Ldap Injection in Cassandra

LDAP injection in a Cassandra context does not target Cassandra's CQL query language directly, as Cassandra does not natively process LDAP queries. Instead, the vulnerability arises in applications that use Cassandra's PasswordAuthenticator configured for LDAP authentication. Cassandra itself delegates authentication to an external LDAP server. The injection flaw occurs when an application (or an API layer) constructs the LDAP bind DN or search filter using unsanitized user input, typically from an API request, before passing it to Cassandra's authentication mechanism.

Consider a Java application using the DataStax Java driver with Cassandra's LDAP authentication. A common vulnerable pattern is dynamically building the bind DN or search filter string:

// VULNERABLE: Direct concatenation of user input into LDAP query
String username = request.getParameter("username");
String password = request.getParameter("password");

// This bind DN is constructed from user input without sanitization
String bindDN = "uid=" + username + ",ou=users,dc=example,dc=com";

// The application then uses this bindDN with Cassandra's PasswordAuthenticator
// If an attacker provides username: "admin)(&(userPassword=*))"
// The resulting bindDN becomes: uid=admin)(&(userPassword=*)),ou=users,dc=example,dc=com
// This changes the LDAP query logic, potentially allowing authentication as 'admin'.

The attacker's payload admin)(&(userPassword=*)) closes the uid= filter prematurely and injects a new condition that always evaluates to true ((userPassword=*)), effectively bypassing password verification. This is a classic LDAP injection (CWE-90) manifesting through the Cassandra authentication pathway.

Detecting LDAP injection in a Cassandra-secured API requires testing the authentication endpoints that ultimately interact with Cassandra's LDAP authenticator. middleBrick performs black-box scanning by sending crafted payloads to the API's login or token endpoints and analyzing responses for authentication bypass indicators.

During its Input Validation and Authentication checks, middleBrick submits payloads like:

• username=*)(uid=*)
• username=admin)(&(userPassword=*))
• username=*)(|(userPassword=*))

It then compares the HTTP status codes, response bodies, and timing against baseline (valid/invalid credential) responses. A successful LDAP injection might return a 200 OK with an authentication token for an otherwise unauthorized user, or a different error message that reveals query structure.

If the API's OpenAPI/Swagger specification documents an authentication parameter (e.g., a username field in a login request body), middleBrick cross-references this with its runtime findings. A mismatch where the spec indicates a simple string but runtime testing shows it's used in an LDAP context can be a finding. The scanner's report will highlight the specific endpoint, parameter, and payload that succeeded, along with a severity rating (typically High or Critical).

You can manually verify this using the middleBrick CLI tool:

middlebrick scan https://api.example.com/v1/login

The resulting report will include a per-category breakdown. A detection under the Authentication or Input Validation categories with a finding description like "Potential LDAP injection via username parameter" indicates this specific issue.

Remediation occurs at the application layer that interfaces with Cassandra's LDAP authentication. The core principle is to never concatenate user input into LDAP query strings. Instead, use proper escaping or, where supported, parameterized LDAP queries. Since the DataStax driver and Cassandra's PasswordAuthenticator typically accept a pre-constructed bind DN or search filter, the application must sanitize input before it reaches Cassandra.

1. Use LDAP-Escaping Utilities

Java applications can use the javax.naming.ldap.LdapName and javax.naming.ldap.Rdn classes to safely construct Distinguished Names (DNs) from user input. This automatically escapes special characters like ), (, *, and \.

// SECURE: Using LdapName to safely build the DN
String unsafeUsername = request.getParameter("username");

// LdapName will escape any special characters in the username
LdapName safeUserDN = new LdapName("uid=" + unsafeUsername + ",ou=users,dc=example,dc=com");

// The escaped DN is now safe to use as the bind DN
String bindDN = safeUserDN.toString();
// Example: if unsafeUsername is "admin)(&(userPassword=*))",
// safeUserDN.toString() becomes: uid=admin\29\28\26\28userPassword=\2a\29,ou=users,dc=example,dc=com

2. Configure Cassandra's LDAP Search Filter with Placeholders

In cassandra.yaml, the ldap.search.filter setting can use numbered placeholders like {0}. The application must then provide a sanitized value that replaces {0}. Ensure the value passed is already escaped using the method above.

# cassandra.yaml
authenticator: PasswordAuthenticator
...
ldap:
  search_filter: "(uid={0})"  # {0} will be replaced by the application-provided username

3. Implement an Allowlist

For usernames, consider an allowlist of permitted characters (e.g., alphanumeric, dots, hyphens) at the application API layer before any LDAP processing.

// Simple allowlist check
String username = request.getParameter("username");
if (!username.matches("^[a-zA-Z0-9._-]+$")) {
    throw new IllegalArgumentException("Invalid username format");
}
// Proceed with safe username

4. Defense in Depth

Ensure the LDAP server itself is configured with strict access controls. The Cassandra service account should have only bind and search permissions on the specific user OU, limiting the blast radius of a successful injection.

Remember: middleBrick will detect the presence of this vulnerability but does not fix it. Use its remediation guidance to locate the vulnerable code path in your application that constructs the LDAP query for Cassandra's authenticator.