From 7231921b0bfce69255369a2bc7933d40cef3cbda Mon Sep 17 00:00:00 2001
From: Pavel Djundik <xPaw@users.noreply.github.com>
Date: Thu, 19 Nov 2020 10:58:23 +0200
Subject: [PATCH] Add 1200 byte padding to all requests

https://steamcommunity.com/discussions/forum/14/2989789048633291344/
---
 SourceQuery/BaseSocket.php  |  1 +
 SourceQuery/Socket.php      | 20 ++++++++++++++++++++
 SourceQuery/SourceQuery.php | 13 ++++++++-----
 Tests/Tests.php             |  5 +++++
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/SourceQuery/BaseSocket.php b/SourceQuery/BaseSocket.php
index 33fa9c4..462d235 100644
--- a/SourceQuery/BaseSocket.php
+++ b/SourceQuery/BaseSocket.php
@@ -41,6 +41,7 @@
 		abstract public function Close( ) : void;
 		abstract public function Open( string $Address, int $Port, int $Timeout, int $Engine ) : void;
 		abstract public function Write( int $Header, string $String = '' ) : bool;
+		abstract public function WritePadded( int $Header, string $String = '' ) : bool;
 		abstract public function Read( int $Length = 1400 ) : Buffer;
 		
 		protected function ReadInternal( Buffer $Buffer, int $Length, callable $SherlockFunction ) : Buffer
diff --git a/SourceQuery/Socket.php b/SourceQuery/Socket.php
index 4f5cf9f..51c9851 100644
--- a/SourceQuery/Socket.php
+++ b/SourceQuery/Socket.php
@@ -61,6 +61,26 @@
 			return $Length === FWrite( $this->Socket, $Command, $Length );
 		}
 		
+		/**
+		 * Write a request packge to the socket. Pads it up to 1200 bytes to prevent reflective DoS.
+		 *
+		 * @see https://steamcommunity.com/discussions/forum/14/2989789048633291344/
+		 * @return bool Whether fwrite succeeded.
+		 */
+		public function WritePadded( int $Header, string $String = '' ) : bool
+		{
+			$Command = pack( 'ccccca*', 0xFF, 0xFF, 0xFF, 0xFF, $Header, $String );
+			$Length  = strlen( $Command );
+
+			if( $Length < 1200 )
+			{
+				$Command .= str_repeat( "\0", 1200 - $Length );
+				$Length = 1200;
+			}
+
+			return $Length === fwrite( $this->Socket, $Command, $Length );
+		}
+
 		/**
 		 * Reads from socket and returns Buffer.
 		 *
diff --git a/SourceQuery/SourceQuery.php b/SourceQuery/SourceQuery.php
index ecc9757..3dda7ee 100644
--- a/SourceQuery/SourceQuery.php
+++ b/SourceQuery/SourceQuery.php
@@ -200,7 +200,7 @@
 				throw new SocketException( 'Not connected.', SocketException::NOT_CONNECTED );
 			}
 			
-			$this->Socket->Write( self::A2S_INFO, "Source Engine Query\0" );
+			$this->Socket->WritePadded( self::A2S_INFO, "Source Engine Query\0" );
 			$Buffer = $this->Socket->Read( );
 			
 			$Type = $Buffer->GetByte( );
@@ -365,7 +365,7 @@
 			
 			$this->GetChallenge( self::A2S_PLAYER, self::S2A_PLAYER );
 			
-			$this->Socket->Write( self::A2S_PLAYER, $this->Challenge );
+			$this->Socket->WritePadded( self::A2S_PLAYER, $this->Challenge );
 			$Buffer = $this->Socket->Read( 14000 ); // Moronic Arma 3 developers do not split their packets, so we have to read more data
 			// This violates the protocol spec, and they probably should fix it: https://developer.valvesoftware.com/wiki/Server_queries#Protocol
 			
@@ -411,7 +411,7 @@
 			
 			$this->GetChallenge( self::A2S_RULES, self::S2A_RULES );
 			
-			$this->Socket->Write( self::A2S_RULES, $this->Challenge );
+			$this->Socket->WritePadded( self::A2S_RULES, $this->Challenge );
 			$Buffer = $this->Socket->Read( );
 			
 			$Type = $Buffer->GetByte( );
@@ -452,10 +452,13 @@
 			
 			if( $this->UseOldGetChallengeMethod )
 			{
-				$Header = self::A2S_SERVERQUERY_GETCHALLENGE;
+				$this->Socket->Write( self::A2S_SERVERQUERY_GETCHALLENGE, "\xFF\xFF\xFF\xFF" );
+			}
+			else
+			{
+				$this->Socket->WritePadded( $Header, "\xFF\xFF\xFF\xFF" );
 			}
 			
-			$this->Socket->Write( $Header, "\xFF\xFF\xFF\xFF" );
 			$Buffer = $this->Socket->Read( );
 			
 			$Type = $Buffer->GetByte( );
diff --git a/Tests/Tests.php b/Tests/Tests.php
index dc0ebda..ec79583 100644
--- a/Tests/Tests.php
+++ b/Tests/Tests.php
@@ -38,6 +38,11 @@
 			return true;
 		}
 		
+		public function WritePadded( int $Header, string $String = '' ) : bool
+		{
+			return true;
+		}
+		
 		public function Read( int $Length = 1400 ) : Buffer
 		{
 			$Buffer = new Buffer( );