Fix Insecure Webhooks in Rocket

#[post("/webhook", data = "")]
fn handle_webhook(payload: Json) -> Status {
    // VULNERABILITY: No signature verification.
    // Anyone can send a POST request to this endpoint with a malicious JSON body.
    process_data(payload.into_inner());
    Status::Ok
}

use hmac::{Hmac, Mac};
use sha2::Sha256;
use rocket::data::{Data, ToByteUnit};
use rocket::http::Status;
use rocket::request::{self, Request, FromRequest, Outcome};
type HmacSha256 = Hmac;
struct VerifiedWebhook(Vec);
#[rocket::async_trait]
impl<‘r> FromRequest<‘r> for VerifiedWebhook {
type Error = ();
async fn from_request(req: &'r Request<'_>) -> Outcome<Self, Self::Error> {
    let secret = std::env::var("WEBHOOK_SECRET").expect("SECRET NOT SET");
    let signature = req.headers().get_one("X-Hub-Signature-256").and_then(|s| s.strip_prefix("sha256="));
    
    // In a real implementation, you'd buffer the body here.
    // Rocket 0.5 requires handling Data in the route, but a Guard can check headers.
    match signature {
        Some(sig) => Outcome::Success(VerifiedWebhook(vec![])), // Simplified for example
        None => Outcome::Error((Status::Unauthorized, ())),
    }
}
}
#[post(“/webhook”, data = "")]
async fn secure_webhook(sig_guard: VerifiedWebhook, body: Data<’_>) -> Status {
let secret = “shared_secret”;
let bytes = body.open(1.mebibytes()).into_bytes().await.unwrap();
let mut mac = HmacSha256::new_from_slice(secret.as_bytes()).unwrap();
mac.update(&bytes);

// Use constant-time comparison to prevent timing attacks
if mac.verify_slice(&hex::decode(provided_sig).unwrap()).is_ok() {
    process_data(bytes);
    Status::Ok
} else {
    Status::Unauthorized
}
}