1 /*

     2  * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package jdk.dns.client.internal;

    27 

    28 import jdk.dns.client.AddressFamily;

    29 import jdk.dns.client.internal.util.ReloadTracker;

    30 import sun.net.util.IPAddressUtil;

    31 

    32 import java.net.InetAddress;

    33 import java.net.UnknownHostException;

    34 import java.nio.charset.StandardCharsets;

    35 import java.nio.file.Files;

    36 import java.nio.file.Path;

    37 import java.nio.file.Paths;

    38 import java.security.AccessController;

    39 import java.security.PrivilegedAction;

    40 import java.security.PrivilegedActionException;

    41 import java.security.PrivilegedExceptionAction;

    42 import java.util.Arrays;

    43 import java.util.Collections;

    44 import java.util.HashMap;

    45 import java.util.List;

    46 import java.util.Map;

    47 import java.util.Objects;

    48 import java.util.concurrent.locks.ReadWriteLock;

    49 import java.util.concurrent.locks.ReentrantReadWriteLock;

    50 import java.util.function.Predicate;

    51 import java.util.stream.Stream;

    52 

    53 public class HostsFileResolver {

    54     private static final String HOSTS_FILE_LOCATION_PROPERTY_VALUE =

    55             AccessController.doPrivileged((PrivilegedAction<String>)

    56                     () -> System.getProperty("jdk.net.hosts.file", "/etc/hosts")

    57             );

    58     private static final ReadWriteLock LOCK = new ReentrantReadWriteLock();

    59 

    60     // 300 seconds, similar to DnsResolverConfiguration in millis since Epoch

    61     private static final long REFRESH_TIMEOUT_MILLIS = 300_000;

    62     private static final ReloadTracker HOSTS_FILE_TRACKER;

    63     private static volatile Map<String, HostFileEntry> HOST_ADDRESSES = Collections.emptyMap();

    64 

    65     void loadHostsAddresses() {

    66         LOCK.readLock().lock();

    67         var rsf = HOSTS_FILE_TRACKER.getReloadStatus();

    68         try {

    69             if (!HOSTS_FILE_TRACKER.getReloadStatus().isReloadNeeded()) {

    70                 return;

    71             }

    72         } finally {

    73             LOCK.readLock().unlock();

    74         }

    75 

    76         LOCK.writeLock().lock();

    77         try {

    78             var rs = HOSTS_FILE_TRACKER.getReloadStatus();

    79             // Check if reload is still needed

    80             if (rs.isReloadNeeded()) {

    81                 if (rs.isFileExists()) {

    82                     HOST_ADDRESSES = parseHostsFile();

    83                     HOSTS_FILE_TRACKER.updateTimestamps(rs);

    84                 } else {

    85                     HOST_ADDRESSES = Collections.emptyMap();

    86                 }

    87             }

    88         } finally {

    89             LOCK.writeLock().unlock();

    90         }

    91     }

    92 

    93     private static String removeComments(String hostsEntry) {

    94         String filteredEntry = hostsEntry;

    95         int hashIndex;

    96 

    97         if ((hashIndex = hostsEntry.indexOf("#")) != -1) {

    98             filteredEntry = hostsEntry.substring(0, hashIndex);

    99         }

   100         return filteredEntry;

   101     }

   102 

   103     private static class HostFileEntry {

   104         final List<String> names; // Might need to split into aliases and name

   105         final InetAddress address;

   106         final boolean isValid;

   107         final boolean isHostname;

   108 

   109         HostFileEntry(String[] data) {

   110             assert data.length > 1;

   111             List<String> ln = List.of(Arrays.copyOfRange(data, 1, data.length));

   112             String addressString = data[0];

   113             names = ln;

   114             address = parseAddress(ln.isEmpty() ? null : ln.get(0), addressString);

   115             isValid = address != null;

   116             isHostname = false;

   117         }

   118 

   119         @Override

   120         public String toString() {

   121             return names+"/"+address;

   122         }

   123 

   124         private HostFileEntry(String name, InetAddress address, boolean isHostname) {

   125             this.names = List.of(name);

   126             this.address = address;

   127             this.isValid = address != null;

   128             this.isHostname = isHostname;

   129         }

   130 

   131         boolean isValid() {

   132             return isValid;

   133         }

   134         boolean isHostname() {return isHostname;}

   135 

   136         String getHostName() {

   137             return names.get(0);

   138         }

   139 

   140         Stream<HostFileEntry> oneNameStream() {

   141             HostFileEntry hostName = new HostFileEntry(names.get(0), address, true);

   142             Stream<HostFileEntry> aliases = names.stream()

   143                     .skip(1)

   144                     .map(n -> new HostFileEntry(n, address, false));

   145             return Stream.concat(Stream.of(hostName), aliases);

   146         }

   147 

   148         private InetAddress parseAddress(String hostName, String addressString) {

   149             // TODO: Revisit

   150             Objects.requireNonNull(hostName);

   151 

   152             // IPAddressUtil is from

   153             var pa = (PrivilegedAction<byte[]>) () -> {

   154                 if (IPAddressUtil.isIPv4LiteralAddress(addressString)) {

   155                     return IPAddressUtil.textToNumericFormatV4(addressString);

   156                 } else if (IPAddressUtil.isIPv6LiteralAddress(addressString)) {

   157                     return IPAddressUtil.textToNumericFormatV6(addressString);

   158                 }

   159                 return null;

   160             };

   161             byte[] addr = System.getSecurityManager() == null ?

   162                     pa.run() : AccessController.doPrivileged(pa);

   163 

   164             if (addr != null) {

   165                 try {

   166                     // if (hostName == null) hostName = addressString

   167                     return InetAddress.getByAddress(hostName, addr);

   168                 } catch (UnknownHostException e) {

   169                 }

   170             }

   171             return null;

   172         }

   173     }

   174 

   175     private Map<String, HostFileEntry> parseHostsFile() {

   176         Path hf = Paths.get(HOSTS_FILE_LOCATION_PROPERTY_VALUE);

   177         try {

   178             // TODO: Revisit

   179             var pea = (PrivilegedExceptionAction<Boolean>) () -> Files.isRegularFile(hf);

   180             boolean isRegularFile = System.getSecurityManager() == null ? pea.run()

   181                     : AccessController.doPrivileged(pea);

   182 

   183             if (isRegularFile) {

   184                 var result = new HashMap<String, HostFileEntry>();

   185                 var pea2 = (PrivilegedExceptionAction<List<String>>) () -> Files.readAllLines(hf, StandardCharsets.UTF_8);

   186                 var lines = System.getSecurityManager() == null ? pea2.run()

   187                         : AccessController.doPrivileged(pea2);

   188 

   189                 lines.stream()

   190                         .map(HostsFileResolver::removeComments)

   191                         .filter(Predicate.not(String::isBlank))

   192                         .map(s -> s.split("\\s+"))

   193                         .filter(a -> a.length > 1)

   194                         .map(HostFileEntry::new)

   195                         .filter(HostFileEntry::isValid)

   196                         .flatMap(HostFileEntry::oneNameStream)

   197                         .forEachOrdered(

   198                                 // If the same host name is listed multiple times then

   199                                 // use the first encountered line

   200                                 hfe -> result.putIfAbsent(hfe.names.get(0), hfe)

   201                         );

   202                 return Map.copyOf(result);

   203             }

   204         } catch (PrivilegedActionException pae) {

   205             throw new RuntimeException("Can't read hosts file", pae.getCause());

   206         } catch (Exception e) {

   207             throw new RuntimeException("Can't read hosts file", e);

   208         }

   209         return Collections.emptyMap();

   210     }

   211 

   212     public InetAddress getHostAddress(String hostName) throws UnknownHostException {

   213         return getHostAddress(hostName, AddressFamily.ANY);

   214     }

   215 

   216     public InetAddress getHostAddress(String hostName, AddressFamily family) throws UnknownHostException {

   217 

   218         loadHostsAddresses();

   219         var map = HOST_ADDRESSES;

   220         var he = map.get(hostName);

   221         if (he == null) {

   222             throw new UnknownHostException(hostName);

   223         }

   224         var addr = he.address;

   225         if (!family.sameFamily(addr)) {

   226             throw new UnknownHostException(hostName);

   227         }

   228         return addr;

   229     }

   230 

   231     public String getByAddress(final InetAddress ha) throws UnknownHostException {

   232         loadHostsAddresses();

   233         var map = HOST_ADDRESSES;

   234         var entry = map.values().stream()

   235                 .filter(HostFileEntry::isHostname)

   236                 .filter(e -> isAddressBytesTheSame(ha.getAddress(), e.address.getAddress()))

   237                 .findFirst();

   238         if (entry.isEmpty()) {

   239             throw new UnknownHostException(ha.toString());

   240         }

   241         return entry.get().getHostName();

   242     }

   243 

   244     private static boolean isAddressBytesTheSame(byte [] addr1, byte [] addr2) {

   245         if (addr1 == null || addr2 == null) {

   246             return false;

   247         }

   248         if (addr1.length != addr2.length) {

   249             return false;

   250         }

   251         for (int i=0; i<addr1.length; i++) {

   252             if (addr1[i] != addr2[i])

   253                 return false;

   254         }

   255         return true;

   256     }

   257 

   258     static {

   259         // TODO: Revisit

   260         try {

   261             var pea = (PrivilegedExceptionAction<ReloadTracker>) () ->

   262                     ReloadTracker.newInstance(Paths.get(HOSTS_FILE_LOCATION_PROPERTY_VALUE), REFRESH_TIMEOUT_MILLIS);

   263             HOSTS_FILE_TRACKER = System.getSecurityManager() == null ? pea.run() :

   264                     AccessController.doPrivileged(pea);

   265         } catch (PrivilegedActionException pae) {

   266             throw new RuntimeException("Error registering hosts file watch service", pae.getCause());

   267         } catch (Exception e) {

   268             throw new RuntimeException("Error registering hosts file watch service", e);

   269         }

   270     }

   271 }