Graphql Introspection in Chi with Dynamodb

GraphQL introspection in a Chi application that uses DynamoDB as a backend can expose metadata about queries, types, and resolvers that an attacker may leverage for reconnaissance. Introspection is a core GraphQL feature that returns the schema, including types, queries, mutations, and field arguments. When enabled in production, it allows an unauthenticated or low-privileged actor to map the API surface, including DynamoDB-backed fields, filter capabilities, and resolver logic. In Chi, which is a lightweight routing library for Clojure, GraphQL endpoints are typically implemented as HTTP handlers that forward requests to a GraphQL server (e.g., using libraries such as com.walmartlabs/lacinia or com.taoensso/timbre). If the GraphQL server exposes introspection and the endpoint is publicly reachable, an attacker can programmatically retrieve the full schema to identify DynamoDB-related types and operations.

Specifically, introspection queries can reveal field names that correspond to DynamoDB operations, such as attributes used for partition keys, sort keys, or secondary indexes. This information, combined with knowledge of DynamoDB access patterns, may help an attacker infer data structure and potential access control weaknesses. For example, an introspection query might return a type User with fields like userId (partition key) and email, alongside a query getUser that accepts an id argument. If authorization is not properly enforced at the resolver level, an attacker could attempt IDOR by iterating over plausible IDs. middleBrick detects such risks under the BOLA/IDOR and Property Authorization checks, flagging introspection-enabled endpoints that expose sensitive schema details without proper access controls.

Additionally, introspection can expose argument names and types that hint at DynamoDB query patterns, such as filter expressions or conditional writes. An attacker might use this information to craft malicious input that probes for validation or error handling differences. Because Chi handlers are typically small functions that compose middleware, misconfigured routes can inadvertently expose introspection alongside production traffic. middleBrick’s 12 security checks run in parallel against the unauthenticated attack surface, including Input Validation and SSRF, to identify whether introspection is reachable and whether downstream DynamoDB interactions are sufficiently guarded. By mapping findings to frameworks like OWASP API Top 10 and providing remediation guidance, middleBrick helps teams understand how GraphQL introspection in Chi with DynamoDB can widen the attack surface if not tightly managed.

To mitigate GraphQL introspection risks in Chi when using DynamoDB, disable introspection in production and enforce strict authorization in resolvers. Below are concrete code examples using Clojure and common GraphQL libraries compatible with Chi routes.

1. Disable introspection in production

Configure your GraphQL server to skip introspection when the environment is not development. Using com.walmartlabs/lacinia:

(ns myapp.graphql.schema
  (:require [com.walmartlabs.lacinia :as lacinia]
            [com.walmartlabs.lacinia.util :as util]
            [myapp.resolvers :as resolvers]))

(defn build-schema [include-introspection?]
  (let [raw-schema (util/attach-resolvers myapp.schema.core/schema resolvers)
        schema (if include-introspection?
                 raw-schema
                 ;; Remove introspection types and fields
                 (-> raw-schema
                     (update :types (fn [types]
                                      (remove #(or (= (:name %) "__Schema")
                                                   (= (:name %) "__Type")
                                                   (= (:name %) "__Field")
                                                   (= (:name %) "__InputValue")
                                                   (= (:name %) "__EnumValue")
                                                   (= (:name %) "__Directive"))
                                              types))))]
    (lacinia/schema-map schema)))

;; In your Chi handler, conditionally build schema based on env
(def graphql-schema
  (build-schema (not= :prod (:env (System/getenv)))))

2. Enforce authorization in resolvers referencing DynamoDB

Ensure each resolver that maps to a DynamoDB operation validates the request context. Example resolver for getUser with user-context checks:

(ns myapp.resolvers
  (:require [aws.sdk.dynamodb :as ddb]
            [com.fulcrologic.guardrails.core :refer [>defn =>]]))

(>defn resolve-get-user
  "Fetches a user from DynamoDB after verifying that the requester is allowed."
  [context user-id requester-id]
  {:post [(map? %)]}
  (if (= user-id requester-id)
    (ddb/get-item {:table-name "users"
                   :key {:userId (dynamodb-expression-type->val :string user-id)}})
    (throw (ex-info "Unauthorized" {:status 403}))))

;; Chi route wiring
(defn user-route [request]
  (let [user-id (get-in request [:params :path :id])
        requester-id (:user-id request)] ;; Assume authenticated via middleware
    (resolve-get-user {:request request} user-id requester-id)))

3. Validate and sanitize input for DynamoDB queries

Use input validation to prevent unexpected query patterns. For example, validate ID format before constructing DynamoDB keys:

(ns myapp.validation
  (:require [malli.core :as m]
            [malli.util :as mu]))

(def user-id-schema
  [:and :string
   #(re-matches #"^[a-zA-Z0-9-]+$" %)
   (complement empty?)])

(defn validate-user-id [id]
  (if (m/validate user-id-schema id)
    id
    (throw (ex-info "Invalid user ID" {:status 400}))))

Combine these practices with middleware in Chi to ensure introspection is not exposed publicly, that DynamoDB access is guarded by context-aware checks, and that inputs are strictly validated before interacting with the database. middleBrick’s CLI can scan your Chi endpoints to verify that these controls are effective and that no unintended schema details are exposed.