Simple green pass decoder in JavaScript

greenpass.js

/**
 * Simple green pass decoder inspired by https://git.gir.st/greenpass.git/blob_plain/master:/greenpass.py
 *
 * 2021 Lorenzo Millucci
 * 
 * Before usage install following dependecies `npm install base45 cbor jpeg-js jsqr pako`
 */

const base45 = require('base45');
const cbor = require('cbor');
const fs = require('fs')
const jpeg = require('jpeg-js');
const jsQR = require("jsqr");
const pako = require('pako');

// Set the path to the green pass QR
const FILE_PATH = __dirname + '/greenpass.jpg';

// Read image file
const greenpassJpeg = fs.readFileSync(FILE_PATH);
const greenpassImageData = jpeg.decode(greenpassJpeg, {useTArray: true});

// Decode QR
const decodedGreenpass = jsQR(greenpassImageData.data, greenpassImageData.width, greenpassImageData.height);

// Remove `HC1:` from the string
const greenpassBody = decodedGreenpass.data.substr(4);

// Data is Base45 encoded
const decodedData = base45.decode(greenpassBody);

// And zipped
const output = pako.inflate(decodedData);

const results = cbor.decodeAllSync(output);

[headers1, headers2, cbor_data, signature] = results[0].value;

const greenpassData = cbor.decodeAllSync(cbor_data);

console.log(JSON.stringify(greenpassData[0].get(-260).get(1), null, 2));

Hello! Do you know why I get errors on [headers1, headers2, cbor_data, signature] = results[0].value; -> 'headers1' is not defined, 'headers2 is not defined, 'cbor_data' is not defined, 'signature' is not defined ? Thank you!

I don't know. I assume that something went wrong during CBOR decoding

Add some debug lines as follows, to figure out where the process failed:

// Data is Base45 encoded
const decodedData = base45.decode(greenpassBody);
console.log("decodedData ", decodedData );

// And zipped
const output = pako.inflate(decodedData);
console.log("output ",output );

const results = cbor.decodeAllSync(output);
console.log("results ",results );

[headers1, headers2, cbor_data, signature] = results[0].value;

const greenpassData = cbor.decodeAllSync(cbor_data);

You can also have a look at my page for greenpass decoding in browser standalone:
https://github.com/jumpjack/greenpass

Hello! Do you know why I get errors on [headers1, headers2, cbor_data, signature] = results[0].value; -> 'headers1' is not defined, 'headers2 is not defined, 'cbor_data' is not defined, 'signature' is not defined ? Thank you!

Because you have to declare those variables first. Like this:

let headers1, headers2, cbor_data, signature;

And then write this:

[headers1, headers2, cbor_data, signature] = results[0].value;

Suggestion for decoding/reading (not checking) the "signature" variable?
It should result in something like:

kid: 53FOjX/4aJs=
key: <EllipticCurvePublicNumbers(curve=secp256r1, x=59224424711316661084877973301841821584140021680113528472675651838972371380627, y=54841068689176540860306147861276004028606373898471432794562118907413910993957>

Suggestion for decoding/reading (not checking) the "signature" variable? It should result in something like:

kid: 53FOjX/4aJs=
key: <EllipticCurvePublicNumbers(curve=secp256r1, x=59224424711316661084877973301841821584140021680113528472675651838972371380627, y=54841068689176540860306147861276004028606373898471432794562118907413910993957>

I have the same question

Hi Lorenzo!

Lorenzo can you advise a library to encrypt and sign cbor message ?