Nest.js: Global AuthGuard but with exceptions

Question

I would like to register my AuthenticationGuard, which checks for Authentication, globally on my application, so that by default all routes require authentication.

const authGuard = app
    .select(AuthModule)
    .get(AuthGuard);
app.useGlobalGuards(authGuard);

What is the best/nest.js way to add route exceptions, so that anonymous routes can also be implemented?

Answer 1

You can actually set metadata for the global AuthGuard so it can determine if it should allow an unauthorized request.

e.g.

Set Global Auth Guard

import { Module } from '@nestjs/common';
import { APP_GUARD } from '@nestjs/core';
import { AuthGuard } from './auth.guard';

@Module({
  providers: [
    {
      provide: APP_GUARD,
      useClass: AuthGuard,
    },
  ],
})
export class AppModule {}

---

Use SetMetadata to pass in data to the AuthGuard

import { SetMetadata } from '@nestjs/common';
// Convienience Function
const AllowUnauthorizedRequest = () => SetMetadata('allowUnauthorizedRequest', true);
@Controller()
export class AppController {

  @Get('my-unauthorized-path')
  @AllowUnauthorizedRequest()
  myHandler () {
    return { unauthorized: true };
  }

}

---

Use data passed in from SetMetadata to determine if unauthorized request is allowed.

import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common';
import { Reflector } from '@nestjs/core';
import { validateRequest } from './validateRequest' // your custom implementation

@Injectable()
export class AuthGuard implements CanActivate {

  constructor(private reflector: Reflector) {}
  canActivate(context: ExecutionContext) {
    const request = context.switchToHttp().getRequest();
    const allowUnauthorizedRequest = this.reflector.get<boolean>('allowUnauthorizedRequest', context.getHandler());
    return allowUnauthorizedRequest || validateRequest(request);
  }

}