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Custom Extension and SPI on Keycloak ​

A custom extension in Keycloak is a tailored implementation that extends or modifies the platform’s behavior by leveraging its modular architecture. This involves developing your own custom provider or integrating one from an external source that connects with Keycloak's Service Provider Interfaces (SPI).

Custom extensions enable you to, but are not limited to:

  • Add new features
  • Modify existing functionality
  • Integrate with external systems
  • Customize user experience

These extensions are typically developed in Java, packaged as JAR files, and deployed to your Keycloak instance.

For detailed implementation guidance and how to upload, update, or delete your custom extensions on Cloud-IAM, see the Custom Extensions How-To Guide.

Examples of common custom extensions using Keycloak SPIs ​

  • Custom Login Flows: Build login processes that integrate with external authentication providers or enforce specific policies.
  • Custom Authenticators: Create authenticators to verify user credentials against external data sources or multi-factor authentication services.
  • Custom Authorization Providers: Implement authorization logic that queries external permission systems or enforces complex access rules.
  • Custom Themes: Develop custom UI themes to match your organization's branding and improve user experience.

By leveraging custom extensions, you gain granular control over your Keycloak deployment, ensuring it fits perfectly within your environment and fulfills specialized use cases.

Best Practices and Considerations for Custom Extensions ​

1. Compatibility ​

  • Ensure your custom extensions are compatible with the specific Keycloak version used in your Cloud-IAM deployment.
  • New Keycloak releases may introduce breaking changes, so always test your extensions thoroughly before deploying to production.

2. Security ​

  • Avoid deploying untrusted or experimental code directly in production environments.
  • Follow security best practices to prevent vulnerabilities within your custom extensions.
  • Rigorously validate all external inputs and interactions to safeguard against attacks.

3. Performance ​

  • Keep your extensions optimized to avoid negatively impacting authentication and authorization workflows.
  • Monitor the resource consumption and performance impact of your extensions on the Keycloak server.

4. Maintainability ​

  • Document your extension’s purpose, configuration, and dependencies clearly.
  • Use version control and CI/CD pipelines to manage the lifecycle and updates of your custom extensions effectively.

5. Extension Behavior ​

  • Custom code can introduce unexpected behaviors or conflicts if not carefully managed.
  • Be aware of potential class loading issues, especially when relying on Keycloak internal dependencies — proper MANIFEST.MF configuration is essential.
  • Regularly maintain and update your extensions to prevent incompatibility with newer Keycloak versions.

External resources ​