<?php
/**
 * This module documents the main interface with the OpenID consumer
 * library.  The only part of the library which has to be used and
 * isn't documented in full here is the store required to create an
 * Auth_OpenID_Consumer instance.  More on the abstract store type and
 * concrete implementations of it that are provided in the
 * documentation for the Auth_OpenID_Consumer constructor.
 *
 * OVERVIEW
 *
 * The OpenID identity verification process most commonly uses the
 * following steps, as visible to the user of this library:
 *
 *   1. The user enters their OpenID into a field on the consumer's
 *      site, and hits a login button.
 *   2. The consumer site discovers the user's OpenID server using the
 *      YADIS protocol.
 *   3. The consumer site sends the browser a redirect to the identity
 *      server.  This is the authentication request as described in
 *      the OpenID specification.
 *   4. The identity server's site sends the browser a redirect back
 *      to the consumer site.  This redirect contains the server's
 *      response to the authentication request.
 *
 * The most important part of the flow to note is the consumer's site
 * must handle two separate HTTP requests in order to perform the full
 * identity check.
 *
 * LIBRARY DESIGN
 * 
 * This consumer library is designed with that flow in mind.  The goal
 * is to make it as easy as possible to perform the above steps
 * securely.
 *
 * At a high level, there are two important parts in the consumer
 * library.  The first important part is this module, which contains
 * the interface to actually use this library.  The second is the
 * Auth_OpenID_Interface class, which describes the interface to use
 * if you need to create a custom method for storing the state this
 * library needs to maintain between requests.
 *
 * In general, the second part is less important for users of the
 * library to know about, as several implementations are provided
 * which cover a wide variety of situations in which consumers may use
 * the library.
 *
 * This module contains a class, Auth_OpenID_Consumer, with methods
 * corresponding to the actions necessary in each of steps 2, 3, and 4
 * described in the overview.  Use of this library should be as easy
 * as creating an Auth_OpenID_Consumer instance and calling the
 * methods appropriate for the action the site wants to take.
 *
 * STORES AND DUMB MODE
 *
 * OpenID is a protocol that works best when the consumer site is able
 * to store some state.  This is the normal mode of operation for the
 * protocol, and is sometimes referred to as smart mode.  There is
 * also a fallback mode, known as dumb mode, which is available when
 * the consumer site is not able to store state.  This mode should be
 * avoided when possible, as it leaves the implementation more
 * vulnerable to replay attacks.
 *
 * The mode the library works in for normal operation is determined by
 * the store that it is given.  The store is an abstraction that
 * handles the data that the consumer needs to manage between http
 * requests in order to operate efficiently and securely.
 *
 * Several store implementation are provided, and the interface is
 * fully documented so that custom stores can be used as well.  See
 * the documentation for the Auth_OpenID_Consumer class for more
 * information on the interface for stores.  The implementations that
 * are provided allow the consumer site to store the necessary data in
 * several different ways, including several SQL databases and normal
 * files on disk.
 *
 * There is an additional concrete store provided that puts the system
 * in dumb mode.  This is not recommended, as it removes the library's
 * ability to stop replay attacks reliably.  It still uses time-based
 * checking to make replay attacks only possible within a small
 * window, but they remain possible within that window.  This store
 * should only be used if the consumer site has no way to retain data
 * between requests at all.
 *
 * IMMEDIATE MODE
 *
 * In the flow described above, the user may need to confirm to the
 * lidentity server that it's ok to authorize his or her identity.
 * The server may draw pages asking for information from the user
 * before it redirects the browser back to the consumer's site.  This
 * is generally transparent to the consumer site, so it is typically
 * ignored as an implementation detail.
 *
 * There can be times, however, where the consumer site wants to get a
 * response immediately.  When this is the case, the consumer can put
 * the library in immediate mode.  In immediate mode, there is an
 * extra response possible from the server, which is essentially the
 * server reporting that it doesn't have enough information to answer
 * the question yet.
 *
 * USING THIS LIBRARY
 *
 * Integrating this library into an application is usually a
 * relatively straightforward process.  The process should basically
 * follow this plan:
 *
 * Add an OpenID login field somewhere on your site.  When an OpenID
 * is entered in that field and the form is submitted, it should make
 * a request to the your site which includes that OpenID URL.
 *
 * First, the application should instantiate the Auth_OpenID_Consumer
 * class using the store of choice (Auth_OpenID_FileStore or one of
 * the SQL-based stores).  If the application has a custom
 * session-management implementation, an object implementing the
 * {@link Auth_Yadis_PHPSession} interface should be passed as the
 * second parameter.  Otherwise, the default uses $_SESSION.
 *
 * Next, the application should call the Auth_OpenID_Consumer object's
 * 'begin' method.  This method takes the OpenID URL.  The 'begin'
 * method returns an Auth_OpenID_AuthRequest object.
 *
 * Next, the application should call the 'redirectURL' method of the
 * Auth_OpenID_AuthRequest object.  The 'return_to' URL parameter is
 * the URL that the OpenID server will send the user back to after
 * attempting to verify his or her identity.  The 'trust_root' is the
 * URL (or URL pattern) that identifies your web site to the user when
 * he or she is authorizing it.  Send a redirect to the resulting URL
 * to the user's browser.
 *
 * That's the first half of the authentication process.  The second
 * half of the process is done after the user's ID server sends the
 * user's browser a redirect back to your site to complete their
 * login.
 *
 * When that happens, the user will contact your site at the URL given
 * as the 'return_to' URL to the Auth_OpenID_AuthRequest::redirectURL
 * call made above.  The request will have several query parameters
 * added to the URL by the identity server as the information
 * necessary to finish the request.
 *
 * Lastly, instantiate an Auth_OpenID_Consumer instance as above and
 * call its 'complete' method, passing in all the received query
 * arguments.
 *
 * There are multiple possible return types possible from that
 * method. These indicate the whether or not the login was successful,
 * and include any additional information appropriate for their type.
 *
 * PHP versions 4 and 5
 *
 * LICENSE: See the COPYING file included in this distribution.
 *
 * @package OpenID
 * @author JanRain, Inc. <openid@janrain.com>
 * @copyright 2005-2008 Janrain, Inc.
 * @license http://www.apache.org/licenses/LICENSE-2.0 Apache
 */

/**
 * Require utility classes and functions for the consumer.
 */
require_once "Auth/OpenID.php";
require_once "Auth/OpenID/Message.php";
require_once "Auth/OpenID/HMAC.php";
require_once "Auth/OpenID/Association.php";
require_once "Auth/OpenID/CryptUtil.php";
require_once "Auth/OpenID/DiffieHellman.php";
require_once "Auth/OpenID/KVForm.php";
require_once "Auth/OpenID/Nonce.php";
require_once "Auth/OpenID/Discover.php";
require_once "Auth/OpenID/URINorm.php";
require_once "Auth/Yadis/Manager.php";
require_once "Auth/Yadis/XRI.php";

/**
 * This is the status code returned when the complete method returns
 * successfully.
 */
define('Auth_OpenID_SUCCESS', 'success');

/**
 * Status to indicate cancellation of OpenID authentication.
 */
define('Auth_OpenID_CANCEL', 'cancel');

/**
 * This is the status code completeAuth returns when the value it
 * received indicated an invalid login.
 */
define('Auth_OpenID_FAILURE', 'failure');

/**
 * This is the status code completeAuth returns when the
 * {@link Auth_OpenID_Consumer} instance is in immediate mode, and the
 * identity server sends back a URL to send the user to to complete his
 * or her login.
 */
define('Auth_OpenID_SETUP_NEEDED', 'setup needed');

/**
 * This is the status code beginAuth returns when the page fetched
 * from the entered OpenID URL doesn't contain the necessary link tags
 * to function as an identity page.
 */
define('Auth_OpenID_PARSE_ERROR', 'parse error');

/**
 * An OpenID consumer implementation that performs discovery and does
 * session management.  See the Consumer.php file documentation for
 * more information.
 *
 * @package OpenID
 */
class Auth_OpenID_Consumer {
  
  /**
   * @access private
   */
  var $discoverMethod = 'Auth_OpenID_discover';
  
  /**
   * @access private
   */
  var $session_key_prefix = "_openid_consumer_";
  
  /**
   * @access private
   */
  var $_token_suffix = "last_token";

  /**
   * Initialize a Consumer instance.
   *
   * You should create a new instance of the Consumer object with
   * every HTTP request that handles OpenID transactions.
   *
   * @param Auth_OpenID_OpenIDStore $store This must be an object
   * that implements the interface in {@link
   * Auth_OpenID_OpenIDStore}.  Several concrete implementations are
   * provided, to cover most common use cases.  For stores backed by
   * MySQL, PostgreSQL, or SQLite, see the {@link
   * Auth_OpenID_SQLStore} class and its sublcasses.  For a
   * filesystem-backed store, see the {@link Auth_OpenID_FileStore}
   * module.  As a last resort, if it isn't possible for the server
   * to store state at all, an instance of {@link
   * Auth_OpenID_DumbStore} can be used.
   *
   * @param mixed $session An object which implements the interface
   * of the {@link Auth_Yadis_PHPSession} class.  Particularly, this
   * object is expected to have these methods: get($key), set($key),
   * $value), and del($key).  This defaults to a session object
   * which wraps PHP's native session machinery.  You should only
   * need to pass something here if you have your own sessioning
   * implementation.
   *
   * @param str $consumer_cls The name of the class to instantiate
   * when creating the internal consumer object.  This is used for
   * testing.
   */
  function Auth_OpenID_Consumer(&$store, $session = null, $consumer_cls = null) {
    if ($session === null) {
      $session = new Auth_Yadis_PHPSession();
    }
    
    $this->session = & $session;
    
    if ($consumer_cls !== null) {
      $this->consumer = & new $consumer_cls($store);
    } else {
      $this->consumer = & new Auth_OpenID_GenericConsumer($store);
    }
    
    $this->_token_key = $this->session_key_prefix . $this->_token_suffix;
  }

  /**
   * Used in testing to define the discovery mechanism.
   *
   * @access private
   */
  function getDiscoveryObject(&$session, $openid_url, $session_key_prefix) {
    return new Auth_Yadis_Discovery($session, $openid_url, $session_key_prefix);
  }

  /**
   * Start the OpenID authentication process. See steps 1-2 in the
   * overview at the top of this file.
   *
   * @param string $user_url Identity URL given by the user. This
   * method performs a textual transformation of the URL to try and
   * make sure it is normalized. For example, a user_url of
   * example.com will be normalized to http://example.com/
   * normalizing and resolving any redirects the server might issue.
   *
   * @param bool $anonymous True if the OpenID request is to be sent
   * to the server without any identifier information.  Use this
   * when you want to transport data but don't want to do OpenID
   * authentication with identifiers.
   *
   * @return Auth_OpenID_AuthRequest $auth_request An object
   * containing the discovered information will be returned, with a
   * method for building a redirect URL to the server, as described
   * in step 3 of the overview. This object may also be used to add
   * extension arguments to the request, using its 'addExtensionArg'
   * method.
   */
  function begin($user_url, $anonymous = false) {
    $openid_url = $user_url;
    
    $disco = $this->getDiscoveryObject($this->session, $openid_url, $this->session_key_prefix);
    
    // Set the 'stale' attribute of the manager.  If discovery
    // fails in a fatal way, the stale flag will cause the manager
    // to be cleaned up next time discovery is attempted.
    

    $m = $disco->getManager();
    $loader = new Auth_Yadis_ManagerLoader();
    
    if ($m) {
      if ($m->stale) {
        $disco->destroyManager();
      } else {
        $m->stale = true;
        $disco->session->set($disco->session_key, serialize($loader->toSession($m)));
      }
    }
    
    $endpoint = $disco->getNextService($this->discoverMethod, $this->consumer->fetcher);
    
    // Reset the 'stale' attribute of the manager.
    $m = & $disco->getManager();
    if ($m) {
      $m->stale = false;
      $disco->session->set($disco->session_key, serialize($loader->toSession($m)));
    }
    
    if ($endpoint === null) {
      return null;
    } else {
      return $this->beginWithoutDiscovery($endpoint, $anonymous);
    }
  }

  /**
   * Start OpenID verification without doing OpenID server
   * discovery. This method is used internally by Consumer.begin
   * after discovery is performed, and exists to provide an
   * interface for library users needing to perform their own
   * discovery.
   *
   * @param Auth_OpenID_ServiceEndpoint $endpoint an OpenID service
   * endpoint descriptor.
   *
   * @param bool anonymous Set to true if you want to perform OpenID
   * without identifiers.
   *
   * @return Auth_OpenID_AuthRequest $auth_request An OpenID
   * authentication request object.
   */
  function &beginWithoutDiscovery($endpoint, $anonymous = false) {
    $loader = new Auth_OpenID_ServiceEndpointLoader();
    $auth_req = $this->consumer->begin($endpoint);
    $this->session->set($this->_token_key, $loader->toSession($auth_req->endpoint));
    if (! $auth_req->setAnonymous($anonymous)) {
      return new Auth_OpenID_FailureResponse(null, "OpenID 1 requests MUST include the identifier " . "in the request.");
    }
    return $auth_req;
  }

  /**
   * Called to interpret the server's response to an OpenID
   * request. It is called in step 4 of the flow described in the
   * consumer overview.
   *
   * @param string $current_url The URL used to invoke the application.
   * Extract the URL from your application's web
   * request framework and specify it here to have it checked
   * against the openid.current_url value in the response.  If
   * the current_url URL check fails, the status of the
   * completion will be FAILURE.
   *
   * @param array $query An array of the query parameters (key =>
   * value pairs) for this HTTP request.  Defaults to null.  If
   * null, the GET or POST data are automatically gotten from the
   * PHP environment.  It is only useful to override $query for
   * testing.
   *
   * @return Auth_OpenID_ConsumerResponse $response A instance of an
   * Auth_OpenID_ConsumerResponse subclass. The type of response is
   * indicated by the status attribute, which will be one of
   * SUCCESS, CANCEL, FAILURE, or SETUP_NEEDED.
   */
  function complete($current_url, $query = null) {
    if ($current_url && ! is_string($current_url)) {
      // This is ugly, but we need to complain loudly when
      // someone uses the API incorrectly.
      trigger_error("current_url must be a string; see NEWS file " . "for upgrading notes.", E_USER_ERROR);
    }
    
    if ($query === null) {
      $query = Auth_OpenID::getQuery();
    }
    
    $loader = new Auth_OpenID_ServiceEndpointLoader();
    $endpoint_data = $this->session->get($this->_token_key);
    $endpoint = $loader->fromSession($endpoint_data);
    
    $message = Auth_OpenID_Message::fromPostArgs($query);
    $response = $this->consumer->complete($message, $endpoint, $current_url);
    $this->session->del($this->_token_key);
    
    if (in_array($response->status, array(Auth_OpenID_SUCCESS, Auth_OpenID_CANCEL))) {
      if ($response->identity_url !== null) {
        $disco = $this->getDiscoveryObject($this->session, $response->identity_url, $this->session_key_prefix);
        $disco->cleanup(true);
      }
    }
    
    return $response;
  }
}

/**
 * A class implementing HMAC/DH-SHA1 consumer sessions.
 *
 * @package OpenID
 */
class Auth_OpenID_DiffieHellmanSHA1ConsumerSession {
  var $session_type = 'DH-SHA1';
  var $hash_func = 'Auth_OpenID_SHA1';
  var $secret_size = 20;
  var $allowed_assoc_types = array('HMAC-SHA1');

  function Auth_OpenID_DiffieHellmanSHA1ConsumerSession($dh = null) {
    if ($dh === null) {
      $dh = new Auth_OpenID_DiffieHellman();
    }
    
    $this->dh = $dh;
  }

  function getRequest() {
    $math = & Auth_OpenID_getMathLib();
    
    $cpub = $math->longToBase64($this->dh->public);
    
    $args = array('dh_consumer_public' => $cpub);
    
    if (! $this->dh->usingDefaultValues()) {
      $args = array_merge($args, array(
          'dh_modulus' => $math->longToBase64($this->dh->mod), 
          'dh_gen' => $math->longToBase64($this->dh->gen)));
    }
    
    return $args;
  }

  function extractSecret($response) {
    if (! $response->hasKey(Auth_OpenID_OPENID_NS, 'dh_server_public')) {
      return null;
    }
    
    if (! $response->hasKey(Auth_OpenID_OPENID_NS, 'enc_mac_key')) {
      return null;
    }
    
    $math = & Auth_OpenID_getMathLib();
    
    $spub = $math->base64ToLong($response->getArg(Auth_OpenID_OPENID_NS, 'dh_server_public'));
    $enc_mac_key = base64_decode($response->getArg(Auth_OpenID_OPENID_NS, 'enc_mac_key'));
    
    return $this->dh->xorSecret($spub, $enc_mac_key, $this->hash_func);
  }
}

/**
 * A class implementing HMAC/DH-SHA256 consumer sessions.
 *
 * @package OpenID
 */
class Auth_OpenID_DiffieHellmanSHA256ConsumerSession extends Auth_OpenID_DiffieHellmanSHA1ConsumerSession {
  var $session_type = 'DH-SHA256';
  var $hash_func = 'Auth_OpenID_SHA256';
  var $secret_size = 32;
  var $allowed_assoc_types = array('HMAC-SHA256');
}

/**
 * A class implementing plaintext consumer sessions.
 *
 * @package OpenID
 */
class Auth_OpenID_PlainTextConsumerSession {
  var $session_type = 'no-encryption';
  var $allowed_assoc_types = array('HMAC-SHA1', 'HMAC-SHA256');

  function getRequest() {
    return array();
  }

  function extractSecret($response) {
    if (! $response->hasKey(Auth_OpenID_OPENID_NS, 'mac_key')) {
      return null;
    }
    
    return base64_decode($response->getArg(Auth_OpenID_OPENID_NS, 'mac_key'));
  }
}

/**
 * Returns available session types.
 */
function Auth_OpenID_getAvailableSessionTypes() {
  $types = array('no-encryption' => 'Auth_OpenID_PlainTextConsumerSession', 
      'DH-SHA1' => 'Auth_OpenID_DiffieHellmanSHA1ConsumerSession', 
      'DH-SHA256' => 'Auth_OpenID_DiffieHellmanSHA256ConsumerSession');
  
  return $types;
}

/**
 * This class is the interface to the OpenID consumer logic.
 * Instances of it maintain no per-request state, so they can be
 * reused (or even used by multiple threads concurrently) as needed.
 *
 * @package OpenID
 */
class Auth_OpenID_GenericConsumer {
  /**
   * @access private
   */
  var $discoverMethod = 'Auth_OpenID_discover';
  
  /**
   * This consumer's store object.
   */
  var $store;
  
  /**
   * @access private
   */
  var $_use_assocs;
  
  /**
   * @access private
   */
  var $openid1_nonce_query_arg_name = 'janrain_nonce';
  
  /**
   * Another query parameter that gets added to the return_to for
   * OpenID 1; if the user's session state is lost, use this claimed
   * identifier to do discovery when verifying the response.
   */
  var $openid1_return_to_identifier_name = 'openid1_claimed_id';

  /**
   * This method initializes a new {@link Auth_OpenID_Consumer}
   * instance to access the library.
   *
   * @param Auth_OpenID_OpenIDStore $store This must be an object
   * that implements the interface in {@link Auth_OpenID_OpenIDStore}.
   * Several concrete implementations are provided, to cover most common use
   * cases.  For stores backed by MySQL, PostgreSQL, or SQLite, see
   * the {@link Auth_OpenID_SQLStore} class and its sublcasses.  For a
   * filesystem-backed store, see the {@link Auth_OpenID_FileStore} module.
   * As a last resort, if it isn't possible for the server to store
   * state at all, an instance of {@link Auth_OpenID_DumbStore} can be used.
   *
   * @param bool $immediate This is an optional boolean value.  It
   * controls whether the library uses immediate mode, as explained
   * in the module description.  The default value is False, which
   * disables immediate mode.
   */
  function Auth_OpenID_GenericConsumer(&$store) {
    $this->store = & $store;
    $this->negotiator = & Auth_OpenID_getDefaultNegotiator();
    $this->_use_assocs = ($this->store ? true : false);
    
    $this->fetcher = Auth_Yadis_Yadis::getHTTPFetcher();
    
    $this->session_types = Auth_OpenID_getAvailableSessionTypes();
  }

  /**
   * Called to begin OpenID authentication using the specified
   * {@link Auth_OpenID_ServiceEndpoint}.
   *
   * @access private
   */
  function begin($service_endpoint) {
    $assoc = $this->_getAssociation($service_endpoint);
    $r = new Auth_OpenID_AuthRequest($service_endpoint, $assoc);
    $r->return_to_args[$this->openid1_nonce_query_arg_name] = Auth_OpenID_mkNonce();
    
    if ($r->message->isOpenID1()) {
      $r->return_to_args[$this->openid1_return_to_identifier_name] = $r->endpoint->claimed_id;
    }
    
    return $r;
  }

  /**
   * Given an {@link Auth_OpenID_Message}, {@link
   * Auth_OpenID_ServiceEndpoint} and optional return_to URL,
   * complete OpenID authentication.
   *
   * @access private
   */
  function complete($message, $endpoint, $return_to) {
    $mode = $message->getArg(Auth_OpenID_OPENID_NS, 'mode', '<no mode set>');
    
    $mode_methods = array('cancel' => '_complete_cancel', 'error' => '_complete_error', 
        'setup_needed' => '_complete_setup_needed', 'id_res' => '_complete_id_res');
    
    $method = Auth_OpenID::arrayGet($mode_methods, $mode, '_completeInvalid');
    
    return call_user_func_array(array(&$this, $method), array($message, $endpoint, $return_to));
  }

  /**
   * @access private
   */
  function _completeInvalid($message, &$endpoint, $unused) {
    $mode = $message->getArg(Auth_OpenID_OPENID_NS, 'mode', '<No mode set>');
    
    return new Auth_OpenID_FailureResponse($endpoint, sprintf("Invalid openid.mode '%s'", $mode));
  }

  /**
   * @access private
   */
  function _complete_cancel($message, &$endpoint, $unused) {
    return new Auth_OpenID_CancelResponse($endpoint);
  }

  /**
   * @access private
   */
  function _complete_error($message, &$endpoint, $unused) {
    $error = $message->getArg(Auth_OpenID_OPENID_NS, 'error');
    $contact = $message->getArg(Auth_OpenID_OPENID_NS, 'contact');
    $reference = $message->getArg(Auth_OpenID_OPENID_NS, 'reference');
    
    return new Auth_OpenID_FailureResponse($endpoint, $error, $contact, $reference);
  }

  /**
   * @access private
   */
  function _complete_setup_needed($message, &$endpoint, $unused) {
    if (! $message->isOpenID2()) {
      return $this->_completeInvalid($message, $endpoint);
    }
    
    $user_setup_url = $message->getArg(Auth_OpenID_OPENID2_NS, 'user_setup_url');
    return new Auth_OpenID_SetupNeededResponse($endpoint, $user_setup_url);
  }

  /**
   * @access private
   */
  function _complete_id_res($message, &$endpoint, $return_to) {
    $user_setup_url = $message->getArg(Auth_OpenID_OPENID1_NS, 'user_setup_url');
    
    if ($this->_checkSetupNeeded($message)) {
      return new Auth_OpenID_SetupNeededResponse($endpoint, $user_setup_url);
    } else {
      return $this->_doIdRes($message, $endpoint, $return_to);
    }
  }

  /**
   * @access private
   */
  function _checkSetupNeeded($message) {
    // In OpenID 1, we check to see if this is a cancel from
    // immediate mode by the presence of the user_setup_url
    // parameter.
    if ($message->isOpenID1()) {
      $user_setup_url = $message->getArg(Auth_OpenID_OPENID1_NS, 'user_setup_url');
      if ($user_setup_url !== null) {
        return true;
      }
    }
    
    return false;
  }

  /**
   * @access private
   */
  function _doIdRes($message, $endpoint, $return_to) {
    // Checks for presence of appropriate fields (and checks
    // signed list fields)
    $result = $this->_idResCheckForFields($message);
    
    if (Auth_OpenID::isFailure($result)) {
      return $result;
    }
    
    if (! $this->_checkReturnTo($message, $return_to)) {
      return new Auth_OpenID_FailureResponse(null, sprintf("return_to does not match return URL. Expected %s, got %s", $return_to, $message->getArg(Auth_OpenID_OPENID_NS, 'return_to')));
    }
    
    // Verify discovery information:
    $result = $this->_verifyDiscoveryResults($message, $endpoint);
    
    if (Auth_OpenID::isFailure($result)) {
      return $result;
    }
    
    $endpoint = $result;
    
    $result = $this->_idResCheckSignature($message, $endpoint->server_url);
    
    if (Auth_OpenID::isFailure($result)) {
      return $result;
    }
    
    $result = $this->_idResCheckNonce($message, $endpoint);
    
    if (Auth_OpenID::isFailure($result)) {
      return $result;
    }
    
    $signed_list_str = $message->getArg(Auth_OpenID_OPENID_NS, 'signed', Auth_OpenID_NO_DEFAULT);
    if (Auth_OpenID::isFailure($signed_list_str)) {
      return $signed_list_str;
    }
    $signed_list = explode(',', $signed_list_str);
    
    $signed_fields = Auth_OpenID::addPrefix($signed_list, "openid.");
    
    return new Auth_OpenID_SuccessResponse($endpoint, $message, $signed_fields);
  
  }

  /**
   * @access private
   */
  function _checkReturnTo($message, $return_to) {
    // Check an OpenID message and its openid.return_to value
    // against a return_to URL from an application.  Return True
    // on success, False on failure.
    

    // Check the openid.return_to args against args in the
    // original message.
    $result = Auth_OpenID_GenericConsumer::_verifyReturnToArgs($message->toPostArgs());
    if (Auth_OpenID::isFailure($result)) {
      return false;
    }
    
    // Check the return_to base URL against the one in the
    // message.
    $msg_return_to = $message->getArg(Auth_OpenID_OPENID_NS, 'return_to');
    if (Auth_OpenID::isFailure($return_to)) {
      // XXX log me
      return false;
    }
    
    $return_to_parts = parse_url(Auth_OpenID_urinorm($return_to));
    $msg_return_to_parts = parse_url(Auth_OpenID_urinorm($msg_return_to));
    
    // If port is absent from both, add it so it's equal in the
    // check below.
    if ((! array_key_exists('port', $return_to_parts)) && (! array_key_exists('port', $msg_return_to_parts))) {
      $return_to_parts['port'] = null;
      $msg_return_to_parts['port'] = null;
    }
    
    // If path is absent from both, add it so it's equal in the
    // check below.
    if ((! array_key_exists('path', $return_to_parts)) && (! array_key_exists('path', $msg_return_to_parts))) {
      $return_to_parts['path'] = null;
      $msg_return_to_parts['path'] = null;
    }
    
    // The URL scheme, authority, and path MUST be the same
    // between the two URLs.
    foreach (array('scheme', 'host', 'port', 'path') as $component) {
      // If the url component is absent in either URL, fail.
      // There should always be a scheme, host, port, and path.
      if (! array_key_exists($component, $return_to_parts)) {
        return false;
      }
      
      if (! array_key_exists($component, $msg_return_to_parts)) {
        return false;
      }
      
      if (Auth_OpenID::arrayGet($return_to_parts, $component) !== Auth_OpenID::arrayGet($msg_return_to_parts, $component)) {
        return false;
      }
    }
    
    return true;
  }

  /**
   * @access private
   */
  function _verifyReturnToArgs($query) {
    // Verify that the arguments in the return_to URL are present in this
    // response.
    

    $message = Auth_OpenID_Message::fromPostArgs($query);
    $return_to = $message->getArg(Auth_OpenID_OPENID_NS, 'return_to');
    
    if (Auth_OpenID::isFailure($return_to)) {
      return $return_to;
    }
    // XXX: this should be checked by _idResCheckForFields
    if (! $return_to) {
      return new Auth_OpenID_FailureResponse(null, "Response has no return_to");
    }
    
    $parsed_url = parse_url($return_to);
    
    $q = array();
    if (array_key_exists('query', $parsed_url)) {
      $rt_query = $parsed_url['query'];
      $q = Auth_OpenID::parse_str($rt_query);
    }
    
    foreach ($q as $rt_key => $rt_value) {
      if (! array_key_exists($rt_key, $query)) {
        return new Auth_OpenID_FailureResponse(null, sprintf("return_to parameter %s absent from query", $rt_key));
      } else {
        $value = $query[$rt_key];
        if ($rt_value != $value) {
          return new Auth_OpenID_FailureResponse(null, sprintf("parameter %s value %s does not match " . "return_to value %s", $rt_key, $value, $rt_value));
        }
      }
    }
    
    // Make sure all non-OpenID arguments in the response are also
    // in the signed return_to.
    $bare_args = $message->getArgs(Auth_OpenID_BARE_NS);
    foreach ($bare_args as $key => $value) {
      if (Auth_OpenID::arrayGet($q, $key) != $value) {
        return new Auth_OpenID_FailureResponse(null, sprintf("Parameter %s = %s not in return_to URL", $key, $value));
      }
    }
    
    return true;
  }

  /**
   * @access private
   */
  function _idResCheckSignature($message, $server_url) {
    $assoc_handle = $message->getArg(Auth_OpenID_OPENID_NS, 'assoc_handle');
    if (Auth_OpenID::isFailure($assoc_handle)) {
      return $assoc_handle;
    }
    
    $assoc = $this->store->getAssociation($server_url, $assoc_handle);
    
    if ($assoc) {
      if ($assoc->getExpiresIn() <= 0) {
        // XXX: It might be a good idea sometimes to re-start
        // the authentication with a new association. Doing it
        // automatically opens the possibility for
        // denial-of-service by a server that just returns
        // expired associations (or really short-lived
        // associations)
        return new Auth_OpenID_FailureResponse(null, 'Association with ' . $server_url . ' expired');
      }
      
      if (! $assoc->checkMessageSignature($message)) {
        return new Auth_OpenID_FailureResponse(null, "Bad signature");
      }
    } else {
      // It's not an association we know about.  Stateless mode
      // is our only possible path for recovery.  XXX - async
      // framework will not want to block on this call to
      // _checkAuth.
      if (! $this->_checkAuth($message, $server_url)) {
        return new Auth_OpenID_FailureResponse(null, "Server denied check_authentication");
      }
    }
    
    return null;
  }

  /**
   * @access private
   */
  function _verifyDiscoveryResults($message, $endpoint = null) {
    if ($message->getOpenIDNamespace() == Auth_OpenID_OPENID2_NS) {
      return $this->_verifyDiscoveryResultsOpenID2($message, $endpoint);
    } else {
      return $this->_verifyDiscoveryResultsOpenID1($message, $endpoint);
    }
  }

  /**
   * @access private
   */
  function _verifyDiscoveryResultsOpenID1($message, $endpoint) {
    $claimed_id = $message->getArg(Auth_OpenID_BARE_NS, $this->openid1_return_to_identifier_name);
    
    if (($endpoint === null) && ($claimed_id === null)) {
      return new Auth_OpenID_FailureResponse($endpoint, 'When using OpenID 1, the claimed ID must be supplied, ' . 'either by passing it through as a return_to parameter ' . 'or by using a session, and supplied to the GenericConsumer ' . 'as the argument to complete()');
    } else if (($endpoint !== null) && ($claimed_id === null)) {
      $claimed_id = $endpoint->claimed_id;
    }
    
    $to_match = new Auth_OpenID_ServiceEndpoint();
    $to_match->type_uris = array(Auth_OpenID_TYPE_1_1);
    $to_match->local_id = $message->getArg(Auth_OpenID_OPENID1_NS, 'identity');
    
    // Restore delegate information from the initiation phase
    $to_match->claimed_id = $claimed_id;
    
    if ($to_match->local_id === null) {
      return new Auth_OpenID_FailureResponse($endpoint, "Missing required field openid.identity");
    }
    
    $to_match_1_0 = $to_match->copy();
    $to_match_1_0->type_uris = array(Auth_OpenID_TYPE_1_0);
    
    if ($endpoint !== null) {
      $result = $this->_verifyDiscoverySingle($endpoint, $to_match);
      
      if (is_a($result, 'Auth_OpenID_TypeURIMismatch')) {
        $result = $this->_verifyDiscoverySingle($endpoint, $to_match_1_0);
      }
      
      if (Auth_OpenID::isFailure($result)) {
        // oidutil.log("Error attempting to use stored
      //             discovery information: " + str(e))
      //             oidutil.log("Attempting discovery to
      //             verify endpoint")
      } else {
        return $endpoint;
      }
    }
    
    // Endpoint is either bad (failed verification) or None
    return $this->_discoverAndVerify($to_match->claimed_id, array($to_match, 
        $to_match_1_0));
  }

  /**
   * @access private
   */
  function _verifyDiscoverySingle($endpoint, $to_match) {
    // Every type URI that's in the to_match endpoint has to be
    // present in the discovered endpoint.
    foreach ($to_match->type_uris as $type_uri) {
      if (! $endpoint->usesExtension($type_uri)) {
        return new Auth_OpenID_TypeURIMismatch($endpoint, "Required type " . $type_uri . " not present");
      }
    }
    
    // Fragments do not influence discovery, so we can't compare a
    // claimed identifier with a fragment to discovered
    // information.
    list($defragged_claimed_id, $_) = Auth_OpenID::urldefrag($to_match->claimed_id);
    
    if ($defragged_claimed_id != $endpoint->claimed_id) {
      return new Auth_OpenID_FailureResponse($endpoint, sprintf('Claimed ID does not match (different subjects!), ' . 'Expected %s, got %s', $defragged_claimed_id, $endpoint->claimed_id));
    }
    
    if ($to_match->getLocalID() != $endpoint->getLocalID()) {
      return new Auth_OpenID_FailureResponse($endpoint, sprintf('local_id mismatch. Expected %s, got %s', $to_match->getLocalID(), $endpoint->getLocalID()));
    }
    
    // If the server URL is None, this must be an OpenID 1
    // response, because op_endpoint is a required parameter in
    // OpenID 2. In that case, we don't actually care what the
    // discovered server_url is, because signature checking or
    // check_auth should take care of that check for us.
    if ($to_match->server_url === null) {
      if ($to_match->preferredNamespace() != Auth_OpenID_OPENID1_NS) {
        return new Auth_OpenID_FailureResponse($endpoint, "Preferred namespace mismatch (bug)");
      }
    } else if ($to_match->server_url != $endpoint->server_url) {
      return new Auth_OpenID_FailureResponse($endpoint, sprintf('OP Endpoint mismatch. Expected %s, got %s', $to_match->server_url, $endpoint->server_url));
    }
    
    return null;
  }

  /**
   * @access private
   */
  function _verifyDiscoveryResultsOpenID2($message, $endpoint) {
    $to_match = new Auth_OpenID_ServiceEndpoint();
    $to_match->type_uris = array(Auth_OpenID_TYPE_2_0);
    $to_match->claimed_id = $message->getArg(Auth_OpenID_OPENID2_NS, 'claimed_id');
    
    $to_match->local_id = $message->getArg(Auth_OpenID_OPENID2_NS, 'identity');
    
    $to_match->server_url = $message->getArg(Auth_OpenID_OPENID2_NS, 'op_endpoint');
    
    if ($to_match->server_url === null) {
      return new Auth_OpenID_FailureResponse($endpoint, "OP Endpoint URL missing");
    }
    
    // claimed_id and identifier must both be present or both be
    // absent
    if (($to_match->claimed_id === null) && ($to_match->local_id !== null)) {
      return new Auth_OpenID_FailureResponse($endpoint, 'openid.identity is present without openid.claimed_id');
    }
    
    if (($to_match->claimed_id !== null) && ($to_match->local_id === null)) {
      return new Auth_OpenID_FailureResponse($endpoint, 'openid.claimed_id is present without openid.identity');
    }
    
    if ($to_match->claimed_id === null) {
      // This is a response without identifiers, so there's
      // really no checking that we can do, so return an
      // endpoint that's for the specified `openid.op_endpoint'
      return Auth_OpenID_ServiceEndpoint::fromOPEndpointURL($to_match->server_url);
    }
    
    if (! $endpoint) {
      // The claimed ID doesn't match, so we have to do
      // discovery again. This covers not using sessions, OP
      // identifier endpoints and responses that didn't match
      // the original request.
      // oidutil.log('No pre-discovered information supplied.')
      return $this->_discoverAndVerify($to_match->claimed_id, array(
          $to_match));
    } else {
      
      // The claimed ID matches, so we use the endpoint that we
      // discovered in initiation. This should be the most
      // common case.
      $result = $this->_verifyDiscoverySingle($endpoint, $to_match);
      
      if (Auth_OpenID::isFailure($result)) {
        $endpoint = $this->_discoverAndVerify($to_match->claimed_id, array($to_match));
        if (Auth_OpenID::isFailure($endpoint)) {
          return $endpoint;
        }
      }
    }
    
    // The endpoint we return should have the claimed ID from the
    // message we just verified, fragment and all.
    if ($endpoint->claimed_id != $to_match->claimed_id) {
      $endpoint->claimed_id = $to_match->claimed_id;
    }
    
    return $endpoint;
  }

  /**
   * @access private
   */
  function _discoverAndVerify($claimed_id, $to_match_endpoints) {
    // oidutil.log('Performing discovery on %s' % (claimed_id,))
    list($unused, $services) = call_user_func($this->discoverMethod, $claimed_id, $this->fetcher);
    
    if (! $services) {
      return new Auth_OpenID_FailureResponse(null, sprintf("No OpenID information found at %s", $claimed_id));
    }
    
    return $this->_verifyDiscoveryServices($claimed_id, $services, $to_match_endpoints);
  }

  /**
   * @access private
   */
  function _verifyDiscoveryServices($claimed_id, &$services, &$to_match_endpoints) {
    // Search the services resulting from discovery to find one
    // that matches the information from the assertion
    

    foreach ($services as $endpoint) {
      foreach ($to_match_endpoints as $to_match_endpoint) {
        $result = $this->_verifyDiscoverySingle($endpoint, $to_match_endpoint);
        
        if (! Auth_OpenID::isFailure($result)) {
          // It matches, so discover verification has
          // succeeded. Return this endpoint.
          return $endpoint;
        }
      }
    }
    
    return new Auth_OpenID_FailureResponse(null, sprintf('No matching endpoint found after discovering %s', $claimed_id));
  }

  /**
   * Extract the nonce from an OpenID 1 response.  Return the nonce
   * from the BARE_NS since we independently check the return_to
   * arguments are the same as those in the response message.
   *
   * See the openid1_nonce_query_arg_name class variable
   *
   * @returns $nonce The nonce as a string or null
   *
   * @access private
   */
  function _idResGetNonceOpenID1($message, $endpoint) {
    return $message->getArg(Auth_OpenID_BARE_NS, $this->openid1_nonce_query_arg_name);
  }

  /**
   * @access private
   */
  function _idResCheckNonce($message, $endpoint) {
    if ($message->isOpenID1()) {
      // This indicates that the nonce was generated by the consumer
      $nonce = $this->_idResGetNonceOpenID1($message, $endpoint);
      $server_url = '';
    } else {
      $nonce = $message->getArg(Auth_OpenID_OPENID2_NS, 'response_nonce');
      
      $server_url = $endpoint->server_url;
    }
    
    if ($nonce === null) {
      return new Auth_OpenID_FailureResponse($endpoint, "Nonce missing from response");
    }
    
    $parts = Auth_OpenID_splitNonce($nonce);
    
    if ($parts === null) {
      return new Auth_OpenID_FailureResponse($endpoint, "Malformed nonce in response");
    }
    
    list($timestamp, $salt) = $parts;
    
    if (! $this->store->useNonce($server_url, $timestamp, $salt)) {
      return new Auth_OpenID_FailureResponse($endpoint, "Nonce already used or out of range");
    }
    
    return null;
  }

  /**
   * @access private
   */
  function _idResCheckForFields($message) {
    $basic_fields = array('return_to', 'assoc_handle', 'sig', 'signed');
    $basic_sig_fields = array('return_to', 'identity');
    
    $require_fields = array(
        Auth_OpenID_OPENID2_NS => array_merge($basic_fields, array('op_endpoint')), 
        
        Auth_OpenID_OPENID1_NS => array_merge($basic_fields, array('identity')));
    
    $require_sigs = array(
        Auth_OpenID_OPENID2_NS => array_merge($basic_sig_fields, array('response_nonce', 
            'claimed_id', 'assoc_handle')), 
        Auth_OpenID_OPENID1_NS => array_merge($basic_sig_fields, array('nonce')));
    
    foreach ($require_fields[$message->getOpenIDNamespace()] as $field) {
      if (! $message->hasKey(Auth_OpenID_OPENID_NS, $field)) {
        return new Auth_OpenID_FailureResponse(null, "Missing required field '" . $field . "'");
      }
    }
    
    $signed_list_str = $message->getArg(Auth_OpenID_OPENID_NS, 'signed', Auth_OpenID_NO_DEFAULT);
    if (Auth_OpenID::isFailure($signed_list_str)) {
      return $signed_list_str;
    }
    $signed_list = explode(',', $signed_list_str);
    
    foreach ($require_sigs[$message->getOpenIDNamespace()] as $field) {
      // Field is present and not in signed list
      if ($message->hasKey(Auth_OpenID_OPENID_NS, $field) && (! in_array($field, $signed_list))) {
        return new Auth_OpenID_FailureResponse(null, "'" . $field . "' not signed");
      }
    }
    
    return null;
  }

  /**
   * @access private
   */
  function _checkAuth($message, $server_url) {
    $request = $this->_createCheckAuthRequest($message);
    if ($request === null) {
      return false;
    }
    
    $resp_message = $this->_makeKVPost($request, $server_url);
    if (($resp_message === null) || (is_a($resp_message, 'Auth_OpenID_ServerErrorContainer'))) {
      return false;
    }
    
    return $this->_processCheckAuthResponse($resp_message, $server_url);
  }

  /**
   * @access private
   */
  function _createCheckAuthRequest($message) {
    $signed = $message->getArg(Auth_OpenID_OPENID_NS, 'signed');
    if ($signed) {
      foreach (explode(',', $signed) as $k) {
        $value = $message->getAliasedArg($k);
        if ($value === null) {
          return null;
        }
      }
    }
    $ca_message = $message->copy();
    $ca_message->setArg(Auth_OpenID_OPENID_NS, 'mode', 'check_authentication');
    return $ca_message;
  }

  /**
   * @access private
   */
  function _processCheckAuthResponse($response, $server_url) {
    $is_valid = $response->getArg(Auth_OpenID_OPENID_NS, 'is_valid', 'false');
    
    $invalidate_handle = $response->getArg(Auth_OpenID_OPENID_NS, 'invalidate_handle');
    
    if ($invalidate_handle !== null) {
      $this->store->removeAssociation($server_url, $invalidate_handle);
    }
    
    if ($is_valid == 'true') {
      return true;
    }
    
    return false;
  }

  /**
   * Adapt a POST response to a Message.
   *
   * @param $response Result of a POST to an OpenID endpoint.
   *
   * @access private
   */
  function _httpResponseToMessage($response, $server_url) {
    // Should this function be named Message.fromHTTPResponse instead?
    $response_message = Auth_OpenID_Message::fromKVForm($response->body);
    
    if ($response->status == 400) {
      return Auth_OpenID_ServerErrorContainer::fromMessage($response_message);
    } else if ($response->status != 200 and $response->status != 206) {
      return null;
    }
    
    return $response_message;
  }

  /**
   * @access private
   */
  function _makeKVPost($message, $server_url) {
    $body = $message->toURLEncoded();
    $resp = $this->fetcher->post($server_url, $body);
    
    if ($resp === null) {
      return null;
    }
    
    return $this->_httpResponseToMessage($resp, $server_url);
  }

  /**
   * @access private
   */
  function _getAssociation($endpoint) {
    if (! $this->_use_assocs) {
      return null;
    }
    
    $assoc = $this->store->getAssociation($endpoint->server_url);
    
    if (($assoc === null) || ($assoc->getExpiresIn() <= 0)) {
      
      $assoc = $this->_negotiateAssociation($endpoint);
      
      if ($assoc !== null) {
        $this->store->storeAssociation($endpoint->server_url, $assoc);
      }
    }
    
    return $assoc;
  }

  /**
   * Handle ServerErrors resulting from association requests.
   *
   * @return $result If server replied with an C{unsupported-type}
   * error, return a tuple of supported C{association_type},
   * C{session_type}.  Otherwise logs the error and returns null.
   *
   * @access private
   */
  function _extractSupportedAssociationType(&$server_error, &$endpoint, $assoc_type) {
    // Any error message whose code is not 'unsupported-type'
    // should be considered a total failure.
    if (($server_error->error_code != 'unsupported-type') || ($server_error->message->isOpenID1())) {
      return null;
    }
    
    // The server didn't like the association/session type that we
    // sent, and it sent us back a message that might tell us how
    // to handle it.
    

    // Extract the session_type and assoc_type from the error
    // message
    $assoc_type = $server_error->message->getArg(Auth_OpenID_OPENID_NS, 'assoc_type');
    
    $session_type = $server_error->message->getArg(Auth_OpenID_OPENID_NS, 'session_type');
    
    if (($assoc_type === null) || ($session_type === null)) {
      return null;
    } else if (! $this->negotiator->isAllowed($assoc_type, $session_type)) {
      return null;
    } else {
      return array($assoc_type, $session_type);
    }
  }

  /**
   * @access private
   */
  function _negotiateAssociation($endpoint) {
    // Get our preferred session/association type from the negotiatior.
    list($assoc_type, $session_type) = $this->negotiator->getAllowedType();
    
    $assoc = $this->_requestAssociation($endpoint, $assoc_type, $session_type);
    
    if (Auth_OpenID::isFailure($assoc)) {
      return null;
    }
    
    if (is_a($assoc, 'Auth_OpenID_ServerErrorContainer')) {
      $why = $assoc;
      
      $supportedTypes = $this->_extractSupportedAssociationType($why, $endpoint, $assoc_type);
      
      if ($supportedTypes !== null) {
        list($assoc_type, $session_type) = $supportedTypes;
        
        // Attempt to create an association from the assoc_type
        // and session_type that the server told us it
        // supported.
        $assoc = $this->_requestAssociation($endpoint, $assoc_type, $session_type);
        
        if (is_a($assoc, 'Auth_OpenID_ServerErrorContainer')) {
          // Do not keep trying, since it rejected the
          // association type that it told us to use.
          // oidutil.log('Server %s refused its suggested association
          //             'type: session_type=%s, assoc_type=%s'
          //             % (endpoint.server_url, session_type,
          //                assoc_type))
          return null;
        } else {
          return $assoc;
        }
      } else {
        return null;
      }
    } else {
      return $assoc;
    }
  }

  /**
   * @access private
   */
  function _requestAssociation($endpoint, $assoc_type, $session_type) {
    list($assoc_session, $args) = $this->_createAssociateRequest($endpoint, $assoc_type, $session_type);
    
    $response_message = $this->_makeKVPost($args, $endpoint->server_url);
    
    if ($response_message === null) {
      // oidutil.log('openid.associate request failed: %s' % (why[0],))
      return null;
    } else if (is_a($response_message, 'Auth_OpenID_ServerErrorContainer')) {
      return $response_message;
    }
    
    return $this->_extractAssociation($response_message, $assoc_session);
  }

  /**
   * @access private
   */
  function _extractAssociation(&$assoc_response, &$assoc_session) {
    // Extract the common fields from the response, raising an
    // exception if they are not found
    $assoc_type = $assoc_response->getArg(Auth_OpenID_OPENID_NS, 'assoc_type', Auth_OpenID_NO_DEFAULT);
    
    if (Auth_OpenID::isFailure($assoc_type)) {
      return $assoc_type;
    }
    
    $assoc_handle = $assoc_response->getArg(Auth_OpenID_OPENID_NS, 'assoc_handle', Auth_OpenID_NO_DEFAULT);
    
    if (Auth_OpenID::isFailure($assoc_handle)) {
      return $assoc_handle;
    }
    
    // expires_in is a base-10 string. The Python parsing will
    // accept literals that have whitespace around them and will
    // accept negative values. Neither of these are really in-spec,
    // but we think it's OK to accept them.
    $expires_in_str = $assoc_response->getArg(Auth_OpenID_OPENID_NS, 'expires_in', Auth_OpenID_NO_DEFAULT);
    
    if (Auth_OpenID::isFailure($expires_in_str)) {
      return $expires_in_str;
    }
    
    $expires_in = Auth_OpenID::intval($expires_in_str);
    if ($expires_in === false) {
      
      $err = sprintf("Could not parse expires_in from association " . "response %s", print_r($assoc_response, true));
      return new Auth_OpenID_FailureResponse(null, $err);
    }
    
    // OpenID 1 has funny association session behaviour.
    if ($assoc_response->isOpenID1()) {
      $session_type = $this->_getOpenID1SessionType($assoc_response);
    } else {
      $session_type = $assoc_response->getArg(Auth_OpenID_OPENID2_NS, 'session_type', Auth_OpenID_NO_DEFAULT);
      
      if (Auth_OpenID::isFailure($session_type)) {
        return $session_type;
      }
    }
    
    // Session type mismatch
    if ($assoc_session->session_type != $session_type) {
      if ($assoc_response->isOpenID1() && ($session_type == 'no-encryption')) {
        // In OpenID 1, any association request can result in
        // a 'no-encryption' association response. Setting
        // assoc_session to a new no-encryption session should
        // make the rest of this function work properly for
        // that case.
        $assoc_session = new Auth_OpenID_PlainTextConsumerSession();
      } else {
        // Any other mismatch, regardless of protocol version
        // results in the failure of the association session
        // altogether.
        return null;
      }
    }
    
    // Make sure assoc_type is valid for session_type
    if (! in_array($assoc_type, $assoc_session->allowed_assoc_types)) {
      return null;
    }
    
    // Delegate to the association session to extract the secret
    // from the response, however is appropriate for that session
    // type.
    $secret = $assoc_session->extractSecret($assoc_response);
    
    if ($secret === null) {
      return null;
    }
    
    return Auth_OpenID_Association::fromExpiresIn($expires_in, $assoc_handle, $secret, $assoc_type);
  }

  /**
   * @access private
   */
  function _createAssociateRequest($endpoint, $assoc_type, $session_type) {
    if (array_key_exists($session_type, $this->session_types)) {
      $session_type_class = $this->session_types[$session_type];
      
      if (is_callable($session_type_class)) {
        $assoc_session = $session_type_class();
      } else {
        $assoc_session = new $session_type_class();
      }
    } else {
      return null;
    }
    
    $args = array('mode' => 'associate', 'assoc_type' => $assoc_type);
    
    if (! $endpoint->compatibilityMode()) {
      $args['ns'] = Auth_OpenID_OPENID2_NS;
    }
    
    // Leave out the session type if we're in compatibility mode
    // *and* it's no-encryption.
    if ((! $endpoint->compatibilityMode()) || ($assoc_session->session_type != 'no-encryption')) {
      $args['session_type'] = $assoc_session->session_type;
    }
    
    $args = array_merge($args, $assoc_session->getRequest());
    $message = Auth_OpenID_Message::fromOpenIDArgs($args);
    return array($assoc_session, $message);
  }

  /**
   * Given an association response message, extract the OpenID 1.X
   * session type.
   *
   * This function mostly takes care of the 'no-encryption' default
   * behavior in OpenID 1.
   *
   * If the association type is plain-text, this function will
   * return 'no-encryption'
   *
   * @access private
   * @return $typ The association type for this message
   */
  function _getOpenID1SessionType($assoc_response) {
    // If it's an OpenID 1 message, allow session_type to default
    // to None (which signifies "no-encryption")
    $session_type = $assoc_response->getArg(Auth_OpenID_OPENID1_NS, 'session_type');
    
    // Handle the differences between no-encryption association
    // respones in OpenID 1 and 2:
    

    // no-encryption is not really a valid session type for OpenID
    // 1, but we'll accept it anyway, while issuing a warning.
    if ($session_type == 'no-encryption') {
      // oidutil.log('WARNING: OpenID server sent "no-encryption"'
    //             'for OpenID 1.X')
    } else if (($session_type == '') || ($session_type === null)) {
      // Missing or empty session type is the way to flag a
      // 'no-encryption' response. Change the session type to
      // 'no-encryption' so that it can be handled in the same
      // way as OpenID 2 'no-encryption' respones.
      $session_type = 'no-encryption';
    }
    
    return $session_type;
  }
}

/**
 * This class represents an authentication request from a consumer to
 * an OpenID server.
 *
 * @package OpenID
 */
class Auth_OpenID_AuthRequest {

  /**
   * Initialize an authentication request with the specified token,
   * association, and endpoint.
   *
   * Users of this library should not create instances of this
   * class.  Instances of this class are created by the library when
   * needed.
   */
  function Auth_OpenID_AuthRequest(&$endpoint, $assoc) {
    $this->assoc = $assoc;
    $this->endpoint = & $endpoint;
    $this->return_to_args = array();
    $this->message = new Auth_OpenID_Message($endpoint->preferredNamespace());
    $this->_anonymous = false;
  }

  /**
   * Add an extension to this checkid request.
   *
   * $extension_request: An object that implements the extension
   * request interface for adding arguments to an OpenID message.
   */
  function addExtension(&$extension_request) {
    $extension_request->toMessage($this->message);
  }

  /**
   * Add an extension argument to this OpenID authentication
   * request.
   *
   * Use caution when adding arguments, because they will be
   * URL-escaped and appended to the redirect URL, which can easily
   * get quite long.
   *
   * @param string $namespace The namespace for the extension. For
   * example, the simple registration extension uses the namespace
   * 'sreg'.
   *
   * @param string $key The key within the extension namespace. For
   * example, the nickname field in the simple registration
   * extension's key is 'nickname'.
   *
   * @param string $value The value to provide to the server for
   * this argument.
   */
  function addExtensionArg($namespace, $key, $value) {
    return $this->message->setArg($namespace, $key, $value);
  }

  /**
   * Set whether this request should be made anonymously. If a
   * request is anonymous, the identifier will not be sent in the
   * request. This is only useful if you are making another kind of
   * request with an extension in this request.
   *
   * Anonymous requests are not allowed when the request is made
   * with OpenID 1.
   */
  function setAnonymous($is_anonymous) {
    if ($is_anonymous && $this->message->isOpenID1()) {
      return false;
    } else {
      $this->_anonymous = $is_anonymous;
      return true;
    }
  }

  /**
   * Produce a {@link Auth_OpenID_Message} representing this
   * request.
   *
   * @param string $realm The URL (or URL pattern) that identifies
   * your web site to the user when she is authorizing it.
   *
   * @param string $return_to The URL that the OpenID provider will
   * send the user back to after attempting to verify her identity.
   *
   * Not specifying a return_to URL means that the user will not be
   * returned to the site issuing the request upon its completion.
   *
   * @param bool $immediate If true, the OpenID provider is to send
   * back a response immediately, useful for behind-the-scenes
   * authentication attempts.  Otherwise the OpenID provider may
   * engage the user before providing a response.  This is the
   * default case, as the user may need to provide credentials or
   * approve the request before a positive response can be sent.
   */
  function getMessage($realm, $return_to = null, $immediate = false) {
    if ($return_to) {
      $return_to = Auth_OpenID::appendArgs($return_to, $this->return_to_args);
    } else if ($immediate) {
      // raise ValueError(
      //     '"return_to" is mandatory when
      //using "checkid_immediate"')
      return new Auth_OpenID_FailureResponse(null, "'return_to' is mandatory when using checkid_immediate");
    } else if ($this->message->isOpenID1()) {
      // raise ValueError('"return_to" is
      // mandatory for OpenID 1 requests')
      return new Auth_OpenID_FailureResponse(null, "'return_to' is mandatory for OpenID 1 requests");
    } else if ($this->return_to_args) {
      // raise ValueError('extra "return_to" arguments
      // were specified, but no return_to was specified')
      return new Auth_OpenID_FailureResponse(null, "extra 'return_to' arguments where specified, " . "but no return_to was specified");
    }
    
    if ($immediate) {
      $mode = 'checkid_immediate';
    } else {
      $mode = 'checkid_setup';
    }
    
    $message = $this->message->copy();
    if ($message->isOpenID1()) {
      $realm_key = 'trust_root';
    } else {
      $realm_key = 'realm';
    }
    
    $message->updateArgs(Auth_OpenID_OPENID_NS, array($realm_key => $realm, 'mode' => $mode, 
        'return_to' => $return_to));
    
    if (! $this->_anonymous) {
      if ($this->endpoint->isOPIdentifier()) {
        // This will never happen when we're in compatibility
        // mode, as long as isOPIdentifier() returns False
        // whenever preferredNamespace() returns OPENID1_NS.
        $claimed_id = $request_identity = Auth_OpenID_IDENTIFIER_SELECT;
      } else {
        $request_identity = $this->endpoint->getLocalID();
        $claimed_id = $this->endpoint->claimed_id;
      }
      
      // This is true for both OpenID 1 and 2
      $message->setArg(Auth_OpenID_OPENID_NS, 'identity', $request_identity);
      
      if ($message->isOpenID2()) {
        $message->setArg(Auth_OpenID_OPENID2_NS, 'claimed_id', $claimed_id);
      }
    }
    
    if ($this->assoc) {
      $message->setArg(Auth_OpenID_OPENID_NS, 'assoc_handle', $this->assoc->handle);
    }
    
    return $message;
  }

  function redirectURL($realm, $return_to = null, $immediate = false) {
    $message = $this->getMessage($realm, $return_to, $immediate);
    
    if (Auth_OpenID::isFailure($message)) {
      return $message;
    }
    
    return $message->toURL($this->endpoint->server_url);
  }

  /**
   * Get html for a form to submit this request to the IDP.
   *
   * form_tag_attrs: An array of attributes to be added to the form
   * tag. 'accept-charset' and 'enctype' have defaults that can be
   * overridden. If a value is supplied for 'action' or 'method', it
   * will be replaced.
   */
  function formMarkup($realm, $return_to = null, $immediate = false, $form_tag_attrs = null) {
    $message = $this->getMessage($realm, $return_to, $immediate);
    
    if (Auth_OpenID::isFailure($message)) {
      return $message;
    }
    
    return $message->toFormMarkup($this->endpoint->server_url, $form_tag_attrs);
  }

  /**
   * Get a complete html document that will autosubmit the request
   * to the IDP.
   *
   * Wraps formMarkup.  See the documentation for that function.
   */
  function htmlMarkup($realm, $return_to = null, $immediate = false, $form_tag_attrs = null) {
    $form = $this->formMarkup($realm, $return_to, $immediate, $form_tag_attrs);
    
    if (Auth_OpenID::isFailure($form)) {
      return $form;
    }
    return Auth_OpenID::autoSubmitHTML($form);
  }

  function shouldSendRedirect() {
    return $this->endpoint->compatibilityMode();
  }
}

/**
 * The base class for responses from the Auth_OpenID_Consumer.
 *
 * @package OpenID
 */
class Auth_OpenID_ConsumerResponse {
  var $status = null;

  function setEndpoint($endpoint) {
    $this->endpoint = $endpoint;
    if ($endpoint === null) {
      $this->identity_url = null;
    } else {
      $this->identity_url = $endpoint->claimed_id;
    }
  }

  /**
   * Return the display identifier for this response.
   *
   * The display identifier is related to the Claimed Identifier, but the
   * two are not always identical.  The display identifier is something the
   * user should recognize as what they entered, whereas the response's
   * claimed identifier (in the identity_url attribute) may have extra
   * information for better persistence.
   *
   * URLs will be stripped of their fragments for display.  XRIs will
   * display the human-readable identifier (i-name) instead of the
   * persistent identifier (i-number).
   *
   * Use the display identifier in your user interface.  Use
   * identity_url for querying your database or authorization server.
   *
   */
  function getDisplayIdentifier() {
    if ($this->endpoint !== null) {
      return $this->endpoint->getDisplayIdentifier();
    }
    return null;
  }
}

/**
 * A response with a status of Auth_OpenID_SUCCESS. Indicates that
 * this request is a successful acknowledgement from the OpenID server
 * that the supplied URL is, indeed controlled by the requesting
 * agent.  This has three relevant attributes:
 *
 * claimed_id - The identity URL that has been authenticated
 *
 * signed_args - The arguments in the server's response that were
 * signed and verified.
 *
 * status - Auth_OpenID_SUCCESS.
 *
 * @package OpenID
 */
class Auth_OpenID_SuccessResponse extends Auth_OpenID_ConsumerResponse {
  var $status = Auth_OpenID_SUCCESS;

  /**
   * @access private
   */
  function Auth_OpenID_SuccessResponse($endpoint, $message, $signed_args = null) {
    $this->endpoint = $endpoint;
    $this->identity_url = $endpoint->claimed_id;
    $this->signed_args = $signed_args;
    $this->message = $message;
    
    if ($this->signed_args === null) {
      $this->signed_args = array();
    }
  }

  /**
   * Extract signed extension data from the server's response.
   *
   * @param string $prefix The extension namespace from which to
   * extract the extension data.
   */
  function extensionResponse($namespace_uri, $require_signed) {
    if ($require_signed) {
      return $this->getSignedNS($namespace_uri);
    } else {
      return $this->message->getArgs($namespace_uri);
    }
  }

  function isOpenID1() {
    return $this->message->isOpenID1();
  }

  function isSigned($ns_uri, $ns_key) {
    // Return whether a particular key is signed, regardless of
    // its namespace alias
    return in_array($this->message->getKey($ns_uri, $ns_key), $this->signed_args);
  }

  function getSigned($ns_uri, $ns_key, $default = null) {
    // Return the specified signed field if available, otherwise
    // return default
    if ($this->isSigned($ns_uri, $ns_key)) {
      return $this->message->getArg($ns_uri, $ns_key, $default);
    } else {
      return $default;
    }
  }

  function getSignedNS($ns_uri) {
    $args = array();
    
    $msg_args = $this->message->getArgs($ns_uri);
    if (Auth_OpenID::isFailure($msg_args)) {
      return null;
    }
    
    foreach ($msg_args as $key => $value) {
      if (! $this->isSigned($ns_uri, $key)) {
        return null;
      }
    }
    
    return $msg_args;
  }

  /**
   * Get the openid.return_to argument from this response.
   *
   * This is useful for verifying that this request was initiated by
   * this consumer.
   *
   * @return string $return_to The return_to URL supplied to the
   * server on the initial request, or null if the response did not
   * contain an 'openid.return_to' argument.
   */
  function getReturnTo() {
    return $this->getSigned(Auth_OpenID_OPENID_NS, 'return_to');
  }
}

/**
 * A response with a status of Auth_OpenID_FAILURE. Indicates that the
 * OpenID protocol has failed. This could be locally or remotely
 * triggered.  This has three relevant attributes:
 *
 * claimed_id - The identity URL for which authentication was
 * attempted, if it can be determined.  Otherwise, null.
 *
 * message - A message indicating why the request failed, if one is
 * supplied.  Otherwise, null.
 *
 * status - Auth_OpenID_FAILURE.
 *
 * @package OpenID
 */
class Auth_OpenID_FailureResponse extends Auth_OpenID_ConsumerResponse {
  var $status = Auth_OpenID_FAILURE;

  function Auth_OpenID_FailureResponse($endpoint, $message = null, $contact = null, $reference = null) {
    $this->setEndpoint($endpoint);
    $this->message = $message;
    $this->contact = $contact;
    $this->reference = $reference;
  }
}

/**
 * A specific, internal failure used to detect type URI mismatch.
 *
 * @package OpenID
 */
class Auth_OpenID_TypeURIMismatch extends Auth_OpenID_FailureResponse {
}

/**
 * Exception that is raised when the server returns a 400 response
 * code to a direct request.
 *
 * @package OpenID
 */
class Auth_OpenID_ServerErrorContainer {

  function Auth_OpenID_ServerErrorContainer($error_text, $error_code, $message) {
    $this->error_text = $error_text;
    $this->error_code = $error_code;
    $this->message = $message;
  }

  /**
   * @access private
   */
  function fromMessage($message) {
    $error_text = $message->getArg(Auth_OpenID_OPENID_NS, 'error', '<no error message supplied>');
    $error_code = $message->getArg(Auth_OpenID_OPENID_NS, 'error_code');
    return new Auth_OpenID_ServerErrorContainer($error_text, $error_code, $message);
  }
}

/**
 * A response with a status of Auth_OpenID_CANCEL. Indicates that the
 * user cancelled the OpenID authentication request.  This has two
 * relevant attributes:
 *
 * claimed_id - The identity URL for which authentication was
 * attempted, if it can be determined.  Otherwise, null.
 *
 * status - Auth_OpenID_SUCCESS.
 *
 * @package OpenID
 */
class Auth_OpenID_CancelResponse extends Auth_OpenID_ConsumerResponse {
  var $status = Auth_OpenID_CANCEL;

  function Auth_OpenID_CancelResponse($endpoint) {
    $this->setEndpoint($endpoint);
  }
}

/**
 * A response with a status of Auth_OpenID_SETUP_NEEDED. Indicates
 * that the request was in immediate mode, and the server is unable to
 * authenticate the user without further interaction.
 *
 * claimed_id - The identity URL for which authentication was
 * attempted.
 *
 * setup_url - A URL that can be used to send the user to the server
 * to set up for authentication. The user should be redirected in to
 * the setup_url, either in the current window or in a new browser
 * window.  Null in OpenID 2.
 *
 * status - Auth_OpenID_SETUP_NEEDED.
 *
 * @package OpenID
 */
class Auth_OpenID_SetupNeededResponse extends Auth_OpenID_ConsumerResponse {
  var $status = Auth_OpenID_SETUP_NEEDED;

  function Auth_OpenID_SetupNeededResponse($endpoint, $setup_url = null) {
    $this->setEndpoint($endpoint);
    $this->setup_url = $setup_url;
  }
}
