Security Misconfiguration in Chi with Mongodb

Security misconfiguration in a Chi application that uses MongoDB often arises from defaults or oversights that leave the database endpoint exposed or overly permissive. Chi is a lightweight HTTP routing library for Clojure, and when combined with MongoDB drivers such as the official MongoDB Clojure driver, developers must manage connection strings, authentication, and network exposure carefully.

One common misconfiguration is binding the MongoDB listener on all network interfaces (0.0.0.0) without authentication, especially in local development environments that are later promoted to production. An attacker who discovers the exposed mongod port can attempt unauthorized access or reconnaissance, leading to unauthorized data reads or writes. Another misconfiguration is embedding MongoDB connection strings with hardcoded credentials in source code or configuration files that are committed to version control, which can result in credential leakage and data compromise.

Additionally, improper TLS settings, such as not enforcing SSL/TLS for client-server communication, can expose data in transit. Without proper role-based access control (RBAC), a user or service account may have more privileges than necessary (e.g., readWrite on databases where read-only is sufficient), amplifying the impact of a compromised application. Insecure default configurations in standalone MongoDB instances—such as no authorization enabled—interact dangerously with Chi routes that directly proxy or forward database commands based on user input.

These issues map to broader API risk patterns such as BFLA (Business Logic Flaws) and Improper Authorization, where lack of constraints on data access leads to excessive permissions. For example, a Chi endpoint that accepts an :id parameter and directly uses it in a MongoDB query without proper validation or ownership checks can become an IDOR vector if the underlying MongoDB user has broad access.

Using middleBrick, you can scan the public-facing API surface of a Chi service that interacts with MongoDB to detect exposed endpoints, missing authentication requirements, and misconfigured CORS or TLS settings. The scanner runs without agents or credentials, providing a security risk score and findings that reference the OWASP API Top 10 and common misconfiguration patterns.

Remediation centers on tightening configuration, enforcing authentication and encryption, and scoping permissions to the least privilege necessary. Below are concrete examples using the official MongoDB Clojure driver in a Chi application.

1. Secure MongoDB connection configuration

Define connection options that enforce authentication and SSL, and avoid binding to all interfaces in production.

(ns myapp.db
  (:require [com.mongodb :as m]
            [com.mongodb.client :as mc]))

(def conn-string "mongodb+srv://user:password@cluster0.example.net/dbname?retryWrites=true&tls=true")

(def client
  (m/mongo-client {:connection-string conn-string}))

(def db (.getDatabase client "appdb"))

Ensure the connection string uses TLS (tls=true) and SRV records are used with a proper DNS setup. Never embed passwords in code; use environment variables or a secrets manager instead.

2. Binding Chi routes with scoped access

Create routes that validate input and use a dedicated database user with minimal privileges.

(ns myapp.routes
  (:require [compojure.core :refer [GET POST defroutes]]
            [ring.util.response :as resp]
            [myapp.db :as db]))

(defn get-document [id]
  (when (re-matches #"^[a-f0-9]{24}$" id)
    (let [coll (.getCollection db "documents")
          doc (.findOne coll (doto (com.mongodb.BasicDBObject.) (.append "_id" id)))]
      (if doc
        (resp/json-response doc)
        (resp/not-found "Not found")))))

(defroutes app-routes
  (GET "/documents/:id" [id] (get-document id))
  (route/not-found "Not found"))

The route validates the :id format before using it in a MongoDB query, preventing some injection risks. The MongoDB user used by the connection string should be restricted to read-only on the necessary collections.

3. Principle of least privilege example

Create users in MongoDB with specific roles rather than using the root account.

# In MongoDB shell or admin setup:
use appdb
db.createUser({
  user: "chi-app-reader",
  pwd: "StrongPasswordHere",
  roles: [
    { role: "read", db: "appdb" }
  ]
})

This user can read data but cannot write or alter collections, limiting the blast radius if a Chi endpoint is compromised.

4. Environment-based configuration

Use environment variables to switch between development and production settings.

(defn get-connection-string []
  (or (System/getenv "MONGODB_URI")
      "mongodb://localhost:27017/devdb"))

In production, set MONGODB_URI to a full connection string with TLS and credentials; in development, a local instance without auth may be acceptable but should never be used in staging or production.

5. MiddleBrick integration

For continuous assurance, use the middleBrick CLI to scan your Chi service and verify that endpoints interacting with MongoDB are not exposing unauthenticated access or excessive permissions.

$ middlebrick scan https://api.example.com

The scan will identify misconfigurations such as missing authentication on routes, unencrypted connections, and overly permissive roles, with remediation guidance tied to frameworks like OWASP API Top 10 and compliance standards.