Xpath Injection in Adonisjs with Mutual Tls

XPath Injection occurs when untrusted input is concatenated into an XPath expression without proper validation or escaping, enabling attackers to alter query logic and access unauthorized data. In AdonisJS, this typically arises when user-controlled values are used directly with XML/HTML parsers or custom XPath helpers. Mutual TLS (mTLS) adds client certificate authentication to the transport layer, ensuring that only authorized clients can reach the server. While mTLS strengthens authentication and integrity, it does not reduce the risk of injection flaws in application code; a compromised or malicious authenticated client can still supply malicious XPath input if the server does not sanitize it. Thus, the combination of AdonisJS with mTLS creates a scenario where an authenticated attacker who possesses a valid client certificate can exploit XPath Injection to bypass authorization checks or extract sensitive data, provided the server builds dynamic XPath expressions from unchecked inputs.

Consider an AdonisJS route that authenticates a user by querying an XML credential store using an XPath expression built from request parameters:

const { request } = use('request')
const xpath = `//user[username='${request.input('username')}' and password='${request.input('password')}']`
// hypothetical XML XPath lookup
const result = evaluateXPath(xpath)

An attacker supplying username as admin' or '1'='1 can manipulate the expression to return the first user node, potentially bypassing authentication. Even with mTLS ensuring the request originates from a trusted client, the server must treat all inputs as untrusted. mTLS does not mitigate injection because it operates at the transport layer, whereas XPath Injection is a data validation and query construction issue at the application layer. Proper remediation requires strict input validation, parameterized queries, or using dedicated XML libraries that support compiled XPath expressions with bound variables rather than string interpolation.

XPath Injection maps to the OWASP API Top 10 category 'Broken Object Level Authorization' and can lead to unauthorized data access or privilege escalation when combined with other weaknesses. In the context of middleBrick scans, this would be flagged under Property Authorization and Input Validation checks. Developers should avoid constructing XPath via string concatenation, prefer XPath functions that accept parameters, and enforce strict allowlists on input patterns. Security testing with tools that include unauthenticated and authenticated attack paths, such as active probes that include XPath manipulation, helps identify these issues before deployment.

Remediation centers on preventing untrusted input from affecting XPath construction and ensuring mTLS is correctly enforced. The most effective approach is to avoid dynamic XPath strings entirely. Use libraries or frameworks that support parameterized XPath or compile expressions with bound variables. If you must construct XPath, apply strict allowlist validation and escape dangerous characters. Below are concrete AdonisJS examples that demonstrate secure handling alongside mTLS configuration.

1) Example mTLS setup in AdonisJS (server-side configuration):

// start/hooks.ts or a dedicated tls configuration file
import { defineConfig } from '@ioc:Adonis/Core/Application'
import { join } from 'path'

export default defineConfig({
  https: {
    enabled: true,
    key: join(__dirname, '../certs/server.key'),
    cert: join(__dirname, '../certs/server.crt'),
    ca: join(__dirname, '../certs/ca.crt'),
    requestCert: true,
    rejectUnauthorized: true,
  },
})

This configuration ensures the server requests and validates client certificates. Only clients presenting a certificate signed by the trusted CA can establish a connection. Note that mTLS configuration does not alter how XPath expressions are built; it simply controls who can reach the endpoint.

2) Secure XPath handling using parameterized approaches or strict validation:

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

// Input validation schema to enforce allowlist patterns
const userQuerySchema = schema.create({
  username: schema.string({ trim: true, escape: false }, [
    (value) => /^[a-zA-Z0-9_]{3,30}$/.test(value) || 'username_format',
  ]),
})

// In a controller, validate before any XML processing
export async def authenticate({ request, response }) {
  const payload = await request.validate({ schema: userQuerySchema })
  // Use a library that supports compiled XPath with parameters
  const compiled = xpath.compile('//user[username=$username and password=$password]')
  const result = compiled({
    username: payload.username,
    password: hashPassword(payload.password),
  })
  // proceed with authenticated logic
}

3) Alternative: Use a dedicated XML library that avoids string-based XPath construction:

import { parse } from 'fast-xml-parser'
// Validate and transform XML to a structured object, then apply application-level checks
const xmlData = parse(xmlString, { ignoreAttributes: false })
const users = xmlData['users']['user']
const user = users.find(u => u.username === payload.username && u.password === hashed)

These approaches ensure that even authenticated requests cannot inject malicious XPath. MiddleBrick scans can verify that inputs are properly constrained and that XPath construction does not concatenate raw user input. Remediation guidance from middleBrick will highlight insecure patterns and map findings to relevant compliance frameworks such as OWASP API Top 10 and SOC2 controls.