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Rust

If you want to verify Lagom micro transactions directly from your Rust server, you can use the following function.

This is a function we use on the Fastly Compute at Edge service that runs our demo website. It comes with a few dependencies, feel free to explore the repository to learn more about how to integrate this on your platform.

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(())
}