Terraform Security

What Is Terraform Security?

Terraform security refers to the set of practices and techniques used to ensure the security of Terraform infrastructure as code (IaC) deployments. Terraform is an open-source tool that enables organizations to automate the creation and management of infrastructure across multiple cloud providers and on-premises environments. As such, if your organization uses Terraform, Terraform security is an essential component of your security posture.

This is part of a series of articles about cloud security.

In this article:

• Terraform Security Risks
• Terraform Security Basics
• Terraform Authorization Model
• Terraform Threat Model
• Terraform Security Best Practices
• Execute Terraform Programmatically
• Only Use Safe Terraform Modules
• Secure the Data Store When Remotely Storing State Data
• Avoid Storing Secrets In State Files
• Use Terraform Security Scanners

Terraform Security Risks 

Like any tool used to manage infrastructure and data, Terraform has security risks and threats that organizations need to be aware of. Here are some common security risks and threats associated with Terraform:

1. Unauthorized access: If an attacker gains unauthorized access to the Terraform infrastructure code or state files, they could modify or delete infrastructure resources, steal sensitive data, or cause other damage.
2. Injection attacks: Terraform configurations may include input from external sources, such as user data or environmental variables. If an attacker is able to inject malicious code or commands into these inputs, they could cause damage to the infrastructure.
3. Misconfigured access control: Misconfigured access control mechanisms can lead to unauthorized access to Terraform resources and sensitive data.
4. Data breaches: Terraform state files may contain sensitive data, such as passwords, access keys, or other secrets. If these state files are compromised, it could result in a data breach.
5. Malware: Malware or other malicious code could be introduced into the Terraform infrastructure code or state files, compromising the security of the infrastructure.
6. Insider threats: Insider threats, such as employees or contractors with access to Terraform resources, could intentionally or accidentally cause damage to the infrastructure or compromise sensitive data.

Terraform Security Basics 

Terraform Authorization Model

The Terraform authorization model governs access control and permissions within Terraform Cloud. It uses a role-based access control (RBAC) system to manage user access to workspaces, resources, and operations. 

The RBAC system has pre-defined roles with specific permissions, which can be assigned to users, teams, or service accounts. The authorization model enables secure collaboration by ensuring that users have the appropriate permissions for their tasks, preventing unauthorized access, and maintaining a clear separation of duties.

Key components of the Terraform authorization model include:

• Organizations: Collections of users, teams, and workspaces.
• Teams: Groups of users with specific roles and permissions within an organization.
• Workspaces: Isolated environments where Terraform configurations are executed and managed.
• Roles: Pre-defined sets of permissions that can be assigned to users or teams.

Terraform Threat Model

The Terraform threat model outlines the potential risks and vulnerabilities that can impact the security of Terraform Cloud infrastructure. It helps in identifying, assessing, and addressing threats to ensure the confidentiality, integrity, and availability of resources.

Some common threats in the Terraform threat model include:

• Unauthorized access to resources or sensitive information.
• Leakage of secrets or sensitive data through misconfigurations or insecure storage.
• Infrastructure tampering, leading to unapproved changes or unauthorized deployments.
• Denial of Service (DoS) attacks, affecting the availability of resources.

To mitigate these threats, Terraform Cloud implements security best practices such as:

• Encryption of sensitive data, both in transit and at rest.
• Secure storage of secrets and sensitive information using Vault or other secret management solutions.
• Monitoring and auditing of infrastructure changes, with detailed logs to track user activities and identify potential security incidents.
• Integration with external identity providers (e.g., SAML, OAuth) for secure user authentication and access management.

Terraform Security Best Practices 

Execute Terraform Programmatically

Running Terraform commands manually can be error-prone, as it relies on individuals remembering the correct sequence of commands and parameters. Automating Terraform execution using CI/CD pipelines:

• Provides a consistent and repeatable process for deploying infrastructure changes.
• Enforces version control, ensuring all changes are tracked and can be easily rolled back.
• Facilitates code reviews and approval processes, minimizing the risk of introducing vulnerabilities or errors.
• Ensures access to the infrastructure is restricted to authorized personnel.

Popular CI/CD tools that can be used to automate Terraform execution include Jenkins, GitLab CI/CD, GitHub Actions, and CircleCI.

Only Use Safe Terraform Modules

Terraform modules allow you to encapsulate common infrastructure components into reusable units of code. When using modules:

• Verify the source: Ensure the module comes from a reputable and trusted source, like the Terraform Registry or your organization’s private registry.
• Review third-party modules: Perform a thorough code review to ensure the module adheres to security best practices and doesn’t introduce vulnerabilities or undesired behavior.
• Version pinning: Pin the module version to a specific release to prevent unexpected changes when the module is updated.

Secure the Data Store When Remotely Storing State Data

Terraform state files store information about your infrastructure’s resources and configuration. Storing these files remotely in a secure backend, such as Terraform Cloud or AWS S3, ensures that they are encrypted, versioned, and protected from unauthorized access. Configure the backend to use strong access controls, and enable versioning and state file locking to prevent conflicts and accidental deletion.

Avoid Storing Secrets In State Files

Sensitive information like passwords, API keys, and tokens should not be stored in plain text in Terraform configurations or state files. To manage secrets securely:

• Use secret management solutions: Tools like HashiCorp Vault, AWS Secrets Manager, or Azure Key Vault provide secure storage and access control for sensitive data.
• Leverage Terraform providers and data sources: Fetch secrets during runtime and pass them to resources without storing them in the state file.
• Use encryption functions: If you must store secrets in the state file, use built-in encryption functions like pgp or kms to encrypt the data.

Use Terraform Security Scanners 

A Terraform security scanner is a tool that analyzes Terraform infrastructure code and identifies potential security issues and vulnerabilities. These scanners are designed to identify security risks and threats in Terraform code, such as misconfigured access control, injection attacks, data breaches, and malware.

Terraform security scanners use a variety of techniques to analyze infrastructure code, including static analysis, pattern recognition, and machine learning. These techniques can identify patterns and structures in Terraform code that are associated with common security issues and vulnerabilities.

The output of a Terraform security scanner typically includes a list of potential security issues and vulnerabilities, along with recommendations for how to remediate these issues. For example, a scanner may recommend that an organization improve access control by implementing RBAC policies, or that sensitive data be encrypted and stored securely.

Terraform security scanners can be run as part of a CI/CD pipeline or as a standalone tool, depending on the needs of the organization. Some Terraform security scanners are available as open-source tools, while others are offered as commercial products with additional features and support.