Keystone is the identity service component of OpenStack, which provides authentication, authorization, and token-based access control for the various services within an OpenStack deployment. The Keystone service issues security tokens called “keystone tokens” that are used to authenticate and authorize access to resources in an OpenStack environment.
A keystone token is a digital credential that represents the identity and permissions of a user or service in the OpenStack system. It contains information such as the user or service’s ID, name, and role assignments. Tokens are used to authenticate users or services when they interact with other OpenStack services like Nova (compute), Neutron (networking), Cinder (block storage), etc.
Here are some key aspects of keystone tokens:
- Token Format: Keystone tokens are typically represented using the JSON Web Token (JWT) format. JWT is an open standard for representing claims securely between two parties. It consists of three parts: a header, a payload, and a signature.
- Token Lifecycle: Keystone tokens have a defined lifecycle, including an expiration time. When a user or service authenticates with Keystone, a token is issued with a specific expiration time. The token can be used to make API requests to other OpenStack services until it expires. After expiration, the token becomes invalid, and the user or service needs to obtain a new token by authenticating with Keystone again.
- Authorization: Keystone tokens also contain information about the user or service’s role assignments and project memberships. These role assignments determine what actions the user or service can perform on specific resources within the OpenStack environment. When a token is presented to an OpenStack service, the service verifies the token’s validity and checks the user’s roles and permissions before allowing or denying access to the requested resource.
- Token Validation: OpenStack services can validate keystone tokens by communicating with the Keystone service directly or by using a token validation middleware. The middleware caches validated tokens to improve performance and reduce the load on the Keystone service.
- Revocation: Keystone supports token revocation, which allows administrators to invalidate a token before its expiration time. Revocation can be triggered if, for example, a user’s permissions change or if the user’s account is compromised. Revoked tokens are no longer considered valid and cannot be used to access OpenStack resources.
- Scope: Keystone tokens can have different scopes. A token can be scoped to a specific project, allowing access only to resources within that project, or it can be unscoped, allowing access to resources across multiple projects.
Overall, keystone tokens play a crucial role in enabling secure authentication and authorization within an OpenStack environment. They provide a standardized way for users and services to prove their identities and access resources while enforcing role-based access control policies.