Extract JSON object from https://smarthealth.cards QR code

shc.js

// Extract JSON payload from SHC QR code (without any kind of private/public key verification)

// Credits + inspiration
// https://github.com/dvci/health-cards-walkthrough/blob/main/SMART%20Health%20Cards.ipynb

// Usage
// $ node shc.js "shc:/01234569…"

const zlib = require("zlib");

// Extract the QR data from arguments
const data = process.argv[2];

// Convert the data to a JWT and extract its base64-encode payload
const payload = data
  .split("/")[1]
  .match(/(..?)/g)
  .map((number) => String.fromCharCode(parseInt(number, 10) + 45))
  .join("")
  .split(".")[1];

// Decode the payload
const buffer = Buffer.from(payload, "base64");

// Uncompress the payload and print the result
zlib.inflateRaw(buffer, (err, result) => {
  console.log(result.toString("utf8"));
});