Introduce server query padding

For compatibility with security patches to future game servers versions
this adds a 1200 byte padding to all requests packets as defined in the
following HLDS mailing list post:

https://www.mail-archive.com/[email protected]/msg01194.html

See koraktor/steam-condenser#331

lib/steam-condenser/servers/packets/a2s_info_packet.rb

@@ -1,9 +1,9 @@
 # This code is free software; you can redistribute it and/or modify it under
 # the terms of the new BSD License.
 #
-# Copyright (c) 2008-2012, Sebastian Staudt
+# Copyright (c) 2008-2020, Sebastian Staudt
 
-require 'steam-condenser/servers/packets/base_packet'
+require 'steam-condenser/servers/packets/query_packet'
 
 module SteamCondenser::Servers::Packets
 
@@ -16,7 +16,7 @@ module SteamCondenser::Servers::Packets
   # @see GameServer#update_server_info
   class A2S_INFO_Packet
 
-    include BasePacket
+    include QueryPacket
 
     # Creates a new A2S_INFO request object
     def initialize

lib/steam-condenser/servers/packets/a2s_player_packet.rb

@@ -1,10 +1,9 @@
 # This code is free software; you can redistribute it and/or modify it under
 # the terms of the new BSD License.
 #
-# Copyright (c) 2008-2012, Sebastian Staudt
+# Copyright (c) 2008-2020, Sebastian Staudt
 
 require 'steam-condenser/servers/packets/base_packet'
-require 'steam-condenser/servers/packets/request_with_challenge'
 
 module SteamCondenser::Servers::Packets
 
@@ -20,14 +19,13 @@ module SteamCondenser::Servers::Packets
   class A2S_PLAYER_Packet
 
     include BasePacket
-    include RequestWithChallenge
 
     # Creates a new A2S_PLAYER request object including the challenge number
     #
     # @param [Numeric] challenge_number The challenge number received from the
     #        server
     def initialize(challenge_number = -1)
-      super A2S_PLAYER_HEADER, challenge_number
+      super A2S_PLAYER_HEADER, [challenge_number.to_i].pack('l')
     end
 
   end

lib/steam-condenser/servers/packets/a2s_rules_packet.rb

@@ -1,10 +1,9 @@
 # This code is free software; you can redistribute it and/or modify it under
 # the terms of the new BSD License.
 #
-# Copyright (c) 2008-2012, Sebastian Staudt
+# Copyright (c) 2008-2020, Sebastian Staudt
 
-require 'steam-condenser/servers/packets/base_packet'
-require 'steam-condenser/servers/packets/request_with_challenge'
+require 'steam-condenser/servers/packets/query_packet'
 
 module SteamCondenser::Servers::Packets
 
@@ -20,15 +19,14 @@ module SteamCondenser::Servers::Packets
   # @see GameServer#update_rules_info
   class A2S_RULES_Packet
 
-    include BasePacket
-    include RequestWithChallenge
+    include QueryPacket
 
     # Creates a new A2S_RULES request object including the challenge number
     #
     # @param [Numeric] challenge_number The challenge number received from the
     #        server
     def initialize(challenge_number = -1)
-      super A2S_RULES_HEADER, challenge_number
+      super A2S_RULES_HEADER, [challenge_number.to_i].pack('l')
     end
 
   end

lib/steam-condenser/servers/packets/query_packet.rb

@@ -0,0 +1,31 @@
+# This code is free software; you can redistribute it and/or modify it under
+# the terms of the new BSD License.
+#
+# Copyright (c) 2020, Sebastian Staudt
+
+require 'steam-condenser/servers/packets/base_packet'
+
+module SteamCondenser::Servers::Packets
+
+  # This is used as a wrapper to create padding of request packets to a minimum
+  # size of 1200 bytes. This was introduced in November 2020 as a counter-measure
+  # to DoS attacks on game servers.
+  #
+  # @author Sebastian Staudt
+  module QueryPacket
+
+    include BasePacket
+
+    # The minimum package size as defined by Valve
+    STEAM_GAMESERVER_MIN_CONNECTIONLESS_PACKET_SIZE = 1200
+
+    # Creates a new query packet including data padding
+    #
+    # @param [Fixnum] header The packet header
+    # @param [String] content The raw data of the packet
+    def initialize(header, content)
+      super header, content.to_s.ljust(STEAM_GAMESERVER_MIN_CONNECTIONLESS_PACKET_SIZE - 5, "\0")
+    end
+
+  end
+end

test/steam-condenser/servers/packets/test_query_packet.rb

@@ -0,0 +1,26 @@
+# This code is free software; you can redistribute it and/or modify it under
+# the terms of the new BSD License.
+#
+# Copyright (c) 2020, Sebastian Staudt
+
+require 'helper'
+
+class TestQueryPacket < Test::Unit::TestCase
+
+  class GenericQueryPacket
+    include Servers::Packets::QueryPacket
+  end
+
+  context 'A query packet' do
+
+    setup do
+      @packet = GenericQueryPacket.new 0x61, 'test'
+    end
+
+    should 'pad its content to at least 1200 bytes' do
+      assert_equal [255, 255, 255, 255, 'atest' + "\0" * 1191].pack('c4a*'), @packet.to_s
+    end
+
+  end
+
+end