concatenated
     * @param array2 second byte array to be concatenated
     */
    private static byte[] concatBytes(byte[] array1, byte[] array2) {
        byte[] cBytes = new byte[array1.length + array2.length];
        try {
            System.arraycopy(array1, 0, cBytes, 0, array1.length);
            System.arraycopy(array2, 0, cBytes, array1.length, array2.length);
        } catch(Exception e) {
            throw new FacesException(e);
        }
        return cBytes;
    }    
}

And reload this jar. JSF_REFERENCE