Dangling Dns in Axum with Cockroachdb

A dangling DNS configuration in an Axum service that uses CockroachDB can expose connection and routing weaknesses that affect authentication, input validation, and data exposure checks. Axum is a Rust web framework, and when it initializes a database client it typically resolves a hostname (for example, cockroachdb.internal.svc) to an IP address. If this resolution happens once at startup and the resulting IP is cached, changes in the underlying DNS records (such as a failover or a temporary test endpoint) may not be reflected in the runtime connection pool. CockroachDB deployments often rely on service discovery via DNS, especially in Kubernetes environments where a headless Service provides a stable DNS name that resolves to multiple pod IPs.

If the Axum application does not re-resolve the DNS name periodically or on failure, it may continue to route traffic to an outdated or unintended endpoint. This can lead to connections being sent to a non-production cluster, an intercepting proxy, or a host that no longer serves CockroachDB. In a black-box scan, middleBrick tests such scenarios under unauthenticated attack surface conditions: it checks whether the API allows unexpected redirection or whether input validation around hostnames is lax. A weak hostname configuration can amplify risks categorized under Authentication and Data Exposure, because traffic may be directed to an unintended party that could observe or manipulate database responses.

Moreover, if the Axum application embeds the DNS name directly in logs, error messages, or HTTP redirects, it may contribute to information leakage. middleBrick’s Data Exposure and Input Validation checks look for sensitive data in responses and traces, and a hostname that reveals internal infrastructure can aid an attacker in crafting further attacks, such as SSRF against the CockroachDB HTTP admin UI or probing for misconfigured authentication endpoints. The LLM/AI Security checks do not apply here because this scenario involves infrastructure misconfiguration rather than prompt injection or model abuse, but the overall risk score is influenced by how the combination of Axum routing logic and CockroachDB DNS-based service discovery interacts.

Remediation focuses on ensuring that DNS resolution in Axum remains accurate over time and that connection handling does not assume a static endpoint. Use a connection pool that supports re-resolution or implement periodic refresh logic. Below are concrete, realistic examples for an Axum application connecting to CockroachDB via sqlx with TLS disabled for simplicity (enable it in production).

// Cargo.toml dependencies
// [dependencies]
// axum = "0.6"
// sqlx = { version = "0.7", features = ["runtime-tokio", "postgres", "uuid"] }
// tokio = { version = "1", features = ["full"] }
// tracing = "0.1"

use axum::{routing::get, Router};
use sqlx::postgres::PgPoolOptions;
use std::net::SocketAddr;

#[tokio::main]
async fn main() {
    // Use a DNS name that is stable and managed by your service discovery.
    let database_url = "postgresql://[email protected]:26257/defaultdb?sslmode=disable";

    // Create a pool with reasonable timeouts to avoid holding stale connections.
    let pool = PgPoolOptions::new()
        .max_connections(10)
        .connect_timeout(std::time::Duration::from_secs(5))
        .idle_timeout(std::time::Duration::from_secs(30))
        .max_lifetime(std::time::Duration::from_secs(300))
        .connect(database_url)
        .await
        .expect("Failed to create connection pool");

    let app = Router::new().route("/health", get(health));

    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr)
        .serve(app.into_make_service_with_connective_fn(move |_| {
            let pool = pool.clone();
            async move {
                Ok::<_, std::convert::Infallible>(tower::service_fn(move |req| {
                    handle_request(req, pool.clone())
                }))
            }
        }))
        .await
        .unwrap();
}

async fn health(pool: sqlx::PgPool) -> String {
    // Simple query to verify connectivity; ensure it does not expose sensitive data.
    let row: (i64,) = sqlx::query_as("SELECT 1")
        .fetch_one(&pool)
        .await
        .expect("Query failed");
    format!("OK: {}", row)
}

Key practices to reduce risk:

• Set max_lifetime and idle_timeout to force periodic re-resolution of the DNS name, preventing long-lived stale connections.
• Avoid embedding raw hostnames in logs; if logging is necessary, sanitize or abstract internal identifiers.
• Use service mesh or Kubernetes DNS policies that guarantee timely updates, and monitor DNS TTL settings to ensure they align with your refresh intervals.
• Enable TLS for CockroachDB connections in production to protect data in transit; disable it only for local testing as shown.

These steps address Authentication and Data Exposure risks by ensuring connections target the intended endpoint and do not leak internal network details.