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[mediawiki.git] / includes / session / SessionProvider.php

<?php
/**
 * MediaWiki session provider base class
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Session
 */

namespace MediaWiki\Session;

use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Config;
use Language;
use User;
use WebRequest;

/**
 * A SessionProvider provides SessionInfo and support for Session
 *
 * A SessionProvider is responsible for taking a WebRequest and determining
 * the authenticated session that it's a part of. It does this by returning an
 * SessionInfo object with basic information about the session it thinks is
 * associated with the request, namely the session ID and possibly the
 * authenticated user the session belongs to.
 *
 * The SessionProvider also provides for updating the WebResponse with
 * information necessary to provide the client with data that the client will
 * send with later requests, and for populating the Vary and Key headers with
 * the data necessary to correctly vary the cache on these client requests.
 *
 * An important part of the latter is indicating whether it even *can* tell the
 * client to include such data in future requests, via the persistsSessionId()
 * and canChangeUser() methods. The cases are (in order of decreasing
 * commonness):
 *  - Cannot persist ID, no changing User: The request identifies and
 *    authenticates a particular local user, and the client cannot be
 *    instructed to include an arbitrary session ID with future requests. For
 *    example, OAuth or SSL certificate auth.
 *  - Can persist ID and can change User: The client can be instructed to
 *    return at least one piece of arbitrary data, that being the session ID.
 *    The user identity might also be given to the client, otherwise it's saved
 *    in the session data. For example, cookie-based sessions.
 *  - Can persist ID but no changing User: The request uniquely identifies and
 *    authenticates a local user, and the client can be instructed to return an
 *    arbitrary session ID with future requests. For example, HTTP Digest
 *    authentication might somehow use the 'opaque' field as a session ID
 *    (although getting MediaWiki to return 401 responses without breaking
 *    other stuff might be a challenge).
 *  - Cannot persist ID but can change User: I can't think of a way this
 *    would make sense.
 *
 * Note that many methods that are technically "cannot persist ID" could be
 * turned into "can persist ID but not change User" using a session cookie,
 * as implemented by ImmutableSessionProviderWithCookie. If doing so, different
 * session cookie names should be used for different providers to avoid
 * collisions.
 *
 * @ingroup Session
 * @since 1.27
 * @see https://www.mediawiki.org/wiki/Manual:SessionManager_and_AuthManager
 */
abstract class SessionProvider implements SessionProviderInterface, LoggerAwareInterface {

        /** @var LoggerInterface */
        protected $logger;

        /** @var Config */
        protected $config;

        /** @var SessionManager */
        protected $manager;

        /** @var int Session priority. Used for the default newSessionInfo(), but
         * could be used by subclasses too.
         */
        protected $priority;

        /**
         * @note To fully initialize a SessionProvider, the setLogger(),
         *  setConfig(), and setManager() methods must be called (and should be
         *  called in that order). Failure to do so is liable to cause things to
         *  fail unexpectedly.
         */
        public function __construct() {
                $this->priority = SessionInfo::MIN_PRIORITY + 10;
        }

        public function setLogger( LoggerInterface $logger ) {
                $this->logger = $logger;
        }

        /**
         * Set configuration
         * @param Config $config
         */
        public function setConfig( Config $config ) {
                $this->config = $config;
        }

        /**
         * Set the session manager
         * @param SessionManager $manager
         */
        public function setManager( SessionManager $manager ) {
                $this->manager = $manager;
        }

        /**
         * Get the session manager
         * @return SessionManager
         */
        public function getManager() {
                return $this->manager;
        }

        /**
         * Provide session info for a request
         *
         * If no session exists for the request, return null. Otherwise return an
         * SessionInfo object identifying the session.
         *
         * If multiple SessionProviders provide sessions, the one with highest
         * priority wins. In case of a tie, an exception is thrown.
         * SessionProviders are encouraged to make priorities user-configurable
         * unless only max-priority makes sense.
         *
         * @warning This will be called early in the MediaWiki setup process,
         *  before $wgUser, $wgLang, $wgOut, $wgParser, $wgTitle, and corresponding
         *  pieces of the main RequestContext are set up! If you try to use these,
         *  things *will* break.
         * @note The SessionProvider must not attempt to auto-create users.
         *  MediaWiki will do this later (when it's safe) if the chosen session has
         *  a user with a valid name but no ID.
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param WebRequest $request
         * @return SessionInfo|null
         */
        abstract public function provideSessionInfo( WebRequest $request );

        /**
         * Provide session info for a new, empty session
         *
         * Return null if such a session cannot be created. This base
         * implementation assumes that it only makes sense if a session ID can be
         * persisted and changing users is allowed.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param string|null $id ID to force for the new session
         * @return SessionInfo|null
         *  If non-null, must return true for $info->isIdSafe(); pass true for
         *  $data['idIsSafe'] to ensure this.
         */
        public function newSessionInfo( $id = null ) {
                if ( $this->canChangeUser() && $this->persistsSessionId() ) {
                        return new SessionInfo( $this->priority, [
                                'id' => $id,
                                'provider' => $this,
                                'persisted' => false,
                                'idIsSafe' => true,
                        ] );
                }
                return null;
        }

        /**
         * Merge saved session provider metadata
         *
         * This method will be used to compare the metadata returned by
         * provideSessionInfo() with the saved metadata (which has been returned by
         * provideSessionInfo() the last time the session was saved), and merge the two
         * into the new saved metadata, or abort if the current request is not a valid
         * continuation of the session.
         *
         * The default implementation checks that anything in both arrays is
         * identical, then returns $providedMetadata.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param array $savedMetadata Saved provider metadata
         * @param array $providedMetadata Provided provider metadata (from the SessionInfo)
         * @return array Resulting metadata
         * @throws MetadataMergeException If the metadata cannot be merged.
         *  Such exceptions will be handled by SessionManager and are a safe way of rejecting
         *  a suspicious or incompatible session. The provider is expected to write an
         *  appropriate message to its logger.
         */
        public function mergeMetadata( array $savedMetadata, array $providedMetadata ) {
                foreach ( $providedMetadata as $k => $v ) {
                        if ( array_key_exists( $k, $savedMetadata ) && $savedMetadata[$k] !== $v ) {
                                $e = new MetadataMergeException( "Key \"$k\" changed" );
                                $e->setContext( [
                                        'old_value' => $savedMetadata[$k],
                                        'new_value' => $v,
                                ] );
                                throw $e;
                        }
                }
                return $providedMetadata;
        }

        /**
         * Validate a loaded SessionInfo and refresh provider metadata
         *
         * This is similar in purpose to the 'SessionCheckInfo' hook, and also
         * allows for updating the provider metadata. On failure, the provider is
         * expected to write an appropriate message to its logger.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param SessionInfo $info Any changes by mergeMetadata() will already be reflected here.
         * @param WebRequest $request
         * @param array|null &$metadata Provider metadata, may be altered.
         * @return bool Return false to reject the SessionInfo after all.
         */
        public function refreshSessionInfo( SessionInfo $info, WebRequest $request, &$metadata ) {
                return true;
        }

        /**
         * Indicate whether self::persistSession() can save arbitrary session IDs
         *
         * If false, any session passed to self::persistSession() will have an ID
         * that was originally provided by self::provideSessionInfo().
         *
         * If true, the provider may be passed sessions with arbitrary session IDs,
         * and will be expected to manipulate the request in such a way that future
         * requests will cause self::provideSessionInfo() to provide a SessionInfo
         * with that ID.
         *
         * For example, a session provider for OAuth would function by matching the
         * OAuth headers to a particular user, and then would use self::hashToSessionId()
         * to turn the user and OAuth client ID (and maybe also the user token and
         * client secret) into a session ID, and therefore can't easily assign that
         * user+client a different ID. Similarly, a session provider for SSL client
         * certificates would function by matching the certificate to a particular
         * user, and then would use self::hashToSessionId() to turn the user and
         * certificate fingerprint into a session ID, and therefore can't easily
         * assign a different ID either. On the other hand, a provider that saves
         * the session ID into a cookie can easily just set the cookie to a
         * different value.
         *
         * @protected For use by \MediaWiki\Session\SessionBackend only
         * @return bool
         */
        abstract public function persistsSessionId();

        /**
         * Indicate whether the user associated with the request can be changed
         *
         * If false, any session passed to self::persistSession() will have a user
         * that was originally provided by self::provideSessionInfo(). Further,
         * self::provideSessionInfo() may only provide sessions that have a user
         * already set.
         *
         * If true, the provider may be passed sessions with arbitrary users, and
         * will be expected to manipulate the request in such a way that future
         * requests will cause self::provideSessionInfo() to provide a SessionInfo
         * with that ID. This can be as simple as not passing any 'userInfo' into
         * SessionInfo's constructor, in which case SessionInfo will load the user
         * from the saved session's metadata.
         *
         * For example, a session provider for OAuth or SSL client certificates
         * would function by matching the OAuth headers or certificate to a
         * particular user, and thus would return false here since it can't
         * arbitrarily assign those OAuth credentials or that certificate to a
         * different user. A session provider that shoves information into cookies,
         * on the other hand, could easily do so.
         *
         * @protected For use by \MediaWiki\Session\SessionBackend only
         * @return bool
         */
        abstract public function canChangeUser();

        /**
         * Returns the duration (in seconds) for which users will be remembered when
         * Session::setRememberUser() is set. Null means setting the remember flag will
         * have no effect (and endpoints should not offer that option).
         * @return int|null
         */
        public function getRememberUserDuration() {
                return null;
        }

        /**
         * Notification that the session ID was reset
         *
         * No need to persist here, persistSession() will be called if appropriate.
         *
         * @protected For use by \MediaWiki\Session\SessionBackend only
         * @param SessionBackend $session Session to persist
         * @param string $oldId Old session ID
         * @codeCoverageIgnore
         */
        public function sessionIdWasReset( SessionBackend $session, $oldId ) {
        }

        /**
         * Persist a session into a request/response
         *
         * For example, you might set cookies for the session's ID, user ID, user
         * name, and user token on the passed request.
         *
         * To correctly persist a user independently of the session ID, the
         * provider should persist both the user ID (or name, but preferably the
         * ID) and the user token. When reading the data from the request, it
         * should construct a User object from the ID/name and then verify that the
         * User object's token matches the token included in the request. Should
         * the tokens not match, an anonymous user *must* be passed to
         * SessionInfo::__construct().
         *
         * When persisting a user independently of the session ID,
         * $session->shouldRememberUser() should be checked first. If this returns
         * false, the user token *must not* be saved to cookies. The user name
         * and/or ID may be persisted, and should be used to construct an
         * unverified UserInfo to pass to SessionInfo::__construct().
         *
         * A backend that cannot persist sesison ID or user info should implement
         * this as a no-op.
         *
         * @protected For use by \MediaWiki\Session\SessionBackend only
         * @param SessionBackend $session Session to persist
         * @param WebRequest $request Request into which to persist the session
         */
        abstract public function persistSession( SessionBackend $session, WebRequest $request );

        /**
         * Remove any persisted session from a request/response
         *
         * For example, blank and expire any cookies set by self::persistSession().
         *
         * A backend that cannot persist sesison ID or user info should implement
         * this as a no-op.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param WebRequest $request Request from which to remove any session data
         */
        abstract public function unpersistSession( WebRequest $request );

        /**
         * Prevent future sessions for the user
         *
         * If the provider is capable of returning a SessionInfo with a verified
         * UserInfo for the named user in some manner other than by validating
         * against $user->getToken(), steps must be taken to prevent that from
         * occurring in the future. This might add the username to a blacklist, or
         * it might just delete whatever authentication credentials would allow
         * such a session in the first place (e.g. remove all OAuth grants or
         * delete record of the SSL client certificate).
         *
         * The intention is that the named account will never again be usable for
         * normal login (i.e. there is no way to undo the prevention of access).
         *
         * Note that the passed user name might not exist locally (i.e.
         * User::idFromName( $username ) === 0); the name should still be
         * prevented, if applicable.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param string $username
         */
        public function preventSessionsForUser( $username ) {
                if ( !$this->canChangeUser() ) {
                        throw new \BadMethodCallException(
                                __METHOD__ . ' must be implmented when canChangeUser() is false'
                        );
                }
        }

        /**
         * Invalidate existing sessions for a user
         *
         * If the provider has its own equivalent of CookieSessionProvider's Token
         * cookie (and doesn't use User::getToken() to implement it), it should
         * reset whatever token it does use here.
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @param User $user;
         */
        public function invalidateSessionsForUser( User $user ) {
        }

        /**
         * Return the HTTP headers that need varying on.
         *
         * The return value is such that someone could theoretically do this:
         * @code
         *  foreach ( $provider->getVaryHeaders() as $header => $options ) {
         *      $outputPage->addVaryHeader( $header, $options );
         *  }
         * @endcode
         *
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @return array
         */
        public function getVaryHeaders() {
                return [];
        }

        /**
         * Return the list of cookies that need varying on.
         * @protected For use by \MediaWiki\Session\SessionManager only
         * @return string[]
         */
        public function getVaryCookies() {
                return [];
        }

        /**
         * Get a suggested username for the login form
         * @protected For use by \MediaWiki\Session\SessionBackend only
         * @param WebRequest $request
         * @return string|null
         */
        public function suggestLoginUsername( WebRequest $request ) {
                return null;
        }

        /**
         * Fetch the rights allowed the user when the specified session is active.
         *
         * This is mainly meant for allowing the user to restrict access to the account
         * by certain methods; you probably want to use this with MWGrants. The returned
         * rights will be intersected with the user's actual rights.
         *
         * @param SessionBackend $backend
         * @return null|string[] Allowed user rights, or null to allow all.
         */
        public function getAllowedUserRights( SessionBackend $backend ) {
                if ( $backend->getProvider() !== $this ) {
                        // Not that this should ever happen...
                        throw new \InvalidArgumentException( 'Backend\'s provider isn\'t $this' );
                }

                return null;
        }

        /**
         * @note Only override this if it makes sense to instantiate multiple
         *  instances of the provider. Value returned must be unique across
         *  configured providers. If you override this, you'll likely need to
         *  override self::describeMessage() as well.
         * @return string
         */
        public function __toString() {
                return get_class( $this );
        }

        /**
         * Return a Message identifying this session type
         *
         * This default implementation takes the class name, lowercases it,
         * replaces backslashes with dashes, and prefixes 'sessionprovider-' to
         * determine the message key. For example, MediaWiki\Session\CookieSessionProvider
         * produces 'sessionprovider-mediawiki-session-cookiesessionprovider'.
         *
         * @note If self::__toString() is overridden, this will likely need to be
         *  overridden as well.
         * @warning This will be called early during MediaWiki startup. Do not
         *  use $wgUser, $wgLang, $wgOut, $wgParser, or their equivalents via
         *  RequestContext from this method!
         * @return \Message
         */
        protected function describeMessage() {
                return wfMessage(
                        'sessionprovider-' . str_replace( '\\', '-', strtolower( get_class( $this ) ) )
                );
        }

        public function describe( Language $lang ) {
                $msg = $this->describeMessage();
                $msg->inLanguage( $lang );
                if ( $msg->isDisabled() ) {
                        $msg = wfMessage( 'sessionprovider-generic', (string)$this )->inLanguage( $lang );
                }
                return $msg->plain();
        }

        public function whyNoSession() {
                return null;
        }

        /**
         * Hash data as a session ID
         *
         * Generally this will only be used when self::persistsSessionId() is false and
         * the provider has to base the session ID on the verified user's identity
         * or other static data. The SessionInfo should then typically have the
         * 'forceUse' flag set to avoid persistent session failure if validation of
         * the stored data fails.
         *
         * @param string $data
         * @param string|null $key Defaults to $this->config->get( 'SecretKey' )
         * @return string
         */
        final protected function hashToSessionId( $data, $key = null ) {
                if ( !is_string( $data ) ) {
                        throw new \InvalidArgumentException(
                                '$data must be a string, ' . gettype( $data ) . ' was passed'
                        );
                }
                if ( $key !== null && !is_string( $key ) ) {
                        throw new \InvalidArgumentException(
                                '$key must be a string or null, ' . gettype( $key ) . ' was passed'
                        );
                }

                $hash = \MWCryptHash::hmac( "$this\n$data", $key ?: $this->config->get( 'SecretKey' ), false );
                if ( strlen( $hash ) < 32 ) {
                        // Should never happen, even md5 is 128 bits
                        // @codeCoverageIgnoreStart
                        throw new \UnexpectedValueException( 'Hash fuction returned less than 128 bits' );
                        // @codeCoverageIgnoreEnd
                }
                if ( strlen( $hash ) >= 40 ) {
                        $hash = \Wikimedia\base_convert( $hash, 16, 32, 32 );
                }
                return substr( $hash, -32 );
        }

}