Nestjs + Passport: Prevent user 1 to access information of user 2 - node.js

Question

How can I prevent user 1 to access information of user 2 using passport in a Nesjs app ?
I already have 2 strategies:
the local strategy which validate a user with email/password. The route protected by this strategy return a jwt token.
the jwt strategy which validate the given jwt token.
Now, I want to restrict access to routes such as users/:id to jwt token which actually have the same userId encrypted.
How to do that ?

Answer 1

EDIT
I was mixing Authentication and Authorization: what I want to achieve is about authorization, once the user has been authenticated.
I had to use Guard:
own.guard.ts
#Injectable()
export class OwnGuard implements CanActivate {
canActivate(context: ExecutionContext): boolean {
const req = context.switchToHttp().getRequest();
return req.user.id === req.params.id;
}
}
Then use it in my route:
#Get(':id')
#UseGuards(OwnGuard)
async get(#Param('id') id: string) {
return await this.usersService.get(id);
}
ORIGINAL ANSWER
What I did was to create a third strategy based on the jwt one:
#Injectable()
export class OwnStrategy extends PassportStrategy(Strategy, 'own') {
constructor() {
super({
jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
secretOrKey: SECRET,
passReqToCallback: true
});
}
async validate(req: Request, payload: { sub: string }) {
if (req.params.id !== payload.sub) {
throw new UnauthorizedException();
}
return { userId: payload.sub };
}
}
Note how I pass the custom name 'own' as second parameter of PassportStrategy to differentiate it from the 'jwt' one. Its guard:
#Injectable()
export class OwnAuthGuard extends AuthGuard('own') {}
This works but I wonder if it is the good way of doing it...
What if later I want to able user modification for admin users ?
Should I create a forth strategy which check if role === Role.ADMIN || req.params.id === payload.sub ?
I think I'm missing something. There should be a way to create a strategy which validate only the jwt, another one only the userId, another one only the role, and combine them as I want when applying guards to my routes.

Answer 2

same case. you can use handleRequest method in guard.
here you can access user auth and req, then doing validation for resource appropriate. check out my code
#Injectable()
export class JwtAuthGuard extends AuthGuard('jwt') {
canActivate(context: ExecutionContext) {
return super.canActivate(context);
}
handleRequest(err, user, info, context: ExecutionContext) {
const request = context.switchToHttp().getRequest<Request>();
const params = request.params;
if (user.id !== +params.id) {
throw new ForbiddenException();
}
return user;
}
}
look more here https://docs.nestjs.com/security/authentication#extending-guards