Java tutorial
/* * Copyright (c) 2011, Martijn Brinkers, Djigzo. * * This file is part of Djigzo email encryption. * * Djigzo is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License * version 3, 19 November 2007 as published by the Free Software * Foundation. * * Djigzo 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 Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public * License along with Djigzo. If not, see <http://www.gnu.org/licenses/> * * Additional permission under GNU AGPL version 3 section 7 * * If you modify this Program, or any covered work, by linking or * combining it with aspectjrt.jar, aspectjweaver.jar, tyrex-1.0.3.jar, * freemarker.jar, dom4j.jar, mx4j-jmx.jar, mx4j-tools.jar, * spice-classman-1.0.jar, spice-loggerstore-0.5.jar, spice-salt-0.8.jar, * spice-xmlpolicy-1.0.jar, saaj-api-1.3.jar, saaj-impl-1.3.jar, * wsdl4j-1.6.1.jar (or modified versions of these libraries), * containing parts covered by the terms of Eclipse Public License, * tyrex license, freemarker license, dom4j license, mx4j license, * Spice Software License, Common Development and Distribution License * (CDDL), Common Public License (CPL) the licensors of this Program grant * you additional permission to convey the resulting work. */ package mitm.application.djigzo.james.mailets; import java.io.IOException; import java.io.StringReader; import java.security.KeyPair; import java.security.PrivateKey; import javax.mail.MessagingException; import javax.mail.internet.MimeMessage; import javax.mail.internet.MimeUtility; import mitm.common.mail.HeaderUtils; import mitm.common.mail.MailUtils; import org.apache.commons.lang.StringUtils; import org.apache.james.jdkim.DKIMCommon; import org.apache.james.jdkim.DKIMSigner; import org.apache.james.jdkim.exceptions.FailException; import org.apache.mailet.Mail; import org.bouncycastle.openssl.PEMReader; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Digitally signs a message with the DKIM protocol * * @author Martijn Brinkers * */ public class DKIMSign extends AbstractDjigzoMailet { private final static Logger logger = LoggerFactory.getLogger(DKIMSign.class); @Override protected Logger getLogger() { return logger; } /* * The mailet initialization parameters used by this mailet. */ private enum Parameter { PRIVATE_KEY("privateKey"), CONVERT_TO_7BIT("convertTo7Bit"), DKIM_HEADER("dkimHeader"), SIGNATURE_TEMPLATE( "signatureTemplate"), FOLD_SIGNATURE("foldSignature"); private String name; private Parameter(String name) { this.name = name; } }; /* * The private key used to sign the message with */ private PrivateKey privateKey; /* * If true and the message contains 8bit parts, the message will be converted * to 7bit prior to signing. */ private boolean convertTo7Bit; /* * If true the signature will be folded. Only enable foldSignature if header signing * is relaxed otherwise folding will break the DKIM sigature. */ private boolean foldSignature; /* * The DKIM header to use (defaults to DKIM-Signature) */ private String dkimHeader; /* * The DKIM signature template */ private String signatureTemplate; @Override protected void initMailet() throws MessagingException { convertTo7Bit = getBooleanInitParameter(Parameter.CONVERT_TO_7BIT.name, true); foldSignature = getBooleanInitParameter(Parameter.FOLD_SIGNATURE.name, false); dkimHeader = getInitParameter(Parameter.DKIM_HEADER.name, DKIMCommon.DEFAULT_DKIM_HEADER); signatureTemplate = StringUtils.trimToNull(getInitParameter(Parameter.SIGNATURE_TEMPLATE.name)); if (signatureTemplate == null) { throw new MessagingException("signatureTemplate is missing."); } loadPrivateKey(); } protected static PrivateKey parseKey(String pkcs8) throws MessagingException { PrivateKey key = null; pkcs8 = StringUtils.trimToNull(pkcs8); if (pkcs8 != null) { PEMReader pem = new PEMReader(new StringReader(pkcs8)); Object o; try { o = pem.readObject(); } catch (IOException e) { throw new MessagingException("Unable to read PEM encoded private key", e); } if (o instanceof PrivateKey) { key = (PrivateKey) o; } else if (o instanceof KeyPair) { key = ((KeyPair) o).getPrivate(); } else if (o == null) { throw new MessagingException("The PEM encoded blob did not return any object."); } else { throw new MessagingException("The PEM input is not a PrivateKey or KeyPair but a " + o.getClass()); } } return key; } private void loadPrivateKey() throws MessagingException { privateKey = parseKey(getInitParameter(Parameter.PRIVATE_KEY.name)); } protected PrivateKey getPrivateKey(Mail mail) throws MessagingException { return privateKey; } protected String getSignatureTemplate() { return signatureTemplate; } @Override public void serviceMail(Mail mail) { try { MimeMessage message = mail.getMessage(); if (convertTo7Bit) { /* * Before signing, the message should be converted to 7bit to make sure * the signature 'survives' the internet. */ boolean converted = MailUtils.convertTo7Bit(message); if (converted) { message.saveChanges(); } } PrivateKey privateKey = getPrivateKey(mail); if (privateKey != null) { DKIMSigner signer = new DKIMSigner(getSignatureTemplate(), privateKey); signer.setDKIMHeader(dkimHeader); String signature = signer.sign(message); /* * the signature field cannot be folded after signing in the simple mode * because that would break the signature */ if (foldSignature) { signature = MimeUtility.fold(dkimHeader.length(), signature); } HeaderUtils.prependHeaderLine(message, signature); /* * Validate the message to make sure that James can write the message. * * Note: Because normally only a header is added, the message-id is not changed. The * exception to this is when the message is converted from 8bit to 7bit (see above). * When the message is converted from 7bit to 8bit the message-id is changed. */ MailUtils.validateMessage(message); } else { logger.warn("Unable to sign the message because the private key is missing."); } } catch (MessagingException e) { logger.error("DKIM signing failed.", e); } catch (IOException e) { logger.error("DKIM signing failed.", e); } catch (FailException e) { logger.error("DKIM signing failed.", e); } } }