AccountFoundation audit-delivery S3 bucket could be silently weakened

Affected: @hulumi/baseline < 1.4.0 — Fixed in: 1.4.0 — Severity: High — CWE-1059 (Insufficient Technical Documentation / Behavioral Inconsistency)

Summary

The S3 bucket that AccountFoundation creates to receive CloudTrail and AWS Config audit logs is meant to be tamper-resistant — if someone with delete access can erase from it, the forensic trail is gone. There were three independent ways the protection could be silently weakened:

1. No Write-Once-Read-Many on the startup-hardened audit bucket. The startup-hardened tier hard-coded objectLock: false on the audit bucket. (The reason was real — bucket-wide Object Lock blocks an AWS Config write-then-delete probe — but the fix was a sledgehammer that disabled WORM for all objects, not just the probe key.)
2. forceDestroy was forwarded to the audit bucket. Nothing prevented a downstream stack from setting logBucketForceDestroy: true, which made pulumi destroy purge every audit-log object on teardown.
3. Sandbox tier dropped everything. Sandbox-tier AccountFoundation created its audit bucket with tier: "sandbox", which skipped Object Lock, server access logging, AND the CloudTrail-Lake EventDataStore (the independent immutable mirror) — leaving sandbox accounts with no audit immutability at all.

Impact

Consumers using AccountFoundation could ship an AWS account whose CloudTrail / Config audit logs were deletable by any S3-delete-capable principal — while believing the startup-hardened tier guaranteed tamper-resistance. Sandbox-tier deployments had no audit immutability at all (defects 1 and 3 compounded).

Patches

Upgrade to @hulumi/baseline@1.4.0. A single invariant in SecureBucket now fires whenever the bucket actually backs CloudTrail/Config delivery (i.e. awsServiceLogDelivery.cloudTrail === true || .config === true):

• refuses forceDestroy: true on the startup-hardened tier;
• emits the CloudTrail-Lake EventDataStore regardless of parent tier (so sandbox accounts regain immutable audit capture);
• adds a deny-s3:DeleteObject* bucket-policy statement scoped to the CloudTrail and Config history/snapshot prefixes (a retention floor on the audit objects). The deny excludes the AWS Config ConfigWritabilityCheckFile probe key so Config's write-then-delete still works, which is why bucket-wide Object Lock is intentionally NOT re-enabled.

Workarounds

Replicating audit logs out-of-account to an Object-Locked archive bucket partially mitigates while you upgrade.

References

• PR #178 (Cluster C); see CHANGELOG ### Migration for the forceDestroy behaviour change.