HashSyslogMessageModifier.java

package org.graylog2.syslog4j.impl.message.modifier.hash;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import org.graylog2.syslog4j.SyslogIF;
import org.graylog2.syslog4j.SyslogRuntimeException;
import org.graylog2.syslog4j.impl.message.modifier.AbstractSyslogMessageModifier;
import org.graylog2.syslog4j.util.Base64;
import org.graylog2.syslog4j.util.SyslogUtility;

/**
 * HashSyslogMessageModifier is an implementation of SyslogMessageModifierIF
 * that provides support for Java Cryptographic hashes (MD5, SHA1, SHA256, etc.).
 * <p/>
 * <p>Syslog4j is licensed under the Lesser GNU Public License v2.1.  A copy
 * of the LGPL license is available in the META-INF folder in all
 * distributions of Syslog4j and in the base directory of the "doc" ZIP.</p>
 *
 * @author <syslog4j@productivity.org>
 * @version $Id: HashSyslogMessageModifier.java,v 1.5 2010/10/28 05:10:57 cvs Exp $
 */
public class HashSyslogMessageModifier extends AbstractSyslogMessageModifier {
    private static final long serialVersionUID = 7335757344826206953L;

    protected HashSyslogMessageModifierConfig config = null;

    public static final HashSyslogMessageModifier createMD5() {
        HashSyslogMessageModifier md5 = new HashSyslogMessageModifier(HashSyslogMessageModifierConfig.createMD5());

        return md5;
    }

    public static final HashSyslogMessageModifier createSHA1() {
        HashSyslogMessageModifier sha1 = new HashSyslogMessageModifier(HashSyslogMessageModifierConfig.createSHA1());

        return sha1;
    }

    public static final HashSyslogMessageModifier createSHA160() {
        return createSHA1();
    }

    public static final HashSyslogMessageModifier createSHA256() {
        HashSyslogMessageModifier sha256 = new HashSyslogMessageModifier(HashSyslogMessageModifierConfig.createSHA256());

        return sha256;
    }

    public static final HashSyslogMessageModifier createSHA384() {
        HashSyslogMessageModifier sha384 = new HashSyslogMessageModifier(HashSyslogMessageModifierConfig.createSHA384());

        return sha384;
    }

    public static final HashSyslogMessageModifier createSHA512() {
        HashSyslogMessageModifier sha512 = new HashSyslogMessageModifier(HashSyslogMessageModifierConfig.createSHA512());

        return sha512;
    }

    public HashSyslogMessageModifier(HashSyslogMessageModifierConfig config) throws SyslogRuntimeException {
        super(config);

        this.config = config;

        if (this.config == null) {
            throw new SyslogRuntimeException("Hash config object cannot be null");
        }

        if (this.config.getHashAlgorithm() == null) {
            throw new SyslogRuntimeException("Hash algorithm cannot be null");
        }

        try {
            MessageDigest.getInstance(config.getHashAlgorithm());

        } catch (NoSuchAlgorithmException nsae) {
            throw new SyslogRuntimeException(nsae);
        }
    }

    protected MessageDigest obtainMessageDigest() {
        MessageDigest digest = null;

        try {
            digest = MessageDigest.getInstance(this.config.getHashAlgorithm());

        } catch (NoSuchAlgorithmException nsae) {
            throw new SyslogRuntimeException(nsae);
        }

        return digest;
    }

    public HashSyslogMessageModifierConfig getConfig() {
        return this.config;
    }

    public String modify(SyslogIF syslog, int facility, int level, String message) {
        byte[] messageBytes = SyslogUtility.getBytes(syslog.getConfig(), message);

        MessageDigest digest = obtainMessageDigest();
        byte[] digestBytes = digest.digest(messageBytes);

        String digestString = Base64.encodeBytes(digestBytes, Base64.DONT_BREAK_LINES);

        StringBuffer buffer = new StringBuffer(message);

        buffer.append(this.config.getPrefix());
        buffer.append(digestString);
        buffer.append(this.config.getSuffix());

        return buffer.toString();
    }

    public boolean verify(String message, String base64Hash) {
        byte[] hash = Base64.decode(base64Hash);

        return verify(message, hash);
    }

    public boolean verify(String message, byte[] hash) {
        byte[] messageBytes = SyslogUtility.getBytes(this.config, message);

        MessageDigest digest = obtainMessageDigest();
        byte[] digestBytes = digest.digest(messageBytes);

        return Arrays.equals(digestBytes, hash);
    }
}