OAuth/For Developers

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This page explains how to develop applications that can integrate with a wiki running Extension:OAuth (an extension which turns MediaWiki into an OAuth server) to securely request permission to act on the user's behalf.

Note Note:If you are developing a bot or similar application where the same consumer is always used with the same user account, you might prefer the simpler owner-only consumers.

OAuth in a nutshell[edit]

OAuth allows an application to request permission from a user to act through that user's wiki account, without knowing the user's password, and without being able to do everything the user could (e.g. the app might be able to edit articles but not delete them, so even users with extended permissions can safely use OAuth-enabled tools).

This happens via the OAuth 1.0a protocol, and has three components:

  1. The developer must register the application (often called "consumer" in the OAuth terminology) on the wiki, possibly go through some sort of review process, and will receive some credentials.
  2. When a user wants to use it, the application must initiate an authorization process. This will involve sending the user to a special page on the wiki, which will display an authorization dialog. If the user accepts, the application will receive another set of credentials (which are specific to that user, and can be revoked by the user at any time).
  3. When the application actually needs to make an action (API request) on the user's behalf, it can combine the credentials received in steps 1 and 2 to sign the request.

OAuth is a widely used open standard (you can see it on sites like Google or Facebook or Github, e.g. when using accounts at those sites to log in elsewhere). It is not to be confused with OATH (a second-factor authentication protocol, commonly known as "type the six numbers you see on your mobile app", now enabled on Wikimedia sites) and OpenID Connect (an authentication protocol based on OAuth 2.0 - the OAuth MediaWiki extension does include a somewhat OpenID-like custom protocol for determining user identity though).

For a slightly larger nutshell, see these slides.

OAuth in detail[edit]

Registration[edit]

To register a new OAuth application, submit the form at Special:OAuthConsumerRegistration/propose. Try to give sufficient information about the application for admins and users to decide whether it can be trusted. URLs to places with more information (such as the application itself, the source code or on-wiki documentation) can be useful. For OAuth applications to be used on Wikimedia projects, see app guidelines.

Besides the descriptive ones, the fields have the following meaning:

  • This consumer is for use only by <user>: for owner-only consumers (which do not need to be reviewed or authorized but are only usable by yourself)
  • callback URL: the URL where the user return after authorization is checked against this. (This is an extra layer of security against an attacker trying to steal credentials during authorization.) If the "use as prefix" option is enabled, the URL must start with this (the check is dumb so make sure to add at least a / after the domain name), otherwise it must be an exact match.
  • Applicable project (for wiki farms only): you can limit the application to a single wiki or have it work everywhere.
  • Types of grants / Applicable grants: the permissions needed by your application (be conservative). The actual permissions will be an intersection of this and what permissions the user has. At this time, the user must authorize all permissions together (T59505).
  • Allowed IP ranges: OAuth requests not matching this will be rejected. (This is an optional extra layer of security against an attacker stealing your application's credentials and trying to impersonate it.) One of the few settings that you'll be able to change later.
  • Public RSA key: public key used by your application for signing requests. You can just leave this empty (most applications do) to use a slightly simpler shared-secret mechanism instead. One of the few settings that you'll be able to change later.

After registration, you'll receive the credentials needed to use OAuth. You will be able to use it immediately with your own user account (this is meant for testing); others will only be able to use it once it is approved by an administrator.

If you have changed your mind, you can disable the application under Special:OAuthConsumerRegistration/list. The list of applications (approved or otherwise) is public and can be browsed at Special:OAuthListConsumers.

Authorization[edit]

Authorization dialog shown to users

When registering the application, you receive two pieces of credentials: the application token (a public ID for the application) and the application secret (sort of like a password). To be able to identify a user or make API requests in their name, you need to get another set of credentials (these ones specific to that user): the access token and access secret.[1] To get them, you need to go through the authorization process, which consists of three steps:[2]

  1. Get a request token from the wiki by sending a GET request to Special:OAuth/initiate,[3] signed with the application key and secret, with the callback URL (where the user will be sent after a successful authorization) passed as the oauth_callback query parameter (if you have set a constant URL at registration, the value of the parameter must be oob). If you are successful, the response will be a JSON object with token and key fields - the request token and request secret. (If not, it will have an error field.)
  2. Ask the user to authorize the application by sending them to Special:OAuth/authorize,[4] with the application token and request token passed as query parameters (oauth_consumer_key and oauth_token, respectively). The user will see an authorization dialog with some basic information about the application and the list of grants, and can decide to authorize or cancel.
  3. If the user did choose to authorize, they will be redirected to the callback URL you have given (at registration, or as an URL parameter in step 1). A query parameter called oauth_verifier will contain the verification code that you can use to exchange the request token and secret for the access token and secret. To do this, send a request to Special:OAuth/token[3] which includes the oauth_verifier parameter you just received and is signed with the application token and secret and the request token and secret. The response will contain the access token/secret (in the same format as the request token/secret in step 1).

The access token and secret is what you'll need to sign API requests. The request token and secret is not useful anymore and can be discarded. The access token will remain valid indefinitely, unless the user revokes it. (If you prefer not to store it, you can just repeat the authorization process at any time though.)

Applications which only need minimal privileges (have been registered as User identity verification only) can use /authenticate instead of /authorize in step 2. This works the same way but the user will only see the authorization dialog if they have not authorized this application before; otherwise the authorization will silently succeed.

Chances are whatever language/framework you are using will have a library to support this procedure so you don't have to implement it manually - each step will be a single function call. See below for examples.

Making requests on the user's behalf[edit]

To take advantage of the authorization, requests have to be signed with the application token/secret and access token/secret. When that's successfully done, the wiki will treat the request as if it was made by the authorizing user. Only API requests can be made via OAuth, with one exception (see next section). Certain API modules which would not make sense with OAuth (such as login/logout) or would allow privilege escalation (such as the centralauthtoken API) are disabled.

Applications which need minimal privileges (have been registered as User identity verification only) cannot use the API at all.

Identifying the user[edit]

The OAuth extension includes a custom protocol (similar to OpenID Connect) for authenticating the user. To user this, send a signed OAuth request to Special:OAuth/identify;[3] the response will be a JWT (a signed JSON object) including the name of the user, their central ID (under the key sub) and various other information (such as their user groups and whether they are blocked; also the email address if the application was registered with the right grant type). This is more secure than using the API (e.g. the userinfo module) for authentication, which could be subject to man-in-the-middle attacks; always use this if you need to identify a user! Also, make sure you properly validate the JWT (there are many libraries which can help with that). You should check each of the following: the issuer (iss) matches the domain name of the wiki, the audience (aud) matches your application key, the issued-at time (iat) is in the past and reasonably close to current time, the expiration time (exp) is in the future, the nonce (nonce) matches the one you sent in the request.

Signing requests[edit]

Steps 1 and 3 of the authorization process require signing the request; API requests and Special:OAuth/identify must likewise be signed. The signing process is detailed in section 9 of the OAuth spec, but it is cumbersome to do implement by hand and many libraries are available. You can find code samples and an overview of how to do it by hand in the owner-only consumer documentation. (That is for signing with the consumer token/secret and access token/secret. Modify as appropriate to sign with the consumer token/secret and request token/secret (authorization step 3) or consumer token/secret only (authorization step 1)

Setting up a development environment[edit]

OAuth is now available in your MediaWiki-Vagrant development environment. Add the oauth role, and your wiki will be able to authorize OAuth apps.

$ vagrant roles enable oauth
$ vagrant provision

Once the code is nearly ready, you can register an OAuth application on the real wiki. You will be able to test it with the same user account used for registering, even before it gets reviewed by admins.

If you are creating an application for Wikimedia projects, consider hosting it at Wikimedia Tools, a free tool forge and hosting platform for Wikimedia-related services.

Security benefits and trade-offs[edit]

  • Unlike password-based authentication, the protocol prevents any man-in-the-middle attack even if the wiki does not require HTTPS: all interactions between MediaWiki and the application are signed with either a shared secret (using HMAC-SHA1), or a public key (RSA). HTTPS is still required for certain steps though (for obtaining the shared secret in the second step of authorization when not using RSA, and during app registration).
  • Actions via OAuth happen under the user's name but will be tagged with the application's name as well so rogue applications can be identified. Wiki admins can revoke the application's permissions (and thus bar it from any further action) if needed.
  • The user can revoke the permission of the application to use that specific user account if they don't like how it works or don't trust it anymore. Unlike a password change, this is not disruptive for the user.
  • Sufficiently flexible applications might allow users to circumvent IP blocks (since MediaWiki will see the IP of the application server, not that of the user). This can be handled the same way proxies are, by trusting XFF headers set by the application (see T159889 for some limitations).
  • The application secret must be kept secret. Submitting it to source control or putting it into user-accessible code (such as mobile app or desktop application; even if it is obfuscated) undermines the security model and will result in admins forcefully disabling the application. Exceptions are made for example applications demoing OAuth usage, if they are explicitly labeled as such and request limited rights.

Libraries[edit]

PHP[edit]

Python[edit]

Ruby[edit]

Node.js[edit]

  • passport-mediawiki-oauth - MediaWiki strategy for the Passport auth framework (which can be used effortlessly as a middleware with Express JS and similar frameworks)
  • oauth-fetch-json - library for signing OAuth requests

Go[edit]

Example code[edit]

PHP client without using any libraries[edit]

OAuth Hello World – easy to understand demo application written in PHP without any libraries.

PHP command-line client with RSA keys, using oauthclient-php[edit]

PHP application using classes from the OAuth extension codebase. (TODO convert this to actually use oauthclient-php! Probably just a bunch of use declarations.)

Before Starting:

$ openssl genrsa -out appkey.pem 4096
$ openssl rsa -in appkey.pem -pubout > appkey.pub

Python command-line client using mwoauth[edit]

Python Toolforge tutorial using mwoauth[edit]

See: wikitech:Help:Toolforge/My first Flask OAuth tool

Go command-line client using mrjones/auth[edit]

Before you begin:

$ go get github.com/mrjones/oauth

Full applications using OAuth[edit]

Notes[edit]

  1. With an RSA key the credentials are slightly different. It is assumed that people choosing to use an RSA key know what they are doing, so this tutorial will assume you have chosen the non-RSA option.
  2. This is sometimes called three-legged OAuth flow. In certain circumstances a simpler, one-step alternative (one-legged OAuth) is also available. See owner-only consumers for that.
  3. 3.0 3.1 3.2 Due to a bug you must currently use a non-nice URL such as en.wikipedia.org/w/index.php?title=Special:OAuth/initiate.
  4. Due to another bug you must use a nice URL here, such as en.wikipedia.org/wiki/Special:OAuth/authorize. A bit embarrassing, we know.