@nathapp/nestjs-auth

JWT authentication + CASL authorization library for NestJS.

Installation

npm install @nathapp/nestjs-auth @nestjs/passport

Note for Fastify users: There is slightly different request/response handling for Fastify. Interceptors and middleware check req.raw for Fastify vs Express compatibility.

JWKS (Remote Identity Provider)

To verify tokens issued by an external IdP (Auth0, Cognito, Okta, Keycloak), install the optional jwks-rsa peer dependency:

npm install jwks-rsa

Then configure your module:

import { Module } from '@nestjs/common';
import { AuthenticationModule, createJwksStrategyProvider } from '@nathapp/nestjs-auth';
import { MyAuthProvider } from './my-auth-provider';

@Module({
  imports: [
    AuthenticationModule.forRoot({
      jwtOptions: {
        signOption: { algorithm: 'RS256' },
        issuer: 'https://my-tenant.auth0.com/',
        audience: 'https://api.example.com',
        jwks: {
          jwksUri: 'https://my-tenant.auth0.com/.well-known/jwks.json',
          // optional tuning:
          // cacheMaxAge: 600000,
          // jwksRequestsPerMinute: 10,
          // algorithms: ['RS256'],
        },
      },
      authProvider: MyAuthProvider,
    }),
  ],
  // Override the default JwtStrategyProvider with the JWKS factory.
  // Must be registered AFTER AuthenticationModule so DI resolves this provider.
  providers: [createJwksStrategyProvider()],
})
export class AppModule {}

Note: Don't pass strategyProvider: JwksJwtStrategyProvider directly — this monorepo uses useFactory registration (see CLAUDE.md). The createJwksStrategyProvider() helper wires JWT_OPTIONS + AUTH_PROVIDER injection for you.

JWKS Security Defaults

• issuer is required when using JWKS (prevents accepting tokens from any key the URI serves).
• algorithms defaults to ['RS256']. HMAC algorithms (HS*) and none are rejected.
• jwksUri must use HTTPS (set allowInsecure: true only for local dev against a mock server).
• sign() throws in JWKS mode — the strategy is verify-only.

validate<T> is an unchecked cast

DefaultJwtStrategyProvider.validate<T>() returns the principal produced by your AuthProvider via an unchecked cast (principal as any as T). The library cannot verify that your provider actually returns the declared type: if your AuthProvider is typed to return IPrincipal but returns a differently shaped object, the mismatch surfaces at runtime, not compile time. Consumers must ensure their AuthProvider.getPrincipal() returns data compatible with the T declared at the call site (defaults to IPrincipal).

Token purpose (typ) and refresh configuration

Access and refresh tokens carry a purpose payload claim typ: 'access' | 'refresh' (distinct from the JWT JOSE header's typ). The built-in access provider signs object payloads with typ: 'access'; the refresh provider always signs with typ: 'refresh'. Verification enforces the matching purpose, so an access token can no longer be replayed at a refresh endpoint (or vice versa) even when both use the same signing key.

Migration policy

• Existing unmarked refresh tokens stop working. A refresh token without typ: 'refresh' is rejected by JwtRefreshStrategy and by the built-in refresh provider. There is no opt-out to accept unmarked refresh tokens.
• Mint refresh tokens through the refresh strategy provider (e.g. JwtRefreshStrategyProvider.sign({ sub })) or, for external issuers, include the typ: 'refresh' payload claim in the token you issue.
• Distinct access/refresh secrets alone are not a substitute for marking newly issued refresh tokens under this policy. Purpose is enforced independently of the key.
• Because previously issued refresh tokens cannot be re-marked, a planned rollout may require reauthentication of existing sessions before the new library is deployed.
• Refresh signing requires an object payload so the claim can be attached. Previously accepted string/Buffer payloads must be converted to objects (e.g. provider.sign(String(payload)) → provider.sign({ value: payload })). Access signing still accepts opaque string/Buffer payloads, which are treated as legacy unmarked access tokens and remain valid.

Refresh options are independent of access options

Refresh options reuse the access secrets/keys only when the refresh provides no key material of its own, and the refresh TTL defaults to 7h regardless of the access TTL (the access algorithm is inherited only when keys are shared and the refresh algorithm is absent). Access TTL, issuer/audience sign claims, and unrelated validation flags are not inherited. Configure refresh issuer/audience and their matching verification claims explicitly when the refresh tokens need issuer/audience scoping:

AuthenticationModule.forRoot({
  jwtOptions: {
    secret: 'access-secret',
    signOption: { expiresIn: '15m', issuer: 'my-issuer' },
    issuer: 'my-issuer',
  },
  refreshJwtOptions: {
    secret: 'refresh-secret',           // or omit to share the access key
    signOption: { expiresIn: '7h', issuer: 'my-issuer' },
    issuer: 'my-issuer',                // verification must match the signed claim
  },
});