Merge pull request #393 from sasjs/auth-diagram

docs(api): document the current authentication flow, comment non-obvi…

api/src/controllers/auth.ts

@@ -100,8 +100,13 @@ const token = async (data: any): Promise<TokenResponse> => {
 
   AuthController.deleteCode(userInfo.userId, clientId)
 
-  // get tokens from DB
+  // Re-exchanging a code for the same user/client while a still-valid token
+  // pair already exists returns that pair instead of minting a new one -
+  // keeps other tabs/sessions using the old tokens alive instead of
+  // silently invalidating them (saveTokensInDB below overwrites, it doesn't
+  // append).
   const existingTokens = await getTokensFromDB(userInfo.userId, clientId)
+
   if (existingTokens) {
     return {
       accessToken: existingTokens.accessToken,
@@ -109,7 +114,12 @@ const token = async (data: any): Promise<TokenResponse> => {
     }
   }
 
+  // Only used to look up token expirations - clientSecret is intentionally
+  // not checked here. The credential for this exchange is the auth code
+  // itself (single-use, 30s-lived, only obtainable by a caller that already
+  // held a valid session - see verifyAuthCode below and web.ts's authorize()).
   const client = await Client.findOne({ clientId })
+
   if (!client) throw new Error('Invalid clientId.')
 
   const accessToken = generateAccessToken(

api/src/middlewares/authenticateToken.ts

@@ -113,6 +113,9 @@ const authenticateToken = async (
 
     throw 'Unauthorized'
   } catch (error) {
+    // A missing/invalid/expired token doesn't necessarily mean 401 - if an
+    // admin has granted the built-in Public group access to this exact
+    // path, an unauthenticated caller still gets through as publicUser.
     if (await isPublicRoute(req)) {
       req.user = publicUser
       return next()

api/src/middlewares/desktop.ts

@@ -5,6 +5,11 @@ import { ModeType } from '../utils'
 
 const regexUser = /^\/SASjsApi\/user\/[0-9]*$/ // /SASjsApi/user/1
 
+// Desktop mode has no login/logout (see authenticateAccessToken's desktop
+// bypass) and every request runs as the single fixed desktopUser, but the
+// desktop UI still needs to read/update that user's own profile (e.g.
+// autoExec) - so these two routes stay reachable while every other
+// /SASLogon/* and user-management route is blocked below.
 const allowedInDesktopMode: { [key: string]: RegExp[] } = {
   GET: [regexUser],
   PATCH: [regexUser]

api/src/routes/api/client.ts

@@ -5,8 +5,16 @@ import { authenticateAccessToken, verifyAdmin } from '../../middlewares'
 
 const clientRouter = express.Router()
 
+// Neither this route nor the router itself declares auth middleware - both
+// POST and GET are actually gated by authenticateAccessToken/verifyAdmin
+// applied at the mount point in routes/api/index.ts (`router.use('/client',
+// ..., authenticateAccessToken, verifyAdmin, clientRouter)`), which runs for
+// every method under /client before requests reach the handlers below. GET's
+// own authenticateAccessToken/verifyAdmin a few lines down is therefore
+// redundant, not the thing actually protecting it.
 clientRouter.post('/', async (req, res) => {
   const { error, value: body } = registerClientValidation(req.body)
+
   if (error) return res.status(400).send(error.details[0].message)
 
   const controller = new ClientController()

api/src/utils/getAuthorizedRoutes.ts

@@ -2,6 +2,10 @@ import { Request } from 'express'
 
 export const TopLevelRoutes = ['/AppStream', '/SASjsApi']
 
+// Being authenticated is enough for most routes. These specifically also
+// require a granted Permission (checked by the authorize middleware) because
+// they run arbitrary submitted code or manipulate arbitrary files on disk -
+// a narrower blast radius than everything else a logged-in user can do.
 const StaticAuthorizedRoutes = [
   '/SASjsApi/code/execute',
   '/SASjsApi/stp/execute',

api/src/utils/verifyTokenInDB.ts

@@ -20,6 +20,13 @@ export const fetchLatestAutoExec = async (
   }
 }
 
+// Access/refresh tokens are JWTs, so they're self-verifying - but that
+// alone would make them impossible to revoke before expiry. Requiring the
+// exact token string to still be the one stored on the user's tokens array
+// (written by saveTokensInDB, cleared by removeTokensInDB) turns them into
+// revocable credentials: logout, or issuing a fresh pair via /auth/refresh,
+// immediately invalidates the old token even though its signature is still
+// valid.
 export const verifyTokenInDB = async (
   userId: number,
   clientId: string,

docs/diagrams/authentication-flow.md

@@ -0,0 +1,188 @@
+# Authentication flow
+
+How a client (browser SPA or CLI/SDK) turns a username/password into an
+authenticated `SASjsApi` request, and how that request is subsequently
+authorized. The mechanism is a self-hosted session-then-authorization-code
+flow, optionally backed by LDAP for credential verification.
+
+```mermaid
+sequenceDiagram
+    participant Browser as Client<br/>(browser SPA, or CLI/SDK<br/>simulating one with a cookie jar)
+    participant Web as Web routes + controller<br/>(routes/web/web.ts,<br/>controllers/web.ts)
+    participant Mid as authenticateAccessToken<br/>(middlewares/authenticateToken.ts)
+    participant Authz as authorize<br/>(middlewares/authorize.ts)
+    participant AuthCtrl as Auth routes + controller<br/>(routes/api/auth.ts,<br/>controllers/auth.ts)
+    participant Sess as Session store<br/>(MongoDB via connect-mongo)
+    participant DB as MongoDB<br/>(User / Client / Permission)
+    participant LDAP as LDAP server<br/>(optional, AUTH_PROVIDERS=ldap)
+    participant API as Any SASjsApi route
+
+    Note over Browser,Web: STEP 0 - load the app, get a CSRF token
+    Browser->>Web: GET /
+    Web-->>Browser: index.html with an inline script that sets<br/>document.cookie = XSRF-TOKEN=...<br/>(routes/web/web.ts:14-32, csrfProtection.ts:7)
+
+    Note over Browser,LDAP: STEP 1 - username/password login, establishes a session
+    Browser->>Web: POST /SASLogon/login { username, password }
+    Web->>Web: desktopRestrict - 403 if MODE=desktop (desktop.ts:19-28)
+    Web->>Web: bruteForceProtection + RateLimiter.consume(ip, username)<br/>(routes/web/web.ts:37, controllers/web.ts:106-113)
+    Web->>DB: User.findOne({ username }) (controllers/web.ts:86)
+    alt AUTH_PROVIDERS=ldap and user.authProvider=ldap
+        Web->>LDAP: LDAPClient.verifyUser(username, password) -<br/>looks up the user's DN, then binds as them<br/>(controllers/web.ts:95-98, utils/ldapClient.ts)
+        LDAP-->>Web: bind succeeds or rejects
+    else local user (default)
+        Web->>Web: user.comparePassword(password) - bcrypt<br/>compare against the stored hash (controllers/web.ts:100)
+    end
+    Web->>Sess: req.session.loggedIn = true<br/>req.session.user = { userId, clientId: "web_app",<br/>username, isAdmin, autoExec, ... } (controllers/web.ts:122-132)
+    Sess-->>Browser: Set-Cookie: connect.sid=...<br/>(httpOnly, 24h maxAge, connect-mongo backed,<br/>app-modules/configureExpressSession.ts:30-46)
+    Web-->>Browser: 200 { loggedIn: true, user: {...} }<br/>(controllers/web.ts:134-143) - note: no token yet
+
+    Note over Browser,DB: STEP 2 - exchange the session for a short-lived auth code
+    Browser->>Web: POST /SASLogon/authorize { clientId }<br/>Cookie: connect.sid=...<br/>X-XSRF-TOKEN: <value read from the XSRF-TOKEN cookie>
+    Web->>Mid: authenticateAccessToken (routes/web/web.ts:58)
+    Mid->>Mid: req.session.loggedIn is true, so this request<br/>is validated via the session branch, not a JWT<br/>(authenticateToken.ts:32-44)
+    Mid->>DB: fetchLatestAutoExec(req.session.user) - re-reads<br/>the User row so isActive/isAdmin/autoExec are current,<br/>not whatever was cached at login time (authenticateToken.ts:34,<br/>utils/verifyTokenInDB.ts:4-21)
+    Mid->>Mid: csrfProtection - verify the submitted token<br/>against the server-held secret (authenticateToken.ts:39,<br/>csrfProtection.ts:9-32)
+    Mid-->>Web: next()
+    Web->>DB: Client.findOne({ clientId }) (controllers/web.ts:153)
+    Web->>Web: generateAuthCode({ clientId, userId }) - a JWT<br/>signed with AUTH_CODE_SECRET, 30s expiry<br/>(utils/generateAuthCode.ts:4-7)
+    Web->>Web: AuthController.saveCode(userId, clientId, code) -<br/>kept in an in-memory map on the Node process,<br/>not persisted to DB (controllers/auth.ts:30-36)
+    Web-->>Browser: 200 { code }
+
+    Note over Browser,DB: STEP 3 - exchange the auth code for access/refresh tokens
+    Browser->>AuthCtrl: POST /SASjsApi/auth/token { clientId, code }
+    AuthCtrl->>AuthCtrl: verifyAuthCode() - jwt.verify(code, AUTH_CODE_SECRET),<br/>then check the payload's clientId matches (controllers/auth.ts:229-248)
+    AuthCtrl->>AuthCtrl: code must equal AuthController.authCodes[userId][clientId],<br/>then it is deleted - single use (controllers/auth.ts:92-101)
+    AuthCtrl->>DB: Client.findOne({ clientId }) - reads<br/>accessTokenExpiration/refreshTokenExpiration (controllers/auth.ts:112-113)
+    Note right of AuthCtrl: no clientSecret check happens here -<br/>the short-lived, single-use auth code from<br/>step 2 is the actual credential
+    AuthCtrl->>AuthCtrl: generateAccessToken() / generateRefreshToken() -<br/>JWTs signed with ACCESS_TOKEN_SECRET / REFRESH_TOKEN_SECRET<br/>(utils/generateAccessToken.ts, utils/generateRefreshToken.ts)
+    AuthCtrl->>DB: saveTokensInDB() - persists both tokens on<br/>the User document's tokens array, keyed by clientId<br/>(utils/saveTokensInDB.ts, controllers/auth.ts:124)
+    AuthCtrl-->>Browser: 200 { accessToken, refreshToken }
+
+    Note over Browser,API: STEP 4 - authenticated API request (this is also how<br/>CLI/SDK clients authenticate on every call after<br/>obtaining a token once via steps 0-3)
+    Browser->>API: any /SASjsApi/... request<br/>Authorization: Bearer <accessToken>
+    API->>Mid: authenticateAccessToken - no session cookie this<br/>time, so it falls through to JWT verification (authenticateToken.ts:46-52)
+    Mid->>Mid: jwt.verify(token, ACCESS_TOKEN_SECRET) (authenticateToken.ts:97)
+    Mid->>DB: verifyTokenInDB(userId, clientId, token, "accessToken") -<br/>token must still equal the one on file for this user+client,<br/>not just be a validly-signed JWT (authenticateToken.ts:99-104,<br/>utils/verifyTokenInDB.ts:23-49)
+    alt token missing, invalid, or no longer matches DB (e.g. after logout)
+        Mid->>DB: isPublicRoute(req)? - is there a Permission<br/>granting the built-in Public group access to this path?<br/>(utils/isPublicRoute.ts:8-22)
+        Mid-->>API: req.user = publicUser and continue,<br/>or 401 Unauthorized if not public (authenticateToken.ts:116-121)
+    else token valid and user.isActive
+        Mid->>Mid: req.user = user, req.accessToken = token (authenticateToken.ts:107-110)
+        opt request path is in getAuthorizedRoutes()<br/>(utils/getAuthorizedRoutes.ts:16-20)
+            Mid->>Authz: authorize middleware (authenticateToken.ts:26-27)
+            Authz->>DB: Permission lookups, first grant wins:<br/>admin bypass, public bypass, then user-specific<br/>route permission, user top-level permission,<br/>each of the user's groups at route level,<br/>each of the user's groups at top level (authorize.ts:10-87)
+            Authz-->>API: next(), or 401 if nothing grants access
+        end
+    end
+    API-->>Browser: 200 + response
+
+    Note over Browser,DB: Token refresh, once the access token nears/hits expiry
+    Browser->>AuthCtrl: POST /SASjsApi/auth/refresh<br/>Authorization: Bearer <refreshToken>
+    AuthCtrl->>Mid: authenticateRefreshToken - same JWT + DB<br/>cross-check as step 4, against REFRESH_TOKEN_SECRET<br/>and the stored refreshToken (authenticateToken.ts:55-67)
+    AuthCtrl->>AuthCtrl: generateAccessToken() / generateRefreshToken() again<br/>(controllers/auth.ts:133-140)
+    AuthCtrl->>DB: saveTokensInDB() - overwrites the stored pair,<br/>the previous refreshToken stops working (controllers/auth.ts:142-147)
+    AuthCtrl-->>Browser: 200 { accessToken, refreshToken }
+
+    Note over Browser,Sess: Logout
+    Browser->>AuthCtrl: DELETE /SASjsApi/auth/logout (bearer clients)
+    AuthCtrl->>DB: removeTokensInDB() - clears this clientId's<br/>entry from User.tokens (utils/removeTokensInDB.ts, controllers/auth.ts:152-153)
+    AuthCtrl-->>Browser: 204
+    Browser->>Web: GET /SASLogon/logout (session/browser clients)
+    Web->>Sess: req.session.destroy() (controllers/web.ts:63-67)
+    Web-->>Browser: 200 OK! - the session document is deleted<br/>server-side and connect.sid is no longer valid
+```
+
+## Two credentials, not one
+
+Unlike a typical single-token OAuth setup, this system layers two distinct
+credential checks:
+
+1. **The session cookie** (`connect.sid`) - proves "this browser already
+   logged in with a password (or LDAP bind)". Only used for the
+   `/SASLogon/*` routes. Stored server-side in MongoDB via `connect-mongo`
+   (`app-modules/configureExpressSession.ts`), so it can't be forged without
+   the `SESSION_SECRET`, and expires after 24 hours regardless of activity.
+2. **The bearer JWT** (`accessToken`/`refreshToken`) - proves "this caller
+   was issued a token by exchanging a valid auth code". Used for every
+   `SASjsApi` route. Despite being a self-verifying JWT, it is *also*
+   cross-checked against a copy stored on the `User` document
+   (`utils/verifyTokenInDB.ts:23-49`) - this is what makes server-side
+   revocation possible (logout, or issuing a new token pair via refresh,
+   immediately invalidates the old token even though its JWT signature is
+   still technically valid until expiry).
+
+A CLI/SDK client (e.g. `@sasjs/adapter`) does not have a real browser, so it
+plays the role of "Browser" in the diagram above by keeping its own cookie
+jar for steps 0-2, then switches to bearer-token auth for everything after -
+it does not need a session for any request beyond obtaining the initial
+token pair.
+
+## Branches and edge cases
+
+- **Desktop mode** (`MODE=desktop`): `authenticateAccessToken` short-circuits
+  to a fixed, always-admin `desktopUser` before any session/token logic runs
+  (`authenticateToken.ts:20-24`, `middlewares/desktop.ts:30-38`) - no
+  password, session, or CSRF check ever happens. `desktopRestrict`
+  additionally blocks all three `/SASLogon/*` routes outright in this mode
+  (`middlewares/desktop.ts:19-28`), since there is no concept of logging in
+  or out of a single-user desktop install.
+- **Public routes**: if token/session auth fails outright, the request is
+  not necessarily rejected - `isPublicRoute()` checks whether an admin has
+  granted the built-in Public group access to that specific path
+  (`utils/isPublicRoute.ts`). If so, the request proceeds as the fixed
+  `publicUser` (`userId: 0`, `isAdmin: false`) instead of getting a 401.
+- **LDAP**: when `AUTH_PROVIDERS=ldap`, only users whose `User.authProvider`
+  is `ldap` take the LDAP bind path at login; this flag is set when an admin
+  runs `POST /SASjsApi/authConfig/synchroniseWithLDAP`
+  (`controllers/authConfig.ts`), which provisions local `User`/`Group`
+  documents from the LDAP directory. Users created directly in this app
+  (`authProvider` unset) always use the local bcrypt path, even if LDAP is
+  configured.
+- **`Client` registration** (`model/Client.ts`) is a separate, lightweight
+  concept from end-user accounts: a `clientId`/`clientSecret` pair with
+  configurable access/refresh token lifetimes, used only to look up token
+  expirations during the exchange in step 3 - `clientSecret` is stored but
+  never actually checked in the token exchange (see the note in the
+  diagram). Both `POST` and `GET /SASjsApi/client` (`routes/api/client.ts`)
+  require an authenticated admin - not via anything in that file, but via
+  `authenticateAccessToken`/`verifyAdmin` applied to the whole `/client`
+  prefix at the mount point in `routes/api/index.ts:28-34`, which runs
+  before any request reaches `clientRouter`'s own handlers.
+- **`authorize` middleware permission model** (`middlewares/authorize.ts`):
+  admins and requests to already-public routes always pass. Otherwise,
+  the first matching `Permission` wins, checked in this order: the specific
+  user on the exact route, the specific user on the route's top-level
+  prefix (`/SASjsApi` or `/AppStream`), then each of the user's groups on
+  the exact route, then each of the user's groups on the top-level prefix.
+  This middleware only runs at all for routes listed in
+  `getAuthorizedRoutes()` (`utils/getAuthorizedRoutes.ts:5-20`) - a fixed
+  set of sensitive routes (code/STP execution, drive file operations) plus
+  `/SASjsApi`, `/AppStream`, and any configured streaming app sub-routes.
+  Routes outside that list only require authentication, not a granted
+  permission.
+
+## Key source files
+
+- `api/src/routes/web/web.ts`, `api/src/controllers/web.ts` - `/SASLogon/login`,
+  `/SASLogon/authorize`, `/SASLogon/logout`; the browser-facing,
+  session-based half of the flow.
+- `api/src/routes/api/auth.ts`, `api/src/controllers/auth.ts` - `/SASjsApi/auth/token`,
+  `/refresh`, `/logout`, `/updatePassword`; the token-based half used by
+  every API caller.
+- `api/src/middlewares/authenticateToken.ts` - `authenticateAccessToken` /
+  `authenticateRefreshToken`, the single entry point that decides between
+  desktop bypass, session validation, and JWT validation.
+- `api/src/middlewares/authorize.ts` - permission checks layered on top of
+  authentication, for routes in `getAuthorizedRoutes()`.
+- `api/src/middlewares/csrfProtection.ts` - CSRF token generation/verification
+  for session-authenticated (cookie-based) requests.
+- `api/src/utils/verifyTokenInDB.ts` - `verifyTokenInDB` (DB-backed
+  revocation check) and `fetchLatestAutoExec` (refreshes session-cached user
+  fields).
+- `api/src/utils/isPublicRoute.ts`, `api/src/utils/getAuthorizedRoutes.ts` -
+  the Public-group fallback and the authorization-required route list.
+- `api/src/app-modules/configureExpressSession.ts` - session cookie/store
+  configuration (MongoDB via `connect-mongo`).
+- `api/src/model/User.ts`, `api/src/model/Client.ts`,
+  `api/src/model/Permission.ts`, `api/src/model/Group.ts` - the underlying
+  data model.