Laravel Lighthouse 限制突变字段

Question

I would like to protect some specific fields of a content type to only allow admin user to modify the value but allow users to access it.

Imagine for instance the User type with a is_admin field. Only admin should be able to update it but everyone should be able to read it.

type User {
    id: ID!
    name: String!
    email: String!
    is_admin: Boolean!
}

The can directive doesn't seem to work with field in mutation. At first I tried adding @can(ability: "setAdmin") with a custom policy but it didn't had any effect. That same can/policy used on the mutation "worked" but this was not granular enough.

It appears that custom field restrictions using a custom directive should help, but this too doesn't seem to work on a field level in a mutation input type.

type mutation {
    updateUser(
        input: UpdateUserInput! @spread
    ): User @update @middleware(checks: ["auth:api"])
}

input UpdateUserInput {
    id: ID!
    name: String!
    email: String!
    is_admin: Boolean! @adminOnly
}

With this custom directive in app/GraphQL/Directives/AdminOnlyDirective.php

<?php

namespace App\GraphQL\Directives;

use Closure;
use GraphQL\Type\Definition\ResolveInfo;
use Nuwave\Lighthouse\Exceptions\DefinitionException;
use Nuwave\Lighthouse\Schema\Directives\BaseDirective;
use Nuwave\Lighthouse\Schema\Values\FieldValue;
use Nuwave\Lighthouse\Support\Contracts\DefinedDirective;
use Nuwave\Lighthouse\Support\Contracts\FieldMiddleware;
use Nuwave\Lighthouse\Support\Contracts\GraphQLContext;

class AdminOnlyDirective extends BaseDirective implements FieldMiddleware, DefinedDirective
{
    /**
     * Name of the directive as used in the schema.
     *
     * @return string
     */
    public function name(): string
    {
        return 'adminOnly';
    }

    public static function definition(): string
    {
        return /** @lang GraphQL */ <<<GRAPHQL
"""
Limit field update to only admin.
"""
directive @adminOnly() on FIELD_DEFINITION
GRAPHQL;
    }

    public function handleField(FieldValue $fieldValue, Closure $next): FieldValue
    {
        $originalResolver = $fieldValue->getResolver();

        return $next(
            $fieldValue->setResolver(
                function ($root, array $args, GraphQLContext $context, ResolveInfo $resolveInfo) use ($originalResolver) {
                    $user = $context->user();
                    if (
                        // Unauthenticated users don't get to see anything
                        ! $user
                        // The user's role has to match have the required role
                        || !$user->is_admin
                    ) {
                        return null;
                    }

                    return $originalResolver($root, $args, $context, $resolveInfo);
                }
            )
        );
    }
}

So, is there a way to prevent "update" of specific fields with laravel lighthouse?

Answer 1

For now, you can use https://lighthouse-php.com/4.16/custom-directives/argument-directives.html#argtransformerdirective to transform that field to null before inserting the database or just throw error out to avoid changes on your specific field, it's like how the @trim behaves;

In lighthouse v5, it's class ArgTransformerDirective has renamed to ArgSanitizerDirective and method transform to sanitize

https://github.com/nuwave/lighthouse/blob/v5.0-alpha.3/src/Schema/Directives/TrimDirective.php

Extra:

I'm still figuring how @can works, cause i still need to drop the whole attribute instead of passing null to my database;

Update: @can only apply to input type instead of input type

Answer 2

The first idea I have in mind here is to create two different inputs and/or mutations. Eg for admins with access to the field:

updateUserAsAdmin(
    input: UpdateUserFullInput! @spread
): User @update 
        @middleware(checks: ["auth:api"]) 
        @can("users.update.full")

And UpdateUserFullInput contains the is_admin field.

I also came across this discussion a few times: https://github.com/nuwave/lighthouse/issues/325 Maybe you can also find some useful ideas here.

You may also want to look at the official docs: https://github.com/nuwave/lighthouse/blob/master/docs/master/security/authorization.md#custom-field-restrictions