Configure OIDC Back-Channel Logout

OIDC Back-Channel Logout is available for all Enterprise plan customers. You should check the OIDC standard /.well-known/* metadata endpoint to determine if your application meets the requirements.

GET https://acme.eu.auth0.com/.well-known/openid-configuration

HTTP 200
{ ..., "backchannel_logout_supported": true, 
  "backchannel_logout_session_supported": true }

Back-Channel Logout URLs are called on publicly-exposed endpoints and must adhere to certain restrictions:

1. You must use the HTTPS protocols. Unencrypted HTTP or other protocols are not permitted.

2. You must not use Auth0 subdomains. Some Auth0 subdomains are:

   • auth0.com

   • auth0app.com

   • webtask.io

   • webtask.run

3. We do not recommend using IP addresses without domains. IP addresses must be public IPs to use Back-Channel Logout. IP addresses from internal, reserved, or loopback ranges are not permitted.

Register your application to receive Logout Tokens via Auth0 Dashboard or Management API.

PATCH /api/v2/clients/{id}
"oidc_logout": {
  "backchannel_logout_urls": ["http://acme.eu.auth0.com/events"]
}

PATCH https://acme.eu.auth0.com/api/v2/clients/{id}
{
  "oidc_logout": {
    "backchannel_logout_urls": []
  }
}

Once you have configured Back-Channel Logout via the Auth0 Dashboard or Management API, configure your application to use the service based on the technology or framework.

1. Implement end-user authentication according to your application type. 

   1. End-users should be able to log in to the application, and a session should be created. 

   2. An ID token should be issued from Auth0 and should be accessible in the application backend for further processing.

2. Extend the login process to save the sid and, optionally, sub claims after the ID token is validated. 

   1. These claims must be saved against the current application session. 

   2. The session management functions should be able to retrieve a specific session by the sid value.

3. Configure the Back-Channel Logout endpoint:

   1. The endpoint must process only HTTP POST requests.

   2. Extract the logout_token parameter and validate it as a regular JWT according to the spec.

   3. Verify that the token contains an events claim with a JSON object value and a member named http://schemas.openid.net/event/backchannel-logout.

   4. Verify that the token contains the sid and/or sub claims.

   5. Verify that the token does NOT contain the nonce claim. This is required to prevent abuse by distinguishing the Logout Token from the ID token.

   6. Once the token is validated, retrieve the session corresponding to the received sid and/or sub value and terminate it. The exact application session termination process depends on the implementation details. For example, this event may need to be communicated to the front-end.

Coded token payload:

POST /backchannel-logout HTTP/1.1
Host: rp.example.org
Content-Type: application/x-www-form-urlencoded

logout_token=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6ImdwY3ZFT0FPREE2T3pXRmw3ODVxbCJ9.eyJpc3MiOiJodHRwczovL2FydGV4LWRldi5ldS5hdXRoMC5jb20vIiwic3ViIjoiYXV0aDB8NjAyZTkzZGI4M2ZhNmYwMDc0OWEyM2U2IiwiYXVkIjoiVHVoTkx2N3VsWEQzUmZ5TGxTTWJPdnN6endKSkZQcE8iLCJpYXQiOjE2OTgxNjA5MjgsImV4cCI6MTY5ODE2MTA0OCwianRpIjoiNDRhOTEyMTUtZGZiNC00ZGZlLWExZWItZmNhZmE5MTFkZWJhIiwiZXZlbnRzIjp7Imh0dHA6Ly9zY2hlbWFzLm9wZW5pZC5uZXQvZXZlbnQvYmFja2NoYW5uZWwtbG9nb3V0Ijp7fX0sInRyYWNlX2lkIjoiODFiMzM2YTk0YTRhNTcwNyIsInNpZCI6IjM3NVVJcF9JRDVtQ1RDbEllQkVIcFhmR3dxNTF0Rl9MIn0.aEoAL_U-EPlf3f7Fup-bu7Yv0S0GOnrkL8Njd6j6UNqZcr5VrWWFf3CWvkRi7Cm6wMgU2qIMhb7643ca8-ajR7zHlMu0Z3r-gfd2D1xudKLyUSC3v2D5WJZz5I8xMZ_LWtIN2W3l4SQFO9MgK_7F3x0WIWXo9KPC9tgOaOLPnsiv__MutM1ZakoCsJPddl5gVM4TYtHOue6WM7SOXZNa3SSiv57YQOX2KNCL7sWmZp_J1OXKy8lsgkNFqiOVwu39p4sgjKYEXQU0G-I0yY_aeNbnlnxFG6OuxaDt_zwg6AvKglLSNGqrrvzy4GsYJi5HMGZ1GsSs7rQLg7Iuu6JM-A

Decoded token payload:

{
  "iss": "https://artex-dev.eu.auth0.com/",
  "sub": "auth0|602e93db83fa6f00749a23e6",
  "aud": "TuhNLv7ulXD3RfyLlSMbOvszzwJJFPpO",
  "iat": 1698160928,
  "exp": 1698161048,
  "jti": "44a91215-dfb4-4dfe-a1eb-fcafa911deba",
  "events": {
    "http://schemas.openid.net/event/backchannel-logout": {}
  },
  "trace_id": "81b336a94a4a5707",
  "sid": "375UIp_ID5mCTClIeBEHpXfGwq51tF_L"
}

• HTTP 200:  Confirms user logout from the specific application.

• HTTP 400: Indicates an incorrect request. The request is not understood or the token failed validation. Auth0 records the problem in tenant logs but does not attempt further requests for this specific session.

If your application did not receive a logout request after a logout event.

1. Make sure your application has a Back-Channel Logout URL registered in Auth0 Dashboard.

2. Ensure the Back-Channel Logout URL is reachable from the Auth0 tenant.

3. Ensure a valid session is established. The end-user must log in to your specific application via Auth0.

   Applications receive logout events only if end-users log in to that specific app with Auth0.  If the end-user logs in to other applications, logout events do not trigger.

4. Check Auth0 tenant logs for messages about unsuccessful logout message delivery.

5. Make sure the logout is triggered via the standard logout endpoint. Other events do not trigger the logout events.

6. If possible, check for blocked requests on the web server and/or application firewall logs.

This feature will be gradually released to all tenants starting 3 October 2023. You may still receive tenant log event codes sslo for oidc_backchannel_logout_succeeded or fslo for oidc_backchannel_logout_failed.

If the transaction still fails with a 400 error:

1. Check if the token is a standard base64-encoded JWT. Some web servers may truncate long parameters. To learn more, read Signing Algorithms.

2. If possible, capture a token and verify that it’s a JWT. Use a verified source, like JWT.IO.

3. Make sure the verification function fetches the tenant signing key dynamically via JSON Web Key Sets (JWKS).

   We do not recommend hardcoding a static key. If your configuration requires the static key to be hardcoded, ensure the configuration contains the latest public key from the Auth0 tenant.

Auth0 will wait five seconds for the application OIDC Back-Channel Logout URL to respond. After this time, it will record a "Failed OIDC Back-Channel Logout request" in the tenant logs with an empty response description.

• Check Login and Logout Issues
• Log Users Out of Auth0 with OIDC Endpoint
• Log Users Out of Applications
• Log Users Out of Identity Providers