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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* This code 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 General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
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package com.sun.jndi.dns;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import javax.naming.*;
import javax.naming.spi.*;
import com.sun.jndi.toolkit.url.UrlUtil;
import sun.net.dns.ResolverConfiguration; // available since 1.4.1
/**
* A DnsContextFactory serves as the initial context factory for DNS.
*
* <p> When an initial context is being created, the environment
* property "java.naming.provider.url" should contain a DNS pseudo-URL
* (see DnsUrl) or a space-separated list of them. Multiple URLs must
* all have the same domain value.
* If the property is not set, the default "dns:" is used.
*
* @author Scott Seligman
*/
public class DnsContextFactory implements InitialContextFactory {
private static final String DEFAULT_URL = "dns:";
private static final int DEFAULT_PORT = 53;
public Context getInitialContext(Hashtable<?,?> env) throws NamingException {
if (env == null) {
env = new Hashtable(5);
}
return urlToContext(getInitCtxUrl(env), env);
}
public static DnsContext getContext(String domain,
String[] servers, Hashtable<?,?> env)
throws NamingException {
return new DnsContext(domain, servers, env);
}
/*
* "urls" are used to determine the servers, but any domain
* components are overridden by "domain".
*/
public static DnsContext getContext(String domain,
DnsUrl[] urls, Hashtable env)
throws NamingException {
String[] servers = serversForUrls(urls);
DnsContext ctx = getContext(domain, servers, env);
if (platformServersUsed(urls)) {
ctx.setProviderUrl(constructProviderUrl(domain, servers));
}
return ctx;
}
/*
* Public for use by product test suite.
*/
public static boolean platformServersAvailable() {
return !filterNameServers(
ResolverConfiguration.open().nameservers(), true
).isEmpty();
}
private static Context urlToContext(String url, Hashtable env)
throws NamingException {
DnsUrl[] urls;
try {
urls = DnsUrl.fromList(url);
} catch (MalformedURLException e) {
throw new ConfigurationException(e.getMessage());
}
if (urls.length == 0) {
throw new ConfigurationException(
"Invalid DNS pseudo-URL(s): " + url);
}
String domain = urls[0].getDomain();
// If multiple urls, all must have the same domain.
for (int i = 1; i < urls.length; i++) {
if (!domain.equalsIgnoreCase(urls[i].getDomain())) {
throw new ConfigurationException(
"Conflicting domains: " + url);
}
}
return getContext(domain, urls, env);
}
/*
* Returns all the servers specified in a set of URLs.
* If a URL has no host (or port), the servers configured on the
* underlying platform are used if possible. If no configured
* servers can be found, then fall back to the old behavior of
* using "localhost".
* There must be at least one URL.
*/
private static String[] serversForUrls(DnsUrl[] urls)
throws NamingException {
if (urls.length == 0) {
throw new ConfigurationException("DNS pseudo-URL required");
}
List<String> servers = new ArrayList<>();
for (int i = 0; i < urls.length; i++) {
String server = urls[i].getHost();
int port = urls[i].getPort();
if (server == null && port < 0) {
// No server or port given, so look to underlying platform.
// ResolverConfiguration does some limited caching, so the
// following is reasonably efficient even if called rapid-fire.
List<String> platformServers = filterNameServers(
ResolverConfiguration.open().nameservers(), false);
if (!platformServers.isEmpty()) {
servers.addAll(platformServers);
continue; // on to next URL (if any, which is unlikely)
}
}
if (server == null) {
server = "localhost";
}
servers.add((port < 0)
? server
: server + ":" + port);
}
return servers.toArray(new String[servers.size()]);
}
/*
* Returns true if serversForUrls(urls) would make use of servers
* from the underlying platform.
*/
private static boolean platformServersUsed(DnsUrl[] urls) {
if (!platformServersAvailable()) {
return false;
}
for (int i = 0; i < urls.length; i++) {
if (urls[i].getHost() == null &&
urls[i].getPort() < 0) {
return true;
}
}
return false;
}
/*
* Returns a value for the PROVIDER_URL property (space-separated URL
* Strings) that reflects the given domain and servers.
* Each server is of the form "server[:port]".
* There must be at least one server.
* IPv6 literal host names include delimiting brackets.
*/
private static String constructProviderUrl(String domain,
String[] servers) {
String path = "";
if (!domain.equals(".")) {
try {
path = "/" + UrlUtil.encode(domain, "ISO-8859-1");
} catch (java.io.UnsupportedEncodingException e) {
// assert false : "ISO-Latin-1 charset unavailable";
}
}
StringBuffer buf = new StringBuffer();
for (int i = 0; i < servers.length; i++) {
if (i > 0) {
buf.append(' ');
}
buf.append("dns://").append(servers[i]).append(path);
}
return buf.toString();
}
/*
* Reads environment to find URL(s) of initial context.
* Default URL is "dns:".
*/
private static String getInitCtxUrl(Hashtable env) {
String url = (String) env.get(Context.PROVIDER_URL);
return ((url != null) ? url : DEFAULT_URL);
}
/**
* Removes any DNS server that's not permitted to access
* @param input the input server[:port] list, must not be null
* @param oneIsEnough return output once there exists one ok
* @return the filtered list, all non-permitted input removed
*/
private static List filterNameServers(List input, boolean oneIsEnough) {
SecurityManager security = System.getSecurityManager();
if (security == null || input == null || input.isEmpty()) {
return input;
} else {
List output = new ArrayList();
for (Object o: input) {
if (o instanceof String) {
String platformServer = (String)o;
int colon = platformServer.indexOf(':',
platformServer.indexOf(']') + 1);
int p = (colon < 0)
? DEFAULT_PORT
: Integer.parseInt(
platformServer.substring(colon + 1));
String s = (colon < 0)
? platformServer
: platformServer.substring(0, colon);
try {
security.checkConnect(s, p);
output.add(platformServer);
if (oneIsEnough) {
return output;
}
} catch (SecurityException se) {
continue;
}
}
}
return output;
}
}
}