From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: egg82 <eggys82@gmail.com>
Date: Sat, 11 Sep 2021 22:55:14 +0200
Subject: [PATCH] Add root/admin user detection

This patch detects whether or not the server is currently executing as a privileged user and spits out a warning.
The warning serves as a sort-of PSA for newer server admins who don't understand the risks of running as root.
We've seen plenty of bad/malicious plugins hit markets, and there's been a few close-calls with exploits in the past.
Hopefully this helps mitigate some potential damage to servers, even if it is just a warning.

Co-authored-by: Noah van der Aa <ndvdaa@gmail.com>

diff --git a/src/main/java/io/papermc/paper/util/ServerEnvironment.java b/src/main/java/io/papermc/paper/util/ServerEnvironment.java
new file mode 100644
index 0000000000000000000000000000000000000000..68098dfe716e93aafcca4d8d5b5a81d8648b3654
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/ServerEnvironment.java
@@ -0,0 +1,23 @@
+package io.papermc.paper.util;
+
+import com.sun.security.auth.module.NTSystem;
+import com.sun.security.auth.module.UnixSystem;
+import java.util.Set;
+import org.apache.commons.lang.SystemUtils;
+
+public class ServerEnvironment {
+    private static final boolean RUNNING_AS_ROOT_OR_ADMIN;
+    private static final String WINDOWS_HIGH_INTEGRITY_LEVEL = "S-1-16-12288";
+
+    static {
+        if (SystemUtils.IS_OS_WINDOWS) {
+            RUNNING_AS_ROOT_OR_ADMIN = Set.of(new NTSystem().getGroupIDs()).contains(WINDOWS_HIGH_INTEGRITY_LEVEL);
+        } else {
+            RUNNING_AS_ROOT_OR_ADMIN = new UnixSystem().getUid() == 0;
+        }
+    }
+
+    public static boolean userIsRootOrAdmin() {
+        return RUNNING_AS_ROOT_OR_ADMIN;
+    }
+}
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index 4bc7b3d7c5214b3272614fe3fce8e4d8d2264867..784788d8d3d1a07efbd406b6c463e046699081e2 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -192,6 +192,16 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
             DedicatedServer.LOGGER.warn("To start the server with more ram, launch it as \"java -Xmx1024M -Xms1024M -jar minecraft_server.jar\"");
         }
 
+        // Paper start - detect running as root
+        if (io.papermc.paper.util.ServerEnvironment.userIsRootOrAdmin()) {
+            DedicatedServer.LOGGER.warn("****************************");
+            DedicatedServer.LOGGER.warn("YOU ARE RUNNING THIS SERVER AS AN ADMINISTRATIVE OR ROOT USER. THIS IS NOT ADVISED.");
+            DedicatedServer.LOGGER.warn("YOU ARE OPENING YOURSELF UP TO POTENTIAL RISKS WHEN DOING THIS.");
+            DedicatedServer.LOGGER.warn("FOR MORE INFORMATION, SEE https://madelinemiller.dev/blog/root-minecraft-server/");
+            DedicatedServer.LOGGER.warn("****************************");
+        }
+        // Paper end - detect running as root
+
         DedicatedServer.LOGGER.info("Loading properties");
         DedicatedServerProperties dedicatedserverproperties = this.settings.getProperties();
 
