Arp Spoofing in Axum with Redis

Arp spoofing is a network-layer attack where an attacker sends falsified Address Resolution Protocol messages to associate their MAC address with the IP address of another host, such as a Redis server used by an Axum application. In an Axum service that communicates with Redis over TCP, an attacker on the same local network can intercept traffic by poisoning the ARP caches of either the Axum process or the Redis instance. This enables man-in-the-middle interception or modification of Redis commands and responses that are not encrypted in transit.

When Axum applications connect to Redis using standard TCP streams without additional protections, the Redis protocol (RESP) is exchanged in clear text. An attacker who successfully spoofs the Redis server’s IP can observe authentication payloads, keys, and potentially session or token data. If the Redis instance is bound to a public interface or improperly exposed within a container network, the attack surface increases. Although Redis can be configured with password authentication and TLS, arp spoofing may still facilitate credential harvesting or command injection before TLS handshakes are enforced, especially during initial connection attempts.

The combination of Axum’s runtime behavior and Redis’s default configuration can inadvertently support this scenario. For example, Axum services using the redis-rs client may establish connections with hardcoded or environment-derived host values without verifying network context. If Redis is deployed without binding to localhost in restricted network zones or without firewall rules limiting source IPs, an attacker can spoof the MAC address of the Redis host and redirect traffic through their machine. This exposes commands like GET, SET, and CONFIG to interception or manipulation, potentially leading to data leakage or injection of malicious operations.

While middleBrick does not perform active network testing and focuses on API surface analysis, understanding these attack patterns helps contextualize findings related to data exposure and encryption checks. The scanner may flag unencrypted Redis communications or missing transport protections when OpenAPI or runtime analysis indicates risk factors that align with insecure deployment practices.

To mitigate arp spoofing risks when Axum communicates with Redis, implement network, client, and transport hardening measures. These include binding Redis to loopback or restricted networks, enforcing TLS, and validating server identity in the client code.

1. Bind Redis to a restricted network interface

Configure Redis to bind only to trusted interfaces. In redis.conf, prefer 127.0.0.1 for local-only access or a specific private subnet IP instead of 0.0.0.0:

# redis.conf
bind 127.0.0.1 ::1
protected-mode yes

This reduces the chance that an attacker can reach the Redis port from external network segments where ARP spoofing is feasible.

2. Enforce TLS for Redis connections in Axum

Use TLS to protect data in transit, making intercepted RESP payloads difficult to exploit. With redis-rs, enable TLS via the RedisConnectionOptions:

use redis::{Client, RedisResult};
use redis::tls::TlsConfiguration;

let tls_config = TlsConfiguration::new("path/to/ca.pem")
    .with_check_hostname(false); // Set to true in production with valid CN/SAN
let client = Client::open("rediss://:[email protected]:6379")?;
let mut conn = client.get_connection()?;

The rediss:// scheme ensures the client attempts a secure connection. Always validate certificates in production environments to prevent man-in-the-middle attacks, including spoofed endpoints introduced via ARP manipulation.

3. Validate server identity and restrict client configuration

In Axum code, avoid relying on implicit host resolution for Redis. Explicitly define allowed hosts and use environment variables with strict validation:

use std::env;

let redis_host = env::var("REDIS_HOST").unwrap_or_else(|_| "127.0.0.1".to_string());
let redis_port = env::var("REDIS_PORT").unwrap_or_else(|_| "6379".to_string());
let address = format!("{}:{}", redis_host, redis_port);

// Only allow known hosts
if !["127.0.0.1", "10.0.0.5"].contains(&redis_host.as_str()) {
    panic!("Redis host not allowed");
}

let client = Client::open(format!("redis://:{}", address))?;

This prevents runtime redirection to unexpected IPs that could be injected through ARP spoofing. Combine this with firewall rules that limit which sources can reach the Redis port.

4. Use ACLs and minimal privileges in Redis

Define a Redis user with limited commands and keyspace access. In redis.conf or via ACL rules:

# Example ACL rule to restrict a user used by Axum
user axumuser on >mypassword~cache:* +get +set +del

Even if an attacker intercepts traffic, the impact is limited by the restricted command set and key patterns.

5. Employ network-level protections

Use static ARP entries or enable ARP spoofing detection tools on the host. While these are outside the Axum application code, they complement client and server configurations. Combine with middleBrick scans to verify that encryption and network exposure findings are addressed based on your deployment topology.