OpenStack Keystone is an open-source identity service, and the Keystone API is the interface through which users can interact with and manage identity-related operations in an OpenStack cloud environment. It provides authentication, authorization, and service catalog services for other OpenStack services, enabling secure access to resources and managing user identities and credentials.
Here are some key aspects of the Keystone API:
- Authentication: Keystone handles user authentication and verification. It supports various authentication methods, such as username/password, token-based authentication, and external authentication mechanisms like LDAP or OAuth. Users can authenticate themselves using their credentials, and Keystone generates an authentication token upon successful validation.
- Authorization: Once authenticated, Keystone performs authorization checks to determine the privileges and access rights of the user. It enforces policies and access controls to ensure that users can only perform operations for which they have appropriate permissions. Keystone supports role-based access control (RBAC), where users are assigned roles that define their level of access to resources.
- Service Catalog: Keystone maintains a catalog of services available in the OpenStack environment. It provides information about the endpoints and capabilities of various services, allowing users and other OpenStack components to discover and interact with them. The service catalog helps users locate and access the specific services they need.
- Domains, Projects, and Users: Keystone organizes resources using domains, projects, and users. Domains represent administrative boundaries and can be used to segregate resources and define separate policies. Projects, also known as tenants, group resources for a particular purpose or project. Users are associated with projects and have specific roles within those projects, determining their level of access.
- Tokens: After successful authentication, Keystone issues a token that represents the user’s session. Tokens have an expiration time and can be used to access other OpenStack services during their validity period. Tokens are used to authorize subsequent API requests made by the user without needing to re-authenticate for each request.
- Identity Federation: Keystone supports identity federation, allowing users from external identity providers (IdPs) to access resources in the OpenStack environment. It enables Single Sign-On (SSO) capabilities by establishing trust relationships with external IdPs and mapping their user identities to Keystone users.
- Integration with Other OpenStack Services: Keystone serves as a central identity service for other OpenStack services. It integrates with services like Nova (compute), Neutron (networking), Glance (image), Cinder (block storage), and more, providing them with authentication and authorization services. Other services rely on Keystone for user management and access control.
The Keystone API is RESTful and supports HTTP methods such as GET, POST, PUT, and DELETE. It follows the OpenStack API guidelines and leverages the JSON format for data representation. API endpoints are typically accessed using the Keystone service endpoint URL. Overall, the Keystone API plays a critical role in ensuring secure access and managing user identities and permissions within an OpenStack cloud environment, enabling users to interact with various OpenStack services.