Graphql Introspection in Chi with Firestore

GraphQL introspection allows clients to query the schema for types, queries, and mutations. When running in a Chi web application that exposes a GraphQL endpoint backed by Firestore, enabling introspection in production can expose detailed schema information, including field names, types, and resolver behavior. This information can help an attacker map data models and identify sensitive paths.

Chi is a lightweight routing library for Clojure that typically requires explicit route definitions. If a GraphQL route is defined without restricting introspection, the endpoint will respond to introspection queries regardless of authentication. Firestore data structures often include user IDs, timestamps, and references that become visible through introspection, increasing the risk of information disclosure.

For example, a Chi route that mounts a GraphQL handler might look like this:

(def app
  (routes
    (GET "/graphql" [] graphql-handler)
    (route/not-found "Not Found")))

If graphql-handler is configured to allow introspection, an unauthenticated attacker can send an introspection query and learn about Firestore document structures, such as collections named users or fields like email and created_at. This becomes especially risky when combined with overly permissive Firestore security rules, as the exposed schema may hint at accessible data.

Introspection can also reveal whether the GraphQL server batches Firestore reads, which may indicate patterns like getAll or where queries. These patterns can guide injection or enumeration attempts. Unlike REST, where endpoints are explicit, GraphQL’s single endpoint consolidates metadata discovery into one location, making introspection a high-impact concern in Chi applications using Firestore.

Organizations using the middleBrick CLI can scan this setup by running middlebrick scan <url> to detect exposed introspection. The report will flag the GraphQL endpoint and highlight risks tied to schema exposure, supporting compliance checks mapped to OWASP API Top 10 and SOC2 controls.

To mitigate GraphQL introspection risks in Chi while using Firestore, disable introspection in production environments and enforce strict schema exposure. This can be done at the GraphQL server configuration level, independent of Chi routing.

One common approach is to conditionally enable introspection based on the request environment. Below is an example of how to wrap the GraphQL handler in Chi so that introspection is only available locally:

(defn allow-introspection? [req]
  (= "dev" (System/getenv "ENV")))

(def app
  (routes
    (GET "/graphql" []
         (if (allow-introspection? request)
           graphql-handler
           (response/bad-request "Introspection disabled")))
    (route/not-found "Not Found")))

Additionally, structure Firestore security rules to avoid leaking data through generic queries. For instance, instead of allowing broad read access, scope reads to the authenticated user’s data:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
  }
}

When using the middleBrick Pro plan, continuous monitoring can help detect when introspection remains enabled in staging or production. The GitHub Action can fail a build if the scan identifies an active introspection endpoint, preventing insecure configurations from reaching deployment.

For teams using the MCP Server, scanning APIs directly from the IDE provides early feedback during development. This helps maintain secure schema practices without relying solely on scheduled scans via the CLI tool.

Finally, prefer using strongly typed GraphQL schemas and avoid dynamic field exposure. Combine this with environment-aware middleware in Chi to ensure that introspection is never unintentionally available to external consumers.