Ldap Injection in Actix with Mongodb

Ldap Injection occurs when an attacker can manipulate LDAP query construction, typically by injecting special characters such as *, (, ), or & into input that is concatenated into an LDAP filter string. In an Actix web service that uses an LDAP server for authentication and then stores or references user state in MongoDB, the LDAP interaction is often the injection surface while MongoDB may be used for application data or logging. If user-controlled input is passed unsanitized into the LDAP filter, an attacker can bypass authentication or extract additional data via crafted responses.

Consider an Actix handler that builds an LDAP filter directly from a username parameter:

let filter = format!("(&(objectClass=user)(sAMAccountName={}))", username);

If username contains *)(objectClass=user)(sAMAccountName=*, the resulting filter can return unintended entries, potentially allowing authentication as another user. Even if authentication ultimately relies on LDAP, the application may record authentication events or user metadata in MongoDB. In such flows, the LDAP injection grants initial access or information, and MongoDB may be leveraged for persistence or data exfiltration if additional logic trusts the LDAP-derived identity without further validation.

Because middleBrick tests unauthenticated attack surfaces, it can detect endpoints where LDAP-related inputs are exposed without validation or escaping. The scanner’s checks for Input Validation and Authentication highlight these risks, and findings can map to relevant compliance frameworks such as OWASP API Top 10 and SOC2. Note that middleBrick detects and reports these issues without fixing them; it provides remediation guidance to help developers adjust how inputs are handled before being used in LDAP filters.

To prevent LDAP injection in Actix, avoid concatenating user input into LDAP filter strings. Use parameterized approaches or an LDAP library that supports proper escaping. For MongoDB interaction, use the official MongoDB Rust driver safely with strongly typed data models and avoid injecting LDAP-derived values directly into queries without validation.

Below are concrete, realistic examples for Actix with MongoDB.

1. Safe LDAP filter construction with escaping

Use an LDAP escape function to neutralize special characters in user input before building the filter. In Rust, you can implement a simple escaping helper or rely on an LDAP crate that provides escaping utilities.

/// Escape special characters for LDAP filter substrings.
fn ldap_escape(input: &str) -> String {
    // Replace * with \2a, ( with \28, ) with \29, \ with \5c, and NUL with \00
    input.replace('\\', "\\5c")
        .replace('*', "\\2a")
        .replace('(', "\\28")
        .replace(')', "\\29")
        .replace('\u0000', "\\00")
}

async fn authenticate_escaped(username: web::Form<Login>, ldap_client: &LdapConnAsync) -> Result<HttpResponse, Error> {
    let safe_username = ldap_escape(&username.id);
    let filter = format!("(&(objectClass=user)(sAMAccountName={}))", safe_username);
    // Perform LDAP search/bind using the escaped filter
    // ...
    Ok(HttpResponse::Ok().finish())
}

This ensures that characters used in LDAP filters cannot alter the filter structure.

2. Using a parameterized LDAP crate (example concept)

If your LDAP library supports bind with structured filters, prefer that over manual string formatting. The following is illustrative, showing intent rather than a specific crate API:

// Assume a higher-level LDAP API that accepts filter components safely:
// ldap_client.search(base_dn, scope, Filter::eq("sAMAccountName", &username), vec!["dn"]);
// The library handles encoding and prevents injection.

3. MongoDB operations using safe Rust types in Actix

Use the official MongoDB Rust driver with strongly typed documents. Do not directly embed LDAP-derived values into MongoDB queries without validation.

use mongodb::{bson::{doc, oid::ObjectId}, options::ClientOptions, Client};

async fn store_auth_event(client: &Client, username: &str, ldap_result: &str) -> mongodb::error::Result<()> {
    let db = client.database("events");
    let coll = db.collection("auth_logs");
    let document = doc! {
        "username": username,
        "ldap_result": ldap_result,
        "timestamp": chrono::Utc::now(),
    };
    coll.insert_one(document, None).await?;
    Ok(())
}

Validate and sanitize any data derived from LDAP before using it in MongoDB queries. For example, if you must query MongoDB using a field that originated from LDAP, ensure it matches an expected pattern (e.g., a known user ID format) and use exact matches rather than raw string concatenation.

4. Actix handler combining safe LDAP and MongoDB usage

async fn login_handler(
    form: web::Form<Login>,
    ldap_client: web::Data<LdapConnAsync>,
    mongo_client: web::Data<Client>,
) -> Result<HttpResponse, Error> {
    let safe_username = ldap_escape(&form.id);
    let filter = format!("(&(objectClass=user)(sAMAccountName={}))", safe_username);
    // Perform LDAP bind/search with `filter`
    let ldap_valid = perform_ldap_bind(&ldap_client, &filter, &form.password).await?;

    if ldap_valid {
        // Safe: store an event in MongoDB using typed documents, not LDAP-derived filter strings.
        store_auth_event(&mongo_client, &form.id, "success").await?;
        Ok(HttpResponse::Ok().json(json!({ "status": "ok" })))
    } else {
        // Safe: log failed attempts without exposing internal details.
        store_auth_event(&mongo_client, &form.id, "failed").await?;
        Ok(HttpResponse::Unauthorized().json(json!({ "error": "invalid credentials" })))
    }
}

By escaping user input for LDAP and using typed MongoDB operations, you reduce the risk of injection across both systems. middleBrick can help identify endpoints where input validation is missing and where LDAP-related parameters are exposed, supporting a more secure implementation.