User:DAlangi (WMF)/Sandbox/CentralAuth docs revamp

**MediaWiki extensions manual**
DAlangi (WMF)/Sandbox/CentralAuth docs revamp; Release status: stable
Implementation	User identity, Database, Special page, API
Description	Allows to merge accounts into global accounts
Author(s)	Brooke Vibbertalk
Compatibility policy	Snapshots releases along with MediaWiki. Master is not backward compatible.
MediaWiki
Virtual domain	virtual-centralauth
Tables	globalnames; localnames; globaluser; localuser; global_user_groups; global_group_permissions; wikiset; global_group_restrictions; renameuser_status; renameuser_queue; users_to_rename; global_edit_count; global_user_autocreate_serial
License	No license specified
Download	Download extension ; Git [?]: Download Git master; browse repository (Phabricator · GitHub); commit history; repository contributors (GitHub); code review;
	Hooks provided CentralAuthIsUIReloadRecommended; CentralAuthLoginRedirectData; CentralAuthPostLoginRedirect; CentralAuthSilentLoginRedirect; CentralAuthWikiList;
	Translate the DAlangi (WMF)/Sandbox/CentralAuth docs revamp extension if it is available at translatewiki.net
Issues	Open tasks · Report a bug

This page contains changes which are not marked for translation.

CentralAuth allows merging several existing separate account systems into one global account system.

Warning:

CentralAuth was designed specifically for Wikimedia projects which already had millions of accounts that needed to be merged into a global table.

If you are starting a new wiki farm from scratch and have no need to merge existing accounts into a global table, it is much easier to set up global accounts using $wgSharedDB rather than using CentralAuth.^[1]^[2]

However, $wgSharedDB is only useful for preventing conflicts of username creations, and does not handle anything such as universal sign-on (instead, users are required to sign in to each wiki), or cross-cluster account rights and management. This extension provides said functionality at the cost of complexity.

If you end up using this extension on a third-party wiki, it is likely that you will end up having to troubleshoot complex issues that potentially require diving into the source code to resolve.

You have been warned.

Installation

See the setup section below for prerequisites to using CentralAuth. Then follow these instructions when you are ready to activate CentralAuth:

Install Extension:AntiSpoof , since it is a required dependency.
Download the latest snapshot and extract it to your extensions directory.
Pick a database and create the CentralAuth database tables. You can use an existing database or create a new one; the extension by default uses a database named centralauth (see $wgVirtualDomainsMapping['virtual-centralauth'] below). Use this database then run tables-generated.sql.
- If you use Extension:AntiSpoof you'll need to create a global spoofuser table (to block new usernames that look similar to existing usernames in any wiki). One way to do this is dump the spoofuser table from the local wiki's database and import it into the new $wgVirtualDomainsMapping['virtual-centralauth'].
Add wfLoadExtension( 'CentralAuth' ); to your LocalSettings.php for each of your wikis, or in another PHP file that is included in LocalSettings.php on each of your wikis.
The CentralAuth extension should be now active.

Create a new database

Here are sample shell and SQL commands to create the centralauth database, copy the spoofuser table to it, and migrate existing user data to it. Replace $wgDBname and $wgDBuser with the values for your own wiki installation credentials.

Create the new database (Remember this step is optional, you can instead use one of your existing databases, in which case skip to the create tables step):

$ cd extensions/CentralAuth
$ mysql -u root -p
(enter password for root SQL user)

CREATE DATABASE centralauth;
USE centralauth;
GRANT all on centralauth.* to '$wgDBuser'@'localhost';
quit

Run maintenance scripts

The following assumes your present working directory is your MediaWiki installation (not your CentralAuth directory). Create the central auth tables (using sql.php is preferred).

php maintenance/run.php sql --wikidb centralauth extensions/CentralAuth/schema/<db_type>/tables-generated.sql

If AntiSpoof is installed, create the table via (Alternatively, you can copy an existing AntiSpoof table if you want to keep previous entries):

php maintenance/run.php sql --wikidb centralauth extensions/AntiSpoof/sql/<db_type>/tables-generated.sql

Run the user migration scripts

$ php maintenance/run.php CentralAuth:migratePass0.php
$ php maintenance/run.php CentralAuth:migratePass1.php

Upgrading

CentralAuth is designed for large wiki farms who run database updates manually in order to enable zero-downtime upgrades. For that reason, the CentralAuth database will not be updated with the usual upgrade process. Third-party users are expected to follow CentralAuth development and apply database migrations manually instead.

Setup

Warning:

A central login wiki is required if you want to have a universal sign-on across different primary domains (i.e. if your wikis are not under subdomains of the same domain). See below for detail.

First, you'll need to configure your wiki family using $wgConf , or CentralAuth can't be used for your wiki family. This includes setting $wgLocalDatabases and assigning it to $wgConf->wikis, and $wgConf->settings (minimum is $wgCanonicalServer , $wgServer and $wgArticlePath ). Follow the examples carefully. If you are creating a new wiki family, bear in mind that it may be easier if the databases for the wikis in each group have the same suffix (e.g. hypothetical databases enwiki, dewiki, frwiki, etc., pertaining to wikis belonging to the same group, all have the suffix "wiki").

After installing the extension, you have to gather some data in the CentralAuth database. In order to retroactively set up global accounts, you will have to run the migratePass0.php and migratePass1.php scripts. The first one stores information about your wikis in the CentralAuth database, while the second one uses automatic migration heuristics to generate global accounts. A user can merge their accounts manually via Special:MergeAccount. Dry runs can be used for testing purposes.

To enable global groups, you will have to make an entry into the global_group_permissions table in your CentralAuth database, with ggp_group='steward' and (for access to the group management interface) ggp_permission=globalgrouppermissions. A sample query that is recommended to use is:

INSERT INTO global_group_permissions (ggp_group,ggp_permission) VALUES ('steward','globalgrouppermissions'), ('steward','globalgroupmembership');

Then, promote some users into stewards:

INSERT IGNORE INTO global_user_groups (gug_user, gug_group) VALUES ((SELECT gu_id FROM globaluser WHERE gu_name='Admin'), 'steward');

There are various settings you may wish to modify (e.g. whether to provide single sign-on across a whole domain) listed in CentralAuth.php. In particular, you will want to override the default value of $wgVirtualDomainsMapping['virtual-centralauth'] if your CentralAuth database is named something other than 'centralauth'. Make sure you put such settings after the wfLoadExtension line in LocalSettings.php, e.g.:

wfLoadExtension( 'CentralAuth' );
$wgVirtualDomainsMapping['virtual-centralauth'] = [ 'db' => 'centralauth' ];

"SUL2" behavior

Warning:

As all logged in users will have a session in the central login wiki, you are recommended to set up a new wiki with as few extensions installed as possible (not using an existing wiki for this purpose). This will reduce the risk for XSS vulnerabilities.

Warning:

Universal sign-on may be broken in newer Google Chrome versions due to SameSite cookie policy. To fix it, you need to add:

$wgCookieSameSite = "None";
$wgUseSameSiteLegacyCookies = true;

In addition, you must run your site under HTTPS.

In July 2013 WMF changed its approach to logging users into multiple wikis. When configured for this new approach, after successful login and account creation CentralAuth redirects to Special:CentralLogin/start?token=<somevalue> on a "central login wiki", which sets cookies on that wiki and then redirects back to the logged-into wiki. It omits the "login/account creation success" page, instead redirecting back to the "returnto" page that the user was originally on. It places 1x1 pixel images in the footer of that page, in place of the icons formerly used on the "login/account creation success" page.

The settings for this are, roughly,

# General CentralAuth configuration
$wgCentralAuthCookies = true;
// default is 'centralauth'
$wgVirtualDomainsMapping['virtual-centralauth'] = [ 'db' => 'centralauthDatabaseName' ];
$wgCentralAuthAutoMigrate = true;
$wgCentralAuthAutoLoginWikis = [
    # Mapping from domain name to wiki id for other wikis to automatically login into
    'enwiki.mediawiki.mwdd.localhost' => 'enwiki',
];

# Activates the redirect to the "central login wiki"
$wgCentralAuthLoginWiki = 'WikiIdOfLoginWiki';

$wgCentralAuthLoginWiki is the ID (usually the database-name) of the wiki to which CentralAuth will redirect on login and create account actions.

Cache issues

For best results, it is recommended to use memcached or a more persistent cache. If you have only a single server, accelerator caches (CACHE_ACCEL) like APCu can also work, but do not use them if you have multiple servers. If you have no cache set up (i.e. CACHE_NONE) for $wgMainCacheType, or are using CACHE_DB, then you need to make sure all your wikis use the same caching table.

By default, each wiki in your wiki farm will use the objectcache table in its own database (with its own db prefix) when $wgMainCacheType is set to CACHE_NONE or CACHE_DB. To make this work with CentralAuth, we need to tell the wikis to use a central cache table.

If you want to make a central caching table in the centralauth database (and assuming one of your existing wikis has a database name of enwiki), run code like the following to copy the table to your other database (assuming you have an installed wiki with database called "enwiki" and another database called "centralauth"):

CREATE TABLE centralauth.objectcache LIKE enwiki.objectcache

Then add the following config to all wikis to tell them to use the central table instead of their own table:

$wgSharedDB = 'centralauth'; // or whatever database you use for central data
$wgSharedTables = [ 'objectcache' ]; // remember to copy the table structure's to the central database first
$wgCentralAuthSessionCacheType = CACHE_DB; // Tell mediawiki to use objectcache database for central auth.

When running PHPUnit tests locally with your wiki farm and do not want them to fail due to an attempt to clone database tables with the shared tables config above, use:

if ( defined( 'MW_PHPUNIT_TEST' ) ) {
	$wgSharedTables = [];
} else {
	$wgSharedTables = [ 'objectcache' ];
}

HTTP and HTTPS

Since 2023, CentralAuth does not support mixed-protocol HTTP/HTTPS wikis, only pure-HTTPS wikis (with $wgForceHTTPS set to true) and pure-HTTP wikis (primarily for local testing). See: issue T348852.

Configuration

Database Virtual Domains Mapping

Since MediaWiki 1.41, you can configure database virtual domains mapping for CentralAuth, and this replaced $wgCentralAuthDatabase. To setup virtual domains mapping with CentralAuth, use:

// 'centralauth' is the name of the your CentralAuth database.
$wgVirtualDomainsMapping['virtual-centralauth'] = [ 'db' => 'centralauth' ];

Configuration settings in Extension.json Config section
parameter	default	comment
(`deprecated`) `$wgCentralAuthDatabase`	`'centralauth'`	Database name you keep central auth data in. If this is not on the primary database connection, don't forget to also set up `$wgDBservers` to have an entry with a `groupLoads` setting for the `'CentralAuth'` group. Alternatively you can use `$wgLBFactoryConf` to set up an `LBFactoryMulti` object. To use a database with a table prefix, set this variable to "`{$database}-{$prefix}`". NOTE: This setting has been deprecated, use virtual domains mapping as described above.
`$wgCentralAuthAutoMigrate`	`false`	If `true`, existing unattached accounts will be automatically migrated if possible at first login. Any new account creations will be required to attach. If `false`, unattached accounts will not be harassed unless the individual account has opted in to migration.
`$wgCentralAuthAutoMigrateNonGlobalAccounts`	`false`	If `true`, existing unattached accounts where no global account exists will be compared to see if a merge can be made based on passwords and emails with no clashes (all accounts merge). This was formerly controlled by `$wgCentralAuthAutoMigrate`
`$wgCentralAuthStrict`	`false`	If `true`, remaining accounts which have not been attached will be forbidden from logging in until they are resolved.
`$wgCentralAuthDryRun`	`false`	If `true`, merging won't actually be possible through the Special:MergeAccount interface.
`$wgCentralAuthCookies`	`false`	If `true`, global session and token cookies will be set alongside the per-wiki session and login tokens when users log in with a global account. This allows other wikis on the same domain to transparently log them in.
`$wgCentralAuthLoginWiki`	`false`	Database name of a central login wiki. This is an alternative to directly setting cross-domain cookies for each wiki in `$wgCentralAuthAutoLoginWikis`. If set, a single login wiki will use a session/cookie to handle unified login sessions across wikis. On login, users will be redirected to the login wiki's Special:CentralLogin/login page and then redirected to Special:CentralLogin back on the originating wiki. In the process, the central login wiki cookie and session will be set. As the user accesses other wikis, the login wiki will be checked via JavaScript to check login status and set the local session and cookies. This requires `$wgCentralAuthCookies`.
`$wgCentralAuthCookieDomain`	`''`	Domain to set global cookies for. For instance, `'.wikipedia.org'` to work on all `wikipedia.org` subdomains instead of just the current one. Leave blank to set the cookie for the current domain only, such as if all your wikis are hosted on the same subdomain.
`$wgCentralAuthCookiePrefix`	`'centralauth_'`	Prefix for CentralAuth global authentication cookies.
`$wgCentralAuthCookiePath`	`'/'`	Path for CentralAuth global authentication cookies. Set this variable if you want to restrict cookies to a certain path within the domain specified by `$wgCentralAuthCookieDomain`.
`$wgCentralAuthAutoLoginWikis`	`[]`	List of wiki IDs which should be called on login to try to set third-party cookies for the global session state. The wiki ID is typically the database name, except when table prefixes are used, in which case it is the database name, a hyphen separator, and then the table prefix. This allows a farm with multiple second-level domains to set up a global session on all of them by hitting one wiki from each domain (en.wikipedia.org, en.wikinews.org, etc.). Done by accessing `Special:CentralAutoLogin/start` on each wiki. If empty, no other wikis will be hit. The key should be set to the cookie domain name.
`$wgCentralAuthAutoCreateWikis`	`[]`	List of wiki IDs on which an attached local account should be created automatically when the global account is created. The wiki ID is typically the database name, except when table prefixes are used, in which case it is the database name, a hyphen separator, and then the table prefix.
`$wgCentralAuthLoginIcon`	`false`	Local filesystem path to the icon returned by `Special:CentralAutoLogin` should be a 20x20px PNG.
`$wgCentralAuthPrefsForUIReload`	`[ 'skin', 'language', 'thumbsize', 'underline', 'stubthreshold', 'showhiddencats', 'justify', 'numberheadings', 'editondblclick', 'editsection', 'editsectiononrightclick', 'usenewrc', 'extendwatchlist' ]`	User preferences for which we should recommend reloading the page after a successful central login query. If you need to do something more complicated than just `$userOptionsLookup->getOption( $user, $pref ) !== $userOptionsLookup->getDefaultOption( $pref )`, use the hook `CentralAuthIsUIReloadRecommended`.
`$wgCentralAuthRC`	`[]`	Array of settings for sending the CentralAuth events to the RC Feeds. `@example $wgRCFeeds['example'] = [ 'uri' => "udp://localhost:1336" ];`
`$wgCentralAuthWikisPerSuppressJob`	`10`	Size of wikis handled in one suppress user job. Keep in mind that one wiki requires `~10` queries.
`$wgCentralAuthReadOnly`	`false`	Like `$wgReadOnly`, used to set extension to database read only mode. `@var bool`
`$wgCentralAuthEnableGlobalRenameRequest`	`false`	Feature flag for `Special:GlobalRenameRequest`. `@var bool`
`$wgCentralAuthGlobalPasswordPolicies`	`[]`	Global password policies. These are applied like local password policies, the strongest policy applicable to a user is used. Policies can apply to either a local group (if the user is a member of that group on any wiki, the policy will apply to that user) or global group. `@var array`
`$wgGlobalRenameDenylist`	`null`	A list of users who won't be allowed to create new global rename requests through Special:GlobalRenameRequest. There are two ways to set it: Using a wiki-page: use a Title object to have a wiki-page (`MediaWiki:GlobalRenameDenylist` for example) as the banned-list. The wiki-page must be a list with one item per line, and must exist otherwise `Special:GlobalRenameRequest` will throw a MWException. Example: `$wgGlobalRenameDenylist = Title::makeTitle( NS_MEDIAWIKI, 'GlobalRenameDenylist' );`. Using a URL: put a complete URL which must return, using HTTP, a plain-text list of the banned users (and nothing else). For example, with a URL pointing to a wiki page: `$wgGlobalRenameDenylist = "https://yourwiki/yourpath/index.php?title=MediaWiki:GlobalRenameDenylist&action=raw";` You can use the exact names or regular expressions. `@var Title\|string\|null`
`$wgCentralAuthGlobalBlockInterwikiPrefix`	`"global"`	When globally suppressing a user, a block against this user is inserted in all wikis. CentralAuth will set the author of theses blocks as `$wgCentralAuthGlobalBlockInterwikiPrefix>(user-who-made-the-suppression's nickname)`. For example, if `$wgCentralAuthGlobalBlockInterwikiPrefix = "Admins";`, and Joe suppresses John, all wikis will show in BlockList a block against John made by `Admins>Joe`. `@var string`

Use

Allows for a single-user login (SUL) system using MediaWiki's AuthPlugin system. User creation and login is done globally using one central user table across all wikis. Note that local user accounts are automatically created on account creation/login however.

This extension also implements global user groups, to which global accounts can belong to.

User rights

CentralAuth defines several new user rights:

User right	Abilities	Default group	Status
`centralauth-createlocal`	Forcibly create a local account for a global account	Stewards and sysops	Active in MW 1.36+
`centralauth-lock`	Prevent users from logging in on any wiki	Stewards	Active
`centralauth-suppress`	Suppress or unhide global accounts	Stewards	Active
`centralauth-rename`	Rename global accounts	Stewards	Active
`centralauth-unmerge`	Unmerge global accounts from a local account	Stewards	Active
`centralauth-merge`	Merge all CentralAuth accounts globally	All users	Active; usually automatic
`globalgrouppermissions`	Manage permissions of global groups	Global Stewards	Active; not assigned to local stewards by default
`globalgroupmembership`	Edit membership to global groups	Global Stewards	Active; not assigned to local stewards by default

Functions

Single-user login (SUL)

A user with an account on more than one wiki may use Special:MergeAccount to create their global user account, which can then be used on any wiki. Users with the centralauth-unmerge permission (given to stewards by default) can undo a merging of a global account, where the passwords are all reset back to the pre-merge setting. User accounts can now also be renamed globally.

Locking and hiding global users

A global account can be locked or hidden by a user with the centralauth-lock and centralauth-suppress permissions, respectively, given to the local group 'stewards' by default. A locked global account will be immediately logged out of any session on any wiki it is currently logged in to. A hidden global account's username is not visible in any logs except the global account log.

Wiki sets

A wiki set is a group of wikis specified by a user with the globalgrouppermissions right. Sets can be opt-in (wikis are not in it by default) or opt-out (wikis are in it unless opted out).

Global user groups

Once you have enabled global user groups as described in the installation section, a migrated steward can use the Special:GlobalGroupPermissions interface to configure global user groups, and their rights. A global user group is active on all wikis (the users in it have its rights on all the wikis) by default, unless the group has been specified to only be active on a specific wiki set (the users in the group only have the rights if they are on a wiki in the set). Global group permissions are not listed at Special:ListUsers, but instead Special:GlobalUsers. They are assigned by a user with the globalgroupmembership permission (by default the global group stewards), and give the specified rights to the user even if the local rights defined by $wgGroupPermissions do not do so.

Licensing and downloads

The extension is available under the GNU General Public License 2.0 or later, and can be downloaded from Git, or accessed via the web-based viewer.

The software is provided as-is. Updates will be made according to the needs of Wikimedia wikis; or where critical vulnerabilities are discovered.

API

See Extension:CentralAuth/API .

DAlangi (WMF)/Sandbox/CentralAuth docs revamp Release status: stable

Implementation	User identity , Database , Special page , API
Description	Allows to merge accounts into global accounts
Author(s)	Brooke Vibber^talk
Compatibility policy	Snapshots releases along with MediaWiki. Master is not backward compatible.
MediaWiki
Virtual domain	virtual-centralauth
Tables	globalnames localnames globaluser localuser global_user_groups global_group_permissions wikiset global_group_restrictions renameuser_status renameuser_queue users_to_rename global_edit_count global_user_autocreate_serial
License	No license specified
Download	Download extension Git ^[?]: Download Git master browse repository (Phabricator · GitHub) commit history repository contributors (GitHub) code review
Hooks provided CentralAuthIsUIReloadRecommended CentralAuthLoginRedirectData CentralAuthPostLoginRedirect CentralAuthSilentLoginRedirect CentralAuthWikiList
Translate the DAlangi (WMF)/Sandbox/CentralAuth docs revamp extension if it is available at translatewiki.net
Issues	Open tasks · Report a bug

User:DAlangi (WMF)/Sandbox/CentralAuth docs revamp

Installation

Create a new database

Run maintenance scripts

Upgrading

Setup

"SUL2" behavior

Cache issues

HTTP and HTTPS

Configuration

Database Virtual Domains Mapping

Use

User rights

Functions

Single-user login (SUL)

Locking and hiding global users

Wiki sets

Global user groups

Licensing and downloads

API

References

See also