Casbin is an authorization library that provides a model-based engine for enforcing access control across diverse application environments. It decouples authorization logic from application code by using a configuration-driven approach, allowing developers to define access rules and evaluation logic independently. The system supports a wide range of access control models, including role-based, attribute-based, and relationship-based patterns, which are evaluated at runtime to determine if a subject is permitted to perform an action on a resource.
The project distinguishes itself through a highly modular architecture that includes adapter-based storage abstraction, enabling the engine to connect to various persistent backends for policy management. It supports complex, context-aware policy execution by allowing developers to inject custom functions for domain-specific matching and validation. Furthermore, the engine handles hierarchical role resolution and provides mechanisms for aggregating multiple policy outcomes, such as allow-override or deny-override, to resolve conflicting permissions.
The platform covers a broad capability surface, including middleware integration for web frameworks, API gateways, and service mesh architectures. It offers extensive tooling for policy administration, observability, and performance optimization, such as result caching and asynchronous execution. The system also supports multi-tenancy through domain-aware authorization and provides programmatic interfaces for automating policy updates and lifecycle management.
The library is designed for integration into existing stacks, offering middleware components and support for distributed deployments to ensure consistent authorization state across multiple service instances.
