Terraform

Tunnel supports the scanners listed in the table below.

Scanner	Supported
Misconfiguration	✓
Secret	✓

It supports the following formats:

Format	Supported
JSON	✓
HCL	✓
Plan Snapshot	✓
Plan JSON	✓

Tunnel can scan Terraform Plan files (snapshots) or their JSON representations. To create a Terraform Plan and scan it, run the following command:

terraform plan --out tfplan
tunnel config tfplan

To scan a Terraform Plan representation in JSON format, run the following command:

terraform show -json tfplan > tfplan.json
tunnel config tfplan.json

Misconfiguration

Tunnel recursively searches directories and scans all found Terraform files. It also evaluates variables, imports, and other elements within Terraform files to detect misconfigurations.

Value Overrides

You can provide tf-vars files to Tunnel to override default values specified in the Terraform HCL code.

tunnel config --tf-vars dev.terraform.tfvars ./infrastructure/tf

Exclude Downloaded Terraform Modules

By default, downloaded modules are also scanned. If you don't want to scan them, you can use the --tf-exclude-downloaded-modules flag.

tunnel config --tf-exclude-downloaded-modules ./configs

Secret

The secret scan is performed on plain text files, with no special treatment for Terraform.

Limitations

Terraform Plan JSON

For each and count objects in expression

The plan created by Terraform does not provide complete information about references in expressions that use each or count objects. For this reason, in some situations it is not possible to establish references between resources that are needed for checks when detecting misconfigurations. An example of such a configuration is:

locals {
  buckets = toset(["test"])
}

resource "aws_s3_bucket" "this" {
  for_each = local.buckets
  bucket = each.key
}

resource "aws_s3_bucket_acl" "this" {
  for_each = local.buckets
  bucket = aws_s3_bucket.this[each.key].id
  acl    = "private"
}

With this configuration, the plan will not contain information about which attribute of the aws_s3_bucket resource is referenced by the aws_s3_bucket_acl resource.

See more here.