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* 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
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package jdk.dns.client.internal;
import jdk.dns.client.internal.util.ReloadTracker;
import jdk.dns.conf.DnsResolverConfiguration;
import sun.net.util.IPAddressUtil;
import java.net.InetAddress;
import java.net.ProtocolFamily;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Predicate;
import java.util.stream.Stream;
public class HostsFileResolver {
private static final String HOSTS_FILE_LOCATION_PROPERTY_VALUE =
AccessController.doPrivileged((PrivilegedAction<String>)
() -> System.getProperty("jdk.dns.client.hosts.file",
DnsResolverConfiguration.getDefaultHostsFileLocation())
);
private static final ReadWriteLock LOCK = new ReentrantReadWriteLock();
// 300 seconds, similar to DnsResolverConfiguration in millis since Epoch
private static final long REFRESH_TIMEOUT_NANOS = 300_000_000_000L;
private static final ReloadTracker HOSTS_FILE_TRACKER;
private static volatile Map<String, HostFileEntry> HOST_ADDRESSES = Collections.emptyMap();
void loadHostsAddresses() {
LOCK.readLock().lock();
var rsf = HOSTS_FILE_TRACKER.getReloadStatus();
try {
if (!rsf.isReloadNeeded()) {
return;
}
} finally {
LOCK.readLock().unlock();
}
LOCK.writeLock().lock();
try {
var rs = HOSTS_FILE_TRACKER.getReloadStatus();
// Check if reload is still needed
if (rs.isReloadNeeded()) {
if (rs.isFileExists()) {
HOST_ADDRESSES = parseHostsFile();
HOSTS_FILE_TRACKER.updateTimestamps(rs);
} else {
HOST_ADDRESSES = Collections.emptyMap();
}
}
} finally {
LOCK.writeLock().unlock();
}
}
private static String removeComments(String hostsEntry) {
String filteredEntry = hostsEntry;
int hashIndex;
if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
filteredEntry = hostsEntry.substring(0, hashIndex);
}
return filteredEntry;
}
private static class HostFileEntry {
final List<String> names; // Might need to split into aliases and name
final InetAddress address;
final boolean isValid;
final boolean isHostname;
HostFileEntry(String[] data) {
assert data.length > 1;
List<String> ln = List.of(Arrays.copyOfRange(data, 1, data.length));
String addressString = data[0];
names = ln;
address = parseAddress(ln.isEmpty() ? null : ln.get(0), addressString);
isValid = address != null;
isHostname = false;
}
@Override
public String toString() {
return names + "/" + address;
}
private HostFileEntry(String name, InetAddress address, boolean isHostname) {
this.names = List.of(name);
this.address = address;
this.isValid = address != null;
this.isHostname = isHostname;
}
boolean isValid() {
return isValid;
}
boolean isHostname() {
return isHostname;
}
String getHostName() {
return names.get(0);
}
Stream<HostFileEntry> oneNameStream() {
HostFileEntry hostName = new HostFileEntry(names.get(0), address, true);
Stream<HostFileEntry> aliases = names.stream()
.skip(1)
.map(n -> new HostFileEntry(n, address, false));
return Stream.concat(Stream.of(hostName), aliases);
}
private InetAddress parseAddress(String hostName, String addressString) {
// TODO: Revisit
Objects.requireNonNull(hostName);
// IPAddressUtil is from
var pa = (PrivilegedAction<byte[]>) () -> {
if (IPAddressUtil.isIPv4LiteralAddress(addressString)) {
return IPAddressUtil.textToNumericFormatV4(addressString);
} else if (IPAddressUtil.isIPv6LiteralAddress(addressString)) {
return IPAddressUtil.textToNumericFormatV6(addressString);
}
return null;
};
byte[] addr = System.getSecurityManager() == null ?
pa.run() : AccessController.doPrivileged(pa);
if (addr != null) {
try {
// if (hostName == null) hostName = addressString
return InetAddress.getByAddress(hostName, addr);
} catch (UnknownHostException e) {
}
}
return null;
}
}
private Map<String, HostFileEntry> parseHostsFile() {
Path hf = Paths.get(HOSTS_FILE_LOCATION_PROPERTY_VALUE);
try {
// TODO: Revisit
var pea = (PrivilegedExceptionAction<Boolean>) () -> Files.isRegularFile(hf);
boolean isRegularFile = System.getSecurityManager() == null ? pea.run()
: AccessController.doPrivileged(pea);
if (isRegularFile) {
var result = new HashMap<String, HostFileEntry>();
var pea2 = (PrivilegedExceptionAction<List<String>>) () -> Files.readAllLines(hf, StandardCharsets.UTF_8);
var lines = System.getSecurityManager() == null ? pea2.run()
: AccessController.doPrivileged(pea2);
lines.stream()
.map(HostsFileResolver::removeComments)
.filter(Predicate.not(String::isBlank))
.map(s -> s.split("\\s+"))
.filter(a -> a.length > 1)
.map(HostFileEntry::new)
.filter(HostFileEntry::isValid)
.flatMap(HostFileEntry::oneNameStream)
.forEachOrdered(
// If the same host name is listed multiple times then
// use the first encountered line
hfe -> result.putIfAbsent(hfe.names.get(0), hfe)
);
return Map.copyOf(result);
}
} catch (PrivilegedActionException pae) {
throw new RuntimeException("Can't read hosts file", pae.getCause());
} catch (Exception e) {
throw new RuntimeException("Can't read hosts file", e);
}
return Collections.emptyMap();
}
public InetAddress getHostAddress(String hostName) throws UnknownHostException {
return getHostAddress(hostName, null);
}
public InetAddress getHostAddress(String hostName, ProtocolFamily family) throws UnknownHostException {
var af = AddressFamily.fromProtocolFamily(family);
loadHostsAddresses();
var map = HOST_ADDRESSES;
var he = map.get(hostName);
if (he == null) {
throw new UnknownHostException(hostName);
}
var addr = he.address;
if (!af.sameFamily(addr)) {
throw new UnknownHostException(hostName);
}
return addr;
}
public String getByAddress(final InetAddress ha) throws UnknownHostException {
loadHostsAddresses();
var map = HOST_ADDRESSES;
var entry = map.values().stream()
.filter(HostFileEntry::isHostname)
.filter(e -> isAddressBytesTheSame(ha.getAddress(), e.address.getAddress()))
.findFirst();
if (entry.isEmpty()) {
throw new UnknownHostException(ha.toString());
}
return entry.get().getHostName();
}
private static boolean isAddressBytesTheSame(byte[] addr1, byte[] addr2) {
if (addr1 == null || addr2 == null) {
return false;
}
if (addr1.length != addr2.length) {
return false;
}
for (int i = 0; i < addr1.length; i++) {
if (addr1[i] != addr2[i])
return false;
}
return true;
}
static {
// TODO: Revisit
try {
var pea = (PrivilegedExceptionAction<ReloadTracker>) () ->
ReloadTracker.newInstance(Paths.get(HOSTS_FILE_LOCATION_PROPERTY_VALUE), REFRESH_TIMEOUT_NANOS);
HOSTS_FILE_TRACKER = System.getSecurityManager() == null ? pea.run() :
AccessController.doPrivileged(pea);
} catch (PrivilegedActionException pae) {
throw new RuntimeException("Error registering hosts file watch service", pae.getCause());
} catch (Exception e) {
throw new RuntimeException("Error registering hosts file watch service", e);
}
}
}