Signing using Deno + QZ Tray

sign-message.deno.js

/**
 * Author: A. Tres Finocchiaro
 * License: Public Domain
 */

import "https://raw.githubusercontent.com/qzind/tray/v2.2.2/js/qz-tray.js";
import { encode, decode } from "https://deno.land/std/encoding/base64.ts";

// Load certificate
qz.security.setCertificatePromise(function(resolve, reject) {
    Deno.readTextFile("./digital-certificate.txt").then(text => {
        resolve(text);
    }).catch((err) => reject(err));
});

// Load private key
Deno.readTextFile("./private-key.pem").then(text => {
    // Clean "-----BEGIN PRIVATE KEY-----" and newlines
    let cleaned = text.split("-----")[2].replace(/\s+/g, '');
    let bytes = decode(cleaned);

    crypto.subtle.importKey(
        "pkcs8",
        bytes,
        { name: "RSASSA-PKCS1-v1_5",  hash: "SHA-512" },
        true,
        ["sign"]
    ).then(cryptoKey => {
        qz.security.setSignatureAlgorithm("SHA512");
        qz.security.setSignaturePromise((toSign) => {
            return (resolve, reject) => {
                let encoder = new TextEncoder();
                crypto.subtle.sign(
                    "RSASSA-PKCS1-v1_5",
                    cryptoKey,
                    encoder.encode(toSign)
                ).then(signature => {
                    console.log(encode(signature));
                    resolve(encode(signature));
                });
            };
        });
    })
}).catch((err) => console.error(err));

// Connect and print
qz.websocket.connect().then(() => {
    return qz.printers.find("PDF");
}).then((printer) => {
    console.log(printer);
}).catch((err) => {
    console.error(err);
});