The recommended design patterns for implementing authorization and access control within an application include:
1. **Enforce CRUD/FLS**: Always enforce Create, Read, Update, and Delete (CRUD) and Field-Level Security (FLS) permissions for all operations. Use `WITH USER_MODE` for SOQL queries and `AccessLevel.USER_MODE` for Database methods to automatically enforce permissions, or use traditional methods like `isUpdateable()` and `isCreateable()` for upsert operations.
2. **Use "With Sharing" or "Inherited Sharing" Classes**: Use "with sharing" to respect user sharing rules. For flexibility, "inherited sharing" can dynamically apply sharing rules based on the caller's context.
3. **Custom Authorization Logic**: Implement custom authorization models as needed, ensuring access control logic is specific and sound. Validate user roles and permissions before sensitive operations.
4. **Guest User Access**: For community sites or guest user scenarios, document access requirements and enforce CRUD/FLS and sharing rules. Follow Salesforce's recommended patterns for guest user record access.
5. **OAuth Scopes and Permissions**: When using OAuth, request only the minimum permissions necessary. Store sensitive tokens and secrets securely in protected custom settings or metadata.
6. **Avoid "Without Sharing" Unless Justified**: If using "without sharing," include explicit access control checks to prevent unauthorized operations.
7. **Static Resources and Secure Endpoints**: Load static resources from the static resources folder and ensure all callouts use HTTPS. Avoid dynamically loading resources from untrusted sources.
8. **Access Control Validation**: Regularly review and validate access control logic, especially for operations involving sensitive data or elevated privileges.
These patterns ensure robust and secure access control within your application.