Dns Cache Poisoning in Chi with Cockroachdb

DNS cache poisoning can affect applications built with Chi when service discovery or configuration relies on external DNS lookups that return manipulated records. If your Chi application dynamically resolves hostnames—such as database endpoints or backend services—using standard library lookups, a poisoned cache may redirect traffic to an attacker-controlled host. With CockroachDB, this is relevant when you resolve cluster nodes or load balancers by hostname instead of using static or configuration-driven endpoints. Because CockroachDB clusters often advertise internal hostnames and require consistent network identity, a poisoned DNS response can cause the client to connect to a rogue node or an unintended address, bypassing intended network segregation.

In a typical Chi service, you might use a configuration-driven approach that queries DNS at startup or runtime. For example, resolving a CockroachDB node hostname on each connection attempt without validation increases exposure. If an attacker compromises a resolver or exploits a weak TTL, the poisoned record can route your Chi application’s SQL traffic to a malicious server. CockroachDB’s client libraries do not inherently validate DNS freshness beyond initial resolution, so repeated lookups from Chi handlers can perpetuate the poisoned mapping. This is especially relevant in environments without strict DNSSEC validation or where intermediate resolvers are untrusted. The risk is compounded when TLS verification is misconfigured or when hostname verification is bypassed, allowing a malicious server to present a valid certificate for a different node.

middleBrick detects DNS-related misconfigurations as part of its unauthenticated security scans, including checks that highlight missing input validation and unsafe consumption patterns around external endpoints. While the scanner does not test Chi or CockroachDB directly, it can surface indicators such as unvalidated hostname usage in OpenAPI specs or runtime endpoints that rely on dynamic resolution. By correlating spec definitions with observed runtime behavior, middleBrick helps identify where DNS-dependent flows might intersect with API surface areas that expose cluster metadata or administrative endpoints. This insight supports proactive hardening before an attacker exploits a poisoned cache in production.

To mitigate DNS cache poisoning when using CockroachDB with Chi, prefer static configuration or environment-driven endpoints rather than runtime DNS resolution. When hostnames must be used, validate and sanitize them at startup, and avoid repeated lookups in request handlers. Below are concrete examples that demonstrate secure patterns for connecting from a Chi application.

First, resolve the CockroachDB node address once during application initialization and reuse the resolved IP or stable hostname. This reduces reliance on the DNS cache during request processing.

(ns myapp.db
  (:require [cheshire.core :as json]
            [clj-http.client :as http]))

(defonce cockroach-node (atom nil))

(defn resolve-db-endpoint []
  ;; Perform resolution once and cache the result
  (when (nil? @cockroach-node)
    (let [host (System/getenv "COCKROACH_HOST")
          port (System/getenv "COCKROACH_PORT")
          resolved (java.net.InetAddress/getByName host)]
      (reset! cockroach-node (str (.getHostAddress resolved) ":" port))))
  @cockroach-node)

(defn db-client []
  ;; Reuse resolved endpoint for connections
  {:host (resolve-db-endpoint)
   :port 26257
   :ssl {:truststore "path/to/certs"}})

Second, enforce strict hostname verification and certificate pinning when using TLS. This prevents an attacker from using a valid certificate for a different hostname to bypass checks.

(defn secure-client []
  {:host "cockroachdb.example.com"
   :port 26257
   :ssl {:cert-file "client.pem"
         :key-file "client.key"
         :truststore "ca.pem"
         :verify-hostname true}})

Third, if you must perform lookups at runtime, validate the resolved address against an allowlist and log anomalies. This approach aligns with the findings that middleBrick surfaces regarding input validation and unsafe consumption patterns.

(def allowed-domains #{"cockroachdb.internal.example.com" "backup.cockroachdb.internal.example.com"})

(defn validate-and-resolve [hostname]
  (when (some #(hostname.endswith %)) allowed-domains)
    (InetAddress/getByName hostname))