Archived

This repository has been archived on 2026-08-04. You can view files and clone it, but cannot push or open issues or pull requests.

Adam Moussa 77302a1ebb feat(secrev): Phase-3 IAM artifacts for cross-review (aws-posture gated)

Authored FILES (not applied to AWS — provisioning gated behind the mandatory
GPT-4.1 IAM cross-review + Adam, design §7 B3) for the aws-posture checker's
read-only AWS identity. Decision D5: box stays read-only, auths via IAM Roles
Anywhere short-lived leaf certs from a new internal step-ca; NO long-lived AWS key.

  - aws-posture-readonly-policy.json  least-privilege read-only (ce:Get*,
      cloudwatch:GetMetric*/DescribeAlarms, ec2/elb/rds:Describe*, lambda list +
      GetFunctionConfiguration, s3:ListAllMyBuckets/GetBucketLocation). No write,
      no iam:* mutation, no s3:GetObject/secrets/kms/logs data reads, no wildcard
      actions. Resource:* only where AWS has no resource-level support.
  - aws-posture-readonly-policy.rationale.md  per-statement least-privilege rationale.
  - aws-posture-trust-policy.json  pins Roles Anywhere principal + leaf subject CN +
      issuer CN + trust-anchor SourceArn (three conditions, all required).
  - roles-anywhere-config.json  trust anchor (pins step-ca root) + profile (1h session).
  - step-ca-config-sketch.md  internal CA config + systemd-timer leaf auto-renewal.
  - CROSS-REVIEW-PACKET.md  end-to-end trust model, blast radius, EXERCISED rollback,
      reviewer scrutiny list.

Does NOT build aws-posture.sh, touch checker_coordinator.sh, or requirements.txt.

2026-06-18 16:17:56 -04:00

3.8 KiB

Raw Blame History

aws-posture-readonly-policy.json — least-privilege rationale

This is the annotated companion to aws-posture-readonly-policy.json. The policy JSON itself is kept strictly valid (no inline Comment keys — IAM rejects those), so all rationale lives here. This policy is the permission set for the aws-posture checker (design D5 / §4): idle / anomalous-spend watch on the Sea Haven AWS account (328440206208, us-east-1).

aws-posture itself is NOT built in this change — it is hard-gated behind the mandatory GPT-4.1 IAM cross-review (design §7, B3). This file + the policy are the review inputs.

Design principle

The box stays read-only. There is no write action, no iam:* mutating action, no Resource wildcard where AWS supports resource-level scoping. Idle-spend posture is an account-wide, list-oriented read: most of the actions below are AWS APIs that do not support resource-level ARNs at all (Cost Explorer, the CloudWatch metric-data calls, and the EC2/ELB/ RDS Describe* list operations). For those, least-privilege is enforced by the action allow-list (only the specific read verbs), not by narrowing Resource.

Statement-by-statement

Sid	Why aws-posture needs it	Why read-only / why `Resource: "*"`
`CostAndUsageReadOnly`	The core idle/anomalous-spend signal (the design flags ≈$330/mo). `GetCostAndUsage`, forecasts, dimensions, and the native CE anomaly detectors.	Cost Explorer is an account-scoped service; its API has no resource-level ARNs, so `Resource:` is the only valid form. Only `Get` verbs — no `ce:Update/Create/Delete*`, no budget mutation.
`CloudWatchMetricsReadOnly`	Correlate spend with utilization (an instance billing but at ~0% CPU is idle). `GetMetricData`/`GetMetricStatistics`/`ListMetrics`; `DescribeAlarms*` to see whether an idle resource is already alarmed.	These metric-read APIs do not support resource-level permissions. No `PutMetricData`, no alarm create/modify/delete.
`Ec2DescribeReadOnly`	The classic idle-spend inventory: stopped instances still paying for EBS, unattached volumes, unassociated Elastic IPs, idle NAT gateways, orphan snapshots/AMIs.	`Describe` is read-only; these list calls don't take resource ARNs. No `Run/Start/Stop/Terminate/Modify/Create/Delete`.**
`ElbAndRdsDescribeReadOnly`	Idle load balancers (no healthy targets) and idle/oversized RDS are frequent waste. `Describe*` only.	List APIs without resource-level ARNs. *No `rds:Modify/Delete/Reboot`, no ELB mutation.**
`LambdaAndStorageInventoryReadOnly`	Inventory functions + buckets to correlate against CloudWatch idle metrics.	Deliberately excludes `s3:GetObject` — the role never reads object data, only `ListAllMyBuckets` + `GetBucketLocation` (existence/region). No `lambda:InvokeFunction`, no Lambda mutation. This is the tightest the inventory can be while still seeing what exists.

What is deliberately NOT here (blast-radius containment)

No iam:*, sts:AssumeRole onward-chaining, organizations:*, or account:*.
No s3:GetObject / s3:GetObjectVersion (no data-plane read of any bucket).
No secretsmanager:GetSecretValue / ssm:GetParameter* (no secret read).
No kms:Decrypt, no logs:GetLogEvents (no log/data exfil path).
No write/modify/delete verb in any service.

A leaked session from this role can enumerate and price the account, and nothing more — it cannot read application data, secrets, or change a single resource.

Comparison to the AWS-managed alternatives

ReadOnlyAccess / ViewOnlyAccess are far broader (they include s3:GetObject, dynamodb:GetItem, secretsmanager list, etc.). This custom policy is intentionally a small fraction of those — only the cost + idle-inventory surface the checker actually queries.

3.8 KiB Raw Blame History