Dns Cache Poisoning in Adonisjs with Dynamodb

AdonisJS is a Node.js web framework that relies on standard Node runtime DNS resolution for outbound HTTP requests, such as calls to Amazon DynamoDB. When an AdonisJS application running in certain environments resolves DNS names for DynamoDB endpoints, it may use the operating system or Node.js DNS cache. Cache poisoning can occur if an attacker can inject a malicious DNS record into that cache, redirecting a legitimate DynamoDB hostname to a rogue IP address. This can redirect database traffic, enable credential interception, or facilitate SSRF against internal services that the application trusts.

In practice, this risk is realized when the application code does not enforce strict endpoint validation and relies on implicit DNS resolution for DynamoDB. For example, if the application uses environment variables to set the DynamoDB region endpoint and those variables are influenced by unvalidated input or are constructed dynamically, an attacker who can poison DNS may control which network address the SDK communicates with. Because DynamoDB operations often include sensitive data, this can lead to data exposure or unauthorized data modification. The vulnerability is not in middleBrick itself but in how the application and runtime handle DNS resolution for DynamoDB calls made from an AdonisJS codebase.

Consider an AdonisJS service that builds a DynamoDB client using a region-based endpoint derived from user input without strict validation:

const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
const region = appConfig.get('dynamoRegion'); // could be influenced by env or user data
const client = new DynamoDBClient({ region });

If the region or endpoint hostname is malleable and DNS is poisoned, the client may connect to a malicious host. AdonisJS applications that use unvalidated configuration for service endpoints are more susceptible. Additionally, if the application runs in containerized or shared network environments, the DNS cache behavior may differ, increasing the window for poisoning. The risk is compounded when the application does not pin endpoints or use AWS SDK’s built-in mechanisms to enforce known-good hosts.

Remediation focuses on ensuring that DynamoDB connections use explicit, validated endpoints and that DNS dependencies are minimized. In AdonisJS, you should avoid deriving service endpoints from mutable configuration or unvalidated input. Instead, hardcode or securely manage endpoint URLs and leverage the AWS SDK’s configuration options to reduce DNS-based risks.

First, validate and constrain the region and endpoint values used by the DynamoDB client. Do not allow these to be set from untrusted sources. If you must support multiple regions, maintain an allowlist of permitted region identifiers and validate against it:

const allowedRegions = ['us-east-1', 'us-west-2', 'eu-west-1'];
const region = appConfig.get('dynamoRegion');
if (!allowedRegions.includes(region)) {
  throw new Error('Unsupported region');
}
const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
const client = new DynamoDBClient({ region });

Second, when possible, prefer using AWS SDK defaults that rely on the well-known global endpoint for DynamoDB in the specified region. Avoid overriding the endpoint unless necessary, and if you must use a custom endpoint, ensure it is a fixed, trusted hostname and not derived from external input:

const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
const client = new DynamoDBClient({
  region: 'us-east-1',
  endpoint: 'https://dynamodb.us-east-1.amazonaws.com' // fixed, validated endpoint
});

Third, enforce HTTPS to prevent on-path manipulation of DNS responses and ensure that the SDK’s HTTP layer uses TLS verification. The AWS SDK for JavaScript enforces HTTPS by default, but verify that no custom HTTP agents or configurations inadvertently allow HTTP or skip certificate validation:

const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
const { defaultProvider } = require('@aws-sdk/credential-provider-node');
const client = new DynamoDBClient({
  region: 'us-east-1',
  requestHandler: {
    httpsAgent: new (require('https').Agent)({ rejectUnauthorized: true })
  },
  credentialDefaultProvider: defaultProvider()
});

Fourth, implement runtime integrity checks for critical responses when feasible. For high-sensitivity operations, validate that the service endpoint matches an expected hash or fingerprint. While this does not prevent cache poisoning, it can reduce impact by ensuring that responses originate from the intended host. Combine this with logging and monitoring for anomalous endpoint resolutions:

const crypto = require('crypto');
const expectedFingerprint = 'a1b2c3d4e5f6...';
// Example: verify endpoint hash in logs or custom hooks
function verifyEndpoint(host) {
  const hash = crypto.createHash('sha256').update(host).digest('hex');
  if (hash !== expectedFingerprint) {
    console.warn('Unexpected endpoint fingerprint:', host);
  }
}

Finally, review your deployment environment’s DNS settings. Prefer using DNS servers that support DNSSEC and disable caching on nodes where appropriate. In containerized deployments, configure the node’s DNS options explicitly to reduce reliance on shared caches. These measures complement application-level fixes and reduce the feasibility of DNS cache poisoning against DynamoDB traffic from AdonisJS services.