Arp Spoofing in Rocket with Mutual Tls

Arp Spoofing is a Layer 2 attack where an adversary sends falsified Address Resolution Protocol messages to associate their MAC address with the IP of a legitimate host, such as a server or another client. In a Rocket application that uses Mutual TLS (mTLS) for transport security, Arp Spoofing does not break the TLS handshake itself—mTLS still validates certificates—but it can undermine the network perimeter assumptions that many deployments rely on for access control and logging.

When Rocket binds to an interface and relies on network-level controls (firewalls, VLANs, or IP-based allowlists) instead of strict endpoint authentication, an attacker on the same broadcast domain can redirect traffic to their machine. The attacker can intercept or modify unencrypted internal communications before TLS termination or perform session hijacking on long-lived connections. Since mTLS verifies peer certificates at the TLS layer, the application may still accept the intercepted requests if the attacker presents a valid client certificate obtained through other means (e.g., theft or misconfiguration). This makes it critical to treat mTLS as a host-to-host guarantee and not as a replacement for network segmentation.

In environments where Rocket services are deployed in shared or multi-tenant networks, misconfigured switch ports or compromised internal hosts increase the risk of successful Arp Spoofing. While mTLS ensures confidentiality and integrity of the HTTP messages, it does not prevent an attacker from being a man-in-the-middle on the local network if they can consistently respond to ARP requests. Observability gaps also matter: without correlating network telemetry with mTLS session logs, detecting an active Arp Spoofing campaign becomes harder. This is why middleBrick’s scans highlight insecure network boundaries alongside certificate validation issues, ensuring you address both the cryptographic and the topological aspects of risk.

Remediation centers on reducing reliance on network-layer isolation and hardening mTLS configuration in Rocket. Use explicit peer certificate validation, prefer strong cipher suites, and enforce strict transport policies. Below are concrete, working examples that demonstrate secure mTLS setups in Rocket.

1. Configure mTLS with rustls and enforce peer verification

This example shows how to configure Rocket with TLS and require client certificates. It uses rustls and ensures that only certificates signed by your trusted CA are accepted.

// Cargo.toml dependencies:
// rocket = { version = "0.5", features = ["tls"] }
// tokio = { version = "1", features = ["rt-multi-thread", "macros"] }

use rocket::Config;
use std::path::PathBuf;

#[rocket::main]
async fn main() {
    let config = Config::build(rocket::Config::figment())
        .address("0.0.0.0")
        .port(8443)
        .tls(rocket::tls::Config {
            certs: PathBuf::from("/path/to/server-cert.pem"),
            key: PathBuf::from("/path/to/server-key.pem"),
            client_ca_cert: PathBuf::from("/path/to/ca-chain.pem"),
            client_auth: rocket::tls::ClientAuthMode::Require,
            ..Default::default()
        })
        .expect("Failed to build TLS config")
        .finalize();

    rocket::custom(config)
        .mount("/", routes![secure_endpoint])
        .launch()
        .await
        .unwrap();
}

#[get("/secure")]
fn secure_endpoint() -> &'static str {
    "Authenticated and encrypted"
}

2. Enforce strict hostname verification and modern ciphers

Even with mTLS, you should restrict acceptable peer identities and disable weak protocols. This snippet demonstrates setting custom rustls root store and client authentication options to mitigate downgrade and spoofing risks.

use rocket::tls::{Certificate, PrivateKey, ClientAuthMode, TlsConfig};
use std::sync::Arc;
use rustls::{RootCertStore, ServerConfig, ProtocolVersion, CipherSuite};
use std::io::Cursor;

fn build_tls_config() -> TlsConfig {
    // Load server cert and key
    let cert = Certificate::from_pem(include_bytes!("server-cert.pem").to_vec()).unwrap();
    let key = PrivateKey::from_pem(include_bytes!("server-key.pem").to_vec()).unwrap();

    // Build trusted CA pool for client verification
    let mut root_store = RootCertStore::empty();
    root_store.add(&Certificate::from_pem(include_bytes!("ca-chain.pem").to_vec()).unwrap()).unwrap();

    let mut server_config = ServerConfig::builder()
        .with_safe_defaults()
        .with_no_client_auth() // replaced by Require below
        .with_client_cert_verifier(Arc::new(rocket_tls_rustls::WebPKIResolver(root_store)))
        .with_single_cert(vec![cert.into()], key.into())
        .unwrap();

    // Enforce modern protocol versions and strong ciphers
    server_config.versions = vec![ProtocolVersion::TLSv1_2, ProtocolVersion::TLSv1_3];
    server_config.ciphersuites = vec![
        CipherSuite::TLS13_CHACHA20_POLY1305_SHA256,
        CipherSuite::TLS13_AES_256_GCM_SHA384,
    ];

    TlsConfig::Rustls(server_config)
}

#[rocket::main]
async fn main() {
    let tls = build_tls_config();
    let config = Config::build(rocket::Config::figment())
        .tls(tls)
        .client_auth(Some(ClientAuthMode::Require))
        .port(8443)
        .finalize();

    rocket::custom(config)
        .mount("/", routes![secure_endpoint])
        .launch()
        .await
        .unwrap();
}

3. Complement mTLS with network-level controls

Use Rocket’s configuration to limit exposure and integrate with monitoring. While mTLS authenticates peers, combining it with restricted bind addresses and firewall policies reduces the attack surface for Arp Spoofing.

#[rocket::main]
async fn main() {
    let config = Config::build(rocket::Config::figment())
        .address("127.0.0.1") // bind to loopback or internal interface only
        .port(8443)
        .tls(rocket::tls::Config {
            certs: PathBuf::from("/path/to/server-cert.pem"),
            key: PathBuf::from("/path/to/server-key.pem"),
            client_ca_cert: PathBuf::from("/path/to/ca-chain.pem"),
            client_auth: rocket::tls::ClientAuthMode::Require,
            ..Default::default()
        })
        .finalize()
        .expect("Invalid TLS configuration");

    rocket::custom(config)
        .mount("/", routes![secure_endpoint])
        .launch()
        .await
        .unwrap();
}

These examples ensure that Rocket services using mTLS are resilient to network-based redirection by combining cryptographic identity verification with disciplined network boundaries. For ongoing assurance, middleBrick’s scans can surface weak configurations and missing certificate validation issues in your endpoints.