94ed6ea224
* feat(secrev): doc-drift Plane-1 Tier-1 checker (UNGATED)
Third Plane-1 checker on the Phase-0 shared substrate, mirroring
compliance-drift.sh / dependency-cve.sh conventions verbatim (set -euo pipefail,
sourced substrate, --canary/--dry-run/--no-api/--refresh/--targets, mode-600
reports under $REPORT_ROOT/doc-drift/<UTC-date>/, ALARM-only, finding.schema
spirit JSON, exit 0/2/3, dotgit->.git fixture trick).
Detects documentation drift deterministically (design §4 doc-drift row):
- readme-omits-component: README omits an existing major component in the tree
(top-level service dir, SAM/CDK stack, Lambda handler dir, openapi/docs spec)
- readme-stale-vs-code: README last-touch far older than newest code commit
(two-factor: >=DOC_DRIFT_STALE_DAYS AND >=DOC_DRIFT_STALE_COMMITS)
A repo with NO README is SKIPPED (compliance-drift owns readme-present; no
double-flag). Future Gemini large-context judge (§4) is an inert stub (maybe_judge),
off in canary/dry-run/offline.
Planted-drift fixture corpus + EXPECTED_DRIFT_COUNT=4, canary-asserted (exit 3 on
miss). shellcheck -x clean (only accepted SC1091 source-line info).
Does NOT touch checker_coordinator.sh, requirements.txt, or aws-posture.
Wiring/systemd is gated (PROVISIONING footer). Design refs §4, §7 Phase 3.
* 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.
* fix(secrev): apply IAM cross-review FIXes
GPT-4.1 IAM cross-review 2026-06-18: APPROVE, no BLOCKs. Applied FIXes:
- trust policy: add aws:SourceAccount=328440206208 (confused-deputy guard)
alongside the existing aws:SourceArn trust-anchor pin
- readonly policy: remove ec2:DescribeImages (data minimization — AMIs are
not an idle-spend signal)
- aws:RequestedRegion NIT: deliberately SKIPPED — ce:* and s3:ListAllMyBuckets
are global-endpoint services a blanket region condition could DENY; rationale
recorded in aws-posture-readonly-policy.rationale.md
- rationale.md + CROSS-REVIEW-PACKET.md: record APPROVE + FIXes + NIT answers
(snapshots=account-owned idle signal; s3 list=names-only; no logs:* needed)
* feat(secrev): aws-posture checker (Tier-2, provisioning-gated)
Read-only Tier-2 idle/anomalous-spend + idle-resource posture checker for the
R720 agent-team (design D5 / §4 / §6.3 / §7 Phase 3). Mirrors the Tier-1 checker
conventions verbatim (flags --canary/--dry-run/--no-api/--targets, mode-600
report under $REPORT_ROOT/aws-posture/<date>/, ALARM-only, finding.schema.json
spirit, exit 0/2/3, shared substrate redact/post_slack_alarm).
Detectors (complement GuardDuty/SecurityHub/Config, do not replace):
- anomalous Cost Explorer deltas (ce get-anomalies, $-impact threshold)
- stopped EC2 still paying for attached EBS
- unattached EBS volumes
- unassociated Elastic IPs
- idle NAT gateways (≈0 bytes out)
- idle load balancers (0 healthy targets)
- idle RDS (0 connections over window)
Live AWS calls are PROVISIONING-GATED: they run ONLY when Roles Anywhere creds
are available (STS identity probe) AND not --no-api/--canary. With no creds or
--no-api/--canary the checker SKIPS live calls and notes them — NEVER alarms on
missing data (memory feedback_cloudwatch_alarms). Roles Anywhere/step-ca are not
stood up (IAM cross-review PASSED 2026-06-18; see security-review/iam/).
Offline canary: fixtures of mocked AWS responses (cost/describe-* JSON) under
fixtures/aws-posture/ + EXPECTED_FINDING_COUNT=7, asserted fully offline (no aws,
no network). Identical detector code runs online and offline. shellcheck-clean
(only accepted SC1091), chmod +x.
* fix(secrev): doc-drift fixture py ruff-clean (root CI runs check + format --check)
The repo-root CI lint runs both 'ruff check .' and 'ruff format --check .' over
all fixtures. Fixed E701 one-liners and ruff-formatted the sample-service .py
files (handlers/*, feature_*.py). Fixture content is irrelevant to doc-drift
(keys on file/dir presence + git staleness).
77 lines
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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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