# Admin Authentication — Ed25519 Foundation

Status: **FRONTEND PREPARED, NOT LIVE.** Everything in this document describes
code that exists in `src/app/core/auth/` today, wired to endpoints that do
not exist on the backend yet. No route currently requires this flow — the
live admin gate remains the Telegram-QR-based `AdminAuthService` /
`adminAuthGuard` (`src/app/core/admin-auth/`, documented in
`docs/BACKEND_API.md` §2.4–2.5). This module is the
integration target once the backend ships the endpoints below.

Do not point any live route's `canActivate` at `ed25519AuthGuard` until the
backend endpoints in §API Contracts exist and have been verified — doing so
before then would lock every admin out.

## 1. Why this exists

`docs/BACKEND_API.md` §2.5 documents the current system's
biggest security gap: admin and customer login hit the *same* Telegram
session endpoint, so the backend has no way to distinguish an admin login
attempt from a customer one at the moment of login — authorization is
effectively unenforced. Ed25519 challenge/response auth closes this by
requiring proof of possession of a specific, pre-registered private key
before a session is ever issued, instead of "any Telegram account that
happened to scan the right QR code."

## 2. Sequence diagram

```mermaid
sequenceDiagram
    participant Admin as Admin (browser)
    participant FE as Frontend (AuthService)
    participant BE as Backend

    Admin->>FE: Click "Sign in"
    FE->>BE: GET /api/admin/auth/challenge
    BE-->>FE: { nonce, issuedAt, expiresAt }
    FE->>FE: Ed25519KeypairService.sign(nonce)<br/>(WebCrypto, non-extractable private key)
    FE->>BE: POST /api/admin/auth/verify<br/>{ publicKey, signature, nonce }
    alt signature valid & publicKey is a provisioned admin key
        BE-->>FE: 200 { token, refreshToken }
        FE->>FE: SessionService.activate(tokens)<br/>decode JWT claims, schedule refresh
        FE-->>Admin: Redirect to /backoffice
    else invalid signature / unknown key / expired nonce
        BE-->>FE: 401/403
        FE-->>Admin: Redirect to /admin-login/error/invalid-signature
    end
```

### Refresh sequence

```mermaid
sequenceDiagram
    participant FE as Frontend (SessionService)
    participant IC as authInterceptor
    participant BE as Backend

    Note over FE: Timer fires ~60s before JWT exp
    FE->>BE: POST /api/admin/auth/refresh { refreshToken }
    alt refresh token still valid
        BE-->>FE: 200 { token, refreshToken }
        FE->>FE: activate(tokens) - reschedules next refresh
    else refresh token expired/revoked
        BE-->>FE: 401
        FE->>FE: SessionService.markExpired()
        FE-->>FE: Route to /admin-login/error/session-expired
    end

    Note over IC: Reactive path - any 401 on an admin request
    IC->>BE: Admin API request (expired token)
    BE-->>IC: 401
    IC->>BE: POST /api/admin/auth/refresh (single retry)
    alt refresh succeeds
        BE-->>IC: 200 tokens
        IC->>BE: Retry original request with new token
    else refresh fails
        IC-->>FE: Propagate error, route to session-expired
    end
```

## 3. Ed25519 flow, step by step

1. **Key generation (once per device):** `Ed25519KeypairService.getOrCreateKeyPair()`
   generates a non-extractable Ed25519 keypair via `crypto.subtle.generateKey`
   and persists the `CryptoKey` handles in IndexedDB (`admin-auth-ed25519` DB).
   The private key is never exported, serialized, or transmitted — by
   construction, not by convention.
2. **Registering the public key with the backend is out of scope for this
   frontend.** An Owner/Administrator must associate a new device's
   `publicKeyBase64` with an admin account through some out-of-band
   mechanism (e.g. a backend admin tool, a one-time enrollment link) before
   that device can complete step 4. This document does not prescribe that
   mechanism — it is a backend/ops concern.
3. **Challenge:** `GET /api/admin/auth/challenge` returns a fresh `nonce` the
   client must sign before `expiresAt`.
4. **Sign:** the raw `nonce` string is signed with the device's private key
   (`Ed25519KeypairService.sign`), producing a base64 signature.
5. **Verify:** `POST /api/admin/auth/verify` sends `{ publicKey, signature,
   nonce }`. The backend re-derives the signed message from the nonce it
   issued, verifies the signature against its own record of that
   `publicKey → admin account` mapping, and only then issues tokens.
6. **Session:** the returned `{ token, refreshToken }` pair is stored
   (`SessionService`, `localStorage: ed25519AdminToken` /
   `ed25519AdminRefreshToken`) and the JWT is decoded client-side for
   `role`/`exp` — decoding only, never signature verification (the frontend
   has no trusted key to check it against).

## 4. API contracts

All under `{environment.authApiUrl}/api/admin/auth` (see
`src/environments/environment.ts`). None of these exist on the backend
today — this is the contract the frontend was built against, not a
confirmed backend spec.

| Method | Path | Request body | Response | Notes |
|---|---|---|---|---|
| GET | `/challenge` | — | `200 AuthChallenge` | `{ nonce, issuedAt, expiresAt }`, all ISO 8601 except `nonce` |
| POST | `/verify` | `VerifySignatureRequest` | `200 AuthTokenPair` \| `401` \| `403` | `{ publicKey, signature, nonce }` → `{ token, refreshToken }` |
| POST | `/refresh` | `RefreshTokenRequest` | `200 AuthTokenPair` \| `401` | `{ refreshToken }` → new pair (rotation expected — old refresh token should be invalidated server-side) |
| POST | `/logout` | `{ refreshToken }` | `204` | Should revoke the refresh token server-side; frontend clears local state regardless of response |

Types: `src/app/core/auth/models/auth-api.model.ts`.

## 5. JWT claims

```ts
interface JwtClaims {
  sub: string;        // admin account id
  role: AdminRole;     // 'Owner' | 'Administrator' | 'Editor' | 'Support' | 'ReadOnly'
  iat: number;         // seconds since epoch
  exp: number;         // seconds since epoch
  publicKey: string;    // the Ed25519 public key this token was issued for
}
```

The frontend decodes these (`JwtService.decode`) for UX only — role-based UI
gating, expiry countdowns, refresh scheduling. **Every admin API request
must be independently authorized server-side**; a decoded-but-unverified
claim is not proof of anything to the backend.

## 6. Permission model

Five roles, coarse-grained permission keys (`src/app/core/auth/models/permission.model.ts`):

| Role | Permissions |
|---|---|
| Owner | `backoffice.read`, `backoffice.write`, `builder.read`, `builder.write`, `users.manage`, `settings.manage` |
| Administrator | `backoffice.read`, `backoffice.write`, `builder.read`, `builder.write`, `users.manage` |
| Editor | `backoffice.read`, `backoffice.write`, `builder.read`, `builder.write` |
| Support | `backoffice.read` |
| ReadOnly | `backoffice.read`, `builder.read` |

This is deliberately coarse and mirrors the existing bootstrap-level
`PermissionsConfig` shape (`src/app/shared/models/config/permissions.model.ts`).
Finer-grained, per-domain permissions (e.g. "can edit prices but not delete
products") stay server-side until a real permission model exists there —
see `docs/BACKEND_API.md` §"Admin-role-required". Use
`PermissionService.has(permission)` / `permissionGuard(permission)` to gate
UI and routes; never treat a passing client-side check as authorization by
itself.

## 7. Error screens

Single component (`AuthErrorPageComponent`, `/admin-login/error/:code`)
renders all five, keyed by route param:

| Code | Trigger | User action offered |
|---|---|---|
| `session-expired` | Refresh token rejected/expired | Sign in again |
| `invalid-signature` | `verify` returns 401/403 during login | Try again |
| `unauthorized` | Route guard sees no active session | Sign in |
| `forbidden` | `permissionGuard` denies (authenticated but insufficient role) | Back to dashboard |
| `backend-unavailable` | Network error / 5xx / status 0 | Retry |

`authErrorCodeFromStatus` (`models/auth-error.model.ts`) maps HTTP status →
code: `401→unauthorized`, `403→forbidden`, `0→backend-unavailable`,
`5xx→backend-unavailable`, else `unauthorized`. `AuthService.login()`
additionally maps any failure during the challenge/sign/verify sequence to
`invalid-signature` when it isn't a clearer HTTP-status-derived code.

## 8. Refresh lifecycle

- On `SessionService.activate(tokens)`, a timer is scheduled for
  `max(exp - now - 60s, 5s)` — refresh fires ~60 seconds before expiry so a
  concurrent request never races an expiring token.
- **Proactive path:** the timer fires `AuthService.refresh()` directly.
- **Reactive path:** `authInterceptor` catches a 401 on any admin-gated
  request, attempts one `refresh()`, retries the original request once on
  success, and routes to `session-expired` on failure. It does not retry
  more than once — a second 401 after a successful-looking refresh means
  something is wrong server-side, not a transient race.
- `SessionService.restore()` runs on app bootstrap (call
  `AuthFacade.restoreSession()` from an app initializer once this flow goes
  live) — reads persisted tokens, decodes claims, and either resumes with a
  scheduled refresh or marks `expired` without any network call, so a stale
  session is caught before it reaches any component.

## 9. Module map

```
src/app/core/auth/
├── auth.routes.ts                        # /admin-login, /admin-login/error/:code
├── models/
│   ├── auth-api.model.ts                 # AuthChallenge, VerifySignatureRequest, AuthTokenPair, JwtClaims
│   ├── auth-error.model.ts               # AuthErrorCode, authErrorCodeFromStatus()
│   └── permission.model.ts               # AdminRole, Permission, ROLE_PERMISSIONS
├── services/
│   ├── ed25519-keypair.service.ts        # WebCrypto keygen/sign, IndexedDB persistence
│   ├── auth-api.service.ts               # HttpClient calls to the 4 endpoints in §4
│   ├── jwt.service.ts                    # decode-only JWT parsing
│   ├── session.service.ts                # token/claims state, persistence, refresh scheduling
│   ├── permission.service.ts             # role -> permission set
│   ├── auth.service.ts                   # orchestrates challenge -> sign -> verify -> refresh -> logout
│   └── auth-facade.service.ts            # public surface for components
├── interceptors/
│   └── auth.interceptor.ts               # Authorization: Bearer + 401 refresh-and-retry
├── guards/
│   ├── ed25519-auth.guard.ts             # requires SessionService.isAuthenticated()
│   └── permission.guard.ts               # permissionGuard(permission) factory
└── pages/
    ├── admin-login-page.component.*      # sign-in UI
    └── auth-error-page.component.*       # parameterized error screen (§7)
```

`AuthFacade` is the only thing components/pages should depend on;
`AuthService`/`SessionService`/`PermissionService` are internal
collaborators reachable through it.

## 10. Cutover plan (when the backend ships)

1. Verify the four endpoints in §4 against a real backend, including error
   shapes.
2. Register `authInterceptor` in `app.config.ts`'s `withInterceptors([...])`
   list (currently not registered).
3. Decide the relationship to the existing Telegram flow: replace
   `adminAuthGuard` with `ed25519AuthGuard` outright, or run both and let
   role/tenant config pick — this is a product decision, not made here.
4. Wire `AuthFacade.restoreSession()` into an `APP_INITIALIZER` (or root
   component `ngOnInit`) so a page refresh restores state before any guard
   runs.
5. Only after 1–4: point `/backoffice` and `/edit`'s `canActivate` at
   `ed25519AuthGuard` (and `permissionGuard(...)` where a route needs a
   specific role).

## 11. Security considerations

- **Private key never leaves the device.** Generated non-extractable via
  WebCrypto; `Ed25519KeypairService` has no export path. Losing the device
  means losing the key — key rotation/recovery (revoking a lost device's
  public key, provisioning a new one) is a backend/ops process, not
  implemented here.
- **The frontend is not the authorization boundary.** Every admin
  request must be independently checked server-side against the caller's
  actual role, exactly as `docs/BACKEND_API.md` §2.5
  already states for the Telegram flow. A decoded JWT claim or a passing
  `PermissionService.has()` check is UX, not proof.
- **Refresh tokens should rotate.** Every `POST /refresh` response is
  expected to include a *new* refresh token; the backend should invalidate
  the one just used. The frontend always stores whatever pair it receives
  and never reuses an old refresh token after a successful rotation.
- **CSRF/replay:** the nonce from `/challenge` must be single-use and
  time-boxed server-side (`expiresAt`) — the frontend enforces nothing here
  beyond passing the nonce back unmodified; replay protection is the
  backend's responsibility.
- **No fallback to unsigned auth.** There is no code path in this module
  that issues a session without a valid signature. If the backend is
  unreachable, the user sees `backend-unavailable`, never a degraded or
  bypassed login.
- **Dev bypass exclusion:** unlike `AdminAuthService.devBypassLogin()` in
  the Telegram flow, this module intentionally has no dev bypass — an
  Ed25519 keypair is cheap to generate locally, so local testing should
  point at a real (even if mocked-in-dev) `/challenge`/`/verify` pair
  rather than fabricating a session.