@oxeye/rls

Description

Row level security utilitary package to apply to NestJS and TypeORM.

This solution does not work by having multiple connections to database (eg: one connection / tenant). Instead, this solution works by applying the database policies for RLS as described in this aws blog post (under the Alternative approach).

Install

$ npm install @avallone-io/rls

Usage

To create a RLSConnection instance you'll need the original connection to db. Setup the typeorm config as usual, then wrap its connection into a RLSConnection instance, for each request.

This will run a set "rls.tenant_id" and set "rls.actor_id" for each request and will reset them after the query is executed.

---

RLS Policies

Your database policies will have to make use of rls.tenant_id and rls.actor_id in order to apply the isolation. Policy example:

CREATE POLICY tenant_isolation ON public."category" for ALL
USING ("tenant_id" = current_setting('rls.tenant_id'))
with check ("tenant_id" = current_setting('rls.tenant_id'));

---

Express/KOA

For example, assuming an express application:

app.use((req, res, next) => {
  const connection = getConnection(); // get default typeorm connection

  // get tenantId and actorId from somewhere (headers/token etc)
  const rlsConnection = new RLSConnection(connection, {
    actorId,
    tenantId,
  });

  res.locals.connection = rlsConnection;
  next();
});

// your handlers
const userRepo = res.locals.connection.getRepository(User);
await userRepo.find(); // will return only the results where the db rls policy applies

In the above example, you'll have to work with the supplied connection. Calling TypeORM function directly will work with the original connection which is not RLS aware.

NestJS integration

If you are using NestJS, this library provides helpers for making your connections and queries tenant aware.

Create your TypeORM config and load the TypeORM module using .forRoot. Then you'll need to load the RLSModule with .forRoot where you'll define where to take the tenantId and actorId from. The second part is that you now need to replace the TypeOrmModule.forFeature with RLSModule.forFeature. You can inject non-entity dependent Modules and Providers. First array imports modules, second array injects providers.

When using RLSModule.forRoot it will set your scope to REQUEST! Be sure you understand the implications of this and especially read about the request-scoped authentication strategy on Nestjs docs.

app.controller.ts

@Module({
  imports: [
    TypeOrmModule.forRoot(...),
    RLSModule.forRoot([/*Module*/], [/*Service*/], (req: Request, /*serviceInstance*/) => {
      // You can take the tenantId and actorId from headers/tokens etc
      const tenantId = req.headers['tenant_id'];
      const actorId = req.headers['actor_id'];

      return {
        actorId,
        tenantId,
      };
    }),
    RLSModule.forFeature([Post, Category]) // <- this
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

Now you can use the normal module injection for repositories, services etc.

To inject the RLS connection within a service, you can do by using @Inject(TENANT_CONNECTION) where TENANT_CONNECTION is imported from @avallone-io/rls.

export class AppService {
  constructor(
    @InjectRepository(Category)
    private categoryRepo: Repository<Category>,
    @Inject(TENANT_CONNECTION)
    private connection: RLSConnection,
  ) {}

  // you can now use categoryRepo as normal but it will
  // be scoped for RLS. Same with the connection.
}

Same as before, do not use the TypeORM functions directly (eg: getConnection()) as that will give you the default connection to the database, not the wrapped instance.

For more specific examples, check the test/nestjs/src.