Dangling Dns in Hapi with Dynamodb

A dangling DNS record in the context of a Hapi server that uses Amazon DynamoDB can expose an API to unintended data access or SSRF-like confusion during service discovery. When Hapi resolves a hostname at startup or runtime—commonly used for DynamoDB endpoint overrides, proxy resolution, or region-specific endpoints—a stale DNS entry may point to an external or internal service that no longer reflects the intended network topology.

Consider a Hapi service that resolves dynamodb.us-east-1.amazonaws.com (or a custom domain CNAME) at startup. If the DNS record later changes—perhaps due to decommissioned infrastructure, route changes, or a misconfigured failover—the hostname may resolve to an IP that belongs to a different environment or even a third party. Because the Hapi application caches or infrequently revalidates the DNS resolution, outbound requests to DynamoDB may be directed to this unintended host. In a black-box scan, middleBrick tests unauthenticated endpoints and checks whether hostname resolution can be influenced or observed; a dangling DNS setup may surface inconsistent responses that indicate reliance on mutable external resolution rather than fixed, validated endpoints.

DynamoDB-specific risks emerge when the dangling hostname resolves to a service that accepts or returns sensitive data. For example, if the hostname resolves to a test or legacy endpoint that does not enforce strict IAM policies or VPC boundaries, the Hapi service might inadvertently read or write data to an incorrect table. MiddleBrick’s checks for Data Exposure and Input Validation highlight scenarios where endpoint misconfiguration could allow cross-environment interactions or exposure of metadata. Because DynamoDB endpoints are often region-scoped and tied to IAM policies, a misresolved host can bypass intended network controls, effectively weakening isolation between services.

The interplay of Hapi’s routing layer and DynamoDB’s endpoint configuration means developers must ensure hostnames are statically defined or refreshed securely. Relying on public DNS for critical service endpoints without validation increases the attack surface probed by middleBrick’s parallel security checks, particularly around SSRF, Inventory Management, and Unsafe Consumption. The scanner does not assume internal architecture; it flags inconsistencies between declared endpoints and runtime behavior, emphasizing that DNS-based resolution in Hapi integrations requires hardening.

To mitigate dangling DNS risks in a Hapi application that interacts with DynamoDB, use explicit endpoint configuration and avoid runtime DNS-based discovery for production traffic. Prefer static SDK endpoints combined with strict IAM policies and VPC endpoints. Below are concrete code examples for a Hapi server using the AWS SDK for JavaScript v3.

1. Static endpoint with forced region and disable DNS resolution

Configure the DynamoDB client with a fixed endpoint URL and disable the SDK’s default DNS resolution behavior. This ensures the client never follows a dangling CNAME or external DNS change.

const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");

const client = new DynamoDBClient({
  region: "us-east-1",
  endpoint: "https://dynamodb.us-east-1.amazonaws.com", // static, avoid CNAMEs
  forcePathStyle: false, // prefer standard virtual-hosted style when using fixed endpoints
  // Do not rely on runtime DNS for this endpoint
});

exports.handler = async (event) => {
  const command = new GetItemCommand({
    TableName: process.env.DYNAMO_TABLE,
    Key: { id: { S: event.params.id } },
  });
  const response = await client.send(command);
  return { statusCode: 200, body: JSON.stringify(response.Item) };
};

2. Hapi route with validated input and explicit credential scope

Ensure route parameters are validated and that the DynamoDB client is reused to avoid repeated resolution. Use Joi validation in Hapi to constrain IDs and prevent SSRF or parameter pollution that could interact with a misresolved endpoint.

const Hapi = require("@hapi/hapi");
const { DynamoDBClient, GetItemCommand } = require("@aws-sdk/client-dynamodb");

const client = new DynamoDBClient({
  region: "us-east-1",
  endpoint: "https://dynamodb.us-east-1.amazonaws.com",
});

const init = async () => {
  const server = Hapi.server({ port: 4000, host: "localhost" });

  server.route({
    method: "GET",
    path: "/items/{id}",
    options: {
      validate: {
        params: {
          id: Joi.string().pattern(/^[a-zA-Z0-9_-]{1,64}$/).required(),
        },
      },
    },
    handler: async (request, h) => {
      const command = new GetItemCommand({
        TableName: process.env.DYNAMO_TABLE,
        Key: { id: { S: request.params.id } },
      });
      const { Item } = await client.send(command);
      return Item ? { data: Item } : { statusCode: 404, message: "Not found" };
    },
  });

  await server.start();
  console.log("Server running on %s", server.info.uri);
};

init().catch((err) => {
  console.error(err);
});

3. Use VPC endpoints and environment-controlled configuration

In deployment environments, prefer VPC endpoints for DynamoDB and inject the endpoint via secure configuration rather than DNS. This reduces exposure to public internet path changes and dangling DNS records. The following environment-based setup avoids runtime DNS lookups.

const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");

// endpoint injected via secure configuration (e.g., secrets manager), not DNS
const client = new DynamoDBClient({
  region: process.env.AWS_REGION,
  endpoint: process.env.DYNAMODB_ENDPOINT, // e.g., https://vpce-xxx-dynamodb.vpce.us-east-1.amazonaws.com
  forcePathStyle: true,
});

// Use client as shown in previous examples

By combining static endpoints, strict input validation in Hapi routes, and controlled configuration, you reduce the risks associated with dangling DNS and ensure findings from middleBrick scans remain low severity for Data Exposure and Input Validation categories.