Allow a user to only see his own data?

Question

Imagine an app where a user can manage some kind of items (his tasks, his book collection or whatever). The user shall only have access to his own items, not those of other users. How would I ensure that in my HotChocolate GraphQl backend? Do I always have to remember to write queries restricted to the users's id or is there a better way? I fear one could simply forget to restrict the query to the user's id and then leak data from other users.

[Authorize]
public class Items
{
    public int Id { get; set; } // id of the item
    public int UserId { get; set; } // id of the user who owns the item
    public string Title { get; set; } = null!; // title of the item, e.g. title of a book
}

[QueryType]
public class ItemQueries
{
    public IQueryable<Contract> GetItems(ApplicationDbContext context, [UserId] int userId)
    {
        // I think it's error prone (e.g. one could easily forget about it)
        // that I always have to remember to query by the user id.
        // Is there a better solution to that?
        return context.Items.Where(item => item.UserId == userId);
    }
}

Answer 1

While directly filtering queries by the user's ID to ensure that users only access their own data in a GraphQL API is a straightforward approach, it might be worth to explore other options like:

1. Middleware for Automatic Filtering You can create a custom GraphQL middleware that automatically applies user-specific filtering to all queries. This middleware can inspect the incoming GraphQL query and, based on the operation type and the entity being accessed, append the necessary Where clause to ensure data is filtered based on the current user's ID.

2. Custom Attributes and Reflection Another approach is to create a custom attribute, e.g., [UserScoped], which you can apply to your model properties that represent user ownership. Then, use reflection within your base query class or middleware to automatically inject user ID filters into queries for models marked with this attribute.

3. Utilize Global Query Filters in Entity Framework Core If you're using Entity Framework Core, you can leverage Global Query Filters to automatically apply filters to your queries. For instance, you could define a global filter on your Items DbSet to only include items where UserId matches the current user's ID. This approach centralizes your access control logic, reducing the risk of accidentally exposing user data.

Hope this helps!