Ldap Injection in Express with Cockroachdb

LDAP Injection is an attack technique where untrusted input is concatenated into LDAP query strings, enabling attackers to bypass authentication, enumerate users, or modify directory queries. When an Express application uses CockroachDB as a backend data store while also integrating with an LDAP directory service (for authentication or user lookup), improper handling of user-supplied input can lead to LDAP Injection. This typically occurs when the application builds LDAP filter strings using string concatenation or interpolation rather than parameterized approaches.

In this specific stack, an Express route might accept a username or search term and forward it to an LDAP client library to perform a user search before interacting with CockroachDB for additional profile or session data. If the input is not strictly validated or escaped, an attacker can inject LDAP metacharacters such as (, ), &, |, !, or * to manipulate the LDAP query logic. For example, an input of admin)(uid=*))(|(uid= could turn a benign filter like (uid=alice) into (uid=alice)(uid=*))(|(uid=), potentially returning all users or bypassing authentication checks.

The exposure is amplified because the Express application may rely on the LDAP result to determine whether to proceed with CockroachDB operations, such as granting access tokens or logging audit records. An attacker who manipulates the LDAP query might cause the application to treat an unauthorized subject as authenticated, leading to vertical or horizontal privilege escalation. Moreover, if the LDAP client is misconfigured to follow referrals or expose verbose error messages, those responses can be leveraged to infer directory structure, which may complement reconnaissance against the CockroachDB instance.

middleBrick detects such risks through its unauthenticated black-box scanning and its dedicated LLM/AI Security checks, which include active prompt injection testing and system prompt leakage detection. While middleBrick does not fix the vulnerability, its findings include prioritized guidance to ensure input is escaped and queries are constructed safely.

To prevent LDAP Injection in an Express service that uses CockroachDB, you must ensure that any user-controlled data used in LDAP filters is either avoided or rigorously sanitized. Use parameterized LDAP APIs where available, and apply strict allowlist validation on identifiers such as usernames. Below are concrete examples demonstrating secure patterns.

First, validate and normalize the username using a strict allowlist. Only permit alphanumeric characters and a limited set of safe symbols:

const validateUsername = (username) => {
  return /^[a-zA-Z0-9._-]{3,32}$/.test(username);
};

Second, when constructing an LDAP filter, prefer an OR filter with equality checks on a single attribute rather than building complex concatenated strings. If your LDAP library supports parameterized filters, use them. Here is an example using a hypothetical ldapjs client where you bind safely:

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

const authenticate = (username, password, callback) => {
  if (!validateUsername(username)) {
    return callback(new Error('Invalid username format'));
  }

  const opts = {
    filter: '(uid={{username}})', // Use placeholders supported by your LDAP client
    scope: 'sub',
    timeout: 5000
  };

  // Example using a templating approach with strict escaping:
  const safeFilter = opts.filter.replace('{{username}}', username);

  client.bind(safeFilter, password, (err) => {
    if (err) {
      return callback(err);
    }
    // Proceed to verify session or interact with CockroachDB
    callback(null, { user: username });
  });
};

When the application subsequently interacts with CockroachDB, use parameterized SQL queries to avoid SQL Injection and maintain separation of concerns:

const { Client } = require('pg'); // Assuming a PostgreSQL-compatible driver for CockroachDB
const dbClient = new Client({ connectionString: process.env.COCKROACHDB_URI });

dbClient.connect();

const getUserProfile = async (username) => {
  if (!validateUsername(username)) {
    throw new Error('Invalid username format');
  }

  const query = 'SELECT id, email, last_login FROM users WHERE username = $1';
  const values = [username];
  const res = await dbClient.query(query, values);
  return res.rows[0];
};

By combining strict input validation, safe LDAP filter construction, and parameterized SQL queries against CockroachDB, you reduce the attack surface significantly. middleBrick’s scans can verify that your endpoints follow these practices by checking for unsafe string concatenation in API logic and ensuring that security headers and error messages do not leak directory service details.