Cedar Policy Language (CPL): 2024 Complete Guide

Cedar was born out of the need to extend policy definition beyond the confines of AWS-specific constructs that characterize IAM policies. Unlike IAM policies that are highly optimized for AWS with constructs like ARNs, Cedar is a generalist language devoid of implicit AWS constructs, making it suitable for authorizing non-AWS applications. This characteristic positions Cedar at the core of the Amazon Verified Permissions service, where AWS manages the policy dataset and authorization calls are made directly against the evaluation engine.

Cedar Guiding Principles

Simplicity and Efficiency

Cedar Policy Language is written in Rust, which allows it to execute in milliseconds. It's designed to be simple to reason about the effect of policies, facilitating the creation of tools that can compare policies and determine their exact equivalence or identify differences in authorization requests when evaluated against each policy.

The language is designed to be easily understandable and to allow for the straightforward expression of access permissions, which is critical for authoring policies and understanding their effects.

Fine-grained Permission Control

Cedar allows for expressing fine-grained permissions through easily understandable policies, enabling a decoupling of access control from application logic.

Open-Source and Extensible

Cedar is open-source and has a software development kit (SDK) for writing and enforcing authorization policies. This open-source nature facilitates its integration directly into applications via the provided SDK and language specification, making it a versatile choice for different authorization use cases.

Expressiveness and Performance

The language is simple yet expressive, purpose-built to support authorization use cases for standard authorization models like RBAC (Role-Based Access Control) and ABAC (Attribute-Based Access Control) and new models like ReBAC (Relationship-Based Access Control) and *BAC (prouncounced StarBAC, it is  Anything-Based Access Control). It's also highlighted for its performance, being fast and scalable.

Modular and Reusable Authorization

Cedar enables modular and reusable authorization by controlling access to application resources in a structured manner. The policy evaluation engine takes one or more policies to evaluate whether a requested action is permitted or forbidden, requiring the principal to make the request, the action being taken, the resource being accessed, and optionally, additional request context at the time of the authorization call.

Cedar Language Structure

A typical Cedar policy statement has three main parts: the effect, the scope, and, optionally, condition clauses. The outcome will always be either `permit` or `forbid.` The scope specifies the principals, actions, and resources to which the effect applies. Condition clauses further limit whether a policy takes effect for the specific request based on the principal, action, resource, or Context of the request, as well as the attributes or nested hierarchy of these entities where a list of entities has been defined.

Cedar Evaluation Logic

When evaluating a request, Cedar considers all statements within the policy, and in the case of StrongDM Dynamic Access Management (DAM), all policies provided in a policy store. If any `forbid` statement matches the request, the request will be denied, regardless of any `permit` statements. If at least one `permit` statement matches the request (and no `forbid` statements match), the request will be allowed. If no statements match, the request will be implicitly denied.

The creation and design of Cedar underline AWS's commitment to providing a robust, intuitive, and flexible framework for managing access permissions in and outside the AWS ecosystem. Through Cedar, AWS has extended the frontier of policy definition and authorization, embracing modern requirements of fine-grained access control, simplicity, and efficiency in policy evaluation and enforcement.

Cedar Policy Language (CPL) is designed to provide a modular and reusable approach for authorizing access to application resources. The language allows developers to write, update, audit, and reuse authorization policies independently from the application code. Although originally developed by AWS, Cedar policies can be used by applications not run in AWS. By expressing permissions through Cedar policies, applications can leverage Cedar's authorization engine to evaluate which access requests should be allowed​​.

Operationalizing Cedar Policy Language

Operationalizing the Cedar Policy Language (CPL) entails implementing and managing it in a real-world environment for authorization purposes. Here are some tips for operationalizing Cedar:

• Adhere to Naming Conventions: Establish and follow clear naming conventions for policies, actions, resources, and other entities within CPL to ensure consistency and readability​.
• Normalize Data Input: Normalize data input to ensure it's in a consistent format, which can help in simplifying policy evaluations and reducing errors​.
• Utilize Context Effectively: Use the Context provided in authorization requests to make more informed and precise authorization decisions​.
• Populate the Policy Scope Appropriately: Define the scope of policies accurately to ensure they cover the required actions, resources, and principals​.
• Employ Meta-permissions: Use meta-permissions to manage permissions at a higher level, which can simplify the policy management and enforcement process​​.
• Avoid Mutable Identifiers: Avoid using mutable identifiers, which can change over time, as they can lead to inconsistencies and potential security issues​.
• Ensure Human-Readability: Write policies in a human-readable manner to facilitate easier management, debugging, and compliance checking.
• Leverage Policy-as-Code: Embrace policy-as-code to maintain policies in version control systems easily, automate policy testing and deployment, monitor for compliance, and ensure a high level of transparency and auditability​​.
• Optimize for Performance: Cedar policies compress for efficient storage and transmission. 

Ensure that your Cedar implementation is optimized for performance to handle the authorization demands of your environment efficiently​. 

• Educate and Train Your Team: Ensure your team is well-versed in Cedar, its syntax, and its operational nuances. Providing sufficient training and resources can help in effectively operationalizing Cedar.
• Engage with the Community: Join the CPL community of users on Slack, engage with it to learn from others' experiences, ask questions, and get insights into best practices for operationalizing Cedar.
• Monitor and Audit Regularly: Establish mechanisms for monitoring policy enforcement and conducting regular audits to ensure compliance with organizational and regulatory requirements.
• Iterate and Improve: Continuously review and improve your CPL implementation based on feedback, monitoring data, and evolving requirements to ensure it remains effective and efficient.

Advanced Cedar Policy Configuration

Advanced configuration might involve optimizing the compression of policies for different use cases or setting up a pre-built dictionary for compression, as discussed under operationalizing Cedar. 

As noted in the Cedarland blog by Darin McAdams, compression rates for Cedar policies are generally favorable, especially when many policies need to be considered. For instance, files containing more than 50 policies will likely achieve over 80% space saving when compressed. When dealing with fewer policies, utilizing a pre-built dictionary for compression can help maintain a lower bound of around 50% compression rate​​. An alternative method McAdams suggests involves pre-parsing and pre-compiling Cedar policies into a byte-code representation to reduce policy size. This method could minimize storage while reducing evaluation costs because the policies are pre-compiled and ready for use. 

Advanced configuration may also entail defining complex authorization scenarios and customizing Cedar policies to fit unique authorization requirements.

Transitioning to Cedar Policy Language

Transitioning to Cedar requires a comprehensive understanding of Cedar's syntax, structure, and evaluation mechanisms. Various tutorials and guides, like the Cedar Tutorial, Language Guide, or the Cedar Playground, can aid developers in learning how to write policies and create schema using the Cedar Policy Language​.

Cedar Policy Language has emerged as a robust tool for managing authorization in applications, especially in environments that require a high degree of security and control over resource access. By understanding and adhering to the best practices for CPL implementation and operation, organizations can significantly enhance their cybersecurity posture while ensuring seamless access control management.

Cedar Policy Integration

Integrating a robust authorization framework like Cedar Policy Language (CPL) into existing systems and applications is a pivotal step towards fortifying security posture: various techniques can be employed, each with unique advantages and capabilities.

Techniques for integrating CPL into existing systems and applications

Cedar API: Cedar extends a suite of APIs to integrate its policy language into the existing infrastructure. The APIs facilitate real-time policy enforcement and decision-making within applications, thus acting as the nervous system that transmits authorization signals across the application ecosystem. By employing Cedar's APIs, organizations unlock the avenue to a seamless integration experience, allowing for real-time interactions and decisions crucial for maintaining a robust security perimeter.

Cedar SDKs:  SDKs are tailored for various programming environments. These SDKs are the bedrock for embedding policy decision points within applications, thus forging a symbiotic relationship between the application logic and the authorization framework. The beauty of Cedar's SDKs lies in their ability to assimilate within different programming paradigms, offering a versatile solution for integrating the Cedar Policy Language into a diverse range of applications. 

Custom Adapters: Adapters are crafted to bridge the chasm between Cedar and existing systems, acting as the translators that decode the language of Cedar so that it is understandable to the existing systems. 

Benefits and challenges associated with Cedar Policy integration

Integrating Cedar Policy Language (CPL) into existing systems brings notable benefits. Primarily, it enhances security by providing a robust framework for defining and enforcing authorization policies. The granular access control feature of Cedar allows precise permissions management, ensuring that resources are accessed only by authorized entities. Moreover, real-time policy enforcement is a critical advantage, enabling immediate response to authorization requests, essential in dynamic and high-stakes environments. Compliance with industry regulations is another benefit, as Cedar can be configured to enforce policies that adhere to various regulatory standards, making it a viable choice for regulated industries like finance and healthcare.

On the flip side, developers may encounter challenges during the integration of Cedar. The initial setup can be complex, requiring a good understanding of Cedar to ensure correct configuration and integration. This highlights the necessity for expertise in Cedar for successful implementation. Additionally, thorough testing is crucial to validate that the policies are enforced correctly and identify potential issues early in the implementation process. This testing phase is not just a one-off task but an ongoing requirement to ensure the Cedar integration continues functioning as expected amidst evolving system and application landscapes.

For StrongDM customers, we’ve done the difficult work of integrating Cedar into our Dynamic Access Management Platform. Utilizing Cedar policies for fine-grained authorization requires no rewrites to your existing applications. Amazing! 

Cedar Policy Management & Administration

Policy management and policy administration, though closely related, serve distinct functions within an organization's security framework.

Policy Management

Definition and Revision: Policy management primarily involves the creation, updating, and deletion of security policies. It entails defining the rules and conditions under which resources can be accessed within a system.

Deployment: It includes deploying these policies across the organization's network, ensuring they are applied correctly wherever necessary.

Monitoring and Enforcement: Policy management also involves monitoring the enforcement of these policies and making adjustments as needed to maintain the desired level of security.

Compliance Checking: Ensuring that the set policies comply with external regulations and internal standards is a part of policy management. 

Performance Monitoring: Monitoring how policies affect system performance and making necessary adjustments falls under policy management.

For effective Cedar policy management across different applications, a centralized policy repository is essential. It acts as a single source of truth for all authorization policies, ensuring consistency in enforcement across applications. Automated deployment pipelines are another critical requirement, facilitating the swift propagation of policy updates across different environments. Real-time monitoring and alerting mechanisms are also vital to keep track of policy enforcement and to identify any anomalies promptly.

The robust Strong Policy Engine by StrongDM™ is powered by the Cedar Policy Language. This enables distributed enforcement of centralized policies, creating a secure and unified access control framework across your infrastructure. The engine allows for policy evaluation with sub-millisecond response times, aligning with the high-performance standards that StrongDM users expect.

With centralized policy management policies are written once and enforced everywhere. StrongDM simplifies policy management by extending existing RBAC and ABAC policies 
with new signals and controls. This centralized approach streamlines administration, reducing the complexity of access control. With StrongDM, you can establish security measures that are uniformly enforced across all your diverse applications and infrastructure components. It builds upon the natural strengths of these resources by adding layers of security policies, thereby improving the existing controls and safeguards.

Cedar Policy Management & Administration

Policy management and policy administration, though closely related, serve distinct functions within an organization's security framework.

Policy Management

Definition and Revision: Policy management primarily involves the creation, updating, and deletion of security policies. It entails defining the rules and conditions under which resources can be accessed within a system.

Deployment: It includes deploying these policies across the organization's network, ensuring they are applied correctly wherever necessary.

Monitoring and Enforcement: Policy management also involves monitoring the enforcement of these policies and making adjustments as needed to maintain the desired level of security.

Compliance Checking: Ensuring that the set policies comply with external regulations and internal standards is a part of policy management. 

Performance Monitoring: Monitoring how policies affect system performance and making necessary adjustments falls under policy management.

For effective Cedar policy management across different applications, a centralized policy repository is essential. It acts as a single source of truth for all authorization policies, ensuring consistency in enforcement across applications. Automated deployment pipelines are another critical requirement, facilitating the swift propagation of policy updates across different environments. Real-time monitoring and alerting mechanisms are also vital to keep track of policy enforcement and to identify any anomalies promptly.

Policy Administration

Centralized Control: Policy administration usually refers to the centralized control and oversight of all policy management activities. It's about overseeing how policies are created, modified, and deleted.

Access Control: This includes managing who has the authorization to create, modify, or delete policies, thereby ensuring only qualified individuals can make changes to policies.

Audit Trail: Maintaining a comprehensive audit trail of all policy changes, including who made the changes and when, is a crucial aspect of policy administration.

Reporting and Analysis: Generating reports and analyzing data regarding policy enforcement, violations, and compliance levels fall under policy administration.

Training and Awareness: Ensuring that staff is adequately trained on policy-related matters and is aware of the importance of compliance is also a part of policy administration.

​​Having centralized administration for managing and monitoring Cedar policies is crucial. It simplifies governance by consolidating management and monitoring into a single point, providing clear oversight on policy enforcement and compliance. Centralized administration is necessary for compliance auditing as it offers a coherent audit trail of policy configurations and enforcement actions.

In a nutshell, policy management is more about the lifecycle of the policies themselves (creation, deployment, monitoring, and enforcement). In contrast, policy administration is about governance, control, and oversight of policy management activities. Both are crucial for maintaining a robust and compliant cybersecurity posture within an organization.

The Cedar Policy Language: Features, Syntax and Ecosystem 

Cedar Policy Language enables precise and intelligible authorization policy authoring. This structured approach accelerates integration into existing systems and simplifies the management of policies, ensuring coherent governance over authorization. Moreover, the real-time policy evaluation capability of CPL is crucial for dynamic environments where authorization decisions need to be made swiftly. When juxtaposed with other policy languages, Cedar's emphasis on application-level authorization and its ability to articulate fine-grained policies shine through. The comparative simplicity and precision in policy definition give CPL an edge, making it a preferred choice for many cybersecurity professionals.

In this document, we will not detail the specifics of the Cedar syntax, operators, validation, grammar, or templates. For those details, please refer to the Cedar documentation. 

Cedar Syntax

A standout feature of Cedar is its structured syntax, designed to articulate policies clearly, thus facilitating easy integration and management. Each policy statement describes how a user (Principal) is allowed to interact (Action) with a service/application (Resource) under a particular condition (Context). This is also known as the PARC model. 

While Open Policy Agent (OPA) utilizes Rego as its policy language, Cedar's syntax is constructed to provide a potentially more straightforward approach to policy definition. To illustrate, consider a simple policy that allows read access to a resource:

Cedar Policy

In a distributed enforcement setup, compliance with organizational and regulatory policies is inherently baked into the system. The automated enforcement of policies ensures that access controls are consistently applied, reducing the likelihood of compliance violations. Moreover, automation minimizes the scope for manual errors, often a source of security breaches or compliance lapses. The continuous enforcement and real-time evaluation of policies also facilitate prompt detection and remediation of deviations from the defined access control standards.

Utilizing centralized policies in conjunction with distributed enforcement powered by the Strong Policy Engine in StrongDM, you benefit from a structured framework that significantly aids in achieving both regulatory compliance and internal compliance. Here's how.

Structured Policy Definition

Cedar provides a robust and structured way to define authorization policies. This structure ensures that policies are articulated in a clear, consistent, and comprehensive manner, making it easier to align them with regulatory and internal compliance requirements.

Consistent Policy Application

By employing consistent policies, organizations ensure that the same rules are applied uniformly across various systems and applications. This uniformity is crucial for compliance as it ensures that all parts of the organization adhere to the required standards, whether regulatory or internal.

Real-Time Policy Enforcement

Cedar facilitates real-time policy enforcement, which is crucial for maintaining compliance. Immediate enforcement ensures that non-compliant actions are promptly denied or flagged, thus reducing the risk of compliance violations.

Distributed Enforcement

Distributed enforcement allows organizations to enforce policies at various points within their infrastructure. This distributed nature ensures that compliance is maintained across the entire organization, regardless of the diversity and distribution of systems and applications.

Auditability

The clear policy definitions and enforcement logs generated by Cedar enable straightforward auditing. Auditors can quickly review and verify compliance by examining the defined policies and the enforcement logs. This audit trail is invaluable for both regulatory compliance, where proof of compliance is often required, and internal compliance, where auditing helps to identify and rectify compliance issues.

Compliance Monitoring and Reporting

The integration of Cedar allows for continuous monitoring and reporting on the compliance status. These real-time insights are critical for staying ahead of potential compliance issues and for providing the necessary documentation to regulatory bodies.

Adaptability to Changing Regulations

Regulations often evolve, and Cedar's structured yet flexible framework allows for the efficient updating of policies to reflect these changes. This adaptability ensures that organizations can quickly align with new compliance requirements, both regulatory and internal.

Policy Versioning

Cedar supports policy versioning, which is essential for tracking changes over time and ensuring that only the latest, compliant policies are in effect. This feature further aids in audit scenarios where understanding policy evolution is crucial.

Reduced Error

By defining policies in a clear, standardized manner and automating enforcement, the possibility of human error - which could lead to compliance violations - is significantly reduced.

Documentation and Visibility

Having a well-documented set of policies and a clear visibility into how those policies are enforced across the organization helps ensure that all stakeholders know the compliance status and that potential issues are addressed promptly.

Cross-Boundary Compliance

In a distributed environment, ensuring compliance across different jurisdictional and organizational boundaries is challenging. Leveraging Cedar with distributed enforcement helps in maintaining compliance even in complex, cross-boundary scenarios.

Integration with Other Compliance Tools

Cedar can be integrated with other compliance monitoring and management tools to provide a comprehensive compliance solution. This integration enhances the organization's ability to maintain and demonstrate compliance across all operational facets.

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Cedar Policy Language (CPL) Resources

• Cedar Policy Language Documentation
• Join Cedar Policy Language on Slack
• Cedar Go Implementation: Simplifying Security for Developers
• Unlocking Continuous Zero Trust Authorization with Strong Policy Engine
• Dynamic Access Management (DAM): Innovating PAM
• The Definitive Guide to Role-Based Access Control (RBAC)
• What Is Zero Trust Security? How to Implement It & More
• AWS IAM Roles vs Policies: What's the Difference?
• Fine-Grained vs. Coarse-Grained Access Control Explained