Ldap Injection in Adonisjs with Mutual Tls

Ldap Injection occurs when untrusted input is concatenated into LDAP query strings, allowing attackers to manipulate filter logic. In Adonisjs applications that integrate LDAP for authentication or directory lookups, this typically manifests in search filters built via string concatenation or insecure parameter interpolation. When Mutual Transport Layer Security (Mutual TLS) is used, the TLS channel is strongly authenticated and encrypted, which may create a false sense of overall security. Teams often assume Mutual TLS alone prevents injection, but it does not sanitize or validate application-level inputs. As a result, an attacker who can reach the endpoint (e.g., via a compromised client certificate subject or a trusted network path) can still exploit injection flaws in LDAP query construction. Mutual TLS secures the transport, but the application must independently validate and escape user-controlled data used in LDAP filters to prevent bypassing authorization or extracting sensitive directory entries.

Consider an Adonisjs controller that builds an LDAP filter using a username directly from a request:

const ldap = require('ldapjs');
const client = ldap.createClient({ url: 'ldaps://ldap.example.com' });

async login({ request }) {
  const { username, password } = request.only(['username', 'password']);
  // Unsafe: direct concatenation into filter
  const filter = `(uid=${username})`;
  const opts = {
    filter: filter,
    scope: 'sub'
  };
  return new Promise((resolve, reject) => {
    client.bind('cn=' + username + ',ou=users,dc=example,dc=com', password, (err) => {
      if (err) return reject(err);
      // ...issue token
    });
  });
}

An attacker can supply username as *)(uid=admin)(uid=admin -, turning the filter into (&(uid=*)(uid=admin)(uid=admin -), which may bypass authentication or extract entries via global matching. Even with Mutual TLS ensuring the client presenting the certificate is known, the LDAP query remains vulnerable because the application did not escape or parameterize the input. Adonisjs does not automatically escape values used in LDAP filter construction; developers must implement sanitization or use libraries that support parameterized filters. Additionally, logging or error messages triggered by malformed filters might disclose internal directory structure, aiding further attacks.

Mutual TLS also introduces a subtle risk: it may encourage less rigorous validation of inputs, since operators trust the channel. Attackers who obtain a valid client certificate (e.g., via compromise or misissuance) can interact with the Adonisjs app as a trusted client, but the application’s LDAP logic remains unchanged. Therefore, the combination of Mutual TLS and unchecked LDAP injection expands the potential impact: authenticated clients with valid certs can trigger injection paths that escalate to directory-wide searches or unauthorized binds. Defense requires treating Mutual TLS as a transport safeguard, not an application-level filter, and enforcing strict input validation and parameterized queries for all LDAP interactions.

Remediation focuses on preventing LDAP injection by avoiding string concatenation, using parameterized filters or escaping, and hardening Mutual TLS usage. Below are concrete patterns for Adonisjs that align with secure LDAP practices.

1. Parameterized LDAP filters

Use an LDAP library that supports structured filter objects or manual escaping. For ldapjs, construct filters using an array or object notation when possible, and escape special characters in untrusted input:

const ldap = require('ldapjs');
const client = ldap.createClient({ url: 'ldaps://ldap.example.com' });

function escapeLDAPValue(value) {
  if (!value || typeof value !== 'string') return value;
  return value.replace(/([*\\()&])/g, '\\$1');
}

async login({ request }) {
  const { username } = request.only(['username']);
  const safeUsername = escapeLDAPValue(username);
  // Use an object filter to avoid concatenation
  const filter = {
    '&': [
      { 'uid': safeUsername },
      { 'objectClass': 'inetOrgPerson' }
    ]
  };
  // Example bind using parameterized DN construction with escaping
  const bindDN = `uid=${safeUsername},ou=users,dc=example,dc=com`;
  return new Promise((resolve, reject) => {
    client.bind(bindDN, password, (err) => {
      if (err) return reject(err);
      // proceed
    });
  });
}

2. Validate and constrain input

Reject unexpected characters early. For identifiers like usernames, enforce a strict pattern:

function validateUsername(input) {
  const pattern = /^[a-zA-Z0-9._-]{3,64}$/;
  return pattern.test(input);
}

async login({ request, response }) {
  const { username, password } = request.only(['username', 'password']);
  if (!validateUsername(username)) {
    return response.badRequest({ error: 'Invalid username' });
  }
  const safeUsername = escapeLDAPValue(username);
  const filter = `(&(uid=${safeUsername})(objectClass=inetOrgPerson))`;
  // ... proceed with search or bind
}

3. Mutual TLS hardening and verification

Ensure Mutual TLS is configured to require and verify client certificates, and that the application does not skip validation when a cert is presented. In Adonisjs, you can enforce TLS settings at the HTTP server level and log anomalies without trusting the channel implicitly:

// Example: configuring an HTTPS server with mutual TLS in Adonisjs
const https = require('https');
const fs = require('fs');

const server = https.createServer({
  key: fs.readFileSync('/path/to/server-key.pem'),
  cert: fs.readFileSync('/path/to/server-cert.pem'),
  ca: fs.readFileSync('/path/to/ca-cert.pem'),
  requestCert: true,
  rejectUnauthorized: true
}, (req, res) => {
  // Your Adonisjs bootstrap
});

server.listen(443);

4. Combine with security checks

Run scans that include authentication and authorization checks to ensure that even with Mutual TLS, access controls are enforced at the application level. Use parameterized queries, strict input validation, and avoid embedding untrusted data directly in LDAP filters or DNs.