How Cedar Works
Cedar is an authorization policy language and evaluation engine designed to enforce fine-grained permissions in applications and agent tool use. It operates by decoupling authorization logic from business logic, allowing developers to preface requests with authorization checks before executing operations. When a request is made, Cedar evaluates whether the request should be allowed or denied based on predefined policies, entities, and context. If the decision is allow, the operation proceeds; if denied, an error is returned. This separation ensures that security teams can update permissions without modifying application code, reducing coordination overhead in distributed systems.
Cedar policies are structured around four core elements: principals, actions, resources, and context. A principal represents the entity making the request, such as a user or service. An action defines the operation being requested, like viewing a photo or reading a record. A resource is the target of the action, such as a photo or a document. Context includes transient data like the request timestamp, IP address, or authentication method, which can influence authorization decisions. For example, a policy might restrict access to HR records to employees from specific IP addresses or require multi-factor authentication for administrative actions.
Entities in Cedar are application-specific data types that the authorization engine uses to evaluate requests. These include principals, resources, actions, and their associated attributes. For instance, a request to view a photo might involve checking whether the user belongs to a group with viewing permissions and whether the photo belongs to an album the user has access to. The engine requires access to these entities and their attributes to make accurate decisions. Contextual data, such as time or location, is also provided during evaluation to ensure policies account for dynamic conditions.
Cedar uses a schema to define the structure of entities, actions, and context, ensuring policies are validated against a consistent model. This design helps prevent misconfigurations by ensuring policies align with the intended application logic. For example, a media-sharing application might define users, nested groups, photos, and albums in its schema, along with actions like viewing or commenting. The schema also enforces attribute consistency, such as requiring a user to have a name or an HR record to include a department.
The evaluation process in Cedar is dynamic and real-time. When a request is made, the engine retrieves the relevant policies, entities, and context, then evaluates them to produce an allow or deny decision. Policies are written as rules with conditions that assess attributes of principals, resources, and context. Cedar supports logical operators (AND, OR, NOT) and comparison operators for integers, enabling fine-grained control. This flexibility ensures policies can adapt to evolving business rules without system downtime.
Cedar’s design emphasizes scalability and performance. Policies are indexed for quick retrieval, and the evaluation engine is optimized for low-latency, real-time decisions. Additionally, Cedar’s policies are designed to be human-readable, facilitating collaboration between technical and non-technical stakeholders.
Use Cases
Cedar is primarily used to enforce authorization in custom applications and as the policy language for managed authorization services. In custom applications, Cedar allows developers to embed authorization logic directly into their codebase, ensuring that only authorized users can access specific resources or perform actions. For example, a social media platform might use Cedar to restrict photo viewing to members of a user’s friends group while allowing comments only from verified accounts. This granular control is achieved without coupling authorization logic with business logic, simplifying maintenance and updates.
Beyond custom applications, Cedar serves as the foundation for several managed authorization services. These services host Cedar policies centrally and provide APIs for managing permissions and evaluating requests on behalf of multiple applications. This approach eliminates the need for each application to implement its own authorization engine, reducing operational complexity and improving consistency across systems. For instance, Amazon Verified Permissions is a managed service built on Cedar, offering scalable and secure authorization for AWS customers without requiring them to manage infrastructure.
Cedar supports common authorization models such as Role-Based Access Control (RBAC) and Attribute-Based Access Control (ABAC). In RBAC, access is granted based on the roles assigned to users, such as administrator or editor. Cedar extends this model by incorporating attributes, enabling ABAC scenarios where decisions depend on dynamic conditions like time, location, or user attributes. For example, a policy might grant access to financial records only to auditors during business hours from company-owned devices.
Agents often require fine-grained permissions to interact with resources securely. Cedar’s policy language allows administrators to define precise rules for agent behavior, such as restricting an AI assistant to access only specific datasets or requiring approval for sensitive operations. This capability is particularly valuable in environments where automation and delegation are critical, such as DevOps pipelines or customer support bots.
Cedar is also employed in scenarios requiring compliance with regulatory frameworks. For example, a healthcare application might use Cedar to enforce HIPAA requirements by ensuring that patient records are accessible only to authorized personnel under specific conditions. Similarly, financial institutions can use Cedar to implement GDPR or other data protection regulations by controlling access to personal data based on user roles, consent, and audit trails. The language’s formal verification and auditability make it well-suited for industries with stringent compliance demands.
Key Features and Capabilities
- Policy Language and Evaluation Engine: Cedar provides a domain-specific language for writing authorization policies and an engine to evaluate those policies at runtime. Policies are expressed in a declarative syntax that defines who can perform which actions on which resources under what conditions. The engine processes these policies dynamically, ensuring real-time decision-making without requiring application restarts or code changes.
- Schema Validation: Cedar uses a schema to define the structure of entities, actions, and context. This schema is used to validate policies during creation or updates, ensuring they conform to the application’s design. Validation helps prevent misconfigurations by catching errors early, such as referencing undefined entities or using incorrect attribute types.
- Dynamic and Scalable Evaluation: The Cedar evaluation engine is optimized for performance, supporting high-throughput applications with low-latency decisions. Policies are indexed for efficient retrieval, and the engine scales horizontally to handle increasing request volumes.
- Support for RBAC and ABAC: Cedar natively supports Role-Based Access Control (RBAC) and Attribute-Based Access Control (ABAC). RBAC assigns permissions based on user roles, while ABAC incorporates additional attributes like time, location, or user properties. This dual support allows organizations to implement flexible authorization models tailored to their specific needs. For example, a policy might grant access to a resource based on both a user’s role and their current location.
- Context-Aware Policies: Cedar policies can incorporate contextual data such as the request timestamp, IP address, or authentication method. This context-awareness enables fine-grained control over access decisions. For instance, a policy might restrict administrative actions to requests originating from within a company’s network or require multi-factor authentication for sensitive operations.
- Separation of Concerns: Cedar decouples authorization logic from business logic, allowing security teams to manage policies independently of application code. This separation simplifies policy updates, as changes can be applied immediately without coordinating across development teams. It also improves maintainability, as policies can be tested and versioned separately from the application. This modular approach is especially beneficial in large-scale systems with multiple backend services.
- Human-Readable Policies: Cedar’s syntax is designed to be intuitive and accessible to both technical and non-technical stakeholders. Policies are written in plain language, making them easier to review, audit, and collaborate on. This readability reduces the learning curve for new team members and fosters better communication between security, development, and business teams. Clear policies also improve compliance and reduce the risk of misconfigurations.
- Integration with Managed Services: Cedar is the policy language for several managed authorization services, including Amazon Verified Permissions. These services abstract away the complexity of policy management, allowing organizations to focus on defining rules rather than maintaining infrastructure. Managed services also provide additional features like centralized policy storage, audit logging, and real-time monitoring, further enhancing security and operational efficiency.
- For example, a policy might restrict an AI tool to access only specific datasets or require approval for actions that modify critical resources.
- Performance and Scalability: Cedar’s architecture is optimized for performance, with policies indexed for fast retrieval and evaluation. The engine supports real-time decisions with bounded latency, making it suitable for high-demand applications.