Man In The Middle in Dynamodb

Man-in-the-Middle (MITM) attacks against applications using Amazon DynamoDB typically target the communication channel between the application and the DynamoDB service, or between a client and an API that proxies DynamoDB operations. While DynamoDB itself enforces TLS 1.2+ for its public endpoints, vulnerabilities arise from client-side misconfigurations, custom endpoint setups, or compromised network infrastructure. The attack surface is not the DynamoDB service itself but the application code that interacts with it.

Common Attack Patterns in DynamoDB Workloads:

• HTTP Endpoint Usage: Developers sometimes configure the AWS SDK to use HTTP (port 80) instead of HTTPS (port 443) for local testing with DynamoDB Local. If this configuration accidentally propagates to production, credentials and data are transmitted in plaintext.
• Disabled Certificate Validation: The AWS SDK allows overriding TLS certificate validation, often used to accept self-signed certificates in development environments. Setting rejectUnauthorized: false in the HTTPS agent disables validation, making the connection vulnerable to MITM.
• Custom Endpoints Over Insecure Channels: Using a custom DynamoDB endpoint (e.g., a proxy or VPC endpoint) that does not enforce TLS, or connecting to it via HTTP, exposes the traffic.
• Compromised DNS or Network: An attacker on the same network could redirect DynamoDB requests to a malicious server if the application does not properly validate the TLS certificate chain or hostname.

DynamoDB-Specific Code Vulnerabilities:

Consider this vulnerable Node.js configuration using AWS SDK v3:

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

const client = new DynamoDBClient({
  region: 'us-east-1',
  endpoint: 'http://dynamodb.example.com', // Using HTTP
  credentials: {
    accessKeyId: 'AKIA...',
    secretAccessKey: '...'
  },
  tls: false // Explicitly disabling TLS
});

Here, both the HTTP endpoint and disabled TLS create a MITM risk. Even if using AWS's standard endpoint, overriding the HTTPS agent to skip validation is equally dangerous:

const https = require('https');

const client = new DynamoDBClient({
  region: 'us-east-1',
  credentials: {...},
  // Disabling certificate validation
  requestHandler: new NodeHttpHandler({
    httpsAgent: new https.Agent({ rejectUnauthorized: false })
  })
});

An attacker intercepting such traffic can steal AWS credentials, read/write sensitive data, or inject malicious items into tables.

Detecting MITM risks in DynamoDB integrations requires examining both the API endpoint that applications use to access DynamoDB (or a proxy) and the client-side configuration. Since middleBrick performs black-box scanning of API endpoints, it assesses the TLS configuration of the API itself, which is the entry point for DynamoDB operations if the API directly interacts with DynamoDB. The scanner's Encryption check evaluates TLS protocol versions, cipher suite strength, certificate validity, and whether HTTP is accepted.

How middleBrick Identifies These Issues:

• TLS Enforcement: The scanner tests if the API endpoint redirects HTTP to HTTPS and supports only TLS 1.2 or 1.3. Accepting HTTP or TLS 1.0/1.1 indicates a MITM vulnerability.
• Certificate Validation: middleBrick checks for common TLS misconfigurations like self-signed certificates, expired certificates, or certificate chain errors that clients might be configured to ignore.
• Cipher Suite Strength: It flags weak ciphers (e.g., RC4, 3DES) that are susceptible to cryptographic attacks.

A middleBrick scan of an API endpoint that proxies DynamoDB requests might produce a finding like:

{
  "check": "Encryption",
  "severity": "critical",
  "title": "TLS 1.0/1.1 Supported",
  "description": "The endpoint accepts connections using TLS 1.0 or 1.1, which are deprecated and vulnerable to MITM attacks.",
  "remediation": "Disable TLS 1.0/1.1. Configure your server to only support TLS 1.2 and 1.3. For AWS services, ensure your SDK uses the default endpoint (https://dynamodb.{region}.amazonaws.com) and does not override TLS settings."
}

Limitations of Black-Box Scanning: middleBrick cannot inspect the application's internal DynamoDB client configuration (e.g., rejectUnauthorized: false). However, if the API endpoint itself has weak TLS, the scanner will detect it. For full coverage, combine middleBrick with static code analysis of your application's AWS SDK usage.

Remediating MITM risks in DynamoDB integrations involves enforcing strict TLS settings in both your application code and infrastructure. The goal is to ensure all traffic to DynamoDB (or any proxy) is encrypted and that certificates are rigorously validated.

1. Use AWS SDK Defaults and HTTPS Endpoints

The AWS SDKs for DynamoDB default to HTTPS endpoints with certificate validation enabled. Always use the standard regional endpoint (https://dynamodb.{region}.amazonaws.com) and avoid custom HTTP endpoints unless absolutely necessary for local testing, and never in production.

Secure Example (Node.js SDK v3):

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

// Correct: Uses default HTTPS endpoint and validates certificates
const client = new DynamoDBClient({ region: 'us-east-1' });

// Or explicitly ensure TLS is enabled
const clientSecure = new DynamoDBClient({
  region: 'us-east-1',
  endpoint: 'https://dynamodb.us-east-1.amazonaws.com', // Explicit HTTPS
  tls: true // This is the default, but being explicit helps
});

2. Never Disable Certificate Validation

Do not set rejectUnauthorized: false or equivalent in any environment. If you must use a custom endpoint with a self-signed certificate (e.g., in a test VPC), import the CA certificate into your trust store instead of disabling validation.

3. Enforce TLS at the Infrastructure Level

If your API communicates with DynamoDB via a VPC endpoint (AWS PrivateLink), ensure the endpoint's security groups and network ACLs only allow TLS traffic. Use security group rules to restrict outbound traffic to DynamoDB's IP ranges on port 443.

4. Rotate and Protect AWS Credentials

Even with perfect TLS, stolen credentials are catastrophic. Use IAM roles for EC2/ECS/Lambda instead of long-term access keys. If using access keys, rotate them regularly and store them in AWS Secrets Manager or Parameter Store, never in code.

5. Monitor and Alert

Enable AWS CloudTrail to log DynamoDB API calls. Set up alerts for unusual access patterns (e.g., requests from unexpected IP ranges). middleBrick's Pro tier can continuously monitor your API endpoints for TLS regressions, alerting you if weak ciphers or HTTP support reappear.

6. Validate SDK Versions

Keep AWS SDKs updated. Older versions may have deprecated TLS defaults. Check the SDK documentation for your language to ensure TLS 1.2+ is enforced.

Remediation Workflow:

1. Audit all DynamoDB client instantiations for HTTP endpoints or disabled TLS.
2. Run middleBrick on your API endpoints to identify server-side TLS issues.
3. Update SDK configurations to use HTTPS and validate certificates.
4. Deploy changes and rescan with middleBrick to confirm the Encryption check passes.