org.simplejavamail.utils.mail.dkim.DomainKeyUtil Maven / Gradle / Ivy
/*
* Copyright © 2021 Benny Bottema ([email protected])
*
* Licensed 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.simplejavamail.utils.mail.dkim;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
/**
* @author Torsten Krause (tk at markenwerk dot net)
* @author Florian Sager
* @since 1.0.0
*/
public final class DomainKeyUtil {
private static final Map CACHE = new HashMap();
private static final Pattern RECORD_PATTERN = Pattern
.compile("(?:\"(.*?)\"(?: |$))|(?:'(.*?)'(?: |$))|(?:(.*?)(?: |$))");
private static final long DEFAULT_CACHE_TTL = 2 * 60 * 60 * 1000;
private static long cacheTtl = DEFAULT_CACHE_TTL;
private DomainKeyUtil() {
}
/**
* Returns the configured TTL (time to live) for retrieved {@link DomainKey} s.
*
* @return The configured TTL for retrieved {@link DomainKey}s.
*/
public static synchronized long getCacheTtl() {
return cacheTtl;
}
/**
* Sets the TTL (time to live) for retrieved {@link DomainKey}s.
*
* @param cacheTtl The TTL for retrieved {@link DomainKey}s.
*/
public static synchronized void setCacheTtl(long cacheTtl) {
if (cacheTtl < 0) {
cacheTtl = DEFAULT_CACHE_TTL;
}
DomainKeyUtil.cacheTtl = cacheTtl;
}
/**
* Retrieves the {@link DomainKey} for the given signing domain and selector.
*
* @param signingDomain The signing domain.
* @param selector The selector.
* @return The retrieved {@link DomainKey}.
* @throws DkimException If the domain key couldn't be retrieved or if either
* the version, key type or service type given in the tags
* of the retrieved domain key is incompatible to this
* library ('DKIM1', 'RSA' and 'email' respectively).
*/
public static synchronized DomainKey getDomainKey(String signingDomain, String selector) throws DkimException {
return getDomainKey(getRecordName(signingDomain, selector));
}
private static synchronized DomainKey getDomainKey(String recordName) throws DkimException {
DomainKey domainKey = CACHE.get(recordName);
if (null != domainKey && 0 != cacheTtl && isRecent(domainKey)) {
return domainKey;
} else {
domainKey = new DomainKey(getTags(recordName));
CACHE.put(recordName, domainKey);
return domainKey;
}
}
private static boolean isRecent(DomainKey domainKey) {
return domainKey.getTimestamp() + cacheTtl > System.currentTimeMillis();
}
/**
* Retrieves the tags of a domain key for the given signing domain and selector.
*
* @param signingDomain The signing domain.
* @param selector The selector.
* @return The retrieved tags.
* @throws DkimException If the domain key couldn't be retrieved.
*/
public static Map getTags(String signingDomain, String selector) throws DkimException {
return getTags(getRecordName(signingDomain, selector));
}
private static Map getTags(String recordName) throws DkimException {
Map tags = new HashMap();
String recordValue = getValue(recordName);
for (String tag : recordValue.split(";")) {
try {
tag = tag.trim();
tags.put(tag.charAt(0), tag.substring(2));
} catch (IndexOutOfBoundsException e) {
throw new DkimException("The tag " + tag + " in RR " + recordName + " couldn't be decoded.", e);
}
}
return tags;
}
/**
* Retrieves the raw domain key for the given signing domain and selector.
*
* @param signingDomain The signing domain.
* @param selector The selector.
* @return The raw domain key.
* @throws DkimException If the domain key couldn't be retrieved.
*/
public static String getValue(String signingDomain, String selector) throws DkimException {
return getValue(getRecordName(signingDomain, selector));
}
private static String getValue(String recordName) throws DkimException {
try {
DirContext dnsContext = new InitialDirContext(getEnvironment());
Attributes attributes = dnsContext.getAttributes(recordName, new String[] { "TXT" });
Attribute txtRecord = attributes.get("txt");
if (txtRecord == null) {
throw new DkimException("There is no TXT record available for " + recordName);
}
StringBuilder builder = new StringBuilder();
NamingEnumeration e = txtRecord.getAll();
while (e.hasMore()) {
builder.append((String) e.next());
}
String value = builder.toString();
if (value.isEmpty()) {
throw new DkimException("Value of RR " + recordName + " couldn't be retrieved");
}
return unquoteRecordValue(value);
} catch (NamingException ne) {
throw new DkimException("Selector lookup failed", ne);
}
}
/*
* Unquote a recordValue string.
*
* The Java DNS provider does something very odd. In the instance there are
* multiple entries for the TXT record, the first is quoted however the second
* is unquoted. That makes removing quotes difficult. In the normal case, we
* should be a "\" \"" string, however, as confirmed in actual records, the last
* item may not be quoted. This seems to happen if there are no spaces.
*
* @param recordValue Domain record value.
*
* @return Domain record value unquoted.
*/
private static String unquoteRecordValue(String recordValue) {
Matcher recordMatcher = RECORD_PATTERN.matcher(recordValue);
StringBuilder builder = new StringBuilder();
while (recordMatcher.find()) {
for (int i = 1; i <= recordMatcher.groupCount(); i++) {
String match = recordMatcher.group(i);
if (null != match) {
builder.append(match);
}
}
}
String unquotedRecordValue = builder.toString();
if (unquotedRecordValue.length() == 0) {
throw new DkimException("Unable to parse DKIM record: " + recordValue);
}
return unquotedRecordValue;
}
private static String getRecordName(String signingDomain, String selector) {
return selector + "._domainkey." + signingDomain;
}
private static Hashtable getEnvironment() {
Hashtable environment = new Hashtable();
environment.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
return environment;
}
}