Dangling Dns in Actix with Firestore

A dangling DNS configuration in an Actix service that interacts with Google Cloud Firestore can expose unauthenticated or over-privileged endpoints, increasing the risk of data exposure or unauthorized access. When an Actix application resolves a DNS name that points to an internal or restricted Firestore endpoint, misconfigured DNS records or stale entries may route traffic to a resource that should not be publicly reachable. If the Firestore rules are not strictly limiting access to authenticated requests, the Actix service might inadvertently allow unauthenticated scans or calls through the exposed DNS name.

In a black-box scan, middleBrick tests unauthenticated attack surfaces across 12 security checks, including Authentication, BOLA/IDOR, and Data Exposure. When an Actix endpoint resolves to a Firestore host with weak rules, the scan can detect whether unauthenticated reads or writes are possible. For example, if a DNS name like firestore-internal.example.com resolves to a Firestore instance that allows list or get operations without proper authentication tokens, middleBrick flags this as a data exposure finding. The scanner does not rely on internal architecture details, but the observable behavior—successful unauthenticated requests to the Firestore REST or gRPC endpoints via the DNS name—triggers a high-severity alert.

The combination is risky because Actix services often handle dynamic requests that may forward credentials or tokens to Firestore. If DNS resolution is misconfigured, requests meant for a private backend might reach a public or improperly restricted Firestore instance. This can lead to sensitive document reads or writes, especially if Firestore security rules rely on request origin checks that DNS manipulation can bypass. middleBrick’s LLM/AI Security checks do not apply here, but the scan’s Authentication and Data Exposure checks will highlight the missing controls. Remediation guidance typically involves tightening Firestore rules, validating DNS targets, and ensuring Actix clients use authenticated client libraries rather than raw HTTP calls to Firestore endpoints.

To remediate dangling DNS and access issues between Actix and Firestore, implement strict authentication and validated DNS usage. Use the official Google Cloud Firestore client for Rust, which ensures requests are signed with appropriate service account credentials and avoids raw HTTP calls that might bypass security rules. Configure your Actix service to resolve DNS names only from a controlled list of approved hosts and avoid relying on environment variables that can be overridden at runtime.

Example using the Firestore client with service account authentication in an Actix handler:

use actix_web::{web, HttpResponse, Result};
use google_cloud_firestore::client::{Client, ClientConfig};
use google_cloud_firestore::auth::Authenticator;
use std::sync::Arc;

async fn get_document(
    path: web::Path,
    client_data: web::Data>,
) -> Result {
    let doc_path = path.into_inner();
    let client = &*client_data;
    let doc = client.get_document(&doc_path).await.map_err(|e| {
        actix_web::error::ErrorInternalServerError(format!("Firestore error: {:?}", e))
    })?;
    Ok(HttpResponse::Ok().json(doc))
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    // Configure using a service account key file or workload identity
    let config = ClientConfig::default().with_auth().await.expect("auth");
    let client = Arc::new(Client::new(config));

    actix_web::HttpServer::new(move || {
        actix_web::App::new()
            .app_data(web::Data::new(Arc::clone(&client)))
            .route("/documents/{id}", actix_web::web::get().to(get_document))
    })
    .bind("127.0.0.1:8080")?
    .run()
    .await
}

In this example, the Firestore client is initialized once and shared across Actix handlers via web::Data. The client uses Application Default Credentials, which should point to a service account with least-privilege Firestore IAM roles. Avoid constructing Firestore URLs manually or using raw HTTP requests to hostnames that may be affected by DNS misconfigurations. middleBrick’s CLI can verify that your endpoints require authentication by running middlebrick scan <url> against your Actix base URL and reviewing the Authentication and Data Exposure findings.

Additionally, validate DNS resolution at build time and avoid runtime overrides that could redirect to unintended hosts. In CI/CD, you can integrate the GitHub Action to fail builds if security scores drop below your defined threshold, ensuring that changes to Firestore rules or DNS references are reviewed before deployment. For continuous monitoring, the Pro plan supports scheduled scans and alerts, which can notify you if unauthenticated access patterns are detected on any DNS-resolved endpoint.