Extract EU Digital COVID Certificate QR code data from images and PDFs

digital_covid_cert_decoder.py

import argparse
import json
import pathlib
import sys
import zlib

import cbor2
from base45 import b45decode
from cose.messages import CoseMessage
from PIL import Image
from pygments import formatters, highlight, lexers
from pyzbar import pyzbar
from pyzbar.wrapper import ZBarSymbol

__doc__ = """Extracts EU Digital COVID Certificate QR code data from images and PDFs"""


def detect_dcc_qr_codes(image):
    """Extracts EU Digital COVID Certificate QR codes from an image"""
    qr_codes = pyzbar.decode(image, symbols=[ZBarSymbol.QRCODE])
    decoded = [qr.data.decode("utf-8") for qr in qr_codes]
    return [qr for qr in decoded if qr.startswith("HC1:")]


def parse_digital_green_cert(qr_code_data):
    """Extracts the payload from an EU Digital COVID Certificate QR code"""
    base45_data = qr_code_data[len("HC1:") :]
    compressed_data = b45decode(base45_data)
    cose_signed_document = zlib.decompress(compressed_data)
    cose_message = CoseMessage.decode(cose_signed_document)
    payload = cbor2.loads(cose_message.payload)
    return payload


def highlight_json(obj):
    """Prints an object as syntax-highlighted JSON"""
    formatted_json = json.dumps(obj, indent=2)
    return highlight(formatted_json, lexers.JsonLexer(), formatters.TerminalFormatter())


def main(arguments):
    parser = argparse.ArgumentParser(
        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
    )
    parser.add_argument("infile", help="QR code image or PDF", type=pathlib.Path)

    args = parser.parse_args(arguments)

    # PIL can't read PDFs, so render these first
    if args.infile.suffix == ".pdf":
        import pdf2image

        images = pdf2image.convert_from_path(args.infile)
    else:
        images = [Image.open(args.infile)]

    # Detect all DCC QR codes
    qr_codes = []
    for image in images:
        qr_codes.extend(detect_dcc_qr_codes(image))

    # Print formatted results to the terminal
    for qr_code in qr_codes:
        payload = parse_digital_green_cert(qr_code)
        print(highlight_json(payload))

    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))