1 files changed, 88 insertions, 0 deletions
diff --git a/patches/server/0839-Validate-usernames.patch b/patches/server/0839-Validate-usernames.patch
new file mode 100644
index 0000000000..2b952eef57
--- /dev/null
+++ b/patches/server/0839-Validate-usernames.patch
@@ -0,0 +1,88 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <[email protected]>
+Date: Sat, 1 Jan 2022 05:19:37 -0800
+Subject: [PATCH] Validate usernames
+
+
+diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+index d1868e8521ea923587f3364fc83e1aaa98dc0288..15ed7b66aefc5665ebbe81dc491f4944269ace14 100644
+--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
++++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+@@ -493,6 +493,12 @@ public class PaperConfig {
+         set("settings.unsupported-settings.allow-tnt-duplication", null);
+     }
+ 
++    public static boolean performUsernameValidation;
++    private static void performUsernameValidation() {
++        performUsernameValidation = getBoolean("settings.unsupported-settings.perform-username-validation", true);
++    }
++
++
+     public static int playerAutoSaveRate = -1;
+     public static int maxPlayerAutoSavePerTick = 10;
+     private static void playerAutoSaveRate() {
+diff --git a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
+index f5c1dff1d571e89f960f11400edbcbbea0620575..7065aa4522431d08018fec8e591ba7c255398140 100644
+--- a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
++++ b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
+@@ -61,6 +61,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener
+     private ServerPlayer delayedAcceptPlayer;
+     public String hostname = ""; // CraftBukkit - add field
+     private int velocityLoginMessageId = -1; // Paper - Velocity support
++    public boolean iKnowThisMayNotBeTheBestIdeaButPleaseDisableUsernameValidation = false; // Paper - username validation overriding
+ 
+     public ServerLoginPacketListenerImpl(MinecraftServer server, Connection connection) {
+         this.state = ServerLoginPacketListenerImpl.State.HELLO;
+@@ -226,11 +227,39 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener
+         // Paper end
+     }
+ 
++    // Paper start - validate usernames
++    public static boolean validateUsername(String in) {
++        if (in == null || in.isEmpty() || in.length() > 16) {
++            return false;
++        }
++
++        for (int i = 0, len = in.length(); i < len; ++i) {
++            char c = in.charAt(i);
++
++            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || (c == '_' || c == '.')) {
++                continue;
++            }
++
++            return false;
++        }
++
++        return true;
++    }
++    // Paper end - validate usernames
++
+     @Override
+     public void handleHello(ServerboundHelloPacket packet) {
+         Validate.validState(this.state == ServerLoginPacketListenerImpl.State.HELLO, "Unexpected hello packet", new Object[0]);
+         this.gameProfile = packet.getGameProfile();
+         Validate.validState(ServerLoginPacketListenerImpl.isValidUsername(this.gameProfile.getName()), "Invalid characters in username", new Object[0]);
++        // Paper start - validate usernames
++        if (com.destroystokyo.paper.PaperConfig.isProxyOnlineMode() && com.destroystokyo.paper.PaperConfig.performUsernameValidation) {
++            if (!this.iKnowThisMayNotBeTheBestIdeaButPleaseDisableUsernameValidation && !validateUsername(this.gameProfile.getName())) {
++                ServerLoginPacketListenerImpl.this.disconnect("Failed to verify username!");
++                return;
++            }
++        }
++        // Paper end - validate usernames
+         if (this.server.usesAuthentication() && !this.connection.isMemoryConnection()) {
+             this.state = ServerLoginPacketListenerImpl.State.KEY;
+             this.connection.send(new ClientboundHelloPacket("", this.server.getKeyPair().getPublic().getEncoded(), this.nonce));
+diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
+index 6a3d444fcac8c7d561dcadb02f64eaa3c3d7b1cd..fae67931849eb0c19598def9f538c7971c36c575 100644
+--- a/src/main/java/net/minecraft/server/players/PlayerList.java
++++ b/src/main/java/net/minecraft/server/players/PlayerList.java
+@@ -707,7 +707,7 @@ public abstract class PlayerList {
+ 
+         for (int i = 0; i < this.players.size(); ++i) {
+             entityplayer = (ServerPlayer) this.players.get(i);
+-            if (entityplayer.getUUID().equals(uuid)) {
++            if (entityplayer.getUUID().equals(uuid) || (com.destroystokyo.paper.PaperConfig.isProxyOnlineMode() && entityplayer.getGameProfile().getName().equalsIgnoreCase(gameprofile.getName()))) { // Paper - validate usernames
+                 list.add(entityplayer);
+             }
+         }