A simple EUDCC verifier implementation with Python CWT.

python_cwt_sample_eudcc_02.py

import json
import os
import zlib

import requests
from base45 import b45decode

import cwt
from cwt import load_pem_hcert_dsc


class Verifier:
    def __init__(self, base_url: str, trustlist_store_path: str):
        self._base_url = base_url
        self._trustlist_store_path = trustlist_store_path
        self._dscs = []
        self._trustlist = []
        self._load_trustlist()

    @classmethod
    def new(cls, base_url: str, trustlist_store_path: str):
        return cls(base_url, trustlist_store_path)

    def refresh_trustlist(self):
        status = 200
        headers = None

        # Get new DSCs
        x_resume_token = (
            self._trustlist[len(self._trustlist) - 1]["x_resume_token"]
            if self._trustlist
            else ""
        )
        while status == 200:
            if x_resume_token:
                headers = {"X-RESUME-TOKEN": x_resume_token}
            r = requests.get(
                self._base_url + "/signercertificateUpdate", headers=headers
            )
            status = r.status_code
            if status == 204:
                break
            if status != 200:
                raise Exception("Received %d from signercertificateUpdate" % status)

            x_resume_token = r.headers["X-RESUME-TOKEN"]
            self._trustlist.append(
                {
                    "x_kid": r.headers["X-KID"],
                    "x_resume_token": x_resume_token,
                    "dsc": r.text,
                }
            )

        # Filter expired/revoked DSCs
        r = requests.get(self._base_url + "/signercertificateStatus")
        if r.status_code != 200:
            raise Exception("Received %d from signercertificateStatus" % r.status_code)
        active_kids = r.json()
        self._dscs = []
        for v in self._trustlist:
            if v["x_kid"] not in active_kids:
                continue
            dsc = f"-----BEGIN CERTIFICATE-----\n{v['dsc']}\n-----END CERTIFICATE-----"
            self._dscs.append(load_pem_hcert_dsc(dsc))

        # Update trustlist store.
        with open(self._trustlist_store_path, "w") as f:
            json.dump(
                [v for v in self._trustlist if v["x_kid"] in active_kids], f, indent=4
            )
        return

    def verify_and_decode(self, eudcc: bytes) -> bytes:
        if eudcc.startswith(b"HC1:"):
            # Decode Base45 data.
            eudcc = b45decode(eudcc[4:])
            # Decompress with zlib.
            eudcc = zlib.decompress(eudcc)
        # Verify and decode CWT.
        return cwt.decode(eudcc, keys=self._dscs)

    def _load_trustlist(self):
        try:
            with open(self._trustlist_store_path) as f:
                self._trustlist = json.load(f)
        except Exception as err:
            if type(err) != FileNotFoundError:
                raise err
            self._trustlist = []
        return


# An endpoint of Digital Green Certificate Verifier Service compliant with:
# https://eu-digital-green-certificates.github.io/dgca-verifier-service/
BASE_URL = os.environ["CWT_SAMPLES_EUDCC_BASE_URL"]

# e.g., "./dscs.json"
TRUSTLIST_STORE_PATH = os.environ["CWT_SAMPLES_EUDCC_TRUSTLIST_STORE_PATH"]

# quoted from https://github.com/eu-digital-green-certificates/dgc-testdata/blob/main/AT/2DCode/raw/1.json
BASE45_FORMATTED_EUDCC = b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
# RAW_EUDCC = bytes.fromhex(
#     "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"
# )

if __name__ == "__main__":
    v = Verifier.new(BASE_URL, TRUSTLIST_STORE_PATH)
    v.refresh_trustlist()
    try:
        res = v.verify_and_decode(BASE45_FORMATTED_EUDCC)  # or RAW_EUDCC
    except Exception as err:
        print("Verification failed: %s" % err)
        exit(1)
    hcert = res[-260]
    print(hcert)
    exit(0)

Is there an official (from the EU?) API available for the DGCA verifier service? Or a list of endpoints? What endpoint was used for this script?

Actually, I am searching for this as well. So far I believe that this is not intended (for whatever reason).
Take a look at EU Digital COVID Certificate: Overview, there it is said:

A note on using the apps and released APK files found in this GitHub organization: The apps are reference implementations that cannot be used in production environments as-is, but rather need to be configured by EU member states to access their national backends. The released APK files are configured to work with the test environments and will not report correct results on "live" DCCs.