Arp Spoofing in Hapi with Dynamodb

Arp spoofing is a network-layer attack where an attacker sends falsified Address Resolution Protocol (ARP) replies to associate their MAC address with the IP of a legitimate host, such as a DynamoDB endpoint or a backend service running Hapi. When Hapi applications communicate with DynamoDB over the local network (for example, in EC2, ECS, or on-prem environments), an attacker on the same subnet can intercept or redirect traffic. This can lead to credential theft if the application uses IAM credentials sourced from the instance metadata service, or it can enable injection of malicious DynamoDB API requests crafted to bypass authorization logic.

In a Hapi server, routes that perform DynamoDB operations typically rely on the AWS SDK for JavaScript. If the server resolves the DynamoDB hostname to an IP that has been spoofed, the SDK may unknowingly send data to the attacker. Since DynamoDB requests often include sensitive information such as table names, keys, and IAM policies, intercepted requests can expose data and enable privilege escalation. The combination of Hapi’s route handling and DynamoDB’s low-level API calls means that spoofed responses can manipulate query results, leading to unauthorized data access or injection of malicious condition expressions.

Additionally, if the Hapi application exposes an endpoint that queries DynamoDB based on user-supplied input without strict validation, an attacker conducting ARP spoofing can manipulate in-flight requests to alter query parameters. For example, changing a TableName or Key value to point to a different table or item. Because the AWS SDK does not inherently protect against layer-2 manipulation, the server must enforce network-level integrity controls and validate endpoint identity independently of the transport layer.

Defending against ARP spoofing when using Hapi with DynamoDB focuses on ensuring request authenticity, using encrypted channels, and validating all inputs that affect DynamoDB operations. Below are concrete code examples for a Hapi server that securely interacts with DynamoDB.

1. Use AWS SDK with explicit credential configuration and HTTPS

Ensure the AWS SDK is configured to use explicit credentials and that all communication with DynamoDB occurs over HTTPS. In Hapi, initialize the SDK outside of route handlers to reuse connections safely.

const Hapi = require('@hapi/hapi');
const { DynamoDBDocumentClient, GetCommand } = require('@aws-sdk/lib-dynamodb');
const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');

const client = new DynamoDBClient({
  region: process.env.AWS_REGION,
  credentials: {
    accessKeyId: processEnv.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
  },
  endpoint: process.env.DYNAMODB_ENDPOINT, // optional, for custom endpoints
});
const ddbDocClient = DynamoDBDocumentClient.from(client);

const init = async () => {
  const server = Hapi.server({ port: 4000, host: '0.0.0.0' });

  server.route({
    method: 'GET',
    path: '/items/{id}',
    handler: async (request, h) => {
      const params = {
        TableName: process.env.DYNAMODB_TABLE,
        Key: { id: request.params.id },
      };
      try {
        const data = await ddbDocClient.send(new GetCommand(params));
        return data.Item;
      } catch (err) {
        request.log(['error', 'dynamodb'], err);
        throw h.response({ error: 'Unable to fetch item' }).code(500);
      }
    },
  });

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

init().catch((err) => {
  console.error(err);
  process.exit(1);
});

2. Validate and sanitize all inputs that affect DynamoDB requests

Even when ARP spoofing is a concern, input validation prevents manipulation of table names and keys. Use Joi validation in Hapi routes to enforce strict patterns for IDs and table references.

const Joi = require('joi');

server.route({
  method: 'POST',
  path: '/update',
  options: {
    validate: {
      payload: Joi.object({
        id: Joi.string().pattern(/^[a-zA-Z0-9_-]{1,64}$/).required(),
        tableName: Joi.string().valid('users', 'orders', 'products').required(),
        updates: Joi.object().min(1),
      }),
    },
  },
  handler: async (request, h) => {
    const { id, tableName, updates } = request.payload;
    const params = {
      TableName: tableName,
      Key: { id },
      UpdateExpression: 'set #data = :val',
      ExpressionAttributeNames: { '#data': 'data' },
      ExpressionAttributeValues: { ':val': JSON.stringify(updates) },
      ReturnValues: 'UPDATED_NEW',
    };
    try {
      const data = await ddbDocClient.send(new UpdateCommand(params));
      return data.Attributes;
    } catch (err) {
      request.log(['error', 'dynamodb'], err);
      throw h.response({ error: 'Update failed' }).code(500);
    }
  },
});

3. Enforce mutual TLS and network segmentation where possible

While Hapi does not manage TLS termination, ensure that the Node.js process uses HTTPS agents for DynamoDB and that the environment restricts which hosts can communicate. Use IAM policies and VPC endpoints to limit exposure. The following AWS SDK configuration enforces HTTPS and disables legacy HTTP endpoints.

const client = new DynamoDBClient({
  region: 'us-east-1',
  requestHandler: new NodeHttpHandler({
    httpsAgent: new https.Agent({ rejectUnauthorized: true }),
  }),
  forcePathStyle: false,
  endpoint: 'https://dynamodb.us-east-1.amazonaws.com',
});