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How to fix BFLA (Broken Function Level Authorization)
in Salvo

Executive Summary

BFLA occurs when an application fails to verify if an authenticated user has the specific permissions required to execute a sensitive function. In the Salvo framework, this typically manifests when developers assume authentication (knowing who the user is) equals authorization (knowing what the user can do). To secure this, we must implement fine-grained access control using Salvo's 'Hoop' middleware to intercept and validate user roles before they reach administrative or privileged handlers.

The Vulnerable Pattern

VULNERABLE CODE
use salvo::prelude::*;

#[handler]
async fn delete_system_log(req: &mut Request, res: &mut Response) {
// VULNERABILITY: No role check. Any authenticated user can call this.
let log_id = req.param::(“id”).unwrap();
res.render(format!(“Log {} deleted”, log_id));
}


#[tokio::main]
async fn main() {
let router = Router::with_path(“admin/logs/“).delete(delete_system_log);
let acceptor = TcpListener::new(“127.0.0.1:5800”).bind().await;
Server::new(acceptor).serve(router).await;
}

The Secure Implementation

The secure implementation introduces a 'Hoop' middleware named `auth_guard`. This middleware acts as a gatekeeper for the administrative route. It inspects the user's role (extracted from a header, JWT, or session) and compares it against the required privilege level. If the user is not an 'admin', it sets a 403 Forbidden status and calls `ctrl.skip_rest()`, preventing the `delete_system_log` handler from ever being executed. This enforces the Principle of Least Privilege at the function level.

SECURE CODE
use salvo::prelude::*;

#[handler]
async fn auth_guard(req: &mut Request, res: &mut Response, ctrl: &mut FlowCtrl) {
// In a real app, extract this from a JWT or session store
let user_role = req.headers().get(“X-User-Role”).and_then(|v| v.to_str().ok()).unwrap_or(“user”);


if user_role != "admin" {
    res.status_code(StatusCode::FORBIDDEN).render("Error: Insufficient Permissions");
    ctrl.skip_rest(); // Stop the request chain here
    return;
}
ctrl.call_next().await;


}


#[handler]
async fn delete_system_log(req: &mut Request, res: &mut Response) {
let log_id = req.param::(“id”).unwrap();
res.render(format!(“Log {} deleted securely”, log_id));
}


#[tokio::main]
async fn main() {
// SECURE: The ‘hoop’ acts as a mandatory authorization layer
let admin_router = Router::with_path(“admin/logs/”)
.hoop(auth_guard)
.delete(delete_system_log);


let acceptor = TcpListener::new("127.0.0.1:5800").bind().await;
Server::new(acceptor).serve(admin_router).await;


}

System Alert • ID: 5276
Target: Salvo API
Potential Vulnerability

Your Salvo API might be exposed to BFLA (Broken Function Level Authorization)

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

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