What is GraphQL? #
GraphQL is a query language for APIs and a runtime for executing those queries by using a type system you define for your data. It allows clients to request exactly the data they need, and nothing more, making it more efficient than traditional REST APIs. With GraphQL, developers can ask for specific fields in a single request, reducing the number of API calls needed and improving performance.
What is Rate limiting? #
Rate limiting controls the number of requests a user can make to a system within a set time period. It helps prevent overloading the system, protects against abuse, and ensures fair use for all users. For example, a website might limit a user to 100 requests per minute to stop excessive use and maintain performance.
Rate limiting in GraphQL #
In a GraphQL API, rate limiting typically works at the query or mutation level by restricting how often a user can request data or perform certain actions in a specified time window. For instance, you could limit how many times a user can run a specific query (like fetching a large dataset) or a mutation (like updating data) within a period.
Role of Aliases #
In GraphQL, aliases are a feature that allows clients to rename the fields they request in a query. This is useful when a client wants to request the same field multiple times with different arguments, but each field needs to have a unique name in the response.
Without aliases, if you try to request the same field multiple times in a query, it will cause a conflict since the field names must be unique within a query. Aliases solve this problem by allowing to rename the fields in the query.
Bypassing Rate Limits Using Aliases #
Imagine a GraphQL API has a rate limit of 5 requests per IP within 60 seconds. Without the use of aliases, a client can only make 5 queries in that time frame. However, by using aliases, the same query can be repeated multiple times with different names, thereby exceeding the rate limit.
Normal Request #
A typical GraphQL query might look like this:
{
getPosts {
id
title
content
}
}
This query requests a list of posts, and it would count as one request.
Bypassing Rate Limit Using Aliases #
An attacker can exploit aliases to repeat the same request with different names, like this:
{
getPost1: getPosts {
id
title
content
}
getPost2: getPosts {
id
title
content
}
getPost3: getPosts {
id
title
content
}
getPost4: getPosts {
id
title
content
}
getPost5: getPosts {
id
title
content
}
}
In this example, the same getPosts query is executed five times, but each instance is aliased (getPosts1, getPosts2, etc.). While the server sees this as a single query with multiple parts, an attacker can send multiple aliases and bypass the rate limiting, effectively making five requests instead of one.
Vulnerable Code #
Here’s an example of a vulnerable code that could allow alias abuse to bypass rate limits:
const express = require('express');
const { graphqlHTTP } = require('express-graphql');
const { RateLimiterMemory } = require('rate-limiter-flexible');
const { buildSchema } = require('graphql');
// Create a simple GraphQL schema
const schema = buildSchema(`
type Query {
getPosts: [Post]
}
type Post {
id: ID!
title: String!
content: String!
}
`);
// Define posts for demonstration
const posts = [
{ id: '1', title: 'GraphQL Basics', content: 'Learn the basics of GraphQL' },
{ id: '2', title: 'Advanced GraphQL', content: 'Deep dive into GraphQL features' },
];
// Rate limiter allowing 5 requests per IP in 60 seconds
const rateLimiter = new RateLimiterMemory({
points: 5,
duration: 60,
});
const rootValue = {
// Resolver for 'getPosts'
getPosts: async (args, context, info) => {
try {
// Rate limit check for 'getPosts'
await rateLimiter.consume(context.ip); // checks IP for rate limit
return posts;
} catch (rejRes) {
throw new Error('Too many requests, please try again later');
}
}
};
--------- rest of the code ----------
In this code, the rate limiter is set up to limit the number of requests from an IP address. However, it doesn’t account for aliases in the GraphQL queries. An attacker could exploit this by sending a single query with multiple aliases. Since the rate limit is applied only to the IP address and not the specific query structure or the number of times a field is called, the system will still allow excessive requests if aliases are used.
Fixed Code with Query Structure Tracking #
const express = require('express');
const { graphqlHTTP } = require('express-graphql');
const { RateLimiterMemory } = require('rate-limiter-flexible');
const { buildSchema } = require('graphql');
// Create a simple GraphQL schema
const schema = buildSchema(`
type Query {
getPosts: [Post]
}
type Post {
id: ID!
title: String!
content: String!
}
`);
// Define posts for demonstration
const posts = [
{ id: '1', title: 'GraphQL Basics', content: 'Learn the basics of GraphQL' },
{ id: '2', title: 'Advanced GraphQL', content: 'Deep dive into GraphQL features' },
];
// Rate limiter allowing 5 requests per IP in 60 seconds
const rateLimiter = new RateLimiterMemory({
points: 5,
duration: 60,
});
// Track the number of times each field is queried, including aliases
const fieldLimiter = new RateLimiterMemory({
points: 3, // Limit to 3 times per field (per query)
duration: 60, // per 60 seconds
});
const rootValue = {
// Resolver for 'getPosts'
getPosts: async (args, context, info) => {
try {
// Apply global rate limit based on IP address
await rateLimiter.consume(context.ip);
// Apply per-field rate limit to avoid alias abuse
const fieldName = info.fieldName;
await fieldLimiter.consume(context.ip + fieldName); // Track per field, including aliases
return posts;
} catch (rejRes) {
// Handle the rejection (rate limit exceeded)
if (rejRes instanceof Error) {
throw new Error('Too many requests, please try again later');
}
throw new Error('Request rate limit exceeded');
}
}
};
------- rest of the code ----------
The key changes in the code focus on enhancing the rate-limiting logic to prevent alias abuse. First, global rate limiting based on IP remains unchanged, ensuring that the server limits requests from a specific IP address. Additionally, a new per-field rate limiter is introduced, which tracks how many times a particular field (like getPosts) appears in the query, including any aliases. This is achieved by concatenating the IP address with the field name, ensuring that each field usage, even if aliased, is treated as a separate request. Finally, by tracking field names and aliases, the server enforces rate limits on a per-field basis, preventing attackers from bypassing the limits by using multiple aliases in a single query.
Impact of No Rate Limit in GraphQL #
Bypassing rate limits using aliases can lead to significant security vulnerabilities. Attackers can send multiple requests disguised as a single query by using aliases, which overloads the server without hitting the set rate limits. This can lead to a Denial of Service (DoS) attack, where the system becomes slow or unresponsive due to excessive requests being processed, potentially causing downtime or service degradation.
Mitigating the Issue #
Developers can implement several strategies to prevent alias abuse and maintain effective rate limits. These measures help protect the system from overload and ensure fair usage of resources.
Track Per Alias #
Tracking requests based on the query structure or field aliases is another approach to mitigate alias abuse. Rather than just limiting requests by IP address, this method tracks how many times a specific field or alias is requested. By doing so, even if the same query is repeated with different aliases, the server can detect the duplication and block requests that exceed the allowed threshold.
Limit Aliases #
Some GraphQL implementations allow developers to set restrictions on the use of aliases. By limiting the number of aliases that can appear in a query, you can reduce the risk of alias abuse. For example, you might configure the server to allow only a specific number of aliases per query, thus preventing clients from overwhelming the system with multiple requests disguised under different names. This restriction helps maintain fair usage of the API and keeps rate limits effective.
General Request Throttling #
Implementing general request throttling across all queries is another way to control the abuse of aliases. Instead of only applying rate limits based on the IP address, the server can apply throttling to the entire query. This ensures that regardless of whether aliases are used, the request is still subject to a maximum number of allowed operations. By throttling based on the structure of the query itself, the server can prevent users from submitting complex queries that bypass traditional rate limits and reduce the risk of overloading the system.
Final Thoughts #
Bypassing rate limits using aliases poses a significant security risk by enabling attackers to overload the system without triggering traditional safeguards. This abuse can lead to resource exhaustion, slow performance, or even service outages. It is crucial for developers to implement robust rate-limiting strategies that account for aliases and query structure. By tracking query fields and limiting aliases, we can ensure fair usage and protect the system from malicious exploits.