https://DevOpsCloud.io -- Cloud Monk Losang Jinpa, Ph.D., MCSE/MCT, GitOps DevOps Engineer

• Definition: HashiCorp Sentinel is a policy-as-code framework used to define, enforce, and manage policies within HashiCorp products. It allows for the creation of policies that can be used to control and govern the behavior of infrastructure and applications.
• Function: Provides a way to write and enforce policies as code, integrating with HashiCorp tools such as Terraform, Vault, Consul, and Nomad to ensure compliance, security, and best practices.
• Components:

   * '''Policy Language''': A domain-specific language (DSL) designed to write policies.
   * '''Sentinel CLI''': A command-line interface for testing and managing Sentinel policies.
   * '''Integrations''': Built-in support for HashiCorp products to apply policies during runtime.
   * '''Mock Data and Test Cases''': Tools to simulate and validate policy behavior before deployment.

• Features:

   * '''Policy Enforcement''': Ensures that infrastructure and applications adhere to defined policies.
   * '''Extensibility''': Custom policies can be written to cover a wide range of use cases.
   * '''Integration with HashiCorp Tools''': Seamlessly integrates with Terraform, Vault, Consul, and Nomad.
   * '''Version Control''': Policies can be versioned and managed like code.
   * '''Logical Expressions and Conditionals''': Supports complex policy logic using conditionals and expressions.

• Usage: Ideal for organizations looking to enforce governance, security, and compliance policies across their infrastructure and applications managed by HashiCorp tools.

• Writing a basic Sentinel policy:

   ```hcl
   import "tfplan/v2" as tfplan

 # Ensure that all S3 buckets have versioning enabled
 main = rule {
   all tfplan.resources.aws_s3_bucket as _, bucket {
     bucket.config.versioning.enabled is true
   }
 }
 ```

• Running a Sentinel policy test:

   ```bash
   sentinel test my-policy.sentinel
   ```

• Integrating Sentinel with Terraform:

   * Define a policy set in Terraform Cloud or Enterprise.
   * Add policies to the policy set to enforce during Terraform runs.

• Example of a Sentinel policy test case:

   ```hcl
   test "S3 bucket versioning" {
     description = "Test to ensure S3 buckets have versioning enabled"
     mock = {
       "tfplan/v2" = {
         "resources": {
           "aws_s3_bucket": {
             "my-bucket": {
               "config": {
                 "versioning": {
                   "enabled": true
                 }
               }
             }
           }
         }
       }
     }
     result = true
   }
   ```

• HashiCorp Sentinel: A policy-as-code framework used to define, enforce, and manage policies within HashiCorp products. It integrates with tools like Terraform, Vault, Consul, and Nomad to ensure infrastructure and applications comply with defined policies, supporting governance, security, and compliance through customizable policies written in a domain-specific language.