Fix Lack of Resources & Rate Limiting in Actix Web

In the wild, an Actix Web app without resource constraints is a sitting duck for Denial of Service (DoS). Attackers can trigger OOM (Out of Memory) kills by sending massive payloads or exhaust the worker pool via request flooding. We mitigate this by enforcing strict payload limits and integrating a robust rate-limiting middleware to drop malicious traffic before it hits your business logic.

The Vulnerable Pattern

use actix_web::{web, App, HttpServer, HttpResponse};
async fn upload_data(body: String) -> HttpResponse {
// VULNERABLE: No limit on body size, no rate limiting.
// An attacker can send a multi-gigabyte string to crash the node.
HttpResponse::Ok().body(format!(“Processed {} bytes”, body.len()))
}
#[actix_web::main]
async fn main() -> std::io::Result<()> {
HttpServer::new(|| {
App::new()
.route(“/data”, web::post().to(upload_data))
})
.bind(“127.0.0.1:8080”)?
.run()
.await
}

The Secure Implementation

The hardened configuration implements two critical defenses: 1. Payload Constraints: By injecting `web::PayloadConfig`, we explicitly limit the maximum size of incoming request bodies. This prevents memory exhaustion from 'Mega-Payload' attacks. 2. Rate Limiting: Using `actix-extensible-rate-limit` with an `InMemoryBackend`, we track the request frequency per IP. If a client exceeds 100 requests per minute, the middleware returns a 429 Too Many Requests, protecting the asynchronous workers from being overwhelmed by automated brute-force or flooding tools.

use actix_web::{web, App, HttpServer, HttpResponse};
use actix_extensible_rate_limit::{backend::memory::InMemoryBackend, RateLimiter, backend::SimpleInputFunctionBuilder};
use std::time::Duration;
#[actix_web::main]
async fn main() -> std::io::Result<()> {
// Initialize memory backend for rate limiting
let backend = InMemoryBackend::builder().build();
HttpServer::new(move || {
    // Define: 100 requests per 1 minute per IP
    let input = SimpleInputFunctionBuilder::new(Duration::from_secs(60), 100)
        .real_ip_key()
        .build();
    
    let rate_limiter = RateLimiter::builder(backend.clone(), input)
        .add_headers()
        .build();

    App::new()
        .wrap(rate_limiter)
        // Hard limit: global payload size set to 64KB
        .app_data(web::PayloadConfig::new(65536))
        .route("/data", web::post().to(|| async { HttpResponse::Ok().finish() }))
})
.bind("127.0.0.1:8080")?
.run()
.await
}

Protect your Actix Web API

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The Vulnerable Pattern

The Secure Implementation

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Verified by Ghost Labs Security Team