Authenticating to the Che server using OpenID

OpenID authentication on the Che server implies the presence of an external OpenID Connect provider and has the following main steps:

Authenticate the user through a JWT token that is retrieved from an HTTP request or, in case of a missing or invalid token, redirect the user to the Keycloak login page.
Send authentication tokens in an Authorization header. In limited cases, when it is not possible to use the Authorization header, the token can be sent in the token query parameter. Example: OAuth authentication initialization.
Compose an internal subject object that represents the current user inside the Che server code.

The only supported and tested OpenID provider is Keycloak.

Procedure

To authenticate to the Che server using OpenID authentication:

Request the OpenID settings service where clients can find all the necessary URLs and properties of the OpenId provider, such as jwks.endpoint, token.endpoint, logout.endpoint, realm.name, or client_id returned in the JSON format.

The service URL is <che.host>:<che.port>/api/keycloak/settings, and it is only available in the Che multi-user mode. The presence of the service in the URL confirms that the authentication is enabled in the current deployment.

Example output:

{
    "che.keycloak.token.endpoint": "http://172.19.20.9:5050/auth/realms/che/protocol/openid-connect/token",
    "che.keycloak.profile.endpoint": "http://172.19.20.9:5050/auth/realms/che/account",
    "che.keycloak.client_id": "che-public",
    "che.keycloak.auth_server_url": "http://172.19.20.9:5050/auth",
    "che.keycloak.password.endpoint": "http://172.19.20.9:5050/auth/realms/che/account/password",
    "che.keycloak.logout.endpoint": "http://172.19.20.9:5050/auth/realms/che/protocol/openid-connect/logout",
    "che.keycloak.realm": "che"
}

The service allows downloading the JavaScript client library to interact with the provider using the <che.host>:<che.port>/api/keycloak/OIDCKeycloak.js URL.

Redirect the user to the appropriate provider’s login page with all the necessary parameters, including client_id and the return redirection path. This can be done with any client library (JS or Java).
When the user is logged in to the provider, the client side-code is obtained, and the JWT token has validated the token, the creation of the subject begins.

The verification of the token signature occurs in two main steps:

Authentication: The token is extracted from the Authorization header or from the token query parameter and is parsed using the public key retrieved from the provider. In case of expired, invalid, or malformed tokens, a 403 error is sent to the user. The use of the query parameter should be minimised because its support may be limited or removed in future versions.

If the validation is successful, the parsed form of the token is passed to the environment initialization step:
Environment initialization: The filter extracts data from the JWT token claims, creates the user in the local database if it is not yet present, and constructs the subject object and sets it into the per-request EnvironmentContext object, which is statically accessible everywhere.

If the request was made using only a machine token, the following single authentication filter is used:

org.eclipse.che.multiuser.machine.authentication.server.MachineLoginFilter: The filter finds the user that the userId token belongs to, retrieves the user instance, and sets the principal to the session. The Che server-to-server requests are performed using a dedicated request factory that signs every request with the current subject token obtained from the EnvironmentContext object.

Providing user-specific data

Since Keycloak may store user-specific information (first and last name, phone number, job title), there is a special implementation of the ProfileDao that can provide this data to consumers. The implementation is read-only, so users cannot perform create and update operations.

Obtaining the token from credentials through Keycloak

Clients that cannot run JavaScript or other clients (such as command-line clients or Selenium tests) must request the authorization token directly from Keycloak.

To obtain the token, send a request to the token endpoint with the username and password credentials. This request can be schematically described as the following cURL request:

$ curl --data "grant_type=password&client_id=<client_name>&username=<username>&password=<password>" \
  http://<keyckloak_host>:5050/auth/realms/<realm_name>/protocol/openid-connect/token

The Che dashboard uses a customized Keycloak login page and an authentication mechanism based on grant_type=authorization_code. It is a two-step authentication process:

Logging in and obtaining the authorization code.
Obtaining the token using this authorization code.

Obtaining the token from the OpenShift token through Keycloak

When Che has been installed on OpenShift using the Operator, and the OpenShift OAuth integration has been enabled (it is by default), then the Che authentication token of a user can also be retrieved from the user OpenShift token.

To do this, send a request to the token endpoint that can be schematically described as the following cURL request:

$ curl -X POST -d "client_id=<client_name>" \
--data-urlencode "grant_type=urn:ietf:params:oauth:grant-type:token-exchange" \
-d "subject_token=<user_openshift_token>" \
 -d "subject_issuer=<openshift_identity_provider_name>" \
 --data-urlencode "subject_token_type=urn:ietf:params:oauth:token-type:access_token" \
 http://<keyckloak_host>:5050/auth/realms/<realm_name>/protocol/openid-connect/token

The default values for <openshift_identity_provider_name> are:

On OpenShift 3.11: openshift-v3
On OpenShift 4.x: openshift-v4

<user_openshift_token> is the token retrieved by the end-user with the command:

$ oc whoami --show-token

Before using this token exchange feature for an end user, the end user should have logged in at least once interactively to the Che Dashboard through the OpenShift login page. This is required to properly link OpenShift and Keycloak user accounts, and set the required user profile information (email, first and last names).