From 0e5395c59bdc0d130eafa6c9b385075214988e52 Mon Sep 17 00:00:00 2001
From: Dylan T <dktapps@pmmp.io>
Date: Mon, 18 Mar 2024 16:48:17 +0000
Subject: [PATCH] PocketMine-MP.phar self-extraction to decompressed cache
 (#6217)

Because ext-phar sucks, tmp gets spammed by cache files for every thread when loading files from the phar on the fly.

Instead, we convert the `.phar` into a decompressed `.tar` in the tmp directory and require files from inside it. Surprisingly, this works because `ext-phar` supports `tar` and `zip` natively. No stream wrapper is required, as the `PocketMine.php` bootstrap loads files relative to its location, so the cache is automatically used for everything.

To be honest I would rather get rid of phars entirely, but they are still the easiest way to have PhpStorm load PocketMine-MP API information for now, and the alternatives are more complicated and inconvenient.

### Caveats
Everywhere that previously used `new Phar(Phar::running(false))` in the core code needs to be updated to use `PharData` for this to work correctly. Plugins don't need to do anything.

### Why not just use `Phar::decompressFiles()`?
This requires setting `phar.readonly` to `0`, which is a security issue. Technically, we could have used a subprocess to do this, but it just didn't seem right.

### WTF? `phar://` can be used on `tar` files???
Yup. I was just as surprised to find out that `require` works in such contexts.

### Relevant issues
- Closes #6214

## Changes
### API changes
None.

### Behavioural changes
Server startup will be slightly slower, as the phar has to decompress and convert itself into a `.tar`. However, testing showed that this generally takes less than 200 ms, so it should be barely noticeable.

## Backwards compatibility
No BC issues.

## Tests
Locally tested and the CI will also verify
---
 build/server-phar-stub.php | 168 +++++++++++++++++++++++++++++++++++++
 build/server-phar.php      |  18 +---
 src/VersionInfo.php        |   6 +-
 3 files changed, 175 insertions(+), 17 deletions(-)
 create mode 100644 build/server-phar-stub.php

diff --git a/build/server-phar-stub.php b/build/server-phar-stub.php
new file mode 100644
index 000000000..b4018e3a7
--- /dev/null
+++ b/build/server-phar-stub.php
@@ -0,0 +1,168 @@
+<?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\server_phar_stub;
+
+use function clearstatcache;
+use function copy;
+use function fclose;
+use function fflush;
+use function flock;
+use function fopen;
+use function fwrite;
+use function getmypid;
+use function hrtime;
+use function is_dir;
+use function is_file;
+use function mkdir;
+use function number_format;
+use function str_replace;
+use function stream_get_contents;
+use function sys_get_temp_dir;
+use function tempnam;
+use function unlink;
+use const DIRECTORY_SEPARATOR;
+use const LOCK_EX;
+use const LOCK_NB;
+use const LOCK_UN;
+
+/**
+ * Finds the appropriate tmp directory to store the decompressed phar cache, accounting for potential file name
+ * collisions.
+ */
+function preparePharCacheDirectory() : string{
+	clearstatcache();
+
+	$i = 0;
+	do{
+		$tmpPath = sys_get_temp_dir() . '/PocketMine-MP-phar-cache.' . $i;
+		$i++;
+	}while(is_file($tmpPath));
+	if(!@mkdir($tmpPath) && !is_dir($tmpPath)){
+		throw new \RuntimeException("Failed to create temporary directory $tmpPath. Please ensure the disk has enough space and that the current user has permission to write to this location.");
+	}
+
+	return $tmpPath;
+}
+
+/**
+ * Deletes caches left behind by previous server instances.
+ * This ensures that the tmp directory doesn't get flooded by servers crashing in restart loops.
+ */
+function cleanupPharCache(string $tmpPath) : void{
+	clearstatcache();
+
+	/** @var string[] $matches */
+	foreach(new \RegexIterator(
+		new \FilesystemIterator(
+			$tmpPath,
+			\FilesystemIterator::CURRENT_AS_PATHNAME | \FilesystemIterator::SKIP_DOTS | \FilesystemIterator::UNIX_PATHS
+		),
+		'/(.+)\.lock$/',
+		\RegexIterator::GET_MATCH
+	) as $matches){
+		$lockFilePath = $matches[0];
+		$baseTmpPath = $matches[1];
+
+		$file = @fopen($lockFilePath, "rb");
+		if($file === false){
+			//another process probably deleted the lock file already
+			continue;
+		}
+
+		if(flock($file, LOCK_EX | LOCK_NB)){
+			//this tmpfile is no longer in use
+			flock($file, LOCK_UN);
+			fclose($file);
+
+			unlink($lockFilePath);
+			unlink($baseTmpPath . ".tar");
+			unlink($baseTmpPath);
+			echo "Deleted stale phar cache at $baseTmpPath\n";
+		}else{
+			$pid = stream_get_contents($file);
+			fclose($file);
+
+			echo "Phar cache at $baseTmpPath is still in use by PID $pid\n";
+		}
+	}
+}
+
+function convertPharToTar(string $tmpName, string $pharPath) : string{
+	$tmpPharPath = $tmpName . ".phar";
+	copy($pharPath, $tmpPharPath);
+
+	$phar = new \Phar($tmpPharPath);
+	//phar requires phar.readonly=0, and zip doesn't support disabling compression - tar is the only viable option
+	//we don't need phar anyway since we don't need to directly execute the file, only require files from inside it
+	$phar->convertToData(\Phar::TAR, \Phar::NONE);
+	unset($phar);
+	\Phar::unlinkArchive($tmpPharPath);
+
+	return $tmpName . ".tar";
+}
+
+/**
+ * Locks a phar tmp cache to prevent it from being deleted by other server instances.
+ * This code looks similar to Filesystem::createLockFile(), but we can't use that because it's inside the compressed
+ * phar.
+ */
+function lockPharCache(string $lockFilePath) : void{
+	//this static variable will keep the file(s) locked until the process ends
+	static $lockFiles = [];
+
+	$lockFile = fopen($lockFilePath, "wb");
+	if($lockFile === false){
+		throw new \RuntimeException("Failed to open temporary file");
+	}
+	flock($lockFile, LOCK_EX); //this tells other server instances not to delete this cache file
+	fwrite($lockFile, (string) getmypid()); //maybe useful for debugging
+	fflush($lockFile);
+	$lockFiles[$lockFilePath] = $lockFile;
+}
+
+/**
+ * Prepares a decompressed .tar of PocketMine-MP.phar in the system temp directory for loading code from.
+ *
+ * @return string path to the temporary decompressed phar (actually a .tar)
+ */
+function preparePharCache(string $tmpPath, string $pharPath) : string{
+	clearstatcache();
+
+	$tmpName = tempnam($tmpPath, "PMMP");
+	if($tmpName === false){
+		throw new \RuntimeException("Failed to create temporary file");
+	}
+
+	lockPharCache($tmpName . ".lock");
+	return convertPharToTar($tmpName, $pharPath);
+}
+
+$tmpDir = preparePharCacheDirectory();
+cleanupPharCache($tmpDir);
+echo "Preparing PocketMine-MP.phar decompressed cache...\n";
+$start = hrtime(true);
+$cacheName = preparePharCache($tmpDir, __FILE__);
+echo "Cache ready at $cacheName in " . number_format((hrtime(true) - $start) / 1e9, 2) . "s\n";
+
+require 'phar://' . str_replace(DIRECTORY_SEPARATOR, '/', $cacheName) . '/src/PocketMine.php';
diff --git a/build/server-phar.php b/build/server-phar.php
index 8b4d410ce..f6bb29d51 100644
--- a/build/server-phar.php
+++ b/build/server-phar.php
@@ -23,7 +23,9 @@ declare(strict_types=1);
 
 namespace pocketmine\build\server_phar;
 
+use pocketmine\utils\Filesystem;
 use pocketmine\utils\Git;
+use Symfony\Component\Filesystem\Path;
 use function array_map;
 use function count;
 use function dirname;
@@ -169,21 +171,7 @@ function main() : void{
 			'git' => $gitHash,
 			'build' => $build
 		],
-		<<<'STUB'
-<?php
-
-$tmpDir = sys_get_temp_dir();
-if(!is_readable($tmpDir) or !is_writable($tmpDir)){
-	echo "ERROR: tmpdir $tmpDir is not accessible." . PHP_EOL;
-	echo "Check that the directory exists, and that the current user has read/write permissions for it." . PHP_EOL;
-	echo "Alternatively, set 'sys_temp_dir' to a different directory in your php.ini file." . PHP_EOL;
-	exit(1);
-}
-
-require("phar://" . __FILE__ . "/src/PocketMine.php");
-__HALT_COMPILER();
-STUB
-,
+		Filesystem::fileGetContents(Path::join(__DIR__, 'server-phar-stub.php')) . "\n__HALT_COMPILER();",
 		\Phar::SHA1,
 		\Phar::GZ
 	) as $line){
diff --git a/src/VersionInfo.php b/src/VersionInfo.php
index 24428cc48..420b12e58 100644
--- a/src/VersionInfo.php
+++ b/src/VersionInfo.php
@@ -63,7 +63,8 @@ final class VersionInfo{
 			if(\Phar::running(true) === ""){
 				$gitHash = Git::getRepositoryStatePretty(\pocketmine\PATH);
 			}else{
-				$phar = new \Phar(\Phar::running(false));
+				$pharPath = \Phar::running(false);
+				$phar = \Phar::isValidPharFilename($pharPath) ? new \Phar($pharPath) : new \PharData($pharPath);
 				$meta = $phar->getMetadata();
 				if(isset($meta["git"])){
 					$gitHash = $meta["git"];
@@ -82,7 +83,8 @@ final class VersionInfo{
 		if(self::$buildNumber === null){
 			self::$buildNumber = 0;
 			if(\Phar::running(true) !== ""){
-				$phar = new \Phar(\Phar::running(false));
+				$pharPath = \Phar::running(false);
+				$phar = \Phar::isValidPharFilename($pharPath) ? new \Phar($pharPath) : new \PharData($pharPath);
 				$meta = $phar->getMetadata();
 				if(is_array($meta) && isset($meta["build"]) && is_int($meta["build"])){
 					self::$buildNumber = $meta["build"];