gnu-social/plugins/Oembed/OembedPlugin.php

<?php
/**
 * GNU social - a federating social network
 *
 * OembedPlugin implementation for GNU Social
 *
 * LICENCE: This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * @category  Plugin
 * @package   GNUsocial
 * @author    GNU Social
 * @copyright 2010 Free Software Foundation http://fsf.org
 * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
 * @link      https://www.gnu.org/software/social/
 */
if (!defined ('GNUSOCIAL')) {
        exit (1);
}

// ============================================================================
// OembedPlugin class
//    extends Plugin
//
// Base class for the oEmbed plugin that does most of the heavy lifting to get
// and display representations for remote content.
class OembedPlugin extends Plugin
{

    // settings which can be set in config.php with addPlugin('Oembed', array('param'=>'value', ...));
    // WARNING, these are _regexps_ (slashes added later). Always escape your dots and end your strings
    public $domain_whitelist = array(       // hostname => service provider
                                    '^i\d*\.ytimg\.com$' => 'YouTube',
                                    '^i\d*\.vimeocdn\.com$' => 'Vimeo',
                                    );
    public $append_whitelist = array();  // fill this array as domain_whitelist to add more trusted sources
    public $check_whitelist  = false;    // security/abuse precaution
    public $keep_original = false;

    protected $imgData = array();

    // ------------------------------------------------------------------------
    // OembedPlugin::initialize() function
    // Institiate the oEmbed plugin and set up the environment it needs for it.
    // Returns true if it initialized properly, the exception object if it
    // doesn't.
    public function initialize()
    {
        parent::initialize();

        $this->domain_whitelist = array_merge($this->domain_whitelist, $this->append_whitelist);
    }

    // ------------------------------------------------------------------------
    // OembedPlugin::onCheckSchema() function
    // The code executed on GNU Social checking the database schema, which in
    // this case is to make sure we have the plugin table we need.
    // Returns true if it ran successfully, the exception object if it doesn't.
    public function onCheckSchema()
    {
        $schema = Schema::get();
        $schema->ensureTable('file_oembed', File_oembed::schemaDef());
        return true;
    }

    // -------------------------------------------------------------------------
    // OembedPlugin::onRouterInitialized($m) function
    //   args: $m (URLMapper) = the router that was initialized.
    // This code executes when GNU Social creates the page routing, and we hook
    // on this event to add our action handler for oEmbed.
    // Returns true if successful, the exception object if it isn't.
    public function onRouterInitialized(URLMapper $m)
    {
        $m->connect('main/oembed', array('action' => 'oembed'));
    }

    // --------------------------------------------------------------------------
    // OembedPlugin::onGetRemoteUrlMetadataFromDom($url, $dom, $metadata) function
    //    args: $url      = the remote URL we're looking at
    //          $dom      = the document we're getting metadata from
    //          $metadata = class representing the metadata
    // This event executes when GNU Social encounters a remote URL we then decide
    // to interrogate for metadata.  oEmbed gloms onto it to see if we have an
    // oEmbed endpoint or image to try to represent in the post.
    // Returns true if successful, the exception object if it isn't.
    public function onGetRemoteUrlMetadataFromDom($url, DOMDocument $dom, stdClass &$metadata)
    {
        try {
            common_log(LOG_INFO, 'Trying to discover an oEmbed endpoint using link headers.');
            $api = oEmbedHelper::oEmbedEndpointFromHTML($dom);
            common_log(LOG_INFO, 'Found oEmbed API endpoint ' . $api . ' for URL ' . $url);
            $params = array(
                'maxwidth' => common_config('thumbnail', 'width'),
                'maxheight' => common_config('thumbnail', 'height'),
            );
            $metadata = oEmbedHelper::getOembedFrom($api, $url, $params);

            // Facebook just gives us javascript in its oembed html,
            // so use the content of the title element instead
            if(strpos($url,'https://www.facebook.com/') === 0) {
              $metadata->html = @$dom->getElementsByTagName('title')->item(0)->nodeValue;
            }

            // Wordpress sometimes also just gives us javascript, use og:description if it is available
            $xpath = new DomXpath($dom);
            $generatorNode = @$xpath->query('//meta[@name="generator"][1]')->item(0);
            if ($generatorNode instanceof DomElement) {
                // when wordpress only gives us javascript, the html stripped from tags
                // is the same as the title, so this helps us to identify this (common) case
                if(strpos($generatorNode->getAttribute('content'),'WordPress') === 0
                && trim(strip_tags($metadata->html)) == trim($metadata->title)) {
                    $propertyNode = @$xpath->query('//meta[@property="og:description"][1]')->item(0);
                    if ($propertyNode instanceof DomElement) {
                        $metadata->html = $propertyNode->getAttribute('content');
                    }
                }
            }
        } catch (Exception $e) {
            // FIXME - make sure the error was because we couldn't get metadata, not something else! -mb
            common_log(LOG_INFO, 'Could not find an oEmbed endpoint using link headers, trying OpenGraph from HTML.');
            // Just ignore it!
            $metadata = OpenGraphHelper::ogFromHtml($dom);
        }

        if (isset($metadata->thumbnail_url)) {
            // sometimes sites serve the path, not the full URL, for images
            // let's "be liberal in what you accept from others"!
            // add protocol and host if the thumbnail_url starts with /
            if(substr($metadata->thumbnail_url,0,1) == '/') {
                $thumbnail_url_parsed = parse_url($metadata->url);
                $metadata->thumbnail_url = $thumbnail_url_parsed['scheme']."://".$thumbnail_url_parsed['host'].$metadata->thumbnail_url;
            }

            // some wordpress opengraph implementations sometimes return a white blank image
            // no need for us to save that!
            if($metadata->thumbnail_url == 'https://s0.wp.com/i/blank.jpg') {
                unset($metadata->thumbnail_url);
            }

            // FIXME: this is also true of locally-installed wordpress so we should watch out for that.
        }
       return true;
    }

    public function onEndShowHeadElements(Action $action)
    {
        switch ($action->getActionName()) {
        case 'attachment':
            $action->element('link',array('rel'=>'alternate',
                'type'=>'application/json+oembed',
                'href'=>common_local_url(
                    'oembed',
                    array(),
                    array('format'=>'json', 'url'=>
                        common_local_url('attachment',
                            array('attachment' => $action->attachment->getID())))),
                'title'=>'oEmbed'),null);
            $action->element('link',array('rel'=>'alternate',
                'type'=>'text/xml+oembed',
                'href'=>common_local_url(
                    'oembed',
                    array(),
                    array('format'=>'xml','url'=>
                        common_local_url('attachment',
                            array('attachment' => $action->attachment->getID())))),
                'title'=>'oEmbed'),null);
            break;
        case 'shownotice':
            if (!$action->notice->isLocal()) {
                break;
            }
            try {
                $action->element('link',array('rel'=>'alternate',
                    'type'=>'application/json+oembed',
                    'href'=>common_local_url(
                        'oembed',
                        array(),
                        array('format'=>'json','url'=>$action->notice->getUrl())),
                    'title'=>'oEmbed'),null);
                $action->element('link',array('rel'=>'alternate',
                    'type'=>'text/xml+oembed',
                    'href'=>common_local_url(
                        'oembed',
                        array(),
                        array('format'=>'xml','url'=>$action->notice->getUrl())),
                    'title'=>'oEmbed'),null);
            } catch (InvalidUrlException $e) {
                // The notice is probably a share or similar, which don't
                // have a representational URL of their own.
            }
            break;
        }

        return true;
    }

    public function onEndShowStylesheets(Action $action) {
        $action->cssLink($this->path('css/oembed.css'));
        return true;
    }

    /**
     * Save embedding information for a File, if applicable.
     *
     * Normally this event is called through File::saveNew()
     *
     * @param File   $file       The newly inserted File object.
     *
     * @return boolean success
     */
    public function onEndFileSaveNew(File $file)
    {
        $fo = File_oembed::getKV('file_id', $file->getID());
        if ($fo instanceof File_oembed) {
            common_log(LOG_WARNING, "Strangely, a File_oembed object exists for new file {$file->getID()}", __FILE__);
            return true;
        }

        if (isset($file->mimetype)
            && (('text/html' === substr($file->mimetype, 0, 9)
            || 'application/xhtml+xml' === substr($file->mimetype, 0, 21)))) {

            try {
                $oembed_data = File_oembed::_getOembed($file->url);
                if ($oembed_data === false) {
                    throw new Exception('Did not get oEmbed data from URL');
                }
                $file->setTitle($oembed_data->title);
            } catch (Exception $e) {
                common_log(LOG_WARNING, sprintf(__METHOD__.': %s thrown when getting oEmbed data: %s', get_class($e), _ve($e->getMessage())));
                return true;
            }

            File_oembed::saveNew($oembed_data, $file->getID());
        }
        return true;
    }

    public function onEndShowAttachmentLink(HTMLOutputter $out, File $file)
    {
        $oembed = File_oembed::getKV('file_id', $file->getID());
        if (empty($oembed->author_name) && empty($oembed->provider)) {
            return true;
        }
        $out->elementStart('div', array('id'=>'oembed_info', 'class'=>'e-content'));
        if (!empty($oembed->author_name)) {
            $out->elementStart('div', 'fn vcard author');
            if (empty($oembed->author_url)) {
                $out->text($oembed->author_name);
            } else {
                $out->element('a', array('href' => $oembed->author_url,
                                         'class' => 'url'),
                                $oembed->author_name);
            }
        }
        if (!empty($oembed->provider)) {
            $out->elementStart('div', 'fn vcard');
            if (empty($oembed->provider_url)) {
                $out->text($oembed->provider);
            } else {
                $out->element('a', array('href' => $oembed->provider_url,
                                         'class' => 'url'),
                                $oembed->provider);
            }
        }
        $out->elementEnd('div');
    }

    public function onFileEnclosureMetadata(File $file, &$enclosure)
    {
        // Never treat generic HTML links as an enclosure type!
        // But if we have oEmbed info, we'll consider it golden.
        $oembed = File_oembed::getKV('file_id', $file->getID());
        if (!$oembed instanceof File_oembed || !in_array($oembed->type, array('photo', 'video'))) {
            return true;
        }

        foreach (array('mimetype', 'url', 'title', 'modified', 'width', 'height') as $key) {
            if (isset($oembed->{$key}) && !empty($oembed->{$key})) {
                $enclosure->{$key} = $oembed->{$key};
            }
        }
        return true;
    }

    public function onStartShowAttachmentRepresentation(HTMLOutputter $out, File $file)
    {
        try {
            $oembed = File_oembed::getByFile($file);
        } catch (NoResultException $e) {
            return true;
        }

        // Show thumbnail as usual if it's a photo.
        if ($oembed->type === 'photo') {
            return true;
        }

        $out->elementStart('article', ['class'=>'h-entry oembed']);
        $out->elementStart('header');
        try  {
            $thumb = $file->getThumbnail(128, 128);
            $out->element('img', $thumb->getHtmlAttrs(['class'=>'u-photo oembed']));
            unset($thumb);
        } catch (Exception $e) {
            $out->element('div', ['class'=>'error'], $e->getMessage());
        }
        $out->elementStart('h5', ['class'=>'p-name oembed']);
        $out->element('a', ['class'=>'u-url', 'href'=>$file->getUrl()], common_strip_html($oembed->title));
        $out->elementEnd('h5');
        $out->elementStart('div', ['class'=>'p-author oembed']);
        if (!empty($oembed->author_name)) {
            // TRANS: text before the author name of oEmbed attachment representation
            // FIXME: The whole "By x from y" should be i18n because of different language constructions.
            $out->text(_('By '));
            $attrs = ['class'=>'h-card p-author'];
            if (!empty($oembed->author_url)) {
                $attrs['href'] = $oembed->author_url;
                $tag = 'a';
            } else {
                $tag = 'span';
            }
            $out->element($tag, $attrs, $oembed->author_name);
        }
        if (!empty($oembed->provider)) {
            // TRANS: text between the oEmbed author name and provider url
            // FIXME: The whole "By x from y" should be i18n because of different language constructions.
            $out->text(_(' from '));
            $attrs = ['class'=>'h-card'];
            if (!empty($oembed->provider_url)) {
                $attrs['href'] = $oembed->provider_url;
                $tag = 'a';
            } else {
                $tag = 'span';
            }
            $out->element($tag, $attrs, $oembed->provider);
        }
        $out->elementEnd('div');
        $out->elementEnd('header');
        $out->elementStart('div', ['class'=>'p-summary oembed']);
        $out->raw(common_purify($oembed->html));
        $out->elementEnd('div');
        $out->elementStart('footer');
        $out->elementEnd('footer');
        $out->elementEnd('article');

        return false;
    }

    public function onShowUnsupportedAttachmentRepresentation(HTMLOutputter $out, File $file)
    {
        try {
            $oembed = File_oembed::getByFile($file);
        } catch (NoResultException $e) {
            return true;
        }

        // the 'photo' type is shown through ordinary means, using StartShowAttachmentRepresentation!
        switch ($oembed->type) {
        case 'video':
        case 'link':
            if (!empty($oembed->html)
                    && (GNUsocial::isAjax() || common_config('attachments', 'show_html'))) {
                require_once INSTALLDIR.'/extlib/HTMLPurifier/HTMLPurifier.auto.php';
                $purifier = new HTMLPurifier();
                // FIXME: do we allow <object> and <embed> here? we did that when we used htmLawed, but I'm not sure anymore...
                $out->raw($purifier->purify($oembed->html));
            }
            return false;
        }

        return true;
    }

    // -------------------------------------------------------------------------
    // OembedPlugin::onCreateFileImageThumbnailSource($file, $imgPath, $media)
    //   public function
    //   args: $file = the file of the created thumbnail
    //         $imgPath = the path to the created thumbnail
    //         $media = media type the thumbnail was created for
    // This event executes when GNU Social is creating a file thumbnail entry in
    // the database.  We glom onto this to create proper information for oEmbed
    // object thumbnails.  Returns true if it succeeds (including non-action
    // states where it isn't oEmbed data, so it doesn't mess up the event handle
    // for other things hooked into it), or the exception if it fails.
    public function onCreateFileImageThumbnailSource(File $file, &$imgPath)
    {
        // If we are on a private node, we won't do any remote calls (just as a precaution until
        // we can configure this from config.php for the private nodes)
        if (common_config('site', 'private')) {
            return true;
        }

        // All our remote Oembed images lack a local filename property in the File object
        if (!is_null($file->filename)) {
            common_debug(sprintf('Filename of file id==%d is not null (%s), so nothing oEmbed should handle.', $file->getID(), _ve($file->filename)));
            return true;
        }

        try {
            // If we have proper oEmbed data, there should be an entry in the File_oembed
            // and File_thumbnail tables respectively. If not, we're not going to do anything.
            $thumbnail   = File_thumbnail::byFile($file);
        } catch (NoResultException $e) {
            // Not Oembed data, or at least nothing we either can or want to use.
            common_debug('No oEmbed data found for file id=='.$file->getID());
            return true;
        }

        try {
            $this->storeRemoteFileThumbnail($thumbnail);
        } catch (AlreadyFulfilledException $e) {
            // aw yiss!
        } catch (Exception $e) {
            common_debug(sprintf('oEmbed encountered an exception (%s) for file id==%d: %s', get_class($e), $file->getID(), _ve($e->getMessage())));
            throw $e;
        }

        $imgPath = $thumbnail->getPath();

        return false;
    }

    /**
     * @return boolean          false on no check made, provider name on success
     * @throws ServerException  if check is made but fails
     */
    protected function checkWhitelist($url)
    {
        if (!$this->check_whitelist) {
            return false;   // indicates "no check made"
        }

        $host = parse_url($url, PHP_URL_HOST);
        foreach ($this->domain_whitelist as $regex => $provider) {
            if (preg_match("/$regex/", $host)) {
                return $provider;    // we trust this source, return provider name
            }
        }

        throw new ServerException(sprintf(_('Domain not in remote thumbnail source whitelist: %s'), $host));
    }

    // -------------------------------------------------------------------------
    // OembedFunction::getRemoteFileSize($url)
    // Check the file size of a remote file using a HEAD request and checking
    // the content-length variable returned.  This isn't 100% foolproof but is
    // reliable enough for our purposes.  Returns the file size if it succeeds
    // or the exception if it fails.
    private function getRemoteFileSize($url)
    {
        try {
            if (empty($url)) {
                return false;
            }
            stream_context_set_default(array('http' => array('method' => 'HEAD')));
            $head = @get_headers($url,1);
            if (gettype($head)=="array") {
                $head = array_change_key_case($head);
                $size = isset($head['content-length']) ? $head['content-length'] : 0;

                if (!$size) {
                    return false;
                }
            } else {
                return false;
            }
            return $size; // return formatted size
        } catch (Exception $err) {
            common_log(LOG_ERR, __CLASS__.': getRemoteFileSize on URL : '._ve($url).' threw exception: '.$err->getMessage());
            return false;
        }
    }

    // -------------------------------------------------------------------------
    // OembedPlugin::isRemoteImage($url) private function.
    // A private helper function that uses a CURL lookup to check the mime type
    // of a remote URL to see it it's an image.  Returns true if the remote URL
    // is an image, or false otherwise.
    private function isRemoteImage($url)
    {
        if (!filter_var ($url, FILTER_VALIDATE_URL)) {
            common_log (LOG_ERR,"Invalid URL in OEmbed::isRemoteImage()");
            return false;
        }
        if ($url==null) {
            common_log(LOG_ERR,"URL not specified in OEmbed::isRemoteImage()");
            return false;
        }
        try {
            $curl = curl_init($url);
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($curl, CURLOPT_HEADER, TRUE);
            curl_setopt($curl, CURLOPT_NOBODY, TRUE);
            curl_exec($curl);
            $type    = curl_getinfo($curl, CURLINFO_CONTENT_TYPE);
            if (strpos($type, 'image') !== false) {
                return true;
            } else {
                return false;
            }
        } finally {
            return false;
        }
    }

    // -------------------------------------------------------------------------
    // OembedPlugin::getPHPUploadLimit() private function
    // An internal helper function that parses the php.ini file size limit from
    // the 'human-readable' shorthand into something we can use to test against
    // in conditionals.
    // Returns the php.ini upload limit in machine-readable format, or the
    // exception if it fails.
    // FIXME: We could probably move this to a public utility library.
    private function getPHPUploadLimit()
    {
        $size   = ini_get("upload_max_filesize");
        $suffix = substr($size, -1);
        $size   = substr($size, 0, -1);
        switch(strtoupper($suffix)) {
        case 'P':
            $size *= 1024;
        case 'T':
            $size *= 1024;
        case 'G':
            $size *= 1024;
        case 'M':
            $size *= 1024;
        case 'K':
            $size *= 1024;
            break;
        }
        return $size;
    }

    /**
     * Creates a dummy image with dimensions of original image in order to cheat
     * core GNU Social file handler. Used by remove_original.
     *
     * @author Diogo Cordeiro <diogo@fc.up.pt>
     * @param int32 $width Image's width
     * @param int32 $height Image's height
     * @return string dummy file's filename
     */
    private function create_dummy ($width, $height)
    {
        $filename = "oembed-dummy-".$width."-".$height.".png";
        $filepath = File_thumbnail::path ($filename);
        if (file_exists ($filepath)) {
            return $filename;
        }

        $im = @imagecreate ($width, $height)
            or exit ("Cannot Initialize new GD image stream");
        imagecolorallocate ($im, 0, 0, 0);
        imagepng ($im, File_thumbnail::path ($filename));
        imagedestroy ($im);
        return $filename;
    }

    /**
     * Removes the original thumbnail and updates the entry on database to the
     * dummy object. Depends on create_dummy.
     *
     * @author Diogo Cordeiro <diogo@fc.up.pt>
     * @param File_thumbnail $thumbnail object containing the file thumbnail
     * @return boolean true if had to remove, false if it was already all okay
     */
    private function remove_original ($thumbnail)
    {
        // Do not remove when original is needed
        if ($this->keep_original ||
            (isset ($config['thumbnail']) &&
             ($config['thumbnail']['width']  <= $thumbnail->width) &&
             ($config['thumbnail']['height'] <= $thumbnail->height))
           ) {
            return false;
        }

        $dummy_filename = $this->create_dummy ($thumbnail->width, $thumbnail->height);
        if ($thumbnail->filename == $dummy_filename) {
            return false;
        }
        $original_filepath = File_thumbnail::path ($thumbnail->filename);
        unlink ($original_filepath);

        $orig = clone ($thumbnail);
        $thumbnail->filename = $dummy_filename;
        // Throws exception on failure.
        $thumbnail->updateWithKeys ($orig);

        return true;
    }

    // -------------------------------------------------------------------------
    // OembedPlugin::storeRemoteFileThumbnail($thumbnail) protected function
    //    args: $thumbnail = object containing the file thumbnail
    // Function to create and store a thumbnail representation of a remote image
    // Returns true if it succeeded, the exception if it fails, or false if it
    // is limited by system limits (ie the file is too large.)
    protected function storeRemoteFileThumbnail(File_thumbnail $thumbnail)
    {
        if (!empty($thumbnail->filename) && file_exists($thumbnail->getPath())) {
            $this->remove_original($thumbnail);
            throw new AlreadyFulfilledException(sprintf('A thumbnail seems to already exist for remote file with id==%u', $thumbnail->file_id));
        }

        $url = $thumbnail->getUrl();
        $this->checkWhitelist($url);

        try {
            $isImage = $this->isRemoteImage($url);
            if ($isImage==true) {
                $max_size  = $this->getPHPUploadLimit();
                $file_size = $this->getRemoteFileSize($url);
                if (($file_size!=false) && ($file_size > $max_size)) {
                    common_debug("Went to store remote thumbnail of size " . $file_size . " but the upload limit is " . $max_size . " so we aborted.");
                    return false;
                }
            }
        } catch (Exception $err) {
            common_debug("Could not determine size of remote image, aborted local storage.");
            return $err;
        }

        // First we download the file to memory and test whether it's actually an image file
        // FIXME: To support remote video/whatever files, this needs reworking.
        common_debug(sprintf('Downloading remote thumbnail for file id==%u with thumbnail URL: %s', $thumbnail->file_id, $url));
        $imgData = HTTPClient::quickGet($url);
        $info = @getimagesizefromstring($imgData);
        if ($info === false) {
            throw new UnsupportedMediaException(_('Remote file format was not identified as an image.'), $url);
        } elseif (!$info[0] || !$info[1]) {
            throw new UnsupportedMediaException(_('Image file had impossible geometry (0 width or height)'));
        }

        $ext = File::guessMimeExtension($info['mime']);

        try {
            // We'll trust sha256 (File::FILEHASH_ALG) not to have collision issues any time soon :)
            $filename = 'oembed-'.hash(File::FILEHASH_ALG, $imgData) . ".{$ext}";
            $fullpath = File_thumbnail::path($filename);
            // Write the file to disk. Throw Exception on failure
            if (!file_exists($fullpath) && file_put_contents($fullpath, $imgData) === false) {
                throw new ServerException(_('Could not write downloaded file to disk.'));
            }
        } catch (Exception $err) {
            common_log(LOG_ERROR, "Went to write a thumbnail to disk in OembedPlugin::storeRemoteThumbnail but encountered error: ".$err);
            return $err;
        } finally {
            unset($imgData);
        }

        try {
            // Updated our database for the file record
            $orig = clone($thumbnail);
            $thumbnail->filename = $filename;
            $thumbnail->width = $info[0];    // array indexes documented on php.net:
            $thumbnail->height = $info[1];   // https://php.net/manual/en/function.getimagesize.php
            // Throws exception on failure.
            $thumbnail->updateWithKeys($orig);
        } catch (exception $err) {
            common_log(LOG_ERROR, "Went to write a thumbnail entry to the database in OembedPlugin::storeRemoteThumbnail but encountered error: ".$err);
            return $err;
        }
        return true;
    }

    // -------------------------------------------------------------------------
    // onPluginVersion($versions) function
    //   args: $versions - inherited from parent
    // Event raised when GNU Social polls the plugin for information about it.
    // Creates a $versions array with the info that GNU Social accesses for that
    // information.
    // Returns true if it execures successfully, the exception if it doesn't,
    // but if assigning an array fails, we uh, got issues.
    public function onPluginVersion(array &$versions)
    {
        $versions[] = array('name' => 'Oembed',
                            'version' => GNUSOCIAL_VERSION,
                            'author' => 'GNU Social',
                            'homepage' => 'http://gnu.io/social/',
                            'description' =>
                            // TRANS: Plugin description.
                            _m('Plugin for using and representing Oembed data.'));
        return true;
    }
}