Non-interactive SSO

The non-interactive SSO authentication flow

Non-interactive SSO authentication flow is very much similar to its interactive counterpart, but, as the name suggests, it doesn’t require any interaction from the user.

When activated, the Non-interactive switch changes the behaviour of the SSO authentication. The user won’t see any login popup, but the whole process will be executed in the background.

Triggering non-interactive SSO flow

One of the crucial differences with the interactive flow is that the authentication must be triggered either externally, or automatically by using the auto-non-interactive-sso attribute — which is by far the simplest way.

Triggering externally

If you chose not to enable automatic SSO login by adding auto-non-interactive-sso="true", you’ll need to add some code to the page that triggers that process after the page has finished loading. That code should contain a call to the nonInteractiveSsoLogin() method of the <comentario-comments> HTML element.

Please be mindful of the following:

  1. Non-interactive SSO must be enabled and configured in the domain properties; otherwise, a rejected Promise with the string Non-interactive SSO is not enabled. will be returned.
  2. Comentario initialisation has to finish before nonInteractiveSsoLogin() can be called; otherwise, a rejected Promise with the string Initialisation hasn't finished yet. will be returned.

Because of the second item, the only reliable way to trigger SSO login externally is disabling automatic initialisation, then using the Promise returned by the main() method to synchronise with the init process.

Below is an example of how it might look like:

<comentario-comments id="comments" auto-init="false"></comentario-comments>
    window.onload = () => {
        const cc = document.getElementById('comments');
        cc.main().then(() => cc.nonInteractiveSsoLogin());

See below for more details about the nonInteractiveSsoLogin() method.

Login redirect in iframe

After the SSO login flow is triggered, Comentario will create a hidden iframe and point it to the SSO URL, providing the following two query parameters:

  • token, a value consisting of 64 hexadecimal digits representing a user session token, and
  • hmac, a value consisting of 64 hexadecimal digits, which is a SHA256 HMAC signature of the token. The signature is created using the shared SSO secret.

Callback endpoint

The SSO identity provider has to authenticate the user non-interactively (for instance, using session cookies) and, once succeeded, redirect the user to Comentario’s callback URL (<Comentario base URL>/api/oauth/sso/callback), adding the following two query parameters to it:

  • payload — hexadecimal-encoded payload describing the user (see below), and
  • hmac — SHA256 HMAC signature of the payload, also created using the shared SSO secret.

Comentario will redeem the login token and remove the hidden iframe.


The payload value holds a JSON-formatted user data, providing the following properties:

  • token, which must be the same value that was passed during the initial SSO call;
  • email, specifying the user’s email address;
  • name, providing the user’s full name;
  • photo, an optional user avatar URL.

For example:

  "token": "0a3577213987d24993ef20d335f7b9769c1d1719b40767c6948d6c3882403a96",
  "email": "",
  "name": "John Doe"

nonInteractiveSsoLogin() method



Return value


The return value can be used to check the outcome of the SSO login process.


  • options optional — Object containing additional options:
    • force: boolean — If true, the flow will be triggered even if the user is already logged in, in which case a logout sequence will be executed first. If false, the call is a no-op in the case the user is signed in.

See also