/*
* Copyright 2009-2016 the original author or authors.
*
* 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.springframework.security.remoting.dns;
import java.util.Arrays;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.NameNotFoundException;
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;
/**
* Implementation of DnsResolver which uses JNDI for the DNS queries.
*
* Uses an <b>InitialContextFactory</b> to get the JNDI DirContext. The default
* implementation will just create a new Context with the context factory
* <b>com.sun.jndi.dns.DnsContextFactory</b>
*
* @author Mike Wiesner
* @since 3.0
* @see DnsResolver
* @see InitialContextFactory
*/
public class JndiDnsResolver implements DnsResolver {
private InitialContextFactory ctxFactory = new DefaultInitialContextFactory();
/**
* Allows to inject an own JNDI context factory.
*
* @param ctxFactory factory to use, when a DirContext is needed
* @see InitialDirContext
* @see DirContext
*/
public void setCtxFactory(InitialContextFactory ctxFactory) {
this.ctxFactory = ctxFactory;
}
/*
* (non-Javadoc)
*
* @see
* org.springframework.security.remoting.dns.DnsResolver#resolveIpAddress(java.lang
* .String)
*/
public String resolveIpAddress(String hostname) {
return resolveIpAddress(hostname, this.ctxFactory.getCtx());
}
/*
* (non-Javadoc)
*
* @see
* org.springframework.security.remoting.dns.DnsResolver#resolveServiceEntry(java.
* lang.String, java.lang.String)
*/
public String resolveServiceEntry(String serviceType, String domain) {
return resolveServiceEntry(serviceType, domain, this.ctxFactory.getCtx());
}
/*
* (non-Javadoc)
*
* @see
* org.springframework.security.remoting.dns.DnsResolver#resolveServiceIpAddress(java
* .lang.String, java.lang.String)
*/
public String resolveServiceIpAddress(String serviceType, String domain) {
DirContext ctx = this.ctxFactory.getCtx();
String hostname = resolveServiceEntry(serviceType, domain, ctx);
return resolveIpAddress(hostname, ctx);
}
// This method is needed, so that we can use only one DirContext for
// resolveServiceIpAddress().
private String resolveIpAddress(String hostname, DirContext ctx) {
try {
Attribute dnsRecord = lookup(hostname, ctx, "A");
// There should be only one A record, therefore it is save to return
// only the first.
return dnsRecord.get().toString();
}
catch (NamingException e) {
throw new DnsLookupException("DNS lookup failed for: " + hostname, e);
}
}
// This method is needed, so that we can use only one DirContext for
// resolveServiceIpAddress().
private String resolveServiceEntry(String serviceType, String domain,
DirContext ctx) {
String result = null;
try {
String query = new StringBuilder("_").append(serviceType).append("._tcp.")
.append(domain).toString();
Attribute dnsRecord = lookup(query, ctx, "SRV");
// There are maybe more records defined, we will return the one
// with the highest priority (lowest number) and the highest weight
// (highest number)
int highestPriority = -1;
int highestWeight = -1;
for (NamingEnumeration<?> recordEnum = dnsRecord.getAll(); recordEnum
.hasMoreElements();) {
String[] record = recordEnum.next().toString().split(" ");
if (record.length != 4) {
throw new DnsLookupException("Wrong service record for query " + query
+ ": [" + Arrays.toString(record) + "]");
}
int priority = Integer.parseInt(record[0]);
int weight = Integer.parseInt(record[1]);
// we have a new highest Priority, so forget also the highest weight
if (priority < highestPriority || highestPriority == -1) {
highestPriority = priority;
highestWeight = weight;
result = record[3].trim();
}
// same priority, but higher weight
if (priority == highestPriority && weight > highestWeight) {
highestWeight = weight;
result = record[3].trim();
}
}
}
catch (NamingException e) {
throw new DnsLookupException(
"DNS lookup failed for service " + serviceType + " at " + domain, e);
}
// remove the "." at the end
if (result.endsWith(".")) {
result = result.substring(0, result.length() - 1);
}
return result;
}
private Attribute lookup(String query, DirContext ictx, String recordType) {
try {
Attributes dnsResult = ictx.getAttributes(query, new String[] { recordType });
return dnsResult.get(recordType);
}
catch (NamingException e) {
if (e instanceof NameNotFoundException) {
throw new DnsEntryNotFoundException("DNS entry not found for:" + query,
e);
}
throw new DnsLookupException("DNS lookup failed for: " + query, e);
}
}
private static class DefaultInitialContextFactory implements InitialContextFactory {
public DirContext getCtx() {
Hashtable<String, String> env = new Hashtable<String, String>();
env.put(Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.dns.DnsContextFactory");
env.put(Context.PROVIDER_URL, "dns:"); // This is needed for IBM JDK/JRE
InitialDirContext ictx;
try {
ictx = new InitialDirContext(env);
}
catch (NamingException e) {
throw new DnsLookupException(
"Cannot create InitialDirContext for DNS lookup", e);
}
return ictx;
}
}
}