Open Redirect Chain in Axum (Rust)
Open Redirect Chain in Axum with Rust — how this specific combination creates or exposes the vulnerability
An Open Redirect Chain occurs when an application accepts a user-supplied URL or path component and uses it to perform a redirect without strict validation. In Axum with Rust, this typically arises in handler functions that read a query parameter such as next or redirect_to and pass it to a redirect response. If the application does not enforce an allowlist of trusted domains or does not ensure the target is a relative path, an attacker can craft a URL that chains through multiple redirects, potentially obfuscating the final destination.
For example, a route like /login?next=https://evil.com that issues Redirect::to(next) enables phishing and credential harvesting by leading the user through a chain of untrusted sites. Axum does not inherently validate redirect targets, so it is the developer’s responsibility to sanitize inputs. An attacker may exploit this to bypass referrer policies, evade logging, or exploit downstream clients that trust the final URL. Because Axum is a minimal, extension-based framework, missing validation middleware or helper functions increases the likelihood of insecure redirect implementations.
When combined with other insecure patterns—such as accepting user-controlled URLs for SSRF-prone fetch operations or failing to validate Host headers—redirect chains can become part of a broader attack surface. The scanner’s checks for BOLA/IDOR and Property Authorization help surface these issues when redirect logic depends on object ownership or insufficient constraints. Without strict validation, even seemingly benign features like “return to dashboard” links can be weaponized in an Open Redirect Chain that erodes user trust and enables social engineering.
Rust-Specific Remediation in Axum — concrete code fixes
To remediate Open Redirect Chain risks in Axum, validate and restrict redirect targets using allowlists, enforce relative paths, and avoid directly using user input in Redirect::to. Below are concrete, safe patterns for Rust Axum handlers.
1. Allowlist-based redirect validation
Only permit redirects to known, safe origins. Parse the target and compare against a set of allowed hosts.
use axum::response::Redirect;
use url::Url;
async fn login_handler(
Query(params): Query<HashMap2. Force relative paths for internal redirects
If the redirect must stay within your app, accept only path segments and reconstruct a relative URL.
use axum::response::Redirect;
use axum::http::StatusCode;
async fn safe_redirect(
Path(segment): Path<String>,
) -> Result<impl IntoResponse, (StatusCode, String)> {
// Only allow alphanumeric, dashes, and underscores in the segment
if !segment.chars().all(|c| c.is_alphanumeric() || c == '-' || c == '_') {
return Err((StatusCode::BAD_REQUEST, "invalid segment".to_string()));
}
// Build a relative path to prevent external redirects
Ok(Redirect::to(&format!("/dashboard/{}", segment)))
}
3. Reject URLs with non‑http(s) schemes and enforce HTTPS
Ensure user-supplied URLs use an expected scheme and, if external, require HTTPS.
use url::Url;
fn is_safe_redirect_url(raw: &str) -> bool {
let url = match Url::parse(raw) {
Ok(u) => u,
Err(_) => return false,
};
if url.scheme() != "https" {
return false;
}
let allowed_hosts = ["app.example.com", "trusted.example.com"];
allowed_hosts.contains(&url.host_str().unwrap_or(""))
}
// In a handler:
// if !is_safe_redirect_url(next) { return Err(...); }
4. Middleware approach to centralize validation
Implement a reusable function or extractor to avoid repeating validation logic across routes.
use axum::extract::rejection::QueryRejection;
use axum::extract::Query;
use std::collections::HashMap;
struct SafeRedirect(String);
impl FromQuery for SafeRedirect {
type Error = QueryRejection;
async fn from_query(query: &HashMap<String, String>) -> Result<Self, Self::Error> {
let next = query.get("next").ok_or_else(|| QueryRejection::MissingField("next"))?;
let parsed = match url::Url::parse(next) {
Ok(u) => u,
Err(_) => return Err(QueryRejection::InvalidQuery),
};
let allowed_hosts = ["app.example.com"];
if allowed_hosts.contains(&parsed.host_str().unwrap_or("")) {
Ok(SafeRedirect(next.clone()))
} else {
Err(QueryRejection::InvalidQuery)
}
}
}
// Usage: async fn handler(Redirect(SafeRedirect(url)): SafeRedirect) { ... }
These Rust-specific practices—leveraging strong typing, pattern matching, and the url crate—reduce the risk of Open Redirect Chain exploits in Axum applications. Combine them with the scanner’s checks for BOLA/IDOR and Property Authorization to detect misconfigurations early.
Frequently Asked Questions
Why is input validation critical for redirects in Axum?
url crate to parse and verify hosts against an allowlist before passing user input to Redirect::to.Can I allow relative paths only to avoid external redirects?
Redirect::to("/path/"). This eliminates chaining to external origins while keeping navigation within your app.