CacheHandler.php

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<?php
namespace Elgg\Application;

use Elgg\Application;
use Elgg\Config;


class CacheHandler {
    
    public static $extensions = [
        'bmp' => "image/bmp",
        'css' => "text/css",
        'gif' => "image/gif",
        'html' => "text/html",
        'ico' => "image/x-icon",
        'jpeg' => "image/jpeg",
        'jpg' => "image/jpeg",
        'js' => "application/javascript",
        'png' => "image/png",
        'svg' => "image/svg+xml",
        'swf' => "application/x-shockwave-flash",
        'tiff' => "image/tiff",
        'webp' => "image/webp",
        'xml' => "text/xml",
        'eot' => "application/vnd.ms-fontobject",
        'ttf' => "application/font-ttf",
        'woff' => "application/font-woff",
        'woff2' => "application/font-woff2",
        'otf' => "application/font-otf",
    ];

    public static $utf8_content_types = [
        "text/css",
        "text/html",
        "application/javascript",
        "image/svg+xml",
        "text/xml",
    ];

    private $application;

    private $config;

    private $server_vars;

    public function __construct(Application $app, Config $config, $server_vars) {
        $this->application = $app;
        $this->config = $config;
        $this->server_vars = $server_vars;
    }

    public function handleRequest($path) {
        $config = $this->config;
        
        $request = $this->parsePath($path);
        if (!$request) {
            $this->send403();
        }
        
        $ts = $request['ts'];
        $view = $request['view'];
        $viewtype = $request['viewtype'];

        $content_type = $this->getContentType($view);
        if (empty($content_type)) {
            $this->send403("Asset must have a valid file extension");
        }

        if (in_array($content_type, self::$utf8_content_types)) {
            header("Content-Type: $content_type;charset=utf-8");
        } else {
            header("Content-Type: $content_type");
        }

        // this may/may not have to connect to the DB
        $this->setupSimplecache();

        // we can't use $config->get yet. It fails before the core is booted
        if (!$config->getVolatile('simplecache_enabled')) {

            $this->application->bootCore();

            if (!$this->isCacheableView($view)) {
                $this->send403("Requested view is not an asset");
            } else {
                $content = $this->renderView($view, $viewtype);
                $etag = '"' . md5($content) . '"';
                $this->sendRevalidateHeaders($etag);
                $this->handle304($etag);

                echo $content;
            }
            exit;
        }

        $etag = "\"$ts\"";
        $this->handle304($etag);

        // trust the client but check for an existing cache file
        $filename = $config->getVolatile('cacheroot') . "views_simplecache/$ts/$viewtype/$view";
        if (file_exists($filename)) {
            $this->sendCacheHeaders($etag);
            readfile($filename);
            exit;
        }

        // the hard way
        $this->application->bootCore();

        elgg_set_viewtype($viewtype);
        if (!$this->isCacheableView($view)) {
            $this->send403("Requested view is not an asset");
        }

        $lastcache = (int)$config->get('lastcache');

        $filename = $config->getVolatile('cacheroot') . "views_simplecache/$lastcache/$viewtype/$view";

        if ($lastcache == $ts) {
            $this->sendCacheHeaders($etag);

            $content = $this->getProcessedView($view, $viewtype);

            $dir_name = dirname($filename);
            if (!is_dir($dir_name)) {
                // PHP and the server accessing the cache symlink may be a different user. And here
                // it's safe to make everything readable anyway.
                mkdir($dir_name, 0775, true);
            }

            file_put_contents($filename, $content);
            chmod($filename, 0664);
        } else {
            // if wrong timestamp, don't send HTTP cache
            $content = $this->renderView($view, $viewtype);
        }

        echo $content;
        exit;
    }

    public function parsePath($path) {
        // no '..'
        if (false !== strpos($path, '..')) {
            return array();
        }
        // only alphanumeric characters plus /, ., -, and _
        if (preg_match('#[^a-zA-Z0-9/\.\-_]#', $path)) {
            return array();
        }

        // testing showed regex to be marginally faster than array / string functions over 100000 reps
        // it won't make a difference in real life and regex is easier to read.
        // <ts>/<viewtype>/<name/of/view.and.dots>.<type>
        if (!preg_match('#^/cache/([0-9]+)/([^/]+)/(.+)$#', $path, $matches)) {
            return array();
        }

        return array(
            'ts' => $matches[1],
            'viewtype' => $matches[2],
            'view' => $matches[3],
        );
    }

    protected function isCacheableView($view) {
        if (preg_match('~^languages/(.*)\.js$~', $view, $m)) {
            return in_array($m[1],  _elgg_services()->translator->getAllLanguageCodes());
        }
        return _elgg_services()->views->isCacheableView($view);
    }

    protected function setupSimplecache() {
        // we can't use Elgg\Config::get yet. It fails before the core is booted
        $config = $this->config;
        $config->loadSettingsFile();

        if ($config->getVolatile('cacheroot') && $config->getVolatile('simplecache_enabled') !== null) {
            // we can work with these...
            return;
        }

        $db = $this->application->getDb();

        try {
            $rows = $db->getData("
                SELECT `name`, `value`
                FROM {$db->prefix}datalists
                WHERE `name` IN ('dataroot', 'simplecache_enabled')
            ");
            if (!$rows) {
                $this->send403('Cache error: unable to get the data root');
            }
        } catch (\DatabaseException $e) {
            if (0 === strpos($e->getMessage(), "Elgg couldn't connect")) {
                $this->send403('Cache error: unable to connect to database server');
            } else {
                $this->send403('Cache error: unable to connect to Elgg database');
            }
            exit; // unnecessary, but helps PhpStorm understand
        }

        foreach ($rows as $row) {
            $config->set($row->name, $row->value);
        }

        if (!$config->getVolatile('cacheroot')) {
            $dataroot = $config->getVolatile('dataroot');
            if (!$dataroot) {
                $this->send403('Cache error: unable to get the cache root');
            }
            $config->set('cacheroot', $dataroot);
        }
    }

    protected function sendCacheHeaders($etag) {
        header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', strtotime("+6 months")), true);
        header("Pragma: public", true);
        header("Cache-Control: public", true);
        header("ETag: $etag");
    }

    protected function sendRevalidateHeaders($etag) {
        header_remove('Expires');
        header("Pragma: public", true);
        header("Cache-Control: public, max-age=0, must-revalidate", true);
        header("ETag: $etag");
    }

    protected function handle304($etag) {
        if (!isset($this->server_vars['HTTP_IF_NONE_MATCH'])) {
            return;
        }

        // strip -gzip for #9427
        $if_none_match = str_replace('-gzip', '', trim($this->server_vars['HTTP_IF_NONE_MATCH']));
        if ($if_none_match === $etag) {
            header("HTTP/1.1 304 Not Modified");
            exit;
        }
    }

    protected function getContentType($view) {
        $extension = $this->getViewFileType($view);
        
        if (isset(self::$extensions[$extension])) {
            return self::$extensions[$extension];
        } else {
            return null;
        }
    }
    
    private function getViewFileType($view) {
        $extension = (new \SplFileInfo($view))->getExtension();
        $hasValidExtension = isset(self::$extensions[$extension]);

        if ($hasValidExtension) {
            return $extension;
        }
        
        if (preg_match('~(?:^|/)(css|js)(?:$|/)~', $view, $m)) {
            return $m[1];
        }
        
        return 'unknown';
    }

    protected function getProcessedView($view, $viewtype) {
        $content = $this->renderView($view, $viewtype);

        $hook_type = $this->getViewFileType($view);
        $hook_params = array(
            'view' => $view,
            'viewtype' => $viewtype,
            'view_content' => $content,
        );
        return \_elgg_services()->hooks->trigger('simplecache:generate', $hook_type, $hook_params, $content);
    }

    protected function renderView($view, $viewtype) {
        elgg_set_viewtype($viewtype);

        if ($viewtype === 'default' && preg_match("#^languages/(.*?)\\.js$#", $view, $matches)) {
            $view = "languages.js";
            $vars = ['language' => $matches[1]];
        } else {
            $vars = [];
        }

        if (!elgg_view_exists($view)) {
            $this->send403();
        }

        // disable error reporting so we don't cache problems
        $this->config->set('debug', null);

        // @todo elgg_view() checks if the page set is done (isset($GLOBALS['_ELGG']->pagesetupdone)) and
        // triggers an event if it's not. Calling elgg_view() here breaks submenus
        // (at least) because the page setup hook is called before any
        // contexts can be correctly set (since this is called before page_handler()).
        // To avoid this, lie about $CONFIG->pagehandlerdone to force
        // the trigger correctly when the first view is actually being output.
        $GLOBALS['_ELGG']->pagesetupdone = true;

        return elgg_view($view, $vars);
    }

    protected function send403($msg = 'Cache error: bad request') {
        header('HTTP/1.1 403 Forbidden');
        echo $msg;
        exit;
    }
}