Middlewares

Middlewares are functions that are execute before the request reaches the controller. They can be used to modify the request, check for authentication and more. Middlewares can be applied globally, per module or per controller.

Example of a Middleware

@Injectable()
export class AuthMiddleware implements NestMiddleware {
  private readonly jwks: ReturnType<typeof createRemoteJWKSet>

  constructor (
    private readonly configService: ConfigService,
    private readonly authStorage: AuthStorage,
    private readonly userAuthService: UserAuthService
  ) {
    this.jwks = createRemoteJWKSet(
      new URL(this.configService.getOrThrow('AUTH_JWKS_ENDPOINT'))
    )
  }

  public async use (req: Request, _res: Response, next: NextFunction): Promise<void> {
    if (req.headers.authorization == null) {
      next()

      return
    }

    if (!req.headers.authorization.startsWith('Bearer ')) {
      throw new UnauthorizedError()
    }

    const token = req.headers.authorization.split(' ')[1]

    try {
      const content = await this.verify(token)

      this.authStorage.run(content, next)
    } catch (_error) {
      next()
    }
  }

  public async verify (token: string): Promise<AuthContent> {
    const { payload } = await jwtVerify<TokenContent>(token, this.jwks, {
      issuer: this.configService.getOrThrow('AUTH_ISSUER'),
      audience: this.configService.getOrThrow('AUTH_PROJECT_ID')
    })

    return await this.userAuthService.findOneByUserId(payload)
  }
}