Issue146 OIDC plan april

[Benettonkkb]

Addresses Issue 146

What changes did you make?

• Split plan/apply roles in aws-gha-oidc-providers.tf
• Registered new policy IncubatorTfPlanSecretsRead in aws-custom-policies.tf`
• new policy file: incubator-tf-plan-secrets-read-policy.tf

Why did you make the changes (we will use this info to test)?

• The original intention was to separate the Plan and Apply priv origin such that Plan didn't excessively have Admin-level privileges.
• New PR is made to navigate around issues in the old one. Will close and document this one as superseding it.

[Copilot]

Pull request overview

This PR aims to split GitHub Actions OIDC permissions for the hackforla/incubator Terraform workflows into separate Plan vs Apply IAM roles, reducing Plan privileges while keeping Apply capable of administering infrastructure.

Changes:

• Added distinct IAM roles for Terraform plan (incubator-tf-plan) and apply (incubator-tf-apply) with different OIDC trust conditions and policy attachments.
• Added a new custom IAM policy (IncubatorTfPlanSecretsRead) and registered it in the custom policy module.
• Introduced a new JSON policy document granting Terraform plan access to specific Secrets Manager secrets.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
terraform/aws-gha-oidc-providers.tf	Adds separate plan/apply OIDC-assumable roles and attaches policies.
terraform/aws-custom-policies.tf	Registers the new custom policy in the custom policies module.
terraform/aws-custom-policies/incubator-tf-plan-secrets-read-policy.json	Defines Secrets Manager read permissions for Terraform plan.

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[Copilot]

Attaching only the AWS managed ReadOnlyAccess policy to the Terraform plan role is likely insufficient for a remote S3 backend with DynamoDB state locking (this repo configures dynamodb_table in prod.backend.tfvars). Terraform plan/init typically needs write permissions to the lock table (e.g., dynamodb:PutItem, DeleteItem, UpdateItem) and appropriate S3 backend access; otherwise CI plans will fail when locking the state. Consider adding a minimal backend-access policy (S3 state bucket + DynamoDB lock table) to this role, instead of (or in addition to) ReadOnlyAccess.

[Copilot]

PR description mentions a new policy file incubator-tf-plan-secrets-read-policy.tf, but the change here references incubator-tf-plan-secrets-read-policy.json. If the PR description is outdated/typo, consider updating it to match the actual file name/type to avoid confusion for reviewers and future maintainers.

[github-actions]

Terraform plan in terraform
With backend config files: terraform/prod.backend.tfvars

Plan: 3 to add, 0 to change, 0 to destroy.

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
+   create

Terraform will perform the following actions:

  # aws_iam_role_policy_attachment.incubator_tf_plan_secrets_read will be created
+   resource "aws_iam_role_policy_attachment" "incubator_tf_plan_secrets_read" {
+       id         = (known after apply)
+       policy_arn = (known after apply)
+       role       = "incubator-tf-plan"
    }

  # module.aws_custom_policies.aws_iam_policy.custom_policy["IncubatorTfPlanSecretsRead"] will be created
+   resource "aws_iam_policy" "custom_policy" {
+       arn              = (known after apply)
+       attachment_count = (known after apply)
+       description      = "Allows incubator tf plan role to read specific Secrets Manager secrets needed for terraform plan"
+       id               = (known after apply)
+       name             = "IncubatorTfPlanSecretsRead"
+       name_prefix      = (known after apply)
+       path             = "/"
+       policy           = jsonencode(
            {
+               Statement = [
+                   {
+                       Action   = [
+                           "secretsmanager:GetSecretValue",
                        ]
+                       Effect   = "Allow"
+                       Resource = [
+                           "arn:aws:secretsmanager:us-west-2:035866691871:secret:*",
                        ]
+                       Sid      = "AllowReadSpecificSecretsForTerraformPlan"
                    },
                ]
+               Version   = "2012-10-17"
            }
        )
+       policy_id        = (known after apply)
+       tags_all         = (known after apply)
    }

  # module.iam_oidc_gha_incubator.aws_iam_role_policy_attachment.github_actions_oidc["arn:aws:iam::aws:policy/AdministratorAccess"] will be created
+   resource "aws_iam_role_policy_attachment" "github_actions_oidc" {
+       id         = (known after apply)
+       policy_arn = "arn:aws:iam::aws:policy/AdministratorAccess"
+       role       = "gha-incubator"
    }

Plan: 3 to add, 0 to change, 0 to destroy.

📝 Plan generated in Write Terraform Plan to Pull Request #101