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

<?php
/**
 * MediaWiki session
 *
 * 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\LoggerInterface;
use User;
use WebRequest;

/**
 * Manages data for an an authenticated session
 *
 * A Session represents the fact that the current HTTP request is part of a
 * session. There are two broad types of Sessions, based on whether they
 * return true or false from self::canSetUser():
 * * When true (mutable), the Session identifies multiple requests as part of
 *   a session generically, with no tie to a particular user.
 * * When false (immutable), the Session identifies multiple requests as part
 *   of a session by identifying and authenticating the request itself as
 *   belonging to a particular user.
 *
 * The Session object also serves as a replacement for PHP's $_SESSION,
 * managing access to per-session data.
 *
 * @ingroup Session
 * @since 1.27
 */
final class Session implements \Countable, \Iterator, \ArrayAccess {
        /** @var null|string[] Encryption algorithm to use */
        private static $encryptionAlgorithm = null;

        /** @var SessionBackend Session backend */
        private $backend;

        /** @var int Session index */
        private $index;

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

        /**
         * @param SessionBackend $backend
         * @param int $index
         * @param LoggerInterface $logger
         */
        public function __construct( SessionBackend $backend, $index, LoggerInterface $logger ) {
                $this->backend = $backend;
                $this->index = $index;
                $this->logger = $logger;
        }

        public function __destruct() {
                $this->backend->deregisterSession( $this->index );
        }

        /**
         * Returns the session ID
         * @return string
         */
        public function getId() {
                return $this->backend->getId();
        }

        /**
         * Returns the SessionId object
         * @private For internal use by WebRequest
         * @return SessionId
         */
        public function getSessionId() {
                return $this->backend->getSessionId();
        }

        /**
         * Changes the session ID
         * @return string New ID (might be the same as the old)
         */
        public function resetId() {
                return $this->backend->resetId();
        }

        /**
         * Fetch the SessionProvider for this session
         * @return SessionProviderInterface
         */
        public function getProvider() {
                return $this->backend->getProvider();
        }

        /**
         * Indicate whether this session is persisted across requests
         *
         * For example, if cookies are set.
         *
         * @return bool
         */
        public function isPersistent() {
                return $this->backend->isPersistent();
        }

        /**
         * Make this session persisted across requests
         *
         * If the session is already persistent, equivalent to calling
         * $this->renew().
         */
        public function persist() {
                $this->backend->persist();
        }

        /**
         * Make this session not be persisted across requests
         *
         * This will remove persistence information (e.g. delete cookies)
         * from the associated WebRequest(s), and delete session data in the
         * backend. The session data will still be available via get() until
         * the end of the request.
         */
        public function unpersist() {
                $this->backend->unpersist();
        }

        /**
         * Indicate whether the user should be remembered independently of the
         * session ID.
         * @return bool
         */
        public function shouldRememberUser() {
                return $this->backend->shouldRememberUser();
        }

        /**
         * Set whether the user should be remembered independently of the session
         * ID.
         * @param bool $remember
         */
        public function setRememberUser( $remember ) {
                $this->backend->setRememberUser( $remember );
        }

        /**
         * Returns the request associated with this session
         * @return WebRequest
         */
        public function getRequest() {
                return $this->backend->getRequest( $this->index );
        }

        /**
         * Returns the authenticated user for this session
         * @return User
         */
        public function getUser() {
                return $this->backend->getUser();
        }

        /**
         * Fetch the rights allowed the user when this session is active.
         * @return null|string[] Allowed user rights, or null to allow all.
         */
        public function getAllowedUserRights() {
                return $this->backend->getAllowedUserRights();
        }

        /**
         * Indicate whether the session user info can be changed
         * @return bool
         */
        public function canSetUser() {
                return $this->backend->canSetUser();
        }

        /**
         * Set a new user for this session
         * @note This should only be called when the user has been authenticated
         * @param User $user User to set on the session.
         *   This may become a "UserValue" in the future, or User may be refactored
         *   into such.
         */
        public function setUser( $user ) {
                $this->backend->setUser( $user );
        }

        /**
         * Get a suggested username for the login form
         * @return string|null
         */
        public function suggestLoginUsername() {
                return $this->backend->suggestLoginUsername( $this->index );
        }

        /**
         * Whether HTTPS should be forced
         * @return bool
         */
        public function shouldForceHTTPS() {
                return $this->backend->shouldForceHTTPS();
        }

        /**
         * Set whether HTTPS should be forced
         * @param bool $force
         */
        public function setForceHTTPS( $force ) {
                $this->backend->setForceHTTPS( $force );
        }

        /**
         * Fetch the "logged out" timestamp
         * @return int
         */
        public function getLoggedOutTimestamp() {
                return $this->backend->getLoggedOutTimestamp();
        }

        /**
         * Set the "logged out" timestamp
         * @param int $ts
         */
        public function setLoggedOutTimestamp( $ts ) {
                $this->backend->setLoggedOutTimestamp( $ts );
        }

        /**
         * Fetch provider metadata
         * @protected For use by SessionProvider subclasses only
         * @return mixed
         */
        public function getProviderMetadata() {
                return $this->backend->getProviderMetadata();
        }

        /**
         * Delete all session data and clear the user (if possible)
         */
        public function clear() {
                $data = &$this->backend->getData();
                if ( $data ) {
                        $data = [];
                        $this->backend->dirty();
                }
                if ( $this->backend->canSetUser() ) {
                        $this->backend->setUser( new User );
                }
                $this->backend->save();
        }

        /**
         * Renew the session
         *
         * Resets the TTL in the backend store if the session is near expiring, and
         * re-persists the session to any active WebRequests if persistent.
         */
        public function renew() {
                $this->backend->renew();
        }

        /**
         * Fetch a copy of this session attached to an alternative WebRequest
         *
         * Actions on the copy will affect this session too, and vice versa.
         *
         * @param WebRequest $request Any existing session associated with this
         *  WebRequest object will be overwritten.
         * @return Session
         */
        public function sessionWithRequest( WebRequest $request ) {
                $request->setSessionId( $this->backend->getSessionId() );
                return $this->backend->getSession( $request );
        }

        /**
         * Fetch a value from the session
         * @param string|int $key
         * @param mixed $default Returned if $this->exists( $key ) would be false
         * @return mixed
         */
        public function get( $key, $default = null ) {
                $data = &$this->backend->getData();
                return array_key_exists( $key, $data ) ? $data[$key] : $default;
        }

        /**
         * Test if a value exists in the session
         * @note Unlike isset(), null values are considered to exist.
         * @param string|int $key
         * @return bool
         */
        public function exists( $key ) {
                $data = &$this->backend->getData();
                return array_key_exists( $key, $data );
        }

        /**
         * Set a value in the session
         * @param string|int $key
         * @param mixed $value
         */
        public function set( $key, $value ) {
                $data = &$this->backend->getData();
                if ( !array_key_exists( $key, $data ) || $data[$key] !== $value ) {
                        $data[$key] = $value;
                        $this->backend->dirty();
                }
        }

        /**
         * Remove a value from the session
         * @param string|int $key
         */
        public function remove( $key ) {
                $data = &$this->backend->getData();
                if ( array_key_exists( $key, $data ) ) {
                        unset( $data[$key] );
                        $this->backend->dirty();
                }
        }

        /**
         * Fetch a CSRF token from the session
         *
         * Note that this does not persist the session, which you'll probably want
         * to do if you want the token to actually be useful.
         *
         * @param string|string[] $salt Token salt
         * @param string $key Token key
         * @return Token
         */
        public function getToken( $salt = '', $key = 'default' ) {
                $new = false;
                $secrets = $this->get( 'wsTokenSecrets' );
                if ( !is_array( $secrets ) ) {
                        $secrets = [];
                }
                if ( isset( $secrets[$key] ) && is_string( $secrets[$key] ) ) {
                        $secret = $secrets[$key];
                } else {
                        $secret = \MWCryptRand::generateHex( 32 );
                        $secrets[$key] = $secret;
                        $this->set( 'wsTokenSecrets', $secrets );
                        $new = true;
                }
                if ( is_array( $salt ) ) {
                        $salt = implode( '|', $salt );
                }
                return new Token( $secret, (string)$salt, $new );
        }

        /**
         * Remove a CSRF token from the session
         *
         * The next call to self::getToken() with $key will generate a new secret.
         *
         * @param string $key Token key
         */
        public function resetToken( $key = 'default' ) {
                $secrets = $this->get( 'wsTokenSecrets' );
                if ( is_array( $secrets ) && isset( $secrets[$key] ) ) {
                        unset( $secrets[$key] );
                        $this->set( 'wsTokenSecrets', $secrets );
                }
        }

        /**
         * Remove all CSRF tokens from the session
         */
        public function resetAllTokens() {
                $this->remove( 'wsTokenSecrets' );
        }

        /**
         * Fetch the secret keys for self::setSecret() and self::getSecret().
         * @return string[] Encryption key, HMAC key
         */
        private function getSecretKeys() {
                global $wgSessionSecret, $wgSecretKey, $wgSessionPbkdf2Iterations;

                $wikiSecret = $wgSessionSecret ?: $wgSecretKey;
                $userSecret = $this->get( 'wsSessionSecret', null );
                if ( $userSecret === null ) {
                        $userSecret = \MWCryptRand::generateHex( 32 );
                        $this->set( 'wsSessionSecret', $userSecret );
                }
                $iterations = $this->get( 'wsSessionPbkdf2Iterations', null );
                if ( $iterations === null ) {
                        $iterations = $wgSessionPbkdf2Iterations;
                        $this->set( 'wsSessionPbkdf2Iterations', $iterations );
                }

                $keymats = hash_pbkdf2( 'sha256', $wikiSecret, $userSecret, $iterations, 64, true );
                return [
                        substr( $keymats, 0, 32 ),
                        substr( $keymats, 32, 32 ),
                ];
        }

        /**
         * Decide what type of encryption to use, based on system capabilities.
         * @return array
         */
        private static function getEncryptionAlgorithm() {
                global $wgSessionInsecureSecrets;

                if ( self::$encryptionAlgorithm === null ) {
                        if ( function_exists( 'openssl_encrypt' ) ) {
                                $methods = openssl_get_cipher_methods();
                                if ( in_array( 'aes-256-ctr', $methods, true ) ) {
                                        self::$encryptionAlgorithm = [ 'openssl', 'aes-256-ctr' ];
                                        return self::$encryptionAlgorithm;
                                }
                                if ( in_array( 'aes-256-cbc', $methods, true ) ) {
                                        self::$encryptionAlgorithm = [ 'openssl', 'aes-256-cbc' ];
                                        return self::$encryptionAlgorithm;
                                }
                        }

                        if ( function_exists( 'mcrypt_encrypt' )
                                && in_array( 'rijndael-128', mcrypt_list_algorithms(), true )
                        ) {
                                $modes = mcrypt_list_modes();
                                if ( in_array( 'ctr', $modes, true ) ) {
                                        self::$encryptionAlgorithm = [ 'mcrypt', 'rijndael-128', 'ctr' ];
                                        return self::$encryptionAlgorithm;
                                }
                                if ( in_array( 'cbc', $modes, true ) ) {
                                        self::$encryptionAlgorithm = [ 'mcrypt', 'rijndael-128', 'cbc' ];
                                        return self::$encryptionAlgorithm;
                                }
                        }

                        if ( $wgSessionInsecureSecrets ) {
                                // @todo: import a pure-PHP library for AES instead of this
                                self::$encryptionAlgorithm = [ 'insecure' ];
                                return self::$encryptionAlgorithm;
                        }

                        throw new \BadMethodCallException(
                                'Encryption is not available. You really should install the PHP OpenSSL extension, ' .
                                'or failing that the mcrypt extension. But if you really can\'t and you\'re willing ' .
                                'to accept insecure storage of sensitive session data, set ' .
                                '$wgSessionInsecureSecrets = true in LocalSettings.php to make this exception go away.'
                        );
                }

                return self::$encryptionAlgorithm;
        }

        /**
         * Set a value in the session, encrypted
         *
         * This relies on the secrecy of $wgSecretKey (by default), or $wgSessionSecret.
         *
         * @param string|int $key
         * @param mixed $value
         */
        public function setSecret( $key, $value ) {
                list( $encKey, $hmacKey ) = $this->getSecretKeys();
                $serialized = serialize( $value );

                // The code for encryption (with OpenSSL) and sealing is taken from
                // Chris Steipp's OATHAuthUtils class in Extension::OATHAuth.

                // Encrypt
                // @todo: import a pure-PHP library for AES instead of doing $wgSessionInsecureSecrets
                $iv = \MWCryptRand::generate( 16, true );
                $algorithm = self::getEncryptionAlgorithm();
                switch ( $algorithm[0] ) {
                        case 'openssl':
                                $ciphertext = openssl_encrypt( $serialized, $algorithm[1], $encKey, OPENSSL_RAW_DATA, $iv );
                                if ( $ciphertext === false ) {
                                        throw new \UnexpectedValueException( 'Encryption failed: ' . openssl_error_string() );
                                }
                                break;
                        case 'mcrypt':
                                // PKCS7 padding
                                $blocksize = mcrypt_get_block_size( $algorithm[1], $algorithm[2] );
                                $pad = $blocksize - ( strlen( $serialized ) % $blocksize );
                                $serialized .= str_repeat( chr( $pad ), $pad );

                                $ciphertext = mcrypt_encrypt( $algorithm[1], $encKey, $serialized, $algorithm[2], $iv );
                                if ( $ciphertext === false ) {
                                        throw new \UnexpectedValueException( 'Encryption failed' );
                                }
                                break;
                        case 'insecure':
                                $ex = new \Exception( 'No encryption is available, storing data as plain text' );
                                $this->logger->warning( $ex->getMessage(), [ 'exception' => $ex ] );
                                $ciphertext = $serialized;
                                break;
                        default:
                                throw new \LogicException( 'invalid algorithm' );
                }

                // Seal
                $sealed = base64_encode( $iv ) . '.' . base64_encode( $ciphertext );
                $hmac = hash_hmac( 'sha256', $sealed, $hmacKey, true );
                $encrypted = base64_encode( $hmac ) . '.' . $sealed;

                // Store
                $this->set( $key, $encrypted );
        }

        /**
         * Fetch a value from the session that was set with self::setSecret()
         * @param string|int $key
         * @param mixed $default Returned if $this->exists( $key ) would be false or decryption fails
         * @return mixed
         */
        public function getSecret( $key, $default = null ) {
                // Fetch
                $encrypted = $this->get( $key, null );
                if ( $encrypted === null ) {
                        return $default;
                }

                // The code for unsealing, checking, and decrypting (with OpenSSL) is
                // taken from Chris Steipp's OATHAuthUtils class in
                // Extension::OATHAuth.

                // Unseal and check
                $pieces = explode( '.', $encrypted );
                if ( count( $pieces ) !== 3 ) {
                        $ex = new \Exception( 'Invalid sealed-secret format' );
                        $this->logger->warning( $ex->getMessage(), [ 'exception' => $ex ] );
                        return $default;
                }
                list( $hmac, $iv, $ciphertext ) = $pieces;
                list( $encKey, $hmacKey ) = $this->getSecretKeys();
                $integCalc = hash_hmac( 'sha256', $iv . '.' . $ciphertext, $hmacKey, true );
                if ( !hash_equals( $integCalc, base64_decode( $hmac ) ) ) {
                        $ex = new \Exception( 'Sealed secret has been tampered with, aborting.' );
                        $this->logger->warning( $ex->getMessage(), [ 'exception' => $ex ] );
                        return $default;
                }

                // Decrypt
                $algorithm = self::getEncryptionAlgorithm();
                switch ( $algorithm[0] ) {
                        case 'openssl':
                                $serialized = openssl_decrypt( base64_decode( $ciphertext ), $algorithm[1], $encKey,
                                        OPENSSL_RAW_DATA, base64_decode( $iv ) );
                                if ( $serialized === false ) {
                                        $ex = new \Exception( 'Decyption failed: ' . openssl_error_string() );
                                        $this->logger->debug( $ex->getMessage(), [ 'exception' => $ex ] );
                                        return $default;
                                }
                                break;
                        case 'mcrypt':
                                $serialized = mcrypt_decrypt( $algorithm[1], $encKey, base64_decode( $ciphertext ),
                                        $algorithm[2], base64_decode( $iv ) );
                                if ( $serialized === false ) {
                                        $ex = new \Exception( 'Decyption failed' );
                                        $this->logger->debug( $ex->getMessage(), [ 'exception' => $ex ] );
                                        return $default;
                                }

                                // Remove PKCS7 padding
                                $pad = ord( substr( $serialized, -1 ) );
                                $serialized = substr( $serialized, 0, -$pad );
                                break;
                        case 'insecure':
                                $ex = new \Exception(
                                        'No encryption is available, retrieving data that was stored as plain text'
                                );
                                $this->logger->warning( $ex->getMessage(), [ 'exception' => $ex ] );
                                $serialized = base64_decode( $ciphertext );
                                break;
                        default:
                                throw new \LogicException( 'invalid algorithm' );
                }

                $value = unserialize( $serialized );
                if ( $value === false && $serialized !== serialize( false ) ) {
                        $value = $default;
                }
                return $value;
        }

        /**
         * Delay automatic saving while multiple updates are being made
         *
         * Calls to save() or clear() will not be delayed.
         *
         * @return \Wikimedia\ScopedCallback When this goes out of scope, a save will be triggered
         */
        public function delaySave() {
                return $this->backend->delaySave();
        }

        /**
         * Save the session
         *
         * This will update the backend data and might re-persist the session
         * if needed.
         */
        public function save() {
                $this->backend->save();
        }

        /**
         * @name Interface methods
         * @{
         */

        public function count() {
                $data = &$this->backend->getData();
                return count( $data );
        }

        public function current() {
                $data = &$this->backend->getData();
                return current( $data );
        }

        public function key() {
                $data = &$this->backend->getData();
                return key( $data );
        }

        public function next() {
                $data = &$this->backend->getData();
                next( $data );
        }

        public function rewind() {
                $data = &$this->backend->getData();
                reset( $data );
        }

        public function valid() {
                $data = &$this->backend->getData();
                return key( $data ) !== null;
        }

        /**
         * @note Despite the name, this seems to be intended to implement isset()
         *  rather than array_key_exists(). So do that.
         */
        public function offsetExists( $offset ) {
                $data = &$this->backend->getData();
                return isset( $data[$offset] );
        }

        /**
         * @note This supports indirect modifications but can't mark the session
         *  dirty when those happen. SessionBackend::save() checks the hash of the
         *  data to detect such changes.
         * @note Accessing a nonexistent key via this mechanism causes that key to
         *  be created with a null value, and does not raise a PHP warning.
         */
        public function &offsetGet( $offset ) {
                $data = &$this->backend->getData();
                if ( !array_key_exists( $offset, $data ) ) {
                        $ex = new \Exception( "Undefined index (auto-adds to session with a null value): $offset" );
                        $this->logger->debug( $ex->getMessage(), [ 'exception' => $ex ] );
                }
                return $data[$offset];
        }

        public function offsetSet( $offset, $value ) {
                $this->set( $offset, $value );
        }

        public function offsetUnset( $offset ) {
                $this->remove( $offset );
        }

        /**@}*/

}