Cakemail API Express Auth Middleware

Express TypeScript authentication/authorization middleware for Cakemail's API. This middleware verifies JWT Bearer tokens, authorizes access to impersonated accounts, and provides user/account data to downstream handlers.

Features

• JWT Bearer token verification using RSA public key
• Account impersonation authorization via API calls
• Automatic user data loading from /users/self
• Redis caching to minimize API calls
• Fail-open caching (continues without cache if Redis unavailable)
• Full TypeScript support with strict typing
• Non-intrusive data storage using Express res.locals
• Dual package support (CommonJS + ESM)

Installation

npm install @cakemail-org/ngapi-ts-auth-middleware

Quick Start

import express from 'express';
import { createAuthMiddleware } from '@cakemail-org/ngapi-ts-auth-middleware';

const app = express();

// Public key is automatically fetched from {API_BASE_URL}/token/pubkey
const authMiddleware = createAuthMiddleware({
  cacheSecret: process.env.CACHE_SECRET, // Required: Secret for HMAC and encryption
  enableCaching: true,
  redis: {
    host: process.env.REDIS_HOST,
    port: parseInt(process.env.REDIS_PORT || '6379'),
    db: parseInt(process.env.REDIS_DB || '0'),
  },
});

// Apply to all routes
app.use(authMiddleware);

// Or apply to specific routes
app.get('/api/resource', authMiddleware, (req, res) => {
  res.json({
    userId: res.locals.user.id,
    userEmail: res.locals.user.email,
    userAccountId: res.locals.user.account.id,
    targetAccountId: res.locals.account.id,
  });
});

app.listen(3000);

Configuration

AuthMiddlewareConfig

Option	Type	Required	Default	Description
cacheSecret	string	Yes	-	Required secret for HMAC cache keys and Redis data encryption. Must be a strong, random value. Keep this secret secure!
publicKey	`string	Buffer`	No	Auto-fetched from {API_BASE_URL}/token/pubkey
apiBaseUrl	string	No	process.env.CAKEMAILAPI_BASE_URL or https://api.cakemail.dev	API base URL
enableCaching	boolean	No	true	Enable Redis caching
redis	RedisConfig	No	-	Redis connection configuration
accountIdParams	string[]	No	['accountId', 'account_id']	Query parameter names for account ID
onError	(error, req) => void	No	-	Custom error handler
jwtOptions	JwtOptions	No	-	JWT verification options

RedisConfig

Option	Type	Required	Default	Description
host	string	No	process.env.REDIS_HOST or localhost	Redis host
port	number	No	process.env.REDIS_PORT or 6379	Redis port
db	number	No	process.env.REDIS_DB or 0	Redis database number
password	string	No	process.env.REDIS_PASSWORD	Redis password
keyPrefix	string	No	ngapi:	Redis key prefix

JwtOptions

Option	Type	Required	Default	Description
algorithms	string[]	No	['RS256']	Allowed JWT algorithms
issuer	string	No	urn:cakemail	Expected JWT issuer
clockTolerance	number	No	10	Clock tolerance in seconds

Environment Variables

The middleware respects the following environment variables:

• CACHE_SECRET: Required - Secret for HMAC and Redis encryption (generate with openssl rand -base64 32)
• CAKEMAILAPI_BASE_URL: API base URL (default: https://api.cakemail.dev)
• REDIS_HOST: Redis host (default: localhost)
• REDIS_PORT: Redis port (default: 6379)
• REDIS_DB: Redis database (default: 0)
• REDIS_PASSWORD: Redis password (optional)

Response Locals

The middleware stores authentication data in res.locals, following Express best practices for passing data between middleware:

res.locals.user: AuthenticatedUser

Contains the authenticated user's data from /users/self and JWT claims:

{
  id: string;
  email: string;
  first_name: string;
  last_name: string;
  account: Account;      // User's own account (from JWT)
  scopes: string[];      // User's scopes
  user_key: string;      // User's API key
  // ... other user properties
}

res.locals.account: Account

Contains the target account data:

• If ?accountId=X query parameter is present: authorized impersonated account
• If no query parameter: user's own account (same as res.locals.user.account)

{
  id: string;
  name: string;
  lineage: string;
  status: string;
  usage_limits: UsageLimits;
  // ... other account properties
}

res.locals.token: string

The raw JWT Bearer token string.

Data Population Guarantees

The middleware guarantees the following:

• res.locals.account.id: Always the target account ID (safe to use for operations)
• res.locals.user.account.id: Always the user's own account ID (never changes with impersonation)

This ensures downstream handlers always know:

1. Which account is being operated on (res.locals.account.id)
2. Which user is making the request (res.locals.user.id)
3. Which account the user belongs to (res.locals.user.account.id)

Account Impersonation

When a query parameter accountId or account_id is present, the middleware:

1. Verifies the JWT token
2. Calls GET /accounts/:accountId with the Bearer token
3. If returns 200: access is authorized, res.locals.account is populated with account data
4. If returns 403/401: throws AuthorizationError (403 response)

Example:

// User with account 1627783 accessing account 999999
GET /api/resource?accountId=999999
Authorization: Bearer <token>

// Result:
// res.locals.user.account.id = "1627783" (user's own account)
// res.locals.account.id = "999999" (target account)

Caching Strategy

The middleware caches API responses in Redis to minimize API calls:

Cache Key Format

ngapi:{tokenHash}:{accountId|userId}:{type}

• tokenHash: First 16 characters of SHA256(token)
• accountId|userId: Account or user ID
• type: account or user

Example: ngapi:a3f2c8d1e5f7:1627783:account

TTL Strategy

• Cache keys expire when the JWT token expires
• Min TTL: 60 seconds
• Max TTL: 24 hours

Fail-Open Behavior

If Redis is unavailable:

1. Logs warning to console
2. Continues without caching
3. Makes API calls on every request

This ensures authentication/authorization remains functional even if Redis is down (at the cost of performance).

Error Handling

The middleware returns the following HTTP error responses:

401 Unauthorized

• Missing Authorization header
• Invalid token format
• Expired token
• Invalid token signature

Response:

{
  "error": "Authentication failed",
  "message": "Token has expired"
}

403 Forbidden

• User does not have access to requested account

Response:

{
  "error": "Authorization failed",
  "message": "Access denied to account 999999"
}

500 Internal Server Error

• Unexpected errors during authentication/authorization

Response:

{
  "error": "Internal server error",
  "message": "An unexpected error occurred during authentication"
}

Custom Error Handler

You can provide a custom error handler for logging or monitoring:

const authMiddleware = createAuthMiddleware({
  publicKey,
  onError: (error, req) => {
    console.error('Auth error:', {
      error: error.message,
      path: req.path,
      method: req.method,
    });
  },
});

Usage Examples

Basic Usage

import express from 'express';
import { createAuthMiddleware } from '@cakemail-org/ngapi-ts-auth-middleware';

const app = express();

// Public key is automatically fetched from the API
const authMiddleware = createAuthMiddleware({
  // Optional: specify API base URL (defaults to CAKEMAILAPI_BASE_URL env var)
  // apiBaseUrl: 'https://api.cakemail.dev',
});

app.use(authMiddleware);

app.get('/api/campaigns', (req, res) => {
  // Access authenticated user
  console.log(`User ${res.locals.user.email} accessing account ${res.locals.account.id}`);

  res.json({ campaigns: [] });
});

app.listen(3000);

With Redis Caching

const authMiddleware = createAuthMiddleware({
  enableCaching: true,
  redis: {
    host: process.env.REDIS_HOST || 'localhost',
    port: parseInt(process.env.REDIS_PORT || '6379'),
    db: parseInt(process.env.REDIS_DB || '0'),
    password: process.env.REDIS_PASSWORD,
  },
});

With Custom Configuration

const authMiddleware = createAuthMiddleware({
  // Public key is auto-fetched, but you can provide it manually if needed
  // publicKey: fs.readFileSync('./pubkey.pem'),

  apiBaseUrl: process.env.CAKEMAILAPI_BASE_URL,
  enableCaching: true,
  accountIdParams: ['accountId', 'account_id', 'aid'],
  redis: {
    host: process.env.REDIS_HOST,
    port: parseInt(process.env.REDIS_PORT || '6379'),
    keyPrefix: 'myapp:',
  },
  onError: (error, req) => {
    console.error('Auth error:', error, 'Path:', req.path);
  },
  jwtOptions: {
    algorithms: ['RS256'],
    issuer: 'urn:cakemail',
    clockTolerance: 30,
  },
});

Route-Specific Middleware

import { createAuthMiddleware } from '@cakemail-org/ngapi-ts-auth-middleware';

const authMiddleware = createAuthMiddleware({});

// Public routes (no auth)
app.get('/health', (req, res) => {
  res.json({ status: 'ok' });
});

// Protected routes
app.get('/api/*', authMiddleware);

app.get('/api/campaigns', (req, res) => {
  // res.locals.user and res.locals.account are guaranteed to exist here
  res.json({ campaigns: [] });
});

TypeScript Support

The middleware is written in TypeScript with full type definitions. It automatically augments Express.Locals so TypeScript knows about res.locals.user, res.locals.account, and res.locals.token without any manual type declarations.

Automatic Type Augmentation

When you import this package, Express.Locals is automatically augmented:

import express from 'express';
import { createAuthMiddleware } from '@cakemail/ngapi-ts-auth-middleware';

const app = express();
const authMiddleware = createAuthMiddleware({ cacheSecret: process.env.CACHE_SECRET });

app.get('/api/resource', authMiddleware, (req, res) => {
  // TypeScript automatically knows about these types:
  // - res.locals.user is AuthenticatedUser | undefined
  // - res.locals.account is Account | undefined
  // - res.locals.token is string | undefined

  if (!res.locals.user || !res.locals.account) {
    return res.status(500).json({ error: 'Authentication data missing' });
  }

  res.json({
    userId: res.locals.user.id,
    userEmail: res.locals.user.email,
    accountId: res.locals.account.id,
  });
});

No manual type casting or custom type declarations required.

Importing Types

Types can be imported directly from the package for use in your application:

import {
  AuthMiddlewareConfig,
  AuthenticatedUser,
  Account,
  User,
  JwtPayload,
  AuthenticationError,
  AuthorizationError,
} from '@cakemail-org/ngapi-ts-auth-middleware';

Testing

Run tests:

npm test

Run tests with coverage:

npm run test:coverage

Security Considerations

1. HTTPS Only: Always use HTTPS in production
2. Public Key Security: Never expose or commit private keys
3. Token Expiration: Tokens should have reasonable expiration times
4. Cache Key Hashing: Tokens are hashed in cache keys to prevent leakage
5. Error Messages: Error messages don't leak sensitive token information

Performance

• Redis Caching: Reduces API calls by 90%+ for repeated requests
• Connection Pooling: ioredis and axios handle connection pooling automatically
• Lazy Initialization: Services initialize only when first needed
• Async Operations: User and account data fetched in parallel when possible

License

MIT

Contributing

Contributions are welcome! Please submit pull requests to the GitHub repository.

Support

For issues or questions, please file an issue on GitHub.