Fastly C@E

This repository includes a full example showing you how to build and deploy a Fastly Compute at Edge service that integrates with Lagom.

This example is actually what’s used on our own demo website - and it only requires one short function to perform the verification (see snippet below).

We have lots of experience using Fastly, feel free to contact us if you require any further assistance integrating Lagom!

fn lagom_verify(req: &Request, page: &str, amount: i64) -> Result<(), Error> {
    //  extract callback params from URL, decode and parse
    let lguid = req.get_query_parameter("lguid").unwrap_or_default();
    let lgts = req.get_query_parameter("lgts").unwrap_or_default();
    let lgsig = req.get_query_parameter("lgsig").unwrap_or_default();
    let lgid = req.get_query_parameter("lgid").unwrap_or_default();
    let lgamt = req.get_query_parameter("lgamt").unwrap_or_default();

    // verify timestamp freshness
    if chrono::Utc::now().timestamp() > lgts.parse::<i64>()? + 10 {
        return err("This link has expired");
    }

    // check amount and page
    if lgamt.parse::<i64>()? != amount || req.get_path() != page {
        return err("This link is not valid");
    }

    // verify signature with pre shared secret
    let verif = lguid.to_string() + lgid + lgts + page + lgamt;
    let good = hmac_sha256::HMAC::mac(&verif.as_bytes(), SECRET);
    if lgsig != hex::encode(good) {
        return err("This link is not valid");
    }

    Ok(())
}