includes/session/SessionProvider.php

   1 <?php
   2 /**
   3  * MediaWiki session provider base class
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Session
  22  */
  23
  24 namespace MediaWiki\Session;
  25
  26 use Psr\Log\LoggerAwareInterface;
  27 use Psr\Log\LoggerInterface;
  28 use Config;
  29 use Language;
  30 use User;
  31 use WebRequest;
  32
  33 /**
  34  * A SessionProvider provides SessionInfo and support for Session
  35  *
  36  * A SessionProvider is responsible for taking a WebRequest and determining
  37  * the authenticated session that it's a part of. It does this by returning an
  38  * SessionInfo object with basic information about the session it thinks is
  39  * associated with the request, namely the session ID and possibly the
  40  * authenticated user the session belongs to.
  41  *
  42  * The SessionProvider also provides for updating the WebResponse with
  43  * information necessary to provide the client with data that the client will
  44  * send with later requests, and for populating the Vary and Key headers with
  45  * the data necessary to correctly vary the cache on these client requests.
  46  *
  47  * An important part of the latter is indicating whether it even *can* tell the
  48  * client to include such data in future requests, via the persistsSessionId()
  49  * and canChangeUser() methods. The cases are (in order of decreasing
  50  * commonness):
  51  *  - Cannot persist ID, no changing User: The request identifies and
  52  *    authenticates a particular local user, and the client cannot be
  53  *    instructed to include an arbitrary session ID with future requests. For
  54  *    example, OAuth or SSL certificate auth.
  55  *  - Can persist ID and can change User: The client can be instructed to
  56  *    return at least one piece of arbitrary data, that being the session ID.
  57  *    The user identity might also be given to the client, otherwise it's saved
  58  *    in the session data. For example, cookie-based sessions.
  59  *  - Can persist ID but no changing User: The request uniquely identifies and
  60  *    authenticates a local user, and the client can be instructed to return an
  61  *    arbitrary session ID with future requests. For example, HTTP Digest
  62  *    authentication might somehow use the 'opaque' field as a session ID
  63  *    (although getting MediaWiki to return 401 responses without breaking
  64  *    other stuff might be a challenge).
  65  *  - Cannot persist ID but can change User: I can't think of a way this
  66  *    would make sense.
  67  *
  68  * Note that many methods that are technically "cannot persist ID" could be
  69  * turned into "can persist ID but not changing User" using a session cookie,
  70  * as implemented by ImmutableSessionProviderWithCookie. If doing so, different
  71  * session cookie names should be used for different providers to avoid
  72  * collisions.
  73  *
  74  * @ingroup Session
  75  * @since 1.27
  76  */
  77 abstract class SessionProvider implements SessionProviderInterface, LoggerAwareInterface {
  78
  79         /** @var LoggerInterface */
  80         protected $logger;
  81
  82         /** @var Config */
  83         protected $config;
  84
  85         /** @var SessionManager */
  86         protected $manager;
  87
  88         /** @var int Session priority. Used for the default newSessionInfo(), but
  89          * could be used by subclasses too.
  90          */
  91         protected $priority;
  92
  93         /**
  94          * @note To fully initialize a SessionProvider, the setLogger(),
  95          *  setConfig(), and setManager() methods must be called (and should be
  96          *  called in that order). Failure to do so is liable to cause things to
  97          *  fail unexpectedly.
  98          */
  99         public function __construct() {
 100                 $this->priority = SessionInfo::MIN_PRIORITY + 10;
 101         }
 102
 103         public function setLogger( LoggerInterface $logger ) {
 104                 $this->logger = $logger;
 105         }
 106
 107         /**
 108          * Set configuration
 109          * @param Config $config
 110          */
 111         public function setConfig( Config $config ) {
 112                 $this->config = $config;
 113         }
 114
 115         /**
 116          * Set the session manager
 117          * @param SessionManager $manager
 118          */
 119         public function setManager( SessionManager $manager ) {
 120                 $this->manager = $manager;
 121         }
 122
 123         /**
 124          * Get the session manager
 125          * @return SessionManager
 126          */
 127         public function getManager() {
 128                 return $this->manager;
 129         }
 130
 131         /**
 132          * Provide session info for a request
 133          *
 134          * If no session exists for the request, return null. Otherwise return an
 135          * SessionInfo object identifying the session.
 136          *
 137          * If multiple SessionProviders provide sessions, the one with highest
 138          * priority wins. In case of a tie, an exception is thrown.
 139          * SessionProviders are encouraged to make priorities user-configurable
 140          * unless only max-priority makes sense.
 141          *
 142          * @warning This will be called early in the MediaWiki setup process,
 143          *  before $wgUser, $wgLang, $wgOut, $wgParser, $wgTitle, and corresponding
 144          *  pieces of the main RequestContext are set up! If you try to use these,
 145          *  things *will* break.
 146          * @note The SessionProvider must not attempt to auto-create users.
 147          *  MediaWiki will do this later (when it's safe) if the chosen session has
 148          *  a user with a valid name but no ID.
 149          * @protected For use by \MediaWiki\Session\SessionManager only
 150          * @param WebRequest $request
 151          * @return SessionInfo|null
 152          */
 153         abstract public function provideSessionInfo( WebRequest $request );
 154
 155         /**
 156          * Provide session info for a new, empty session
 157          *
 158          * Return null if such a session cannot be created. This base
 159          * implementation assumes that it only makes sense if a session ID can be
 160          * persisted and changing users is allowed.
 161          *
 162          * @protected For use by \MediaWiki\Session\SessionManager only
 163          * @param string|null $id ID to force for the new session
 164          * @return SessionInfo|null
 165          *  If non-null, must return true for $info->isIdSafe(); pass true for
 166          *  $data['idIsSafe'] to ensure this.
 167          */
 168         public function newSessionInfo( $id = null ) {
 169                 if ( $this->canChangeUser() && $this->persistsSessionId() ) {
 170                         return new SessionInfo( $this->priority, [
 171                                 'id' => $id,
 172                                 'provider' => $this,
 173                                 'persisted' => false,
 174                                 'idIsSafe' => true,
 175                         ] );
 176                 }
 177                 return null;
 178         }
 179
 180         /**
 181          * Merge saved session provider metadata
 182          *
 183          * The default implementation checks that anything in both arrays is
 184          * identical, then returns $providedMetadata.
 185          *
 186          * @protected For use by \MediaWiki\Session\SessionManager only
 187          * @param array $savedMetadata Saved provider metadata
 188          * @param array $providedMetadata Provided provider metadata
 189          * @return array Resulting metadata
 190          * @throws MetadataMergeException If the metadata cannot be merged
 191          */
 192         public function mergeMetadata( array $savedMetadata, array $providedMetadata ) {
 193                 foreach ( $providedMetadata as $k => $v ) {
 194                         if ( array_key_exists( $k, $savedMetadata ) && $savedMetadata[$k] !== $v ) {
 195                                 $e = new MetadataMergeException( "Key \"$k\" changed" );
 196                                 $e->setContext( [
 197                                         'old_value' => $savedMetadata[$k],
 198                                         'new_value' => $v,
 199                                 ] );
 200                                 throw $e;
 201                         }
 202                 }
 203                 return $providedMetadata;
 204         }
 205
 206         /**
 207          * Validate a loaded SessionInfo and refresh provider metadata
 208          *
 209          * This is similar in purpose to the 'SessionCheckInfo' hook, and also
 210          * allows for updating the provider metadata. On failure, the provider is
 211          * expected to write an appropriate message to its logger.
 212          *
 213          * @protected For use by \MediaWiki\Session\SessionManager only
 214          * @param SessionInfo $info
 215          * @param WebRequest $request
 216          * @param array|null &$metadata Provider metadata, may be altered.
 217          * @return bool Return false to reject the SessionInfo after all.
 218          */
 219         public function refreshSessionInfo( SessionInfo $info, WebRequest $request, &$metadata ) {
 220                 return true;
 221         }
 222
 223         /**
 224          * Indicate whether self::persistSession() can save arbitrary session IDs
 225          *
 226          * If false, any session passed to self::persistSession() will have an ID
 227          * that was originally provided by self::provideSessionInfo().
 228          *
 229          * If true, the provider may be passed sessions with arbitrary session IDs,
 230          * and will be expected to manipulate the request in such a way that future
 231          * requests will cause self::provideSessionInfo() to provide a SessionInfo
 232          * with that ID.
 233          *
 234          * For example, a session provider for OAuth would function by matching the
 235          * OAuth headers to a particular user, and then would use self::hashToSessionId()
 236          * to turn the user and OAuth client ID (and maybe also the user token and
 237          * client secret) into a session ID, and therefore can't easily assign that
 238          * user+client a different ID. Similarly, a session provider for SSL client
 239          * certificates would function by matching the certificate to a particular
 240          * user, and then would use self::hashToSessionId() to turn the user and
 241          * certificate fingerprint into a session ID, and therefore can't easily
 242          * assign a different ID either. On the other hand, a provider that saves
 243          * the session ID into a cookie can easily just set the cookie to a
 244          * different value.
 245          *
 246          * @protected For use by \MediaWiki\Session\SessionBackend only
 247          * @return bool
 248          */
 249         abstract public function persistsSessionId();
 250
 251         /**
 252          * Indicate whether the user associated with the request can be changed
 253          *
 254          * If false, any session passed to self::persistSession() will have a user
 255          * that was originally provided by self::provideSessionInfo(). Further,
 256          * self::provideSessionInfo() may only provide sessions that have a user
 257          * already set.
 258          *
 259          * If true, the provider may be passed sessions with arbitrary users, and
 260          * will be expected to manipulate the request in such a way that future
 261          * requests will cause self::provideSessionInfo() to provide a SessionInfo
 262          * with that ID. This can be as simple as not passing any 'userInfo' into
 263          * SessionInfo's constructor, in which case SessionInfo will load the user
 264          * from the saved session's metadata.
 265          *
 266          * For example, a session provider for OAuth or SSL client certificates
 267          * would function by matching the OAuth headers or certificate to a
 268          * particular user, and thus would return false here since it can't
 269          * arbitrarily assign those OAuth credentials or that certificate to a
 270          * different user. A session provider that shoves information into cookies,
 271          * on the other hand, could easily do so.
 272          *
 273          * @protected For use by \MediaWiki\Session\SessionBackend only
 274          * @return bool
 275          */
 276         abstract public function canChangeUser();
 277
 278         /**
 279          * Notification that the session ID was reset
 280          *
 281          * No need to persist here, persistSession() will be called if appropriate.
 282          *
 283          * @protected For use by \MediaWiki\Session\SessionBackend only
 284          * @param SessionBackend $session Session to persist
 285          * @param string $oldId Old session ID
 286          * @codeCoverageIgnore
 287          */
 288         public function sessionIdWasReset( SessionBackend $session, $oldId ) {
 289         }
 290
 291         /**
 292          * Persist a session into a request/response
 293          *
 294          * For example, you might set cookies for the session's ID, user ID, user
 295          * name, and user token on the passed request.
 296          *
 297          * To correctly persist a user independently of the session ID, the
 298          * provider should persist both the user ID (or name, but preferably the
 299          * ID) and the user token. When reading the data from the request, it
 300          * should construct a User object from the ID/name and then verify that the
 301          * User object's token matches the token included in the request. Should
 302          * the tokens not match, an anonymous user *must* be passed to
 303          * SessionInfo::__construct().
 304          *
 305          * When persisting a user independently of the session ID,
 306          * $session->shouldRememberUser() should be checked first. If this returns
 307          * false, the user token *must not* be saved to cookies. The user name
 308          * and/or ID may be persisted, and should be used to construct an
 309          * unverified UserInfo to pass to SessionInfo::__construct().
 310          *
 311          * A backend that cannot persist sesison ID or user info should implement
 312          * this as a no-op.
 313          *
 314          * @protected For use by \MediaWiki\Session\SessionBackend only
 315          * @param SessionBackend $session Session to persist
 316          * @param WebRequest $request Request into which to persist the session
 317          */
 318         abstract public function persistSession( SessionBackend $session, WebRequest $request );
 319
 320         /**
 321          * Remove any persisted session from a request/response
 322          *
 323          * For example, blank and expire any cookies set by self::persistSession().
 324          *
 325          * A backend that cannot persist sesison ID or user info should implement
 326          * this as a no-op.
 327          *
 328          * @protected For use by \MediaWiki\Session\SessionManager only
 329          * @param WebRequest $request Request from which to remove any session data
 330          */
 331         abstract public function unpersistSession( WebRequest $request );
 332
 333         /**
 334          * Prevent future sessions for the user
 335          *
 336          * If the provider is capable of returning a SessionInfo with a verified
 337          * UserInfo for the named user in some manner other than by validating
 338          * against $user->getToken(), steps must be taken to prevent that from
 339          * occurring in the future. This might add the username to a blacklist, or
 340          * it might just delete whatever authentication credentials would allow
 341          * such a session in the first place (e.g. remove all OAuth grants or
 342          * delete record of the SSL client certificate).
 343          *
 344          * The intention is that the named account will never again be usable for
 345          * normal login (i.e. there is no way to undo the prevention of access).
 346          *
 347          * Note that the passed user name might not exist locally (i.e.
 348          * User::idFromName( $username ) === 0); the name should still be
 349          * prevented, if applicable.
 350          *
 351          * @protected For use by \MediaWiki\Session\SessionManager only
 352          * @param string $username
 353          */
 354         public function preventSessionsForUser( $username ) {
 355                 if ( !$this->canChangeUser() ) {
 356                         throw new \BadMethodCallException(
 357                                 __METHOD__ . ' must be implmented when canChangeUser() is false'
 358                         );
 359                 }
 360         }
 361
 362         /**
 363          * Invalidate existing sessions for a user
 364          *
 365          * If the provider has its own equivalent of CookieSessionProvider's Token
 366          * cookie (and doesn't use User::getToken() to implement it), it should
 367          * reset whatever token it does use here.
 368          *
 369          * @protected For use by \MediaWiki\Session\SessionManager only
 370          * @param User $user;
 371          */
 372         public function invalidateSessionsForUser( User $user ) {
 373         }
 374
 375         /**
 376          * Return the HTTP headers that need varying on.
 377          *
 378          * The return value is such that someone could theoretically do this:
 379          * @code
 380          *  foreach ( $provider->getVaryHeaders() as $header => $options ) {
 381          *      $outputPage->addVaryHeader( $header, $options );
 382          *  }
 383          * @endcode
 384          *
 385          * @protected For use by \MediaWiki\Session\SessionManager only
 386          * @return array
 387          */
 388         public function getVaryHeaders() {
 389                 return [];
 390         }
 391
 392         /**
 393          * Return the list of cookies that need varying on.
 394          * @protected For use by \MediaWiki\Session\SessionManager only
 395          * @return string[]
 396          */
 397         public function getVaryCookies() {
 398                 return [];
 399         }
 400
 401         /**
 402          * Get a suggested username for the login form
 403          * @protected For use by \MediaWiki\Session\SessionBackend only
 404          * @param WebRequest $request
 405          * @return string|null
 406          */
 407         public function suggestLoginUsername( WebRequest $request ) {
 408                 return null;
 409         }
 410
 411         /**
 412          * Fetch the rights allowed the user when the specified session is active.
 413          * @param SessionBackend $backend
 414          * @return null|string[] Allowed user rights, or null to allow all.
 415          */
 416         public function getAllowedUserRights( SessionBackend $backend ) {
 417                 if ( $backend->getProvider() !== $this ) {
 418                         // Not that this should ever happen...
 419                         throw new \InvalidArgumentException( 'Backend\'s provider isn\'t $this' );
 420                 }
 421
 422                 return null;
 423         }
 424
 425         /**
 426          * @note Only override this if it makes sense to instantiate multiple
 427          *  instances of the provider. Value returned must be unique across
 428          *  configured providers. If you override this, you'll likely need to
 429          *  override self::describeMessage() as well.
 430          * @return string
 431          */
 432         public function __toString() {
 433                 return get_class( $this );
 434         }
 435
 436         /**
 437          * Return a Message identifying this session type
 438          *
 439          * This default implementation takes the class name, lowercases it,
 440          * replaces backslashes with dashes, and prefixes 'sessionprovider-' to
 441          * determine the message key. For example, MediaWiki\Session\CookieSessionProvider
 442          * produces 'sessionprovider-mediawiki-session-cookiesessionprovider'.
 443          *
 444          * @note If self::__toString() is overridden, this will likely need to be
 445          *  overridden as well.
 446          * @warning This will be called early during MediaWiki startup. Do not
 447          *  use $wgUser, $wgLang, $wgOut, $wgParser, or their equivalents via
 448          *  RequestContext from this method!
 449          * @return Message
 450          */
 451         protected function describeMessage() {
 452                 return wfMessage(
 453                         'sessionprovider-' . str_replace( '\\', '-', strtolower( get_class( $this ) ) )
 454                 );
 455         }
 456
 457         public function describe( Language $lang ) {
 458                 $msg = $this->describeMessage();
 459                 $msg->inLanguage( $lang );
 460                 if ( $msg->isDisabled() ) {
 461                         $msg = wfMessage( 'sessionprovider-generic', (string)$this )->inLanguage( $lang );
 462                 }
 463                 return $msg->plain();
 464         }
 465
 466         public function whyNoSession() {
 467                 return null;
 468         }
 469
 470         /**
 471          * Hash data as a session ID
 472          *
 473          * Generally this will only be used when self::persistsSessionId() is false and
 474          * the provider has to base the session ID on the verified user's identity
 475          * or other static data. The SessionInfo should then typically have the
 476          * 'forceUse' flag set to avoid persistent session failure if validation of
 477          * the stored data fails.
 478          *
 479          * @param string $data
 480          * @param string|null $key Defaults to $this->config->get( 'SecretKey' )
 481          * @return string
 482          */
 483         final protected function hashToSessionId( $data, $key = null ) {
 484                 if ( !is_string( $data ) ) {
 485                         throw new \InvalidArgumentException(
 486                                 '$data must be a string, ' . gettype( $data ) . ' was passed'
 487                         );
 488                 }
 489                 if ( $key !== null && !is_string( $key ) ) {
 490                         throw new \InvalidArgumentException(
 491                                 '$key must be a string or null, ' . gettype( $key ) . ' was passed'
 492                         );
 493                 }
 494
 495                 $hash = \MWCryptHash::hmac( "$this\n$data", $key ?: $this->config->get( 'SecretKey' ), false );
 496                 if ( strlen( $hash ) < 32 ) {
 497                         // Should never happen, even md5 is 128 bits
 498                         // @codeCoverageIgnoreStart
 499                         throw new \UnexpectedValueException( 'Hash fuction returned less than 128 bits' );
 500                         // @codeCoverageIgnoreEnd
 501                 }
 502                 if ( strlen( $hash ) >= 40 ) {
 503                         $hash = \Wikimedia\base_convert( $hash, 16, 32, 32 );
 504                 }
 505                 return substr( $hash, -32 );
 506         }
 507
 508 }