fix(terraform_plan): fix CloudStorageSelfLogging for buckets without logging

[jeffreytolar]

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Description

When running checkov on a plan for a GCS bucket without logging defined:

resource "google_storage_bucket" "bucket" {
  name                        = "5bc85a21-7150-48f7-be36-0a8570c6209f"
  location                    = "us-central1"
  storage_class               = "STANDARD"
  force_destroy               = true
  uniform_bucket_level_access = true
  public_access_prevention    = "enforced"
}

checkov complains:

Check: CKV_GCP_63: "Bucket should not log to itself"
	FAILED for resource: google_storage_bucket.bucket
	File: /tfplan.json:0-0
	Guide: https://docs.prismacloud.io/en/enterprise-edition/policy-reference/google-cloud-policies/google-cloud-storage-gcs-policies/bc-gcp-logging-3

This is because in the plan, Terraform populates an empty array as the logging value (likely refreshed from the live resource):

      "resources": [
        {
          "address": "google_storage_bucket.bucket",
          "values": {
            "logging": [],
          }
        }

New/Edited policies (Delete if not relevant)

• CKV_GCP_63

Fix

How does someone fix the issue in code and/or in runtime?

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas n/a
• I have made corresponding changes to the documentation n/a
• I have added tests that prove my feature, policy, or fix is effective and works
• New and existing tests pass locally with my changes
  • though I didn't run the full suite

[jeffreytolar]

I'm not sure in what other cases conf["logging"][0] would be empty. This appears to date back to the initial introduction of this resource way back in #878.

From the test plan, the "logging": [] gets translated to conf["logging"] = [[]], i.e., an array containing an empty array.

[jeffreytolar]

This is a real plan, but I did edit it slightly to remove my project details