docs: add ADR-0009 for Akrites CDP public API authentication (CM-1333)

docs/adr/0009-akrites-cdp-public-api-authentication.md

@@ -0,0 +1,204 @@
+# ADR-0009: Akrites → CDP public API authentication
+
+**Date**: 2026-07-15
+**Status**: proposed
+**Deciders**: CDP team, LF Auth, Akrites team
+
+## Context
+
+Akrites is a new upstream consumer that needs read-only access to CDP's public
+API. LF Auth provisions LF-managed M2M credentials using RSA keypair
+authentication: Akrites signs a JWT `client_assertion` with a vault-resident
+private key, exchanges it at LFX Auth0 for a short-lived Bearer token, then
+calls CDP. CDP verifies the token, enforces a single-consumer restriction, and
+gates endpoints on a dedicated scope.
+
+The Auth0 audience (resource-server identifier) is not yet finalized — it is
+referenced throughout as `{{AKRITES_CDP_AUDIENCE}}`.
+
+High-level overview: https://linuxfoundation-dxwx.dsp.so/fkNtkFCx-akrites-cdp-auth
+
+## Decision
+
+Authenticate Akrites via **LFX Auth0 with a dedicated resource server and
+required scopes**. On the CDP side, add an `azp` allowlist middleware
+after JWT verification that asserts the token was issued specifically to
+`{{AKRITES_AUTH0_CLIENT_ID}}`, so no other M2M client granted the same
+audience can reach the `/akrites` router.
+
+## Auth Flow
+
+```mermaid
+sequenceDiagram
+    participant Vault as LF Vault
+    participant Akrites
+    participant Auth0 as LFX Auth0
+    participant CDP
+
+    Note over Akrites,Vault: On startup or after rotation
+    Akrites->>Vault: read RSA private key
+    Vault-->>Akrites: private key
+
+    Note over Akrites,Auth0: Token exchange (repeated on expiry)
+    Akrites->>Akrites: sign client_assertion JWT (RS256)
+    Akrites->>Auth0: POST /oauth/token (client_credentials + jwt-bearer)
+    Auth0-->>Akrites: Bearer access_token (scope=read:<resource>)
+
+    Note over Akrites,CDP: API call
+    Akrites->>CDP: GET /public/v1/akrites/* + Bearer token
+    CDP->>Auth0: fetch JWKS (cached)
+    CDP->>CDP: oauth2Middleware: verify sig + iss + aud
+    CDP->>CDP: azpAllowlistMiddleware: assert azp == AKRITES_CLIENT_ID
+    CDP->>CDP: requireScopes: assert read:<resource>
+    CDP-->>Akrites: 200 OK
+
+    Note over Akrites,Auth0: On invalid_client (key rotated by LF)
+    Akrites->>Vault: re-read private key
+    Akrites->>Auth0: retry token exchange once
+```
+
+## Affected Repositories
+
+### `auth0-terraform`
+
+Three changes. The existing `auth0_resource_server.cdp_public_api` (lines 400–494
+of `resource_servers.tf`) and `grants_cdp.tf` are the direct reference — Akrites
+gets its own isolated resource server, not a grant on the shared CDP one.
+
+**`resource_servers.tf`** — add these two blocks:
+```hcl
+resource "auth0_resource_server" "cdp_akrites_api" {
+  name = "CDP Akrites API"
+  identifier = {
+    "dev"     = "{{AKRITES_CDP_AUDIENCE_DEV}}"
+    "staging" = "{{AKRITES_CDP_AUDIENCE_STAGING}}"
+    "prod"    = "{{AKRITES_CDP_AUDIENCE_PROD}}"
+  }[terraform.workspace]
+
+  signing_alg = "RS256"
+  token_lifetime = {
+    "dev"     = 3600
+    "staging" = 10800
+    "prod"    = 10800
+  }[terraform.workspace]
+  token_dialect        = "access_token"
+  allow_offline_access = false
+
+  subject_type_authorization {
+    user   { policy = "deny_all" }
+    client { policy = "require_client_grant" }
+  }
+}
+
+resource "auth0_resource_server_scopes" "cdp_akrites_api" {
+  resource_server_identifier = auth0_resource_server.cdp_akrites_api.identifier
+
+  scopes {
+    name        = "read:<resource>"
+    description = "Read-only access to CDP data via the Akrites API"
+  }
+}
+```
+
+**`clients_m2m.tf`** — add one entry to `local.m2m_clients` (line ~10):
+```hcl
+"Akrites" = { oidc_conformant = true },
+```
+The existing `auth0_client.m2m_clients` `for_each` resource instantiates it
+automatically with `grant_types = ["client_credentials"]`. Auth method starts
+as `client_secret_post`; `lfx-secrets-management` rotation converts it to
+Private Key JWT — same as all other M2M clients.
+
+**`grants_akrites.tf`** _(new file)_
+```hcl
+resource "auth0_client_grant" "akrites_cdp" {
+  client_id  = auth0_client.m2m_clients["Akrites"].id
+  audience   = auth0_resource_server.cdp_akrites_api.identifier
+  scopes     = ["read:<resource>"]
+  depends_on = [auth0_resource_server_scopes.cdp_akrites_api]
+}
+```
+
+---
+
+### `lfx-secrets-management`
+
+No structural changes. Add Akrites as a new entry in the sync config:
+
+- **Source**: Auth0 — uses existing `Auth0JWTConfig` model
+  (`secretsmanagement/services/auth0.py`)
+- **Destinations**:
+  - AWS Secrets Manager (prod) — `secretsmanagement/services/aws.py` via `boto3`
+  - 1Password (dev) — `secretsmanagement/services/onepassword.py` via `op` CLI
+- **Orchestration**: `secretsmanagement/sync.py` lines 37–96 — Akrites follows
+  same source → destination pattern as all other M2M clients
+
+CDP holds no private key. Token verification is JWKS-only.
+
+---
+
+### `crowd.dev` (CDP — this repo)
+
+**`backend/config/custom-environment-variables.json`** (currently lines 161–166)
+
+Add alongside the existing `auth0` block:
+```json
+"auth0Akrites": {
+  "issuerBaseURLs": "CROWD_AUTH0_AKRITES_ISSUER_BASE_URLS",
+  "audience":       "CROWD_AUTH0_AKRITES_AUDIENCE",
+  "clientId":       "CROWD_AUTH0_AKRITES_CLIENT_ID"
+}
+```
+
+**`backend/src/conf/index.ts`** (line 106)
+
+Add:
+```ts
+export const AKRITES_AUTH0_CONFIG: Auth0Configuration = config.get<Auth0Configuration>('auth0Akrites')
+```
+`Auth0Configuration` interface (`backend/src/conf/configTypes.ts` lines 68–73) is reused as-is.
+
+**`backend/src/security/scopes.ts`**
+
+Add to `SCOPES` const:
+```ts
+READ_RESOURCE: 'read:<resource>',
+```
+
+**`backend/src/api/public/middlewares/azpAllowlistMiddleware.ts`** _(new file)_
+
+Reads `req.auth.payload.azp`. Throws `UnauthorizedError` if not in the
+configured allowlist. Fails closed — any unknown client ID is rejected even if
+Auth0 is misconfigured to grant it the same audience.
+
+**`backend/src/api/public/v1/index.ts`** (line 44)
+
+Replace:
+```ts
+router.use('/akrites', oauth2Middleware(AUTH0_CONFIG), akritesRouter())
+```
+With:
+```ts
+router.use(
+  '/akrites',
+  oauth2Middleware(AKRITES_AUTH0_CONFIG),
+  azpAllowlistMiddleware([AKRITES_AUTH0_CONFIG.clientId]),
+  requireScopes([SCOPES.READ_AKRITES], 'all'),
+  akritesRouter(),
+)
+```
+
+---
+
+### Akrites (external repo)
+
+Implement the token exchange described in the Auth Flow diagram above:
+
+1. Read RSA private key from vault (AWS Secrets Manager in prod via
+   `lfx-secrets-management`, 1Password in dev).
+2. Build and sign `client_assertion` JWT (RS256).
+3. POST to Auth0 `/oauth/token` — cache the returned Bearer token until it
+   expires.
+4. Attach Bearer token to all CDP requests via `Authorization` header.
+5. On `invalid_client`: discard cached key → re-read from vault → retry token
+   exchange once. LF rotates the keypair without notice.

docs/adr/README.md

@@ -15,6 +15,7 @@ Use the `/adr` skill in Claude Code to record new ADRs or query past decisions.
 | [ADR-0006](./0006-database-schema-types-as-source-of-truth.md) | Database schema types as the source of truth | accepted | 2026-07-09 |
 | [ADR-0007](./0007-test-factory-primitives-and-defaults.md) | Test factory primitives and defaults | accepted | 2026-07-10 |
 | [ADR-0008](./0008-how-we-write-unit-tests.md) | How we write unit tests | accepted | 2026-07-13 |
+| [ADR-0009](./0009-akrites-cdp-public-api-authentication.md) | Akrites → CDP public API authentication | proposed | 2026-07-14 |
 
 ## Why ADRs?