Security Misconfiguration in Chi with Dynamodb

Security misconfiguration in a Chi application that uses DynamoDB often arises from overly permissive IAM policies, missing resource-level permissions, or incomplete validation of request parameters. When a Chi service calls DynamoDB without least-privilege permissions, an attacker who compromises the application or tricks a user into making malicious requests can invoke unintended operations on DynamoDB tables.

Chi is a lightweight, functional web framework for Clojure projects, and its routes typically forward requests to data access functions that interact with AWS services. If these functions construct DynamoDB API calls using user-supplied input without strict validation, they may be vulnerable to NoSQL injection or excessive permissions abuse. For example, a route that accepts a table name or key condition from query parameters and passes them directly to the DynamoDB client can enable attackers to scan tables or read other users’ data.

Additionally, misconfigured AWS credentials or endpoints can expose sensitive data. If the application uses shared credentials or hardcoded keys with broad access, and the Chi service does not enforce strict authorization checks before issuing DynamoDB requests, findings such as BOLA/IDOR or Data Exposure may be surfaced by middleBrick. Unauthenticated endpoints that expose DynamoDB-related functionality further increase risk, because unauthenticated callers can probe or trigger operations that should be restricted.

The combination introduces risks such as information disclosure, data tampering, or privilege escalation via BFLA when conditional expressions in DynamoDB are derived from unchecked user input. Proper input validation, resource-based authorization, and scoped IAM roles reduce the likelihood of exploitation in a Chi + DynamoDB stack.

Remediation focuses on tightening IAM permissions, validating and sanitizing all inputs, and ensuring authorization checks before DynamoDB operations. Use scoped IAM roles and avoid wildcard actions; prefer condition expressions and explicit attribute checks in DynamoDB requests.

Example: Secure DynamoDB get-item in Chi

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

(defn get-user-by-id
  "Fetches a user record by UUID after confirming the caller owns the resource."
  [caller-uuid user-uuid]
  (when (not= caller-uuid user-uuid)
    (throw (ex-info "Unauthorized" {:status 403})))
  (ddb/get-item
   {:table-name "users"
    :key {:user-id {:s user-uuid}}
    :attributes-to-get ["user-id" "email" "profile"]}))

Example: Parameterized query with strict key condition

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

(defn list-orders-by-user
  "Uses a parameterized query with explicit key condition; avoids concatenating raw input."
  [user-id sort-value limit]
  (ddb/query
   {:table-name "orders"
    :key-condition-expression "user-id = :uid AND sort-key BETWEEN :start AND :end"
    :expression-attribute-values {":uid" {:s user-id}
                                 ":start" {:s (str sort-value "_start")}
                                 ":end" {:s (str sort-value "_end")}}
    :limit (int (min limit 50))}))

IAM policy guidance

Define policies that restrict DynamoDB actions to specific resources and conditions. For example, allow dynamodb:GetItem only on a table prefix tied to the user’s tenant:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:GetItem",
        "dynamodb:Query"
      ],
      "Resource": "arn:aws:dynamodb:region:account-id:table/users-${aws:userid}",
      "Condition": {
        "ForAllValues:StringEquals": {
          "dynamodb:LeadingKeys": ["${aws:userid}"]
        }
      }
    }
  ]
}

Input validation and error handling

Validate and sanitize all inputs and avoid passing raw user input into expression attribute names. Use allowlists for table or attribute names, and prefer prepared statements or SDK constructs that separate data from expression syntax.

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

(def user-uuid-schema
  [:re #"^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$"])

(defn validate-uuid [value]
  (if (m/validate user-uuid-schema value)
    value
    (throw (ex-info "Invalid UUID format" {:status 400}))))

By combining least-privilege IAM roles, strict input validation, and explicit resource-level checks, you reduce misconfiguration risks for Chi applications using DynamoDB.