Allow responding to cookie requests

api/src/main/java/com/velocitypowered/api/event/player/CookieRequestEvent.java

@@ -68,15 +68,19 @@ public String toString() {
    */
   public static final class ForwardResult implements Result {
 
-    private static final ForwardResult ALLOWED = new ForwardResult(true, null);
-    private static final ForwardResult DENIED = new ForwardResult(false, null);
+    private static final ForwardResult ALLOWED = new ForwardResult(true, null, false, null);
+    private static final ForwardResult DENIED = new ForwardResult(false, null, false, null);
 
     private final boolean status;
     private final Key key;
+    private final boolean respond;
+    private final byte[] data;
 
-    private ForwardResult(final boolean status, final Key key) {
+    private ForwardResult(final boolean status, final Key key, boolean respond, byte[] data) {
       this.status = status;
       this.key = key;
+      this.respond = respond;
+      this.data = data;
     }
 
     @Override
@@ -88,6 +92,14 @@ public Key getKey() {
       return key;
     }
 
+    public boolean shouldRespond() {
+      return respond;
+    }
+
+    public byte[] getData() {
+      return data;
+    }
+
     @Override
     public String toString() {
       return status ? "forward to client" : "handled by proxy";
@@ -112,6 +124,16 @@ public static ForwardResult handled() {
       return DENIED;
     }
 
+    /**
+     * Sends this response to the request to the server.
+     *
+     * @param data the data to send, null will mean missing data
+     * @return a result with the data
+     */
+    public static ForwardResult respond(final byte [] data) {
+      return new ForwardResult(false, null, true, data);
+    }
+
     /**
      * Allows the cookie request to be forwarded to the client, but silently replaces the
      * identifier of the cookie with another.
@@ -121,7 +143,7 @@ public static ForwardResult handled() {
      */
     public static ForwardResult key(final Key key) {
       Preconditions.checkNotNull(key, "key");
-      return new ForwardResult(true, key);
+      return new ForwardResult(true, key, false, null);
     }
   }
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -62,6 +62,7 @@
 import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.ServerDataPacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TabCompleteResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TransferPacket;
 import com.velocitypowered.proxy.protocol.packet.UpsertPlayerInfoPacket;
@@ -435,6 +436,8 @@ public boolean handle(ClientboundCookieRequestPacket packet) {
                 ? event.getOriginalKey() : event.getResult().getKey();
 
             playerConnection.write(new ClientboundCookieRequestPacket(resultedKey));
+          } else if (event.getResult().shouldRespond()) {
+            serverConn.ensureConnected().write(new ServerboundCookieResponsePacket(packet.getKey(), event.getResult().getData()));
           }
         }, playerConnection.eventLoop());
 

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/ConfigSessionHandler.java

@@ -46,6 +46,7 @@
 import com.velocitypowered.proxy.protocol.packet.RemoveResourcePackPacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackResponsePacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TransferPacket;
 import com.velocitypowered.proxy.protocol.packet.config.ClientboundCustomReportDetailsPacket;
 import com.velocitypowered.proxy.protocol.packet.config.ClientboundServerLinksPacket;
@@ -324,6 +325,8 @@ public boolean handle(ClientboundCookieRequestPacket packet) {
                 ? event.getOriginalKey() : event.getResult().getKey();
 
             serverConn.getPlayer().getConnection().write(new ClientboundCookieRequestPacket(resultedKey));
+          } else if (event.getResult().shouldRespond()) {
+            serverConn.ensureConnected().write(new ServerboundCookieResponsePacket(event.getOriginalKey(), event.getResult().getData()));
           }
         }, serverConn.ensureConnected().eventLoop());
 

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/LoginSessionHandler.java

@@ -41,6 +41,7 @@
 import com.velocitypowered.proxy.protocol.packet.LoginPluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.LoginPluginResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.ServerLoginSuccessPacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.SetCompressionPacket;
 import com.velocitypowered.proxy.util.except.QuietRuntimeException;
 import io.netty.buffer.ByteBuf;
@@ -189,6 +190,8 @@ public boolean handle(ClientboundCookieRequestPacket packet) {
                 ? event.getOriginalKey() : event.getResult().getKey();
 
             serverConn.getPlayer().getConnection().write(new ClientboundCookieRequestPacket(resultedKey));
+          } else if (event.getResult().shouldRespond()) {
+            serverConn.ensureConnected().write(new ServerboundCookieResponsePacket(event.getOriginalKey(), event.getResult().getData()));
           }
         }, serverConn.ensureConnected().eventLoop());
 

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -78,6 +78,7 @@
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.RemoveResourcePackPacket;
+import com.velocitypowered.proxy.protocol.packet.ServerboundCookieResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TransferPacket;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatQueue;
 import com.velocitypowered.proxy.protocol.packet.chat.ChatType;
@@ -1071,6 +1072,8 @@ public void requestCookie(final Key key) {
                 ? event.getOriginalKey() : event.getResult().getKey();
 
             connection.write(new ClientboundCookieRequestPacket(resultedKey));
+          } else if (event.getResult().shouldRespond()) {
+            this.ensureBackendConnection().write(new ServerboundCookieResponsePacket(event.getOriginalKey(), event.getResult().getData()));
           }
         }, connection.eventLoop());
   }