Dangling Dns in Adonisjs with Api Keys

A dangling DNS record in an AdonisJS application becomes a security exposure when API keys are resolved or validated through hostnames that no longer point to a controlled service. AdonisJS often uses configuration-driven DNS lookups—for example, when validating webhook signatures, authorizing API key origins, or resolving service endpoints via environment variables. If a hostname configured in .env (such as API_WEBHOOK_HOST) resolves to an orphaned or unmanaged DNS record, an attacker who can control the target at that address may intercept or manipulate traffic intended for your service.

Consider an API key validation flow where AdonisJS checks the origin of a request by resolving a hostname from a trusted list. If the trusted hostname is a dangling CNAME pointing to a decommissioned infrastructure domain, an attacker who re-registers that domain can present a valid TLS certificate and intercept API key–bound requests. This scenario maps to BOLA/IDOR and Property Authorization checks in middleBrick’s scan, where unauthenticated access is tested by manipulating references that should be strictly scoped. The presence of API keys does not inherently prevent this; if the application relies on DNS resolution to enforce trust boundaries, a dangling record breaks that boundary.

In a middleBrick scan, such misconfigurations are surfaced under Authorization and Input Validation checks, with references to OWASP API Top 10 A01:2023 (Broken Object Level Authorization) and A05:2023 (Broken Function Level Authorization). Real-world patterns include CNAME chains that point to recycled cloud assets or expired internal services, enabling indirect privilege escalation when API keys are accepted based on hostname rather than robust token-bound metadata. Encryption and Data Exposure checks may also flag the risk if API keys are transmitted over routes that depend on unresolved or mutable DNS targets.

Remediation focuses on removing DNS as a trust anchor and binding API key validation to immutable, verifiable properties. In AdonisJS, prefer explicit IP allowlists, certificate pinning, or signed tokens with embedded metadata instead of hostname-based checks. When API keys must be scoped, encode scope directly in the key or in a separate reference that does not depend on DNS resolution.

Example 1: Validate API keys against a hardcoded allowlist of fingerprints or issuer IDs instead of a hostname. This removes reliance on DNS entirely.

import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'

export default class ApiKeyValidator {
  private allowedKeyMetadata = {
    'ak_live_abc123': { scope: 'billing', issuerFingerprint: 'sha256:9a:b3:7c:...' },
    'ak_live_def456': { scope: 'reporting', issuerFingerprint: 'sha256:e2:f1:8a:...' }
  }

  public validate({ request, response }: HttpContextContract) {
    const apiKey = request.header('X-API-Key')
    if (!apiKey) {
      return response.unauthorized('Missing API key')
    }
    const metadata = this.allowedKeyMetadata[apiKey]
    if (!metadata) {
      return response.unauthorized('Invalid API key')
    }
    // Optionally verify a client certificate or JWT issuer fingerprint here
    return { scope: metadata.scope, key: apiKey }
  }
}

Example 2: Use environment variables for endpoints but enforce strict validation and avoid dynamic DNS re-resolution at runtime. If you must use hostnames, pin them to specific IPs or use SRV records with strict fallback logic, and log mismatches for investigation.

import Env from '@ioc:Adonis/Core/Env'
import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'

export default class WebhookVerifier {
  private trustedOrigin = Env.get('API_WEBHOOK_HOST') // e.g., 'hooks.example.com' — should resolve to a controlled, static address

  public verifySignature(ctx: HttpContextContract) {
    const origin = ctx.request.headers().host
    if (origin !== this.trustedOrigin) {
      // Fail closed: reject if host does not match pinned expectation
      throw new Error('Host mismatch: potential dangling DNS target')
    }
    // Proceed with signature validation using a static secret
    const signature = ctx.request.header('X-Signature')
    // ... verify signature
    return true
  }
}

Example 3: Prefer short-lived, scoped tokens (e.g., JWTs) with embedded claims and rotate keys via a controlled mechanism that does not rely on external DNS. MiddleBrick’s CLI can be used to verify that your API key handling does not depend on mutable DNS by running middlebrick scan <url> and reviewing findings under Authorization and Input Validation.