Sentinel is a policy as code framework developed by HashiCorp that enables users to define, manage, and enforce policies across their infrastructure and applications. It operates as a rules engine that evaluates policies against requests made to various HashiCorp tools, including Terraform, Nomad, and Vault, and makes decisions based on those policies. Sentinel is designed to be flexible and extensible, allowing users to define policies in their preferred language, including HCL, JSON, YAML, and others. It supports a variety of use cases, such as preventing users from launching non-compliant infrastructure, ensuring compliance with regulatory standards, and enforcing access controls. Sentinel's architecture consists of a set of rules and policies defined by the user, a runtime engine responsible for evaluating those rules and policies against incoming requests, and a policy authoring and management interface. Sentinel also provides integration points for other tools and services, enabling users to extend their policy coverage beyond the HashiCorp ecosystem.

Sentinel covers the following use casesInfrastructure as code (IaC) compliance: Sentinel can be used to define and enforce policies that ensure infrastructure deployments adhere to organizational standards, best practices, and compliance regulations. For example, Sentinel can enforce policies related to network security, access control, and data protection.Access control: Sentinel can be used to enforce access control policies that restrict access to sensitive data and resources. This can include policies that require multi-factor authentication, restrict access based on location or device, and ensure that only authorized personnel have access to critical resources.Cost management: Sentinel can be used to enforce policies that help organizations manage cloud costs by ensuring that resources are provisioned efficiently and in line with organizational requirements. This can include policies that enforce tagging standards, limit the creation of expensive resources, and ensure that unused resources are deleted.Compliance and regulatory requirements: Sentinel can be used to enforce policies that ensure compliance with various regulatory requirements, such as HIPAA, PCI DSS, and GDPR. This can include policies that ensure sensitive data is encrypted, audit logs are retained, and access to sensitive data is restricted.Custom policies: Sentinel is highly flexible and can be used to define custom policies tailored to specific organizational requirements. For example, Sentinel can be used to enforce policies related to naming conventions, resource quotas, and service level agreements (SLAs).