Channel validation

common/cpw/mods/fml/common/FMLHooks.java

@@ -13,17 +13,21 @@
  */
 package cpw.mods.fml.common;
 
+import java.io.UnsupportedEncodingException;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
+import net.minecraft.src.EntityPlayer;
+
 
 
 public class FMLHooks {
   private static final FMLHooks INSTANCE=new FMLHooks();
   private Map<ModContainer,Set<String>> channelList=new HashMap<ModContainer,Set<String>>();
   private Map<String,ModContainer> modChannels=new HashMap<String,ModContainer>();
+  private Map<Object,Set<String>> activeChannels=new HashMap<Object,Set<String>>();
   
   public void gameTickStart() {
     for (ModContainer mod : Loader.getModList()) {
@@ -57,8 +61,7 @@ public class FMLHooks {
   
   public void registerChannel(ModContainer container, String channelName) {
     if (modChannels.containsKey(channelName)) {
-      Loader.log.severe(String.format("Mod %s tried to register network channel %s, already registered to %s", container, channelName, modChannels.get(channelName)));
-      throw new LoaderException();
+      // NOOP
     }
     Set<String> list=channelList.get(container);
     if (list==null) {
@@ -67,4 +70,55 @@ public class FMLHooks {
     }
     list.add(channelName);
   }
+
+  /**
+   * @param player
+   */
+  public void activateChannel(Object player, String channel) {
+    Set<String> active=activeChannels.get(player);
+    if (active==null) {
+      active=new HashSet<String>();
+      activeChannels.put(player, active);
+    }
+    active.add(channel);
+  }
+
+  /**
+   * @param player
+   * @param channel
+   */
+  public void deactivateChannel(EntityPlayer player, String channel) {
+    Set<String> active=activeChannels.get(player);
+    if (active==null) {
+      active=new HashSet<String>();
+      activeChannels.put(player, active);
+    }
+    active.remove(channel);
+  }
+
+  /**
+   * @return
+   */
+  public byte[] getPacketRegistry() {
+    StringBuffer sb=new StringBuffer();
+    for (String chan : modChannels.keySet()) {
+      sb.append(chan).append("\0");
+    }
+    try {
+      return sb.toString().getBytes("UTF8");
+    } catch (UnsupportedEncodingException e) {
+      Loader.log.warning("Error building registration list");
+      Loader.log.throwing("FMLHooks", "getPacketRegistry", e);
+      return new byte[0];
+    }
+  }
+
+  /**
+   * @param channel
+   * @param player
+   * @return
+   */
+  public boolean isChannelActive(String channel, Object player) {
+    return activeChannels.get(player).contains(channel);
+  }
 }

server/cpw/mods/fml/server/FMLHandler.java

@@ -12,6 +12,7 @@
  */
 package cpw.mods.fml.server;
 
+import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.Random;
 import java.util.logging.Logger;
@@ -184,17 +185,47 @@ public class FMLHandler {
   }
   
   public void handlePacket250(Packet250CustomPayload packet, EntityPlayer player) {
+    if ("REGISTER".equals(packet.field_44005_a) || "UNREGISTER".equals(packet.field_44005_a)) {
+      handleClientRegistration(packet, player);
+      return;
+    }
     ModContainer mod = FMLHooks.instance().getModForChannel(packet.field_44005_a);
     if (mod!=null) {
       mod.getNetworkHandler().onPacket250Packet(packet, player);
     }
   }
 
-  public void handleLogin(Packet1Login packet, NetworkManager networkManager) {
-    for (ModContainer mod : Loader.getModList()) {
-      if (mod.wantsNetworkPackets()) {
-        mod.getNetworkHandler().onLogin(packet, networkManager);
+  /**
+   * @param packet
+   */
+  private void handleClientRegistration(Packet250CustomPayload packet, EntityPlayer player) {
+    try {
+      for (String channel : new String(packet.field_44004_c,"UTF8").split("\0")) {
+        // Skip it if we don't know it
+        if (FMLHooks.instance().getModForChannel(channel)==null) {
+          continue;
+        }
+        if ("REGISTER".equals(packet.field_44005_a)) {
+          FMLHooks.instance().activateChannel(player,channel);
+        } else {
+          FMLHooks.instance().deactivateChannel(player,channel);
+        }
       }
+    } catch (UnsupportedEncodingException e) {
+      getMinecraftLogger().warning("Received invalid registration packet");
     }
   }
+
+  public void handleLogin(Packet1Login loginPacket, NetworkManager networkManager) {
+    for (ModContainer mod : Loader.getModList()) {
+      if (mod.wantsNetworkPackets()) {
+        mod.getNetworkHandler().onLogin(loginPacket, networkManager);
+      }
+    }
+    Packet250CustomPayload packet=new Packet250CustomPayload();
+    packet.field_44005_a="REGISTER";
+    packet.field_44004_c=FMLHooks.instance().getPacketRegistry();
+    packet.field_44003_b=packet.field_44004_c.length;
+    networkManager.func_745_a(packet);
+  }
 }

server/net/minecraft/src/ModLoader.java

@@ -516,4 +516,16 @@ public class ModLoader {
   public static MinecraftServer getMinecraftServerInstance() {
     return FMLHandler.instance().getServer();
   }
+  
+  /**
+   * To properly implement packet 250 protocol you should always check your channel
+   * is active prior to sending the packet
+   * 
+   * @param player
+   * @param channel
+   * @return
+   */
+  public static boolean isChannelActive(EntityPlayer player, String channel) {
+    return FMLHooks.instance().isChannelActive(channel,player);
+  }
 }