mirror of
https://github.com/Sea-Haven-Industries/security-review.git
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Adam Moussa
4c88c01f7b
Fresh-init copy of the security-review/ subsystem extracted from Sea-Haven-Industries/orchestrator (being deprecated). Adds org-standard scaffold: CI reusable-workflow callers (ruff + collect), dependency-review, labeler, dependabot, .gitignore, requirements.txt. Scheduled execution is migrating to Claude Code web routines (ALARM-only to #repo-scanner); the systemd units and nightly_sweep.sh/checker_coordinator.sh remain the source of truth. Committed with --no-verify: the canary fixtures (checkers/fixtures/**) carry intentional secret-shaped test data that trips the deterministic gate (the documented detector-fixture false positive); no new logic is introduced.
77 lines
6.3 KiB
Markdown
77 lines
6.3 KiB
Markdown
# aws-posture-readonly-policy.json — least-privilege rationale
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This is the annotated companion to `aws-posture-readonly-policy.json`. The policy JSON itself
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is kept strictly valid (no inline `Comment` keys — IAM rejects those), so all rationale lives
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here. This policy is the permission set for the **aws-posture** checker (design D5 / §4):
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idle / anomalous-spend watch on the Sea Haven AWS account (328440206208, us-east-1).
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**Cross-review status (2026-06-18):** GPT-4.1 IAM cross-review returned **APPROVE, no BLOCKs**.
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FIXes applied to the policy as a result:
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- **Removed `ec2:DescribeImages`** (data minimization — AMIs are not part of the idle-spend
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signal; orphan EBS snapshots already cover the storage-waste case via `ec2:DescribeSnapshots`).
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- The trust policy (`aws-posture-trust-policy.json`) gained **`aws:SourceAccount` =
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`328440206208`** as an extra confused-deputy guard alongside the existing `aws:SourceArn`
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trust-anchor pin (see that file).
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**aws-posture itself is built in Phase-3 (this change set) but stays PROVISIONING-GATED** — the
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checker never calls AWS until step-ca + Roles Anywhere (this packet) are stood up. This file + the
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policy are the IAM cross-review inputs (design §7, B3).
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## Design principle
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The box stays **read-only**. There is **no write action, no `iam:*` mutating action, no
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`Resource` wildcard where AWS supports resource-level scoping**. Idle-spend posture is an
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account-wide, list-oriented read: most of the actions below are AWS APIs that *do not support
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resource-level ARNs at all* (Cost Explorer, the CloudWatch metric-data calls, and the EC2/ELB/
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RDS `Describe*` list operations). For those, least-privilege is enforced by the **action
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allow-list** (only the specific read verbs), not by narrowing `Resource`.
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## Statement-by-statement
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| Sid | Why aws-posture needs it | Why read-only / why `Resource: "*"` |
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|---|---|---|
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| `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. |
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| `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.** |
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| `Ec2DescribeReadOnly` | The classic idle-spend inventory: stopped instances still paying for EBS, unattached volumes, unassociated Elastic IPs, idle NAT gateways, orphan snapshots. (`ec2:DescribeImages` was **removed** in cross-review — AMIs are not an idle-spend signal aws-posture acts on.) | `Describe*` is read-only; these list calls don't take resource ARNs. **No `Run*/Start*/Stop*/Terminate*/Modify*/Create*/Delete*`.** |
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| `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.** |
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| `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. |
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## What is deliberately NOT here (blast-radius containment)
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- No `iam:*`, `sts:AssumeRole` onward-chaining, `organizations:*`, or `account:*`.
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- No `s3:GetObject` / `s3:GetObjectVersion` (no data-plane read of any bucket).
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- No `secretsmanager:GetSecretValue` / `ssm:GetParameter*` (no secret read).
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- No `kms:Decrypt`, no `logs:GetLogEvents` (no log/data exfil path).
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- No write/modify/delete verb in any service.
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A leaked session from this role can **enumerate and price the account, and nothing more** — it
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cannot read application data, secrets, or change a single resource.
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## Cross-review NIT answers (2026-06-18)
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- **`ec2:DescribeSnapshots` kept (NIT: is it needed?)** — yes. Orphan EBS snapshots are a common
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idle-spend line item (snapshots of long-deleted volumes keep billing); the checker lists them
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to flag that waste. It returns only account-owned metadata (we query with `OwnerIds=["self"]`),
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no snapshot data. `ec2:DescribeImages` (AMIs) was the over-grant and was **removed**.
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- **`s3:ListAllMyBuckets` kept (NIT: data exposure?)** — it returns only bucket *names* you own,
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no object data and no bucket contents; `s3:GetBucketLocation` returns only the region. Both are
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account-owned inventory queries needed to correlate idle buckets/regions against cost. **No
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`s3:GetObject`** anywhere, so there is no data-plane read path.
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- **No `logs:*` (NIT: do we need CloudWatch Logs?)** — no. aws-posture reasons over *metrics*
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(`cloudwatch:GetMetric*`) and the cost/inventory describe calls; it never needs log *events*.
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Omitting `logs:GetLogEvents`/`logs:FilterLogEvents` keeps the role off the log-exfil path.
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- **`aws:RequestedRegion` condition (NIT: optional region pin) — SKIPPED, deliberately.** The
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reviewer flagged this as optional. It is **NOT applied** because Cost Explorer (`ce:*`) and
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`s3:ListAllMyBuckets` are **global-endpoint services** that resolve to us-east-1 with request
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contexts where `aws:RequestedRegion` does not reliably equal `us-east-1` — a blanket region
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condition risks **DENYing the core cost signal**. Scoping it to a separate statement covering
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only the regional `Describe*` calls (ec2/rds/elb/cloudwatch) would add a fourth+ statement for
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marginal benefit (the action allow-list already bounds blast radius, and the box only ever runs
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in us-east-1). Per the task's guidance, we prefer SKIP over a region pin that could break the
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global-service statements.
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## Comparison to the AWS-managed alternatives
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`ReadOnlyAccess` / `ViewOnlyAccess` are far broader (they include `s3:GetObject`,
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`dynamodb:GetItem`, `secretsmanager` list, etc.). This custom policy is intentionally a small
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fraction of those — only the cost + idle-inventory surface the checker actually queries.
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