Implement runtimeID table randomization, closes #2841

src/pocketmine/network/mcpe/protocol/StartGamePacket.php

@@ -30,9 +30,8 @@ use pocketmine\math\Vector3;
 use pocketmine\network\mcpe\NetworkBinaryStream;
 use pocketmine\network\mcpe\NetworkSession;
 use pocketmine\network\mcpe\protocol\types\PlayerPermissions;
+use pocketmine\network\mcpe\protocol\types\RuntimeBlockMapping;
 use function count;
-use function file_get_contents;
-use function json_decode;
 
 class StartGamePacket extends DataPacket{
 	public const NETWORK_ID = ProtocolInfo::START_GAME_PACKET;
@@ -251,7 +250,7 @@ class StartGamePacket extends DataPacket{
 		if(self::$runtimeIdTable === null){
 			//this is a really nasty hack, but it'll do for now
 			$stream = new NetworkBinaryStream();
-			$data = json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . "runtimeid_table.json"), true);
+			$data = RuntimeBlockMapping::getBedrockKnownStates();
 			$stream->putUnsignedVarInt(count($data));
 			foreach($data as $v){
 				$stream->putString($v["name"]);

src/pocketmine/network/mcpe/protocol/types/RuntimeBlockMapping.php

@@ -0,0 +1,118 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\network\mcpe\protocol\types;
+
+use pocketmine\block\BlockIds;
+use function file_get_contents;
+use function getmypid;
+use function json_decode;
+use function mt_rand;
+use function mt_srand;
+use function shuffle;
+
+/**
+ * @internal
+ */
+final class RuntimeBlockMapping{
+
+	/** @var int[] */
+	private static $legacyToRuntimeMap = [];
+	/** @var int[] */
+	private static $runtimeToLegacyMap = [];
+	/** @var mixed[] */
+	private static $bedrockKnownStates;
+
+	private function __construct(){
+		//NOOP
+	}
+
+	public static function init() : void{
+		$legacyIdMap = json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . "legacy_id_map.json"), true);
+
+		self::$bedrockKnownStates = self::randomizeTable(json_decode(file_get_contents(\pocketmine\RESOURCE_PATH . "runtimeid_table.json"), true));
+
+		foreach(self::$bedrockKnownStates as $k => $obj){
+			//this has to use the json offset to make sure the mapping is consistent with what we send over network, even though we aren't using all the entries
+			if(!isset($legacyIdMap[$obj["name"]])){
+				continue;
+			}
+			self::registerMapping($k, $legacyIdMap[$obj["name"]], $obj["data"]);
+		}
+	}
+
+	/**
+	 * Randomizes the order of the runtimeID table to prevent plugins relying on them.
+	 * Plugins shouldn't use this stuff anyway, but plugin devs have an irritating habit of ignoring what they
+	 * aren't supposed to do, so we have to deliberately break it to make them stop.
+	 *
+	 * @param array $table
+	 *
+	 * @return array
+	 */
+	private static function randomizeTable(array $table) : array{
+		$postSeed = mt_rand(); //save a seed to set afterwards, to avoid poor quality randoms
+		mt_srand(getmypid() ?: 0); //Use a seed which is the same on all threads. This isn't a secure seed, but we don't care.
+		shuffle($table);
+		mt_srand($postSeed); //restore a good quality seed that isn't dependent on PID
+		return $table;
+	}
+
+	/**
+	 * @param int $id
+	 * @param int $meta
+	 *
+	 * @return int
+	 */
+	public static function toStaticRuntimeId(int $id, int $meta = 0) : int{
+		/*
+		 * try id+meta first
+		 * if not found, try id+0 (strip meta)
+		 * if still not found, return update! block
+		 */
+		return self::$legacyToRuntimeMap[($id << 4) | $meta] ?? self::$legacyToRuntimeMap[$id << 4] ?? self::$legacyToRuntimeMap[BlockIds::INFO_UPDATE << 4];
+	}
+
+	/**
+	 * @param int $runtimeId
+	 *
+	 * @return int[] [id, meta]
+	 */
+	public static function fromStaticRuntimeId(int $runtimeId) : array{
+		$v = self::$runtimeToLegacyMap[$runtimeId];
+		return [$v >> 4, $v & 0xf];
+	}
+
+	private static function registerMapping(int $staticRuntimeId, int $legacyId, int $legacyMeta) : void{
+		self::$legacyToRuntimeMap[($legacyId << 4) | $legacyMeta] = $staticRuntimeId;
+		self::$runtimeToLegacyMap[$staticRuntimeId] = ($legacyId << 4) | $legacyMeta;
+	}
+
+	/**
+	 * @return array
+	 */
+	public static function getBedrockKnownStates() : array{
+		return self::$bedrockKnownStates;
+	}
+}
+RuntimeBlockMapping::init();