Detecting GraphQL Injection: Tools and Techniques for Security Testers

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Introduction

GraphQL has gained popularity as a flexible API query language, but its powerful features can also introduce security risks if not implemented correctly. One of the critical vulnerabilities in GraphQL APIs is GraphQL Injection, which can lead to data leaks, unauthorized access, or even complete system compromise.

This post explores tools and techniques used by security testers to detect GraphQL Injection vulnerabilities and secure APIs effectively.

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Understanding GraphQL Injection

GraphQL Injection occurs when attackers manipulate queries, mutations, or variables to execute unauthorized operations or retrieve sensitive data. Unlike traditional SQL injection, GraphQL Injection targets the query language syntax and server-side resolvers.

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Tools for Detecting GraphQL Injection

1. Burp Suite with Plugins

Burp Suite is a staple for web application security testing, and its extensibility makes it effective for testing GraphQL APIs.

Plugins:

InQL Scanner:

Automates introspection and detects vulnerable query patterns.

Generates queries for fuzzing and exploitation.

GraphQL Raider:

Helps create malicious queries to test GraphQL endpoints.

Example: Modify variables in intercepted GraphQL requests to identify injection points.

2. InQL Scanner (Standalone)

A Python-based tool that enumerates schema, queries, and mutations using introspection.

Detects fields that may lead to over-fetching or injection vulnerabilities.

python3 inql.py -t http://example.com/graphql -o output.json

3. GraphQLmap

Inspired by SQLmap, this Python tool automates injection testing on GraphQL APIs.

Supports payload injection in queries and variables to detect flaws.

python3 graphqlmap.py -u http://example.com/graphql --inject

4. Altair GraphQL Client

A developer-friendly GUI tool to craft and send GraphQL queries.

Useful for manual injection testing by tweaking queries and observing responses.

5. Postman

While primarily an API testing tool, Postman allows for crafting and sending custom GraphQL queries.

Enables detailed control over request headers, query structure, and variables.

6. GraphQL Voyager

Visualizes the GraphQL schema, helping identify sensitive fields and endpoints.

Facilitates the identification of potential attack surfaces.

7. WAFW00F

Helps detect and bypass Web Application Firewalls (WAFs) that might block malicious GraphQL queries.

wafw00f http://example.com/graphql

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Techniques for Detecting GraphQL Injection

1. Schema Introspection Abuse:

If introspection is enabled, query the schema to map the entire API and identify sensitive operations.

{
  __schema {
    types {
      name
      fields {
        name
      }
    }
  }
}

2. Over-fetching and Under-fetching:

Test for excessive data exposure by crafting queries that request more or fewer fields than necessary.

3. Variable and Input Fuzzing:

Use tools like Burp Intruder or ffuf to inject malicious payloads into variables and inputs.

4. Error Message Analysis:

Analyze server responses to malformed queries for hints about the underlying logic or database.

5. Injection Testing:

Inject payloads like the following to detect vulnerabilities:

query {
  user(id: "1 OR 1=1") {
    name
    email
  }
}

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Best Practices for Secure GraphQL APIs

Disable Introspection: Prevent attackers from mapping the API schema in production.

Implement Validation: Validate all inputs, including queries, mutations, and variables.

Limit Query Depth: Restrict the depth of nested queries to prevent abuse.

Rate Limiting and Authentication: Enforce strict access controls and monitor query usage patterns.

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Wrapping Up

GraphQL Injection is a serious security concern that requires careful attention during API development and testing. By leveraging tools like Burp Suite, InQL, and GraphQLmap, security testers can effectively identify and mitigate these vulnerabilities.

By responsibly applying these techniques, testers and developers can work together to build more secure APIs and protect sensitive data from exploitation.

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