Infrastructure as Code (IaC) has revolutionized how we provision and manage infrastructure, enabling speed, repeatability, and scalability. However, as with any code, IaC introduces new security considerations. Misconfigurations, exposed secrets, and lack of visibility can lead to significant risks in production environments.

This guide explores actionable best practices for securing your Terraform, Ansible, and other IaC pipelines-helping you build robust, compliant, and resilient infrastructure. Sample code and how-to notes included!

1. Treat IaC Like Application Code

Just as you would with application code, store your IaC in version control systems (e.g., Git). This enables:

• Change tracking: Who changed what, when, and why.
• Peer reviews: Enforce code reviews and approvals before merging.
• Rollback: Revert to previous known-good states if issues arise.

Tip:
Use branch protection rules and require pull request reviews for all changes.

2. Secrets Management

Never hard-code secrets or sensitive data (API keys, passwords, certificates) in your IaC files. Instead:

• Use secret management tools like HashiCorp Vault, AWS Secrets Manager, or Azure Key Vault.
• Integrate secrets into your pipelines at runtime, not in code.
• Leverage environment variables or encrypted files for sensitive values.

Sample: Fetching Secrets from Vault in Terraform

provider "vault" {
  address = "https://vault.example.com"
}

resource "vault_generic_secret" "example" {
  path = "secret/data/myapp"
}

output "db_password" {
  value = vault_generic_secret.example.data["password"]
}

How-to:

• Replace https://vault.example.com with your Vault server address.
• The vault_generic_secret resource fetches secrets dynamically.
• Output blocks can reference secrets securely-never hardcode them!

Sample: Encrypting Secrets in Ansible with ansible-vault

- hosts: all
  vars_files:
    - secrets.yml
  tasks:
    - name: Use secret password
      debug:
        msg: "The password is {{ secret_password }}"

How-to:

• Create and encrypt the secrets file: ansible-vault create secrets.yml
• Reference the encrypted file in your playbook under vars_files.
• Access secrets in tasks using Jinja2 templating, e.g., {{ secret_password }}.

3. Automated Security Scanning

Integrate security tools into your CI/CD pipeline to catch misconfigurations and vulnerabilities early:

• Terraform: Use tfsec, Checkov, or TFLint.
• Ansible: Use ansible-lint and custom playbook checks.
• General: Tools like Snyk and Bridgecrew support multiple IaC formats.

Sample: Terraform Security Scanning with tfsec in GitHub Actions

name: Terraform Security Scan

on: [push]

jobs:
  tfsec:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Run tfsec
        uses: aquasecurity/tfsec-action@v1
        with:
          tfsec_version: 'latest'

How-to:

• Add this workflow to your .github/workflows directory.
• The scan will fail the build if critical security issues are found, helping you catch problems early.

4. Principle of Least Privilege

Ensure that your IaC tools, pipelines, and the resources they provision follow the principle of least privilege:

• Limit IAM permissions for automation accounts.
• Avoid using overly broad roles or root accounts.
• Regularly audit permissions and remove unnecessary access.

5. Policy as Code

Define and enforce security and compliance policies programmatically:

• Use tools like Open Policy Agent (OPA), Sentinel (for Terraform Cloud), or Conftest.
• Enforce rules such as “no public S3 buckets,” “encryption enabled,” or “no hardcoded credentials.”

Example:
OPA policies can block deployments that violate security standards before they reach production.

6. Continuous Monitoring and Drift Detection

Even after deployment, infrastructure can drift from the desired state:

• Use tools like Terraform Cloud, AWS Config, or Driftctl to detect and remediate drift.
• Set up alerts for unauthorized changes and automate remediation where possible.

7. Regular Reviews and Updates

IaC modules and dependencies evolve-so should your security practices:

• Schedule regular reviews of your IaC codebase and third-party modules.
• Update modules to patch vulnerabilities and leverage new security features.
• Document your security practices and train your team.

Conclusion

Securing Infrastructure as Code is not a one-time task, but a continuous process woven into your development and deployment lifecycle. By treating IaC like application code, managing secrets securely, automating scanning, enforcing least privilege, and using policy as code, you can drastically reduce risk and build trust in your automation.