Arp Spoofing in Axum with Dynamodb

Arp spoofing is a Layer 2 attack where an adversary sends falsified ARP responses to associate their MAC address with the IP of a legitimate host, such as a backend server or database endpoint. In an Axum service that uses Amazon DynamoDB, this can expose data in transit and enable interception or manipulation of database operations. Axum routes HTTP requests to handlers that often perform multiple DynamoDB calls to retrieve or mutate application state. If an attacker conducts ARP spoofing on the local network segment (for example, within a container orchestration environment or a cloud VPC with insufficient network segmentation), they can position themselves between the Axum runtime and the DynamoDB endpoint or an intermediate proxy.

The exposure arises because ARP is inherently trust-based; there is no cryptographic binding between IP and MAC in typical Ethernet networks. When Axum services communicate with DynamoDB over HTTP/TLS, the TLS layer protects payload integrity, but ARP spoofing can redirect traffic to an unauthorized host that terminates the connection or relays it after inspection. This becomes critical in shared environments where multiple services or tenants share underlying infrastructure. The attacker does not need to break TLS to conduct reconnaissance; they can observe metadata, timing, or inject disruptions that affect availability. In a CI/CD or staging setup where middleBrick scans a publicly reachable Axum endpoint, misconfigured network boundaries can amplify exposure by allowing unauthenticated network-level tampering.

While DynamoDB itself is a managed service accessed over HTTPS, the client-side HTTP layer in Axum remains vulnerable to disruption and observation during ARP spoofing. An attacker can intercept connection attempts, alter DNS or host resolution, or poison caches that influence endpoint selection. This does not decrypt TLS, but it can redirect requests to malicious proxies that log TLS handshake metadata or enforce altered routing logic. middleBrick’s unauthenticated black-box scans highlight such network exposure by testing authentication weaknesses and data exposure, emphasizing the need to harden the network path between Axum and DynamoDB.

To contextualize risk, consider the 12 security checks run by middleBrick: Authentication, BOLA/IDOR, Input Validation, and Data Exposure are particularly relevant when ARP spoofing intersects with Axum-to-DynamoDB communication. Findings from scans can indicate whether network segmentation is insufficient or whether transport-layer protections are inconsistently applied. Remediation focuses on ensuring that ARP-level trust is augmented with cryptographic guarantees and strict network controls rather than attempting to secure ARP directly.

Remediation centers on minimizing the attack surface for ARP spoofing by ensuring that all communication with DynamoDB is authenticated, encrypted, and verified. In Axum, this involves using strong TLS configurations, validating server certificates, and applying network-level controls such as VPC endpoints and security groups. Below are concrete code examples for a robust Axum service that integrates with DynamoDB using the official AWS SDK for Rust.

First, configure the AWS SDK client with explicit TLS settings and endpoint resolution to avoid reliance on potentially spoofable DNS. Use region-based endpoints and enforce HTTPS. The following Rust snippet shows how to create a DynamoDB client with a custom HTTPS connector that verifies server certificates:

use aws_config::meta::region::RegionProviderChain;
use aws_sdk_dynamodb::Client;
use hyper_rustls::{HttpsConnector, HttpsConnectorBuilder};
use std::sync::Arc;

async fn create_dynamodb_client() -> Client {
    // Use a region provider that defaults to a safe region and can be overridden by env vars
    let region_provider = RegionProviderChain::default_provider().or_else("us-east-1");
    let config = aws_config::from_env().region(region_provider).load().await;

    // Build an HTTPS connector that enforces TLS verification
    let https_connector = HttpsConnectorBuilder::new()
        .with_native_roots()
        .https_or_http_and_encrypted()
        .enable_http1()
        .build();

    let client = Client::from_conf(config.into_client_config().with_connector(https_connector));
    client
}

This approach ensures that each connection to DynamoDB validates the server’s certificate against trusted roots, reducing the risk of man-in-the-middle attacks that could be facilitated by ARP spoofing. Avoid disabling certificate validation or using custom root stores unless absolutely necessary, and if required, pin certificates explicitly.

Second, structure your Axum routes to avoid leaking sensitive data in logs or error messages that could aid an attacker. Use typed request extraction and validate inputs before constructing DynamoDB queries. Here is an example handler that retrieves an item by a validated ID:

use axum::extract::Path;
use aws_sdk_dynamodb::types::AttributeValue;
use std::convert::Infallible;

async fn get_item_handler(
    Path(id): Path,
    client: Arc<aws_sdk_dynamodb::Client>
) -> Result<axum::Json<serde_json::Value>, (axum::http::StatusCode, String)> {
    // Validate ID format to prevent injection or malformed requests
    if !id.chars().all(|c| c.is_alphanumeric() || c == '-' || c == '_') {
        return Err((axum::http::StatusCode::BAD_REQUEST, "Invalid ID".to_string()));
    }

    let response = client
        .get_item()
        .table_name("MyTable")
        .key(
            "id",
            AttributeValue::S(id),
        )
        .send()
        .await
        .map_err(|e| (axum::http::StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;

    match response.item {
        Some(item) => Ok(axum::Json(serde_json::to_value(item).unwrap())),
        None => Err((axum::http::StatusCode::NOT_FOUND, "Item not found".to_string())),
    }
}

Network-level mitigations include placing Axum services and DynamoDB endpoints within the same VPC and using VPC endpoints for DynamoDB to ensure traffic does not traverse the public internet. Security groups and network ACLs should restrict egress to known DynamoDB endpoints only. These controls reduce the opportunity for successful ARP spoofing by limiting lateral movement and exposure to untrusted hosts.