The GraphQL query language is an excellent tool for increasing the ease of data sharing. The premise is that you request the fields you need in a single bundled request, avoiding multiple network calls. Due to its usability, GraphQL is a growing area of development. Yet, as with any new technology, it comes with caveats.
REST APIs function as a request-and-response paradigm in which the receiver accesses one resource at a time. On the other hand, GraphQL exposes many fields at once, requiring additional rate-limiting and time-outs to avoid nefarious queries. Additionally, the ability to traverse the entire schema could be abused by attackers to expose intricate data linkages. There are also some usability features with GraphQL that could be abused if misconfigured.
GraphQL is a friendly alternative to REST. But how do we handle the security implications of GraphQL? I recently chatted with Mike Benjamin, vice president of security research, Fastly, to dive deeper into the security repercussions of adopting GraphQL. Below, we’ll consider the unique insecurities associated with GraphQL and suggest specific steps to limit the impact of these risks.
Four GraphQL Security Vulnerabilities
1. Introspection
GraphQL provides built-in documentation that tells developers what the fields are, providing a schema of everything you can query. You’ve essentially given the entire dataset schema to a developer, meaning they can perform introspection to capture attack surface information. Hackers will most commonly look for injection or mutation capabilities that they can exploit, explained Benjamin. Or, they might seek to leverage the interlinkages between data to map a way through to classified information.
To mitigate this problem, Benjamin cautioned against over-exposing all documentation publicly. Instead, he suggested using a restrictive security model for external viewers. “Provide appropriate user documentation in a different method,” he says. This may end up looking more like the standard REST API view of documentation.
2. Field Suggestions
Another usability benefit in GraphQL could also be a potential security concern—field suggestions. Field suggestions occur when you don’t enter the correct field name or enter a partial input and the system returns a hint. You might type in 0 or user, and the system makes a suggestion to fill out the rest of the field.
This user interaction improves the developer experience, but, unfortunately, it could be abused by a hacker, said Benjamin. Thus, he recommended disabling hints after initial development. Or, if you decide to keep it in, he recommended placing a limit on its use. For example, if you try this more than five times in a second, the system could flag it as a bot.
Right now, this attack vector is pretty limited, but Benjamin anticipated that, over time, hackers could automate this introspection with mass scanners to divulge more information.
3. Denial-of-Service-Oriented Attacks
Without the proper guardrails, all web APIs are prone to denial-of-service (DoS) attacks. Such an attack may pummel a service with a million queries per second to shut it off completely. In the case of GraphQL, these queries can dive very deep in a nested data relationship. A social network, for example, might expose friends of users, friends of users’ friends and so on.
Or, hackers might utilize GraphQL’s bulk query ability to perform reconnaissance, brute-forcing the enumeration of data to query hundreds of user IDs to see which are valid. If you’re allowing unlimited data retrieval bundled within a single request, you could be inviting hundreds of bundled queries that could expose large swaths of the underlying database in one fell swoop.
To counter these actions, Benjamin recommended limiting the testing depth. This could involve placing limits on how long a query can run, which would cause a time-out for requests that require suspiciously high degrees of processing. Another option is to limit how deep the bundling can get, said Benjamin. For example, perhaps the system restricts going three levels deep into a graph database, as that could expose millions of interconnected endpoints.
4. Lack of Object-Level Authorization
Another vulnerability that GraphQL endpoints may be prone to is a lack of object-level authorization, which hackers could leverage to get at a datapoint through its edges, said Benjamin. Since the idea is that you can access any data from one all-encompassing endpoint, authorization rules are often too abstracted away from the actual data. Queries may be able to access nested data or query relationships between data, too, which may unintentionally divulge information.
Benjamin recommended placing authorization closer to your objects or data to rectify this issue. Use authorization-level controls that align permissions structure and roles with users. “Everyone needs a common authorization model,” said Benjamin.
Future Evolution: GraphQL Security Matures
As I’ve written before, the greatest strength of GraphQL is also its greatest weakness. Using GraphQL with default settings is a security trade-off in favor of usability. But according to Benjamin, we’re seeing more GraphQL servers disabling some introspection features, which he sees as a very positive move and a sign of maturity of the base configuration.
GraphQL might suffer from similar threats that all APIs are vulnerable to, such as XSS, injection, DDoS attacks and broken authorization. However, Benjamin stressed that the added complexity of GraphQL makes it a unique case. “The most important thing for folks to consider is that GraphQL is more complicated than a REST endpoint—much more complicated,” said Benjamin. “GraphQL is unique in that it has linkages of data which contributes to complexity. It takes a little more time to think about how that’s confirmed, how it’s presented and how it would be attacked.”
In other words, with great power comes great responsibility.
Although exploits in public GraphQL APIs are still rare, we should stay vigilant. Benjamin encouraged developers to continue reading about, understanding and thinking about these attack vectors when designing their interfaces, as these risks will become more prominent as GraphQL usage grows and hackers become more familiar with these specific frailties.
