Missing Authentication in Chi with Dynamodb

Missing authentication in a Chi application that interacts with DynamoDB exposes data and operations to any network participant. Chi is a lightweight routing library for Clojure, often used to build HTTP APIs that query or mutate DynamoDB tables directly or via a service layer. When endpoints do not enforce identity verification, an unauthenticated caller can invoke routes that execute DynamoDB operations such as GetItem, Scan, PutItem, or UpdateItem.

Because DynamoDB is a managed backend, the risk is not primarily about bypassing a local database connection, but about allowing unauthorized API calls that map directly to sensitive table operations. For example, a route like /users/{id} that performs a GetItem using the ID from the request without confirming the caller is allowed to view that user makes the table readable by anyone who can reach the endpoint. In a black-box scan, this maps to the Authentication check in middleBrick, which flags endpoints that execute DynamoDB calls without validating credentials or tokens.

Additionally, missing authentication combined with宽松的 IAM policies on DynamoDB can amplify impact. If the DynamoDB role attached to the service allows broad actions (e.g., dynamodb:Scan or dynamodb:GetItem on * resources), an unauthenticated endpoint can lead to mass data exposure. Attack patterns such as IDOR become trivial when authentication is absent, because there is no identity context to enforce row-level boundaries. middleBrick tests this by checking whether authenticated context is required and whether the unauthenticated attack surface includes DynamoDB operations that should be restricted.

Real-world implications include exposure of PII, session tokens, or configuration data stored in DynamoDB. For instance, a Scan operation without authentication could return all user records, including emails and phone numbers. This aligns with OWASP API Top 10 API1:2023 broken object level authorization, where missing or weak authentication enables unauthorized data access. middleBrick’s Authentication check highlights such misconfigurations and maps findings to compliance frameworks including PCI-DSS and SOC2, emphasizing the need for explicit authentication on every DynamoDB-interacting route.

To detect this during a scan, middleBrick runs active probes against the Chi endpoints, attempting to invoke DynamoDB-related routes without credentials and inspecting responses for unauthorized success or data leakage. The tool does not fix the configuration but provides remediation guidance, such as enforcing authentication middleware and scoping DynamoDB IAM policies to least privilege per route and principal.

Remediation focuses on two areas: ensuring every Chi route that uses DynamoDB validates identity and applying scoped IAM policies so that even if authentication is bypassed, the impact is limited. Below are concrete examples using the AWS SDK for JavaScript v3 within a Chi handler.

1. Enforce authentication in Chi routes

Wrap your route handler with an authentication check that validates a session or token before proceeding to DynamoDB operations.

(ns myapp.routes.user
  (:require [compojure.core :refer [GET]]
            [ring.util.response :as resp]
            [myapp.auth :refer [authenticate]]))

(def user-routes
  (GET \"/users/:id" request
    (if-let [user-identity (authenticate request)]
      (do
        (when-not (= (:user-id user-identity) (:id (:params request)))
          (resp/status resp/forbidden))
        (myapp.dynamo/get-user (:id (:params request))))
      (resp/unauthorized \"Missing or invalid token\"))))

2. Scoped IAM policies and least-privilege DynamoDB access

Ensure the IAM role used by the Chi service has tightly scoped permissions. For example, allow GetItem only on a table with a condition that the partition key matches the authenticated user’s ID.

{
  \"Version\": \"2012-10-17\",
  \"Statement\": [
    {
      \"Effect\": \"Allow\",
      \"Action\": \"dynamodb:GetItem\",
      \"Resource\": \"arn:aws:dynamodb:us-east-1:123456789012:table/Users\",
      \"Condition\": {
        \"ForAllValues:StringEquals\": {
          \"dynamodb:LeadingKeys\": [\"${aws:username}\"]
        }
      }
    }
  ]
}

3. Example DynamoDB GetItem with authenticated identity

Use the authenticated identity to construct a safe request, avoiding any direct reliance on request-supplied IDs without verification.

(ns myapp.dynamo
  (:require [aws.sdk.dynamodb :as ddb]))

(defn get-user [user-id]
  (let [identity (authenticated-identity) ;; from auth middleware
        request  {:request-method :get-item
                  :table-name \"Users\"
                  :key {\"id\" {\"S\" (str user-id)}}}
        response (ddb/invoke request)]
    (when (= (:user-id identity) user-id)
      (:item response))))

4. Avoid Scan in production; use Query with partition key

Replace broad Scan operations with Query calls that leverage a known partition key derived from authenticated context.

(ns myapp.dynamo
  (:require [aws.sdk.dynamodb :as ddb]))

(defn list-user-orders [user-id]
  (let [request {:request-method :query
                 :table-name \"Orders\"
                 :key-condition-expression \"user_id = :uid\"
                 :expression-attribute-values {\":uid\" {\"S\" user-id}}}]
    (:items (ddb/invoke request))))

5. Use middleware to inject identity into request context

In Chi, you can use middleware to attach identity to the request map, ensuring downstream handlers can safely use it for DynamoDB calls.

(defn wrap-auth [handler]
  (fn [request]
    (if-let [identity (authenticate request)]
      (handler (assoc request :identity identity))
      (resp/unauthorized \"Missing or invalid token\"))))

(def user-routes
  (-> (GET \"/users/:id" request
       (myapp.dynamo/get-user (:id (:params request))))
      (wrap-auth)))

These fixes ensure that DynamoDB operations in Chi are gated by proper authentication and least-privilege access, reducing the risk found by middleBrick’s Authentication and BOLA/IDOR checks.