Allow cache files inside web root

Cache files now use PHP to avoid being readable. We also prevent access with .htaccess (for the common Apache setup).

.gitignore

 # Ignore config file in development
 qa-config.php
+qa-cache/*/
 
 # Other files
 .DS_Store
@@ -9,5 +10,4 @@ qa-config.php
 .Trashes
 ehthumbs.db
 Thumbs.db
-
 .idea/

qa-cache/.htaccess

+Deny from all

qa-config-example.php

@@ -86,10 +86,10 @@
 */
 
 /*
-	If you wish to use caching, you must define QA_CACHE_DIRECTORY to store the cache files. The
-	directory must be writable by the web server. It also must be OUTSIDE the public root. For
-	example if your site resides in '/var/www/yoursite/public_html', then the cache directory could
-	be '/var/www/yoursite/qa-cache', but it cannot be '/var/www/yoursite/public_html/qa-cache'.
+	If you wish to use file-based caching, you must define QA_CACHE_DIRECTORY to store the cache
+	files. The directory must be writable by the web server. For maximum security it's STRONGLY
+	recommended to place the folder outside of the web root (so they can never be accessed via a
+	web browser).
 
 	define('QA_CACHE_DIRECTORY', '/path/to/writable_cache_directory/');
 */

qa-include/Q2A/Storage/FileCacheDriver.php

@@ -30,6 +30,8 @@ class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 	private $error;
 	private $cacheDir;
 
+	private $phpProtect = '<?php header($_SERVER[\'SERVER_PROTOCOL\'].\' 404 Not Found\'); die; ?>';
+
 	/**
 	 * Creates a new FileCache instance and checks we can write to the cache directory.
 	 * @param array $config Configuration data, including cache storage directory.
@@ -46,12 +48,8 @@ class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 
 		if (isset($config['dir'])) {
 			$this->cacheDir = realpath($config['dir']);
-
 			if (!is_writable($this->cacheDir)) {
 				$this->error = qa_lang_html_sub('admin/caching_dir_error', $config['dir']);
-			} elseif (strpos($this->cacheDir, realpath($_SERVER['DOCUMENT_ROOT'])) === 0 || strpos($this->cacheDir, realpath(QA_BASE_DIR)) === 0) {
-				// check the folder is outside the public root - checks against server root and Q2A root, in order to handle symbolic links
-				$this->error = qa_lang_html_sub('admin/caching_dir_public', $config['dir']);
 			}
 		} else {
 			$this->error = qa_lang_html('admin/caching_dir_missing');
@@ -77,6 +75,7 @@ class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 
 		if (is_readable($file)) {
 			$lines = file($file, FILE_IGNORE_NEW_LINES);
+			$skipLine = array_shift($lines);
 			$actualKey = array_shift($lines);
 
 			// double check this is the correct data
@@ -114,7 +113,7 @@ class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 		if ($this->enabled && $ttl > 0) {
 			$encData = serialize($data);
 			$expiry = time() + ($ttl * 60);
-			$cache = $fullKey . "\n" . $expiry . "\n" . $encData;
+			$cache = $this->phpProtect . "\n" . $fullKey . "\n" . $expiry . "\n" . $encData;
 
 			$file = $this->getFilename($fullKey);
 			$dir = dirname($file);
@@ -279,6 +278,6 @@ class Q2A_Storage_FileCacheDriver implements Q2A_Storage_CacheDriver
 	private function getFilename($fullKey)
 	{
 		$filename = sha1($fullKey);
-		return $this->cacheDir . '/' . substr($filename, 0, 1) . '/' . substr($filename, 1, 2) . '/' . $filename;
+		return $this->cacheDir . '/' . substr($filename, 0, 1) . '/' . substr($filename, 1, 2) . '/' . $filename . '.php';
 	}
 }