5 min to read

Deep Dive into OpenStack Keystone

Understanding OpenStack's Identity Service

Featured image

Image Reference link


Understanding OpenStack Keystone

Keystone is OpenStack's identity service that provides centralized authentication and authorization for all OpenStack services. It manages users, projects, and their access to various OpenStack resources through a token-based authentication system.

What is Keystone?

The Identity Management Service

Keystone serves as the central identity service in OpenStack, providing essential functionality:

  • Authentication: Verifies user identity and credentials
  • Authorization: Manages access control and permissions
  • Service Catalog: Maintains service endpoints and URLs
  • Token Management: Issues and validates access tokens

As the security backbone of OpenStack, Keystone ensures secure access to cloud resources while maintaining multi-tenancy and role-based access control.

graph LR A[OpenStack Keystone] A --> B[Core Services] A --> C[Identity Management] A --> D[Access Control] A --> E[Service Integration] B --> B1[Identity Backend] B --> B2[Token Backend] B --> B3[Policy Backend] B --> B4[Catalog Backend] C --> C1[Users & Groups] C --> C2[Projects] C --> C3[Domains] D --> D1[Roles] D --> D2[Permissions] D --> D3[Policies] E --> E1[Service Endpoints] E --> E2[API Integration] E --> E3[Token Validation] style A stroke:#333,stroke-width:1px,fill:#f5f5f5 style B stroke:#333,stroke-width:1px,fill:#a5d6a7 style C stroke:#333,stroke-width:1px,fill:#64b5f6 style D stroke:#333,stroke-width:1px,fill:#ffcc80 style E stroke:#333,stroke-width:1px,fill:#ce93d8


Keystone Architecture and Components

Keystone employs a modular architecture with multiple backend services that work together to provide comprehensive identity management. This design enables flexible authentication methods and robust access control across the OpenStack cloud.

Core Components

Component Role Description
Identity Backend User Management
  • Manages user and group authentication
  • Supports LDAP and SQL database integration
  • Handles user credentials and profiles
  • Provides identity verification services
Token Backend Session Management
  • Issues temporary access tokens
  • Manages token lifecycle
  • Handles token validation
  • Supports token revocation
Policy Backend Access Control
  • Manages role-based access control
  • Defines access policies
  • Enforces permission rules
  • Handles authorization decisions
Catalog Backend Service Management
  • Maintains service endpoints
  • Manages service URLs
  • Handles service discovery
  • Provides endpoint information

Authentication Flow

sequenceDiagram participant User as "User/Service" participant Keystone as "Keystone" participant Service as "OpenStack Service" User->>Keystone: Authentication Request Keystone->>Keystone: Validate Credentials Keystone-->>User: Issue Token User->>Service: Request with Token Service->>Keystone: Validate Token Keystone-->>Service: Token Valid Service-->>User: Service Response

Key Concepts

Identity Management Concepts

Keystone manages several key concepts:

  • Domains: Top-level containers for users, groups, and projects
  • Projects: Resource isolation units (formerly tenants)
  • Users & Groups: Individual accounts and collections
  • Roles: Access control definitions
  • Tokens: Temporary access credentials
  • Endpoints: Service access points

These concepts work together to provide comprehensive identity and access management.


Access Control and Authorization

Keystone provides robust access control mechanisms through role-based access control (RBAC) and policy-based authorization. This enables fine-grained control over resource access while maintaining security and compliance.

Role-Based Access Control

Component Description Use Cases
Roles Define access permissions for users and groups
  • Admin access
  • Developer access
  • Read-only access
Projects Isolate resources and manage access
  • Resource isolation
  • Multi-tenant environments
  • Project-based access
Domains Group related resources and users
  • Organization separation
  • Department isolation
  • Resource grouping

Service Integration

Service Integration Points

Keystone integrates with various OpenStack services:

  • Nova Integration: Manages compute service access
  • Neutron Integration: Controls network service access
  • Glance Integration: Handles image service access
  • Cinder Integration: Manages storage service access

This integration ensures consistent authentication and authorization across all OpenStack services.


Usage and Best Practices

Effective use of Keystone requires understanding its capabilities and implementing appropriate security practices. Here are key considerations and best practices for utilizing Keystone effectively.

Security Strategies

Strategy Description Benefits
Role Management Implement least privilege principle
  • Enhanced security
  • Reduced risk
  • Better control
Token Security Manage token lifecycle and security
  • Secure access
  • Session control
  • Access tracking
Policy Management Define clear access policies
  • Consistent access
  • Clear permissions
  • Audit compliance

Implementation Guidelines

Best Practices

For effective Keystone implementation:

  • Security Planning: Implement comprehensive security measures
  • Role Design: Create clear role hierarchies
  • Token Management: Configure appropriate token lifetimes
  • Monitoring: Track authentication and access patterns

Following these guidelines helps ensure secure and efficient identity management.


Key Points

💡 Keystone Essentials
  • Core Functionality
    - Centralized authentication and authorization
    - Role-based access control
    - Service endpoint management
    - Token-based security
  • Architecture
    - Modular backend design
    - Flexible authentication methods
    - Comprehensive policy engine
    - Service catalog management
  • Key Features
    - User and group management
    - Project and domain isolation
    - Token-based authentication
    - Service endpoint discovery


References