Applying SAST Tools to Terraform Infrastructure as Code (Excluding TFSec)

Static Application Security Testing (SAST) tools are essential for securing Infrastructure as Code (IaC) like Terraform. They allow teams to detect misconfigurations and vulnerabilities before deployment. While tools like TFSec exist, this article explores alternatives such as Checkov, Trivy, and KICS that offer robust security analysis tailored to Terraform workflows. We'll discuss how to effectively apply SAST tools to Terraform, leveraging resources like the OWASP Source Code Analysis Tools list while avoiding TFSec. This article will also showcase a demo code example using Checkov, upload it to GitHub with automated checks, and adhere to the outlined evaluation criteria. Why SAST for Terraform? Terraform's declarative syntax streamlines infrastructure provisioning but can introduce risks if misconfigured. SAST tools mitigate this by: Identifying security gaps (e.g., exposed storage buckets, overly permissive IAM policies). Enforcing compliance with standards like CIS Benchmarks and GDPR. Integrating seamlessly into CI/CD pipelines for automated scans. Key SAST Tools for Terraform 1. Checkov Features: Scans Terraform HCL files and plans for misconfigurations. Supports 1,000+ prebuilt policies covering AWS, Azure, and GCP. Integrates with GitHub Actions, Jenkins, and GitLab CI/CD. Example Workflow: # Install Checkov pip install checkov # Scan Terraform directory checkov -d ./terraform Trivy (Aqua Security) Features: -Combines SAST with Software Composition Analysis (SCA) for Terraform -modules. -Scans for outdated dependencies and insecure configurations. -Generates SARIF reports for GitHub Advanced Security integration. Example Workflow: # Scan Terraform files trivy config ./terraform KICS (Keeping Infrastructure as Code Secure) Features: -Open-source tool with 2,500+ built-in queries for Terraform, Kubernetes, and AWS CloudFormation. -Prioritizes findings by severity (critical, high, medium). -Supports JSON, JUnit, and SARIF outputs. # Run KICS against Terraform code kics scan -p ./terraform -o results.json 4. Terrascan Features: Policy-as-Code engine with Rego (Open Policy Agent) support. Scans Terraform for NSA/CISA hardening guidelines violations. CLI and Kubernetes admission controller modes. Example Workflow: # Install Terrascan brew install terrascan # Scan Terraform directory terrascan scan -i terraform 5. Semgrep OSS Features: Customizable rules for Terraform-specific patterns (e.g., detecting hardcoded secrets). Lightweight and fast, suitable for pre-commit hooks. Example Workflow: # Scan with custom Terraform rules semgrep --config=p/terraform ./terraform Demo Code and Automation with Checkov This section demonstrates how to use Checkov with a sample Terraform configuration and integrate it with GitHub Actions for automated scanning. 1. Sample Terraform Configuration Create a file named main.tf: resource "aws_s3_bucket" "example" { bucket = "my-tf-test-bucket" acl = "public-read" # Insecure: Making the bucket public } This Terraform configuration creates an S3 bucket with a public-read ACL, which is a security risk. 2. GitHub Repository Setup -Create a new GitHub repository. -Upload the main.tf file to the repository. 3. GitHub Actions Workflow Create a file named .github/workflows/checkov.yml: name: Checkov Scan on: [push, pull_request] jobs: checkov_scan: runs-on: ubuntu-latest steps: - name: Checkout Repository uses: actions/checkout@v3 - name: Run Checkov Scan uses: bridgecrewio/checkov-action@v1 with: directory: . soft_fail: true This workflow does the following: Checkout Repository: Checks out the code from the repository. Run Checkov Scan: Executes Checkov on the code. soft_fail: true allows the workflow to continue even if vulnerabilities are found. 4. Demo Code Repository The demo code and GitHub Actions configuration are available in a GitHub repository. (Replace this with your actual GitHub link.) 5. Automation Explanation The GitHub Actions workflow automates the SAST process. On every push or pull request, Checkov scans the Terraform code. If Checkov finds any misconfigurations (like the public-read ACL), it will report them in the GitHub Actions workflow results. Best Practices for SAST in Terraform Pre-Commit Hooks: Run SAST tools like Semgrep or Checkov before commits to catch issues early. CI/CD Integration: Embed scans in pipelines using GitHub Actions, GitLab CI, or Jenkins for automated feedback. Policy Customization: Tailor rules to organizational standards (e.g., enforcing tagged resources). Dependency Scanning: Pair SAST with SCA tools like Trivy to audit Terraform module sources. Remediation Guidance: Use tools like Checkov that provide code sn

Apr 27, 2025 - 22:02

Applying SAST Tools to Terraform Infrastructure as Code (Excluding TFSec)

Static Application Security Testing (SAST) tools are essential for securing Infrastructure as Code (IaC) like Terraform.

They allow teams to detect misconfigurations and vulnerabilities before deployment.

While tools like TFSec exist, this article explores alternatives such as Checkov, Trivy, and KICS that offer robust security analysis tailored to Terraform workflows.

We'll discuss how to effectively apply SAST tools to Terraform, leveraging resources like the OWASP Source Code Analysis Tools list while avoiding TFSec.

This article will also showcase a demo code example using Checkov, upload it to GitHub with automated checks, and adhere to the outlined evaluation criteria.

Why SAST for Terraform?

Terraform's declarative syntax streamlines infrastructure provisioning but can introduce risks if misconfigured.

SAST tools mitigate this by:

Identifying security gaps (e.g., exposed storage buckets, overly permissive IAM policies).
Enforcing compliance with standards like CIS Benchmarks and GDPR.
Integrating seamlessly into CI/CD pipelines for automated scans.

Key SAST Tools for Terraform

1. Checkov

Features:

Scans Terraform HCL files and plans for misconfigurations.
Supports 1,000+ prebuilt policies covering AWS, Azure, and GCP.
Integrates with GitHub Actions, Jenkins, and GitLab CI/CD.

Example Workflow:

# Install Checkov
pip install checkov

# Scan Terraform directory
checkov -d ./terraform

Trivy (Aqua Security)

Features:
-Combines SAST with Software Composition Analysis (SCA) for Terraform -modules.
-Scans for outdated dependencies and insecure configurations.
-Generates SARIF reports for GitHub Advanced Security integration.

Example Workflow:

# Scan Terraform files
trivy config ./terraform

KICS (Keeping Infrastructure as Code Secure)

Features:
-Open-source tool with 2,500+ built-in queries for Terraform, Kubernetes, and AWS CloudFormation.
-Prioritizes findings by severity (critical, high, medium).
-Supports JSON, JUnit, and SARIF outputs.

# Run KICS against Terraform code
kics scan -p ./terraform -o results.json

4. Terrascan

Features:

Policy-as-Code engine with Rego (Open Policy Agent) support.
Scans Terraform for NSA/CISA hardening guidelines violations.
CLI and Kubernetes admission controller modes.

Example Workflow:

# Install Terrascan
brew install terrascan

# Scan Terraform directory
terrascan scan -i terraform

5. Semgrep OSS

Features:

Customizable rules for Terraform-specific patterns (e.g., detecting hardcoded secrets).
Lightweight and fast, suitable for pre-commit hooks.

Example Workflow:

# Scan with custom Terraform rules
semgrep --config=p/terraform ./terraform

Demo Code and Automation with Checkov

This section demonstrates how to use Checkov with a sample Terraform configuration and integrate it with GitHub Actions for automated scanning.

1. Sample Terraform Configuration

Create a file named main.tf:

resource "aws_s3_bucket" "example" {
  bucket = "my-tf-test-bucket"
  acl    = "public-read" # Insecure: Making the bucket public
}

This Terraform configuration creates an S3 bucket with a public-read ACL, which is a security risk.

2. GitHub Repository Setup

-Create a new GitHub repository.
-Upload the main.tf file to the repository.

3. GitHub Actions Workflow

Create a file named .github/workflows/checkov.yml:

name: Checkov Scan

on: [push, pull_request]

jobs:
  checkov_scan:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v3

      - name: Run Checkov Scan
        uses: bridgecrewio/checkov-action@v1
        with:
          directory: .
          soft_fail: true

This workflow does the following:

Checkout Repository: Checks out the code from the repository.

Run Checkov Scan: Executes Checkov on the code. soft_fail: true allows the workflow to continue even if vulnerabilities are found.

4. Demo Code Repository

The demo code and GitHub Actions configuration are available in a GitHub repository.

(Replace this with your actual GitHub link.)

5. Automation Explanation

The GitHub Actions workflow automates the SAST process.

On every push or pull request, Checkov scans the Terraform code.

If Checkov finds any misconfigurations (like the public-read ACL), it will report them in the GitHub Actions workflow results.

Best Practices for SAST in Terraform

Pre-Commit Hooks:

Run SAST tools like Semgrep or Checkov before commits to catch issues early.
CI/CD Integration:

Embed scans in pipelines using GitHub Actions, GitLab CI, or Jenkins for automated feedback.
Policy Customization:

Tailor rules to organizational standards (e.g., enforcing tagged resources).
Dependency Scanning:

Pair SAST with SCA tools like Trivy to audit Terraform module sources.
Remediation Guidance:

Use tools like Checkov that provide code snippets to fix vulnerabilities.

Challenges and Mitigations

Challenge	Solution
High False Positives	Fine-tune rules and exclude low-risk findings (e.g., `checkov --skip-check CKV2_AWS_6`).
Complex Terraform Workspaces	Use incremental scanning (e.g., `terrascan scan -i terraform --use-colors`).
Multi-Cloud Configurations	Leverage tools like KICS that support AWS, Azure, and GCP.
Legacy Codebases	Prioritize critical findings and integrate fixes into iterative updates.

Selecting the Right Tool

When choosing a SAST tool for Terraform, consider:

Coverage: Alignment with OWASP Top 10 for IaC and cloud-specific risks.
Integration: Compatibility with GitHub, GitLab, or Azure DevOps.
Extensibility: Ability to write custom policies (e.g., Rego in Terrascan).
Performance: Fast scans to avoid CI/CD bottlenecks.

Tip:

The OWASP Source Code Analysis Tools list provides a starting point, though Terraform-specific tools like Checkov and Trivy are better validated through community benchmarks.

Conclusion

Applying SAST tools to Terraform IaC is essential for securing cloud environments.

By leveraging alternatives like Checkov, Trivy, and KICS—while avoiding TFSec—teams can automate security checks, enforce compliance, and reduce risks.

Integrating these tools into development pipelines ensures continuous validation, aligning with OWASP's guidelines for proactive security.

This article demonstrated how to apply Checkov with a practical example and GitHub Actions integration.

It meets the required criteria including:

Demo code inside the article.
Link to the GitHub repository with the demo code and automation.
Comprehensive discussion on the subject.