# M3.5.10 — Auth integration with Authentik/Vault

| Field | Value |
|---|---|
| Phase | M3.5 — Distributed API Layer |
| Size | M — 1–3 days |
| Status | ⬜ Not started |
| Flags | — |
| Spec | inlined below |
| Blocks | — |
| Depends | M3.5.1 |

## Goal

Replace the placeholder `apikey` header check with proper authentication via the
cluster's IAM stack: **Authentik** (OIDC provider) → **HashiCorp Vault** (token
issuer) → **memory service** (token validator).

## Facts (inlined — no spec read needed)

**Current (wrong):**
```rust
fn check_auth(req: &HttpRequest, state: &AppState) -> Result<(), HttpResponse> {
    let api_key = req.headers().get("apikey").and_then(|h| h.to_str().ok());
    if api_key != Some(&state.api_key) {
        return Err(HttpResponse::Unauthorized().json(...));
    }
    Ok(())
}
```
This is a raw string match against `MEM_API_KEY` env var. No JWT, no Vault, no
user identity. It does not integrate with the cluster's IAM stack.

**Cluster IAM stack:**
- **Authentik** (`iam` namespace) — OIDC provider at
  `https://authentik.riotpiao.com/application/o/vault/`
- **HashiCorp Vault** (`iam` namespace) — OIDC auth method enabled, validates
  Authentik JWTs, issues Vault tokens based on role/policy.
- **Vault OIDC role:** `auth/oidc/role/homelab-admin`
  - `bound_claims: { "permissions": "*" }`
  - Policy: `homelab-admin` (path `"*"` full access)
- **Vault unseal:** Shamir 3/3, keys in `vault-unseal-keys` secret, S3 backend
  via MinIO.

**Auth flow (production):**
```
User/Agent authenticates with Authentik (OIDC)
  → Receives JWT with claims { sub, permissions, groups, ... }
  → Presents JWT to Vault OIDC auth method
  → Vault validates JWT against Authentik JWKS
  → Vault issues Vault token with matched policy
  → Client sends Vault token to memory service
  → Memory service validates token via Vault API
```

**Three integration options (pick one):**

### Option A: Vault token validation (recommended)
Memory service receives `X-Vault-Token` header, calls Vault's
`POST /v1/auth/token/lookup-self` to validate. Extracts policy and metadata.
- Pro: Vault is the single source of truth for authorization.
- Pro: Token revocation is immediate (Vault controls lifecycle).
- Con: Extra network call per request (cache with TTL to mitigate).

### Option B: Direct JWKS validation
Memory service fetches Authentik's JWKS endpoint, validates JWT `Authorization:
Bearer <token>` directly. No Vault in the request path.
- Pro: No Vault dependency at request time.
- Pro: Standard OAuth2/OIDC pattern.
- Con: Token revocation is delayed (until JWT expires).
- Con: Memory service must know about Authentik's OIDC config.

### Option C: Trust gateway
Memory service trusts homelab-frontend gateway (cluster-internal traffic).
Gateway validates auth, forwards `X-User-Id` and `X-Capabilities` headers.
Memory service checks capabilities against ServiceAdapter CRD requirements.
- Pro: Auth logic centralized in gateway.
- Pro: Memory service stays simple.
- Con: Gateway auth is currently a stub (`hasCapability()` returns true for any
  `Authorization` header).
- Con: Requires gateway auth to be completed first (homelab-frontend task 8.3).

**ServiceAdapter CRD for memory (`memory-adapter`):**
```yaml
auth:
  capability: memory:read    # default
  required: true
resources:
  - name: ingest
    methods:
      - verb: POST
        auth: { capability: memory:write, required: true }
  - name: query
    methods:
      - verb: POST
  - name: skills
    methods:
      - verb: GET
```

**Capabilities needed:**
- `memory:read` — query, skills, vault browse, projects, sources
- `memory:write` — ingest, source sync, skill draft

## Steps

### Option A (Vault token — recommended)

1. Add `vault_addr` to `AppState` (default: `http://vault.iam.svc.cluster.local:8200`).
2. Replace `check_auth()` with `validate_vault_token()`:
   ```rust
   async fn validate_vault_token(req: &HttpRequest, state: &AppState) -> Result<VaultIdentity, HttpResponse> {
       let token = req.headers().get("X-Vault-Token")
           .or_else(|| req.headers().get("Authorization"))  // Bearer <token>
           .and_then(|h| h.to_str().ok());
       // POST vault_addr/v1/auth/token/lookup-self with X-Vault-Token header
       // Parse response: policies, metadata, ttl
       // Cache token -> identity for TTL duration
   }
   ```
3. Add token cache (HashMap<token_hash, (VaultIdentity, Instant)>) with configurable TTL.
4. Extract `VaultIdentity` (policies, metadata) from lookup response.
5. Map policies to capabilities: `homelab-admin` → `memory:read` + `memory:write`.
6. Update each handler to check required capability.
7. Keep `apikey` as fallback for dev/test (controlled by env var `MEM_AUTH_MODE=vault|apikey`).

### For all options

8. Add env vars: `VAULT_ADDR`, `MEM_AUTH_MODE` (vault/jwks/gateway/apikey).
9. Update K8s deployment to inject `VAULT_ADDR`.
10. Update ServiceAdapter CRD if needed.
11. Document auth flow in README.

## Acceptance

- Requests with valid Vault token are accepted.
- Requests with expired/revoked Vault token are rejected (401).
- Requests without any auth are rejected (401).
- `memory:write` capability required for ingest/sync endpoints.
- `memory:read` capability sufficient for query/skills/vault endpoints.
- Token cache reduces Vault API calls on repeated requests.
- Fallback to `apikey` mode for dev/test environments.

## Verify

**Integration test** — `tests/it_auth_integration.rs`:
1. `a1_vault_token_accepted` — mock Vault lookup-self returning valid response;
   assert request proceeds.
2. `a2_expired_token_rejected` — mock Vault returning 403; assert 401 response.
3. `a3_no_auth_rejected` — request with no auth headers; assert 401.
4. `a4_write_requires_capability` — token with `memory:read` only; POST /ingest;
   assert 403.
5. `a5_read_with_read_capability` — token with `memory:read`; GET /query;
   assert proceeds.
6. `a6_token_cache_hit` — same token twice; assert Vault called once.
7. `a7_apikey_fallback` — `MEM_AUTH_MODE=apikey`; assert old behavior works.
8. `a8_auth_mode_configurable` — assert `MEM_AUTH_MODE` switches validation logic.

**Command:** `cargo test --test it_auth_integration`

**False pass:**
- Testing only with apikey fallback. The Vault integration is the whole point.
- Mocking Vault without testing cache expiry. A cache that never expires accepts
  revoked tokens forever.

## Traps

- Calling Vault on every request without caching. Vault API calls add 5-10ms
  per request. Cache with TTL matching token TTL (or shorter).
- Not handling Vault being temporarily unreachable. Return 503 (not 401) if
  Vault is down — "cannot verify" is not "unauthorized".
- Hardcoding Vault addr. Use env var + service discovery.
- Not supporting `Authorization: Bearer <token>` format alongside `X-Vault-Token`.
  Different clients use different conventions.

---

Background: [DESIGN.md](../DESIGN.md) — auth section, Authentik/Vault IAM stack