Api Rate Abuse in Chi with Jwt Tokens

Rate abuse in Chi applications that rely on JWT tokens often occurs because authentication is validated on every request but rate limits are applied before token validation or after token exhaustion. When JWT tokens are accepted without an initial rate-limiting checkpoint, an unauthenticated or low-cost attacker can issue many requests with different tokens or with the same token within its validity window. This shifts the problem to the authorization layer, where tokens are verified only after work has been done, allowing resource exhaustion, authentication bypass via token flooding, or brute-force attacks on token identifiers.

Chi routes typically define pipelines that include authentication guards. If rate limiting is implemented as a separate middleware placed before the authentication guard, the system may still allocate resources for routing, parameter parsing, and JWT parsing before rejecting the request. An attacker can send many requests with valid JWT tokens obtained through low-cost means, such as leaked test tokens or tokens issued to low-privilege accounts, to consume connection pools, memory, or CPU. Even with JWT signature verification in place, tokens may be accepted structurally while their claims are not tightly scoped for rate contexts, enabling enumeration or token reuse attacks.

Another vector involves per-user claims stored in JWTs, such as a subject identifier or role. If rate limiting is applied globally or by IP only, a single attacker with one token can exhaust a global quota, while a more dangerous scenario occurs when tokens are issued with high quotas and reused across multiple sessions. In Chi, if token validation does not enforce per-subject rate limits and the API lacks a mechanism to revoke or throttle tokens dynamically, abuse can persist until token expiry. This is especially risky when tokens have long lifetimes or when refresh flows do not incorporate additional rate checks.

OpenAPI specifications analyzed by middleBrick can highlight missing rate-limit annotations for token-based endpoints, and the scanner can correlate runtime findings with spec definitions to flag unprotected paths. For example, an endpoint that issues JWT tokens without explicit rate constraints or an endpoint that accepts tokens but does not enforce scope-bound rate controls may be flagged. middleBrick’s checks run in parallel and include Authentication, Rate Limiting, and Unsafe Consumption, helping to surface these gaps without requiring credentials or agent deployment, with scans typically completing in 5–15 seconds.

In practice, this means developers must treat JWT tokens as rate-limit keys, not merely as credentials. The token subject, issuer, or a derived identifier should be part of the rate-limiting key, and limits should be enforced before expensive operations like database queries or external calls. middleBrick’s findings can map these risks to frameworks such as OWASP API Top 10 and provide remediation guidance that aligns with compliance requirements like PCI-DSS and SOC2.

To remediate rate abuse in Chi when using JWT tokens, enforce rate limits at the earliest point in the pipeline and tie limits to token claims. Use a key derived from the token subject or a stable identifier present in the validated JWT. Below are concrete examples using Chi and popular libraries.

Example 1: Rate limiting by JWT subject in a Chi pipeline

// deps: require("cheshire3")
// deps: require("buddy.auth.jwt")
// deps: require("buddy.core")
// deps: require("hiccup.core")

(ns myapp.routes
  (:require [cheshire.core :as json]
            [buddy.auth.jwt :as jwt]
            [buddy.core.codecs :as codecs]
            [hiccup.core :refer [html]]
            [compojure.core :refer [GET defroutes]]))

(defn get-subject-from-token [token]
  (when-let [claims (jwt/unsign token {:alg :hs256 :key "secret"})]
    (:sub claims)))

(def rate-limiter (atom {})) ; Replace with Redis or similar in production

(defn rate-limit-middleware [handler]
  (fn [request]
    (let [token (get-in request [:headers "authorization"])
          subject (when token (get-subject-from-token (subs token 7)))]
      (if (and subject (<= 10 (swap! rate-limiter update subject (fnil inc 0)))))
        {:status 429 :body (json/generate-string {:error "rate limit exceeded"})}
        (handler request)))))

(defroutes app-routes
  (GET "/profile" [] {:status 200 :body "profile"}))

(def app
  (-> app-routes
      rate-limit-middleware))

Example 2: Using authenticated routes with token-based keys in Chi

// deps: require("cheshire3")
; deps: require("buddy.auth.jwt")
; deps: require("buddy.auth.backends.token")

(ns myapp.auth
  (:require [cheshire.core :as json]
            [buddy.auth :refer [authenticated?]]
            [buddy.auth.backends.token :refer [jwt-backend]]
            [buddy.auth.middleware :refer [wrap-authentication]]))

(def jwt-backend (jwt-backend {:secret "secret" :alg :hs256}))

(defn wrap-rate-limit-by-subject [handler]
  (fn [request]
    (when-let [token (get-in request [:headers "authorization"])]
      (when-let [claims (jwt/unsign (subs token 7) {:alg :hs256 :key "secret"})]
        (let [subject (:sub claims)
              key (str "rate:" subject)]
          ; Implement rate limit check using key
          (if (should-rate-limit? key)
            {:status 429 :body (json/generate-string {:error "too many requests"})}
            (handler request))))))

(defn authenticated-handler [request]
  {:status 200 :body "ok"})

(def app
  (-> authenticated-handler
      wrap-authentication
      wrap-rate-limit-by-subject))

Example 3: Token-aware rate limiting with middleware that checks claims early

// deps: require("cheshire3")
; deps: require("buddy.auth.jwt")

(ns myapp.middleware
  (:require [cheshire.core :as json]
            [buddy.auth.jwt :as jwt]))

(defn token-subject [token]
  (some-> (jwt/unsign token {:alg :hs256 :key "secret"}) :sub))

(defn enforce-rate-limit [handler limit]
  (let [store (atom {})]
    (fn [request]
      (let [token (get-in request [:headers "authorization"])
            subject (when token (token-subject (subs token 7)))]
        (if (and subject (<= limit (swap! store update subject (fnil inc 0))))
          {:status 429 :body (json/generate-string {:error "rate limit reached"})}
          (handler request))))))

(defn wrap-jwt-rate-limit [handler]
  (-> handler
      (enforce-rate-limit 10)))

These examples focus on deriving a rate-limit key from the JWT subject and enforcing limits before request processing proceeds. In production, replace the in-memory atom with a distributed store such as Redis to support multi-node Chi deployments. Ensure token validation and rate limiting are tightly coupled so that tokens are checked early, reducing exposure window. middleBrick can validate that your OpenAPI spec documents rate-limit constraints on JWT-protected endpoints and that runtime findings do not show unprotected paths accepting tokens without appropriate throttling.