Fix Unrestricted Resource Consumption in Gorilla
Unrestricted resource consumption in Gorilla/Mux applications typically manifests as memory exhaustion (OOM) or thread starvation. By default, Go's net/http (and by extension Gorilla) doesn't enforce strict body size limits or aggressive timeouts. An attacker can pipe gigabytes of junk data or hold connections open indefinitely (Slowloris), effectively pinning CPU and draining RAM until the process is killed by the kernel.
The Vulnerable Pattern
func main() {
r := mux.NewRouter()
r.HandleFunc("/api/data", func(w http.ResponseWriter, r *http.Request) {
// VULNERABILITY: io.ReadAll reads the entire body into memory without limits.
// A 10GB request will crash the service.
body, _ := io.ReadAll(r.Body)
fmt.Fprintf(w, "Received %d bytes", len(body))
})
http.ListenAndServe(":8080", r)
}The Secure Implementation
The fix involves two layers of defense. First, we use `http.MaxBytesReader` to bound the input stream; if the client sends more than the allocated threshold (e.g., 1MB), the reader returns an error and closes the connection, preventing memory ballooning. Second, we transition from `http.ListenAndServe` to a custom `http.Server` struct. This allows us to set `ReadTimeout` and `WriteTimeout`, ensuring that stale or intentionally slow connections are reaped, preventing file descriptor exhaustion and thread pinning.
func main() { r := mux.NewRouter() r.HandleFunc("/api/data", func(w http.ResponseWriter, r *http.Request) { // FIX 1: Wrap the body in a MaxBytesReader to enforce a hard limit at the protocol level. r.Body = http.MaxBytesReader(w, r.Body, 1048576) // 1MB Limitbody, err := io.ReadAll(r.Body) if err != nil { http.Error(w, "Request Entity Too Large", http.StatusRequestEntityTooLarge) return } fmt.Fprintf(w, "Securely processed %d bytes", len(body)) }) // FIX 2: Define strict timeouts on the server instance to prevent Slowloris attacks. srv := &http.Server{ Addr: ":8080", Handler: r, ReadTimeout: 5 * time.Second, WriteTimeout: 10 * time.Second, IdleTimeout: 120 * time.Second, } srv.ListenAndServe()
}
Your Gorilla API
might be exposed to Unrestricted Resource Consumption
74% of Gorilla apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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