A Comprehensive Guide to LDAP Injection

What is LDAP Injection?

LDAP Injection is a type of cybersecurity attack that targets web applications by exploiting vulnerabilities in the implementation of the Lightweight Directory Access Protocol (LDAP). LDAP is widely used for directory services and enables functionalities like single sign-on. The attack occurs when an application constructs LDAP queries based on unsanitized user input, allowing attackers to manipulate these queries.

How Bug Hunters Can Identify LDAP Injection

Bug hunters play a crucial role in identifying LDAP Injection vulnerabilities. Here are targeted strategies they can use:

Identify User Input Points: Start by mapping out all the points in an application where user input is accepted. This could be login forms, search boxes, or any other input fields.
Fuzz Testing: Use fuzzing techniques to send unexpected, malformed, or semi-malicious data to these input points. Observe the application’s response for any behavior indicative of LDAP Injection, such as unusual error messages or unexpected application behavior.
Error Message Analysis: Pay close attention to LDAP error messages. These messages can sometimes reveal information about how the LDAP query is structured and processed, which can be leveraged to identify injection vulnerabilities.
Payload Crafting: Develop and test various LDAP Injection payloads. This includes manipulating LDAP query syntax by injecting special characters or operators (*, |, &, !, etc.) to alter the query’s logic.
Use of Automated Tools: Employ automated tools like Burp Suite to intercept, modify, and replay requests with potentially malicious LDAP queries. Tools like OWASP ZAP can also be used for automated scanning.
Check Authentication and Escaping Mechanisms: Examine how user inputs are authenticated and whether special characters in LDAP queries are properly escaped. Improper handling of these aspects often leads to LDAP Injection vulnerabilities.
Consult Documentation and Forums: Regularly check cybersecurity forums, bug bounty program updates, and LDAP-related documentation for new vulnerabilities and techniques.

LDAP Injection Example in Burp Repeater

Imagine a scenario where a web application uses LDAP for user authentication. The user supplies their username, and the application checks this against the LDAP server.

Normal Query: (uid=userInput)
Injected Query: (uid=*)(userPassword=*))(|(uid=*

In Burp Suite, you would capture the request to the server where the user input is sent. Then, using Burp Repeater, you could modify the request to include the injected query. The modified request might look like this:

POST /login HTTP/1.1
Host: vulnerable-app.com
Content-Length: 70
Content-Type: application/x-www-form-urlencoded

username=*)(userPassword=*))(|(uid=*)&password=pass

If the server responds with a successful authentication (despite the odd input), it’s a clear sign of vulnerability to LDAP Injection.

LDAP Injection Prevention

Preventing LDAP Injection primarily involves input validation and sanitization. Here are key strategies:

Sanitize Inputs: Ensure that all user inputs are sanitized before they are processed in LDAP queries. This includes escaping special characters.
Use Prepared Statements: Similar to SQL, using prepared statements with LDAP can help prevent injection.
Least Privilege Access: Configure LDAP permissions to adhere to the principle of least privilege, limiting what each query can access or modify.
Regular Audits and Updates: Regularly audit LDAP implementations for vulnerabilities and keep the LDAP services updated with the latest security patches.
Security Training: Educate developers about the risks of LDAP Injection and best practices for secure coding.

Conclusion

LDAP Injection is a critical vulnerability that can compromise the integrity of web applications using LDAP. By understanding what LDAP Injection is, how to detect it, and implement effective prevention measures, organizations can significantly bolster their cybersecurity posture against such attacks.