From 46072eb4652ec581b071291554f58a8cf348596e Mon Sep 17 00:00:00 2001
From: Luck <git@lucko.me>
Date: Thu, 21 Feb 2019 14:14:00 +0000
Subject: [PATCH] Attempt to detect and warn about CraftBukkit + offline mode
 problems (#1439)

---
 .../listeners/BukkitConnectionListener.java   | 28 +++++++++++++++++++
 .../common/locale/message/Message.java        |  1 +
 2 files changed, 29 insertions(+)

diff --git a/bukkit/src/main/java/me/lucko/luckperms/bukkit/listeners/BukkitConnectionListener.java b/bukkit/src/main/java/me/lucko/luckperms/bukkit/listeners/BukkitConnectionListener.java
index 2a11c8cdb..f18b7fb09 100644
--- a/bukkit/src/main/java/me/lucko/luckperms/bukkit/listeners/BukkitConnectionListener.java
+++ b/bukkit/src/main/java/me/lucko/luckperms/bukkit/listeners/BukkitConnectionListener.java
@@ -50,12 +50,32 @@ import java.util.concurrent.TimeUnit;
 public class BukkitConnectionListener extends AbstractConnectionListener implements Listener {
     private final LPBukkitPlugin plugin;
 
+    private final boolean detectedCraftBukkitOfflineMode;
+
     private final Set<UUID> deniedAsyncLogin = Collections.synchronizedSet(new HashSet<>());
     private final Set<UUID> deniedLogin = Collections.synchronizedSet(new HashSet<>());
 
     public BukkitConnectionListener(LPBukkitPlugin plugin) {
         super(plugin);
         this.plugin = plugin;
+
+        // check for craftbukkit + offline mode combination
+        String version = plugin.getBootstrap().getServer().getVersion();
+        boolean onlineMode = plugin.getBootstrap().getServer().getOnlineMode();
+
+        if (!onlineMode && version.startsWith("git-Bukkit-")) {
+            printCraftBukkitOfflineModeError();
+            this.detectedCraftBukkitOfflineMode = true;
+        } else {
+            this.detectedCraftBukkitOfflineMode = false;
+        }
+    }
+
+    private void printCraftBukkitOfflineModeError() {
+        this.plugin.getLogger().warn("It appears that your server is running CraftBukkit and configured in offline (cracked) mode.");
+        this.plugin.getLogger().warn("Due to a CraftBukkit limitation, LuckPerms cannot function correctly in this setup.");
+        this.plugin.getLogger().warn("To resolve this, please either a) upgrade from CraftBukkit to Spigot or Paper, or b) enable online-mode.");
+        this.plugin.getLogger().warn("For more info, please see: https://github.com/lucko/LuckPerms/wiki/Installation#craftbukkit-and-offline-mode");
     }
 
     @EventHandler(priority = EventPriority.LOW)
@@ -134,9 +154,17 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
             this.deniedLogin.add(player.getUniqueId());
 
             if (!getUniqueConnections().contains(player.getUniqueId())) {
+
                 this.plugin.getLogger().warn("User " + player.getUniqueId() + " - " + player.getName() +
                         " doesn't have data pre-loaded, they have never been processed during pre-login in this session." +
                         " - denying login.");
+
+                if (this.detectedCraftBukkitOfflineMode) {
+                    printCraftBukkitOfflineModeError();
+                    e.disallow(PlayerLoginEvent.Result.KICK_OTHER, Message.LOADING_STATE_ERROR_CB_OFFLINE_MODE.asString(this.plugin.getLocaleManager()));
+                    return;
+                }
+
             } else {
                 this.plugin.getLogger().warn("User " + player.getUniqueId() + " - " + player.getName() +
                         " doesn't currently have data pre-loaded, but they have been processed before in this session." +
diff --git a/common/src/main/java/me/lucko/luckperms/common/locale/message/Message.java b/common/src/main/java/me/lucko/luckperms/common/locale/message/Message.java
index 90c8d97dc..ac7b80f68 100644
--- a/common/src/main/java/me/lucko/luckperms/common/locale/message/Message.java
+++ b/common/src/main/java/me/lucko/luckperms/common/locale/message/Message.java
@@ -65,6 +65,7 @@ public enum Message {
     PLAYER_OFFLINE("&cOffline", false),
     LOADING_DATABASE_ERROR("&cA database error occurred whilst loading permissions data. Please try again later.", true),
     LOADING_STATE_ERROR("&cPermissions data for your user was not loaded during the pre-login stage - unable to continue. Please try again later.", true),
+    LOADING_STATE_ERROR_CB_OFFLINE_MODE("&cPermissions data for your user was not loaded during the pre-login stage - this is likely due to a conflict between CraftBukkit and the online-mode setting. Please check the server console for more information.", true),
     LOADING_SETUP_ERROR("&cAn unexpected error occurred whilst setting up your permissions data. Please try again later.", true),
     OP_DISABLED("&bThe vanilla OP system is disabled on this server.", false),
     OP_DISABLED_SPONGE("&2Please note that Server Operator status has no effect on Sponge permission checks when a permission plugin is installed. Please edit user data directly.", true),