feat(auth): enforce session idle and absolute timeouts (#1387)

* feat(auth): enforce session idle and absolute timeouts Hosted browser sessions now carry an HMAC-signed, HttpOnly cookie holding session start, last activity and sign-in method, bound to the Supabase session. Middleware enforces a 30 min idle and 12 h absolute limit (reason-coded redirects to /login), a heartbeat route advances idle activity from real user input, and a client controller warns 2 minutes before expiry. BankID users are routed back to BankID on re-auth via a short-lived method hint. API-key and MCP bearer surfaces are exempt; self-hosted installs default off and can opt in via env vars. Fixes #362 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * fix(auth): derive session-timeout signing key via HKDF The HMAC key is now HKDF-derived with a purpose-bound info string, so the SUPABASE_SERVICE_ROLE_KEY fallback never uses the privileged credential directly as a signing key. Addresses the security review finding on PR #1387. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * fix(auth): back signature bytes with a plain ArrayBuffer crypto.subtle.verify requires a BufferSource; Uint8Array.from is typed over ArrayBufferLike, which the Vercel TypeScript build rejects. Decode base64url into a Uint8Array constructed over a fresh ArrayBuffer. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * fix(auth): address session-timeout review findings - signSessionTimeoutState returns null on signing failure instead of throwing, so a missing secret degrades the timeout feature in line with verifySessionTimeoutState rather than crashing authenticated requests; middleware and heartbeat skip the cookie write when null - heartbeat initializes a fresh signed state for a missing or session-mismatched cookie, mirroring middleware, instead of returning SESSION_EXPIRED during normal initialization - sessionStateMatchesUser treats an unresolved current session id as a mismatch for session-bound state so another session's cookie is never accepted on the userId fallback alone - drop aria-live from the countdown DialogDescription so screen readers are not interrupted every second Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> --------- Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
2026-08-04 09:59:42 +02:00
parent f55bfc478b
commit 1c9d378df8
21 changed files with 1610 additions and 13 deletions
@@ -0,0 +1,330 @@
+import {
+  SESSION_TIMEOUT_COOKIE,
+  type SessionAuthMethod,
+  type SessionTimeoutClientState,
+  type SessionTimeoutReason,
+} from './session-timeout-shared'
+
+const DEFAULT_IDLE_TIMEOUT_MS = 30 * 60 * 1000
+const DEFAULT_ABSOLUTE_TIMEOUT_MS = 12 * 60 * 60 * 1000
+const DEFAULT_WARNING_MS = 2 * 60 * 1000
+const COOKIE_MAX_AGE_SECONDS = 365 * 24 * 60 * 60
+const SIGNING_CONTEXT = 'accounted-session-timeout-v1:'
+
+export interface SessionTimeoutConfig {
+  enabled: boolean
+  idleTimeoutMs: number
+  absoluteTimeoutMs: number
+  warningMs: number
+}
+
+export interface SessionTimeoutState {
+  version: 1
+  userId: string
+  sessionId: string | null
+  startedAt: number
+  lastActivityAt: number
+  method: SessionAuthMethod
+}
+
+type Environment = Record<string, string | undefined>
+
+function parseDuration(value: string | undefined, fallback: number): number {
+  if (value === undefined || value.trim() === '') return fallback
+
+  const parsed = Number(value)
+  if (!Number.isSafeInteger(parsed) || parsed < 0) return fallback
+  return parsed
+}
+
+export function getSessionTimeoutConfig(
+  env: Environment = process.env,
+): SessionTimeoutConfig {
+  const defaultTimeout = env.NEXT_PUBLIC_SELF_HOSTED === 'true' ? 0 : undefined
+  const idleTimeoutMs = parseDuration(
+    env.NEXT_PUBLIC_SESSION_IDLE_TIMEOUT_MS,
+    defaultTimeout ?? DEFAULT_IDLE_TIMEOUT_MS,
+  )
+  const absoluteTimeoutMs = parseDuration(
+    env.NEXT_PUBLIC_SESSION_ABSOLUTE_TIMEOUT_MS,
+    defaultTimeout ?? DEFAULT_ABSOLUTE_TIMEOUT_MS,
+  )
+  const configuredWarningMs = parseDuration(
+    env.NEXT_PUBLIC_SESSION_WARNING_MS,
+    DEFAULT_WARNING_MS,
+  )
+  const enabledTimeouts = [idleTimeoutMs, absoluteTimeoutMs]
+    .filter((timeout) => timeout > 0)
+  const warningMs = enabledTimeouts.length > 0
+    ? Math.min(configuredWarningMs, ...enabledTimeouts)
+    : 0
+
+  return {
+    enabled: idleTimeoutMs > 0 || absoluteTimeoutMs > 0,
+    idleTimeoutMs,
+    absoluteTimeoutMs,
+    warningMs,
+  }
+}
+
+export function createSessionTimeoutState(args: {
+  userId: string
+  sessionId: string | null
+  method: SessionAuthMethod
+  now?: number
+}): SessionTimeoutState {
+  const now = args.now ?? Date.now()
+  return {
+    version: 1,
+    userId: args.userId,
+    sessionId: args.sessionId,
+    startedAt: now,
+    lastActivityAt: now,
+    method: args.method,
+  }
+}
+
+export function evaluateSessionTimeout(
+  state: SessionTimeoutState,
+  config: SessionTimeoutConfig,
+  now = Date.now(),
+): SessionTimeoutReason | null {
+  if (
+    config.absoluteTimeoutMs > 0 &&
+    now - state.startedAt >= config.absoluteTimeoutMs
+  ) {
+    return 'absolute'
+  }
+
+  if (
+    config.idleTimeoutMs > 0 &&
+    now - state.lastActivityAt >= config.idleTimeoutMs
+  ) {
+    return 'idle'
+  }
+
+  return null
+}
+
+function getSigningSecret(env: Environment): string {
+  const dedicated = env.SESSION_TIMEOUT_SECRET?.trim()
+  if (dedicated) return dedicated
+
+  const serviceRole = env.SUPABASE_SERVICE_ROLE_KEY?.trim()
+  if (serviceRole) return serviceRole
+
+  throw new Error(
+    'Session timeout enforcement requires SESSION_TIMEOUT_SECRET or SUPABASE_SERVICE_ROLE_KEY',
+  )
+}
+
+function bytesToBase64Url(bytes: Uint8Array): string {
+  let binary = ''
+  for (const byte of bytes) binary += String.fromCharCode(byte)
+  return btoa(binary)
+    .replaceAll('+', '-')
+    .replaceAll('/', '_')
+    .replace(/=+$/u, '')
+}
+
+function base64UrlToBytes(value: string): Uint8Array<ArrayBuffer> | null {
+  try {
+    const base64 = value.replaceAll('-', '+').replaceAll('_', '/')
+    const padded = base64.padEnd(Math.ceil(base64.length / 4) * 4, '=')
+    const binary = atob(padded)
+    const bytes = new Uint8Array(binary.length)
+    for (let index = 0; index < binary.length; index += 1) {
+      bytes[index] = binary.charCodeAt(index)
+    }
+    return bytes
+  } catch {
+    return null
+  }
+}
+
+function encodePayload(state: SessionTimeoutState): string {
+  return bytesToBase64Url(new TextEncoder().encode(JSON.stringify(state)))
+}
+
+function decodePayload(payload: string): unknown {
+  const bytes = base64UrlToBytes(payload)
+  if (!bytes) return null
+
+  try {
+    return JSON.parse(new TextDecoder().decode(bytes))
+  } catch {
+    return null
+  }
+}
+
+function isValidState(value: unknown): value is SessionTimeoutState {
+  if (!value || typeof value !== 'object') return false
+  const state = value as Partial<SessionTimeoutState>
+
+  return (
+    state.version === 1 &&
+    typeof state.userId === 'string' &&
+    state.userId.length > 0 &&
+    (state.sessionId === null || typeof state.sessionId === 'string') &&
+    Number.isSafeInteger(state.startedAt) &&
+    Number.isSafeInteger(state.lastActivityAt) &&
+    (state.method === 'password' || state.method === 'bankid') &&
+    (state.startedAt as number) > 0 &&
+    (state.lastActivityAt as number) >= (state.startedAt as number)
+  )
+}
+
+async function importSigningKey(secret: string): Promise<CryptoKey> {
+  // The signing key is HKDF-derived with a purpose-bound info string, never
+  // the raw secret: the SUPABASE_SERVICE_ROLE_KEY fallback must not use the
+  // privileged credential itself as an HMAC key.
+  const baseKey = await crypto.subtle.importKey(
+    'raw',
+    new TextEncoder().encode(secret),
+    'HKDF',
+    false,
+    ['deriveKey'],
+  )
+  return crypto.subtle.deriveKey(
+    {
+      name: 'HKDF',
+      hash: 'SHA-256',
+      salt: new Uint8Array(32),
+      info: new TextEncoder().encode(SIGNING_CONTEXT),
+    },
+    baseKey,
+    { name: 'HMAC', hash: 'SHA-256', length: 256 },
+    false,
+    ['sign', 'verify'],
+  )
+}
+
+export async function signSessionTimeoutState(
+  state: SessionTimeoutState,
+  env: Environment = process.env,
+): Promise<string | null> {
+  // A missing signing secret must degrade the timeout feature, never crash
+  // authenticated requests: verifySessionTimeoutState already returns null in
+  // the same misconfiguration, so returning null here keeps both halves of
+  // the feature consistently disabled.
+  try {
+    const payload = encodePayload(state)
+    const key = await importSigningKey(getSigningSecret(env))
+    const signature = await crypto.subtle.sign(
+      'HMAC',
+      key,
+      new TextEncoder().encode(`${SIGNING_CONTEXT}${payload}`),
+    )
+    return `${payload}.${bytesToBase64Url(new Uint8Array(signature))}`
+  } catch (error) {
+    console.error(
+      '[session-timeout] signing failed; timeout state not persisted',
+      error,
+    )
+    return null
+  }
+}
+
+export async function verifySessionTimeoutState(
+  value: string | undefined,
+  env: Environment = process.env,
+): Promise<SessionTimeoutState | null> {
+  if (!value) return null
+  const [payload, signature, extra] = value.split('.')
+  if (!payload || !signature || extra !== undefined) return null
+
+  const signatureBytes = base64UrlToBytes(signature)
+  if (!signatureBytes) return null
+
+  try {
+    const key = await importSigningKey(getSigningSecret(env))
+    const valid = await crypto.subtle.verify(
+      'HMAC',
+      key,
+      signatureBytes,
+      new TextEncoder().encode(`${SIGNING_CONTEXT}${payload}`),
+    )
+    if (!valid) return null
+  } catch {
+    return null
+  }
+
+  const state = decodePayload(payload)
+  return isValidState(state) ? state : null
+}
+
+interface SessionTimeoutCookieOptions {
+  path: '/'
+  httpOnly: true
+  secure: boolean
+  sameSite: 'lax'
+  maxAge: number
+}
+
+export function sessionTimeoutCookieOptions(): SessionTimeoutCookieOptions {
+  return {
+    path: '/',
+    httpOnly: true,
+    secure: process.env.NODE_ENV === 'production',
+    sameSite: 'lax',
+    maxAge: COOKIE_MAX_AGE_SECONDS,
+  }
+}
+
+export function sessionTimeoutClearCookieOptions(): SessionTimeoutCookieOptions {
+  return {
+    ...sessionTimeoutCookieOptions(),
+    maxAge: 0,
+  }
+}
+
+export function toSessionTimeoutClientState(
+  state: SessionTimeoutState,
+  config: SessionTimeoutConfig,
+  serverNow = Date.now(),
+): SessionTimeoutClientState {
+  return {
+    enabled: config.enabled,
+    idleTimeoutMs: config.idleTimeoutMs,
+    absoluteTimeoutMs: config.absoluteTimeoutMs,
+    warningMs: config.warningMs,
+    serverNow,
+    startedAt: state.startedAt,
+    lastActivityAt: state.lastActivityAt,
+    method: state.method,
+  }
+}
+
+export function sessionStateMatchesUser(
+  state: SessionTimeoutState,
+  userId: string,
+  sessionId: string | null,
+): boolean {
+  if (state.userId !== userId) return false
+  if (state.sessionId === null) return true
+  // The state is bound to a specific Supabase session. If the current session
+  // id cannot be resolved it is unknown, not a wildcard: report a mismatch so
+  // the caller mints a fresh state instead of accepting another session's.
+  if (sessionId === null) return false
+  return state.sessionId === sessionId
+}
+
+export function apiRequestSkipsSessionTimeout(
+  pathname: string,
+  hasAuthorizationHeader: boolean,
+): boolean {
+  if (
+    pathname === '/api/health' ||
+    pathname === '/api/log' ||
+    pathname.startsWith('/api/mcp-oauth/')
+  ) {
+    return true
+  }
+
+  return hasAuthorizationHeader && (
+    pathname.startsWith('/api/v1/') ||
+    pathname.startsWith('/api/extensions/ext/mcp-server/mcp')
+  )
+}
+
+export { SESSION_TIMEOUT_COOKIE }