Session Layers

There are typically three session layers that can be created when your users log in:

• Application Session Layer: This layer is the session inside your application. Though your application uses Auth0 to authenticate users, your application also tracks that the user has logged in to your application; in a regular web application, for example, you achieve this by storing this information inside a cookie.

• Auth0 Session Layer: Auth0 also maintains a session on the Authorization Server for the user and stores their user information inside a cookie. This layer is used so that the next time a user is redirected to Auth0 for login the user's information will be remembered. This session layer makes the SSO experience possible for inbound SSO implementations.

• Identity Provider Session Layer: When users attempt to sign in using an identity providers such as Facebook or Google, and they already have a valid sign-in (with whichever provider they choose) they will not be prompted again to sign in though they may be asked to give permission to share their information with Auth0 and, in turn, your application.

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Logout in the context of Auth0 implementations is the act of terminating an authenticated session. It is a security best practice to terminate sessions when they’re no longer needed to avoid a potential takeover by unauthorized parties.

Auth0 provides tools to help you give users the ability to log out; this includes options for providing different levels of logout and also determining where the user will land after the logout is complete.

• Application Session Layer Logout: Logging users out of your applications typically results in their application session being cleared, and this should be handled by your application: for the Application Session Layer, there is nothing within your Auth0 tenant that you need to use to facilitate session termination. This will require you to utilize whatever application session stack you are using to clear out any session related information. Note that some of the Auth0 SDKs do provide some support for application sessions; please check the documentation to see if there is any local SDK session removal that needs to be done.

• Auth0 Session Layer Logout: You can log users out of the Auth0 session layer by redirecting them to the Auth0 Logout endpoint so Auth0 can clear the SSO cookie.

  Generally, you clear an Auth0 session by diverting users to the /logout endpoint. However, if you call the Update a User endpoint to reset user attributes (passing values email, email_verified, phone_number, and password), auth0.checkSession does not renew the session, and the user must re-login.

• Identity Provider Session Layer Logout: It is not necessary to log the users out of this session layer, but you can use Auth0 to force the logout if required.

Logging out of your Auth0 Session Layer will require you to redirect the user to https://<{yourCNAME} or {yourTenant}.auth0.com>/oidc/logout - typically performed via use of the appropriate method in the Auth0 SDK for your technology stack. This will clear your Auth0 session. You will also want to add a query parameter for that request called id_token_hint - this parameter should contain a URL that has been pre-registered and protects you against open redirect attacks.

Auth0 only redirects to AllowListed URLs after logout and there are two places you can configure these. The first place you can set this is at your Auth0 tenant level where you can put the set of logout URLs that are shared between all applications. The second place is in the application settings: if you need different redirects for each application, you can allowlist the URLs in your application settings. This allows you to set logout URLs in an application-specific context.

You can set the behavior in cases where a user doesn’t explicitly log out of your application. Auth0 provides session lifetime limits to deal with Auth0 session termination in this scenario.

You can also log the users out of the identity provider session layer. While this is not recommended, for many providers, Auth0 provides this behavior by having you add the federated query parameter to the redirect to /oidc/logout. This redirects the user to their identity provider and logs them out there as well. To learn more about federated logout, review the article Log Users Out of Identity Providers.

• Session Lifetime Limits