Identification Failures in Actix with Mongodb

Identification failures occur when an API incorrectly identifies or fails to identify the user or resource being accessed. In Actix applications using MongoDB as the backend, this typically manifests as Insecure Direct Object References (IDOR) or Broken Object Level Authorization (BOLA). The combination is common because Actix is a Rust web framework often paired with MongoDB for flexible document storage, but it does not enforce authorization checks at the database or handler level by default.

Actix routes map HTTP methods to handler functions. If a handler retrieves a record by an identifier provided in the request (e.g., /users/{user_id}) and only validates that the identifier is well-formed, but does not confirm that the authenticated subject owns or is permitted to access that specific document, an identification failure occurs. MongoDB’s document-oriented model can inadvertently support this: a query such as users.find_one(filter) may return a document if the ID exists, regardless of whether the requester should be allowed to view it.

Consider an endpoint that fetches a user profile using a user-supplied ID. If the handler only checks authentication (e.g., a valid JWT) and then queries MongoDB with that ID, an attacker can modify the ID to enumerate other users’ profiles. Because MongoDB does not inherently understand application-level authorization, it will return the document if the ID exists. Actix does not automatically correlate route parameters with access control rules, so the developer must explicitly enforce ownership or role-based checks before returning data.

More complex identification failures arise when related resources are referenced by indirect identifiers. For example, an endpoint might accept an order_id, fetch the order from MongoDB, and return details without verifying that the order belongs to the authenticated user or that the user has permission to view that order. In MongoDB, if the query uses a simple equality filter like { "_id": ObjectId("..."), "user_id": user_id } and the user_id is taken directly from the request instead of from the authenticated session, the check can be trivially bypassed.

Another subtlety involves the use of string vs. ObjectId types. If Actix deserializes an ID as a string but MongoDB stores ObjectId, a type mismatch can lead to a failed lookup that may be misinterpreted as “not found” rather than “not permitted,” potentially causing the application to leak existence information or handle errors inconsistently. This can complicate logging and monitoring, making it harder to detect enumeration attempts.

In practice, identification failures with Actix and MongoDB stem from missing or incomplete authorization checks, over-reliance on route-level security, and improper handling of identifiers. Because MongoDB is a powerful query engine, developers must ensure that every query incorporates the subject’s identity or permissions as a core filter condition, not an afterthought.

To remediate identification failures in Actix with MongoDB, enforce authorization at the handler level by ensuring every MongoDB query includes the authenticated subject’s identifier or role as part of the filter. Never trust client-supplied identifiers alone; derive access context from the session or token and combine it with the requested resource identifier.

Use strongly typed IDs and consistent ObjectId handling to avoid type confusion. In Actix, extract the authenticated user’s ID from the request extensions or session, then build a filter that combines the requested resource identifier with the subject’s identity.

The following example demonstrates a secure handler pattern. First, define a structure for the authenticated context:

struct AuthContext {
    user_id: mongodb::bson::oid::ObjectId,
    roles: Vec,
}

In your Actix handler, retrieve the context from request extensions and use it to scope the MongoDB query:

use actix_web::{web, HttpRequest, HttpResponse};
use mongodb::{bson::doc, Client};

async fn get_user_profile(
    req: HttpRequest,
    client: web::Data,
    path: web::Path,
) -> HttpResponse {
    let auth_ctx = req.extensions().get::().unwrap();
    let requested_id = match mongodb::bson::oid::ObjectId::parse_str(&path) {
        Ok(id) => id,
        Err(_) => return HttpResponse::BadRequest().finish(),
    };

    let filter = doc! {
        "_id": requested_id,
        "user_id": auth_ctx.user_id,
    };
    let collection = client.database("app").collection("users");
    match collection.find_one(filter, None).await {
        Ok(Some(doc)) => HttpResponse::Ok().json(doc),
        Ok(None) => HttpResponse::NotFound().finish(),
        Err(_) => HttpResponse::InternalServerError().finish(),
    }
}

This ensures that even if an attacker changes the _id in the URL, the query will only return the document if the user_id field matches the authenticated subject’s ID. For endpoints that involve related resources, such as orders, apply the same principle by including the subject’s identifier or a tenant/workspace identifier in the filter:

async fn get_order(
    req: HttpRequest,
    client: web::Data,
    path: web::Path<(String, String)>,
) -> HttpResponse {
    let auth_ctx = req.extensions().get::().unwrap();
    let (user_id, order_id) = path.into_inner();
    let user_oid = match mongodb::bson::oid::ObjectId::parse_str(&user_id) {
        Ok(id) => id,
        Err(_) => return HttpResponse::BadRequest().finish(),
    };
    let order_oid = match mongodb::bson::oid::ObjectId::parse_str(&order_id) {
        Ok(id) => id,
        Err(_) => return HttpResponse::BadRequest().finish(),
    };

    let filter = doc! {
        "_id": order_oid,
        "user_id": user_oid,
    };
    let collection = client.database("app").collection("orders");
    match collection.find_one(filter, None).await {
        Ok(Some(order)) => HttpResponse::Ok().json(order),
        Ok(None) => HttpResponse::Forbidden().finish(),
        Err(_) => HttpResponse::InternalServerError().finish(),
    }
}

For role-based access, extend the filter with additional conditions derived from roles, but always keep the subject’s identity as a mandatory clause. Avoid building filters by concatenating strings or using raw user input directly in the query structure. Validate and sanitize all identifiers, and prefer ObjectId parsing over string-based lookups to reduce injection risks and type mismatches.