<?php
// $Id: mollom.inc,v 1.10 2010-12-22 17:54:53 sun Exp $

/**
 * @file
 * Mollom client/server interaction functions.
 */

/**
 * Generate authentication data for XML-RPC communication with Mollom servers.
 *
 * This function generates an array with all information required to
 * authenticate against Mollom.  To prevent forged requests where you are
 * impersonated, each request is signed with a hash based on a private
 * key and a timestamp.
 *
 * Both the client and the server share the secret key used to create
 * the authentication hash.  They both hash a timestamp with the secret
 * key, and if the hashes match, the authenticity of the message is
 * validated.
 *
 * To avoid someone intercepting a (hash, timestamp)-pair and using it
 * to impersonate a client, Mollom reject any request where the timestamp
 * is more than 15 minutes off.
 *
 * Make sure your server's time is synchronized with the world clocks,
 * and that you don't share your private key with anyone else.
 *
 * @param $public_key
 *   (optional) The public key to use for authentication. Only used internally.
 * @param $private_key
 *   (optional) The private key to use for authentication. Only used internally.
 */
function _mollom_authentication($public_key = NULL, $private_key = NULL) {
  if (!isset($public_key)) {
    $public_key = variable_get('mollom_public_key', '');
  }
  if (!isset($private_key)) {
    $private_key = variable_get('mollom_private_key', '');
  }

  // Generate a timestamp according to the dateTime format (http://www.w3.org/TR/xmlschema-2/#dateTime):
  $time = gmdate("Y-m-d\TH:i:s.\\0\\0\\0O", REQUEST_TIME);

  // Generate a random number:
  $nonce = md5(mt_rand());

  // Calculate a HMAC-SHA1 according to RFC2104 (http://www.ietf.org/rfc/rfc2104.txt):
  $hash = base64_encode(
    pack('H*', sha1((str_pad($private_key, 64, chr(0x00)) ^ (str_repeat(chr(0x5c), 64))) .
    pack('H*', sha1((str_pad($private_key, 64, chr(0x00)) ^ (str_repeat(chr(0x36), 64))) .
    $time . ':' . $nonce . ':' . $private_key))))
  );

  // Store everything in an array.  Elsewhere in the code, we'll add the
  // actual data before we pass it onto the XML-RPC library:
  $data['public_key'] = $public_key;
  $data['time'] = $time;
  $data['hash'] = $hash;
  $data['nonce'] = $nonce;

  return $data;
}

/**
 * Refreshes the list of Mollom's XML-RPC servers.
 */
function _mollom_retrieve_server_list() {
  // Start from a hard-coded list of servers.
  $servers = array('http://xmlrpc1.mollom.com', 'http://xmlrpc2.mollom.com', 'http://xmlrpc3.mollom.com');
  $messages = array();

  // mollom.getServerList cannot use mollom() as we need to prevent infinite
  // recursion. In addition, we handle returned error codes differently here,
  // since MOLLOM_REDIRECT and MOLLOM_REFRESH, as well as any other
  // communication error requires us to skip to the next server to retrieve a
  // new server list. We only ever abort, if a server returns MOLLOM_ERROR, in
  // which case there must be a configuration error (e.g., invalid API keys).
  $method = 'mollom.getServerList';
  foreach ($servers as $server) {
    $result = xmlrpc($server . '/' . MOLLOM_API_VERSION, array($method => array(_mollom_authentication())));
    if ($result === FALSE && ($error = xmlrpc_error())) {
      // In any case, log the error.
      $messages[] = array(
        'Error @errno from %server for %method: %message' => array(
          '@errno' => $error->code,
          '%server' => $server,
          '%method' => $method,
          '%message' => $error->message,
        ),
      );
      // Skip to the next server in case of any error, except if we have a
      // MOLLOM_ERROR, which indicates a bogus configuration. In this case, stop
      // trying, since all servers will fail.
      if ($error->code === MOLLOM_ERROR) {
        break;
      }
    }
    // Otherwise, we have a valid result.
    else {
      break;
    }
  }

  // Allow other modules to alter the server list. Internal use only.
  drupal_alter('mollom_server_list', $result);

  if (is_array($result)) {
    _mollom_watchdog_multiple($messages, WATCHDOG_DEBUG);
    return $result;
  }
  else {
    _mollom_watchdog_multiple($messages, WATCHDOG_ERROR);
    return xmlrpc_errno();
  }
}