Dns Cache Poisoning in Feathersjs with Dynamodb

DNS cache poisoning is a network-level attack where an attacker injects false DNS responses, causing a resolver to return an attacker-controlled IP for a legitimate hostname. In a FeathersJS application that uses Amazon DynamoDB as its persistence layer, this attack surface is realized through service discovery and data routing decisions that depend on hostnames, such as connecting to DynamoDB endpoints or downstream services.

FeathersJS does not perform DNS resolution itself; it relies on the Node.js runtime and underlying operating system libraries. If a FeathersJS service resolves a hostname—such as a DynamoDB endpoint, a custom API host, or an internal service name—at startup or runtime, and the DNS response is poisoned, the application may send traffic to a malicious host. This becomes critical when environment-driven configuration (e.g., database hostnames) is supplied via variables that are not validated beyond format checks.

When combined with DynamoDB, a poisoned DNS entry pointing to a rogue endpoint can redirect database traffic. An attacker who controls the resolved IP could run a malicious server that accepts connections, potentially intercepting or manipulating unencrypted metadata, or exploiting weak authentication to perform unauthorized operations. FeathersJS channels typically invoke DynamoDB via the AWS SDK, which relies on the standard Node.js dns module for endpoint resolution. If the SDK or application code uses hostnames without enforcing strict validation or certificate pinning, the poisoned DNS record can lead to connections being established with an unintended peer.

Although DynamoDB itself is a managed service accessed over HTTPS with strong server certificate validation, the risk arises from how the hostname is resolved before the TLS handshake. For example, if a FeathersJS service reads DYNAMODB_ENDPOINT from environment variables and passes it to the AWS SDK, and that hostname resolves to a malicious IP due to cache poisoning, the SDK may establish a TLS connection with the attacker’s server. The attacker’s server may present a valid certificate for a different domain, and if the SDK or application does not strictly validate the server identity, sensitive data or credentials could be exposed.

Additionally, FeathersJS hooks and services that construct URLs dynamically—such as generating pre-signed URLs or invoking third‑party APIs based on data stored in DynamoDB—can be influenced if the stored hostnames are compromised via DNS. An attacker who can poison DNS for a hostname used across multiple services can redirect a broad set of requests, including those initiated by the FeathersJS application, thereby expanding the impact beyond the DynamoDB channel.

Mitigating this risk requires ensuring that hostnames are verified, connections use strict TLS validation, and where possible, IP addresses or resilient service discovery mechanisms are preferred over mutable DNS-dependent configurations. Tools like middleBrick can scan a FeathersJS endpoint to detect whether insecure patterns—such as unvalidated hostname usage or missing certificate checks—are present, providing prioritized findings with remediation guidance aligned with frameworks such as OWASP API Top 10.

To reduce DNS cache poisoning risk in a FeathersJS application using DynamoDB, harden hostname resolution and enforce strict validation of endpoints and certificates. Prefer environment-managed IPs or service discovery mechanisms where feasible, and ensure that all AWS SDK communications validate server identity.

Use Explicit IPs or VPC Endpoints for DynamoDB

Where possible, avoid DNS-based resolution for DynamoDB by using VPC endpoints (AWS PrivateLink) or specifying IPs in a controlled DNS environment. This reduces reliance on external DNS for critical endpoints. When using the AWS SDK for JavaScript, you can configure a custom endpoint with an explicit hostname or IP, and disable default hostname resolution logic.

const { DynamoDB } = require('aws-sdk');
const customEndpoint = 'https://dynamodb.us-east-1.amazonaws.com'; // Prefer VPC endpoint URL in production
const db = new DynamoDB({
  endpoint: customEndpoint,
  sslEnabled: true,
  httpOptions: {
    // Disable default hostname verification override; rely on TLS verification
  },
  // Ensure region is explicitly set to avoid resolution ambiguities
  region: 'us-east-1'
});
module.exports = db;

Enforce Strict TLS and Hostname Verification

Ensure that the AWS SDK validates the server certificate hostname. Do not disable certificate checks. In environments where custom CA bundles are required, provide them explicitly instead of relaxing validation.

const https = require('https');
const fs = require('fs');
const { DynamoDB } = require('aws-sdk');

const agent = new https.Agent({
  ca: fs.readFileSync('/path/to/trusted-ca-bundle.pem'),
  rejectUnauthorized: true // Do not set to false
});

const db = new DynamoDB({
  httpOptions: {
    agent: agent
  },
  region: 'us-east-1'
});

Validate and Sanitize Environment-Driven Hostnames

If hostnames must be supplied via environment variables (e.g., for multi-region or tenant-aware routing), validate them against an allowlist or a strict pattern before passing them to the SDK or using them to construct URLs. Avoid direct concatenation of user-influenced data into endpoint URLs.

const allowedHosts = ['dynamodb.us-east-1.amazonaws.com', 'vpce-xxx-dynamodb.vpce.us-east-1.vpce.amazonaws.com'];
function isValidEndpoint(host) {
  return allowedHosts.includes(host);
}

const rawHost = process.env.DYNAMODB_ENDPOINT;
if (!rawHost || !isValidHost(rawHost)) {
  throw new Error('Invalid or unauthorized DynamoDB endpoint');
}

const db = new DynamoDB({ endpoint: `https://${rawHost}`, region: 'us-east-1' });

Leverage FeathersJS Hooks for Pre-Request Validation

Use FeathersJS hooks to validate any data that influences service endpoints or DynamoDB parameters. This ensures that runtime values are checked before any service call is made.

const hooks = require('feathers-hooks-common');
app.service('records').hooks({
  before: {
    create: [hooks.validateSchema({
      type: 'object',
      required: ['resourceId'],
      properties: {
        resourceId: { type: 'string', pattern: '^[a-zA-Z0-9_-]+$' }
      }
    })]
  }
});

Use middleBrick for Continuous Scanning

Integrate middleBrick into your workflow to detect insecure hostname usage, missing TLS verification, and other patterns that increase DNS poisoning risk. The CLI can be run locally or in CI/CD pipelines using the GitHub Action to fail builds if risk thresholds are exceeded. Findings include prioritized remediation steps mapped to frameworks such as OWASP API Top 10.