Club Drupal

<?php

/**

 * @file

 * Pubsubhubbub subscriber library.

 *

 * Readme

 * http://github.com/lxbarth/PuSHSubscriber

 *

 * License

 * http://github.com/lxbarth/PuSHSubscriber/blob/master/LICENSE.txt

 */

/**

 * PubSubHubbub subscriber.

 */

class PuSHSubscriber {

  protected $domain;

  protected $subscriber_id;

  protected $subscription_class;

  protected $env;

  /**

   * Singleton.

   *

   * PuSHSubscriber identifies a unique subscription by a domain and a numeric

   * id. The numeric id is assumed to e unique in its domain.

   *

   * @param $domain

   *   A string that identifies the domain in which $subscriber_id is unique.

   * @param $subscriber_id

   *   A numeric subscriber id.

   * @param $subscription_class

   *   The class to use for handling subscriptions. Class MUST implement

   *   PuSHSubscriberSubscriptionInterface

   * @param PuSHSubscriberEnvironmentInterface $env

   *   Environmental object for messaging and logging.

   */

  public static function instance($domain, $subscriber_id, $subscription_class, PuSHSubscriberEnvironmentInterface $env) {

    static $subscribers;

    if (!isset($subscriber[$domain][$subscriber_id])) {

      $subscriber = new PuSHSubscriber($domain, $subscriber_id, $subscription_class, $env);

    }

    return $subscriber;

  }

  /**

   * Protect constructor.

   */

  protected function __construct($domain, $subscriber_id, $subscription_class, PuSHSubscriberEnvironmentInterface $env) {

    $this->domain = $domain;

    $this->subscriber_id = $subscriber_id;

    $this->subscription_class = $subscription_class;

    $this->env = $env;

  }

  /**

   * Subscribe to a given URL. Attempt to retrieve 'hub' and 'self' links from

   * document at $url and issue a subscription request to the hub.

   *

   * @param $url

   *   The URL of the feed to subscribe to.

   * @param $callback_url

   *   The full URL that hub should invoke for subscription verification or for

   *   notifications.

   * @param $hub

   *   The URL of a hub. If given overrides the hub URL found in the document

   *   at $url.

   */

  public function subscribe($url, $callback_url, $hub = '') {

    // Fetch document, find rel=hub and rel=self.

    // If present, issue subscription request.

    $request = curl_init($url);

    curl_setopt($request, CURLOPT_FOLLOWLOCATION, TRUE);

    curl_setopt($request, CURLOPT_RETURNTRANSFER, TRUE);

    $data = curl_exec($request);

    if (curl_getinfo($request, CURLINFO_HTTP_CODE) == 200) {

      try {

        $xml = @ new SimpleXMLElement($data);

        $xml->registerXPathNamespace('atom', 'http://www.w3.org/2005/Atom');

        if (empty($hub) && $hub = @current($xml->xpath("//atom:link[attribute::rel='hub']"))) {

          $hub = (string) $hub->attributes()->href;

        }

        if ($self = @current($xml->xpath("//atom:link[attribute::rel='self']"))) {

          $self = (string) $self->attributes()->href;

        }

      }

      catch (Exception $e) {

        // Do nothing.

      }

    }

    curl_close($request);

    // Fall back to $url if $self is not given.

    if (!$self) {

      $self = $url;

    }

    if (!empty($hub) && !empty($self)) {

      $this->request($hub, $self, 'subscribe', $callback_url);

    }

  }

  /**

   * @todo Unsubscribe from a hub.

   * @todo Make sure we unsubscribe with the correct topic URL as it can differ

   * from the initial subscription URL.

   *

   * @param $topic_url

   *   The URL of the topic to unsubscribe from.

   * @param $callback_url

   *   The callback to unsubscribe.

   */

  public function unsubscribe($topic_url, $callback_url) {

    if ($sub = $this->subscription()) {

      $this->request($sub->hub, $sub->topic, 'unsubscribe', $callback_url);

      $sub->delete();

    }

  }

  /**

   * Request handler for subscription callbacks.

   */

  public function handleRequest($callback) {

    if (isset($_GET['hub_challenge'])) {

      $this->verifyRequest();

    }

    // No subscription notification has ben sent, we are being notified.

    else {

      if ($raw = $this->receive()) {

        $callback($raw, $this->domain, $this->subscriber_id);

      }

    }

  }

  /**

   * Receive a notification.

   *

   * @param $ignore_signature

   *   If FALSE, only accept payload if there is a signature present and the

   *   signature matches the payload. Warning: setting to TRUE results in

   *   unsafe behavior.

   *

   * @return

   *   An XML string that is the payload of the notification if valid, FALSE

   *   otherwise.

   */

  public function receive($ignore_signature = FALSE) {

    /**

     * Verification steps:

     *

     * 1) Verify that this is indeed a POST reuest.

     * 2) Verify that posted string is XML.

     * 3) Per default verify sender of message by checking the message's

     *    signature against the shared secret.

     */

    if ($_SERVER['REQUEST_METHOD'] == 'POST') {

      $raw = file_get_contents('php://input');

      if (@simplexml_load_string($raw)) {

        if ($ignore_signature) {

          return $raw;

        }

        if (isset($_SERVER['HTTP_X_HUB_SIGNATURE']) && ($sub = $this->subscription())) {

          $result = array();

          parse_str($_SERVER['HTTP_X_HUB_SIGNATURE'], $result);

          if (isset($result['sha1']) && $result['sha1'] === hash_hmac('sha1', $raw, $sub->secret)) {

            return $raw;

          }

          else {

            $this->log('Could not verify signature.', 'error');

          }

        }

        else {

          $this->log('No signature present.', 'error');

        }

      }

    }

    return FALSE;

  }

  /**

   * Verify a request. After a hub has received a subscribe or unsubscribe

   * request (see PuSHSubscriber::request()) it sends back a challenge verifying

   * that an action indeed was requested ($_GET['hub_challenge']). This

   * method handles the challenge.

   */

  public function verifyRequest() {

    if (!isset($_GET['hub_challenge'])) {

      return $this->rejectRequest();

    }

    // Don't accept modes of 'subscribed' or 'unsubscribed'.

    if ($_GET['hub_mode'] !== 'subscribe' && $_GET['hub_mode'] !== 'unsubscribe') {

      return $this->rejectRequest();

    }

    // No available subscription.

    if (!$sub = $this->subscription()) {

      return $this->rejectRequest();

    }

    // Not what we asked for.

    if ($_GET['hub_mode'] !== $sub->status) {

      return $this->rejectRequest();

    }

    // Wrong URL.

    if ($_GET['hub_topic'] !== $sub->topic) {

      return $this->rejectRequest();

    }

    if ($sub->status === 'subscribe') {

      $sub->status = 'subscribed';

      $this->log('Verified "subscribe" request.');

    }

    else {

      $sub->status = 'unsubscribed';

      $this->log('Verified "unsubscribe" request.');

    }

    $sub->post_fields = array();

    $sub->save();

    header('HTTP/1.1 200 "Found"', NULL, 200);

    print check_plain($_GET['hub_challenge']);

    drupal_exit();

  }

  /**

   * Issue a subscribe or unsubcribe request to a PubsubHubbub hub.

   *

   * @param $hub

   *   The URL of the hub's subscription endpoint.

   * @param $topic

   *   The topic URL of the feed to subscribe to.

   * @param $mode

   *   'subscribe' or 'unsubscribe'.

   * @param $callback_url

   *   The subscriber's notifications callback URL.

   *

   * Compare to http://pubsubhubbub.googlecode.com/svn/trunk/pubsubhubbub-core-0.2.html#anchor5

   *

   * @todo Make concurrency safe.

   */

  protected function request($hub, $topic, $mode, $callback_url) {

    $secret = drupal_random_key(40);

    $post_fields = array(

      'hub.callback' => $callback_url,

      'hub.mode' => $mode,

      'hub.topic' => $topic,

      'hub.verify' => 'sync',

      'hub.lease_seconds' => '', // Permanent subscription.

      'hub.secret' => $secret,

    );

    $sub = new $this->subscription_class($this->domain, $this->subscriber_id, $hub, $topic, $secret, $mode, $post_fields);

    $sub->save();

    // Issue subscription request.

    $request = curl_init($hub);

    curl_setopt($request, CURLOPT_POST, TRUE);

    curl_setopt($request, CURLOPT_POSTFIELDS, $post_fields);

    curl_setopt($request, CURLOPT_RETURNTRANSFER, TRUE);

    curl_exec($request);

    $code = curl_getinfo($request, CURLINFO_HTTP_CODE);

    if (in_array($code, array(202, 204))) {

      $this->log("Positive response to \"$mode\" request ($code).");

    }

    else {

      $sub->status = $mode . ' failed';

      $sub->save();

      $this->log("Error issuing \"$mode\" request to $hub ($code).", 'error');

    }

    curl_close($request);

  }

  /**

   * Get the subscription associated with this subscriber.

   *

   * @return

   *   A PuSHSubscriptionInterface object if a subscription exist, NULL

   *   otherwise.

   */

  public function subscription() {

    return call_user_func(array($this->subscription_class, 'load'), $this->domain, $this->subscriber_id);

  }

  /**

   * Determine whether this subscriber is successfully subscribed or not.

   */

  public function subscribed() {

    if ($sub = $this->subscription()) {

      if ($sub->status == 'subscribed') {

        return TRUE;

      }

    }

    return FALSE;

  }

  /**

   * Helper for messaging.

   */

  protected function msg($msg, $level = 'status') {

    $this->env->msg($msg, $level);

  }

  /**

   * Helper for logging.

   */

  protected function log($msg, $level = 'status') {

    $this->env->log("{$this->domain}:{$this->subscriber_id}\t$msg", $level);

  }

  /**

   * Rejects a request subscription request.

   */

  protected function rejectRequest() {

    header('HTTP/1.1 404 "Not Found"', NULL, 404);

    $this->log('Could not verify subscription.', 'error');

    drupal_exit();

  }

}

/**

 * Implement to provide a storage backend for subscriptions.

 *

 * Variables passed in to the constructor must be accessible as public class

 * variables.

 */

interface PuSHSubscriptionInterface {

  /**

   * @param $domain

   *   A string that defines the domain in which the subscriber_id is unique.

   * @param $subscriber_id

   *   A unique numeric subscriber id.

   * @param $hub

   *   The URL of the hub endpoint.

   * @param $topic

   *   The topic to subscribe to.

   * @param $secret

   *   A secret key used for message authentication.

   * @param $status

   *   The status of the subscription.

   *   'subscribe' - subscribing to a feed.

   *   'unsubscribe' - unsubscribing from a feed.

   *   'subscribed' - subscribed.

   *   'unsubscribed' - unsubscribed.

   *   'subscribe failed' - subscribe request failed.

   *   'unsubscribe failed' - unsubscribe request failed.

   * @param $post_fields

   *   An array of the fields posted to the hub.

   */

  public function __construct($domain, $subscriber_id, $hub, $topic, $secret, $status = '', $post_fields = '');

  /**

   * Save a subscription.

   */

  public function save();

  /**

   * Load a subscription.

   *

   * @return

   *   A PuSHSubscriptionInterface object if a subscription exist, NULL

   *   otherwise.

   */

  public static function load($domain, $subscriber_id);

  /**

   * Delete a subscription.

   */

  public function delete();

}

/**

 * Implement to provide environmental functionality like user messages and

 * logging.

 */

interface PuSHSubscriberEnvironmentInterface {

  /**

   * A message to be displayed to the user on the current page load.

   *

   * @param $msg

   *   A string that is the message to be displayed.

   * @param $level

   *   A string that is either 'status', 'warning' or 'error'.

   */

  public function msg($msg, $level = 'status');

  /**

   * A log message to be logged to the database or the file system.

   *

   * @param $msg

   *   A string that is the message to be displayed.

   * @param $level

   *   A string that is either 'status', 'warning' or 'error'.

   */

  public function log($msg, $level = 'status');

}