Fix Lack of Resources & Rate Limiting in Revel
Unbounded endpoints in Revel are a prime target for DoS and resource exhaustion. Without explicit rate limiting, an attacker can saturate the Go runtime's scheduler or exhaust database connection pools. In Revel, we fix this by injecting a custom Filter into the request pipeline that implements a token-bucket algorithm before the controller logic is ever hit.
The Vulnerable Pattern
package controllersimport “github.com/revel/revel”
type API struct { *revel.Controller }
// VULNERABLE: No rate limiting or resource constraints. // Attackers can spam this to trigger expensive logic or DB queries. func (c API) ProcessData() revel.Result { data := c.Params.Get(“payload”) // Expensive operation here… return c.RenderJSON(map[string]string{“status”: “success”}) }
The Secure Implementation
The fix involves creating a thread-safe middleware (Filter) using 'golang.org/x/time/rate'. This filter tracks requests by IP address using a map and a sync.Mutex. We use a token-bucket strategy where 'rate.NewLimiter(1, 5)' allows 1 request per second with a burst capacity of 5. By placing this filter early in the 'revel.Filters' stack in 'init.go', we drop malicious traffic at the edge, preserving CPU and memory for legitimate users. For production, replace the in-memory map with Redis to support distributed rate limiting across multiple app instances.
package filtersimport ( “github.com/revel/revel” “golang.org/x/time/rate” “net/http” “sync” )
var visitors = make(map[string]*rate.Limiter) var mu sync.Mutex
func getLimiter(ip string) *rate.Limiter { mu.Lock() defer mu.Unlock() limiter, exists := visitors[ip] if !exists { limiter = rate.NewLimiter(1, 5) // 1 req/sec, burst of 5 visitors[ip] = limiter } return limiter }
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 app/init.go, add RateLimitFilter to revel.Filters
Your Revel API
might be exposed to Lack of Resources & Rate Limiting
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