From 4f80d2b261d0a90d9076474e9e5d55f63fd171d9 Mon Sep 17 00:00:00 2001
From: Andrew Steinborn <git@steinborn.me>
Date: Fri, 29 Jan 2021 23:08:14 -0500
Subject: [PATCH] Revert strict handshake hostname checks

These will break TCPShield and Cosmic Guard plugins. Sad as this was a worthwhile mitigation.
---
 .../proxy/protocol/ProtocolUtils.java         | 20 +------------------
 .../proxy/protocol/packet/Handshake.java      |  8 +-------
 2 files changed, 2 insertions(+), 26 deletions(-)

diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
index 7da858d9f..2c4f50a99 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
@@ -97,30 +97,12 @@ public enum ProtocolUtils {
     }
   }
 
-  /**
-   * Reads a VarInt length-prefixed ASCII string from the {@code buf}, making sure to not go over
-   * {@code cap} size. This method is specialized for select parts of the Minecraft protocol where
-   * ASCII characters are guaranteed to be used.
-   *
-   * @param buf the buffer to read from
-   * @param cap the maximum size of the string, in UTF-8 character length
-   * @return the decoded string
-   */
-  public static String readAsciiString(ByteBuf buf, int cap) {
-    int length = readVarInt(buf);
-    checkFrame(length >= 0, "Got a negative-length string (%s)", length);
-    checkFrame(length <= cap, "Bad string size (got %s, maximum is %s)", length, cap);
-    String str = buf.toString(buf.readerIndex(), length, StandardCharsets.US_ASCII);
-    buf.skipBytes(length);
-    return str;
-  }
-
   public static String readString(ByteBuf buf) {
     return readString(buf, DEFAULT_MAX_STRING_SIZE);
   }
 
   /**
-   * Reads a VarInt length-prefixed UTF-8 string from the {@code buf}, making sure to not go over
+   * Reads a VarInt length-prefixed string from the {@code buf}, making sure to not go over
    * {@code cap} size.
    * @param buf the buffer to read from
    * @param cap the maximum size of the string, in UTF-8 character length
diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/Handshake.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/Handshake.java
index a1c902057..cf64b7b93 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/Handshake.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/Handshake.java
@@ -1,19 +1,13 @@
 package com.velocitypowered.proxy.protocol.packet;
 
-import static com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants.HANDSHAKE_HOSTNAME_TOKEN;
-
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
-import com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import io.netty.buffer.ByteBuf;
 
 public class Handshake implements MinecraftPacket {
 
-  // This size was chosen to ensure Forge clients can still connect even with very long hostnames.
-  // While DNS technically allows any character to be used, in practice ASCII is used.
-  private static final int MAXIMUM_HOSTNAME_LENGTH = 255 + HANDSHAKE_HOSTNAME_TOKEN.length() + 1;
   private ProtocolVersion protocolVersion;
   private String serverAddress = "";
   private int port;
@@ -65,7 +59,7 @@ public class Handshake implements MinecraftPacket {
   public void decode(ByteBuf buf, ProtocolUtils.Direction direction, ProtocolVersion ignored) {
     int realProtocolVersion = ProtocolUtils.readVarInt(buf);
     this.protocolVersion = ProtocolVersion.getProtocolVersion(realProtocolVersion);
-    this.serverAddress = ProtocolUtils.readAsciiString(buf, MAXIMUM_HOSTNAME_LENGTH);
+    this.serverAddress = ProtocolUtils.readString(buf);
     this.port = buf.readUnsignedShort();
     this.nextStatus = ProtocolUtils.readVarInt(buf);
   }