LDAP Injection in Symfony: How to Detect and Prevent Attacks

Lightweight Directory Access Protocol (LDAP) is a widely-used protocol to query and manage directory services. If improperly handled, user-supplied input to LDAP queries can lead to LDAP Injection attacks, enabling attackers to bypass authentication or extract sensitive data.

This article explores how to detect and prevent LDAP Injection vulnerabilities in Symfony applications, including coding examples, and showcases free tools and services you can use to keep your web app secure.

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🚨 What is LDAP Injection?

LDAP Injection is similar to SQL Injection but targets LDAP queries. An attacker manipulates inputs to alter the query logic.

For example:

$filter = "(uid=" . $_POST['username'] . ")";
$result = ldap_search($conn, $dn, $filter);

If the attacker sends:

*)(|(uid=*))  

The filter becomes:

(uid=*)(|(uid=*))

— matching all users!

🔍 How to Detect LDAP Injection in Symfony

✅ Input fields that get passed to LDAP queries without sanitization are prime suspects.
✅ Use automated tools like our Website Vulnerability Scanner to scan for injection flaws.

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Screenshot of the free tools webpage where you can access security assessment tools.

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🧰 Secure Coding: Preventing LDAP Injection in Symfony

1️⃣ Always Escape LDAP Special Characters

Symfony does not escape LDAP filters by default. Use PHP’s ldap_escape() properly:

use Symfony\Component\Ldap\Ldap;

$ldap = Ldap::create('ext_ldap', [...]);
$dn = 'dc=example,dc=com';

$username = ldap_escape($_POST['username'], '', LDAP_ESCAPE_FILTER);

$filter = sprintf('(uid=%s)', $username);
$result = $ldap->query($dn, $filter)->execute();

2️⃣ Whitelist and Validate Inputs

Validate inputs against a strict whitelist of allowed characters or formats:

if (!preg_match('/^[a-zA-Z0-9_]{3,20}$/', $_POST['username'])) {
    throw new \Exception("Invalid username format.");
}

3️⃣ Use Parameterized LDAP Queries (if possible)

Some libraries support a kind of parameterization. In Symfony’s Ldap component, you still have to manually sanitize.

4️⃣ Least Privilege Principle

Configure LDAP service accounts with the minimum privileges required. Even if injected, the damage is limited.

🧪 Testing LDAP Injection

You can test LDAP Injection vulnerabilities in development with payloads like:

*)(uid=*)

or

*)(!(uid=admin))

Use penetration testing services or automated scanners to ensure nothing is missed.

💡 Why You Should Test Regularly

LDAP Injection can creep in over time as your codebase evolves. Regular vulnerability assessments are crucial.
We recommend scheduling monthly vulnerability scans and quarterly penetration tests.

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Summary Table

If you enjoyed this post, don’t forget to visit our blog at 👉 Pentest Testing Corp for more articles like this!

🔗 TL;DR

✅ Escape inputs with ldap_escape()
✅ Use our free scanner for a website security check
✅ Regularly test & patch vulnerabilities
✅ Subscribe for more insights here

Want a free scan? DM me or check https://free.pentesttesting.com/