Dns Cache Poisoning in Fiber with Cockroachdb

DNS cache poisoning (also known as DNS spoofing) occurs when a malicious actor injects forged DNS responses, causing a resolver to return an attacker-controlled IP address for a legitimate domain. When a Fiber-based application relies on CockroachDB and uses hostnames rather than direct IPs for database connections, poisoned DNS records can redirect traffic to an attacker-controlled database server. This exposes the application to data interception, unauthorized data modification, or authentication bypass if the application does not enforce strict network-level controls.

In a typical Fiber + CockroachDB deployment, the application resolves a hostname such as secure-cockroachdb.example.com to a CockroachDB cluster address. If an attacker compromises a DNS caching layer between the application and the resolver—such as a misconfigured local resolver, a compromised enterprise DNS server, or a public resolver vulnerable to cache poisoning—the application may establish a TLS-terminated connection to a malicious server that presents a valid certificate for the target hostname. Because CockroachDB supports TLS encryption by default, the handshake may succeed, allowing the attacker to eavesdrop on or alter queries and responses.

The risk is compounded when the application uses unvalidated hostname resolution for dynamic database routing or multi-region deployments. For example, if the application queries a service discovery endpoint that returns a hostname, and that hostname is later resolved via DNS without additional verification, poisoned cache entries can persist across retries. MiddleBrick scans can detect whether DNS resolution paths are consistent and whether unexpected IPs are returned during repeated scans, helping identify environments where DNS spoofing could affect database connectivity.

It is important to note that middleBrick performs black-box scanning and does not modify infrastructure. It identifies whether endpoints exhibit signs of insecure resolution behavior by analyzing responses and reported configurations. The scanner checks for missing validation controls around external dependencies and highlights findings related to input validation and data exposure that may intersect with DNS-related risks.

To reduce exposure, applications should treat DNS resolution as an untrusted network layer and apply additional verification where feasible. This includes pinning expected IP ranges, using encrypted connections with strict certificate validation, and avoiding reliance on dynamically resolved hostnames for critical database paths. middleBrick’s findings can guide teams in identifying weak points in their external dependency handling.

Remediation focuses on ensuring that database connections remain resilient to DNS manipulation. The most effective approach is to bypass DNS caching for critical connections by using direct IP addresses or by enforcing strict verification at the application layer. Below are concrete Fiber + CockroachDB code examples demonstrating secure connection practices.

1. Use IP addresses with explicit port and TLS

Instead of relying on a hostname, specify the CockroachDB node IP directly in the connection string. This removes DNS as an attack surface for that connection.

const { Pool } = require('pg');

const pool = new Pool({
  host: '192.0.2.10',       // Use direct IP address
  port: 26257,
  database: 'mydb',
  user: 'myuser',
  password: 'secure-password',
  ssl: {
    cert: fs.readFileSync('client.crt'),
    key: fs.readFileSync('client.key'),
    ca: fs.readFileSync('ca.crt'),
    rejectUnauthorized: true   // Enforce strict certificate validation
  }
});

2. Validate resolved hostnames against allowlists

If hostnames must be used (e.g., in dynamic cloud environments), resolve the hostname once at startup, validate it against an allowlist of expected IPs, and then use the validated IP for all subsequent connections.

const dns = require('dns').promises;
const expectedIps = new Set(['192.0.2.10', '192.0.2.11']); // Pre-approved IPs

async function getVerifiedHost() {
  const hostname = 'secure-cockroachdb.example.com';
  const records = await dns.resolve4(hostname);
  const verified = records.filter(ip => expectedIps.has(ip));
  if (verified.length === 0) {
    throw new Error('No verified IPs found for CockroachDB');
  }
  return verified[0];
}

// Usage at startup
getVerifiedHost().then(ip => {
  const pool = new Pool({
    host: ip,
    port: 26257,
    database: 'mydb',
    user: 'myuser',
    password: 'secure-password',
    ssl: {
      rejectUnauthorized: true
    }
  });
});

3. Enforce certificate hostname verification

Ensure that the TLS certificate presented by the CockroachDB server matches the expected hostname pattern. Even when using IPs, strict certificate validation prevents acceptance of certificates issued for arbitrary domains.

const tls = require('tls');
const fs = require('fs');

const connection = tls.connect({
  host: '192.0.2.10',
  port: 26257,
  cert: fs.readFileSync('client.crt'),
  key: fs.readFileSync('client.key'),
  ca: fs.readFileSync('ca.crt'),
  checkServerIdentity: function(host, cert) {
    // Additional verification beyond default TLS checks
    if (!cert.subjectaltname.includes('DNS:secure-cockroachdb.example.com')) {
      throw new Error('Certificate hostname mismatch');
    }
    return undefined; // Use default verification
  }
});

These practices reduce reliance on potentially poisoned DNS caches. middleBrick can support this remediation workflow by scanning endpoints to confirm that DNS resolution paths are stable and that unexpected IPs are not introduced during repeated tests.