Broken Access Control in Axum

Detecting Broken Access Control in Axum requires examining both the route structure and the data flow through extractors. Start by auditing your Router configuration:

let app = Router::new()
    .route("/admin", Method::GET, admin_route)
    .route("/user/:id", Method::GET, user_route)
    .layer(Trace::new_for_http());

Look for routes that handle sensitive resources without explicit authorization middleware. In Axum, this means checking if your handlers use Extension<User> or similar extractors and then verify permissions.

middleBrick's black-box scanning can identify these vulnerabilities without requiring source code access. The scanner tests for:

• IDOR vulnerabilities by manipulating path parameters across different authenticated sessions
• Missing authorization checks by attempting privileged actions with regular user credentials
• Property exposure by analyzing response structures for sensitive data leakage
• Authentication bypass attempts on endpoints that should require authentication

For Axum applications specifically, middleBrick examines the unauthenticated attack surface and tests authorization boundaries. The scanner will attempt to access admin endpoints with regular user credentials, modify resource identifiers in requests, and analyze response payloads for data that shouldn't be exposed to the requesting user.

You can integrate middleBrick into your development workflow using the CLI:

npx middlebrick scan https://api.your-app.com --output json

Or add it to your CI/CD pipeline with the GitHub Action to automatically scan staging APIs before deployment:

- name: Run middleBrick Security Scan
  uses: middlebrick/middlebrick-action@v1
  with:
    target_url: ${{ secrets.API_URL }}
    fail_below_score: B

The scanner provides specific findings about authorization failures, including which endpoints are vulnerable and what data could be accessed by unauthorized users.

Remediating Broken Access Control in Axum requires a defense-in-depth approach using the framework's native capabilities. Start with a robust authorization middleware that checks permissions before reaching handlers:

use axum_extra::extract::Extension;

struct AuthenticatedUser {
    id: UserId,
    role: Role,
}

struct AdminGuard;

#[async_trait]
impl FromRequest for AdminGuard
where
    B: Send,
{
    type Rejection = StatusCode;

    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
        let user = Extension::AuthenticatedUser::from_request(req)
            .await
            .map_err(|_| StatusCode::UNAUTHORIZED)?;
            
        if user.role != Role::Admin {
            return Err(StatusCode::FORBIDDEN);
        }
        
        Ok(AdminGuard)
    }
}

// Now enforce admin role at the route level
app.route("/admin", Method::GET)
   .with(AdminGuard)
   .with(admin_handler);

This pattern ensures authorization is checked before the handler executes, preventing accidental exposure.

For IDOR prevention, implement resource ownership verification:

async fn get_user_profile(
    Extension(db): Extension<PgPool>,
    Path(user_id): Path<UserId>,
    Extension(user): Extension<AuthenticatedUser>,
) -> Result<Json<UserProfile>> {
    // Verify the authenticated user owns this profile
    if user.id != user_id {
        return Err(StatusCode::FORBIDDEN.into());
    }
    
    let profile = db.get_user_profile(user_id).await?;
    Ok(Json(profile))
}

For property-level authorization, create response DTOs that explicitly control what data is exposed:

#[derive(Serialize)]
struct UserProfileResponse {
    id: UserId,
    username: String,
    email: String,
    // Sensitive fields omitted
}

async fn get_user_profile(
    Extension(db): Extension<PgPool>,
    Path(user_id): Path<UserId>,
    Extension(user): Extension<AuthenticatedUser>,
) -> Result<Json<UserProfileResponse>> {
    let profile = db.get_user_profile(user_id).await?;
    
    // Only return safe fields
    let response = UserProfileResponse {
        id: profile.id,
        username: profile.username,
        email: profile.email,
    };
    
    Ok(Json(response))
}

Consider using the tower::auth crate for more sophisticated authorization policies:

use tower::auth::{AsyncAuthorize, AuthorizeRequest};

struct PermissionAuthorizer;

#[async_trait]
impl AuthorizeRequest for PermissionAuthorizer {
    type Request = Request;
    type Response = Request;
    type Error = StatusCode;
    type Future = Ready<Result<Request, StatusCode>>;

n    async fn authorize(&mut self, req: Request) -> Self::Future {
        let user = req.extensions().get::<AuthenticatedUser>();
        
        if let Some(user) = user {
            if user.has_permission("access_profile") {
                return ready(Ok(req));
            }
        }
        
        ready(Err(StatusCode::FORBIDDEN))
    }
}

// Apply as a middleware layer
let app = Router::new()
    .route("/profile/:id", Method::GET, get_profile)
    .layer(PermissionAuthorizer::new());

Finally, implement comprehensive logging for authorization failures to detect and respond to attacks:

use tracing::{info, error};

async fn sensitive_operation(
    Extension(db): Extension<PgPool>,
    Extension(user): Extension<AuthenticatedUser>,
) -> Result<Json<SensitiveData>> {
    if !user.has_permission("access_sensitive") {
        error!(user_id = %user.id, "Unauthorized access attempt to sensitive data");
        return Err(StatusCode::FORBIDDEN.into());
    }
    
    let data = db.get_sensitive_data().await?;
    Ok(Json(data))
}