12.1. Terraform

12.1.1. Static Code Analyzer with TFLint

As your Terraform codebase grows, it’s more prone to errors.

And they can become nasty.

To analyze your files, use TFLint.

TFLint is a linting tool to check for common smells and issues before you even run your code.

You can even define custom rules to tailor it to your team’s standards.

tflint

Error: "type_abc" is an invalid value as instance_type (aws_instance_invalid_type)

  on main.tf line 15:
   15: instance_type = "invalid_type"
When you run TFLint again, you’ll receive an error message indicating that the
instance_type value is invalid. TFLint identifies this issue without applying the Terraform configuration,
helping you catch errors early in your development workflow.

12.1.2. Check for Security Risks with Tfsec

To check your Terraform files for common security issues, use Tfsec.

TFsec is a static code analyzer to detect security risks, with hundreds of built-in rules.

It’s easy to set-up and run. Perfect for CI pipelines too.

brew install tfsec
tfsec .

Result #1 CRITICAL Storage account uses an insecure TLS version.
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
  deployment/modules/storage_account/main.tf:1-8
   via deployment/main.tf:23-28 (module.storage_account)
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
    1    resource "azurerm_storage_account" "storage_account" {
    2      name                     = var.account_name
    3      resource_group_name      = var.resource_group_name
    4      location                 = var.location
    5      account_kind             = "Storage"
    6      account_tier             = "Standard"
    7      account_replication_type = "LRS"
    8    }

12.1.3. Generate Least Privileges with Pike

When managing your infrastructure, follow the Principle of Least Privilege (PoLP).

PoLP says that a user should only have the minimum level of access required for a particular resource to function correctly.

For your infrastructure managed by Terraform, you can use 𝐏𝐢𝐤𝐞.

𝐏𝐢𝐤𝐞 is a tool that determines the minimum permissions required to run your Terraform code with one command.

It supports the big cloud providers (Azure, AWS, GCP).

Check it out: github(dot)com/JamesWoolfenden/pike

!brew tap jameswoolfenden/homebrew-tap
!brew install jameswoolfenden/tap/pike

pike scan -d .\terraform\
{
    "Version": "2012-10-17",
    "Statement": {
        "Effect": "Allow",
        "Action": [
            "ec2:MonitorInstances",
            "ec2:UnmonitorInstances",
            "ec2:DescribeInstances",
            "ec2:DescribeTags",
            "ec2:DescribeInstanceAttribute",
            "ec2:DescribeVolumes",
            "ec2:DescribeInstanceTypes",
            "ec2:RunInstances",
            "ec2:DescribeInstanceCreditSpecifications",
            "ec2:StopInstances",
            "ec2:StartInstances",
            "ec2:ModifyInstanceAttribute",
            "ec2:TerminateInstances",
            "ec2:AuthorizeSecurityGroupIngress",
            "ec2:AuthorizeSecurityGroupEgress",
            "ec2:CreateSecurityGroup",
            "ec2:DescribeSecurityGroups",
            "ec2:DescribeAccountAttributes",
            "ec2:DescribeNetworkInterfaces",
            "ec2:DeleteSecurityGroup",
            "ec2:RevokeSecurityGroupEgress"
        ],
        "Resource": "*"
    }
}