Fix Business Logic Errors in Rocket
Logic flaws are the silent killers of Rust web apps. While Rocket's type system prevents memory corruption, it won't stop you from letting User A delete User B's data if your request guards are shallow. In a secure Rocket architecture, we move authorization logic out of the function body and into the type signatures using Request Guards to enforce invariant business rules.
The Vulnerable Pattern
#[post("/account/withdraw/", data = "")]
fn withdraw(id: i32, amount: Json, _auth: UserSession) {
// VULNERABILITY: Insecure Direct Object Reference (IDOR).
// We verify the user is logged in (_auth), but we never verify
// that the logged-in user actually owns the account 'id'.
db::deduct_funds(id, amount.value);
} The Secure Implementation
The vulnerable example relies on manual checks that are easily forgotten as the codebase grows. The secure implementation leverages Rocket's 'FromRequest' trait to create an 'AccountOwner' guard. This pattern enforces 'Authorization as a Type': the business logic (deducting funds) cannot execute unless the request successfully resolves the 'AccountOwner' type, which internally validates the relationship between the session and the resource ID. This eliminates IDOR and state-manipulation errors at the routing level.
struct AccountOwner(i32);#[rocket::async_trait] impl<‘r> FromRequest<‘r> for AccountOwner { type Error = (); async fn from_request(req: &‘r Request<’_>) -> Outcome<Self, Self::Error> { let session = req.guard::
().await?; let account_id: i32 = req.param(2).and_then(|p| p.parse().ok())?; if db::is_owner(session.user_id, account_id) { Outcome::Success(AccountOwner(account_id)) } else { Outcome::Failure((Status::Forbidden, ())) } }}
#[post(“/account/withdraw/”, data = " ")] fn withdraw(id: i32, amount: Json , _owner: AccountOwner) { // SECURE: This code is unreachable unless the AccountOwner guard validates ownership. db::deduct_funds(id, amount.value); }
Your Rocket API
might be exposed to Business Logic Errors
74% of Rocket apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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