Arp Spoofing in Chi with Jwt Tokens

Arp Spoofing is a Layer 2 attack where an attacker sends falsified ARP messages to associate their MAC address with the IP address of another host, typically the gateway or another API service in Chi. When JWT tokens are transmitted over a network compromised by Arp Spoofing, the tokens can be intercepted, read, or tampered with, depending on transport protections. In Chi, which is often used to build HTTP APIs, JWT tokens are commonly passed in the Authorization header as a Bearer token. If the communication is not strictly enforced over TLS, Arp Spoofing enables man-in-the-middle (MITM) interception, exposing the JWT to theft. An attacker positioned via Arp Spoofing can capture valid JWTs and reuse them to impersonate users or escalate privileges. Even if the JWT is cryptographically signed, interception alone does not break the signature; however, in a Chi application that does not mandate HTTPS, the token can be modified in transit if the attacker also performs SSL stripping or if the application accidentally allows HTTP fallback. Because Chi applications sometimes parse JWTs on every request to enforce authorization, a stolen token grants the attacker the same access as the compromised user until expiration. The combination is particularly risky in microservice setups where services communicate internally over LAN, and Arp Spoofing is easier due to lack of network segmentation. The risk is not in the JWT format itself but in the exposure and potential tampering enabled by the L2 attack when transport security is weak or inconsistently applied in Chi endpoints.

Remediation focuses on ensuring JWTs are never exposed to network-level attacks like Arp Spoofing by enforcing strict transport security and validating tokens properly in Chi. First, always enforce HTTPS across all routes so that even if an attacker spoofs ARP entries, the JWT cannot be read or altered without breaking TLS. In Chi, you can enforce HTTPS by configuring your web server or reverse proxy to redirect HTTP to HTTPS and by setting secure headers. Below is a concrete example of a JWT validation middleware in Chi that ensures requests include a valid token and are served over secure connections.

(require '[cheshire.core :as json]
         '[buddy.sign.jwt :as jwt]
         '[compojure.core :refer [defroutes GET]]
         '[ring.util.response :refer [response unauthorized]])

(defn verify-jwt [request]
  (let [auth-header (get-in request [:headers "authorization"])
        token (when (and auth-header (re-find #"^Bearer \S+$" auth-header))
                (subs auth-header 7))]
    (try
      (when token
        (jwt/verify token "your-secret-key" {:alg :hs256}))
      (catch Exception _
        nil))))

(defroutes api-routes
  (GET "/protected"
       request
       (if-let [claims (verify-jwt request)]
         (response {:status :ok :claims claims})
         (unauthorized {:error "Invalid or missing JWT"}))))

;; Enforce HTTPS in production by configuring your server (e.g., Jetty, NGINX) to use TLS.
;; Example NGINX snippet to redirect HTTP to HTTPS:
;; server {
;;   listen 80;
;;   return 301 https://$host$request_uri;
;; }

This middleware extracts the JWT from the Authorization header, verifies its signature using a strong secret and expected algorithm (e.g., HS256), and rejects requests with invalid tokens. Note that the secret key must be stored securely, for example using environment variables or a secrets manager, never hard-coded in source. Additionally, configure your Chi application to use secure cookies with the :secure flag and :http-only attribute if storing tokens client-side, and set the Strict-Transport-Security header to prevent protocol downgrade attacks. These steps ensure that even if an attacker performs Arp Spoofing, the JWT remains unreadable and unverifiable without TLS, and any tampering will break the signature or be rejected by the server.