Unlocking the Power of GraphQL Permissions

The Basics of Access Control and Permissions

Access control is the process of verifying whether a user is authorized to access an API. Permissions, on the other hand, are sets of rules that determine what actions a user can perform on a particular resource. Let’s consider a Twitter-like app as an example:

• A user can create a tweet
• The author can delete their own tweet
• Other users can like, retweet, or share the tweet
• Other users can report a tweet
• Both the author and other users can participate in the comment thread

As you can see, both the author and other users have different levels of permissions, despite having the same level of authorization.

Implementing Permissions in GraphQL

GraphQL offers various ways to implement permissions, including using directives, middleware resolvers, and the GraphQL Shield library. We’ll explore each of these techniques in-depth.

Depth of Permissions

GraphQL allows you to implement permissions at various levels, including:

• Query level permissions: controlling access to specific queries
• Object level permissions: controlling access to entire objects across all queries
• Field level permissions: controlling access to specific fields within an object

Building a Simple GraphQL API

Let’s create a simple GraphQL server example to demonstrate these concepts. We’ll start by creating a new npm project, adding the necessary packages, and setting up our GraphQL schema.

const express = require('express');
const graphqlHTTP = require('express-graphql');
const { GraphQLSchema } = require('graphql');

const app = express();

const schema = new GraphQLSchema({
  typeDefs: `
    type Query {
      tweets: [Tweet]
    }
    type Tweet {
      id: ID!
      text: String!
    }
  `,
  resolvers: {
    Query: {
      tweets: () => [
        { id: 1, text: 'Hello, world!' },
        { id: 2, text: 'This is a tweet.' },
      ],
    },
  },
});

app.use('/graphql', graphqlHTTP({
  schema,
  graphiql: true,
}));

app.listen(4000, () => {
  console.log('Server listening on port 4000');
});

Query Level Permissions

We’ll implement query level permissions using a naive solution, GraphQL directives, and middleware resolvers. Each approach has its pros and cons, and we’ll explore them in detail.

const authenticatedDirective = (context) => {
  if (!context.user) {
    throw new Error('You must be logged in to access this data.');
  }
};

const schema = new GraphQLSchema({
  typeDefs: `
    type Query {
      tweets: [Tweet] @authenticated
    }
    type Tweet {
      id: ID!
      text: String!
    }
  `,
  resolvers: {
    Query: {
      tweets: authenticatedDirective((parent, args, context) => {
        // Return data for authenticated users only
      }),
    },
  },
});

Object Level Permissions

We’ll apply object level permissions to our Tweet type, protecting the entire object across all queries.

const tweetPermissions = (context) => {
  if (!context.user) {
    return null;
  }
  return {
    // Allow authenticated users to see all tweets
    tweets: () => [...],
  };
};

const schema = new GraphQLSchema({
  typeDefs: `
    type Query {
      tweets: [Tweet]
    }
    type Tweet {
      id: ID!
      text: String!
    }
  `,
  resolvers: {
    Query: {
      tweets: (parent, args, context) => tweetPermissions(context),
    },
  },
});

Field Level Permissions

We’ll use the GraphQL Shield library to implement field level permissions, controlling access to specific fields within an object.

const shield = require('graphql-shield');

const schema = new GraphQLSchema({
  typeDefs: `
    type Query {
      tweets: [Tweet]
    }
    type Tweet {
      id: ID!
      text: String!
      privateField: String! @shield(mask: "Can only be seen by administrators")
    }
  `,
  resolvers: {
    Query: {
      tweets: () => [...],
    },
  },
});

const permissions = shield({
  Tweet: {
    privateField: (context) => {
      if (context.user && context.user.isAdmin) {
        return true;
      }
      return false;
    },
  },
});

Choosing the Right Approach

With so many options available, it’s essential to choose the right approach for your project. Consider the complexity of your permissions system, the scalability requirements, and the maintainability of your code.

Monitoring and Debugging GraphQL Requests

Monitoring and debugging tools can help you track failed and slow requests, inspect GraphQL queries, and identify performance bottlenecks.