Security review (6 detectors + proof-or-kill verifier) confirmed 1 critical and
1 high in the first revision, both inherited by mirroring the SAM copy's
Resource "*" role grants:
- C1 (critical): iam:UpdateAssumeRolePolicy on "*" with DenySelfMutation
covering only three name patterns lets the principal repoint the
AdministratorAccess CDK bootstrap role's trust policy to an external account.
- C2 (high): the SAM justification for role/* (SAM auto-roles land at path /
with no settable RolePath) does not transfer -- Terraform's aws_iam_role
supports path.
Fixes, closing the class at the root rather than by denylist:
- All role writes, boundary sets and PassRole confined to role/tf-managed/*;
reads split into a separate statement that keeps Resource "*".
- DenySelfMutation extended to cdk-hnb659fds-*, OrganizationAccountAccessRole
and seahaven-* as defense in depth.
- OIDC provider made conditional (CreateOIDCProvider), mirroring the sibling
substrate, so a first-create rollback is recoverable rather than wedging the
stack in ROLLBACK_COMPLETE against a Retained orphan.
- README corrected: the guardrail policy is NOT Retain (only the provider is),
so the Deny backstops do not survive a stack delete.
checkov CKV_AWS_109 no longer fires on this template, so no suppression is
needed. The template header records every divergence from the SAM copy.
New stack seahaven-terraform-substrate (instances terraform-substrate-prod +
terraform-substrate-dev): app.terraform.io OIDC provider and the shared
boundary-gated guardrail policy seahaven-hcptf-iam-management that
per-workspace Terraform apply roles attach at migration time. No roles are
pre-provisioned (accumulator pattern, parallel to githubdeploy-*).
Guardrail statements mirror seahaven-cfn-exec-iam-management byte-identically
except DenySelfMutation, whose scope extends to hcptf-* alongside the
GitHub-substrate principals. Explicit stack dependency on the same-account
deploy-substrate stack (boundary ARN appears only in Condition strings, so
CFN infers no edge).
