Integrity Failures in Actix with Mongodb

An integrity failure occurs when an application allows unauthorized or unexpected changes to data, bypassing business rules or ownership checks. In an Actix web service that uses MongoDB as the primary data store, this typically arises from a mismatch between how Actix enforces route-level authorization and how the application constructs and trusts MongoDB queries. If Actix passes user-supplied identifiers directly into a database operation without validating ownership or schema constraints, the unauthenticated attack surface examined by middleBrick can expose BOLA/IDOR and BFLA/Privilege Escalation patterns.

Consider a typical Actix handler that retrieves and updates a user profile stored in MongoDB. If the handler extracts a user_id from the path (e.g., /users/{user_id}/profile) and uses it to build a MongoDB filter without verifying that the authenticated actor is indeed that user, an attacker can change the user_id in the request to access or modify another user’s document. Because Actix routes often rely on extractor patterns that do not inherently enforce ownership, and MongoDB queries may be built naively by string interpolation or unchecked unwraps, the effective permission boundary collapses. middleBrick’s checks for BOLA/IDOR and Property Authorization are designed to detect such missing ownership gates in the runtime behavior of the API.

Compounding the issue, MongoDB’s flexible schema and rich query operators can inadvertently permit privilege escalation if updates use unrestricted modifiers (e.g., $set on nested fields) without stripping administrative flags like is_admin. In Actix, if a handler applies an update based on user input without a strict allowlist, an attacker may supply fields that modify permissions or roles stored in the document. Because the scan tests unauthenticated attack surfaces and runs checks in parallel for Privilege Escalation and Property Authorization, it can surface these routes where trust is placed in the client to decide which fields are mutable.

Data integrity can also be undermined by insufficient input validation. If Actix deserializes incoming JSON into a MongoDB document without enforcing strict type constraints or schema requirements, an attacker can inject unexpected operators (e.g., $inc, $unset) or malformed structures that either corrupt data or change semantics. middleBrick’s Input Validation checks look for such risky patterns by correlating OpenAPI specifications with runtime behavior, and it flags endpoints where untrusted input directly shapes database operations without sanitization.

When an API exposes an unauthenticated MongoDB-derived response that includes sensitive or computed fields, data exposure follows. For example, an Actix endpoint that returns a full document after a find_one call might leak fields such as internal IDs, hashes, or tokens if projection is not explicitly limited. Because middleBrick performs unauthenticated scans and analyzes the API surface without credentials, it can identify endpoints where sensitive data is returned without proper field-level restrictions, aligning with Data Exposure checks and informing the need for explicit projection in queries.

Remediation centers on enforcing ownership at the handler level, using strict schemas, and ensuring update operators are scoped safely. Below are concrete, realistic code examples for an Actix service using the official MongoDB Rust driver.

1) Enforce ownership by validating the actor against the document owner before constructing the filter:

use actix_web::{web, HttpResponse};
use mongodb::{bson::{doc, oid::ObjectId}};

async fn get_user_profile(
    user_id: web::Path,
    actor_id: String, // from extractor or auth middleware
    coll: web::Data>,
) -> HttpResponse {
    let filter = doc! {
        "_id": ObjectId::parse_str(&user_id).unwrap(),
        "owner_id": actor_id,
    };
    match coll.find_one(filter, None).await {
        Ok(Some(doc)) => HttpResponse::Ok().json(doc),
        Ok(None) => HttpResponse::NotFound().finish(),
        Err(_) => HttpResponse::InternalServerError().finish(),
    }
}

async fn update_user_profile(
    user_id: web::Path,
    actor_id: String,
    update_body: web::Json,
    coll: web::Data>,
) -> HttpResponse {
    let allowed = ["display_name", "email", "theme"];
    let update = update_body.iter().filter(|(k, _)| allowed.contains(&k.as_str())).collect::>();
    // Ensure immutable admin fields are not present
    let update_doc = doc! { "$set": update };
    let filter = doc! {
        "_id": ObjectId::parse_str(&user_id).unwrap(),
        "owner_id": actor_id,
    };
    match coll.update_one(filter, update_doc, None).await {
        Ok(result) if result.matched_count == 1 => HttpResponse::NoContent().finish(),
        Ok(_) => HttpResponse::NotFound().finish(),
        Err(_) => HttpResponse::InternalServerError().finish(),
    }
}

async fn list_public_fields(
    actor_id: String,
    coll: web::Data>,
) -> HttpResponse {
    let filter = doc! { "owner_id": actor_id };
    let projection = doc! { "display_name": 1, "email": 1, "_id": 0 };
    match coll.find_one_with_options(filter, mongodb::options::FindOneOptions::builder().projection(projection).build()).await {
        Ok(Some(doc)) => HttpResponse::Ok().json(doc),
        Ok(None) => HttpResponse::NotFound().finish(),
        Err(_) => HttpResponse::InternalServerError().finish(),
    }
}

fn validate_string_field(value: &str) -> bool {
    // Basic alphanumeric and space/underscore allowlist
    value.chars().all(|c| c.is_alphanumeric() || c == ' ' || c == '_')
}