Add IPv6 support for isLocal checks (#1592)

* Add IPv6 support for isLocal checks

* Replace magic values like 127.0.0.1 and use our utility
* Support for IPv6 local adresses in IPv6 only or dual stack environments
    * Loopback [::1]
    * Site-Local fc00::/7
    * Link-local fe80::/10

* Introduce extra method for loopback addresses

* Use public IP for passMaxLogin check

* Use non-local IP addresses in test after change in verification

src/main/java/fr/xephi/authme/process/join/AsynchronousJoin.java

@@ -18,6 +18,7 @@ import fr.xephi.authme.settings.commandconfig.CommandManager;
 import fr.xephi.authme.settings.properties.HooksSettings;
 import fr.xephi.authme.settings.properties.RegistrationSettings;
 import fr.xephi.authme.settings.properties.RestrictionSettings;
+import fr.xephi.authme.util.InternetProtocolUtils;
 import fr.xephi.authme.util.PlayerUtils;
 import org.bukkit.GameMode;
 import org.bukkit.Server;
@@ -183,8 +184,7 @@ public class AsynchronousJoin implements AsynchronousProcess {
     private boolean validatePlayerCountForIp(final Player player, String ip) {
         if (service.getProperty(RestrictionSettings.MAX_JOIN_PER_IP) > 0
             && !service.hasPermission(player, PlayerStatePermission.ALLOW_MULTIPLE_ACCOUNTS)
-            && !"127.0.0.1".equalsIgnoreCase(ip)
-            && !"localhost".equalsIgnoreCase(ip)
+            && !InternetProtocolUtils.isLoopbackAddress(ip)
             && countOnlinePlayersByIp(ip) > service.getProperty(RestrictionSettings.MAX_JOIN_PER_IP)) {
 
             bukkitService.scheduleSyncTaskFromOptionallyAsyncTask(

src/main/java/fr/xephi/authme/process/login/AsynchronousLogin.java

@@ -30,6 +30,7 @@ import fr.xephi.authme.settings.properties.EmailSettings;
 import fr.xephi.authme.settings.properties.HooksSettings;
 import fr.xephi.authme.settings.properties.PluginSettings;
 import fr.xephi.authme.settings.properties.RestrictionSettings;
+import fr.xephi.authme.util.InternetProtocolUtils;
 import fr.xephi.authme.util.PlayerUtils;
 import fr.xephi.authme.util.Utils;
 import org.bukkit.ChatColor;
@@ -325,8 +326,7 @@ public class AsynchronousLogin implements AsynchronousProcess {
         // Do not perform the check if player has multiple accounts permission or if IP is localhost
         if (service.getProperty(RestrictionSettings.MAX_LOGIN_PER_IP) <= 0
             || service.hasPermission(player, PlayerStatePermission.ALLOW_MULTIPLE_ACCOUNTS)
-            || "127.0.0.1".equalsIgnoreCase(ip)
-            || "localhost".equalsIgnoreCase(ip)) {
+            || InternetProtocolUtils.isLoopbackAddress(ip)) {
             return false;
         }
 

src/main/java/fr/xephi/authme/process/register/AsyncRegister.java

@@ -16,6 +16,7 @@ import fr.xephi.authme.service.bungeecord.BungeeSender;
 import fr.xephi.authme.service.bungeecord.MessageType;
 import fr.xephi.authme.settings.properties.RegistrationSettings;
 import fr.xephi.authme.settings.properties.RestrictionSettings;
+import fr.xephi.authme.util.InternetProtocolUtils;
 import fr.xephi.authme.util.PlayerUtils;
 import org.bukkit.entity.Player;
 
@@ -119,8 +120,7 @@ public class AsyncRegister implements AsynchronousProcess {
         final int maxRegPerIp = service.getProperty(RestrictionSettings.MAX_REGISTRATION_PER_IP);
         final String ip = PlayerUtils.getPlayerIp(player);
         if (maxRegPerIp > 0
-            && !"127.0.0.1".equalsIgnoreCase(ip)
-            && !"localhost".equalsIgnoreCase(ip)
+            && !InternetProtocolUtils.isLoopbackAddress(ip)
             && !service.hasPermission(player, ALLOW_MULTIPLE_ACCOUNTS)) {
             List<String> otherAccounts = database.getAllAuthsByIp(ip);
             if (otherAccounts.size() >= maxRegPerIp) {

src/main/java/fr/xephi/authme/util/InternetProtocolUtils.java

@@ -1,16 +1,13 @@
 package fr.xephi.authme.util;
 
-import java.util.regex.Pattern;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
 
 /**
  * Utility class about the InternetProtocol
  */
 public final class InternetProtocolUtils {
 
-    private static final Pattern LOCAL_ADDRESS_PATTERN =
-        Pattern.compile("(^127\\.)|(^(0)?10\\.)|(^172\\.(0)?1[6-9]\\.)|(^172\\.(0)?2[0-9]\\.)"
-            + "|(^172\\.(0)?3[0-1]\\.)|(^169\\.254\\.)|(^192\\.168\\.)");
-
     // Utility class
     private InternetProtocolUtils() {
     }
@@ -19,10 +16,57 @@ public final class InternetProtocolUtils {
      * Checks if the specified address is a private or loopback address
      *
      * @param address address to check
-     *
-     * @return true if the address is a local or loopback address, false otherwise
+     * @return true if the address is a local (site and link) or loopback address, false otherwise
      */
     public static boolean isLocalAddress(String address) {
-        return LOCAL_ADDRESS_PATTERN.matcher(address).find();
+        try {
+            InetAddress inetAddress = InetAddress.getByName(address);
+
+            // Examples: 127.0.0.1, localhost or [::1]
+            return isLoopbackAddress(address)
+                    // Example: 10.0.0.0, 172.16.0.0, 192.168.0.0, fec0::/10 (deprecated)
+                    // Ref: https://en.wikipedia.org/wiki/IP_address#Private_addresses
+                    || inetAddress.isSiteLocalAddress()
+                    // Example: 169.254.0.0/16, fe80::/10
+                    // Ref: https://en.wikipedia.org/wiki/IP_address#Address_autoconfiguration
+                    || inetAddress.isLinkLocalAddress()
+                    // non deprecated unique site-local that java doesn't check yet -> fc00::/7
+                    || isIPv6UniqueSiteLocal(inetAddress);
+        } catch (UnknownHostException e) {
+            return false;
+        }
+    }
+
+    /**
+     * Checks if the specified address is a loopback address. This can be one of the following:
+     * <ul>
+     * <li>127.0.0.1</li>
+     * <li>localhost</li>
+     * <li>[::1]</li>
+     * </ul>
+     *
+     * @param address address to check
+     * @return true if the address is a loopback one
+     */
+    public static boolean isLoopbackAddress(String address) {
+        try {
+            InetAddress inetAddress = InetAddress.getByName(address);
+            return inetAddress.isLoopbackAddress();
+        } catch (UnknownHostException e) {
+            return false;
+        }
+    }
+
+    private static boolean isLoopbackAddress(InetAddress address) {
+        return address.isLoopbackAddress();
+    }
+
+    private static boolean isIPv6UniqueSiteLocal(InetAddress address) {
+        // ref: https://en.wikipedia.org/wiki/Unique_local_address
+
+        // currently undefined but could be used in the near future fc00::/8
+        return (address.getAddress()[0] & 0xFF) == 0xFC
+                // in use for unique site-local fd00::/8
+                || (address.getAddress()[0] & 0xFF) == 0xFD;
     }
 }