# Authority Plug-in Developer Guide

> **Status:** Updated 2025-10-11 (AUTHPLUG-DOCS-01-001) with lifecycle + limiter diagrams and refreshed rate-limit guidance aligned to PLG6 acceptance criteria.

## 1. Overview
Authority plug-ins extend the **StellaOps Authority** service with custom identity providers, credential stores, and client-management logic. Unlike Feedser plug-ins (which ingest or export advisories), Authority plug-ins participate directly in authentication flows:

- **Use cases:** integrate corporate directories (LDAP/AD), delegate to external IDPs, enforce bespoke password/lockout policies, or add client provisioning automation.
- **Constraints:** plug-ins load only during service start (no hot-reload), must function without outbound internet access, and must emit deterministic results for identical configuration and input data.
- **Ship targets:** target the same .NET 10 preview as the host, honour offline-first requirements, and provide clear diagnostics so operators can triage issues from `/ready`.

## 2. Architecture Snapshot
Authority hosts follow a deterministic plug-in lifecycle. The flow below can be rendered as a sequence diagram in the final authored documentation, but all touchpoints are described here for offline viewers:

1. **Configuration load** – `AuthorityPluginConfigurationLoader` resolves YAML manifests under `etc/authority.plugins/`.
2. **Assembly discovery** – the shared `PluginHost` scans `PluginBinaries/Authority` for `StellaOps.Authority.Plugin.*.dll` assemblies.
3. **Registrar execution** – each assembly is searched for `IAuthorityPluginRegistrar` implementations. Registrars bind options, register services, and optionally queue bootstrap tasks.
4. **Runtime** – the host resolves `IIdentityProviderPlugin` instances, uses capability metadata to decide which OAuth grants to expose, and invokes health checks for readiness endpoints.

![Authority plug-in lifecycle diagram](../assets/authority/authority-plugin-lifecycle.svg)

_Source:_ `docs/assets/authority/authority-plugin-lifecycle.mmd`

**Data persistence primer:** the standard Mongo-backed plugin stores users in collections named `authority_users_<pluginName>` and lockout metadata in embedded documents. Additional plugins must document their storage layout and provide deterministic collection naming to honour the Offline Kit replication process.

## 3. Capability Metadata
Capability flags let the host reason about what your plug-in supports:

- Declare capabilities in your descriptor using the string constants from `AuthorityPluginCapabilities` (`password`, `mfa`, `clientProvisioning`, `bootstrap`). The configuration loader now validates these tokens and rejects unknown values at startup.
- `AuthorityIdentityProviderCapabilities.FromCapabilities` projects those strings into strongly typed booleans (`SupportsPassword`, etc.). Authority Core will use these flags when wiring flows such as the password grant. Built-in plugins (e.g., Standard) will fail fast or force-enable required capabilities if the descriptor is misconfigured, so keep manifests accurate.
- Typical configuration (`etc/authority.plugins/standard.yaml`):
  ```yaml
  plugins:
    descriptors:
      standard:
        assemblyName: "StellaOps.Authority.Plugin.Standard"
        capabilities:
          - password
          - bootstrap
  ```
- Only declare a capability if the plug-in genuinely implements it. For example, if `SupportsClientProvisioning` is `true`, the plug-in must supply a working `IClientProvisioningStore`.

**Operational reminder:** the Authority host surfaces capability summaries during startup (see `AuthorityIdentityProviderRegistry` log lines). Use those logs during smoke tests to ensure manifests align with expectations.

**Configuration path normalisation:** Manifest-relative paths (e.g., `tokenSigning.keyDirectory: "../keys"`) are resolved against the YAML file location and environment variables are expanded before validation. Plug-ins should expect to receive an absolute, canonical path when options are injected.

**Password policy guardrails:** The Standard registrar logs a warning when a plug-in weakens the default password policy (minimum length or required character classes). Keep overrides at least as strong as the compiled defaults—operators treat the warning as an actionable security deviation.

## 4. Project Scaffold
- Target **.NET 10 preview**, enable nullable, treat warnings as errors, and mark Authority plug-ins with `<IsAuthorityPlugin>true</IsAuthorityPlugin>`.
- Minimum references:
  - `StellaOps.Authority.Plugins.Abstractions` (contracts & capability helpers)
  - `StellaOps.Plugin` (hosting/DI helpers)
  - `StellaOps.Auth.*` libraries as needed for shared token utilities (optional today).
- Example `.csproj` (trimmed from `StellaOps.Authority.Plugin.Standard`):
  ```xml
  <Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
      <TargetFramework>net10.0</TargetFramework>
      <Nullable>enable</Nullable>
      <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
      <IsAuthorityPlugin>true</IsAuthorityPlugin>
    </PropertyGroup>
    <ItemGroup>
      <ProjectReference Include="..\StellaOps.Authority.Plugins.Abstractions\StellaOps.Authority.Plugins.Abstractions.csproj" />
      <ProjectReference Include="..\..\StellaOps.Plugin\StellaOps.Plugin.csproj" />
    </ItemGroup>
  </Project>
  ```
  (Add other references—e.g., MongoDB driver, shared auth libraries—according to your implementation.)

## 5. Implementing `IAuthorityPluginRegistrar`
- Create a parameterless registrar class that returns your plug-in type name via `PluginType`.
- Use `AuthorityPluginRegistrationContext` to:
  - Bind options (`AddOptions<T>(pluginName).Bind(...)`).
  - Register singletons for stores/enrichers using manifest metadata.
  - Register any hosted bootstrap tasks (e.g., seed admin users).
- Always validate configuration inside `PostConfigure` and throw meaningful `InvalidOperationException` to fail fast during startup.
- Use the provided `ILoggerFactory` from DI; avoid static loggers or console writes.
- Example skeleton:
  ```csharp
  internal sealed class MyPluginRegistrar : IAuthorityPluginRegistrar
  {
      public string PluginType => "my-custom";

      public void Register(AuthorityPluginRegistrationContext context)
      {
          var name = context.Plugin.Manifest.Name;

          context.Services.AddOptions<MyPluginOptions>(name)
              .Bind(context.Plugin.Configuration)
              .PostConfigure(opts => opts.Validate(name));

          context.Services.AddSingleton<IIdentityProviderPlugin>(sp =>
              new MyIdentityProvider(context.Plugin, sp.GetRequiredService<MyCredentialStore>(),
                                     sp.GetRequiredService<MyClaimsEnricher>(),
                                     sp.GetRequiredService<ILogger<MyIdentityProvider>>()));
      }
  }
  ```

## 6. Identity Provider Surface
- Implement `IIdentityProviderPlugin` to expose:
  - `IUserCredentialStore` for password validation and user CRUD.
  - `IClaimsEnricher` to append roles/attributes onto issued principals.
  - Optional `IClientProvisioningStore` for machine-to-machine clients.
  - `AuthorityIdentityProviderCapabilities` to advertise supported flows.
- Password guidance:
  - Standard plug-in hashes via `ICryptoProvider` using Argon2id by default and emits PHC-compliant strings. Successful PBKDF2 logins trigger automatic rehashes so migrations complete gradually. See `docs/security/password-hashing.md` for tuning advice.
  - Enforce password policies before hashing to avoid storing weak credentials.
- Health checks should probe backing stores (e.g., Mongo `ping`) and return `AuthorityPluginHealthResult` so `/ready` can surface issues.
- When supporting additional factors (e.g., TOTP), implement `SupportsMfa` and document the enrolment flow for resource servers.

## 7. Configuration & Secrets
- Authority looks for manifests under `etc/authority.plugins/`. Each YAML file maps directly to a plug-in name.
- Support environment overrides using `STELLAOPS_AUTHORITY_PLUGINS__DESCRIPTORS__<NAME>__...`.
- Never store raw secrets in git: allow operators to supply them via `.local.yaml`, environment variables, or injected secret files. Document which keys are mandatory.
- Validate configuration as soon as the registrar runs; use explicit error messages to guide operators. The Standard plug-in now enforces complete bootstrap credentials (username + password) and positive lockout windows via `StandardPluginOptions.Validate`.
- Cross-reference bootstrap workflows with `docs/ops/authority_bootstrap.md` (to be published alongside CORE6) so operators can reuse the same payload formats for manual provisioning.
- `passwordHashing` inherits defaults from `authority.security.passwordHashing`. Override only when hardware constraints differ per plug-in:
  ```yaml
  passwordHashing:
    algorithm: Argon2id
    memorySizeInKib: 19456
    iterations: 2
    parallelism: 1
  ```
  Invalid values (≤0) fail fast during startup, and legacy PBKDF2 hashes rehash automatically once the new algorithm succeeds.

### 7.1 Token Persistence Contract
- The host automatically persists every issued principal (access, refresh, device, authorization code) in `authority_tokens`. Plug-in code **must not** bypass this store; use the provided `IAuthorityTokenStore` helpers when implementing custom flows.
- When a plug-in disables a subject or client outside the standard handlers, call `IAuthorityTokenStore.UpdateStatusAsync(...)` for each affected token so revocation bundles stay consistent.
- Supply machine-friendly `revokedReason` codes (`compromised`, `rotation`, `policy`, `lifecycle`, etc.) and optional `revokedMetadata` entries when invalidating credentials. These flow straight into `revocation-bundle.json` and should remain deterministic.
- Token scopes should be normalised (trimmed, unique, ordinal sort) before returning from plug-in verification paths. `TokenPersistenceHandlers` will keep that ordering for downstream consumers.

### 7.2 Claims & Enrichment Checklist
- Authority always sets the OpenID Connect basics: `sub`, `client_id`, `preferred_username`, optional `name`, and `role` (for password flows). Plug-ins must use `IClaimsEnricher` to append additional claims in a **deterministic** order (sort arrays, normalise casing) so resource servers can rely on stable shapes.
- Recommended enrichment keys:
  - `stellaops.realm` – plug-in/tenant identifier so services can scope policies.
  - `stellaops.subject.type` – values such as `human`, `service`, `bootstrap`.
  - `groups` / `projects` – sorted arrays describing operator entitlements.
- Claims visible in tokens should mirror what `/token` and `/userinfo` emit. Avoid injecting sensitive PII directly; mark values with `ClassifiedString.Personal` inside the plug-in so audit sinks can tag them appropriately.
- For client-credential flows, remember to enrich both the client principal and the validation path (`TokenValidationHandlers`) so refresh flows keep the same metadata.

### 7.3 Revocation Bundles & Reasons
- Use `IAuthorityRevocationStore` to record subject/client/token revocations when credentials are deleted or rotated. Stick to the standard categories (`token`, `subject`, `client`, `key`).
- Include a deterministic `reason` string and optional `reasonDescription` so operators understand *why* a subject was revoked when inspecting bundles offline.
- Plug-ins should populate `metadata` with stable keys (e.g., `revokedBy`, `sourcePlugin`, `ticketId`) to simplify SOC correlation. The keys must be lowercase, ASCII, and free of secrets—bundles are mirrored to air-gapped agents.

## 8. Rate Limiting & Lockout Interplay
Rate limiting and account lockouts are complementary controls. Plug-ins must surface both deterministically so operators can correlate limiter hits with credential rejections.

**Baseline quotas** (from `docs/dev/authority-rate-limit-tuning-outline.md`):

| Endpoint | Default policy | Notes |
|----------|----------------|-------|
| `/token` | 30 requests / 60s, queue 0 | Drop to 10/60s for untrusted ranges; raise only with WAF + monitoring. |
| `/authorize` | 60 requests / 60s, queue 10 | Reduce carefully; interactive UX depends on headroom. |
| `/internal/*` | Disabled by default; recommended 5/60s when enabled | Keep queue 0 for bootstrap APIs. |

**Retry metadata:** The middleware stamps `Retry-After` plus tags `authority.client_id`, `authority.remote_ip`, and `authority.endpoint`. Plug-ins should keep these tags intact when crafting responses or telemetry so dashboards remain consistent.

**Lockout counters:** Treat lockouts as **subject-scoped** decisions. When multiple instances update counters, reuse the deterministic tie-breakers documented in `src/DEDUP_CONFLICTS_RESOLUTION_ALGO.md` (freshness overrides, precedence, and stable hashes) to avoid divergent lockout states across replicas.

**Alerting hooks:** Emit structured logs/metrics when either the limiter or credential store rejects access. Suggested gauges include `aspnetcore_rate_limiting_rejections_total{limiter="authority-token"}` and any custom `auth.plugins.<pluginName>.lockouts_total` counter.

![Authority rate limit and lockout flow](../assets/authority/authority-rate-limit-flow.svg)

_Source:_ `docs/assets/authority/authority-rate-limit-flow.mmd`

## 9. Logging, Metrics, and Diagnostics
- Always log via the injected `ILogger<T>`; include `pluginName` and correlation IDs where available.
- Activity/metric names should align with `AuthorityTelemetry` constants (`service.name=stellaops-authority`).
- Expose additional diagnostics via structured logging rather than writing custom HTTP endpoints; the host will integrate these into `/health` and `/ready`.
- Emit metrics with stable names (`auth.plugins.<pluginName>.*`) when introducing custom instrumentation; coordinate with the Observability guild to reserve prefixes.

## 10. Testing & Tooling
- Unit tests: use Mongo2Go (or similar) to exercise credential stores without hitting production infrastructure (`StandardUserCredentialStoreTests` is a template).
- Determinism: fix timestamps to UTC and sort outputs consistently; avoid random GUIDs unless stable.
- Smoke tests: launch `dotnet run --project src/StellaOps.Authority/StellaOps.Authority` with your plug-in under `PluginBinaries/Authority` and verify `/ready`.
- Example verification snippet:
  ```csharp
  [Fact]
  public async Task VerifyPasswordAsync_ReturnsSuccess()
  {
      var store = CreateCredentialStore();
      await store.UpsertUserAsync(new AuthorityUserRegistration("alice", "Pa55!", null, null, false,
          Array.Empty<string>(), new Dictionary<string, string?>()), CancellationToken.None);

      var result = await store.VerifyPasswordAsync("alice", "Pa55!", CancellationToken.None);
      Assert.True(result.Succeeded);
      Assert.True(result.User?.Roles.Count == 0);
  }
  ```

## 11. Packaging & Delivery
- Output assembly should follow `StellaOps.Authority.Plugin.<Name>.dll` so the host’s search pattern picks it up.
- Place the compiled DLL plus dependencies under `PluginBinaries/Authority` for offline deployments; include hashes/signatures in release notes (Security Guild guidance forthcoming).
- Document any external prerequisites (e.g., CA cert bundle) in your plug-in README.
- Update `etc/authority.plugins/<plugin>.yaml` samples and include deterministic SHA256 hashes for optional bootstrap payloads when distributing Offline Kit artefacts.

## 12. Checklist & Handoff
- ✅ Capabilities declared and validated in automated tests.
- ✅ Bootstrap workflows documented (if `bootstrap` capability used) and repeatable.
- ✅ Local smoke test + unit/integration suites green (`dotnet test`).
- ✅ Operational docs updated: configuration keys, secrets guidance, troubleshooting.
- Submit the developer guide update referencing PLG6/DOC4 and tag DevEx + Docs reviewers for sign-off.

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Mermaid sources for the embedded diagrams live under `docs/assets/authority/`. Regenerate the SVG assets with your preferred renderer before committing future updates so the visuals stay in sync with the `.mmd` definitions.
