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Fix API Rate Limit Exhaustion in Revel

Revel is a high-productivity Go framework, but it lacks native rate-limiting middleware out of the box. This leaves your endpoints vulnerable to distributed denial-of-service (DDoS) attacks, brute-force attempts, and resource exhaustion. To secure a Revel app, we must implement a custom Filter using a token-bucket algorithm to intercept requests before they hit the ActionInvoker.

The Vulnerable Pattern

package controllers

import “github.com/revel/revel”

type App struct { *revel.Controller }

// VULNERABLE: No rate limiting logic. An attacker can spam this endpoint to exhaust DB connections or CPU. func (c App) SensitiveData() revel.Result { data := fetchHeavyData() return c.RenderJSON(data) }

The Secure Implementation

The secure implementation introduces a custom Revel Filter that utilizes 'golang.org/x/time/rate'. It identifies clients by RemoteAddr and maintains a map of token-bucket limiters. The 'Allow()' method non-blockingly checks if a token is available; if not, it short-circuits the request chain by returning a 429 'Too Many Requests' status. This prevents the 'ActionInvoker' from ever executing the expensive controller logic for abusive clients. For production, replace the in-memory map with a Redis-backed store to handle distributed scaling.

package filters

import ( “github.com/revel/revel” “golang.org/x/time/rate” “net/http” “sync” )

var ( mu sync.Mutex clients = make(map[string]*rate.Limiter) )

func GetLimiter(ip string) *rate.Limiter { mu.Lock() defer mu.Unlock() v, exists := clients[ip] if !exists { limiter := rate.NewLimiter(1, 5) // 1 request per second, burst of 5 clients[ip] = limiter return limiter } return v }

func RateLimitFilter(c *revel.Controller, fc []revel.Filter) { ip := c.Request.RemoteAddr limiter := GetLimiter(ip) if !limiter.Allow() { c.Response.Status = http.StatusTooManyRequests c.Result = c.RenderJSON(map[string]string{“error”: “Rate limit exceeded”}) return } fc[0](c, fc[1:]) }

// In init.go, add RateLimitFilter to revel.Filters before revel.ActionInvoker

System Alert • ID: 3395
Target: Revel API
Potential Vulnerability

Your Revel API might be exposed to API Rate Limit Exhaustion

74% of Revel apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.

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