Brute Force Attack in Chi (Go)

A brute force attack exploits the unauthenticated rate limiting gap in Chi when deployed with Go-based services that lack explicit request throttling. Chi, as a minimal routing framework, does not enforce authentication or request quotas by default. When an API endpoint is exposed without authentication — such as a password reset or session validation endpoint — attackers can script high-volume credential trials using Go's efficient HTTP client libraries.

Consider a Chi-powered endpoint like:

func handler(w http.ResponseWriter, r *http.Request) {
    // No auth, no rate limit
    fmt.Fprintf(w, "%s", "Password reset initiated")
}

func main() {
    r := chi.NewRouter()
    r.Post("/reset-password", handler)
    http.ListenAndServe(":3000", r)
}

An attacker can use Go to parallelize 500 requests per second across multiple goroutines, targeting the /reset-password endpoint. This overwhelms the system and eventually bypasses any superficial retry logic. Since Chi provides no built-in rate limiting or session throttling, the attack surface remains wide open.

The vulnerability maps to the OWASP API Top 10 category Broken Object Level Authorization and aligns with real-world CVEs like CVE-2022-22978 (Spring Cloud Function SSRF/Brute Force via unauthenticated endpoints). While not a CVE in Chi itself, similar flaws have been observed in frameworks that rely on developer-added security layers.

In this scenario, the combination of Chi’s minimalism and Go’s concurrency model amplifies risk when security controls are omitted. The scanner flags this as a critical issue under the Authentication and Rate Limiting checks.

Without proper safeguards, any unauthenticated POST endpoint becomes a target for credential stuffing or password spraying attacks. The absence of exponential backoff or IP masking in client code further enables large-scale attempts.

To mitigate brute force risks in Chi, enforce authentication and add rate limiting at the framework level. Use Go’s net/http middleware to throttle requests per IP and integrate Chi with a middleware stack that validates tokens or session identifiers.

Here is a corrected implementation using Chi with rate limiting and basic auth checks:

import (
    "github.com/go-chi/chi/v5"
    "github.com/go-chi/httprate/v2"
    "net/http"
)

func main() {
    r := chi.NewRouter()
    // Apply rate limiting: 10 requests per minute per IP
    r.Use(httprate.Limit(10, 1 * time.Minute))
    
    // Add middleware to require a token
    r.Use(func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            token := r.URL.Query().Get("token")
            if token != "valid-secret-token" {
                http.Error(w, "Unauthorized", http.StatusUnauthorized)
                return
            }
            next.ServeHTTP(w, r)
        })
    })
    
    r.Post("/reset-password", handler)
    http.ListenAndServe(":3000", r)
}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "%s", "Password reset initiated")
}

This version introduces two key protections:

• Rate limiting via httprate to cap requests per IP
• Token-based authentication in a lightweight middleware

For production, replace token checks with JWT validation or session cookies. The scanner will then downgrade the Authentication and Rate Limiting risk scores, eliminating the critical finding.

Additionally, integrate middleBrick via CLI to validate the fix:

middlebrick scan https://api.example.com/reset-password

This ensures continuous verification in CI/CD pipelines.