Data Model: OIDC Proxy Script Authentication

Feature: 001-oidc-proxy-script
Phase: 1 — Design
Date: 2025-07-17

Entities

1. AdapterSettings

Persisted as src/globalVariables/adapter_settings.json. Loaded at server startup by loadGlobalVariables() and injected into every VM context as the adapter_settings variable.

Field	Type	Required	Description
`tokenUrl`	`string`	✅	Full HTTPS URL of the OIDC token endpoint
`username`	`string`	✅	Resource owner username (ROPC grant)
`password`	`string`	✅	Resource owner password
`clientId`	`string`	✅	OAuth 2.0 client identifier
`scope`	`string`	✅	Space-separated scopes, e.g. `"openid tags content_entitlements"`

JSON Schema:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "required": ["tokenUrl", "username", "password", "clientId", "scope"],
  "additionalProperties": false,
  "properties": {
    "tokenUrl":  { "type": "string", "format": "uri" },
    "username":  { "type": "string", "minLength": 1 },
    "password":  { "type": "string", "minLength": 1 },
    "clientId":  { "type": "string", "minLength": 1 },
    "scope":     { "type": "string", "minLength": 1 }
  }
}

Example (src/globalVariables/adapter_settings.json):

{
  "tokenUrl":  "https://auth.kme.example.com/protocol/openid-connect/token",
  "username":  "service-account@example.com",
  "password":  "s3cr3t",
  "clientId":  "kme-content-adapter",
  "scope":     "openid tags content_entitlements"
}

Security: This file MUST be excluded from version control (.gitignore). Provide src/globalVariables/adapter_settings.json.example with placeholder values.

2. TokenCache (Redis-backed)

Persisted in Redis as a hash under the key authorization. Written by proxy.js after a successful token fetch; read on every request to check validity.

Redis field	Type (stored)	Description
`token`	`string`	The cached `id_token` value
`expiry`	`string` (numeric)	Absolute Unix epoch timestamp (seconds) from `expires_in`; `"0"` or absent means expired

Initialisation: No pre-seeding required. redis.hGet returns null for absent fields, which proxy.js treats as expired.

In-process stampede guard (not in Redis):

// adapter_settings._pendingFetch — set by proxy.js at runtime
adapter_settings._pendingFetch = fetchPromise;   // set before fetch
adapter_settings._pendingFetch = null;           // cleared in finally block

Read pattern (proxy.js):

const token  = await redis.hGet('authorization', 'token');
const expiry = parseFloat(await redis.hGet('authorization', 'expiry') ?? '0');
const isValid = token !== null && Date.now() / 1000 < expiry;

Write pattern (proxy.js, after successful fetch):

await redis.hSet('authorization', 'token', idToken);
await redis.hSet('authorization', 'expiry', String(expiresIn));

State transitions:

                  ┌──────────────────────────────────────────────────────────┐
                  │                                                          │
     ┌────────────▼──────────────┐     fetch starts     ┌──────────────────┐│
     │  EMPTY / EXPIRED          │─────────────────────▶│  FETCHING        ││
     │  token: null / expiry ≤ now│                      │  pendingFetch: P ││
     └───────────────────────────┘                      └──────┬───────────┘│
               ▲                                               │             │
               │ token expires                    fetch settles│             │
               │ (Date.now()/1000 ≥ expiry)       ┌───────────┴──────────┐  │
               │                                  │                       │  │
               │                          success │               failure │  │
               │                                  ▼                       ▼  │
               │                      ┌──────────────────┐  ┌──────────────┐│
               │                      │  VALID           │  │  ERROR       ││
               └──────────────────────│  token: "abc…"   │  │  token: null ││
                                      │  expiry: 99999…  │  │  expiry: 0   ││
                                      └──────────────────┘  └──────────────┘│
                                               │                             │
                                               └─────────────────────────────┘
                                               (back to EMPTY / EXPIRED)

Validity rule (FR-006):

const token  = await redis.hGet('authorization', 'token');
const expiry = parseFloat(await redis.hGet('authorization', 'expiry') ?? '0');
const isValid = token !== null && Date.now() / 1000 < expiry;

3. OidcTokenResponse (external — token service)

Returned by the OIDC token service in response to a successful POST. Only the fields used by proxy.js are listed; additional fields may be present and are ignored.

Field	Type	Description
`id_token`	`string`	Bearer token to cache and use for authentication (FR-004)
`expires_in`	`number`	Absolute Unix epoch timestamp (seconds) when token expires (FR-006)

Error response (HTTP 4xx from token service): Not parsed; the HTTP status code alone is sufficient to trigger a 401 response to the caller.

4. ProxyResponse (outbound HTTP)

The HTTP response sent by proxy.js back to the caller via the injected res object.

Scenario	Status	Content-Type	Body
Authentication success	`200 OK`	`text/plain`	`Authorized`
Auth failure (any cause)	`401 Unauthorized`	`text/plain`	`Unauthorized: <message>`

Relationships

server.js
  │
  ├── loadGlobalVariables()
  │     └── reads adapter_settings.json ──────────► AdapterSettings
  │
  ├── redis (injected into VM context) ───────────► Redis Store
  │                                                  └── hash: authorization
  │                                                       ├── token
  │                                                       └── expiry
  │
  └── vm.createContext({ ...globalVariableContext, redis, req, res })
        │
        └── script.runInContext(context)  [proxy.js]
              │
              ├── reads adapter_settings ─────────► AdapterSettings
              ├── reads/writes redis ──────────────► Redis Store (token + expiry)
              ├── sets adapter_settings._pendingFetch (stampede guard, in-process)
              ├── POST tokenUrl ────────────────────► OIDC Token Service
              │     └── receives ─────────────────► OidcTokenResponse
              └── writes res ──────────────────────► ProxyResponse

Validation Rules

Rule	Location	Behaviour on violation
`tokenUrl` present	proxy.js startup	401 with `'missing required field: tokenUrl'`
`username` present	proxy.js startup	401 with `'missing required field: username'`
`password` present	proxy.js startup	401 with `'missing required field: password'`
`clientId` present	proxy.js startup	401 with `'missing required field: clientId'`
`scope` present	proxy.js startup	401 with `'missing required field: scope'`
`id_token` present in response	proxy.js after fetch	401 with `'id_token missing from response'`
`expires_in` present in response	proxy.js after fetch	401 with `'expires_in missing from response'`
Redis `hSet` / `hGet` available	proxy.js on every request	`ReferenceError` (server.js must inject `redis`)

Validation errors are caught by the top-level catch block in proxy.js and result in a 401 Unauthorized response, never a process crash (SC-004).

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