HashiCorp Sentinel with HashiCorp Terraform and Terraform Cloud

HashiCorp Sentinel is a powerful policy-as-code framework that allows for the enforcement of security and compliance policies for infrastructure as code (IaC). When used in conjunction with HashiCorp Terraform and HCP Terraform, Sentinel offers numerous benefits that we will explore in this article.

Introduction to HashiCorp Sentinel

Sentinel is a flexible and extensible policy-as-code framework that can be integrated into HashiCorp products. It allows the definition, implementation, and enforcement of policies to ensure your infrastructure meets desired standards and requirements. By integrating Sentinel with Terraform and HCP Terraform, you can create a variety of policies that govern your Terraform deployments.

Benefits of Sentinel in Terraform and HCP Terraform

Enforcing Security Policies

One of the biggest challenges in managing cloud infrastructure is ensuring security. With Sentinel, you can define security policies that ensure all Terraform configurations adhere to specific security standards. For example, you can create policies to prevent security groups from having open ports or to ensure database instances are provisioned with encryption.

 1import "tfplan/v2"
 2import "strings"
 3
 4# Security policy to prevent open ports
 5open_ports = func(resource) {
 6    ports = []
 7    if "ingress" in resource {
 8        for ingress in resource.ingress {
 9            if ingress.cidr_blocks contains "0.0.0.0/0" {
10                ports = append(ports, ingress.from_port)
11            }
12        }
13    }
14    return ports
15}
16
17# Filter resources
18resource_types = [
19    "aws_security_group",
20    "azurerm_network_security_rule",
21]
22
23main = rule {
24    all tfplan.resources[resource_types] as resource {
25        open_ports(resource) is empty
26    }
27}

Ensuring Compliance

Compliance is a critical factor for many companies, especially in heavily regulated industries such as finance or healthcare. Sentinel allows you to define compliance policies that ensure all infrastructure deployments meet legal and internal corporate requirements. You can, for example, set policies to ensure all resources are provisioned in specific regions or that certain tags are used.

 1import "tfplan/v2"
 2
 3# Compliance policy to check for required tags
 4required_tags = ["Environment", "Owner"]
 5
 6main = rule {
 7    all tfplan.resources.aws_instance as resource {
 8        all required_tags as tag {
 9            tag in keys(resource.applied.tags)
10        }
11    }
12}

Consistent Policies for All Deployments

Using Sentinel with HCP Terraform ensures that all deployments are consistent and follow the same policies. This is particularly useful in large teams or organizations where multiple people manage Terraform configurations. Sentinel ensures that all configurations adhere to defined standards and best practices.

1import "tfplan/v2"
2import "strings"
3
4# Policy to ensure consistent resource naming
5main = rule {
6    all tfplan.resources.aws_instance as resource {
7        strings.has_prefix(resource.applied.tags.Name, "prod-")
8    }
9}

Easy Integration and Management

Sentinel is seamlessly integrated into Terraform and HCP Terraform, simplifying the implementation and management of policies. You can manage Sentinel policies directly in HCP Terraform and apply them to your workspaces. This allows for centralized management and enforcement of policies without the need for additional tools or complex processes.

Flexibility and Extensibility

Sentinel offers high flexibility and extensibility, allowing you to create policies tailored to your specific requirements. You can create custom functions and modules to implement complex policies. Additionally, Sentinel supports a variety of data sources, enabling you to create policies based on external data.

 1import "tfplan/v2"
 2import "strings"
 3
 4# Custom function to validate tag values
 5valid_tag_values = func(tag_value) {
 6    return strings.contains(tag_value, "approved")
 7}
 8
 9main = rule {
10    all tfplan.resources.aws_instance as resource {
11        valid_tag_values(resource.applied.tags.Environment)
12    }
13}

Conclusion

HashiCorp Sentinel is an indispensable tool for Terraform and HCP Terraform users who want to secure their infrastructure deployments and ensure compliance. By enforcing security and compliance policies, ensuring consistent deployments, and providing easy integration, Sentinel offers numerous benefits that help keep your infrastructure secure and compliant. Leverage Sentinel to optimize your Terraform workflows and improve the quality of your deployments.

For more information on Sentinel or assistance with implementation, visit the official HashiCorp Sentinel documentation.