Rules

Rules are functions written in JavaScript that are executed in Auth0 as part of the transaction every time a user authenticates to your application. Rules allow you to easily customize and extend Auth0's capabilities. Rules can be chained together for modular coding and can be turned on and off individually.

  • Step 1: An app initiates an authentication request to Auth0.
  • Step 2: Auth0 routes the request to an Identity Provider through a configured connection.
  • Step 3: The user authenticates successfully.
  • Step 4: The user object representing the logged in user is passed through the Rules pipeline, and returned to the app.

Among many possibilities, Rules can be used to:

  • Profile enrichment: query for information on the user from a database/API, and add it to the user profile object.
  • Create authorization rules based on complex logic (anything that can be written in JavaScript).
  • Normalize attributes from different providers beyond what is provided by Auth0.
  • Reuse information from existing databases or APIs for migration scenarios.
  • Keep a white-list of users and deny access based on email.
  • Notify other systems through an API when a login happens in real-time.
  • Enable counters or persist other information. (For information on storing user data, see: Metadata in Rules.)
  • Enable multifactor authentication, based on context (e.g. last login, IP address of the user, location, etc.).

NOTE: You can find more examples of common Rules on Github at auth0/rules.

Rule Syntax

A Rule is a function with the following arguments:

  • user: the user object as it comes from the identity provider. (For a complete list of the user properties, see: User Profile Structure.)
  • context: an object containing contextual information of the current authentication transaction, such as user's IP address, application, location. (A complete list of context properties is available here: Context Argument Properties in Rules.)
  • callback: a function to send back the potentially modified user and context objects back to Auth0 (or an error).

NOTE: Because of the async nature of node.js, it is important to always call the callback function, or else the script will timeout.

Examples

To create a Rule, or try the examples below, go to New Rule in the Rule Editor on the dashboard.

Hello World

This rule will add a hello attribute to all users authenticating through any provider.

function (user, context, callback) {
  user.hello = 'world';
  console.log('===> set "hello" for ' + user.name);
  callback(null, user, context);
}

NOTE: You can add console.log lines for debugging or use the Real-time Webtask Logs Extension.

Add roles to a user

In this example, all authenticated users will get a guest role, but johnfoo@gmail.com will also be an admin:

function (user, context, callback) {
  user.roles = [];
  // only johnfoo is admin
  if (user.email === 'johnfoo@gmail.com') {
    user.roles.push('admin');
  }

  // all users are guest
  user.roles.push('guest');

  callback(null, user, context);
}

At the beginning of the rules pipeline, John's user object will be:

{
  "email": "johnfoo@gmail.com",
  "family_name": "Foo",
  "user_id": "google-oauth2|103547991597142817347"
  //... other properties ...
}

The context object will be:

{
  "clientID": "...client_id_of_the_app...",
  "clientName": "my app",
  "connection": "google-oauth2"
}

After the rule executes, the output that the application will receive is the following user object:

{
  "email": "johnfoo@gmail.com",
  "family_name": "Foo",
  "user_id": "google-oauth2|103547991597142817347",

  //... other props ...

  "roles": ["guest", "admin"]  // NEW PROPERTY ADDED BY THE RULE
}

Properties added in a rule are not persisted in the Auth0 user store. Persisting properties requires calling the Auth0 API.

Deny access based on a condition

In addition to adding and removing properties from the user object, you can return an access denied error.

function (user, context, callback) {
  if (user.roles.indexOf('admin') === -1) {
    return callback(new UnauthorizedError('Only admins can use this'));
  }

  callback(null, user, context);
}

This will cause a redirect to your callback url with an error querystring parameter containing the message you set. (e.g.: https://yourapp.com/callback?error=unauthorized&error_description=Only%20admins%20can%20use%20this)

Error reporting to the app depends on the protocol. OpenID Connect apps will receive the error in the querystring. SAML apps will receive the error in a SAMLResponse.

Debugging

You can add console.log lines in the rule's code for debugging. The Rule Editor provides two ways for seeing the output:

  1. TRY THIS RULE: opens a pop-up where you can run a rule in isolation. The tool provides a mock user and context objects. Clicking TRY will result on the the Rule being run with those two objects as input. console.log output will be displayed too.

  1. REALTIME LOGS: an extension that displays all logs in real-time for all custom code in your account. This includes all console.log output, and exceptions.

  2. DEBUG RULE: similar to the above, displays instructions for installing, configuring and running the webtask CLI for debugging rules. Paste these commands into a terminal to see the console.log output and any unhandled exceptions that occur during Rule execution.

For example:

~  npm install -g wt-cli
~  wt init --container "youraccount" --url "https://sandbox.it.auth0.com" --token "eyJhbGci...WMPGI" -p "youraccount-default-logs"
~  wt logs -p "youraccount-default-logs"
[18:45:38.179Z]  INFO wt: connected to streaming logs (container=youraccount)
[18:47:37.954Z]  INFO wt: webtask container assigned
[18:47:38.167Z]  INFO wt: ---- checking email_verified for some-user@mail.com! ----

This debugging method works for rules tried from the dashboard and those actually running during user authentication.

Caching expensive resources

The code sandbox Rules run on allows storing expensive resources that will survive individual execution.

This example, shows how to use the global object to keep a mongodb connection:

  
  ...

  //If the db object is there, use it.
  if(!global.db){
    return query(global.db,callback); 
  }

  //If not, get the db (mongodb in this case)
  mongo('mongodb://user:pass@mymongoserver.com/my-db',  function (db){
    global.db = db;
    return query(db,callback);
  });

  //Do the actual work
  function query(db,cb){
    //Do something with db
    ...
  });  
  
  ...

Notice that the code sandbox in which Rules run on, can be recycled at any time. So your code must always check global to contain what you expect.

Available modules

For security reasons, the Rules code runs in a JavaScript sandbox based on webtask.io where you can use the full power of the ECMAScript 5 language.

For a list of currently supported sandbox modules, see: Modules Supported by the Sandbox.

Further reading

Suggestions? Typos? Edit this document on GitHub
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