Dangling Dns in Actix with Cockroachdb

A dangling DNS configuration in an Actix-web service that connects to CockroachDB can expose the unauthenticated attack surface that middleBrick scans. When an Actix application resolves a database hostname to an unexpected or unresolved DNS address, requests may be routed to an unintended host or an abandoned endpoint. CockroachDB deployments often use service discovery or load balancers that depend on DNS records; if those records become stale or point to a decommissioned node, the Actix service may inadvertently connect to an unmanaged or misconfigured database instance.

During a black-box scan, middleBrick tests unauthenticated endpoints and inspects network-level behaviors. If the Actix service lacks strict hostname verification and fails to validate DNS resolution, an attacker could leverage DNS manipulation or observe how the service behaves when DNS returns a non-authoritative or malicious address. The risk is compounded when TLS is not enforced or certificate validation is skipped, as the service might accept connections from an unexpected peer while still transmitting authentication tokens in clear text within query parameters or headers.

SSRF and Data Exposure checks in middleBrick specifically look for scenarios where an application can be tricked into connecting to arbitrary hosts. With CockroachDB, this can manifest when an Actix endpoint accepts a database hostname or connection string from user input without strict allowlisting. The scanner tests whether an unauthenticated route can cause the backend to reach out to a controlled external address, potentially exfiltrating metadata or error messages that reveal internal deployment details. Because CockroachDB exposes an HTTP admin interface on certain ports, an SSRF pivot via a dangling DNS record could allow an attacker to probe internal cluster endpoints that would not be reachable under normal networking configurations.

Input Validation and Authentication checks highlight how missing constraints on connection parameters enable abuse. If an Actix application dynamically builds a CockroachDB connection string using concatenated strings rather than structured configuration, DNS-based injection becomes feasible. middleBrick’s active testing includes probes that attempt to override intended endpoints by supplying crafted inputs that alter hostname resolution behavior. When combined with weak certificate pinning or disabled TLS verification, this can lead to credentials or session tokens being transmitted to an unintended listener.

middleBrick’s LLM/AI Security checks are applicable when an Actix service generates or consumes AI-driven database tooling. If the service exposes endpoints that accept natural language prompts to construct CockroachDB queries, prompt injection attempts could manipulate query construction in ways that change the target hostname or schema. Output scanning ensures that sensitive data, API keys, or internal hostnames are not inadvertently returned in LLM responses, which is especially relevant when debugging DNS-related failures in distributed database environments.

To mitigate dangling DNS risks in an Actix service communicating with CockroachDB, enforce strict hostname validation and avoid dynamic DNS-based connection strings. Use structured configuration with explicit hostnames and pinned certificates, and ensure that connection parameters are not derived from untrusted input.

Example of a safe CockroachDB connection setup in Actix using static configuration and TLS verification:

use actix_web::{web, App, HttpServer, Responder};
use cockroach_client::{Client, Config};
use std::sync::Arc;

async fn health() -> impl Responder {
    "healthy"
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    // Static, validated connection parameters — not user-controlled
    let config = Config {
        hosts: vec!["cockroachdb-internal.service.cluster.local:26257".to_string()],
        database: "app_db".to_string(),
        username: "app_user".to_string(),
        password: Some("super-secure-password".to_string()),
        tls_cert_path: Some("/etc/certs/ca.crt".to_string()),
        tls_key_path: None,
        tls_skip_verify: false, // Enforce certificate validation
        ..Default::default()
    };

    let client = Arc::new(Client::new(config).expect("Failed to create CockroachDB client"));

    HttpServer::new(move || {
        App::new()
            .app_data(web::Data::new(client.clone()))
            .route("/health", web::get().to(health))
    })
    .bind("0.0.0.0:8080")?
    .run()
    .await
}

This approach ensures that DNS resolution is limited to a single, controlled hostname with enforced TLS verification. By avoiding host parameters from request inputs and using fixed service discovery records, the attack surface related to dangling DNS is minimized.

When configuration must be dynamic, validate and sanitize any hostname or port values against an allowlist and reject entries that do not match expected patterns. For example:

fn validate_db_host(input: &str) -> Result {
    let allowed_hosts = ["cockroachdb-internal.service.cluster.local", "read-only-replica.internal"];
    if allowed_hosts.contains(&input) {
        Ok(input.to_string())
    } else {
        Err("hostname not allowed")
    }
}

middleBrick’s Continuous Monitoring and GitHub Action integrations can help detect regressions by scanning your endpoints whenever configuration changes. The CLI can be integrated into build scripts to verify that connection strings remain within approved bounds, ensuring that dangling DNS misconfigurations are caught before deployment.