If you are having issues logging in to Keycloak, you might receive the code_to_token_error. This error occurs when the token used in authentication is missing. The keycloak server will try to get a new token using the request parameter ‘grant_type’, which defaults to zero. Then it will need to generate a new nonce value, which must be hard to guess, and send it to the client.

KC_RESTART token not being present error

The KC_RESTART token not being available error can occur when the client does not have the right authentication method for the website. This error usually indicates that the access token that the client used is invalid. In this case, the client should reauthenticate. To do this, the client should use the /login/refreshToken URL.


Redirect from Keycloak with an auth code

Authenticating users is tricky when working with public applications secured with Keycloak. In such cases, users must log in through a browser, which can be tricky for command-line applications. Luckily, there’s an easy way around this: you can copy the authentication token and pass it to a CLI command instead of using the browser’s login mechanism. Then, you can use that token to authenticate users via the authorization server’s web page.

You’ll need to configure Rancher to support Keycloak’s OIDC or SAML protocol. You must also enable HTTPS/SSL on your Keycloak server. If you don’t see the IdP login page, make sure to disable popup blockers on your browser. Once you’ve done that, you can sign in using your Keycloak login. Make sure you provide your secret when prompted.


If you’re using Keycloak with a web application, you should enable auto-detect-bearer-only. It will redirect unauthenticated users to a login page on your website. This feature is useful for applications that use SOAP or REST clients to access your web application. Then, you can enable basic authentication by enabling enable-basic-auth in the Keycloak configuration. You’ll need a secret to use this feature, and you should configure it in the Keycloak administration console.

If you’re using Keycloak with group-based authorization, you can use the OIDC Auth Provider. This will populate the X-Forwarded-Groups header with the appropriate authorization code. You can also use Keycloak’s group management tree.

If you have an authorization code, your client application should use this to authenticate with your keycloak server. It can also use the OIDC Authorization Code Flow to secure your application’s HTTP endpoints. If the authentication is successful, you should send the user to the OIDC provider and exchange their authorization code. In return, you’ll receive an ID token or access token from the OIDC provider.

If a user rejects an authorization request, you should provide a human-readable error description. The human-readable error description should be suitable for developers and should not contain backslash, double quotes, or hex codes. The URL you receive must match the original request to avoid cross-site request forgery.

How to prevent

Sometimes when connecting to a Keycloak server, you’ll receive a code-to-token-error message. This is caused by a security flaw in the Keycloak protocol. Fortunately, there are ways to avoid getting this error.