How to fix Improper Error Handling
in Salvo
Executive Summary
Improper error handling in Salvo applications leads to Information Disclosure (CWE-209). By default, piping raw Rust errors or panics to the response body leaks stack traces, file paths, and database schema details. This guide demonstrates how to intercept failures and return sanitized, generic responses while maintaining internal observability.
The Vulnerable Pattern
#[handler]
async fn get_data(req: &mut Request, res: &mut Response) {
let id = req.param::("id").unwrap();
// VULNERABLE: Directly returning the error string from the database
match db::query_user(&id).await {
Ok(user) => res.render(Json(user)),
Err(e) => {
res.status_code(StatusCode::INTERNAL_SERVER_ERROR);
res.render(Text::Plain(format!("Database Error: {}", e)));
}
}
} The Secure Implementation
The vulnerable code leaks internal implementation details by formatting the raw error object directly into the response body. An attacker can trigger specific errors (e.g., SQL syntax errors or connection timeouts) to map the backend infrastructure. The secure implementation decouples internal logging from external responses. It uses a structured `ApiError` type to provide consistent, non-revealing feedback to the user, while using `tracing` or `log` to capture the technical details in a secure location. Furthermore, implementing `CatchPanic` middleware ensures that even unhandled `panic!` calls don't dump stack traces to the HTTP stream.
use salvo::prelude::*; use serde::Serialize;#[derive(Serialize)] struct ApiError { message: &‘static str }
#[handler] async fn get_data(req: &mut Request, res: &mut Response) { let id = req.param::
(“id”).unwrap_or_default(); match db::query_user(&id).await { Ok(user) => res.render(Json(user)), Err(e) => { // Log the actual error for internal debugging tracing::error!(err = %e, “failed to query user”); // Return a sanitized, generic error to the client res.status_code(StatusCode::INTERNAL_SERVER_ERROR); res.render(Json(ApiError { message: "An internal server error occurred." })); } }}
// Add CatchPanic middleware in main.rs to prevent raw panic leaks // Service::new(router).hoop(CatchPanic::new())
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might be exposed to Improper Error Handling
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