Buffer Overflow in Adonisjs with Basic Auth

A buffer overflow in an AdonisJS application that uses HTTP Basic Authentication arises when the runtime reads the Authorization header and copies credential data into a fixed-size buffer without proper length checks. AdonisJS itself does not introduce the overflow, but application code that parses or forwards the header value unsafely can trigger it. For example, if route handlers or custom auth providers directly copy the decoded username or password into a fixed-length character array, an attacker can supply credentials longer than the buffer, overwriting adjacent memory and potentially altering control flow or causing crashes.

During a black-box scan, middleBrick tests the unauthenticated attack surface and flags risky patterns such as missing input validation on authentication headers. In the context of Basic Auth, this includes long usernames or passwords, malformed base64-encoded credentials, or header smuggling attempts that bypass expected size limits. The LLM/AI Security checks further probe whether authentication endpoints expose behaviors that could be leveraged in prompt injection or data exfiltration scenarios, though the primary concern here is memory safety rather than AI-specific attacks.

Real-world examples in other frameworks illustrate the risk: CVE-2021-23337 involved CORS mishandling that permitted cross-origin credential leakage, and similar logic errors can appear in custom AdonisJS auth flows. Because Basic Auth credentials are base64-encoded rather than encrypted, any additional exposure—such as improper logging of headers—amplifies the impact. middleBrick’s authentication and data exposure checks highlight such misconfigurations by correlating runtime behavior with the OpenAPI specification, ensuring that credential handling aligns with secure design expectations.

Secure handling of Basic Auth in AdonisJS focuses on avoiding fixed buffers, validating header length, and using framework-provided utilities instead of manual parsing. Always prefer AdonisJS built-in auth mechanisms or well-maintained packages that manage credentials safely.

Example: Safe Basic Auth provider using built-in validation

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

const authSchema = schema.create({
  username: schema.string({}, [rules.minLength(1), rules.maxLength(128)]),
  password: schema.string({}, [rules.minLength(1), rules.maxLength(256)])
})

export default class AuthController {
  public async login({ request, auth, response }: HttpContextContract) {
    // Validate header presence and shape before decoding
    const header = request.header('authorization')
    if (!header || !header.startsWith('Basic ')) {
      return response.unauthorized()
    }

    const base64 = header.split(' ')[1]
    if (!base64) {
      return response.badRequest({ message: 'Missing credentials' })
    }

    // Use validator to enforce length and type constraints
    const payload = request.validate({ schema: authSchema, from: 'header' })

    // Delegate to AdonisJS auth guard to avoid manual credential handling
    const token = await auth.attempt(payload.username, payload.password)
    return response.ok({ token })
  }
}

Example: Reject suspiciously long credentials early

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

export default class SecureAuthController {
  public async login({ request, response }: HttpContextContract) {
    const header = request.header('authorization') || ''
    const prefix = 'Basic '
    if (!header.startsWith(prefix)) {
      return response.unauthorized()
    }

    const base64 = header.slice(prefix.length)
    if (base64.length > 4096) { // reasonable upper bound for encoded credentials
      return response.badRequest({ message: 'Credential header too long' })
    }

    try {
      const decoded = Buffer.from(base64, 'base64').toString('utf8')
      const separator = ':'
      const index = decoded.indexOf(separator)
      if (index <= 0) throw new Error('Invalid format')

      const username = decoded.slice(0, index)
      const password = decoded.slice(index + 1)

      if (username.length > 128 || password.length > 256) {
        return response.badRequest({ message: 'Credential length exceeds limit' })
      }

      // Proceed with framework-managed authentication
      // e.g., await auth.use('api').attempt(username, password)
      response.ok({ status: 'ok' })
    } catch (error) {
      return response.badRequest({ message: 'Invalid credentials' })
    }
  }
}

Key remediation practices include: enforcing maximum header and credential lengths, validating base64 format before decoding, using framework-native auth guards to avoid manual string handling, and ensuring errors do not leak sensitive information. These steps reduce the attack surface that could lead to buffer overflow conditions or credential exposure.