GraphQL Penetration Testing Methodology

GraphQL pentesting focuses on finding security issues in a GraphQL API. Security teams examine queries, mutations, and the structure of the API to uncover risks like unauthorized access, data leaks, and misconfigurations. This helps ensure that security teams well-protect the API against potential cyberattacks.

This blog discusses GraphQL Pentesting, its significance, vulnerabilities it uncovers, and pentest methodology, and provides related tools and resources.

What is GraphQL Pentesting?

GraphQL pentesting assesses the security of GraphQL APIs to identify vulnerabilities and potential attack vectors. It involves interacting with GraphQL endpoints, sending queries and mutations to manipulate data, and uncover security flaws.

The process analyzes schema definitions, query structures, and input validation mechanisms to find weaknesses that could lead to unauthorized access, data leaks, or other security breaches. By probing for injection, authentication, authorization, and other common vulnerabilities, security teams aim to ensure the robustness of GraphQL APIs against malicious exploitation.

Why It’s Important?

GraphQL APIs, like any other APIs, are potential targets for attacks, making it critical to conduct thorough testing. Security engineers must create a comprehensive set of test cases to uncover vulnerabilities that attackers could exploit. Proper testing allows for the identification of issues before they lead to potential breaches.

By testing GraphQL APIs, security engineers can detect various security vulnerabilities, such as SQL Injection, Cross-Site Scripting (XSS), path traversal, and command injection. These vulnerabilities, if left unaddressed, can lead to severe consequences like data theft, unauthorized data access, and compromise of sensitive information.

Identifying and remediating these weaknesses not only strengthens the API's defenses but also helps maintain the confidentiality, integrity, and availability of data. Regular and thorough testing plays a pivotal role in preventing attacks and ensuring robust security.

Key GraphQL Vulnerabilities

GraphQL APIs face several key vulnerabilities that security teams must address to protect against potential attacks and data breaches. These include:

Nested Query Depth Abuse

Security teams identify GraphQL endpoints vulnerable to nested query depth abuse, a type of attack where attackers send deeply nested queries to the server to overload its resources.

This form of abuse takes advantage of the flexibility of GraphQL's query structure to request data in an excessively nested manner, leading to server performance issues or denial of service.

For example, consider the following code:

POST /graphql HTTP/1.1 
Host: example.com 
Content-Type: application/json 
{ 
    "query": "{ user { posts { comments { author { posts { comments { author { 
... } } } } } } } }" 
  
}

In this request, the attacker sends a deeply nested query to the GraphQL endpoint of the server example.com. The query starts by requesting a user and then goes multiple levels deep, asking for posts, comments, and further authors and their posts and comments in a recursive pattern. Each level of nesting requires additional processing power from the server to fetch and return the data, which can quickly overwhelm server resources.

The intention behind this attack is to force the server to handle extremely complex and resource-intensive queries. Such queries can result in slow responses, degraded server performance, or even cause the server to crash, leading to a denial of service.

Input Validation Bypass

Security teams look for weak spots in GraphQL systems that don't properly check user inputs. These weaknesses let attackers get around security measures and insert harmful code into GraphQL queries. This can lead to unauthorized access or data breaches. This type of attack manipulates how the GraphQL API handles inputs, enabling an attacker to craft queries that execute unintended actions or access data without proper authorization.

Consider the following example:

POST /graphql HTTP/1.1 
Host: example.com 
Content-Type: application/json 
{ 
  "query": "query { user(id: \\\\"1 OR 1=1\\\\") { name } }" 
}

In this request, the attacker injects a malicious payload into the id parameter of the query. Instead of simply passing a user ID, the attacker includes the string "1 OR 1=1" to manipulate the query. The condition 1 OR 1=1 is always true, which can trick the server into returning unintended data, potentially exposing information from the database that the attacker is not authorized to access.

This kind of attack can lead to input validation bypass and possible SQL injection, allowing attackers to extract or manipulate data.

Server-Side Request Forgery (SSRF)

Security teams identify SSRF vulnerabilities in GraphQL queries that allow attackers to make unauthorized requests from the server. In these scenarios, the attacker manipulates the GraphQL query to force the server to initiate requests to external or internal resources, potentially leading to data leaks or access to restricted services.

Consider the example below:

POST /graphql HTTP/1.1 
Host: example.com 
Content-Type: application/json 
{ 
  "query": "query { userProfile(imageUrl: \\"<http://attacker.com/malicious-image.png\\>") { id name } }"
}

In this query, the attacker includes a malicious external URL (http://attacker.com/malicious-image.png) as the imageUrl parameter. If the server processes this input without validation, it may attempt to fetch the image from the specified URL.

This behavior can be exploited to perform server-side requests to unauthorized external servers, internal network resources, or sensitive internal services that are not meant to be exposed publicly.

Over-Permissive Permissions

Security teams identify over-permissive permissions in GraphQL endpoints, where excessive access rights allow users to perform unauthorized actions. Such permissions often grant all users, including those with limited roles, the ability to interact with sensitive resources or execute privileged operations, potentially leading to security breaches.

Consider the following example:

POST /graphql HTTP/1.1 
Host: example.com 
Content-Type: application/json 
{ 
  "query": "mutation { updateUserRole(id: \\"123\\", role: \\"admin\\") { success message } }" 
}

In this query, an authenticated user attempts to update the role of another user by setting the role to "admin". If the GraphQL endpoint has over-permissive permissions, any authenticated user could execute this mutation, not just administrators.

This misconfiguration allows unauthorized users to escalate their privileges, granting themselves administrative access to the application or performing actions beyond their intended permissions.

Insecure Direct Object References (IDOR)

Security teams identify vulnerabilities in object references within GraphQL endpoints, where attackers can access or manipulate sensitive data by tampering with query parameters. These flaws occur when object references such as user IDs are exposed in a way that allows attackers to modify them and access data or perform actions without authorization.

Consider this example:

POST /graphql HTTP/1.1
Host: example.com 
Content-Type: application/json 
{ 
  "query": "query { user(id: \\"123456\\") { email } }" 
}

In this query, a user requests their account details by specifying their id parameter (123456). If the GraphQL server does not properly verify that the requester owns this ID, an attacker can modify the id value to target other user IDs.

For instance, changing the ID to another value could grant access to the private information of another user, such as their email or other sensitive data, leading to data leaks and unauthorized actions. IDOR vulnerabilities often stem from insufficient access control checks, allowing users to tamper with object references freely.

GraphQL Pentest Methodology

GraphQL pentesting follows a structured methodology to systematically identify vulnerabilities and assess the security of GraphQL APIs. This approach encompasses several key steps:

Reconnaissance

Reconnaissance involves gathering as much information as possible about the GraphQL API, such as endpoint URLs, schema documentation, and available queries and mutations.

This process may include manual inspection of web applications, analyzing network traffic, or using tools like Burp Suite or OWASP ZAP to intercept and study HTTP requests to the API. If the GraphQL API provides a playground or GraphiQL interface, it serves as a helpful tool for exploring queries, mutations, and the overall schema documentation in a user-friendly manner.

Schema Analysis

Schema analysis begins by using GraphQL introspection queries to dynamically explore the API's schema. Introspection allows for querying metadata about the schema, including its types, fields, and directives.

Once the security teams obtain the introspection query response, tools like GraphQL Voyager can help visualize the schema comprehensively, displaying relationships between data types, objects, and fields exposed by the API. Analyzing the schema in this way is critical for understanding the structure and relationships of data, revealing potential attack vectors and areas to test for security issues.

Query Fuzzing

Query fuzzing is the process of crafting and sending various queries and mutations to a GraphQL endpoint to test input validation, identify vulnerabilities, and analyze how the API behaves under different conditions. The goal is to detect issues such as injection attacks, excessive data exposure, or other potential flaws in the API's security.

Identify Input Parameters

The first step in query fuzzing is identifying input parameters within the GraphQL schema. This includes finding all arguments, variables, and fields used in queries and mutations. These elements become the primary targets for fuzzing to discover vulnerabilities and test the robustness of input handling.

Craft Fuzzing Payloads

The next step is crafting a variety of payloads to test for input validation issues and security vulnerabilities. Some of the techniques include:

• Special Character Injections: Generate payloads containing special characters like single quotes ('), double quotes ("), backticks (```), and symbols like !, @, #, $, and %. Securtiy teams use these to test for injection vulnerabilities within the GraphQL API.

• SQL Injection Payloads: Formulate payloads designed to inject SQL code into query arguments. The aim is to exploit potential vulnerabilities in how the API handles database queries. For example:

POST /graphql HTTP/1.1 
Host: example.com 
Content-Type: application/json 
{ 
  "query": "{ user(id: \\"1 OR 1=1\\") { id name email } }" 
}

• In this example, the payload 1 OR 1=1 is injected into the id parameter to test for possible SQL injection vulnerabilities.

• XSS Payloads: Create payloads to inject JavaScript code into input fields. These payloads help identify cross-site scripting (XSS) vulnerabilities by observing how the server responds to the injected scripts.

Send Fuzzing Requests

Send the crafted fuzzing payloads as queries or mutations to the GraphQL endpoint using tools like cURL, Postman, or custom scripts. Experiment with different combinations of payloads and input parameters to thoroughly explore the endpoint and potential attack vectors.

Analyze Responses

Analyze the responses returned by the GraphQL endpoint for any anomalies, errors, or unexpected behavior. Signs of successful exploitation may include error messages revealing sensitive information, unusual outputs, or unintended data access. Monitoring these responses helps identify and confirm the presence of vulnerabilities within the API.

Authentication Testing

Authentication testing focuses on examining the mechanisms used by the GraphQL API, such as token-based authentication or session management, to ensure they enforce access controls and protect against unauthorized access. Testers first identify the authentication mechanisms implemented by the GraphQL API. Common methods include JWT (JSON Web Tokens), OAuth 2.0, Basic Authentication, API keys, and Session cookies. Understanding the type of authentication in use allows testers to target specific vulnerabilities and weaknesses effectively, ensuring robust security measures are in place.

Understand Authentication Requirements

Review the GraphQL API documentation or specifications to understand the authentication criteria required for accessing different queries, mutations, or resources. Note which operations necessitate authentication and which are accessible publicly, as these details help identify potential entry points for unauthorized access.

Verify Authentication Tokens

When JWT or OAuth tokens are used, verify their integrity, expiration, and signature. Use tools like jwt.io to decode tokens and validate their structure. Checking the token properties helps uncover issues such as weak signatures, missing expiry times, or improper token validation.

Probe Weak Authentication Methods

Probe for endpoints utilizing Basic Authentication and test the security of credentials transmitted in plaintext. Attempt to intercept these credentials to check for vulnerabilities. Additionally, test for susceptibility to brute force attacks by automating login attempts with commonly used credentials or password dictionaries to determine if the authentication can be easily bypassed.

Exploit Custom Authentication Implementations

Investigate endpoints that use custom authentication mechanisms, such as token generation or password storage. Look for weaknesses like insufficient randomness in token generation, improper password hashing, or lack of protection against injection attacks. Custom implementations often have unique vulnerabilities that can be exploited to bypass authentication controls.

Test Login Security Measures

Assess the effectiveness of login security measures like Max Retry limits. Exceed the allowed number of login attempts to determine if the application enforces lockouts or introduces delays to prevent brute force attacks. Also, explore potential flaws in the jail feature by attempting to bypass or manipulate account lockout mechanisms. Identifying these weaknesses can help uncover potential vectors for unauthorized access.

Test Batching Attack

A batching attack in GraphQL exploits the ability to send multiple queries or mutations within a single request to the GraphQL server. Attackers leverage this batching feature to conduct malicious activities or gather sensitive information more efficiently. Tools like BatchQL are commonly used for testing and exploiting such vulnerabilities.

Common Types of Batching Attacks in GraphQL

Overloading the Server

Attackers craft batched requests containing numerous complex queries or mutations to overload the server's resources. By sending a single request packed with computationally intensive operations, they can force the server to process multiple heavy tasks simultaneously. This may lead to attackers causing a Denial-of-Service (DoS) attack or degrading performance for legitimate users, disrupting normal application usage.

Data Extraction

By combining multiple queries in a single batched request, attackers can efficiently extract sensitive data from the GraphQL server. Instead of making individual requests for different pieces of information, a batched request can retrieve multiple data points at once. This can expose user data, system configurations, or any other sensitive information that attackers can access through the GraphQL API, potentially leading to data breaches.

Rate Limit Bypass

Attackers may abuse batching to bypass rate limiting or throttling mechanisms implemented by the server. Since a batch allows multiple operations in a single request, an attacker can send a large volume of combined requests to circumvent rate limits. This could result in exceeding the allowed request rate or evading access controls, allowing the attacker to perform malicious actions without detection or blocking by standard security measures.

Reporting

Document all findings from the testing process, detailing each identified vulnerability, its associated severity, and clear recommendations for remediation.

The report should be comprehensive yet accessible, allowing stakeholders, developers, and security engineers to gain actionable insights to improve the security of the GraphQL API. Proper categorization of vulnerabilities, supported by evidence and impact analysis, helps prioritize remediation efforts and guides secure development practices.

Tools for GraphQL Pentesting

Explore these powerful tools designed to enhance GraphQL pentesting and secure the APIs effectively.

Akto

Akto provides a comprehensive way to secure GraphQL APIs by identifying and mitigating vulnerabilities in authentication, authorization, and data handling. Security teams can easily integrate their GraphQL APIs within Akto to perform automated scans, checking for issues like Broken Authentication, IDOR, and misconfigured CORS policies.

Akto analyzes GraphQL queries and mutations to enforce access controls, ensuring that only authenticated and authorized users interact with the API. Real-time insights and actionable reports help security teams quickly identify and address security flaws before they become exploitable. With continuous testing and monitoring features, Akto helps maintain security.

GraphiQL

GraphiQL is an in-browser tool that allows writing, validating, and testing GraphQL queries seamlessly. It provides an easy interface to interact with the GraphQL schema, helping to explore different queries and mutations. The tool enhances development workflows by providing real-time feedback on queries. It is essential for debugging and testing GraphQL APIs effectively.

GraphQL Playground

GraphQL Playground is a robust GraphQL IDE designed to improve the development experience. It offers features like query autocompletion, schema exploration, and interactive documentation. The tool makes it easier to test queries and understand the API structure. It serves as a comprehensive platform for exploring and debugging GraphQL queries.

Apollo Client Developer Tools

Apollo Client Developer Tools is a browser extension designed for developers and security engineers working with Apollo Client. It provides features for inspecting queries, mutations, and cache data, enabling efficient debugging. The extension integrates seamlessly into development workflows, offering real-time monitoring of GraphQL operations. It's highly useful for understanding how data flows within an Apollo Client setup.

GraphQL Voyager

GraphQL Voyager visualizes any GraphQL API as an interactive graph, providing an intuitive overview of the schema. This graphical representation helps identify relationships between data types, fields, and operations. It enables developers and security engineers to explore complex schemas more easily. The tool is valuable for understanding the structure and design of GraphQL APIs.

Burp Suite

Burp Suite is a leading cybersecurity platform offering tools for web application security testing, including GraphQL. It allows security professionals to intercept, modify, and analyze GraphQL requests and responses. The suite aids in finding vulnerabilities and performing automated or manual security assessments. It's widely used for pentesting and securing APIs.

Final Thoughts

GraphQL is a powerful tool that offers flexibility and efficiency in handling data. However, like any technology, it can be susceptible to various security risks. Therefore, it's crucial to implement robust security measures and conduct regular pentesting. This way, security teams can uncover potential vulnerabilities and address them before attackers exploit them.

To achieve comprehensive API security and improve development practices, explore the benefits of Akto. With Akto's solutions, organizations can proactively protect their APIs from vulnerabilities. Book your demo today and take the first step toward more secure and efficient API management.