Use After Free in Adonisjs with Mutual Tls

Use After Free occurs when memory is deallocated but references to it remain, and those references are later accessed. In AdonisJS, this typically manifests through asynchronous operations (e.g., HTTP request handling, file I/O, or database connections) that retain references to objects after their underlying memory has been reclaimed. When Mutual TLS (mTLS) is enabled, the server performs strict client certificate validation, which involves parsing and storing certificate data for the duration of the TLS handshake and often beyond into request-scoped contexts.

The combination of AdonisJS and mTLS can expose Use After Free risks when certificate objects or related buffers are freed or reused while asynchronous handlers still hold pointers to them. For example, if an application caches client certificate information in request-local storage and the underlying buffer is deallocated (e.g., due to garbage collection or manual cleanup in native addons) before the request lifecycle completes, subsequent access to that cached data can lead to undefined behavior, crashes, or potential data exposure.

Consider a scenario where AdonisJS uses a native HTTPS module with mTLS configured. The server receives a request with a client certificate, parses it into a structured object, and passes it to an async middleware chain. If the native layer deallocates the certificate buffer after validation but before the async operation completes (e.g., a slow database query or an event emitted later in the request lifecycle), the middleware might attempt to read from a dangling pointer. This could leak sensitive certificate metadata or cause the process to crash.

Real-world attack patterns mirror classic OWASP API Top 10 risks such as API1:2023 – Broken Object Level Authorization when freed memory is repurposed to manipulate authorization state. In mTLS contexts, an attacker might induce conditions that increase object churn—such as rapid certificate renegotiation or malformed certificates—to heighten the likelihood of accessing freed memory. Instrumentation for this class of issue is often absent in typical API scans, but middleBrick’s 12 security checks, including Input Validation and Unsafe Consumption, can surface anomalous runtime behavior that hints at memory safety issues.

From a compliance perspective, Use After Free in this configuration may violate expectations around data integrity under GDPR and availability under SOC2. middleBrick’s LLM/AI Security checks do not directly probe memory safety, but its runtime analysis combined with OpenAPI/Swagger spec validation can highlight inconsistent handling of certificate-bound request contexts, especially when specs define strict security schemes but implementations retain references beyond their intended scope.

Because middleBrick scans unauthenticated attack surfaces and tests 12 security checks in parallel, it can identify instability patterns that suggest underlying memory handling flaws when testing AdonisJS endpoints secured with mTLS. While the tool does not fix or patch, its prioritized findings include remediation guidance to review native module lifecycle handling and ensure certificate objects remain valid for the full request duration.

To mitigate Use After Free in AdonisJS with mTLS, focus on ensuring that certificate data and related resources remain valid for the entire request lifecycle and are not prematurely deallocated. Below are concrete remediation steps and code examples.

1. Use AdonisJS Built-in HTTPS Server with Proper TLS Options

AdonisJS uses the underlying Node.js HTTPS server. Configure it to retain certificate references safely by avoiding manual buffer reuse and relying on AdonisJS’s lifecycle management.

// start/server.ts
import { HttpServer } from '@adonisjs/core'

export const http = new HttpServer({
  https: {
    key: '/path/to/server.key',
    cert: '/path/to/server.crt',
    ca: '/path/to/ca.crt',
    requestCert: true,
    rejectUnauthorized: true,
  },
})

// In .env
HTTPS_KEY=server.key
HTTPS_CERT=server.crt
HTTPS_CA=ca.crt

Ensure that certificate files are read once at startup and not reloaded or freed during request handling. This reduces the risk of buffers being garbage-collected or freed while async operations reference them.

2. Pin Certificate Data to the Request Context

Store parsed certificate information in the request context (e.g., `ctx.session` or a dedicated request-scoped map) and avoid holding references in global or long-lived caches. Use deep copies or immutable structures if necessary.

// middleware/validate_client_cert.ts
import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'
import { X509Certificate } from 'crypto'

export default async function validateClientCert({ request, response, next }: HttpContextContract) {
  const certHeader = request.headers().['x-client-cert']
  if (!certHeader) {
    return response.unauthorized('Client certificate required')
  }

  try {
    // Parse certificate and attach to request context
    const cert = new X509Certificate(certHeader)
    // Ensure the cert remains valid for the duration of the request
    request.ctx.clientCert = {
      subject: cert.subject,
      issuer: cert.issuer,
      validFrom: cert.validFrom,
      validTo: cert.validTo,
    }
    await next()
  } catch (error) {
    logger.error('Failed to parse client certificate', { error })
    return response.badRequest('Invalid client certificate')
  }
}

By attaching the parsed data to `request.ctx`, you ensure it persists for the request and is not subject to premature garbage collection. Avoid storing raw buffers or external handles beyond the request scope.

3. Avoid Native Addons That Manually Manage Certificate Memory

If using native modules for mTLS, verify that they do not free certificate buffers before async callbacks complete. Prefer maintained npm packages that follow Node.js memory management best practices, or wrap native calls to ensure retained references.

// Example: safe use of tls.connect with mTLS
import * as tls from 'tls'
import { readFileSync } from 'fs'

const options = {
  key: readFileSync('/path/to/client.key'),
  cert: readFileSync('/path/to/client.crt'),
  ca: readFileSync('/path/to/ca.crt'),
  rejectUnauthorized: true,
}

const socket = tls.connect(8443, 'api.example.com', options, () => {
  console.log('Client connected with mTLS')
  // Perform operations while references are alive
  socket.end()
})

// Ensure socket and related buffers are not reused after destruction
socket.on('close', () => {
  // Clean up any references here, not before
})

This pattern ensures that buffers are not freed while the socket is active. In AdonisJS, wrap such connections in services that manage lifecycle explicitly and avoid reusing objects after `close` events.

4. Implement Request-Scoped Cleanup

Use AdonisJS middleware hooks to clean up request-specific data only after the response is finished, preventing access to freed memory during async operations.

// middleware/cleanup_after_response.ts
import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'

export default async function cleanupAfterResponse({ request, response, next }: HttpContextContract) {
  await next()

  response.on('finish', () => {
    // Safe to release request-scoped resources here
    request.ctx.clientCert = null
  })
}

This ensures that certificate data persists until the response is fully sent, eliminating Use After Free risks from early deallocation.

5. Validate and Sanitize Certificate Inputs

Even with mTLS, treat certificate data as untrusted. Validate structure, length, and fields to avoid edge cases that might trigger unsafe memory handling in native dependencies.

// Example validation using schema
import { schema } from '@ioc:Adonis/Core/Validator'

const certSchema = schema.create({
  subject: schema.string({ trim: true, escape: true }),
  issuer: schema.string({ trim: true, escape: true }),
  validFrom: schema.date(),
  validTo: schema.date({}, [ (value, data) => {
    if (value <= new Date()) {
      throw new Error('Certificate expired')
    }
  } ]),
})

// Use in middleware
const payload = await request.validate({ schema: certSchema })

Proper validation reduces the chance of malformed inputs causing erratic memory behavior in parsing libraries.