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Chapter 2. Understanding authentication
For users to interact with OpenShift Dedicated, they must first authenticate to the cluster. The authentication layer identifies the user associated with requests to the OpenShift Dedicated API. The authorization layer then uses information about the requesting user to determine if the request is allowed.
2.1. Users
A user in OpenShift Dedicated is an entity that can make requests to the OpenShift Dedicated API. An OpenShift Dedicated User object represents an actor which can be granted permissions in the system by adding roles to them or to their groups. Typically, this represents the account of a developer or administrator that is interacting with OpenShift Dedicated.
Several types of users can exist:
| User type | Description |
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This is the way most interactive OpenShift Dedicated users are represented. Regular users are created automatically in the system upon first login or can be created via the API. Regular users are represented with the |
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Many of these are created automatically when the infrastructure is defined, mainly for the purpose of enabling the infrastructure to interact with the API securely. They include a cluster administrator (with access to everything), a per-node user, users for use by routers and registries, and various others. Finally, there is an |
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These are special system users associated with projects; some are created automatically when the project is first created, while project administrators can create more for the purpose of defining access to the contents of each project. Service accounts are represented with the |
Each user must authenticate in some way to access OpenShift Dedicated. API requests with no authentication or invalid authentication are authenticated as requests by the anonymous system user. After authentication, policy determines what the user is authorized to do.
2.2. Groups
A user can be assigned to one or more groups, each of which represent a certain set of users. Groups are useful when managing authorization policies to grant permissions to multiple users at once, for example allowing access to objects within a project, versus granting them to users individually.
In addition to explicitly defined groups, there are also system groups, or virtual groups, that are automatically provisioned by the cluster.
The following default virtual groups are most important:
| Virtual group | Description |
|---|---|
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| Automatically associated with all authenticated users. |
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| Automatically associated with all users authenticated with an OAuth access token. |
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| Automatically associated with all unauthenticated users. |
2.3. API authentication
Requests to the OpenShift Dedicated API are authenticated using the following methods:
- OAuth access tokens
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Obtained from the OpenShift Dedicated OAuth server using the
<namespace_route>/oauth/authorizeand<namespace_route>/oauth/tokenendpoints. -
Sent as an
Authorization: Bearer…header. -
Sent as a websocket subprotocol header in the form
base64url.bearer.authorization.k8s.io.<base64url-encoded-token>for websocket requests.
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Obtained from the OpenShift Dedicated OAuth server using the
- X.509 client certificates
- Requires an HTTPS connection to the API server.
- Verified by the API server against a trusted certificate authority bundle.
- The API server creates and distributes certificates to controllers to authenticate themselves.
Any request with an invalid access token or an invalid certificate is rejected by the authentication layer with a 401 error.
If no access token or certificate is presented, the authentication layer assigns the system:anonymous virtual user and the system:unauthenticated virtual group to the request. This allows the authorization layer to determine which requests, if any, an anonymous user is allowed to make.
2.3.1. OpenShift Dedicated OAuth server
The OpenShift Dedicated master includes a built-in OAuth server. Users obtain OAuth access tokens to authenticate themselves to the API.
When a person requests a new OAuth token, the OAuth server uses the configured identity provider to determine the identity of the person making the request.
It then determines what user that identity maps to, creates an access token for that user, and returns the token for use.
2.3.1.1. OAuth token requests
Every request for an OAuth token must specify the OAuth client that will receive and use the token. The following OAuth clients are automatically created when starting the OpenShift Dedicated API:
| OAuth client | Usage |
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Requests tokens at |
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Requests tokens with a user-agent that can handle |
<namespace_route>refers to the namespace route. This is found by running the following command:$ oc get route oauth-openshift -n openshift-authentication -o json | jq .spec.host
All requests for OAuth tokens involve a request to <namespace_route>/oauth/authorize. Most authentication integrations place an authenticating proxy in front of this endpoint, or configure OpenShift Dedicated to validate credentials against a backing identity provider. Requests to <namespace_route>/oauth/authorize can come from user-agents that cannot display interactive login pages, such as the CLI. Therefore, OpenShift Dedicated supports authenticating using a WWW-Authenticate challenge in addition to interactive login flows.
If an authenticating proxy is placed in front of the <namespace_route>/oauth/authorize endpoint, it sends unauthenticated, non-browser user-agents WWW-Authenticate challenges rather than displaying an interactive login page or redirecting to an interactive login flow.
To prevent cross-site request forgery (CSRF) attacks against browser clients, only send Basic authentication challenges with if a X-CSRF-Token header is on the request. Clients that expect to receive Basic WWW-Authenticate challenges must set this header to a non-empty value.
If the authenticating proxy cannot support WWW-Authenticate challenges, or if OpenShift Dedicated is configured to use an identity provider that does not support WWW-Authenticate challenges, you must use a browser to manually obtain a token from <namespace_route>/oauth/token/request.
