Skip kerberos sso authentication in keycloak

user_2343011 0
Viewed 725

In certain cases we need to skip automatic login through Kerberos. According to the documentation this should be done through the parameter ?prompt=login:

prompt - Keycloak supports these settings:

  • login - SSO will be ignored and the Keycloak login page will be always shown, even if the user is already authenticated

This works in most cases (we also use a NTLM waffle implementation) but with Kerberos the user is always signed in automatically.

Any hint or idea why?
Are there alternative ways to force forwarding to the login page?

EDIT: The reason I need to skip the Kerberos authentication is because I need to login with an admin-account where I have to enter username+password.

EDIT2: We are using Keycloak.x version 14.0.0, also applies to version 15.0.2.

spnego keycloak kerberos single-sign-on java
2 Answers

The parameter ?prompt=login will only skip the Cookie authenticator in your authentication flow. Execution of the Cookie authenticator will be marked as attempted but not as successful. So Keycloak will fallback to an alternative authenticator. I am assuming the Kerberos authenticator is configured as an alternative. If this is the case, you will be (automatically) authenticated by the Kerberos authenticator.

If you only need this behaviour for a particular client, you may want to create an additional authentication flow for that client without the Kerberos authenticator. Use Authentication flow overrides to configure the new flow for the client.

user_163573340

I just created a feature-request with a possible solution on the code side.
skip kerberos SSO authentication to use login-form

Might be able to override the default SpnegoAuthenticator with a custom one containing the login parameter handling.
I patched and tested it in a kerberos environment and it worked.

@Override
public void authenticate(AuthenticationFlowContext context) {
// +++ BEGIN CHANGE +++
    AuthenticationSessionModel session = context.getAuthenticationSession();
    Map<String, String> clientNotes = session.getClientNotes();

    if ("login".equals(clientNotes.get("prompt"))) {
        logger.info("skip SPNEGO authenticator because of client requests login prompt: " + clientNotes); //$NON-NLS-1$
        context.attempted();
        return;
    }
// +++ END CHANGE +++

    HttpRequest request = context.getHttpRequest();
    String authHeader = request.getHttpHeaders().getRequestHeaders().getFirst(HttpHeaders.AUTHORIZATION);
    if (authHeader == null) {
        Response challenge = challengeNegotiation(context, null);
        context.forceChallenge(challenge);
        return;
    }
user_23430110
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