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- Added `SchedulerWorkerOptions` class to encapsulate configuration for the scheduler worker. - Introduced `PlannerBackgroundService` to manage the planner loop, fetching and processing planning runs. - Created `PlannerExecutionService` to handle the execution logic for planning runs, including impact targeting and run persistence. - Developed `PlannerExecutionResult` and `PlannerExecutionStatus` to standardize execution outcomes. - Implemented validation logic within `SchedulerWorkerOptions` to ensure proper configuration. - Added documentation for the planner loop and impact targeting features. - Established health check endpoints and authentication mechanisms for the Signals service. - Created unit tests for the Signals API to ensure proper functionality and response handling. - Configured options for authority integration and fallback authentication methods.
153 lines
8.9 KiB
Markdown
153 lines
8.9 KiB
Markdown
# Policy Exception Effects
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> **Audience:** Policy authors, reviewers, operators, and governance owners.
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> **Scope:** How exception definitions are authored, resolved, and surfaced by the Policy Engine during evaluation, including precedence rules, metadata flow, and simulation/diff behaviour.
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Exception effects let teams codify governed waivers without compromising determinism. This guide explains the artefacts involved, how the evaluator selects a single winning exception, and where downstream consumers observe the applied override.
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---
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## 1 · Exception Building Blocks
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| Artefact | Description |
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|----------|-------------|
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| **Exception Effect** | Declared inside a policy pack (`exceptions.effects`). Defines the override behaviour plus governance metadata. See effect fields in §2. |
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| **Routing Template** | Optional mapping (`exceptions.routingTemplates`) used by Authority to route approvals/MFA. Effects reference templates by id. |
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| **Exception Instance** | Stored outside the policy pack (Authority/API). Captures who requested the waiver, scope filters, metadata, and creation time. |
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Effects are validated at bind time (`PolicyBinder`), while instances are ingested alongside policy evaluation inputs. Both are normalized to case-insensitive identifiers to avoid duplicate conflicts.
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---
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## 2 · Effect Fields
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| Field | Required | Purpose | Notes |
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|-------|----------|---------|-------|
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| `id` | ✅ | Stable identifier (`[A-Za-z0-9-_]+`). | Must be unique per policy pack. |
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| `name` | — | Friendly label for consoles/reports. | Forwarded to verdict metadata if present. |
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| `effect` | ✅ | Behaviour enum: `suppress`, `defer`, `downgrade`, `requireControl`. | Case-insensitive. |
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| `downgradeSeverity` | ⚠️ | Target severity for `downgrade`. | Must map to DSL severities (`high`, `medium`, etc.). Validation enforced in `PolicyBinder` (`policy.exceptions.effect.downgrade.missingSeverity`). |
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| `requiredControlId` | ⚠️ | Control catalogue key for `requireControl`. | Required when effect is `requireControl`. |
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| `routingTemplate` | — | Connects to an Authority approval flow. | CLI/Console resolve to `authorityRouteId`. |
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| `maxDurationDays` | — | Soft limit for temporary waivers. | Must be > 0 when provided. |
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| `description` | — | Rich-text rationale. | Displayed in approvals centre (optional). |
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Authoring invalid combinations returns structured errors with JSON paths, preventing packs from compiling (see `src/StellaOps.Policy.Tests/PolicyBinderTests.cs:33`). Routing templates additionally declare `authorityRouteId` and `requireMfa` flags for governance routing.
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---
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## 3 · Exception Instances & Scope
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Instances are resolved from Authority or API collections and injected into the evaluation context (`PolicyEvaluationExceptions`). Each instance contains:
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| Field | Source | Usage |
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|-------|--------|-------|
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| `id` | Authority storage | Propagated to annotations and `appliedException.exceptionId`. |
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| `effectId` | Links to pack-defined effect | Must resolve to a known effect; otherwise ignored. |
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| `scope.ruleNames` | Optional list | Limits to specific rule identifiers. |
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| `scope.severities` | Optional list (`severity.normalized`) | Normalized against the evaluator’s severity string. |
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| `scope.sources` | Optional advisory sources (`GHSA`, `NVD`, …) | Compared against the advisory context. |
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| `scope.tags` | Optional SBOM tags | Matched using `sbom.has_tag(...)`. |
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| `createdAt` | RFC3339 UTC timestamp | Used as tie-breaker when specificity scores match. |
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| `metadata` | Arbitrary key/value bag | Copied to verdict annotations (`exception.meta.*`). |
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Scopes are case-insensitive and trimmed. Empty scopes behave as global waivers but still require routing and metadata supplied by Authority workflows.
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---
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## 4 · Resolution & Specificity
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Only one exception effect is applied per finding. Evaluation proceeds as follows:
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1. Filter instances whose `effectId` resolves to a known effect.
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2. Discard instances whose scope does not match the candidate finding (rule name, severity, advisory source, SBOM tags).
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3. Score remaining instances for **specificity**:
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- `ruleNames` ⇒ `1000 + (count × 25)`
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- `severities` ⇒ `500 + (count × 10)`
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- `sources` ⇒ `250 + (count × 10)`
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- `tags` ⇒ `100 + (count × 5)`
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4. Highest score wins. Ties fall back to the newest `createdAt`, then lexical `id` (stable sorting).
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These rules guarantee deterministic selection even when multiple waivers overlap. See `src/StellaOps.Policy.Engine.Tests/PolicyEvaluatorTests.cs:209` for tie-break coverage.
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---
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## 5 · Effect Behaviours
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| Effect | Status impact | Severity impact | Warnings / metadata |
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|--------|---------------|-----------------|---------------------|
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| `suppress` | Forces status `suppressed`. | No change. | `exception.status=suppressed`. |
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| `defer` | Forces status `deferred`. | No change. | `exception.status=deferred`. |
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| `downgrade` | No change. | Sets severity to configured `downgradeSeverity`. | `exception.severity` annotation. |
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| `requireControl` | No change. | No change. | Adds warning `Exception '<id>' requires control '<requiredControlId>'`. Annotation `exception.requiredControl`. |
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All effects stamp shared annotations: `exception.id`, `exception.effectId`, `exception.effectType`, optional `exception.effectName`, optional `exception.routingTemplate`, plus `exception.maxDurationDays`. Instance metadata is surfaced both in annotations (`exception.meta.<key>`) and the structured `AppliedException.Metadata` payload for downstream APIs. Behaviour is validated by unit tests (`src/StellaOps.Policy.Engine.Tests/PolicyEvaluatorTests.cs:130` & `src/StellaOps.Policy.Engine.Tests/PolicyEvaluatorTests.cs:169`).
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---
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## 6 · Explain, Simulation & Outputs
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- **Explain traces / CLI simulate** – Verdict payloads include `appliedException` capturing original vs applied status/severity, enabling diff visualisation in Console and CLI previews.
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- **Annotations** – Deterministic keys make it trivial for exports or alerting pipelines to flag waived findings.
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- **Warnings** – `requireControl` adds runtime warnings so operators can enforce completion of compensating controls.
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- **Routing** – When `routingTemplate` is populated, verdict metadata includes `routingTemplate`, allowing UI surfaces to deep-link into the approvals centre.
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Example verdict excerpt (JSON):
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```json
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{
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"status": "suppressed",
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"severity": "Critical",
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"annotations": {
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"exception.id": "exc-001",
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"exception.effectId": "suppress-critical",
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"exception.effectType": "Suppress",
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"exception.status": "suppressed",
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"exception.meta.requestedBy": "alice"
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},
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"appliedException": {
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"exceptionId": "exc-001",
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"effectId": "suppress-critical",
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"effectType": "Suppress",
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"originalStatus": "blocked",
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"appliedStatus": "suppressed",
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"metadata": {
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"effectName": "Rule Critical Suppress",
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"requestedBy": "alice"
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}
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}
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}
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```
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---
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## 7 · Operational Notes
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- **Authoring** – Policy packs must ship effect definitions before Authority can issue instances. CLI validation (`stella policy lint`) fails if required fields are missing.
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- **Approvals & MFA** – Effects referencing routing templates inherit `requireMfa` rules from `exceptions.routingTemplates`. Governance guidance in `/docs/11_GOVERNANCE.md` captures Authority approval flows and audit expectations.
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- **Presence in exports** – Even when an exception suppresses a finding, explain traces and effective findings retain the applied exception metadata for audit parity.
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- **Determinism** – Specificity scoring plus tie-breakers ensure repeatable outcomes across runs, supporting sealed/offline replay.
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---
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## 8 · Testing References
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- `src/StellaOps.Policy.Tests/PolicyBinderTests.cs:33` – Validates schema rules for defining effects, routing templates, and downgrade guardrails.
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- `src/StellaOps.Policy.Engine.Tests/PolicyEvaluatorTests.cs:130` – Covers suppression, downgrade, and metadata propagation.
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- `src/StellaOps.Policy.Engine.Tests/PolicyEvaluatorTests.cs:209` – Confirms specificity ordering and metadata forwarding for competing exceptions.
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---
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## 9 · Compliance Checklist
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- [ ] **Effect catalogue maintained:** Each policy pack documents available effects and routing templates for auditors.
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- [ ] **Authority alignment:** Approval routes in Authority mirror `routingTemplate` definitions and enforce MFA where required.
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- [ ] **Explain coverage:** Console/CLI surfaces display `appliedException` details and `exception.*` annotations for every waived verdict.
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- [ ] **Simulation parity:** `stella policy simulate` outputs include exception metadata, ensuring PR/CI reviews catch unintended waivers.
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- [ ] **Audit retention:** Effective findings history retains `appliedException` payloads so exception lifecycle reviews remain replayable.
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- [ ] **Tests locked:** Binder and evaluator tests covering exception paths remain green before publishing documentation updates.
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---
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*Last updated: 2025-10-27 (Sprint 25).*
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