Sputnik

A lightweight layer on top of Hyper to facilitate building web applications.

Sputnik provides:

• convenience wrappers around hyper's Request & Response
  • parse, set and delete cookies (powered by the cookie crate)
  • parse query strings and HTML form data (powered by the serde_urlencoded crate)
• an Error enum that makes it easy to centrally control the presentation of all error messages
• cookie-based CSRF tokens
• Key: a convenience wrapper around HMAC (stolen from the cookie crate, so that you don't have to use CookieJars if you don't need them)
• decode_expiring_claim & encode_expiring_claim, which can be combined with Key to implement signed & expiring cookies (with the expiry date encoded into the signed cookie value)

Sputnik does not:

• handle routing: for most web apps matching on (method, path) suffices
• handle configuration: we recommend toml
• handle persistence: we recommend diesel
• handle templating: we recommend maud

Error handling

Sputnik defines the following error types:

pub struct SimpleError {
    pub code: StatusCode,
    pub message: String,
}

pub enum Error {
    Simple(SimpleError),
    Response(hyper::Response<hyper::Body>),
}

Sputnik implements Into<Error::Simple> for all of its client error types (e.g. deserialization errors), allowing you to easily customize the error presentation. Sometimes however a SimpleError doesn't suffice, e.g. you might want to redirect unauthorized users to your login page instead of showing them an error, for such cases you can return an Error::Response.

CsrfToken example

use std::convert::Infallible;
use hyper::service::{service_fn, make_service_fn};
use hyper::{Method, Server};
use serde::Deserialize;
use sputnik::security::CsrfToken;
use sputnik::{Error, request::{Parts, Body}, response::Response};

async fn route(req: &mut Parts, body: Body) -> Result<Response,Error> {
    match (req.method(), req.uri().path()) {
        (&Method::GET, "/form") => get_form(req).await,
        (&Method::POST, "/form") => post_form(req, body).await,
        _ => return Err(Error::not_found("page not found".to_owned()))
    }
}

async fn get_form(req: &mut Parts) -> Result<Response, Error> {
    let mut response = Response::new();
    let csrf_token = CsrfToken::from_parts(req, &mut response);
    *response.body() = format!("<form method=post>
        <input name=text>{}<button>Submit</button></form>", csrf_token.html_input()).into();
    Ok(response)
}

#[derive(Deserialize)]
struct FormData {text: String}

async fn post_form(req: &mut Parts, body: Body) -> Result<Response, Error> {
    let mut response = Response::new();
    let csrf_token = CsrfToken::from_parts(req, &mut response);
    let msg: FormData = body.into_form_csrf(&csrf_token).await?;
    *response.body() = format!("hello {}", msg.text).into();
    Ok(response)
}

/// adapt between Hyper's types and Sputnik's convenience types
async fn service(req: hyper::Request<hyper::Body>) -> Result<hyper::Response<hyper::Body>, Infallible> {
    let (mut parts, body) = sputnik::request::adapt(req);
    match route(&mut parts, body).await {
        Ok(res) => Ok(res.into()),
        Err(err) => match err {
            Error::Simple(err) => {
                Ok(err.response_builder().body(err.message.into()).unwrap())
                // you can easily wrap or log errors here
            }
            Error::Response(err) => Ok(err)
        }
    }
}

#[tokio::main]
async fn main() {
    let service = make_service_fn(move |_| {
        async move {
            Ok::<_, hyper::Error>(service_fn(move |req| {
                service(req)
            }))
        }
    });

    let addr = ([127, 0, 0, 1], 8000).into();
    let server = Server::bind(&addr).serve(service);
    println!("Listening on http://{}", addr);
    server.await;
}

Signed & expiring cookies

After a successful authentication you can build a session id cookie for example as follows:

let expiry_date = OffsetDateTime::now_utc() + Duration::hours(24);
let mut cookie = Cookie::new("userid",
    key.sign(
        &encode_expiring_claim(&userid, expiry_date)
    ));
cookie.set_secure(Some(true));
cookie.set_expires(expiry_date);
cookie.set_same_site(SameSite::Lax);
resp.set_cookie(cookie);

This session id cookie can then be retrieved and verified as follows:

let userid = req.cookies().get("userid")
    .ok_or_else(|| Error::unauthorized("expected userid cookie".to_owned()))
    .and_then(|cookie| key.verify(cookie.value()).map_err(Error::unauthorized))
    .and_then(|value| decode_expiring_claim(value).map_err(|e| Error::unauthorized(format!("failed to decode userid cookie: {}", e))))?;

Tip: If you want to store multiple claims in the cookie, you can (de)serialize a struct with serde_json. This approach can pose a lightweight alternative to JWT, if you don't care about the standardization aspect.