MediaWiki

Extension:JWTAuth

This extension requires the PluggableAuth extension to be installed first.
MediaWiki extensions manual
JWTAuth
Release status: stable
Implementation User identity , User rights
Description Adds support for using JSON Web Tokens to log in to MediaWiki
Author(s) Jeffrey Wang (MyWikis-JeffreyWangtalk)
Latest version 2.0.0
Compatibility policy Main branch maintains backward compatibility.
MediaWiki 1.35.0+
Database changes Yes
License MIT License
Download
Download extension
Git [?]:
Parameters
$wgJWTAuthAlgorithm, $wgJWTAuthKey, $wgJWTGroupMapping, $wgJWTAuthDebugMode
Hooks used
Quarterly downloads 5 (Ranked 137th)
Translate the JWTAuth extension if it is available at translatewiki.net

The JWTAuth extension adds support for using JSON Web Tokens to log in to MediaWiki. JWTs are a common medium for conveying an authentication assertion in the tangible form of a token.

JWTAuth 2.0.0 was released on July 24, 2023. The extension was rewritten to use PluggableAuth.

Prerequisites edit

JWTAuth is not a complete auth system. It is simply the last mile of processing JWTs. To learn more about how JWTs work, go to JWT.io. JWTAuth only facilitates the verification of JWTs that were already issued. Therefore, an auth system that issues JWTs is the primary prerequisite.

As of JWTAuth 2.0.0, the extension is based off of PluggableAuth and requires PluggableAuth 7.0 or higher to be installed on the wiki.

The JWT needs to be passed into the wiki's Special:JWTLogin page. It will take whatever content is POSTed in the Authorization parameter (query string) and process it. The content should begin with Bearer  (with a space after the word "Bearer") or Bearer:, followed by the actual JWT.

Why use JWTAuth? edit

 
Presentation about JWTAuth at EMWCon Spring 2023 (before it was rewritten to use PluggableAuth)

JSON Web Tokens are a widely used medium to encode session data. They are issued by an identity provider (IdP) and consumed by service providers (SPs) by using a mutually agreed upon key (whether symmetric or asymmetric) to check if a given token is valid or not. If the SP is presented with a supposedly valid token supposedly issued by the IdP, it is taken for face value and the user is authenticated into the service.

Advantages edit

JWTs are useful for persisting auth session throughout the token's life because it means it can reuse token across multiple services and avoids needing to log in multiple times. It's best for systems where user will be logged in to several sites at once, including MediaWiki, and when sites are accessed from a central login system.

The JWTAuth extension doesn't require a JWT to be sent with each request to the web server. It only needs it to be sent once to Special:JWTLogin per login session. Once the JWTAuth extension authenticates the user based on the validity of the token, a cookie is set in MediaWiki to authenticate them for the rest of the MediaWiki session. The rest of the session is managed by MediaWiki and JWTAuth doesn't interface with it after that point.

Limitations edit

One inherent limitation of JWTAuth is its inability to check for whether tokens are revoked. This is not a bug; it is expected behavior because of the design of this auth process. It is able to detect whether the token is expired or forged, but if a token were to be revoked before the scheduled expiry time, the JWTAuth extension would have no way of knowing, as it doesn't talk back with the IdP who issued the token. Most PluggableAuth-based extensions don't suffer from this limitation. Usually, it's best to use the JWTAuth extension in an environment where the ability to immediate revoke a token is either unnecessary because another layer of auth would take care of it (like a company-issued computer shutting down when its associated employee's employment comes to an end), or not important. The best way to mitigate this issue would be to set the validity period to be as short as possible.

This also means JWTAuth doesn't include single sign-out.

There are many discussions of the merits of using JWTs versus other authentication mechanisms, and especially about what the best way to use them would be, but they are beyond the scope of this page. Please see JWT.io to learn more about JWTs.

Installation edit

  • Download and move the extracted JWTAuth folder to your extensions/ directory.
    Developers and code contributors should install the extension from Git instead, using:cd extensions/
    git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/JWTAuth
  • Add the following code at the bottom of your LocalSettings.php file: 
    wfLoadExtension( 'JWTAuth' );
$wgJWTAuth_Algorithm = ''; // can be: HS256, RS256, EdDSA
$wgJWTAuth_Key = ''; // Depends on which algorithm you are using
  •   Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.

Configuration edit

$wgJWTAuth_Algorithm
The algorithm used to encode and decode the JWT. Currently, only HS256, RS256, and EdDSA are supported. The former uses a simple passphrase, whereas the latter two use a public/private keypair.
$wgJWTAuth_Key
When using a symmetric algorithm like HS256, this is the shared passkey used to encode and decode the JWT.
When using an asymmetric algorithm such as RS256 or EdDSA, this is the public key. (The private key would be stored on side of the issuer of the JWT.)

Integrating your auth system with JWTAuth on MediaWiki edit

The following procedure must be followed to successfully authenticate a user into the wiki:

  1. A JWT claim must be well formed and encoded into the JWT payload format using the key that has already been agreed upon.
  2. Find the path to your wiki's location of Special:JWTLogin. For instance, if your wiki is under https://wiki.example.com and $wgArticlePath = "/wiki/$1"; then the location is https://wiki.example.com/wiki/Special:JWTLogin.
  3. The payload must be POSTed to this aforementioned URL. The URL should have a parameter called Authorization with the content Bearer: JWTTOKENHERE. For instance, Bearer: eyJhbGciOiJIUzI...66Vkfljr.
  4. The payload must conform to the claim names promulgated by IANA: https://www.iana.org/assignments/jwt/jwt.xhtml

Below are the claims that are required by the JWTAuth extension. If any of these are missing, the authentication process will fail. If you are unsure of what these mean, or the allowed values for them, please visit https://jwt.io for more details.

  • preferred_username: Username. This is used by JWTAuth to form the user's username on MediaWiki. Please make sure the usernames conform to MediaWiki's allowed username rules.
  • exp: Expiry timestamp.
  • iat: Issued at timestamp.
  • nbf: Not valid before timestamp.
  • iss: Issuer
  • aud: Audience
  • sub: Subject

You can put nonsense (but nonempty) values for iss, aud, and sub, as they are not checked by JWTAuth, but our JWT decoding library (Firebase JWT) will cause the auth process to fail if they are not set.

The following claims are optional, but are highly recommended because they will be added to users' profiles:

  • email
  • family_name
  • given_name

As of 0.1.0, most of these claim names cannot be changed to match the token generator's preferences because these claim names are standard conventions. The party generating the token is responsible for sending well-formed responses that conform to internet standards. As of JWTAuth 2.0.0, the groups claim name cannot be changed anymore.

If you want to assign groups to a user, pass them in, separated by commas, by using the groups claim. The groups will be synced using the group sync mechanism present in PluggableAuth. To configure it, see Extension:PluggableAuth#Group_Synchronization.

Please see the README for this extension for more details.

See also edit

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