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[mediawiki.git] / includes / installer / Installer.php

<?php
/**
 * Base code for MediaWiki installer.
 *
 * 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 Deployment
 */

/**
 * This documentation group collects source code files with deployment functionality.
 *
 * @defgroup Deployment Deployment
 */

/**
 * Base installer class.
 *
 * This class provides the base for installation and update functionality
 * for both MediaWiki core and extensions.
 *
 * @ingroup Deployment
 * @since 1.17
 */
abstract class Installer {

        /**
         * The oldest version of PCRE we can support.
         *
         * Defining this is necessary because PHP may be linked with a system version
         * of PCRE, which may be older than that bundled with the minimum PHP version.
         */
        const MINIMUM_PCRE_VERSION = '7.2';

        /**
         * @var array
         */
        protected $settings;

        /**
         * List of detected DBs, access using getCompiledDBs().
         *
         * @var array
         */
        protected $compiledDBs;

        /**
         * Cached DB installer instances, access using getDBInstaller().
         *
         * @var array
         */
        protected $dbInstallers = array();

        /**
         * Minimum memory size in MB.
         *
         * @var int
         */
        protected $minMemorySize = 50;

        /**
         * Cached Title, used by parse().
         *
         * @var Title
         */
        protected $parserTitle;

        /**
         * Cached ParserOptions, used by parse().
         *
         * @var ParserOptions
         */
        protected $parserOptions;

        /**
         * Known database types. These correspond to the class names <type>Installer,
         * and are also MediaWiki database types valid for $wgDBtype.
         *
         * To add a new type, create a <type>Installer class and a Database<type>
         * class, and add a config-type-<type> message to MessagesEn.php.
         *
         * @var array
         */
        protected static $dbTypes = array(
                'mysql',
                'postgres',
                'oracle',
                'mssql',
                'sqlite',
        );

        /**
         * A list of environment check methods called by doEnvironmentChecks().
         * These may output warnings using showMessage(), and/or abort the
         * installation process by returning false.
         *
         * For the WebInstaller these are only called on the Welcome page,
         * if these methods have side-effects that should affect later page loads
         * (as well as the generated stylesheet), use envPreps instead.
         *
         * @var array
         */
        protected $envChecks = array(
                'envCheckDB',
                'envCheckRegisterGlobals',
                'envCheckBrokenXML',
                'envCheckMagicQuotes',
                'envCheckMbstring',
                'envCheckSafeMode',
                'envCheckXML',
                'envCheckPCRE',
                'envCheckMemory',
                'envCheckCache',
                'envCheckModSecurity',
                'envCheckDiff3',
                'envCheckGraphics',
                'envCheckGit',
                'envCheckServer',
                'envCheckPath',
                'envCheckShellLocale',
                'envCheckUploadsDirectory',
                'envCheckLibicu',
                'envCheckSuhosinMaxValueLength',
                'envCheckCtype',
                'envCheckIconv',
                'envCheckJSON',
        );

        /**
         * A list of environment preparation methods called by doEnvironmentPreps().
         *
         * @var array
         */
        protected $envPreps = array(
                'envPrepExtension',
                'envPrepServer',
                'envPrepPath',
        );

        /**
         * MediaWiki configuration globals that will eventually be passed through
         * to LocalSettings.php. The names only are given here, the defaults
         * typically come from DefaultSettings.php.
         *
         * @var array
         */
        protected $defaultVarNames = array(
                'wgSitename',
                'wgPasswordSender',
                'wgLanguageCode',
                'wgRightsIcon',
                'wgRightsText',
                'wgRightsUrl',
                'wgMainCacheType',
                'wgEnableEmail',
                'wgEnableUserEmail',
                'wgEnotifUserTalk',
                'wgEnotifWatchlist',
                'wgEmailAuthentication',
                'wgDBtype',
                'wgDiff3',
                'wgImageMagickConvertCommand',
                'wgGitBin',
                'IP',
                'wgScriptPath',
                'wgScriptExtension',
                'wgMetaNamespace',
                'wgDeletedDirectory',
                'wgEnableUploads',
                'wgShellLocale',
                'wgSecretKey',
                'wgUseInstantCommons',
                'wgUpgradeKey',
                'wgDefaultSkin',
        );

        /**
         * Variables that are stored alongside globals, and are used for any
         * configuration of the installation process aside from the MediaWiki
         * configuration. Map of names to defaults.
         *
         * @var array
         */
        protected $internalDefaults = array(
                '_UserLang' => 'en',
                '_Environment' => false,
                '_SafeMode' => false,
                '_RaiseMemory' => false,
                '_UpgradeDone' => false,
                '_InstallDone' => false,
                '_Caches' => array(),
                '_InstallPassword' => '',
                '_SameAccount' => true,
                '_CreateDBAccount' => false,
                '_NamespaceType' => 'site-name',
                '_AdminName' => '', // will be set later, when the user selects language
                '_AdminPassword' => '',
                '_AdminPasswordConfirm' => '',
                '_AdminEmail' => '',
                '_Subscribe' => false,
                '_SkipOptional' => 'continue',
                '_RightsProfile' => 'wiki',
                '_LicenseCode' => 'none',
                '_CCDone' => false,
                '_Extensions' => array(),
                '_Skins' => array(),
                '_MemCachedServers' => '',
                '_UpgradeKeySupplied' => false,
                '_ExistingDBSettings' => false,

                // $wgLogo is probably wrong (bug 48084); set something that will work.
                // Single quotes work fine here, as LocalSettingsGenerator outputs this unescaped.
                'wgLogo' => '$wgScriptPath/resources/assets/wiki.png',
        );

        /**
         * The actual list of installation steps. This will be initialized by getInstallSteps()
         *
         * @var array
         */
        private $installSteps = array();

        /**
         * Extra steps for installation, for things like DatabaseInstallers to modify
         *
         * @var array
         */
        protected $extraInstallSteps = array();

        /**
         * Known object cache types and the functions used to test for their existence.
         *
         * @var array
         */
        protected $objectCaches = array(
                'xcache' => 'xcache_get',
                'apc' => 'apc_fetch',
                'wincache' => 'wincache_ucache_get'
        );

        /**
         * User rights profiles.
         *
         * @var array
         */
        public $rightsProfiles = array(
                'wiki' => array(),
                'no-anon' => array(
                        '*' => array( 'edit' => false )
                ),
                'fishbowl' => array(
                        '*' => array(
                                'createaccount' => false,
                                'edit' => false,
                        ),
                ),
                'private' => array(
                        '*' => array(
                                'createaccount' => false,
                                'edit' => false,
                                'read' => false,
                        ),
                ),
        );

        /**
         * License types.
         *
         * @var array
         */
        public $licenses = array(
                'cc-by' => array(
                        'url' => 'https://creativecommons.org/licenses/by/3.0/',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/cc-by.png',
                ),
                'cc-by-sa' => array(
                        'url' => 'https://creativecommons.org/licenses/by-sa/3.0/',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/cc-by-sa.png',
                ),
                'cc-by-nc-sa' => array(
                        'url' => 'https://creativecommons.org/licenses/by-nc-sa/3.0/',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/cc-by-nc-sa.png',
                ),
                'cc-0' => array(
                        'url' => 'https://creativecommons.org/publicdomain/zero/1.0/',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/cc-0.png',
                ),
                'pd' => array(
                        'url' => '',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/public-domain.png',
                ),
                'gfdl' => array(
                        'url' => 'https://www.gnu.org/copyleft/fdl.html',
                        'icon' => '{$wgResourceBasePath}/resources/assets/licenses/gnu-fdl.png',
                ),
                'none' => array(
                        'url' => '',
                        'icon' => '',
                        'text' => ''
                ),
                'cc-choose' => array(
                        // Details will be filled in by the selector.
                        'url' => '',
                        'icon' => '',
                        'text' => '',
                ),
        );

        /**
         * URL to mediawiki-announce subscription
         */
        protected $mediaWikiAnnounceUrl =
                'https://lists.wikimedia.org/mailman/subscribe/mediawiki-announce';

        /**
         * Supported language codes for Mailman
         */
        protected $mediaWikiAnnounceLanguages = array(
                'ca', 'cs', 'da', 'de', 'en', 'es', 'et', 'eu', 'fi', 'fr', 'hr', 'hu',
                'it', 'ja', 'ko', 'lt', 'nl', 'no', 'pl', 'pt', 'pt-br', 'ro', 'ru',
                'sl', 'sr', 'sv', 'tr', 'uk'
        );

        /**
         * UI interface for displaying a short message
         * The parameters are like parameters to wfMessage().
         * The messages will be in wikitext format, which will be converted to an
         * output format such as HTML or text before being sent to the user.
         * @param string $msg
         */
        abstract public function showMessage( $msg /*, ... */ );

        /**
         * Same as showMessage(), but for displaying errors
         * @param string $msg
         */
        abstract public function showError( $msg /*, ... */ );

        /**
         * Show a message to the installing user by using a Status object
         * @param Status $status
         */
        abstract public function showStatusMessage( Status $status );

        /**
         * Constructor, always call this from child classes.
         */
        public function __construct() {
                global $wgMessagesDirs, $wgUser;

                // Disable the i18n cache
                Language::getLocalisationCache()->disableBackend();
                // Disable LoadBalancer and wfGetDB etc.
                LBFactory::disableBackend();

                // Disable object cache (otherwise CACHE_ANYTHING will try CACHE_DB and
                // SqlBagOStuff will then throw since we just disabled wfGetDB)
                $GLOBALS['wgMemc'] = new EmptyBagOStuff;
                ObjectCache::clear();
                $emptyCache = array( 'class' => 'EmptyBagOStuff' );
                $GLOBALS['wgObjectCaches'] = array(
                        CACHE_NONE => $emptyCache,
                        CACHE_DB => $emptyCache,
                        CACHE_ANYTHING => $emptyCache,
                        CACHE_MEMCACHED => $emptyCache,
                );

                // Load the installer's i18n.
                $wgMessagesDirs['MediawikiInstaller'] = __DIR__ . '/i18n';

                // Having a user with id = 0 safeguards us from DB access via User::loadOptions().
                $wgUser = User::newFromId( 0 );

                $this->settings = $this->internalDefaults;

                foreach ( $this->defaultVarNames as $var ) {
                        $this->settings[$var] = $GLOBALS[$var];
                }

                $this->doEnvironmentPreps();

                $this->compiledDBs = array();
                foreach ( self::getDBTypes() as $type ) {
                        $installer = $this->getDBInstaller( $type );

                        if ( !$installer->isCompiled() ) {
                                continue;
                        }
                        $this->compiledDBs[] = $type;
                }

                $this->parserTitle = Title::newFromText( 'Installer' );
                $this->parserOptions = new ParserOptions; // language will be wrong :(
                $this->parserOptions->setEditSection( false );
        }

        /**
         * Get a list of known DB types.
         *
         * @return array
         */
        public static function getDBTypes() {
                return self::$dbTypes;
        }

        /**
         * Do initial checks of the PHP environment. Set variables according to
         * the observed environment.
         *
         * It's possible that this may be called under the CLI SAPI, not the SAPI
         * that the wiki will primarily run under. In that case, the subclass should
         * initialise variables such as wgScriptPath, before calling this function.
         *
         * Under the web subclass, it can already be assumed that PHP 5+ is in use
         * and that sessions are working.
         *
         * @return Status
         */
        public function doEnvironmentChecks() {
                // Php version has already been checked by entry scripts
                // Show message here for information purposes
                if ( wfIsHHVM() ) {
                        $this->showMessage( 'config-env-hhvm', HHVM_VERSION );
                } else {
                        $this->showMessage( 'config-env-php', PHP_VERSION );
                }

                $good = true;
                // Must go here because an old version of PCRE can prevent other checks from completing
                list( $pcreVersion ) = explode( ' ', PCRE_VERSION, 2 );
                if ( version_compare( $pcreVersion, self::MINIMUM_PCRE_VERSION, '<' ) ) {
                        $this->showError( 'config-pcre-old', self::MINIMUM_PCRE_VERSION, $pcreVersion );
                        $good = false;
                } else {
                        foreach ( $this->envChecks as $check ) {
                                $status = $this->$check();
                                if ( $status === false ) {
                                        $good = false;
                                }
                        }
                }

                $this->setVar( '_Environment', $good );

                return $good ? Status::newGood() : Status::newFatal( 'config-env-bad' );
        }

        public function doEnvironmentPreps() {
                foreach ( $this->envPreps as $prep ) {
                        $this->$prep();
                }
        }

        /**
         * Set a MW configuration variable, or internal installer configuration variable.
         *
         * @param string $name
         * @param mixed $value
         */
        public function setVar( $name, $value ) {
                $this->settings[$name] = $value;
        }

        /**
         * Get an MW configuration variable, or internal installer configuration variable.
         * The defaults come from $GLOBALS (ultimately DefaultSettings.php).
         * Installer variables are typically prefixed by an underscore.
         *
         * @param string $name
         * @param mixed $default
         *
         * @return mixed
         */
        public function getVar( $name, $default = null ) {
                if ( !isset( $this->settings[$name] ) ) {
                        return $default;
                } else {
                        return $this->settings[$name];
                }
        }

        /**
         * Get a list of DBs supported by current PHP setup
         *
         * @return array
         */
        public function getCompiledDBs() {
                return $this->compiledDBs;
        }

        /**
         * Get an instance of DatabaseInstaller for the specified DB type.
         *
         * @param mixed $type DB installer for which is needed, false to use default.
         *
         * @return DatabaseInstaller
         */
        public function getDBInstaller( $type = false ) {
                if ( !$type ) {
                        $type = $this->getVar( 'wgDBtype' );
                }

                $type = strtolower( $type );

                if ( !isset( $this->dbInstallers[$type] ) ) {
                        $class = ucfirst( $type ) . 'Installer';
                        $this->dbInstallers[$type] = new $class( $this );
                }

                return $this->dbInstallers[$type];
        }

        /**
         * Determine if LocalSettings.php exists. If it does, return its variables.
         *
         * @return array
         */
        public static function getExistingLocalSettings() {
                global $IP;

                // You might be wondering why this is here. Well if you don't do this
                // then some poorly-formed extensions try to call their own classes
                // after immediately registering them. We really need to get extension
                // registration out of the global scope and into a real format.
                // @see https://bugzilla.wikimedia.org/67440
                global $wgAutoloadClasses;
                $wgAutoloadClasses = array();

                wfSuppressWarnings();
                $_lsExists = file_exists( "$IP/LocalSettings.php" );
                wfRestoreWarnings();

                if ( !$_lsExists ) {
                        return false;
                }
                unset( $_lsExists );

                require "$IP/includes/DefaultSettings.php";
                require "$IP/LocalSettings.php";

                return get_defined_vars();
        }

        /**
         * Get a fake password for sending back to the user in HTML.
         * This is a security mechanism to avoid compromise of the password in the
         * event of session ID compromise.
         *
         * @param string $realPassword
         *
         * @return string
         */
        public function getFakePassword( $realPassword ) {
                return str_repeat( '*', strlen( $realPassword ) );
        }

        /**
         * Set a variable which stores a password, except if the new value is a
         * fake password in which case leave it as it is.
         *
         * @param string $name
         * @param mixed $value
         */
        public function setPassword( $name, $value ) {
                if ( !preg_match( '/^\*+$/', $value ) ) {
                        $this->setVar( $name, $value );
                }
        }

        /**
         * On POSIX systems return the primary group of the webserver we're running under.
         * On other systems just returns null.
         *
         * This is used to advice the user that he should chgrp his mw-config/data/images directory as the
         * webserver user before he can install.
         *
         * Public because SqliteInstaller needs it, and doesn't subclass Installer.
         *
         * @return mixed
         */
        public static function maybeGetWebserverPrimaryGroup() {
                if ( !function_exists( 'posix_getegid' ) || !function_exists( 'posix_getpwuid' ) ) {
                        # I don't know this, this isn't UNIX.
                        return null;
                }

                # posix_getegid() *not* getmygid() because we want the group of the webserver,
                # not whoever owns the current script.
                $gid = posix_getegid();
                $getpwuid = posix_getpwuid( $gid );
                $group = $getpwuid['name'];

                return $group;
        }

        /**
         * Convert wikitext $text to HTML.
         *
         * This is potentially error prone since many parser features require a complete
         * installed MW database. The solution is to just not use those features when you
         * write your messages. This appears to work well enough. Basic formatting and
         * external links work just fine.
         *
         * But in case a translator decides to throw in a "#ifexist" or internal link or
         * whatever, this function is guarded to catch the attempted DB access and to present
         * some fallback text.
         *
         * @param string $text
         * @param bool $lineStart
         * @return string
         */
        public function parse( $text, $lineStart = false ) {
                global $wgParser;

                try {
                        $out = $wgParser->parse( $text, $this->parserTitle, $this->parserOptions, $lineStart );
                        $html = $out->getText();
                } catch ( DBAccessError $e ) {
                        $html = '<!--DB access attempted during parse-->  ' . htmlspecialchars( $text );

                        if ( !empty( $this->debug ) ) {
                                $html .= "<!--\n" . $e->getTraceAsString() . "\n-->";
                        }
                }

                return $html;
        }

        /**
         * @return ParserOptions
         */
        public function getParserOptions() {
                return $this->parserOptions;
        }

        public function disableLinkPopups() {
                $this->parserOptions->setExternalLinkTarget( false );
        }

        public function restoreLinkPopups() {
                global $wgExternalLinkTarget;
                $this->parserOptions->setExternalLinkTarget( $wgExternalLinkTarget );
        }

        /**
         * Install step which adds a row to the site_stats table with appropriate
         * initial values.
         *
         * @param DatabaseInstaller $installer
         *
         * @return Status
         */
        public function populateSiteStats( DatabaseInstaller $installer ) {
                $status = $installer->getConnection();
                if ( !$status->isOK() ) {
                        return $status;
                }
                $status->value->insert(
                        'site_stats',
                        array(
                                'ss_row_id' => 1,
                                'ss_total_edits' => 0,
                                'ss_good_articles' => 0,
                                'ss_total_pages' => 0,
                                'ss_users' => 0,
                                'ss_images' => 0
                        ),
                        __METHOD__, 'IGNORE'
                );

                return Status::newGood();
        }

        /**
         * Exports all wg* variables stored by the installer into global scope.
         */
        public function exportVars() {
                foreach ( $this->settings as $name => $value ) {
                        if ( substr( $name, 0, 2 ) == 'wg' ) {
                                $GLOBALS[$name] = $value;
                        }
                }
        }

        /**
         * Environment check for DB types.
         * @return bool
         */
        protected function envCheckDB() {
                global $wgLang;

                $allNames = array();

                // Messages: config-type-mysql, config-type-postgres, config-type-oracle,
                // config-type-sqlite
                foreach ( self::getDBTypes() as $name ) {
                        $allNames[] = wfMessage( "config-type-$name" )->text();
                }

                $databases = $this->getCompiledDBs();

                $databases = array_flip( $databases );
                foreach ( array_keys( $databases ) as $db ) {
                        $installer = $this->getDBInstaller( $db );
                        $status = $installer->checkPrerequisites();
                        if ( !$status->isGood() ) {
                                $this->showStatusMessage( $status );
                        }
                        if ( !$status->isOK() ) {
                                unset( $databases[$db] );
                        }
                }
                $databases = array_flip( $databases );
                if ( !$databases ) {
                        $this->showError( 'config-no-db', $wgLang->commaList( $allNames ), count( $allNames ) );

                        // @todo FIXME: This only works for the web installer!
                        return false;
                }

                return true;
        }

        /**
         * Environment check for register_globals.
         * Prevent installation if enabled
         * @return bool
         */
        protected function envCheckRegisterGlobals() {
                if ( wfIniGetBool( 'register_globals' ) ) {
                        $this->showMessage( 'config-register-globals-error' );
                        return false;
                }

                return true;
        }

        /**
         * Some versions of libxml+PHP break < and > encoding horribly
         * @return bool
         */
        protected function envCheckBrokenXML() {
                $test = new PhpXmlBugTester();
                if ( !$test->ok ) {
                        $this->showError( 'config-brokenlibxml' );

                        return false;
                }

                return true;
        }

        /**
         * Environment check for magic_quotes_(gpc|runtime|sybase).
         * @return bool
         */
        protected function envCheckMagicQuotes() {
                $status = true;
                foreach ( array( 'gpc', 'runtime', 'sybase' ) as $magicJunk ) {
                        if ( wfIniGetBool( "magic_quotes_$magicJunk" ) ) {
                                $this->showError( "config-magic-quotes-$magicJunk" );
                                $status = false;
                        }
                }

                return $status;
        }

        /**
         * Environment check for mbstring.func_overload.
         * @return bool
         */
        protected function envCheckMbstring() {
                if ( wfIniGetBool( 'mbstring.func_overload' ) ) {
                        $this->showError( 'config-mbstring' );

                        return false;
                }

                return true;
        }

        /**
         * Environment check for safe_mode.
         * @return bool
         */
        protected function envCheckSafeMode() {
                if ( wfIniGetBool( 'safe_mode' ) ) {
                        $this->setVar( '_SafeMode', true );
                        $this->showMessage( 'config-safe-mode' );
                }

                return true;
        }

        /**
         * Environment check for the XML module.
         * @return bool
         */
        protected function envCheckXML() {
                if ( !function_exists( "utf8_encode" ) ) {
                        $this->showError( 'config-xml-bad' );

                        return false;
                }

                return true;
        }

        /**
         * Environment check for the PCRE module.
         *
         * @note If this check were to fail, the parser would
         *   probably throw an exception before the result
         *   of this check is shown to the user.
         * @return bool
         */
        protected function envCheckPCRE() {
                wfSuppressWarnings();
                $regexd = preg_replace( '/[\x{0430}-\x{04FF}]/iu', '', '-АБВГД-' );
                // Need to check for \p support too, as PCRE can be compiled
                // with utf8 support, but not unicode property support.
                // check that \p{Zs} (space separators) matches
                // U+3000 (Ideographic space)
                $regexprop = preg_replace( '/\p{Zs}/u', '', "-\xE3\x80\x80-" );
                wfRestoreWarnings();
                if ( $regexd != '--' || $regexprop != '--' ) {
                        $this->showError( 'config-pcre-no-utf8' );

                        return false;
                }

                return true;
        }

        /**
         * Environment check for available memory.
         * @return bool
         */
        protected function envCheckMemory() {
                $limit = ini_get( 'memory_limit' );

                if ( !$limit || $limit == -1 ) {
                        return true;
                }

                $n = wfShorthandToInteger( $limit );

                if ( $n < $this->minMemorySize * 1024 * 1024 ) {
                        $newLimit = "{$this->minMemorySize}M";

                        if ( ini_set( "memory_limit", $newLimit ) === false ) {
                                $this->showMessage( 'config-memory-bad', $limit );
                        } else {
                                $this->showMessage( 'config-memory-raised', $limit, $newLimit );
                                $this->setVar( '_RaiseMemory', true );
                        }
                }

                return true;
        }

        /**
         * Environment check for compiled object cache types.
         */
        protected function envCheckCache() {
                $caches = array();
                foreach ( $this->objectCaches as $name => $function ) {
                        if ( function_exists( $function ) ) {
                                if ( $name == 'xcache' && !wfIniGetBool( 'xcache.var_size' ) ) {
                                        continue;
                                }
                                $caches[$name] = true;
                        }
                }

                if ( !$caches ) {
                        $this->showMessage( 'config-no-cache' );
                }

                $this->setVar( '_Caches', $caches );
        }

        /**
         * Scare user to death if they have mod_security or mod_security2
         * @return bool
         */
        protected function envCheckModSecurity() {
                if ( self::apacheModulePresent( 'mod_security' )
                        || self::apacheModulePresent( 'mod_security2' ) ) {
                        $this->showMessage( 'config-mod-security' );
                }

                return true;
        }

        /**
         * Search for GNU diff3.
         * @return bool
         */
        protected function envCheckDiff3() {
                $names = array( "gdiff3", "diff3", "diff3.exe" );
                $versionInfo = array( '$1 --version 2>&1', 'GNU diffutils' );

                $diff3 = self::locateExecutableInDefaultPaths( $names, $versionInfo );

                if ( $diff3 ) {
                        $this->setVar( 'wgDiff3', $diff3 );
                } else {
                        $this->setVar( 'wgDiff3', false );
                        $this->showMessage( 'config-diff3-bad' );
                }

                return true;
        }

        /**
         * Environment check for ImageMagick and GD.
         * @return bool
         */
        protected function envCheckGraphics() {
                $names = array( wfIsWindows() ? 'convert.exe' : 'convert' );
                $versionInfo = array( '$1 -version', 'ImageMagick' );
                $convert = self::locateExecutableInDefaultPaths( $names, $versionInfo );

                $this->setVar( 'wgImageMagickConvertCommand', '' );
                if ( $convert ) {
                        $this->setVar( 'wgImageMagickConvertCommand', $convert );
                        $this->showMessage( 'config-imagemagick', $convert );

                        return true;
                } elseif ( function_exists( 'imagejpeg' ) ) {
                        $this->showMessage( 'config-gd' );
                } else {
                        $this->showMessage( 'config-no-scaling' );
                }

                return true;
        }

        /**
         * Search for git.
         *
         * @since 1.22
         * @return bool
         */
        protected function envCheckGit() {
                $names = array( wfIsWindows() ? 'git.exe' : 'git' );
                $versionInfo = array( '$1 --version', 'git version' );

                $git = self::locateExecutableInDefaultPaths( $names, $versionInfo );

                if ( $git ) {
                        $this->setVar( 'wgGitBin', $git );
                        $this->showMessage( 'config-git', $git );
                } else {
                        $this->setVar( 'wgGitBin', false );
                        $this->showMessage( 'config-git-bad' );
                }

                return true;
        }

        /**
         * Environment check to inform user which server we've assumed.
         *
         * @return bool
         */
        protected function envCheckServer() {
                $server = $this->envGetDefaultServer();
                if ( $server !== null ) {
                        $this->showMessage( 'config-using-server', $server );
                }
                return true;
        }

        /**
         * Environment check to inform user which paths we've assumed.
         *
         * @return bool
         */
        protected function envCheckPath() {
                $this->showMessage(
                        'config-using-uri',
                        $this->getVar( 'wgServer' ),
                        $this->getVar( 'wgScriptPath' )
                );
                return true;
        }

        /**
         * Environment check for preferred locale in shell
         * @return bool
         */
        protected function envCheckShellLocale() {
                $os = php_uname( 's' );
                $supported = array( 'Linux', 'SunOS', 'HP-UX', 'Darwin' ); # Tested these

                if ( !in_array( $os, $supported ) ) {
                        return true;
                }

                # Get a list of available locales.
                $ret = false;
                $lines = wfShellExec( '/usr/bin/locale -a', $ret );

                if ( $ret ) {
                        return true;
                }

                $lines = array_map( 'trim', explode( "\n", $lines ) );
                $candidatesByLocale = array();
                $candidatesByLang = array();

                foreach ( $lines as $line ) {
                        if ( $line === '' ) {
                                continue;
                        }

                        if ( !preg_match( '/^([a-zA-Z]+)(_[a-zA-Z]+|)\.(utf8|UTF-8)(@[a-zA-Z_]*|)$/i', $line, $m ) ) {
                                continue;
                        }

                        list( , $lang, , , ) = $m;

                        $candidatesByLocale[$m[0]] = $m;
                        $candidatesByLang[$lang][] = $m;
                }

                # Try the current value of LANG.
                if ( isset( $candidatesByLocale[getenv( 'LANG' )] ) ) {
                        $this->setVar( 'wgShellLocale', getenv( 'LANG' ) );

                        return true;
                }

                # Try the most common ones.
                $commonLocales = array( 'en_US.UTF-8', 'en_US.utf8', 'de_DE.UTF-8', 'de_DE.utf8' );
                foreach ( $commonLocales as $commonLocale ) {
                        if ( isset( $candidatesByLocale[$commonLocale] ) ) {
                                $this->setVar( 'wgShellLocale', $commonLocale );

                                return true;
                        }
                }

                # Is there an available locale in the Wiki's language?
                $wikiLang = $this->getVar( 'wgLanguageCode' );

                if ( isset( $candidatesByLang[$wikiLang] ) ) {
                        $m = reset( $candidatesByLang[$wikiLang] );
                        $this->setVar( 'wgShellLocale', $m[0] );

                        return true;
                }

                # Are there any at all?
                if ( count( $candidatesByLocale ) ) {
                        $m = reset( $candidatesByLocale );
                        $this->setVar( 'wgShellLocale', $m[0] );

                        return true;
                }

                # Give up.
                return true;
        }

        /**
         * Environment check for the permissions of the uploads directory
         * @return bool
         */
        protected function envCheckUploadsDirectory() {
                global $IP;

                $dir = $IP . '/images/';
                $url = $this->getVar( 'wgServer' ) . $this->getVar( 'wgScriptPath' ) . '/images/';
                $safe = !$this->dirIsExecutable( $dir, $url );

                if ( !$safe ) {
                        $this->showMessage( 'config-uploads-not-safe', $dir );
                }

                return true;
        }

        /**
         * Checks if suhosin.get.max_value_length is set, and if so generate
         * a warning because it decreases ResourceLoader performance.
         * @return bool
         */
        protected function envCheckSuhosinMaxValueLength() {
                $maxValueLength = ini_get( 'suhosin.get.max_value_length' );
                if ( $maxValueLength > 0 && $maxValueLength < 1024 ) {
                        // Only warn if the value is below the sane 1024
                        $this->showMessage( 'config-suhosin-max-value-length', $maxValueLength );
                }

                return true;
        }

        /**
         * Convert a hex string representing a Unicode code point to that code point.
         * @param string $c
         * @return string
         */
        protected function unicodeChar( $c ) {
                $c = hexdec( $c );
                if ( $c <= 0x7F ) {
                        return chr( $c );
                } elseif ( $c <= 0x7FF ) {
                        return chr( 0xC0 | $c >> 6 ) . chr( 0x80 | $c & 0x3F );
                } elseif ( $c <= 0xFFFF ) {
                        return chr( 0xE0 | $c >> 12 ) . chr( 0x80 | $c >> 6 & 0x3F )
                        . chr( 0x80 | $c & 0x3F );
                } elseif ( $c <= 0x10FFFF ) {
                        return chr( 0xF0 | $c >> 18 ) . chr( 0x80 | $c >> 12 & 0x3F )
                        . chr( 0x80 | $c >> 6 & 0x3F )
                        . chr( 0x80 | $c & 0x3F );
                } else {
                        return false;
                }
        }

        /**
         * Check the libicu version
         */
        protected function envCheckLibicu() {
                $utf8 = function_exists( 'utf8_normalize' );
                $intl = function_exists( 'normalizer_normalize' );

                /**
                 * This needs to be updated something that the latest libicu
                 * will properly normalize.  This normalization was found at
                 * http://www.unicode.org/versions/Unicode5.2.0/#Character_Additions
                 * Note that we use the hex representation to create the code
                 * points in order to avoid any Unicode-destroying during transit.
                 */
                $not_normal_c = $this->unicodeChar( "FA6C" );
                $normal_c = $this->unicodeChar( "242EE" );

                $useNormalizer = 'php';
                $needsUpdate = false;

                /**
                 * We're going to prefer the pecl extension here unless
                 * utf8_normalize is more up to date.
                 */
                if ( $utf8 ) {
                        $useNormalizer = 'utf8';
                        $utf8 = utf8_normalize( $not_normal_c, UtfNormal::UNORM_NFC );
                        if ( $utf8 !== $normal_c ) {
                                $needsUpdate = true;
                        }
                }
                if ( $intl ) {
                        $useNormalizer = 'intl';
                        $intl = normalizer_normalize( $not_normal_c, Normalizer::FORM_C );
                        if ( $intl !== $normal_c ) {
                                $needsUpdate = true;
                        }
                }

                // Uses messages 'config-unicode-using-php', 'config-unicode-using-utf8',
                // 'config-unicode-using-intl'
                if ( $useNormalizer === 'php' ) {
                        $this->showMessage( 'config-unicode-pure-php-warning' );
                } else {
                        $this->showMessage( 'config-unicode-using-' . $useNormalizer );
                        if ( $needsUpdate ) {
                                $this->showMessage( 'config-unicode-update-warning' );
                        }
                }
        }

        /**
         * @return bool
         */
        protected function envCheckCtype() {
                if ( !function_exists( 'ctype_digit' ) ) {
                        $this->showError( 'config-ctype' );

                        return false;
                }

                return true;
        }

        /**
         * @return bool
         */
        protected function envCheckIconv() {
                if ( !function_exists( 'iconv' ) ) {
                        $this->showError( 'config-iconv' );

                        return false;
                }

                return true;
        }

        /**
         * @return bool
         */
        protected function envCheckJSON() {
                if ( !function_exists( 'json_decode' ) ) {
                        $this->showError( 'config-json' );

                        return false;
                }

                return true;
        }

        /**
         * Environment prep for the server hostname.
         */
        protected function envPrepServer() {
                $server = $this->envGetDefaultServer();
                if ( $server !== null ) {
                        $this->setVar( 'wgServer', $server );
                }
        }

        /**
         * Helper function to be called from envPrepServer()
         * @return string
         */
        abstract protected function envGetDefaultServer();

        /**
         * Environment prep for setting the preferred PHP file extension.
         */
        protected function envPrepExtension() {
                // @todo FIXME: Detect this properly
                if ( defined( 'MW_INSTALL_PHP5_EXT' ) ) {
                        $ext = '.php5';
                } else {
                        $ext = '.php';
                }
                $this->setVar( 'wgScriptExtension', $ext );
        }

        /**
         * Environment prep for setting $IP and $wgScriptPath.
         */
        protected function envPrepPath() {
                global $IP;
                $IP = dirname( dirname( __DIR__ ) );
                $this->setVar( 'IP', $IP );
        }

        /**
         * Get an array of likely places we can find executables. Check a bunch
         * of known Unix-like defaults, as well as the PATH environment variable
         * (which should maybe make it work for Windows?)
         *
         * @return array
         */
        protected static function getPossibleBinPaths() {
                return array_merge(
                        array( '/usr/bin', '/usr/local/bin', '/opt/csw/bin',
                                '/usr/gnu/bin', '/usr/sfw/bin', '/sw/bin', '/opt/local/bin' ),
                        explode( PATH_SEPARATOR, getenv( 'PATH' ) )
                );
        }

        /**
         * Search a path for any of the given executable names. Returns the
         * executable name if found. Also checks the version string returned
         * by each executable.
         *
         * Used only by environment checks.
         *
         * @param string $path Path to search
         * @param array $names Array of executable names
         * @param array|bool $versionInfo False or array with two members:
         *   0 => Command to run for version check, with $1 for the full executable name
         *   1 => String to compare the output with
         *
         * If $versionInfo is not false, only executables with a version
         * matching $versionInfo[1] will be returned.
         * @return bool|string
         */
        public static function locateExecutable( $path, $names, $versionInfo = false ) {
                if ( !is_array( $names ) ) {
                        $names = array( $names );
                }

                foreach ( $names as $name ) {
                        $command = $path . DIRECTORY_SEPARATOR . $name;

                        wfSuppressWarnings();
                        $file_exists = file_exists( $command );
                        wfRestoreWarnings();

                        if ( $file_exists ) {
                                if ( !$versionInfo ) {
                                        return $command;
                                }

                                $file = str_replace( '$1', wfEscapeShellArg( $command ), $versionInfo[0] );
                                if ( strstr( wfShellExec( $file ), $versionInfo[1] ) !== false ) {
                                        return $command;
                                }
                        }
                }

                return false;
        }

        /**
         * Same as locateExecutable(), but checks in getPossibleBinPaths() by default
         * @see locateExecutable()
         * @param array $names Array of possible names.
         * @param array|bool $versionInfo Default: false or array with two members:
         *   0 => Command to run for version check, with $1 for the full executable name
         *   1 => String to compare the output with
         *
         * If $versionInfo is not false, only executables with a version
         * matching $versionInfo[1] will be returned.
         * @return bool|string
         */
        public static function locateExecutableInDefaultPaths( $names, $versionInfo = false ) {
                foreach ( self::getPossibleBinPaths() as $path ) {
                        $exe = self::locateExecutable( $path, $names, $versionInfo );
                        if ( $exe !== false ) {
                                return $exe;
                        }
                }

                return false;
        }

        /**
         * Checks if scripts located in the given directory can be executed via the given URL.
         *
         * Used only by environment checks.
         * @param string $dir
         * @param string $url
         * @return bool|int|string
         */
        public function dirIsExecutable( $dir, $url ) {
                $scriptTypes = array(
                        'php' => array(
                                "<?php echo 'ex' . 'ec';",
                                "#!/var/env php5\n<?php echo 'ex' . 'ec';",
                        ),
                );

                // it would be good to check other popular languages here, but it'll be slow.

                wfSuppressWarnings();

                foreach ( $scriptTypes as $ext => $contents ) {
                        foreach ( $contents as $source ) {
                                $file = 'exectest.' . $ext;

                                if ( !file_put_contents( $dir . $file, $source ) ) {
                                        break;
                                }

                                try {
                                        $text = Http::get( $url . $file, array( 'timeout' => 3 ), __METHOD__ );
                                } catch ( Exception $e ) {
                                        // Http::get throws with allow_url_fopen = false and no curl extension.
                                        $text = null;
                                }
                                unlink( $dir . $file );

                                if ( $text == 'exec' ) {
                                        wfRestoreWarnings();

                                        return $ext;
                                }
                        }
                }

                wfRestoreWarnings();

                return false;
        }

        /**
         * Checks for presence of an Apache module. Works only if PHP is running as an Apache module, too.
         *
         * @param string $moduleName Name of module to check.
         * @return bool
         */
        public static function apacheModulePresent( $moduleName ) {
                if ( function_exists( 'apache_get_modules' ) && in_array( $moduleName, apache_get_modules() ) ) {
                        return true;
                }
                // try it the hard way
                ob_start();
                phpinfo( INFO_MODULES );
                $info = ob_get_clean();

                return strpos( $info, $moduleName ) !== false;
        }

        /**
         * ParserOptions are constructed before we determined the language, so fix it
         *
         * @param Language $lang
         */
        public function setParserLanguage( $lang ) {
                $this->parserOptions->setTargetLanguage( $lang );
                $this->parserOptions->setUserLang( $lang );
        }

        /**
         * Overridden by WebInstaller to provide lastPage parameters.
         * @param string $page
         * @return string
         */
        protected function getDocUrl( $page ) {
                return "{$_SERVER['PHP_SELF']}?page=" . urlencode( $page );
        }

        /**
         * Finds extensions that follow the format /$directory/Name/Name.php,
         * and returns an array containing the value for 'Name' for each found extension.
         *
         * Reasonable values for $directory include 'extensions' (the default) and 'skins'.
         *
         * @param string $directory Directory to search in
         * @return array
         */
        public function findExtensions( $directory = 'extensions' ) {
                if ( $this->getVar( 'IP' ) === null ) {
                        return array();
                }

                $extDir = $this->getVar( 'IP' ) . '/' . $directory;
                if ( !is_readable( $extDir ) || !is_dir( $extDir ) ) {
                        return array();
                }

                $dh = opendir( $extDir );
                $exts = array();
                while ( ( $file = readdir( $dh ) ) !== false ) {
                        if ( !is_dir( "$extDir/$file" ) ) {
                                continue;
                        }
                        if ( file_exists( "$extDir/$file/$file.php" ) ) {
                                $exts[] = $file;
                        }
                }
                closedir( $dh );
                natcasesort( $exts );

                return $exts;
        }

        /**
         * Returns a default value to be used for $wgDefaultSkin: normally the one set in DefaultSettings,
         * but will fall back to another if the default skin is missing and some other one is present
         * instead.
         *
         * @param string[] $skinNames Names of installed skins.
         * @return string
         */
        public function getDefaultSkin( array $skinNames ) {
                $defaultSkin = $GLOBALS['wgDefaultSkin'];
                if ( !$skinNames || in_array( $defaultSkin, $skinNames ) ) {
                        return $defaultSkin;
                } else {
                        return $skinNames[0];
                }
        }

        /**
         * Installs the auto-detected extensions.
         *
         * @return Status
         */
        protected function includeExtensions() {
                global $IP;
                $exts = $this->getVar( '_Extensions' );
                $IP = $this->getVar( 'IP' );

                /**
                 * We need to include DefaultSettings before including extensions to avoid
                 * warnings about unset variables. However, the only thing we really
                 * want here is $wgHooks['LoadExtensionSchemaUpdates']. This won't work
                 * if the extension has hidden hook registration in $wgExtensionFunctions,
                 * but we're not opening that can of worms
                 * @see https://bugzilla.wikimedia.org/show_bug.cgi?id=26857
                 */
                global $wgAutoloadClasses;
                $wgAutoloadClasses = array();

                require "$IP/includes/DefaultSettings.php";

                foreach ( $exts as $e ) {
                        require_once "$IP/extensions/$e/$e.php";
                }

                $hooksWeWant = isset( $wgHooks['LoadExtensionSchemaUpdates'] ) ?
                        $wgHooks['LoadExtensionSchemaUpdates'] : array();

                // Unset everyone else's hooks. Lord knows what someone might be doing
                // in ParserFirstCallInit (see bug 27171)
                $GLOBALS['wgHooks'] = array( 'LoadExtensionSchemaUpdates' => $hooksWeWant );

                return Status::newGood();
        }

        /**
         * Get an array of install steps. Should always be in the format of
         * array(
         *   'name'     => 'someuniquename',
         *   'callback' => array( $obj, 'method' ),
         * )
         * There must be a config-install-$name message defined per step, which will
         * be shown on install.
         *
         * @param DatabaseInstaller $installer DatabaseInstaller so we can make callbacks
         * @return array
         */
        protected function getInstallSteps( DatabaseInstaller $installer ) {
                $coreInstallSteps = array(
                        array( 'name' => 'database', 'callback' => array( $installer, 'setupDatabase' ) ),
                        array( 'name' => 'tables', 'callback' => array( $installer, 'createTables' ) ),
                        array( 'name' => 'interwiki', 'callback' => array( $installer, 'populateInterwikiTable' ) ),
                        array( 'name' => 'stats', 'callback' => array( $this, 'populateSiteStats' ) ),
                        array( 'name' => 'keys', 'callback' => array( $this, 'generateKeys' ) ),
                        array( 'name' => 'updates', 'callback' => array( $installer, 'insertUpdateKeys' ) ),
                        array( 'name' => 'sysop', 'callback' => array( $this, 'createSysop' ) ),
                        array( 'name' => 'mainpage', 'callback' => array( $this, 'createMainpage' ) ),
                );

                // Build the array of install steps starting from the core install list,
                // then adding any callbacks that wanted to attach after a given step
                foreach ( $coreInstallSteps as $step ) {
                        $this->installSteps[] = $step;
                        if ( isset( $this->extraInstallSteps[$step['name']] ) ) {
                                $this->installSteps = array_merge(
                                        $this->installSteps,
                                        $this->extraInstallSteps[$step['name']]
                                );
                        }
                }

                // Prepend any steps that want to be at the beginning
                if ( isset( $this->extraInstallSteps['BEGINNING'] ) ) {
                        $this->installSteps = array_merge(
                                $this->extraInstallSteps['BEGINNING'],
                                $this->installSteps
                        );
                }

                // Extensions should always go first, chance to tie into hooks and such
                if ( count( $this->getVar( '_Extensions' ) ) ) {
                        array_unshift( $this->installSteps,
                                array( 'name' => 'extensions', 'callback' => array( $this, 'includeExtensions' ) )
                        );
                        $this->installSteps[] = array(
                                'name' => 'extension-tables',
                                'callback' => array( $installer, 'createExtensionTables' )
                        );
                }

                return $this->installSteps;
        }

        /**
         * Actually perform the installation.
         *
         * @param callable $startCB A callback array for the beginning of each step
         * @param callable $endCB A callback array for the end of each step
         *
         * @return array Array of Status objects
         */
        public function performInstallation( $startCB, $endCB ) {
                $installResults = array();
                $installer = $this->getDBInstaller();
                $installer->preInstall();
                $steps = $this->getInstallSteps( $installer );
                foreach ( $steps as $stepObj ) {
                        $name = $stepObj['name'];
                        call_user_func_array( $startCB, array( $name ) );

                        // Perform the callback step
                        $status = call_user_func( $stepObj['callback'], $installer );

                        // Output and save the results
                        call_user_func( $endCB, $name, $status );
                        $installResults[$name] = $status;

                        // If we've hit some sort of fatal, we need to bail.
                        // Callback already had a chance to do output above.
                        if ( !$status->isOk() ) {
                                break;
                        }
                }
                if ( $status->isOk() ) {
                        $this->setVar( '_InstallDone', true );
                }

                return $installResults;
        }

        /**
         * Generate $wgSecretKey. Will warn if we had to use an insecure random source.
         *
         * @return Status
         */
        public function generateKeys() {
                $keys = array( 'wgSecretKey' => 64 );
                if ( strval( $this->getVar( 'wgUpgradeKey' ) ) === '' ) {
                        $keys['wgUpgradeKey'] = 16;
                }

                return $this->doGenerateKeys( $keys );
        }

        /**
         * Generate a secret value for variables using our CryptRand generator.
         * Produce a warning if the random source was insecure.
         *
         * @param array $keys
         * @return Status
         */
        protected function doGenerateKeys( $keys ) {
                $status = Status::newGood();

                $strong = true;
                foreach ( $keys as $name => $length ) {
                        $secretKey = MWCryptRand::generateHex( $length, true );
                        if ( !MWCryptRand::wasStrong() ) {
                                $strong = false;
                        }

                        $this->setVar( $name, $secretKey );
                }

                if ( !$strong ) {
                        $names = array_keys( $keys );
                        $names = preg_replace( '/^(.*)$/', '\$$1', $names );
                        global $wgLang;
                        $status->warning( 'config-insecure-keys', $wgLang->listToText( $names ), count( $names ) );
                }

                return $status;
        }

        /**
         * Create the first user account, grant it sysop and bureaucrat rights
         *
         * @return Status
         */
        protected function createSysop() {
                $name = $this->getVar( '_AdminName' );
                $user = User::newFromName( $name );

                if ( !$user ) {
                        // We should've validated this earlier anyway!
                        return Status::newFatal( 'config-admin-error-user', $name );
                }

                if ( $user->idForName() == 0 ) {
                        $user->addToDatabase();

                        try {
                                $user->setPassword( $this->getVar( '_AdminPassword' ) );
                        } catch ( PasswordError $pwe ) {
                                return Status::newFatal( 'config-admin-error-password', $name, $pwe->getMessage() );
                        }

                        $user->addGroup( 'sysop' );
                        $user->addGroup( 'bureaucrat' );
                        if ( $this->getVar( '_AdminEmail' ) ) {
                                $user->setEmail( $this->getVar( '_AdminEmail' ) );
                        }
                        $user->saveSettings();

                        // Update user count
                        $ssUpdate = new SiteStatsUpdate( 0, 0, 0, 0, 1 );
                        $ssUpdate->doUpdate();
                }
                $status = Status::newGood();

                if ( $this->getVar( '_Subscribe' ) && $this->getVar( '_AdminEmail' ) ) {
                        $this->subscribeToMediaWikiAnnounce( $status );
                }

                return $status;
        }

        /**
         * @param Status $s
         */
        private function subscribeToMediaWikiAnnounce( Status $s ) {
                $params = array(
                        'email' => $this->getVar( '_AdminEmail' ),
                        'language' => 'en',
                        'digest' => 0
                );

                // Mailman doesn't support as many languages as we do, so check to make
                // sure their selected language is available
                $myLang = $this->getVar( '_UserLang' );
                if ( in_array( $myLang, $this->mediaWikiAnnounceLanguages ) ) {
                        $myLang = $myLang == 'pt-br' ? 'pt_BR' : $myLang; // rewrite to Mailman's pt_BR
                        $params['language'] = $myLang;
                }

                if ( MWHttpRequest::canMakeRequests() ) {
                        $res = MWHttpRequest::factory( $this->mediaWikiAnnounceUrl,
                                array( 'method' => 'POST', 'postData' => $params ), __METHOD__ )->execute();
                        if ( !$res->isOK() ) {
                                $s->warning( 'config-install-subscribe-fail', $res->getMessage() );
                        }
                } else {
                        $s->warning( 'config-install-subscribe-notpossible' );
                }
        }

        /**
         * Insert Main Page with default content.
         *
         * @param DatabaseInstaller $installer
         * @return Status
         */
        protected function createMainpage( DatabaseInstaller $installer ) {
                $status = Status::newGood();
                try {
                        $page = WikiPage::factory( Title::newMainPage() );
                        $content = new WikitextContent(
                                wfMessage( 'mainpagetext' )->inContentLanguage()->text() . "\n\n" .
                                wfMessage( 'mainpagedocfooter' )->inContentLanguage()->text()
                        );

                        $page->doEditContent( $content,
                                '',
                                EDIT_NEW,
                                false,
                                User::newFromName( 'MediaWiki default' )
                        );
                } catch ( Exception $e ) {
                        //using raw, because $wgShowExceptionDetails can not be set yet
                        $status->fatal( 'config-install-mainpage-failed', $e->getMessage() );
                }

                return $status;
        }

        /**
         * Override the necessary bits of the config to run an installation.
         */
        public static function overrideConfig() {
                define( 'MW_NO_SESSION', 1 );

                // Don't access the database
                $GLOBALS['wgUseDatabaseMessages'] = false;
                // Don't cache langconv tables
                $GLOBALS['wgLanguageConverterCacheType'] = CACHE_NONE;
                // Debug-friendly
                $GLOBALS['wgShowExceptionDetails'] = true;
                // Don't break forms
                $GLOBALS['wgExternalLinkTarget'] = '_blank';

                // Extended debugging
                $GLOBALS['wgShowSQLErrors'] = true;
                $GLOBALS['wgShowDBErrorBacktrace'] = true;

                // Allow multiple ob_flush() calls
                $GLOBALS['wgDisableOutputCompression'] = true;

                // Use a sensible cookie prefix (not my_wiki)
                $GLOBALS['wgCookiePrefix'] = 'mw_installer';

                // Some of the environment checks make shell requests, remove limits
                $GLOBALS['wgMaxShellMemory'] = 0;
        }

        /**
         * Add an installation step following the given step.
         *
         * @param callable $callback A valid installation callback array, in this form:
         *    array( 'name' => 'some-unique-name', 'callback' => array( $obj, 'function' ) );
         * @param string $findStep The step to find. Omit to put the step at the beginning
         */
        public function addInstallStep( $callback, $findStep = 'BEGINNING' ) {
                $this->extraInstallSteps[$findStep][] = $callback;
        }

        /**
         * Disable the time limit for execution.
         * Some long-running pages (Install, Upgrade) will want to do this
         */
        protected function disableTimeLimit() {
                wfSuppressWarnings();
                set_time_limit( 0 );
                wfRestoreWarnings();
        }
}